Synergistic Electron Transfer Research Articles

Sustainable hydrogen production with synergistic electron transfer enhancement in nickel-based alkaline HER electrocatalyst empowered by graphene oxide

The hydrogen evolution reaction (HER) plays a crucial role in driving forward the transition to a hydrogen-based economy by providing a means to generate pure hydrogen. However, the efficient and cost-effective production of hydrogen via HER faces significant challenges, particularly at the cathode. To address these challenges, we produced a hybrid material – 2D graphene oxide (GO) sheets coated onto nickel sulfide (NiS) microspheres anchored on Ni Foam (GO@NiS/Ni Foam) using a straightforward synthesis technique. Our research highlights the significant influence of the interaction between GO and NiS on the performance of HER, attributed to the enhancement of electron transport at the interface. Furthermore, the GO@NiS/Ni Foam composite exhibits remarkable durability over extended periods, maintaining its superior functionality for up to 40 h of continuous operation. This underscores its potential for practical implementation in efficient water-splitting processes, offering a promising solution to the challenges hindering widespread adoption of hydrogen technology.

Trimetallic FeCoNi Metal-Organic Framework with Enhanced Peroxidase-like Activity for the Construction of a Colorimetric Sensor for Rapid Detection of Thiophenol in Water Samples.

In recent years, nanozymes have attracted particular interest and attention as catalysts because of their high catalytic efficiency and stability compared with natural enzymes, whereas how to use simple methods to further improve the catalytic activity of nanozymes is still challenging. In this work, we report a trimetallic metal-organic framework (MOF) based on Fe, Co and Ni, which was prepared by replacing partial original Fe nodes of the Fe-MOF with Co and Ni nodes. The obtained FeCoNi-MOF shows both oxidase-like activity and peroxidase-like activity. FeCoNi-MOF can not only oxidize the chromogenic substrate 3,3,5,5-tetramethylbenzidine (TMB) to its blue oxidation product oxTMB directly, but also catalyze the activation of H2O2 to oxidize the TMB. Compared with corresponding monometallic/bimetallic MOFs, the FeCoNi-MOF with equimolar metals hereby prepared exhibited higher peroxidase-like activity, faster colorimetric reaction speed (1.26-2.57 folds), shorter reaction time (20 min) and stronger affinity with TMB (2.50-5.89 folds) and H2O2 (1.73-3.94 folds), owing to the splendid synergistic electron transfer effect between Fe, Co and Ni. Considering its outstanding advantages, a promising FeCoNi-MOF-based sensing platform has been designated for the colorimetric detection of the biomarker H2O2 and environmental pollutant TP, and lower limits of detection (LODs) (1.75 μM for H2O2 and 0.045 μM for TP) and wider linear ranges (6-800 μM for H2O2 and 0.5-80 μM for TP) were obtained. In addition, the newly constructed colorimetric platform for TP has been applied successfully for the determination of TP in real water samples with average recoveries ranging from 94.6% to 112.1%. Finally, the colorimetric sensing platform based on FeCoNi-MOF is converted to a cost-effective paper strip sensor, which renders the detection of TP more rapid and convenient.

High‐Efficiency Flexible Cs2AgBiBr6‐Based Visible Photodetector with Transferable TiO2 Nanorod Electron‐Transport Layer

AbstractIn this work, a flexible perovskite photodetector is demonstrated with a transferable TiO2 nanorod (NR) as an electron transport layer (ETL). The TiO2 NRs are grown by the hydrothermal method on Ni metal buffer layer/Si (100) substrates. During the growth process of TiO2 NRs in solution, the Ni sacrificial buffer layer is removed by hydrochloric acid in the initial stage. The resulting suspended seed layer can then sustain the growth of TiO2 NRs in both the top and bottom directions. The successfully grown TiO2 NRs are now transferred onto an ITO‐coated PET substrate as an ETL for the flexible Cs2AgBiBr6 perovskite photodetectors. The fabricated photodetector operates under a wavelength of 405 nm, and at an external bias voltage of −0.3 V, it exhibits an outstanding performance with an on/off ratio of 1.23 × 104, photoresponsivity (R) of 0.666 A W−1, and a detectivity (D*) of 9.29 × 1012 Jones. In terms of flexibility, the optoelectronic performance of each device is well kept within 5% after 300 bending test cycles with a radius of 1 cm. The suggested transferable TiO2 NRs can improve the efficiency of flexible optoelectronic devices that require synergistic electron transfer effects by using heterostructures with TiO2 nanostructures.

