Gas Sensitivity Of Cerium And Silver Doped Tin Oxide Single Nanobelts

Nanomaterials with particular structures have special physical and chemical properties such as small size effect, surface effect, quantum effect, macroscopic quantum tunneling effect, etc. As a result they are widely used in gas sensors. SnO₂ is one of the important metal oxide semiconductors and employed in gas sensitive field, which can be widely used to detect various toxic, flammable, explosive gases. Nowadays, many methods have been developed to prepare nanophases with various morphology and large specific surface area, which contribute to enhance the contact area between nanomaterials and target gases. Consequently the gas sensing properties have been improved. The researched results show that doping of rare earth or noble metals can effectively enhance the response and selectivity of the gas sensors. Therefore, in this paper Ce-SnO₂ nanobelts（NBs） and Ag-SnO₂ NBs have been prepared by simple thermal evaporation, and the single Ce-SnO₂ NB and Ag-SnO₂ NB devices have been designed and fabricated. Then the gas sensing properties have been measured systematically so that it is favorable to develop gas sensors with high response and sensitivity to ethanol or other volatile poisonous liquids, which can improve the detection and monitoring ability.Firstly, pure SnO₂ NBs have been synthesized in the vacuum tube furnace. The morphology, microstructure and elemental composition of the NBs have been characterized by scanning electron microscope（SEM）, transmission electron microscopy（TEM）, high-resolution transmission electron microscope（HRTEM）, X-ray diffraction（XRD）, energy dispersive X-ray spectrometer（EDS）, and X-ray photoelectron spectroscopy（XPS）. After that, nanobelts with great morphology have been selected to develop single nanodevices and then their gas sensitive properties have been studied. It is found that the optimum operating temperature of the single SnO₂ nanobelt device to ethanol, acetone, formaldehyde, ethanediol, and carbon monoxide is 230 °C, and the response of it to 100 ppm of ethanol is 3.3.Secondly, the Ce-doped SnO₂ NBs have been prepared at the same condition. The results revealed that the width of the NBs becomes larger obviously, and the Ce-doped SnO₂ NBs consist of Sn, O, Ce; Ce has entered into the SnO₂ lattice with Ce3+ ion. Afer measurements of the above mentioned five gases, it is found that the optimum temperature of the Ce-doped SnO₂ NB sensor is 230 °C. The response of it to 100 ppm of ethanol is 8.4, which is about 2.6 times as large as that of its pure one. Besides, the responses of it to 100 ppm of acetone, formaldehyde, ethanediol, and carbon monoxide are 3.32, 2.03, 1.97, and 1.21, respectively. The calculated theoretical detection limit of the Ce-SnO₂ NB sensor to ethanol is 156 ppb. The experiments have also revealed that the humidity has little influence on the response.In addition, Ag-doped SnO₂ NBs have been obtained and their structures have been characterized. The optimum working temperature of the device to acetone, ethanol, formaldehyde, ethanediol, and carbon monoxide is 220 °C, and the response of the Ag-SnO₂ NB to 100 ppm of acetone is 7.6, 2.38 times as large as that of pure one. The responses of Ag-doped SnO₂ NB to 100 ppm of ethanol, formaldehyde, ethanediol, and carbon monoxide are 3.5, 1.67, 1.78, and 1.2 respectively. Doping of Ag indeed promotes the response of the device to acetone.Finally, we summarized the studied work, and compared the performance of the doped two gas sensors. As potential applications, the two sensors can be extended to detect ethanol and acetone, respectively.