Photoelectrochemical Sensors Based On Gold Nano-particals/Quantum Dots Composite

Photoelectrochemical detection is a potential analytical method because of its highsensitivity, simple equipment, easy microminiaturization and so on. It is widely appliedin chemistry, biology, medicine, environment and food security. Among thephotoelectric active substances, inorganic semiconductor materials, namely quantumdots (QDs), and its composites exhibit special advantages. As researched, single QDsshow low photoelectric conversion rate. However compositing QDs with metal nano-particles is an effective way to improve the conversion rate. Gold nano-particles (Au-NPs) have exellent stability and electroconductivity. When composited with QDs, Au-NPs can facilitate the transmission of photo-induced electrons. Then the photo-inducedelectrons and holes can be separated more efficiently and their life-time is prolonged.The more electrons that participate in the chemical reaction the more obvious electricalsingals can be detected by electrochemical work station. So photoelectrochemicalsensors based on QDs/Au-NPs show higher sensitivity and properties than the sensorsbased on single QDs.There are two research sections for this thesis:First section, we prepare Au/ITO, ZnS/ITO, ZnS-Au/ITO, CdS/ITO, CdS-Au/ITOmodified electrodes by electrochemical method. Then Scan Electron Microscope (SEM),Ultraviolet visible absorption spectra (Uv-vis), Electrochemical Impedance, Spectrosco-py (EIS) are employed to characterize the modified electrodes. Amperometry i-t curves(I-T) and Cyclic Voltammetry (CV) are used to investigate the properties of modifiedelectrodes and the optimal experimental conditions.Then use the modified electrodes todetect H2O2and compare their properties with each other to choose the best one. Theresults indicate that after composited with Au-NPs, the photoeletrochemical propertiesof ZnS-QDs and CdS-QDs are both improved. The sensitivity and the linear range ofZnS-Au/ITO is33.7nA/μM and0.2-28μM. And that of CdS-Au/ITO is21.5nA/μM and1-210μM. ZnS-Au/ITO shows higher sensitivity. These results can demomstratethat nontoxic ZnS-QDs can supersede toxic CdS-QDs, which is significative forenvironment protection.Second section, here we mainly discuss the influence of Au-NPs on the photoeletr-ochemical properties of ITO. Au-NPs are eletrodeposited on the ITO surface and SEM,Uv-vis, SEM and EIS are employed to characterize the resulting Au-NPs. Au/ITO andbare ITO are used as work electrodes repectively to research their photoeletrochemicalproperties. Then the hydroquinone is detected by the modified electode. The resultsindicate that the sensitivity of Au/ITO is29times and8times higher than bare ITOunder illumination and dark condition respectively, indicating that Au-NPs evidentlyimprove the photoeletrochemical properties of bare ITO.