Stability of nanodiamonds and carbon dots in aqueous environment: insights into aggregation behavior and additive influence

Abstract

This study investigated the stability of carbon-based nanoparticles, specifically carbon dots (CD) and nanodiamonds (NDs), in model systems designed to mimic a natural water environment. Dynamic light scattering (DLS) and zeta potential measurements were performed to evaluate particle size distribution, surface charge and their stability both as standalone nanoparticles and in the presence of additives such as bovine serum albumin (BSA), dextran sulfate sodium salt (DSS), fulvic acid (FA) and natural organic matter (NOM). The results showed significant differences in stability between CD and NDs, with CD showing a tendency to aggregate, while NDs exhibited higher stability under different conditions. The addition of BSA, FA and NOM significantly affected the zeta potential, although the ND suspensions remained stable under acidic conditions. Conversely, DSS had minimal effects on the zeta potential, resulting in stabilization effect in Mili-Q water. In NaCl suspensions, addition of additives resulted in aggregation, with the exception of NOM, which improved the stability of ND under alkaline conditions. These results improve our understanding of the environmental behaviour of carbon-based nanoparticles and highlight the role of environmental factors and additives in their stability. This knowledge is crucial not only for evaluating their behaviour and potential impact on the aquatic environment but also for developing novel technologies that exploit their unique properties for sustainable and innovative applications.