Monolayers of silver nanoparticles on positively charged polymer microspheres

Abstract

Abstract The deposition of silver nanoparticles on positively charged polystyrene microspheres was studied by micro-electrophoretic and concentration depletion methods involving UV–vis spectrometry. The influence of ionic strength varied between 10 −4 to 3 × 10 −2 M, was determined. Primarily, the electrophoretic mobility variations of latex upon the addition of controlled amount of silver nanoparticles were measured. These dependencies were quantitatively interpreted in terms of the 3D electrokinetic model previously used for planar interface. This allowed to determine the coverage of nanoparticles on microspheres under in situ conditions for incomplete monolayer range. Additionally, the maximum coverage of silver nanoparticles was precisely determined by measuring the absorption spectrum of the silver suspension acquired by ultrafiltration after the deposition step. It was shown that maximum coverage monotonically increased with ionic strength attaining 0.52 for the ionic strength of 3 × 10 −2 M. This effect, attributed to the decreasing range of lateral electrostatic interactions among deposited particles, was accounted for by the random sequential adsorption model. The obtained results proved the feasibility of preparing silver nanoparticle shells on polymeric carrier microspheres having well-defined coverage and structure. Also, our measurements confirmed the validity of the 3D electrokinetic method for a quantitative interpretation of nanoparticle deposition on microspheres.