Photochemical Tuning of Plasmon Resonances in Single Gold Nanoparticles

We report on the spectrally controlled photochemical tuning of the size, shape, and localized surface plasmon resonances of individual gold nanoparticles. Single spheres, extracted from a colloidal solution, and elongated nanodiscs, fabricated by electron beam lithography, were exposed to a gold salt solution while being illuminated one by one by a focused 532-nm laser beam. The photochemical reduction of tetrachloroaureate complexes, followed by the subsequent agglomeration of gold atoms at the particle surface, lead to a well-controlled single-particle growth. This fully in situ monitored method allows us to tune the radius of single spheres as well as the aspect ratio of single ellipsoidal particles, enabling spectral control of their respective localized surface plasmon resonances.