TOP RCPTM journal publications 2021

K. Jayaramulu, M. Horn, A. Schneemann, H. Saini, A. Bakandritsos, V. Ranc, M. Petr, V. Stavila, C. Narayana, B. Scheibe, Š. Kment, M. Otyepka, N. Motta, D. Dubal, R. Zbořil and R. A. Fischer, "Covalent Graphene‐MOF Hybrids for High‐Performance Asymmetric Supercapacitors," ADVANCED MATERIALS, vol. 33, iss. 4, pp. 2004560, 2021.
DOI: 10.1002/adma.202004560, IF = 30.849

Abstract: In this work, the covalent attachment of an amine functionalized metal‐organic framework (UiO‐66‐NH2 = Zr6O4(OH)4(bdc‐NH2)6; bdc‐NH2 = 2‐amino‐1,4‐benzenedicarboxylate) (UiO‐Universitetet i Oslo) to the basal‐plane of carboxylate functionalized graphene (graphene acid = GA) via amide bonds is reported. The resultant GA@UiO‐66‐NH2 hybrid displayed a large specific surface area, hierarchical pores and an interconnected conductive network. The electrochemical characterizations demonstrated that the hybrid GA@UiO‐66‐NH2 acts as an effective charge storing material with a capacitance of up to 651 F g−1, significantly higher than traditional graphene‐based materials. The results suggest that the amide linkage plays a key role in the formation of a π‐conjugated structure, which facilitates charge transfer and consequently offers good capacitance and cycling stability. Furthermore, to realize the practical feasibility, an asymmetric supercapacitor using a GA@UiO‐66‐NH2 positive electrode with Ti3C2TX MXene as the opposing electrode has been constructed. The cell is able to deliver a power density of up to 16 kW kg−1 and an energy density of up to 73 Wh kg−1, which are comparable to several commercial devices such as Pb‐acid and Ni/MH batteries. Under an intermediate level of loading, the device retained 88% of its initial capacitance after 10 000 cycles.


M. Delfi, R. Sartorius, M. Ashrafizadeh, E. Sharifi, Y. Zhang, P. De Berardinis, A. Zarrabi, R. S. Varma, F. R. Tay, B. R. Smith and P. Makvandi, "Self-assembled peptide and protein nanostructures for anti-cancer therapy: Targeted delivery, stimuli-responsive devices and immunotherapy," NANO TODAY, vol. 38, art. no. 101119, 2021.
DOI: 10.1016/j.nantod.2021.101119, IF = 20.722

Abstract: Self-assembled peptides and proteins possess tremendous potential as targeted drug delivery systems and key applications of these well-defined nanostructures reside in anti-cancer therapy. Peptides and proteins can self-assemble into nanostructures of diverse sizes and shapes in response to changing environmental conditions such as pH, temperature, ionic strength, as well as host and guest molecular interactions; their countless benefits include good biocompatibility and high loading capacity for hydrophobic and hydrophilic drugs. These self-assembled nanomaterials can be adorned with functional moieties to specifically target tumor cells. Stimuli-responsive features can also be incorporated with respect to the tumor microenvironment. This review sheds light on the growing interest in self-assembled peptides and proteins and their burgeoning applications in cancer treatment and immunotherapy.


V. M. Santhini, O. Stetsovych, M. Ondráček, J. I. Mendieta Moreno, P. Mutombo, B. Torre, M. Švec, J. Klívar, I. G. Stará, H. Vázquez, I. Starý and P. Jelínek, "On‐Surface Synthesis of Polyferrocenylene and its Single‐Chain Conformational and Electrical Transport Properties," ADVANCED FUNCTIONAL MATERIALS, vol. 31, iss. 5, pp. 2006391, 2021.
DOI: 10.1002/adfm.202006391, IF = 18.808

Abstract: Unlike intrinsically conductive organic polymers, which are central to organic electronics/photovoltaics, metallopolymers contain multiple redox-active centers allowing extra control of their intriguing properties. Ferrocene polymers are particularly attractive in this regard, but research of the iconic poly(1,1′-ferrocenylene), a main-chain ferrocene polymer with the most densely bound redox-active iron centers, has practically stopped because it is an insoluble and rather inhomogeneous material. Herein, its synthesis on the Ag(111) surface is reported, based on the Ullmann coupling of 1′,1″′-diiodo-1,1″-biferrocene. Conformationally flexible single-chain nanowires up to 50 nm in length, thus overcoming the limits of conventional solution polymerization, are characterized by scanning probe microscopy techniques achieving atomic resolution. Single-chain electrical conductivity measurements are performed in the longitudinal directions revealing apparent metal-to-semiconductor transition (depending on the number of ferrocene units lifted from the surface). A simple transport model is established to rationalize this observation.


X. Zhou, I. Hwang, O. Tomanec, D. Fehn, A. Mazare, R. Zboril, K. Meyer and P. Schmuki, "Advanced Photocatalysts: Pinning Single Atom Co‐Catalysts on Titania Nanotubes," ADVANCED FUNCTIONAL MATERIALS, vol. 31, iss. 30, pp. 2102843, 2021.
DOI: 10.1002/adfm.202102843, IF = 18.808

Abstract: Single atom (SA) catalysis, over the last 10 years, has become a forefront in heterogeneous catalysis, electrocatalysis, and most recently also in photocatalysis. Most crucial when engineering a SA catalyst/support system is the creation of defined anchoring points on the support surface to stabilize reactive SA sites. Here, a so far unexplored but evidently very effective approach to trap and stabilize SAs on a broadly used photocatalyst platform is introduced. In self-organized anodic TiO2 nanotubes, a high degree of stress is incorporated in the amorphous oxide during nanotube growth. During crystallization (by thermal annealing), this leads to a high density of Ti3+-Ov surface defects that are hardly present in other common titania nanostructures (as nanoparticles). These defects are highly effective for SA iridium trapping. Thus a SA-Ir photocatalyst with a higher photocatalytic activity than for any classic co-catalyst arrangement on the semiconductive substrate is obtained. Hence, a tool for SA trapping on titania-based back-contacted platforms is provided for wide application in electrochemistry and photoelectrochemistry. Moreover, it is shown that stably trapped SAs provide virtually all photocatalytic reactivity, with turnover frequencies in the order of 4 × 106 h−1 in spite of representing only a small fraction of the initially loaded SAs.


I. Tantis, A. Bakandritsos, D. Zaoralová, M. Medveď, P. Jakubec, J. Havláková, R. Zbořil and M. Otyepka, "Covalently Interlinked Graphene Sheets with Sulfur‐Chains Enable Superior Lithium–Sulfur Battery Cathodes at Full‐Mass Level," ADVANCED FUNCTIONAL MATERIALS, vol. 31, iss. 30, pp. 2101326, 2021.
DOI: 10.1002/adfm.202101326, IF = 18.808

Abstract: Sulfur represents a low‑cost, sustainable, and high theoretical capacity cathode material for lithium–sulfur batteries, which can meet the growing demand in portable power sources, such as in electric vehicles and mobile information technologies. However, the shuttling effect of the formed lithium polysulfides, as well as their low conductivity, compromise the electrochemical performance of lithium–sulfur cells. To tackle this challenge, a so far unexplored cathode, composed of sulfur covalently bonded directly on graphene is developed. This is achieved by leveraging the nucleophilicity of polysulfide chains, which react readily with the electrophilic centers in fluorographene, as experimental and theoretical data unveil. The reaction leads to the formation of carbon–sulfur covalent bonds and a particularly high sulfur content of 80 mass%. Owing to these features, the developed cathode exhibits excellent performance with only 5 mass% of conductive carbon additive, delivering very high full‑cathode‑mass capacities and rate capability, combined with superior cycling stability. In combination with a fluorinated ether as electrolyte additive, the capacity persists at ≈700 mAh g−1 after 100 cycles at 0.1 C, and at ≈644 mAh g−1 after 250 cycles at 0.2 C, keeping ≈470 mAh g−1 even after 500 cycles.


H. L. Chia, C. C. Mayorga‐Martinez, Z. Sofer, P. Lazar, R. D. Webster and M. Pumera, "Vanadium Dopants: A Boon or a Bane for Molybdenum Dichalcogenides‐Based Electrocatalysis Applications," ADVANCED FUNCTIONAL MATERIALS, vol. 31, iss. 8, pp. 2009083, 2021.
DOI: 10.1002/adfm.202009083, IF = 18.808

Abstract: The ever-rising concerns with regards to energy shortages and climate change have made the search for clean and renewable energy sources a pressing priority for the sustainable development of societies. Although, conventional precious metal-based catalysts such as platinum, iridium, and ruthenium are able to efficiently catalyze the conversion of chemical to electrical energy, they are often very costly, scarce, and suffer from poor stability, hence impeding their widespread applications. The limitations of the current state-of art catalysts have propelled tremendous efforts in search for alternative catalysts. Notably, transition metal dichalcogenides (TMDs) have spurred much enthusiasm because of their natural abundance, low cost, and remarkable catalytic activity. Numerous studies have recounted that doping can tune the properties of TMDs and that vanadium dopants reportedly improve the electrical properties of Group 6 TMDs. Herein, the authors aspire to investigate the effects of doping varying amounts of vanadium on molybdenum dichalcogenides on their electrocatalytic activities toward hydrogen evolution reaction, oxygen evolution reaction, and oxygen reduction reaction. Despite previous studies bespeaking promising effects, the results here demonstrate both improvements and worsening of electrocatalytic performances from varying the stoichiometry of vanadium dopants in molybdenum dichalcogenides, depending on the type of materials and intended electrochemical applications.


L. Mascaretti, A. Schirato, R. Zbořil, Š. Kment, P. Schmuki, A. Alabastri and A. Naldoni, "Solar steam generation on scalable ultrathin thermoplasmonic TiN nanocavity arrays," NANO ENERGY, vol. 83, art. no. 105828, 2021.
DOI: 10.1016/j.nanoen.2021.105828, IF = 17.881

Abstract: Plasmonic-based solar absorbers exhibit complete light absorption in a sub-µm thickness, representing an alternative to mm-thick carbon-based materials most typically employed for solar-driven steam generation. In this work, we present the scalable fabrication of ultrathin plasmonic titanium nitride (TiN) nanocavity arrays that exhibit 90% broadband solar light absorption within ~ 250 nm from the illuminated surface and show a fast non-linear increase of performance with light intensity. At 14 Suns TiN nanocavities reach ~ 15 kg h–1 m–2 evaporation rate and ~ 76% thermal efficiency, a steep increase from ~ 0.4 kg h−1 m−2 and ~ 20% under 1.4 Suns. Electromagnetic, thermal and diffusion modeling of our system reveals the contribution of each material and reactor component to heat dissipation and shows that a quasi-two-dimensional heat dissipation regime significantly accelerates water evaporation. Our approach to ultrathin plasmonic absorbers can boost the performance of devices for evaporation/desalination and holds promise for a broader range of phase separation processes.


J. Chen, M. Cheng, G. Salgado, P. Stadlbauer, X. Zhang, S. Amrane, A. Guédin, F. He, J. Šponer, H. Ju, J. Mergny and J. Zhou, "The beginning and the end: flanking nucleotides induce a parallel G-quadruplex topology," NUCLEIC ACIDS RESEARCH, Article in press, 2021.
DOI: 10.1093/nar/gkab681, IF = 16.971

Abstract: Genomic sequences susceptible to form G-quadruplexes (G4s) are always flanked by other nucleotides, but G4 formation in vitro is generally studied with short synthetic DNA or RNA oligonucleotides, for which bases adjacent to the G4 core are often omitted. Herein, we systematically studied the effects of flanking nucleotides on structural polymorphism of 371 different oligodeoxynucleotides that adopt intramolecular G4 structures. We found out that the addition of nucleotides favors the formation of a parallel fold, defined as the ‘flanking effect’ in this work. This ‘flanking effect’ was more pronounced when nucleotides were added at the 5′-end, and depended on loop arrangement. NMR experiments and molecular dynamics simulations revealed that flanking sequences at the 5′-end abolish a strong syn-specific hydrogen bond commonly found in non-parallel conformations, thus favoring a parallel topology. These analyses pave a new way for more accurate prediction of DNA G4 folding in a physiological context.


