Tunable color upconverison emissions in erbium(III)-doped BiOCl microplates for simultaneous thermometry and optical heating

The authors have synthesized Er(III)-doped BiOCl microplates by a solid-state reaction method. Under irradiation with 980 nm light, the microplates emit both green and red upconversion emissions originating from the transitions of Er(III) ions. By properly adjusting the concentration of the Er(III) ions, the colors can be tuned from pure green to yellowish green. The optimal doping concentration is 3 mol%. Furthermore, the ratio of the two green emission bands of the Er(III) ions is strongly temperature-dependent. The doped microplates can be used to sense temperature in the 298 to 778 K range, indicating a maximum sensitivity of 2.8 × 10⁻³ K⁻¹. The sensitivity is independent of Er(III) ion concentration. The internal heating properties of the microplates induced by the laser excitation are also discussed. Theoretical analysis reveals that the temperature of the doped BiOCl microplates increases from 276 to 324 K with elevating the laser power from 246 to 445 mW. [Figure not available: see fulltext.].