Assembly And Application Of Functional Thin Films

The self-assembled monolayers (SAMs) technique and Langmuir-Blodget (LB)technique can be used to fabricate functional ultrathin films. These films havepotential applications in the field of sensors because of their controllable thickness,ordered and stable structure. In this paper, the octadecyltrichlorosilane (OTS) self-assembled monolayer with the cholesterol molecular imprinting layer was prepared,which can be used for detecting the cholesterol content of the eggs. We alsofabricated the amphiphilic polyaniline derivative (p-C₁₆OAn)/silver and silver core-gold shell (Ag@Au) nanoparticle composite films, p-C₁₆OAn/gold and gold core-silver shell (Au@Ag) nanoparticle composite films, and studied their properties andapplication. The paper is separated into three parts that are shown as follows:1. The SAMs technique and molecular imprinting technique (MIP) have been usedfor the fabrication of OTS self-assembled monolayer with the cholesterol molecularimprinting layer. The results of the polarization modulation infrared reflectionabsorption spectroscopy (PM-IRAS), atomic force microscope (AFM) and electro-chemical measurements showed that the specific recognition sites to cholesterolmolecules were formed on the monolayer. The cholesterol content of three differenteggs was detected through the combined molecular imprinting and self-assembledmonolayer electrochemical sensor. The results indicated that the molecular imprintedbiosensor has wide linear range and high sensitivity.2. The amphiphilic aniline derivative 2-hexadecyloxyaniline (2-C₁₆OAn) wasspread on silver sulfate aqueous solution subphase, then the p-C₁₆OAn/silvernanoparticle composite films were prepared through one-step reduction of silver ions(Ag⁺) in the basic subphase by 2-C₁₆OAn, which was oxidated to p-C₁₆OAn. Thep-C₁₆OAn/Ag@Au nanoparticle composite films were fabricated by the reactionbetween the silver nanoparticles on the films and AuCl₄^- in the solution. Thecomposite films were characterized by the transmission electron microscopy (TEM),Fourier transform infrared spectroscopy (FT-IR), X-ray Photoemission Spectroscopy (XPS), Ultraviolet-visible spectroscopy (UV-vis), Fluorescence spectroscopy andelectrochemical method. The results indicated that the spheric Ag@Au nanoparticleson composite films were formed with a diameter of about 25nm, the thickness of Agcore and Au shell was about 15nm and 10nm, respectively. The p-C₁₆OAn/silvernanoparticle composite films and p-C₁₆OAn/Ag@Au nanoparticle composite filmsall have excellent optics property and electrochemical property. And theelectrocatalytic activity of p-C₁₆OAn/Ag@Au nanoparticle composite films on theelectrochemical behavior of L-cysteine was better than that of p-C₁₆OAn/silvernanoparticle composite films.3. The p-C₁₆OAn/gold nanoparticle composite monolayer were prepared atair/water interface by one-step oxidation-reduction reaction between 2-C₁₆OAn andchloroauric acid in solution subphase, and the diameter of the produced spheric goldnanoparticles was only 5nm. Then we assembled the p-C₁₆OAn/gold nanoparticlecomposite monolayer to LB films, and used the L-tyrosine molecules to pack goldnanoparticles on the films because of their strong coordination. Thep-C₁₆OAn/Au@Ag nanoparticle composite films were fabricated by the redoxreaction between L-tyrosine molecules on films and silver ions under alkalineconditions. The results revealed that the Au@Ag nanoparticles formed on thecomposite films were spheric with a diameter of about 20nm, and the thickness ofsilver shell was about 15nm。The phenolic groups of L-tyrosine molecules changed toquinone after oxygenation. And the p-C₁₆OAn/Au@Ag nanoparticle composite filmsexhibit better electrochemical property and catalytic activity on the electrochemicalbehavior of methanol than the p-C₁₆OAn/gold nanoparticle composite films. We alsoinvestigated the application of p-C₁₆OAn/gold nanoparticle composite films on thedetection of SCN^- in saliva of smokers and non-smokers. This method is simple, fastand sensitive, and the results are satisfied.