T. Raček, O. Schindler, D. Toušek, V. Horský, K. Berka, J. Koča and R. Svobodová, "Atomic Charge Calculator II: web-based tool for the calculation of partial atomic charges," NUCLEIC ACIDS RESEARCH, vol. 48, iss. W1, pp. W591-W596, 2020.
DOI: 10.1093/nar/gkaa367, IF = 16.971

Abstract: Partial atomic charges serve as a simple model for the electrostatic distribution of a molecule that drives its interactions with its surroundings. Since partial atomic charges are frequently used in computational chemistry, chemoinformatics and bioinformatics, many computational approaches for calculating them have been introduced. The most applicable are fast and reasonably accurate empirical charge calculation approaches. Here, we introduce Atomic Charge Calculator II (ACC II), a web application that enables the calculation of partial atomic charges via all the main empirical approaches and for all types of molecules. ACC II implements 17 empirical charge calculation methods, including the highly cited (QEq, EEM), the recently published (EQeq, EQeq+C), and the old but still often used (PEOE). ACC II enables the fast calculation of charges even for large macromolecular structures. The web server also offers charge visualization, courtesy of the powerful LiteMol viewer. The calculation setup of ACC II is very straightforward and enables the quick calculation of high-quality partial charges. The application is available at https://acc2.ncbr.muni.cz.


I. Sillitoe, N. Bordin, N. Dawson, V. P. Waman, P. Ashford, H. M. Scholes, C. S. M. Pang, L. Woodridge, C. Rauer, N. Sen, M. Abbasian, S. Le Cornu, S. D. Lam, K. Berka, I. Varekova, R. Svobodova, J. Lees and C. A. Orengo, "CATH: increased structural coverage of functional space," NUCLEIC ACIDS RESEARCH, vol. 49, iss. D1, pp. D266-D273, 2021.
DOI: 10.1093/nar/gkaa1079, IF = 16.971

Abstract: CATH (https://www.cathdb.info) identifies domains in protein structures from wwPDB and classifies these into evolutionary superfamilies, thereby providing structural and functional annotations. There are two levels: CATH-B, a daily snapshot of the latest domain structures and superfamily assignments, and CATH+, with additional derived data, such as predicted sequence domains, and functionally coherent sequence subsets (Functional Families or FunFams). The latest CATH+ release, version 4.3, significantly increases coverage of structural and sequence data, with an addition of 65,351 fully-classified domains structures (+15%), providing 500 238 structural domains, and 151 million predicted sequence domains (+59%) assigned to 5481 superfamilies. The FunFam generation pipeline has been re-engineered to cope with the increased influx of data. Three times more sequences are captured in FunFams, with a concomitant increase in functional purity, information content and structural coverage. FunFam expansion increases the structural annotations provided for experimental GO terms (+59%). We also present CATH-FunVar web-pages displaying variations in protein sequences and their proximity to known or predicted functional sites. We present two case studies (1) putative cancer drivers and (2) SARS-CoV-2 proteins. Finally, we have improved links to and from CATH including SCOP, InterPro, Aquaria and 2DProt.


D. Panáček, L. Hochvaldová, A. Bakandritsos, T. Malina, M. Langer, J. Belza, J. Martincová, R. Večeřová, P. Lazar, K. Poláková, J. Kolařík, L. Válková, M. Kolář, M. Otyepka, A. Panáček and R. Zbořil, "Silver Covalently Bound to Cyanographene Overcomes Bacterial Resistance to Silver Nanoparticles and Antibiotics," ADVANCED SCIENCE, vol. 8, iss. 12, pp. 2003090, 2021.
DOI: 10.1002/advs.202003090, IF = 16.806

Abstract: The ability of bacteria to develop resistance to antibiotics is threatening one of the pillars of modern medicine. It was recently understood that bacteria can develop resistance even to silver nanoparticles by starting to produce flagellin, a protein which induces their aggregation and deactivation. This study shows that silver covalently bound to cyanographene (GCN/Ag) kills silver-nanoparticle-resistant bacteria at concentrations 30 times lower than silver nanoparticles, a challenge which has been so far unmet. Tested also against multidrug resistant strains, the antibacterial activity of GCN/Ag is systematically found as potent as that of free ionic silver or 10 nm colloidal silver nanoparticles. Owing to the strong and multiple dative bonds between the nitrile groups of cyanographene and silver, as theory and experiments confirm, there is marginal silver ion leaching, even after six months of storage, and thus very high cytocompatibility to human cells. Molecular dynamics simulations suggest strong interaction of GCN/Ag with the bacterial membrane, and as corroborated by experiments, the antibacterial activity does not rely on the release of silver nanoparticles or ions. Endowed with these properties, GCN/Ag shows that rigid supports selectively and densely functionalized with potent silver-binding ligands, such as cyanographene, may open new avenues against microbial resistance.


S. Iravani and R. S. Varma, "Plant Pollen Grains: A Move Towards Green Drug and Vaccine Delivery Systems," NANO-MICRO LETTERS, vol. 13, iss. 1, pp. , 2021.
DOI: 10.1007/s40820-021-00654-y, IF = 16.419

Abstract: Pollen grains and plant spores have emerged as innovative biomaterials for various applications such as drug/vaccine delivery, catalyst support, and the removal of heavy metals. The natural microcapsules comprising spore shells and pollen grain are designed for protecting the genetic materials of plants from exterior impairments. Two layers make up the shell, the outer layer (exine) that comprised largely of sporopollenin, and the inner layer (intine) that built chiefly of cellulose. These microcapsule shells, namely hollow sporopollenin exine capsules have some salient features such as homogeneity in size, non-toxic nature, resilience to both alkalis and acids, and the potential to withstand at elevated temperatures; they have displayed promising potential for the microencapsulation and the controlled drug delivery/release. The important attribute of mucoadhesion to intestinal tissues can prolong the interaction of sporopollenin with the intestinal mucosa directing to an augmented effectiveness of nutraceutical or drug delivery. Here, current trends and prospects related to the application of plant pollen grains for the delivery of vaccines and drugs and vaccine are discussed.


T. Qin, Z. Wang, Y. Wang, F. Besenbacher, M. Otyepka and M. Dong, "Recent Progress in Emerging Two-Dimensional Transition Metal Carbides," NANO-MICRO LETTERS, vol. 13, art. no. 183, 2021.
DOI: 10.1007/s40820-021-00710-7, IF = 16.419

Abstract: As a new member in two-dimensional materials family, transition metal carbides (TMCs) have many excellent properties, such as chemical stability, in-plane anisotropy, high conductivity and flexibility, and remarkable energy conversation efficiency, which predispose them for promising applications as transparent electrode, flexible electronics, broadband photodetectors and battery electrodes. However, up to now, their device applications are in the early stage, especially because their controllable synthesis is still a great challenge. This review systematically summarized the state-of-the-art research in this rapidly developing field with particular focus on structure, property, synthesis and applicability of TMCs. Finally, the current challenges and future perspectives are outlined for the application of 2D TMCs.


P. Mayorga-Burrezo, J. Muñoz, D. Zaoralová, M. Otyepka and M. Pumera, "Multiresponsive 2D Ti3C2Tx MXene via Implanting Molecular Properties," ACS NANO, vol. 15, iss. 6, pp. 10067-10075, 2021.
DOI: 10.1021/acsnano.1c01742, IF = 15.881

Abstract: The design and fabrication of active nanomaterials exhibiting multifunctional properties is a must in the so-called global “Fourth Industrial Revolution”. In this sense, molecular engineering is a powerful tool to implant original capabilities on a macroscopic scale. Herein, different bioinspired 2D-MXenes have been developed via a versatile and straightforward synthetic approach. As a proof of concept, Ti3C2Tx MXene has been exploited as a highly sensitive transducing platform for the covalent assembly of active biomolecular architectures (i.e., amino acids). All pivotal properties originated from the anchored targets were proved to be successfully transferred to the resulting bioinspired 2D-MXenes. Appealing applications have been devised for these 2D-MXene prototypes showing (i) chiroptical activity, (ii) fluorescence capabilities, (iii) supramolecular π–π interactions, and (iv) stimuli-responsive molecular switchability. Overall, this work demonstrates the fabrication of programmable 2D-MXenes, taking advantage of the inherent characteristics of the implanted (bio)molecular components. Thus, the current bottleneck in the field of 2D-MXenes can be overcome after the significant findings reported here.


Y. Zuo, T. Li, N. Zhang, T. Jing, D. Rao, P. Schmuki, Š. Kment, R. Zbořil and Y. Chai, "Spatially Confined Formation of Single Atoms in Highly Porous Carbon Nitride Nanoreactors," ACS NANO, vol. 15, iss. 4, pp. 7790-7798, 2021.
DOI: 10.1021/acsnano.1c01872, IF = 15.881

Abstract: Reducing the size of a catalyst to a single atom (SA) level can dramatically change its physicochemical properties and significantly boost its catalytic activity. However, the massive synthesis of SA catalysts still remains a grand challenge mainly because of the aggregation and nucleation of the generated atoms during the reaction. Here, we design and implement a spatially confined synthetic strategy based on a porous-hollow carbon nitride (p-CN) coordinated with 1-butyl-3-methylimidazole hexafluorophosphate, which can act as a nanoreactor and allow us to obtain metal SA catalysts (p-CN@M SAs). This relatively easy and highly effective method provides a way to massively synthesize single/multiple atoms (p-CN@M SAs, M = Pt, Pd, Cu, Fe, etc.). Moreover, the amorphous NiB-coated p-CN@Pt SAs can further increase the loading amount of Pt SAs to 3.7 wt %. The synthesized p-CN@Pt&NiB electrocatalyst exhibits an extraordinary hydrogen evolution reaction activity with the overpotential of 40.6 mV@10 mA/cm–2 and the Tofel slope of 29.26 mV/dec.


S. Kalytchuk, L. Zdražil, Z. Bad’ura, M. Medved’, M. Langer, M. Paloncýová, G. Zoppellaro, S. V. Kershaw, A. L. Rogach, M. Otyepka and R. Zbořil, "Carbon Dots Detect Water-to-Ice Phase Transition and Act as Alcohol Sensors via Fluorescence Turn-Off/On Mechanism," ACS NANO, vol. 15, iss. 4, pp. 6582–6593, 2021.
DOI: 10.1021/acsnano.0c09781, IF = 15.881

Abstract: Highly fluorescent carbon nanoparticles called carbon dots (CDs) have been the focus of intense research due to their simple chemical synthesis, nontoxic nature, and broad application potential including optoelectronics, photocatalysis, biomedicine, and energy-related technologies. Although a detailed elucidation of the mechanism of their photoluminescence (PL) remains an unmet challenge, the CDs exhibit robust, reproducible, and environment-sensitive PL signals, enabling us to monitor selected chemical phenomena including phase transitions or detection of ultralow concentrations of molecular species in solution. Herein, we report the PL turn-off/on behavior of aqueous CDs allowing the reversible monitoring of the water–ice phase transition. The bright PL attributable to molecular fluorophores present on the CD surface was quenched by changing the liquid aqueous environment to solid phase (ice). Based on light-induced electron paramagnetic resonance (LEPR) measurements and density functional theory (DFT) calculations, the proposed kinetic model assuming the presence of charge-separated trap states rationalized the observed sensitivity of PL lifetimes to the environment. Importantly, the PL quenching induced by freezing could be suppressed by adding a small amount of alcohols. This was attributed to a high tendency of alcohol to increase its concentration at the CD/solvent interface, as revealed by all-atom molecular dynamics simulations. Based on this behavior, a fluorescence “turn-on” alcohol sensor for exhaled breath condensate (EBC) analysis has been developed. This provided an easy method to detect alcohols among other common interferents in EBC with a low detection limit (100 ppm), which has a potential to become an inexpensive and noninvasive clinically useful diagnostic tool for early stage lung cancer screening.


V. Urbanová, N. Antonatos, J. Plutnar, P. Lazar, J. Michalička, M. Otyepka, Z. Sofer and M. Pumera, "Rhenium Doping of Layered Transition-Metal Diselenides Triggers Enhancement of Photoelectrochemical Activity," ACS NANO, vol. 15, iss. 2, pp. 2374-2385, 2021.
DOI: 10.1021/acsnano.0c04437, IF = 15.881

Abstract: The ever decreasing sources of fossil fuels have launched extensive research of alternative materials that might play a key role in their replacement. Therefore, the scientific community continuously investigates the possibilities of maximizing the working capacity of such materials in order to fulfill energy challenges in the near future. In this context, doping of the semiconducting materials is a versatile strategy to trigger their physicochemical properties as well their electrochemical performance. Herein, the impact of rhenium doping toward photoelectrochemical activity of MoSe2 and WSe2 was studied. Our results indicate that rhenium as a dopant contributes to better overall electrochemical performance, that is, an easier electron transfer of these materials compared to pristine compounds. Additionally, the photoelectrochemical measurements revealed that the doping with rhenium generated an enhancement of the photocurrent response of MoSe2 as well as WSe2 under UV light illumination.


