Direct Electrochemistry and Electrocatalysis of Hemoglobin Based on Nafion‐Room Temperature Ionic Liquids‐Multiwalled Carbon Nanotubes Composite Film

A robust and effective composite film combined the benefits of Nafion, room temperature ionic liquid (RTIL) and multi‐wall carbon nanotubes (MWNTs) was prepared. Hemoglobin (Hb) was successfully immobilized on glassy carbon electrode surface by entrapping in the composite film. Direct electrochemistry and electrocatalysis of immobilized Hb were investigated in detail. A pair of well‐defined and quasi‐reversible redox peaks of Hb was obtained in 0.10 mol·L^?1 pH 7.0 phosphate buffer solution (PBS), indicating that the Nafion‐RTIL‐MWNTs film showed an obvious promotion for the direct electron transfer between Hb and the underlying electrode. The immobilized Hb exhibited an excellent electrocatalytic activity towards the reduction of H₂O₂. The catalysis current was linear to H₂O₂ concentration in the range of 2.0×10^?6 to 2.5×10^?4 mol·L^?1, with a detection limit of 8.0×10^?7 mol·L^?1 (S/N=3). The apparent Michaelis‐Menten constant (K_m^app) was calculated to be 0.34 mmol·L^?1. Moreover, the modified electrode displayed a good stability and reproducibility. Based on the composite film, a third‐generation reagentless biosensor could be constructed for the determination of H₂O₂.     

Simultaneous Detection of Dopamine and Uric Acid under Coexistence of Ascorbic Acid with DNA/Pt Nanocluster Modified Electrode

A novel biosensor by electrochemically codeposited Pt nanoclusters and DNA film was constructed and applied to detection of dopamine (DA) and uric acid (UA) in the presence of high concentration ascorbic acid (AA). Scanning electron microscopy and X‐ray photoelectron spectroscopy were used for characterization. This electrode was successfully used to resolve the overlapping voltammetric response of DA, UA and AA into three well‐defined peaks with a large anodic peak difference (ΔE_pa) of about 184 mV for DA and 324 mV for UA. The catalytic peak current obtained from differential pulse voltammetry was linearly dependent on the DA concentration from 1.1× 10^?7 to 3.8×10^?5 mol·L^?1 with a detection limit of 3.6×10^?8 mol·L^?1 (S/N=3) and on the UA concentration from 3.0×10^?7 to 5.7×10^?5 mol·L^?1 with a detection limit of 1.0×10^?7 mol·L^?1 with coexistence of 1.0×10^?3 mol·L^?1 AA. The modified electrode shows good sensitivity and selectivity.     

Electrochemical Responses and Sensitivities of Films Based on Multi-Walled Carbon Nanotubes in Aqueous Solutions

Novel films consisting of multi-walled carbon nanotubes (MWCNTs) were fabricated by means of chemical vapor deposition with decomposition of either acetonitrile (ACN) or benzene (BZ) using ferrocene as catalyst. The electrochemical responses of MWCNT-based films towards the ferrocyanide/ferricyanide, [Fe(CN)₆]^3?/4? redox couple were probed by means of cyclic voltammetry and electrochemical impedance spectroscopy at 25.0?±?0.5?°C. Both MWCNT-based films exhibit Nernstian response towards [Fe(CN)₆]^3?/4? with some slight kinetic differences. Namely, heterogeneous electron transfer rate constants lying in ranges of 2.69?×?10^?2?C1.7?×?10^?3 and 9.0?×?10^?3?C2.6?×?10^?3?cm·s^?1 were obtained at v?=?0.05?V·s^?1 for MWCNT_ACN and MWCNT_BZ, respectively. The detection limit of MWCNT_ACN, estimated to be about 4.70?×?10^?7?mol·L^?1 at v?=?0.05?V·s^?1, tends to become slightly poorer with the increase of the scan rate, namely at v?=?0.10?V·s^?1 the detection limit of 1.70?×?10^?6?mol·L^?1 was determined. Slightly poorer response ability was exhibited by MWCNT_BZ; specifically the detection limits of 1.57?×?10^?6 and 4.35?×?10^?6?mol·L^?1 were determined at v?=?0.05 and v?=?0.10?V·s^?1, respectively. The sensitivities of MWCNT_ACN and MWCNT_BZ towards [Fe(CN)₆]^3?/4? were determined as 1.60?×?10^?7 and 1.51?×?10^?7?A·L·mol^?1·cm^?2, respectively. The excellent electrochemical performance of MWCNT_ACN is attributed to the presence of incorporated nitrogen in the nanotube??s structure.     

