Electrocatalytic oxidation of <Emphasis Type="SmallCaps">l</Emphasis>-tyrosine at carboxylic acid functionalized multi-walled carbon nanotubes modified carbon paste electrode

The electrocatalytic oxidation of l-tyrosine (Tyr) was investigated on a carboxylic acid functionalised multi-walled carbon nanotubes modified carbon paste electrode using cyclic voltammetry and amperometry. The surface morphology of the electrodes was studied using field emission (FE)-SEM images, and the interface properties of bare and modified electrodes were investigated by electrochemical impedance spectroscopy (EIS). The influence of the amount of modifier loading and the variation of the pH of the solution on the electrochemical parameters have been investigated. Cyclic voltammetry was carried out to study the electrochemical oxidation mechanism of Tyr, which showed an irreversible oxidation process at a potential of 637.0 mV at modified electrode. The anodic peak current linearly increased with the scan rate, suggesting that the oxidation of Tyr at modified electrode is an adsorption-controlled process. A good linear relationship between the oxidation peak current and the Tyr concentration in the range of 0.8–100.0 μM was obtained in a phosphate buffer solution at pH 7.0 with a detection limit of 14.0?±?1.36 nM (S/N?=?3). The practical utility of the sensor was demonstrated by determining Tyr in spiked cow’s milk and human blood serum. The modified electrode showed excellent reproducibility, long-term stability and antifouling effects.     

Improvement in performance of a hyoscine butylbromide potentiometric sensor using a new nanocomposite carbon paste: a comparison study with polymeric membrane sensor

Multiwalled carbon nanotubes and TiO₂ nanoparticles were used for the improvement of a hyoscine butylbromide (HYBB) potentiometric carbon paste electrode response. The electrode was based on the ammonium reineckate-hyoscine ion association complex as an ion-exchange site dissolved in 2-nitrophenyloctyl ether as pasting liquid. The characteristics of the suggested potentiometric nanocomposite-modified HYBB carbon paste electrode in comparison with the PVC membrane sensor show better responses in terms of sensitivity, dynamic concentration range, detection limit, Nernstain slope, low potential drift, response time, lifetime, and mechanical stability. The electrode exhibits good selectivity for HYB ion with respect to a large number of cations. For investigation of the effects of carbon nanotubes and TiO₂ nanoparticles on the conductivity property of the electrode surface, electrochemical impedance spectroscopy measurements were done. The prepared electrode was successfully applied to the determination of hyoscine butylbromide in pharmaceutical formulations and biological samples.     

Gold nanoparticles modified GC electrodes: electrochemical behaviour dependence of different neurotransmitters and molecules of biological interest on the particles size and shape

Gold colloidal nanoparticles (AuNps), synthesized by gold chloride hydrate (HAuCl₄) chemical reduction were used to realize a modified glassy carbon electrode (GCE). Different shapes and sizes were observed, varying the molar ratio of HAuCl₄ and polyvinylpyrrolidone (PVP). The electrochemical behaviour of different neurotransmitters and molecules of biological interest (dopamine, caffeic acid, catechol, uric acid, epinephrine and serotonin) were investigated by cyclic voltammetry (CV) at the AuNps modified GCE and a dependence of the electrochemical response on the size and the shape of the particles was observed. The electrochemical responses were stable during time with a generic decreasing of the peak current after 10 days ranging from 5–10% for catechol, uric acid and serotonine to 10–15% for the other analytes. A study on the electrochemical interface of modified electrodes was also carried out by means of electrochemical impedance spectroscopy (EIS).     

Elevated performances of SnS anodes with MWNTs as conductive agent for rechargeable lithium-ion batteries

SnS nanoparticles were mechanochemically synthesized and fabricated into electrodes with two kinds of conductive agents, acetylene black and multi-wall carbon nanotubes (MWNTs), respectively. The morphology and structure of as-synthesized SnS powder were characterized by scanning electron microscopy and X-ray diffraction. The electrochemical properties of as-prepared electrodes were investigated by discharge–charge test, cyclic voltammogram, and electrochemical impedance spectrum. By comparing the variation of the charge-transfer impedance R _ct at different discharge states, it was found that the value of R _ct of the electrode with MWNTs as conductive agent was less than that of the electrode with acetylene black as conductive agent. The electrode with MWNTs as conductive agent had preferable cycling performances, which was believed to be attributed to the tenacity and good conductivity of MWNTs.     

