Construction And Applications Of Photoelectrochemical And Electrochemical Sensors Based On Nanocomposite

In this thesis, CdS quantum dots(QDs) and TiO2 were synthesized, and then functionalized with graphene or hemin to fabricate high-performance photoelectrochemical/electrochemical sensors. FESEM, XRD, UV-Vis, electrochemical analysis were performed to analysis their morphology, structure, optical, electrochemical and photoelectrochemical properties. The novel photoelectrochemical/electrochemical sensors were applied for sensitive detection of organic pollutants and H2O2. The photovoltaic behavior of p-phenylenediamine(PPD) and relevant mechanism of catalytic process were also studied. The main contents include the following two parts:1. Water soluble CdS QDs were synthesized by a low-temperature hydrothermal method. By doping appropriate amount of GS, Photoelectrochemical performance of CdS QDs was promoted and CdS-GS/FTO electrodes were fanbricated. The result indicated that the cyclic voltammogram of PPD on CdS-GS hybrid film became sigmoidal in shape after exposed under visible light, due to the photoelectrocatalytic reaction. Such a photovoltammetric response was used to rapidly optimize the photoelectrocatalytic activity of hybrid films composed of different ratios of CdS to GS toward PPD. The influences of scan rate and pH on the photovoltammetric behavior of PPD on CdS-GS film revealed that although the controlled step for electrochemical process was not changed under photoirradiation, more electrons than protons might participate the photoelectrocatalytic process. Furthermore, the photoelectroactive film-modified electrodes were explored for PPD determination based on the photocurrent response of electrodes toward PPD. Under optimal conditions, the photocurrent signal on CdS-GS film was linearly proportional to the concentration of PPD ranging from 1.0?10-7 to 3.0?10-6 mol·L-1, with a detection limit(3S/N) of 4.3?10-8 mol·L-1. Our work based on CdS-GS hybrid film not only demonstrated a new facile photovoltammetric way to study the photoinduced electron transfer process of PPD, but also developed a sensitive photoelectrochemical strategy for PPD determination.2. The TiO2 nanoparticles were prepared using flame aerosol synthesis technology. After anchoring of Hemin molecules on the surface of TiO2, the prepared Hemin-TiO2/GCE electrodes showed enhanced electrocatalytic and photoelectrocatalytic properties. The cyclic voltammetric measurement indicated that the Hemin-TiO2 hybrid film clearly yielded a pair of redox peaks of Hemin, and the influences of scan rate and pH on the electrochemical behavior of modified electrodes were investigated. Due to the electrocatalytic activity of Hemin towards H2O2, the Hemin-TiO2/GCE electrodes could be utilized as a H2O2 sensor, which showed a sensitive voltammetric response proportional to the concentration of H2O2 in the range of 3.0?10-7 mol·L-1 to 4.7?10-4 mol·L-1, with a detection limit(3S/N) of 7.2?10-8 mol·L-1. At the same time, the Hemin-Ti O2 hybrid film preserved the photoelectrochemical activity of TiO2. The photoelectrochemical performance of Hemin-TiO2 film to visible light was promoted, due to the TiO2 nanoparticles supporting hemin could adsorb visible light and the recombination of photogenerated electrons and holes(e-/h+) of TiO2 was reduced. The Hemin-TiO2/GCE film-modified electrodes could used as photoelectrochemical sensor to detect hydroquinone. The photocurrent response was linearly proportional to hydroquinone in the concentration range from 4.0?10-7 mol·L-1 to 3.0?10-5 mol·L-1 with a detection limit(3S/N) of 9.8?10-8 mol·L-1. The photoelectrochemical sensor was also used to measure the degradation efficiency of hydroquinone and the results were in agreement with that of UV-Visible spectrophotometry.