Laser dye doped nanoparticles for highly photostable optical nanoamplifiers

Much research on organic advanced materials is currently focused on reducing the size of optical devices and fluorescent probes, and, moreover, on avoiding the photobleaching processes which hinder their extensive use for durable devices. To fulfil both goals, we propose the encapsulation of the laser dye pyrromethene 567 in small (<30 nm) polymeric nanoparticles. These ultra-stable nanoshells are used as vessels which efficiently protect included compounds from the external environment, and especially from O 2, by transforming the doped NPs themselves into a durable optically active gain material. An improved resistance to photobleaching has been observed, while the unbeaten gain properties of the liquid lasing system are fully preserved after encapsulation. Their small size and their amplification efficiency make fluorescent NPs particularly suitable for biological imaging and drug delivery applications when the tissue porosity requires nanometre size vectors, such as in solid tumors. © The Royal Society of Chemistry 2012.