Hydrophilic Gold Nanoparticles Adaptable for Hydrophobic Solvents

Abstract

Surface ligand molecules enabling gold nanoparticles to disperse in both polar and nonpolar solvents through changes in conformation are presented. Gold nanoparticles coated with alkyl-head-capped PEG derivatives were initially well dispersed in water through exposure of the PEG residue (bent form). When chloroform was added to the aqueous solution of gold nanoparticles, the gold nanoparticles were transferred from an aqueous to a chloroform phase through exposure of the alkyl-head residue (straight form). The conformational change (bent to straight form) of immobilized ligands in response to the polarity of the solvents was supported by NMR analyses and water contact angles.

Comparative study of alkylthiols and alkylamines for the phase transfer of gold nanoparticles from an aqueous phase to n-hexane

“…Moreover, the proposed method can preserve the shape and size of the Au-NPs, which was confirmed by UV-vis spectra and TEM analysis. Meanwhile, the transferred AuNPs can be well dispersed in the n-hexane and kept stable for some weeks, which appears reasonable when compared to available literature [5,21].…”

“…The phase transfer of Au-NPs with 5-25 nm was ignored in the previous studies [13,[20][21][22][23]. In this study, the molar ratio of DDT to Au-NPs is a critical factor affecting the transfer efficiency, and 270-310 is found to be the optimum range, under which the transfer efficiency of this method is >96%.…”

“…McMahon and Emory [20] developed a method to transfer large Au-NPs (d > 45 nm) from aqueous solutions to chloroform with dicyclohexylamine (DCHA). In addition, Sekiguchi et al [21] also developed an octanethiol-assisted method for transferring small Au-NPs (5 nm) from an aqueous phase to chloroform. However, in the existing reports, most of the phase transfer methods are only applicable to small (d < 5 nm) and/or large (d > 20 nm) Au-NPs [13,[20][21][22][23], and very few studies have focused on whether alkylthiols and/or alkylamines can transfer Au-NPs (d: 5-20 nm) from an aqueous to an organic phase.…”

“…In addition, Sekiguchi et al [21] also developed an octanethiol-assisted method for transferring small Au-NPs (5 nm) from an aqueous phase to chloroform. However, in the existing reports, most of the phase transfer methods are only applicable to small (d < 5 nm) and/or large (d > 20 nm) Au-NPs [13,[20][21][22][23], and very few studies have focused on whether alkylthiols and/or alkylamines can transfer Au-NPs (d: 5-20 nm) from an aqueous to an organic phase. Moreover, there have been no studies reported on the comparison between alkylthiols and alkylamines for phase transfer of Au-NPs, although some recent studies have investigated the effect of ligands on phase transfer of Au-NPs [5,[17][18][19][20][21][22][23].…”

A convenient phase transfer protocol to functionalize gold nanoparticles with short alkylamine ligands

“…Transfer from aqueous to organic media is normally done with the assistance of alkylthiols, alkyamines, or other similar ligands [29][30][31][32][33][34][35]. For example, octadecylamine (ODA) was used to transfer Au NPs produced in water to toluene by vigorously shaking the biphasic mixture [29].…”