UV–visible light reshaping of gold nanorods

The photostability of gold nanoparticles prepared via laser ablation in water or aqueous micellar solution and by wet chemical method was studied using irradiation from diode laser of wavelengths 620, 560, 520, 460 nm and UV-light sources. The results showed that gold nanoparticles prepared in micellar solution were not affected by irradiation from all light sources, whereas aggregates were observed in case of that prepared by laser ablation in distilled water. This may be attributed to the stabilizing role of the capping micelles which prevent nanoparticles from aggregation during the irradiation time course. Moreover, UV-irradiation of gold nanorods of aspect ratios ∼2.6, 3.1, 3.6, and 3.8 with absorption maxima at 700, 730, 760 and 780 nm, respectively, leads to a change in particles morphology and shape as well as photodecomposition of the rods. The rate of photodecomposition decreases with decreasing the aspect ratio and the critical photodecomposition was found to be at aspect ratio 2.3 ± 0.1. The decreasing was explained by the dissolution of the surfactant around the gold nanorods.