• Korean Journal of Materials Research
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• v.32 no.1
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• pp.14-22
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• 2022

To improve light absorption ability in the visible light region and the efficiency of the charge transfer reaction, Pd nanoparticles decorated with reduced TiO₂ nanotube photocatalyst were synthesized. The reduced TiO₂ nanotube photocatalyst was fabricated by anodic oxidation of Ti plate, followed by an electrochemical reduction process using applied cathodic potential. For TiO₂ photocatalyst electrochemically reduced using an applied voltage of -1.3 V for 10 min, 38% of Ti⁴⁺ ions on TiO₂ surface were converted to Ti³⁺ ion. The formation of Ti³⁺ species leads to the decrease in the band gap energy, resulting in an increase in the light absorption ability in the visible range. To obtain better photocatalytic efficiency, Pd nanoparticles were decorated through photoreduction process on the surface of reduced TiO₂ nanotube photocatalyst (r10-TNT). The Pd nanoparticles decorated with reduced TiO₂ nanotube photocatalyst exhibited enhanced photocurrent response, and high efficiency and rate constant for aniline blue degradation; these were ascribed to the synergistic effect of the new electronic state of the TiO₂ band gap energy induced by formation of Ti³⁺ species on TiO₂, and by improvement of the charge transfer reaction.

• Journal of Korean Society on Water Environment
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• v.35 no.6
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• pp.459-469
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• 2019

The ozonation of sulfamethoxazole (SMX) was performed at 20℃ using a pilot scale countercurrent bubble column reactor. Ozonation systems were combined with UV irradiation and TiO₂ addition. As the oxidation reaction proceeded in each treatment system, the pH of the sample decreased and in the O₃/UV/TiO₂ system, the pH change was the largest from 4.54 to 2.02. Under these experimental conditions, the scavenger impact of carbonate is negligible. The highest COD and TOC removal rate was observed in the O₃/UV/TiO₂ system due to the UV irradiation and the photocatalytic effect of TiO₂. Also, the highest mineralization ratio(ε) value is 0.2 in the O₃/UV/TiO₂ system, which means theoxidation capacity of the systems. The highest SMX degradation rate constants calculated by COD and TOC values (COD and TOC) were 2.15 × 10^-4 sec^-1 and 1.00 × 10^-4 sec^-1 in the O₃/UV/TiO₂ system, respectively. The activation energy (E_a) of ozone treatment follows the Arrhenius law. It was calculated based on _COD and _TOC. Each activation energy decreased in order of single O₃> O₃/TiO₂> O₃/UV > O₃/UV/TiO₂ system. The result showed that ΔH^≠ is more effective than ΔS^≠ in each SMX ozontaionsystem, that is characteristic of the common oxidation reaction.

• International Journal of Oral Biology
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• v.46 no.3
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• pp.105-110
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• 2021

The physicochemical properties of crystalline titanium dioxide nanoparticles (TiO₂ NPs) were investigated by comparing amorphous (amTiO₂), anatase (aTiO₂), metaphase of anatase-rutile (arTiO₂), and rutile (rTiO₂) NPs, which were prepared at various calcination temperatures (100℃, 400℃, 600℃, and 900℃). X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses confirmed that the phase-transformed TiO₂ had the characteristic features of crystallinity and average size. The surface chemical properties of the crystalline phases were different in the spectral analysis. As anatase transformed to the rutile phase, the band of the hydroxyl group at 3,600-3,100 cm^-1 decreased gradually, as assessed using Fourier transform infrared spectroscopy (FT-IR). For ultraviolet-visible (UV-Vis) spectra, the maximum absorbance of anatase TiO₂ NPs at 309 nm was blue-shifted to 290 nm at the rutile phase with reduced absorbance. Under the electric field of capillary electrophoresis (CE), TiO₂ NPs in anatase migrated and detected as a broaden peak, whereas the rutile NPs did not. In addition, anatase showed the highest photocatalytic activity in an UV-irradiated dye degradation assay in the following order: aTiO₂ > arTiO₂ > rTiO₂. Overall, the phases of TiO₂ NPs showed characteristic physicochemical properties regarding size, surface chemical properties, UV absorbance, CE migration, and photocatalytic activity.

