1：Experimental Design and Method Selection:

The study involved synthesizing yttrium vanadate particles doped with Yb3+ and Tm3+ via colloidal conversion of hydroxycarbonate precursors, followed by a protected annealing process to improve crystallinity. Luminescence spectra were measured under UV and NIR excitation for thermometric analysis.

2：Sample Selection and Data Sources:

Hydroxycarbonate precursors were prepared using rare earth nitrates, urea, and ethylene glycol/water mixtures. The converted vanadate particles were characterized and used for luminescence measurements.

3：List of Experimental Equipment and Materials:

Chemicals included rare earth nitrate hydrates, tetraethyl orthosilicate, hydrofluoric acid, urea, ethylene glycol, ethanol, ammonia, and polymers (PE6800 and PAA). Equipment included FTIR spectrometer, thermogravimetry analyzer, X-ray diffractometer, TEM microscope, DLS equipment, luminescence spectrometer, diode laser, Xenon arc lamp, temperature-controlled stage, Peltier-controlled sample holder, and optical tweezers setup.

4：Experimental Procedures and Operational Workflow:

Precursors were synthesized, converted to vanadates, annealed, and characterized. Luminescence spectra were acquired at various temperatures and excitation powers. Single particles were trapped and analyzed using optical tweezers.

5：Data Analysis Methods:

Data were analyzed using exponential fitting for intensity ratios vs. temperature, calculation of relative thermal sensitivities and temperature uncertainties, and power dependence analysis for upconversion mechanisms.