Optical extinction spectra of the aqueous suspensions of Ag nanoparticles

The experimental results on the extinction spectra of aqueous suspensions of silver nanoparticles are presented. It is shown that optical properties of suspensions are strongly affected by the size and shape of the particles. Extinction spectra of monodisperse Ag colloid consist of two characteristic bands centered at about 430 and 540 nm, which can be explained in terms of Mie theory. These bands arise from the excitation of dipole and quadrupole components of surface plasmon resonance respectively. Presence of rod-like particles in colloid leads to broadening and tailing of the dipole component of the extinction spectra.