Synthesis And Properties Study Of Gas Sensors For Toxic Gases Such As H₂S

In order to adapt to the increasingly stringent requirements in the industrial environment nowadays,the sensors with high property,low cost and good stability,which are used in detecting the environment,have received wide attention.In varies of toxic gases,H₂S gas is widely distributed in daily life,very toxic and valuable in industry.Therefore,this article regards it as the key research object,know and master its basic property to prepare varies H₂S gas sensor with good sensing property.The research can be divided into four main parts:Firstly,from the previous scientific research,we know and master the basic property of H₂S gas,and then we choose the suitable materials as the sensing films.The article chose CuO as sensing materials,due to their wide contribution,stable properties and low cost.Secondly,refer to relevant literatures,we know and master the mechanism and preparation of varies kinds of sensors in order to choose the suitable sensor.The key points of this article are impedance sensors and surface acoustic wave?SAW?sensors.And we have prepared these two kinds of H₂S sensors with good properties.Thirdly,the sensing film of impedance sensors was synthesized by a method combining a hydrothermal reducing process and a thermal oxidation process.Octadecylene was used as solvent to dissolve copper chloride dehydrate powder in alkaline environment.Copper oxide powder with"grape"nanostructure can be obtained by washing and drying the solution.The sensor based on this special CuO powder showed outstanding selectivity and high sensitivity to H₂S gas,and achieved a ppb level detection limit.In addition,the temperature and humidity was also found to be significantly influential on the sensitivity of the sensor.Fourthly,the core of SAW sensors is also the sensitive film.Due to particularity of SAW sensors'selecting frequency,the previous CuO cannot satisfy the requirements and we need a new kind of CuO.Porous and nanoparticulate CuO films were obtained through a sol–gel process.Surface acoustic wave?SAW?sensors based these films were explored for H₂S detection operated at room temperature.The SAW sensor showed a negative frequency shift when exposed to H₂S gas,mainly due to the mass loading effect on the sensitive CuO film.It has a high sensitivity of H₂S,a detection limit of 500ppb and a good selectivity to H₂S gas.For the first time,we found that the responses became much faster and stronger with the increase of RH.The significant enhancement in the sensing performance is attributed to that the chemical reaction between H₂S and CuO is hindered and the physical adsorption of CuO to H₂S is enhanced.Besides,the sensor showed good selectivity and reproducibility.