Amphiphilic N-Heterocyclic Carbene-Stabilized Gold Nanoparticles and Their Self-Assembly in Polar Solvents

Abstract

Soft matter-directed self-assembly of amphiphilic inorganic nanoparticles (NPs) has recently emerged as a promising approach to access NP ensembles with superior collective properties. While thiol-terminated molecules are primarily employed to tether the amphiphilic ligand to the metal, concerns remain regarding the stabilities of the resulting NPs and their corresponding aggregates. As an alternative, we report amphiphilic N-heterocyclic carbene (NHC)-functionalized gold nanoparticles (AuNPs). To accomplish this, an amphiphilic NHC-Au complex based on an asymmetric triethylene glycol-/dodecyl-functionalized benzimidazole was first synthesized and used to prepare the corresponding stable amphiphilic NHC-decorated AuNPs. The resulting NPs were comprehensively characterized using both solution- and solid-state-based techniques such as proton nuclear magnetic resonance spectroscopy, dynamic light scattering, transmission electron microscopy, thermogravimetric analysis, and X-ray photoelectron spectroscopy. By optimizing the self-assembly behavior of these amphiphilic AuNPs in deionized water, ethanol, and their mixtures, we were able to fine-tune the plasmonic properties of the AuNPs in the wide range of 525-640 nm. Furthermore, when treated with thiols, the ensembles showed greater stability compared to their parent discrete AuNP counterparts at room temperature.

A Benchtop Method for Appending Protic Functional Groups to N‐Heterocyclic Carbene Protected Gold Nanoparticles

“…The TGA data is consistent with 2‐Cl (Figure S53) displacing the citrate (Figure S54) and forming 1 ‐ AuNPs (Figure S55). The lower onset temperature of 1‐AuNPs (240 °C vs. 200 °C) is a feature consistent of NHC coated AuNPs …”

A Benchtop Method for Appending Protic Functional Groups to N‐Heterocyclic Carbene Protected Gold Nanoparticles

“…Thel ower onset temperature of 1-AuNPs (240 8 8Cv s. 200 8 8C) is af eature consistent of NHC coated AuNPs. [22] Thea mine NHC-functionalized particles, 3-AuNPs,w ere achieved by reducing the nitro group on 2-AuNPs.Initial tests with sodium borohydride degraded 2-AuNPs,though amilder reducing agent, sodium hydrosulfite,w as effective (Figure 6a). Upon reduction of the nitro-NHC,S ERS analysis (Figure 6b)shows alarge decrease in the NO 2 stretching band at 1342 cm À1 and asimultaneous appearance of the NH 2 band at 1359 cm À1 .T he spectrum is otherwise unperturbed, indicating the NHC is modified only at the nitro position.…”

Multilayer onion‐like vesicles self‐assembled from amphiphilic hyperbranched multiarm copolymers via simulation

“…Delicate nanostructures can be designed by self‐assembly of amphiphilic molecules and have been successfully applied biomimetic, nanoscale devices, drug, and gene delivery . As an important kind of nanostructures, vesicles with specific structures and functions have attracted more attentions due to the potential applications in biomedicine and nanotechnology .…”

“…Delicate nanostructures can be designed by self-assembly of amphiphilic molecules and have been successfully applied biomimetic, nanoscale devices, drug, and gene delivery. [1][2][3][4][5][6][7][8][9][10][11] As an important kind of nanostructures, vesicles with specific structures and functions have attracted more attentions due to the potential applications in biomedicine and nanotechnology. [12][13][14][15][16][17][18][19][20][21][22][23] However, the shape of vesicles cannot be maintained for long time in organisms because of the interaction of them with the surrounding proteins and blood.…”