Enhanced corrosion of 2205 duplex stainless steel by Acetobacter aceti through synergistic electron transfer and organic acids acceleration

Acetobacter aceti is a microbe that produces corrosive organic acids, causing severe corrosion of industrial equipment. Previous studies have focused on the organic acid corrosion of A. aceti, but neglected the possibility that it has electron transfer corrosion. This study found that electron transfer and organic acids can synergistically promote the corrosion of 2205 duplex stainless steel (DSS). Electrochemical measurement results showed that corrosion of 2205 DSS was more severe in the presence of A. aceti. Surface analysis indicated a thick biofilm formed on the steel surface, with low pH and dissolved oxygen concentrations under the biofilm. Corrosion intensified when A. aceti lacked a carbon source, suggesting that A. aceti can corrode metals by using metallic substrates as electron donors, in addition to its acidic by-products.

Photodeposition synthesis of hollow g-C3N4/Ag nanotubes with high oxidation properties to enhance visible-light photocatalytic performance

A hollow Ag-deposited g-C3N4 nanotube (CNNT/Ag) with high oxidation properties was synthesized using a simple photodeposition method. The g-C3N4 nanotubes provided abundant active sites and a large specific surface area for effective deposition of Ag nanoparticles. The Ag NPs expanded the light absorption range of g-C3N4 through surface plasmon resonance (SPR) effects and acted as an electron acceptor, effectively inhibiting the recombination of photogenerated carriers, thereby improving the charge separation efficiency. The CNNT/Ag composites exhibited excellent photocatalytic performance in the visible light degradation of rhodamine B and tetracycline, 6.42 and 2.16 times higher than pure g-C3N4, respectively. The increased photocatalytic activity of CNNT/Ag composites was attributed to the synergistic electron transfer interface between CNNT and Ag NPs, promoting the migration efficiency of photo-generated carriers. This work presented a promising strategy for constructing effective photocatalysts for degrading organic pollutants using morphology optimization and SPR effects on noble metal surfaces.

Construction of g-C3N4/Fe-MOFs Type-Ⅱ heterojunction promotes photo-Fenton degradation of doxycycline

A type-II heterojunction photo-Fenton catalyst g-C3N4/Fe-MOFs was synthesized with the utilization of waste PET by dielectric barrier discharge (DBD) plasma. The coupling of Fe-MOFs enhanced the visible-light absorption regions of g-C3N4, and induced the formation of type-II heterojunction, which inhibited the recombination of photo-generated electrons and holes. g-C3N4/Fe-MOFs exhibited a much higher photo-Fenton catalytic performance, which was 4.42 and 3.30 times higher than that of g-C3N4 and Fe-MOFs for the degradation of doxycycline (DOX), respectively. The enhanced photo-Fenton catalytic performance could be attributed to the synergistic electron transfer interface between g-C3N4 and Fe-MOFs, thus inhibiting the recombination of photo-generated electrons and holes. The possible mechanism of photo-Fenton degradation of DOX with g-C3N4/Fe-MOFs was proposed based on the radical trapping experiments, as well as the characterization of EPR and Mott-Schottky. This research could provide an efficient and green method for the utilization of waste PET and the treatment of antibiotic wastewater.

Surface oxygenation of non-oxide boosts oxidation activity on polyoxometalate subunits: An enhanced Venus flytrap mechanism

