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In order to reduce infection risk of novel coronavirus (SARS-CoV-2), we developed nano-photocatalysts with nanoscale rutile TiO2 (4–8 nm) and CuxO (1–2 nm or less). Their extraordinarily small size leads to high dispersity and good optical transparency, besides large active surface area. Those photocatalysts can be applied to white and translucent latex paints. Although Cu2O clusters involved in the paint coating undergo gradual aerobic oxidation in the dark, the oxidized clusters are re-reduced under > 380 nm light. The paint coating inactivated the original and alpha variant of novel coronavirus under irradiation with fluorescent light for 3 h. The photocatalysts greatly suppressed binding ability of the receptor binding domain (RBD) of coronavirus (the original, alpha and delta variants) spike protein to the receptor of human cells. The coating also exhibited antivirus effects on influenza A virus, feline calicivirus, bacteriophage Qβ and bacteriophage M13. The photocatalysts would be applied to practical coatings and lower the risk of coronavirus infection via solid surfaces.

In order to reduce infection risk of novel coronavirus (SARS-CoV-2), we developed photocatalysts with nanoscale rutile TiO2 (4–8 nm) and CuxO (1–2 nm or less). Their extraordinarily small size leads to high dispersity and good optical transparency, besides large active surface area. Those photocatalysts can be applied to white and translucent latex paints and a transparent varnish. Although Cu2O clusters involved in the paint coating undergo gradual aerobic oxidation in the dark, the oxidized clusters are re-reduced under >380 nm light. The paint coating inactivated novel coronavirus and its alpha (B.1.1.7) variant under irradiation with fluorescent light for 3 h. The coating also exhibited antivirus effects on influenza A virus, feline calicivirus and bacteriophage Qβ. The photocatalysts would be applied to practical coatings and lower the risk of coronavirus infection via solid surfaces.

The influence of pre-coating Li7La3Zr2O12 (LLZ) with Au on the charge transfer resistance (Rint) at the interface of LLZ and lithium (Li) is examined by AC impedance spectroscopy using a three-electrode system. The Au diffuses into Li after physical contact with Li, and the open-circuit potential reaches approximately 0 mV (vs. Li/Li+) accompanied by a decrease in Rint. During the Li dissolution/deposition cycles, the electrode potential changes with 0 mV as the central potential, indicating that Li metal dissolution/deposition on Li metal proceeds predominantly at the interface. Rint increases and decreases during Li dissolution and deposition, respectively, regardless of the presence or absence of the Au coating; however, the increase in Rint during Li dissolution is suppressed at the Li/Au-coated LLZ (Au-LLZ) interface. The decreased Rint is considered to be due to an increase in the effective contact area at the electrode/LLZ interface, which is achieved by pre-coating Au onto the LLZ surface.

The interplay among magnetism, electronic nematicity, and superconductivity is the key issue in strongly correlated materials including iron-based, cuprate, and heavy-fermion superconductors. Magnetic fluctuations have been widely discussed as a pairing mechanism of unconventional superconductivity, but recent theory predicts that quantum fluctuations of nematic order may also promote high-temperature superconductivity. This has been studied in FeSe1−xSx superconductors exhibiting nonmagnetic nematic and pressure-induced antiferromagnetic orders, but its abrupt suppression of superconductivity at the nematic end point leaves the nematic-fluctuation driven superconductivity unconfirmed. Here we report on systematic studies of high-pressure phase diagrams up to 8 GPa in high-quality single crystals of FeSe1−xTex. When Te composition x(Te) becomes larger than 0.1, the high-pressure magnetic order disappears, whereas the pressure-induced superconducting dome near the nematic end point is continuously found up to x(Te) ≈ 0.5. In contrast to FeSe1−xSx, enhanced superconductivity in FeSe1−xTex does not correlate with magnetism but with the suppression of nematicity, highlighting the paramount role of nonmagnetic nematic fluctuations for high-temperature superconductivity in this system.

A copper-modified covalent triazine framework (Cu-CTF) catalyzed the selective electrochemical reduction of nitrobenzene to aniline in neutral aqueous solutions with a faradaic efficiency reaching up to 65% at −0.6 V versus Ag/AgCl. Electrochemical characterization indicated that the organic-framework part of Cu-CTF reduced nitrobenzene to phenylhydroxylamine, followed by the reduction of phenylhydroxylamine to aniline at single Cu sites. This is the first example of a cooperative electrocatalytic reaction at metal centers and at the framework with a metal-modified CTF.

