Fabrication of thermo-sensitive optical switches based on lanthanide-polyoxometalates and their “on-off” luminescence controlled by temperature

The temperature-responsive luminescent nanocomposites were prepared by the combination of poly (N-isopropylacrylamide) (PNIPAM) with lanthanide-polyoxometalates/SiO 2 spheres, exhibiting controlled reversible luminescent behavior with change in temperature. The structures and properties of nanocomposites were characterized by transmission electron microscopy, scanning electron microscope, FT-IR, UV-vis, dynamic light scattering and luminescence spectra. The research shows that the nanocomposites in aqueous solution display “on–off” luminescence by simple temperature stimuli. For example, the hybrid nanocomposites of PNIPAM/Eu-polyoxometalate/SiO 2 in aqueous solution show bright red luminescence under UV light, which could be observed by the naked eye when the temperature is below the lower critical solution temperature (LCST), showing the “on” state. However, the red luminescence of nanocomposites in aqueous solution is significantly decreased when temperature is above LCST, showing the “off” state.