Benzene sensing properties and sensing mechanism of Pd-decorated Bi₂O₃-core/ZnO-shell nanorods

Bonyani, Maryam,Lee, Jae Kyung,Sun, Gun-Joo,Lee, Sangmin,Ko, Taekyung,Lee, Chongmu Elsevier S.A. 2017 Thin Solid Films Vol.636 No.-

<P><B>Abstract</B></P> <P>We report the effects of a combination of Pd-decoration and Bi<SUB>2</SUB>O<SUB>3</SUB>-ZnO core-shell formation on the response of the Bi<SUB>2</SUB>O<SUB>3</SUB> nanorod gas sensor to benzene. Pd-decorated Bi<SUB>2</SUB>O<SUB>3</SUB>–ZnO core–shell nanorods were synthesized by a four-step process including thermal evaporation of Bi powders in an oxygen atmosphere, atomic layer deposition of ZnO, and Pd decoration, followed by high-temperature annealing. The formation of Pd-decorated Bi<SUB>2</SUB>O<SUB>3</SUB>–ZnO core–shell nanorods was confirmed by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and energy-dispersive spectrometric elemental mapping. The Pd-decorated Bi<SUB>2</SUB>O<SUB>3</SUB>–ZnO core–shell nanorod sensor showed far stronger response to benzene improved compared to those of the Bi<SUB>2</SUB>O<SUB>3</SUB>–ZnO core–shell nanorod and Pd-decorated ZnO nanorod sensors. The Pd-decorated Bi<SUB>2</SUB>O<SUB>3</SUB>–ZnO core–shell nanorod sensor exhibited a response (<I>R</I> <SUB> <I>a</I> </SUB> <I>/R</I> <SUB> <I>g</I> </SUB>) of 28.0 to 200ppm of benzene at 300°C, whereas those of the Bi<SUB>2</SUB>O<SUB>3</SUB>–ZnO core–shell nanorod, and Pd-decorated ZnO nanorod sensors were 9.1 and 8.3, respectively. The extraordinarily strong response of the Pd-decorated Bi<SUB>2</SUB>O<SUB>3</SUB>–ZnO core–shell nanorod sensor compared to other sensors might be attributed to the intensified potential barrier modulation at the Bi<SUB>2</SUB>O<SUB>3</SUB>–ZnO interface due to the Pd-induced enhanced generation of electrons. The Pd-decorated Bi<SUB>2</SUB>O<SUB>3</SUB>–ZnO core–shell nanorod sensor also showed very good selectivity toward benzene against other reducing gases, such as ethanol, toluene, carbon monoxide, and acetone.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Pd-decorated Bi<SUB>2</SUB>O<SUB>3</SUB>–ZnO core–shell nanorods were synthesized by a four-step process. </LI> <LI> A combination of Pd decoration and core-shell formation showed a synergistic effect in sensitivity. </LI> <LI> The underlying mechanism of the synergistic effects is discussed. </LI> <LI> The sensor showed very good selectivity toward benzene against other reducing gases. </LI> </UL> </P>

Enhanced Sensitivity and Selectivity of Co₃O₄ Nanoparticle-Decorated SnO₂ Nanowire Sensors to Ethanol Gas

Bonyani, Maryam,Sun, Gun-Joo,Lee, Jae Kyung,Choi, Seungbok,Lee, Chongmu,Lee, Sangmin American Scientific Publishers 2017 Journal of Nanoscience and Nanotechnology Vol.17 No.11

<P>Co3O4-decorated SnO2 nanowires were synthesized using a simple two-step process: thermal evaporation and solvothermal techniques. For comparison purposes, pristine SnO2 nanowires were also synthesized using the same procedure. The crystallinity and phase formation of the synthesized products were analyzed by X-ray diffraction, while the morphology was examined by scanning electron microscopy. Gas sensing tests were performed using both pristine SnO2 nanowire and Co3O4-decorated SnO2 nanowire sensors, The pristine SnO2 nanowire and Co3O4-decorated SnO2 nanowire sensors showed a response of 15.29 and 46.73 to 100 ppm of ethanol at 300 degrees C, respectively, resulting in a 205.62% increase in the'response after Co3O4 decoration. Furthermore, both response and recovery times of the Co3O4-decorated SnO2 nanowire sensor were shorter than those of the pristine SnO2 nanowire sensor. Finally, the selectivity towards ethanol was much higher for the Co3O4-decorated SnO2 nanowire sensor than for the pristine SnO2 nanowire sensor. The sensing mechanisms for the enhanced sensing performance of the Co3O4-decorated SnO2 nanowire sensor towards ethanol are discussed in detail.</P>

Cr₂O₃ nanoparticle-functionalized WO₃ nanorods for ethanol gas sensors

Choi, Seungbok,Bonyani, Maryam,Sun, Gun-Joo,Lee, Jae Kyung,Hyun, Soong Keun,Lee, Chongmu Elsevier 2018 APPLIED SURFACE SCIENCE - Vol.432 No.2

