Electron Mediator Research Articles

Role of Semiconductive Property on Selective Cementation Mechanism of Iron Oxides to Gold in Galvanic Interaction with Zero-Valent Aluminum from Gold–Copper Ammoniacal Thiosulfate Solutions

Iron oxides (hematite, Fe2O3, and magnetite, Fe3O4), previously used as electron mediators in the galvanic system with zero-valent aluminum (ZVAl), have been shown to recover Au upon cementation in Au–Cu ammoniacal thiosulfate media selectively, and this warrants further investigation. This research is focused on investigating the role of the semiconductive properties of metal oxides by performing a cementation experiment by mixing 0.15 g of electron mediators (Fe3O4, Fe2O3, TiO2 (anatase and rutile)) and 0.15 g of zero-valent aluminum powder as an electron donor in various electrochemical experiments. The results revealed that upon the cementation experiment, synthetic Fe2O3 and Fe3O4 were consistently able to selectively recover Au at around 90% and Cu at around 20%. Compared to activated carbon (AC), TiO2, in anatase and rutile forms, obtained selective recovery of gold, but the recovery was utterly insignificant compared to that of iron oxides, obtaining an average of 93% Au and 63% Cu recovery. The electrochemical and surface analysis supports the results obtained upon the cementation process, where TiO2, upon cyclic voltammetry (CV), obtained two reduction peaks centered at −1.0 V and −0.5 V assigned to reducing Au and Cu ions, respectively. Furthermore, various electrochemical impedance spectroscopic analyses revealed that the flat band potential obtained in the Mott–Schottky plot is around −1.0 V and −0.2 V for iron oxides and titanium oxides, respectively, suggesting that the electrons travel from semiconductor interface to electrolyte interface, and electrons are accessible only to Au ions in the electrolyte interface (reduction band edge around −1.0 V). The determination of this selective cementation mechanism is one of a kind. It has been proposed that the semiconductive properties of Fe2O3, Fe3O4, and, by configuring their relative energy band diagram, the travel of electrons from the iron oxide–electrolyte interface facilitate the selective cementation towards Au(S2O3)23+ ions in gold–copper ammoniacal thiosulfate solutions.

Photocatalytic regeneration of nicotinamide cofactor biomimetics drives biocatalytic reduction by Old Yellow enzymes

A key approach in developing green chemistry involves converting solar energy into chemical energy of biomolecules through photocatalysis. Photocatalysis can facilitate the regeneration of nicotinamide cofactors during redox processes. Nicotinamide cofactor biomimetics (NCBs) are economical substitutes for natural cofactors. Here, photocatalytic regeneration of NADH and reduced NCBs (NCBsred) using graphitic carbon nitride (g-C3N4) was developed. The process involves g-C3N4 as the photocatalyst, Cp*Rh(bpy)H2O2+ as the electron mediator, and Triethanolamine as the electron donor, facilitating the reduction of NAD+ and various oxidative NCBs (NCBsox) under light irradiation. Notably, the highest reduction yield of 48.32 % was achieved with BANA+, outperforming the natural cofactor NAD+. Electrochemical analysis reveals that the reduction efficiency and capacity of cofactors relies on their redox potentials. Additionally, a coupled photo-enzymatic catalysis system was explored for the reduction of 4-Ketoisophorone by Old Yellow Enzyme XenA. Among all the NCBsox and NAD+, the highest conversion ratio of over 99 % was obtained with BANA+. After recycled for 8 times, g-C3N4 maintained over 93.6 % catalytic efficiency. The photocatalytic cofactor regeneration showcases its outstanding performance with NAD+ as well as NCBsox. This work significantly advances the development of photocatalytic cofactor regeneration for artificial cofactors and its potential application.

Poly Meta-Aminophenol (PmAP) as a Solid-State Electron Mediator in the Z-Scheme, Ag3PO4/CoFe2O4 Heterojunction: Mineralization of Highly Concentrated Bisphenol-A and Reactive Dyes Water Pollutants.

