Engineering amphiphilic gold thiolate clusters for enhanced luminescence and controlled assembly

Abstract

Amphiphilic gold thiolate clusters have garnered significant interest due to their versatile structural and optical properties, making them valuable for applications in nanotechnology and biophotonics. This study outlines a systematic approach to synthesizing AuS-C11H23-PEG17 gold thiolate nanoparticles through a multi-step process. The thiol ligand, HS-C11-PEG17, is synthesized via reactions involving PEG modification, thiol introduction, and disulfide reduction, with structural confirmation through ¹H NMR and elemental analysis. The subsequent formation of gold thiolate clusters involves reacting AuCl₄·4H₂O with HS-C11-PEG17, followed by purification to yield nanoparticles with a molecular size of 10 nm as measured by DLS (Dynamic Light Scattering). SAXS (Small Angle X-ray Scattering), and HPLC (High-Performance Liquid Chromatography) analyses reveal time-dependent nanoparticle growth and reaction progress, while mass spectrometry identifies cyclic and open tetramer cluster species. AFM imaging highlights solvent- and concentration-dependent assembly morphologies, ranging from multilayers to needle-like structures. Photophysical studies demonstrate an 800-fold increase in emission intensity within 24 h, with emission influenced by alkyl chain length and PEG chain properties. These findings underline the amphiphilic ligand's role in cluster assembly, aurophilic interactions, and optical properties, showcasing the potential of AuS-C11-PEG17 clusters in advanced nanotechnological applications.