Elsevier

Sensors and Actuators B: Chemical

Volume 186, September 2013, Pages 103-108
Sensors and Actuators B: Chemical

Giant Chemo-Resistance of SnO disk-like structures

https://doi.org/10.1016/j.snb.2013.05.087Get rights and content

Abstract

Single crystalline SnO micro-disks, synthesized by a carbothermal reduction process, exhibited a nearly 1000-fold increase in resistance upon exposure to 100 ppm of NO2 without addition of catalysts or dopants nor the existence of nano-sized dimensions. Moreover, the SnO displayed a greater than 100-fold selectivity to NO2 over potential interferents including CO, H2 and CH4. The high sensor signal and exceptional selectivity for this novel sensor material are attributed to the existence of a high density of active lone pair electrons on the exposed (0 0 1) planes of the single crystalline SnO disks. This, thereby, identifies new means, not utilizing nano-dimensions, to achieve high gas sensitivity.

Introduction

The increase in harmful gas emissions and the resultant threat to public health, particularly in urban environments, has stimulated research aimed at the development of highly sensitive and selective gas sensors suitable for air-quality monitoring [1]. NOx, CO, H2S are considered particularly harmful to public health, even at low concentrations, given their negative impact on the human respiratory system [2], [3]. Detection of these pollutant gases at ppm and ppb levels, with high sensitivity and selectivity, remains a major challenge [4]. While there are a number of means for detecting gases based on optical, gravimetric and electrical approaches, those based on monitoring changes in resistance of semiconducting oxides upon surface adsorption/desorption of gases (chemoresistance) offer key advantages including low cost processing, simple design and measurement, coupled with relatively high sensitivity [5], [6], [7], [8], [9]. SnO2 has been the most highly investigated material in this class of sensors [10]. This has included investigation of different fabrication approaches to form thin films [11], nano [12], [13], [14], mesoporous [15], and macroporous structures [16], [17], as well as the impact of various catalysts and dopants on sensor response [18], [19], [20]. To achieve higher sensitivity and selectivity, more complex multilayered and metal functionalized structures based on SnO2 have been reported [21], [22], [23]. Despite these efforts, it has been difficult to obtain simple devices which combine high sensitivity and selectivity with long-term stability.

While SnO2 is one of most studied materials for gas sensors applications, to the best of our knowledge, no sensor response has been reported for tin monoxide, SnO. This is not surprising given the difficulty in synthesizing this phase and its thermal decomposition at temperatures above 400 °C [24], [25]. SnO is reportedly a p-type semiconductor with a tetragonal litharge (alpha lead monoxide) structure, layered in [0 0 1] direction and a band gap between 2.5 and 3.0 eV [26], [27]. Recently, we have successfully synthesized SnO structures by a carbothermal reduction method, displaying both thermal and chemical stability for temperatures below 400 °C [25], [28]. In this work, we report, for the first time, the gas sensor properties of SnO disk-like structures. As demonstrated below, these disk-like structures exhibit nearly three orders of magnitude change in resistance upon exposure to nitrogen dioxide gas at temperatures below that typical for oxide chemiresistors. The observation of “Giant Chemo-Resistance” (GCR) in SnO, not dependent on nanosize dimensions, we believe, opens up a new class of promising materials with exceptional gas sensor capabilities and unique surface chemistry.

Section snippets

Experimental

Disk-like structures were synthesized by a carbothermal reduction method using SnO2 powder (Sigma–Aldrich, 99.9% purity) and carbon black (Union Carbide, >99% purity) in the molar ratio of 1.5:1(SnO2:C). Optimized parameters used and details of this synthesis were previously reported [29]. Following synthesis, a dark wool-like material was removed from the inner walls of the alumina tube which had been maintained at a temperature between 350 and 450 °C. Both SnO nanobelts and disk-like

Results and discussion

Fig. 1 presents FEG-SEM images of the collected material, following separation by sedimentation, showing it to be predominantly composed of disk-like structures with flat and smooth surfaces. These disks have diameters ranging from about 100 nm up to dozens of micrometers. The smaller disks (in general, disks less than 1 μm diameter – Fig. 1b) exhibit an octagon-like faceted shape, while the larger disks are nearly perfectly circular in shape (Fig. 1c). Most disks have diameters greater than 1 μm

