CuS/RGO hybrid by one-pot hydrothermal method for efficient electrochemical sensing of hydrogen peroxide

In this study,a non-enzymatic hydrogen peroxide sensor was successfully fabricated on the basis of copper sulfide nanoparticles/reduced graphene oxide(CuS/RGO) electrocatalyst.Using thiourea as reducing agent and sulfur donor,CuS/RGO hybrid was synthesized through a facile one-pot hydrothermal method,where the reduction of GO and deposition of CuS nanoparticles on RGO occur simultaneously.The results confirmed that the CuS/RGO hybrid helps to prevent the aggregation of CuS nanoparticles.Electrochemical investigation showed that the as-prepared hydrogen peroxide sensor exhibited a low detection limit of 0.18μmol/L(S/N = 3),a good reproducibility(relative standard deviation(RSD) of4.21%),a wide linear range(from 3 to 1215 μmol/L) with a sensitivity of 216.9 μA L/mmol/cm~2 under the optimal conditions.Moreover,the as-prepared sensor also showed excellent selectivity and stability for hydrogen peroxide detection.The excellent performance of CuS/RGO hybrid,especially the lower detection limit than certain enzymes and noble metal nanomaterials ever reported,makes it a promising candidate for non-enzymatic H_2O_2 sensors.     

Hydrogen peroxide biosensor based on electrodeposition of zinc oxide nanoflowers onto carbon nanotubes film electrode

A new amperometric biosensor for hydrogen peroxide was developed based on adsorption of horseradish peroxidase at the glassy carbon electrode modified with zinc oxide nanoflowers produced by electrodeposition onto multi-walled carbon nanotubes （MWNTs） film. The morphology of the MWNTs/nano-ZnO electrode has been investigated by scanning electron microscopy （SEM）, and the electrochemical performance of the electrode has also been studied by amperometric method. The resulting electrode offered an excellent detection for hydrogen peroxide at -0.11 V with a linear response range of 9.9×10^-7 to 2.9×10^-3 mol/L with a correlation coefficient of 0.991, and response time 〈5 s. The biosensor displays rapid response and expanded linear response range, and excellent stability.     

A New Amperometric Biosensor Based on HRP/Nano-Au/L-Cysteine/Poly（o-Aminobenzoic acid）-Membrane-Modified Platinum Electrode for the Determination of Hydrogen Peroxide

The third generation amperometric biosensor for the determination of hydrogen peroxide （H2O2） has been described. For the fabrication of biosensor, o-aminobenzoic acid （oABA） was first electropolymerized on the surface of platinum （Pt） electrode as an electrostatic repulsion layer to reject interferences. Horseradish peroxidase （HRP） absorbed by nano-scaled particulate gold （nano-Au） was immobilized on the electrode modified with polymerized o-aminobenzoic acid （poABA） with L-cysteine as a linker to prepare a biosensor for the detection of H2O2. Amperometric detection of H2O2 was realized at a potential of ＋20 mV versus SCE. The resulting biosensor exhibited fast response, excellent reproducibility and sensibility, expanded linear range and low interferences. Temperature and pH dependence and stability of the sensor were investigated. The optimal sensor gave a linear response in the range of 2.99×10^-6 to 3.55×10^-3 mol·L^-1 to H2O2 with a sensibility of 0.0177 A·L^-1·mol^-1 and a detection limit （S/N = 3） of 4.3×10^-7 mol·L^-1. The biosensor demonstrated a 95% response within less than 10 s.     

A Novel Reagentless Biosensor Constructed by Layer-by-Layer Assembly of HRP and Nile Blue Premixed with Polyanion

A novel reagentless biosensor constructed by the organic dye nile blue (NB) and horseradish peroxidase (HRP) has been fabricated via layer-by-layer (LBL) self-assembly technique. NB premixed with polyanion poly (sodium-p-styrenesulfonate) (PSS) acts as the mediator between the immobilized HRP and the electrode surface. The response of the biosensor to hydrogen peroxide has been investigated. The linear range of the biosensor to hydrogen peroxide was from 0.20 mmol/L to 7.03 mmol/L with a sensitivity of 8.45 μA/(mmol/L).     

