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Metal oxide nanowires chemical sensors for security application

Elisabetta Comini 1Guido Faglia Matteo Ferroni Andrea Ponzoni Giorgio Sberveglieri 

1. SENSOR, CNR-INFM, Brescia University (SENSOR), via valotti 9, Brescia 25136, Italy

Abstract

Increasing concern on health hazard due to pollution or terrorist attacks encouraged an increasing research effort on gas sensing for real-time monitoring of all aspects of indoor and outdoor environments. Industrial requirements for a sensor are high sensitivity, high selectivity and good stability, together with low fabrication costs.

Among all possible technological approaches, conductometric gas sensors based on metal oxide semiconductors are the most promising for the development of low cost and reliable sensors. It has been confirmed that the sensitivity of metal oxide is improved as the crystallite size is decreased down to nanometer scale, thanks to the increased surface to volume ratio and the grains carriers’ depletion. Unfortunately polycrystalline metal oxides suffer from grain coalescence induced by the high operating temperatures required to enhance chemical reactions. This affects sensor stability over long-term operation. On the contrary single crystalline nanosized metal oxide are stable materials and have the dimensions and surface to volume ratio necessary to obtain high chemical sensitivity. The better stoichiometry and greater crystallinity degree compared to polycrystalline oxides make these materials very promising for a better understanding of sensing principles and the development of a new generation of chemical sensors.

After the first publication demonstrating the capability of nanowires to detect gaseous species, huge research activity was carried out as demonstrated by the high number of publications and conferences on this topic. The challenge is the integration into sensing platforms necessary for the exploitation in the sensor market. Concerning gas sensing application metal oxide nanowires demonstrate performace suited to detect chemical warfare agents (CWAs) simulants at concentrations close or lower than the toxicity values of the real CWAs. 

 

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Related papers

Presentation: Invited oral at E-MRS Fall Meeting 2009, Symposium F, by Elisabetta Comini
See On-line Journal of E-MRS Fall Meeting 2009

Submitted: 2009-05-11 10:59
Revised:   2009-06-07 00:48