Synthesis and Characterization of Nanostructured Manganese Dioxide Used as Positive Electrode Material for Electrochemical Capacitor with Lithium Hydroxide Electrolyte

A nanostructured manganese dioxide electrode material was prepared using a solid‐reaction route starting with MnCl₂·4H₂O and NH₄HCO₃, and its electrochemical performance as a positive electrode for MnO₂/activated carbon hybrid supercapacitor with 1 mol·L^?1 LiOH electrolyte was reported. The material was proved to be a mixture of nanostructured γ‐MnO₂ and α‐MnO₂ containing some bound water in the structure, which was characterized by X‐ray diffraction analysis, infrared spectrum analysis, and transmission electron microscope observation. Electrochemical properties of the MnO₂ electrode and the MnO₂/AC capacitor were investigated by cyclic voltammetry, ac impedance and galvanostatic charge/discharge methods. Experimental results showed that the MnO₂ electrode exhibited faradaic pseudocapacitance behavior and higher specific capacitance in 1 mol·L^?1 LiOH electrolyte. The MnO₂/AC hybrid capacitor with 1 mol·L^?1 LiOH electrolyte presented excellent rate charge/discharge ability and cyclic stability.     

Kinetic Studies on the Reaction of Sodium Hexacyanoferrate（ll） Complex with Peroxydisulfate Anion

The oxidation of Na₄Fe(CN)₆ complex by S₂O anion was found to follow an outer‐sphere electron transfer mechanism. We firstly carried out the reaction at pH=1. The specific rate constants of the reaction, k_ox, are (8.1±0.07)×10^?2 and (4.3±0.1)×10^?2 mol^?1·L·s^?1 at μ=1.0 mol·L^?1 NaClO₄, T=298 K for pH=1 (0.1 mol·L^?1 HCl0₄) and 8, respectively. The activation parameters, obtained by measuring the rate constants of oxidation 283–303 K, were ΔH^≠=(69.0±5.6) kJ·mol^?1, ΔS^≠=(?0.34±0.041)×10² J·mol^?1·K^?1 at pH=l and ΔH^≠=(41.3±5.5) kJ·mol^?1, ΔS^≠=(?1.27±0.33)×10² J·mol^?1·K^?1 at pH=8, respectively. The cyclic voltammetry of Fe(CN) shows that the oxidation is a one‐electron reversible redox process with E_1/2 values of 0.55 and 0.46 V vs. normal hydrogen electrode at μ=1.0 mol·L^?1 LiClO₄, for pH=1 and pH=8 (Tris). respectively. The kinetic results were discussed on the basis of Marcus theory.     

Electrodeposition CaCO3 Nanoparticles‐chitosan Composite Film on Carbon Ionic Liquid Electrode as a Platform for Hemoglobin Electrochemical Biosensor

By one‐step co‐electrodeposition CaCO₃ nanoparticles‐chitosan composite film on carbon ionic liquid electrode (CILE), and then by spreading the composition of hemoglobin (Hb) and chitosan on the nanoCaCO₃‐chi/CILE, a Hb‐chi/nanoCaCO₃‐chi/CILE was fabricated and the direct electrochemistry and electrocatalysis of Hb at the electrode was investigated. The electrochemical impedance spectroscopy of the modified electrode showed the electron transfer resistance was 1166 Ω. Investigation results of cyclic voltammetrys showed a pair of well‐defined and quasireversible redox peak of Hb with the formal potentials of ‐0.295 V (vs. SCE) in 0.1 mol·L^‐1 pH 7.0 PBS; the response time of the reduction peak currents of Hb was lower than 3s; a linear range for determination of H₂O₂ was from 5.0 μmol·L^‐1 to 1.3 mmol·L^‐1 with a detection limit of 1.6 μmol·L^‐1 (S/N = 3) and a sensitivity of 0.16 A·M^‐1·cm^‐2; the electron transfer rate constant and the apparent Michaelis‐Menten constant of Hb were 1.98 s^‐1 and 0.81 mmol·L^‐1, respectively. As a result, the case of the one‐step co‐electrodeposition and the promising feature of biocomposite could serve as a versatile platform for the fabrication of electrochemical biosensors.     

