Reduction Peak Potential Research Articles

Electrochemical Discrimination of Dihydroxybenzene Isomer at Different Thiols Self-Assembled Monolayers on Gold and Simultaneous Determination of Catechol and Hydroquinone

The discrimination effect of dihydroxybenzene isomer including catechol (CAT), hydroquinone (HQ) and resorcinol (RE) on bare gold, and a series of thiols self-assembled monolayers (SAMs) including mercaptohexanol (MCH), 6-mercaptohexanoic acid (MHA), mercaptoethylamine (MEA), thiol-modified double-stranded DNA (ds-DNA), single-stranded DNA (ss-DNA) is first investigated by cyclic voltammetry (CV) and linear scan voltammetry (LSV). Results show that CAT, HQ and RE can not be electrochemically discriminated simultaneously by bare gold or thiols SAMs based on their oxidation or reduction peaks. Furthermore, RE has a big interference on the electrochemical response of CAT and HQ. At acidic solution (pH 4.4), in presence of RE, CAT and HQ can not be discriminated on bare gold, ds-DNA or ss-DNA SAMs. However, CAT and HQ can be discriminated well at MCH, MHA, and MEA SAMs on gold based on the difference of reduction peak potentials (ΔE pc) as 219, 212 and 165 mV respectively. MCH SAMs is chosen to study simultaneous determination of CAT and HQ due to bigger ΔE pc and current response. We fix the potential at 0.7 V for 60 s to enrich the oxidation products of CAT and HQ, then investigated the relationships of reduction peak current (i pc) with the concentrations of CAT and HQ. The i pc values are linear with the concentrations of CAT and HQ in the range of 7.0 × 10−6∼1.04 × 10−3 M. The limit of detection (LOD) is calculated to be 5.9 × 10−7 M for CAT and 8.3 × 10−7 M for HQ (S/N = 3). The MCH SAMs on gold is applied to the simultaneous determination of CAT and HQ in lake water sample and satisfactory result is obtained.

Synthesis, characterization, and cyclic voltammetry of nickel sulphide and nickel oxide nanoparticles obtained from Ni(II) dithiocarbamate

Nickel sulphides and nickel oxides nanoparticles have been synthesized from Ni(II) bis (N-alkyl-N-ethanoldithiocarbamate), represented as NiL12 (L1, with methyl group) and NiL22 (L2, with ethyl group). Both complexes were characterized using Fourier transform infra-red (FTIR), nuclear magnetic resonance spectroscopy and elemental analysis. The sulphides were prepared by solvothermal route in hexadecylamine, and X-ray diffraction analyses revealed that Heazlewoodite Ni3S2 and hexagonal α-NiS1.19 were the phases obtained from compounds NiL12 and NiL22 respectively. The nickel oxides nanoparticles were synthesized via calcination process in air, and presented as NiO1 and NiO2 of which both oxides are Bunsenite phase. The optical and morphology of the nanoparticles were studied using UV–visible spectroscopy and transmission emission microscopy (TEM) techniques. Cyclic voltammetry (CV) and impedance spectroscopy were used for their electrochemical evaluation in 1 M NaOH solution. The Au/NiO2 modified electrode was more electroactive and displayed faster electron transport at the electrode surface than the bare Au and Au/NiO1 electrodes. The modified Au/NiS electrode, showed poor voltammogram which could be due to the poor interaction between the nanoparticles and the electrolyte solution, while the CV of uncapped NiS showed redox peak with oxidation peak potential at 0.36 V and the reduction peak potential at 0.30 V.

Electroreduction of CO2 using modified boron-doped diamond electrode as the working electrode

Electroreduction of CO2 becomes a popular study to resolve the problems due to the increase of CO2 in atmosphere. In this work, electroreduction of CO2 was studied using various working electrodes in 0.1 M NaCl solutions. A reduction peak potential around -1.5, -1.1 and -1.2 V, respectively, was observed at BDD, Cu, Cu-BDD, while Cu2O-BDD with different deposition times showed typical peaks at around -1.3 V. Liquid chromatography analysis on the solutions after CO2 electroreduction at the applied potential of -1.3 V (vs Ag/AgCl) showed that by using BDD and Cu electrodes only formic acid and formaldehyde could be produced. However, the use of various Cu2O concentrations deposited on BDD electrodes can produce not only formic acid and formaldehyde, but also acetic acid and methanol with high selectivity of the products, indicating the electrode is promising to have more various products in the electrochemical reduction of CO2.

