Phase transition of silver nanoparticles from aqueous solution to chloroform with the help of inclusioncomplexes of p-sulfonated calix[4]arene and alkanethiol molecules and its application in the size sorting ofnanoparticles

Abstract

Silver nanoparticles were synthesized in aqueous solution andcapped with an inclusion complex of octadecanethiol (ODT) andp-sulfonated calix[4]arene (pSC4). By vigorous shaking of a biphasic mixture of thepSC4-threaded ODT-stabilized silver hydrosol and chloroform, the phase transitionof the silver nanoparticles could be observed in the course of the transition ofcolour from the aqueous phase to the organic phase. The procedure of phasetransition was independently verified by UV–vis spectroscopy, transmissionelectron microscopy (TEM), Fourier transform infrared (FTIR) spectra, and1H nuclear magnetic resonance (NMR). In shaking the biphasic mixture, it was believed thatpSC4 molecules were desorbed from the inclusion complex and the protective layer of silvernanoparticles shifted from hydrophilic to hydrophobic, which drove the phase transition ofsilver nanoparticles from aqueous solution into chloroform. More interestingly, the efficiencyin the phase transition of aqueous silver nanoparticles rigidly depended on their sizes,which maybe used in the size sorting of nanoparticles.