• 대한화학회지
• /
• 제27권6호
• /
• pp.399-404
• /
• 1983

아미드와 아미드-용매계의 C=O stretching band에 해당하는 Raman 스펙트럼으로 부터 카르보닐기와 질소에 치환된 알킬기가 수소결합에 미치는 영향을 조사하였다. Formamide 계에서는 상호작용의 세기가 아미드-아미드>아미드-물>아미드-알코올 순으로 감소했으며, acetamide와 propionamide 계에서는 아미드-물>아미드-아미드>아미드-알코올 순으로 감소하였다. 카르보닐기에 알킬기가 치환되면 카르보닐기의 proton acceptor의 세기가 증가되며, 질소에 알킬기가 치환되면 proton donorcity가 감소함을 보이는데 이는 이론적인 계산 결과와도 일치한다.

• Bulletin of the Korean Chemical Society
• /
• 제25권12호
• /
• pp.1817-1821
• /
• 2004

Fourier transform Raman spectra of methyl red adsorbed on untreated and pretreated ${\gamma}$-alumina and silicaalumina calcined at 900 $^{\circ}C$ under 1 atm steam flowing were recorded. Spectral analysis shows that the active species adsorbed on ${\gamma}$-alumina was to be deprotonated methyl red, and on silica-alumina to be di-protonated. This indicates that ${\gamma}$-alumina adapted in this work holds Bronsted basicity, and silica-alumina Bronsted acidity. Raman intensities of methyl red on pretreated ${\gamma}$-alumina are about three times stronger than on untreated ${\gamma}$-alumina, while spectral features are unchanged. For silica-alumina, spectral features show modified vibrational characteristics upon surface hydroxylations generated from pretreatment. Consequently, the acidity loss for silica-alumina and the basicity gain for ${\gamma}$-alumina were observed by increasing the surface hydroxyl groups on the catalysts through pretreatment of the steam calcination.

• Bulletin of the Korean Chemical Society
• /
• 제34권2호
• /
• pp.470-474
• /
• 2013

Surfaced-enhanced Raman scattering (SERS) of 4,4'-biphenyldithiol (BPDT) has been investigated at a silver island film. Ordinary Raman (OR) spectra of neat sample in solid state and in basic solution have also been taken for comparison. The spectral feature in the SERS spectrum was similar to that for the OR spectrum in basic solution, except for the broadening of ring stretching bands indicative of the presence of surface-phenyl ring $\pi$ interaction. In contrast, only absence of the C-H stretching band with very small Raman scattering cross-section seemed not pertinent in judging the definitive orientation of molecule. The observed vibrational bands in the SERS spectrum have been assigned by referring to the normal modes and wavenumbers from density functional theory (DFT) calculations of the simple model as 4,4'-biphenyldithiolates bound to two Ag atoms at the both ends. Excellent agreement between the experimental and the calculated results was achieved, which is remarkable considering the level of theory applied.

• 대한화학회지
• /
• 제62권5호
• /
• pp.358-363
• /
• 2018

화석연료의 사용과 그 2차오염으로 인해 매년 수도권의 초미세먼지(PM2.5)는 점점 증가하는 추세에 있다. 본 연구는 초미세먼지의 주된 원인물질이라고 알려져 있는 자동차의 매연에서 발생하는 $NO_x$의 제거에 저렴한 Cu 촉매의 이용 가능성에 초점을 두었다. 이를 위하여 일산화질소(NO) 분자가 Cu에 결합하여 형성할 수 있는 Cu-NO 복합체의 가능한 3가지 구조에서의 에너지와 결합길이, IR 및 라만 스펙트럼의 변화를 알아보기 위하여 Gaussian 09 프로그램에서 MPW1PW91 법을 이용하여 기저함수 6-311(+)G(d,p) 수준에서 계산을 수행하였다. 그 결과, Cu-NO 복합체의 생성 엔탈피는 선형, 굽은형, 다리형 구조에 대하여 각각 ${\Delta}H=104.89$, 91.98, -127.48 kJ/mol의 값을 얻었고, NO 결합길이는 복합체가 되었을 때 약 $0.03{\sim}0.10{\AA}$ 정도 NO 분자보다 길어지는 경향을 보여 Cu-NO 결합으로부터 O가 보다 쉽게 환원될 수 있음을 보여준다. 또한 NO와 Cu-NO 복합체의 IR 및 라만 스펙트럼은 각 진동 모드에 대한 피크의 위치와 세기가 확연히 달라져 Cu 촉매에서 Cu-NO 복합체의 생성 여부도 적외선 또는 라만 분광법으로 손쉽게 확인될 수 있음을 알 수 있었다.

• 조명전기설비학회논문지
• /
• 제28권9호
• /
• pp.45-51
• /
• 2014

This work carried out for the effective synthesis characteristics of graphene nanowall film by controlling the electric field in a RF plasma CVD process. For that, the bipolar bias voltage was applied to the substrate such as Si and glass materials for the best chemical reaction of positive and negative charges existing in the plasma. For supplying the seed formation sites on substrate and removing the oxidation layer on the substrate surface, the electron bombardment into substrates was performed by a positive few voltage in hydrogen plasma. After that, hydrocarbon film, which is not a graphene nanowall, was deposited on substrates under a negative bias voltage with hydrogen and methane gases. At this step, the film on substrates could not easily identify due to its transparent characteristics. However, the transparent film was easily changed into graphene nanowall by the final hydrogen plasma treatment process. The resultant raman spectra shows the existence of significant large 2D peaks corresponding to the graphene.

