• Journal of the Korean Chemical Society
• /
• v.40 no.1
• /
• pp.44-49
• /
• 1996

The cadmium(Ⅱ)-carboxylate complexes of monocarboxylates and poly(acrylic acid) (PAA) in an aqueous solution were investigated using 113Cd NMR spectroscopy. From these spectral data the chemical shifts of the monocarboxylate (e.g. acetate, benzoate and propanoate) complexes of Cd(Ⅱ) were evaluated (CdL+: -22 to -24 ppm range; CdL2: -39 to -40 ppm range; L: carboxylate). The chemical shift of cadmium(Ⅱ) bound on PAA changed in value from -36.6 to -38.2 ppm when the [PAA]/[Cd] ratios were varied from 12 to 118 eq/mol at a constant pH of 6. The 113Cd chemical shift was sensitive to the change in solution pH: the chemical shift changed from 1.6 to -37.6 ppm when the pH was rasied from 1 to 6 at a constant [PAA]/[Cd] ratio of 39 eq/mol. These results show that under these conditions, the dominant species formed in solution is 1 : 2 complex (CdL2), and 1 : 1 complex (CdL+) is only formed at low pH, when polyanion concentration is low.

• Bulletin of the Korean Chemical Society
• /
• v.25 no.6
• /
• pp.833-837
• /
• 2004

DeniLite$^{TM}$ laccase immobilized platinum electrode was used for amperometric detection of hydroquinone (HQ) and homogentisic acid (HGA) by means of substrate recycling. In case of HQ, the obtained sensitivity is 280 nA/ ${\mu}$M with linear range of 0.2-35 ${\mu}$M ($r^2$ = 0.998) and detection limit (S/N = 3) of 50 nM. This high sensitivity can be attributed to chemical amplification due to the cycling of the substrate caused by enzymatic oxidation and following electrochemical regeneration. In case of HGA, the obtained sensitivity is 53 nA/ ${\mu}$M with linear range of 1-50 $[\mu}M\;(r^2$ = 0.999) and detection limit of 0.3 ${\mu}$M. The response times ($t_{90%}$) are about 2 seconds for the two substrates and the long-term stability is 60 days for HQ and around 40-50 days for HGA with retaining 80% of initial activities. The very fast response and the durable long-term stability are the principal advantages of this sensor. pH studies show that optimal pH of the sensor for HQ is 6.0 and that for HGA is 4.5-5.0. This shift of optimal pH towards acidic range for HGA can be attributed to the balance between enzyme activity and accessibility of the substrate to the active site of the enzyme.

• Bulletin of the Korean Chemical Society
• /
• v.26 no.3
• /
• pp.428-432
• /
• 2005

Squarylium or squaraine dyes are derived from 1,2-dihydroxycyclobuten-3,4-dione, otherwise known as squaric acids. They are two principal types: the 1,2-bisdonorsubstituted derivatives, and the 1,3-bisdonorsubstituted derivatives. The former are essentially merocyanines and have no distinctive properties, whereas the latter represent a unique type of chromophore, which is neither a merocyanines nor cyanine and has exceptional light absorption characteristics. They also have many functional applications based on their special properties. Thus it was the objective of this research project to synthesize a range of 1,3-squarylium dyes of widely differing structural types, and to investigate their light absorption and fluorescence properties in general, and the color change properties of appropriate examples in particular. Also in this study, the various pHinduced colour change processes were examined.

• Transactions of the Korean hydrogen and new energy society
• /
• v.25 no.6
• /
• pp.577-585
• /
• 2014

