A “Plug-and-Play” Method to Prepare Water-Soluble Photoresponsive Encapsulated Upconverting Nanoparticles Containing Hydrophobic Molecular Switches

A convenient and versatile protocol to encapsulate lanthanide doped upconverting nanoparticles by an amphiphilic polymer shell containing photoresponsive diarylethene chromophores was developed. The assemblies are all water-soluble and fluoresce in the visible region of the spectrum when excited with 980 nm near-infrared light. The fluorescent emission can be selectively and reversibly modulated by alternatively irradiating the photoresponsive nanoparticles with UV light and visible light, which triggers ring-closing and ring-opening reactions of the chromophores, respectively. Fluorescence lifetime experiments suggest that the quenching mechanism is a combination of energy transfer and emission-reabsorption processes. These photoresponsive upconverting nanoparticles have the potential to advance bioimaging and other applications in nanophotonics.