• Applied Chemistry for Engineering
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• v.31 no.6
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• pp.674-678
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• 2020

In this study, a Pd/TiO2 catalyst which oxidized H2 at room temperature without an additional energy source was prepared. And a specific surface area of TiO2 as a support was not proportional to H2 oxidation reaction performance of Pd/TiO2 catalyst. In addition La2O3 was added to Pd/TiO2 catalyst in order to evaluate the performance effect due to the change of catalysts physical properties. A Pd/La2O3-TiO2 was prepared by adding different amounts of La2O3 to TiO2 and CO chemisorption analysis was performed. Compared to the conversion rate (14% at 0.5% H2) of the Pd/TiO2(G) catalyst, the Pd/La2O3-TiO2 catalyst showed 74% which was improved by more than five times. It was found that the larger the metal dispersion of Pd as an active metal is, the more favorable to H2 oxidation reaction is. However, when the added La2O3 amount exceeded 10%, the catalyst performance decreased again. Finally, it was concluded that the physical properties of the Pd/La2O3-TiO2 catalyst have a dominant influence on the catalytic activity until 0.3~0.5% of injected H2 concentrations and the catalyst reaction rate was controlled by substance transfer from 1% or more concentrations of H2.

• Korean Journal of Materials Research
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• v.32 no.2
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• pp.94-97
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• 2022

We fabricated 3 types of ETL, mp TiO₂, ZnO, and ZnO coated on mp TiO₂(ZMT) to compare the photoelectric conversion efficiency (PCE) and fill factor (FF) of Perovskite solar cells. The structure of the cells was FTO/ETL/Perovskite (CH₃NH₃PbI₃)/spiro-MeOTAD/Ag. SEM morphology assessment of the ETLs showed that mp TiO₂ was porous, ZnO was flat, and the ZMT porous surface was filled with a thin layer. Via XRD measurements, the crystal structures of mp TiO₂ and ZnO ETL were found to be anatase and wurtzite, respectively. The XPS patterns showing energy bonding of mp TiO₂, ZnO, and ZMT O 1s confirmed these materials to be metal oxides such as ETL. The electrical characteristics of the Perovskite solar cells were measured using a solar simulator. Perovskite solar cells with ZMT ETL showed showed PCE of 10.29 % than that of conventional mp TiO₂ ETL devices. This was considered a result of preventing Perovskite from seeping into the ETL and preventing recombination of electrons and holes.

• Korean Journal of Materials Research
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• v.31 no.10
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• pp.552-561
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• 2021

For the purpose of manufacturing a high efficiency TiO₂ photocatalyst, B-doped TiO₂ photocatalysts are synthesized using a plasma electrolytic oxidation method in 0.5 M H₂SO₄ electrolyte with different concentrations of H₃BO₃ as additive. For the B doped TiO₂ layer fabricated from sulfuric electrolyte having a higher concentration of H₃BO₃ additive, the main XRD peaks of (101) and (200) anatase phase shift gradually toward the lower angle direction, indicating volume expansion of the TiO₂ anatase lattice by incorporation of boron, when compared with TiO₂ layers formed in sulfuric acid with lower concentration of additive. Moreover, XPS results indicate that the center of the binding energy peak of B1s increases from 191.45 eV to 191.98 eV, which suggests that most of boron atoms are doped interstitially in the TiO₂ layer rather than substitutionally. The B doped TiO₂ catalyst fabricated in sulfuric electrolyte with 1.0 M H₃BO₃ exhibits enhanced photocurrent response, and high efficiency and rate constant for dye degradation, which is ascribed to the synergistic effect of the new impurity energy band induced by introducing boron to the interstitial site and the improvement of charge transfer reaction.