Nanorod and particle shape $CeO_2$ were synthesized via hydrothermal process and precipitation method, respectively, and used as supports of Pt catalyst for water gas shift (WGS) reaction. Three different durations (12, 48, and 96h) for hydrothermal process were applied for the preparation of nanorod type $CeO_2$. 1.0 wt% of Pt was loaded on the prepared supports with incipient wetness method prior to the catalytic activity tests that were carried out at a GHSV of $95,541h^{-1}$, and a temperature range of 200 to $360^{\circ}C$. Varying duration of hydrothermal process led to the difference in physical characteristics of $CeO_2$ nanorods, such as aspect ratio, BET surface area, pore diameter, and pore volume. Consequently, the catalytic activities of Pt/$CeO_2$ nanorods were affected by the physical characteristics of the supports and appeared to be in the order of Pt/$CeO_2$(12) > Pt/$CeO_2$(48) > Pt/$CeO_2$(96). The comparison of the catalytic activities and results of the analysis (XPS, XRD, SEM, BET and TPR) for the supports revealed that the activity of the catalysts depends on chemical states of the Pt and the support materials in the temperature range that is lower than $280^{\circ}C$. However, the activity is rather dependent on the physical characteristic of the supports because the increased gas velocity limits the mass transfer of reactants in micropores of the supports.

• Proceedings of the Korean Vacuum Society Conference
• /
• 1999.07a
• /
• pp.83-83
• /
• 1999

본 연구에서는 Auger Elecrtron Spectroscopy (AES) 장비를 이용하여 Silicone Wafer 표면에 BF 이온을 주입시킨 후 Dopping 농도 및 Implantation 에너지에 따른 Si KLL Peak의 변화를 관찰하였다. 또한 PVD Ti 계열 화학물의 시료에 대하여 Peak의 Shape 변화를 관찰하였다. 1)Dopping 농도 및 Implantation 에너지에 따른 Si KLL Peak의 변화 관찰 일반적으로 Silicone 기판에 Arsenic(3가)을 Dopping 하였을 경우, Si KLL Peak의 Kinetic Energy 값은 순수 Si Peak보다 더 작은 값으로 Shift 하며, Boron (5가)을 Dopping하였을 경우에는 더 큰 값으로 Shift 한다. 이론적으로 N-type Si의 에너지 차이는 약 1.0eV로 보고되어 있으며, AES를 이용하여 실험적으로 측정된 값은 약 0.6eV정도로 알려져 있다. 이러한 차이는 Dopping 농도에 따라 Valance Band의 에너지 값이 변화하기 때문이라고 알려져 있다. 본 연구에서는 BF2를 Si에 이온 주입하여 입사 에너지 및 dose 량에 따른 Si KLL Peak의 변화를 관찰하였다. 그림1과 같이 Si KLL Peak는 Implantation Energy가 작을수록 Kinetic Energy가 높은 곳으로 Shift 한다. 이는 LOw Energy로 이온 주입하면, Projected Range (Rp)가 High Energy로 이온 주입할 때보다 작기 때문이며, 이 결과를 Secondary Ion Mass Spectroscopy (SIMS) 및 TRIM simulation을 이용하여 확인하였다. 또한 표면에서의 전자 Density의 변화와 Implantation energy와의 관계를 시료의 표면에서 반사되어 나오는 전자의 에너지 손실(Reflected Electron Energy Loss Spectroscopy:REELS)을 통하여 고찰하였다. 2) PVD Ti 계열화합물의 시료에 대한 peak의 shape 가 변화하며, TiL3M23V (Ti2) 및 TiL3M23M23 (Til) Peak의 Intensity Ratio가 변화한다. 따라서 본 연구에서는 그림 2와 같이 Ti 결합 화합물에서의 Ti Auger Peak의 특성 에너지 값과 Peak Shape를 관찰하여, AES를 이용하여 Ti 계열의 화합물에 대한 Chemical state 분석의 가능성을 평가하였다.

• Bulletin of the Korean Chemical Society
• /
• v.32 no.9
• /
• pp.3433-3436
• /
• 2011

Some of metal nanoparticles have the potential for use as colorimetric assays for estimating solution properties, such as pH and temperature due to localized surface plasmon (LSP) phenomena. This report describes the use of silver nanoparticles (AgNP) conjugated with cytochrome c (Cyt c) for the colorimetric determination of solution pHs. When the pH of a solution decreases, the Cyt c immobilized on the AgNP undergoes a conformational change, leading to a decrease in the interparticle distance between Cyt c-AgNP probes and consequent red-shift in LSP. As a result, the color of the Cyt c-AgNP probe solution changes from yellow to red and finally to a grayish blue in the pH range from 11 to 3. This gradual color change can be used to determine the pH of a solution over a wide pH range, compared to other colorimetric methods that use gold nanoparticles.

