Retardation of Shape Change of Au Nanorods Using Photo-Cross-Linkable Ligands

The thermal reshaping of gold nanorods has been slowed by grafting a diblock copolymer [P(S-b-S-N-3)] containing an outer polystyrene (PS) brush and a short, inner photocross-linkable PS-azide block. The P(S-b-S-N-3)-Au NRs were dispersed in a PS thin film and reshaping was investigated using scanning electron microscopy and UV-Vis spectroscopy. For P(S-b-S-N-3)-Au NRs in PS, the longitudinal surface plasmon resonance decreased from about 880 toward 750 nm upon annealing at 100 degrees C, 150 degrees C, and 200 degrees C. This blue shift increased in strength as temperature increased. However, this reshaping of P(S-b-S-N-3)-Au NRs was slower than that of Au NRs grafted with a poly(ethylene glycol) brush that was dispersed in poly(methyl methacrylate). By slowing down reshaping at elevated temperature, polymer thin film devices that heat during use (e.g., polarization dependent filters) can exhibit a longer lifetime. (C) 2015 Wiley Periodicals, Inc.