Surface-segregated monolayers (SSMs) based on two poly(3-alkylthiophene)s with semifluoroalkyl groups at either the side chains (P3DDFT) or one end of the main chain (P3BT-F17) were used as self-organized buffer layers at the electrode interfaces in bulk heterojunction (BHJ) organic photovoltaic devices. Both of the SSMs greatly shifted the vacuum levels of the BHJ films at the surface due to the aligned permanent dipole moments of the semifluoroalkyl chains. Hole extraction in the BHJ of poly(3-hexylthiophene) (P3HT):[6,6]-phenyl C61-butyric acid methyl ester (PCBM) became more efficient in the presence of the P3DDFT buffer layer, resulting in an improved power conversion efficiency. In contrast, the SSM of P3BT-F17 induced changes in the chain orientation of P3HT and the morphology of the BHJ films, resulting in decreased performance. These results indicate that the molecular design of polymer-based SSMs can affect not only the energy structure at the interface but also the morphology and the molecular ...

Dynamic changes in the charge-transfer resistance at a Li/Li 7 La 3 Zr 2 O 12 (LLZ) interface during lithium (Li) dissolution/deposition cycles are investigated with an alternative current (AC) impedance technique in a three-electrode system. The resistance respectively increases and decreases during electrodissolution and electrodeposition of Li. The resistance does not return to the initial value after one cycle of Li dissolution and deposition, which indicates that the change in resistance during dissolution is larger than that during deposition. Furthermore, the resistance is almost constant when Li deposition proceeds without prior Li dissolution. The respective increase and decrease in the interfacial resistance during Li dissolution and deposition is most likely due to the formation and disappearance of voids at the Li/LLZ interface, and the voids formation during Li dissolution is suggested to be a critical factor that influences the interfacial resistance.

We established whole-cell circular dichroism difference spectroscopy to identify the inter-heme interaction in deca-heme cytochrome protein MtrC in whole cell. Our data showed that the heme alignment of reduced MtrC in whole cell is distinct from that in purified one, suggesting the in vivo specific electron transport kinetics.

The present work demonstrates that a single platinum atom-modified covalent triazine framework hybridized with carbon nanoparticle (Pt-CTF/CP) exhibited selective activity for the electrochemical reduction of nitrogen oxides. Pt-CTF/CP had low nitrate reduction activity, but efficiently catalyzed the reduction of nitric oxide (NO) molecules derived from the decomposition of nitrite. In contrast, a bulk Pt surface exhibited high activity for both reactions. The selectivity of Pt-CTF/CP for NO is likely due to the unique adsorption behavior of hydrogen atoms and/or nitrate ions on the single Pt atoms.

To construct photoresponsive unidirectional charge transfer units for the activation of oxygen-evolving manganese oxide (MnOx) catalyst, metal-oxide nanoclusters consisting of cerium (CeIII) or cobalt (CoII) ions and Keggin-type polyoxotungstate (PW12O403–) were synthesized in a polymer matrix as visible-light-absorbing chromophores. The utilization of the polymer matrix enabled the molecularly dispersed PW12O403– states and was advantageous to achieve product-separable energy conversion systems. The reaction of PW12O403– with Ce(NO3)3 or CoCl2 in the polymer matrix generated the new broad absorption tails extending from the UV to visible region, assignable to metal-to-metal charge transfer (MMCT) transitions of oxo-bridged binuclear WVI–O–CeIII and WVI–O–CoII units. Cyclic voltammetry analysis of the oxo-bridged binuclear units in the polymer membrane revealed that the CoIII/CoII couple had a 300 mV more positive redox potential than that of CeIV/CeIII and was capable of extracting electrons from MnOx ca...

