• Bulletin of the Korean Chemical Society
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• v.34 no.9
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• pp.2819-2821
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• 2013

• Bulletin of the Korean Chemical Society
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• v.28 no.12
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• pp.2514-2516
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• 2007

• Advances in nano research
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• v.13 no.2
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• pp.187-197
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• 2022

The synthesis of organic and hybrid organic-inorganic perovskites directly from solution improves the cost- and energy-efficiency of processing. To date, numerous research efforts have been devoted to investigating the influence of the various solvent parameters for the synthesis of lead halide perovskites, focused on the effects of different single solvents on the efficiency of the resulting perovskites. In this work, we investigated the effect of solvent blends for the first time on the structure and phase of perovskites produced via the Lewis base vapor diffusion method to develop a new synthetic approach for water-stable CsPbBr₃ particles with nanometer-sized dimensions. Solvent blends prepared with DMF and water-miscible solvents with different Gutmann's donor numbers (D_N) affect the Pb ions differently, resulting in a variety of lead bromide species with various colors. The use of a DMF/isopropanol solvent mixture was found to induce the formation of the Ruddlesden-Popper perovskite based on lead bromide. This perovskite undergoes a blue color shift in the solvated state owing to the separation of nanoplatelets. In contrast, the replacement of isopropanol with DMSO, which has a high DN, induces the formation of spherical CsPbBr₃ perovskite nanoparticles that exhibit green emission. Finally, the integration of acetone in the solvent system leads to the formation of lead bromide complexes with a yellow-orange color and the perovskite CsPbBr₃.

• Journal of Electrochemical Science and Technology
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• v.13 no.1
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• pp.54-62
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• 2022

The preparation of low-cost, simple, and scalable electrodes is crucial for the commercialization of water electrolyzers for H₂ production. Herein, we demonstrate the fabrication of cathodes through Mo-modified Zn phosphating of Ni foam (NiF) for water electrolysis, which has been largely utilized in surface coating industry. In situ growth of electrocatalytically active layers in the hydrogen evolution reaction (HER) was occurred after 1 min of phosphating to form ZnNiMoP_i, and subsequent thermal treatment and electrochemical activation resulted in the formation of ZnNiMoPO_xH_y. ZnNiMoPO_xH_y exhibited superior HER performance than NiF, primarily because of the increased electrochemically active surface area of ZnNiMoPO_xH_y compared to that of bare NiF. Although further investigations to improve the intrinsic electrochemical activity toward the HER and detailed mechanistic studies are required, these results suggest that phosphating is a promising coating method and will possibly advance the fabrication procedure of electrodes for water electrolyzers with better practical applications.

• Proceedings of the Korean Society of Soil and Groundwater Environment Conference
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• 2004.04a
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• pp.499-502
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• 2004

Groundwater chemistry in a coastal region having complex contaminant sources was investigated. Water analysis data for 197 groundwater samples collected from the uniformly distributed sixty-six wells were used. Chemical analysis rand results indicate that groundwaters show wide concentration ranges in major inorganic ions, reflecting complex hydrochemical processes of pollutants. Due to the complexity of groundwater chemistry, Results illustrate that thirty five percent of the wells do not fit for drinking based on nitrate and chloride concentration in the study area. the samples were classified into four groups based on Cl and NO$_3$ concentrations and the processes controlling water chemistry were evaluated based on the reaction stoichiometry. The results explained the importance of mineral weathering, anthropogenic activities (nitrification and oxidation of organic matters), and Cl-salt inputs (seawater, deicer, NaCl, etc.) on groundwater chemistry. It was revealed that mineral dissolution is the major process controlling the water chemistry of the low Cl and NO$_3$ group (Group 1). Groundwaters high in NO$_3$ (Groups 2 and 4) are acidic in nature, and their chemistry is largely influenced by nitrification, oxidation of organic matters and mineral dissolution. In the case of chloride rich waters (Group 3), groundwater chemistry is highly influenced by mineral weathering and seawater intrusion associated with cation-exchange reactions.

