Nanotechnology V 1505Porous Silicon and Alumina as Chemically Reactive Templates for the Synthesis of Tubes and Wires of SnSe, Sn, and SnO2. -The selective reactivity of the pore walls of porous alumina and macroporous silicon allows the preparation of monodisperse tubes and nanowires of SnSe, SnO2, and Sn from a single-source precursor, Sn(SePh)4. For a given template system, the reduction or oxidation is initiated easily by increasing the temperature to about 650°C. The enhanced reaction temperature for the oxidation within the pores facilitates the formation of single-crystalline nanowires of SnO2. -(ZHAO, L.; YOSEF, M.; STEINHART, M.; GOERING, P.; HOFMEISTER, H.; GOESELE, U.; SCHLECHT*, S.; Angew. Chem., Int. Ed. 45 (2006) 2, 311-315; Inst. Chem.

In this paper the state-of-the-art for exploiting the unique physical and chemical properties of crystalline materials and their possible applications for development of crystalline nanocomposites with the tailored anisotropy were discussed. Using a method of growing crystals from a solution the KDP and TGS nanocrystalites were grown in the mezopores of the Al2O3 matrix. To investigate the developed nanocrystalline samples the X-ray analysis was used. A form of the obtained diffractograms and our calculations show the predominant crystallization of the KDP and TGS in the direction [100], which coincides with the direction of the cylindrical pores. Thus, diffractograms contain only reflexes of crystallographic planes (200) and (400). The achieved result indicates the possibility of growing of nanocrystals in mesopores of such Al2O3 structures developed by us and provides the prospect of creating optical cells with increased energy efficiency.

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The optical polarimetry technique is used to explore molecular ordering of nematic liquid crystals 5FPFFPP3 embedded in parallel cylindrical channels of alumina membranes with pore walls covered by a SE-1211 polymer film enhancing normal anchoring. A chemical film deposition from organic solution apparently results in inhomogeneous coverage with local islands on the channels walls. Accordingly, a coexistence of differently ordered LC regions (nanodomains), characterized by positive and negative anisotropy, results in a weak effective (average) optical birefringence. Repeated polymer deposition reduces the size of uncovered pore walls regions and thus leads to a strengthening of negative optical anisotropy observed in the experiments.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.