Heteroatom doped carbon nanosheets from waste tires as electrode materials for electrocatalytic oxygen reduction reaction: Effect of synthesis techniques on properties and activity

The effective method for synthesis of heteroatom doped carbon nanosheets (CNS) from waste tires was developed. The process employed NiO loaded CaCO3 catalyst for catalytic chemical vapor deposition (CCVD) of the CNS from the non-condensable pyrolysis gas. The promotion of CaCO3 with NiO had beneficial effect on carbon growth compared to pure CaCO3, increasing the carbon yield by 2.8 and 8.0 times for the CCVD at 700 and 750 °C, respectively. On the contrary, the morphology and structure of synthesized S,O-doped CNS as well as oxygen reduction reaction (ORR) electrocatalytic activity were not influenced by the NiO addition. Based on the carbon yields and ORR electrocatalytic activities, the preferred CCVD temperature was 700–750 °C, resulting in the CNS with the ORR peak reduction potentials of −0.217 V to −0.220 V (versus −0.167 V for Pt electrode). The improvement of CCVD process was proposed decreasing the ORR peak reduction potential to −0.191 V. A mixture of NH3 and H2O was added to pyrolysis gas, promoting the development of mesoporosity and incorporation of N into the material structure. The developed technique is a viable solution for the conversion of non-condensable gases from tire pyrolysis into S,N,O-doped CNS for ORR.

State-Dependent Photochemical and Photophysical Behavior of Dithiolate Ester and Trithiocarbonate Reversible Addition-Fragmentation Chain Transfer Polymerization Agents.

The rise in popularity of photochemically initiated reversible addition-fragmentation chain transfer (RAFT) polymerization (photoRAFT) along with the broad spectrum of proposed, and possible, initiation mechanisms result in the need for careful characterization of the photophysical properties of some common RAFT agents. Direct irradiation of the RAFT agent as a means to generate radicals, also known as the photoiniferter mechanism, is one commonly proposed mechanism. The current study shows that dithioesters and trithiocarbonates have the lowest singlet and triplet excited-state energy levels that are close to, or lower than, the C-S bond dissociation energies. Excitation of these agents into their S1 band results in negligible radical production, while excitation into the S2 band or higher results in the decomposition of dithioesters and trithiocarbonates, resulting in radical formation but with low quantum yields. Likewise, there is significant literature precedence for an electron transfer initiation mechanism, PET-RAFT. It is shown that the dithioesters and trithiocarbonates all show peak reduction potentials at ca. -1.0 V (vs SCE). However, transient absorption spectroscopy studies of the electron transfer from a mediator show that these reactions occur rapidly only when the mediator potential is more negative than -1.2 V (vs SCE).

Electrochemical extraction of metallic Y using solid and liquid double cathodes

To select proper electrode material for the extraction of rare earth elements and purification of salt, double cathode electrolysis cell was designed to compare the extraction of Y on solid and liquid electrodes. The electrode process kinetic and thermodynamic data of Y(III) on liquid Zn electrode and solid Cu electrode were studied employing cyclic voltammetry (CV), open-circuit chronopotentiometry (OCP) and linear polarization (LP), respectively. The thermodynamic results indicated that the reduction peak potentials of (Y–Zn)solution and Zn-rich Y–Zn compound are more positive than that of Cu-richest Y–Cu compound, and the standard molar Gibbs energy of formation for (Y–Zn)solution is smaller than those for Y–Cu compounds, which meant (Y–Zn)solution formed easily. Furthermore, the dynamic properties, such as exchange current densities and charge-transfer resistances of Y(III)/Cu7Y and Y(III)/(Y–Zn)solution couples, were determined employing LP technique. The reaction activation energies for the two couples were also estimated according to the relationship of exchange current density and temperature, which showed the reaction activation energy for Y(III)/Cu7Y couple is larger than that for Y(III)/(Y–Zn)solution couple. To compare to the extraction rate and efficiency, the electrochemical extracting Y on single cathode (solid Cu or liquid Zn) and double cathodes (solid Cu and liquid Zn) was executed by constant current electrolysis under same conditions. The results displayed that the extraction rate and efficiency of metallic Y is higher on liquid Zn electrode in the first 6 h, and only a small amount of metallic Y was deposited on solid Cu electrode in double cathode system.