Electrochemical and surface characterisation of carbon-film-coated piezoelectric quartz crystals

The electrochemical properties of carbon films, of thickness between 200 and 500 nm, sputter-coated on gold- and platinum-coated 6 MHz piezoelectric quartz crystal oscillators, as new electrode materials have been investigated. Comparative studies under the same experimental conditions were performed on bulk electrodes. Cyclic voltammetry was carried out in 0.1 M KCl electrolyte solution, and kinetic parameters of the model redox systems Fe(CN)₆^3−/4− and [Ru(NH₃)₆]^3+/2+ as well as the electroactive area of the electrodes were obtained. Atomic force microscopy was used in order to examine the surface morphology of the films, and the properties of the carbon films and the electrode-solution interface were studied by electrochemical impedance spectroscopy. The results obtained demonstrate the feasibility of the preparation and development of nanometer thick carbon film modified quartz crystals. Such modified crystals should open up new opportunities for the investigation of electrode processes at carbon electrodes and for the application of electrochemical sensing associated with the EQCM.     

Electrooxidation of hydrazine in alkaline medium at carbon paste electrode decorated with poly(<Emphasis Type="Italic">P</Emphasis>-phenylendiamine/ZnO) nanocomposite

In this study, poly(P-phenylenediamine/ZnO) (PpPD/ZnO) nanocomposite (NC) under ultrasonic conditions was synthesized and characterized. The presence of zinc oxide nanoparticles changed the morphology of PpPD considerably as confirmed by SEM observations. Hydrazine electrooxidation at novel modified carbon paste electrodes (CPE) with supported NC was investigated by cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and chronoamperometry (CA) techniques. Obtained results showed that the NC increases the surface catalytic activity of CPE toward hydrazine electrooxidation. The electrocatalytic current density increased linearly with hydrazine concentration, and the detection limit and sensitivity are determined to be 24 μM and 0.172 mA cm^?2 mM^?1, respectively. As revealed by the EIS measurements, the increased conductivity and decreased R _ct are owing to the presence of ZnO NPs in the PpPD matrix. The CA results indicated that hydrazine electrooxidation results in higher steady-state current density on CPE/PpDP/ZnO electrode system compared to the CPE/PpDP and CPE electrodes.     

离子液体[BDMIM]PF_6修饰碳糊电极的制备及其电化学性能

以离子液体1,2-二甲基-3-丁基咪唑六氟磷酸盐（[BDMIM]PF6）代替传统液态石蜡为粘合剂与石墨粉相混合,制备了一种新型的离子液体修饰碳糊电极（IL/CPE）。采用扫描电子显微镜分别对其表面形貌和石蜡碳糊电极（CPE）表面形貌进行了表征。以亚铁氰化钾为电化学探针对IL/CPE的电化学行为进行了研究,并与CPE进行了比较。结果表明,[BDMIM]PF6由于具有较高的导电性,使IL/CPE比CPE具有更高的导电效率,铁氰化钾在电极上的可逆性变好,ΔEP值变小,峰电流响应增加10倍,电极过程由CPE上的吸附控制变为扩散控制,根据计时库仑法求解出铁氰化钾的扩散系数为5.52×10^-6cm2/s（25℃）。电化学交流阻抗图亦表明与不导电的液态石蜡油相比,离子液体的存在加快了电子传递。     

Electrocatalytic properties of glassy carbon electrodes modified with hydroxy derivatives of 9,10-anthraquinone for oxygen reduction reaction

The electrochemical and electrocatalytic behavior of glassy carbon electrodes modified by one mono and four dihydroxy derivatives of anthra-9,10-quinone compounds have been investigated by cyclic voltammetric technique. The stability of the modified electrodes was ascertained in acidic and neutral media. The surface morphology of modified electrode was characterized by scanning electron microscope. The influence of pH on the electrochemical and electrocatalytic behavior was studied and pH?6.0 or 7.0 was chosen as the optimum working pH by comparing the shift in oxygen reduction potential. The anthraquinone-adsorbed glassy carbon electrodes possess excellent electrocatalytic ability for oxygen reduction with overpotential ranging from 388 to 547?mV lower than that at a plain glassy carbon electrode. Hydrodynamic volatammetric studies were performed to determine the heterogeneous rate constants for the reduction of O₂ at the surface of the modified electrodes, mass specific activity of the anthraquinones used, and the apparent diffusion coefficient of O₂ in buffered aqueous O₂-saturated solutions.     

