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Vol. 93, Issue 6, June 2008, pp. 82-91




CuO-modified WO3 Sensor for the Detection of a ppm Level H2S Gas at Room Temperature



Nano-Materials Research Lab, Pratap College, Amalner, 425 401, India

*Corresponding author Tel.: +91-02587-224226

E-mail: lapresearch@rediffmail.com



Received:  13 May 2008   /Accepted: 24 June 2008   /Published: 30 June 2008


Abstract: Thick films of pure WO3 were prepared by screen-printing technique. The films were modified with Cu2+ by dipping them into an aqueous solution of copper chloride for different intervals of time and fired at 5500C for 30 min. The copper chloride would be transformed upon firing into copper oxide. The p-type CuO grains around n-type WO3 grains would form n- WO3/p-CuO heterojunctions. Upon exposure to H2S gas, the barrier height of n- WO3/p-CuO heterojunctions decreases markedly due to the chemical transformation of p-CuO into well conducting Cu2S, leading to a drastic change in resistance. These sensors were observed to operate at room temperature. An exceptional sensitivity was found to low concentrations (below threshold limit value = 10 ppm) of H2S gas at room temperature, and no cross sensitivity was observed even to high concentrations of other hazardous and polluting gases. The efforts have, therefore, been made to develop the heterocontact type gas sensor based on tin oxide surface-modified with cupric oxide. The effects of microstructure and surfactant concentration on the sensitivity, selectivity, response and recovery of the sensor in the presence of H2S gas were studied and discussed.


Keywords: WO3, Heterojunctions, Thick film, Room temperature gas sensor


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