A simple method to fabricate a Prussian Blue nanoparticles/carbon nanotubes/poly(1,2-diaminobenzene) based glucose biosensor

A novel Prussian Blue nanoparticles/carbon nanotubes/poly(1,2-diaminobenzene) based glucose biosensor was fabricated by a simple and fast method. Firstly, the Prussian Blue (PB) nanoparticles were direct electrodeposited onto the surface of a glassy carbon electrode modified with multiwall carbon nanotubes (MWNTs) in a short time. Then an ultrathin conducting poly(1,2-diaminobenzene) film was electrodeposited onto the surface of PB/MWNTs nanocomposite to immobilize the glucose oxidase via glutaraldehyde cross-linking. The experiments results showed that the stability of the PB nanoparticles was greatly improved by the MWNTs and the PB/MWNTs nanocomposite exhibited an excellent synergistic electrocatalytic effect toward reduction of hydrogen peroxide. The biosensor showed excellent performances toward determination of glucose. The linear range of the glucose biosensor is from 10 μM to 2.5 mM, with a detection limit of about 5 μM. The response is within less than 5 sec. Correspondence: Wanzhi Wei, State Key Laboratory of Chemo/Biosensing and Chemometrics, College of Chemistry and Chemical Engineering, Hunan University, Hunan, Changsha 410082, P.R. China     

Amperometric Hydrogen Peroxide Biosensor Based on Multiwall Carbon Nanotubes and Cadmium Sulfide Quantum Dots

<正>A novel third-generation hydrogen peroxide(H_2O_2) biosensor(Hb/CdS/MWNTs/GCE) was fabricated through hemoglobin(Hb) adsorbed onto the mercaptoacetic acid modified CdS QDs/carboxyl multiwall carbon nanotubes'(MWNTs) films.Cyclic voltammogram of Hb/CdS/MWNTs/GCE showed a pair of well-defined and quasi-reversible redox peaks with a formal potential(E~0) of-0.230 V(vs.Ag/AgCl) in 0.1 mol/L pH=8.0 phosphate buffer solution(PBS),which was the characteristic of the Hb heme Fe(Ⅲ)/Fe(Ⅱ) redox couple.The biosensor shows an excellent electrocatalytic activity to the reduction of H_2O_2.The response time of the designed biosensor to H_2O_2 at a potential of -0.30 V was less than 2 s and linear relationships were obtained in the concentration ranges of 2.0×10~(-6)—2.7×10~(-3) mol/L and 2.7×10~(-3)—7.7×10~(-3) mol/L with a detection limit of 3.0×10~(-7)mol/L(S/N=3).The apparent Michaelis-Menten constant K_m was estimated to be 1.324 mmol/L that illustrated the excellent biological activity of the fixed Hb.     

Porous microtubes of nickel-cobalt double oxides as non-enzymatic hydrogen peroxide sensors

Non-enzymatic electrochemical sensors for the determination of hydrogen peroxide(H_2 O_2) have attracted more and more concerns.A series of nickel and cobalt double oxides(Ni_xCo_y-DO) with the different ratios of Ni/Co have been prepared by a polyol-mediated solvothermal method for H_2 O_2 detection.The obtained products exhibit honeycomb-like open porous microtubes constituted with the low-dimensional nanostructured Ni_xCo_y-DO blocks after the calcination treatment.Compared with nickel oxides,the introduced Co ions in Ni_xCo_y-DO can induce the production of surficial oxygen vacancies,and further enhance the electrode surface activity.In particular,the NiCo-DO sample(with an atomic ratio of Ni/Co=4:3) shows the richest surficial oxygen vacancies and presents the highest H_2 O_2 detection activity among all the as-prepared samples,demonstrating an excellent sensitivity of698.60 μAL mmol ~1 cm~(-2)(0～0.4 mmol/L),low detection limit(0.28 μmol/L,S/N=3),as well as long stability,high selectivity and good reproducibility.This work lends a new impetus to the potential application of double metal oxides for the next generation of non-enzymatic sensors.     

