• Bulletin of the Korean Chemical Society
• /
• v.22 no.9
• /
• pp.948-952
• /
• 2001

Periodic mesoporous organosilicas with rope-based morphology from a reaction gel composition of 1 BTME : 0.57 ODTMABr : 2.36 NaOH : 353 H2O were synthesized. While long rope-shaped product dominated in case of static synthesis condition , gyroid type products instead of rope shaped product appeared and rope shaped product disappeared with agitation. PMO with such a long rope shaped morphology is firstly reported. Additionally, various rope-based morphologies depending on the degree of bending, twisting, folding and winding of rope such as spirals, discoids, toroids, and worm-like aggregates were observed. White powdered products were characterized by X-ray diffraction, N2 sorption measurement, SEM and TEM. From XRD pattern and TEM image, ODTMA-PMO with hexagonal symmetry was identified. The pore diameter and BET surface area of ODTMA-PMO are $32.9{\AA}$ and 799 m2g-1 , respectively. Hexagonally arrayed channels run with long axis of rope and rope-based shapes with various degree of curvature, which was elucidated by using TEM images.

• Bulletin of the Korean Chemical Society
• /
• v.13 no.6
• /
• pp.613-620
• /
• 1992

The solvent-dependent photophysical properties of 2-biphenylcarboxylic acid (2BPCA) and 4-biphenylcarboxylic acid(4BPCA), which have a pre-twisted conformation in the ground state, have been investigated. The fluorescence spectra of 4BPCA show vibrational structure with a non-mirror image to the absorption spectra in nonpolar solvent while those of 2BPCA show no structure even in nonpolar solvents. As the solvent polarity increases, the fluorescence spectra become diffuse and broad with a strong red shift resulting in the large Stokes shift. The large fluorescence Stokes shift of BPCA's in polar solvent is also partially due to an intramolecular charge transfer (ICT) interaction in the excited state, as demonstrated by the large dipole moment in the excited state (7.6-10.6 D). The fluorescence decay behaviors of BPCA's (decay-times and their pre-exponential factors) also depend on solvent polarity in agreement with the solvent-dependent properties of the steady-state fluorecence. The data have been discussed in terms of change in the excited-state potential energy surface with respect to change of the dihedral angle of biphenyl moiety.

• Bulletin of the Korean Chemical Society
• /
• v.22 no.3
• /
• pp.267-270
• /
• 2001

The adsorption of chlorine on a Pt(111) surface at 90 K has been studied using scanning tunneling microscopy (STM) in ultra-high vacuum environments. The adsorbed chlorine atoms give rise to two different ordered structures, (3${\times}$3)-Cl and c(4${\times}$2)- Cl, depending on the coverage. It has been determined from the STM image that the absolute coverage of (3${\times}$3)-Cl structure is 0.44, which is not in agreement with coverage calibrated by a low energy electron diffraction technique together with an Auger electron spectrometer and a thermal desorption spectrometer. The Cl atoms bound to on-top sites at the Pt(111)(3${\times}$3)-Cl surface appeared to effectively perturb the density of states of Pt atoms, as compared with that bound to bridging sites. The other ordered structure, c(4${\times}$2)-Cl, with small domain sizes, consists of both on-top and bridge-bonded species with a saturation coverage of 0.5.

• Bulletin of the Korean Chemical Society
• /
• v.19 no.3
• /
• pp.308-313
• /
• 1998

A thermally irreversible photochromic system, 2,3-bis(2,4,5-trimethyl-3-thienyl)maleic anhydride (MTMA), has been studied by semi-empirical molecular orbital methods. There are one pair of stable conformations for the closed-ring form and three pairs for the open-ring form, each pair consisting of two mirror-image conformations. Interconversion between the parallel and anti-parallel conformations of the open-ring form is restricted due to high energy barriers. Only the anti-parallel conformation appears to be responsible for photochromic cyclization. Thermostability of the compound is attributed to an avoided crossing at high energy in the ground states of the isomers, whereas the photoreactivity can be explained by the mutually connected excited singlet (S1) states of the isomers, forming a double well potential with a low energy barrier. The large solvent effects can be partly explained with the low dipole moment of the anti-parallel conformation of MTMA in the S1 state. The large variation of quantum efficiency suggests that excess vibronic energy can be utilized to provide the activation energy for the photochromic reaction.