A multi-methodological inquiry of the behavior of cisplatin-based Pt(IV) derivatives in the presence of bioreductants with a focus on the isolated encounter complexes.

The study of Pt(IV) antitumor prodrugs able to circumvent some drawbacks of the conventional Pt(II) chemotherapeutics is the focus of a lot of attention. This paper reports a thorough study based on experimental methods (reduction kinetics, electrochemistry, tandem mass spectrometry and IR ion spectroscopy) and quantum-mechanical DFT calculations on the reduction mechanism of cisplatin-based Pt(IV) derivatives having two hydroxido (1), one hydroxido and one acetato (2), or two acetato ligands (3) in axial position. The biological reductants glutathione and ascorbic acid were taken into consideration. The presence of a hydroxido ligand resulted to play an important role in the chemical reduction with ascorbic acid, as verified by 15N-NMR kinetic analysis using 15N-enriched complexes. The reactivity trend (1 > 2 > 3) does not reflect the respective reduction peak potentials (1 < 2 < 3), an inverse relationship already documented in similar systems. Turning to a simplified environment, the Pt(IV) complexes associated with a single reductant molecule (corresponding to the encounter complex occurring along the reaction coordinate in bimolecular reactions in solution) were characterized by IR ion spectroscopy and sampled for their reactivity under collision-induced dissociation (CID) conditions. The complexes display a comparable reduction reactivity ordering as that observed in solution. DFT calculations of the free energy pathways for the observed fragmentation reactions provide theoretical support for the CID patterns and the mechanistic hypotheses on the reduction process are corroborated by the observed reaction paths. The bulk of these data offers a clue of the intricate pathways occurring in solution.Graphic abstract.

Voltammetrically Measuring pH of Strong Basic Solution on Au Electrode Modified with Ag3PO4 Shell@Ag Core Nanoparticles

AbstractPrecise determination of pH values of strong basic solution is appealing and challenging. Herein, a voltammetric method for measuring pH of strong basic solution was developed using Ag3PO4 shell@Ag core nanoparticles as a pH indicator. Ag nanoparticles (AgNPs) were electrodeposited on Au electrode surface and then were electrochemically oxidized to form Ag+. A layer of Ag3PO4 was in‐situ formed on the surface of AgNPs by precipitation with PO43− in solution. As an electroactive species, Ag3PO4 can undertake an electrochemical redox reaction and its reduction peak potential is linear with pH values of solution in the range of 10–14. The slope of the linear equation is about −0.0196, which is consistent with that calculated by the Nernst equation. The resultant AgNPs/Ag3PO4 modified electrode has been successfully applied in the determination of pH of strong basic solution. The proposed voltammetic method for measuring pH value overcomes the shortcoming of pH glass electrode under strong basic environments.

High‐performance N, P‐CNL nanocomposites as catalyst for oxygen reduction reaction in fuel cell

Transition metal and heteroatom codoped carbon materials have become the most promising materials to replace commercial platinum carbon (Pt / C) catalysts due to their low cost, high stability, and methanol resistance. In this work, iron-nitrogen and phosphorus codoped carbon nanorod-layer composites (N, P-CNL) derived from phosphorus-doped polyaniline (P-PANI) by phytic acid (PA) and iron salt were successfully obtained after high-temperature pyrolysis. As a result, the N, P-CNL materials exhibited good electrocatalytic performance due to abundant active sites. The N, P-CNL with 50% mass filling ratio of iron salt (named as N, P-CNL-1:1) displayed an enhanced limiting current density of −5.97 mA cm−2 at 1600 rpm and outstanding onset potential (−0.004 V) and oxygen reduction peak potential (−0.144 V). In general, this work can give insights into understanding the mechanism of codoped catalysts and synthesis the catalyst with excellent long-term stability and resistance to methanol crossover and poisoning better than commercial Pt/C.

