Study On Gas Sensors Based On Fluorescence Quenching Of ZnS Nanomaterials

Industrial production and living exhaust emissions have led to serious pollution, such as ozone depletion, acid rain, and greenhouse effect, etc. With the improvement of human safety and health awareness, monitoring for toxic gas is imminent in order to prevent the occurrence of safety accidents. At present, major threatening for the environment and human security is from sulfur compounds, such as H2 S and SO2, which have been largely concerned. Developing a low-cost, effective, highly sensitive, and portable semiconductor gas sensor to detect toxic gases is a new research direction.Nano-sensitive semiconductor material is applied to detect toxic gases in explosive environments because of its various advantages. ZnS as a wide-band-gap semiconductor material has good prospects in data storage, data conversion, gas sensors and UV-sensitive coating instruments. Ultrasound-assisted hydrothermal / solvothermal growth method is used to prepare the high-quality ZnS nanomaterials. Rare earth ion Eu can enhance the fluorescence emission of ZnS nanomaterials. Optical fiber gas sensor based on the fluorescence quenching mechanism can be achieved to detect H2 S, CO, NH3, alcohol, and so on. In this work, ZnS-based fiber-optic fluorescence quenching gas sensor has a strong stability, fast response, strong anti-jamming ability, which can be used to detect flammable toxic gases in the combustible and explosive environment and meet gas real-time monitoring. Specific studies are as follows:(1) The theoretical model of the optical sensor have been investigated and established. The optical systems, sensitive devices and the principle of the fluorescence quenching gas sensor have been analyzed.With the mathematical model of the non-uniform distribution gas sensor based on excitation quenching fluorescent mechanism.(2)The synthetic mechanism of ZnS nano-materials has been studied. ZnS Nano materials have been synthesized by the ultrasonic assisted hydrothermal / solvothermal method, Eu doped ZnS can largely enhance the luminescent properties, which helps to devise the sensitive sensor devices based on ZnS:Eu2+.(3) A fiber-optic fluorescence quenching gas sensor based on nano-ZnS sensitive material has been designed and used for gas detection. At the same time a simple homemade gas chamber based on sensitive components has been manufactured.(4) The fluorescence quenching fiber-optic sensing system, including Stellar Net company’s Blue-Wave(VIS25) miniature fiber optic spectrometer, two-way mixed gas device, iron sets, simple homemade gas chamber, and sensitive devices, etc., has been established.(5) The test gas H2 S is prepared flows into the gas chamber to check the sensitivity. The results have shown that fluorescent emission of ZnS: Eu2+ sensitive materials can be quickly and efficiently quenched by H2 S gas, which meets the fluorescence quenching theory(Stern-Volmer equation) within its linear range. The test characteristics and conditions under multi-component gases have a good selectivity for H2 S gas.