Lanthanide-based luminescent nanothermometers play a crucial role in optical temperature determination. However, due to the strong thermal quenching of the luminescence, as well as the deterioration of their sensitivity and resolution with temperature elevation, they can operate in a relative low temperature range, usually from cryogenic to ≈800 K. In this work we show how to overcome these limitations and monitor very high temperature values, with high sensitivity (≈2.1 %K^-1) and good thermal resolution (≈1.4 K) at around 1000 K. As an optical probe of temperature we chose upconverting, Yb³⁺-Tm³⁺ co-doped YVO₄ nanoparticles. For ratiometric sensing in the low temperature range, we used the relative intensities of the Tm3+ emissions associated with the ³F_2,3 and ³H₄ thermally coupled levels, i.e. ³F_2,3→³H₆/ ³H₄→³H₆ (700/800 nm) band intensity ratio. In order to improve sensitivity and resolution in the high-temperature range, we used the 940/800 nm band intensity ratio of the non-thermally coupled levels of Yb³⁺ (²F_5/2→²F_7/2) and Tm³⁺ (³H₄→³H₆). These NIR bands are very intense, even at extreme temperature values, and their intensity ratio changes significantly, allowing accurate temperature sensing with high thermal and spatial resolutions. The results presented in this work may be particularly important for industrial applications, such as metallurgy, catalysis, high-temperature synthesis, materials processing and engineering, etc., which require rapid, contactless temperature monitoring at extreme conditions.

Endowing a single material with various types of luminescence, that is, exhibiting a simultaneous optical response to different stimuli, is vital in various fields. A photoluminescence (PL)‐ and mechanoluminescence (ML)‐based multifunctional sensing platform is built by combining heterojunctioned ZnS/CaZnOS:Mn²⁺ mechano‐photonic materials using a 3D‐printing technique and fiber spinning. ML‐active particles are embedded in micrometer‐sized cellulose fibers for flexible optical devices capable of emitting light driven by mechanical force. Individually modified 3D‐printed hard units that exhibit intense ML in response to mechanical deformation, such as impact and friction, are also fabricated. Importantly, they also allow low‐pressure sensing up to ≈100 bar, a range previously inaccessible by any other optical sensing technique. Moreover, the developed optical manometer based on the PL of the materials demonstrates a superior high‐pressure sensitivity of ≈6.20 nm GPa⁻¹. Using this sensing platform, four modes of temperature detection can be achieved: excitation‐band spectral shifts, emission‐band spectral shifts, bandwidth broadening, and lifetime shortening. This work supports the possibility of mass production of ML‐active mechanical and optoelectronic parts integrated with scientific and industrial tools and apparatus.

Bright green-yellow high-pressure luminescence of up-converting lanthanide nanocrystals – SrF₂:Yb³⁺/Er³⁺, for lifetime nanomanometry.