Catalytic Rate Constant Research Articles

Facile synthesis of porous hollow Au nanoshells with enhanced catalytic properties towards reduction of p-nitrophenol

We presented a facile synthesis of porous hollow Au nanoshells (PHASs) with excellent catalytic properties by galvanic replacement and dealloying process. The addition amount of HAuCl4 during galvanic replacement played the important role in controlling structure, catalytic and optical properties of PHASs. The PHASs exhibited shorter induction time and highly catalytic rate constant towards reduction of p-nitrophenol by NaBH4. The catalytic rate constant of PHASs (17.2 × 10−3 s−1) was 25 times that of sacrificial Ag particles, 4.2 times that of Ag@Au with dense Au shell and 1.5 times that of Ag-Au alloys at same particle concentration. The normalized rate constant of PHASs (143 s-1 mmol−1) was 5.3 times that of Ag@Au and 1.6 times that of Ag-Au alloys. The as-synthesized PHASs with unique structures and tunable properties have fantastic potential applications in catalysis, biosensors, drug delivery and cancer therapy.

Photochemically Synthesized Ruthenium Nanoparticle-Decorated Carbon-Dot Nanochains: An Efficient Catalyst for Synergistic Redox Reactions.

Ruthenium nanoparticle (NP)-decorated carbon dots (Ru/C-dots) were fabricated as a potential catalyst in the application of both oxidation and reduction. The photochemical method was used to synthesize Ru/C-dot nanohybrids. The as-prepared Ru/C-dots exhibited a core-shell-based nanochain structure, in which the spherical nature of C-dots further evolved to a layer structure to homogeneously encapsulate Ru NPs. Such Ru/C-dots have excellent catalytic properties, which were demonstrated in the oxidation of flavonoids and concomitantly reduction of inorganic complex and organic dyes, each yielding a high catalytic rate constant. We also proposed an appropriate catalytic mechanism for each reaction. Higher catalytic activity was achieved by the synergistic effect of the encapsulated Ru NPs and the C-dots layer. Further, this nanohybrid was successfully applied to inspect a real aqueous sample. We anticipated that Ru/C-dots nanohybrid may open up a broad platform for the design of efficient multifunctional catalysts.

Modulation of conformational equilibrium by phosphorylation underlies the activation of deubiquitinase A

Deubiquitinases deconjugate ubiquitin modifications from target proteins and are involved in many cellular processes in eukaryotes. The functions of deubiquitinases are regulated by post-translational modifications, mainly phosphorylation and ubiquitination. Post-translational modifications can result in subtle changes in structural and dynamic properties, which are difficult to identify but functionally important. In this work, we used NMR spectroscopy to characterize the conformational properties of the human deubiquitinase A (DUBA), a negative regulator of type I interferon. DUBA activity is regulated by phosphorylation at a single serine residue, Ser-177. We found that the catalytic rate constant of DUBA is enhanced by phosphorylation. By comparing NMR and enzyme kinetics data among different forms of DUBA with low and high activities, we concluded that a two-state equilibrium that was present only in phosphorylated DUBA is important for DUBA activity. Our results highlight the importance of defining conformational dynamics in understanding the mechanism of DUBA activation.

Elucidating the Catalytic Reaction Mechanism of Orotate Phosphoribosyltransferase by Means of X-ray Crystallography and Computational Simulations

Orotate phosphoribosyltransferase (OPRTase) catalyzes the reaction between the ribose donor α-d-5-phosphoribosyl-1-pyrophosphate (PRPP) and orotate (OA) in the presence of Mg2+ ion to obtain pyrophosphate and pyrimidine nucleotide orotidine 5′-monophosphate (OMP), a key precursor in de novo biosynthesis of pyrimidine nucleotides. In this work, several structures of the dimeric Escherichia coli OPRTase (EcOPRTase) have been determined at high resolution, and kinetic measurements have been carried out to obtain the catalytic rate and Michaelis constants. Molecular dynamics (MD) simulations have been carried out, and structural analysis from the X-ray and MD simulation structures reveals conformational changes related to the flexible catalytic loop that establishes hydrogen bond interactions with the pyrophosphoryl group of PRPP. It is proposed that the OA substrate can be in equilibrium in its tautomeric forms. Starting from the most stable tautomeric form, all the plausible mechanisms have been explored by...

