基于微纳加工电化学超微电极制备与表征新方法研究

Study on the New Methods in theFabrication and Characterization of Ultramicroelectrodes in Electrochemistry Based on Micro/NanofabricationZhu MingzhiABSTRACTThe electrodes are the key components of the instruments of electroanalytical chemistry. Ultramicroelectrodes (UMEs) have led to unprecedented advances in the instruments of electroanalytical chemistry since their introduction to electroanalytical chemistry. The advantages brought by UMEs are: improved sensitivity, enhanced mass transport, increased temporal resolution, reduced ohmic voltage drops, low charging currents, greater signal-to-noise ratio, and better adoptability for extremely small microenvironments. The UMEs have extended electrochemical methodology into the broad new domains of spaces (single cells, membrane pores), chemical mediums (nonaqueous solvents, unsupported electrolytes, ice, air), and methodologies (single molecule studies, AFM, STM, SECM).The development of the fabrication technologies of UMEs should directly impacts the resolution, sensitivity, accuracy, repeatability, and application domains of electrochemical instruments. The main problems are that UMEs can be fabricated with small size in all dimensions of electrode tip, reproducible and well-defined geometries and the technologies can offer a wide range of electrode materials and insulating materials.The aim of this dissertation is the study on the new fabrication technologies of UMEs. The main research works and obtained conclusions are as follows:1 A procedure of insulating the low melting or softening point metal fibers for preparing individual disk UMEs is presented. The insulating thin film techniques are used to concentrically insulate the metal fibers. Presently, the most popular UMEs geometry is the individual disk UMEs that can be manufactured with the smallest size in all dimensions of electrode tip.The procedure has introduced the low temperature insulating thin films techniques of micro/nanofabrication technologies to the fabrication of individual disk UMEs. The procedure can provide controllability and reproducibility for the fabrications of individual disk UMEs with the substrates of the low melting or softening point metal fibers. The thickness of insulating thin film of individual disk UMEs can be controlled. The insulating layers have been concentrically and uniformly deposited, so individual disk UMEs can be manufactured with well-defined geometries of electrode tips. The good adhesion has been obtained at the interfaces of the insulating layers and the substrates. The well-defined geometries of electrode tips and excellent adhesion to the substrates are critical to achieving a reproducible and definite electrochemical response. The rigid insulating thin films can eliminate the need for bulky support materials in order to fabricate the individual disk UMEs with small overall size of electrode tip. For the different purposes and environments the techniques can offer a wide range of insulating materials (such as: SiO2, Al2O3, SiC) and the insulating thin films can even be duplex (such as: SiO2/Si3N4) and triplex layers(such as: SiO2/Si3N4/SiO2).Specially, the fabrication of 12.5μm Au individual disk UMEs were described. The 25μm diameter Au fibers were concentrically coated by low temperature plasma enhanced chemical vapor deposition with an insulating layer of 0.7μm silicon nitride thin film. The individual disk UMEs with the substrates of Au fibers had been firstly fabricated with small overall size of electrode tip that employed the low temperature insulating thin films techniques of micro/nanofabrication technologies.（The results has been published “Development of disk ultramicroelectrodes based on low melting or softening point metal fibers by low temperature plasma enhanced chemical vapor deposition. Analytica Chimica Acta [J], 2005. M. Z. Zhu, Z. D. Jiang, W. X. Jing.”and the impact factor is 2.760.）2 A procedure for the fabrication of individual ring UMEs is presented. The conducting thin film techniques are utilized to concentrically deposit electrode materials onto the walls of cylindrical insulating supports and the insulating thin films technique is then used to concentrically insulate the cylindrical lengths of the electrode material-coated supports. The procedure can be extended to the fabrication of multiplicate combined probes by functionalizing insulating supports. The ring UMEs have large perimeter-to-area ratio and provide an ideal geometry for kinetic measurement. The procedure has introduced the conducting thin film techniques and the insulating thin films techniques of micro/nanofabrication technologies to the fabrication of individual disk UMEs. The conducting thin film techniques can produce high-quality conducting thin films with well adhesion to the substrates. The techniques are highly controlled and reproducible. For the different purposes and environments, the different electrode material thin films can be chosen (such as: Ag, Pt). Specially, the fabrication of 300nm Au individual ring UMEs was described. The 125μm diameter optical fibers were concentrically coated with Au films of 300nm thickness by RF magnetron sputtering and then insulated with silicon nitride thin films of 0.7μm thichness by low temperature plasma enhanced chemical vapor deposition. The fabricated Au individual ring UMEs can be used as the photoelectrochemical microscopy (PEM) probes. The individual ring UMEs had been firstly fabricated with small overall size of electrode tip that employed the conducting thin film techniques and the insulating thin films techniques of micro/nanofabrication technologies.The combined scanning probe microscopy (SPM) techniques have higher sensitivity and selectivity. The techniques have been used to provide diverse information about substrate surfaces and interfacial processes. The