Synthesis of Hexagonal Co3O4 and Ag/Co3O4 Composite Nanosheets and their Electrocatalytic Performances

Sheet-like precursors of Co₃O₄ and Ag/Co₃O₄ composites with different Ag contents were synthesized with assistance of triethylamine via a hydrothermal process. The final samples were fabricated by calcing each precursor at 400 °C. The as-prepared samples were identified and characterized by thermogravimetric analysis and differential thermal analysis, X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, and field emission scanning electron microscopy, respectively. The Co₃O₄ and Ag/Co₃O₄ composite samples were used as electrocatalysts modified on a glassy carbon electrode for p-nitrophenol reduction in a basic solution. The electrocatalytic results indicated that all the samples showed enhanced electrocatalytic performance for p-nitrophenol by comparing a bare glass carbon electrode, and p-nitrophenol could be reduced by Co₃O₄ at a high peak current but a rather higher peak potential but be reduced effectively by Ag/Co₃O₄ composites at lower potential. Ag/Co₃O₄ composites with 4 % Ag displayed the highest electrocatalytic activity.     

Synthesis of NiO nanomaterials with various morphologies and their electrocatalytic performances for <Emphasis Type="Italic">p</Emphasis>-nitrophenol reduction

In the work, several facile and easily controlled procedures were designed to successfully synthesize a few NiO samples with various morphologies, including nanosheets, nanobelts, nanoparticles and empty microspheres, via a hydrothermal method. The as-prepared samples were characterized by X-ray powder diffractometer, TEM and field emission scanning electron microscopy technologies. The results revealed that the as-synthesized NiO samples displayed expected nanosheets, nanobelts, nanoparticles and empty microspheres in shape. The electrocatalytic performance of each NiO sample modified on a glassy carbon electrode for p-nitrophenol reduction in a basic solution using cyclic voltammetry method was investigated. The results indicated that the glassy carbon electrode modified with each NiO sample showed enhanced electrocatalytic activity by comparing a bare glassy carbon electrode, and especially NiO nanopatricles and empty microsphere exhibited the higher electrocatalytic activty for p-nitrophenol reduction.     

一维纳米Co_3O_4,Ag/Co_3O_4及CuO/Co_3O_4的合成与电催化性能(英文)

采用水热合成法制备了Co3O4及复合Ag/Co3O4、CuO/Co3O4一维纳米产品。用XRD,FE-SEM和TEM手段对产品进行了表征。采用循环伏安法研究了合成产品修饰的玻碳电极在碱性溶液中对对硝基苯酚的电催化还原性能。与裸玻碳电极相比,1mmol·L-1的对硝基苯酚在用Co3O4、特别是CuO/Co3O4修饰的玻碳电极上还原的峰电流明显增大,用Ag/Co3O4(Ag/Co原子比分别为1∶5和2∶5)修饰的玻碳电极催化还原对硝基苯酚时,尽管还原峰电流增大不是太大,但其峰电位明显降低(分别降低0.265和0.371V)。     

Facile synthesis of Co3O4 and Ag/Co3O4 nanosheets and their electrocatalytic properties

The precursors of Co₃O₄ and Ag/Co₃O₄ composites with different Ag contents were synthesized with assistance of (NH₄)₂CO₃ via a facile hydrothermal process. The final samples were fabricated by calcining each precursor at 400 °C according to TG experiment. The as-prepared samples were identified and characterized by thermogravimetric analysis, X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, and field emission scanning electron microscopy, respectively. The results showed that the morphology of Co₃O₄ and Ag/Co₃O₄ composites were sheet-like. Ag nanoparticles were dispersed well in the nanosheets. The samples were used as electrocatalysts modified directly on a glassy carbon electrode for p-nitrophenol reduction in a basic solution. The results showed that p-nitrophenol could be reduced at a large peak current but a higher peak potential with Co₃O₄, at lower potentials with Ag/Co₃O₄ composites. Ag/Co₃O₄ composite with 3 % Ag showed more efficiently electrocatalytic activity than other composites. The present method suggested the potential application of Ag/Co₃O₄ composites in electrocatalysis.     

