FABRICATION AND CHARACTERIZATION OF GOLD NANOPARTICLES LOADED MICROCAPSULES
纳米金掺杂中空微胶囊的制备与表征

A convenient method was developed to fabricate gold nanoparticles loaded microcapsules in one step and with high efficiency.First of all,the gold colloidal solution was prepared through reduction of AuCl~-_4 ions with NaBH_4 under stirring,and poly(vinylpyrrolidone)(PVP) was added quickly under severe agitation to prevent the aggregation of the gold nanoparticles during the dialyses.The gold nanoparticles in the colloidal solution had a diameter of about 7 nm and had a maximum absorption at 516 nm.Next,template polymerization of acrylic acid(AA) in the presence of PVP and 3-(trimethoxysilyl) propyl methacrylate(MPS) modified silica particles was carried out in the gold colloidal solution.The polymerization was initiated by K_2S_2O_8 and maintained for about 2 h under nitrogen atmosphere.After polymerization,the resulting composite particles were separated from the dispersion through centrifugation and were washed with triply-distilled water for several times.Finally,the gold nanoparticle-loaded microcapsules were obtained after core-removal with HF.In this process,the pre-adsorption of the complex of PVP/AA onto the gold nanoparticles made the nanoparticles polymerizable with free AA monomers during the template polymerization,and the gold nanoparticles doped PAA/PVP complex films were formed on the surfaces of the silica particles.After the core-removal process,the hollow nature and the integrity of the obtained microcapsules in both dry and wet states were demonstrated by scanning electron microscopy and confocal laser scanning microscopy,respectively.The entrapment of the gold nanoparticles in the capsules was confirmed by transmission electron microscopy.Electron diffraction pattern of the nanoparticles-loaded microcapsules showed the gold polycrystalline diffraction rings,from which the lattice constant of crystal plane {1 1 1} was calculated as 0.4174 nm,further confirming the existence of the gold nanoparticles.The gold nanoparticles were distributed uniformly in the microcapsule shells with no sign of aggregations.The amount of nanoparticles loaded in the microcapsule shells could be tuned by the concentration of the gold colloidal solution,(i.e.)higher concentration resulted in microcapsules with larger amount of gold nanoparticles in the shells.This process can be extended to other types of nanoparticles and polymers,thus can be widely applied to obtain composite microcapsules with desired functions.