Silica Nanobubbles Containing an Organic Dye in a Multilayered Organic/Inorganic Heterostructure with Enhanced Luminescence

We report the preparation, luminescent properties, and bioimaging applications of a novel zinc sulfide (core)-two-photon dye−silica (shell) multilayered heterostructure. The method utilizes reverse micelles synthesis involving multistep reactions as a result of which composite nanoparticles having different sizes and morphology can be obtained. The size of these composite nanoparticles is typically 15−30 nm. An increase in the luminescence intensity (∼70 times higher) and in fluorescence lifetime is observed for the dye encapsulated within the silica nanobubble. Photobleaching results indicate that the dye is truly encapsulated and the silica shell provides a barrier to penetration of oxygen, thereby making the dye more photostable. The application of these particles as nanoprobes for bioimaging of cells using two-photon laser scanning microscopy is also presented.