Synthesis of Fe3O4, Fe2O3, Ag/Fe3O4 and Ag/Fe2O3 nanoparticles and their electrocatalytic properties

Two important iron oxides:Fe3O4 and Fe2O3,as well as Fe3O4 and Fe2O3 nanoparticles mingling with Ag were successfully synthesized via a hydrothermal procedure.The samples were confirmed and characterized by X-ray diffraction(XRD),and X-ray photoelectron spectroscopy(XPS).The morphology of the samples was observed by transmission electron microscopy(TEM).The results indicated Fe3O4,Fe2O3,Ag/Fe3O4 and Ag/Fe2O3 samples all were nanoparticles with smaller sizes.The samples were modified on a glassy carbon electrode and their elctrocatalytic properties for p-nitrophenol in a basic solution were investigated.The results revealed all the samples showed enhanced catalytic performances by comparison with a bare glassy carbon electrode.Furthermore,p-nitrophenol could be reduced at a lower peak potential or a higher peak current on a glassy carbon electrode modified with Ag/Fe3O4 or Ag/Fe2O3 composite nanoparticles.     

Multilayer films of carbon nanotubes and redox polymer on screen-printed carbon electrodes for electrocatalysis of ascorbic acid

Multilayer films containing multiwall carbon nanotubes and redox polymer were successfully fabricated on a screen-printed carbon electrode using layer-by-layer (LBL) assembled method. UV-vis spectroscopy, X-ray photoelectron spectroscopy, field-emission scanning electron microscopy and electrochemical method were used to characterize the assembled multilayer films. The multilayer films modified electrodes exhibited good electrocatalytic activity towards the oxidation of ascorbic acid (AA). Compared with the bare electrode, the oxidation peak potential negatively shifted about 350 mV (versus Ag/AgCl). Furthermore, the modified screen-printed carbon electrodes (SPCEs) could be used for the determination of ascorbic acid in real samples.     

Electrochemically polymerised composites of multi-walled carbon nanotubes and poly(vinylferrocene) and their use as modified electrodes: application to glucose sensing

We report electrochemical composites of multi-walled carbon nanotubes (MWCNTs) with poly(vinylferrocene) (PVF). The polymeric architecture is prepared by first immobilising the MWCNTs onto a glassy carbon substrate, which acts to introduce electrical current into the composite, with the MWCNTs acting as 'molecular wires'. PVF films of varying surface coverages can be obtained by simply controlling the time a constant potential of +0.7 V (vs. Ag) wire is applied; with the characteristics of the derivatised MWCNTs examined by cyclic voltammetry and scanning electron microscopy.The application of the composite for glucose determination in aqueous solutions was investigated using linear sweep voltammetry, where it was found that the composites supported on glassy carbon substrates are superior to bare glassy carbon electrodes polymerised with PVF, likely due to the comparatively higher number of electrocatalytic centres in the former. This protocol was successfully transferred to prepare a PVF-MWCNT-paste electrode which was applied to glucose detection in diluted laked horse blood. The obtained results show potential and promising practical application for the polymer-derivatised MWCNT-modified electrodes in amperometric sensors for glucose determination.     

Electrocatalytic Reduction of Oxygen at Multi‐Walled Carbon Nanotubes and Cobalt Porphyrin Modified Glassy Carbon Electrode

The multi‐walled carbon nanotubes (MWNTs) modified glassy carbon electrode exhibited electrocatalytic activity to the reduction of oxygen in 0.1 M HAc‐NaAc (pH 3.8) buffer solution. Further modification with cobalt porphyrin film on the MWNTs by adsorption, the resulted modified electrode showed more efficient catalytic activity to O₂ reduction. The reduction peak potential of O₂ is shifted much more positively to 0.12 V (vs. Ag/AgCl), and the peak current is increased greatly. Cyclic voltammetry (CV), transmission electron microscopy (TEM), X‐ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM), were used to characterize the material and the modified film on electrode surface. Electrochemical experiments gave the total number of electron transfer for oxygen reduction as about 3, which indicated a co‐exist process of 2 electrons and 4 electrons for reduction of oxygen at this modified electrode. Meanwhile, the catalytic activities of the multilayer film (MWNTs/CoTMPyP)_n prepared by layer‐by‐layer method were investigated, and the results showed that the peak current of O₂ reduction increased and the peak potential shifted to a positive direction with the increase of layer numbers.     

