Photodegradation of PAMAM G5-stabilized aqueous suspensions of gold nanoparticles

Gold nanoparticles are produced in the form of colloidal suspensions in water by ps laser ablation of a metallic target. The fifth generation of ethylenediamine-core poly(amidoamine) (PAMAM G5) is used as a capping agent. Thanks to the ability of PAMAM to encapsulate and stabilize gold cations within its inner cavities, it is possible to evidence, by simple UV-visible spectroscopy, a photo-fragmentation process induced by the 532 nm radiation, which is resonant with the absorption plasmon band of gold nanoparticles. This effect, that can be also exploited to control the size and shape of gold nanoparticles obtained with different procedures, arises from electron photo-ejection and subsequent charging and disintegration of existing gold nanoparticles into smaller size products.