Transformation of Gold Nanorods in Liquid Media Induced by nIR, Visible, and UV Laser Irradiation

Gold nanorods (GNRs) were initially prepared with three different aspect ratios (2.5, 2.9, and 3.8) via a seed-mediated chemical route, using cetyltrimethylammonium bromide (CTAB) as the organic surfactant. These rods were then irradiated under continuous-wave (lambda = 1064 nm) and pulsed (lambda = 1064, 532, 355 nm) emission modes using Nd:YVO4 and Nd:YAG lasers, respectively. The photostability and behavior of the Au nanorods under these laser irradiation conditions were studied using UV-vis-nIR spectroscopy and electron microscopy. Photofragmentation and melting mechanisms were provoked as a function of laser irradiation parameters (emission mode and wavelength) and caused the GNRs to undergo considerable morphological changes. Important differences were observed between the wavelengths used for irradiation, indicating significantly different nanorod breakdown mechanisms