NO2 sensing properties of WO3-decorated In2O3 nanorods and In2O3-decorated WO3 nanorods

이중무,현승균,Tae-Kyoung Ko,Bumhee Nam 나노기술연구협의회 2019 Nano Convergence Vol.6 No.40

n2O3 nanoparticle (NP)-decorated WO3 nanorods (NRs) were prepared using sol–gel and hydrothermal methods. The In2O3 NRs and WO3 NPs were crystalline. WO3 NP-decorated In2O3 NRs were also prepared using thermal evaporation and hydrothermal methods. The NO2 sensing performance of the In2O3 NP-decorated WO3 NR sensor toward NO2 was compared to that of the WO3 NP-decorated In2O3 NR sensor. The former showed a high response to NO2 due to a significant reduction of the conduction channel width upon exposure to NO2. In contrast, the latter showed a far less pronounced response due to limited reduction of the conduction channel width upon exposure to NO2. When the sensors were exposed to a reducing gas instead of an oxidizing gas (NO2), the situation was reversed, i.e., the WO3 NP-decorated In2O3 NR exhibited a stronger response to the reducing gas than the In2O3 NP-decorated WO3 NR sensor. Thus, a semiconducting metal oxide (SMO) with a smaller work function must be used as the decorating material in decorated heterostructured SMO sensors for detection of oxidizing gases. The In2O3 NP-decorated WO3 NR sensor showed higher selectivity for NO2 compared to other gases, including reducing gases and other oxidizing gases, as well as showed high sensitivity to NO2.

E-textile gas sensors composed of molybdenum disulfide and reduced graphene oxide for high response and reliability

Yun, Yong Ju,Hong, Won G.,Kim, Do Yeob,Kim, Hae Jin,Jun, Yongseok,Lee, Hyung-Kun Elsevier Sequoia 2017 Sensors and actuators. B Chemical Vol.248 No.-

<P><B>Abstract</B></P> <P>Textiles with electronic functions (<I>e</I>-textiles) have been investigated due to a raise of internet-of-things (IoTs) and wearable electronics. The authors reported <I>e</I>-textile gas sensors based on reduced graphene oxides (RGOs) which were coated on the commercially available yarns treated with Bovine Serum Albumin (BSA) as a molecular glue. The <I>e</I>-textiles show sensitive responses to NO<SUB>2</SUB> (25%@4.5ppm) and durabilities to washing and bending stresses. This study reports an ultrasensitive response of an <I>e</I>-textile to NO<SUB>2</SUB> using combined sensing materials of transition metal disulfide (TMD) and RGO. The <I>e</I>-textile covered with MoS<SUB>2</SUB> and RGO shows a 28% response to 0.45ppm of NO<SUB>2</SUB> gas which is one of the most sensitive responses using RGOs as sensing materials.</P> <P><B>Highlights</B></P> <P> <UL> <LI> This manuscript reports bendable and washable electronic textile (<I>e</I>-textile) gas sensors composed of molybdenum disulfide(MoS<SUB>2</SUB>) and reduced graphene oxides (RGOs) using commercially available cotton yarn and molecular glue through an electrostatic self-assembly. </LI> <LI> The <I>e</I>-textile gas sensor possesses chemical durability to detergent washing treatments up to 100 times and mechanical stability under 1,000 bending tests as well as a high response to NO<SUB>2</SUB> gas at room temperature. </LI> <LI> Raman spectroscopy, scanning electron microscopy, and energy-dispersive X-ray spectroscopy confirm the wrapping of sensing materials composed of RGO and MoS<SUB>2</SUB> on cotton yarn. The large accessible surface of the yarn, composed of several hundreds of fibrils, and a robust wrapping method using molecular glue and 2D sensing material are considered the origins of the high sensor performances, such as the gas response and stability. </LI> <LI> Furthermore, the authors found that the combination of 2D sensing materials has a synergic effect on sensing NO<SUB>2</SUB> with 48% response to 4.5ppm of NO<SUB>2</SUB> gas </LI> </UL> </P>

