• Bulletin of the Korean Chemical Society
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• v.31 no.5
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• pp.1241-1246
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• 2010

Ternary Cu/ZnO/$Al_2O_3$ catalysts were prepared by a co-precipitation method. The precursor structures were monitored during the aging. The first precipitate structure was amorphous georgeite, which transformed into the unknown crystalline structure. The transition crystalline structure was assigned to the crystalline georgeite, which was suggested with elemental analysis, IR and XRD. The final structure of precursors was malachite. The Cu surface area of the resulting Cu/ZnO/$Al_2O_3$ was maximized to be 30.6 $m^2$/g at the aging time of 36 h. The further aging rapidly decreased Cu surface areas of Cu/ZnO/$Al_2O_3$. ZnO characteristic peaks in oxide samples almost disappeared after 24 h aging, indicating that ZnO was dispersed in around bulk CuO. TOF of the prepared catalysts of the Cu surface area ranges from 13.0 to 30.6 $m^2/g_{cat}$ was to be 2.67 ${\pm}$ 0.27 mmol/$m^2$.h in methanol synthesis at the condition of $250^{\circ}C$, 50 atm and 12,000 mL/$g_{cat}$. h irrespective of the XRD and TPR patterns of CuO and ZnO structure in CuO/ZnO/$Al_2O_3$. The pH of the precipitate solution during the aging time can be maintained at 7 by $CO_2$ bubbling into the precipitate solution. Then, the decrease of Cu surface area by a long aging time can be prevented and minimize the aging time to get the highest Cu surface area.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.31 no.6
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• pp.270-275
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• 2021

ZnO was synthesized according to the transformation behavior and crystallization conditions of Zn-intermediate obtained by zinc sulfate as a precursor and NaOH, Na₂CO₃ as a alkali agents. For ZnO crystallization, Zn₄(OH)₆SO₄·H₂O and Zn₅(OH)₆(CO₃)₂·H₂O as a Zn-intermediate were calcined at 400℃ and 800℃ for 1 h, respectively, based on decomposition temperature from TGA. Zn₄(OH)₆SO₄·H₂O was confirmed to have mixed Zn₄(OH)₆SO₄·H₂O and ZnO at 400℃, and was completely thermally decomposed at 800℃ to form ZnO phase. The prepared Zn₅(OH)₆(CO₃)₂·H₂O as a Zn-intermediate by the reaction with Na₂CO₃ was transformed to a complete ZnO crystallization over 400℃. Nano-sized ZnO can be synthesized at a relatively lower calcination temperature through the reaction with Na₂CO₃.

• Korean Journal of Materials Research
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• v.25 no.11
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• pp.598-601
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• 2015

Using reverse micelle processing, $ZnAl_2O_4$ nanopowders were synthesized from a mixed precursor(consisting of $Zn(NO_3)_2$ and $Al(NO_3)_3$). The $ZnAl_2O_4$ was prepared by mixing the aqueous solution at a molar ratio of Zn : Al = 1 : 2. The average size and distribution of the synthesized powders with heat treatment at $600^{\circ}C$ for 2 h were in the range of 10-20 nm and narrow, respectively. The average size of the synthesized powders increased with increasing water to surfactant molar ratio. The XRD diffraction patterns show that the phase of $ZnAl_2O_4$ was spinel(JCPDS No. 05-0669). The synthesized and calcined powders were characterized using a thermogravimetric - differential scanning calorimeter(TG-DSC), X-ray diffraction analysis (XRD), and high resolution transmission electron microscopy(HRTEM). The effects of the synthesis parameter, such as the molar ratio of water to surfactant, are discussed.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.26 no.3
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• pp.109-114
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• 2016

Monodispersed $ZnGa_2O_4$ microspheres were synthesized by a facile two-step process consisting of a solvothermal method and calcination process. The prepared monodispersed $ZnGa_2O_4$ microspheres were aggregated into 3D microstructures by self-assembly with a large number of small $ZnGa_2O_4$ particles generated in nucleation. This nucleation and self-assembly making hierarchical microstructures were depended on the concentration of PEG (polyethylene glycol) due to CAC (critical aggregation concentration) theory. And also we controlled the amount of zinc acetate to make pure $ZnGa_2O_4$ phase. Additionally, to fix the optimized calcination condition, sample was characterized by TG-DTA to prove the thermal property in the calcination process and by FT-IR to identify the changes of functional group bonding between each element of the $ZnGa_2O_4$ precursor and oxide calcined at $900^{\circ}C$ for 1 h.

• Korean Journal of Materials Research
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• v.25 no.12
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• pp.655-658
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• 2015

The development of glucose biosensors has been attracting much attention because of their importance in monitoring glucose in the human body; such sensors are used to diagnose diabetes and related human diseases. Thanks to the high selectivity, sensitivity to glucose detection, and relatively low-cost fabrication of enzyme-immobilized electrochemical glucose sensors, these devices are recognized as one of the most intensively investigated glucose sensor types. In this work, ZnO nanofibers were synthesized using an electrospinning method with polyvinyl alcohol zinc acetate as precursor material. Using the synthesized ZnO nanofibers, we fabricated glucose biosensors in which glucose oxidase was immobilized on the ZnO nanofibers. The sensors were used to detect a wide range of glucose from 10 to 700 M with a sensitivity of $10.01nA/cm^2-{\mu}M$, indicating that the ZnO nanofiber-based glucose sensor can be used for the detection of glucose in the human body. The control of nanograins in terms of the size and crystalline quality of the individual nanofibers is required for improving the glucose-sensing abilities of the nanofibers.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.8 no.2
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• pp.370-376
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• 1998

The powder preparation of Zinc-Silicate phosphors compound was studied by hydrothermal reaction starting from the precursor which prepared by spray pyrolysis method. This process protect including of impuritied from crushing process and Mineralizing in hydrothermal reactions. Using spray pyrolysis precursor, ${\alpha}-Zn_2SiO_4$ powder was prepared by the hydrothermal reaction under $250^{\circ}C$.

