• Bulletin of the Korean Chemical Society
• /
• v.32 no.7
• /
• pp.2316-2318
• /
• 2011

A novel technology has been developed for the synthesis of thioglycolic acid (TGA)-capped CdSe quantum dots (QDs) in aqueous medium. The reaction was carried out in air atmosphere with one-pot by using $SeO_2$ to replace Se or $Na_2Se$. The technological parameters including refluxing time, pH values and molar ratios of selenium to cadmium had significant influence on the luminescence properties of CdSe QDs. Furthermore, the obtained QDs were characterized by fluorescent spectroscopy, X-ray powder diffraction (XRD) and transmission electron microscopy (TEM), respectively. The results demonstrated that the CdSe QDs were of zinc-blended crystal structure in a sphere-like shape.

• Bulletin of the Korean Chemical Society
• /
• v.29 no.3
• /
• pp.571-574
• /
• 2008

The well-known Cu2+-selective chemodosimetric behavior of rhodamine B hydrazide was successfully switched to selectivity for Hg2+. The fluorescence signaling is remarkably selective toward Hg2+ ions compared to other common biologically and environmentally important metal ions, including Cu2+ ions. The detection limit was 0.2 mM in an acetate-buffered aqueous 10% methanol solution at pH 5. The OFF-ON type of signaling is due to the selective Hg2+-induced hydrolysis of the lactam ring of the hydrazide as has been reported for the standard Cu2+-signaling process of the same compound. A simple change in medium resulted in clear switching of selective signaling from Cu2+ to Hg2+, which extends the applicability of the easily accessible hydrazide derivative.

• Bulletin of the Korean Chemical Society
• /
• v.25 no.8
• /
• pp.1211-1216
• /
• 2004

The interaction of the antitumour agent doxorubicin with calf thymus DNA is investigated in an aqueous solution at a pH level of 6-7 with molar ratios of 1/10. A UV-resonance Raman spectroscopy and surface enhanced Raman spectroscopy are used to determine the doxorubicin binding sites and the structural variations of doxorubicin-DNA complexes in an aqueous solution. Doxorubicin intercalates with adenine and guanine via a hydrogen bond formation between the N7 positions of purine bases and the hydroxyl group of doxorubicin.

• Bulletin of the Korean Chemical Society
• /
• v.25 no.6
• /
• pp.869-872
• /
• 2004

Newly synthesized 8-hydroxyquinoline based benzothiazole derivative 2 showed a distinctive $Hg^{2+}$-selectivity over other transition metal ions in aqueous solution. The fluorescence emission at 455 nm of 2 was completely quenched upon interaction with $Hg^{2+}$ ions in dioxane-$H_2O$ system (9 : 1, v/v). The selectivity was decreased in the order of $Hg^{2+}\;>>\;Cu^{2+}\;>\;Cd^{2+}\;>\;Pb^{2+}\;{\thickapprox}\;Zn^{2+}\;{\thickapprox}\;Ni^{2+},\;and\;Hg^{2+}$ concentration dependent fluorescence quenching profile was observed in the presence of common interfering metal ions as background. The fluorescence behavior of 2 suggests that the prepared compound could be used as a fluorescent signaling subunit for the construction of new $Hg^{2+}$-sensitive ON-OFF type supramolecular switching systems.

• Polymer(Korea)
• /
• v.31 no.2
• /
• pp.93-97
• /
• 2007

Phenyl styryl ketone ligands 1-5 containing different functional groups were synthesized and attached to the aminated poly (styrene-divinvlbenzene) copolymer through diazotization. The coupling of the ligand with polymer was confirmed by FT-IR. The variation of the uptakes of Pb (II) or Cu (II) ions loaded in the prepared polymers (6-10) was examined at different pH values. An increase of metal uptake in the polymers was observed with the increase in pH value in aqueous solution.

• Journal of the Korean Chemical Society
• /
• v.57 no.6
• /
• pp.703-711
• /
• 2013

In the present investigation, kinetic studies of oxidation of formic acid with and without catalyst and promoter in aqueous acid media were studied under the pseudo-first order conditions [formic acid]T ${\gg}[Cr(VI)]_T$ at room temperature. In the 1,10-phenanthroline (phen) promoted path, the cationic Cr(VI) phen complex is the main active oxidant species undergoes a nucleophilic attack by the substrate to form a ternary complex which subsequently experiences a redox decomposition through several steps leading to the products $CO_2$ and $H_2$ along with the Cr(III) phen complex. The anionic surfactant (i.e., sodium dodecyl sulfate, SDS) and neutral surfactant (i.e., Triton X-100, TX-100) act as catalyst and the reaction undergo simultaneously in both aqueous and micellar phase with an enhanced rate of oxidation in the micellar phase. Whereas the cationic surfactant (i.e., N-cetyl pyridinium chloride, CPC) acts as an inhibitor restricts the reaction to aqueous phase. The observed net enhancement of rate effects has been explained by considering the hydrophobic and electrostatic interaction between the surfactants and reactants. The neutral surfactant TX-100 has been observed as the suitable micellar catalyst for the phen promoted chromic acid oxidation of formic acid.