This study demonstrated the effectiveness of poly meta-aminophenol (PmAP) as a solid electron mediator in the Z-scheme photocatalytic system for organic pollutants (viz. bisphenol-A and reactive dyes) mineralization and also illustrated how PmAP transported the photogenerated electrons from an O2-emitting photocatalyst (Ag3PO4) to a H2-emitting photocatalyst (CoFe2O4) enabling enhanced photocatalytic activity under visible light irradiation. The PmAP/Ag3PO4-CoFe2O4 (PAC-10), was prepared by a two-step process and characterized by various analytical methods to assess the impact of PmAP on optical, photocatalytic, and electrochemical characteristics of the CoFe2O4 (CFO)/Ag3PO4 composite. The morphological investigation revealed that the PmAP sheet was nicely decorated with evenly distributed Ag3PO4 and CoFe2O4 particles. The M-S plot and impedance analyses were used to assess the electrochemical capabilities of the catalyst. Z-scheme charge transfer pathways were well supported by the radical trapping experiment and HRTEM analysis of Pt photodeposited PAC-10 photocatalysts during the photoreaction. Because of its magnetic nature and ease of synthesis, the PAC-10 offers an easily recyclable Z-scheme photocatalytic system that has the potential for purifying wastewater with high concentrations (up to 100 mg/L) of organic pollutants within 30 min of visible light exposition.

Dual role of pyrogenic carbon in mediating electron transfer from clay minerals to chromium in aqueous and solid media

Clay minerals (CMs) and pyrogenic carbons (PCs) often co-exist in the environment and participate in the redox cycling of pollutants. This study unveiled the dual role of PCs in CM-dominated chromium transformation in both aqueous and agar solidification media. The findings showed that CMs and PCs adsorbed minimal Cr(VI), while reduced CMs and PCs displayed a substantial difference by directly reducing Cr(VI) to solid/dissolved Cr(III) through reactive structural Fe(II) and functional groups, respectively. Moreover, dissolved PCs were found to mediate electron transfer from reduced CMs to Cr(VI) in aqueous and solid media. Interestingly, the effect of solid PCs on Cr(VI) reduction by reduced CMs was concentration-dependent. At lower concentrations, solid PCs dispersed reduced CMs, acting as electron mediators and facilitating both direct and indirect Cr(VI) reduction, resulting in solid Cr(III) rather than dissolved Cr(III). Conversely, at higher concentrations, solid PCs served as redox buffers, storing electrons transferred from reduced CMs to Cr(VI). In either case, the transformed chromium was primarily immobilized on the surface of CMs rather than PCs. These findings offer valuable insights into pollutant transformations associated with CMs and PCs, deepening our understanding of their geochemical processes.

Fulvic acid-mediated efficient anaerobic digestion for kitchen wastewater: Electrochemical and biochemical mechanisms

Fulvic acid, prevalent in humus derived from the anaerobic digestion of kitchen wastewater, is crucial in organic matter transformation. However, its effects and underlying mechanisms remain unclear. In this study, the fate of anaerobic digestion of artificial and kitchen wastewater with different fulvic acid contents was investigated. The results showed that 125 mg/L fulvic acid resulted in a 64.02 and 51.72 % increase in methane production in synthetic and kitchen wastewater, respectively. Fulvic acid acted as an electron mediator and increased substrate oxidation by boosting NAD and ATP levels, thereby increasing microbial metabolic rates and ensuring an adequate substrate for methane generation. Isotope analysis suggested that fulvic acid boosts the conversion of volatile fatty acids to methane via the interspecies electron transfer pathway. Gene expression analysis revealed that cytochrome c, FAD, and other electron transport coenzymes were upregulated by fulvic acid, thereby enhancing substrate utilisation and biogas quality. Fulvic acid presented a dual stimulatory and inhibitory effect on anaerobic digestion, with concentrations over 125 mg/L diminishing its positive impact. This dual effect may stem from the properties and concentrations of fulvic acid. This study revealed the effect mechanism of fulvic acid and provided insights into the humus performance in anaerobic digestion

