• WON-CHUN OH

      Articles written in Bulletin of Materials Science

    • Visible light photocatalytic properties of novel molybdenum treated carbon nanotube/titania composites

      Feng-Jun Zhang Won-Chun Oh

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      Two types of molybdenum–carbon nanotubes and molybdenum treated carbon nanotubes/titania composites were prepared using a sol–gel method. These composites were characterized comprehensively by the Brauer–Emett–Teller (BET) surface area, scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, X-ray diffraction (XRD), transmission electron microscopy (TEM) and UV-vis absorption spectroscopy. It was found that the photocatalytic degradation of a methylene blue solution could be attributed to the combined effects caused by the photo-degradation of titania, the electron assistance of carbon nanotube network, and the enhancement of molybdenum. The proposed redox mechanism of the photodegradation of methylene blue on Mo-CNT/TiO2 composites is suggested.

    • UV and visible light photodegradation effect on Fe–CNT/TiO2 composite catalysts

      Zhen Li Jin Liu Feng-Jun Zhang Won-Chun Oh

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      Using multi-walled carbon nanotube (CNT) as an one-dimensional support, we have succeeded in uniformly anchoring of TiO2 and Fe nanoparticles at its surface. The as-prepared Fe–CNT/TiO2 composite photocatalysts have been investigated by degrading methylene blue (MB) under UV and differently intensified visible light irradiation. The ability of CNT to store and shuttle electrons, and Fe nanoparticles demonstrate its capability to serve as a yield and transfer electrons on demand to separate h+/e- pairs. Moreover, the MB photodegradation increase with an increase of visible light intensity can be ascribed to the enhancement MB cationic radical. In addition, chemical oxygen demand (COD) of piggery waste and reduction efficiency of Cr (IV) was done at regular intervals, which gave a good idea about mineralization of wastewater.

    • Synthesis of Ag$_2$Se–graphene–TiO$_2$ nanocomposite and analysis of photocatalytic activity of CO$_2$ reduction to CH$_3$OH

      ASGHAR ALI WON-CHUN OH

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      The present work deals with the development of a new ternary composite, Ag$_2$Se–G–TiO$_2$, using ultrasonic techniques as well as X-ray diffraction (XRD), scanning electron microscopy (SEM), high transmission electron microscopy(HTEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy and UV–Vis diffuse reflectance spectra (DRS)analyses. The photocatalytic potential of nanocomposites is examined for CO$_2$ reduction to methanol under ultraviolet(UV) and visible light irradiation. Ag$_2$Se–TiO$_2$ with an optimum loading graphene of 10wt% exhibited the maximumphotoactivity, obtaining a total CH3OH yield of 3.52 $\mu$mol g$^{−1}$ h$^{−1}$ after 48 h. This outstanding photoreduction activity is due to the positive synergistic relation between Ag$_2$Se and graphene components in our heterogeneous system.

    • Electroanalytical characteristic of a novel biosensor designed with graphene–polymer-based quaternary and mesoporous nanomaterials

      KAMRUN NAHAR FATEMA MD ROKON UD DOWLA BISWAS SEONG HO BANG KWANG YOUN CHO WON-CHUN OH

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      Here, we propose the novel fabrication of graphene–polymer (GP)-based quaternary nanocomposite and mesoporous (MS) nanomaterials sensor [NaLa(MoO$_4$)$_2$-GO-PPy (NLMG-PPy), CuZnSnSe-GO-PPy (CZSG-PPy) and In$_2$O$_3$-G-SiO$_2$ 20% (IGS20)] to address ignored challenges for Escherichia coli bacteria recognition in polluted samples.Synthesized samples were characterized through X-ray diffraction (XRD), scanning electron microscopy (SEM), energydispersive X-ray spectrometry (EDX), transmission electron microscopy (TEM), high-resolution transmission electron microscopy (HRTEM), Raman spectroscopy, nitrogen adsorption–desorption isotherms, X-ray photoelectron spectroscopy (XPS) and diffuse reflectance spectroscopy (DRS). The sensor could recognize an individual E. coli cell in 1$\mu$l sample volume within 50 s. Through a low identification point of an individual cell, the MS and GP sensor had an absolute scope of 1–100 CFU per μl volume of sample (i.e. 103–105 CFU ml$^{−1}$). The high thickness of negative charge on the surface of E. coli cells actively regulates the concentration of dominant part charge carriers in the mesoporous and G-polymer monolayer, permitting an ongoing check of E. coli concentration in a known sample. Our biosensor is simple and low-cost with great selectivity and fast identification was effectively shown for E. coli detection.

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