Au@SiO2 colloids: effect of temperature on the surface plasmon absorption
The effect of temperature on the surface plasmon absorption of Au@SiO2 particles has been measured from 14 to 70°C in aqueous solutions and from 16 to 50°C in ethanolic solutions. The particles remain completely dispersed at elevated temperatures because of the silica shell. As the temperature is increased, there is pronounced damping of the surface plasmon absorption band. There are four effects contributing to the spectral changes. These are (i) changes in the metal plasma frequency due to metal volume expansion, (ii) changes in the solvent refractive index, (iii) changes in the solvent density and (iv) changes to the conduction electron scattering frequency with increasing temperature. We find that factors (iii) and (iv) dominate.