Reversible formation and dissolution of gold nanoparticles through turning on and off sequences of UV light.

Reversible formation and dissolution of gold nanoparticles through turning on and off UV light was reported. Gold ions (Au(3+)) were reduced to monodispersed gold nanoparticles by UV irradiation from a mixture of comb-like poly(oxyethylene)s and a gold salt. The prepared gold nanoparticles dissolved to yield gold ions (Au(3+)) when the UV light was switched off. Such formation and dissolution could be repeated persistently by turning the UV light on and off repeatedly.