Photoinduced charge property of Ag‐TiO2 films and its relationships with photocatalytic activity under visible illumination

In this article, TiO₂ films were synthesized by traditional spin coating method. To improve their photocatalytic activities, we deposited silver on these films by photodeposition. These films also were characterized by several testing techniques, such as X‐ray diffraction, ultraviolet–visible diffuse reflection spectrum, XPS, Raman spectroscopy (Raman), surface photovoltage spectroscopy, and SEM. The activity of different films was evaluated for degrading rhodamine B solution under visible illumination. The effects of AgNO₃ solution concentration on photoinduced charge property and photocatalytic activity were investigated. The results show that the Ag‐TiO₂ film immersed in 10^?3 mol·L^?1 AgNO₃ solution exhibits higher activity, which is in good agreement with the characterization results. The weaker the surface photovoltage spectroscopy signal, the higher the photocatalytic activity. Moreover, the activity of some films is higher than that of international Degussa P‐25 TiO₂ under visible illumination. Copyright © 2012 John Wiley & Sons, Ltd.     

Electrochemical polymerization of polyaniline doped with Zn2+ as the electrode material for electrochemical supercapacitors

Polyaniline doped with Zn²⁺ (PANI/Zn²⁺) films was synthesized by cyclic voltammetric method on stainless steel mesh substrates in 0.2 mol L^?1 aniline and 0.5 mol L^?1 sulfuric acid electrolyte with various concentrations of zinc sulfate (ZnSO₄·7H₂O). The structure and morphology of PANI and PANI/Zn²⁺ films were characterized by Fourier transform infrared, X-ray diffraction, scanning electron microscopy, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy techniques, respectively. The electrochemical properties of PANI and PANI/Zn²⁺ films were investigated by cyclic voltammetry, galvanostatic charge–discharge test, and electrochemical impedance spectroscopy in 0.5 mol L^?1 H₂SO₄ electrolyte in a three-electrode system. The results show that the surface morphology of PANI/Zn²⁺ is more rough than that of pure PANI. The specific capacitance of the PANI/Zn²⁺ film displays a larger specific capacitance of 738 F g^?1, lower resistance, and better stability as compared with the pure PANI film. Thus, good capacitive performance demonstrates its potential superiority for supercapacitors.     

Direct Electron Transfer of Glucose Oxidase and Glucose Biosensor Based on Nano-structural Attapulgite Clay Matrix

The direct electrochemistry of glucose oxidase (GOD) was achieved based on the immobilization of GOD on a natural nano‐structural attapulgite (ATP) clay film modified glassy carbon (GC) electrode. The immobilized GOD displayed a pair of well‐defined quasi‐reversible redox peaks with a formal potential (E^0′) of ?457.5 mV (vs. SCE) in 0.1 mol·L^?1 pH 7.0 phosphate buffer solution. The peak current was linearly dependent on the scan rate, indicating that the direct electrochemistry of GOD in that case was a surface‐controlled process. The immobilized glucose oxidase could retain bioactivity and catalyze the oxidation of glucose in the presence of ferrocene monocarboxylic acid (FMCA) as a mediator with the apparent Michaelis‐Menten constant K^app_m of 1.16 mmol·L^?1. The electrocatalytic response showed a linear dependence on the glucose concentration ranging widely from 5.0×10^?6 to 6.0×10^?4 mol·L^?1 (with correlation coefficient of 0.9960). This work demonstrated that the nano‐structural attapulgite clay was a good candidate material for the direct electrochemistry of the redox‐active enzyme and the construction of the related enzyme biosensors. The proposed biosensors were applied to determine the glucose in blood and urine samples with satisfactory results.     

