Modification Method for Preparation Gold Nanoshells

Nanoshells are a novel class of optically tunable nanoparticlesthat consist of a dielectric core  surrounded by a thin gold shell. Nanoshells are fabricated the silica cores were made by reducing tetraethylorthosilicate ,the gold colloid adsorbs onto the aminated surface and the gold shell was then grown by reacting sodium tetra chloroaurate (gold salt) with the gold –seeded aminated particles in the presence of formaldehyde . The absorbance characteristics of nanoshell were monitored using UV-Vis spectrophotometer ( at 528 nm  ) and the average size of the silica core nanoparticles were then the determined by scanning prope  microscopy  ( 349 nm  ).But size of  gold nanoparticles (25 nm), Fourier transform infra-red spectroscopy (FTIR) SiO2--Au particles peak 1098, 80 cm?1 can be assigned to Si–O–Si bond and peak 947 cm?1 can be attributed to Si–OH bond and for functionalized silica particles peaks at 3215 cm?1 is assigned to NH bond. The present method, the combination of citrate and borohydride method, gives much better results and it works at room temperature. The presence of gold coating was confirmed by FTIR spectroscopy. Keywards: Gold nanoshells ,Silicon dioxide nanoparticles , Nanoparticles