Gold nanoparticle sizing based on differential static light scattering spectroscopy, absorption spectroscopy, and dynamic light scattering

Three procedures for determining the average size of colloidal gold (CG) nanoparticles are described. The first procedure is the dynamic light scattering (DLS) method. The others are based on the estimation of extinction or differential static light scattering (DSLS, at 90 degrees) peak positions. Experimental studies were carried out with four samples of CG (the average DLS-diameters were equal to 15, 20, 25, and 30 nm). In the case of DSLS, the angular slope of the calibration curve "peak position versus particle size" was 2.4 times greater than the extinction curve slope. In experiments with controlled polydispersity, two different colloid mixtures were used. Extinction spectra of samples were almost identical, whereas the DSLS spectra showed noticeable differences with a red shifted maximum. The theoretical simulations by the Mie theory are in agreement with these experimental observations. The DSLS technique seems more reliable and accurate in CG particle sizing, as compared with the usual absorption spectroscopy.