K. Keiji Kanazawa

The oscillation frequency of a quartz resonator in contact with liquid

A simple relationship is derived which expresses the change in oscillation frequency of a quartz crystal in contact with a fluid in terms of material parameters of the fluid and the quartz. The relationship is Δf = −f320(ηLϱL/πμQϱQ)12, where f0 is the oscillation frequency of the free (dry) crystal, ηL and ϱL are the absolute viscosity and density of the liquid, respectively, and μQ and ϱQ are the elastic modulus and density of the quartz. This relation is obtained from a simple physical model which couples the shear wave in the quartz to a damped shear wave in the fluid. Quantitative comparisons with two test cases, aqueous solutions of glucose and ethanol at various concentrations, demonstrate the accuracy of this model.

Preparation and characterization of neutral and oxidized polypyrrole films

Abstract Oxidized and neutral films of polypyrrole have been prepared electrochemically in the absence of oxygen and water. The neutral films are insulating and can be readily oxidized by chemical oxidizing agents to give films of greater conductivity than can be achieved by electrochemical oxidation. Optical spectroscopy provides evidence for the similarity of the polymeric carbonium ion produced by both types of oxidation. NMR studies are consistent with the α,α’ bonding in these polymers; they also show the expected downfield shifts relative to the neutral polymer on both chemical and electrochemical oxidation. ESR studies of both the electrochemically oxidized and the neutral polymer suggest the presence of highly mobile spins.

Polypyrrole: An electrochemically synthesized conducting organic polymer

Abstract The simple, one-step electrooxidation of pyrrole from an organic solvent on a platinum electrode results in the formation of a flexible, metallic polymer. The black films stripped from the electrode are found to be unchanged under ambient storage and thermally stable to temperatures exceeding 300 °C. They are space filling, unlike the fibrillar (CH)x and show considerable disorder. The room temperature conductivity ranges from 10–100 (ohm cm)−1. The thermopower is small and positive, decreasing linearly with decreasing temperature, consistent with p-type metallic conduction. The very small Hall constant is anomalous in both sign and magnitude.

Physical description of a viscoelastically loaded AT‐cut quartz resonator

In this work, the electrical admittance of this plane‐parallel resonator loaded on one face with a viscoelastic medium is described directly in terms of the physical properties of the system. This description is based on the detailed matrix equations for the piezoelectric quartz and includes the piezoelectric effect of the quartz transducer and the shear modulus and viscosity of the overlayer. This physically based analysis has proven invaluable in relating the admittance behavior directly to the materials’ properties. Initial comparisons of the theory with experimental data are given, including the appearance of even harmonics as described by Benes [E. Benes, J. Appl. Phys. 56, 608 (1984)] for the asymmetrically loaded resonator. Additionally, measurements on a series of perfluoropolyether fluids of differing molecular weights indicate that they cannot be described as simple viscous liquids in the MHz range. The assignment of a frequency‐dependent viscosity with a relaxation time proportional to the mole...

‘Organic metals’: polypyrrole, a stable synthetic ‘metallic’ polymer

Highly stable, flexible films of polypyrrole with p-type conductivities of 100 Ω–1 cm–1 have been prepared by electrolytic oxidation of the appropriate pyrrole monomers; similarly prepared films of mixtures of pyrrole and N-methylpyrrole have conductivities between 5 × 10–3 and 100 Ω–1 cm–1 depending upon the composition.

Conducting poly-N-alkylpyrrole polymer films

Abstract A series of N-substituted polymer films have been synthesized. The initial characterization of these polymeric films when in the oxidized form indicates that the degree of oxidation of the polymer and the conductivity is reduced with the introduction of N-alkyl substituents. The oxidation potential of the polymer is also changed by the presence of the substituent, whereas polypyrrole oxidizes at −0.2 V, the substituted polypyrrole films with N-alkyl substituents oxidize in the region 0.45–0.64 V.

Electrochemical polymerization of pyrrole

The electrochemical polymerization of pyrrole on platinum produces a strongly adhered, durable film with enhanced conductivity and good electrode properties.

Electrical properties of pyrrole and its copolymers

Abstract Electrochemically prepared polypyrrole films have metallic conductivities in the range 40–100 S cm −1 whereas poly - N -methyl pyrrole films have conductivities more typical of a semiconductor, t / if 10 −3 S cm −1 . Films made by the electrochemical polymerization of mixtures of pyrrole and N -methyl pyrrole have redox potentials intermediate between those of either monomer, indicating that they are in fact random copolymers. The electrical conductivity and thermopower measured as a function of copolymer composition show no evidence for an abrupt metal-semiconductor transition. All these polymers are stable in air to temperatures in excess of 100°C.

An in-situ electrochemical quartz crystal microbalance study of the underpotential deposition of copper on Au(111) electrodes

The combination of the quartz crystal microbalance (QCM) with electrochemical methods has made possi- ble the in situ measurement of minute mass changes that may accompany electrode processes, such as elec- trodeposition, film growth, oxide formation, ion update into polymer films, and ionic adsorption [ll. While the electrochemical QCM provides valuable coverage in- formation which is often difficult to obtain by other means and complements other surface-sensitive in situ probes of smooth electrodes such as infrared (IR) spectroelectrochemistry, X-ray absorption and scatter- ing, scanning tunneling microscopy @TM), and non- linear optical spectroscopy [2], a significant limitation has been the inability to apply the QCM to ordered single crystal surfaces. We report here the first preparation of a highly ordered Au(lll) electrode on a quartz crystal. We also report results obtained using this electrode in an elec- trochemical QCM in conjunction with cyclic voltamme- try and coulometry to investigate the underpotential deposition (UPD) of copper onto the Au(ll1) surface. Even though copper UPD on gold has been studied using a QCM on polycrystalline surfaces [3,4] and by many other in situ interfacial techniques such as sur- face extended X-ray absorption fine structure (SEXAFS) [5], STM [6,7], and IR spectroelectrochem- istry [S], etc. on both single crystal and polycrystalline surfaces, there is still controversy as to the structure and composition of the adlayer at various stages in the UPD process. The QCMs consisted of 2.5 cm diameter AT-cut quartz crystal disks (Valpey-Fisher), which were pol- ished to an optical finish on both sides. Gold elec- trodes were vapor deposited by a modification of, the procedure described previously [3]. First, ca. 50 A of chromium metal (99.99%, Aldrich) was evaporated onto one side of the crystal to enhance the adhesion of gold. Then 2000 A of gold (99.999%, Aldrich) was evapo- rated onto the Tame side. These evaporations were done at room temperature in a vacuum ff 2

Charge‐Carrier Dynamics Following Pulsed Photoinjection

The transient behavior of charge carriers generated by pulse illumination of arbitrary intensity is investigated. The configuration treated is that in which one surface of a photoinsulating sample is grounded and the other charged to an initial potential V0 and left floating. Within the framework of the assumed model, expressions have been derived which completely describe the spatial and temporal dependence of the carrier density, electric field, and conduction current density. These expressions provide a physical picture of the charge‐carrier dynamics within the photoinsulator and allow a qualitative discussion of possible trapping effects. Solutions are also obtained for the physically observable surface potential and its time rate of change. The geometry considered here is that usually employed in electrophotographic applications of photoinsulators for information copying and image conversion devices.