Metal Modification And Gas Sensing Properties Of Nano TiO₂

Titanium dioxide,as typical n-type semiconductor,owing to its manifold characteristics like low cost,non-toxic and pollution-free,high sensitivity,and wide operating temperature range,have attracted extensive attention for gas sensing applications.However,dracbacks of poor selectivity and insufficient stability have limited its practical application as a gas sensor.Accepted strategies to improve the gas-sensitive performance of TiO₂ are mainly morphology control and metal-assisted modification.In this paper,nano TiO₂ was synthesized by sol-gel and hydrothermal method and the sensing performance was improved via metal dopand and modification.Based on the previous literature research and preliminary experimental exploration,the research was carried out into two parts:(1)Sol-gel route is adopted to facilely synthesize powders containing TiO₂ nanoparticles with chromium(0-10 mol%)surface modification and the structure and morphology of synthesized nanoparticles were analysed.The p-type response of pure TiO₂ toward H₂gas at elevated temperature(300-500°C)results from the formation of inversion layer.Despite lower response values,the Cr modified TiO₂ based samples show stability and non-drift in baseline resistance at high temperature.(2)This report also demonstrates a facile one-pot hydrothermal method to synthesize porous TiO₂ nanoparticles modified with sliver(0-5 mol%).The gas sensing performance of the sensors is investigated by testing their gas response to acetone,which is proved of highly effective for sensor applications.For instance,the sensor based on 2 mol%Ag-TiO₂ showed high response(S_R?13.9),fast response(11 s)and recovery(14s)time,good long-term stability and good selectivity to toward 100 ppm acetone against other VOCs.In our case,we believe that the response enhancement is dominated by the electronic sensitization,as the resistance of the TiO₂(R_air?465 M?)sensor is higher that Ag modified TiO₂(R_air?133 M?).