Coupled and non-coupled high sensitivity multi-mode ratiometric thermometry of Ho3+/Er3+/Yb3+ tri-doped YP0.5V0.5O4 phosphors

Abstract

Luminescent YP0.5V0.5O4 (YPVO) nanoparticle tri-doped with 2 % Er3+, 15 % Yb3+ and 1 % Ho3+ were successfully synthesized via a sol gel reaction for their application as a multi-range optical temperature sensor. The structural, morphological and optical properties of the synthesized phosphor were studied in detail. Upon 975 nm excitation, temperature sensing in the range from 298 to 488 K for both visible and NIR regions is achieved through efficient up-converted emissions of Er3+ and Ho3+ rare earth ions. The intensities of the observed emission bands of Er3+ and Ho3+ were significantly changed with the temperature. The phosphor exhibits a significant temperature dependence, manifesting a change in the up-conversion luminescence color from green to white and the color coordinate from (x = 0.40, y = 0.57) to (x = 0.39, y = 0.39) as the temperature rises from 298 to 488 K. By studying the temperature dependence of the emission intensities, it was suggested that several strategies can be used for temperature sensing, involving the 2H11/2 → 4 I15/2 (Er3+), 5S2/5F4 → 5I8 (Ho3+) + 4S3/2 → 4I15/2 (Er3+), 5F5→5I8 (Ho3+) + 4F9/2 → 4I15/2(Er3+) and 4I13/2 →4I15/2 (Er3+) transitions corresponding to 525, 547, 659 and 1550 nm emission bands, respectively. Relative sensitivity was obtained with a maximum for the I1550/I547 ratio of 1.00 % K−1 at 360 K. The current approach could be instructive for the development of new high sensitivity luminescent materials.