Ionic Liquid-Responsive Phase Transfer of Gold Nanoparticles: Anionic Metathesis

Abstract

In this work, a fresh approach has been proposed for the efficient transfer of gold nanoparticles (AuNPs) from an aqueous to organic phase by the metathesis reaction or anion exchange reaction. Here, we synthesized ionic liquid 1-butyl 3-hexadecyl imidazolium bromide [C 4 C 16 Im]-Br-stabilized AuNPs which exhibit excellent stability in solution. Transfer of Au@[C 4 C 16 Im]Br from an aqueous to organic phase was investigated by the metathesis reaction with different hydrophobic ionic liquid-forming salts such as LiNTf 2 , LiClO 4 , and KPF 6 . The anionic exchange process in ionic liquids at the AuNP surface to make hydrophilic to hydrophobic AuNPs is demonstrated. It was found that hydrophobic ionic liquids provide the most effective transfer of AuNPs from the aqueous to organic phase. Interestingly, we have noticed no change in color, size, and shape of AuNPs for more than a month, indicating more efficient transfer of AuNPs in organic solvents, which remained stable for over a month. The ionic liquids with anions NTf 2 − , ClO 4 − , and PF 6 − make the AuNP surface hydrophobic, indicating their good dispersibility in nonpolar solvents. Finally, these AuNPs exhibit excellent sensitivity toward the refractive index of organic solvents, which is correlated with the surface plasmon resonance (SPR) λ SPR bands.

Solvent Quality-Mediated Regioselective Modification of Gold Nanorods with Thiol-Terminated Polymers

“…With the development of nanotechnology, gold nanoparticles (AuNPs) have emerged as an important family of nanomaterials due to their unique localized surface plasmon resonance (LSPR). − Among others, gold nanorods (AuNRs) with anisotropic shape exhibit tunable LSPR bands that are dependent on the aspect ratio of rods, which makes them attractive for applications in microelectronic, catalysis, bioimaging, tumor therapy, and others. − The implementation of AuNRs in these applications often necessitates the modification of the surface of NPs to enhance their compatibility, colloidal stability, or functionality. − In particular, functionalization of AuNRs with ligands on specific surface regions (i.e., chemical patches) further promotes the anisotropy in the plasmonic-enhanced physical properties (e.g., photothermal conversion, plasmon coupling, and fluorescence enhancement). − Moreover, chemical patches regioselectively decorated on NRs can enable the molecular-mimicking self-assembly of block copolymers into hierarchically complex functional structures. , …”

Cellulose Film-Integrated Gold Nanoparticles Synthesized in Ionic Liquids for Heterogeneous Catalysis

“…Several studies have explored the chemical synthesis of AuNPs in aqueous media by adding ionic liquids as an additional component. − It is worth mentioning that the presence of water, in most cases, is essential due to the inherent limitations of the reagent́s solubility that exist in ionic liquids . Due to this, only a few reports have delved into the direct chemical reduction of gold salts exclusively in ionic liquids.…”

A novel thermoregulated phase-transfer catalysis system for chiral nano-Pt-catalyzed asymmetric hydrogenation

“…10 Among these studies, ionic liquids (ILs), as effective phase-transfer vehicles, have received significant attention. [11][12][13][14] In our previous study, a thermoregulated phase-transfer catalysis system was developed based on the cloud point (Cp) of the chiral ionic liquid CIL TPT [CH 3 (OCH 2 CH 2 ) 16 CD] + [PF 6 ]  (CD = cinchonidine). 15 The CIL TPT -stabilized chiral Pt nanocatalyst could realize transfer in a H 2 O-1-pentanol biphasic system.…”

“…Hence, the chiral Pt nanocatalyst can be easily separated and recycled. However, up to now, almost all the ILs involved in phase transfer of a catalyst are limited to using fluorine-containing anions, [10][11][12][13] which are expensive and environmentally unfriendly. This of course pertains to our previously reported thermoregulated phase-transfer catalysis system.…”