Au@SiO2 colloids: effect of temperature on the surface plasmon absorption

The effect of temperature on the surface plasmon absorption of Au@SiO2 part icles has been measured from 14 to 70 degrees C in aqueous solutions and fr om 16 to 50 degrees C in ethanolic solutions. The particles remain complete ly dispersed at elevated temperatures because of the silica shell. As the t emperature is increased, there is pronounced damping of the surface plasmon absorption band. There are four effects contributing to the spectral chang es. 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.