J. Kolařík, A. Bakandritsos, Z. Bad’ura, R. Lo, G. Zoppellaro, Š. Kment, A. Naldoni, Y. Zhang, M. Petr, O. Tomanec, J. Filip, M. Otyepka, P. Hobza and R. Zbořil, "Carboxylated Graphene for Radical-Assisted Ultra-Trace-Level Water Treatment and Noble Metal Recovery," ACS NANO, vol. 15, iss. 2, pp. 3349-3358, 2021.
DOI: 10.1021/acsnano.0c10093, IF = 15.881

Abstract: Sorption technologies, enabling removal of heavy metals, play a pivotal role in meeting the global demands for unrestricted access to drinking water. Standard sorption technologies suffer from limited efficiency related to the weak sorbent–metal interaction. Further challenges include the development of technologies enabling smart metal recovery and sorbent regeneration. To this end, a densely functionalized graphene, with 33% by mass content of carboxyl groups, linked through direct C–C bonds (graphene acid, GA) represents a previously unexplored solution to this challenge. GA revealed excellent efficiency for removal of highly toxic metals, such as Cd2+ and Pb2+. Due to its selective chemistry, GA can bind heavy metals with high affinity, even at concentrations of 1 mg L–1 and in the presence of competing ions of natural drinking water, and reduce them down to drinking water allowance levels of a few μg L–1. This is not only due to carboxyl groups but also due to the stable radical centers of the GA structure, enabling metal ion–radical interactions, as proved by EPR, XPS, and density functional theory calculations. GA offers full structural integrity during the highly acidic and basic treatment, which is exploited for noble metal recovery (Ga3+, In3+, Pd2+) and sorbent regeneration. Owing to these attributes, GA represents a fully reusable metal sorbent, applicable also in electrochemical energy technologies, as illustrated with a GA/Pt catalyst derived from Pt4+-contaminated water.


V. M. Santhini, C. Wäckerlin, A. Cahlík, M. Ondráček, S. Pascal, A. Matěj, O. Stetsovych, P. Mutombo, P. Lazar, O. Siri and P. Jelínek, "1D Coordination π–d Conjugated Polymers with Distinct Structures Defined by the Choice of the Transition Metal: Towards a New Class of Antiaromatic Macrocycles," ANGEWANDTE CHEMIE INTERNATIONAL EDITION, vol. 60, iss. 1, pp. 439-445, 2021.
DOI: 10.1002/anie.202011462, IF = 15.336

Abstract: Recently π–d conjugated coordination polymers have received a lot of attention owing to their unique material properties, although synthesis of long and defect‐free polymers remains challenging. Herein we introduce a novel on‐surface synthesis of coordination polymers with quinoidal ligands under ultra‐high vacuum conditions, which enables formation of flexible coordination polymers with lengths up to hundreds of nanometers. Moreover, this procedure allows the incorporation of different transition‐metal atoms with four‐ or two‐fold coordination. Remarkably, the two‐fold coordination mode revealed the formation of wires constituted by (electronically) independent 12‐membered antiaromatic macrocycles linked together through two C−C single bonds.


M. Lamanec, R. Lo, D. Nachtigallová, A. Bakandritsos, E. Mohammadi, M. Dračínský, R. Zbořil, P. Hobza and W. Wang, "The Existence of a N→C Dative Bond in the C60–Piperidine Complex," ANGEWANDTE CHEMIE INTERNATIONAL EDITION, vol. 60, iss. 4, pp. 1942-1950, 2021.
DOI: 10.1002/anie.202012851, IF = 15.336

Abstract: The complexes formed between carbon allotropes (C20, C60 fullerenes, graphene, and single‐wall carbon nanotubes) and piperidine have been investigated by means of computational quantum chemical and experimental IR and NMR techniques. Alongside hydrogen bonds, the C⋅⋅⋅N tetrel bond, and lone‐pair⋅⋅⋅π interactions, the unexpected N→C dative/covalent bond has been detected solely in complexes of fullerenes with piperidine. Non‐planarity and five‐member rings of carbon allotropes represent the key structural prerequisites for the unique formation of a dative N→C bond. The results of thermodynamics calculations, molecular dynamics simulations, and NMR and FTIR spectroscopy explain the specific interactions between C60 and piperidine. The differences in behavior of individual carbon allotropes in terms of dative bonding formation brings a new insight into their controllable organic functionalization.


M. Mistrik, Z. Skrott, P. Muller, A. Panacek, L. Hochvaldova, K. Chroma, T. Buchtova, V. Vandova, L. Kvitek and J. Bartek, "Microthermal-induced subcellular-targeted protein damage in cells on plasmonic nanosilver-modified surfaces evokes a two-phase HSP-p97/VCP response," NATURE COMMUNICATIONS, vol. 12, iss. 1, art. no. 713, 2021.
DOI: 10.1038/s41467-021-20989-9, IF = 14.919

Abstract: Despite proteotoxic stress and heat shock being implicated in diverse pathologies, currently no methodology to inflict defined, subcellular thermal damage exists. Here, we present such a single-cell method compatible with laser-scanning microscopes, adopting the plasmon resonance principle. Dose-defined heat causes protein damage in subcellular compartments, rapid heat-shock chaperone recruitment, and ensuing engagement of the ubiquitin–proteasome system, providing unprecedented insights into the spatiotemporal response to thermal damage relevant for degenerative diseases, with broad applicability in biomedicine. Using this versatile method, we discover that HSP70 chaperone and its interactors are recruited to sites of thermally damaged proteins within seconds, and we report here mechanistically important determinants of such HSP70 recruitment. Finally, we demonstrate a so-far unsuspected involvement of p97(VCP) translocase in the processing of heat-damaged proteins. Overall, we report an approach to inflict targeted thermal protein damage and its application to elucidate cellular stress-response pathways that are emerging as promising therapeutic targets.


P. Makvandi, Z. Baghbantaraghdari, W. Zhou, Y. Zhang, R. Manchanda, T. Agarwal, A. Wu, T. K. Maiti, R. S. Varma and B. R. Smith, "Gum polysaccharide/nanometal hybrid biocomposites in cancer diagnosis and therapy," BIOTECHNOLOGY ADVANCES, vol. 48, art. no. 107711, 2021.
DOI: 10.1016/j.biotechadv.2021.107711, IF = 14.227

Abstract: Biopolymers are of prime importance among which gum polysaccharides hold an eminent standing owing to their high availability and non-toxic nature. Gum biopolymers offer a greener alternative to synthetic polymers and toxic chemicals in the synthesis of metal nanostructures. Metal nanostructures accessible via eco-friendly means endow astounding characteristics to gum-based biocomposites in the field of diagnosis and therapy towards cancer diseases. In this review, assorted approaches for the assembly of nanomaterials mediated by gum biopolymers are presented and their utility in cancer diagnosis and therapy, e.g., bioimaging, radiotherapy, and phototherapy, are deliberated to provide a groundwork for future stimulative research.


M. Telychko, G. Li, P. Mutombo, D. Soler-Polo, X. Peng, J. Su, S. Song, M. J. Koh, M. Edmonds, P. Jelínek, J. Wu and J. Lu, "Ultrahigh-yield on-surface synthesis and assembly of circumcoronene into a chiral electronic Kagome-honeycomb lattice," SCIENCE ADVANCES, vol. 7, iss. 3, pp. eabf0269, 2021.
DOI: 10.1126/sciadv.abf0269, IF = 14.136

Abstract: On-surface synthesis has revealed remarkable potential in the fabrication of atomically precise nanographenes. However, surface-assisted synthesis often involves multiple-step cascade reactions with competing pathways, leading to a limited yield of target nanographene products. Here, we devise a strategy for the ultrahigh-yield synthesis of circumcoronene molecules on Cu(111) via surface-assisted intramolecular dehydrogenation of the rationally designed precursor, followed by methyl radical-radical coupling and aromatization. An elegant electrostatic interaction between circumcoronenes and metallic surface drives their self-organization into an extended superlattice, as revealed by bond-resolved scanning probe microscopy measurements. Density functional theory and tight-binding calculations reveal that unique hexagonal zigzag topology of circumcoronenes, along with their periodic electrostatic landscape, confines two-dimensional electron gas in Cu(111) into a chiral electronic Kagome-honeycomb lattice with two emergent electronic flat bands. Our findings open up a new route for the high-yield fabrication of elusive nanographenes with zigzag topologies and their superlattices with possible nontrivial electronic properties.


E. N. Zare, X. Zheng, P. Makvandi, H. Gheybi, R. Sartorius, C. K. Y. Yiu, M. Adeli, A. Wu, A. Zarrabi, R. S. Varma and F. R. Tay, "Nonspherical Metal‐Based Nanoarchitectures: Synthesis and Impact of Size, Shape, and Composition on Their Biological Activity," SMALL, vol. 17, iss. 17, pp. 2007073, 2021.
DOI: 10.1002/smll.202007073, IF = 13.281

Abstract: In this study a mesoporous silica nanoparticle (MSNP) based platform is developed for high-dose loading of a range of activated platinum (Pt) chemo agents that can be attached to the porous interior through the use of electrostatic and coordination chemistry under weak-basic pH conditions. In addition to the design feature for improving drug delivery, the MSNP can also be encapsulated in a coated lipid bilayer (silicasome), to improve the colloidal stability after intravenous (IV) injection. Improved pharmacokinetics and intratumor delivery of encapsulated activated oxaliplatin (1,2-diamminocyclohexane platinum(II) (DACHPt)) over free drug in an orthotopic Kras-derived pancreatic cancer (PDAC) model is demonstrated. Not only does IV injection of the DACHPt silicasome provide more efficacious cytotoxic tumor cell killing, but can also demonstrate that chemotherapy-induced cell death is accompanied by the features of immunogenic cell death (ICD) as well as a dramatic reduction in bone marrow toxicity. The added ICD features are reflected by calreticulin and high-mobility group box 1 expression, along with increased CD8+/FoxP3+ T-cell ratios and evidence of perforin and granzyme B release at the tumor site. Subsequent performance of a survival experiment, demonstrates that the DACHPt silicasome generates a significant improvement in survival outcome, which can be extended by delayed administration of the anti-PD-1 antibody.


R. G. Kadam, T. Zhang, D. Zaoralová, M. Medveď, A. Bakandritsos, O. Tomanec, M. Petr, J. Zhu Chen, J. T. Miller, M. Otyepka, R. Zbořil, T. Asefa and M. B. Gawande, "Single Co‐Atoms as Electrocatalysts for Efficient Hydrazine Oxidation Reaction," SMALL, vol. 17, iss. 16, pp. 2006477.
DOI: 10.1002/smll.202006477, IF = 13.281

Abstract: Single‐atom catalysts (SACs) have aroused great attention due to their high atom efficiency and unprecedented catalytic properties. A remaining challenge is to anchor the single atoms individually on support materials via strong interactions. Herein, single atom Co sites have been developed on functionalized graphene by taking advantage of the strong interaction between Co2+ ions and the nitrile group of cyanographene. The potential of the material, which is named G(CN)Co, as a SAC is demonstrated using the electrocatalytic hydrazine oxidation reaction (HzOR). The material exhibits excellent catalytic activity for HzOR, driving the reaction with low overpotential and high current density while remaining stable during long reaction times. Thus, this material can be a promising alternative to conventional noble metal‐based catalysts that are currently widely used in HzOR‐based fuel cells. Density functional theory calculations of the reaction mechanism over the material reveal that the Co(II) sites on G(CN)Co can efficiently interact with hydrazine molecules and promote the NH bond‐dissociation steps involved in the HzOR.


B. Singh, V. Sharma, R. P. Gaikwad, P. Fornasiero, R. Zbořil and M. B. Gawande, "Single‐Atom Catalysts: A Sustainable Pathway for the Advanced Catalytic Applications," SMALL, vol. 17, iss. 16, pp. 2006473, 2021.
DOI: 10.1002/smll.202006473, IF = 13.281

Abstract: A heterogeneous catalyst is a backbone of modern sustainable green industries; and understanding the relationship between its structure and properties is the key for its advancement. Recently, many upscaling synthesis strategies for the development of a variety of respectable control atomically precise heterogeneous catalysts are reported and explored for various important applications in catalysis for energy and environmental remediation. Precise atomic‐scale control of catalysts has allowed to significantly increase activity, selectivity, and in some cases stability. This approach has proved to be relevant in various energy and environmental related technologies such as fuel cell, chemical reactors for organic synthesis, and environmental remediation. Therefore, this review aims to critically analyze the recent progress on single‐atom catalysts (SACs) application in oxygen reduction reaction, oxygen evolution reaction, hydrogen evolution reaction, and chemical and/or electrochemical organic transformations. Finally, opportunities that may open up in the future are summarized, along with suggesting new applications for possible exploitation of SACs.


