Earticle

신소재(고분자, 금속, 세라믹)는 기존의 재료와는 다른 우수한 특성과 새로운 기능이 있어 우리 인류 복지에 매우 중요하며 우리는 무한대 생존 경쟁에 몰리고 있다. 이 중 무기고분자는 유기고분자의 단점을 보완하는 동시에 새로운 기능성을 가지므로 산업발전에 매우 중요하다. 다양한 무기고분자의 응용분야 중 세라믹 전구체로의 사용은 첨단 산업 분야에 막대한 발전을 초래하였다. 특히 규소를 함유하는 비산화성 세라믹인 탄화규소 (SiC) 및 질화규소 (Si3N4) 세라믹은 그 산업적 용도가 다양하다. 규소 고분자는 원료 물질이 값싸고 중합 수율이 높아서 경제적이고, 분자 내 Si와 C 또는 N의 비율을 자유자제로 조정할 수가 있고, 용융성 또는 용해성이 있으므로 성형가공이 가능하며, 세라믹 잔여 수율을 증대시키기 위해서 여러 화학반응에 의해 가교도 시킬 수가 있다. 열분해 조건에 따라서 SiC와 Si3N4 등 선택의 조절이 쉬우며, 금속과 섞어서 열분해 함으로서 세멧도 제조할 수가 있다. 이런 종류의 연구는 신소재의 총아인 금속, 고분자, 세라믹 연구들이 함께 어우러진 종합 작품이라 할 수 있겠다. 여러 유형의 유기규소 고분자들을 다양하게 합성해서 그 열분해 과정을 좀 더 면밀히 연구한다면 산업적 응용 가능성은 매우 크리라 기대된다.

The new MPV-type reagent, Al-fluorodiisobutylalane (DIBAF), has been prepared and their reducing characteristics in the reduction of selected organic compounds containing representative functional groups have been examined in order to find out a new reducing system with unique applicability in organic synthesis. In general, the reagent is extremely mild, showing only reactivity toward aldehydes, ketones, and epoxides. The reagent achives a clean 1,2-reduction of enals to the corresponding allylic alcohols in a 100% purity, but shows no reactivity toward enones. The reagent also shows an excellent regioselective cleavage of substituted epoxides. In addition, DIBAF produces the thermodynamically more stable alcohol epimer in high stereoselectivity in the reduction of cyclic ketones.

Bis(silyl)palladinum(II) and -platinum(II) complexes are key intermediates for the synthesis of organic silyllated compounds by the Pd or Pt-catalyzed reactions. Reactions of dialkylpalladinum and -platinum complexes with diphenylsilane gave the bis(silyl)palladinum and -platinum complexe in moderate to good yields. Isolated complexes were characterized by 1H, 13C and 31P-NMR spectroscopy and elemental analyses. Some of the complexes were determined by X-ray crystallographic studies.

Organometallic containing silole unit has been interested, since silole has a unique optical and electronic properties. The main goal of this work is to develop new selective sensors for organosilicon of 1-methyl-2,3,4,5-tetraphenyl-1H-silole and 1-methyl-1-(3-aminopropyl)-2,3,4,5-tetraphenylsilole based on new silole have been characterized by UV-vis absorption spectroscopy. their optical characteristics have been also investigate using photoluminescence spectroscopy.

Dithiocarbamoic acid and their derivatives were found to readily react with potassium and sodium hydroxide to give the corresponding alkali metal dithiocarbamoic acid derivatives 8-17 in moderate to good yields.

Optical images based on the porous silicon exhibiting photoluminescence have been prepared from an electrochemical etching of n-type silicon wafer (boron-doped,<100> orientation, resistivity 1~10 Ω-cm) by using a beam projector. The images remained in the substrate displayed an optical images correlating to the optical pattern and could be useful for optical data storage. This provides the ability to fabricate complex optical encoding in the surface of silicon.

Multiple rugate structures can be etched on a silicon wafer and placed in the same physical location, showing that many sharp spectral lines can be obtained in the optical reflectivity spectrum. Porous silicon samples were prepared by electrochemical etch of heavily doped p-type silicon wafers. The etching solution consisted of a 3:1 volume mixture of aqueous 48% hydrofluoric acid and absolute ethanol. Galvanostatic etch was carried out in a Teflon cell by using a twoelectrode configuration with a Pt mesh counterelectrode. A sinusoidal current density waveform varying between 51.5 and 74.6 mA/cm2 is applied. The anodization current was supplied by a Keithley 2420 high-precision constant current source which is controlled by a computer to allow the formation of PSi multilayer.

A new porous silicon (PSi) microcavity sensor for the detection of volatile organic compounds (VOCs) was developed. PSi microcavity sensor exhibiting unique reflectivity was successfully obtained by an electrochemical etching of silicon wafer. When PSi was fabricated into a structure consisting of two high reflectivity muktilayer mirrors separated by an active layer, a microcavity was formed. This PSi microcavity is very sensitive structures. Reflection spectrum of PSi microcavity indicated that the full-width at half-maximum (FWHM) was of 10 nm and much narrower than that of fluorescent organic molecules or quantum dot. The detection of volatile organic compounds (VOCs) using PSi microcavity was achieved. When the vapor of VOCs condensed in the nanopores, the refractive indices of entire particle increased. When PSi microcavity was exposed to acetone, ether, and toluene, PSi microcavity in reflectivity was red shifted by 28 nm, 33 nm, and 20 nm for 2 sec, respectively.

A silaspirotropylidene has been obtained from the reaction of the lithium salt of tetraphenylsilole dianion with 2 equiv of diphenylcyclopropene, followed by quenching with Me3SiCl. Silaspirotropylidene exhibits an unusual optical property its optical property was characterized by UV-vis and fluorescence spectroscopy. Absorption wavelength maxima of silaspirotropylidene was 420 nm. silaspirotropylidene displayed an emission band at 550 nm with excitation wavelength of 420 nm.

Easy and simple synthesis of CdSe nanocrystals was achieved through sol-gel process. CdSe nanocrystals were synthesized from the reaction of cadmium oxide and selenium in the prescence of trioctylphosphine oxide, tributylphosphine, octadecene, octadecylamine, and stearic acid. The effect of reaction temperature for the determination of size of CdSe nanocrystals was investigated after the addition of selenium. The reaction temperature for the growth of CdSe nanocrystals was increased by every 20oC from 170 to 190, 210, 230, 250, 270, and 290oC. When the reaction temperature was higher, the absorption wavelength in the absorption spectrum was increased which indicated that the size of CdSe nanocrystals was increased. The emission wavelength in the photoluminescence spectrum was increased from 438 to 489, 542, 591, 643, 692, and 745 nm, as the size of CdSe nanocrystals was increased. The control of the reaction temperature illustrated that the color tuning of emission wavelength were successfully obtained.