NO2 감응을 위한 Ag 금속입자가 기능화된 SnO2 나노선 기반 저온동작 센서

최명식,김민영,안지혜,최승준,이규형 한국마이크로전자및패키징학회 2020 마이크로전자 및 패키징학회지 Vol.27 No.2

In this study, Ag-functionalized SnO2 nanowires are presented for NO2 gas sensitive sensors at low temperatures (50oC). SnO2 nanowires were synthesized using vapor-liquid-solid method, and Ag metal particles were functionalized on the surface of SnO2 nanowires using flame chemical vapor deposition method. As a result of the sensing test about Ag-functionalized SnO2 nanowires based sensor, the response (Rg/Ra) to 10 ppm NO2 was 1.252 at 50oC. We believe that metal-functionalizing is a one of good way to increase the feasibility about semiconductor gas sensor. 본 연구에서는 Ag 금속입자가 기능화된 SnO2 나노선을 제작 및 저온 NO2 가스 센싱 특성을 평가하였다. Vapor–liquid–solid 공법을 이용하여 SnO2 나노선을 합성하였고, flame chemical vapour deposition 공법을 이용하여 Ag 금속입자를 SnO2나노선표면에기능화하였다. 합성된 Ag 금속입자가기능화된 SnO2나노선을이용하여 50oC에서 NO2 10 ppm에대한 가스 센싱 테스트를 진행한 결과, 감응도(Rg/Ra) 1.252를얻었다. 본연구를 통하여, 금속입자가 기능화된나노선을 이용한 저온동작 반도체식 가스센서의 산업 적용을 현실화 할 수 있을 것으로 기대된다.

Highly selective and sensitive detection of NO₂ using rGO-In₂O₃ structure on flexible substrate at low temperature

Na, Chan Woong,Kim, Jae-Hyeok,Kim, Hyo-Joong,Woo, Hyung-Sik,Gupta, Arunava,Kim, Han-Ki,Lee, Jong-Heun Elsevier 2018 Sensors and actuators. B Chemical Vol.255 No.2

<P><B>Abstract</B></P> <P>Reduced graphene oxide (rGO)-In<SUB>2</SUB>O<SUB>3</SUB> hybrid materials were prepared by a solvothermal reaction of an In precursor containing rGO sheets, which were coated onto flexible substrates for gas sensors. The rGO-In<SUB>2</SUB>O<SUB>3</SUB> flexible sensors showed a high and reversible response (resistance ratio=22.3) to 500ppb NO<SUB>2</SUB> at 150°C and negligible cross-responses to C<SUB>2</SUB>H<SUB>5</SUB>OH, CO, NH<SUB>3</SUB>, toluene, H<SUB>2</SUB>, and HCHO. The ultrahigh response and selectivity of rGO-In<SUB>2</SUB>O<SUB>3</SUB> hybrid materials to NO<SUB>2</SUB> were attributed to the chemical affinity of rGO to NO<SUB>2</SUB> and the extension of the electron depletion layer in <I>n</I>-type In<SUB>2</SUB>O<SUB>3</SUB> forming a <I>p</I>-<I>n</I> junction with the <I>p</I>-type rGO.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Highly selective and sensitive NO<SUB>2</SUB> sensor using rGO-In<SUB>2</SUB>O<SUB>3</SUB> hybrid structures. </LI> <LI> Flexible gas sensors using polyimide film with ITO/Ag-Pd-Cu (APC)/ITO electrodes. </LI> <LI> High response (resistance ratio=22.3) to 0.5ppm NO<SUB>2</SUB> at 150°C. </LI> <LI> Negligible cross-responses to interference gases. </LI> </UL> </P>

NO2 Sensing Properties of Bead-like TeO2 Nanostructures Fabricated Using Different O2 Flow Rates

신기현,박성식,정학영,노영욱,이동진,최선우,진창현 대한화학회 2015 Bulletin of the Korean Chemical Society Vol.36 No.11

We report the synthesis of bead-like TeO2 nanowire (NW)-based NO2 gas sensors using different O2 flow rates. The performance of these sensors was compared with that of a sensor based on smooth TeO2 NWs. The smooth TeO2 NWs were grown directly from Te powder by thermal evaporation in air (i.e., without using O2 gas), while the bead-like TeO2 NWs were synthesized by transporting the evaporated Te precursor indirectly using reactive O2 gas at flow rates of 20–40 sccm. Scanning electron microscopy showed that the bead-like TeO2 NWs had uneven surfaces on which protruding nanoparticles with sizes of 20–100 nm were attached. The nanoparticle size varied with the O2 flow rate used. The responses of the gas sensors based on the multi-networked bead-like TeO2 NWs were indicative of a higher change in their electrical resistance as well as better selectivity to NO2 gas than those of the sensor based on the smooth TeO2 NWs. The individual responses—to 50 ppm NO2 gas at 350 °C—of the sensors based on TeO2 NWs fabricated without using O2 , using O2 at 20 sccm, using O2 at 30 sccm, and using O2 at 40 sccm were 113, 188, 220, and 345%, respectively. The underlying mechanisms responsible for the improved performances of the bead-like TeO2 NW-based sensors are also discussed.

