Preparation And Properties Of ZnO@ZIF-71(?)Ag Nanorods Array Gas Sensor

Hydrogen is a very common gas,and has been widely used in many fields,especially in the field of energy.In addition,with the increasingly serious problems of environment and energy,traditional fossil fuels have been unable to meet people's needs.And that makes hydrogen energy,which represents a clean,efficient energy source,even more important.Compared to other combustible gases and vapors,such as methane,propane,or gasoline vapor,hydrogen has a number of unusual properties.Especially as a colorless and odorless flammable gas,it cannot be directly felt by human senses,which makes hydrogen leak more likely to produce an explosion and impedes its development as a new type of energy.This is an urgent problem to be solved.Rapid and accurate measurement of hydrogen concentration can effectively avoid the risk of hydrogen explosion.Among the hydrogen gas sensors used today,metal oxide semiconductor gas sensor(MOS)has become the first choice because of its advantages of convenient operation,low cost and good stability.MOS(Metal Oxide Semiconductor)uses the interaction between the surface of the gas to be measured and the Semiconductor material in the process of absorption and desorption to cause the change of charge carriers.The migration of these electrons and holes will generate the change of the resistance of the semiconductor material,eventually resulting in the fulfillment of detection by converting the gas signal into electrical one.Detection is implemented.Among many metal oxide semiconductor materials,ZnO has a long history and a relatively mature process,and has been favored by researchers because of its high conduction electron mobility and good stability.Thus,new research contents have been derived continuously,accompanied by a series of achievements.At the same time,in recent years,MOF(Metal Organic Frameworks)has been greatly developed.Due to its porous structure,large specific surface area and so on,which meet the relevant requirements of gas sensitive exactly,the preparation of MOS@MOF materials has become a research direction of concern by way of combining MOF with the traditional gas sensitive materials.Meanwhile,a series of achievements have been made in encapsulating precious metal nanoparticles in MOF materials.But the exploration of MOS@MOF nanoparticle encapsulation is relatively rare.In this paper,ZnO nanorod arrays were prepared according to a relatively mature process.First,ZnO crystal seed solution was coated on the ceramic plate with electrode to form a crystal seed layer.Finally,the deposition-reduction method was used to encapsulate silver particles.Namely,Ag+ was pressed into the frame by osmotic pressure,followed by the silver ions being reduced to nanoparticles by reducing agents.The nanorods were coated with a layer of ZIF-71 material by hydrothermal method.Then,the deposition-reduction method was used to encapsulate silver particles.Ag+ was first pressed into the frame by osmotic pressure,and then the silver ions were reduced to silver nanoparticles by reducing agents.The results of related characterization showed that the rod-like structure of ZnO nanorods coated by ZIF-71 was formed by this method,and the Ag was encapsulated in the pores of ZIF-71.Gas sensitivity test results indicate that the selectivity of hydrogen of the sensor has been significantly improved by encapsulating Ag in it,accompanied by high sensitivity with a minimum detection limit of 100 ppb.The improvement of selectivity is due to the adjustment of the pores of ZIF-71 by Ag nanoparticles,which makes it impossible for large gas molecules to pass through and blocks out the gas molecules with strong interference.However,small gas molecules such as hydrogen can contact the surface of ZnO nanorods through the interstices to produce a response.At the same time,due to the catalytic action of Ag nanoparticles,the sensitivity is also improved to a certain extent.This provides a new idea for the doping modification of MOS@MOF material,and also broadens the road for the practical application of this type of sensor.