Engineering Visible to Near-Infrared Luminescence through a Selective Doping Strategy for High-Performance...

Luminescence nanothermometers have garnered considerable attention due to their noncontact measurement, high spatial resolution, and rapid response. However, many nanothermometers employing single-mode measurement encounter challenges regarding their relative sensitivity. Herein, a unique class of tunable upconversion (UC) and downshifting (DS) luminescence covering the visible to near-infrared range (400-1700 nm) is reported, characterized by the superior Tm³⁺, Ho³⁺, and Er³⁺ emissions induced by efficient energy transfer. The outstanding negative thermal expansion characteristic of ScF₃ nanocrystals has been found to guide excitation energy toward the relevant emitting states in the Yb³⁺-Ho³⁺-Tm³⁺-codoped system, consequently resulting in remarkable near-infrared III (NIR-III) luminescence at ∼1625 nm (Tm³⁺:³F₄ → ³H₆ transition), which in turn presents numerous opportunities for designing multimode ratiometric luminescence thermometry. Furthermore, by facilitating phonon-assisted energy transfer in Er³⁺-Ho³⁺-codoped systems, the luminescence intensity ratio (LIR) of ⁴I_13/2 of Er³⁺ and ⁵I₆ of Ho³⁺ in ScF₃:Yb³⁺/Ho³⁺/Er³⁺ exhibits a strong temperature dependence, enabling NIR-II/III luminescence thermometry with superior thermal sensitivity and resolution (S_r = 0.78% K^-1, δT = 0.64 K). These findings not only underscore the distinctive and ubiquitous attributes of lanthanide ion-doped nanomaterials but also hold significant implications for crafting luminescence thermometers with unparalleled sensitivity.