Catalytic Adsorptive Stripping Voltammetry at a Carbon Paste Electrode for the Determination of Amiodarone

Voltammetry using solid electrodes usually suffers from the contamination due to the deposition of the redox products of analytes on the electrode surface. The contamination has resulted in poor reproducibility and overelaborate operation procedures. The use of the chemical catalysis of oxidant on the reduction product of analyte not only can eliminate the contamination of analyte to solid electrodes but also can improve the faradaic response of analyte. This work introduced both the catalysis of oxidant K2S2O8 and the enhancement of surfactant Triton X-100 on the faraday response of amiodarone into an adsorptive stripping voltammetry at a carbon paste electrode for the determination of amiodarone. The method exhibits high sensitivity, good reproducibility and simple operation procedure. In 0.2 mol·L^-1 HOAc-NaOAc buffer （pH=5.3） containing 2.2×10^-2 mol·L^-1 K2S2O8 and 0.002% Triton X-100, the 2.5th-order derivative stripping peak current of the catalytic wave at 0.3 V （vs. Ag/AgCl） is rectilinear to amiodarone concentration in the range of 2.0×10^-10-2.3×10^-8 mol·L^-1 with a detection limit of 1.5×10^-10 mol·L^-1 after accumulation at 0 V for 30 s.     

Fabrication of a Sensitive Electrochemical Biosensor for Detection of DNA Hybridization Based on Gold Nanoparticles/CuO Nanospindles Modified Glassy Carbon Electrode

In this work, a sensitive electrochemical DNA biosensor for the detection of sequence‐specific target DNA was reported. Firstly, CuO nanospindles (CuO NS) were immobilized on the surface of a glassy carbon electrode (GCE). Subsequently, gold nanoparticles (Au NPs) were introduced to the surface of CuO NS by the electrochemical deposition mode. Probe DNA with SH (HS‐DNA) at the 5′‐phosphate end was covalently immobilized on the surface of the Au NPs through Au? S bond. Scanning electron microscopy (SEM) was used to elucidate the morphology of the assembled film, and electrochemical impedance spectroscopy technique (EIS) was used to investigate the DNA sensor assembly process. Hybridization detection of DNA was performed with differential pulse voltammetry (DPV) and the methylene blue (MB) was hybridization indicator. Under the optimal conditions, the decline of reduction peak current of MB (ΔI) was linear with the logarithm of the concentration of complementary DNA from 1.0×10^?13 to 1.0×10^?6 mol·L^?1 with a detection limit of 3.5×10^?14 mol·L^?1 (S/N=3). In addition, this DNA biosensor has good selectivity, and even can distinguish single‐mismatched target DNA.     

半晶化双螺旋介孔MnO2的合成和电化学性质

Mesoporous silica KIT-6 has novel three-dimensional gyroidal channel structure, space group of 1a-3d, and ordered tunable pores up to 10 nm. In this paper, such mesostructured silica was employed as hard template to prepare semicrystalline gyroidal mesoporous MnO2. The structure was investigated by XRD, TEM and HRTEM, and found to be of high quality 1a-3d symmetry, in good accordance with the template structure. The material has a BET surface of 118 m2·g^-1 and pore volume of 0.35 cm3·g^- 1 after eliminating template. Mesoporous MnO2 has shown good electrochemical property as supercapacitor material in 1 mol·L^-1 Na2SO4 and 1 mol·L^-1 LiClO4 solutions, but interesting pseudocapacitance behavior was observed in the case of 6 mol·L^-1 KOH. It was found that mesoporous MnO2 performed stable reversible electrochemical behavior with capacitance of 220 F·g^-1 in a potential range of -0.1-0.55 V vs. Hg/HgO in alkaline solution, demonstrating that it is a promising novel electrode material for the fabrication of electrochemical capacitors.     

Fabrication of Tubular Structure Agglomerates of Calcium Carbonate by Using Collodion Film

A novel and simple method for preparing tubular structure agglomerates of calcium carbonate (CC-tube) is described. Calcium chloride and sodium carbonate aqueous solutions were used as reactants separated by a collodion film (a nitrocellulose material) in aqueous solution. The effects of the concentrations of calcium chloride and sodium carbonate aqueous solutions on the morphology and phase structure of the as-obtained samples were investigated. The CC-tube growth was prevented with the increase of reactant concentration from 0.5 to 1.0 mol•L－1. Compared with Na2CO3 aqueous solution, it is favourable to grow calcite crystals in CaCl2 aqueous solution. The products were characterized by X-ray diffraction, Fourier transform infrared spectroscopy and scanning electron- microscopy.     