• Transactions of the Korean hydrogen and new energy society
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• v.32 no.6
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• pp.656-662
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• 2021

For the high efficiencies of quantum dot-sensitized solar cells (QDSCs), it is important to control the severe electron recombination at the interface of photoanode/electrolyte. In this work, we optimize the surface passivation process of ZnS/SiO₂ double overlayers for the enhanced photovoltaic performances of QDSCs. The overlayers of zinc sulfide (ZnS) and SiO₂ are coated on the surface of QD-sensitized photoanode by successive ionic layer adsorption and reaction (SILAR) method, and sol-gel reaction, respectively. In particular, for the sol-gel reaction of SiO₂, the influences of temperature of precursor solution are investigated. By application of SiO₂ overlayers on the ZnS-coated photoanode, the conversion efficiency of QDSCs is increased from 5.04% to 7.35%. The impedance analysis reveals that the electron recombination at the interface of photoanode/electrolyte is obviously reduced by the SiO₂ overlayers.

• Current Photovoltaic Research
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• v.2 no.3
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• pp.110-114
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• 2014

We propose a low temperature sol-gel ZnO/Ag nanowire composite thin film to fulfill low temperature and low cost requirements, which are essential criteria in future flexible electronic devices. In this proposed thin film, Ag nanowire plays the role of electrical conduction, and sol-gel ZnO provides a structural medium with a high visible transmittance. Low temperature restriction in the sol-gel fabrication process prevents sufficient oxidation of Zn acetate precursors, which were solved by a post-coating treatment with ultraviolet light irradiation. Composite thin film formation was performed by spin coating methods with a mixed precursor solution or in a sequential manner. We obtained an average visible transmittance larger than 85% and a sheet resistance smaller than $50{\Omega}/sq$. After optimization in a fabricated composite transparent conductive thin film with the thickness around 100 nm. Similar experimental demonstration in a flexible substrate (polyethyleneterephthalate) was successful, which implies a promising application opportunity of this technology.

• Korean Journal of Materials Research
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• v.20 no.9
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• pp.463-466
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• 2010

We studied the initial reaction mechanism of Zn precursors, namely, di-methylzinc ($Zn(CH_3)_2$, DMZ) and diethylzinc ($Zn(C_2H_5)_2$, DEZ), for zinc oxide thin-film growth on a Si (001) surface using density functional theory. We calculated the migration and reaction energy barriers for DMZ and DEZ on a fully hydroxylized Si (001) surface. The Zn atom of DMZ or DEZ was adsorbed on an O atom of a hydroxyl (-OH) due to the lone pair electrons of the O atom on the Si (001) surface. The adsorbed DMZ or DEZ migrated to all available surface sites, and rotated on the O atom with low energy barriers in the range of 0.00-0.13 eV. We considered the DMZ or DEZ reaction at all available surface sites. The rotated and migrated DMZs reacted with the nearest -OH to produce a uni-methylzinc ($-ZnCH_3$, UMZ) group and methane ($CH_4$) with energy barriers in the range of 0.53-0.78 eV. In the case of the DEZs, smaller energy barriers in the range of 0.21-0.35 eV were needed for its reaction to produce a uni-ethylzinc ($-ZnC_2H_5$, UEZ) group and ethane ($C_2H_6$). Therefore, DEZ is preferred to DMZ due to its lower energy barrier for the surface reaction.

• Environmental Engineering Research
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• v.24 no.3
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• pp.513-520
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• 2019

In this investigation, nano ZnO was sonochemically synthesized by a novel method using a methionine precursor. A narrow size distribution (41-50 nm) of nano ZnO was achieved that was immobilized on perlite and applied as a catalyst in catalytic ozonation. The catalyst was characterized by fourier transform infrared spectroscopy, BET surface area, and field emission scanning electron microscope. The ozonation of recalcitrant Remazol black 5 (RB5) di-azo dye solution by means of the synthesized catalyst was investigated in a bubble column slurry reactor. The influence of pH values (7, 9, 11), catalyst dosage (8, 12, 15, $20g\;L^{-1}$) and reaction time (10, 20, 30, 60 min) was investigated. Although the dye color was completely removed by single ozonation at a higher reaction time, the applied nanocatalyst improved the dye declorination kinetics. Also, the degradation of the hazardous aromatic fraction of the dye was enhanced five-times by catalytic ozonation at a low reaction time (10 min) and a neutral pH. The second-order kinetics was best fitted in terms of both RB5 color and its aromatic fraction removal. The total organic carbon analysis indicated a significant improvement in the mineralization of RB5 by catalytic ozonation using the nano-ZnO/perlite catalyst.