Transition metal oxide (Ni, Co, Fe)-tin oxide nanocomposite sensing electrodes for a mixed-potential based NO₂ sensor

Bhardwaj, Aman,Kim, In-ho,Hong, Jae-woon,Kumar, Aniket,Song, Sun-Ju Elsevier Sequoia 2019 Sensors and actuators. B Chemical Vol.284 No.-

<P><B>Abstract</B></P> <P>A mixed-potential based sensor utilizing transition metal oxide (Ni, Co, Fe)-tin oxide nanocomposite sensing electrodes are fabricated for the first time and investigated for the gas sensing performance towards the highly toxic nitrogen dioxide. The nanocomposites are synthesized by solvo-combustion route and characterized for the physical, gas sensing and electrochemical properties in a temperature range of 600–700 ℃. The sensor equipped with Fe<SUB>2</SUB>O<SUB>3</SUB>-SnO<SUB>2</SUB> (Fe:Sn = 2:1) nanocomposite sensing electrodes sintered at 1000 ℃ shows the maximum response of 60 mV towards 100 ppm NO<SUB>2</SUB> with a relatively fast response and recovery dynamics at an operating temperature of 650 ℃. The sensor also shows a linear dependence of response over the logarithm of NO<SUB>2</SUB> concentration with a sensitivity of ∼44 mV/decade. Additionally, the oxygen concentration dependence, cyclability and cross-sensitivity towards interfering gases are also investigated. Finally, the sensing mechanism and electrochemical activity of the sensing electrodes are studied using polarization curve measurement and electrochemical impedance spectroscopy.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Mixed-potential based sensor utilizing transition metal oxide (Ni, Co, Fe)-tin oxide nanocomposite sensing electrodes. </LI> <LI> Fe<SUB>2</SUB>O<SUB>3</SUB>-SnO<SUB>2</SUB> nanocomposite sensing electrode responded 60mV towards 100ppm NO<SUB>2</SUB> at 650 ℃. </LI> <LI> The sensitivity of the sensor was found to be 44 mV/dec. in 10-100 ppm NO<SUB>2</SUB> concentration. </LI> <LI> The sensor displayed a low oxygen conc. dependence, high selectivity and high cyclability. </LI> <LI> Sensing mechanism and key parameters determining the sensing performance are discussed in details. </LI> </UL> </P>

SnO₂ Nanoslab as NO₂ Sensor: Identification of the NO₂ Sensing Mechanism on a SnO₂ Surface

Maeng, Sunglyul,Kim, Sang-Woo,Lee, Deuk-Hee,Moon, Seung-Eon,Kim, Ki-Chul,Maiti, Amitesh American Chemical Society 2014 ACS APPLIED MATERIALS & INTERFACES Vol.6 No.1

<P>Among the various metal oxides, SnO<SUB>2</SUB> has been most widely exploited as a semiconductor gas sensor for its excellent functionalities. Models illustrating the sensing mechanism of SnO<SUB>2</SUB> have been proposed and tested to explain experimentally derived “power laws”. The models, however, are often based on somewhat simplistic assumptions; for instance, the net charge transfer from an adsorbate to a sensor surface site is assumed to occur only by integer values independent of the crystallographic planes. In this work, we use layer-shaped SnO<SUB>2</SUB> crystallites with one nanodimension (1ND-crystallites) as NO<SUB>2</SUB> gas sensing elements under flat band conditions, and derive appropriate “power laws” by combining the dynamics of gas molecules on the sensor surface with a depletion theory of semiconductor. Our experimentally measured sensor response as a function of NO<SUB>2</SUB> concentration when compared with the theoretically derived power law indicates that sensing occurs primarily through the chemisorption of single NO<SUB>2</SUB> molecules at oxygen vacancy sites on the sensor surface.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2014/aamick.2014.6.issue-1/am404397f/production/images/medium/am-2013-04397f_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am404397f'>ACS Electronic Supporting Info</A></P>

Synthesis, structure, and room-temperature gas sensing of multiple-networked Pd-doped Ga₂O₃ nanowires

박성훈,김현수,진창현,이종무 한국물리학회 2012 THE JOURNAL OF THE KOREAN PHYSICAL SOCIETY Vol.60 No.10

