• Bulletin of the Korean Chemical Society
• /
• v.18 no.9
• /
• pp.916-922
• /
• 1997

A superconducting phase La2CuO4+δ (Tc=44 K) has been prepared by electrochemical oxidation which allows the oxygen to intercalat into the La2O2 layers. According to the Cu K-edge X-ray absorption near edge structure spectroscopic analysis, the oxidized phase shows an overall spectra shift of about 0.5 eV to a higher energy region compared to the as sintered one with the occurrence of an additional peak corresponding to the transition to the |1s13dn+1L-14pσ1 > final state, indicating the oxidation of CuO2 layer. From the X-ray photoelectron spectroscopic studies, it is found that the binding energy of La 3d5/2 is significantly shifted from 834.3 eV (as sintered La2CuO4) to 833.6 eV (as electrochemically oxidized La2CuO4+δ), implying that the covalency of the (La-O) bond is decreased due to the oxygen intercalation. The O 1s spectra do not provide an evidence of the superoxide or peroxide, but the oxide (O2-) with the contaminated carbonate (CO32-) based on the peaks at 529 eV and 532 eV, respectively, which is clearly confirmed by the Auger spectroscopic analysis. Oxygen contents determined by iodometric titration (δ=0.07) and thermogravimetry (δ=0.09) show good coincidence each other, also giving an evidence for the "O2-" nature of excess oxygen. From the above results, it is concluded that "O2-" appeared as O 1s peak at 528.6 eV is responsible for superconductivity of La2CuO4+δ.

• Macromolecular Research
• /
• v.11 no.3
• /
• pp.172-177
• /
• 2003

Biphenyltetracarboximide-phenylene diamine polyimide/silica-titania ternary hybrid composites were Prepared by thermal imidization and sol-gel reaction. Fluorescence spectroscopic, scanning electron microscopy, and atomic force microscopy studies revealed that the addition of small amount of titania showed profound effects on the microstructure and photophysical behaviors of polyimide/silica hybrid composites, when the content of silica-titania mixture was small or when the ratio of silica to titania in the mixture was high.

• Polymer(Korea)
• /
• v.26 no.6
• /
• pp.752-758
• /
• 2002

FTIR, FT-Raman, and X-ray diffraction techniques were used to determine chain segregations and lamellar structures of the mixed binary n-paraffins with different chain lengths. The results of three different techniques, infrared spectroscopic studies of crystal field splitting, the Raman longitudinal acoustic mode, and the SAXS long period measurements were compared one another to understand the crystallization mechanism of separated or mixed n- paraffin lamellae.

• Applied Microscopy
• /
• v.45 no.3
• /
• pp.126-130
• /
• 2015

Raman spectroscopy is one of the most widely used tools in the field of graphene and two-dimensional (2D) materials. It is used not only to characterize structural properties such as the number of layers, defect densities, strain, etc., but also to probe the electronic band structure and other electrical properties. As the field of 2D materials expanded beyond graphene to include new classes of layered materials including transition metal dichalcogenides such as $MoS_2$, new physical phenomena such as anomalous resonance behaviors are observed. In this review, recent results from Raman spectroscopic studies on 2D materials are summarized.

• Bulletin of the Korean Chemical Society
• /
• v.14 no.1
• /
• pp.72-78
• /
• 1993

The application of time-resolved laser induced fluorescence spectroscopy (TRLIF) to the complexation studies of Eu(III) and Cm(III) with humic substances is described. Using this method, three different spectroscopic characteristics(excitation spectra, emission spectra, and lifetimes) of these aquo ions and their complexes can be directly measured. By observing shifts in the wavelength and changes in the lifetime and intensities of the fluorescence emission, the information on the complexation behavior of humic substances with these trivalent metal cations in an aqueous solution, as well as energy transfer mechanisms, can be obtained. In addition, this method allows precise spectroscopic quantification of the complexation processes at very low concentrations of both components.

• Bulletin of the Korean Chemical Society
• /
• v.2 no.3
• /
• pp.105-112
• /
• 1981

Various $3{\alpha}$, $5{\alpha}$-cyclocholestan-6${\beta}-yl$ ethers were synthesized from solvolysis reactions of cholesteryl tosylate. ${3\alpha}$, $5{\alpha}$-Cyclocholestan-6${\beta}-yl$ sulfides were the sole products when cholesteryl tosylate was solvolyzed in thiol solvents. Diol solvolysis products were derivatized to aromatic esters, and nuclear magnetic resonance spectroscopic method was used to show that aromatic rings can approach C-18 methyl group and the side chain.

• Advances in nano research
• /
• v.13 no.5
• /
• pp.437-451
• /
• 2022

Synthesis approaches usually affect the physical and chemical properties of ferrites. This helps ferrite materials to design them for desired applications. Some of these methods are mechanical milling, ultrasonic method, micro-emulsion, co-precipitation, thermal decomposition, hydrothermal, microwave-assisted, sol-gel, etc. These methods are extensively reviewed by taking example of ZnFe₂O₄. These methods also affect the microstructure and local structure of ferrite which ultimately affect the physical and chemical properties of ferrites. Various spectroscopic techniques such as Raman spectroscopy, Fourier Transform Infrared spectroscopy, Ultra Violet-Visible spectroscopy, Mossbauer spectroscopy, extended x-ray absorption fine structure, and electron paramagnetic resonance are found helpful to reveal this information. Hence, the basic principle and the usefulness of these techniques to find out appropriate information in ZnFe₂O₄ nanoparticles is elaborated in this review.

• Journal of Photoscience
• /
• v.11 no.1
• /
• pp.29-33
• /
• 2004

The mechanism of interaction of cyanocobalamin (CB) with bovine serum albumin (BSA) has been investigated by spectrofluorometric and circular dichroism methods. Association constant for the CB-BSA system showed that the interaction is non-covalent in nature. Binding studies in the presence of an hydrophobic probe, 8-anilino-l-naphthalene sulphonic acid, sodium salt (ANS) showed that there is hydrophobic interaction between CB and ANS and they do not share common sites in BSA. Stern-Volmer analysis of fluorescence quenching data showed that the fraction of fluorophore (protein) accessible to the quencher (CB) was close to unity indicating thereby that both tryptophan residues of BSA are involved in drug-protein interaction. The rate constant for quenching, greater than $10^{10}$ $M^{-1}$ $s^{-1}$, indicated that the drug binding site is in close proximity to tryptophan residue of BSA. Thermodynamic parameters obtained from data at different temperatures showed that the binding of CB to BSA involves hydrophobic bonds predominantly. Significant increase in concentration of free drug was observed for CB in presence of paracetamol. Circular dichroism studies revealed the change in helicity of BSA due to binding of CB to BSA.

• Bulletin of the Korean Space Science Society
• /
• 1999.09a
• /
• pp.40-40
• /
• 1999

No Abstract, See Full Text

• Proceedings of the Korean Fiber Society Conference
• /
• 1991.06a
• /
• pp.38-38
• /
• 1991