Study On The Photoelectrochemical And Raman Immunosensor Based On The Mesoporous Titanium Dioxide

TiO2as a semiconductor material plays an important part in physics and chemistry.TiO2has been widely used in dye-sensitized solar cell (DSSC), biosensor and etc.Because of ordered pore structure and high surface area, mesoporous TiO2has greatlyapplications in photoelectrocatalysis. However, the application of the TiO2semiconductor has been limited because of the wide band gap (~3.2eV), and TiO2could only absorb the UV light. Therefore, it is difficulties to achieve thephotoeletrochemical immunoassay using TiO2which could only absorb the UV light asphotoelectric conversion material, because the UV light could damage the biologicalactivity of many biomolecules such as DNA, antigen, antibody, etc. In order to workout this problem, some strategies have been adopted, such as sensitized with dye,doped with other impurities and coupled with the narrow band gap semiconductorwhich could illuminate light to the visible region.1. In this work, a new photoelectrochemical method for the detection of ascorbicacid by using [Ru(bpy)3]2+-functionalized TiO2mesoporous thin film on indium tinoxide electrode (ITO) was reported. The TiO2mesoporous thin film was characterizedby transmission electron microscope (TEM), scanning electron microscope (SEM),X-ray Diffractometer (XRD)，Raman Spectrum and N2adsorption-desorption. The[Ru(bpy)3]2+was immobilized on TiO2mesoporous thin film through electrostaticadsorption. The photoelectrochemical behavior of [Ru(bpy)3]2+-functionalized TiO2mesoporous thin film was studied. In the presence of ascorbic acid as an electrondonor, the photocurrent signal could be enhanced. The detection linear range forascorbic acid was2.0×10-6~2.0×10-2M, and the detection limit was1.0×10-6M. Theproposed sensor was successfully used to detect the ascorbic acid in the fruits.2. In this work, a label-free photoelectrochemical immunosensor based onCdS-modified mesoporous TiO2films was developed. Because of the large specificsurface area of mesoporous TiO2, the adsorption capacity of TiO2was increased. TheCdS quantum dots could be deposited onto the mesoporous TiO2films usingelectrochemical deposition. The obtained CdS/TiO2electrode showed enhancedphotocurrent intensity in visible region. The α-fetoprotein (AFP) antibodies werecovalently conjugated on the surface of the chitosan(CS)-TiO2electrode. AFP could combine with anti-AFP in the CdS/TiO2/ITO which was blocked with BSA. Becauseof the steric hindrances, the photocurrent intensity decreased with the increase of theconcentration of AFP in this photoelectrochemical immunosensor. The detectionlinear range for AFP was0.05~20ng mL-1，and the detection limit of0.02ng mL-1wasobtained. Moreover, the practical determination of AFP in human serum demonstratedthe feasibility of this label-free immunosensor in the analysis of a variety of biologicalspecimens.3. In this work, a new immunosensor was developed for the quantitativedetermination of AFP based the Raman response of mesporous TiO2. Through thecombination of dopamine of TiO2, the amidogen could be connected on mesporousTiO2, and then the AFP antibody was labeled with mesporous TiO2. The mesporousTiO2-labeled AFP antibody was applied to a sandwich-type Raman immunoassay forthe determination of AFP. The mesporous TiO2as an inexpensive label has replacedthe enzyme in immunoassay. The detection linear range for AFP was0.05~20ng mL-1，and the detection limit of0.01ng mL-1was obtained. The sensor could alsobe used to determine AFP in human serum.