Electrosynthesis and characterization of poly aniline/garnet nanoparticles for high-performance electrochemical capacitors

In this work, supercapacitive performance of polyaniline/yttrium aluminum garnet (YAG: Y₃Al₅O₁₂) nanoparticles (PANI/YAGNPs) was studied. YAG nanoparticles were synthesized by pulse electro-deposition method and after that, PANI/YAGNPs electrodeposited on the surface of glassy carbon electrodes through cyclic voltammetry. Morphological studies show that YAG nanoparticles were distributed in the structure of PANI filaments uniformly. XRD and FTIR were used to perform a structural study of materials. Different electrochemical techniques such as cyclic voltammetry (CV), galvano static charge discharge (CD), and impedance spectroscopy (EIS) were used to evaluate the applicability of using PANI/YAGNPs as an active material for supercapacitors. The specific capacitance (SC) of PANI and PANI YAG NPs electrodes calculated using CV technique are 240 and 440 F/g, respectively. Increasing the conductivity and stability of composite electrodes during continuous CD cycles compared to PANI ones are some features of using YAG NPs in the structure of polymer electrodes. Stability of composite electrodes remains about 98% through 1000 continuous cycles whereas the polymeric electrode loses about 91% of its capacitance during this time range.     

An active nano-supported interface designed from gold nanoparticles embedded on ionic liquid for depositing DNA

The use of an active nano-interface designed from gold nanoparticles embedded on ionic liquid for DNA damage resulted from formalehyde (HCHO) is reported in this article. The active nano-interface was fabricated by depositing gold nanoparticles on the ionic liquid 1-butyl-3-methylimidazolium tetrafluroborate ([bmim][BF₄]). A glassy carbon electrode modified by this composite film was fabricated to immobilize DNA for probing into the damage resulted from HCHO. The modifying process was characterized by X-ray photoelectron spectroscopy, atomic force microscopy and electrochemistry involving electrochemical impedance spectroscopy. It was found that the modified film performs effectively in studying the DNA damage by electrocatalytic activity toward HCHO oxidation.     

Au标蛋白自组装表面增强拉曼光谱的研究

采用免疫Au标技术,用尺寸大约在13 nm的Au胶体颗粒标记了人血清蛋白(Human IgG),然后将Au标蛋白复合体固定在通过三氨基三乙氧基硅烷和戊二醛自组装单膜的Si片上。这种方法在基底表面上不仅牢固地固定了单层Au纳米颗粒标记的蛋白分子复合体而且提高了复合体的表面覆盖度,保持了生物分子的结构。利用原子力显微镜(AFM)观察了Au标蛋白的自组装表面。实验结果表明Au标蛋白在Si片表面聚积形成一定的Au标蛋白分子的复合体“岛状”单层,并且在这些岛状单层上获得了很明显的标记蛋白的表面增强拉曼散射(SERS)信号。文章在Si表面自组装了Au标蛋白分子,获得了较好的蛋白分子的SERS信号,提供了一种研究蛋白分子的SERS活性基底。     

A facile and flexible process of β-cyclodextrin grafted on Fe3O4 magnetic nanoparticles and host-guest inclusion studies

In this study, a kind of novel surface-functionalized magnetic nanoparticles was fabricated by the Fe₃O₄ nanoparticles surface modification with mono-6-deoxy-6-(p-tolylsulfonyl)-cyclodextrin (6-TsO-β-CD), which were employed to interact with uric acid and their behavior was investigated by electrochemical methods. The architecture has been characterized by powder X-ray diffraction (XRD), Fourier transform infrared spectra (FT-IR), transmission electron microscopy (TEM), and thermogravimetric analysis (TGA), which confirmed that cyclodextrins have been effectively functionalized on the surface of Fe₃O₄ nanoparticles. The analyses of vibration sample magnetometer (VSM) verified that the nanoparticles owned good magnetic property. The grafted β-cyclodextrin on the Fe3O4 nanoparticles contributed to as a modified electrode for detecting uric acid with cyclic voltammograms. Electrochemical results revealed that the new materials could exhibit excellent molecules recognition ability and show high electrochemical response. The new nanoparticles simultaneously had unique properties of magnetic nanoparticles and cyclodextrins through combining their individual distinct advantages.     