Synthesis and electrocatalytic properties of microsized Ag2WO4 and nanoscaled MWO4 (M=Co, Mn)

Microstructured Ag₂WO₄ with shuttle-like shape was synthesized via a precipitation process with assistance of Arabic gum. MWO₄ (M=Co and Mn) nanocrystals were prepared facilely via a hydrothermal procedure. The as-prepared samples were identified and characterized by X-ray diffraction, transmission electron microscopy, and scanning electron microscopy, respectively. The resultant samples were used directly as electrocatalysts modified on a glassy carbon electrode for p-nitrophenol, K₂CrO₄ and H₂O₂ reduction in a basic solution. The results showed that all peak currents increased markedly but the corresponding peak potential decreased by using CoWO₄, MnWO₄ and Ag₂WO₄ in turn by comparing to a bare glassy carbon electrode, and Ag₂WO₄, CoWO₄ and MnWO₄ exhibited enhanced electrocatalytic activity for p-nitrophenol reduction. Ag₂WO₄ also showed effective electrocatalytic activity for K₂CrO₄ and H₂O₂ reduction, but both CoWO₄ and MnWO₄ almost displayed very weak electrocatalytic properties for K₂CrO₄ and H₂O₂ reduction in basic solution.     

Electrocrystallized Ag nanoparticle on functional multi-walled carbon nanotube surfaces for hydrazine oxidation

4-Aminobenzoic acid was covalently grafted on multi-walled carbon nanotubes (MWNTs) by amine cation radical formation in the electrooxidation process of the amino-containing compound. Then, silver (Ag) nanoparticles were electrocrystallized on 4-aminobenzoic acid monolayer-grafted MWNTs by a potential-step method. The structure and nature of the resulting Ag/MWNT composites were characterized by transmission electron microscopy and X-ray diffraction. The electrocatalytic properties of the Ag/MWNT electrode for hydrazine oxidation have been investigated by cyclic voltammetry, high electrocatalytic activity of the Ag/MWNT electrode can be observed. This may be attributed to the small particle size of the silver particles. The results imply that the Ag/MWNT composites have a good application potential in fuel cells.     

Polyfurfural-Electrochemically Reduced Graphene Oxide Modified Glassy Carbon Electrode for the Direct Determination of Nitrofurazone

An electrochemical sensor based on a polyfurfural-electrochemically reduced graphene oxide modified glassy carbon electrode has been developed for the sensitive and rapid determination of nitrofurazone. The morphologies and properties of the sensor were characterized by electrochemical impedance spectroscopy, scanning electron microscopy, cyclic voltammetry, and differential pulse voltammetry (DPV). In pH 7.0 Britton–Robinson buffer solution, the as-prepared polyfurfural-electrochemically reduced graphene oxide modified glassy carbon electrode shows excellent electrocatalytic performance for the electrochemical reduction of nitrofurazone, and the reduction peak current is about 9.45, 1.31, and 1.25 times higher than that of the bare glassy carbon electrode, polyfurfural modified glassy carbon electrode, and electrochemically reduced graphene oxide modified glassy carbon electrode, respectively. The DPV determination of nitrofurazone indicates that the linear range and detection limit of nitrofurazone are 1–50 and 0.25?µmol/dm³, respectively. In addition, this sensor exhibits high selectivity, reproducibility, stability, and also was successfully used to directly determine nitrofurazone in the commercial antibacterial lotion with comparative sensitivity to high-performance liquid chromatography, showing its promising application prospects.     

Highly improved electrocatalytic behavior of sulfite at carbon ionic liquid electrode: application to the analysis of some real samples

The electrocatalytic oxidation of sulfite was investigated at carbon ionic liquid electrode (CILE). This electrode is a very good alternative to previously described electrodes because the electrocatalytic effect is achieved without any electrode modification. Comparative experiments were carried out using carbon paste electrode (CPE) and glassy carbon electrode (GCE). At CILE, highly reproducible and well-defined cyclic voltammograms were obtained for sulfite with a peak potential of 0.55 V vs. Ag/AgCl. Sulfite oxidation at CILE does not result in deactivation of the electrode surface. The kinetic parameters for this irreversible heterogeneous electron transfer process were determined. Under optimal experimental conditions, the peak current response increased linearly with sulfite concentration over the range of 6-1000 μM. The detection limit of the method was 4 μM. The method was applied to the determination of sulfite in mineral water, grape juice and non-alcoholic beer samples.     