Typically, the interfacial wettability of catalysts, coupled with electronic modulation, is vitally controlled through surface treatments that boost catalytic performance. Simulation of the biomimetic catalytic process, for instance, a Venus Flytrap mechanism, is deemed as one of the most prospective but particularly challenging protocols to achieve efficient redox catalysis. Herein, a green oxidative desulfurization (ODS) system was readily fabricated, which constituted a modular moiety ionic liquid ([Bmim]Br) triggered PW12O40 (BHPW) anchored on oxygenated graphitic carbon nitride (o-CN). The BHPW/o-CN activates the reaction at 50 °C and is almost two times higher activity than that of BHPW/CN, combined ultrastability with handy synthetic availability for the deep oxidation of carbon–sulfur (C–S) bonds. Oxygen content serves as a descriptor for the catalytic performance. We demonstrate through mimicking CS2- and thiophene-TPD that the adsorption and pre-activation of C–S bonds on the hydrophilic CN surface are critically important for proceeding ODS reaction. Further, systematic characterization containing FT-IR, XPS, and UV–vis indicates the nature of the electron acceptor raised by the oxygen moieties for a plausible mechanism of C–S bonds and spilling to reactive centers. 1H NMR and H–D isotopic exchange analysis confirm the transfer of a proton from HPW to protonated [Bmim]– functional groups triggering the active sites for C–S bonds oxidation. Additionally, density functional calculation revealed the electronic modification of the CN properties shows conclusive activation and synergistic electron transfer mechanism for C–S. The catalyst realizes deep ODS of real diesel at 70 °C with negligible decay in successive cycles. Importantly, the extension of this protocol to other non-oxide (boron nitride) and active phases (molybdenum oxide and polyoxometalates) gives to the present widespread versatility and applicability.

Metal-Porphyrin Frameworks Supported by Carbon Nanotubes: Efficient Polysulfide Electrocatalysts for Lithium-Sulfur Batteries

Lithium-sulfide batteries (LSBs) are highly appealing for the next-generation energy storage systems due to their high theoretical energy density and low cost. However, practical applications of LSBs are still largely hindered by the complicated sulfur redox reactions and the fatal polysulfide shuttling. In nature, cytochrome c reductase works as an efficient biocatalyst for oxidative phosphorylation benefiting from the synergistic electron transfer between porphyrins and sulfur clusters. Inspired by this, herein, two porphyrin-based metal-organic frameworks (Hf-H2DPBP and Hf-CoDPBP) supported by carbon nanotubes (CNTs) were demonstrated to be efficient electrocatalysts for accelerating polysulfide redox kinetics when as separator coatings for LSBs. Consequently, the cells exhibited high initial specific capacities of 1345 mAh g-1 (Hf-H2DPBP/CNT) and 1325 mAh g-1 (Hf-CoDPBP/CNT) at 0.1 C, and maintained outstanding stability with capacities of 582 mAh g-1 (Hf-H2DPBP/CNT) and 513 mAh g-1 (Hf-CoDPBP/CNT) after 500 cycles at 2 C with a decay rate of only 0.079% and 0.086% per cycle, respectively. Even at a high sulfur loading up to 6.2 mg/cm2, the cells still demonstrated excellent performances with an initial specific capacity of 911 mAh g-1 (Hf-H2DPBP/CNT) and 952 mAh g-1 (Hf-CoDPBP/CNT) at 0.1 C, and retained the specific capacities of 745 mAh g-1 (Hf-H2DPBP/CNT) and 818 mAh g-1 (Hf-CoDPBP/ CNT) after 60 cycles, respectively. Furthermore, the high and comparable electrochemical performances can be attributed to the remarkable redox kinetics of both free-base and Co porphyrins toward polysulfides, as supported by DFT calculations.

Multifaceted synergistic electron transfer mechanism for enhancing denitrification by clay minerals

The performance and mechanism of denitrification enhanced by three clay minerals, montmorillonite (Mmt), illite and kaolinite, were first studied. Batch experiments indicated that clay minerals significantly enhanced denitrification at certain concentrations (0.1–1 g/L). The denitrification rate with 1 g/L Mmt was increased by 5.0-fold. The mechanism of clay minerals promoting denitrification was analyzed from three aspects: electron transfer characteristics, interfacial interaction and metabolism activity. Electrochemical tests showed that the clay minerals promoted electron transfer rate by improving current efficiency and electronic accommodation capacity. The biofilm formation on the clay minerals interface indicated that micro-domain catalytic phases were formed, which was beneficial to improve the nitrate reduction rate. In addition, nicotinamide adenine dinucleotide, nitrate reductase and nitrite reductase activities in Mmt-supplemented system were increased by 283.3%, 128.1% and 126.2%, respectively; and extracellular polymeric substance secretion was enhanced, indicating that the addition of clay minerals promoted microbial metabolic activity. Higher microbial diversity and enrichment of electroactive bacteria were observed in the Mmt-supplemented system. Based on the above exploration, the multifaceted synergistic mechanism was proposed to account for the enhanced denitrification performance on clay minerals. Overall, this study expanded understanding of the roles of clay minerals on denitrification and provided strategies for accelerating the biological transformation process.

