Reconstruction of Silver Nanoplates by UV Irradiation: Tailored Optical Properties and Enhanced Stability

摘要

Colloidal noble-metal nanoparticles, especially of gold and silver, have proven to be good candidates for applications in catalysis, surface-enhanced Raman scattering (SERS), biosensors, and plasmonics, of which chemical and biological sensing are the most promising. Most of these' attractive applications are based on the particles' surface plasmon resonance (SPR), which strongly depends on their specific composition, size, shape, local dielectric environment, and electromagnetic interactions with proximate parti-cles. Recently, it has been realized that particle shape plays an important role in determining the plasmon wavelength, therefore stimulating great interest in shape-controlled synthesis. For example, excellent work has been done to synthesize silver nanoparticles with shapes varying from spheres to cubes, polyhedrons, plates, and wires, which greatly broaden the range of the SPR wavelength. In principle, the plasmon band of the nanoparticles can be systematically tuned by controlling their shape evolution during particle growth. In practice, however, it is usually difficult to quickly stop the reaction and harvest the growing particles at the desired stage. Moreover, these intermediate particles are not stable and they usually change shape during storage. As a result, in most cases, to obtain multiple samples with desired plasmon bands, the synthetic conditions, including the concentration of reagents and capping ligands, temperature, injection time and so forth, must be fine-tuned, which usually leads to low reproducibility and poor predictability because the nucleation and growth of the nanoparticles are very sensitive to small variations of synthetic conditions.