<P><B>Abstract</B></P> <P>Pristine WO<SUB>3</SUB> nanorods and Cr<SUB>2</SUB>O<SUB>3</SUB>-functionalized WO<SUB>3</SUB> nanorods were synthesized by the thermal evaporation of WO<SUB>3</SUB> powder in an oxidizing atmosphere, followed by spin-coating of the nanowires with Cr<SUB>2</SUB>O<SUB>3</SUB> nanoparticles and thermal annealing in an oxidizing atmosphere. Scanning electron microscopy was used to examine the morphological features and X-ray diffraction was used to study the crystallinity and phase formation of the synthesized nanorods. Gas sensing tests were performed at different temperatures in the presence of test gases (ethanol, acetone, CO, benzene and toluene). The Cr<SUB>2</SUB>O<SUB>3</SUB>-functionalized WO<SUB>3</SUB> nanorods sensor showed a stronger response to these gases relative to the pristine WO<SUB>3</SUB> nanorod sensor. In particular, the response of the Cr<SUB>2</SUB>O<SUB>3</SUB>-functionalized WO<SUB>3</SUB> nanorods sensor to 200ppm ethanol gas was 5.58, which is approximately 4.4 times higher that of the pristine WO<SUB>3</SUB> nanorods sensor. Furthermore, the Cr<SUB>2</SUB>O<SUB>3</SUB>-functionalized WO<SUB>3</SUB> nanorods sensor had a shorter response and recovery time. The pristine WO<SUB>3</SUB> nanorods had no selectivity toward ethanol gas, whereas the Cr<SUB>2</SUB>O<SUB>3</SUB>-functionalized WO<SUB>3</SUB> nanorods sensor showed good selectivity toward ethanol. The gas sensing mechanism of the Cr<SUB>2</SUB>O<SUB>3</SUB>-functionalized WO<SUB>3</SUB> nanorods sensor toward ethanol is discussed in detail.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Pristine WO<SUB>3</SUB> nanorods and Cr<SUB>2</SUB>O<SUB>3</SUB>-functionalized WO<SUB>3</SUB> nanorods were synthesized. </LI> <LI> The Cr<SUB>2</SUB>O<SUB>3</SUB>-functionalized WO<SUB>3</SUB> nanorod sensor showed a stronger response to these gases than the pristine WO<SUB>3</SUB> nanorod sensor. </LI> <LI> The former sensor showed a shorter response and recovery time than the latter one. </LI> <LI> The Cr<SUB>2</SUB>O<SUB>3</SUB>-functionalized WO<SUB>3</SUB> nanorods sensor showed good selectivity toward ethanol. </LI> <LI> The underlying mechanisms for the enhanced sensing performance of the functionalized sensor are discussed in detail. </LI> </UL> </P>

Conducting Polymer Nanofibers based Sensors for Organic and Inorganic Gaseous Compounds

Mirzaei Ali,Kumar Vanish,Bonyani Maryam,Majhi Sanjit Manohar,Bang Jae Hoon,Kim Jin-Young,김현우,김상섭,김기현 한국대기환경학회 2020 Asian Journal of Atmospheric Environment (AJAE) Vol.14 No.2

Resistive-based gas sensors built through the combination of semiconducting metal oxides and conducting polymers (CPs) are widely used for the detection of diverse gaseous components. In light of the great potential of each of these components, electrospun CPs produced by a facile electrospinning method can offer unique opportunities for the fabrication of sensitive gas sensors for diverse gaseous compounds due to their large surface area and favorable nanomorphologies. This review focuses on the progress achieved in gas sensing technology based on electrospun CPs. We offer numerous examples of CPs as gas sensors and discuss the parameters affecting their sensitivity, selectivity, and sensing mechanism. This review paper is expected to offer useful insights into potential applications of CPs as gas sensing systems.

Volatile organic compound sensing properties of MoO₃–ZnO core–shell nanorods

Lee, Wan In,Bonyani, Maryam,Lee, Jae Kyung,Lee, Chongmu,Choi, Seung-Bok ELSEVIER 2018 Current Applied Physics Vol.18 No.supp

<P>MoO3-ZnO core-shell nanorods were synthesized by a simple two-step process. MoO3 nanorods were synthesized by a hydrothermal method, which was followed by atomic layer deposition of a ZnO shell. The phase and crystallinity of the synthesized products were examined by X-ray diffraction, and the morphological features were studied by scanning electron microscopy. Gas sensing tests were performed on both pristine MoO3 nanorods and MoO3-ZnO core-shell nanorods. Sensors containing the pristine MoO3 nanorods and MoO3-ZnO core-shell nanorods showed responses (R-a/R-g where R-a and R-g are the electrical resistances of the sensors in air and the target gas, respectively) of 1.15 and 7.6, respectively, to 200 ppm ethanol at 350 degrees C. Therefore, the response of the MoO3-ZnO core-shell nanorod sensors to ethanol gas was significantly better than that of pristine MoO3 nanorods. The underlying mechanisms for the enhanced sensing performance are discussed in detail. (C) 2017 Elsevier B.V. All rights reserved.</P>

Development of defects in ZnO/RGO composites under wet chemical synthesis

Na, Han Gil,Jung, Taek-Kyun,Ryou, Min,Lee, Ji-Woon,Hyun, Soong-Keun,Kang, Sung Yong,Mirzaei, Ali,Bonyani, Maryam,Kim, Kyung-Taek,Choi, Ho-Joon,Kim, Hyoun Woo,Jin, Changhyun Elsevier 2018 Optik Vol.156 No.-

<P><B>Abstract</B></P> <P>ZnO/reduced graphene oxide (RGO) heterostructures were fabricated using a simple two-step wet chemical technique and post-annealing treatment. ZnO nanoparticles with different sizes (20–200 nm) and shapes were randomly distributed on mono- and/or multi-layered RGO sheets. The microstructures of the ZnO/RGO composites examined using transmission electron microscopy indicated that the heterostructures are polycrystalline in nature, implying the possibilities of diverse defects present in the samples. The photoluminescence spectra examinations revealed the enhancement of defect-level emission peaks observed at a relatively long wavelength ranges (i.e., 779 nm, 666 nm, and 574 nm) as compared with the band to band transition observed at relatively short wavelengths (i.e., 378 nm).</P>