A directional Built-in electric field mediates the electron transfer synergy mechanism of the Radical/Nonradical pathway in FeOCl-CuO

Synergistic free radical/nonradical oxidation can effectively degrade toxic organic pollutants in complex aqueous environments, but a synergistic electron transfer mechanism has not been developed. In this study, a directional built-in electric field was established in FeOCl-CuO for the first time that can synergistically transfer free radical and nonfree radical electrons. The directional built-in electric field provides electron transfer channels, CuO oxidizes peroxymonosulfate (PMS) to produce 1O2 and gains electrons, electrons are transferred to FeOCl through the directional built-in electric field, and FeOCl catalyzes PMS to produce ·OH and SO4·- and loses electrons. Thus, reactive oxygen species are rapidly produced, and toxic organic pollutants are synergistically oxidatively degraded. This directional built-in electric field-mediated radical/nonradical synergistic mechanism can achieve electron synergy and overcome the electron gain/loss limitation of radical or nonradical reactions, which results in an efficient, sustained and stable catalytic degradation of toxic organic pollutants (kinetic reaction rate constant is increased 38.3 times). Pollutants could be stably removed in pilot devices. The developed kinetic model successfully predicted the kinetic reaction rate constants under different conditions. Theoretical calculations and toxicity assessment revealed that this synergistic radical/nonradical oxidation pathway can effectively degrade bisphenol A (BPA) into less toxic or harmless small molecules and capture carbon in an alkaline environment to reduce carbon emissions. This study provides new insights into the efficient, sustained, and low-carbon treatment of toxic organic wastewater by synergistic radical/nonradical oxidation in complex aqueous environments.

Novel core-shell CuMo-oxynitride@N-doped graphene nanohybrid as multifunctional catalysts for rechargeable zinc-air batteries and water splitting

Highly efficient and durable multifunctional catalysts with attractive nanoarchitectures remain challenging for next-generation rechargeable metal-air batteries and water splitting devices. Herein, for the first time, a novel copper molybdenum oxynitride anchored nitrogen-doped graphene (CuMo2[email protected]) is synthesized by a simple, scalable, and cost-effective pyrolysis method. The rational design of CuMo2ON encased in NC shells anchored onto the NG matrix to enhance the electroactive sites and boost the electron-transport behaviors for oxygen reduction/evolution reactions (ORR/OER) and hydrogen evolution reaction (HER). The optimal CuMo2[email protected] reveals tremendous trifunctional activities, outperform benchmark Pt/C and IrO2. First-principles calculations demonstrate that the excellent catalytic activity of CuMo2[email protected] is owing to the synergistic electron transfer between the active CuMo2ON nanoparticles, doped N species, and graphitic carbon. Formation of the O* intermediates on CuMo2ON lattice in the core-shell CuMo2[email protected] nanohybrid is an energetic rate-determining step to attain ORR and OER activities. The CuMo2[email protected] air-cathode based rechargeable quasi solid-state zinc-air battery delivers an ultra-high specific capacity of 736 mAh gzn−1, an exceptional energy density of 800.75 Wh kg−1, a record power density of 176.3 mW cm−2, and excellent reversibility (330 h at 10 mA cm−2). Furthermore, the CuMo2[email protected] water splitting device achieves a cell voltage of 1.49 V at a current density of 10 mA cm−2 and excellent reversibility of 120 h at a high current density of 100 mA cm−2, outperforming the benchmark Pt/C||IrO2 (~1.53 V at 10 mA cm−2) and reported state-of-the-art catalysts.

