Nano Titanium Dioxide Modified Quartz Crystal Microbalance Chemical Sensors

Because of real-time monitoring,simple equipment,easy operation,and low cost,sensor has gained considerable interest in analytical science.The research of normal piezoelectric quartz crystal (PQC)was carried out in earlier 1980's and had been widely applied in the fields of clinic immunology,hemorheology,biochemistry, molecular biology and material physical chemistry.The quality response of quartz crystal microbalance was used to investigate the adsorption behavior of nano-sized TiO₂ particles coating to Pb(â…¡),a lead ion chemistry sensor was established.The difference of adsorption and degeneration speed under ultraviolet illumination on nano-sized TiO₂ particles coating were discussed based on the butenedioic acids' spatial structure difference.The frequency shift of quartz crystal microbalance was also discussed at last under the supersonic vibration when the density and viscosity of the solution were changed.The results indicated that:(1)The best adsorption conditions of nano-sized TiO₂ to Pb(â…¡) were:pH=7,the thickness of TiO₂ coating was 0.4μm,the temperature was 20℃,the adsorption time was 10 minutes.A good linear relationship between the value of frequency shift and the concentration of Pb(â…¡)was obtained in the range of 2.04×10^-6～5.20×10^-8mol·L^-1 with the linear equationâ–³f=1.43-6.47C(r=0.9986),and the detection limit 6.85×10^-8mol·L^-1.The reproductive properties of the nano-sized TiO₂ particles coating were good and satisfactory when applied to the determination of trace lead in environmental water sample.(2)The butenedioic acids were adsorbed on the TiO₂ surface mainly by the static electricity function between their intramolecular carboxyl groups and the TiO₂ surface hydroxyl groups.The infrared spectrogram data indicated that surface coordination may occur through bridging bidentate carboxylates groups.Their adsorption equilibrium constants were 4×10³ L·mol^-1and 2.9×10³ L·mol^-1 respectively.The adsorption of nano-sized TiO₂ to butenedioic acids gradually weakened with the increase of pH.The degeneration rates of butenedioic acids were decreased with the increased pH when pH＜pzc(TiO₂)and rised with the increased pH when pH＞pzc(TiO₂).Also the maleic acid degeneration rate was bigger than the fumaric acid.(3)The ultrasonic wave had certain influence on the oscilation frequency of quartz crystal microbalance.The frequency of quartz crystal microbalance decreased with the density and the increased viscosity of the solution under the supersonic vibration.