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 = 27.398

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.

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, iss. , pp. 105828, 2021.
DOI: 10.1016/j.nanoen.2021.105828, IF = 16.602

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.

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,Article in press, 2021.
DOI: 10.1021/acsnano.0c09781, IF = 14.588

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 = 14.588

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 = 14.588

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 = 12.959

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 = 12.959

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.

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 = 12.264

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.

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, Article in press, 2021.
DOI: 10.1002/smll.202006477, IF = 11.459

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, Article in press, 2021.
DOI: 10.1002/smll.202006473, IF = 11.459

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, Article in press, 2021.
DOI: 10.1002/smll.202006478, IF = 11.459

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.

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 = 9.48

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. 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 = 9.038

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 = 9.038

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. 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 = 8.352

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.

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 = 8.247

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.

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 = 6.71

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.

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 = 5.88

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.

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 = 5.825

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.

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 = 5.774

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.

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, iss. , pp. 100488, 2021.
DOI: 10.1016/j.cogsc.2021.100488, IF = 5.165

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.

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 = 5.011

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.

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.

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, Article in press.
DOI: 10.1021/acs.jctc.0c00976, IF = 5.011

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.