Fast loading of PEG-SH on CTAB-protected gold nanorods

This study aimed to develop a rapid and simple method to functionalize gold nanorods using thiolated polyethylene glycol (PEG-SH), which can be used for plasmonic sensing and other applications. PEG was successfully loaded onto CTAB-protected gold nanorods in 30 min using Tris buffer with a pH of 3.0. In contrast, the functionalization of gold nanorods in water induced the aggregation of gold nanorods and produced a floating layer of randomly aggregated nanorods at the water-air interface. The concentration of mPEG-SH has no significant influence on the optical properties of gold nanorods modified by the proposed method. The results show that the PEG-modified gold nanorods could sustain 1.0 M NaCl, whereas CTAB-protected gold nanorods aggregated immediately after the addition of NaCl. Compared with the traditional 24 h method in a CTAB/ carbonate solution, the proposed method offers a higher loading speed and a higher coverage density of PEG on gold nanorods. It was also found that the PEG-modified NR-610 could form a very uniform monolayer on silicon by slow evaporation of the water content. This method may open a new route for fabricating substrates for bio-medication, detection of food contaminants, and environmental monitoring.