• Journal of Sericultural and Entomological Science
• /
• v.39 no.2
• /
• pp.169-173
• /
• 1997

The behavior of tyrosine(Tyr.) residue of Bombyx mori silk fiber from yellow fluorescent cocoon has been examined for the dependence of pH in aqueous silk solution under the presence of orange II salt. Through the peak separation of angular dependence of spectral pattern of 15N-Tyr. and [1-13C]-Tyr. between the fiber axis and the molecular bond direction, N-H bond in fiber as well as the orientation distribution around the fiber axis were analyzed. Also, and sericin component was obtained from these angular dependence of oriented spectral pattern. The pH dependence of the 13C NMR chemical shift of B. mori silk fibroin was examined in aqueous solution in the presince of orange II are broad at pH$\geq$7.0. However, these become sharper at pH$\geq$8.0 and remain sharp at higher pH. In these higher pH range, a chemical shift change occurs due to the deprotonation of the Tyr. side group of fibroin. At higher pH. such a hydrophobic cluster is destroyed because of the electrostatic interaction according to the deprotonation of the Tyr-OH group.

• Proceedings of the Korean Society of Medical Physics Conference
• /
• 2005.04a
• /
• pp.93-95
• /
• 2005

MRS is to measure very small metabolite signals, whose resonant frequencies spread over the chemical shift range characteristic of the measured nucleus. The MR signal originates from the excited volume, which is a column of tissue divided into slices by gradient or rf encoding. The parameters that acquired data affected by TE, TR, and other variables. The higher spatial resolution of 3D CSI compared to SVS and its ability to examine regional metabolite variations for brain study.

• Bulletin of the Korean Chemical Society
• /
• v.24 no.1
• /
• pp.86-90
• /
• 2003

Reverse-Water-Gas-Shift reaction (RWGSR) was carried out over the ZnO, $Al_2O_3,\;and\;ZnO/Al_2O_3$ catalysts at the temperature range from 400 to 700 ℃. The ZnO showed good specific reaction activity but this catalyst was deactivated. All the catalysts except the $ZnO/Al_2O_3$ catalyst (850 ℃) showed low stability for the RWGSR and was deactivated at the reaction temperature of 600 ℃. The $ZnO/Al_2O_3$ catalyst calcined at 850 ℃ was stable during 210 hrs under the reaction conditions of 600 ℃ and 150,000 GHSV, showing CO selectivity of 100% even at the pressure of 5 atm. The high stability of the $ZnO/Al_2O_3$ catalyst (850 ℃) was attributed to the prevention of ZnO reduction by the formation of $ZnAl_2O_4$ spinel structure. The spinel structure of $ZnAl_2O_4$ phase in the $ZnO/Al_2O_3$ catalyst calcined at 850 ℃ was confirmed by XRD and electron diffraction.

• Bulletin of the Korean Chemical Society
• /
• v.9 no.3
• /
• pp.137-143
• /
• 1988

We have investigated the infrared spectra for carbon monoxide chemisorbed on silica supported ruthenium with and without potassium coating within the frequency range of 1800-2200 $cm^{-1}$ at various ruthenium concentrations and CO pressures. For the system without potassium coating, three bands were observed in the infrared spectra when CO was adsorbed on both the reduced and oxidized form of supported ruthenium. However, the relative intensities of these three bands were found to have no interdependence. Therefore, we have assigned each of these bands as arising from the CO stretching vibration for carbon monoxide molecules adsorbed on the Ru sites of different nature. On coating with potassium, the 2030 $cm^{-1}$ band observed for the system without potassium coating was found to suffer red shift by 10-30 $cm^{-1}$ and we conclude that this bathochromic shift is caused by enhancement in the capability of back donation of electrons from the metal atom to the antibonding ${\pi}{\ast}$ orbitals of CO due to the presence of potassium.