Optimizing light-driven ene-reductase reactions with g-C3N4 and electron mediators

In the realm of green chemistry and sustainable industrial processes, the integration of enzymes with photocatalytic materials offers a promising avenue for achieving efficient, light-driven catalysis while minimizing environmental impact. This study introduces an enzyme-photo-coupled catalytic system (EPCS) using graphitic carbon nitride (g-C3N4) as a photocatalyst and methyl viologen (MV2+) as an electron mediator to drive the reduction of 2-cyclohexen-1-one by the Old Yellow Enzyme (OYE), reducing the reliance on expensive and scarce bioelectronic carriers and demonstrating a sustainable alternative for biocatalytic applications. Furthermore, we explored the incorporation of a Pickering emulsion system to enhance mass transfer, especially in reactions involving highly concentrated substrates. This adaptation not only improves the yield of the EPCS at higher substrate concentrations but also offers a scalable and environmentally benign alternative to traditional photocatalytic systems.

Stabilizing the S-scheme ZnO/ZnCr2O4/Bi6Cr2O15 heterojunction through the application of carbon xerogel as both a solid-state mediator and reducing agent

This study aims to evaluate the application of the carbonaceous material known as carbon xerogel as a solid-state mediator in the ZnO/ZnCr2O4/Bi6Cr2O15 heterojunction, aiming to stabilize the charge transfer pathway to an S-scheme configuration. Furthermore, the carbon xerogel was also chosen as a reducing agent for the formation of the proposed heterojunction under high temperatures, due to the reduction of the Bi6Cr2O15 into Bi0 and Cr2O3, with posterior formation of the ZnCr2O4 phase through solid-state reaction with the ZnO. The photocatalytic performance of the materials was evaluated through sulfamerazine degradation under both simulated sunlight and visible light. The X-ray diffractometry and Raman spectrometry show the formation of the ZnO, ZnCr2O4, Bi6Cr2O15, and Bi0 phases on the composite material, as expected. Furthermore, morphological modifications were observed for the zinc oxide (ZnO) after the addition of both the carbon xerogel and bismuth-based phases, resulting in a significant enhancement of specific surface area and pore volume of the materials. Photocatalysis-wise, the composite material developed obtained the highest efficiency among the materials evaluated, as the stabilization of the S-scheme heterojunction between ZnO, ZnCr2O4, and Bi6Cr2O15 by the carbon xerogel as a solid-state electron mediator and the plasmonic resonance effect provided by the metallic bismuth particles functioned towards an increase in the photocurrent generation capacity and charge carrier lifetime during photonic excitation. The hydroxyl radical was defined as the major species involved in the degradation of the sulfamerazine, indicating the successful stabilization of the S-scheme charge transport pathway between the proposed components of the photocatalyst.

The Implementation of the Republic of Indonesian Supreme Court Regulation Number 3 of 2022 Concerning Electronic Mediation in Court: A Case Study

The current development and progress of communication and information technology has prompted the Lubuk Pakam District Court to change the mediation implementation system which was originally carried out manually to electronic mediation as regulated in Perma Number 3 of 2022.In the implementation of this electronic mediation, problems are still found, due to obstacles from inside or outside the court. This is what drives researchers to conduct research. Formulation of the problem of how to implement Perma and what are the obstacles and how to overcome obstacles in implementing this Perma. The purpose of this research is to find out the implementation of Perma and find out the obstacles and how to overcome these obstacles. The methodology in this study uses an empirical juridical approach where research is carried out directly through interviews with research objects in the field, then connected with secondary data. Results and discussion, Perma has been implemented at the Lubuk Pakam District Court, but not yet fully because there are obstacles such as online mediation carried out by agreement of the parties, there are no internet-based mediation facilities, the internet network is unstable, judge mobility high etc. Conclusion Perma has been implemented at the Lubuk Pakam District Court, but it has not been maximized, due to several obstacles.