Co-MOFs with high selectivity and excellent sensitivity for distinguishing isomeric aromatic derivatives

Co(II)-MOF {[Co2(L)2(H2O)6]·2H2O}n (Co-1, H2L = 2,5-pyridine dicarboxylic acid) was syntheized and coated at an Au electrode (AuE) surface to assemble a modified electrode (Co-1/AuE). It was used as a electrochemical sensor for recognizing and distinguishing isomeric aromatic derivatives 1-naphthylamine (1-NA) and 2-naphthylamine(2-NA). The experiments indicated that Co-1 shows excellent electrochemical stability and electro-conductivity, 1-NA or 2-NA can be detected on Co-1/AuE with different reduction peak potentials 0.28 V or 0.38 V, the DPV response of Co-1/AuE to 1-NA or 2-NA is linear at 0.01–0.09 mM with the detection limits as low as 1.477 μM or 1.932 μM, respectively. Furthermore, Co-1/AuE also been used as a chemical sensor for the selectivity detection of 1-NA or 2-NA from both a single interferent component solution and a mimic environment.

Enhanced characteristics and mechanism of Cu(II) removal from aqueous solutions in electrocatalytic internal micro-electrolysis fluidized-bed

For the purification of heavy metal wastewater, internal micro-electrolysis (IME) was considered as an effective method but some disadvantage greatly restricts its application. Electrocatalytic internal micro-electrolysis (ECIME) fluidized bed using iron–carbon particles was proposed to avoid disadvantaging of IME. The principal aim of this study was to investigate the enhanced removal characteristics, mechanism, and kinetic behavior of Cu(II) that none clear before. ECIME reactor shows a better copper removal performance and depends much on the polarization of the external electric field (EEF). Both the reaction rate and removal efficiency of copper electrodeposition improved obviously. Noteworthy is more than 88.0% of Cu(II) in aqueous solutions was removed by enhanced electrodeposition, and only about 10.0% of Cu(II) was absorbed and flocculated through the in situ formed iron hydroxyl compounds. Through scanning electron microscopy (SEM) and electrochemical analysis, copper can effectively electrodeposition on the surface of iron-carbon particles in ECIME reactor and accordingly the enhanced mechanisms were proposed. 1) Iron-carbon particles of ECIME formation of microelectrodes with high surface potential, larger specific area, and active sites through electrode collision and repolarization. 2) Copper electrodeposition on the formed microelectrodes exhibited greater reduction peak potential, reaction overpotential and exchange current density, which influenced by the polarization voltage significantly. 3) The electrocatalytic environment tend to in situ generate iron polymer hydroxyl compounds help to further remove residual Cu(II). ECIME fluidized-bed has promised potential for heavy metal containing wastewater purification and metal recovery. In addition, the proposed reaction models will be useful for field application.

Preparation of lithium iron phosphate composites by electrodeposition with a tunnel structure on aluminium foil surface

In this paper, aluminium foil with a tunnel structure was used as a cathode to prepare a lithium iron phosphate composite by electrochemical deposition using propylene carbonate as the electrolyte solvent, and lithium nitrate, ferric nitrate and phosphoric acid as raw materials. The results show that the positive electrode composite is composed of a mixture of an olivine structured LiFePO4 and polyanion Li9Al3P8O29. The chemical composition of the mixture is related to the voltage of the electrochemical deposition and the acidity of the electrolyte solution. For a voltage of 1.8V and pH of 1.0, the composite material deposited in the tunnel of the aluminium foil takes the form of a one-dimensional nanotube, with a particle size ranging from 80nm to100nm. The composite material is closely combined with the aluminium foil. The aluminium foil can be directly used as a positive current collector, with a lithium sheet as the negative electrode. After mounting into a battery, an electrochemical performance test is performed. The battery test results show an initial discharge capacity of 95mAh/g, 79mAh/g and 59mAh/g at 0.1C, 0.2C and 0.5C, respectively. After the material is doped with magnesium and cobalt, the initial discharge capacity of the battery is 100mAh/g and 130mAh/g, respectively, at a rate of 0.1C. The cyclic voltammetry analysis of the battery show that after electrochemical deposition of the element, the symmetry between the oxidation and reduction peaks is increased, and the difference between the oxidation and reduction peak potentials is reduced. Element doping improves battery cycle performance. The AC impedance analysis show that the embedding impedance for lithium ions at the SEI interface is reduced from 300Ω to 250Ω, 100Ω after doping with magnesium, and cobalt. And the reaction mechanism of electrochemical deposition is discussed.

