Size-Dependent Hamaker Constant for Silver Nanoparticles

The nonretarded size-dependent Hamaker constant for spherical silver nanoparticles was calculated by using the Lifshitz theory. The size dependence of the Hamaker constant was taken into account based on the size effect of the dielectric permittivity of silver nanoparticles. The experimental data for bulk silver dielectric permittivity was modified to include the intrinsic size effect of the scattering of the conduction electrons by the surface of the nanoparticles. The intrinsic size effect leads to a substantial increase of the Hamaker constant for nanoparticles with radii of the order 1 nm, when the mean free path of conducting electrons in the nanoparticles is limited by the particles' boundaries.