P. Sharma, S. Kumar, O. Tomanec, M. Petr, J. Zhu Chen, J. T. Miller, R. S. Varma, M. B. Gawande and R. Zbořil, "Carbon Nitride‐Based Ruthenium Single Atom Photocatalyst for CO2Reduction to Methanol," SMALL, vol. 17, iss. 16, pp. 2006478, 2021.
DOI: 10.1002/smll.202006478, IF = 13.281

Abstract: With increasing concerns for global warming, the solar‐driven photocatalytic reduction of CO2 into chemical fuels like methanol is a propitious route to enrich energy supplies, with concomitant reduction of the abundant CO2 stockpiles. Herein, a novel single atom‐confinement and a strategy are reported toward single ruthenium atoms dispersion over porous carbon nitride surface. Ruthenium single atom character is well confirmed by EXAFS absorption spectrometric analysis unveiling the cationic coordination environment for the single‐atomic‐site ruthenium center, that is formed by Ru‐N/C intercalation in the first coordination shell, attaining synergism in N–Ru–N connection and interfacial carrier transfer. From time resolved fluorescence decay spectra, the average carrier lifetime of the RuSA–mC3N4 system is found to be higher compared to m‐C3N4; the fact uncovering the crucial role of single Ru atoms in promoting photocatalytic reaction system. A high yield of methanol (1500 µmol g‐1 cat. after 6 h of the reaction) using water as an electron donor and the reusability of the developed catalyst without any significant change in the efficiency represent the superior aspects for its potential application in real industrial technologies.


V. Dileepkumar, C. Pratapkumar, R. Viswanatha, B. M. Basavaraja, R. R. Maphanga, M. Chennabasappa, N. Srinivasa, S. Ashoka, Z. Chen, S. Rtimi, K. Jayaramulu, R. S. Varma, G. Szekely and M. Sridhar Santosh, "Nanostructured NaFeS2 as a cost-effective and robust electrocatalyst for hydrogen and oxygen evolution with reduced overpotentials," CHEMICAL ENGINEERING JOURNAL, vol. 426, pp. 131315, 2021.
DOI: 10.1016/j.cej.2021.131315, IF = 13.273

Abstract: One of the biggest challenges currently in the field of energy generation and conservation is to develop a stable, scalable and cost-effective electrocatalyst with reduced overpotentials for both hydrogen evolution reaction (HER) and oxygen evolution reaction (OER). This unprecedented effort presents a robust, non-costly ternary alkali metal-based chalcogenide (NaFeS2) as an effective and highly active electrocatalyst prepared by the hydrothermal method. The monocrystalline nature of the NaFeS2 nanostructures was shown using SAED patterns. The differences in the atomic radii of Na and Fe favors the formation of Fe-S bonds largely contributing to the enhanced electrocatalytic activity of NaFeS2. Further, a decrease in the kinetic energy of the catalytic reaction increases the electrocatalytic property of NaFeS2. We also highlighted the contribution of the high surface area, the Fermi level and the d-orbitals of Fe in enhancing the OER. NaFeS2/NF shows a current density of 200 mA cm−2 with a small potential of 1.60 V and an overpotential of 370 mV indicating that the material possesses a remarkable electrocatalytic activity outperforming other electrocatalysts in the category. Further, by displaying a potential of −220 mV, NaFeS2/NF attained a current density of −100 mA cm−2, demonstrating a significantly improved HER performance of the electrocatalyst. Also, at a potential of −220 mV, the material exhibited a high stability at a continuous electrolysis of about 30 h. The density functional theory (DFT) calculations indicated that out of the possible adsorption sites on the NaFeS2 surface, only (0 1 0) and (1 0 0) exhibit catalytically preferential adsorption energy (EH) values, which are eventually responsible for the superior electrocatalytic activity. Finally, both the experimental studies and the DFT calculations complement each other and present NaFeS2 as a potentially promising bifunctional electrocatalyst for water splitting applications, which can be scaled-up and deployed for large-scale hydrogen productions.


E. Wierzbicka, M. Altomare, M. Wu, N. Liu, T. Yokosawa, D. Fehn, S. Qin, K. Meyer, T. Unruh, E. Spiecker, L. Palmisano, M. Bellardita, J. Will and P. Schmuki, "Reduced grey brookite for noble metal free photocatalytic H2 evolution," JOURNAL OF MATERIALS CHEMISTRY A, vol. 9, iss. 2, pp. 1168-1179, 2021.
DOI: 10.1039/d0ta09066b, IF = 12.732

Abstract: Herein we introduce for the first time a reduced “grey” brookite TiO2 photocatalyst, produced by thermal hydrogenation of brookite nanoparticles, that shows a remarkable noble metal free photocatalytic H2 evolution. Its activity is substantially higher than that of other TiO2 polymorphs, i.e. anatase or rutile, comparably sized and activated by hydrogenation under optimized conditions. Along with brookite powders, an oriented brookite single crystal was investigated as a defined surface to confirm the effects of the hydrogenation treatment. By a combination of electron paramagnetic resonance (EPR), electron and X-ray characterization techniques applied to the powders and single crystal, we find that hydrogenation forms in brookite a defective crystalline surface layer rich in Ti3+ states. Amorphization effects, i.e. forming the so called “amorphous shell” as reported in previous work for black anatase TiO2, were not detected. Overall, we provide experimental evidence that hydrogenation forms in brookite a surface strained zone with point defects that are mediators for electron transfer to H2O, leading to a significantly enhanced noble metal free photocatalytic H2 evolution in comparison to anatase.


S. Rej, M. Bisetto, A. Naldoni and P. Fornasiero, "Well-defined Cu2O photocatalysts for solar fuels and chemicals," JOURNAL OF MATERIALS CHEMISTRY A, vol. 9, iss. 10, pp. 5915-5951, 2021.
DOI: 10.1039/d0ta10181h, IF = 12.732

Abstract: The shape-controlled synthesis of cuprous oxide (Cu2O) photocatalysts with both low or high index crystal planes has received increasing attention due to their unique facet-dependent properties. Since they are cheap and earth abundant, these well-defined Cu2O nanostructures are extensively used for different photocatalytic reactions, also because of their strong visible light absorption capability. However, further development will still be needed to enhance the efficiency and photostability of Cu2O to expand its industrial application. We start this review by summarizing the synthetic advancement in the facet engineering of Cu2O and other associated hybrid Cu2O-based heterostructures with a special emphasis put on their growth mechanism. We then discuss different facet-dependent properties, which are relevant to photocatalysis. In the subsequent section, we present a critical discussion on the photocatalytic performance of faceted Cu2O nanostructures during organic synthesis, hydrogen production, and carbon dioxide photoreduction. The relation between photocatalytic efficiency and product selectivity with exposed crystal facets or with different compositions of hybrid nanostructures is also discussed. Finally, important strategies are proposed to overcome the photostability issue, while outlining the course of future development to further boost the technological readiness of well-defined Cu2O-based photocatalysts.


J. Su, W. Fan, P. Mutombo, X. Peng, S. Song, M. Ondráček, P. Golub, J. Brabec, L. Veis, M. Telychko, P. Jelínek, J. Wu and J. Lu, "On-Surface Synthesis and Characterization of [7]Triangulene Quantum Ring," NANO LETTERS, vol. 21, iss. 1, pp. 861-867, 2021.
DOI: 10.1021/acs.nanolett.0c04627, IF = 11.189

Abstract: The ability to engineer geometrically well-defined antidots in large triangulene homologues allows for creating an entire family of triangulene quantum rings (TQRs) with tunable high-spin ground state, crucial for next-generation molecular spintronic devices. Herein, we report the synthesis of an open-shell [7]triangulene quantum ring ([7]TQR) molecule on Au(111) through the surface-assisted cyclodehydrogenation of a rationally designed kekulene derivative. Bond-resolved scanning tunneling microscopy (BR-STM) unambiguously imaged the molecular backbone of a single [7]TQR with a triangular zigzag edge topology, which can be viewed as [7]triangulene decorated with a coronene-like antidot in the center. Additionally, dI/dV mapping reveals that both inner and outer zigzag edges contribute to the edge-localized and spin-polarized electronic states of [7]TQR. Both experimental results and spin-polarized density functional theory calculations indicate that [7]TQR retains its open-shell septuple ground state (S = 3) on Au(111). This work demonstrates a new route for the design of high-spin graphene quantum rings for future quantum devices.


T. T. Salunkhe, R. S. Varma, A. N. Kadam, S. Lee, Y. Lee, J. Hur and I. T. Kim, "Scraps to superior anodes for Li-ion batteries: Sustainable and scalable upgrading of waste rust," JOURNAL OF HAZARDOUS MATERIALS, vol. 410, art.no. 124571, 2021.
DOI: 10.1016/j.jhazmat.2020.124571, IF = 10.588

Abstract: The abundant iron rust of no value generated from industrial scraps presents environmental problem and burden. Chemical etching and related methods deployed to convert rust into α-Fe2O3 nanoparticles, however, have serious shortcomings namely higher chemical consumption and generation of secondary pollution. In an unprecedented illustration, herein the intercalation of ammonium bicarbonate (ABC) as a gaseous bubble template into bulky iron rust is described; formation of ammonium iron carbonate hydroxide hydrate and the reduction of particle size using a simple ball milling method followed by calcination is accomplished. The salient features of ABC, optimization of ratios (rust: ABC), and the ideal calcination temperature were optimized for attaining desirable properties of meso-α-Fe2O3 NPs. The electrode obtained at 500 °C delivered a superior reversible capacity of 1,055 mAh g−1 at 1 A g−1 over 100 cycles, which is comparable to the best performance reported for meso-α-Fe2O3 NPs. The superior electrochemical performance is ascribed to the porous nature of meso-α-Fe2O3 NPs maximizing the surface area, ensuring good charge transfer kinetics and enhanced pseudocapacitive contribution. Thus, we believe that the high-energy ball milling (HEBM) process represents a novel route for the scalable recycling of iron rust scraps for promoting the sustainable production of lithium-ion batteries.


M. Brumovský, J. Oborná, P. Lacina, M. Hegedüs, O. Sracek, J. Kolařík, M. Petr, J. Kašlík, T. Hofmann and J. Filip, "Sulfidated nano-scale zerovalent iron is able to effectively reduce in situ hexavalent chromium in a contaminated aquifer," JOURNAL OF HAZARDOUS MATERIALS, vol. 405, pp. 124665, 2021.
DOI: 10.1016/j.jhazmat.2020.124665, IF = 10.588

Abstract: In a number of laboratory studies, sulfidated nanoscale zero-valent iron (S-nZVI) particles showed increased reactivity, reducing capacity, and electron selectivity for Cr(VI) removal from contaminated waters. In our study, core-shell S-nZVI particles were successfully injected into an aquifer contaminated with Cr(VI) at a former chrome plating facility. S-nZVI migrated towards monitoring wells, resulting in a rapid decrease in Cr(VI) and Crtot concentrations and a long-term decrease in groundwater redox potential observed even 35 m downstream the nearest injection well. Characterization of materials recovered from the injection and monitoring wells confirmed the presence of nZVI particles, together with iron corrosion products. Chromium was identified on the surface of the recovered iron particles as Cr(III), and its occurrence was linked to the formation of insoluble chromium-iron (oxyhydr)oxides such as CrxFe(1−x)(OH)3(s). Injected S-nZVI particles formed aggregates, which were slowly transformed into iron (oxyhydr)oxides and carbonate green rust. Elevated contents of Fe0 were detected even several months after injection, indicating good S-nZVI longevity. The sulfide shell was gradually disintegrated and/or dissolved. Geochemical modelling confirmed the overall stability of the resulting Cr(III) phase at field conditions. This study demonstrates the applicability of S-nZVI for the remediation of a Cr(VI)-contaminated aquifer.