Metallo‐Corroles Supported on Carbon Nanostructures as Oxygen Reduction Electrocatalysts in Neutral Media

In this work, we report the investigation of Fe and Co triphenylcorrole complexes supported on two different carbon supports as eletrocatalysts for the ORR in neutral pH media, comparing their performances with the corresponding tetraphenylporphyrin complexes. Cyclic voltammetry experiments were acquired in neutral phosphate buffer demonstrating that corroles exhibit a superior catalytic activity towards ORR than porphyrins, as demonstrated by more positive oxygen reduction peak potential (Epr) and half‐wave potential (E1/2) values of corroles. Also, iron complexes performed better than cobalt ones, showing an ORR activity even superior to that of platinum taken as reference, as demonstrated by RDE experiments. We investigated the role of the axial ligand on the ORR activity of the macrocycles, and we found that Epr and E1/2 values are more positive along the series: PPh3Co &lt; py2Co = µ‐oxoFe2 &lt; FeCl. By contrast, there was not much difference in activity supporting the porphyrinoids on carbon nanotubes or carbon black pearls, indicating that the effect of carbon support is less important to that of the axial ligand. The results allowed pointing at iron corroles as a promising class of molecular catalysts for application as cathodes in biolectrochemical systems at neutral pH, such as microbial fuel cells.

Voltammetric H/D Isotope Effects on Redox‐Active Small Molecules Conjugated with DNA Self‐Assembled Monolayers

AbstractThis paper describes the largest H/D kinetic isotope effect (KIE) at room temperature (25 °C) reported to date (kH/kD=2400). In voltammetric measurements with DNA monolayers on gold electrodes, a maximum shift of −400 mV was recorded for the reduction peak potential of 50 μM hexammine cobalt(III) (CoHex) in 10 mM Tris buffer upon replacing water with deuterium oxide in the electrolyte. In subsequent comparative investigations, a much smaller shift (ca. −80 mV) was recorded with daunomycin, whereas no potential shift was recorded with hexammine ruthenium(III) (RuHex). The interactions of RuHex, CoHex, and daunomycin with a mixed self‐assembled monolayer of single‐stranded DNA and 6‐mercapto‐1‐hexanol (ssDNA/MCH SAM) immobilized on gold electrodes were studied by using cyclic and differential‐pulse voltammetry (CV and DPV, respectively). The hydrogen‐bond network within the ssDNA layer seems to amplify the voltammetric H/D isotope effect with CoHex. Voltammetric studies of H/D isotope effects can provide a platform to investigate amplified isotope effects probably not only on DNA layers, but also on proteins and small organic molecules and may be useful for studies of cell proliferation as well as drug testing.

New series of water-soluble thiosemicarbazones and their copper(II) complexes as potentially promising anticancer compounds

