The isolation of individual nano-objects in a far-field optical microscope completely eliminates conventional ensemble- and time-averages. The method provides a new window on nanometer-scales, for basic physical chemistry, material science, and molecular biology. Single objects can also deliver single photons, opening new experiments in quantum mechanics.
Blinking and bleaching are important processes for single molecules and semiconductor nanocrystals. Recent work has demonstrated the role of charge transfer in these processes. Metal nanoparticles are resistant to both bleaching and blinking. These appealing labels can be efficiently detected via their absorption by photothermal and interferometric pump-probe methods. They also generate second- and third-harmonic nonlinear signals.