Study On The Sensitivity Of Noble Metal Modified Porous ZNO Composites To Benzene Gases

In recent years,with the rapid development of science and technology,the problem of environmental pollution is becoming more and more serious.There may be virulent noxious and flammable explosive gases in the surrounding environment,which potentially impact people's daily life and production activities.How to dealwith these harmful gases timely has caused people's great attention.Benzenes,as the important organic solvents,are widely used in solvent and essential raw materials of.building materials,household products,and industrial processes,so they generally exist in residential and industrial environments.Beonuse of the toxicity and carcinogenicity of benzenes gases,long-term exposure to these gases,even at a low concentration,will cause great harm to human health.Hence,detecting benzenes gases at a low concentration is an urgent task in the field of chemiresistive sensors.Up to now,many kinds of metal oxide semiconductors sensors are extensively investigated for the detection of benzenes.However,the benzenes are usually difficult to detect owning to the low reactivity and high activation energy.Hence,these sensors for benzenes gases detection are limited in some inherent drawbacks,including low sensitivity,high operating temperature,high detection limitation,long response and recovery times.Zinc oxide(ZnO)is a typical metal oxide semiconductor,there have been many reports about it as sensing material to detect benzenes.However,these difficult problems also exist in the research methods.In order to enhance the benzenes gases sensing performance,we have modified precious metal catalyst into ZnO material.(1)Noble metal Au nanoparticles chosen as the modifier,A porous Au/ZnO composite material is readily fabricated via a mild solvothermal process and simple thermal treatment.The as-synthesized products of Au/ZnO composite show enhanced sensing property towards benzenes.The sensor based on 1 wt.%Au/ZnO composite shows the highest response of 60 to 100 ppm benzene at a relatively low operating temperature(260?),which is five times higher than that of pure ZnO sensor.What's more,the sensor exhibits low detecting limit(0.5 ppm),short response and recovery times and good long-term stability.The enhanced sensing performance should be attributed to the catalytic ability of Au nanoparticles and the nano-Schottky type barriers.(2)Through the above preparation method,we prepare the Pt-ZnO composite microspheres,the trace amount of Pt also greatly enhances the sensing properties of ZnO towards benzene,toluene and xylene gases.The 0.1 wt%Pt-ZnO sensor gives the highest response value about 70 to 100 ppm benzene at an operating temperature of 250?.It is worth mentioning that a low detection limit of 100 ppb is achieved to meet the safety requirement of indoor benzene monitoring.The significantly improved gas sensing performances stem from the chemical contribution of Pt catalyst and the electronic sensitization(Schottky barrier,p-n junction)of Pt nanoparticles.