Plasmonic nanoparticles are tiny metallic particles with unique optical features caused by their interaction with light at the nanoscale. Because of the nature of the dielectric-metal interface between the medium and the particles, these particles’ electron density can couple with electromagnetic radiation of wavelengths far larger than the particle, as opposed to a pure metal, where there is a maximum limit on what size wavelength can be effectively coupled based on material size. These nanoparticles range in size from tens to hundreds of nanometers and can be composed of a variety of materials, including gold, silver, and other noble metals.
Plasmonic nanoparticles differ from regular surface plasmons in that they display fascinating scattering, absorbance, and coupling features depending on their geometries and relative positions. These distinct features have made them the subject of research in a variety of fields, including solar cells, spectroscopy, signal amplification for imaging, and cancer therapy. Their high sensitivity also makes them ideal candidates for building mechano-optical instruments.
Some common applications of plasmonic nanoparticles include:
- Surface-enhanced Raman spectroscopy (SERS): Plasmonic nanoparticles can significantly amplify the Raman scattering signal of molecules adsorbed on their surfaces, allowing for highly sensitive detection of trace analytes. This has potential uses in chemical sensing, bioanalysis, and environmental monitoring.
- Biomedical imaging: These can be utilized as contrast agents in a variety of imaging applications, including optical microscopy, photoacoustic imaging, and surface-enhanced imaging techniques. They provide excellent sensitivity and specificity for identifying biomolecules and visualizing biological processes at the cellular and molecular levels.
- Photothermal therapy: These can convert absorbed light into heat very efficiently, making them promising agents for photothermal therapy of cancer and other diseases. By selectively targeting diseased tissues with plasmonic nanoparticles and irradiating them with light, localized heating can be induced to destroy the targeted cells while sparing surrounding healthy tissue.
- Optical sensing: These are used in a wide range of optical sensing applications, such as label-free biomolecule detection, environmental monitoring, and chemical analyte detection. The plasmonic characteristics of nanoparticles alter in reaction to their immediate surroundings, allowing for very sensitive and selective detection of target molecules.
- Plasmonic catalysis: These can improve catalytic reactions by concentrating electromagnetic radiation on their surfaces, which speeds up chemical reactions. This has significance for applications like photocatalysis, which uses light-induced chemical reactions to remediate the environment, convert energy, and synthesize organic compounds.