Electropreparation of Poly(benzophenone‐4) Film Modified Electrode and Its Electrocatalytic Behavior Towards Dopamine,Ascorbic Acid and Nitrite

The oxidation of benzophenone‐4 (2‐hydroxy‐4‐methoxybenzophenone‐5‐sulfonic acid) at glassy carbon electrode gives rise to stable redox active electropolymerized film during repetitive potential cycling between 0 to 1.3 V (Ag/AgCl). Cyclic voltammogram of poly(benzophenone‐4) film shows a redox couple with well‐defined peaks. The redox response of the modified electrode was found to be depending on the pH of the contacting solution. The peak potentials were shifted to a less positive region with increasing pH and the dependence of the peak potential was found to be 51 mV/pH. The electrocatalytic behavior of poly(benzophenone‐4) film modified electrode towards oxidation of dopamine, ascorbic acid and reduction of nitrite was investigated. The oxidation of dopamine and ascorbic acid occurred at less positive potential on poly(benzophenone‐4) film compared to bare glassy carbon electrode. For dopamine, the overpotential was reduced about 180 mV. Feasibility of utilizing poly(benzophenone‐4) film coated electrode in analytical estimation of dopamine, ascorbic acid and nitrite was also demonstrated.     

Electrochemical Determination of Hydrogen Peroxide Using a Glassy Carbon Electrode Modified with Three-Dimensional Copper Hydroxide Nanosupercages and Electrochemically Reduced Graphene Oxide

Three-dimensional copper hydroxide nanosupercages and electrochemically reduced graphene oxide were used to modify the glassy carbon electrode for the selective determination of hydrogen peroxide. The morphology and electrochemistry properties of copper hydroxide nanosupercage/electrochemically reduced graphene oxide/glassy carbon electrode were characterized using transmission electron microscopy, scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectra, Raman spectra, cyclic voltammetry, and electrochemical impedance spectroscopy. The resulting copper hydroxide nanosupercage/electrochemically reduced graphene oxide/glassy carbon electrode showed favorable performance for the electrocatalytic reduction of hydrogen peroxide. The amperometric current–time curve of the electrochemical sensor exhibited a wide linear range from 0.5 to 1030?µM with a limit of detection of 0.23?µM at a signal-to-noise ratio of three. Moreover, the sensor provided favorable selectivity, reproducibility, and stability and was used for the determination of H₂O₂ in tap water.     

吲哚美辛在单壁碳纳米管修饰电极上的电化学行为

运用伏安法研究了吲哚美辛在单壁碳纳米管修饰电极上的电化学行为.在0.1 mol/L HAc-NaAc缓冲溶液(pH 4.5)中,吲哚美辛于0.91 V (vs.SCE)电位处有一个峰形很好的氧化峰.与裸玻碳电极相比,吲哚美辛在修饰电极上的电位正移了约30 mV,峰电流增加了近10倍,表明该修饰电极对吲哚美辛有较强的电催化作用.搅拌条件下开路富集2 min,氧化峰电流与吲哚美辛在5.5×10-7～1.1×10-5 mol/L浓度范围内呈良好的线性关系,检出限为1.1×10-7 mol/L.该方法可用于药剂中吲哚美辛的分析.     

Ternary Ag/Polyaniline/Au nanocomposites: Preparation,characterization and electrochemical properties

Ternary Ag/Polyaniline/Au nanocomposites were synthesized successfully by immobilizing of Au nanoparticles (NPs) on the surface of Ag/Polyaniline (PANI) nanocomposites. Ag/PANI nanocomposites were prepared via in situ chemical polymerization of aniline in the presence of 4-aminothiophenol (4-ATP) capped silver colloidal NPs. Then, uniform gold (Au) NPs were assembled on the surface of resulted Ag/PANI nanocomposites through electrostatic interaction to get Ag/Polyaniline/Au nanocomposites. The nanocomposites were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), ultraviolet visible spectroscopy (UV-Vis), thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR). Moreover, Ag/PANI/Au nanocomposites were immobilized on the surface of a glassy carbon electrode and showed enhanced electrocatalytic activity for the reduction of H₂O₂ compared with Ag/PANI.     