The oxygen evolution reaction (OER; 2H2O → O2 + 4H+ + 4e–) is being intensively studied to generate fossil fuel-independent energy carriers. As 4d/5d rare metal catalysts, such as amorphous iridium oxide (IrOx), display higher activity than 3d metal catalysts, elucidating the critical mechanistic differences between these materials is important for the synthesis of cost-effective OER catalysts. Although most studies of OER catalysts have focused on O–O bond formation energetics, here, we examined the OER mechanism of IrOx based on charge accumulation, which was recently shown to determine the OER activity for Mn and Fe oxides. Kinetic analysis using Tafel and trumpet plots, along with the difference in the pH dependence between the OER onset potential and that of iridium valence change, showed that the valence change of iridium is more favorable than O–O bond formation. In situ evanescent wave spectroscopy revealed that an intermediate assignable to Ir5+ with oxygen ligands in opposite spin serves as the ...

The microbial transfer of electrons to extracellularly located solid compounds, termed extracellular electron transport (EET), is critical for microbial electrode catalysis. Although the components of the EET pathway in the outer membrane (OM) have been identified, the role of electron/cation coupling in EET kinetics is poorly understood. We studied the dynamics of proton transport associated with EET in an OM flavocytochrome complex in Shewanella oneidensis MR‐1. Using a whole‐cell electrochemical assay, a significant kinetic isotope effect (KIE) was observed following the addition of deuterated water (D2O). The removal of a flavin cofactor or key components of the OM flavocytochrome complex significantly increased the KIE in the presence of D2O to values that were significantly larger than those reported for proton channels and ATP synthase, thus indicating that proton transport by OM flavocytochrome complexes limits the rate of EET.

Serpentinization is a geologic process that produces highly reduced, hydrogen-rich fluids that support microbial communities under high pH conditions. We investigated the activity of microbes capable of extracellular electron transfer in a terrestrial serpentinizing system known as 'The Cedars'. Measuring current generation with an on-site two-electrode system, we observed daily oscillations in current with the current maxima and minima occurring during daylight hours. Distinct members of the microbial community were enriched. Current generation in lab-scale electrochemical reactors did not oscillate, but was correlated with carbohydrate amendment in Cedars-specific minimal media. Gammaproteobacteria and Firmicutes were consistently enriched from lab electrochemical systems on δ-MnO2 and amorphous Fe(OH)3 at pH 11. However, isolation of an electrogenic strain proved difficult as transfer cultures failed to grow after multiple rounds of media transfer. Lowering the bulk pH in the media allowed us to isolate a Firmicutes strain (Paenibacillus sp.). This strain was capable of electrode and mineral reduction (including magnetite) at pH 9. This report provides evidence of the in situ activity of microbes using extracellular substrates as sinks for electrons at The Cedars, but also highlights the potential importance of community dynamics for supporting microbial life through either carbon fixation, and/or moderating pH stress.

The effects of water concentration (CH2O) on the coulombic efficiency (CE) of lithium (Li) deposition/dissolution reactions in tetraglyme-based electrolytes are examined. The CE increases from approximately 50% to 80% with increasing CH2O to 1000 ppm, but decreases with further increase in CH2O. X-ray photoelectron spectroscopy analyses of the formed Li deposits reveal that the increase in CE at CH2O values of 1000 ppm is associated with the formation of resistive lithium hydroxide (LiOH). In addition, scanning electron microscopic analysis of the deposits reveals that large Li-aggregates with the size of several tens of μm are formed when the CH2O exceeds 1000 ppm. Taken together, these results indicate that optimized amount of water is beneficial for reversible Li deposition/dissolution reactions.

Redox-active polymers composed of 2-methacryloyloxyethyl phosphorylcholine (MPC) and redox-active units are a new category of cytocompatible electron mediators which possess permeability of cell membranes. However, supply of electrons to living cells through the cytocompatible redox polymers has not been achieved so far due to the high redox potential of the redox polymers. Here we report that electrons were successfully supplied from a cathode into Escherichia coli cells, generating the current density of 7.8 μA cm−2 at −0.40 V vs. SHE. It was also revealed that the cytocompatibility of viologen was improved simply by co-polymerization with MPC. Keywords: Extracellular electron transfer, Intracellular redox state, Redox polymer, Electron mediator

This work demonstrates that a single Ru atom-modified covalent triazine framework (Ru-CTF) has selectivity for the electrooxidation of benzyl alcohol in water over the oxygen evolution reaction. Additionally, Ru-CTF displayed higher stability than an immobilized Ru-organometallic complex due to the covalently cross-linked structure of CTF.

