Preparation, modification and characterization of a novel carbon electrode material for applications in electrochemistry and molecular electronics.

摘要

Conducting carbon films with useful surface and bulk properties were obtained by pyrolyzing a commercial photoresist in a reducing atmosphere of 95% N₂ and 5% H₂ and temperatures ≥1000°C. Pyrolysis of photoresist permits photolithographic fabrication of patterned carbon electrode devices and yields a carbon film that is analogous to a smooth version of glassy carbon with unusual surface properties.; Physicochemical and electrochemical characterization of modified and unmodified pyrolyzed photoresist films (PPF) was performed to evaluate the utility of these films for electroanalytical applications. The PPF surfaces show no visible porosity and are atomically smooth with a root-mean square roughness 5Å. X-ray photoelectron spectroscopy demonstrates that the surface oxygen/carbon ratio is low (∼2%) and is relatively stable. Electron-transfer kinetics of Ru(NH₃)₆3+/2+, Fe(CN)₆3−/4− and chlorpromazine on PPF surfaces show qualitatively similar behavior to glassy carbon but for redox systems like Fe3+/2+, dopamine, ascorbic acid and oxygen, the behavior is quite different due to very weak surface interactions. The PPF surfaces also show very low capacitance and adsorption strength that could be very useful in bioelectrochemical applications. Electrochemical modification of the PPF surfaces by the reduction of aromatic diazonium results in a chemical modified surface that could be useful in diverse electroanalytical applications.; Current-potential (i-V) characteristics of thin films (15 to 50Å) of nitroazobenzene (NAB) chemisorbed on PPF surfaces were studied by positioning the thin films between two conductors. The current is sensitive to film thickness and varies with V1/2. The i-V characteristics of the apparent monolayer films (∼15Å) show weak temperature dependence, but the current depends strongly on temperature for thicker films. The i-V characteristics and the temperature dependence of the i-V curves indicate a thermally activated charge transport mechanism.; A simple electrode preparation procedure using activated carbon powder to act as a “getter” to remove not only the impurities present in organic solvents but also polishing impurities present on the electrode to produce an active electrode surface. The electrodes show increased electron-transfer kinetics for several redox systems and also show higher capacitance and adsorption consistent with electrode cleaning by activated carbon and the purified solvent.