• 한국전기전자재료학회논문지
• /
• 제30권3호
• /
• pp.185-191
• /
• 2017

Cadmium compounds with one dimension (1D) nanostructures have attracted attention for their excellent electrical and optical properties. In this study, vertically aligned CdTe-Si nanostructures with high density were synthesized by several simple chemical reactions. First, l D Te nanostructures were synthesized by silver assisted chemical Si wafer etching followed by a galvanic displacement reaction of the etched Si nanowires. Nanowire length was controlled from 1 to $25{\mu}m$ by adjusting etching time. The Si nanowire galvanic displacement reaction in $HTeO_2{^+}$ electrolyte created hybrid 1D Te-branched Si nanostructures. The sequential topochemical reaction resulted in $Ag_2Te-Si$ nanostructures, and the cation exchange reaction with the hybrid 1D Te-branched Si nanostructures resulted in CdTe-Si nanostructures. Wet chemical processes including metal assisted etching, galvanic displacement, topochemical and cation exchange reactions are proposed as simple routes to fabricate large scale, vertically aligned CdTe-Si hybrid nanostructures with high density.

• Journal of Photoscience
• /
• 제4권3호
• /
• pp.147-160
• /
• 1997

INTRODUCTION : Various types of organic reactions in the crystalline state, so-called "topochemical reaction", have been reported in this century." Among the reactions, [2+2] photocycloaddition of diolefin crystals are one of the most intensively investigated examples. In the topochemical reaction in a pure sense, the space group symmetry is perfectly preserved throughout the reaction as were demonstrated by the crystalline-state photopolymerization of 2,5-distyrylpyrazine (2,5-DSP) and photodimerization of propyl $\alpha$-cyano-4-[2-(4-pyridyl) ethenyl]cinnamate. 2,5-DSP was initially prepared by Franke and in 1958 Koelsch and Gumprecht described briefly in their article of diazine-derivatives that it was found that the compound (2,5-DsP) was converted into a colorless insoluble polymer (\ulcorner) dec. 331~331$\circ$ when the solid was exposed for a few hours to ultraviolet light. Wright described in his book as if Koelsch and Gumprecht had investigated both the structure of the photoproduct and the crystal structure 2,5-DSP in detail. However, in the paper, they have not described any study on chemically correct analysis and crystallography of the resulting photoproduct at all. In 1967, one of present authors (M. H.) independently made the same observation as Franke that brilliant yellow crystal of 2,5-DSP was converted into powdery white substance under the sunlight in the course of a preparative study of pyrazine-2,5-dicarboxylic acid from 2,5-DSP. He investigated this phenomenon and concluded for the first time that a linear highmolecular-weight polymer crystal ([$\eta$] > 3.0 in $CF_3COOH$ solution) with recurring cyclobutane units in the main chain, had been produced from 2,5-DSP crystal by the action of sunlight.on of sunlight.

• Bulletin of the Korean Chemical Society
• /
• 제33권7호
• /
• pp.2305-2308
• /
• 2012

Perovskite structured barium titanate particles ($BaTiO_3$) platelets were synthesized by molten salt synthesis and topochemical microcrystal conversion. As the precursors of $BaTiO_3$, plate-like $BaBi_4Ti_4O_{15}$ particles were first synthesized by the reaction of $Bi_4Ti_3O_{12}$, $BaCO_3$, and $TiO_2$ at $1080^{\circ}C$ for 3 h in $BaCl_2$-KCl molten salt. After the topochemical reactions, layer-structured $BaBi_4Ti_4O_{15}$ particles transformed to the perovskite $BaTiO_3$ platelets. $BaTiO_3$ particles with thickness of approximately $0.5{\mu}m$ and a length of $10-15{\mu}m$ retained the morphology feature of the $BaBi_4Ti_4O_{15}$ precursor. For <001> $Pb(Mg_{1/3}Nb_{2/3})O_3-32.5PbTiO_3$ (PMNT)-5 wt % PbO piezoelectric ceramics textured with 5 vol % of $BaTiO_3$ templates, the Lotgering factor reached 0.82, and $d_{33}$ was 870 pC/N.

• Bulletin of the Korean Chemical Society
• /
• 제6권4호
• /
• pp.251-253
• /
• 1985

• Journal of the Korean Wood Science and Technology
• /
• 제32권3호
• /
• pp.15-24
• /
• 2004

The present work was undertaken to investigate the anatomical and chemical characteristics of transgenic poplar down-regulated with antisense OMT gene. Also the distribution of lignin in transgenic poplar trees was investigated at cellular level. No visible abnormal phenotype was observed in the fibers and vessel elements of transgenic poplar. Any marked differences in the staining intensities of Wiesner and Mäule color reaction were not identified in the transgenic poplar. TEM micrographs did not show any staining intensities in the cell walls stained with KMnO₄. Interestingly, the UV spectroscopy of semi-thin sections exhibited a distinct decrease of lignin absorption at 280 nm in the vessel walls, indicating transgenic poplar wood with lower amount of guaiacyl lignin in vessel elements. Chemical composition of antisense OMT poplar was almost identical to that of wild-type poplar. Klason lignin content of transgenic poplar did not show any significant difference from that of the controls. The solid state NMR spectra revealed the transgenic poplar with only slightly more syringyl lignin than the control. The present work showed that antisense OMT gene constructed in the poplar was not enough to reduce the overall content of Klason lignin, and suggested that the expression of transformation was confined to vessel walls.