Free-radical and surface electron transfer dominated bisphenol A degradation in system of ozone and peroxydisulfate co-activated by CoFe2O4-biochar

We developed a composite material of CoFe2O4-biochar (CoFe2O4@BC) with high performance of peroxydisulfate activation and catalytic ozonation for pollutant degradation in one system. Through single-factor experiments and dynamic fitting calculations, the optimal process (that is, CoFe2O4@BC-peroxydisulfate/ozonation) was used to degrade bisphenol A in water. The system revealed higher catalytic efficiencies for bisphenol A (100 mg·L−1) degradation with the removal ratio of 95.8% and TOC removal ratio of 63.4% within 8.0 min. The reaction kinetic in the CoFe2O4@BC-peroxydisulfate/ozonation process was approximately four-fold higher than that in the peroxydisulfate/ozonation process and eight-fold higher than that without any catalyst in the bare peroxydisulfate process. CoFe2O4@BC, peroxydisulfate, and ozonation showed synergism with one another. A thorough discussion was conducted to explicate the peroxydisulfate activation and catalytic ozonation mechanism via radical quenching experiments, oxygen functional group, and electrochemical analysis. Bisphenol A elimination was determined by the combined effects of free-radical dominated pathway and synergistic electron transfer.

Dissolution reconstruction of electron-transfer enhanced hierarchical NiSx-MoO2 nanosponges as a promising industrialized hydrogen evolution catalyst beyond Pt/C

An industrial electro-catalyst obliges three essential features, such as scalability, generating high current density at low overpotential, and long-term stability. Herein, we tackle those challenges using NiSx-MoO2 nanosponges on carbon cloth based hydrogen evolution catalyst. The target catalyst was synthesized through a series of simple and scalable methods, including dissolution, reconstruction, and chemical vapor deposition. The optimized NiSx-MoO2/CC catalyst exhibits a superior hydrogen evolution catalytic activity far better than commercial Pt/C meanwhile surpasses widely used industrial Raney Ni catalyst by many aspects, namely lower overpotential at 500 mA cm−2 current density and smaller Tafel plot in 30 wt% KOH solution. This excellent electrocatalytic activity is attributed to enhanced mass transfer and faster reaction kinetics due to the unique hierarchical porous structures, as well as the synergistic electron transfer effect between the two components of NiSx and MoO2 species. This work may provide a new strategy for the design of better hydrogen evolution catalyst for industrial application.

Electroactive NPs and D-amino acids oxidase engineered electrochemical chiral sensor for D-alanine detection

A simple and accurate magnetic electrochemical sensor is developed for the ultrasensitive chiral recognition of D-amino acids (D-AAs). Fe3O4@Au@Ag@CuxO nanoparticles (NPs) (x = 1, 2) are controllable prepared and used as the electrochemical beacons. The controllable integration of plasmonic metal NPs, semiconductors and magnetic NPs enables multilayered Fe3O4@Au@Ag@CuxO NPs to display a sharp copper stripping peak at -0.16 V, owning to the electron transfer from Cu+ to Cu2+ and the synergistic electron transfer of Au and Ag double layers. D-AAs can be catalyzed by D-amino acid oxidase (DAAO) to produce H2O2. The autocatalytic oxidation reaction of CuxO shell with the existence of H2O2 induces the decrease of electrochemical signals of Fe3O4@Au@Ag@CuxO NPs. Fe3O4@Au@Ag@CuxO NPs served as electrochemical beacons achieve the sensitive and accurate enantioselective recognition of D-alanine (D-Ala) in the range from 100 pM to 10 μM. The limit of detection (LOD) is as low as 52 pM. This developed protocol can be extended to the fabrication of a large set of electroactive labels by the introduction of plasmonic metal NPs with high electron transfer efficiency, for the reliable enantioselective recognition with high sensitivity.

Effect of treatment on electron transfer mechanism in microbial fuel cell

ABSTRACT Untreated and treated (with chemical electron acceptors like Fe (III) oxide and Fumarate) sludge samples were subjected to microbial fuel cell (MFC) studies. The study focused on both anode biofilm as well as the anolyte consortia developed in the MFC reactor after treatment. Through impedance and voltammogram data, it was seen that untreated inoculum, when used in MFC followed a synergistic electron transfer mechanism (EET), dual EET (3.726 ± 0.130 mWm−3). The Fe (III) oxide treatment promoted the development of electrogenic biofilm that followed direct electron transfer (DET) mechanism (5.439 ± 0.009 mWm−3), whereas Fumarate treatment promoted the growth of electrogenic microbes in anolyte and followed mediator-based electron transfer (MET) mechanism (4.500 ± 0.0009 mWm−3). The microbial cultures like Alcaligenes sp. and Pseudomonas sp. were isolated from MFC reactors having Fe (III) oxide treated biofilm and Fumarate treated anolyte respectively. The occurrence of these microbes indicates their role in the EET mechanism adopted by various MFC reactors.

