Plasmonic metal nanostructures have been intensively studied for a wide range of applications such as chemical sensing, optoelectronics, and photothermal therapy, because of their unique optical properties caused by localized surface plasmon resonance (LSPR). Since the assembly of plasmonic nanoparticles into secondary structures may induce near field coupling of surface plasmons between adjacent particles, new optical properties can be obtained, inducing shifts of plasmonic peaks, and the generation of "hot spots" that are very useful for enhancing Raman scattering. Of particular interest is the reversible assembly of such plasmonic nanostructures, which is expected to enable dynamic tuning of the surface plasmon coupling in response to the external stimuli, and therefore produce active optical materials for applications such as color signage, bio-and chemical detection, and environmental sensing. However, despite extensive studies, on nanoparticle assembly, it remains a great challenge to develop stimuli-responsive systems with reversibly tunable plasmonic properties. In the few available reports for gold nanoparticles (AuNPs), some are designed to respond to pH changes, while others involve thermoresponsive polymers so that the systems are sensitive to temperature variations.
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