Manipulation of Gold Nanoparticles inside Transparent Materials

Abstract

Nanoparticles have a wide range of electrical and optical properties owing to the quantum-size effect, surface effect, and conjoint effect of nanostructures.[1] Materials doped with noble-metal nanoparticles exhibit large third-order nonlinear susceptibility and ultrafast nonlinear responses.[2] They are expected to be promising materials for ultrafast all-optical switches in the THz region. For the applications related to integrated optoelectronics, a well-defined assembly and spatial distribution of nanoparticles in materials are essential.[3] Many studies have been carried out on the fabrication of nanoparticle-doped materials,[4] but there are no effective methods to control the spatial distribution of nanoparticles in these materials. In addition, Zheng and Dickson reported the synthesis of photostable, water-soluble, silver nanodots by direct photoreduction of silver ions under ambient conditions.[5] Photoactivated fluorescence has also been observed from individual silver nanoclusters.[6] Herein, we report a method that can control the precipitation of Au nanoparticles in three dimensions inside transparent materials by using focused femtosecond laser irradiation. In brief, the precipitation involves two processes: the photoreduction of Au ions to atoms induced by multiphoton process, and the precipitation of Au particles driven by heat treatment. The size of nanoparticles and their spatial distribution can be controlled by the conditions of the lasermore » irradiation. Interestingly, the precipitated nanoparticles obtained by this technique can be also space-selectively “dissolved” by the femtosecond laser irradiation, and reprecipitated by annealing. This implies that the laser can be used not only in practical applications, such as the 3D optical memory and the fabrication of integrated alloptical switches, but also in the study of the control of nucleation and crystal growth.« less