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Kheel, Hyejoon,Sun, Gun-Joo,Lee, Jae Kyung,Lee, Sangmin,Dwivedi, Ram Prakash,Lee, Chongmu Elsevier 2016 Ceramics international Vol.42 No.16
<P><B>Abstract</B></P> <P>Pristine and TiO<SUB>2</SUB> nanoparticle-decorated Fe<SUB>2</SUB>O<SUB>3</SUB> nanorods were synthesized via thermal oxidation of Fe thin foils, followed by the solvothermal treatment with titanium tetra isopropoxide (TTIP) and NaOH for TiO<SUB>2</SUB> nanoparticle-decoration. Subsequently, gas sensors were fabricated by connecting the nanorods with metal conductors. The structure and morphology of the pristine and TiO<SUB>2</SUB> nanoparticle-decorated Fe<SUB>2</SUB>O<SUB>3</SUB> nanorods were examined via X-ray diffraction and scanning electron microscopy, respectively. The gas sensing properties of the pristine and TiO<SUB>2</SUB> nanoparticle-decorated Fe<SUB>2</SUB>O<SUB>3</SUB> nanorod sensors with regard to H<SUB>2</SUB>S gas were examined. The TiO<SUB>2</SUB> nanoparticle-decorated Fe<SUB>2</SUB>O<SUB>3</SUB> nanorod sensor showed a stronger response to H<SUB>2</SUB>S than the pristine Fe<SUB>2</SUB>O<SUB>3</SUB> nanorod sensor. The responses of the pristine and TiO<SUB>2</SUB> nanoparticle-decorated Fe<SUB>2</SUB>O<SUB>3</SUB> nanorod sensors were 2.6 and 7.4, respectively, when tested with 200ppm of H<SUB>2</SUB>S at 300°C. The TiO<SUB>2</SUB> nanoparticle-decorated Fe<SUB>2</SUB>O<SUB>3</SUB> nanorod sensor also showed a faster response and recovery than the sensor made from pristine Fe<SUB>2</SUB>O<SUB>3</SUB> nanorods. Both sensors showed selectivity for H<SUB>2</SUB>S over NO<SUB>2</SUB>, SO<SUB>2</SUB>, NH<SUB>3</SUB>, and CO. The enhanced sensing performance of the TiO<SUB>2</SUB> nanoparticle-decorated Fe<SUB>2</SUB>O<SUB>3</SUB> nanorod sensor compared to that of the pristine Fe<SUB>2</SUB>O<SUB>3</SUB> nanorod sensor might be due to enhanced modulation of the conduction channel width, the decorated nanorods’ increased surface-to-volume ratios and the creation of preferential adsorption sites via TiO<SUB>2</SUB> nanoparticle decoration. The dominant sensing mechanism in the TiO<SUB>2</SUB> nanoparticle-decorated Fe<SUB>2</SUB>O<SUB>3</SUB> nanorod sensor is discussed in detail.</P>
Ethanol Sensing Properties of Au-functionalized NiO Nanoparticles
박성훈,Hyejoon Kheel,선건주,현승균,박상언,이종무 대한화학회 2016 Bulletin of the Korean Chemical Society Vol.37 No.5
Pristine and Au-functionalized nickel oxide (NiO) nanoparticles were synthesized via a simple solvothermal route and the ethanol sensing properties of multiple-networked Au-doped and undoped NiO nanoparticle sensors were examined. The pristine and Au-functionalized NiO nanoparticle sensor showed responses of 442 and 273%, respectively, to 1000 ppm of ethanol at 325 °C. The Au-functionalized NiO nanoparticle sensor showed faster response than the pristine NiO counterpart, whereas the recovery time of the former was similar to that of the latter. The optimal operating temperature of the pristine and Au-functionalized NiO nanoparticles was 325 and 350 °C, respectively, by Au-doping. Both the pristine and Au-functionalized NiO nanoparticle sensors showed selectivity for ethanol gas over methanol, acetone, benzene, and toluene gases. The underlying mechanism of the enhanced sensing performance of the Au-functionalized NiO nanoparticles toward ethanol might be due to modulation of the depletion layer formed around Au particles and the Schottky barriers formed at the Au–NiO junction accompanying ethanol adsorption and desorption, the spill-over effect and high catalytic activity of Au nanoparticles and the smaller diameter of the particles in the Au-functionalized NiO sensor.
