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閱讀：230 發布時間：2014-10-16

The aggregation kinetics of silver nanoparticles (AgNPs) that were coated with two commonly use

agents—citrate and polyvinylpyrrolidone (PVP)—were investigated. Time-resolved dynamic light

(DLS) was employed to measure the aggregation kinetics of the AgNPs over a range of monovalen

electrolyte concentrations. The aggregation behavior of citrate-coated AgNPs in NaCl was in excel

with the predictions based on Derjaguin–Landau–Verwey–Overbeek (DLVO) theory, and the Ham

of citrate-coated AgNPs in aqueous solutions was derived to be 3.7 × 10 J. Divalent electrolytes

efficient in destabilizing the citrate-coated AgNPs, as indicated by the considerably lower critical c

concentrations (2.1 mM CaCl and 2.7 mM MgCl vs. 47.6 mM NaCl). The PVP-coated AgNPs w

significantly more stable than citrate-coated AgNPs in both NaCl and CaCl , which is likely due to

repulsion imparted by the large, non-charged polymers. The addition of humic acid resulted in the

the macromolecules on both citrate- and PVP-coated AgNPs. The adsorption of humic acid induce

electrosteric repulsion that elevated the stability of both nanoparticles in suspensions containing Na

concentrations of CaCl . Conversely, enhanced aggregation occurred for both nanoparticles at high

concentrations due to interparticle bridging by humic acid clusters.