G. Asimakopoulos, M. Baikousi, C. Salmas, A. B. Bourlinos, R. Zboril and M. A. Karakassides, "Advanced Cr(VI) sorption properties of activated carbon produced via pyrolysis of the “Posidonia oceanica” seagrass," JOURNAL OF HAZARDOUS MATERIALS, vol. 405, pp. 124274, 2021.
DOI: 10.1016/j.jhazmat.2020.124274, IF = 10.588

Abstract: This research deals with the removal of Cr(VI), one of the most toxic heavy metal in biological systems, from wastewater by using activated carbon produced via pyrolysis and chemical activation of “Posidonia oceanica”. That is the most important and well-studied seagrass species of the Mediterranean Sea. The as produced activated carbon exhibited high specific surface area up to 1563 m2/g and a cumulative pore volume of 0.74 cm3/g, allocated to 74% micro-pores and 26% to meso-macro- pores. The adsorption capacity of Cr(VI) into Posidonia oceanica activated carbon was studied via batch experiments considering the contact time, the initial concentration and the pH parameters. The results were interpreted using four different adsorption kinetic models. The activated carbon material seems to exhibit excellent sorption properties with rapid removal capability for Cr(VI). The estimated maximum uptake capacity at equilibrium stage was ~120 mg/g. Also, the initial adsorption rate ri was dependent on the initial Cr(VI) concentration in aqueous solution and it was from 77 mg/(g*h) to 264 mg/(g*h). The best fitted kinetic model seems to be the Diffusion-Chemisorption model with the rate constant KDC of the Cr(VI) ions transfer from liquid to solid particles extend from 52 to 78 mg/(g*h0.5).


M. Tavakolizadeh, A. Pourjavadi, M. Ansari, H. Tebyanian, S. J. Seyyed Tabaei, M. Atarod, N. Rabiee, M. Bagherzadeh and R. S. Varma, "An environmentally friendly wound dressing based on a self-healing, extensible and compressible antibacterial hydrogel," GREEN CHEMISTRY, vol. 23, iss. 3, pp. 1312-1329, 2021.
DOI: 10.1039/d0gc02719g, IF = 10.182

Abstract: The design of wound dressing hydrogels is of utmost importance in healthcare with desired remedial effects, self-healing ability, cell affinity, and appropriate mechanical properties, particularly for healing skin wounds; excellent wound tissue adhesiveness is imperative. Here, an ultra-tough and self-healable double-network (DN) hydrogel is designed based on salep/poly(vinyl alcohol) that is endowed with superior tissue adhesiveness and cell affinity as demonstrated for critical and burn wound healing in rats. The self-healing capability of the hydrogel is attained via hydrogen bonds and Schiff-base cross-linking between oxidized salep (OSa) and ethylene diamine-modified salep (SaHEA) chains (OSEA network). The interaction of hydroxyl groups of the poly(vinyl alcohol) (PVA) network effectively facilitates to create a stable mechanical structure and endow self-healing ability. The ensuing novel hydrogel is endowed with excellent self-healing ability, high mechanical strength (Young's modulus of up to 14 kPa; high fracture energy of up to 90 kJ m−3; compressive stress of 400 kPa), good tissue adhesiveness (up to 48 N m−1 adhesive strength), and superior therapeutic properties (cell viability of A375 cells >80%; remarkable healing of >60% in 14 and >98% in 21 days). The macroscopic evaluation revealed healing >80% in 14 days and 100% in 21 days that is achieved by combining both networks in a single system along with Arnebia extract and Ag nanoparticles (Ag NPs) in green media. In vitro and in vivo tests affirmed that the PVA/OSEA DN hydrogel could be an excellent candidate for skin tissue regeneration in medical applications.


S. K. Verma, P. K. Panda, P. Kumari, P. Patel, A. Arunima, E. Jha, S. Husain, R. Prakash, R. Hergenröder, Y. K. Mishra, R. Ahuja, R. S. Varma and M. Suar, "Determining factors for the nano-biocompatibility of cobalt oxide nanoparticles: proximal discrepancy in intrinsic atomic interactions at differential vicinage," GREEN CHEMISTRY, vol. 23, iss. 9, pp. 3439-3458, 2021.
DOI: 10.1039/d1gc00571e, IF = 10.182

Abstract: The abounding use of cobalt oxide nanoparticles (Co3O4) requires a detailed understanding of their environmental and biomedical nanotoxicity and an eminent solution to the associated hazards; molecular and atomic aspects of the subject are poorly understood. This study reconnoiters the in vitro and in vivo nanotoxicity of Co3O4 nanoparticles using human colon cell lines and the embryonic zebrafish model. The synthesis of Co3O4 nanoparticles (G-CoONP) is delineated via the deployment of a medicinal herb, Calotropis gigantea, as an alternative greener solution; stable G-CoONP with a size of 41 ± 15 nm are attainable. Gas chromatography-mass spectroscopy (GCMS) analysis revealed the role of floral extract biomolecules in G-CoO NP synthesis. The in vitro and in vivo effects are accompanied by dose-dependent exposure at the molecular level by eliciting Sod1 and P53 genes up to 8.2 and 5.2 fold leading to a significant change in the reactive oxygen species and apoptosis level. It unraveled the toxicity of the cobalt oxide NP as increased apoptosis elicited by higher oxidative stress due to the accumulation and internalization of nanoparticles in cells and embryos. Green synthesized G-CoONP exhibited higher biocompatibility than commercial C-CoONP with reduced apoptosis and ROS in both human colon cell lines and zebrafish embryos. In silico analysis portrayed the intrinsic atomic interaction of Co3O4 NP with cysteine, arginine, and histidine of oxidative stress (SOD1/sod1) and apoptosis (TP53/tp53) proteins leading to dysregulation of their structural and functional integrity in human and zebrafish, respectively. A proximal discrepancy in intrinsic atomic interaction due to the H-bonding and hydrophobic interaction at the differential in vitro and in vivo vicinage served as a key determinant factor for the cellular biocompatibility of Co3O4 nanoparticles.


M. Langer, M. Paloncýová, M. Medveď, M. Pykal, D. Nachtigallová, B. Shi, A. J. Aquino, H. Lischka and M. Otyepka, "Progress and challenges in understanding of photoluminescence properties of carbon dots based on theoretical computations," APPLIED MATERIALS TODAY, vol. 22, pp. 100924, 2021.
DOI: 10.1016/j.apmt.2020.100924, IF = 10.041

Abstract: Carbon dots (CDs), including graphene quantum dots, carbon nanodots, carbon quantum dots, and carbonized polymer dots, belong to extensively studied nanomaterials with a very broad application potential resulting from their bright photoluminescence (PL), high (photo)stability, low toxicity and great biocompatibility. However, the design of CDs with tailored properties is still hampered by a fairly limited understanding of the CD PL, which stems from their rather complex structure and variability of the PL centers. Theoretical calculations provide valuable insights into the nature of the excited states and the source of PL. In this review, we focus on state-of-the-art theoretical methods for the description of absorption and PL of CDs and their limitations, along with providing an overview of theoretical studies addressing structural models and the electronic structure of various types of CDs in the context of their overall optical properties. Besides the assessment of the current state of knowledge, we also highlight the opportunity for further advancements in the field.


M. Medveď, M. W. H. Hoorens, M. Di Donato, A. D. Laurent, J. Fan, M. Taddei, M. Hilbers, B. L. Feringa, W. J. Buma and W. Szymanski, "Tailoring the optical and dynamic properties of iminothioindoxyl photoswitches through acidochromism," CHEMICAL SCIENCE, vol. 12, iss. 12, pp. 4588-4598, 2021.
DOI: 10.1039/d0sc07000a, IF = 9.825

Abstract: Multi-responsive functional molecules are key for obtaining user-defined control of the properties and functions of chemical and biological systems. In this respect, pH-responsive photochromes, whose switching can be directed with light and acid–base equilibria, have emerged as highly attractive molecular units. The challenge in their design comes from the need to accommodate application-defined boundary conditions for both light- and protonation-responsivity. Here we combine time-resolved spectroscopic studies, on time scales ranging from femtoseconds to seconds, with density functional theory (DFT) calculations to elucidate and apply the acidochromism of a recently designed iminothioindoxyl (ITI) photoswitch. We show that protonation of the thermally stable Z isomer leads to a strong batochromically-shifted absorption band, allowing for fast isomerization to the metastable E isomer with light in the 500–600 nm region. Theoretical studies of the reaction mechanism reveal the crucial role of the acid–base equilibrium which controls the populations of the protonated and neutral forms of the E isomer. Since the former is thermally stable, while the latter re-isomerizes on a millisecond time scale, we are able to modulate the half-life of ITIs over three orders of magnitude by shifting this equilibrium. Finally, stable bidirectional switching of protonated ITI with green and red light is demonstrated with a half-life in the range of tens of seconds. Altogether, we designed a new type of multi-responsive molecular switch in which protonation red-shifts the activation wavelength by over 100 nm and enables efficient tuning of the half-life in the millisecond–second range.


D. Rotrekl, P. Šalamúnová, L. Paráková, O. Baďo, I. Saloň, F. Štěpánek, J. Hanuš and J. Hošek, "Composites of yeast glucan particles and curcumin lead to improvement of dextran sulfate sodium-induced acute bowel inflammation in rats," CARBOHYDRATE POLYMERS, vol. 252, iss. , pp. 117142, 2021.
DOI: 10.1016/j.carbpol.2020.117142, IF = 9.381

Abstract: The goal of this work was to assess the usability of yeast glucan particles (GPs) as carriers for curcumin and determine the beneficial effect of a pharmacological composite of curcumin in GPs on dextran sulfate sodium induced colitis in rats. The assessment of the anti-inflammatory effect of particular substances was evaluated on the basis of the calculated disease activity index and by assessment of cytokines and enzymes from the gut tissue – tumor necrosis factor α (TNF-α), transforming growth factor β1, interleukin (IL)-1β, IL-6, IL-10, IL-17, catalase, superoxide dismutase 2, myeloperoxidase (MPO), and matrix metalloproteinase 9. Composites of GPs with incorporated curcumin showed promising results with the capability to lower symptoms of colitis and significantly decrease the production of pro-inflammatory cytokines TNF-α, IL-1β, IL-6, and the activity of MPO, as well. The anti-inflammatory effect of the composites was greater than those of pure GPs or curcumin.


F. Moradnia, S. Taghavi Fardood, A. Ramazani, B. Min, S. W. Joo and R. S. Varma, "Magnetic Mg0.5Zn0.5FeMnO4 nanoparticles: Green sol-gel synthesis, characterization, and photocatalytic applications," JOURNAL OF CLEANER PRODUCTION, vol. 288, art. no. 125632, 2021.
DOI: 10.1016/j.jclepro.2020.125632, IF = 9.297

Abstract: Water pollution is one of the main global concerns affecting humans and numerous people die annually because of the diseases inflicted by contaminated water. Due to the toxicity and carcinogenic potential of the dyes in effluent, it is necessary to attain an efficient method for wastewater treatment using the highly active and reusable photocatalyst. This study presents a promising green approach for the preparation of heterogeneous catalytic nanoparticles by investigating the synergistic effect of metal ions in spinel structure to enhance their photocatalytic activity. Herein, Mg0.5Zn0.5FeMnO4 magnetic nanoparticles (MNPs) were prepared by a green sol-gel process and thoroughly characterized by X-ray Photoelectron Spectroscopy (XPS), powder X-ray diffraction (XRD), Electrochemical Impedance Spectroscopy (EIS), field emission scanning electron microscopy (FESEM), energy dispersive X-ray analysis (EDX), transmission electron microscope (TEM), Brunauer Emmett Teller (BET), Fourier transform infrared spectroscopy (FT-IR), high-solution transmission electron microscopy (HRTEM) images and selected area electron diffraction (SAED), Differential reflectance spectroscopy (DRS), vibrating sample magnetometer (VSM), and elemental mapping. XRD pattern confirmed the spinel structure of Mg0.5Zn0.5FeMnO4 MNPs which displayed good photocatalytic performance for the decolorization of Reactive Blue 21 (RB21) dye under ambient conditions and at natural pH (pH = 6) wherein 96% of dye was degraded in 30 min and total organic carbon removal followed in 30, 60, and 120 min. Mechanistic aspects of the photodegradation were ascertained in presence of scavenger agents and the degradation products were studied by Gas chromatography–mass spectrometry (GC-MS) with identification of smaller ensuing fragmented molecules. Magnetic nanoparticles could be recycled by applying an external magnet, and their efficiency was maintained intact even after five cycles while retaining their structural integrity as attested by XRD, and FESEM analysis after reuse.