Park, Sunghoon,Kheel, Hyejoon,Sun, Gun-Joo,Ko, Taegyung,Lee, Wan In,Lee, Chongmu Hindawi Limited 2015 Journal of nanomaterials Vol.2015 No.-
<P>Fe2O3-decorated CuO nanorods were prepared by Cu thermal oxidation followed by Fe2O3decoration via a solvothermal route. The acetone gas sensing properties of multiple-networked pristine and Fe2O3-decorated CuO nanorod sensors were examined. The optimal operating temperature of the sensors was found to be 240°C. The pristine and Fe2O3-decorated CuO nanorod sensors showed responses of 586 and 1,090%, respectively, to 1,000 ppm of acetone at 240°C. The Fe2O3-decorated CuO nanorod sensor also showed faster response and recovery than the latter sensor. The acetone gas sensing mechanism of the Fe2O3-decorated CuO nanorod sensor is discussed in detail. The origin of the enhanced sensing performance of the multiple-networked Fe2O3-decorated CuO nanorod sensor to acetone gas was explained by modulation of the potential barrier at the Fe2O3-CuO interface, highly catalytic activity of Fe2O3for acetone oxidation, and the creation of active adsorption sites by Fe2O3nanoparticles.</P>
Sunghoon Park,Hyejoon Kheel,Gun-Joo Sun,Hyoun Woo Kim,Taegyung Ko,Chongmu Lee 대한금속·재료학회 2016 METALS AND MATERIALS International Vol.22 No.4
Cr2O3-functionalized Nb2O5 nanoparticles were synthesized via a facile hydrothermal route. The multiple-networked Cr2O3-functionalized Nb2O5 nanostructured sensor showed enhanced H2 gas sensing performance compared to its pristine Nb2O5 nanostructure counterpart. The Cr2O3-functionalized Nb2O5 nanostructure sensor showed responses of 5.24 to 2 ppm of H2 at room temperature, whereas the pristine Nb2O5 nanoparticle sensors showed responses of 2.29. The former also exhibited a faster response to H2. The multiple-networked pristine and Cr2O3-functionalized Nb2O5 nanostructured sensors were stronger and much shorter, respectively, than other nanomaterial-based Schottky diode-type sensors and Nb2O5-based Schottky diode-type sensors. The underlying mechanism for the enhanced sensing performance of the Cr2O3-functionalized Nb2O5 nanostructured sensor towards H2 gas is discussed in detail. Particular emphasis is placed on the role of the Cr2O3-Nb2O5 p-n junction in the Cr2O3-functionalized Nb2O5 nanostructure sensor.
Hydrogen Gas Sensing of Co3O4-Decorated WO3 Nanowires
박성훈,Gun-Joo Sun,Hyejoon Kheel,Soong Keun Hyun,진창현,이종무 대한금속·재료학회 2016 METALS AND MATERIALS International Vol.22 No.1
Co3O4 nanoparticle-decorated WO3 nanowires were synthesized by the thermal oxidation of powders followed by a solvothermal process for Co3O4 decoration. The Co3O4 nanoparticle-decorated WO3 nanowire sensor exhibited a stronger and faster electrical response to H2 gas at 300 °C than the pristine WO3 nanowire counterpart. The former showed faster response and recovery than the latter. The pristine and Co3O4-decorated WO3 nanowire sensors showed the strongest response to H2 gas at 225 and 200 °C, respectively. The Co3O4-decorated WO3 nanowire sensor showed selectivity for H2 gas over other reducing gases. The enhanced sensing performance of the Co3O4-decorated WO3 nanowire sensor was explained by a combination of mechanisms: modulation of the depletion layer width forming at the Co3O4-WO3 interface, modulation of the potential barrier height forming at the interface, high catalytic activity of Co3O4 for the oxidation of H2, active adsorption of oxygen by the Co3O4 nanoparticle surface, and creation of more active adsorption sites by Co3O4 nanoparticles.
Mirzaei, Ali,Park, Sunghoon,Kheel, Hyejoon,Sun, Gun-Joo,Ko, Taegyung,Lee, Sangmin,Lee, Chongmu American Scientific Publishers 2017 Journal of Nanoscience and Nanotechnology Vol.17 No.6
<P>Pure In2O3 and In2O3/Co3O4 composite nanoparticles were synthesized by a hydrothermal process using indium acetate and cobalt acetate as precursors. The In2O3/Co3O4 composite nanoparticles provided enhanced sensing performance. In particular, the responses of the pure In2O3 and In2O3/Co3O4 composite nanoparticle sensors to 200-ppm acetone at 250 degrees C were 5.55 and 15.54, respectively. The response and recovery times of the pure In2O3 sensors to 200-ppm acetone at 250 degrees C were 7 and 30 s, respectively, whereas those of the In2O3/Co3O4 composite nanoparticle sensor were 2.5 and 18 s, respectively. The underlying mechanism for the improved sensing characteristics of the In2O3/Co3O4 sensor were also discussed.</P>