银纳米颗粒的合成及用于抗癌药氟他胺的电化学检测（英文）

Ag nanoparticles were synthesized on the surface of a glassy carbon electrode modified with p‐tert‐butylcalix[4]arene and p‐tert‐butylcalix[6]arene by the deposition of Ag+ at an open circuit potential followed by the electrochemical reduction of the Ag+.The presence of the calixarene layer on the electrode surface controlled the particle size and prevented agglomeration.Cyclic voltam‐metry showed that the Ag nanoparticles on the modified glassy carbon electrode had good catalytic ability for the reduction of flutamide.The effects of calixarene concentration,potential applied for the reduction of Ag+,number of calixarene layers,and p H value on the electrocatalytic activity of the Ag nanoparticles were investigated.The modified electrode had a linear range in differential pulse voltammetry of 10-1000 μmol/L with a detection limit of 9.33 μmol/L for flutamide at an S/N = 3.The method was applied to the detection of flutamide in practical samples.     

Electrochemical deposition of platinum nanoparticles in multiwalled carbon nanotube–Nafion composite for methanol electrooxidation

Platinum nanoparticles were successfully deposited within a multiwalled carbon nanotube (MWCNT)–Nafion matrix by a cyclic voltammetry method. A Pt(IV) complex was reduced to platinum nanoparticles on the surface of MWCNTs. The resulting Pt nanoparticles were characterized by scanning electron microscopy, transmission electron microscopy, and energy-dispersive X-ray spectroscopy. The Pt–MWCNT–Nafion nanocomposite film-modified glassy carbon electrode had a sharp hydrogen desorption peak at about −0.2 V vs. Ag/AgCl (3 M) in a solution of 0.5 M H₂SO₄, which is directly related to the electrochemical activity of the Pt nanoparticles presented on the surface of MWCNTs. The electrocatalytic properties of the Pt–MWCNT–Nafion nanocomposite-modified glassy carbon electrode for methanol electrooxidation were investigated by cyclic voltammetry in a 2 M CH₃OH + 1 M H₂SO₄ solution. In comparison with the Pt-coated glassy carbon electrode and the Pt–Nafion modified glassy carbon electrode, the Pt–MWCNT–Nafion-modified electrode had excellent electrocatalytic activity toward methanol electrooxidation. The stability of the Pt–MWCNT–Nafion nanocomposite-modified electrode had also been evaluated.     

Voltammetric Determination of Neotame by Using Chitosan/Nickelnanoparticles/Multi Walled Carbon Nanotubes Biocomposite as a Modifier

A selective and simple biosensor was prepared by immobilizing chitosan/nickelnanoparticles/multi-walled carbon nanotubes biocomposite on the glassy carbon electrode surface for voltammetric quantification of neotame. The properties and morphology of the modified electrode surfaces were characterized by scanning electron microscope (SEM), energy dispersive X-ray analysis (EDX). Electro oxidation of neotame on this modified surface was examined through cyclic voltammetry (CV) and square wave voltammetry (SWV) techniques. The biocomposite modified surface (Chi/NiNPs/MWCNTs/GCE) proposed in this study showed good electrocatalytic activity for neotame with an improved voltammetric peak current at 1.004 V, unlike the bare glassy carbon electrode (GCE) surface and several other modified surfaces. Under optimum conditions, Chi/NiNPs/MWCNTs/GCE gave linear SWV responses at the range of 2 μM ∼50 μM for neotame with 0.84 μM determination limit. This voltammetric sensor was successfully employed for the quantification of neotame on food samples and showed long-term stability, advanced voltammetric behavior, and good repeatability. Selective, accurate, and precise determination of neotame highlight the importance of this electrode in monitoring the control of food additives and ensures attract a great deal of attention.     

抗坏血酸在铂纳米粒子/碳纳米管/聚吡咯复合修饰电极上的电化学行为

研究了抗坏血酸在铂纳米粒子/碳纳米管/聚吡咯复合膜修饰电极上的电化学行为,发现复合修饰电极对抗坏血酸的电化学反应具有较好的电催化作用,与空白电极相比电化学氧化电流增加了7倍。用电化学阻抗谱研究了电子在修饰电极界面上的传输过程,发现修饰电极的电催化性能与修饰电极可以提高界面电子传输能力是相关的。同时研究了碳纳米管用量、支持电解质、扫速、电沉积条件等因素对抗坏血酸在修饰电极上电化学行为的影响。