Layer-by-layer immobilization of horseradish peroxidase on a gold electrode modified with colloidal gold nanoparticles

An amperometric biosensor, based on layer-by-layer self-assembly of colloidal gold nanoparticles, cysteine and horseradish peroxidase on Nafion modified electrode surface by electrostatic adsorption, has been used for the determination of hydrogen peroxide. The electrochemical behavior of the multilayer film was studied by cyclic voltammetry, linear sweep voltammetry and chronoamperometry. The step layer-by-layer adsorption interface morphology was further characterized by means of electrochemical impedance spectroscopy and cyclic voltammetry. The performance and factors influencing the resulted biosensor were studied in detail. The sensor displayed an excellent electrocatalytic response to the reduction of H₂O₂ without the aid of an electron transfer mediator. Linear response to H₂O₂ was obtained for the concentration range from 1.6 μM to 2.4 mM under optimized conditions. The detection limit of the biosensor was 0.5 μM (S/N = 3), and the sensor achieved 95% of the steady-state current within 10 s. The sensor exhibited high sensitivity, selectivity and stability. Correspondence: Yan Liu, College of Chemistry, Chongqing Normal University, Chongqing 400047, P.R. China     

The electrochemiluminescent behavior of nickel phthalocyanine（NiTSPc）/H2O2 system on a heated ITO electrode

In this study,the electrochemiluminescent（ECL） behavior of Nickel（Ⅱ） tetrasulfophthalocyanine（NiTSPc）/H₂O₂ on a heated indium tin oxide（ITO） electrode was investigated.The effect of pH value,electrochemical scan mode,concentration of NiTSPc and electrode surface temperature on the ECL intensities had been studied in detail.Based on the fact that the ECL of NiTSPc can be greatly enhanced by hydrogen peroxide at the ITO electrode,a new ECL biosensor for hydrogen peroxide has been developed.The possible mechanism for the ECL of NiTSPc has also been proposed.     

Two-dimensional Nitrogen-doped Mesoporous Carbon/Graphene Nanocomposites from the Self-assembly of Block Copolymer Micelles in Solution

The self-assembly of block copolymer in solution has proven to be an effective strategy for building up a wide range of nanomaterials with diverse structures and applications. This paper reports a facile self-assembly approach towards two-dimensional(2D) sandwich-like mesoporous nitrogen-doped carbon/reduced graphene oxide nanocomposites(denoted as m NC/r GO) with well-defined large mesopores. The strategy involves the synergistic self-assembly of polystyrene-block-poly(ethylene oxide)(PS-b-PEO) spherical micelles, m-phenylenediamine(m PD) monomers and GO in solution and the subsequent carbonization at 900 ℃. The resultant m NC/r GO nanosheets have an average pore size of 19 nm, a high specific surface of 812 m~2·g~(-1) and a nitrogen content of 2.2 wt%. As an oxygen reduction reaction(ORR) catalyst, the unique structural features render the metal-free nanosheets excellent electrocatalytic performance. In a 0.1 mol·L~(-1) KOH alkaline medium, m NC/r GO exhibits a four-electron transfer pathway with a high half-wave-potential(E_(1/2)) of +0.77 V versus reversible hydrogen electrode(RHE) and a limiting current density(JL) of 5.2 mA·cm~(-2), which are well comparable with those of the commercial Pt/C catalysts.     

MOF derived Co3O4/N-doped carbon nanotubes hybrids as efficient catalysts for sensitive detection of H2O2 and glucose

Developing enzyme-free sensors with high sensitivity and selectivity for H2O2 and glucose is highly desirable for biological science.Especially,it is attractive to exploit noble-metal-free nanomaterials with large surface area and good conductivity as highly active and selective catalysts for molecular detection in enzyme-free sensors.Herein,we successfully fabricate hollow frameworks of Co3O4/N-doped carbon nanotubes(Co3O4/NCNTs)hybrids by the pyrolysis of metal-organic frameworks followed by calcination in the air.The as-prepared novel hollow Co3O4/NCNTs hybrids exhibit excellent electrochemical performance for H2O2 reduction in neutral solutions and glucose oxidation in alkaline solutions.As sensor electrode,the Co3O4/NCNTs show excellent non-enzymatic sensing ability towards H2O2 response with a sensitivity of 87.40μA(mmol/L)^-1 cm^-2,a linear range of 5.00μmol/L-11.00 mmol/L,and a detection limitation of 1μmol/L in H2O2 detection,and a good glucose detection performance with 5μmol/L.These excellent electrochemical performances endow the hollow Co3O4/NCNTs as promising alternative to enzymes in the biological applications.     