New water soluble thiosemicarbazone ligands, namely 3-(3-{[(aminocarbonothioyl) hydrazono]methyl}-4-hydroxybenzyl)-1-methyl-1H-imidazol-3-ium chloride (H2L1Cl), 3-[4-hydroxy-3-({[(methylamino)carbonothioyl]hydrazono}methyl)benzyl]-1-methyl-1H-imidazol-3-ium chloride (H2L2Cl) and 3-(3-{[(anilinocarbonothioyl)hydrazono]methyl}-4-hydroxybenzyl)-1-methyl-1H-imidazol-3-ium chloride (H2L3Cl) were synthesized through 1:1 condensation reaction of thiosemicarbazide derivatives with 3-(3-formyl-4-hydroxybenzyl)-1-methyl-1H-imidazole-3-ium chloride (SalimiCl) and characterized by elemental analysis and spectroscopic methods (UV–Vis, 1H NMR, FTIR). Single crystals of H2L1Cl and H2L2Cl were prepared for crystallographic analysis, which showed similar X-ray structures for both ligands with chiral P212121 space group. The ligands were used for synthesis of the following copper(II) complexes: [Cu(HL1)Cl]Cl, [Cu(HL2)Cl]Cl·H2O, and [Cu(HL3)Cl]Cl. All complexes were characterized by physico-chemical and spectroscopic methods. The X-ray structure of [Cu(HL1)Cl]Cl was orthorhombic with Pcba space group while [Cu(HL2)Cl]Cl·H2O was triclinic with Pī space group. Both complexes were mononuclear, with tridentate ligands in a thione form. All of the studied compounds showed good solubility and stability in water. The measurement of the molar conductance showed the release of Cl− into solution and substitution of water instead of the coordinated chloride. Among the studied complexes, only [Cu(HL3)Cl]Cl shows a quasi-reversible redox behavior with its reduction and oxidation peak potentials separated by a value of about 0.120V (Epc=−0.310V and Epa=−0.190V) indicating one-step and one-electron transfer for CuII/CuI redox couple. The cytotoxic effect of the compounds was measured using the MTT assay on MCF-7 and K562 cell lines and the results showed that [Cu(HL3)Cl]Cl and H2L3Cl had lower IC50 values compared to the other compounds. Flow cytometry analysis on the MCF-7 cells showed the apoptosis cell death after treating with the H2L3Cl and [Cu(HL3)Cl]Cl. Also studies of cell cycles confirmed the cell cycle arrest in G2 phase for H2L3Cl and [Cu(HL3)Cl]Cl.

Synthesis and characterization of electrodeposited lead telluride films on copper and stainless steel substrate

In the current work, Lead Telluride (PbTe) thin films were grown on stainless steel and copper substrate two electrode electrodeposition technique. Orthorhombic structure of PbTe was determined by x-ray diffraction (XRD) on both substrates. The smooth and non- uniform surface morphology of PbTe film with a crack free appearance was observed on the substrate by SEM micrograph. Presence of orthorhombic crystalline phase of PbTe film was observed by Raman spectra of the synthesized film. Presence of different stretching and bending modes in deposited PbTe film on stainless steel and copper substrate are observed by Fourier Transform Infrared Spectroscopy (FTIR). Cyclic voltammetry at various scan rates gives oxidation and reduction peak potential of the Pb2+ and HTeO2+ was study. PbTe film on stainless steel and copper shows hydrophilic nature shown by the contact angle measurements.

Phenolic profiling and antioxidant capacity of Morchella esculenta L. by chemical and electrochemical methods at multiwall carbon nanotube paste electrode

The present investigation was carried out to know the aboriginal usage of Morchella esculenta L. as an ethnomedicinal food by tribals of Kashmir, an extreme northern state of India for curing of arthritis, osteoporosis, general bone weakness and cure child labour pain and post menopause pain of women. The average long-life expectancy (~ 80 years) and delayed aging ensured the abundant use of M. esculenta L. as the bases of their daily foods as well as their traditional medicine. The antioxidant character of this mushroom was carried out by chemical and electrochemical assays. The chemical assay was done by DPPH, nitric- oxide, super-oxide scavenging and reducing power while as, electrochemical assay was done by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) using multi-wall carbon nanotube paste electrode (MWCNTPE) at 0.02 M acetate buffer (pH 4.5). The phenolic profiling of the mushroom was evaluated through Folin–Ciocalteu reagent using gallic acid/ascorbic acid as standard which were qualified and quantified by HPLC-UV technique, respectively. The IC50 values found were 57.02 µg ml−1, 58.02 µg ml−1 and 40.01 µg ml−1 for DPPH, nitric-oxide and superoxide. The electrochemical results have shown one oxidation potential at 1.12 V and positive potential at 1.119 ± 0.01 V in CV and 1.19 V in DPV. DPV at superoxide radical scavenging level of mushroom at dropping mercury electrode (DME) in 0.1 M KCl, produced a reduction peak potential at − 0.160 V. HPLC-UV have confirmed the presence of eight phenolic compounds namely, p-coumaric acid, tocopherol, catechol, rutin, hyperoside, quercetin, ellagic acid and cinnamic acid with quercetin at highest percentage (169.76%).