Ga2O3-based gas sensors are known to show very poor performance at room temperature even though recent studies on Ga2O3 thin film-based gas sensors demonstrated that they detected O2, H2, CO, and CH4 gases efficiently at high temperatures of 600–1000 °C. This high working temperature limits the practical usage of Ga2O3-based gas sensors. In this study, the NO2 gas sensing properties of multiple-networked Pd-doped Ga2O3 nanowire sensors were examined. Scanning electron microscopy showed nanowires with diameters of 50–100 nm and lengths of a few micrometers. Transmission electron microscopy and X-ray diffraction showed that the nanowires were monoclinic single-crystal Ga2O3. The Pd-doped Ga2O3 nanowire sensors showed far enhanced sensing performance to NO2 gas at room temperature compared to bare-Ga2O3 nanowire sensors. No appreciable dynamic sensing behaviors were observed for bare-Ga2O3 nanowire sensors at room temperature. In contrast, the sensors showed sensitivities of 26.86, 30.19, and 41.44% at NO2 concentrations of 10, 50, and 100 ppm, respectively. In addition, the origin of the enhancement of the sensing properties of the Ga2O3 nanowires by Pd doping is discussed.

ZnO가 첨가된 TeO2 나노와이어의 합성 및 저농도(50 ppm) 이산화질소 가스 센싱 특성

유동재,신가윤,엄완식,강석우,김은비,김형민,김현우 한국재료학회 2022 한국재료학회지 Vol.32 No.10

We report the synthesis and gas sensing properties of bare and ZnO decorated TeO2 nanowires (NWs). A catalyst assisted-vapor-liquid-solid (VLS) growth method was used to synthesize TeO2 NWs and ZnO decoration was performed using an Au-catalyst assisted-VLS growth method followed by a subsequent heat treatment. Structural and morphological analyses using X-ray diffraction (XRD) and scanning/transmission electron microscopies, respectively, demonstrated the formation of bare and ZnO decorated TeO2 NWs with desired phase and morphology. NO2 gas sensing studies were performed at different temperatures ranging from 50 to 400 oC towards 50 ppm NO2 gas. The results obtained showed that both sensors had their best optimal sensing temperature at 350 oC, while ZnO decorated TeO2 NWs sensor showed much better sensitivity towards NO2 relative to a bare TeO2 NWs gas sensor. The reason for the enhanced sensing performance of the ZnO decorated TeO2 NWs sensor was attributed to the formation of ZnO (n)/ TeO2 (p) heterojunctions and the high intrinsic gas sensing properties of ZnO.

Structure and NO2 gas sensing properties of SnO2-core/In2O3-shell nanobelts

김현수,안소연,진창현,이종무 한국물리학회 2012 Current Applied Physics Vol.12 No.4

SnO2-core/In2O3-shell nanobelts were fabricated by a two-step process comprising thermal evaporation of Sn powders and sputter-deposition of In2O3. Transmission electron microscopy and X-ray diffraction analyses revealed that the core of a typical coreeshell nanobelt comprised a simple tetragonal-structured single crystal SnO2 and that the shell comprised an amorphous In2O3. Multiple networked SnO2-core/In2O3-shell nanobelt sensors showed the response of 5.35% at a NO2 concentration of 10 ppm at 300 ℃. This response value is more than three times larger than that of bare-SnO2 nanobelt sensors at the same NO2 concentration. The enhancement in the sensitivity of SnO2 nanobelts to NO2 gas by sheathing the nanobelts with In2O3 can be accounted for by the modulation of electron transport by the In2O3eIn2O3homojunction. SnO2-core/In2O3-shell nanobelts were fabricated by a two-step process comprising thermal evaporation of Sn powders and sputter-deposition of In2O3. Transmission electron microscopy and X-ray diffraction analyses revealed that the core of a typical coreeshell nanobelt comprised a simple tetragonal-structured single crystal SnO2 and that the shell comprised an amorphous In2O3. Multiple networked SnO2-core/In2O3-shell nanobelt sensors showed the response of 5.35% at a NO2 concentration of 10 ppm at 300 ℃. This response value is more than three times larger than that of bare-SnO2 nanobelt sensors at the same NO2 concentration. The enhancement in the sensitivity of SnO2 nanobelts to NO2 gas by sheathing the nanobelts with In2O3 can be accounted for by the modulation of electron transport by the In2O3eIn2O3homojunction.