Identifying a key spot for electron mediator-interaction to tailor CO dehydrogenase’s affinity

Fe‒S cluster-harboring enzymes, such as carbon monoxide dehydrogenases (CODH), employ sophisticated artificial electron mediators like viologens to serve as potent biocatalysts capable of cleaning-up industrial off-gases at stunning reaction rates. Unraveling the interplay between these enzymes and their associated mediators is essential for improving the efficiency of CODHs. Here we show the electron mediator-interaction site on ChCODHs (Ch, Carboxydothermus hydrogenoformans) using a systematic approach that leverages the viologen-reactive characteristics of superficial aromatic residues. By enhancing mediator-interaction (R57G/N59L) near the D-cluster, the strategically tailored variants exhibit a ten-fold increase in ethyl viologen affinity relative to the wild-type without sacrificing the turn-over rate (kcat). Viologen-complexed structures reveal the pivotal positions of surface phenylalanine residues, serving as external conduits for the D-cluster to/from viologen. One variant (R57G/N59L/A559W) can treat a broad spectrum of waste gases (from steel-process and plastic-gasification) containing O2. Decoding mediator interactions will facilitate the development of industrially high-efficient biocatalysts encompassing gas-utilizing enzymes.

Ultrasensitive Aptasensing Platform for the Detection of β-Amyloid-42 Peptide Based on MOF Containing Bimetallic Porphyrin Graphene Oxide and Gold Nanoparticles.

The prompt detection of diseases hinges on the accessibility and the capability to identify relevant biomarkers. The integration of aptamers and the incorporation of nanomaterials into signal transducers have not only expedited but also enhanced the development of nanoaptasensors, enabling heightened sensitivity and selectivity. Here, the bimetallic nickel-cobalt-porphyrin metal-organic framework ((Ni + Cu)TPyP MOF) is regarded as an electron mediator, immobilization platform for an Alzheimer aptamer and to increase the electrochemical signal for the detection of the main biomarker of Alzheimer's disease (AD), amyloid β (Aβ-42). Furthermore, the ((Ni + Cu)TPyP MOF) was combined with reduced graphene oxide (rGO) and gold nanoparticles (AuNPs), on a gold electrode (GE) to provide an efficient interface for immobilizing aptamer strands. Concurrently, the incorporation of rGO and AuNPs imparts enhanced electrical conductivity and efficacious catalytic activity, establishing them as adept electrochemical indicators. Owing to the superior excellent electrical conductivity of rGO and AuNPs, coupled with the presence of ample mesoporous channels and numerous Ni and Cu metal sites within (Ni + Cu)TPyP MOF, this nanostructure with abundant functional groups is proficient in immobilizing a substantial quantity of aptamer. These interactions are achieved through robust π-π stacking and electrostatic interactions, alongside the high affinity between the thiol group of the aptamer and AuNPs concurrently. The as-prepared ternary (Au@(Ni + Cu)TPyP MOF/rGO) nanostructure electrode exhibited an enhancement in its electrochemically active surface area of about 7 times, compared with the bare electrode and the Aβ-42 redox process is highly accelerated, so the peak currents are significantly higher than those obtained with bare GE substrate. Under the optimized conditions, the designed aptasensor had the quantitative detection of Aβ-42 with a low detection limit of 48.6 fg mL-1 within the linear range of 0.05 pg mL-1 to 5 ng mL-1 by differential pulse voltammetry (DPV), accompanied by precise reproducibility, satisfactory stability (95.6% of the initial activity after 10 days), and minimal impact of interfering agents. Recorded results in human blood plasma demonstrated the high efficacy of porphyrin MOF system sensing even in the clinical matrix. The great performance of this aptasensor indicates that our new design of Au@(Ni + Cu)TPyP MOF/rGO nanostructure provides more opportunities for the detection of chemical signals in early diagnosis of Alzheimer's disease.

