2,7-Dialkyl[1]benzothieno[3,2-b]benzothiophenes were tested as solution-processible molecular semiconductors. Thin films of the organic semiconductors deposited on Si/SiO2 substrates by spin coating have well-ordered structures as confirmed by XRD analysis. Evaluations of the devices under ambient conditions showed typical p-channel FET responses with the field-effect mobility higher than 1.0 cm2 V-1 s-1 and Ion/Ioff of approximately 10(7).

Reduction of CO(2) using semiconductors as photocatalysts has recently attracted a great deal of attention again. The effects of organic adsorbates on semiconductors on the photocatalytic products are noteworthy. On untreated TiO(2) (P-25) particles a considerable number of organic molecules such as acetic acid were adsorbed. Although irradiation of an aqueous suspension of this TiO(2) resulted in the formation of a significant amount of CH(4) as a major product, it was strongly suggested that its formation mainly proceeded via the photo-Kolbe reaction of acetic acid. Using TiO(2) treated by calcination and washing procedures for removal of the organic adsorbates, CO was photocatalytically generated as a major product, along with a very small amount of CH(4), from an aqueous suspension under a CO(2) atmosphere. In contrast, by using Pd (>0.5 wt %) deposited on TiO(2) (Pd-TiO(2)) on which organic adsorbates were not detected, CH(4) was the main product, but CO formation was drastically reduced compared with that on the pretreated TiO(2). Experimental data, including isotope labeling, indicated that CO(2) and CO(3)(2-) are the main carbon sources of the CH(4) formation, which proceeds on the Pd site of Pd-TiO(2). Prolonged irradiation caused deactivation of the photocatalysis of Pd-TiO(2) because of the partial oxidation of the deposited Pd to PdO.

Several inorganic-organic hybrid complexes were synthesized from a synthetic clay (Sumecton SA) and cationic porphyrins (+4 charge). In the clay-porphyrin complexes, the λmax values of the Soret bands of the porphyrins were shifted to longer wavelengths compared to those in water. Two types of complexes were formed depending on the preparation method. One is assigned to a complex in which the porphyrin molecules are adsorbed on the external surfaces of the dispersed clay layers (type b complexes). The other is assigned to a complex in which the porphyrin molecules are intercalated within the stacked clay layers (type c complexes). The aqueous solutions of both types of complexes do not scatter light in the UV-visible wavelength region. Surprisingly, the porphyrin molecules were found to adsorb on the clay sheets as densely packed monolayers with controlled intermolecular gap distance. In type b, the porphyrins are adsorbed as flat monolayers, without discernible aggregation, that precisely neutralize the negative charges of the clay surface. According to fluorescence lifetime measurements, the adsorbed porphyrin molecules have sufficiently long lifetimes to be used as sensitizers. The fluorescence lifetimes of tetrakis (N, N, N-trimethyl-anilinium-4-yl) porphyrin were found to be 4.1 ns in type b complexes and 3.2 ns in type c, while that in water is 9.3 ns. We report here a novel method in which highly dense yet controllable structures without aggregation can be produced as adsorbed layers on clay surfaces for the first time. We propose that the mechanism for this extraordinary monolayer adsorption could be a precise matching of distances between the negatively charged sites on the clay sheets and that between the positively charged sites in the porphyrin molecule. We have termed this the "size-matching effect." * To whom correspondence should be addressed.

Intercalation of seven types of cationic surfactants, including polyfluorinated surfactants, into a cationexchangeable clay mineral, saponite, was investigated. All of the surfactants were found to intercalate in amounts exceeding the cation exchange capacity (CEC). This tendency was more evident in the cases of the polyfluorinated surfactants, ((((perfluoroalkanoyl)amino)ethyl)hexadecyl)dimethylammonium bromide (CnF-S, where n indicates the number of carbons in the perfluoroalkyl group, F denotes a fluorinated surfactant, and S denotes a surfactant having a single, long alkyl chain); C3F-S exhibited intercalation up to 4.4 times CEC as a saturated adsorption limit. The saponite interlayer distance increased upon surfactant intercalation and reached a constant value at intercalation levels exceeding CEC. The occupied areas for each surfactant molecule decreased in the order C1F-S > C2F-S > C3F-S among the polyfluorinated surfactants. All of the experimental results, including the saturated intercalation levels, the occupied areas, the interlayer distances, and the DSC measurements, suggest that CnF-S intercalated in saponite forms a rigidly packed bilayer structure in which the long alkyl chains tilt at an angle of ca. 35°with respect to the clay surface. The microscopic structure of the hybrid compounds is discussed.