Tuning the shell thickness-dependent plasmonic absorption of Ag coated Au nanocubes: The effect of synthesis temperature

The temperature dependent synthesis and plasmonic optical properties of Ag coated Au nanocubes have been investigated experimentally. It has been found that the Au nanocubes with more uniform morphology and higher yield could be obtained by decreasing the growth temperature. Because of the non-spherical symmetry of the particles shape and the plasmon coupling between Au-Ag interface and outer Ag surface, four absorption peaks at most have been observed. As the Ag coating thickness is increased, the absorbance intensity of these plasmon peaks gets intense greatly, and the absorption peak at longest wavelength blue shifts firstly and then red shifts. The non-monotonous plasmonic shift has been attributed to the competition between the increase of Ag composition and the enlargement of the particle size. What's more, the wavelength region of both blue shift and red shift could also be enhanced by decreasing the temperature.