超微电极测定单细胞中神经传质的进展

本文评述了近年来用超微电极测定单细胞中神经传质的沿革，方法及进展，着重介绍了超微碳纤维电极的制备以及用超微碳纤维电极测定单细胞中神经传质的技术步骤，对存在的问题，应用前景和该方法进一步发展的方向进行了探讨。     

甲胺磷离子选择性电极的研制及其应用

以四苯硼钠与甲胺磷在盐酸介质中生成的离子缔合物为电活性物质,首次研制出一种甲胺磷PVC涂层玻璃电极。并对该电极的响应机理及性能进行了研究。实验表明,该电极的Nernst响应范围为1×10-2~1×10-4(φ),斜率为50.28 mV/pφ。该电极响应迅速,重复性好,用于蔬菜中残留甲胺磷的测定,方法快速、准确,结果满意。     

一种单细胞电化学模拟分析装置

单细胞分析是近年来生命科学中一个新兴热点研究领域。活细胞具有多种维持细胞生物活性的电化学活性物质 ,所以 ,建立在生物微环境中电极表面的电子传递反应的伏安测定对阐明细胞内发生的生化反应具有重要意义。我们设计制作了一种单细胞电化学模拟分析装置 ,让大体积的溶液生成一个微体积的小液滴 ,小液滴就是单细胞的模拟物 ,其大小与单细胞相仿。由于小液滴的成分与大体积溶液的成分相同 ,这样就可以人为地改变大体积溶液的成分与含量 ,来达到控制微体积小液滴的成分及含量的目的 ,给微电极的测定分析、选择和研究带来很大的方便 ,很容易对测定所用的微电极进行选择 ,找到该微电极对微滴中某成分的响应规律及相应的干扰组分 ,从而应用于单细胞内液中有关成分的实际测定。本装置结构简单 ,具有易建立、易操作的特点     

基于Schiff-base结构化合物载体的汞离子选择性电极的制备与表征

高产率合成了一种新的Schiff-base结构化合物,并将其表征为高选择性聚合物膜汞离子选择性电极载体。考察了不同增塑剂及离子交换剂对膜电极响应性能的影响,在最佳膜组分条件下测得该电极对汞离子的线性响应范围为1.0×10-6~3.0×10-4mol/L,响应斜率为(29.3±0.3)mV/dec,检出限为2.6×10-7mol/L;该电极响应速率快(小于12 s),可在较宽的pH范围内(pH2.8~5.6)使用,且其它常见碱金属、碱土金属以及过渡金属离子对该测试电极的干扰小;可准确检测自来水中汞离子的浓度。     

单细胞水平的分析方法研究及进展

本文评述了近年来单细胞分析的应用及进展，介绍了超微电极电化学分析法和微柱分离法两大类方法在单细胞分析中应用的机理、必要的技术、有关研究内容和最新进展及其发展方向。     

水杨醛肟铜络合物中性载体高选择性水杨酸根电极的研究

采用合成的Schiff碱金属络合物水杨醛肟铜(Ⅱ)、锌(Ⅱ)、镍(Ⅱ)为中性载体制备阴离子选择性电极。结果表明水杨醛肟铜(Ⅱ)对水杨酸根(Sal-)具有高选择性及优良的电位响应性能,电极呈现反Hofmeister选择性行为,其选择性次序为Sal->ClO4->SCN->I->NO2->NO3->Br->Cl->OAc->SO42-。采用交流阻抗技术和紫外可见光谱技术研究了电极的响应机理。该电极具有响应快、重现性好、检出限低和制备简单等优点。将电极用于药品及人体尿液分析,结果令人满意。     

基于双氨基三唑硫醚为中性载体的汞离子选择性电极的研究

研制了基于双氨基三唑硫醚为中性载体的阳离子选择性电极。实验表明,该电极对Hg2 具有良好的电位响应特性,在pH 2.0硝酸盐缓冲液中,电极电位呈近能斯特响应,线性响应范围为4.0 mg/L~20 g/L,斜率为33.4 mV/dec.(25℃),检出限为1.7 mg/L。该电极响应时间短(<10 s),pH范围较宽(1.3~3.3)。将该电极用于实际水样和二元混合溶液中Hg2 的检测,其结果令人满意。     