Enhanced visible light photocatalytic activity of g-C3N4 via the synergistic effect of K atom bridging doping and nanosheets formed by thermal exfoliation

In this study, a type of novel K doped g-C3N4 nanosheets (KCNN) was synthesized by combining K atom bridging doping and thermal exfoliation for the first time. The as-synthesized KCNN had a very efficient ability of photocatalytic degradation of RhB by visible light, and its catalytic rate constant was 8.3 times higher than that of pure g-C3N4. This excellent photocatalytic performance came from the bridging doping of K atom and the morphology of the KCNN nanosheets. The KCNN nanosheets not only had the advantage of the large specific surface area, but also enhanced the electron-hole separation by shortened charge-to-surface migration length. In addition, the bridging doping of K atom increased the absorption of visible light, and promoted the separation of electron-hole due to electrostatic and bridging effects. Our work not only provided a promising material for effective removal of dye contaminants from wastewater but also opened a new window for the mechanism of electron and hole (e− and h+) separation in doped modified and dimensionality tuning materials.

Characterization of Au-Ag nanoparticles biosynthesized by fungus Mariannaea sp. HJ

Biosynthesis of gold-silver alloy nanoparticles (Au-AgNPs) is a simple operation and ecological friendly, but with limited reports on the availability of fungal resources. In this study, cell-free extracts of Mariannaea sp. HJ was used to synthesize Au-AgNPs, and the effects of the different ratios of Au and Ag ion concentrations on the synthesis of Au-AgNPs were also studied. The results clearly showed that the ratio of Au and Ag ion concentrations had an impact on the composition of Au-AgNPs. With the Ag ion increasing, the color of culture supernatant changed from light purple to brown and an obvious blue shift of characteristic absorption peak was observed in UV-vis spectra, indicating an increase of the percentage of Ag in the Au-AgNPs. Transmission electron microscope showed that the morphologies of the Au-AgNPs were mainly spherical and pseudo spherical, and the average particle sizes of the Au-AgNPs at three different ion concentrations, including 0.5:0.5, 0.5:1.5 and 0.5:3.0, were 19.24 nm, 15.99 nm and 19.33 nm, respectively. X-ray diffraction results showed that the Au-AgNPs had a surface-centered cubic structure. Fourier transform infrared spectroscopy was used to characterize and speculate the involvement of -OH, -NH₃ and -COOH functional groups in the reduction and stability process of Au-AgNPs. Furthermore, 4-nitrophenol (4-NP) was used to explore catalytic activity of Au-AgNPs. Catalytic experiments demonstrated that the Au-AgNPs had a good catalytic activity on 4-NP reduction with a catalytic reaction rate constant of 7.85×10⁻³ s⁻¹. In brief, the present study suggested that Mariannaea sp. HJ could synthesize Au-AgNPs with good dispersity, and had a potential application in the catalytic reduction of nitro aromatic hydrocarbons.

Photocatalytic Hydrogen Production Based on a Serial Metal‐Salen Complexes and the Reaction Mechanism

AbstractThree metal‐salen (Ni, Cu, Zn) complexes were firstly introduced into homogeneous photocatalytic hydrogen‐evolution systems. Based on these complexes, we developed noble‐metal‐free hydrogen production systems using disodium salts of Eosin Y (EY2−) as photosensitizers and trimethylamine (TEA) as sacrificial donors. In a Ni(II)‐salen/EY2−/TEA system, a TON of 362 based on Ni(II)‐salen was achieved in 5.5 h with one time complement for EY2−. The stability study revealed the quick photodecomposition of EY2− in the presence of ether Ni(II)‐salen, TEA or both chemicals, and quick dehalogenation of EY2− was observed in the presence of TEA under irradiation. Besides, relatively slower photodecomposition of Ni(II)‐salen was also found. These factors should be responsible for the deactivation of the photolysis system. Investigation of electrocatalytic proton reduction by Ni(II)‐salen showed a CECE mechanism. An overall catalytic rate constant of 7.62×106 M−2 s−1 was achieved. Combined with the stability analysis, photo‐induced electron transfer and electrochemistry investigation, for the first time, the photocatalytic hydrogen production mechanism for metal‐salen complexes (e. g. Ni(II)‐salen) was proposed.

