Probing the Deposition Kinetics of Nanoparticles by Plasmonic Imaging and Counting Single Nanoparticles

Understanding the nanoparticle deposition process is important for predicting the transport and fate of nanoparticles in natural and engineered aquatic environments. Traditional methods for deposition studies are based on ensemble analysis of nanoparticles. Here, a single-nanoparticle imaging method was used to probe the deposition kinetics of nanoparticles by directly counting single nanoparticles with powerful surface plasmon resonance microscopy (SPRM). The ability of SPRM to provide single-nanoparticle imaging and its vertical sensitivity enabled us to differentiate collision and attachment events and, consequently, determine the attachment efficiency without any additional control experiments. As a proof-of-concept application of SPRM in measuring nanoparticle deposition, the relationship of the solution chemistry and surface chemistry with the attachment efficiency of nanoparticles was correlated. These results demonstrated that nanoparticle deposition kinetics at the single-particle level can be obtained with SPRM and that this technology can also be used to investigate other particle-particle or particle-surface interactions in aquatic environments.