Fabricate Micrometer And Nanometer Sized Gold Patterns By SECM And Image Gold Patterns By Fluorescence

In chapter one of this thesis,at first the fabrication and the investigation actuality of gold deposition by SECM were reviewed.Then a new method of gold deposition by SECM was developed . A carbon fiber microelectrode tip served as the auxiliary electrode and a large silicon substrate served as the working electrode. Because of the small tip size and the short distance between the tip and the substrate, the current at the substrate was confined to a small area and gold was locally electrodeposited on the silicon surface. The deposited point gold was imaged by the generation/collection mode of SECM ,and then by the scanning electron microscopy. At last we compared the result of SECM with the result of SEM .We got the conclusion that the result of the SECM was about as six times as the trim size.In chapter two , a new method of gold imaged by fluorescence was developed . The method was preceded by the formation of an amino-terminated monolayer through the adsorption of cysteamine on gold surface,cysteamine was strongly adsorbed on gold surface.they did not chemisob on Si. Then the localization of the self-assemlled monolayer on the surface was monitored by fluorescence microscopy after the sample was tagged with fluorescein isothiocyanate.We got clear image of gold by this method At last we compared the result of this method with the result of SECM .We got that the image size of the fluorescence method was about as 1.6 times as the trim size.The third chapter includes three parts: 1.The tips of fabrication of nano-sized electrodes were reviewed. 2. A novel method for fabricating carbon fiber nanoelectrodes by SECM was developed. The nanoelectrodes were fabricated from an electrochemically sharpened carbon fiber insulated completely with phenol-allylphenol copolymer. We exposed the very end of a nanoelectrode by placing it in a SECM with a bias voltage (+2.5 V vs. Ag/AgCl) and allowing it to approach a solution of 1.00×10^-3 mol/L NaOH. The onset of current flow could remove the insulation coated on the very end of the nanoelectrode, while leaving most of the tip still insulated. This method could produce nanoelectrodes with effective radii varying from 4.5 nm to 576 nm calculated from the diffusion-limiting steady-state currents on the voltammograms. A good fit of the experimental normalized I-L curves and theoretical curves indicated that the fabricated nanoelectrodes could also be used as the SECM tips. 3. We used the carbon fiber nanoelectrodes of 35-300 nm diameter served as the SECM tips to microfabricate gold nanopatterns on the silicon substrate. For that purpose, the nanoelectrode served as the SECM tip, a Si substrate was fixed in a cell containing the electrolyte consisted of KAu(CN)₂, KF, and NaNO₂-And then the carbon fiber microelectrode tip was moved down toward the substrate. The principle of fabricating nanostructures was based on the local generation of protons at the tip to induce the surface reaction of gold deposition on the substrate in the vicinity of the tip. The protons were generated at the tip by oxidizing nitrite ions from the solution. The protons induced the redox reaction between Au(CN)₂^- and silicon. Si was oxidized to SiF₆^2-, meanwhile, the Au(CN)₂^- in the solution was metallized by taking the electrons released from Si. At last we imaged the gold by the scanning electron microscopy.The sizes of the gold micropattern were about 50-500 nm.