Microbial electrode catalysis such as microbial fuel cells or electrosynthesis involves electron exchange with the electrodes located at the cell exterior; i.e., extracellular electron transport (EET). Despite the vast amount of research on the kinetics of EET to optimize the catalysis rate, the relevance of other factors, including upstream metabolic reactions, has scarcely been investigated. Herein, we report an in vivo electrochemical assay to confirm whether EET limits anodic current production (j) for the lactate oxidation of Shewanella oneidensis MR-1. Addition of riboflavin, which specifically enhances the EET rate, increased j only in the early phase before j saturation. In contrast, when we removed a trace metal ion necessary for upstream reactions from the electrolyte, a significant decrease in j and the lactate consumption rate was observed only after j saturation. These data suggest that the limiting factor for j shifted from EET to upstream reactions, highlighting the general importance of enhancing, for example, microbial metabolism, especially for long-standing practical applications. Our concept to specifically control the rate of EET could be applicable to other bioelectrode catalysis systems as a strategy to monitor their rate-limiting factors.

Extracellular electron transport (EET) occurs in environmental iron-reducing bacteria and is mediated by an outer membrane multi-heme cytochrome complex (Cyts). It has critical implications for global mineral cycling and electrochemical microbial catalysis. The rate of EET mediated by multiple heme redox centers significantly increases in the presence of flavins and quinones. Their electron free energy does not entirely account for the fact that differential effects on EET rate enhancement vary significantly by factors ≥100. Here, we report on whole-cell electrochemical analysis ofShewanella oneidensisMR-1 using six flavin analogs and four quinones. We demonstrated that protonation of the nitrogen atom at position 5 (N5) of the isoalloxazine ring is essential for electron outflow acceleration as a bound non-covalent cofactor of Cyts. EET mediated by Cyts was accelerated at a rate dependent on pKa(N5). The EET rate largely decreased in response to the addition of deuterated water (D2O), while low concentration of D2O (4 %) had little impact on electron free energy difference of the heme and non-covalent bound cofactors, strongly suggesting that the protonation of N5 limits the rate of EET. Our findings directly link EET kinetics to proton transport reaction via N5 and provide a basis for the development of novel strategies for controlling EET-associated biological reactions.Significance statementThe potential of various small molecules such as flavins and quinones to enhance the rate of extracellular electron transport (EET) has been exploited to develop environmental energy conversion systems. Flavins and quinones have similar molecular structures but their abilities to enhance EET vary by >100× inShewanella oneidensisMR-1. These large differences are inconsistent with conventional models, which rely on redox potentials or diffusion constant of shuttling electron mediators. In this study, we demonstrated that the basicity of the nitrogen atom of the isoalloxazine ring (N5) enhances the rate of electron outflow when a flavin or quinone is a non-covalent cofactor ofS. oneidensisMR-1 outer membranec-type cytochromes.

Nickel-nitrogen-modified graphene (Ni-N-Gr) is fabricated and Ni-N coordination sites on Ni-N-Gr as active centers effectively reduce CO2 to CO. The faradaic efficiency for CO formation reaches 90% at -0.7 to -0.9 V versus RHE, and the turnover frequency for CO production comes up to ≈2700 h-1 at -0.7 V versus RHE.

Aprotic lithium–oxygen (Li–O2) batteries are promising devices for use in sustainable energy management systems as they have the potential to achieve significantly higher energy densities than current state-of-the-art Li-ion batteries. However, the low electrical conductivity of the main discharge product, lithium peroxide (Li2O2), which forms on the positive electrode, gradually suppresses the electrochemical reactions involved in the discharge process, thereby lowering the energy capacity of these systems. Herein, we demonstrate that the energy capacity of Li–O2 batteries can be significantly improved by simply adding chloride ions to the electrolyte. Scanning electron microscopy analysis revealed that thick chloride (Cl)-incorporated Li2O2 films formed on the positive electrode as the discharge product. Using conductive atomic force microscopy, the Cl-incorporated Li2O2 films were shown to exhibit much higher electric conductivity than pristine Li2O2. Taken together, the present findings suggest that m...

