Single Silver Nanoparticles as Real-Time Optical Sensors with Zeptomole Sensitivity

This work utilizes dark-field optical microscopy to demonstrate the localized surface plasmon resonance λmax response of individual Ag nanoparticles to the formation of a monolayer of small-molecule adsorbates. The adsorption of fewer than 60 000 1-hexadecanethiol molecules on single Ag nanoparticles results in a localized surface plasmon resonance shift of 40.7 nm. Additionally, the kinetics of the single nanoparticle response was shown to be comparable to that of other real-time sensor technologies.