• Bulletin of the Korean Chemical Society
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• v.32 no.6
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• pp.1985-1992
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• 2011

The stable conformers of glycine and the inter-conversions between them were studied theoretically at various levels of theory, B3LYP, MP2, CCSD and CCSD(T), in the gas phase and in aqueous solution. In aqueous solution, the structures examined by use of the conductor-like polarizable continuum model (CPCM) with various cavity models, UA0, UAHF, UAKS, UFF, BONDI and PAULING, and by use of a discrete/continuum solvation model with eight water clusters. The Gibbs free energy differences between the neutral (NE) and zwitterionic conformers (ZW), ${\Delta}G_{Z-N}[=G_{ZW}-G_{NE}]$, in aqueous solution were well reproduced by using the BONDI and PAULING cavity models. However the ${\Delta}G_{Z-N}$ values were underestimated in other cavity models, although the ZW conformers existed as stable species in aqueous solution. In the studies of a discrete/continuum solvation model with eight water clusters, gas phase results are still insufficient to reproduce the experimental findings. However the ${\Delta}G_{Z-N}$ values calculated by use of CPCM method in aqueous solution agreed well with the experimental ones.

• Bulletin of the Korean Chemical Society
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• v.17 no.10
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• pp.925-929
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• 1996

Uranyl hydrolysis precipitates were obtained by increasing pH value of aqueous uranyl solution in the range of neutral to alkaline pH value and their phase transformation during the solubility experiment under various conditions has been examined. The precipitates formed in the hydrolysis reaction of uranyl ion had a layered structure such as a meta-schoepite phase, a schoepite structure, or a mixed phase of meta-schoepite and schoepite. Phase transformation between them was strongly dependent on the pH value at which the precipitate was formed. The distance between the layers in meta-schoepite or schoepite phase was ∼7.35 Å, and it was increased with the pH value at which the precipitate was synthesized as well as the pH values of the aqueous solution. The phase transformation from a meta-schoepite to schoepite was fast for the precipitates formed at low pH values, however, it was not the case for the precipitates formed at high pH values. A small difference of pH value in aqueous solution gave a great change on its solubilities near pH 9.7, because a layered structure of the precipitates became amorphous above that pH value. Greater solubility for the precipitate formed at higher pH value can be explained from the fact that the precipitates formed at low pH value had a better crystallinity and also that the precipitates formed at higher pH value has a slower rate of crystallization.

• Applied Microscopy
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• v.23 no.2
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• pp.1-10
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• 1993

The effect of electrolyte on the extraction replicas of the precipiates in 3% Si steel was investigated. Three Kinds of electrolyte, 2% Nital solution (2% nitric acid+methanol; acid solution),, Sodium Citrate solution (5% sodiumcitrate+1% KBr+0.5KI+$H_{2}O$; aqueous neutral solution) and 10% AA solution (10% acetylacetone+ 1% tetramethylammoniumchloride+methanol; non-aqueous neutral solution), were compared. The preciptiates in 3% Si steel were dissolved in 2% Nital, but they were not dissolved in the Sodium Citrate and 10% AA solution. In Sodium Citrate solution, however, large second artifacts were introduced during sample preparation. Therefore 10% AA solution was found to be most useful for the preparation of extraction replica. The electrolysis condition of a matrix and precipitates were also checked by the measurement of potential-current curve in 10% AA solution. The matrix was electrolyzed at -400mV with respect to SCE(Saturated Calomel Electrode). In contrats precipitates were electrolyzed above 300mV. Precipitates were respected to be stable in 10% AA solution in the range of $-380mV{\sim}-300mV$ usually used to prepare extraction replicas.

• Corrosion Science and Technology
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• v.15 no.1
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• pp.13-17
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• 2016

The aim of this study was to evaluate the use of iron-nickel oxide ($Fe_2O_3$.NiO) nanopowder (FeNi) as an anti-corrosion pigment for a different application. The corrosion protection ability and the mechanism involved was determined using aqueous solution of FeNi prepared in a corrosive solution containing 3.5 wt.% NaCl. Anti-corrosion abilities of aqueous solution were determined using electrochemical impedance spectroscopy (EIS) on line pipe steel (API 5L X-80). The protection mechanism involved the adsorption of metallic cations on the steel surface forming a protective film. Analysis of EIS spectra revealed that corrosion inhibition occurred at low concentration, whereas higher concentration of aqueous solution produced induction behavior.

• Bulletin of the Korean Chemical Society
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• v.16 no.5
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• pp.406-409
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• 1995

The complex formation from Cu(Ⅱ) ion and 2,2-bis(hydroxymethyl)-2,2',2"-nitrilotriethanol (Bistris) in aqueous solution has been studied potentiometrically and spectrophotometrically. Bistris (L) coordinates to Cu(Ⅱ) as tridentate. The complex CuL2+ undergoes deprotonation in neutral and basic media. The deprotonated complexes involve metal-alcoholate coordinate bond in stable chelate structures.

