Enhancing thermometric precision: modulating the temperature of maximum sensitivity via erbium dopant addition in Ba2GdV3O11:Tm3+/Yb3+ nano phosphors†

Abstract

Developing luminescence sensors often prioritizes maximizing relative sensitivity to achieve optimal performance. However, a critical parameter often overlooked is the temperature at which maximum sensitivity occurs. In this study, we delve into this crucial aspect by exploring the impact of erbium doping in Tm³⁺/Yb³⁺ co-doped Ba₂GdV₃O₁₁ nano phosphors. The crystal structure, microscopic morphology, and luminescence mechanism of BGVO:Yb³⁺/Tm³⁺ and Er³⁺/Tm³⁺/Yb³⁺ up conversion nanoparticles, as well as the temperature sensing characteristics are investigated. Under 975 nm laser excitation, the BGVO:Yb³⁺/Tm³⁺ and BGVO:Er³⁺/Tm³⁺/Yb³⁺ nano phosphors exhibited strong blue and green upconversion luminescence, respectively. The luminescence intensity ratio (LIR) approach was used to analyze the temperature-dependent luminescence spectra in the 300–600 K temperature range. The thermometry strategies were based on thermally coupled energy levels (TCLs) and non-thermally coupled energy levels (NTCLs) of Er³⁺ and Tm³⁺ for temperature sensing performance. In the Tm³⁺/Yb³⁺ codoped samples, the relative sensitivity typically peaks around 350 K, attributed to TCLs (1.7% K⁻¹, 700 nm/800 nm) with generally lower relative sensitivity compared to non-TCLs (5.39% K⁻¹, 700 nm/475 nm). However, non-TCL sensitivities in the 300–600 K range lack a clear maximum. In contrast, Er³⁺/Tm³⁺/Yb³⁺ samples exhibit distinct maxima in non-TCL sensitivities within this temperature range (1.91% K⁻¹, 700 nm/550 nm), offering precise temperature determination for specific applications. Our findings underscore the potential of erbium doping to modulate temperature sensitivity peaks, crucial for optimizing performance in tailored luminescence nanosensors and offering fresh concepts for investigating alternative superior optical temperature sensing nano materials.