Construction of detachable core/shell Fe3O4@C supported noble metal catalysts and their catalytic performance

In this article, magnetically responsive catalysts were successfully synthesized by host-guest chemistry and self-assembly strategy. Firstly, β-cyclodextrin (β-CD) was bound directly to the surface of core/shell magnetic Fe3O4@C (MFC) using chemical bonding methods. Then, in view of the host-guest recognition, p-aminothiophenol (pATP) was captured by β-CD to form inclusion complex on the surface of MFC. Lastly, pre-synthesized gold, silver, platinum nanoparticles (AuNPs, AgNPs, PtNPs) could be adsorbed on the surface of MFC@β-CD-pATP through self-assembly strategy to fabricate ternary composites MFC@β-CD-pATP@metal nanoparticles. Catalytic reduction reaction of methylene blue using NaBH4 as reducing agent evaluates the catalytic performance of three as-prepared magnetic nanocomposites. MFC@β-CD-pATP@AuNPs catalyst showed the fast catalytic reaction rate constant. Significantly, we have explored the separation of magnetic supports and novel metal nanoparticles under mild conditions. This strategy will become a green and environmental way for highly efficient separation of precious metals catalysts, and recycle and reuse of catalyst carriers.

Determination of the Kinetic Parameters of a Wild-Type D-Amino Acid Oxidase from Yeast and Its Mutant Forms in a Reaction of Cephalosporin C Oxidation

The oxidation of cephalosporin C (CPC) by D-amino acid oxidase is the first stage in the biocatalytic industrial process of the production of 7-aminocephalosporanic acid, the initial synthon for the production of semisynthetic cephalosporin antibiotics. We determined the kinetic parameters (catalytic constant rate and Michaelis constant) of the wild-type recombinant oxidase from the yeast Trigonopsis variabilis (TvDAAO); three mutant forms of the enzyme with point Met-to-Leu substitutions at positions 104, 156, and 209; and the TvDAAO RDAF quadruple mutant using the dependence of the initial reaction rate on the CPC concentration (the initial rate method). The point substitutions in the mutants are shown to lead primarily to a decrease in the Michaelis constant. The largest (39%) increase in catalytic efficiency kcat/KM is observed for the mutant with the Met156Leu substitution. The Michaelis constant for the increased four times compared to that for the wild-type enzyme in the reaction with CPC, whereas the catalytic efficiency remains almost unchanged due to a four-fold increase in the catalytic rate constant.

An efficient platform for the electrooxidation of formaldehyde based on amorphous NiWO4 nanoparticles modified electrode for fuel cells

We prepared a binary transition metal oxide material of nickel tungstate nanoparticles (NiWO4-NPs) through a simple co-precipitation method. The synthesized NPs were characterized using field emission scanning electron microscopy (FE-SEM), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD) and electrochemical impedance spectroscopy (EIS) techniques. NiWO4-NPs represent nearly spherical morphologies with an average size of ~97nm and tungstate as a dominant phase. Carbon paste electrode (CPE) modified with NiWO4-NPs (NiWO4-NPs/CPE) was used for electrooxidation of formaldehyde in alkaline solution. Cyclic voltammetry demonstrated that NiWO4-NPs/CPE electrode can decrease the overpotential for formaldehyde oxidation while increasing the current density in comparison to CPE. The results revealed that the CPE modified with calcined NiWO4-NPs (NiWO4-cal-NPs/CPE) shows less current response to formaldehyde oxidation compared with the amorphous sample. Moreover, the variation of scan rate and concentration of formaldehyde were investigated on the electrooxidation of formaldehyde and the results indicated that the electrooxidation on the NiWO4-NPs/CPE electrode is a diffusion-controlled mechanism. The diffusion coefficient and catalytic rate constant of formaldehyde, evaluated by chronoamperometry, were 40.4×10−4cm2s−1 and 1.37×104cm3mol−1s−1, respectively. Furthermore, we show that the prepared sensor has a wide linear range of 8μM to 1mM and low detection limit of 3.6μM.

Controlled synthesis of mesoporous zinc oxide containing oxygen vacancies in low annealing temperature for photoelectrochemical biosensor

Abstract In this work, a mesoporous zinc oxide containing different concentrations of oxygen vacancies (VO) was controlled synthesized via low temperature annealing. XPS, Raman spectroscopy and electron paramagnetic resonance spectroscopy were employed to investigate the changes of VO concentrations following the increase of annealing temperature. According to the experiment, the highest concentration of VO was obtained at the annealing temperature of 350 °C. The relationship between photoelectrochemical biosensor performance and VO concentration was discussed in detail in terms of electrochemical measurements and VO characterization. Results showed that increasing the VO could result in high carrier intensity, active sites and catalytic rate constant. In addition, the performance toward glucose detection could be improved by increasing VO.

