Multifunctional Optical Sensors for Nanomanometry & Nanothermometry: High-Pressure and Temperature Upconversion Luminescence of Lanthanide Doped Phosphates - LaPO4/YPO4:Yb3+-Tm3+

Upconversion luminescence of nano-sized Yb3+ and Tm3+ co-doped rare earth phosphates, i.e. LaPO4 and YPO4, has been investigated under high pressure (up to ~25 GPa) and temperature (293-773 K) conditions. The pressure-dependent luminescence properties of the nanocrystals, i.e. energy red-shift of the band centroids, changes of the band ratios, shortening of upconversion lifetimes, etc., make the studied nanomaterials suitable for optical pressure sensing in nanomanometry. Furthermore, thanks to the large energy difference (~1800 cm-1), the thermalized states of Tm3+ ions are spectrally well separated, providing high temperature-resolution, required in optical nanothermometry. The temperature of the system containing such active nanomaterials can be determined on the basis of the thermally-induced changes of the Tm3+ band ratio (3F2,3→3H6/3H4→3H6), observed in the emission spectra. The advantage of such upconverting optical sensors is the use of NIR light, highly penetrable for many materials. The investig...