Ayumu Yasuda

Chemical and electrochemical analyses of polyaniline prepared with FeCl3

Abstract Aniline is polymerized by chemical oxidation with FeCl3 in water. At an optimum reaction condition, the resulting polyaniline has a number average molecular weight of 20 400 and a yield of 51%. Chemical and electrochemical analyses show that the polyaniline is emeraldine. FeCl3 is found to be one of the appropriate oxidants to prepare emeraldine, though its standard electrode potential (0.771 V) is lower than that of (NH4)2S2O8 (1.94 V) which has been conventionally used to prepare emeraldine.

Carbyne : electrochemical preparation and nanotube formation

Carbyne-like or polyyne-containing carbon was prepared by the electrochemical reduction of PTFE. By heating and electron-beam irradiation in vacuum, carbon nanotubes were formed on the surface of the prepared carbon material. Only when the carbon contains the polyyne structure, were the carbon nanotubes found to be formed. From the view of the formation mechanism, the formation route through polyyne is strongly suggested.

Electrochemical carbon monoxide sensor with a Nafion® film

Abstract A solid-state planar electrochemical carbon monoxide sensor was built and studied. The sensor features a planar geometry of the electrodes (working, counter, reference), where all three electrodes are located on the same side of a substrate. The electrodes are covered by the CO-semipermeable proton-conducting polymer film. The sensor shows characteristics of a practical-use level: response time, 30 s; range, 0–2000 ppm; sensitivity, 0.04 nA/ppm; life, more than 2 yr. The sensitivity is governed by both the CO permeability of the polymer film and the CO oxidation rate, in other words, by the intermediate kinetic mechanism.

NANOTUBE TIP FOR STM

We are investigating electrical properties of multiwalled carbon nanotube (CNT) probes for scanning tunneling microscopy (STM). To improve the electrical conduction and reduce the contamination at the interface to the gold base, we selected conductive CNTs and heated the base and CNT during the CNT attaching process. Before STM measurements, the probes were cleaned by annealing in vacuum for 4–8 h. With these treatments, we found a small number of tips exhibiting linear metallic current–voltage (I–V) curves on Au(111), while all the CNT tips attached on gold (not heated) exhibited nonlinear I–V curves. We discuss the possibility that the metallic behavior of the CNT probes may be caused by the diffused gold atoms along the CNT surfaces by the long heat treatment.

Preparation and structure of nitrogen-substituted, highly oriented graphite thin film prepared by chemical vapor deposition

Abstract Highly-oriented, nitrogen-substituted graphite (C/N graphite) thin films were prepared by chemical vapor deposition (CVD) using pyrrole as a starting material and palladium deposited single crystal sapphire as a substrate material whose temperature was kept at 1273K. The interlayer spacing of C/N graphite films, determined by x-ray diffraction, was close to that of single-crystal graphite. The orientation of crystalline of C/N graphite films, evaluated by rocking angle measurement, was higher compared with that of highly oriented pyrolytic graphite. XPS and Raman spectroscopy were also measured for the characterization of these films.