Photoelectrochemical Sensor Based On Titanium Dioxide Nanocomposite

Photoelectrochemical?PEC?biosensing,a new type of analytical detection technology,has been developed rapidly in recent years.Owing to the combination of optical analysis and electrochemical detection technology,it possess the advantages of high sensitivity,fast analysis speed,simple equipment in the detection process.Relevant reports have shown the potential application value of this method in clinical diagnosis,environmental monitoring and food safety.In this paper,a series of high-sensitivity photoelectrochemical biosensors based on semiconductor sensitized TiO₂ composites were constructed for the detection of glutathione and thrombin.These main works are expressed as follows:?1?Titanium dioxide nanotube arrays?TiO₂ NTAs?has been prepared by anodizing method and further sensitized with bismuth sulfide?Bi₂S₃?to obtain Bi₂S₃/TiO₂ NTAs nanocomposites.The nanocomposites were characterized by UV-vis spectroscopy?UV-vis?,scanning electron microscopy?SEM?and X-ray energy spectroscopy?XPS?.Since glutathione?GSH?can enhance the photocurrent as an electron donor,the nanocomposites was used as a photoelectrochemical sensor for the detection of glutathione.Under the 0.65 V bias and the irradiation of light?400-700 nm?,the response photocurrent was proportional to the concentration of glutathione?GSH?with the wide linear range 1.5×10^-5-2×10^-44 mol L^-1 and a detection limit of 7.0×10^-6 mol L^-1?S/N=3?.the proposed method was successfully applied to the analysis of real sample.?2?CdS:Mn/TiO₂/ITO was obtained by Successive Ionic Layer Adsorption and Reaction?SILAR?method wherein TiO₂/ITO was sensitized with Mn²⁺doped CdS.In the presence of target protein,Au NPs labeled DNA?AuNPs-S2?was further bonded to the protein to fabricate sandwich sensing platform.Due to the overlap of the absorption of Au NPs and emission spectra of CdS:Mn/TiO₂,the energy transfer?ET?between the Au NPs and CdS:Mn/TiO₂ will lead to the photocurrent quenching.In this way,the photocurrent will be decreased with the increasing concentration of the thrombin.Under optimum conditions,a linear range of 0.1 pmol L^-1-8 nmol L^-1with a detection limit of 30 fmol L^-1?S/N=3?were achieved by the proposed method.Finally,the established PEC biosensor was applied to the analysis of the real sample and possessed high selectivity and good stability for detection of thrombin.Besides,this method is extremely flexible and can be extended to varieties of protein targets.?3?The burr-shape TiO₂?b-TiO₂?was prepared by hydrothermal method and sensitized with CuInS₂ QDs to obtain CuInS₂/b-TiO₂/ITO electrode.Thus a sandwich type PEC aptamer sensor for thrombin detection was constructed by using Au-rGO-CuS as a beacon molecule of thrombin aptamer S2.Due to the competitive consumption of the electron donor AA and the excitation light with CuInS₂/b-TiO₂,Au-rGO-CuS will lead to the effective photocurrent quenching.In this way,the photocurrent will be decreased with the increasing concentration of the thrombin.Under the optimized experimental conditions,the linear range was 0.1 pmol L^-1-10nmol L^-1 and the detection limit was 30 fmol L^-1?S/N=3?.The proposed method was successfully applied to the analysis of real sample.