Spectrally-selective gold nanorod coatings for window glass

The unique optical properties of gold nanorods, which exhibit tuneable absorption as a function of their aspect ratio, suggest that they might have potential applications in coatings for solar control on windows. Here we explore the properties of coatings produced by attaching gold nanorods to the surface of glass. Such coatings can attenuate solar radiation effectively, even at very low gold contents, but the figure-of-merit, Tvis/Tsol, of our experimental coatings was close to unity, indicating that they are not spectrally selective, However, calculations are presented to show how coatings comprised of a blend of rods with aspect ratios of greater than 3 can produce coatings with Tvis/Tsol of up to at least 1.4. The maximum value possible for perfectly spectrally-selective coating in sunlight is 2.08. Unfortunately, the practical realization of such coatings requires the further development of reliable methods to scale up the production of gold nanorods of longer aspect ratios.