Due to the difficulty in synthesizing perhalogenated metallophthalocyanine,the method of ammonium molybdate solid phase catalysis was introduced,and by using tetrachlorophthalic anhydride and urea as the raw materials,hexadecachloro zinc phthalocyanine(ZnPcCl16) was synthesized.Components of the composite were analyzed by energy spectrum,and its functional group structures and absorption peaks were characterized by IR and UV-vis spectroscopy.The thin films of gas sensors were prepared in a vacuum evaporation system and evaporated onto SiO2 substrates,where sensing electrodes were made by MEMS micromachining.The optimal conditions for the films are:substrate temperature of 150 ℃ evaporation current of 95 A and film thickness of 50 nm.The result showed that the sensors were ideally sensitive to Cl2 gas and could detect the minimum concentration of 0.3 ppm.
Aiming at detecting Cl2 gas,this study was made on how to make In-based compound semiconductor oxide gas sensor.The micro-property and sensitivity of In-based gas sensing material were analyzed and its gas sensitive mechanism was also discussed.Adopting constant temperature chemical coprecipitation,the compound oxides such as In-Nb,In-Cd and In-Mg were synthesized,respectively.The products were sintered at 600 ℃ and characterized by the Scanning Electron Microscope(SEM),showing the grain size almost about 50-60 nm.The test results show that the sensitivities of In-Nb,In-Cd and In-Mg materials under the concentration of 50 × 10-6 in Cl2 gas are above 100 times,4 times and 10 times,respectively.The response time of In-Nb,In-Cd and In-Mg materials is about 30,60 and 30 s,and the recovery time less than 2,10 and 2 min,respectively.Among them,the In-Nb material was found to have a relatively high conductivity and ideal sensitivity to Cl2 gas,which showed rather good selectivity and stability,and could detect the minimum concentration of 0.5 × 10-6 with the sensitivity of 2.2,and the upper limit concentration of 500 × 10-6.The power loss of the device is around 220 mW under the heating voltage of 3 V.
