Temperature responsive plasmonic assembles of amphiphilic nanoparticles at oil-water interfaces.

Abstract

Gold nanoparticle (AuNP) has been widely used in the biotechnology field due to its bio-inert characteristic and other unique physical qualities such as optical and electrical properties. Here, a new class of AuNP with multi-polymer brush coating, which can spontaneously assemble and disassemble under the influence of temperature, is reviewed in this report. This new class of AuNP coated with hydrophilic and hydrophobic multi-polymer brushes allows for self-assembly in temperature condition of more than 40 ̊C and disassembles in temperature condition of less than 20 ̊C in an oil-water interface.

Poly(N-isopropylacrylamide) (PNIPAM) coated AuNP surface provided temperature responsive property with a lower Critical Solution Temperature (LCST) of around 32 ̊C. At temperature around LCST, the AuNP solution undergo reversible phase transition from homogenous solution to precipitation of insoluble AuNP forming a 2D array self-assembly layer at the oil-water interface.

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This amphiphilic AuNP with multi-polymer brushes were synthesized by means of a two-step process, “grafting to” (ligand exchange) and “grafting from” (surface initiated atom transfer radical polymerization) reactions. Such combination of surface reaction, allow high customizability on the surface of AuNP that give contrasting properties between different combinations of well-defined surface polymer brushes. Under this two-step process, we are able to synthesize well-defined multi-polymer brush coated AuNP, displaying highly reversible 2-D array self-assembly characteristic under differentiated ambient temperature in oil-water interface platform.

The synthesized, temperature sensitive, AuNP has shown stability and repeatability in our research which opens opportunities for developing hybrid materials with collective and integrated functionalities suitable for employment in biomedical field that require biological inert property.