Plasmonic Nanoparticles Meet Polymers: Revelation of the Polymer Brush Formation Mechanism

We will present our recent progress on the utilization of plasmonic nanoparticles in polymer sensing. Currently the synthesis of plasmonic nanoparticles for sensing mostly focuses on the shape because it is believed that nanoparticles with sharp tips provide higher sensitivities than those without. By analyzing the sensitivities of more than 74 types of nanoparticles of various shapes, sizes, and compositions, we found that the correlation between shape and sensitivity is much weaker than that between aspect ratio and sensitivity. Among many parameters including size, shape, composition, aspect ratio, cross-sectional area, and initial plasmonic resonance frequency, the aspect ratio is the key parameter that controls the nanoparticle sensitivity. Other parameters have much less influence on the nanoparticle sensitivity to refractive index changes. Based on this finding, we selected Ag nanodisks as sensors to probe the kinetics of polymer brush formation. Unitizing the plasmonic properties of Ag nanodisks, we demonstrated in situ the three-regime kinetics of polymer brush grafting process, and importantly, for the first time we revealed the cause of a latent regime during the polymer brush grafting process, which has been a long-lasting puzzle in the field of polymer brush.