Understanding how the four-electron oxidation of water to dioxygen proceeds in different materials is critical to the rational design of efficient catalysts towards artificial photosynthetic systems. Here, using in situ electrochemical evanescent wave spectroscopy under oxygen-evolving conditions, we report two intermediates of iridium oxide (IrOx), which is the most active and stable catalyst characterized to date in acidic medium. The observed potential dependence of the two intermediates indicated that they were associated with different surface sites, and intermediate scavenging experiments using H2O2 provided insight into their role during catalysis. Notably, an Ir(V) species with an absorption maximum at 450 nm was found to mediate the initial two-electron oxidation of water. Inhibition of the Ir(V) species by H2O2, combined with computational modeling, indicates that the accumulation and concurrent spin-state change of the Ir(V) species is a prerequisite for efficient water oxidation by IrOx electrodes.

Extracellular electron transfer (EET) between outer membrane c-type cytochromes (OM c-Cyts) of Shewanella oneidensis MR-1 and anodic and cathodic electrodes is markedly enhanced by the presence of riboflavin that operates as a redox active center in OM c-Cyt protein OmcA. Here, to obtain insight into the EET mechanism via bound riboflavin in OmcA, we replaced riboflavin with two flavin-like polycyclic molecules, safranin (Saf) and anthraquinone-1-sulfonate (α-AQS), and examined the influence of the interaction with OmcA and the potential of these redox molecules for the rate of cathodic EET by MR-1 in vivo. The results of electrochemical assays with wild-type and mutant strains of MR-1 lacking OmcA showed that both Saf and α-AQS increased the cathodic current production for fumarate reduction at −0.45 V versus SHE as a bound cofactor in OmcA. Dissociation constant and enhancement factor analyses of Saf and α-AQS suggested that the N(5) atom in the isoalloxazine ring of riboflavin is important for the affi...

Highlights • Antiviral activities were comparatively evaluated using copper and silver compounds. • Solid-state Cu2O showed superior activity against enveloped and non-enveloped viruses. • Exposure to Cu2O preferentially inactivated infection ability of influenza viruses. • Cu2O has a unique antiviral mechanism mediated by direct contact., Antiviral activities of insoluble solid-state and soluble ionic copper and silver compounds were evaluated against influenza A virus (A/PR8/H1N1) possessing a viral envelope and bacteriophage Qβ lacking an envelope. The viral solutions were exposed on glass samples uniformly loaded with copper and silver compounds. Exposure to solid-state cuprous oxide (Cu2O) efficiently inactivated both influenza A virus and bacteriophage Qβ, whereas solid-state cupric oxide (CuO) and silver sulfide (Ag2S) showed little antiviral activity. Copper ions from copper chloride (CuCl2) had little effect on the activity of bacteriophage Qβ in spite of the fact that copper ions strongly inactivate influenza A in previous studies. Silver ions from silver nitrate (AgNO3) and silver(I) oxide (Ag2O) in solution showed strong inactivation of influenza A and weak inactivation of bacteriophage Qβ. We also investigated the influence of the compounds on the function of two influenza viral proteins, hemagglutinin and neuraminidase. Silver ions from AgNO3 and Ag2O remarkably decreased enzymatic activity of neuraminidase through the breakage of disulfide (S—S) bonds, corresponding to the selective inactivation of influenza A virus. By contrast, exposure to Cu2O markedly reduced the activity of hemagglutinin rather than neuraminidase. These findings suggest that solid-state Cu2O disrupts host cell recognition by denaturing protein structures on viral surfaces, leading to the inactivation of viruses regardless of the presence of a viral envelope.

It was found that copper-modified covalent triazine frameworks (Cu-CTF) efficiently catalyze the electrochemical reduction of nitrate and promote N–N bond formation of nitrous oxide (N2O), a key intermediate for N2 formation (denitrification). A Cu-CTF electrode exhibited an onset potential of −50 mV versus RHE for the electrochemical nitrate reduction reaction (NRR). The faradaic efficiency for N2O formation by Cu-CTF reached 18% at −200 mV versus RHE, whereas that for Cu metal was negligible. On the basis of density functional calculations for Cu-CTF, both solvated and surface-bound nitric oxide (NO) were generated by the NRR due to the moderate adsorption strength of Cu atoms for NO, a property that facilitated the effective dimerization of NO through an Eley–Rideal-type mechanism.