基于双核三苄基甲醇锡(Ⅳ)对苯二甲酸酯配合物为中性载体的硫氰酸根电极的研究

研究了双核三苄基甲醇锡(Ⅳ)对苯二甲酸酯配合物［Sn(Ⅳ)-BTMTT］为中性载体的PVC膜阴离子选择性电极。这类电极对硫氰酸根离子呈现出优良的电位响应性能和选择性,并呈现反Hofmeister序列行为。其选择性序列为:SCN-＞I-＞Ac-＞－NO＞2－2NO＞－4ClO＞Cl-＞3－4SO,该电极在pH＝3.0的磷酸盐缓冲体系中对SCN-在0.1～8×10-5mol／L浓度范围内呈超能斯特响应,斜率为-77.3mV／dec,检出限为4.0×10-5mol／L。采用交流阻抗及紫外光谱研究了阴离子与载体的作用机理。该电极具有响应快、重现性好、制备简单等优点。将该电极用于废水分析,结果令人满意。     

盐酸雷尼替丁印迹聚合物膜电极的制备与应用

研究了盐酸雷尼替丁印迹聚合物离子选择性电极的制备、特性及应用。该电极在1.0×10-5～1.0×10-2mol/L范围内表现能斯特响应,斜率为-28.18mV/pC,检测下限为5.2×10-6mol/L,原料回收率为96.8%～104.6%。该电极与先前报道的电极相比,具有更高的选择性、灵敏性和抗干扰性。利用该电极对雷尼替丁原料、胶囊含量进行了测定,结果与药典法一致。     

基于Schiff-base结构化合物载体的汞离子选择性电极的制备与表征

高产率合成了一种新的Schiff-base结构化合物,并将其表征为高选择性聚合物膜汞离子选择性电极载体.考察了不同增塑剂及离子交换剂对膜电极响应性能的影响,在最佳膜组分条件下测得该电极对汞离子的线性响应范围为1.0×10-6 ～3.0×10-4 mol/L,响应斜率为(29.3±0.3) mV/dec,检出限为2.6×...     

Fabrication of low-melting-point alloy microelectrode and monolithic spray tip for integration of glass chip with electrospray ionization mass spectrometry

In this paper, a glass microchip-based emitter with a low-melting-point alloy (LMA) microelectrode and a monolithic tip for electrospray ionization mass spectrometry (ESI-MS) was described. So far, the fabrication of metal microelectrode achieving direct electrical contact in the microchannel of glass chip is still a challenge. A novel fabrication approach for LMA microelectrode in the glass chip was developed to achieve direct electrode-solution electrical contact in the microchannel. An electrode channel and a sample channel were firstly fabricated on a glass chip with a micropore connecting the two channels. The melted LMA was filled into the electrode channel under a pressure of ca. 100 kPa, forming a stable and nicely fitted interface at the micropore between the sample and the electrode channels due to surface tension effect. The melted LMA filled in the electrode channel was then allowed to solidify at room temperature. The channel geometries including the distance between the sample and the electrode channels on the mask and the turning angle of the electrode channel were optimized for fabricating the LMA electrode. In this work, an improved fabrication approach for monolithic emitter tip based on pyramid-shaped tip configuration and stepped grinding method was also developed to fabricate well-defined sharp tips with a smallest tip end size of ca. 15 μm × 50 μm. Two types of emitter tip end including puncher-shaped tip and fork-shaped tip were produced. The emitter with the fork-shaped tip showed better working stability (4.4% RSD, TIC) at nanoliter-scale flow rate of 50 nL/min. The fabrication approaches for the LMA microelectrode and emitter tip are simple and robust, and could be carried out in most of routine laboratories without the need of complicated and expensive instruments. The performance of the emitter was evaluated in the analysis of reserpine, angiotensin II and myoglobin. A continuous experiment over 6 h demonstrated good stability of the present system in long-term analysis.     

Scanning electrochemical microscope observation of defects in a hexadecanethiol monolayer on gold with shear force-based tip-substrate positioning

Scanning electrochemical microscopy (SECM) was used for imaging of n-hexadecanethiol-modified Au surfaces. In these studies, small defects were observed in the monolayer when a submicrometer electrode was used as an SECM tip, although a cyclic voltammogram of a Au disk electrode showed that the surface of the Au was completely covered with n-hexadecanethiol. The dependence of the SECM images on the potential of the Au electrode was also examined. A comparison of the current at the Au electrode and the tip current in the SECM images showed that direct electron transfer through the monolayer was dominant, rather than electron transfer at the defects. The size of the defects was estimated from the tip current to be 1-100 nm, under the assumption that the defects were small compared to the SECM probe.     