Electrodeposition of Silver Nanoparticles on MWCNT Film Electrodes for Hydrogen Peroxide Sensing

Silver （Ag） nanoparticles were directly electrodeposited on multi-walled carbon nanotubes （MWCNT） in AgNO3/LiNO3 containing EDTA （ethylenediaminetetraacetic acid）. The structure and nature of the resulting Ag/MWNT composite were characterized by field emission scanning electron microscopy （FE-SEM）, transmission electron microscopy （TEM） and X-ray diffraction （XRD）, and the distribution shape of Ag nanoparticles was found to be dependent on the presence of EDTA. The modified electrode showed excellent electrocatalytic activity to redox reaction of hydrogen peroxide and the mechanism of hydrogen peroxide was partly reversible procession with oxidation and reduction peaks at 0.77 and -0.83 V, respectively. The oxidation and reduction peak currents were linearly related to hydrogen peroxide concentration in the range of 1×10^-6-3×10^-4 and 1 ×10^-8-7× 10^-4 mol·L^-1 with correlation coefficients of 0.996 and 0.986, and 3s-detection limit of 9 × 10^-7 and 7 × 10^-9 mol·L^-1.     

Synthesis,Characterization and SOD Activities of IP-copper（Ⅱ）-L-amino Acid Complexes

Four new ternary complexes： [Cu（IP）（L-Val）（H2O）]ClO4·1.5H2O（1）, [Cu（IP）（L-Leu）（H2O）]ClO4（2）, [Cu（IP）（L-Tyr）（H2O）]ClO4·H2O（3） and [Cu（IP）（L-Trp）（H2O）]ClO4·1.5H2O（4） have been synthesized and character/zed by elementa/analysis, molar conductivity, infrared absorption spectroscopy, electronic absorption spectroscopy and cyclic voltammetry, where IP=imidazo[4,5-f][1,10] phenanthroline, L-Val=L-valinate, L-Leu=L-leucinate, L-Tyr=L-tyrosinate and L-Trp=L-tryptophanate. Complex 3 was structurally characterized by X-ray diffraction method, which crystallizes in orthorhornbic space group P21212 in a unit cell of dimensions a=3.0567（4） nm, b=0.74079（9） nm, c= 1.06198（13） nm, V=2.4047（5） nm^3, Z=4,μ=0.1084 cm^-1. The SOD-like activities of catalytic disrnutation of superoxide anions （O2^-· ） by the complexes were determined by means of modified nitroblue tetrazolium （NBT） photoreduction. The IC50 values of complexes 1, 2, 3 and 4 are 0.072, 0.147, 0.429 and 0.264 μmol·L^-1, respectively     

An H2O2 Biosensor Based on Immobilization of Horseradish Peroxidase Labeled Nano‐Au in Silica Sol‐Gel/Alginate Composite Film

Abstract

A novel approach to assemble an H₂O₂ amperometric biosensor was introduced. The biosensor was constructed by entrapping horseradish peroxidase (HRP) labeled nano‐scaled particulate gold (nano‐Au) (HRP‐nano‐Au electrostatic composite) in a new silica sol‐gel/alginate hybrid film using glassy carbon electrode as based electrode. This suggested strategy fully merged the merits of sol‐gel derived inorganic‐organic composite film and the nano‐Au intermediator. The silica sol‐gel/alginate hybrid material can improve the properties of conventional sol‐gel material and effectively prevent cracking of film. The entrapment of HRP in the form of HRP‐nano‐Au can not only factually prevent the leaking of enzyme out of the film but also provide a favorable microenvironment for HRP. With hydroquinone as an electron mediator, the proposed HRP electrode exhibited good catalytic activity for the reduction of H₂O₂. The parameters affecting both the qualities of sol‐gel/alginate hybrid film and the biosensor response were optimized. The biosensor exhibited high sensitivity of 0.40 Al mol^?1 cm^?2 for H₂O₂ over a wide linear range of concentration from 1.22×10^?5 to 1.46×10^?3 mol L^?1, rapid response of <5 s and a detection limit of 0.61×10^?6 mol L^?1. The enzyme electrode has remarkable stability and retained 86% of its initial activity after 45 days of storage in 0.1 mol L^?1 Tris‐HCl buffer solutions at pH 7.     

