The fabrication and photo-induced melting of networked gold nanostructures and twisted gold nanorods

Fabrications of both networked Au nanostructured particles and twisted gold nanorods (TGNRs) suspended in water were accomplished via a laser ablation technique. They can be further purified by simple filtration. We conducted the photo-induced melting studies on these two types of nanostructures under both 532 and 1064 nm laser irradiation wavelengths. Both structural changes and their absorption spectral responses are reported. The TGNR sample contains particles with a wide distribution of aspect ratios. Its typical absorption spectrum shows a flat and continuously rising feature to the red of ca. 520 mn, which show a similarity with that of the suspended An networks. The photo-induced melting processes corresponding to these two types of An nanostructures demonstrate quite different spectral responses associated with their structural variations. Various observations on the wavelength- and laser power-dependence are presented. Generally, this type of photoannealing results in a formation of spherical shaped particles. Among them, we demonstrate that a spectral 'hole' burning can be uniquely achieved in the case of TGNRs suspension after 1064 nm low-fluence laser beam irradiation. Its contribution based on a selective melting will be addressed. (C) 2001 Elsevier Science Ltd. All rights reserved.