Chitosan modified Cu2O nanoparticles with high catalytic activity for p-nitrophenol reduction

Chitosan modified cuprous oxide (Cu2O-CTS) were prepared via facile chemical reduction method. The morphology and structure of Cu2O-CTS nanoparticles were characterized by transmission electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and UV–vis diffuse reflectance spectroscopy. The catalytic ability of Cu2O-CTS, both in photocatalysis and electrocatalysis, was carried out on p-nitrophenol reduction. In comparison with the pristine Cu2O, Cu2O-CTS exhibits improved photocatalytic abilities with the reduction rate increased by 1.7 times. The catalytic capacity increases along with the increased proportion of CTS in Cu2O-CTS nanoparticles. Cu2O-CTS modified electrodes shows enhanced electrocatalytic capacities as well, with more positive reduction peak potential and higher peak current. Based on the experimental results, a catalytic mechanism for p-NP reduction over Cu2O-CTS catalysts is proposed. The improvement might come from the reduced band gap energy after the chitosan modification, thus Cu2O-CTS nanoparticles have higher catalytic activity. On the other hand, the more beneficial (111) crystal surface involves in the improvement as well, which endows Cu2O-CTS stronger activity and interaction with p-nitrophenol.

Biocatalytic C=C Bond Reduction through Carbon Nanodot-Sensitized Regeneration of NADH Analogues.

Light-driven activation of redox enzymes is an emerging route for sustainable chemical synthesis. Among redox enzymes, the family of Old Yellow Enzyme (OYE) dependent on the nicotinamide adenine dinucleotide cofactor (NADH) catalyzes the stereoselective reduction of α,β-unsaturated hydrocarbons. Here, we report OYE-catalyzed asymmetric hydrogenation through light-driven regeneration of NADH and its analogues (mNADHs) by N-doped carbon nanodots (N-CDs), a zero-dimensional photocatalyst. Our spectroscopic and photoelectrochemical analyses verified the transfer of photo-induced electrons from N-CDs to an organometallic electron mediator (M) for highly regioselective regeneration of cofactors. Light triggered the reduction of NAD+ and mNAD+ s with the cooperation of N-CDs and M, and the reduction behaviors of cofactors were dependent on their own reduction peak potentials. The regenerated cofactors subsequently delivered hydrides to OYE for stereoselective conversions of a broad range of substrates with excellent biocatalytic efficiencies.

Biocatalytic C=C Bond Reduction through Carbon Nanodot‐Sensitized Regeneration of NADH Analogues

AbstractLight‐driven activation of redox enzymes is an emerging route for sustainable chemical synthesis. Among redox enzymes, the family of Old Yellow Enzyme (OYE) dependent on the nicotinamide adenine dinucleotide cofactor (NADH) catalyzes the stereoselective reduction of α,β‐unsaturated hydrocarbons. Here, we report OYE‐catalyzed asymmetric hydrogenation through light‐driven regeneration of NADH and its analogues (mNADHs) by N‐doped carbon nanodots (N‐CDs), a zero‐dimensional photocatalyst. Our spectroscopic and photoelectrochemical analyses verified the transfer of photo‐induced electrons from N‐CDs to an organometallic electron mediator (M) for highly regioselective regeneration of cofactors. Light triggered the reduction of NAD+ and mNAD+s with the cooperation of N‐CDs and M, and the reduction behaviors of cofactors were dependent on their own reduction peak potentials. The regenerated cofactors subsequently delivered hydrides to OYE for stereoselective conversions of a broad range of substrates with excellent biocatalytic efficiencies.