Synthesis Of Organic-Inorganic Hybrid Nanoparticles And Their Catalytic And Optical Properties

Metal nanoparticles have received increasing attention due to their fascinating chemical and physical characteristics and potential technological applications. Because of their high surface-to-volume ratio, metal nanoparticles exhibited excellent catalytic performance in hydrogenation, oxidation, and reduction reactions compared to their bulk materials. Three kinds of hybrid nanoparticles consists of organic (polymer), inorganic (silica) and metallic nanoparticles which are ideal candidates for catalyst and optical device with high performance were prepared.Cationic spherical PAEMH·brushes were prepared by photo-emulsion polymerization. They were employed to be ideal nanoreactors for the generation of platinum (Pt) nanoparticles. The divalent PtCl62- ions were confined and concentrated as counterions within the brush layer and reduced in-situ to nearly monodispersed Pt nanoparticles (average size:3 nm) by sodium borohydride. High catalytic activity of Pt nanoparticles embedded in spherical polyelectrolyte brush (SPB) was found when using it as catalyst in the reduction of p-nitrophenol to p-aminophenol by sodium borohydride. The results reported here suggest that spherical polyelectrolyte brushes are novel nanoreactor for preparation of Pt nanoparticles. The obtained Pt particles are ideal candidates for catalysts. This approach provides a new route to prepare metal nanoparticles.Novel magnetically recoverable platinum nanocatalysts which composed of magnetic spherical polyelectrolyte brush (MSPB) and platinum nanoparticles generated in-situ (average size:3.5 nm) were prepared. High catalytic activity was found when photometrically monitoring the reduction of 4-nitrophenol by NaBH4 in presence of MSPB-Pt nano-composites. The kinetic data showed that the reaction is pseudo-first-order with regard to p-nitrophenol with a rate constant k1= 0.39 s-1 m-2L normalized by surface area of Pt nanocatalyst. The advantage of being superparamagnetic facilitates the separation, recovery and efficient reuse of MSPB-Pt catalyst with almost complete retention of activity and conversion. This synthesis approach opens a new way to prepare recyclable metal nanocatalysts with high activity.In addition, inorganic-organic hybrid yolk-shell nanoparticles containing metallic Au nanoparticle as core and thermosensitive microgel PNIPA as shell were prepared. These hybrid nanoparticles were shown to be an effective catalyst for the reduction of nitrophenol and nitrobenzene in aqueous solution by NaBH4. Temperature can be used as a trigger to enhance the selectivity of the catalysis for a given substrate:NP reacts much faster at low temperature while the reduction of NB is preferred at higher temperature. This selectivity is even enhanced in mixtures of NP and NB. most probably due to the diffusion competition of both reactants through the thermo-sensitive shell. Hence, yolk-shell systems have a great potential to tailor the catalytic activity and selectivity of metal nanoparticles toward a given reaction.Anisotropic core-shell nanoparticles, which contain Au-Ag nanorods as core and inorganic silica as shell were prepared. Coating of Au nanorods with silver shell of various thicknesses (3.1 to 6.2 nm) leads to bimetallic Au-Ag nanorods with controlled surface plasmon bands. Such anisotropic bimetallic Au-Ag nanorods were homogenously encapsulated by silica using straightforward single-step procedure. Selective etching of Au-Ag nanorods core from Au-Ag-SiO2 composite particles resulted in metal-silica yolk-shell or hollow silica structure. The optical properties based on single complex particles were investigated and compared to their behaviour in solution. Single particle studies allow for a detailed investigation on the correlation between shape, morphology and plasmonic properties. Combining structural characterization by AFM and TEM and optical studies on the single particle level allowed a better understanding and quantitative theoretical modelling of complex composite plasmonic nanoparticles.In addition, a novel approach for selective shortening of Au nanorods by hydrogen peroxide oxidation, following by a simple robust procedure to encapsulate CTAB-coated nanoparticles with mesoporous silica has been demonstrated. This method represents a relevant and direct approach to design of novel nanoparticles and promotes the surface modification of various nanoparticles.