Synergistic electron transfer effect-based signal amplification strategy for the ultrasensitive detection of dopamine

The selective and sensitive detection of dopamine (DA) is of great significance for the identification of schizophrenia, Huntington's disease, and Parkinson's disease from the perspective of molecular diagnostics. So far, most of DA fluorescence sensors are based on the electron transfer from the fluorescence nanomaterials to DA-quinone. However, the limited electron transfer ability of the DA-quinone affects the level of detection sensitivity of these sensors. In this work, based on the DA can reduce Ag+ into AgNPs followed by oxidized to DA-quinone, we developed a novel silicon nanoparticles-based electron transfer fluorescent sensor for the detection of DA. As electron transfer acceptor, the AgNPs and DA-quinone can quench the fluorescence of silicon nanoparticles effectively through the synergistic electron transfer effect. Compared with traditional fluorescence DA sensors, the proposed synergistic electron transfer-based sensor improves the detection sensitivity to a great extent (at least 10-fold improvement). The proposed sensor shows a low detection limit of DA, which is as low as 0.1 nM under the optimal conditions. This sensor has potential applicability for the detection of DA in practical sample. This work has been demonstrated to contribute to a substantial improvement in the sensitivity of the sensors. It also gives new insight into design electron transfer-based sensors.

Metal-Organic-Framework-Derived Hybrid Carbon Nanocages as a Bifunctional Electrocatalyst for Oxygen Reduction and Evolution.

The oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) are cornerstone reactions for many renewable energy technologies. Developing cheap yet durable substitutes of precious-metal catalysts, especially the bifunctional electrocatalysts with high activity for both ORR and OER reactions and their streamlined coupling process, are highly desirable to reduce the processing cost and complexity of renewable energy systems. Here, a facile strategy is reported for synthesizing double-shelled hybrid nanocages with outer shells of Co-N-doped graphitic carbon (Co-NGC) and inner shells of N-doped microporous carbon (NC) by templating against core-shell metal-organic frameworks. The double-shelled NC@Co-NGC nanocages well integrate the high activity of Co-NGC shells into the robust NC hollow framework with enhanced diffusion kinetics, exhibiting superior electrocatalytic properties to Pt and RuO2 as a bifunctional electrocatalyst for ORR and OER, and hold a promise as efficient air electrode catalysts in Zn-air batteries. First-principles calculations reveal that the high catalytic activities of Co-NGC shells are due to the synergistic electron transfer and redistribution between the Co nanoparticles, the graphitic carbon, and the doped N species. Strong yet favorable adsorption of an OOH* intermediate on the high density of uncoordinated hollow-site C atoms with respect to the Co lattice in the Co-NGC structure is a vital rate-determining step to achieve excellent bifunctional electrocatalytic activity.

Polydopamine-Coated Fe3O4 Nanoparticles as Synergistic Redox Mediators for Catalytic Reduction of Azo Dyes

Polydopamine-coated Fe3O4 (Fe3O4@PDA) nanoparticles (NPs) were prepared as synergistic redox mediators for the catalytic reduction, by NaBH4, of azo dyes such as methyl orange (MO) and methyl red (MR). Transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) were applied to determine their surface morphology, surface chemistry and detailed chemical composition, respectively. The latter technique confirmed the presence of quinone moieties. Moreover, a vibrating sample magnetometer (VSM) was used to confirm the superparamagnetic properties of these NPs. The characteristic optical absorption maximum of MO at 462[Formula: see text]nm was used to monitor the decolorization process. This was employed to determine the catalytic activity in the reaction. An enhancement of the catalytic activity of the magnetic-separable Fe3O4@PDA nanocatalyst over that of PDA microspheres (MPs) was observed. Moreover, their reusability and stability were also investigated. A synergistic electron transfer mechanism involving both Fe3O4 and PDA moieties was proposed as follows: the quinone moieties and Fe (III) species in Fe3O4@PDA NPs served as systematic redox mediators, with quinone receiving an electron from NaBH4. The reduced quinone next transfers an electron to the Fe (III) moiety, generating an Fe (II) species that in turn transfers an electron to the azo dye. We determined that this process resulted in enhanced reductive degradation of azo dyes when compared with PDA MPs. Moreover, Fe3O4@PDA NPs could be magnetically separated and recycled. We therefore concluded that these NPs show great potential in the immobilization of homogeneous catalysts in the chemical reduction processes of azo dyes.

