Stability and Fate of Hollow Mesoporous Silica Nanoparticles in Aqueous Environment: Effects of Ph and Electrolyte

Abstract

Hollow mesoporous silica nanoparticles (HMSNs) and their carboxyl-functionalized counterparts (C-HMSNs) are promising materials for environmental applications, yet their stability in aquatic environments remains poorly understood. This study investigates the aggregation behavior of HMSNs and C-HMSNs under varying pH and electrolyte conditions. Experimental results combined with Derjaguin-Landau-Verwey-Overbeek (DLVO) theory and molecular dynamics (MD) simulations showed HMSNs exhibit faster aggregation than C-HMSNs due to lower zeta potentials and critical coagulation concentrations (CCC) High concentrations of NaCl and CaCl2 promoted rapid aggregation of HMSNs and C-HMSNs, with CaCl2 being more efficient in promoting aggregation. Both HMSNs and C-HMSNs were more prone to aggregation in acidic environments, and their stability in neutral and alkaline environments was similar. Our findings suggest that HMSNs and C-HMSNs remain stable in rivers, begin to aggregate slightly but do not form micelles in groundwater, and aggregate extensively in seawater. These findings offer critical insights into the environmental fate of silica nanoparticles and their potential ecological risks in varying aquatic matrices, informing future studies on nanoparticle transport and bioavailability in natural waters.

Keywords: Hollow mesoporous silica nanoparticles, Aggregation, Colloidal stability, Environmental behavior, Derjaguin-Landau-Verwey-Overbeek Theory