The Application Of Electroless Deposition And Electrodeposition In Separating Chemistry

In this thesis, two kinds of electrochemical deposition technologies, which were electroless deposition (belongs to the research filed of electrochemistry) and electrodeposition, were used to separate, analyse and determine some metal ion in a complex solution. First of all, the selectively reductive separation of Ag⁺ ions on the catalytic surface of rotating glassy carbon disk electrode (GC-RDE) by using the high selectivity of the electroless deposition, and the mechanism of electroless depositing monolayer Ag film were studied. Second, the gold nanofilms were modified on the surface of the GC-RDE by using electrodeposition, and then the experiment conditions of trace Pb²⁺ ions separation and electroanalysis were optimized. In addition, Ag-W complex films were prepared using the sol-gel method on the ITO glass. The mechanism and property of the films were studied. The emphasis of this thesis is the application of electroless deposition in separation and electroanalysis chemistry.1. The selective reductive separation of Ag on the GC-RDE is described by using the method of electroless deposition in an electroless bath of NH₃·H₂O +HAc (pH 10～10.5). The influence of reducer and metal ion concentrations on electroless Ag deposition were investigated with open circuit potential-time technology (OCP-t) and cyclic voltammetry (CV). The separating effect of Ag was studied by differential pulse anodic stripping voltammertry (DPASV). It was found that the deposition of silver on the GC-RDE possessed good selectivity to a more complex solution system containing many interfering ions. This method was applied to separation, analysis and determination of the Ag⁺ ions in real samples. The analytical results were compared with that of atomic emission spectrometry method. This is a attempt for separation and determination of the Ag⁺ ions and it is very important for the development of analytical chemistry. 2. A electrochemical analysis system has been developed, characterized, and optimized for the determination of lead (Pb(II)) using underpotential deposition (UPD) method on a gold nanofilms modified GC-RDE. The electrochemical system was linear up to 10^-8 mol L^-1 with a detection limit is 1.9924×10^-11 mol L^-1. Gold deposition was studied by X-ray diffraction (XRD). The response to Pb²⁺ was directly related to the frequency of the square wave anodic stripping voltammetry (SWASV) as well as the rotate speed of GC-RDE, deposition time and potential. The reproducibility was far superior if the electrochemical reduction of Pb²⁺ was performed in HNO₃+NaCl instead of HNO₃, HCl or H₂SO₄. This is a novel separate method of metal ion by using gold nanofilms modified electrode and this method is important for the promotion of electroanalytical chemistry.3. The silver-tungsten composite thin films were firstly deposited on the ITO-coated glass substrates by sol-gel processing. The property and composing of Ag-W sol were analyzed by transmission electron microscopy (TEM) and UV-Vis spectra. The structural properties of Ag-W gel powdery were studied using thermal analysis (TG/DTA). The characters and influence of thin films were investigated by cyclic voltammetry (CV), scanning electron microscopy (SEM) and atomic Force microscopy (AFM). A novel method of preparation of Ag-W thin film was studied.