The nanocomposites of ZnO-SnO_2 and In_2O_3-SnO_2 were prepared by wet chemical co-precipitation method as a novel semiconductor gas sensing materials for the detection of environmentally toxic gases.Controlled preparation parameters were critical towards the grain size and crystallinity of the obtained nanocomposites.The results showed that these nanocomposites exhibited high sensitivity and selectivity for the detection of CO and NO_x,and the sensitivity depended on the composition of the composite,calcination temperature and operating temperature.The gas sensing properties of the sensors were further improved through incorporation of dopants and surface additives.The gas sensing mechanism was also discussed by X-ray photoelectron spectroscopic (XPS) and temperature-programmed desorption (TPD) studies.
Dianqing LiZhangfa TongXiaowei HuangShouli BaiRuixian Luo
The nanocomplex oxides of Sn-In and Sn-In-Ti were prepared by controlled co-precipitation method as sensing materials of semiconductor gas sensors for detection of CO, CH4 and NO2. Through manipulating the Sn/In cation ratio, metal salt total concentration, precipitation pH value and aging time, the nanocrystalline powders were successfully derived with chemical homogeneity and superior thermal stability, compared with the single component oxides. The particle size and morphology, surface area, and thermal and phase stabilities were characterized using TEM, TG-DTA, BET and XRD. The sensing tests showed that the Sn-In com-posites exhibit high sensitivity and selectivity for CO and NO2. The introduction of TiO2 enhanced CH4 sensitivity and selectivity, particularly, additives of Pd and Al2O3 as a dopant and surface modification greatly enhanced the sensing properties. The sensitivity depended on the composition of composites, calcination temperature and operating temperature. The optimal values were (25%In2O3- 75%SnO2)-20%TiO2 for ternary composite, 600 and 300℃, respectively. Temperature-programmed de-sorption (TPD) studies were employed to explain the gas adsorption behavior dis-played by the surface of nanocomposites and X-ray photoelectron spectroscopic (XPS) analysis was used to confirm the electronic interactions existing between oxide components. The sensing mechanism of the nanocomposites was attributed to chemical and electronic synergistic effects.
BAI ShouLi1, TONG ZhangFa2, LI DianQing1, HUANG XiaoWei3, LUO RuiXian1 & CHEN AiFan1 1 State Key Laboratory of Chemical Resource Engineering, Beijing University of Chemical Technology, Beijing 100029, China