fabrication procedure of individual ring UMEs in this dissertation can be extended to the fabrication of multiplicate combined probes by functionalizing insulating supports. The fabricated individual ring UMEs combine optical fibers and ring UMEs that results in the PEM probes. The PEM probes can be used in micro- electrogenerated chemiluminescence. The combined scanning electrochemical microscopy (SECM)/Near-field scanning optical microscopy (NSOM) probes can be fabricated by having the substrates of NSOM probes and the SECM/NSOM probes allow simultaneous optical and electrochemical imaging with submicrometer resolution. The radial flow micro-ring electrode (RFMRE) can be fabricated by having the substrates of the pulled capillaries and the RFMRE, a kind of hydrodynamic UMEs, combine ring UMEs and hydrodynamic voltammetric techniques that results in greatly enhanced mass-transfer rates. The configuration extremely attractive for the study of fast kinetics.（The results has been published “Radio frequency magnetron sputtering of Au and low temperature plasma enhanced chemical vapor deposition of silicon nitride for ringultramicroelectrodes fabrication. Journal of Electroanalytical Chemistry [J], 2006. M. Z. Zhu, Z. D. Jiang, W. X. Jing, B. Yang.”and the impact factor is 2.223.）（Four Chinese invention patents are applied. One is “One kind of ring ultramicroelectrodes and its fabrication method, applied No. 200510096451.0, Jiang Zhuangde and Zhu Mingzhi etc”. Two is “One kind of combined scanning electrochemical/optical microscopy probe and its fabrication method, applied No. 200510022733.6, Jiang Zhuangde and Zhu Mingzhi etc”. Three is “One kind of combined injection/ring electrode microprobe and its fabrication method, applied No. 200610042602.9, Jiang Zhuangde and Zhu Mingzhi etc”. Four is “One kind of finite conical ultramicroelectrodes and its fabrication method, applied No. 200610041947.2, Jiang Zhuangde and Zhu Mingzhi etc”. The four Chinese invention patents have been published in Chinese Patent Bulletin.）3 A procedure for the fabrication of recessed interdigitated ultramicroelectrode arrays (IDA) is presented. The IDA appear to be of great analytical interest where particularly low detection limits are needed because the redox cycling arising from the close proximity of the interdigitated electrodes leads to enhanced detection sensitivity.The electrode surfaces of the fabricated IDA are inside the recessed trenches. When the recessed IDA were used as the basal sensing electrodes of chemical and biologic sensors, the recessed trenches can provide adequate membrane adhesion and sufficient mechanical stability for the sensing membranes immobilized in the trenches to improve the quality of sensors. The multilayered technique holds promise as a useful way of increasing the functionality per unit area of substrates for the improvement of sensitivity and conventional microfabrication techniques can be effectively used for making submicro/nanometer band electrode arrays reproducibly and in large numbers.Specially, Au recessed IDA were fabricated by multilayered materials and conventional photolithographic patterning techniques on a quartz substrate. The multilayered recessed IDA structure, which consists of 50 pairs of fingers and has 1.5mm finger length，362nm functional band width and larger than 1.5μm containing trench depth, were fabricated in region of 1.5×2.3mm2. Glucose oxidase/polypyrrole (GOx/PPy) enzyme electrodes were developed based on electropolymerization on the multilayered recessed IDA. The enzyme electrodes were used for detecting glucose concentration in the range of 0-10mmol/L in potassium phosphate buffer solution (pH 7.0), with sensitivity of 13.4nA/(mmol/L) and correlation coefficient of 0.998.（The results has been published “Fabrication of polypyrrole-glucose oxidase biosensor based on multilayered interdigitated ultramicroelelctrode array with containing trenches. Sensors and Actuators, B: Chemical [J], 2005. M. Z. Zhu, Z. D. Jiang, W. X. Jing.”and the impact factor is 2.646.）This work has introduced the micro/nanofabrication technologies to the fabrication of individual UMEs with the substrates of fibers and led to the novel fabrication procedure of individual UMEs. The micro/nanofabrication technologies have more control over well-defined geometries of electrode tips and increased reproducibility in the fabrication process. The individual UMEs can be manufactured with small size in all dimensions of electrode tips. For the different purposes and environments, the different electrode materials and insulating thin films can be chosen in large range. This work supplies the basis for the fabrication of individual UMEs with the substrates of fibers based on micro/nanofabrication technologies. The exploitation of the new microfabrication techniques in fabrication of combined probes will continue as combined SPM are furtherdeveloped. The research results of this dissertation are a significant exploration and an effective exemplification for the development of the new fabrication techniques in fabrication of combined probes.This dissertation was supported by the National Basic Research Program of China (No. 2004CB619302) and the National Natural Science Foundation Key Project of China (No. 50535030). On the basis of the research of this dissertation, as the second member (the supervisor is the first member) the author had obtained the Special Scientific Research Foundation of Chinese University Doctoral Subject “Study on the Related Issues in the Fa brication of Individual Ultramicroelectrodes and Combined Probes”.Key words: Ultramicroelectrodes (UMEs); Micro/nanofabrication; Individual disk UMEs; Individual ring UMEs; Combined probes; Recessed interdigitated ultramicroelectrode arrays论文题目：基于微纳加工电化学超微电极制备与表征新方法研究作者简介：朱明智，男，1973年04月出生，2003年02月师从于西安交通大学蒋庄德教授，于2006年12月获博士学位。