Poly(N-isopropylacrylamide) (PNIPAM) grafted polyamidoamine (PAMAM) was used as stablizer in gold colloid synthesis

and water was used as solvent by using in situ synthesis method.The prepared gold colloid showed different responsive behavior under different temperature both in the aspect of its photo-thermal properties and drug controlled release properties.1H-NMR and FTIR were used for characterizing the polymers on the gold colloid.Transmission electronic microscopy (TEM) was used for the core size determination and it revealed that the core size varied under different synthesis conditions.UV-Vis spectrum was used for its surface plasmon resonances properties study and the results showed that the maximized adsorption was different for gold colloids with different ligand densities.Further study on lower critical solution temperature (LCST) was carried out with UV-Vis spectrum and the results showed that the LCST of the polymer precursor was enhanced after the introduction of gold cores.The LCST of polymer precursor was about 33.5 ℃

and that of the gold colloids were both above 38 ℃.The morphology of the gold core after phase transition detected by TEM showed that severe aggregation occurred after phase transition

which endowed the gold colloids the thermal responsive photo-thermal conversion ability

as a result of that

the side effect of photo-thermal treatment could be reduced significantly.Laser was used to investigate the photo-thermal behavior of the gold colloids and the results showed that significant photo-thermal conversion process occurred for all of gold colloids after phase transition (the temperature after laser excitation increased sharply from 25 ℃ to 43 ℃ and 48 ℃

respectively).The drug release study indicated the controlled release behavior of the gold colloids under thermal stimuli.All these results showed that this kind of thermo-responsive gold nanospheres has great potential to be used in both photo-thermal field and controlled drug release field.