The fabrication and option characteristics of polyethylene glycol-coated gold nanoparticles with different size

Objective To synthesize gold nanoparticles (GNPs) and polyethylene glycol-coated GNPs (PEG-GNPs)modified by sulfhydryl-polyethylene glycol (SH-PEG),chloroauric acid and different reductant agent,such as trisodium citrate and sodium borohydride were used.Methods Chloroauric acid solution was brought to a boil,and then different volume of trisodium citrate solution or sodium borohydride solution was added to the boiling solution.Then the mixture was boiled for a further 30 minutes.Subsequently some SH-PEG was mixed with the GNPs and stirred for 1 hour to fabricate the PEG-GNPs.The optical characteristic and size of GNPs and PEG-GNPs were observed by UV-Vis spectrophotometer and transmission electron microscopic respectively.Results 10,25,and 45 nm GNPs were fabricated using 1％ trisodium citrate,while the 5 nm GNPs were synthesized using 0.11％ sodium borohydride.Meanwhile,SH-PEG was added to the GNPs and obtained the PEG-GNPs.Furthermore,when compared with the GNPs with different size,it can be found that the surface plasmon resonance (SPR) of GNPs have shift to long wavelength region with increasing particles size.The same phenomenon also can be found in the PEG-GNPs with different size.Conclusions The size of GNPs can be modulated by controlling the ratio between chloroauric acid and trisodium citrate or sodium borohydride.Meanwhile,the larger the size of GNPs is,the more significant of the shifting to the long wavelength of SPR is. Key words: Nanostructures; Gold; Polyethylene glycols; Microscopy, electron, transmission