A Simple Preparation Method of Reduced Graphene Oxide‐Incorporated BiVO4 Loaded with CoOx Composites and Application to Z‐Schematic Water Splitting under Visible Light Irradiation

The construction of Z‐scheme systems is an efficient strategy to realize water splitting under visible light irradiation. In particular, various photocatalysts can be employed for Z‐scheme systems when a reduced graphene oxide (RGO) is used as an electron mediator. Herein, a simple 1‐step process for the preparation of RGO‐(CoOx/BiVO4) composites is developed. In the developed preparation method, Co ions are oxidized to CoOx by photogenerated holes in BiVO4 accompanied by simultaneous reduction of GO to RGO by photoexcited electrons. The developed preparation method is simpler than a conventional method that contains loading with CoOx by impregnation and subsequent incorporation of RGO by photocatalytic reduction. Z‐schematic water splitting under visible light irradiation proceeds when RGO‐(CoOx/BiVO4) prepared by the 1‐step process is combined with Pt/(CuGa)0.5ZnS2. Moreover, the developed method is also able to be applied to the preparation of RGO‐(FeOx/BiVO4) composites.

Green synthesis of Ag/Yb2O3 nanostructures based-MIP for tamoxifen detection: Advancing from refractometers to sensor

This study presents a novel optical fiber refractometer based on a single smart functional layer of Ag/Yb2O3 nanostructure, synthesized by a green chemistry method using oak fruit extract. The optical phenomena of surface plasmon resonance (SPR) and lossy mode resonance (LMR) were investigated based on the performance of the real and imaginary parts of the dielectric constant function of nanoparticles and nanostructures coated on the optical fiber. The Ag/Yb2O3 nanostructure enhances the LMR phenomenon and acts as an electron mediator for the detection of tamoxifen (TAM) drug, a widely used anticancer agent. The Ag/Yb2O3 nanostructure was coated on a curved optical fiber surface along with a molecularly imprinted polymer (MIP) layer, which provided selective recognition of TAM molecules. The sensor probe showed rapid and reversible adsorption/desorption of TAM, with a high sensitivity of 5.3611 nm/µM and a limit of detection (LOD) and limit of quantification (LOQ) of 0.0987 μM and 0.32902 μM, respectively. The sensor also exhibited good recovery rate and effectiveness in real samples, demonstrating its potential for sensivity applications.

Study of copper corrosion via extracellular electron transfer by nitrate reducing Halomonas titanicae

The microbiologically influenced corrosion (MIC) of copper via extracellular electron transfer (EET) caused by Halomonas titanicae was investigated using two different methods. Copper corrosion in enriched seawater was accelerated by H. titanicae and was further promoted by riboflavin (RF), an electron mediator that can accelerate EET. Within minutes of 20 ppm RF injection, the copper corrosion started to increase. The copper weight loss for 100% carbon source reduction was 1.4 times that of 0% carbon source reduction. The RF injection data together with carbon starvation data indicate that H. titanicae utilized elemental copper as an electron source to cause EET-MIC.

Conductive magnetic nanowires accelerated electron transfer between C1020 carbon steel and Desulfovibrio vulgaris biofilm

Microbial biofilms are behind microbiologically influenced corrosion (MIC). Sessile cells in biofilms are many times more concentrated volumetrically than planktonic cells in the bulk fluids, thus providing locally high concentrations of chemicals. More importantly, “electroactive” sessile cells in biofilms are capable of utilizing extracellularly supplied electrons (e.g., from elemental Fe) for intracellular reduction of an oxidant such as sulfate in energy metabolism. MIC directly caused by anaerobic biofilms is classified into two main types based on their mechanisms: extracellular electron transfer MIC (EET-MIC) and metabolite MIC (M-MIC). Sulfate-reducing bacteria (SRB) are notorious for their corrosivity. They can cause EET-MIC in carbon steel, but they can also secrete biogenic H2S to corrode other metals such as Cu directly via M-MIC. This study investigated the use of conductive magnetic nanowires as electron mediators to accelerate and thus identify EET-MIC of C1020 by Desulfovibrio vulgaris. The presence of 40 ppm (w/w) nanowires in ATCC 1249 culture medium at 37 °C resulted in 45 % higher weight loss and 57 % deeper corrosion pits after 7-day incubation. Electrochemical tests using linear polarization resistance and potentiodynamic polarization supported the weight loss data trend. These findings suggest that conductive magnetic nanowires can be employed to identify EET-MIC. The use of insoluble 2 μm long nanowires proved that the extracellular section of the electron transfer process is a bottleneck in SRB MIC of carbon steel.