A. Kolokithas-Ntoukas, A. Bakandritsos, J. Belza, P. Kesa, V. Herynek, J. Pankrac, A. Angelopoulou, O. Malina, K. Avgoustakis, V. Georgakilas, K. Polakova and R. Zboril, "Condensed Clustered Iron Oxides for Ultrahigh Photothermal Conversion and In Vivo Multimodal Imaging," ACS APPLIED MATERIALS & INTERFACES, vol. 13, iss. 25, pp. 29247-29256, 2021.
DOI: 10.1021/acsami.1c00908, IF = 9.229

Abstract: Magnetic iron oxide nanocrystals (MIONs) are established as potent theranostic nanoplatforms due to their biocompatibility and the multifunctionality of their spin-active atomic framework. Recent insights have also unveiled their attractive near-infrared photothermal properties, which are, however, limited by their low near-infrared absorbance, resulting in noncompetitive photothermal conversion efficiencies (PCEs). Herein, we report on the dramatically improved photothermal conversion of condensed clustered MIONs, reaching an ultrahigh PCE of 71% at 808 nm, surpassing the so-far MION-based photothermal agents and even benchmark near-infrared photothermal nanomaterials. Moreover, their surface passivation is achieved through a simple self-assembly process, securing high colloidal stability and structural integrity in complex biological media. The bifunctional polymeric canopy simultaneously provided binding sites for anchoring additional cargo, such as a strong near-infrared-absorbing and fluorescent dye, enabling in vivo optical and photoacoustic imaging in deep tissues, while the iron oxide core ensures detection by magnetic resonance imaging. In vitro studies also highlighted a synergy-amplified photothermal effect that significantly reduces the viability of A549 cancer cells upon 808 nm laser irradiation. Integration of such—previously elusive—photophysical properties with simple and cost-effective nanoengineering through self-assembly represents a significant step toward sophisticated nanotheranostics, with great potential in the field of nanomedicine.


I. Safarik, J. Prochazkova, M. A. Schroer, V. M. Garamus, P. Kopcansky, M. Timko, M. Rajnak, M. Karpets, O. I. Ivankov, M. V. Avdeev, V. I. Petrenko, L. Bulavin and K. Pospiskova, "Cotton Textile/Iron Oxide Nanozyme Composites with Peroxidase-like Activity: Preparation, Characterization, and Application," ACS APPLIED MATERIALS & INTERFACES, vol. 13, iss. 20, pp. 23627-23637, 2021.
DOI: 10.1021/acsami.1c02154, IF = 9.229

Abstract: At present, both native and immobilized nanoparticles are of great importance in many areas of science and technology. In this paper, we have studied magnetic iron oxide nanoparticles and their aggregates bound on woven cotton textiles employing two simple modification procedures. One modification was based on the treatment of textiles with perchloric-acid-stabilized magnetic fluid diluted with methanol followed by drying. The second procedure was based on the microwave-assisted conversion of ferrous sulfate at high pH followed by drying. The structure and functional properties of these modified textiles were analyzed in detail. Scanning electron microscopy of native and modified textiles clearly showed the presence of iron oxide nanoparticles on the surface of the modified cotton fibers. All of the modified textile materials exhibited light to dark brown color depending on the amount of the bound iron oxide particles. Magnetic measurements showed that the saturation magnetization values reflect the amount of magnetic nanoparticles present in the modified textiles. Small-angle X-ray and neutron scattering measurements were conducted for the detailed structural characterization at the nanoscale of both the native and magnetically modified textiles, and different structural organization of nanoparticles in the two kinds of textile samples were concluded. The textile-bound iron oxide particles exhibited peroxidase-like activity when the N,N-diethyl-p-phenylenediamine sulfate salt was used as a substrate; this nanozyme activity enabled rapid decolorization of crystal violet in the presence of hydrogen peroxide. The deposition of a sufficient amount of iron oxide particles on textiles enabled their simple magnetic separation from large volumes of solutions; if necessary, the magnetic response of the modified textiles can be simply increased by incorporation of a piece of magnetic iron wire. The simplicity of the immobilized nanozyme preparation and the low cost of all the precursors enable its widespread application, such as decolorization and degradation of selected organic dyes and other important pollutants. Other types of textile-bound nanozymes can be prepared and used as low-cost catalysts for a variety of applications.


R. Yalavarthi, R. Zbořil, P. Schmuki, A. Naldoni and Š. Kment, "Elucidating the role of surface states of BiVO4 with Mo doping and a CoOOH co-catalyst for photoelectrochemical water splitting," JOURNAL OF POWER SOURCES, vol. 483, pp. 229080, 2020.
DOI: 10.1016/j.jpowsour.2020.229080, IF = 9.127

Abstract: Bismuth vanadate (BiVO4) is a promising material for photoelectrochemical (PEC) water splitting, however, its PEC performance is limited by the high surface and bulk charge recombination rates. Here we present a comprehensive study to elucidate a recombination phenomenon of BiVO4 that arises with Mo doping. The Mo doping produces multiple effects including the formation of MoOx (reduced form of Mo6+) species and oxygen vacancies (VOs) on the surface of the BiVO4 that work in tandem with V4+ species (and MoOx) acting as surface-active intermediates (i-SS) providing improved hole transfer to the electrolyte. In contrast, in the absence of V4+ species, the VOs can act as recombination centers (r-SS). Further, CoOOH co-catalyst coating is used to minimize such recombination centers. Eventually, a photocurrent enhancement of ~37 times (1.1 mA/cm2 at 1.23 V vs. RHE) and a cathodic shift in onset potential of ~500 mV compared to that of pristine BiVO4 (0.03 mA/cm2 at 1.23 V vs. RHE) is obtained. We carried out in-depth PEC analysis using hole scavenger measurements, PEC impedance spectroscopy, and intensity-modulated photocurrent spectroscopy to elucidate the effect of the surface reduction process upon doping, the impact of Vos, MoOx species and CoOOH layer on the enhanced PEC performance.


E. C. Vermisoglou, P. Jakubec, A. Bakandritsos, V. Kupka, M. Pykal, V. Šedajová, J. Vlček, O. Tomanec, M. Scheibe, R. Zbořil, and M. Otyepka, "Graphene with Covalently Grafted Amino Acid as a Route Toward Eco-Friendly and Sustainable Supercapacitors," CHEMSUSCHEM, Article in press, 2021.
DOI: 10.1002/cssc.202101039, IF = 8.928

Abstract: Eco-friendly, electrochemically active electrode materials based on covalent graphene derivatives offer enormous potential for energy storage applications. However, covalent grafting of functional groups onto graphene’s surface is challenging due to its low reactivity. We employed fluorographene chemistry to graft an arginine moiety via its guanidine group homogeneously on both sides of graphene. By tuning the reaction conditions and adding a non-toxic, pore-forming agent, we achieved an optimum degree of functionalization and hierarchical porosity in the material. This tripled the specific surface area and yielded a high capacitance value of ~390 F/g at a current density of 0.25 A/g. The applicability of the electrode material was investigated under typical operating conditions by testing an assembled supercapacitor device for up to 30000 charging/discharging cycles, revealing capacitance retention of 82.3%. This work enables the preparation of graphene derivatives with covalently grafted amino acids for technologically important applications, such as supercapacitor-based energy storage.


R. Ahmad, G. V. Nutan, D. Singh, G. Gupta, U. Soni, S. Sapra and R. Srivastava, "Colloidal lead-free Cs2AgBiBr6 double perovskite nanocrystals: Synthesis, uniform thin-film fabrication, and application in solution-processed solar cells," NANO RESEARCH, vol. 14, iss. 4, pp. 1126-1134, 2021.
DOI: 10.1007/s12274-020-3161-6, IF = 8.897

Abstract: Recently developed lead-free double perovskite nanocrystals (NCs) have been proposed for the possible application in solution-processed optoelectronic devices. However, the optoelectronic applications of double perovskite NCs have been hampered due to the structural and chemical instability in the presence of polar molecules. Here, we report a facile strategy for the synthesis and purification of Cs2AgBiBr6 double perovskite NCs that remained stable even after washing with polar solvent. This is realized with our efficient colloidal route to synthesize Cs2AgBiBr6 NCs that involve stable and strongly coordinated precursor such as silver-trioctylphosphine complex together with bismuth neodecanoate, which leads to a significantly improved chemical and colloidal stability. Using layer-by-layer solid-state ligand exchange technique, a compact and crack-free thin film of Cs2AgBiBr6 NCs were fabricated. Finally, perovskite solar cells consisting of Cs2AgBiBr6 as an absorber layer were fabricated and tested.


G. Vilé, P. Sharma, M. Nachtegaal, F. Tollini, D. Moscatelli, A. Sroka-Bartnicka, O. Tomanec, M. Petr, J. Filip, I. S. Pieta, R. Zbořil and M. B. Gawande, "An Earth‐Abundant Ni‐Based Single‐Atom Catalyst for Selective Photodegradation of Pollutants," SOLAR RRL, vol. 5, iss. 7, 2021.
DOI: 10.1002/solr.202100176, IF = 8.582

Abstract: Highly efficient catalytic technologies are urgently needed to remove pharmaceutical pollutants from water. In this work, the preparation, characterization, and photocatalytic performance of an earth-abundant Ni-based heterogeneous catalyst featuring highly dispersed Ni species over nanosheets of carbon nitride are reported. The absence of any metallic nickel phase has been confirmed by spectrometric analyses, unveiling the NiN environment for the metal centers and attaining synergistic interfacial carrier transfer via N-Ni-N coordination. By combining advanced characterizations with kinetic investigations, it is demonstrated that these newly formed isolated single atoms of Ni act as a bridge, facilitating faster electron transfer, increasing the charge density on Ni, and reducing the photocarrier transfer barrier. Compared to literature precedents, this substantially enhances the degradation of gemfibrozil, a model pharmaceutical pollutant found in wastewater, reducing the formation of toxic benzenic byproducts during photooxidation. This effect, which is not observed over conventional nanoparticle-based materials, discriminates the role of single-atom and nanoparticle-based catalysis during degradation of pollutants. This work opens new avenues in designing selective and earth-abundant photocatalysts for advanced oxidation processes, showing the importance of atom coordination to control the surface and catalytic properties of single-atom materials.


M. Nikolaou, K. Avraam, A. Kolokithas-Ntoukas, A. Bakandritsos, F. Lizal, O. Misik, M. Maly, J. Jedelsky, I. Savva, F. Balanean and T. Krasia-Christoforou, "Superparamagnetic electrospun microrods for magnetically-guided pulmonary drug delivery with magnetic heating," MATERIALS SCIENCE AND ENGINEERING: C, vol. 126, art.no. 112117, 2021.
DOI: 10.1016/j.msec.2021.112117, IF = 7.328

Abstract: Controlled pulmonary drug delivery systems employing non-spherical particles as drug carriers attract considerable attention nowadays. Such anisotropic morphologies may travel deeper into the lung airways, thus enabling the efficient accumulation of therapeutic compounds at the point of interest and subsequently their sustained release. This study focuses on the fabrication of electrospun superparamagnetic polymer-based biodegradable microrods consisting of poly(l-lactide) (PLLA), polyethylene oxide (PEO) and oleic acid-coated magnetite nanoparticles (OA·Fe3O4). The production of magnetite-free (0% wt. OA·Fe3O4) and magnetite-loaded (50% and 70% wt. Fe3O4) microrods was realized upon subjecting the as-prepared electrospun fibers to UV irradiation, followed by sonication. Moreover, drug-loaded microrods were fabricated incorporating methyl 4-hydroxybenzoate (MHB) as a model pharmaceutical compound and the drug release profile from both, the drug-loaded membranes and the corresponding microrods was investigated in aqueous media. In addition, the magnetic properties of the produced materials were exploited for remote induction of hyperthermia under AC magnetic field, while the possibility to reduce transport losses and enhance the targeted delivery to lower airways by manipulation of the airborne microrods by DC magnetic field was also demonstrated.


A. Jastrzębska, B. Scheibe, A. Szuplewska, A. Rozmysłowska-Wojciechowska, M. Chudy, C. Aparicio, M. Scheibe, I. Janica, A. Ciesielski, M. Otyepka and M. Barsoum, "On the rapid in situ oxidation of two-dimensional V2CTz MXene in culture cell media and their cytotoxicity," MATERIALS SCIENCE AND ENGINEERING: C, vol. 119, pp. 111431, 2020.
DOI: 10.1016/j.msec.2020.111431, IF = 7.328

Abstract: The plethora of emerging two-dimensional (2D) materials exhibit wide potential application in novel technologies and advanced devices. However, their stability in environmental conditions could be an issue, affecting their application possibilities and posing health risks. Moreover, their decomposed leftovers can also induce a negative influence on human health. In particular, transition metal carbides commonly referred to as MXenes are susceptible to environmental oxidation being decomposed toward transition metal oxides and carbide-derived carbon. In this study we focused on the oxidation-state-related in vitro cytotoxicity of delaminated V2CTz onto immortalized keratinocytes (HaCaT) and malignant melanoma (A375) human cell lines. Due to the fact, that the V2CTx MXenes are least stable from all known obtained MXenes up to date, the vanadium ones were a practical choice to visualize the oxidation-cytotoxic correlation keeping the standards of 24–48 h of cell culturing. We found that the oxidation of V2CTz highly increases their cytotoxicity toward human cells, which is also time and dose dependent. The identified mode of action relates to the cell cycle as well as cellular membrane disintegration through direct physicochemical interactions.


