EPR and DRS evidence for NO2 sensing in Al-doped ZnO

Abstract Zinc oxide (ZnO) is a well-known semiconducting multifunctional material wherein properties right from the morphology to gas sensitivity can be tailor-made by doping or surface modification. Aluminum (Al)-incorporated porous zinc oxide (Al:ZnO) exhibits good response towards NO 2 at low-operating temperature. The NO 2 gas concentration as low as 20 ppm exhibits S  = 17% for 5 wt.% Al-incorporated ZnO. The NO 2 response increases with operating temperature and concentration and reaches to its maximum at 300 °C without any interference from other gases such as SO 3 , HCl, LPG and alcohol. Physico-chemical characterization likes differential thermogravimetric analysis (TG-DTA) electron paramagnetic resonance (EPR) and diffused reflectance spectroscopy (DRS) have been used to understand the sensing behavior for pure and Al-incorporated ZnO. The TG-DTA depicts formation of ZnO phase at 287 °C. The EPR study reveals distinct variation for O − ( g  = 2.003) and Zn interstitial ( g  = 1.98) defect sites in pure and Al:ZnO. The DRS studies elucidate signature of adsorbed NO x species in aluminium-incorporated zinc oxide indicating its tendency to adsorb these species even at low temperatures. This paper is an attempt to correlate the gas sensing behavior with the physico-chemical studies such as EPR and DRS.

[1]  S. Kawi,et al.  Synthesis, characterization and sensing application of novel semiconductor oxides. , 1998, Talanta.

[2]  Chandrakant D. Lokhande,et al.  LPG sensing properties of ZnO films prepared by spray pyrolysis method : Effect of molarity of precursor solution , 2007 .

[3]  张哉根,et al.  Leu-M , 1991 .

[4]  S K Gupta,et al.  NH3 gas sensing properties of nanocrystalline ZnO based thick films. , 2006, Analytica chimica acta.

[5]  C. Rao,et al.  Gas-sensing characteristics of ZnO and copper-impregnated ZnO , 1991 .

[6]  S. Dhage,et al.  Influence of various donors on nonlinear I–V characteristics of tin dioxide ceramics , 2003 .

[7]  S. Gosavi,et al.  Low temperature synthesis and NOx sensing properties of nanostructured Al-doped ZnO , 2007 .

[8]  Yang-Kyu Choi,et al.  Chemical sensors based on nanostructured materials , 2007 .

[9]  M. Vlasova,et al.  Electron Paramagnetic Resonance in the Research of Defect Formation and Thermal Processes During Grinding of ZnO Powders , 2004 .

[10]  K. Hadjiivanov.  Identification of Neutral and Charged N x O y Surface Species by IR Spectroscopy , 2000 .

[11]  H. Morkoç,et al.  A COMPREHENSIVE REVIEW OF ZNO MATERIALS AND DEVICES , 2005 .

[12]  Min-Hsiung Hon,et al.  The effects of thickness and operation temperature on ZnO:Al thin film CO gas sensor , 2002 .

[13]  S. Shishiyanu,et al.  Sensing characteristics of tin-doped ZnO thin films as NO2 gas sensor , 2005 .

[14]  R. P. Gupta,et al.  Oxide Materials for Development of Integrated Gas Sensors—A Comprehensive Review , 2004 .

[15]  N. Yamazoe,et al.  Oxide Semiconductor Gas Sensors , 2003 .

[16]  K. Vijayamohanan,et al.  Hydrocarbon Sensing Mechanism of Surface Ruthenated Tin Oxide: An In Situ IR, ESR, and Adsorption Kinetics Study , 2001 .

[17]  N. Ramgir,et al.  A room temperature nitric oxide sensor actualized from Ru-doped SnO2 nanowires , 2005 .

[18]  U. Lee,et al.  Properties of self-assembled ZnO nanostructures , 2002 .

[19]  G. Rao,et al.  Gas sensitivity of ZnO based thick film sensor to NH3 at room temperature , 1999 .