Clicked BODIPY-Fullerene-Peptide Assemblies: Studies of Electron Transfer Processes in Self-Assembled Monolayers on Gold Surfaces.

Two BODIPY-C60-peptide assemblies were synthesized by CuAAC reactions of BODIPY-C60 dyads and a helical peptide functionalized with a terminal alkyne group and an azide group, respectively. The helical peptide within these assemblies was functionalized at its other end by a disulfide group, allowing formation of self-assembled monolayers (SAMs) on gold surfaces. Characterizations of these SAMs, as well as those of reference molecules (BODIPY-C60-alkyl, C60-peptide and BODIPY-peptide), were carried out by PM-IRRAS and cyclic voltammetry. BODIPY-C60-peptide SAMs are more densely packed than BODIPY-C60-alkyl and BODIPY-peptide based SAMs. These findings were attributed to the rigid peptide helical conformation along with peptide-peptide and C60-C60 interactions within the monolayers. However, less dense monolayers were obtained with the target assemblies compared to the C60-peptide, as the BODIPY entity likely disrupts organization within the monolayers. Finally, electron transfer kinetics measurements by ultra-fast electrochemistry experiments demonstrated that the helical peptide is a better electron mediator in comparison to alkyl chains. This property was exploited along with those of the BODIPY-C60 dyads in a photo-current generation experiment by converting the resulting excited and/or charge separated states from photo-illumination of the dyad into electrical energy.

The Pd (II) Reduction Mechanisms in Bacillus megaterium Y-4 Revealed by Proteomic Analysis.

Many studies have been conducted on the microbial reduction of Pd (II) to palladium nanoparticles (Pd-NPs) due to the environmental friendliness, low cost, and the decreased toxicity of Pd (II) ions. In this study, we investigate the reduction mechanism of Pd (II) by Bacillus megaterium Y-4 through proteomics. The data are available via ProteomeXchange with identifier PXD049711. Our results revealed that B. megaterium Y-4 may use the endogenous electron donor (NAD(P)H) generated by nirB, tdh, and fabG and reductase to reduce Pd (II) to Pd-NPs. The expression levels of fabG, tdh, gudB, and rocG that generate NAD(P)H were further increased, and the number of reduced Pd-NPs was further increased with the exogenous electron donor sodium formate. Endogenous electron mediators such as quinones and flavins in B. megaterium Y-4 can further enhance Pd (II) reduction. The findings provided invaluable information regarding the reduction mechanism of Pd (II) by B. megaterium Y-4 at the proteome level.

Bioinspired Binickel Catalyst for Carbon Dioxide Reduction: The Importance of Metal-ligand Cooperation.

Catalyst design for the efficient CO2 reduction reaction (CO2RR) remains a crucial challenge for the conversion of CO2 to fuels. Natural Ni-Fe carbon monoxide dehydrogenase (NiFe-CODH) achieves reversible conversion of CO2 and CO at nearly thermodynamic equilibrium potential, which provides a template for developing CO2RR catalysts. However, compared with the natural enzyme, most biomimetic synthetic Ni-Fe complexes exhibit negligible CO2RR catalytic activities, which emphasizes the significance of effective bimetallic cooperation for CO2 activation. Enlightened by bimetallic synergy, we herein report a dinickel complex, NiIINiII(bphpp)(AcO)2 (where NiNi(bphpp) is derived from H2bphpp = 2,9-bis(5-tert-butyl-2-hydroxy-3-pyridylphenyl)-1,10-phenanthroline) for electrocatalytic reduction of CO2 to CO, which exhibits a remarkable reactivity approximately 5 times higher than that of the mononuclear Ni catalyst. Electrochemical and computational studies have revealed that the redox-active phenanthroline moiety effectively modulates the electron injection and transfer akin to the [Fe3S4] cluster in NiFe-CODH, and the secondary Ni site facilitates the C-O bond activation and cleavage through electron mediation and Lewis acid characteristics. Our work underscores the significant role of bimetallic cooperation in CO2 reduction catalysis and provides valuable guidance for the rational design of CO2RR catalysts.

