Synthesis, Self-assembly And Electrocatalysis Of Hydrophobic Nanoparticles

Nanoparticle thin-films fabricated by self-assembly have extensive applicationsin the fields of catalysis, photovoltaic, magnetic storage and biochemical analysis.Our group has developed a series of oil-water interfacial self-assembly for a variety ofnanoparticles. However, these methods are applicable only to hydrophilicnanoparticles. As for hydrophobic nanoparticles, Langmuir-Blodgett (LB) techniqueis the most reliable method, but the equipment is expensive. In order to expand theoil-water interfacial self-assembly and make it more general, this thesis will assemblehydrophobic nanoparticles into two-dimensional (2D) nanoparticle film by combiningthe ligand-exchange method and oil-water interfacial self-assembly. The mainresearch contents are as follows:1. Self-assembly of hydrophobic nanoparticles.As-prepared oleylamine-capped nanoparticles, such as Au, Pt, etc., wereredispersed a certain solution containing polyvinylpyrrolidone (PVP). PVP moleculescan partially replace the oleylamine molecules of nanoparticles surface, makingnanoparticles with amphiphilicity. Infrared spectroscopy (IR) and X-rayphotoelectron spectroscopy (XPS) analysis show that PVP molecules were boundparticle surfaces with O atoms. The resultant amphiphilic nanoparticles can beredispersed into the mixed solvent of ethanol and toluene, into which water was addedand nanoparticles were observed to spontaneously form a2D thin-film at an oil-waterinterface. Transmission electron microscope photographs (TEM) show thatas-prepared2D nanoparticle thin-films were closely packed.Oleylamine-capped Au nanoparticles were redispersed into toluene solutioncontaining dodecyl mercaptan (DDT) and11-Mercaptoundecanoic acid (MUA). DDTand MUA can replace oleylamine molecules on the surface of nanoparticles, formingamphiphilic nanoparticles modified with binary thiol ligands. These amphiphilicnanoparticles can spontaneously form a2D nanoparticle monolayer film at theoil-water interface after they were redispersed into toluene and then water was added.Uniformity of nanoparticle monolayer films and interparticle spacing were closelylinked with the amount of DDT and MUA and the feeding ratio.2. Electrocatalysis of2D Pt nanoparticle monolayer films.2D Pt nanoparticle (nanosphere and branch) monolayer films fabricated by the method mentioned above were employed to electrooxidize methanol and formic acid.Preliminary results show that as-prepared nanostructure thin-films after soaked withmethylamine aqueous solution, had a certain catalytic activity, but the catalyticperformance was still less than that of commercial Pt/C, which may be caused byorganic ligands that were not completely removed. To solve this problem, annealingat a certain temperature may be requisite in the future study.