Abstract
Size-controlled synthesis of gold nanoparticles (AuNPs) was successfully achieved through the autoreduction of HAuCl4 using stimuli-responsive PEGylated nanogels, composed of cross-linked polyamine core and tethered PEG chains. Transmission electron microscopy images revealed that the synthesized AuNPs located only in the polyamine gel core of the nanogels. Number of the AuNPs per nanogel decreased with the increase in the N/Au (number of amino groups / number of Au atoms) ratio. Mean diameter of the AuNPs prepared at 60 C was almost constant (~ 8 nm) regardless of the N/Au ratio, whereas that prepared at 25 C was not controllable. Worth noticing that the mean diameter of the AuNPs prepared at N/Au = 1 decreased with the increase in temperature. We found that the degree of protonation of core-polyamine is far different between 25 C and 60 °C. This result indicates that shrinking and hydrophobic polyamine gel core at 60 C may play an important role for the stabilization and size-controlled synthesis of AuNPs. Therefore, stimuli -responsive PEGylated nanogels act as both nanoreactor and nanoreservoir for AuNPs.