• 전기학회논문지P
• /
• 제58권4호
• /
• pp.451-454
• /
• 2009

The $\beta-In_2Te_3$ single crystal was grown by vertical Bridgman method. The $\beta-In_2Te_3$ single crystal had a face centered cubic(fcc) structure. The lattice constants were found to be $a\;=\;0.617\;{\AA}$. The direct optical energy gap ($E_g$) was found to be 1.11 ev at 300 K. Raman spectra peak of $\beta-In_2Te_3$ single crystal showed the low $E_{LO}$ mode at $105\;cm^{-1}$. The electrical conduction type was measured by the thermal method and was p-type. The electrical conductivity was found to be $1.8\;{\times}\;10^{-2}\;{\Omega}^{-1}cm^{-1}$ at 300 K. The activation energy was found to be 0.51 eV.

• Journal of Electrochemical Science and Technology
• /
• 제2권2호
• /
• pp.116-123
• /
• 2011

Herein, a novel preparation method of highly homogeneous carbon-silicon composite materials was presented. In contrast to conventional solvent evaporation method, a milled silicon-graphite or its oxidized material were directly reacted with petroleum-derived pitch precursor. After thermal reaction under high pressure, pitch-graphite-silicon composite was prepared. Carbon-graphite-silicon composite were prepared by an air-oxidization and following carbonization. From energy dispersive spectroscopy, it was observed that small Si particles were highly embedded within carbon, which was confirmed by disappearance of Si peaks in Raman spectra. Furthermore, X-ray diffraction and Raman spectra revealed that carbon crystallinity decreased when the strongly oxidized silicon-graphite was added, which was probably due to oxygen-induced cross-linking. From the anode application in lithium ion batteries, carbon-graphite-silicon composite anode displayed a high capacity ($565\;mAh\;g^{-1}$), a good initial efficiency (68%) and an good cyclability (88% retention at 50 cycles), which were attributed to the high dispersion of Si particles within cabon. In case of the strongly oxidized silicongraphite addtion, a decrease of reversible capacity was observed due to its low crystallinity.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2002년도 하계학술대회 논문집
• /
• pp.330-333
• /
• 2002

The substrate temperature is an important parameter in thin film deposition process. In this paper the effects of the substrate temperature on the properties of CuIn0.75Ga0.25Se2(CIGS) thin films are reported. Structure, surface morphology and optical properties of CIGS thin films deposited at various substrate temperatures have been investigated using a number of analysis techniques. X-ray diffraction (XRD) analysis shows that CIGS films exhibit a strong <112> preferred orientation. As expected, at higher substrate temperatures the films displayed a higher degree of crystallinity. The <112> peak was also enhanced and other CIGS peaks appeared simultaneously These results were supported by experimental work using Raman spectroscopy. The Raman spectra of the as-grown CIGS thin films show only the Al mode peak. The intensity of this peak was enhanced at higher deposition temperatures. Scanning electron microscopy (SEM) results revealed very small grains in films fabricated at 48$0^{\circ}C$ substrate temperature. When the substrate temperature was increased the average grain size also increased together with a reduction in the number and size of the voids. The deposition temperature also had a significant influence on the transmission spectra.

• 대한기계학회논문집B
• /
• 제28권9호
• /
• pp.1081-1092
• /
• 2004

The synthesis of Ni-catalyzed multi-walled carbon nanotubes and nanofibers on a catalytic metal substrate, using an ethylene fueled inverse diffusion flame as a heat source, was investigated. When the gas temperature was varied from 1,400K to 900K, approximately, carbon nanotubes with diameters of 20∼60nm were formed on the substrate. In the regions where the gas temperature was higher than 1,400K or lower than 900K, iron nanorods or carbon nanofibers were synthesized, respectively. Based on the quantitative analyses of large amount of SEM and TEM images, the nanotubes formed closer to the flame had a tendency of having larger diameters. HR-TEM images and Raman spectra revealed that carbon nanotubes synthesized had multi-walled structures with some defective graphite layers at the wall. Based on the graphite mode of the Raman spectra, it was believed that the optimal synthesis could be obtained as the substrate was positioned at between 5.5mm and 5.0mm, from the flame axis.

• 전자공학회논문지A
• /
• 제31A권9호
• /
• pp.96-103
• /
• 1994

The GaAs epilayer was grown at low temperature (LT. 250.deg. C) by molecular beam epitaxy. The properties of the LTT GaAs, before and after Rapid Thermal Annealing(RTA), were analyzed by Reflection of High Energy Electron Diffraction (RHEED), Double Crystal X-ray(DCX), Raman spectroscopy, PL and Photo-Induced Current Transient Spectroscopy (PICTS). The LT GaAs before RTA, was analyzed by RHEED and DCX, with a result of an improved surface morphology under a relatively As-rich(As/Ga ratio :28) condition, and of an increased lattics parameter of 1.1 1.7% in comparison with a GaAs substrate. However DCX and Raman spectroscopy revealed that the expanded lattics parameter and the crystallinity of LT GaAs could be recovered after RTA. On the other hand, PL spectra indicated that LT GaAs after RTA showed low optical sensitivity unlike High Temperature(HT) GaAs, and that its surface morphology and crystallinity were corresponded with those of HT GaAs. Finally PICTS spectra proved the fact that low sensitivity of LT GaAs was due to the deep level defects (Ec-0.85eV) which were strogly formed by raising RTA temperature to 750.deg. C.