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

Area of Science:

• Nanotechnology
• Materials Science
• Chemistry

Background:

• Gold nanoparticles (AuNPs) are widely used in various applications.
• Efficient transfer of AuNPs between aqueous and organic phases is crucial for their utilization in different media.
• Existing methods for AuNP phase transfer can be complex or lead to instability.

Purpose of the Study:

• To develop an efficient and stable method for transferring gold nanoparticles from aqueous to organic phases.
• To investigate the role of ionic liquids and anion exchange in this transfer process.
• To evaluate the stability and sensing capabilities of transferred AuNPs in organic solvents.

Main Methods:

• Synthesis of 1-butyl 3-hexadecyl imidazolium bromide ([C4C16Im]Br)-stabilized AuNPs.
• Investigation of metathesis reactions with hydrophobic ionic liquid-forming salts (LiNTf2, LiClO4, KPF6) for anion exchange.
• Characterization of AuNP stability, size, shape, and optical properties (SPR) in organic solvents.
• Assessment of AuNP sensitivity to the refractive index of organic solvents.

Main Results:

• Successfully transferred [C4C16Im]Br-stabilized AuNPs from aqueous to organic phase using metathesis reactions.
• Hydrophobic ionic liquids facilitated the most effective transfer, rendering AuNP surfaces hydrophobic.
• Transferred AuNPs exhibited excellent stability in organic solvents for over a month, with no changes in color, size, or shape.
• The ionic liquids with NTf2-, ClO4-, and PF6- anions enhanced AuNP dispersibility in nonpolar solvents.
• AuNPs demonstrated high sensitivity to the refractive index of organic solvents, correlated with SPR shifts.

Conclusions:

• The proposed method offers an efficient and stable approach for transferring AuNPs to organic media using ionic liquid-mediated anion exchange.
• The resulting hydrophobic AuNPs are stable and suitable for applications in organic solvents.
• The refractive index sensitivity of these AuNPs highlights their potential as nanoscale sensors in non-aqueous environments.