A high-efficient amperometric hydrazine sensor based on novel electrospun CoFe2O4 spinel nanofibers

HeterojunctionFe_2O_3 nanoparticles(NPs), NiFe_2O_4 nanofibers(NFs), and CoFe_2O_4 NFs were synthesized by electrospinning and the subsequent thermal treatment processes. Characterization results indeed display the three-dimensional net-like textural structures of these as-electrospun spinel-type MFe_2O_4 NFs. The MFe_2O_4 NFs-based film configurations possess abundant micro/meso/macropores on their surface. These structures could afford more accessible transport channels for effective reduction of the mass transport resistance and improvement of the density of exposed catalytic active sites. All these advantages are responsible for the enhanced electro-catalytic performance of these MFe_2O_4 NFs in hydrazine oxidation. When used for hydrazine detection, CoFe_2O_4 NFs show the best catalytic efficiency.For example, the CoFe_2O_4 NFs possess a large sensitivity of 1327 mA cmà2(mmol Là1[à1in the linear range of 0.01 to 0.1 mmol Là1and 503 mA cmà2(mmol Là1)à1in the linear range of 0.1 to 11 mmol Là1, a response time of shorter than 3 s, good reproducibility and remarkable long-term stability. The superior catalytic efficiency, excellent stability, low cost, and ease of fabrication render CoFe_2O_4 NFs very promising materials in developing an electrochemical device that directly detects hydrazine.     

Chlorophyll sensitized BiVO4 as photoanode for solar water splitting and CO2 conversion

Converting solar energy into valuable hydrogen and hydrocarbon fuels through photoelectrocatalytic water splitting and CO_2 reduction is highly promising in addressing the growing demand for renewable and clean energy resources. However, the solar-to-fuel conversion efficiency is still very low due to limited light absorption and rapid bulk recombination of charge carriers. In this work, we present chlorophyll(Chl) and its derivative sodium copper chlorophyllin(ChlCuNa), as dye sensitizers, modified BiVO_4 to improve the photoelectrochemical(PEC) performance. The photocurrent of BiVO_4 is surprisingly decreased after a direct sensitization of Chl while the sensitization of ChlCuNa obviously enhances photocurrent of BiV04 electrodes by improved surface hydrophilicity and extended light absorption.ChlCuNa-sensitized BiV04 achieves an improved H_2 evolution rate of 5.43 μmol h~(-1) cm~(-2) in water splitting and an enhanced HCOOH production rate of 2.15 μmol h~(-1) cm~(-2) in CO_2 PEC reduction, which are1.9 times and 2.4 times higher than pristine BiVO_4, respectively. It is suggested that the derivative ChlCuNa is a more effective sensitizer for solar-to-fuel energy conversion and CO_2 utilization than Chl.     

Electrochemical non-enzymatic glucose sensors based on nano-composite of Co3O4 and multiwalled carbon nanotube

Nanocomposite of Co₃O₄ and MCNT was synthesised using one step solvothermal method, and an electrochemical non-enzymatic glucose sensor (Co₃O₄-MCNT/GCE) was successfully constructed. This sensor was used successfully for the quantitative analysis of trace glucose in serum sample.     

One-step co-electrodeposition of graphene oxide doped poly(hydroxymethylated-3,4-ethylenedioxythiophene) film and its electrochemical studies of indole-3-acetic acid

A novel graphene oxide(GO) doped poly(hydroxymethylated-3,4-ethylenedioxythiophene)(PEDOTM)film has been achieved via one-step co-electrodeposition and utilized for electrochemical studies of indole-3-acetic acid(IAA).The incorporation of GO into PEDOTM film facilitated the electrocatalytic activity and exhibited a favorable interaction between the PEDOTM/GO film and the phytohormone during the oxidation of IAA.Under optimized conditions,differential pulse voltammetry and square wave voltammetry were used for the quantitative analysis of IAA,respectively,each exhibiting a wide linearity range from 0.6 μmol L~(-1) to 10 μmol L~(-1) and 0.05 μmol L~(-1) to 40 μmol L~(-1),good sensitivity with a low detection limit of 0.087 μmol L~(-1) and 0.033 μmol L~(-1) respectively,as well as good stability.With the notable advantages of a green,sensitive method,expeditious response and facile operation,the as-prepared PEDOTM/GO organic-inorganic composite film provides a promising platform for electrochemical studies of IAA.     