• Applied Chemistry for Engineering
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• v.32 no.3
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• pp.243-252
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• 2021

With increasingly strict requirements for advanced energy storage devices in electric vehicles (EVs) and stationary energy storage systems (EES), the development of lithium-ion batteries (LIBs) with high power density and safety has become an urgent task. Because the performance of LIBs is determined primarily by the physicochemical characteristics of its electrode material, TiO₂, owing to its excellent stability, high safety levels, and environmentally friendly properties, has received significant attention as an alternative material for the replacement of commercial carbon-based anode materials. In particular, self-organized TiO₂ micro and nanostructures prepared by anodization have been intensively investigated as promising anode materials. In this review, the mechanism for the formation of anodic TiO₂ nanotubes and microcones and the parameters that influence their morphology are described. Furthermore, recent developments in anodic TiO₂-based composites as anode electrodes for LIBs to overcome the limitations of low conductivity and specific capacity are summarized.

• New & Renewable Energy
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• v.18 no.2
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• pp.40-49
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• 2022

In this study, the phase and electrochemical properties of Co and Ti substituted layered perovskites SmBaCo_2-xTi_xO_5+d (x=0.5, 0.7, 1.0, 1.1, 1.3, and 1.5) were analyzed, and their application as electrodes in solid oxide fuel cells (SOFCs) were evaluated. After calcination at 1300℃ for 6 h, a single phase was observed for two compositions of the SmBaCo_2-xTi_xO_5+d oxide system, SmBaCoTiO_5+d (x=1.0) and SmBaCo_0.9Ti_1.1O_5+d (x=1.1). However, the phases of SmBaCoTiO_5+d (SBCTO) and SmTiO₃ coexisted for compositions with x≥1.3 (Ti content). In contrast, for compositions of x≤0.7, the SmBaCo₂O_5+d phase was observed instead of the SmTiO₃ phase. To evaluate the applicability of these materials as SOFC electrodes, the electrical conductivities were measured under various atmospheres (air, N₂, and H₂). SBCTO exhibited stable semi-conductor electrical conductivity behavior in an air and N₂ atmosphere. However, SBCTO showed insulator behavior at temperatures above 600℃ in a H₂ atmosphere. Therefore, SBCTO may only be used as cathode materials. Moreover, SBCTO had an area specific resistance (ASR) value of 0.140 Ω·cm² at 750℃.

• Clean Technology
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• v.21 no.1
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• pp.39-44
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• 2015

This study investigated the effects of six metal oxide nanoparticles (NPs: CuO, NiO, TiO₂, Fe₂O₃, Co₃O₄, ZnO) on seed germination and germination index (G.I) for five types of seeds: Brassica napus L., Malva verticillata L., Brassica olercea L., Brassica campestris L., Daucus carota L. NPs of CuO, ZnO, NiO show significant toxicity impacts on seed activities [CuO (6-27 mg/L), ZnO (16-86 mg/L), NiO (48-112 mg/L)], while no significant effects were observed at > 1000 mg/L of TiO₂, Fe₂O₃, Co₃O₄. Tested five types of seed showed different sensitivities on seed germination and root activity, especially on NPs of CuO, ZnO, NiO. Malva verticillata L. seed was highly sensitive to toxic metal oxide NPs and showed following EC₅₀s : CuO 5.5 mg/L, ZnO 16.4 mg/L, NiO 53.4 mg/L. Mostly following order of toxicity was observed, CuO > ZnO > NiO > Fe₂O₃ ≈ Co₃O₄ ≈ TiO₂, where slightly different toxicity order was observed for carrot, showing CuO > NiO ≈ ZnO > Fe₂O₃ ≈ Co₃O₄ ≈ TiO₂.

• Journal of the Microelectronics and Packaging Society
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• v.27 no.3
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• pp.69-72
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• 2020

In this study, the inverted structured electroluminescence (EL) devices were fabricated with double electron transport layers (ETLs). The conduction band minimum (CBM) of TiO₂ NPs is lower than SnO₂ NPs. Therefore, it is expected that inserting TiO₂ NPs between the SnO₂ layer and the emission layer (EML) will reduce the energy barrier and transport electrons smoothly. The quantum dot light emitting diodes (QLEDs) with double ETLs showed the enhanced emission characteristics than those with only SnO₂ layer.