Gold nanoparticles (AuNPs) have become important functional materials with a broad range of applications chiefly due to their optical properties, biocompatibility and catalytic activity. Particle agglomeration resulting in plasmon coupling and corresponding dramatic colour change can readily be exploited to create simple and highly sensitive colorimetric test formats for analytical or diagnostic purposes. In recent years, a plethora of chemical and physical stimuli that can trigger the agglomeration of AuNPs have been identified including light, pH, metal ions and temperature. Here we present the development of two different sizes of gold nanoparticles (3 and 7.5nm) coated with a 18-crown-C-SH moiety which imbues the particles with its unique hole-size cation-diameter properties, allowing for the control of their hydrophobicity by changing the concentration of KCl present within solution. This results in a controllable phase transfer behaviour in immiscible liquid-liquid systems, and also leads to entropically driven reversible agglomeration from aqueous dispersion. The transition temperature for the latter process can also be controlled by complexing the crown ether with the corresponding cation. These processes were monitored by multiple analytical techniques such as: Direct video recording, UV-Vis, TEM, DLS and Zeta potential. It is hoped that with further work these particles could prove useful in allowing the transfer of both electrons and cations across bi-lipid membrane interfaces, as an artificial mimic to natures standard methods of membrane transport.

Controllable hydrophobicity of gold nanoparticles coated with 18-CROWN-6-C-SH

255th National Meeting (2018)

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