Preparation of ZnO powders by hydrazine method and its sensitivity to C2H5OH

Abstract

ZnO nanopowders were synthesized by the sol-gel method using hydrazine reduction, and their gas responses to 6 gases (200 ppm of C2H5OH, CH3COCH3, H2, C3H8, 100 ppm of CO, and 5 ppm of NO2) were measured at 300 - 400°C. The prepared ZnO nanopowders showed high gas responses to C2H5OH and CH3COCH3 at 400°C. The sensing materials prepared at the compositions of [ZnCl2]: [N2H4]:[NaOH] = 1:1:1 and 1:2:2 showed particularly high gas responses (S = Ra/Rg, Ra: resistance in air, Rg: resistance in gas) to 200 ppm of C2H5OH(S = 102.8-160.7) and 200 ppm of CH3COCH3 (S = 72.6-166.2), while they showed low gas responses to H2, C3H8, CO, and NO2. The reason for high sensitivity to these 2 gases was discussed in relation to the reaction mechanism, oxidation state, surface area, and particle morphology of the sensing materials.