Ethanol as a ‘Catalyst’ for Effective Phase Transfer and Self-Assembly of Gold Nanorods

Graphical The transfer of gold nanorods (GNRs) to non-polar solvents enhances their self-assembly, biocompatibility, and surface-enhanced Raman scattering (SERS) abilities. However, the strong attachment of CTAB to the GNRs hinders their combination with other substances. Using ethanol as a ′catalyst′ lowers CTAB′s critical micelle concentration, facilitating its efficient combination with selected organosilanes, and the phase transfer process has been studied. The modified GNRs effectively self-assemble at the air-water interface. The plasmonic coupling between particles enhances the SERS activity, which is analyzed using varying concentrations of R6G. Transferring gold nanorods (GNRs) from an aqueous solution to a non-polar solvent enhances self-assembly, promotes biocompatibility, and boosts surface-enhanced Raman scattering (SERS). However, the strong attachment ability of toxic hexadecyltrimethylammonium bromide (CTAB) to GNRs presents a significant challenge in the fall of CTAB and combining with other substances for self-assembly and SERS applications. We propose a solution that employs ethanol as a ‘catalyst’ to lower the critical micelle concentration (CMC) of CTAB and efficiently combine it with the organosilanes formed by the hydrolysis of mercaptopropyltrimethoxysilane (MPS) and octadecyltrimethoxysilane (ODS). The samples were characterized by UV-vis-NIR spectroscopy, transmission electron microscopy (TEM), and energy disperse spectroscopy (EDS) mapping. A detailed interpretation of the phase transfer processes was provided. The modified particles were effectively dispersed in toluene and formed thin films at the air-water interface through self-assembly, which was confirmed by scanning electron microscopy (SEM) and optical microscopy. These films can serve as a platform for SERS.