Voltammetric Characterization of Micro‐ and Submicrometer‐Electrode Arrays of Conical Shape for Electroanalytical Use

Densely packed micro‐ and submicrometer electrode arrays of platinum and gold (the nominal number, N, of electrodes in each array varies between 225 and 3600) are fabricated by photolithographic technique and vapor deposition processes of metal films. The electrodes are conical‐shaped and only their apexes are exposed to the electrolytic solution. The electrode arrays are characterized electrochemically in Ru(NH₃)₆Cl₃ aqueous solutions by using cyclic voltammetry at low scan rates, to establish the number of electrochemically active electrodes (N_ac) in each array; the geometric characterization is performed by scanning electron microscopy. All the investigated arrays provide steady‐state voltammograms, indicating diffusionally independent behavior of each microelectrode. The number of microelectrodes that are active in the fabricated arrays depends on microelectrode density. In particular, for the arrays with N=3600 and N=225, the fraction of active sites is about 45% and 90%, respectively. The analytical performance of some of the Pt version of the arrays is tested in hydrogen peroxide solutions, allowing verifying that linear calibration plots over the concentration range (0.1–20 mM) are obtained. This dynamic range is larger than that typically recorded at smooth polycrystalline platinum electrodes (0.5–5 mM), and the better performance is attributed to both the higher aspect ratio of the cone geometry and the higher mass transport associated to each microelectrode of the array. Reproducibility (within 3.5%, r.s.d.) and long‐term stability (within 5%, r.s.d., after 8 h continuous use) of the electrode systems are satisfactory. A low detection limit, based on the signal to noise ratio equal to 3, of 0.05 mM is found, which is adequate for a rapid monitoring of H₂O₂ in real samples and industrial processes.     

A micrometer head integrated microfluidic device for facile droplet size control and automatic measurement of a droplet size

A novel microfluidic droplet generator is proposed, which can control the droplet size through turning an integrated micrometer head with ease, and the size of the produced micro-droplet can be automatically and real-time monitored by an open-sourced software and off-the-shelf hardware.     

夫琅禾费单缝衍射法测透镜焦距的研究

主要采用激光作为光源,通过不同的接收方法（白屏和测微目镜）,测量了透镜的焦距,同时与自准直法获得的结果进行比较,结果表明采用白屏和测微目镜作为接收屏取得的实验结果更精确.因此,给出了可靠的测量透镜焦距的方法.     

用微电流测试仪测绝缘材料浸水电阻的实验研究

本文介绍了用微电流测试仪测绝缘材料浸水电阻的条件和方法     

计算复杂截面曲梁刚度的一种数值方法

计算复杂形状截面的曲梁的刚度,采用才于料力学和弹性力学的求解方法是十分困难的;使用有限元法,将因形状复杂,计算工作量大,计算费用高而不方便;使用文献[1]中提出的方法,也有弊端。本文对[1]中提出的方法进行了修正。本方法是一种计算量小,程序简单,精度较高的数值方法。已在千分尺尺架的CAD 设计软件中成功地加以应用,在需要反复进行结构分析的最优化设计中更显示出其计算量小、精度高和费用低的优点。     

均质核壳结构ZnS的一步法合成及光催化性能

以硝酸锌和硫脲为原料,十二烷基硫酸钠为保护剂,通过一步水热合成反应,制备了具有核壳结构的微米级Zn S半导体材料.该Zn S材料的核、壳成分相同,晶体构造一致,均为立方闪锌矿结构;调节反应时间,可以方便地控制壳层构造的生长与闭合程度;优化反应条件得到整体尺寸约为3μm、核壳结构特征突出的形貌新颖的Zn S微粒;将Zn S材料用于亚甲基蓝的光降解反应,其对目标降解物的降解效率与形貌特征有紧密联系,壳层闭合程度越高,降解效率越低.在最优条件下,该材料对亚甲基蓝的降解率可达97.3%.     

Preparation of micrometer-sized, monodisperse, hollow polystyrene/poly(ethylene glycol dimethacrylate) particles with a single hole in the shell

Micrometer-sized, monodisperse, hollow polystyrene (PS)/poly(ethylene glycol dimethacrylate) (PEGDM) composite particles with a single hole in the shell were prepared by seeded polymerization using (ethylene glycol dimethacrylate/xylene)-swollen PS particles in the presence of sodium dodecyl sulfate (SDS). Single holes were observed at SDS concentrations above 3 mM, much lower than in the PS/polydivinylbenzene (PDVB) system previously reported (above 45 mM). Phase separation inside droplets occurred at lower conversion in the PEGDM system than the PDVB system. Phase separation in the droplet at the early stage of the polymerization is an important factor for the formation of the single hole in the shell. Part CCCXIII of the series “Studies on Suspension and Emulsion.”     

Monitoring of vesicular exocytosis from single cells using micrometer and nanometer-sized electrochemical sensors

Communication between cells by release of specific chemical messengers via exocytosis plays crucial roles in biological process. Electrochemical detection based on ultramicroelectrodes (UMEs) has become one of the most powerful techniques in real-time monitoring of an extremely small number of released molecules during very short time scales, owing to its intrinsic advantages such as fast response, excellent sensitivity, and high spatiotemporal resolution. Great successes have been achieved in the use of UME methods to obtain quantitative and kinetic information about released chemical messengers and to reveal the molecular mechanism in vesicular exocytosis. In this paper, we review recent developments in monitoring exocytosis by use of UMEs-electrochemical-based techniques including electrochemical detection using micrometer and nanometer-sized sensors, scanning electrochemical microscopy (SECM), and UMEs implemented in lab-on-a-chip (LOC) microsystems. These advances are of great significance in obtaining a better understanding of vesicular exocytosis and chemical communications between cells, and will facilitate developments in many fields, including analytical chemistry, biological science, and medicine. Furthermore, future developments in electrochemical probing of exocytosis are also proposed. Figure In this paper, we review recent developments in monitoring the exocytosis by use of UMEs-electrochemical-based techniques including electrochemical detection using micrometer and nanometer-sized sensors, Scanning Electrochemical Microscopy (SECM) and UMEs implemented in lab-on-a-chip (LOC) microsystems. These advances are of great significance in obtaining a better understanding of vesicular exocytosis and chemical communications between cells, and will facilitate developments in many fields including analytical chemistry, biological science and medicine. Furthermore, future developments in electrochemical probing of exocytosis are proposed.