• Bulletin of the Korean Chemical Society
• /
• v.33 no.8
• /
• pp.2546-2552
• /
• 2012

A novel biguanide-functionalized $Fe_3O_4/SiO_2$ magnetite nanoparticle with a core-shell structure was developed for utilization as a heterogeneous organosuperbase in chemical transformations. The structural, surface, and magnetic characteristics of the nanosized catalyst were investigated by various techniques such as transmission electron microscopy (TEM), powder X-ray diffraction (XRD), vibrating sample magnetometry (VSM), elemental analyzer (EA), thermogravimetric analysis (TGA), $N_2$ adsorption-desorption (BET and BJH) and FT-IR. The biguanide-functionalized $Fe_3O_4/SiO_2$ nanoparticles showed a superpara-magnetic property with a saturation magnetization value of 46.7 emu/g, indicating great potential for application in magnetically separation technologies. In application point of view, the prepared catalyst was found to act as an efficient recoverable nanocatalyst in nitroaldol and domino Knoevenagel condensation/Michael addition/cyclization reactions in aqueous media under mild condition. Additionally, the catalyst was reused six times without significant degradation in catalytic activity and performance.

• Bulletin of the Korean Chemical Society
• /
• v.32 no.9
• /
• pp.3443-3447
• /
• 2011

The spectroscopic behavior of catechin (5,7,3',4'-tetrahydroxyflavan-3-ol), has been studied in the presence and the absence of air using UV-vis absorption spectrophotometry and fluorescence spectroscopy. The UV-vis absorption spectrum of catechin shows a very sharp and strong absorption maximum peak at 275 nm in deaerated water. New absorption maximum peaks appeared in aerated water, as well as in basic aqueous solution, caused by the oxidation of catechin. The absorbances in the UV-vis absorption spectrum of catechin decreased when the solution was left in the dark for a long time. The fluorescence emission spectrum of catechin after a long time period differs markedly from that in freshly prepared solution; the fluorescence maxia shifted as time passes after adding catechin to the solutions. When the deaerated basic catechin solutions were left in the dark for a long time, their fluorescence quantum yields were found to be nearly zero. This suggests that the oxidized catechin molecules were seen to have slowly undergone successive chemical reactions in basic buffer solution.

• The Korean Journal of Ecology
• /
• v.23 no.2
• /
• pp.149-155
• /
• 2000

The allelopathic effects of Artemisia lavandulaefolia were studied using several test plants and microbes. Aqueous extracts and volatile compounds of A. lavandulaefolia inhibited seed germination, seedling and root growth of the test species such as Achyranthes japonica. Lactuca sativa, Artemisia princeps var. orientalis. Oenothera odorata, Plantago asiatica. Aster yomena, Elsholtzia ciliata, and Raphanus sativus var. hortensis for. acanthiformis. The root growth of test species was more affected than shoot growth by allelochemicals of A. lavandulaefolia. Essential oil of A. lavandulaefolia had antibacterial and antifungal effects. However, the antimicrobial activity of the essential oil was dependent upon the microbial species and concentrations. Callus growth of Oryza sativa, Brassica campestris subsp. napus var. pekinensis and Achyranthes japonica was sensitive by the essential oil of A. lavandulaefolia. Twenty three chemicals were identified from A. lavandulaefolia essential oil by gas chromatography. Primary allelochemicals among them were 1, 8-cineole, 1-$\alpha$-terpineol, $\alpha$-terpinene. camphor, 2-buten-1-ol and azulene. We concluded that aqueous extract and essential oil of A. lavandulaefolia were responsible for allelopathic effects.

• Bulletin of the Korean Chemical Society
• /
• v.25 no.1
• /
• pp.79-84
• /
• 2004

The existing technological schemes for processing rhenium-containing raw materials involve the recovery of Re from solutions, which can be effectively achieved by anion exchange method. The application of anion exchange also allows to study rhenium state in aqueous solutions and to develop analytical control methods. The present work is focused on investigation of ion exchange equilibrium in the analytical system Re(VII)-HCl-$SnCl_2$-KSCN-anion exchanger by means of sorption-desorption method as well as by electron, IR- and diffuse reflection spectroscopy. It was shown that rhenium can be quantitatively recovered from this system. It is proposed to use the sorption-spectroscopic method for Re(VII) determination in aqueous solutions. The calibration curve is linear in the concentration range of 0.5-20.0 mg/L (sample volume is 25.0 mL) and the detection limit is 0.05 mg/L. The presence of Mo(VI), Cu(II), Fe(II, III), Ni(II), Zn(II) as well as $K^+,\;Na^+$ do not hinder the solid-phase determination of rhenium. Rhenium (VII) determination by diffuse reflection spectroscopy was carried out in model solutions as well as in samples of river-derived water and in solutions obtained after the dissolution of spent catalysts.