Classical theoretical characterization of the surface plasmon absorption band for silver spherical nanoparticles suspended in water and ethylene glycol

The absorbance of spherical silver nanoparticles in water and in ethylene glycol was calculated by a summation of the Mie series including multipoles ⩽10, for different particle sizes in the range from 3 to 80 nm. These results are presented as absorption spectra, which show a wide absorption band in the visible region. Peak position, maximum absorbance and the bandwidth at half-maximum absorbance of the surface plasmon band were found to depend both on the particle size and the refractive index of the solvent. The position of the peak shifts towards higher wavelengths in ethylene glycol, due to its higher refractive index, and as the particle size increases. The bandwidth at half-maximum absorbance is almost the same in ethylene glycol and in water, but it decreases sharply in the particle size range from 3 to 20 nm and increases significantly from 50 to 80 nm. The maximum concentration of silver nanoparticles was also calculated considering a maximum absorbance of 2.0. Peak maximum evolution was calculated for the growth process for constant concentration of nanoparticles. Experimental spectra of 4.1 nm silver particles in water and in ethylene glycol correlate well with the theoretical spectra calculated for these systems.