D. Silvestri, S. Wacławek, B. Sobel, R. Torres–Mendieta, M. Pawlyta, V. V. Padil, J. Filip and M. Černík, "Modification of nZVI with a bio-conjugate containing amine and carbonyl functional groups for catalytic activation of persulfate," SEPARATION AND PURIFICATION TECHNOLOGY, vol. 257, pp. 117880, 2020.
DOI: 10.1016/j.seppur.2020.117880, IF = 7.312

Abstract: Although the catalytic activation of persulfate by iron is now common in environmental sciences, there are still several obstacles, including the non-selectiveness and high cost of the production of the iron catalyst. Therefore, it is essential to develop fast and easy methods for producing an iron catalyst that exhibits high surface area properties and rapid catalytic activation of persulfate. In the present work, a chitosan-poly(3–hydroxybutyrate) conjugate (CS-PHB) was used to improve the synthesis of nanoscale zero-valent iron (nZVI). CS-PHB possesses among others two functional groups (carbonyl and amine) that are desirable for catalytic applications, including heterogeneous persulfate activation. The produced CS-PHB-nZVI particles showed an extensive surface area (113 m2/g) and, at the same time, superior activity in heterogeneous catalysis, which was tested and compared with others persulfate activation methods (heat, Fe2+, commercial nZVI). The most suitable activation conditions for complete degradation of 0.15 mM of the model pollutant (methyl orange; MO) were determined (i.e., a pH of 7, persulfate and CS-PHB-nZVI concentrations of 2 mM and 50 mg/L, respectively). The role of temperature in MO oxidation was evaluated by the Arrhenius equation, and the results showed that the estimated activation energy (Ea) was 27.1 kJ/mol. The MO degradation may be attributed to the generation of SO4radical dot− in the system as a result of scavenging tests. A magnet can be used to easily separate the remaining catalyst. It is believed that due to it having several advantages over traditionally used nZVI, CS-PHB-nZVI may be successfully applied for catalytic remediation of contaminants that are reactive towards sulfate radicals.


J. Semerád, A. Ševců, N. H. Nguyen, P. Hrabák, R. Špánek, K. Bobčíková, K. Pospíšková, J. Filip, I. Medřík, J. Kašlík, I. Šafařík, A. Filipová, J. Nosek, M. Pivokonský and T. Cajthaml, "Discovering the potential of an nZVI-biochar composite as a material for the nanobioremediation of chlorinated solvents in groundwater: Degradation efficiency and effect on resident microorganisms," CHEMOSPHERE, vol. 281, art. no. 130915, 2021.
DOI: 10.1016/j.chemosphere.2021.130915, IF = 7.086

Abstract: Abiotic and biotic remediation of chlorinated ethenes (CEs) in groundwater from a real contaminated site was studied using biochar-based composites containing nanoscale zero-valent iron (nZVI/BC) and natural resident microbes/specific CE degraders supported by a whey addition. The material represented by the biochar matrix decorated by isolated iron nanoparticles or their aggregates, along with the added whey, was capable of a stepwise dechlorination of CEs. The tested materials (nZVI/BC and BC) were able to decrease the original TCE concentration by 99% in 30 days. Nevertheless, regarding the transformation products, it was clear that biotic as well as abiotic transformation mechanisms were involved in the transformation process when nonchlorinated volatiles (i.e., methane, ethane, ethene, and acetylene) were detected after the application of nZVI/BC and nZVI/BC with whey. The whey addition caused a massive increase in bacterial biomass in the groundwater samples (monitored by 16S rRNA sequencing and qPCR) that corresponded with the transformation of trichloro- and dichloro-CEs, and this process was accompanied by the formation of less chlorinated products. Moreover, the biostimulation step also eliminated the adverse effect caused by nZVI/BC (decrease in microbial biomass after nZVI/BC addition). The nZVI/BC material or its aging products, and probably together with vinyl chloride-respiring bacteria, were able to continue the further reductive dechlorination of dichlorinated CEs into nonhalogenated volatiles. Overall, the results of the present study demonstrate the potential, feasibility, and environmental safety of this nanobioremediation approach.


J. Y. Cheong, A. Venkateshaiah, T. G. Yun, S. Shin, M. Černík, V. V. Padil, I. Kim and R. S. Varma, "Transforming gum wastes into high tap density micron-sized carbon with ultra-stable high-rate Li storage," ELECTROCHIMICA ACTA, vol. 367, iss. , pp. 137419, 2021.
DOI: 10.1016/j.electacta.2020.137419, IF = 6.901

Abstract: Among various natural wastes, gum wastes pose major issues, as they are unusable and hard to be disposed due to their acidic and sticky nature. Herein, a rational synthetic strategy is employed to transform various kinds of gum wastes into micron-sized carbon, which also exhibit high tap density (1.4–1.7 g cm−3) desirable for practical application in lithium-ion batteries (LIBs). Gum karaya (GK) micron-size functional carbon (GKMFC) exhibits the most outstanding electrochemical performance, with a volumetric capacity of 175.4 mAh cm−3 at a current density of 3000 mA g−1 for 5000 cycles, and possesses ultra-stable high-rate cyclability (a capacity decay of only 0.001881% per cycle). Additional electrochemical analyses reveal that GKMFC exhibits stable structural integrity as well as minimal cell resistance even after cycling, showing its practical application as viable electrode for LIBs. This work sheds light on utilizing high tap density carbon from gum wastes for LIBs, which can also be applicable to other natural wastes and carbon.


R. Yalavarthi, A. Naldoni, R. Zbořil and Š. Kment, "Controlling phase fraction and crystal orientation via thermal oxidation of iron foils for enhanced photoelectrochemical performance," CATALYSIS TODAY, vol. 361, pp. 117-123, 2020.
DOI: 10.1016/j.cattod.2020.01.044, IF = 6.766

Abstract: It has been known that the intrinsic properties of a semiconducting photoanodes significantly influence the overall photoelectrochemical (PEC) performance. Here, we report on the fabrication of layered structure of mixed-phase FeO (wustite), Fe3O4 (magnetite), and α-Fe2O3 (hematite) iron oxide nanoflake/nanowire morphologies through the thermal oxidation of pristine Fe foils, and the role of metastable FeO phase on the PEC performance discussed. X-ray diffraction and Raman spectroscopic measurements revealed the variation in phase fraction of wustite, magnetite, and hematite with respect to oxidation temperature. The PEC measurements indicate a dependence of onset potential and photocurrent density on phase proportion. The sample, which contains metastable wustite phase FeO, along with Fe3O4 and α-Fe2O3, shows a lower onset and higher photocurrent density, followed by the sample that contains a nearly equal ratio of magnetite to hematite phase (∼ 42:58) than that of relatively higher magnetite phase content samples. It is attributed to the improvement in the intrinsic transport of photogenerated charge carriers from hematite via the magnetite and wustite phases to the back contact of the photoanode. It consequently led to a decrease in bulk charge recombination across the interfaces of multiple phases. We carried out electrochemical impedance (EIS) and light intensity-modulated photocurrent measurements (IMPS) to elucidate the mechanism behind the charge separation across the multiple phases.


L. Mascaretti, T. Barman, B. R. Bricchi, F. Münz, A. Li Bassi, Š. Kment and A. Naldoni, "Controlling the plasmonic properties of titanium nitride thin films by radiofrequency substrate biasing in magnetron sputtering," APPLIED SURFACE SCIENCE, vol. 554, art. no. 149543, 2021.
DOI: 10.1016/j.apsusc.2021.149543, IF = 6.707

Abstract: Titanium nitride (TiN) is a promising plasmonic material alternative to gold and silver thanks to its refractory character, low resistivity (<100 µΩ cm) and compatibility with microelectronic industry processes. Extensive research is currently focusing on the development of magnetron sputtering as a large-scale technique to produce TiN thin films with low resistivity and optimized plasmonic performance. As such, more knowledge on the correlation between process parameters and the functional properties of TiN is needed. Here we report the effect of radiofrequency (RF) substrate biasing during the sputtering process on the structural, optical and electrical properties of TiN films. We employ spectroscopic ellipsometry as a sensible characterization method and we show that a moderate RF power, despite reducing the grain size, allows to achieve optimal plasmonic quality factors and a low resistivity (<100 µΩ cm). This is attributed to the introduction of a slight under-stoichiometry in the material (i.e., TiN0.85), as opposite to the films synthesized without bias or under intense bombardment conditions. RF substrate biasing during magnetron sputtering appears thus as a viable tool to prepare TiN thin films at room temperature with desired plasmonic properties.


V. Prysiazhnyi, J. Kratochvil, D. Kaftan, R. Ctvrtlik and V. Stranak, "Growth of hard nanostructured ZrN surface induced by copper nanoparticles," APPLIED SURFACE SCIENCE, vol. 562, art. no. 150230, 2021.
DOI: 10.1016/j.apsusc.2021.150230, IF = 6.707

Abstract: Surfaces with defined nanoroughness and topography are appreciated in many applications. However, such surfaces, often built from deposited nanoparticles, suffer from low hardness and overall mechanical stability. This paper reports the research of ZrN surfaces with defined nanoroughness attained by seed-like growth evoked by Cu nanoparticles. The two-step process consists of (i) deposition of Cu nanoparticles by gas aggregation forming seeds (ii) growth of ZrN with surface nanoarchitecture. Our study faces the challenge to stabilize soft Cu nanoparticles by coating them with a hard, crystalline ZrN film deposited by High Power Impulse Magnetron Sputtering (HiPIMS) without any post thermal annealing which can be useful for coating heat-sensitive substrates. It is shown that by tailoring the HiPIMS process we were able to deposit hard Cu/ZrN nanocomposite with roughness and morphology predetermined by the Cu nanoparticles. Nano-indentation carried out with a resolution below 1 nm, confirmed sufficient nanohardness of CuNPs/ZrN nanocomposite.


A. Sánchez-Grande, J. I. Urgel, L. Veis, S. Edalatmanesh, J. Santos, K. Lauwaet, P. Mutombo, J. M. Gallego, J. Brabec, P. Beran, D. Nachtigallová, R. Miranda, N. Martín, P. Jelínek and D. Écija, "Unravelling the Open-Shell Character of Peripentacene on Au(111)," THE JOURNAL OF PHYSICAL CHEMISTRY LETTERS, vol. 12, iss. 1, pp. 330-336, 2021.
DOI: 10.1021/acs.jpclett.0c02518, IF = 6.475

Abstract: Polycyclic aromatic hydrocarbons (PAHs) are a family of organic compounds comprising two or more fused aromatic rings which feature manifold applications in modern technology. Among these species, those presenting an open-shell magnetic ground state are of particular interest for organic electronic, spintronic, and non-linear optics and energy storage devices. Within PAHs, special attention has been devoted in recent years to the synthesis and study of the acene and fused acene (periacene) families, steered by their decreasing HOMO–LUMO gap with length and predicted open-shell character above some size. However, an experimental fingerprint of such magnetic ground state has remained elusive. Here, we report on the in-depth electronic characterization of isolated peripentacene molecules on a Au(111) surface. Scanning tunnelling spectroscopy, complemented by computational investigations, reveals an antiferromagnetic singlet ground state, characterized by singlet–triplet inelastic excitations with an experimental effective exchange coupling (Jeff) of 40.5 meV. Our results deepen the fundamental understanding of organic compounds with magnetic ground states, featuring perspectives in carbon-based spintronic devices.


N. Kaur, A. Khunger, S. L. Wallen, A. Kaushik, G. R. Chaudhary and R. S. Varma, "Advanced green analytical chemistry for environmental pesticide detection," CURRENT OPINION IN GREEN AND SUSTAINABLE CHEMISTRY, vol. 30, art. no. 100488, 2021.
DOI: 10.1016/j.cogsc.2021.100488, IF = 6.457

Abstract: By understanding the adverse effects of pesticide residues on human and aquatic health, the 21st century has awareness to the importance of adopting advanced agriculture based on minimum use of pesticide residues. Such advancements advocate the development of novel and sensitive analytical methods, which can detect ultra-low levels of pesticide residues with minimum complexity and requirement of expensive traditional analytical techniques. The objective of the present work is to bring forth the concept of green analytical chemistry and to assess the recent progress in pesticide detection techniques within the framework of green chemistry and sustainability. Herein, recent advances are outlined in analytical techniques based on nanosystems for convenient, fast, green, and ultrasensitive detection of pesticide residues in food and environmental samples, including deliberations on newer and future cost-effective, analytical approaches in the field of pesticide detection.


