Preparation And Electrochemical Properties Of Self-assembly Multilayer

Over the last ten years, scientists from varying backgrounds have rallied around a versatile new method for the synthesis of thin films. Because the layer-by-layer assembly method provides opportunities for creative design and application of function-specific films, the field has experienced an initial period of exponential growth.The development of self-assembled monolayer technology has mainly experienced three stages, namely Langmuir-Blodgett(LB) film technology, chemical adsorption and electrostatic adsorption self-assembly technology. LB film is prepared by transferring the insoluble matter which is dispersed in solution to solid support. This process is completed in a special equipment, and the film will arrange into monolayer or multi-layer ordered. Chemical adsorption self-assembly technology form chemical bond of adsorption between adsorbate and solid surface. Electron transfer, exchange and sharing are happened between adsorbate molecules and solid surface atoms. This kind of technology usually only form single molecular layer. Electrostatic adsorption self-assembly technology form multilayer films by deposit polyelectrolytes with contrary charge alternately. The mechanism is polyelectrolytes with contrary charge can be adsorbed by each other because of electrostatic interaction.Our work focusing on both the preparation and the modification of self-assembled film on silicon wafer as well as the preparation of polyelectrolyte multilayer thin film with metal nanoparticles are as follows:1. Using the octenyltrichlorosilane as reagent, we have prepared vinyl terminated self-assembling film on the surface of the silicon wafer; Then the vinyl terminated self-assembling film was partially oxidized into carboxyl terminated film through the electron-oxidation method, on which the Octadecyltrichlorosilane bilayer was obtained. Choosing the Potassium permanganate as the main oxidant, at constant temperature 60℃, the vinyl end group can be oxidized into the carboxyl end group which happen to be the single-double membrane surface with different hydrophilic. As we expected, via contact angle measurement, significantly difference of hydrophilic was shown. The IR spectrum measurement also proved the film transformation from vinyl terminated to carboxy1 terminated after the oxidization of Potassium permanganate. Furthermore, the atomic force microscopy has shown heught difference between monolayer and bilayer in our system.This template of self-assemble monolayer with different terminal groups on the same surface can be applied to the surface patterning, local ion adsorption and nano-thin film circuit. In the future, it can also be widely used in preparation of electronic devices of micro and nanometer.2. The Polyelectrolytes multilayer with silver, copper and nickel nanoparticles were electrostatic self-assembled by useing layer by layer self-assembly technology. Reducing Ag⁺, Cu²⁺, Ni²⁺ from the Polyelectrolytes multilayered films, multilayer films with Ag, Cu, Ni nanoparticles can be prepared. Both the UV-visible spectroscopy and the FT-IR have shown that we have successfully synthesized the (metal nanoparticles composite) {CTS/Ag/PSS}n, {CTS/Cu/PSS}n, {CTS/Ni/PSS}n multilayer films which are composited with metal nanoparticles . Besides, the UV-Vis tests have shown the homogeneousness(uniformity) of our assembling multilayer films. Furthermore, results from the atomic force microscopy indicated that the surface morphology of nanocomposite thin films was rather a rough structure than a strictly layered structure, which is due to the interspersion of nanoparticles in polyelectrolytes.Layer by layer self-assembled polyelectrolyte multilayers have extensive application in many fields. In biological and medicine, it usually be used for surface controlled-release technology, targeted drug therapy, preparation of biological sensors and biological microelectronic devices. The mainly applications in separation and detection are wastewater treatment and membrane separation. Moreover Layer-by-layer self-assembled multilayer are used in photocatalysis, electrocatalysis, fabrication of nano-reactor and functional nanostructures.3. Through the Electrochemical test, the Ag, Cu, Ni nanoparticles multilayer film has shown its (strong) catalytic activity in the oxidation of glucose; besides, as catalytic, Nickel-nanoparticle composite film are more active than both the composite films of silver nanoparticles and copper nanoparticles.Polyelectrolyte multilayer films contain metal nanoparticles are usually used for electrochemical detection of organic matter, due to the conductivity of metal nanoparticles, high specific surface area and quantum size effects. So this kind of multilayer shows excellent properties in application of the electrochemical detection.This paper focusing on preparation and characterization of nano self-assembly multilayer, and hoping to design a simple method to prepare organic/inorganic nano-multilayer. Our work also want to realize the control and adjustment of the components and structure. The result will provide a new thought to in-suit synthesis of nanoparticles.