• 한국재료학회지
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• 제33권8호
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• pp.344-351
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• 2023

Cesium lead iodide (CsPbI₃) with a bandgap of ~1.7 eV is an attractive material for use as a wide-gap perovskite in tandem perovskite solar cells due to its single halide component, which is capable of inhibiting halide segregation. However, phase transition into a photo inactive δ-CsPbI₃ at room temperature significantly hinders performance and stability. Thus, maintaining the photo-active phase is a key challenge because it determines the reliability of the tandem device. The dimethylammonium (DMA)-facilitated CsPbI₃, widely used to fabricate CsPbI₃, exhibits different phase transition behaviors than pure CsPbI₃. Here, we experimentally investigated the phase behavior of DMA-facilitated CsPbI₃ when exposed to external factors, such as heat and moisture. In DMA-facilitated CsPbI₃ films, the phase transition involving degradation was observed to begin at a temperature of 150 ℃ and a relative humidity of 65 %, which is presumed to be related to the sublimation of DMA. Forming a closed system to inhibit the sublimation of DMA significantly improved the phase transition under the same conditions. These results indicate that management of DMA is a crucial factor in maintaining the photo-active phase and implies that when employing DMA designs are necessary to ensure phase stability in DMA-facilitated CsPbI₃ devices.

• Journal of Periodontal and Implant Science
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• 제53권5호
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• pp.321-335
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• 2023

Purpose: The aim of this study was to investigate the efficacy of photo-crosslinked gelatin methacryloyl (GelMa) hydrogel containing calcium phosphate nanoparticles (CNp) when applying different fabrication methods for bone regeneration. Methods: Four circular defects were created in the calvaria of 10 rabbits. Each defect was randomly allocated to the following study groups: 1) the sham control group, 2) the GelMa group (defect filled with crosslinked GelMa hydrogel), 3) the CNp-GelMa group (GelMa hydrogel crosslinked with nanoparticles), and 4) the CNp+GelMa group (crosslinked GelMa loaded with nanoparticles). At 2, 4, and 8 weeks, samples were harvested, and histological and micro-computed tomography analyses were performed. Results: Histomorphometric analysis showed that the CNp-GelMa and CNp+GelMa groups at 2 weeks had significantly greater total augmented areas than the control group (P<0.05). The greatest new bone area was observed in the CNp-GelMa group, but without statistical significance (P>0.05). Crosslinked GelMa hydrogel with nanoparticles exhibited good biocompatibility with a minimal inflammatory reaction. Conclusions: There was no difference in the efficacy of bone regeneration according to the synthesized method of photo-crosslinked GelMa hydrogel with nanoparticles. However, these materials could remain within a bone defect up to 2 weeks and showed good biocompatibility with little inflammatory response. Further improvement in mechanical properties and resistance to enzymatic degradation would be needed for the clinical application.

• 한국물환경학회지
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• 제20권5호
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• pp.488-493
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• 2004

The effects were examined from several conditions of $TiO_2$ photocatalysis reaction to phenols degradation by changing it's reacting conditions such as phenol concentration, pH, $TiO_2$ concentration, $H_2O_2$ concentration, flow rate, and intensity of ultraviolet rays. Phenol degradation was more efficient in low concentration of phenol, neutral pH. Phenol degradation appeared to increase as concentration of $TiO_2$ photocatalyst, that of $H_2O_2$ and intensity of ultraviolet rays increased. As $TiO_2$ dosage increased, initial rate constant k linearly increased. When $H_2O_2$ was injected more than optimum, phenol removal rate didn't increase in proportional to the change of $H_2O_2$ concentration as OH radicals was being consumed. When flow rate is less than $4.75m^3/m^2$ day, phenol removal efficiency appeared to decrease as ultraviolet rays transmission rate becomes low by $TiO_2$ suspension coated in photo reaction column. Meanwhile, initial rate constant according to light intensity change in less than $25mW/cm^2$ appeared to be in proportion to light intensity ($mW/cm^2$) Removal efficiency decreased about 12% after 180 minutes of reaction time while showed stable removal efficiency of 100% after 300 minutes when using regenerated $TiO_2$.

