Metallic nanoparticles, used since antiquity to impart intense and vibrant color into materials, have more recently become a central tool in the nanoscale manipulation of light. This interest has led to a virtual explosion of new types of metal-based nanoparticles and nanostructures of various shapes and compositions, and has given rise to new strategies to harvest, control, and manipulate light based on these structures and their properties. As one begins to assemble metallic nanoparticles into useful building blocks, a striking parallel between the plasmons of these structures and wave functions of simple quantum systems is universally observed.  Clusters of metallic nanoparticles behave like coupled oscillators or antennas, introducing effects characteristic of systems as diverse as radio frequency transmitters and coupled pendulums into light-driven nanoscale structures.  Their unique light-controlling properties can be put to use in a multitude of ways: for detecting single molecules and following chemical reactions, for light-based medical diagnostics and therapeutics, and most recently, for high-efficiency solar steam generation poised to tackle our planet’s energy and sustainability challenges.
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