Surrounding organic residues are indispensable for the high water oxidation activity of the Mn4 cluster in photosystem II. Here, the stability of organic compounds on synthetic Mn oxides was analyzed using inlet electrochemical mass spectroscopy. Carboxyl groups, which are the most abundant residues around the Mn4 cluster, were found to stably facilitate the oxygen evolution reaction.

Aromatic polymers with abundant nitrogen-coordinated iron (Fe–Nx) species provide a big opportunity to prepare iron–nitrogen co-doped carbon (Fe–Nx/C) catalysts with highly efficient oxygen reduction reaction (ORR) activity; however, such types of materials have not been reported so far. Herein, we synthesized a metal-coordinated aromatic polymer, Fe(III)–poly(o-phenylene-diamine) (Fe–PPDA), with dense Fe–Nx species by a facile route. Fe–PPDA was obtained by polymerization of the o-phenylenediamine/ferric–ion complex in the presence of sodium bicarbonate, which was essential in retaining abundant Fe–Nx species and increasing the surface area of the polymer. Fe–PPDA polymer derived Fe–Nx/C catalysts demonstrated activity in ORRs, with onset and half-wave potentials (E1/2) of 1.11VRHE and 0.92VRHE, respectively, which were superior to the values obtained for commercial Pt/C (E1/2, 0.85VRHE) and are the best values yet reported for the Fe–Nx/C family in alkaline medium. It also demonstrated comparable ORR activity to that of the commercial Pt/C catalyst in acidic medium (E1/2, 0.76VRHEvs. 0.78VRHE). The excellent ORR activity was ascribed to the abundant Fe–Nx modulated carbon nanostructure and the high surface area.

We synthesized iron (Fe) and nitrogen (N)-modified silicon carbide (Fe/N–SiC) as a novel methane (CH4) combustion catalyst by annealing Fe-deposited SiC under an ammonia atmosphere at 900 °C for 3 h. The rate of CH4 combustion over Fe/N–SiC was 3 times higher than that over Fe–SiC (without N atoms) at 500 °C. Extended X-ray absorption fine structure and X-ray photoelectron spectroscopy analyses of Fe/N–SiC revealed that Fe was atomically distributed and coordinated to N atoms. N-Ligated Fe centers in the catalyst might facilitate the activation of molecular oxygen, and the generated active oxygen species likely react with CH4, resulting in the enhancement of CH4 combustion activity over Fe/N–SiC.

Crystallization of [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) in thin films and in blend films with various polymers was investigated by X-ray diffraction. Thermal annealing induced the crystallization of PCBM in the blend films only through direct contact with a crystallized pure PCBM layer beneath, suggesting that an epitaxial crystallite growth occurred from the bottom interface. The morphology of the crystals depended strongly on the mixing ratio and the crystal structure of the bottom layer, and nanorod-like PCBM crystallites with widths in the range of 100–150 nm and lengths in the range of 150–500 nm were observed. A bulk-heterojunction (BHJ) organic solar cell utilizing the PCBM crystallite as the acceptor showed the highest VOC of 0.83 V for a PTB7:PCBM device to date. These findings offer the ways to use the crystallized PCBM with the controlled nanostructures as the electron conducting materials in organic and hybrid perovskite photovoltaics.

Comprehensive metabolomic analysis of anode-respiring Geobacter sulfurreducens cells revealed that intracellular levels of metabolites related to the tricarboxylic acid (TCA) cycle, gluconeogenesis, consumptions of nicotinamide adenine dinucleotide (NADH) and nicotinamide adenine dinucleotide phosphate (NADPH), and adenosine triphosphate (ATP) generation correlated well with the activity of microbial anode-respiration detected as microbial electric current. Use of a glassy carbon electrode as the anode material in a three-electrode system resulted in a higher microbial current at +0.2 V (vs. Ag/AgCl) than at −0.2 V. A larger current flow resulted in higher concentrations of TCA cycle metabolites and lower concentrations of gluconeogenesis metabolites. Metabolomic analysis also revealed that higher anode-respiration activity resulted in a higher ATP/adenosine diphosphate (ADP) ratio and lower ratios of NADH/NAD+ and NADPH/NADP+. These findings provide direct experimental evidence that microbial anode-respiration activity controlled by the anode potential influences both the flux of central metabolic pathways and the redox balance in microbial fuel cells.