• 한국환경과학회지
• /
• 제8권2호
• /
• pp.241-248
• /
• 1999

The photocatalytic decolorization and photodegradation of wastewater contamininated with dyes such as methyleneblue tetrahydrate(MBT), methyl orange(MO), phenol red(PR) and the mixed dyes have been studied using a batch reactor in the presence of aerotropic and titania. Degussa P25 titanium oxide was used as the photocatalyst and proved to be effective for the dyes-degradation when irradiated with UV-light source emitting the wavelength of 253.7 nm in the presence of air. In addition to removing the color from the wastewater, the photocatalytic reaction simultaneously reduced the COD and optical density which suggests that the dissolved organic compounds have been photooxidized. The reaction rate of disappearance of the dyes were measured as a function of the irradiation times. The photooxidative procedure of the aquatic solution have the first order reaction-kinetics. The rate constants were increased in the order of PR < MBT < $gL^{-1}-TiO_2$ powder were irradiated with the UV -light source.

• 한국진공학회:학술대회논문집
• /
• 한국진공학회 2011년도 제41회 하계 정기 학술대회 초록집
• /
• pp.359-359
• /
• 2011

This study reports the H2S gas sensing properties of CuO / ZnO nano-hetero structure bundle and the investigation of gas sensing mechanism. The 1-Dimensional ZnO nano-structure was synthesized by hydrothermal method and CuO / ZnO nano-heterostructures were prepared by photo chemical reaction. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) spectra confirmed a well-crystalline ZnO of hexagonal structure. In order to improve the H2S gas sensing properties, simple type of gas sensor was fabricated with ZnO nano-heterostructures, which were prepared by photo-chemical deposition of CuO on the ZnO nanorods bundle. The furnace type gas sensing system was used to characterize sensing properties with diluted H2S gas (50 ppm) balanced air at various operating temperature up to 500$^{\circ}C$. The H2S gas response of ZnO nanorods bundle sensor increased with increasing temperature, which is thought to be due to chemical reaction of nanorods with gas molecules. Through analysis of X-ray photoelectron spectroscopy (XPS), the sensing mechanism of ZnO nanorods bundle sensor was explained by well-known surface reaction between ZnO surface atoms and hydrogen sulfide. However at high sensing temperature, chemical conversion of ZnO nanorods becomes a dominant sensing mechanism in current system. Photo-chemically fabricated CuO/ZnO heteronanostructures show higher gas response and higher current level than ZnO nanorods bundle. The gas sensing mechanism of the heteronanostructure can be explained by the chemical conversion of sensing material through the reaction with H2S gas.

• 한국균학회지
• /
• 제17권4호
• /
• pp.202-208
• /
• 1989

N-methylmaleimide와 Harmaline의 혼합용액에서 자외선을 조사시켜 합성한 주생성물을 분광학적으로 분석하였다. 그 결과 harmaline의 아민기와 N-methylmaleimide의 탄소-탄소 이중결합 사이에 광부가 반응을 한 harmaline의 N-methylmaleimide 유도체가 얻어졌으며 이 유도체는 몇 가지의 효모 및 광합성 세균의 성장을 억제하므로 생물학적 독성을 가지고 있는 것으로 보여진다.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2007년도 추계학술대회 논문집
• /
• pp.287-287
• /
• 2007

The ferroelectric and electric properties of UV-irradiated bismuth lanthanum titanate (BLT) films prepared using photosensitive starting precursors were characterized. The effects of lanthanum doping on ferroelectric and electric properties were investigated by polarization-electric field hysteresis loops and leakage current-voltage measurements. X-ray diffractometer and ellipsometry were served to provide the information about the crystalline structure and thickness of the films after annealing. The images of the surface microstructure and direct-patterned BLT films were observed by using scanning electron microscopy. The effects of lanthanum doping on the electric properties of direct-pattern able BLT films and their direct-patterning were studied.

• 한국작물학회지
• /
• 제60권1호
• /
• pp.1-7
• /
• 2015

본 연구는 파종시기와 질소시비 수준에 대한 옥수수의 광화학적 반응을 분석하여 광생리적 특성을 해석하였다. 1. 5월 22일 파종시 질소 함량이 증가함에 따라 생육후기까지 엽록소 형광량 또한 증가하여 질소 배량처리에서 광이용효율이 더 높은 것으로 확인되었다. 2. 생육초기의 형광량이 가장 높았으며, 이후 모든 처리구에서 엽록소 형광량이 50% 가량 감소하여 전자전달을 위한 광화학 반응이 크게 감소했음을 알 수 있었다. 3. 질소 반량구에서 활성화된 RC (RC/ABS)가 감소하며 13% 이상의 에너지가 손실되었으며, 결국 전자전달시 에너지 전환효율(PI, DF 등)이 감소해 광이용효율이 낮았다. 4. 배량 처리구는 생육후기로 갈수록 전자전달 효율(ET2o/CS) 및 단면당 활성화된 RC(RC/CS) 등 광이용 효율이 대조구 대비 크게 증가하여 광합성기구 사이의 전자전달이 잘 이루어지는 것으로 확인되었다.