Conclusions

Using the carbothermal reduction process, it was possible to obtain temperature and chemically stable SnO submicron and micron sized disk-like structures. The SnO disk-like single crystalline structures exhibit an exceptionally high sensitivity to NO2 with the highest sensor signal observed at 200 °C. At this temperature, sensor signal approaching ∼1000 were observed for sensors exposed to 100 ppm NO2. Furthermore, exceptional selectivity against potential interferent gases such as H2, CO and CH4

Acknowledgements

The authors acknowledge the São Paulo Research Foundation (FAPESP) (Procs. 2009/13491-7 and 2010/51959-8), and The National Council for Scientific and Technological Development (CNPq) (Proc. 200703/2011-3) for financial support to the seed project of international MIT/BRAZIL cooperation. TEM and FEG-SEM facilities were provided by the IQ-UNESP. The authors also wish to acknowledge the Brazilian Synchrotron Laboratory for XANES facilities at XAFS2 beamline (proposal 14553) and Prof. Elson Longo

Pedro H. Suman received his degree in Physics from the São Paulo State University (2009) and his Master degree in Materials Science and Technology also from São Paulo State University (2012). He is currently a PhD student at São Paulo State University under supervision of Prof. Marcelo O. Orlandi. His research interest is mainly about the synthesis and application of semiconductor nanostructured materials for gas sensors.

References (44)

  • Z. Ling et al.

    NO2 sensitivity of a heterojunction sensor based on WO3 and doped SnO2

    Journal of European Ceramic Society

    (2003)
  • M.K. Verma et al.

    A highly sensitive SnO2–CuO multilayered sensor structure for detection of H2S gas

    Sensors and Actuators B: Chemical

    (2012)
  • H.W. Ha et al.

    Improvement of electrochemical performance of tin dioxide negative electrode materials upon cobalt substitution

    Electrochimica Acta

    (2010)
  • C. Xu et al.

    Grain-size effects on gas sensitivity of porous SnO2-based elements

    Sensors and Actuators B: Chemical

    (1991)
  • D. Le Bellac et al.

    Electronic lone pair localization and electrostatic energy calculations: application to α-PbO, SnO, Pb1−x(TiO)xO, Pb3O4, Pb3(V,P)2O8, and a BiSrCaCuO-type superconductor

    Journal of Solid State Chemistry

    (1995)
  • N.O. Korolkoff

    Survey of toxic gas sensors and monitoring systems

    Solid State Technology

    (1989)
  • G. Weinmayr et al.

    Short-Term effects of PM10 and NO2 on respiratory health among children with asthma or asthma-like symptoms: a systematic review and meta-analysis

    Environmental Health Perspectives

    (2010)
  • S.J. Kim et al.

    Ultrasensitive and selective C2H5OH sensors using Rh-loaded In2O3 hollow spheres

    Journal of Materials Chemistry

    (2011)
  • I.-D. Kim et al.

    Ultrasensitive chemiresistors based on electrospun TiO2 nanofibers

    Nano Letters

    (2006)
  • Search on Web of Science® reveals over 1400 articles discussing SnO2-based gas...
  • X. Han et al.

    Synthesis of tin dioxide octahedral nanoparticles with exposed high-energy {2 2 1} facets and enhanced gas-sensing properties

    Angewandte Chemie International Edition

    (2009)
  • H.-C. Chiu et al.

    Hydrothermal synthesis of SnO2 nanoparticles and their gas-sensing of alcohol

    Journal of Physical Chemistry C

    (2007)
  • Cited by (30)

    • Shape-controlled SnO and their improved properties in the field of gas sensor, photocatalysis, and lithium-ion battery

      2022, Sensors and Actuators B: Chemical
      Citation Excerpt :

      The results show that in the range of 100 – 1000 ppb, the response continues to rise rapidly in an approximately linear manner, indicating a good linear correlation (Fig. 3b). Among them, the MDL of the square frame sensor is 5 ppb, much lower than other previous reports (e.g. 1 ppm) [8,10,11]. When exposed to 1 ppm NO2 gas, the responses of all gas sensors are 48%, 64%, 71%, 281%, 35%, 31%, respectively (Fig. 3c).

