Designing plasmonic structures: Bi-metallic core-shell nanoparticles

摘要

Chemical approaches allow for the synthesis of highly defined metal hetero-nanostructures, such as core-shell nanospheres. Because the material of metal nanoparticles determines the plasmon resonance-induced absorption band, the control of particle composition results in control of the position of the absorption band. Metal deposition on gold or silver nanoparticles yielded core-shell particles with modified optical properties. Besides the optical characterization, the utilization of AFM and TEM yielded important information about the morphology of the nanoparticle complexes. UV-vis spectroscopy on solution-grown and surface-grown particles was conducted as ensemble measurements in solution. Increasing layers of a second metal lead to a shift in the absorption band, and a shell diameter comparable to the original particle diameter leads to a predominant influence of the shell material. The extent of shell growth could be controlled by reaction time or the concentration of either the metal salt or the reducing agent.