Detection Limits of DLS and UV‐Vis Spectroscopy in Characterization of Polydisperse Nanoparticles Colloids

TLDR

Dynamic light scattering (DLS) is widely used for measuring particle sizes in the 2–500 nm range, but polydispersity can distort results because large particles screen smaller ones, and experimental limits of DLS have not been thoroughly investigated. The authors prepared polydisperse silver nanoparticle colloids by mixing chemically synthesized monodisperse colloids and characterized them with DLS, UV‑Vis, AFM, and TEM to study size and distribution. Their DLS analysis revealed that a few percent of the volume of larger nanoparticles can completely mask the presence of smaller ones, highlighting important metrological implications for researchers relying on DLS and UV‑Vis alone.

Abstract

Dynamic light scattering is a method that depends on the interaction of light with particles. This method can be used for measurements of narrow particle size distributions especially in the range of 2–500 nm. Sample polydispersity can distort the results, and we could not see the real populations of particles because big particles presented in the sample can screen smaller ones. Although the theory and mathematical basics of DLS technique are already well known, little has been done to determine its limits experimentally. The size and size distribution of artificially prepared polydisperse silver nanoparticles (NPs) colloids were studied using dynamic light scattering (DLS) and ultraviolet‐visible (UV‐Vis) spectroscopy. Polydisperse colloids were prepared based on the mixture of chemically synthesized monodisperse colloids well characterized by atomic force microscopy (AFM), transmission electron microscopy (TEM), DLS, and UV‐Vis spectroscopy. Analysis of the DLS results obtained for polydisperse colloids reveals that several percent of the volume content of bigger NPs could screen completely the presence of smaller ones. The presented results could be extremely important from nanoparticles metrology point of view and should help to understand experimental data especially for the one who works with DLS and/or UV‐Vis only.