Polarity-reversal-producing phase transfer of hydrophilic silver nanoclusters capped by a hyperbranched polymer from water to nonpolar organic solvents

摘要

Hyperbranched poly(ethylene imine) (PEI)-capped Ag nanoclusters, synthesized starting from an aqueous environment, dispersed well in water and most polar organic solvents. However, with the addition of 1,4-dioxane, the PEI-capped Ag nanoclusters could be separated completely to obtain hydrophilic and hydrophobic Ag nanoclusters. Through this facile method, the successful phase transfer of PEI-capped Ag nanoclusters from the aqueous phase to the nonpolar organic phase, such as from water to carbon tetrachloride, chloroform, and methylene bichloride, was easily realized. The polarity reversal of Ag nanoclusters were considered to be associated with the conformational change of PEI on the basis of the hydrophobic methylene groups of polymer backbone facing the external side or internal side, and this polarity reversal was irreversible. Moreover, PEIs with higher molecular weights showed a higher efficiency of phase transfer of the Ag nanoclusters. (c) 2015 Wiley Periodicals, Inc.