Unlocking the potential of Ni2+ and Ni2+-Cr3+ synergy for bifunctional pressure and temperature optical sensing.

Reliable simultaneous optical sensing of pressure and temperature under extreme and dynamically fluctuating conditions remains a major challenge due to intrinsic cross-sensitivity between these two thermodynamic parameters. Multimodal systems enabling simultaneous yet fully decoupled monitoring of both parameters are therefore highly sought after. Here, we demonstrate that the synergistic interplay between Cr3+ and Ni2+ luminescence provides a platform for bifunctional temperature-pressure sensing with independent readout channels. Two complementary detection strategies were systematically investigated: ratiometric approach based on luminescence intensity ratio and kinetic approaches exploiting emission decay dynamics. Among the kinetic strategies, a time-gated dual-ion lifetime concept - introduced here for the first time for luminescence manometry - enables pressure readout with record-high relative sensitivity reaching 148.33% GPa-1 while exhibiting complete immunity to temperature fluctuations. Conversely, temperature sensing is achieved via time-gated single-ion Ni2+ luminescence, ensuring high thermometric performance with negligible pressure-induced interference. Importantly, this work study, for the first time, the potential of Ni2+ ions for application in near-infrared luminescence manometry. The unique combination of ultrahigh sensitivity, multimodal readout capability, and possibility of near-infrared operation positions the Ni2+-Cr3+ luminescence synergy as a benchmark platform for next-generation bifunctional optical sensors, enabling reliable operation in complex, dynamically evolving, and optically demanding environments.