Preparation Of Nano-gold Composite For Detection Heavy Metal Ions

Heavy metal pollution is serious threat to human health. Heavy metal ions are the main pollutants in environmental water, and their detection has great significance to environmental hazards detection and control. Therefore, searching for a rapid, sensitive detection of heavy metal ions method is a common goal for all the researchers. At present, many methods was used for detection of heavy metal ions. in our work, the electrochemical analysis was chosen.In recent years, nano-composite material was used to modify electrode and exhibit the excellent electrochemical properties. Mainly because the nano-composite material combined with the characteristics of nano-materials with and function materials. It will be an effective way to solve the environmental pollution problem by using chemically modified electrode.In view of this topic, this thesis has been carried out on the following aspects:1) A sensitive and selective electrochemical sensor consisting of an Au-TiO₂ nanoparticles/Chitosan/Gold（Au-TiO₂ NPs/Chit/gold）-modified electrode and used for the detection of mercury ions（Hg2+）, in which the composite material is synthesized using a sol-gel method followed by a self-assembly strategy. The morphology and microstructure of the Au-TiO₂ NPs are characterized using transmission electron microscopy（TEM） and X-ray diffraction（XRD）. The results demonstrate the presence of a monolayer of well-dispersed Au-TiO₂ NPs with an average size of 5¹5 nm. The electrochemical properties of the resultant modified electrode and its response to Hg2+ are studied using cyclic voltammetry（CV）, AC impedance（EIS） and differential pulse anodic stripping voltammetry（DPASV）. The operational parameters that influence the deposition and stripping, such as the supporting electrolytes, p H value, deposition potential and deposition time, the linear relationship, reproducibility and stability of the modified electrode are carefully studied.2) A novel emulsion polymerisation-carbonisation method was developed to prepare high-temperature-stable gold nanoparticle-doped carbon foams（Au-CFs） using phenolic resins as a carbon source and HAu Cl4 as a gold source and acidic catalyst. The structure, morphology and composition of Au-CFs composite was characterized by scanning electron microscopy（SEM）, TEM, XRD. Then, prepared Au-CFs modified the gold electrode. The modified electrode was characterized by CV and EIS characterized by scanning electrochemical characteristics of the modified electrode. The experimental parameter was optimized, including base solution, p H value, deposition time and deposition potential.3) Under the optimum experimental conditions, the DPASV was applied for individual analysis different concentrations of Pb2+ and Cu2+, respectively. And a good respond was obtained. Due to a large separation potential（0.73 V） between the peaks, we infer that the Au-CFs/gold electrode as an electrochemical sensor can be used for the simultaneous detection Pb2+ and Cu2+. In simultaneous co-detection of Pb2+ and Cu2+, we found that a better performance for Cu2+ was obtained than individual analysis.4) Adding melamine in the aqueous phase, the small size and high dispersion of Au nanoparticals was obtained, due to the strong interaction of amino and gold. By controlling the amounts of melamine, we can control the size and density of Au nanoparticles. Then, the series of composite modified electrode was used to detect Pb2+ and found that the smallest size and bigges density of nano-Au composite have a good responds for detecting of Pb2+.