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Katoch, Akash,Kim, Jae-Hun,Kwon, Yong Jung,Kim, Hyoun Woo,Kim, Sang Sub American Chemical Society 2015 ACS APPLIED MATERIALS & INTERFACES Vol.7 No.21
<P>SnO<SUB>2</SUB>–ZnO composite nanofibers fabricated using an electrospinning method exhibited exceptional hydrogen (H<SUB>2</SUB>) sensing behavior. The existence of tetragonal SnO<SUB>2</SUB> and hexagonal ZnO nanograins was confirmed by an analysis of the crystalline phase of the composite nanofibers. A bifunctional sensing mechanism of the composite nanofibers was proposed in which the combined effects of SnO<SUB>2</SUB>–SnO<SUB>2</SUB> homointerfaces and ZnO–SnO<SUB>2</SUB> heterointerfaces contributed to an improvement in the H<SUB>2</SUB> sensing characteristics. The sensing process with respect to SnO<SUB>2</SUB>–ZnO heterojunctions is associated not only with the high barrier at the junctions, but also the semiconductor-to-metallic transition on the surface of the ZnO nanograins upon the introduction of H<SUB>2</SUB> gas.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2015/aamick.2015.7.issue-21/acsami.5b01817/production/images/medium/am-2015-01817x_0008.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am5b01817'>ACS Electronic Supporting Info</A></P>
TiO<sub>2</sub>/ZnO Inner/Outer Double-Layer Hollow Fibers for Improved Detection of Reducing Gases
Katoch, Akash,Kim, Jae-Hun,Kim, Sang Sub American Chemical Society 2014 ACS APPLIED MATERIALS & INTERFACES Vol.6 No.23
<P>TiO<SUB>2</SUB>/ZnO double-layer hollow fibers (DLHFs) are proposed as a superior sensor material in comparison to regular single-layer hollow fibers (HFs) for the detection of reducing gases. DLHFs were synthesized on sacrificial polymer fibers via atomic layer deposition of a first layer of TiO<SUB>2</SUB> followed by a second layer of ZnO and by a final thermal treatment. The inner TiO<SUB>2</SUB> receives electrons from the ZnO outer layer, which becomes more resistive due to the significant loss of electrons. This highly resistive ZnO layer partially regains its original resistivity when exposed to reducing gases such as CO, thus enabling more resistance variation in DLHFs. DLHFs are a novel material compared to HFs and can be successfully employed to fabricate chemical sensors for the accurate detection of reducing gases.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2014/aamick.2014.6.issue-23/am506499e/production/images/medium/am-2014-06499e_0005.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am506499e'>ACS Electronic Supporting Info</A></P>
Pt nanoparticle-decorated ZnO nanowire sensors for detecting benzene at room temperature.
Katoch, Akash,Choi, Sun-Woo,Sun, Gun-Joo,Kim, Sang Sub American Scientific Publishers 2013 Journal of Nanoscience and Nanotechnology Vol.13 No.10
<P>Room temperature gas sensing ability for low concentrations of benzene was successfully realized with Pt nanoparticle-decorated networked ZnO nanowire sensors. For decoration of Pt nanoparticles, gamma-ray radiolysis was used. The Pt decoration greatly enhanced benzene sensing performances. Importantly, even at room temperature, ppm level benzene was clearly detected, which is likely to be due to the combined effect of electronic and chemical sensitizations by Pt nanoparticles.</P>
Synthesis and Sensing Properties of Pd Nanoparticle-Functionalized SnO2 Nanowires
( Katoch Akash ),( Sun Woo Choi ),( Eun Kyeong Kim ),( Sang Sub Kim ) 한국센서학회 2011 센서학회지 Vol.20 No.5
Networked SnO2 nanowires were uniformly functionalized with Pd nanoparticles via γ-ray radiolysis. The Networked SnO2 nanowires were fabricated through a selective growth method. The sensing properties of the Pd-functionalized SnO2 nanowires were analyzed in terms of their response to NO2 and CO gases. The response time and sensitivity of the sensors were significantly improved for NO2 at lower temperatures by the Pd functionalization. The enhancement in the sensing properties is likely to be due to the spillover effect of the Pd nanoparticles.
