Technical note: optical extinction coefficient of polydisperse spherical gold nanoparticles in water

Abstract

The extinction coefficients of polydispersed gold nanoparticles up to σ = 360 nm were computed via exact solution of Mie theory. A narrow extinction peak around 520 nm occurs for mean particle sizes <d> within dipole approximation limit. Spectral characteristics for extinction coefficient computed based on increasing mean particle sizes, degree of polydispersity, composition ratio of bimodal size distributions and changes in dispersant temperature are compared. As mean particle sizes increases, the plasmon resonance peak red-shifts and broadens skewing towards infrared. Increasing polydispersity on mean particle diameter beyond dipole approximation limit decreases peak extinction coefficient values. Increasing temperature from ambient to boiling changes the peak extinction coefficient intensity value by an order of 10^-13 while resonance wavelength remains unchanged.