    • Shape-controlled and stable hollow frame structures of SnO and their highly sensitive NO<inf>2</inf> gas sensing

      2021, Sensors and Actuators, B: Chemical
      Citation Excerpt :

      In addition, the effects of other experimental parameters (such as reaction temperature and time) on the morphology evolution of SnO were also investigated systematically, as shown in Figs. 6 and S9. As previously reported, Orlandi et al. have shown that SnO has an exceptional selectivity to NO2 gas due to the existence that a high density of active lone pair electrons on the exposed (001) planes the single crystalline SnO disks [20]. We studied the dynamic response of SnO sensors based on convex corner quadrilateral-, square- and octagonal hollow frames to different NO2 concentrations, respectively, as shown in Fig. 7.

    • Investigation of electronic and chemical sensitization effects promoted by Pt and Pd nanoparticles on single-crystalline SnO nanobelt-based gas sensors

      2019, Sensors and Actuators, B: Chemical
      Citation Excerpt :

      It is obvious from these results that metal-decorated SnO nanobelt sensors exhibit lower sensor response to NO2 than pristine devices. Gas sensing studies with 1D SnOx (x<2) materials are relatively new, but it has been proposed that NO2 molecules trap electrons at the SnO surface, increasing the depletion layer and, consequently, the material’s resistance [21,23]. For metal-decorated sensors, electronic effects, such as electron depleted zones induced around nanoparticles and/or potential barriers introduced by heterojunctions, work in competition with the NO2 trapping electron sensing mechanism, resulting in an inhibition of the sensor signal.

    View all citing articles on Scopus

    Pedro H. Suman received his degree in Physics from the São Paulo State University (2009) and his Master degree in Materials Science and Technology also from São Paulo State University (2012). He is currently a PhD student at São Paulo State University under supervision of Prof. Marcelo O. Orlandi. His research interest is mainly about the synthesis and application of semiconductor nanostructured materials for gas sensors.

    Anderson A. Felix received his physics undergraduate degree (2006) and master science degree in materials science (2009) from Faculty of Engineering at São Paulo State University. He has been a PhD Student in Chemistry Institute at São Paulo State University. At present he is working with Prof. Harry L. Tuller as a visiting student at the Department of Materials Science and Engineering at MIT. His research interests are centered mainly in the fields of novel nanomaterial architectures for application as chemical sensors.

    Harry L. Tuller received his S.B. and S.M. degrees in electrical engineering and his EngScD in solid state science and engineering from Columbia University in New York. He is a member of the faculty of the Department of Materials Science and Engineering at MIT, where he serves as professor of ceramics and electronic materials and director of the Crystal Physics and Electroceramics Laboratory. Dr. Tuller's current research emphasizes the integration of sensor and actuator materials into microelectromechanical (MEMS) and microphotonic systems and the modeling, processing, characterization and optimization of solid state ionic devices (sensors, batteries, fuel cells). He has published over 370 articles, coedited 15 books and been awarded 26 patents. Dr. Tuller is editor-in-chief of the Journal of Electroceramics and series editor of Electronic Materials: Science and Technology, Springer Academic Publishers. He is a fellow of the American Ceramic Society, recipient of Fulbright and von Humboldt Awards and former holder of the Sumitomo Electric Industries Faculty Chair at MIT. Dr. Tuller was awarded Docteur Honoris Causa (2004), for life-long contributions to the field of electroceramics by the University of Provence, Marseilles, France and Docteur Honoris Causa (2009) from the University of Oulu, Finland. Dr. Tuller is co-founder of Boston MicroSystems Inc., a pioneer in the design and fabrication of harsh environment compatible micromachined Si and SiC-based sensor arrays.

    José A. Varela is graduated in Physics from University of São Paulo (1968), and received his Master Degree in Physics from Technological Institute of Aeronautics (1975) both in Brazil. He received PhD in Materials Science from University of Washington, Seattle, WA, USA in1981. He has been Professor at São Paulo State University – UNESP, Brazil since 1983. His main research interests are microwave assisted hydrothermal synthesis of inorganic materials as well as ceramic thin films chemical and physical deposition for applications including ferroelectrics, varistors, electro-optical and sensors.

    Marcelo O. Orlandi is physicist with PhD in Material Science and Engineering field by Federal University of São Carlos (2005). He has a professor position at São Paulo State University (UNESP) since 2006. In the last few years the main focus of Dr. Orlandi research has been the controllable growth and modeling of nanomaterials and the sensor response of nanomaterials. Other areas of interest are transport in nanomaterials and electron microscopy.

    View full text