• Carbon letters
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• v.8 no.3
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• pp.214-224
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• 2007

The field of photocatalysis is one of the fastest growing areas both in research and commercial fields. Titanium dioxide is the most investigated semi-conductor material for the photocatalysis applications. Research to achieve $TiO_2$ visible light activation has drawn enormous attentions because of its potential to use solar light. This paper reviews the attempts made to extend its visible photocatalytic activity by carbon doping. Various approaches adopted to incorporate carbon to $TiO_2$ are summarized highlighting the major developments in this active research field. Theoretical features on carbon doping are also presented. Future scenario in the rapidly developing and exciting area is outlined for practical applications with solar light.

• Journal of the Korean Ceramic Society
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• v.54 no.3
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• pp.205-210
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• 2017

In this study, we examined the photo-degradation efficiency of $CoSe_2$-Graphene-$TiO_2$ ($CoSe_2-G-TiO_2$) nanocomposites under visible light irradiation using rhodamine B (RhB) as standard dye. $CoSe_2-G-TiO_2$ nanocomposites were synthesized by ultrasonication and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Raman spectroscopic analysis and UV-Vis absorbance spectra analysis. Our results show that the $CoSe_2-G-TiO_2$ nanocomposite exhibited significant photo degradation efficiency compared to pure $TiO_2$ and $CoSe_2-G$, approximately 85.2% of the rhodamine (Rh B) degraded after 2.5 h. It is concluded that the $CoSe_2-G-TiO_2$ nanocomposite is a promising candidate for use in dye pollutants.

• Journal of the Korean Ceramic Society
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• v.54 no.3
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• pp.167-183
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• 2017

Zinc oxide (ZnO) is one of the most versatile semiconductors, and one-dimensional (1D) ZnO nanostructures have attracted significant interest for use in ultraviolet (UV) lasers, photochemical sensors, and photocatalysts, among other applications. It is known that 1D ZnO nanowires can be fabricated readily owing to the anisotropic growth of ZnO along the [0001] direction. However, this type of growth results in a decrease in the surface area of the (0001) plane, which plays a vital role not only in UV lasing but also in the photocatalytic process. Thus, we attempted to synthesize ZnO crystals with an increased polar surface area by controlling the crystal growth process. The purpose of this review is to propose a simple route for the synthesis of plate-like ZnO crystals with highly enhanced polar surfaces and to explore their feasibility for use in UV lasers as well as as a photocatalyst and antibacterial agent. In addition, we highlight the recent progress made in the pilot-scale synthesis of plate-like ZnO crystals for industrial applications.

• Analytical Science and Technology
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• v.11 no.1
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• pp.13-19
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• 1998

In the dye sensitization for the solar energy conversion with a photoelectrochemical cell containing allylthiourea, the time profile of the sensitized photocurrent showed a rise and fall with the irradiation time. The dye solution before and after irradiation was analyzed by means of spectroscopic methods. A new precipitation reaction between sensitizer and supersensitizer and photobleaching of the dye appeared to be involved in the decreased photocurrent.

• Proceedings of the KAIS Fall Conference
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• 2007.11a
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• pp.397-399
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• 2007

본 연구는 광전자 촉매시스템을 이용해 $TiO_2$ 졸이 코팅된 구형 비드의 광분해 효율에 대해 고찰한 것이다. $TiO_2$ 졸이 코팅된 구형 비드인 실리카비드 화이트겔(1 2 3형) 세 가지 비드를 사용하였고 실험은 1L 크기의 반응기에 유기 물질을 함유한 인공 폐수를 넣어 비드에 코팅된 $TiO_2$의 분해 활성을 고찰할 목적으로 실행되었다. 그 결과, $500^{\circ}C$에서 3hr에서 소성한 실리카 비드가 가장 뛰어난 반응성을 나타내며 인공폐수에서도 분해활성을 나타내는 것을 확인하였다.