A dual-electrode approach for highly selective detection of glucose based on diffusion layer theory: experiments and simulation

A dual-electrode configuration for the highly selective detection of glucose in the diffusion layer of the substrate electrode is presented. In this approach, a glassy carbon electrode (GCE, substrate) modified with a conductive layer of glucose oxidase/Nafion/graphite (GNG) was used to create an interference-free region in its diffusion layer by electrochemical depletion of interfering electroactive species. A Pt microelectrode (tip, 5 microm in radius) was located in the diffusion layer of the GNG-modified GCE (GNG-G) with the help of scanning electrochemical microscopy. Consequently, the tip of the electrode could sense glucose selectively by detecting the amount of hydrogen peroxide (H2O2) formed from the oxidization of glucose on the glucose oxidase layer. The influences of parameters, including tip-substrate distance, substrate potential, and electrolyzing time, on the interference-removing efficiency of this dual-electrode approach have been investigated systematically. When the electrolyzing time was 30 s, the tip-substrate distance was 1.8 a (9.0 microm) (where a is the radius of the tip electrode), the potentials of the tip and substrate electrodes were 0.7 V and 0.4 V, respectively, and a mixture of ascorbic acid (0.3 mM), uric acid (0.3 mM), and 4-acetaminophen (0.3 mM) had no influence on the glucose detection. In addition, the current-time responses of the tip electrode at different tip-substrate distances in a solution containing interfering species were numerically simulated. The results from the simulation are in good agreement with the experimental data. This research provides a concept of detection in the diffusion layer of a substrate electrode, as an interference-free region, for developing novel microelectrochemical devices.     

A glass capillary ultramicroelectrode with an electrokinetic sampling ability.

A glass capillary ultramicroelectrode (tip diameter approximately 1.2 microm) having an electrokinetic sampling ability is described. It is composed of a pulled glass capillary filled with an inner solution and three internal electrodes (Pt working and counter electrodes and an Ag/AgCl reference electrode). The voltammetric response of the capillary electrode is based on electrokinetic transport of analyte ions from the sample solution into the inner solution across the conical tip. It was found that the electrophoretic migration of analytes at the conical tip is faster than electroosmotic flow, enabling electrokinetic transport of analyte ions into the inner solution of the electrode. By using [Fe(CN)6]4- and (ferrocenylmethyl)trimethylammonium (FcTMA+) ions as model analytes, differential pulse voltammetric responses of the capillary electrode were investigated in terms of tip diameter of the capillary, sampling voltage, sampling time, detection limit and selectivity. The magnitude of the response depends on the size and charge of analyte ions. With a capillary electrode having a approximately 1.2-microm tip diameter, which minimizes non-selective diffusional entry of analytes, the response after 1 h sampling at +1.7 V is linearly related to [Fe(CN)6]4- concentration in the range of 0.50-5.0 mM with the detection limit of 30 microM. Application of a potential of the same sign as that of the analyte ion forces the analyte to move out from the electrode to the solution, enabling reuse of the same capillary electrode. The charge-selective detection of analytes with the capillary electrode is demonstrated for [Fe(CN)6]4- in the presence of FcTMA+.     

A simple approach for fabrication of dual-disk electrodes with a nanometer-radius electrode and a micrometer-radius electrode

We developed a new simple approach to fabricate dual-disk electrodes with a nanometer-radius electrode and a micrometer-radius electrode. First, nanometer-sized electrodes and micrometer-sized electrodes were constructed using 10-μm-radius metal wires, respectively. To fabricate the nanometer-sized electrode, after the apex of the 10-μm-radius metal wire was electrochemically etched to an ultrafine point with a nanometer-radius, the metal wire was electrochemically coated with a phenol-allyphenol copolymer film. The micrometer-sized electrode was fabricated by directly electrochemical coating the metal wire with an extremely thin phenol-allyphenol copolymer film. Then, the nanometer-radius electrode (the first electrode) and the 10-μm-radius electrode (the second electrode) were inserted into two sides of a thick-septum borosilicate theta (θ) tubing, respectively. The second electrode protruded from the top of the θ tubing. The top of the θ tubing was sealed with insulating ethyl α-cyanoacrylate. The top of the θ tubing with both electrodes was ground flat and polished successively with fine sandpaper and aluminum oxide powder until the tip of the first electrode was exposed. Since the second electrode protruded from the top of the θ tubing, its 10-μm-radius tip was naturally formed during polishing. The dual-disk electrodes were characterized by scanning electron microscopy and cyclic voltammetry. The success rate for fabrication of the dual-disk electrodes is ∼80% due to double insurance from two coating layers of different polymers.     