• Journal of the Korean Vacuum Society
• /
• v.4 no.S1
• /
• pp.1-6
• /
• 1995

Polycrystalline Si films have been used in many applications such as thin film transistors(TFT), image sensors and LSI applications. In this research deposition of Si films at low temperatures with remote plasma enhanced CVD from Si2H6-SiF4-H2 on SiO2 was studied and their crystallinity was investigated. It was condluded that growth of crystalline Si films was favorable with (1) low Si2H6 flow rates, (2) moderate plasma power, (3) moderate SiF4 flow rates, (4) moderate substrate temperature, and (5) suitable method of surface cleaning.

• Journal of the Korean Graphic Arts Communication Society
• /
• v.3 no.1
• /
• pp.17-24
• /
• 1985

The main purmose of this study is to establish the corelatione between the ink receptivity and the surface 초\ulcorner岺\ulcornerparamenters in the presence of the dampening solution in the Lithographic Printing. The surface chemical parametere are calculated from the components (dispersion part and polar part) of which the surface tension of various surfaces acd ink are estimated from the contact angle The conclusions are; 1) the receptivity of ink depends on the value of polar part of surface tension, ; and ink, ;and decreases as the value of and increase, 2) the adherence of ink depends on the value of ink and dampening solution, and decreases as the value of dampening solution, decreases on the image area.

• Journal of Magnetics
• /
• v.19 no.4
• /
• pp.323-326
• /
• 2014

Superparamagnetic maghemite nanoparticles were prepared by chemical co-precipitation, followed by a temperate oxidation stage, and investigated using FE-SEM, XRD, TGA, VSM, and M$\ddot{o}$ssbauer spectroscopy. Through SEM image and XRD analysis, its average particle size was found to be 13.9 nm. While VSM magnetic measurement showed typical superparamagnetic behavior at room temperature, M$\ddot{o}$ssbauer spectroscopic investigation revealed that non-vanishing magnetic hyperfine structure were retained. Cation distribution estimated from M$\ddot{o}$ssbauer spectroscopy confirmed the formation of maghemite nanophase in the sample.

• Journal of the Korean Graphic Arts Communication Society
• /
• v.7 no.1
• /
• pp.16-30
• /
• 1989

The anodixed aluminium film by sulfuric acid - method has many pores, the inner, called barrier layers, is active. They have strong absorption of dye. on be other, the absorption of dye is lost by Sealing, the surface is not dyed. We make IMAGE FORMATION on the film by the chemical behavior. This study made sure whether ion absorption is not in the barrier layer by IRRS and ESCA, considerated the mechanism of inage formation.

• Bulletin of the Korean Chemical Society
• /
• v.33 no.9
• /
• pp.3043-3047
• /
• 2012

To investigate the scattering layer effect of a $TiO_2$ multilayer in dye-sensitized solar cells (DSSCs), we designed a new DSSC system, assembled with a CdS-$TiO_2$ scattering layer electrode. A high-magnification SEM image exhibited hollyhock-like particles with a width of 1.5-2.0 ${\mu}m$ that were aggregated into 10-nm clumps in a hexagonal petal shape. The efficiency was higher in the DSSC assembled with a CdS-$TiO_2$ scattering layer than in the DSSC assembled with $TiO_2$-only layers, due to the decreased resistance in electrochemical impedance spectroscopy (EIS). The short-circuit current density ($J_{sc}$) was increased by approximately 7.26% and the open-circuit voltage ($V_{oc}$) by 2.44% over the 1.0 wt % CdS-$TiO_2$ composite scattering layer and the incident photon-to-current conversion efficiency (IPCE) in the maximum peak was also enhanced by about 5.0%, compared to the DSSC assembled without the CdS-$TiO_2$scattering layer.

• Membrane Journal
• /
• v.27 no.3
• /
• pp.284-289
• /
• 2017

In this study, natural clay as a filler was systematically integrated into polysulfone nanofibers to prepare polysulfone/clay composite membranes with mechanical properties. The composite nanofibers were formed by electrospinning of a mixed precursor of polysulfone and clay. The pore size of the composite membranes was adjusted by simply controlling the number of layers of nanofibers. The overall membrane properties were examined by SEM, contact angle, pore characteristics, tensile strength and water flux. In particular, the presence of clay within the nanofibers was confirmed with SEM images and the mechanical property of the composite nanofiber membranes was examined by tensile strength measurements. Thus, the prepared composite membranes were expected to be utilized for water treatment system.