Effect of gold loading and TiO2 support composition on the activity of Au/TiO2 photocatalysts for H2 production from ethanol–water mixtures

This paper systematically compares the activity of Au/TiO2 photocatalysts (Au loadings 0–10wt.%) for H2 production from ethanol–water mixtures under UV excitation. Degussa P25 TiO2 was used as the support phase. TEM analyses revealed that the average Au nanoparticle size at all loadings was 5±2nm, with the Au nanoparticles preferentially located at the interfacial sites between TiO2 crystallites. XRD, XRF, XPS, and UV–Vis measurements established that metallic Au was the only gold species on the surface of the photocatalysts. The Au/TiO2 photocatalysts showed an intense absorption maximum centred around 560–570nm due to the localised surface plasmon resonance (LSPR) of the supported gold nanoparticles. Photoluminescence measurements revealed that gold nanoparticles effectively suppress electron–hole pair recombination in TiO2, even at low Au loadings. All of the Au/TiO2 photocatalysts displayed high activity for H2 production from ethanol–water mixtures under UV irradiation, with the highest activities observed in the Au loading range 0.5–2wt.% (H2 production rate 31–34mmolg−1h−1). In order to deconvolute the role of the P25 TiO2 support in promoting H2 production, anatase and rutile nanoparticles were isolated from P25 TiO2 by selective chemical dissolution and then functionalised with gold nanoparticles (3wt.% loading, size 5±2nm). The H2 production activity of the resulting Au/anatase and Au/rutile photocatalysts was 22 and 10mmolg−1h−1, respectively, and substantially lower than the corresponding Au/P25 TiO2 photocatalyst (32mmolg−1h−1). The data provide strong evidence that synergistic electron transfer between the TiO2 polymorphs and supported Au nanoparticles is responsible for the high rates of H2 production observed in the Au/P25 TiO2 system. The interface between anatase and rutile crystallites, where gold nanoparticles preferentially deposit, is identified as a photocatalytic ‘hot spot’ for H2 production. High Au loadings reduce the efficiency of such ‘hot spots’.

Chloroplasts-mediated biosynthesis of nanoscale Au-Ag alloy for 2-butanone assay based on electrochemical sensor

We reported a one-pot, environmentally friendly method for biosynthesizing nanoscale Au-Ag alloy using chloroplasts as reducers and stabilizers. The prepared nanoscale Au-Ag alloy was characterized by UV–visible spectroscopy, X-ray diffraction (XRD) and high resolution transmission electron microscopy (HR-TEM). Fourier transform infrared spectroscopy (FTIR) analysis was further used to identify the possible biomolecules from chloroplasts that are responsible for the formation and stabilization of Au-Ag alloy. The FTIR results showed that chloroplast proteins bound to the nanoscale Au-Ag alloy through free amino groups. The bimetallic Au-Ag nanoparticles have only one plasmon band, indicating the formation of an alloy structure. HR-TEM images showed that the prepared Au-Ag alloy was spherical and 15 to 20 nm in diameter. The high crystallinity of the Au-Ag alloy was confirmed by SAED and XRD patterns. The prepared Au-Ag alloy was dispersed into multiwalled carbon nanotubes (MWNTs) to form a nanosensing film. The nanosensing film exhibited high electrocatalytic activity for 2-butanone oxidation at room temperature. The anodic peak current (Ip) has a linear relationship with the concentrations of 2-butanone over the range of 0.01% to 0.075% (v/v), when analyzed by cyclic voltammetry. The excellent electronic catalytic characteristics might be attributed to the synergistic electron transfer effects of Au-Ag alloy and MWNTs. It can reasonably be expected that this electrochemical biosensor provided a promising platform for developing a breath sensor to screen and pre-warn of early cancer, especially gastric cancer.