In-situ Formation Of Gold On Self-assembly Monodispcrsc Mesoporous Titania For Gas Sensors

Monitoring the concentration of harmful gases is a permanent requirement inmany fields of industrial processes as well as in our daily life. The semiconductingmetal oxide meterials are widely used for gas sensing. In the process of manufacturingwell-performed gas sensor, the reasonable preparation of sensitive materials is a keyto realize the gas sensor with low power consumption, high sensitivity, rapid responseand recovery.The mesoporous titania (TiO2) was prepared by using hexadecylamine (HDA) asstructure-directing agent, and then the gold nanoparticles (AuNPs) were incorporatedinto the mosoporous titania. The formation of Au0is based on the amino groupreduction of AuCl4-which attached on the precursory mesoporous titania. Theprepared Au NPs/TiO2nanocomposite (~10nm Au NPs) is stable after removingtemplates with calcination. Characterization reveals that after the AuNPs were formedon the walls of mesoporous TiO2beads, and the pore structure with a narrow pore sizedistribution (8-15nm) is well maintained by UV-visible Spectroscopy, Scanning andTransimission Electron Microscope, N2adsorption-desorption, and X-ray diffraction,The obtained AuNPs/TiO2nanocomposites gas sensing performance for ethanol, CO,NH3and other gases were tested, the result shows that the sensitivity of ethanolreached to5.65above600ppm at75oC, the response and recovery time were fast(t90≤20s), and the low detection limit (1ppm). In addition, it was found the changes ofconductivity of semiconductive oxides were opposite under different temperature, theAu NPs/TiO2was p-type for NH3gas under45℃, but they tend to be n-type atambient temperature. This slightly changes of temperature lead to the oppositetendency of conductivity, which is significance for the selective detection of NH3.In addition, Microelectronic sensor device are researched on Interdigitated arraymicroelectrodes (IDAM) semiconductor supported by previous research. Gas sensorsare manufactured by using variable microelectronic to achieve a useful sensing device.Therefore, the gas sensor is designed as a model based on MEMS technology, whichcombined with screen printing, magnetron sputtering et al. This mold included thecharacteristics, materials and design parameters (like number of electrodes, the width,et al.)of IDAM，discussed the principle and equivalent circuit of sensor. Additionally, the distribution of temperature and magnetic field on the device are simulated byAnsys software. From the research above, it could give us a very attractive sensingbehavior for applications as real-time monitoring gas sensors.