• 대한화장품학회지
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• 제34권2호
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• pp.75-82
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• 2008

본 연구에서는 금 나노입자 콜로이드를 이용하여 safranin-O의 광촉매적 분해를 관찰하였다. 금 나노입자는 용액상에서 safranin-O의 분해 속도를 빠르게 하기 위해서 사용되었다. 금 나노입자 콜로이드는 수용액상에서 $Na_2CO_3$와 PVP 고분자(poly(vinyl pyrrolidone))를 이용하는 환원방법에 의하여 제조하였다. Safranin-O의 분해현상은 자외선(UV light)와 과산화수소($H_2O_2$)의 존재 하에서 금 나노입자 콜로이드와 염화금의 농도, 반응계의 산도(pH), 반응시간과 같은 실험조건들의 조절을 통해 연구되었다. 분해반응에 사용된 금 나노입자 콜로이드의 농도가 증가함에 따라서 염료가 분해되는 속도가 증가하였다. Safranin-O의 광산화 반응은 광학적으로 측정되었고, 금 나노입자의 기본적인 물성과 촉매 특성은 UV-Vis 광학계를 이용하여 측정되었다.

• 대한환경공학회지
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• 제27권1호
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• pp.59-66
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• 2005

[ $TiO_2$ ]박막은 DC 마그네트론 스퍼터링법을 이용하여 다양한 스퍼터링 파라미터(전력 $0.6{\sim}5.2\;kw$, 기판온도 실온${\sim}350^{\circ}C$, 산소량 $0{\sim}50\;sccm$($O_2+Ar$ 90 sccm, 압력은 약 1 mtorr))를 통하여 증착되었다. TiO-N박막도 가스의 유량비를 제외하고는 $TiO_2$박막과 같은 스퍼터링 조건하에서 증착되었다. 이러한 스퍼터링 파라미터에서 증착된 박막의 전기적 특성을 분석하기 위하여 시트저항을 측정하였고, 박막의 두께(${\alpha}$-step), 표면 거칠기(AFM), 형성 조직(FE-SEM, XRD)을 분석하여 최적 스퍼터링 파라미터를 도출하였다. 최적 스퍼터링 파라미터에서 제조된($TiO_2$, TiO-N)박막을 이용하여 광활성도를 평가하기 위하여 VOCs물질 중 toluene, 반응성 염료인 Suncion Yellow를 대상 물질로 선정하여 적용성 연구를 수행하였다. 실험에서 광촉매 박막은 적용물질에 대해서 광활성을 양호하게 보였으며, 특히 TiO-N광촉매 박막은 가시광 영역에서도 최대 33%의 톨루엔(5 ppm) 제거 효율을 나타내었다.

• 한국환경농학회지
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• 제22권4호
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• pp.284-289
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• 2003

Mesoporous titanium oxo-phosphate(Ti-MCM)은 기존의 유기성 오염물질의 광분해제로 널리 이용되고 있는 $TiO_2$에 비해 표면적이 매우 넓은 장점이 있다. 그러므로 본 연구에서는 Ti-MCM에 의한 chlorothalonil의 흡착 및 광분해 특성을 $TiO_2$와 비교하였다. 합성된 Ti-MCM은 hexagonal 형태로 d-spacing이 4.1 nm이었다. 암조건에서 $TiO_2$에 의한 chlorothalonil의 흡착은 거의 일어나지 않았으나, Ti-MCM에 의한 흡착은 반응 1시간까지 25%로 급격히 증가하여 흡착평형에 도달하였다. UV조사 하에서 반응 9시간 후의 $TiO_2$와 Ti-MCM에 의한 chlorothalonil의 제거율은 각각 88%와 100%로 나타났다. 그러나 정치상태에서의 광분해 속도는 chlorothalonil과 Ti-MCM사이의 낮은 접촉에 의한 반응성의 감소로 느린 경향을 나타내었다. 또한 Ti-MCM에 의한 chlorothalonil의 분해효율은 용액의 초기 농도가 낮을수록, pH 7까지 반응용액의 pH가 높을수록 증가하였다.