银（III）配合物-鲁米诺流动注射化学发光新体系测定肾上腺素

儿茶酚胺是一类非常重要的神经递质,在人体的心血管系统、神经系统、内分泌腺、肾脏、平滑肌等组织系统的生理活动中起着广泛的调节作用。肾上腺素为儿茶酚胺的一种,建立灵敏、高效的肾上腺素检测技术具有重要的临床意义。本文将银（Ⅲ）配合物与鲁米诺组成新的流动注射化学发光体系,利用碱性介质中肾上腺素对三价银配合物－鲁米诺化学发光体系有明显的增强效应来测定肾上腺素的含量,并据此建立了高效测定肾上腺素的流动注射化学发光新方法。在优化的条件下,该方法测定肾上腺素的线型范围为1.0×10－9～1.0×10－7 mol L-1,检出限为8.0×10－10 mol L-1,对1.5×10－8 mol L-1肾上腺素11次平行测定,其相对标偏差为2.9％。利用建立的分析方法测定了药物肾上腺素,并对三价银－鲁米诺化学发光新体系测定肾上腺素的反应机理进行了讨论。     

Molecular imprinting polymer electrosensor based on gold nanoparticles for theophylline recognition and determination

An electrochemical sensor for theophylline (ThPh) was prepared by electropolymerizing o-phenylenediamine on a glassy carbon electrode in the presence of ThPh via cyclic voltammetry, followed by deposition of gold nanoparticles using a potentiostatic method. The effects of pH, ratio between template molecule and monomer, number of cycles for electropolymerization, and of the solution for extraction were optimized. The current of the electro-active model system hexacyanoferrate(III) and hexacyanoferrate(IV) decreased linearly with successive addition of ThPh in the concentration range between 4.0?×?10^?7?~?1.5?×?10^?5 mol·L^?1 and 2.4?×?10^?4?~?3.4?×?10^?3 mol·L^?1, with a detection limit of 1.0?×?10^?7 mol·L^?1. The sensor has an excellent recognition capability for ThPh compared to structurally related molecules, can be regenerated and is stable.

Chemical‐Bath‐Deposited Indium Oxide Microcubes for Solar Water Splitting

We fabricated films of cubic indium oxide (In₂O₃) by chemical bath deposition (CBD) for solar water splitting. The fabricated films were characterized by X‐ray diffraction analysis, Raman scattering, X‐ray photoelectron spectroscopy, and scanning electron microscopy, and the three‐dimensional microstructure of the In₂O₃ cubes was elucidated. The CBD deposition time was varied, to study its effect on the growth of the In₂O₃ microcubes. The optimal deposition time was determined to be 24 h, and the corresponding film exhibited a photocurrent density of 0.55 mA cm^?2. Finally, the film stability was tested by illuminating the films with light from an AM 1.5 filter with an intensity of 100 mW cm^?2.     

健那绿B的荧光猝灭研究及作为核酸测定探针的应用

用紫外可见光谱、稳态荧光发射及荧光寿命测定研究了核酸猝灭十二烷基磺酸钠胶束中的健那绿荧光。水溶液中弱的健那绿荧光在十二烷基磺酸钠胶束中被大大加强，其最大发射从425纳米移至410纳米，核酸的加入将猝灭健那绿的荧光，当健那绿浓度为2.5×10^–5 mol•L^-1时，荧光猝灭(F₀/F)分别与小牛胸腺DNA及鱼精DNA在2.4×10^–8 到 1.08×10^–7及 1.9×10^–8 到 3.8×10^–8 mol•L^-1范围内成正比, 检测限分别为1.3×10^–8 mol•L^-1 (小牛胸腺DNA)及6.3×10^–9 mol•L^-1 (鱼精DNA)。当DNA浓度较高时, 将系统偏离Stern-Volmer方程。这是因为动态猝灭和静态猝灭同时存在。方法已应用于鸡血提取液中DNA的测定, 测定结果与紫外法一致。