PURPOSE: A reversible fluorescence switch for imaging biological system is provided to able to be on switched on and off with high contrast by accepting photochromic material and fluorescent material into a surface and an inside of silica nanoparticles. CONSTITUTION: A reversible fluorescence switch for high contrast bio imaging based on silica nanoparticles of uniform size comprises photochromic material as a photo switch covalently bonded to a surface or an inside of a silica nanoparticles, and has a structure covalent bonded to a surface and an inside of the silica nanoparticles in order to be within a distance capable of enable at least one fluorescence material to conduct fluorescence resonance energy transfer together with the photo transmittance material. The photochromic material is one selected from an azobenzene derivative, a spiropyran derivative, a diarylethene derivative, and a fulgide derivative.
Highly monodisperse silica nanoparticles as reversible internal light switch for living biological systems