Optical trapping and luminescence of silica encapsulated quantum dots(Conference Presentation)

Semiconductor nanocrystals (quantum dots, QDs) represent a milestone in the field of luminescent nanoparticles owing to their unique optical properties. Silica encapsulation of colloidal QDs in optimized synthetic conditions provides an excellent method to reduce their cytotoxicity maintaining, at the same time, their optical properties.1 The ability to optically confine and spatially control these biocompatible nanostructures in liquid media boosts their investigation for bioimaging both as an ensemble as well as at a single particle-level. In this study we explore the optical trapping of silica-encapsulated QDs in a near infrared counter-propagating experimental configuration.2 Optically trapped QDs exhibit two photon-absorption mediated luminescence without additional excitation sources.3,4 We find that the luminescence, collected through one objective, evidences photo-bleaching and wavelength blue-shifts depending on the dispersive medium composition and power density in the laser focus.