| Human beings live in the gas environment.The detection of gas species and concentration plays an important role in environmental monitoring,industrial production,medical health,food safety and other aspects.Although a variety of gas sensing materials have been found,such as metal oxides,organic compounds,carbon materials and so on,their detection range is mainly at part per million(ppm)level,and often has the disadvantages of high working temperature,poor repeatability and low specificity.At present,at room temperature,the high sensitivity detection of ppb level gas is still a huge challenge.In this paper,a series of tin sulfide-based gas sensing materials were prepared by compounding tin sulfide with carbon and other materials,and using functional groups and quantum dots.These materials achieve high sensitivity and specificity detection of nitrogen dioxide and ammonia at ppb level at room temperature,and have great application prospects and commercial value in real-time remote medical monitoring,food corruption monitoring and other fields.In addition,the high-performance gas sensing mechanism of the prepared materials was studied by energy band theory gas adsorption theory and density functional theory.The specific research contents are as follows:(1)Three kinds of carbon materials(graphene,carbon nanotubes and biochar)were used as templates,and tin sulfide composites were grown in situ by hydrothermal method.The carbon material with higher carrier concentration provides a carrier migration path for tin sulfide material,which reduces the resistance of tin sulfide composite to M?level.Furthermore,the gas sensing properties of carbon/tin sulfide for ppb grade nitrogen dioxide at room temperature and the effect of light on the gas sensing properties were studied.The results show that carbon/tin sulfide materials have high sensitivity and specificity.In the experiment,the response in a wide detection range of25ppb to 1ppm is achieved.In addition,the wavelength and intensity of light are the main parameters affecting the gas sensing performance.In general,low light intensity has a better enhancement effect on the gas sensing performance,and the maximum enhancement effect on the sensitivity is 5.86 times.Under the red-light irradiation of1m W/cm2,the actual minimum detection line of graphene/tin sulfide material reaches10ppb.(2)Sulfonated graphene/tin sulfide(S-r GO/Sn S2)and tin sulfide quantum dots/graphene gas sensing materials were prepared.The sensitivity of S-r GO/Sn S2 to 125 ppb nitrogen dioxide and 1 ppm ammonia was 17%and 11%,respectively,and the performance remained stable in the relative humidity range of 30%to 90%.Under the action of ultrasound,the S-r GO/Sn S2 can be rapidly dispersed in ethanol solution.As a gas sensitive ink,it can keep stable for several hours.The ink can be directly written on glass,paper and cloth,and can maintain the response to nitrogen dioxide and ammonia even under bending and twisting conditions.Tin sulfide quantum dots/graphene realizes the dual function sensing properties to gas and light.For 1ppm nitrogen dioxide,the sensitivity is 860%,the response time and recovery time are 114s and 166s respectively,and for 450nm blue light,the optical response is 2.08×103 A/W.In addition,under the red-light irradiation of 1m W/cm2,the sensitivity of the sensor was increased by 5.1 times,and the actual minimum detection concentration reached 1ppb.First principles calculations show that the adsorption energy of graphene/tin sulfide composite for gas molecules is higher than that of single material.Energy band theory and gas adsorption theory explain the influence of light wavelength and intensity on gas adsorption rate and adsorption performance.(3)Using liquid metal flexible electrode,tin sulfide gas sensing material and Bluetooth transmission terminal,a human breathing detection device with wireless transmission function is prepared.The device utilizes the quick response performance of tin sulfide to water molecules to realize the real-time monitoring of normal breathing,deep breathing,rapid breathing,respiratory inhibition and other scenes.The high gas sensitivity of tin sulfide to nitric oxide and the different redox types of water and nitric oxide are used to realize the alarm function of high exhaled nitric oxide concentration.In addition,Cu3(HHTP)2(MOF)materials were grown in situ on tin sulfide substrate to construct MOF@Sn S2 PN heterostructure.Compared with the intrinsic MOF material,the sensitivity of the composite material to ammonia gas is increased by 4 times to the concentration range from 125ppb to 10ppm.The anti-interference of MOF material to other meat spoilage gases is improved.The device can monitor the degree of meat spoilage.Compared with the international standard Conway dish method,this method is fast and simple,and can be widely used in cold chain transportation,market meat sales,household and other aspects. |
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