• 한국전기화학회:학술대회논문집
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• 2002.04a
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• pp.10-10
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• 2002

• Applied Chemistry for Engineering
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• v.4 no.2
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• pp.324-334
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• 1993

Chitin, the natural polymer has been known as harmless and innoxious material to human and has been also known to be biodegradable. Chitosan which was prepared by the deacetylation of chitin, was propionylated to obtain porous bead shaped propionyl chitosan and its possibility as a water-absorbant polymer was investigated. Propionyl chitosan porous bead was synthesized by acylation reaction using emulsion method of acetic acid solution and propionyl chitosan was partially crosslinked using ethyleneglycol diglycidyl ether. Through the experiment varying the moles of propionic anhydride, reaction time and reaction temperature, best results for water-absorption ability was obtained at reaction condition of 5 moles of propionic anhydride, 10 hours of reaction time and $22^{\circ}C$ of reaction temperature. The absorption ability to the distilled water, various salt solutions, artificial urine and artificial blood, absorption time and retention of water of synthesized porous bead were investigated and also mechanical strength after crosslinking was determined.

• Nano
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• v.13 no.11
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• pp.1850134.1-1850134.10
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• 2018

Increasing active sites and enhancing electric conductivity are critical factors to improve sensing performance toward phenol. Herein, Ni nanoparticle was successfully anchored on acidified multiwalled carbon nanotube (a-MWCNT) surface by electroless plating technique to avoid Ni nanoparticle agglomeration and guarantee high conductivity. The crystal structure, phase composition and surface morphology were characterized by XRD, SEM and TEM measurement. The as-prepared Ni/a-MWCNT nanohybrid was immobilized onto glassy carbon electrode (GCE) surface for constructing phenol sensor. The phenol sensing performance indicated that Ni/a-MWCNT/GCE exhibited an amazing detection performance with rapid response time of 4 s, a relatively wide detection range from 0.01 mM to 0.48 mM, a detection limit of $7.07{\mu}M$ and high sensitivity of $566.2{\mu}A\;mM^{-1}\;cm^{-2}$. The superior selectivity, reproducibility, stability and applicability in real sample of Ni/a-MWCNT/GCE endowed it with potential application in discharged wastewater.

• Journal of the Korean Chemical Society
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• v.10 no.3
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• pp.119-128
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• 1966

The glass electrode was empirically calibrated in methanol-and 2-propanol-water mixed solvents, by means of which the pH-meter reading could be converted to stoichiometric hydrogen ion concentration. The thermodynamic dissociation constants of hydrogen cupferrate in methanol-and 2-propanol-water solution were potentiometrically determined with the changes in composition of organic solvents at 0.01 and 0.05 of the ionic strength and 25$^{\circ}C$. The empirical formula of the constants with mole fraction (n) of the organic solvent are as follow: methanol-water solution $pK_a$= 2.24n + 4.29 at ${\mu}$ = 0.01 n = 0.0476∼0.642 $pK_a$ = 2.35n + 4.38 at ${\mu}$ = 0.05 n= 0.0446~0.642 2-propanol-water solution $pK_a$= 5.50n + 4.48 at ${\mu}$ = 0.05 n = 0.0253~0.259 The relationships between $pK_a$ of acetic acid, propionic acid and HCup and dielectric constant of some mixed solvents were discussed. It would be considered that the factors effecting $pK_a$ value of weak acid in mixed-solvent are not only dielectric constants but acid-base character and solvation effect of the solvent, etc.

• Biotechnology and Bioprocess Engineering:BBE
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• v.9 no.3
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• pp.151-155
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• 2004

The bioremediation of water system contaminated with phenolic compounds having endocrine-disrupting activity, i.e. 2,4-dichlorophenol, 2,4-dichlorophenoxy acetic acid (2,4-D), and 2,4,5-trichlorophenoxy acetic acid (2,4,5-T), was investigated by using ozone oxidation and activated sludge treatment. Ozone oxidation (ozonation time: 30 min) followed by activated sludge treatment (incubation time: 5 days) was an efficient treatment method for the conversion of phenolic compounds in water into carbon dioxide and decreased the value of total organic carbon (TOC) up to about 10% of initial value. Furthermore, 2,4-D was dissolved in water containing salt, i.e. artificial seawater (ASW), and this water was used as model coastal water contaminated with phenolic compounds. The activated sludge treatment (incubation time: 5 days) could consume significantly organic acids produced from 2,4-D in the model costal water by the ozone oxidation (ozonation time: 30min) and decrease the value of TOC up to about 35% of initial value.