Trapping and release of citrate-capped gold nanoparticles

An electrical method to trap and release charged gold nanoparticles onto and from the surface of gold electrodes modified by an alkanethiol self-assembled monolayer (SAM) is presented. To form electrodes coated with gold nanoparticles (GNPs), amine-terminated SAMs on gold electrodes were immersed in a solution of negatively charged citrate-capped GNPs. Accumulation of GNPs on the electrode surface was monitored by a decrease in the impedance of the SAM-modified electrode and by an increase in the electrochemical activity at the electrode as shown through cyclic voltammetry (CV). Electrostatic interactions between the GNPs and the amine-terminated SAM trap the GNPs on the electrode surface. Application of a subsequent negative bias to the electrode initiated a partial release of the GNPs from the electrode surface. Impedance spectroscopy, cyclic voltammetry, ultraviolet-visible (UV-Vis) spectroscopy and atomic force microscopy (AFM) were used to monitor and confirm the attraction of GNPs to and release from the aminealkanethiolated gold electrodes. This work describes a method of trapping and release for citrate-capped GNPs that could be used for on-demand nanoparticle delivery applications such as in assessing and modeling nanoparticle toxicology, as well as for monitoring the functionalization of gold nanoparticles.     

Surface modification of permalloy (Ni<Subscript>80</Subscript>Fe<Subscript>20</Subscript>) nanoparticles for biomedical applications

We report a simple and novel method for surface biofunctionalization onto recently reported Ni₈₀Fe₂₀ permalloy nanoparticles (~71 nm) and the immobilization of a model protein, IgG from human serum. The strategy of protein immobilization involved attachment of histidine-tagged streptavidin to the Ni₈₀Fe₂₀ nanoparticles via a non-covalent ligand binding followed by biotinylated human IgG binding on the nanoparticle surface using the specific high affinity avidin–biotin interaction. The biofunctionalization of Ni₈₀Fe₂₀ permalloy nanoparticles was confirmed by Fourier Transform InfraRed (FTIR) spectroscopy and protein denaturing gel electrophoresis (lithium dodecyl sulfate-polyacrylamide gel electrophoresis, LDS-PAGE). This protocol for surface functionalization of the novel nanometer-sized Ni₈₀Fe₂₀ permalloy particles with biological molecules could open diverse applications in disease diagnostics and drug delivery.     

Sonochemical synthesis and fabrication of neodymium sesquioxide entrapped with graphene oxide based hierarchical nanocomposite for highly sensitive electrochemical sensor of anti-cancer (raloxifene) drug

The ultrasound-assisted synthesis of a novel neodymium sesquioxide nanoparticles (Nd₂O₅ NPs) decorated graphene oxide (GO) nanocomposite under ultrasonic probe (Ultrasonic processor model-PR 1000; frequency-30 kHz; power of 100 W/cm²) has been reported. After then, SEM, TEM, XRD, EDX and electrochemical impedance spectroscopy characterized was analyzed using Nd₂O₅ NPs@GO nanomaterial. Furthermore, the nanomaterial modified GCE (glassy carbon electrode) shows excellent electrochemical sensing performance towards anti-cancer drug. Raloxifene is one of the important anti-cancer drug. Moreover, the fabricated electrochemical sensor has showed a wide linear range for raloxifene between 0.03 and 472.5 µM and nanomolar detection limit (18.43 nM). In addition, the Nd₂O₅ NPs@GO modified sensor has been applied to the determination of raloxifene in human blood and urine samples.     

Immobilization of redox mediators on functionalized carbon nanotube: A material for chemical sensor fabrication and amperometric determination of hydrogen peroxide

Chemical functionalization of single-walled carbon nanotubes with redox mediators, namely, toluidine blue and thionin have been carried out and the performance of graphite electrode modified with functionalized carbon nanotubes is described. Mechanical immobilization of functionalized single-walled nanotube (SWNT) on graphite electrode was achieved by gently rubbing the electrode surface on carbon nanotubes supported on a glass slide. The electrochemical behaviour of the modified electrodes was investigated by cyclic voltammetry. The SWNT-modified electrodes showed excellent electrocatalytic effect for the reduction of hydrogen peroxide. A decrease in overvoltage was observed as well as an enhanced peak current compared to a bare graphite electrode for the reduction of hydrogen peroxide. The catalytic current was found to be directly proportional to the amount of hydrogen peroxide taken.     