• Proceedings of the KAIS Fall Conference
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• 2003.06a
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• pp.343-346
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• 2003

본 연구에서는 IPA(isopropyl alcohol)를 분해물질로 선정하여 플라스틱 광섬유(Pastic Optical Fiber, POF)에 TiO₂를 코팅하여 오염물질을 분해하였다. P-25가 코팅된 POF의 표면은 유기계, 무기계, 유ㆍ무기 바인더를 사용한 것 모두 깨끗하였고, 무기계 바인더를 사용하여 코팅한 POF는 부착력이 현저히 떨어졌다. IPA 분해 결과, 무기계 바인더를 사용한 경우, 다른 종류의 바인더와는 다르게 IPA의 초기농도 값이 매우 작게나왔는데 이러한 결과는 반응기에 주입된 IPA가 평형이 될 때까지 기다리는 동안 흡착이 일어났기 때문으로 생각된다. 유기계 바인더를 사용하여 코팅한 POF는 IPA 분해 효율이 매우 저조하였고 유ㆍ무기 바인더를 사용하여 코팅한 POF의 IPA 분해 효율은 우수하였다. P-25와 IPA의 분해 효율이 우수한 유ㆍ무기 바인더의 비율을 10 : 10 : 8, 10 : 6, 10 : 4, 10 : 2로 바꾸어 IPA를 분해한 결과, P-25와 유ㆍ무기 바인더의 비율이 10 : 2일 때 IPA 분해 효율이 가장 우수하였다. 또한 P-25와 코팅액 제조 시 회석제로 사용되는 에탄올의 질량비를 1 : 7, 1 : 11, 1 : 15로 바꾸어 IPA를 분해한 결과, P-25와 에탄올의 비율이 1 : 15 일 때 IPA 분해 효율이 가장 우수하였다.

• Proceedings of the KAIS Fall Conference
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• 2003.06a
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• pp.347-349
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• 2003

Photoelectrocatalytic system is based on the idea that the photogenerated electrons in a layer of TiO$_2$ would move toward a cathode with application of high voltage across the TiO$_2$ coated aluminum plate. In this system, aluminum plate is used as a substrate for TiO$_2$ and also serves as a cathode. According to our scheme, moving photogenerated electrons toward a cathode would have the same effect as moving these electrons away from the holes, which would have the effect of retarding recombination of photogenerated electrons with holes. Recent experiments on benzene and toluene showed higher rates of removal with high voltage on compared to high voltage off, which supported our scheme partially.

• Journal of the Semiconductor & Display Technology
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• v.17 no.4
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• pp.16-20
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• 2018

Graphene is attracting attention due to its outstanding properties as line material for next-generation semiconductor. Graphene pattern technology is essential to apply graphene line. Selective graphene oxide reduction as one of graphene pattern method does not require a substrate thereby a high flexibility device can be applied. Particularly, the method using photon energy has advantages of short process time and environment friendly. In this review, we introduce the photocatalytic method and the photo-thermal energy conversion method using photon energy in the selective reduction process of graphene oxides.

• Korean Chemical Engineering Research
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• v.57 no.5
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• pp.652-665
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• 2019

Analytical solutions of the reactant concentration inside porous spherical catalytic particles were obtained from unsteady reaction-diffusion equation by applying eigenfunction expansion method. Various surface concentrations as exponentially decaying or oscillating function were considered as boundary conditions to solve the unsteady partial differential equation as a function of radial distance and time. Dirac delta function was also used for the instantaneous injection of the reactant as the surface boundary condition to calculate average reactant concentration inside the particles as a function of time by Laplace transform. Besides spherical morphology, other geometries of particles, such as cylinder or slab, were considered to obtain the solution of the reaction-diffusion equation, and the results were compared with the solution in spherical coordinate. The concentration inside the particles based on calculation was compared with the bulk concentration of the reactant molecules measured by photocatalytic decomposition as a function of time.

• Journal of Industrial and Engineering Chemistry
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• v.67
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• pp.437-447
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• 2018

Visible-light-driven wide bandgap semiconductor photocatalysts were commonly developed via doping or coupling with another narrow bandgap metal oxide. However, these approaches required extra processing. The aim of study was to evaluate the photocatalytic performance of narrow bandgap $WO_x$ nanoparticles. A mixture of $WO_2$ and $WO_3$ nanoparticles were synthesized using solution precipitation technique. The photodegradation of RhB by these nanoparticles more effective in UV light than in visible light. In antibacterial susceptibility assay, $WO_x$ nanoparticles demonstrated good antibacterial against Gram-positive bacteria. The cell wall of bacterial was the main determinant in antibacterial effect other than $W^{4+}/W^{6+}$ ions and ROS.