Fabrication And Photoelectrochemical Sensing Of TiO₂-based Nanotube Arrays

Photoelectrochemical (PEC) measurement is a new and promising analyticaltechnique for detection of biomolecules and environmental pollutants with highsensitivity, due to it combines the advantages of both optical methods andelectrochemical sensing. The principle of PEC biosensing is based on the photocatalyticoxidation or reduction of biomolecules to produce photogenerated electron transferingbetween the analyte and semiconductor electrode under light irradiation to amplify thephotocurrent response. Recently, titanium oxide nanotube arrays (TiO2NTAs) become afocal point of PEC sensors due to its good light response, excellent chemical stabilityand biocompatibility. Compared with TiO2nanoparticles and nanofilms, highly orderedTiO2NTAs naturally provides a direct electric channel for photogenerated-electrontransport. At the same time, TiO2NTAs possess large surface area, excellent uniformityand conformability, good adhesion with the substrate, resulting in improvedphotocatalytic and photoelectrochemical performance. In this thesis, the properties ofphotoelectrochemical sensors based on TiO2NTAs have been studied for monitoringheavy mental ions and organic pollutants. The main results are as follows:(1) TiO2NTAs with different morphologies have been prepared by anodization of Tifoil and subsequently annealing at different temperatures in air. The photocurrentresponses of K2Cr2O7at electrode of TiO2NTAs under UV light have beensystematically investigated. Anatase TiO2NTAs annealed at450oC exhibit the mostsignificant photocurrent response to K2Cr2O7with a linear range from0.5to72.5μM, a detection limit of0.06μM and a sensitivity of1.046μA/(μM·cm2). Theresults are well consistent with the analysis via UV-Vis spectrometry and the RSDbetween the two methods is of0.26%, indicating the high reliability of the TiO2NTAs photoelectrochemical sensor for detecting K2Cr2O7in water.(2) N-doped TiO2is prepared by annealed TiO2NTAs under NH3at high temperature.The influence of parameters of nitrogen doping on concentration and PEC properties of N-TiO2NTAs have been systematically investigated. The results indicate thatN-TiO2annealed at500oC exhibit theexcellent photocurrent response tohydroquinone under visible light with a linear range from0.5to112.5μM, a lowdetection limit of0.09μM and a sensitivity of0.154μA/(μM·cm2). The results arewell consistent with UV-Vis spectrometry and the RSD of1.1%between the twomethods.(3) Heterostructured N-SrTiO3/TiO2composite NTAs are prepared by hydrothermaltreatment of anodized TiO2NTAs in a Sr(OH)2solution and following heattreatment in NH3atmosphere. Systematic studies on photocatalytic activity forN-SrTiO3/TiO2to degraded rhodamine B under visible light illumination are made.The results show that N-SrTiO3/TiO2exhibites wider absorbance range of light, andhigher photocatalytic activity with a RhB degradation rate of52%in3h, incompared with pure SrTiO3/TiO2and N-TiO2samples.