Katoch, Akash,Abideen, Zain Ul,Kim, Hyoun Woo,Kim, Sang Sub American Chemical Society 2016 ACS APPLIED MATERIALS & INTERFACES Vol.8 No.4
<P>We investigated the effect of grain size on the H-2-sensing behavior of SnO2-ZnO composite nanofibers. The 0.9SnO(2)-0.1ZnO composite nanofibers were calcined at 700 degrees C for various times to control the size of nanograins. A bifunctional sensing mechanism, which is related not only to the SnO2-SnO2 nanograins, but also to the ZnO-SnO2 nanograins with surface metallization effect, is responsible for the grain-oriented H-2-sensing properties and the selective improvement in sensing behavior to H-2 gas compared to other gases. Smaller grains are much more favorable for superior H-2 sensing in SnO2-ZnO composite nanofibers, which will be an important guideline for their use in H-2 sensors. The one-dimensional nanofiber-based structures in the present study will be efficient in maximizing the sensing capabilities by providing a larger amount of junctions.</P>
Sensing Properties of Au Nanoparticle-Functionalized ZnO Nanowires by γ-Ray Radiolysis
( Akash Katoch ),( Sun Woo Choi ),( Joon Hyuk Byun ),( Sang Sub Kim ) 한국센서학회 2012 센서학회지 Vol.21 No.3
γ-ray radiolysis was used to functionalize networked ZnO nanowires with Au nanoparticles. The networked ZnO nanowires were prepared through a vapor phase selective growth method. The sensing performances of the Au-functionalized ZnO nanowires were investigated in terms of NO2, CO and benzene gases. The Au-funtionalized ZnO nanowire sensors showed an applicable, reliable capability to detect the gases, indicating their potential in chemical gas sensors.
Nanograins in Electrospun Oxide Nanofibers
Akash Katoch,최선우,김상섭 대한금속·재료학회 2015 METALS AND MATERIALS International Vol.21 No.2
Oxide nanofibers synthesized by the electrospinning method have received considerable attention owing totheir potential applications in various fields. This paper provides an overview of the growth behavior and theimportance of the presence of nanograins in oxide nanofibers synthesized by the electrospinning method. The growth behavior of nanograins in various oxide nanofibers is described in terms of its effect on activationenergy and growth exponent, which are then compared with the bulk counterparts. The lower activation energyof nanograins in nanofibers by an order of magnitude revealed that the active participation of nanograinsduring grain growth is due to higher chemical potential of atoms presented in nanosized grains. In addition,the influences of nanograins on the electrical, gas-sensing, magnetic, optical, and photocatalytic propertiesof nanofibers are discussed. It is shown that optimization of the nanograin size is essential to ensure thatthe advantages of oxide nanofibers are utilized in different applications. Oxide nanofibers synthesized by the electrospinning method have received considerable attention owing to their potential applications in various fields. This paper provides an overview of the growth behavior and the importance of the presence of nanograins in oxide nanofibers synthesized by the electrospinning method. The growth behavior of nanograins in various oxide nanofibers is described in terms of its effect on activation energy and growth exponent, which are then compared with the bulk counterparts. The lower activation energy of nanograins in nanofibers by an order of magnitude revealed that the active participation of nanograins during grain growth is due to higher chemical potential of atoms presented in nanosized grains. In addition, the influences of nanograins on the electrical, gas-sensing, magnetic, optical, and photocatalytic properties of nanofibers are discussed. It is shown that optimization of the nanograin size is essential to ensure that the advantages of oxide nanofibers are utilized in different applications.
Crystallinity Dependent Gas-Sensing Abilities of ZnO Hollow Fibers
Akash Katoch,Zain Ul Abideen,김재훈,Sang Sub Kim 대한금속·재료학회 2016 METALS AND MATERIALS International Vol.22 No.5
The grain size and crystallinity are important factors in considering the gas sensing properties of metal oxide based miniaturized gas sensors. This study reports the effects of the grain size and crystallinity on the CO sensing abilities of ZnO hollow fibers (HFs) synthesized by electrospinning. The grain size and crystallinity of the HFs were controlled by changing the heat treatment time during their synthesis and were characterized by SEM, TEM and XRD. Both the nanograin size and crystallinity of the HFs change significantly with increasing heat treatment time. Longer heat treatments result in improved sensing abilities irrespective of the evolution of larger-sized nanograins. Sensing measurements were carried out at various temperatures in the range 300- 400 °C. The improved crystallinity likely compensates the adverse effects of grain growth in terms of the sensor response. That is, crystallinity rather than grain size, is the dominant factor determining the sensing abilities of HFs. This result provides useful guidelines for the fabrication of HF-based chemiresistive-type gas sensors.