Tokihiro Takizawa

Rapid synthesis of phthalocyanine-based discotic liquid crystals by using a novel hand-made microwave-heating apparatus

Phthalocyanine (Pc)-based discotic liquid crystals could be prepared very rapidly by using our developed novel microwave-heating apparatus. It took only 10-20 min to synthesize these Pc metal complexes and metal-free Pc derivatives in an organic solvent (glycerin) by microwave irradiation, whereas it took 24-48 h to synthesize them by the conventional oil bath method. To our knowledge, it is the first example of metal-free Pc derivatives synthesized by microwave methods in an organic solvent. In the vast examples of Pc syntheses by conventional oil bath methods, the Pc metal complexes can be obtained in higher yields by “Template Effect” of the metal than the corresponding metal-free Pc derivatives. Therefore, we expected that the present Pc metal complexes (CnS)8PcCu (2) could be also prepared by microwave methods in higher yields than the metal-free Pc derivatives (CnS)8PcH2 (1). Contrary to our expectation, the yields of the metal complexes (CnS)8PcCu (2) were lower than those of the metal-free derivatives (CnS)8PcH2 (1). It is very interesting that this result by the microwave method is quite opposite to the results by conventional oil bath method. Hence, in this work we have focused our interest on the “Template Effect” in the syntheses of Pc derivatives by the microwave method in order to investigate the relationship between microwave heating and template effect. It is the first attempt in Pc syntheses by the microwave method.

Electrical Conductivity of Microwave Heated Polyaniline Nanotubes and Possible Mechanism of Microwave Absorption by Materials

In the course of experiments to perform deprotonation and carbonization of doped polyaniline (PANI) nanotubes (NTs) by irradiating directly 2.45 GHz microwave (MW) in our microwave heating system (MWHS), we have discovered that the PANI-NTs self heat by absorbing the MW, but the temperature of the PANI-NTs stops rising around 300 °C in spite of the heightened MW power. Furthermore, we have found that the MW irradiated PANI-NTs have transferred from electrical conductor to insulator depending on the temperature of the PANI-NTs. By measuring electron spin resonance (ESR) spectra of the MW heated PANI-NTs, the existence of the unpaired electrons is shown to have a strong correlation between the degree of MW absorption and the transition in the electrical conductivities. In order to deprotonate and carbonize further the PANI-NTs, we have performed heat treatment for the PANI-NTs up to a temperature (T) of about 1200 °C in the same MWHS using carbon fiber which self heats by absorbing MW. The chemical transformations in the PANI-NTs induced by the heat treatments are discussed by measuring the X-ray photoelectron spectroscopy (XPS) spectra. Finally, the temperature dependence of electrical conductivities of the PANI-NTs are measured in order to investigate the mechanism of electrical conduction of the heat treated PANI-NTs.

Controlled Microwave Irradiation for the Synthesis of YBa 2Cu 3O7-x Superconductors

For synthesizing a high-quality YBa2Cu3O7-x superconductor using a domestic microwave oven without any post-heat treatment, the power and time of microwave irradiation are controlled by monitoring continuously the temperature of the microwave-heated sample. The temperature is measured by means of a metal-sheathed chromel-alumel thermocouple which is installed in the oven in the proper way. The conditions of the sample inside the oven are almost the same as the sample environment proposed by Kato et al. [Jpn. J. Appl. Phys. 36 (1997) L1291]. The maximum monitoring temperature where crystal growth occurs rapidly for a high-quality YBa2Cu3O7-x superconductor is shown to be about 500°C which is much lower than the maximum heating temperature in the conventional method.

Discotic liquid crystals of transition metal complexes, 54 : Rapid microwave-assisted synthesis and homeotropic alignment of phthalocyanine-based liquid crystals

The most difficult problem on syntheses of the phthalocyanine-based liquid crystals is the long reaction time. In order to shorten the reaction time, we have developed novel Methods A, B and D, for the syntheses of phthalocyanine-based liquid crystals by using microwave heating and/or adding a phase transfer catalysis of Aliquat 336. A series of phthalocyanine derivatives CnPcZn(1) (n= 10, 12, 14, 16 and 18: a, b, c and e) could be successfully synthesized in a dramatically short reaction time of 30–60 min using Methods A and B by microwave heating. On the other hand, anothor series of the derivatives Cn(OH)PcZn (2a–2e) could not be synthesized by microwave heating. Therefore, all these derivatives were synthesized using conventional Method C by oil bath heating, but the reaction took a very long time (22.5–88 h). To shorten the reaction time, we have developed Method D by oil bath heating with adding a phase transfer catalyst of Aliquat 336. In this method, we successfully shortened the reaction time fro...

BAND LIKE ELECTRONIC STRUCTURES IN SQUARE HOLLOW QUANTUM DOTS BY 3D-MHFKS CALCULATION

To find novel aspects of the electronic structures in quantum dots (QD) from a view point of spatial broken symmetry, 3-dimensional-mesh Hartree-Fock-Kohn-Sham (3D-MHFKS) calculations1 are applied to the interacting electron system of electron number N in a symmetry broken hollow QD. For the case of a square hollow quantum dot confined in square hard wall (HW) potential (SSHQD), the magnetic (B) field dependence of the obtained single particle energy levels and chemical potentials in B-N diagram are shown to have a band like electronic structures over the wide B-field range up to 20T. To clarify the origin of the band like electronic structures in SSHQD, 3D-MHFKS calculations are also applied for the mixed symmetry QDs with a circular hollow in square HW potential (SCHQD) and with a square hollow in circular HW potential (CSHQD).

Formation, Oscillation and Deflection of Liquid Film on a Ring Frame

Image of a liquid film forming on a ring frame attached to a DuNouy surface tensiometer was photographed with a high-speed motion picture camera. Pure water and an aqueous solution with a surfactant were used as the liquids. The formation process and the oscillation of the film were continuously recorded. Observation of the oscillations enabled us to estimate gravitational deflection of the film and the value of the surface tension.