At pH 8 the main acid groups present in alginate (−COOH) are
deprotonated (Rey-Castro et al., 2004) providing the AgNP with a net
negative charge (see ζ-potential values in Table 1). In this case, the alginate
coating stabilizes the AgNP suspension by electro-steric repulsion,
and consequently in low ionic strength solutions aggregation is
prevented. Nevertheless, at enhanced NaCl concentrations a plot of
1/A vs t (Eq. (2)) yielded straight lineswith high regression coefficients,
confirming the aggregation process (Video S2).