磁性印迹纳米粒子固定血红蛋白修饰磁性电极构建过氧化氢传感器

采用表面印迹技术,以磁性二氧化硅纳米粒子（Fe₃O₄@SiO₂ NPs）作为载体、血红蛋白（Hb）为模板分子、正硅酸乙酯（TEOS）为印迹聚合物单体,制备了Hb印迹Fe₃O₄@SiO₂的磁性印迹纳米粒子（MMIPs NPs）. MMIPs NPs具有磁性内核和血红蛋白印迹壳层的核壳结构,可以富集并固定Hb. 使用壳聚糖将MMIPs NPs固定于磁性电极表面,构建血红蛋白类酶生物传感器,研究了Hb对过氧化氢（H₂O₂）的催化活性. MMIPS NPS相比于磁性非印迹纳米粒子（MNIPS NPS）,催化电流增加了14.3%. 采用磁性电极,MMIPS NPS、Hb和O₂的顺磁性使得该类酶生物传感器对H₂O₂的催化电流增加了60.0%. 血红蛋白类酶生物传感器电流响应与H₂O₂浓度在25 ~ 200 μmol·L^-1间呈线性关系,检出限为3 μmol·L^-1（S/N=3）,表明该类酶传感器对H₂O₂具有良好的催化性能.     

基于对羟基苯硼酸为前驱体的金纳米粒子修饰电极电化学检测过氧化氢

以对羟基苯硼酸为前驱体,利用H₂O₂可以定量氧化对羟基苯硼酸产生对羟基苯酚的原理,以反应产物对羟基苯酚为电化学信号物质,结合金纳米粒子修饰玻碳电极（AuNPs/GCE）,发展了一种间接检测H₂O₂的电化学方法. 由于AuNPs/GCE具有有效电子传递性能和比表面积大等优点,对硼酸氧化产物具有较高的催化活性,因此在含1.0 mmol•L^-1对羟基苯硼酸的0.1mol•L^-1 pH 7.5 PBS中,AuNPs/GCE可以检测到1.0 ~ 1.0 × 10³ μmol•L^-1的H₂O₂,检测限为0.5μmol•L^-1. 同时,该方法具有良好的选择性和重现性,且操作简单、速度快、价格低廉,非常适用于实际样品中H₂O₂含量的测定.     

Electronic absorption spectrum of Ba(MnO4)2·3H2O/Ba(ClO4)2·3H2O

Polarized absorption spectra of Ba(MnO₄)₂·3H₂O/Ba(ClO₄)₂·3H₂O mixed single crystals are reported at 4.2°K. Previous ¹T₂ → ¹A₁ assignments for the 5200 Å and 3000 Å absorption bands of MnO₄⁻ are substantiated; further support is provided for the ¹T₁ → ¹A₁ assignment of the 3600 Å absorption band of MnO₄⁻. The site-splitting of the 5200 Å ¹T₂ state is E(¹E)−E(¹A) ≈ −150 cm⁻¹; that of the 3000 Å ¹T₂ state is E(¹E)−E(¹A) ≈ 300 cm⁻¹. A significant e vibronic intensity component is observed in the 5200 Å ¹T₂ state.     

Pt/DNA-MWCNTs/GC电极制备及其H2O2还原的电催化活性

将DNA功能化多壁碳纳米管（MWCNTs）复合材料修饰于玻碳基底（GC）表面制得DNA-MWCNTs/GC电极,并在此基础上电沉积负载Pt纳米颗粒构建了一种新型无酶H₂O₂传感电极. 利用扫描电子显微镜（SEM）表征制得的修饰电极,同时通过循环伏安法和计时电流法研究了该传感电极的H2O2响应性能. 结果表明,该传感电极的H₂O₂检测在0.04 ~ 18.07 mmol·L^-1浓度范围内成线性相关,检出限3.85 μmol·L^-1（S/N = 3）,且有良好的重现性、稳定性与选择性.