Thermal stability of gold nanorods in an aqueous solution

The thermal stability of the gold nanorods in an aqueous solution was investigated by UV–vis absorption spectroscopy and TEM technique. It was found that the longitudinal surface plasmon resonance absorption of the gold nanorods gradually moved to a shorter wavelength at high temperature, suggesting the decrease of the aspect ratio. The decrease of the aspect ratio could be attributed to the increase of the diameter and the decrease of the length, which was associated with Ostwald ripening in the solution. This shape deformation could be inhibited by reducing the concentration of cetyltrimethylammonium bromide or coating the surface of gold nanorods with poly(sodium styrenesulfonate). The results are very important to the future applications of the gold nanorods where they have to be heated to high temperature without change of their optical properties.