Differential pulse anodic stripping voltammetric determination of Hg2+ at poly(Eriochrome Black T)-modified carbon paste electrode

The electrochemical behavior of Hg²⁺ was investigated in poly(Eriochrome Black T)-modified carbon paste electrode (CPE) using cyclic voltammetry (CV). Poly(Eriochrome Black T) was prepared in an alkaline medium on the surface of the CPE using a solution of Eriochrome Black T with the CV technique. The electrochemical impedance study revealed a better charge transfer kinetics at the modified electrode. The effects of variation of the experimental conditions, such as the concentration of electrolytes, pH, deposition time, and the deposition potential, which maximize current efficiency were studied. The optimum response of Hg²⁺ was observed in 1.0 M KCl solution. The differential pulse anodic stripping voltammetric technique was employed successfully to detect Hg²⁺, which gave a good linear response at low concentration levels of Hg²⁺. The detection limit was found to be 2.2?×?10^?10 M (S/N?=?3), which is comparable with that achieved in multiwall carbon nanotube-modified electrode. The remarkable electroanalytical performance of the modified electrode makes it amenable to employ it successfully as an electrochemical sensor for the determination of hazardous pollutant Hg²⁺ in environmental samples.     

Glassy carbon - A promising substrate material for pulsed laser deposition of thin Li1+xMn2O4−δ electrodes

The spinel LiMn₂O₄ is a promising candidate for future battery applications. If used as a positive electrode in a battery, the charging capacity of such a battery element is limited by the formation of a solid electrolyte interphase like layer between the electrolyte and the spinel. To study the electrolyte-electrode interaction during electrochemical cycling, spinel thin films are deposited as model electrodes on glassy carbon substrates by pulsed laser ablation. The obtained polycrystalline oxide thin films show a well defined surface morphology and are electrochemical active. Adhesion of these thin films on glassy carbon is in general poor, but can be improved considerably by a surface pretreatment or adding a thin metallic coating to the substrate prior deposition. The best adhesion is obtained for films deposited on argon plasma pretreated as well as Pt coated glassy carbon substrates. During the electrochemical characterization of Li_1.06Mn₂O_3.8 thin film electrodes, no additional reactions of the substrate are observed independent of the used electrolyte. The best cycle stability is achieved for films on Pt coated glassy carbon substrates.     

碳纳米管表面金纳米颗粒的形成与结构转变

利用分子动力学模拟研究了室温下金纳米颗粒在碳纳米管表面的结构和作用能.研究结果表明,金纳米颗粒随着尺寸的增大会发生不同于孤立状态下的结构转变.当原子数小于130时,颗粒属于无序结构;当原子数大于140时,呈现面心立方晶体结构.小金纳米颗粒和碳纳米管结合紧密,相互作用能正比于面对碳纳米管的颗粒表面面积. 关键词： 金纳米颗粒 碳纳米管 分子动力学模拟     

Preparation and Fluoroimmunoassay Application of New Red-Region Fluorescent Silica Nanoparticles

This is the first report on the preparation and utilization of a novel red-region fluorescent dye (tetracarboxy aluminum phthalocyanine) doped silica nanoparticles. In these nanoparticles, the tetracarboxy aluminum phthalocyanine molecules were covalently bound to silica matrix to protect the dye leaking from nanoparticles in bio-applications. The surface of the nanoparticles was modified by amino groups and easily bioconjugated with goat anti-human IgG antibody. By employing these nanoparticles as fluorescent probe, a sensitive fluoroimmunoassay method has been developed for the determination of trace level of human IgG. The calibration graph for human IgG was linear over the range of 0–500 ng mL⁻¹ with a detection limit of 1.6 ng mL⁻¹. Compared with the corresponding system using free AlC₄Pc as a probe for determining human IgG, the sensitivity of the proposed system was notably increased. The method was applied to the analysis of human IgG in human sera with satisfactory results.