Preparation And Application Of Core-Shell Metal Composite Nanoparticles

Core-shell type metal composite nanoparticles are a kind of composite nanomaterials including nuclear metal nanoparticles.The composite nanoparticles have become a new focus due to their information storage,catalysis,antibacterial,optics and electricity properties which depend on the nanometer effect.The core-shell structure can notably avoid the aggregation of the metal core nanoparticles to ensure the successful application of the metal nanoparticles.At present,the materials of the shell include polymer materials,inorganic nonmetallic materials and metallic materials.And the metal cores mainly cover magnetic nanoparticles and noble metal nanoparticles.The core-shell composite particles can keep all the special qualities and functions of the core and shell.Moreover,the core and shell can make up the shortfalls mutually.The preparation and application of core-shell type metal composite nanoparticles were studied and the main research contents and results are as follows.?1?Copper nanoparticles?Cu NPs?coated by polystyrene?PS?composite nanoparticles?Cu NPs@PS?were prepared by precipitation polymerization.Firstly,Cu NPs were synthesized by chemical reduction method using copper acetate as precursor,sodium polyacrylate?PAANa?as stabilizer,and hydrazine hydrate as reductant.Then Cu NPs were coated by precipitation polymerization using styrene?St?as monomer,3-?trimethoxysilyl?propylacrylate as comonomer,and 2,2'-azobis?2-methylpropionitrile?as initiator.The effects of the amount of PAANa and the stirring rate on Cu NPs@PS were studied.The ultraviolet-visible light?UV-Vis?and transmission electron microscopy?TEM?results showed that the stable composite particles can be synthesized by precipitation polymerization.The amount of PAANa has a significant effection on the size of Cu NPs.The greater PAANa was added,the smaller Cu NPs would be.The spherical Cu NPs@PS would become nanowires with increasing of the stirring rate from350 r/min to 700 r/min in the process of precipitation polymerization.Ag NPs@PS with core-shell structure were also prepared by the similar method.?2?The stable Ag NPs protected by chitosan oligosaccharide grafted with polyethylenimine?COS-g-PEI?were prepared,and the antibacterial properties were studied.First,COS-g-PEI was synthesized using ionic liquid 1-butyl-3-methyl imidazolium chloride?[BMIM]Cl?as solvent and catalyst,and 1,1-carbonyldiimidazole as coupling reagent.Then,Ag NPs@COS-g-PEI composite particles were prepared by in-situ reduction method using COS-g-PEI as stabilizer,sodium borohydride?NaBH₄?as reductant.The results of IR and ¹H-NMR showed that COS-g-PEI was prepared successfully.And the results of UV-Vis and TEM showed that the stable Ag NPs@COS-g-PEI composite particles were prepared.The antimicrobial properties of COS-g-PEI and Ag NPs@COS-g-PEI for staphylococcus aureu and escherichia coli were evaluated by Kirby-Baner test and oxford cup method.Ag NPs@COS-g-PEI showed the larger diameter of inhibiting zone than COS-g-PEI against staphylococcus aureu and escherichia coli.It is suggested that the antibacterial properties of COS and Ag NPs are combined together to give higher antibacterial ability.?3?Core-shell silver nanoparticles@mesoporous silica spherical nanoparticles?Ag NPs@MSNs?were prepared by two-step method.Firstly,Ag NPs were synthesized by chemical reduction using silver nitrate?Ag NO₃?as the precursor,cetyl trimethyl ammonium bromide?CTAB?as the stabilizer,and NaBH₄ as the reductant.Then,MSNs were obtained by employing CTAB-stabilized Ag NPs as the template and hydrolyzing tetraethoxysilane?TEOS?precursor in the presence of the catalyst,triethanolamine?TEOA?.The effects of different preparation routes?core-first vs.shell-first?,type of reductants as well as extraction methods and agents were studied.The obtained core-shell NPs were characterized by IR and TEM.The results showed that core-first route was viable to produce uniform Ag NPs@MSNs with ordered mesostructures.Afterwards,those NPs were used as the catalyst to catalyze the reduction of Rhodamine?RhB?,a model dye compound representing organic pollutants in waste water,in the presence of NaBH₄.It is found that Ag NPs@MSNs were not only efficient catalysts but also participated as co-reductants in the reaction.Moreover,they exhibited almost no loss of catalytic efficacy after several reduction cycles,which promise their future use as efficient recyclable catalysts for organic pollutant treatments.