Lifetime-based ODMR in fluorescent nanodiamonds enables robust quantum sensing in biological medium solution

Understanding nanoscale heat dissipation during cellular thermogenesis is critical for elucidating the interplay between the thermal dynamics and biological functions. Quantum sensing with nitrogen-vacancy centers in fluorescent nanodiamonds (FNDs) is a powerful tool to probe these processes; however, conventional optically detected magnetic resonance (ODMR) based on fluorescence intensity suffers from environmental noise in biological systems. Here, we demonstrate that lifetime-based ODMR overcomes these limitations and delivers robust nanoscale measurements in both aqueous and physiological environments. Comparative studies across dry, deionized water, and simulated body fluid conditions have revealed that lifetime-based ODMR preserves spectral fidelity and contrast despite intensity fluctuations, whereas intensity-based methods fail. In addition, we characterized the microwave-induced thermal effects, showing that lifetime-based sensing enables precise temperature tracking under dynamic conditions. This study established lifetime-based ODMR in FNDs as a superior technique for nanoscale quantum sensing in complex biological medium solutions, paving the way for applications such as intracellular thermometry and real-time biomolecular interaction studies.