Characterization of electrodes modified with nanocomposites of cobalt tetraaminophenoxyphthalocyanine, reduced graphene and multi-walled carbon nanotubes

Glassy carbon electrodes or plates were modified with nanocomposites consisting of cobalt tetraaminophenoxyphthalocyanine (CoTAPhPc), reduced graphene oxide nanosheets (rGONs) and multi-walled carbon nanotubes (MWCNTs). The modified electrodes were characterized using cyclic voltammetry, scanning electrochemical microscopy (SECM) and time-of-flight-secondary ion mass spectrometer (TOF-SIMS). The electrocatalytic activity of the modified electrode was tested for detection of L-cysteine. The presence of CoTAPhPc on sequential layers of MWCNT and rGONs resulted in improved detection currents compared to CoTAPhPc alone or when MWCNT/rGONs are mixed in CoTAPhPc–MWCNT/rGONs (mix)–glassy carbon electrode (GCE). CoTAPhPc–MWCNT–GCE (without rGONS) showed higher sensitivity toward l-cysteine as compared to the probes incorporating rGONs with a catalytic rate constant of 4.62 × 104 M−1s−1 and a detection limit of 30 nM. The presence of rGONs improved the stability of the electrode.

Palladized dysprosium fluoride nanorods as a new performance catalyst in direct methanol fuel cell

Fuel cells are a new type of batteries that produce electricity from a continuous source of alcohols as long as fuel is inserted. In this study, decorated palladium nanoparticles (PdNPs) on dysprosium fluoride (DyF3) nanorods (DyFNRs)-multiwalled carbon nanotubes (MWCNTs) were used for electrooxidation of methanol. DyFNRs were synthesized by the hydrothermal method, and the proposed multifunctional catalyst (DyFNRs/MWCNT-PdNPs) was identified by several methods such as X-ray diffraction, elemental mapping images, field emission scanning electron microscopy, energy dispersive analysis of X-rays, and transmission electron microscopy which demonstrated a uniform distribution and high dispersion of the PdNPs on the supports. The electrocatalytic activity toward methanol electrooxidation on glassy carbon electrode (GCE) with DyFNRs/MWCNT-PdNPs (DyFNRs/MWCNT-PdNPs/GCE) was investigated by cyclic voltammetry (CV) and chronoamperometry (CA). Experimental results showed a high improvement in oxidation potential and peak current of methanol electrooxidation by DyFNRs/MWCNT-PdNPs in comparison to DyFNRs and PdNPs. The values of the catalytic rate constant (k) and physical dimension (Ds) for methanol oxidation on the DyFNRs/MWCNT-PdNPs/GCE catalyst were calculated 0.008 s−1 and 1.43, respectively. Moreover, the order of reaction was determined to be 0.43 and 0.13 for CH3OH and NaOH, repectively. Finally, the synthesized catalyst was evaluated in direct methanol fuel cell (DMFC). The single DMFC with proposed anodic catalyst, DyFNRs/MWCNT-PdNPs, indicated a power density of 4.4 mW·cm−2 at a current density of 18 mA·cm−2 in alcohol (1 M) and NaOH (1 M).

As Catalytic as Silver Nanoparticles Anchored to Reduced Graphene Oxide: Fascinating Activity of Imidazolium Based Surface Active Ionic Liquid for Chemical Degradation of Rhodamine B

A kinetic study, first of its kind, regarding the catalytic activity of imidazolium-based surface-active ionic liquid (SAIL) viz. 1-dodecyl-3-methyl imidazolium chloride ([DDMIM][Cl]) toward the reductive degradation of a model cationic dye viz. rhodamine B (RhB) is presented. The catalytic activity of the pre and post micellar concentrations of SAIL [DDMIM][Cl], its conventional analogue surfactant dodecyltrimethylammonium bromide ([DTAB]) and silver (Ag) nano-particles anchored to the reduced graphene oxide (Ag-rGO) toward reductive degradation of RhB was explored. The catalytic activity observed for the [DDMIM][Cl] is much better than that of DTAB and is almost comparable to the activity exhibited by Ag-rGO. The catalytic rate constants (kcat) estimated in presence of pre-micellar concentrations of [DDMIM][Cl] (10 mM), DTAB (12 mM) and in presence of Ag-rGO as catalyst were found to be 11.48 × 10−2 min−1, 3.4 × 10−2 min−1 and 14.35 × 10−2 min−1 respectively. The results clearly establish the fascinating catalytic activity (almost comparable to that exhibited by Ag-rGO) of [DDMIM][Cl] for the reductive degradation of a widely used carcinogenic, mutagenic and toxic organic dye of great environmental concern. The presented results are expected to stimulate intense research activities that may uncover new opportunities toward exploitation of the catalytic activity of aqueous SAIL solutions. Surface active ionic liquid [DDMIM][Cl] is significantly more active than its conventional analogue DTAB and almost as active as Ag-rGO in facilitating the NaBH4 assisted chemical degradation of rhodamine B (RhB)-one of the most carcinogenic, mutagenic and toxic organic dyes.