Effect of sludge humic acid-derived nano-biochars on anaerobic degradation of sulfamethoxazole by Shewanella oneidensis MR-1

Some nano-biochars (nano-BCs) as electron mediators could enter into cells to directly promote intracellular electron transfer and cell activities. However, little information was available on the effect of nano-BCs on SMX degradation. In this study, nano-BCs were prepared using sludge-derived humic acid (SHA) and their effects on SMX degradation by Shewanella oneidensis MR-1 were investigated. Results showed that nano-BCs (Carbon dots, CDs, <10 nm) synthesized using SHA performed a better accelerating effect than that of the nano-BCs with a larger size (10–100 nm), which could be attributed to the better electron transfer abilities of CDs. The degradation rate of 10 mg/L SMX in the presence of 100 mg/L CDs was significantly increased by 84.6% compared to that without CDs. Further analysis showed that CDs could not only be combined with extracellular Fe(III) to accelerate its reduction, but also participate in the reduction of 4-aminobenzenesulphonic acid as an intermediate metabolite of SMX via coupling with extracellular Fe(III) reduction. Meanwhile, CDs could enter cells to directly participate in intracellular electron transfer, resulting in 32.2% and 25.2% increases of electron transfer system activity and ATP level, respectively. Moreover, the activities of SMX-degrading enzymes located in periplasm and cytoplasm were increased by around 2.2-fold in the presence of CDs. These results provide an insight into the accelerating effect of nano-BCs with the size of <10 nm on SMX degradation and an approach for SHA utilization.

NH4Cl-assisted synthesis of TaON nanoparticle applied to photocatalytic hydrogen and oxygen evolution from water

Oxynitride semiconductors are promising photocatalyst materials for visible light-driven water splitting, while the synthesis of well crystalized oxynitride still remains challenge. In present work, narrow-bandgap TaON nanoparticles are synthesized via heating a vacuum-sealed mixture of KTaO3, Ta and NH4Cl. This method possesses multiple advantages in terms of lower calcination parameter, higher N conversion efficiency and superior photocatalytic activity in comparison with the traditional thermal ammonolysis using NH3 gas as a nitrogen source. Through the analysis of intermediates produced upon the elevation of heating temperature, a gas–solid-phase reaction between TaCl5 and Ta2O5 is demonstrated as the final step, which is conducive to decreasing thermal energy barrier and accelerating nitridation process. Precise control of preparation conditions, including calcination temperature and duration, allows for the regulation of surface O/N ratio of TaON particles to unity, resulting in optimized photocatalytic activity. Photoelectrochemical assessment and intensity modulated photocurrent spectroscopy provide convincing evidence for improved charge transfer efficiency of photoexcited holes at TaON surface. A Z-scheme overall water splitting is accomplished by employing the TaON as an effective oxygen evolution photocatalyst, SrTiO3:Rh as a hydrogen evolution photocatalyst, and reduced graphene oxide (rGO) as a solid-state electron mediator. This work presents a promising strategy for the synthesis of high-quality oxynitride materials in application to photocatalytic water splitting.

Riboflavin-mediated Fe0-to-microbe electron transfer corrosion of EH40 steel by Halomonas titanicae

This study investigated riboflavin (RF)-mediated Fe0-to-microbe electron transfer corrosion of EH40 steel caused by Halomonas titanicae. The addition of 20 ppm RF to the biotic medium increased the weight loss and maximum pitting depth of EH40 steel by 67 % and 64 %, respectively. After 20 ppm RF injection into a 3-d broth, the biotic corrosion started to increase within minutes, reflecting that the H. titanicae extracellular electron transfer (EET) rate was promoted by RF as an electron mediator. Furthermore, RF increased the expression level of cytochrome c (Cyt c) in sessile cells, which further enhanced the EET capacity of H. titanicae.