A. Cerulli, A. Napolitano, J. Hošek, M. Masullo, C. Pizza and S. Piacente, "Antioxidant and In Vitro Preliminary Anti-Inflammatory Activity of Castanea sativa (Italian Cultivar “Marrone di Roccadaspide” PGI) Burs, Leaves, and Chestnuts Extracts and Their Metabolite Profiles by LC-ESI/LTQOrbitrap/MS/MS," ANTIOXIDANTS, vol. 10, iss. 2, pp. 278, 2021.
DOI: 10.3390/antiox10020278, IF = 6.312

Abstract: The Italian “Marrone di Roccadaspide” (Castanea sativa), a labeled Protected Geographical Indication (PGI) product, represents an important economic resource for the Italian market. With the aim to give an interesting opportunity to use chestnuts by-products for the development of nutraceutical and/or cosmetic formulations, the investigation of burs and leaves along with chestnuts of C. sativa, cultivar “Marrone di Roccadaspide”, has been performed. The phenolic, tannin, and flavonoid content of the MeOH extracts of “Marrone di Roccadaspide” burs, leaves, and chestnuts as well as their antioxidant activity by spectrophotometric methods (1,1-diphenyl-2-picrylhydrazyl (DPPH), Trolox Equivalent Antioxidant Capacity (TEAC), and Ferric Reducing Antioxidant Power (FRAP) have been evaluated. Furthermore, a cell-based antioxidant in vitro test along with in vitro assays for the evaluation of the ability to reduce nuclear factor-kappa B (NF-κB) activation and nitric oxide (NO) production have been carried out. In order to identify the secondary metabolites responsible for the high phenolic content and the strong antioxidant activity shown by leaves and burs extracts, and to highlight the differences between their chemical composition, the analysis of the metabolite profile of the MeOH extracts obtained from both by-products and chestnuts by liquid chromatography coupled to electrospray ionization and multiple-stage linear ion-trap and Orbitrap high-resolution mass spectrometry (LC-(-)ESI/LTQOrbitrap/MS/MS) has been performed. LC-MS analysis allowed the identification of different classes of specialized metabolites including hydrolyzable tannins, flavonoids, ellagic acid and phenol glucoside derivatives, and triterpenoids as well as polar lipids. Our results show how the antioxidant activity of the extracts can be correlated to their high tannins and flavonoids content while polar lipids occurring in the MeOH extract of the leaves could contribute to determining its higher anti-inflammatory activity.


P. Sarkar, A. Sarmah and C. Mukherjee, "Synthesis, crystallographic and spectroscopic characterization, and theoretical elucidation of an elusive aminyl radical containing a CuII–aminyl-iminosemiquinone complex," CHEMICAL COMMUNICATIONS, vol. 57, iss. 11, pp. 1352-1355, 2021.
DOI: 10.1039/d0cc07378d, IF = 6.222

Abstract: An elusive aminyl radical and an iminosemiquinone radical-coordinated square pyramidal Cu(II) complex (1) have been isolated by the reaction between the noninnocent ligand H4LPy(AP) and Cu(ClO4)2·6H2O in the presence of Et3N and air as the sole oxidant. The geometry and electronic structure of the complex were concluded by X-ray crystallography, magnetic and EPR measurements, and density functional theory (DFT) calculations. This work reports the first crystallographic example of the two different types of radicals co-existing in a stable complex.


E. Otyepková, K. Skladanová, M. Pykal, B. Blahová Prudilová, J. Kašlík, K. Čépe, P. Banáš, P. Lazar and M. Otyepka, "Molecular insights from theoretical calculations explain the differences in affinity and diffusion of airborne contaminants on surfaces of hBN and graphene," APPLIED SURFACE SCIENCE, vol. 565, pp. 150382, 2021.
DOI: 10.1016/j.apsusc.2021.150382, IF = 6.128

Abstract: Exposed surfaces of two-dimensional (2D) materials are susceptible to the adsorption of various molecules including airborne contaminants, which can affect their performance in real applications. Hexagonal boron nitride (hBN) is structurally the closest relative to graphite and its single layer form to graphene. The adsorption of organic molecules to graphene was subject of extensive research, however, little is known about interaction of adsorbates to hBN surface. We studied the affinity of organic molecules to the surface of hBN by inverse gas chromatography. The adsorption enthalpies of polar molecules including acetonitrile, nitromethane, ethanol, and acetone exhibited strong coverage dependency up to 20 % of a monolayer. Density functional theory and molecular dynamics calculations were employed to understand and interpret experimentally measured adsorption enthalpies. The calculations revealed that the strong affinity of polar molecules at low coverage was due to adsorption on steps and edges of hBN. The calculated surface diffusion barriers of all molecules were rather low, i.e., below 0.5 kcal/mol (except for benzene and cyclohexane), and molecules adsorbed on the surface behaved like a 2D gas. The results demonstrated that coupling inverse gas chromatography with computer simulations can provide vital insights into the mechanism of adsorption at the molecular level.


P. Stadlbauer, B. Islam, M. Otyepka, J. Chen, D. Monchaud, J. Zhou, J. Mergny and J. Šponer, "Insights into G-Quadruplex–Hemin Dynamics Using Atomistic Simulations: Implications for Reactivity and Folding," JOURNAL OF CHEMICAL THEORY AND COMPUTATION, vol. 17, iss. 3, pp. 1883-1899, 2021.
DOI: 10.1021/acs.jctc.0c01176, IF = 6.006

Abstract: Guanine quadruplex nucleic acids (G4s) are involved in key biological processes such as replication or transcription. Beyond their biological relevance, G4s find applications as biotechnological tools since they readily bind hemin and enhance its peroxidase activity, creating a G4-DNAzyme. The biocatalytic properties of G4-DNAzymes have been thoroughly studied and used for biosensing purposes. Despite hundreds of applications and massive experimental efforts, the atomistic details of the reaction mechanism remain unclear. To help select between the different hypotheses currently under investigation, we use extended explicit-solvent molecular dynamics (MD) simulations to scrutinize the G4/hemin interaction. We find that besides the dominant conformation in which hemin is stacked atop the external G-quartets, hemin can also transiently bind to the loops and be brought to the external G-quartets through diverse delivery mechanisms. The simulations do not support the catalytic mechanism relying on a wobbling guanine. Similarly, the catalytic role of the iron-bound water molecule is not in line with our results; however, given the simulation limitations, this observation should be considered with some caution. The simulations rather suggest tentative mechanisms in which the external G-quartet itself could be responsible for the unique H2O2-promoted biocatalytic properties of the G4/hemin complexes. Once stacked atop a terminal G-quartet, hemin rotates about its vertical axis while readily sampling shifted geometries where the iron transiently contacts oxygen atoms of the adjacent G-quartet. This dynamics is not apparent from the ensemble-averaged structure. We also visualize transient interactions between the stacked hemin and the G4 loops. Finally, we investigated interactions between hemin and on-pathway folding intermediates of the parallel-stranded G4 fold. The simulations suggest that hemin drives the folding of parallel-stranded G4s from slip-stranded intermediates, acting as a G4 chaperone. Limitations of the MD technique are briefly discussed.


M. Janeček, P. Kührová, V. Mlýnský, M. Otyepka, J. Šponer and P. Banáš, "W-RESP: Well-Restrained Electrostatic Potential-Derived Charges. Revisiting the Charge Derivation Model," JOURNAL OF CHEMICAL THEORY AND COMPUTATION, vol. 17, iss. 6, pp. 3495–3509, 2021.
DOI: 10.1021/acs.jctc.0c00976, IF = 6.006

Abstract: Representation of electrostatic interactions by a Coulombic pairwise potential between atom-centered partial charges is a fundamental and crucial part of empirical force fields used in classical molecular dynamics simulations. The broad success of the AMBER force-field family originates mainly from the restrained electrostatic potential (RESP) charge model, which derives partial charges to reproduce the electrostatic field around the molecules. However, the description of the electrostatic potential around molecules by standard RESP may be biased for some types of molecules. In this study, we modified the RESP charge derivation model to improve its description of the electrostatic potential around molecules and thus electrostatic interactions in the force field. In particular, we reoptimized the atomic radii for definition of the grid points around the molecule, redesigned the restraining scheme, and included extra point (EP) charges. The RESP fitting was significantly improved for aromatic heterocyclic molecules. Thus, the suggested W-RESP(-EP) charge derivation model shows some potential for improving the performance of the nucleic acid force fields, for which the poor description of nonbonded interactions, such as the underestimated stability of base pairing, is well-established. We also report some preliminary simulation tests (around 1 ms of simulation data) on A-RNA duplexes, tetranucleotides, and tetraloops. The simulations reveal no adverse effects, while the description of base-pairing interactions might be improved. The new charges can thus be used in future attempts to improve the nucleic acid simulation force fields, in combination with reparametrization of the other terms.


G. Niraula, J. A. H. Coaquira, G. Zoppellaro, B. M. G. Villar, F. Garcia, A. F. Bakuzis, J. P. F. Longo, M. C. Rodrigues, D. Muraca, A. I. Ayesh, F. S. M. Sinfrônio, A. S. de Menezes, G. F. Goya and S. K. Sharma, "Engineering Shape Anisotropy of Fe3O4-γ-Fe2O3 Hollow Nanoparticles for Magnetic Hyperthermia," ACS APPLIED NANO MATERIALS, vol. 4, iss. 3, pp. 3148-3158, 2021.
DOI: 10.1021/acsanm.1c00311, IF = 5.097

Abstract: The use of microwave-assisted synthesis (in water) of α-Fe2O3 nanomaterials followed by their transformation onto iron oxide Fe3O4-γ-Fe2O3 hollow nanoparticles encoding well-defined sizes and shapes [nanorings (NRs) and nanotubes (NTs)] is henceforth described. The impact of experimental variables such as concentration of reactants, volume of solvent employed, and reaction times/temperatures during the shape-controlled synthesis revealed that the key factor that gated generation of morphologically diverse nanoparticles was associated to the initial concentration of phosphate anions employed in the reactant mixture. All the nanomaterials presented were fully characterized by powder X-ray diffraction, field emission scanning electron microscopy, Fourier transform infrared, Mössbauer spectroscopy, and superconducting quantum interference device (SQUID). The hollow nanoparticles that expressed the most promising magnetic responses, NTs and NRs, were further tested in terms of efficiencies in controlling the magnetic hyperthermia, in view of their possible use for biomedical applications, supported by their excellent viability as screened by in vitro cytotoxicity tests. These systems NTs and NRs expressed very good magneto-hyperthermia properties, results that were further validated by micromagnetic simulations. The observed specific absorption rate (SAR) and intrinsic loss power of the NRs and NTs peaked the values of 340 W/g and 2.45 nH m2 kg–1 (NRs) and 465 W/g and 3.3 nH m2 kg–1 (NTs), respectively, at the maximum clinical field 450 Oe and under a frequency of 107 kHz and are the highest values among those reported so far in the hollow iron-oxide family. The higher SAR in NTs accounts the importance of magnetic shape anisotropy, which is well-predicted by the modified dynamic hysteresis (β-MDH) theoretical model.


S. Iravani and R. S. Varma, "MXenes and MXene-based materials for tissue engineering and regenerative medicine: recent advances," MATERIALS ADVANCES, vol. 2, iss. 9, pp. 2906-2917, 2021.
DOI: 10.1039/d1ma00189b, IF = N/A

Abstract: In view of their unique planar structure and outstanding physical and chemical properties, two-dimensional (2D) materials have garnered the attention of interdisciplinary researchers in the domain of biomedical and clinical applications. MXenes are 2D transition metal carbides and nitrides with outstanding characteristics, comprising huge surface area, biocompatibility, low toxicity, significant electrical conductivity, antibacterial activity and hydrophilicity. Although numerous investigations have demonstrated the promising potential of MXenes for different biomedical applications that include biosensing, bioimaging, cancer therapy, tissue engineering, regenerative medicine, and drug delivery, there are still important challenging issues pertaining to their stability in physiological environments, sustained/controlled release of drugs, and biodegradability. The well-designed ultra-thin MXene nanosheets are deployable as promising biocompatible inorganic nanoplatforms for assorted biomedical applications via the clinical translation of nanomedicine; MXenes are good candidates for tissue engineering and regenerative medicine. Herein, recent progresses on 2D MXenes for state-of-the-art tissue engineering and regenerative medicine are discussed with emphasis on the significant challenges and future perspectives.