Proton Relay Effects in Pyridyl‐Appended Hydrogenase Mimics for Proton Reduction Catalysis

Hydrogenase enzymes are fast proton reduction catalysts, and their synthetic mimics have been widely studied in the context of solar fuel applications. The mimics are still not nearly as effective as the enzyme, as they lack crucial structural elements, including proton‐relays and electron reservoirs. In this contribution we report di‐iron hydrogenase model complexes of the type Fe2(X4bdt)(PPy3)n(CO)6‐n (X = H, Cl, F; n= 0, 1, 2; PPy3= tris(m‐pyridyl)phosphane), featuring pyridyl‐appended phosphane ligands able to act as proton relays. In organic solvents, in the presence of weak acid, the pyridyl groups remain unprotonated during the catalytic cycle; thus, proton preorganization does not occur, and the complexes display catalytic rate constants in the order of 103 M–1 s–1. Protonation of the pyridine allows for dissolution of the complexes in acidic aqueous media thus facilitating proton pre‐organization, but at the same time counterbalancing the electron‐donating abilities of the phosphane ligands. Catalysis thus occurs at the first reduction potential of the complexes with rate constants up to 108 M–1 s–1, well beyond those observed for the natural enzymes and among the highest reported so far.

Silver oxide nanoparticles in reduced graphene oxide modified electrode for amino acids electrocatalytic oxidation

A glassy carbon electrode (GCE) modified with reduced graphene oxide (RGO) and silver oxide nanoparticles (AgNPs-RGO/GCE) was prepared for electrocatalytic oxidation of amino acids. The modified electrode surface was characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy and Raman spectroscopy. The results showed that the developed AgNPs had a medium diameter of 10±2nm besides being well dispersed on the RGO surface. The electrochemical behavior of the AgNPs-RGO/GCE in the oxidation of glycine, alanine, leucine, aspartic and glutamic acids was carried out by cyclic voltammetry and amperometric techniques. Voltammetric studies indicated a rise in the anodic peak of the silver (III) oxide species in the presence of amino acids. Essentially, this shows that amino acids were oxidized in the redox mediator was electrodeposited on the electrode surface via an electrocatalytic process. Based on Laviron's equation, the values of α and ks for the redox species were found to be 0.51 and 0.61s−1, respectively. The catalytic rate constants of 1.4×108 (alanine) to 5.4×108cm3mol−1s−1 (glycine), the transfer coefficients 0.37 (leucine) to 0.45 (glutamic acid), and the diffusion coefficients of 1.1×10−6 (alanine) to 7.7×10−6cm2s−1 (glycine) for the amino acids are reported. The excellent electrocatalytic activity, high sensitivity and good stability observed in our investigation renders the AgNPs-RGO/GCE promising for application as a suitable sensor for amino acids detection.

CH‐π Interactions Promote the Conversion of Hydroxypyruvate in a Class II Pyruvate Aldolase

AbstractThe class II hydroxy ketoacid aldolase A5VH82 from Sphingomonas wittichii RW1 (SwHKA) accepts hydroxypyruvate as nucleophilic donor substrate, giving access to synthetically challenging 3,4‐dihydroxy‐α‐ketoacids. The crystal structure of holo‐SwHKA in complex with hydroxypyruvate revealed CH‐π interactions between the C−H bonds at C3 of hydroxypyruvate and a phenylalanine residue at position 210, which in this case occupies the position of a conserved leucine residue. Mutagenesis to tyrosine further increased the electron density of the interacting aromatic system and effected a rate enhancement by twofold. While the leucine variant efficiently catalyses the enolisation of hydroxypyruvate as the first step in the aldol reaction, the enol intermediate then becomes trapped in a disfavoured configuration that considerably hinders subsequent C−C bond formation. In SwHKA, micromolar concentrations of inorganic phosphate increase the catalytic rate constant of enolisation by two orders of magnitude. This rate enhancement was now shown to be functionally conserved across the structurally distinct (α/β)8 barrel and αββα sandwich folds of two pyruvate aldolases. Characterisation of the manganese (II) cofactor by electron paramagnetic resonance excluded ionic interactions between the metal centre and phosphate. Instead, histidine 44 was shown to be primarily responsible for the binding of phosphate in the micromolar range and the observed rate enhancement in SwHKA.magnified image

