Size-Dependent Phase Transfer Functionalization of Gold Nanoparticles To Promote Well-Ordered Self-Assembly

Abstract

We present a route for the functionalization of gold nanoparticles (AuNP) based on phase transfer functionalization in order to optimize the stability and the potential for self-assembly. Depending on the desired size, different ligand exchanges have to be employed: The maximum AuNP size that can be stabilized without concentration loss is 46 nm for polystyrene-based ligands with 5 and 10 kDa. Small particles <12 nm are better stabilized by smaller ligands. We are able to demonstrate that well-ordered close-packed monolayers of 28 nm AuNP covering at least 400 μm are possible with a potential for much larger areas. Such monolayers are of great interest for various fundamental experiments in the context of plasmonics and SERS and for sensor applications.

Dark Interlayer Plasmons in Colloidal Gold Nanoparticle Bi- and Few-Layers

“…Close-packed layers of gold nanoparticles can be synthesized with grain sizes of several hundreds of µm 2 . 35 Stacking two monolayers will enable large-area coatings with tunable plasmonic resonances. Finally, we demonstrate that the concept of dark mode excitation in a nanoparticle bilayer can be extended to more than two layers giving rise to a rich variety of dark interlayer plasmons.…”

“…45 Functionalization with polystyrene (PSSH5k): The AuNP@Citrate were functionalized with the PSSH5k ligand based on the phase transfer ligand exchange protocol described recently. 35 PSSH (0.16 mM) and oleylamine (1 mM) in toluene (6 ml) were mixed with the aqueous AuNP@Citrate (6 ml) and ethanol (6 ml) under rapid stirring. The stirring was stopped after 30 minutes and after complete phase separation, the organic phase was carefully extracted and concentrated and purified by centrifugation (12 min × 2,000 g in 1 ml aliquots).…”

“…Self-assembly of AuNP@PSSH at the liquid-liquid interface: AuNP@PSSH5k monoand bilayer films were prepared by self-assembly at the liquid-liquid interface. 35…”

Direct optical excitation of dark plasmons for hot electron generation

“…The well was covered with a quartz slide and le undisturbed at room temperature until the solvent had evaporated and a gold nanoparticle lm had formed. 35,36 For their characterization by transmission electron microscopy (TEM) and microabsorbance measurements, the lms were carefully skimmed off with a carbon-coated copper grid. The probability of bilayer formation was increased by repeating the procedure.…”

“…We recently developed an advanced synthesis technique for d ¼ 46 nm gold particles and their assembly into colloidal hcp structures (see the methods section in ref. 35). Transmission electron microscopy (TEM) images show hexagonal packing due to self-assembly aer drying the solution on a TEM grid with a 10 nm amorphous carbon lm (Fig.…”