• 한국재료학회지
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• 제30권8호
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• pp.383-392
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• 2020

In this paper, AgCl/Ag₃PO₄/diatomite photocatalyst is successfully synthesized by microemulsion method and anion in situ substitution method. X-ray diffraction (XRD), photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), and ultraviolet-visible spectroscopy (UV-Vis) are used to study the structural and physicochemical characteristics of the AgCl/Ag₃PO₄/diatomite composite. Using rhodamine B (RhB) as a simulated pollutant, the photocatalytic activity and stability of the AgCl/Ag₃PO₄/diatomite composite under visible light are evaluated. In the AgCl/Ag₃PO₄/diatomite visible light system, RhB is nearly 100 % degraded within 15 minutes. And, after five cycles of operation, the photocatalytic activity of AgCl/Ag₃PO₄/diatomite remains at 95 % of the original level, much higher than that of pure Ag₃PO₄ (40 %). In addition, the mechanism of enhanced catalytic performance is discussed. The high photocatalytic performance of AgCl/Ag₃PO₄/diatomite composites can be attributed to the synergistic effect of Ag₃PO₄, diatomite and AgCl nanoparticles. Free radical trapping experiments are used to show that holes and oxygen are the main active species. This material can quickly react with dye molecules adsorbed on the surface of diatomite to degrade RhB dye to CO₂ and H₂O. Even more remarkably, AgCl/Ag₃PO₄/diatomite can maintain above 95 % photo-degradation activity after five cycles.

• Environmental Engineering Research
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• 제13권2호
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• pp.85-92
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• 2008

In this present study, we have synthesized Fe-containing AC(activated carbon)/$TiO_2$ composites with titanium (VI) n-butoxide (TNB) as a titanium source to Fe treated AC through an impregnation method. The result of the textural surface properties demonstrates that there is a slight decrease in the BET surface area of composite samples with an increase of the amount of Fe treated. The surface properties of scanning electron microscope (SEM) presented a characterization of a porous texture on the Fe-containing AC/$TiO_2$ composites and homogenous compositions for Fe and titanium dioxide distributed on the sample surfaces. Fe compound peaks and a titanium dioxide structure were observed in the X-ray diffraction patterns for the Fe-containing AC/$TiO_2$ composites. The results of chemical elemental composition for the Fe-containing AC/$TiO_2$ composites showed that most of the spectra for these samples gave stronger peaks for C, O, treated Fe components and Ti metal than that of any other elements. From the photo degradation results for the piggery waste, the Fe-containing AC/$TiO_2$ composites showed an excellent degradation activity for the chemical oxygen demand (COD) due to a photocatalysis of the supported $TiO_2$, radical reaction by Fe species and the adsorptivity and absorptivity of porous carbon.

• 한국환경과학회지
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• 제14권9호
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• pp.889-896
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• 2005

The nanosized $TiO_2$ photocatalysts were prepared by the hydrolysis of $TiCl_4$ and calcined at different temperatures. The resulting materials were characterized by TGA, DSC, XRD, and TEM testing techniques. XRD, TEM, and BET measurements indicated that the particle size of $TiO_2$ was increased with rise of calcination temperature and surface area was decreased with rise of it. The prepared $TiO_2$ photocatalysts were used for the photocatalytic degradation of congo red. The effects of calcination temperature, $TiO_2$ loading, the initial concentration of congo red, and usage frequencies were investigated and the rate constants were determined by regressing the experimental data. Calcination is an effective treatment to increase the photo activity of nanosized $TiO_2$ photocatalysts resulting from the improvement of crystallinity. The optimum calcination temperature of the catalyst for the efficient degradation of congo red was found to be $400^{\cric}C$. The rate constant was decreased with increase in the initial concentration of congo red and increased with increase in the $TiO_2$ loading. In the case of $TiO_2$ photocatalysts, the photocatalytic activity wasn't greatly affected by the usage frequencies.

• 한국세라믹학회지
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• 제48권4호
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• pp.282-287
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• 2011

ACF and $WO_3$ modified $TiO_2$ composites (ACF/$WO_3$/$TiO_2$) were prepared using a sol-gel method. The composites were characterized by Brunauer.Emmett.Teller (BET) surface area measurements, X-ray diffraction (XRD), energy dispersive X-ray (EDX) analysis and scanning electron microscope (SEM) analysis. A methyl orange (MO) solution under visible light irradiation was used to determine the photocatalytic activity. The degradation of the MO was determined using UV/Vis spectrophotometry. An increase in photocatalytic activity was observed and attributed to an increase of the photo-absorption effect by the $WO_3$ and the cooperative effect of the ACF.