Electrospun CuO-ZnO nanohybrid: Tuning the nanostructure for improved amperometric detection of hydrogen peroxide as a non-enzymatic sensor

Hydrogen peroxide (H2O2) is a by-product of some biochemical processes which is catalyzed by enzymes such as glucose oxidase (GOx), cholesterol oxidase (ChoOx), etc and its overproduction in living cells can trigger cancer growth and various diseases. Therefore, H2O2 sensing is of great importance in the determination of diseases as well as industries and environmental health plans. We produced ZnO-CuO nanofibers by electrospinning method for non-enzymatic electrochemical H2O2 sensing. The sensing properties of the carbon paste electrode (CPE) modified with ZnO (0.3 wt%)/CuO (0.7 wt%) nanofibers (named as ZnO3-CuO7) for detection of H2O2 were explored in phosphate-buffered saline (PBS) at pH ∼ 7.4 solution. The ZnO3-CuO7 nanofiber exhibited the lowest charge transfer resistance and the highest electrocatalytic performance among other modified electrodes for detection of H2O2 and considered as an optimized sample. The effect of scan rate and H2O2 concentration in the reduction process were also investigated by cyclic voltammetry (CV) and the mechanism for the electrochemical reaction of H2O2 at the surface of the optimized electrode was studied. The diffusion coefficient of H2O2 and the catalytic rate constant were evaluated by chronoamperometry as 1.65 × 10−5 cm2 s−1 and 6 × 103 cm3 mol−1 s−1, respectively. Furthermore, amperometric detection of H2O2 with a low detection limit of 2.4 µM and a wide linear range of 3 to 530 µM were obtained. Meanwhile, the optimized electrode displayed no recognizable response towards some biomolecules such as ascorbic acid, uric acid, dopamine and glucose. The obtained results confirmed that the modified electrode shows high sensitivity and selectivity as a H2O2 biosensor with improved reproducibility and stability.

Glucose oxidase mimicking half–sandwich nickel(II) complexes of coumarin substituted N–heterocyclic carbenes as novel molecular electrocatalysts for ultrasensitive and selective determination of glucose

Glucose oxidase mimicking nickel–based porous structures with organic anchors are developed as cheap and reliable electrochemical sensors for the quantitative detection of glucose. A series of sterically and electronically modulated, air– and moisture–stable half–sandwich nickel(II) NHC complexes were prepared and characterized. Under the optimized electrocatalytic conditions, the nickel complex immobilized glassy carbon electrodes (GCEs) displayed high sensitivity (0.663, 1.280, 1.990 and 0.182 μA/μM) towards glucose detection, which is much higher than that of 3D porous nickel networks. The limit of detection of modified GCEs is found in the range 1.56–2.09 μM with much wider linear sensing range, and having a catalytic rate constant of 0.273 × 103 M−1s−1. Finally, the selectivity of the modified GCEs towards glucose in presence of other blood constituents was also evaluated.

Simultaneous Electrochemical Detection of Nitrite and Hydrogen Peroxide Based on 3D Au-rGO/FTO Obtained Through a One-Step Synthesis.

In this paper, Au and reduced graphene oxide (rGO) were successively deposited on fluorine-doped SnO2 transparent conductive glass (FTO, 1 × 2 cm) via a facile and one-step electrodeposition method to form a clean interface and construct a three-dimensional network structure for the simultaneous detection of nitrite and hydrogen peroxide (H2O2). For nitrite detection, 3D Au-rGO/FTO displayed a sensitivity of 419 μA mM−1 cm−2 and a linear range from 0.0299 to 5.74 mM, while for the detection of H2O2, the sensitivity was 236 μA mM−1 cm−2 and a range from 0.179 to 10.5 mM. The combined results from scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopy, X-ray diffraction measurements (XRD) and electrochemical tests demonstrated that the properties of 3D Au-rGO/FTO were attributabled to the conductive network consisting of rGO and the good dispersion of Au nanoparticles (AuNPs) which can provide better electrochemical properties than other metal compounds, such as a larger electroactive surface area, more active sites, and a bigger catalytic rate constant.