Light extinction spectrometry for determining the size distribution and concentration of polydisperse gold nanospheres

Size-dependent complex refractive index and resonant optical properties of gold nanoparticles make it possible to characterize nanoparticles using the light extinction spectra. In this article, light extinction spectrometry (LES) of resonant particles was presented to determine both the size distribution and concentration of polydisperse gold nanospheres. The inverse problem was solved by using the improved Tikhonov regularization method, and the extinction matrix was calculated by Mie theory. Numerical simulations were performed to investigate the effects of wavelength range, size distribution width, particle number concentration, and random noise on the inverted results. To validate the reliability of LES, several laboratory samples were measured using the LES with a relatively simple and compact experimental setup. The results showed that the error of mean diameter is smaller than 6 % and the error of concentration is smaller than 11 % for the samples of 40, 60, and 80 nm and for appropriate concentrations. This work provides a simple, fast, and low-cost method to measure the size distribution and concentration of polydisperse gold nanospheres.