Primary Luminescent Nanothermometers for Temperature Measurements Reliability Assessment

The potential applications in disparate fields led to a rapid evolution of luminescence thermometry. In particular, luminescent thermometry based on trivalent lanthanide ions (Ln3+) has become very popular in the past decade due to the unique versatility, stability, and narrow emission band profiles covering a broad spectral range (from ultraviolet to the infrared) with relatively high emission quantum yields. Nevertheless, the reliability of Ln3+ ratiometric nanothermometry measurements is recently questioned in a few works reporting fake temperature readouts caused by experimental artifacts and even intrinsic effects. Using NaYF4:Er3+/Yb3+@NaNdF4@PAA (PAA stands for polyacrylic acid) core–shell nanoparticles, it is shown that how the primary luminescent thermometer concept can be used to correct the thermometric parameter (the intensity ratio of the Er3+ 2H11/2 → 4I15/2 and 4S3/2 → 4I15/2 transitions) from the interference of the intruding 2H9/2 → 4I13/2 emission ensuring, thereafter, reliable temperature measurements. Using the primary luminescent thermometer concept on NaYF4:Er3+/Yb3+@NaNdF4@PAA core–shell nanoparticles under 980 and 808 nm excitation, it is possible to detect the interference of the intruding 2H9/2 → 4I13/2 emission and correct the thermometric parameter (the intensity ratio of the Er3+ 2H11/2→ 4I15/2 and 4S3/2 → 4I15/2 transitions) ensuring, thereafter, reliable temperature measurements.