Preparation And Gas-sensing Characterization Of Nano Sno₂, Tio₂ And Its Composite Materials

It is well known that nano-metal oxide SnO₂ and TiO₂ are wide band semiconductor funational material.They have attracted people's attention as a new type of gas sensitive material.There are a lot of researches reports on the SnO₂ and TiO₂ as the reduction of gas detection sensor,but the reports of nano TiO₂-SnO₂ composite material as sensing material to detect volatile organic compounds(VOCs) is still relatively rare.Semiconductor nano-SnO₂ and TiO₂ metal oxides and TiO₂-SnO₂ composite were systemic studied in this paper.TiO₂,SnO₂-based sensitive materials doped by metal ions and different ratio of TiO₂-SnO₂ composite materials were prepared and their gas sensing performances of for VOCs were investigated.Then the mechanism of the sensitivity was analyzed using Materials Studio software and quantitative calculation software Gaussian03.The results are as follows:(1) The crystal structure of TiO₂ is anatase,the diameter of the particle is between 20nm and 25nm;the crystal structure of SnO₂ is rutile,the diameter of the particle is 30nm.Metal-doping being replacement doping does not change the structure of nano-SnO₂ and TiO₂.TiO₂-SnO₂ composite material contains the anatase TiO₂ and the rutile SnO₂,the diameter of the particles are between 10nm and 20nm,and the size of the particles decrease with the volume of TiO₂ increasing.(2) The gas sensing of the TiO₂ and SnO₂ is improved by adding metallic irons;the sensitivity is remarkably enhanced by adding Ag⁺;and its sensitivity to ethanol gas can reach 120.Sensitivity of SnO₂ can be improved by adding TiO₂,and the TiO₂-SnO₂ sensor is preferably selective for VOCs such as methanol,ethanol,acetone and formaldehyde at different working temperatures.In addition,the resistance and the sensing temperature of TiO₂-SnO₂ sensor is significantly lower than TiO₂-based and SnO₂-based sensors.(3) Some doping bands are brought into being between the band gap of SnO₂ by doping TiO₂.Doping the SnO₂ by TiO₂ makes the conductance bands of SnO₂ towards low energy,gets the conductivity of TiO₂-SnO₂ composite materials increase and the resistance reduce,and causes the working temperature decrease.The TiO₂-SnO₂ sensor shows selectivity at different temperatures,which is related to the ability of gas molecules to capture electrons.The sensitivity temperature of different kinds of gas changes just the same as the changes of gas molecules energy.The result shows that TiO₂-SnO₂ composites have good sensitivity for volatile organic gases.The TiO₂-SnO₂ composites are great potential sensitive materials,but the selectivity and stability of materials need to be improved.It hopes that the work being done can be helpful for future researches.