Study On Properties And Application Of Functional Self-assembled Films

In this thesis, inorganic ions were assembled to films by the interactions of the ions with functional groups of the polyelectrolyte, and then inorganic nanoparticles/polyelectrolyte composites films were prepared through chemical reaction. The properties and application of the films in electrocatalysis were studied.BSA was amphoteric bimolecular, it could have positive electricity and negative electricity by controlling the pH value of solution. Then adsorption of polyanions polyacrylate sodium(PAS) or polycations polyacrylamide(PAM) resulted in the formation of BSA/PAS and PAM/BSA films. CaCO₃ nanoparticles were formed within PAM/BSA films by the adsorption of Ca²⁺ ions onto uncompensated functional groups of BSA(carboxyl or ammonia), following reaction with CO₂. The results of UV-vis showed that the characteristic absorbance and thickness of the films increased with the number of bilayers, and the absorbance intensity increased almost linearly with the number of bilayers. And we knew that the thickness of self-assembled films with same number of bilayers increased significantly when Ca²⁺ was incorporated into films by atomic force microscopy(AFM). The morphology and crystal type of the nanoparticles were confirmed by TEM and FT-IR. The average diameter of CaCO₃ nanoparticles was about 7 nm.Based on the electrostatic self-assembly technique, poly(ethyleneimine)(PEI) complexed with Ag⁺ and AuCl₄^-could alternately adsorb onto the substrate. Composite films containing Ag and Au nanoparticles were synthesized by reduction with NaBH₄ solution. UV-vis and XPS spectra indicated that Ag and Au nanoparticles were reduced from Ag(â… ), Au(â…¢) to Ag(0), Au(0) upon exposure of the film to NaBH₄ solution. TEM confirmed well-dispersed Ag and Au nanoparticles formed, whose size was smaller that Au nanoparticles. From electrochemical measurements of self-assembled films, we knew that composite films containing Ag and Au nanoparticles as catalysts to reduce Vitamin C were more effective than composite films only containing Ag or Au nanoparticles. Meanwhile, the catalysis of films increased linearly with the number of films.Catalytic Pd nanoparticles in self-assembled films could be easily prepared by alternating immersions of a substrate in chitosan(CTS) solution and K₂PdCl₄ solution followed under UV irradiation reduction of Pd(â…¡). FT-IR analysis showed that there existed interactions between CTS and K₂PdCl₄, both of them were fabricated to substrate successfully. XPS indicated that Pd(0) in these films was formed. TEM confirmed that the number of Pd nanoparticles increased with the irradiation time, but the particle size of Pd did not change obviously within 1 h of UV irradiation. However, nanoparticles began to aggregate and increase in the size, but decreased in the number with UV irradiation time over 1 h. From electrochemical measurements, we knew(CTS/Pd⁰)_n films had obvious effect on catalytic reduction of oxygen.