Strong sensitivity enhancement in lifetime-based luminescence thermometry by co-doping of SrTiO3:Mn4+ nanocrystals with trivalent lanthanide ions†
Abstract
The co-doping of SrTiO3:Mn4+ luminescent nanocrystals with trivalent lanthanide ions (Ln3+ = Lu3+, Tm3+, Er3+, Ho3+, Dy3+, Eu3+, and La3+) is demonstrated as a new strategy for significant sensitivity improvement of lifetime-based luminescent thermometers. SrTiO3:Mn4+:Ln3+ nanocrystals of about 25 nm diameter were prepared by the modified Pechini method and characterized using X-ray powder diffraction and electron microscopy techniques. The temperature dependence of Mn4+ emission in SrTiO3 was considerably altered by the co-doping of Ln3+ due to the cooperating effects of Mn4+ → Ti3+ and Mn4+ → Ln3+ energy transfers. A substantial enhancement of the relative sensitivity of lifetime-based thermometry as high as 145% with respect to the unco-doped nanocrystals reveals the success of the approach. The obtained values of maximal relative sensitivity for different Ln3+ co-dopants are 5.10% K−1 at 290 K for Er3+, 5.00% K−1 at 301 K for Eu3+, 4.84% K−1 at 303 K for Dy3+, 4.71% K−1 at 289 K for Ho3+, and 3.87% K−1 at 290.7 K for Lu3+.