• 마이크로전자및패키징학회지
• /
• 제27권1호
• /
• pp.25-29
• /
• 2020

광화학증착법 (PMOD; photochemical metal-organic deposition)을 이용하여 photoresist 및 etching 공정없이 pattern 된 TiO_x resistive switching (RS) 소자를 제작 및 그 특성을 평가하였다. Ti(IV) 2-ethylhexanoate를 출발물질로 사용하였으며 UV 노출시간 10 min에 광화학반응이 완료됨을 FTIR 분석을 통하여 확인하였다. 200 ℃ 이하 저온공정에서 직접패턴 된 20 nm 두께의 비정질 TiO_x 박막의 균일한 두께의 패턴형성을 Atomic Force Microscopy를 통하여 확인하였다. 별도의 상형성을 위한 후 열처리 공정 없이 4 ㎛ 선폭의 전극위에 형성된 20 nm 두께의 비정질 TiO_x RS 소자는 4V 동작전압에서 on/off ratio 20의 forming-less RS 특성을 나타내었다. Electrochemical migration에 영향을 미치는 grain boundary가 없어 소자간 신뢰성 향상이 기대되며, flexible 기판 또는 저온공정이 요구되는 메모리 소자 공정에서 PMOD 공정이 응용될 수 있음을 보여준다. Selector를 이용하여 crossbar array 구조를 도입할 경우 매우 간단한 구조의 저비용 메모리 소자를 구현할 수 있을 것으로 기대 된다.

• Journal of Photoscience
• /
• 제3권2호
• /
• pp.91-93
• /
• 1996

In connection with our interest on the photochemical properties of heteroaryl halides, which are currently the subject of heterocyclic ring formation and haloarene degradation, we have studied the photochemistry of the haloarene linked to N-heteroarene compounds. Imidazo[5,1-a]isoindole was synthesized from N-(ochlorobenzyl)imidazole or N-(o-bromobenzyl) imidazole in acidic aqueous solution or acetonitrile via the intramolgcular photocyclization (Table 1). This type of reaction provides the synthetic methods for 5- and 6-membered polyheteroatomic heterocyclic ring compounds. However, the reaction mechanism for the intramolecular photocyclization of haloarene tethered heteroarenes has not yet been established. Grimshaw et al. suggested a mechanism for homolyric carbonhalogen bond fission assisted by radical complexation to explain their results in the photocyclization of 5-(2-chlorophenyl)-1,3-diphenylpyrazole. They also reported the detection of acyclohexadienyl intermediate involved in the above reaction. Park et al. reported several transient 'intermediates involved in the laser flash photolysis of N-(o-halobenzyl) pyridinium and N-benzyl-2-halopyridinium salts. Thus we performed the laser flash photolysis study on the photocyclization reaction of N-(o-chlorobenzyl) imidazole to identify the intermediate species involved in the reaction. Here, we report on the preliminary results in the photocyclization reaction of N-(o-halobenzyl)imidazole through the detection of reaction intermediates.

• Journal of Photoscience
• /
• 제6권2호
• /
• pp.67-70
• /
• 1999

trans-1-(9-Anthryl)-2-(n-pyridyl)ethene (t-n-APyE, n=2 or 4) and trans-1-(9-anthryl)-2-pyrazinylethene (T-APzE) exhibits solvent-dependent fluorescence and efficient trans)cis photoisomerization. Photochemical reactivities of t-2-APyE, t-4-APyE, and t-APzE have been investigated in nonpolar and polar solvents. In nonpolar solvent, parallel photocyclization reaction occurs very efficiently in competition with the fluorescence and photoisomerization. But, in polar solvent, photocyclization was not observed. It is probably due to the stabilization of charge separated state in polar solvent, which is an intermediate in photoisomerization reaction.

• Bulletin of the Korean Chemical Society
• /
• 제14권4호
• /
• pp.487-490
• /
• 1993

A semiempirical methods (PM3-CI-UHF. etc.) for the evaluation of ground and excited state electronic structures of psoralens are applied to angelicin with thymine. The photocycloaddition reaction of angelicin with thymine were deduced to be formed by their preferable HSOMO-LUMO interactions. The photoadduct was inferred to be a C$_{4-}$cycloaddition product with the stereochemistry of cis-anti formed through [2+2] addition reaction between, the 3,4 double bonds of angelicin and the 5,6-double bond of thymine.

• 한국진공학회지
• /
• 제20권4호
• /
• pp.300-306
• /
• 2011

본 연구는 편극 패턴된 강유전체 단결정 $LiNbO_3$ (0001) 기판에 광화학적 환원반응을 이용하여 금속(Au, Ag) 나노입자를 증착시키고, 금속 입자의 종류와 표면의 극성에 따른 나노입자의 표면 분포를 원자간력현미경(AFM)으로 조사하였다. 전극 인가에 의해 주기적으로 편극 패턴된 강유전체 단결정 $LiNbO_3$ (periodically polarity-patterned $LiNbO_3$: PPLN)을 기판으로 사용하였으며, PPLN의 각 영역의 편극 방향은 Piezoresponse force microscopy로 확인하였다. 금속(Ag, Au) 나노 입자는 금속이 포함된 수용액에 PPLN 기판을 넣고, 자외선 램프로 30초에서 3분간 노출시켜 광환원 반응으로 기판에 증착시켰다. 시료 성장후, 공기 중에서 AFM을 이용하여 나노입자의 형태, 크기, 및 표면분포를 조사하였다. Ag 입자의 경우, -Z 편극 영역보다 +Z 편극 영역에 크고 밀도가 높은 나노 입자가 증착되었으며, 특히 편극 경계 부분에 가장 큰 Ag 나노입자가 증착되어, 나노선 모양으로 성장됨이 확인되었다. 그러나 Au 입자의 경우는 편극 경계부분에 입자가 증착되는 경향이 없었다. 두 입자 모두 자외선 노출시간이 증가함에 따라, 증착된 나노입자의 크기는 증가하는 경향을 보였다. 이와 같이 증착된 금속 나노입자가 강유전체의 표면편극에 따라 다른 분포로 성장되는 것을 강유전체 표면 극성에 따른 표면 밴드구조 변화, 광전 효과 및 표면의 전기장의 불균일성에 의한 수용액 속의 금속 양이온과 자외선에 의해 생성된 전자와의 광화학적 반응에 대한 모델로 논의할 것이다.