Size-controlled fabrication of nanometer-sized gold electrodes with polystyrene coating

We present a simple, convenient procedure for the fabrication of nanometer-sized gold electrodes with the ability to control the electrode size at the construction stage. The electrodes are prepared by etching a gold wire, coating it with a polystyrene film, and then removing the film from the tip apex by thermal stripping in an aqueous solution in conjunction with in situ monitoring of the exposed electrode area by cyclic voltammetry measurements. It is demonstrated that the method produces point-like electrodes with precise control of the apparent electrode radius within a few nanometers.     

Nanoscale intermittent contact-scanning electrochemical microscopy

A major theme in scanning electrochemical microscopy (SECM) is a methodology for nanoscale imaging with distance control and positional feedback of the tip. We report the expansion of intermittent contact (IC)-SECM to the nanoscale, using disk-type Pt nanoelectrodes prepared using the laser-puller sealing method. The Pt was exposed using a focused ion beam milling procedure to cut the end of the electrode to a well-defined glass sheath radius, which could also be used to reshape the tips to reduce the size of the glass sheath. This produced nanoelectrodes that were slightly recessed, which was optimal for IC-SECM on the nanoscale, as it served to protect the active part of the tip. A combination of finite element method simulations, steady-state voltammetry and scanning electron microscopy for the measurement of critical dimensions, was used to estimate Pt recession depth. With this knowledge, the tip-substrate alignment could be further estimated by tip approach curve measurements. IC-SECM has been implemented by using a piezo-bender actuator for the detection of damping of the oscillation amplitude of the tip, when IC occurs, which was used as a tip-position feedback mechanism. The piezo-bender actuator improves significantly on the performance of our previous setup for IC-SECM, as the force acting on the sample due to the tip is greatly reduced, allowing studies with more delicate tips. The capability of IC-SECM is illustrated with studies of a model electrode (metal/glass) substrate.     

STM针尖诱导铜表面纳米刻蚀与沉积

扫描隧道显微技术 ( STM)不但可在小至原子分辩的尺度上现场研究电极表面及其结构变化 ,还能对电极表面进行纳米尺度上的加工、修饰 [1～ 3] .由于 STM探针与被研究样品的表面仅相距～ 1 nm,探针附近区域电极 /溶液界面的结构和性质将不可避免地受到影响 .尽管人们已认识到针尖与样品表面不可忽视的相互作用 ,但利用该相互作用诱导纳米区域电化学反应的研究还很少 ,仅有半导体 Si[4～ 7] 和 Ga As[8] 表面基于强电场诱导或空穴注入的 STM针尖诱导纳米刻蚀等的报道 .本文在控制铜的电位负于其热力学平衡电位 ( Nernst电位 )的情况下 ,…     

Voltammetric Determination of 4‐Nitrophenol Using a Novel Type of Silver Amalgam Paste Electrode

A differential pulse voltammetric (DPV) method was developed for the determination of 4‐nitrophenol (4‐NP) at a newly developed silver amalgam paste electrode (AgA‐PE) in Britton–Robinson buffer pH 3.0. The electrode is based on a disposable plastic pipette tip filled with paste amalgam based on a mixture of mercury and fine silver powder (9 : 1, w/w). The experimental parameters, such as pH of Britton–Robinson buffer and activation and regeneration potential of the electrode surface were optimized. The reduction peak current dependences were linear for the concentration of 4‐NP from 0.2 to 100 μM. The method showed reproducible results with RSD (n=45) of 1.7%. The limit of determination (LOD) was 0.3 μM. The method was successfully applied for the direct determination of 4‐NP in drinking water.     

Sequential electrochemical oxidation and site-selective growth of nanoparticles onto AFM probes

In this work, we reported an approach for the site-selective growth of nanoparticle onto the tip apex of an atomic force microscopy (AFM) probe. The silicon AFM probe was first coated with a self-assembled monolayer (SAM) of octadecyltrichlorosilane (OTS) through a chemical vapor deposition (CVD) method. Subsequently, COOH groups were selectively generated at the tip apex of silicon AFM probes by applying an appropriate bias voltage between the tip and a flat gold electrode. The transformation of methyl to carboxylic groups at the tip apex of the AFM probe was investigated through measuring the capillary force before and after electrochemical oxidation. To prepare the nanoparticle terminated AFM probe, the oxidized AFM probe was then immersed in an aqueous solution containing positive metal ions, for example, Ag+, to bind positive metal ions to the oxidized area (COOH terminated area), followed by chemical reduction with aqueous NaBH 4 and further development (if desired) to give a metal nanoparticle-modified AFM probe. The formation of a metal nanoparticle at the tip apex of the AFM probe was confirmed by scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDXA).