Release mechanism of octadecyl rhodamine B chloride from Au nanorods by ultrafast laser pulses

Abstract

We investigated the release of octadecyl rhodamine B chloride (R[subscript 18]) loaded onto cetyltrimethylammonium bromide (CTAB) coated gold nanorods (NR) by pulsed ultrafast laser excitation. R[subscript 18] intercalates into the hydrophobic CTAB bilayer on the NR surface and can exchange on and off the NR with free CTAB micelles in solution. We find that laser excitation accelerates the rate of both R[subscript 18] release from the NR and R[subscript 18] binding to the NR with increasing fluence. However, at laser fluences >220 μJ/cm[superscript 2] thermal degradation of the R[subscript 18] dominates. We also find that the concentration of CTAB, particularly around the critical micelle concentration, strongly influences the release and binding rates.