• Rapid Communication in Photoscience
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• v.4 no.4
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• pp.88-90
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• 2015

The design and development of fluorescent chemosensors have recently been intensively explored for sensitive and specific detection of environmentally and biologically relevant metal ions in aqueous solution and living cells. Herein, we report the photophysical results of rhodamine B based fluorogenic and chromogenic receptor for selective copper detection in the complete organic or mixed aqueous-organic media at neutral pH under ambient condition. The ligand exhibited the remarkable increment in the fluorescence emission and UV-visible absorption signal intensities at 587 and 547 nm, respectively, on induction of copper ion while the ligand solution remain completely silent on addition of varieties of other metal ions.

• Journal of Power System Engineering
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• v.20 no.1
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• pp.42-49
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• 2016

This study showed that on-site ferrate(VI) solution was synthesized by wet oxidation method and applied aqueous 2,4-dichlorophenol(DCP) solution to evaluate the degradation efficiency. On-site ferrate(VI) solution was synthesized by putting $FeCl_3{\cdot}6H_2O$ in the strong alkali solution with NaClO and NaOH and applied DCP solution directly. DCP solution was extracted by the liquid-liquid method and analyzed by GC-ECD. The factors such as pH, DCP initial concentration, injected ferrate(VI) dosage, temperature were investigated. The optimum pH and temperature conditions of DCP degradation were obtained in neutral condition and $35^{\circ}C$. And the experimental results showed that DCP removal efficiency also increased with the decrease of DCP initial condition and the injected ferrate(VI) dosage.

• Macromolecular Research
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• v.8 no.1
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• pp.26-33
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• 2000

A series of pH/temperature sensitive polymers were synthesized by copolymerizing N-isopro-pyl acrylamide(NIPAAm) and acrylic acid(AAc) . The influence of polyelectrolyte between poly(allyl amine) (PAA) and poly(L-lysine)(PLL) on the lower critical solution temperature(LCST) of pH/temperature sensitive polymer was compared in the range of pH 2∼12. The LCST of PNIPAAm/water in aqueous poly(NIPAAm-co-AAc) solution was determined by cloud point measurements. A polyelectrolyte complex was prepared by mixing poly(NIPAAm-co-AAc) with poly(allyl amine) (PAA) or poly(L-lysine) (PLL) solutions as anionic and cationic polyelectrolytes, respectively. The effect of polyelectrolyte complex formation on the conformation of PLL was studied as a function of temperature by means of circular dichroism(CD). The cloud points of PNIPAAm in the aqueous copolymers solutions were stongly affected by pH, the presence of polyelectrolyte solute, AAc content, and charge density. The polyelectrolyte complex was formed at neutral condition. The influence of more hydrophobic PLL as a polyelectrolyte on the cloud point of PNIPAAm in the aqueous copolymer solution was stronger than that of poly(allyl amine)(PAA). Although polymer-polymer complex was formed between poly(NIPAAm-co-AAc) and PLL, the conformational change of PLL did not occur due to steric hinderance of bulky N-isopropyl groups of PNIPAAm.

• Journal of Electrochemical Science and Technology
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• v.14 no.4
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• pp.311-319
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• 2023

This work was performed to characterize the electrochemical behavior of AZ31 Mg alloy in neutral aqueous solutions where Cl^-, SO₄^2-, PO₄^3-, and F^- ions were present and pH was adjusted to 6 to exclude the contribution of H⁺ and OH^- ions. Open-circuit potential (OCP) transient, electrochemical impedance spectroscopy (EIS) and potnetiodynamic polarization curves were employed. The OCP value appeared to decrease in the order of F^- > Cl^- > SO₄^2- > PO₄^3- ions while corrosion current density increased in the same order. Electrochemical impedance spectroscopy (EIS) data showed two capacitive arcs in all the solutions and one more inductive arc appeared in PO₄^3--containing solution. By fitting of two capacitive arcs, capacitance of dense film (C_df), resistance of porous film (R_pf) and double layer capacitance (C_dl) and charge transfer resistance (R_ct) beneath the porous films were obtained. A simplified model in which various thicknesses and coverages of dense and porous films are assumed to be present on the AZ31 Mg alloy surface, is suggested to explain the effects of four different anions on the electrochemical behavior of AZ31 Mg alloy.

• Environmental Analysis Health and Toxicology
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• v.11 no.3_4
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• pp.33-44
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• 1996

Photolysis of TCBs in aqueous solutions of sodium nitrite and triethylamine (TEA) at neutral pH has been investigated. TCBs yielded trichloronitrobenzenes(TCNBs) as primary photoproducts, and their corresponding trichlorophenols (TCPs) via two types of reaction, one, nitration, and the other, by direct hydroxylation with OH radical. Isomerized products and TCBs were also identified. Photosensitization with TEA resulted in the formation of small yields of dichlorobenzenes(DCBs) by reductive dechlorination of TCBs.