Laser-processed nanodiamond-NaYF4: Yb3+/Er3+ composites for luminescence modulation and temperature sensing

Integrating upconversion nanoparticles (UCNPs) with nanodiamonds (NDs) constitutes a promising platform for the development of multifunctional systems in photonics and sensing. However, achieving strong interfacial coupling while preserving the unique properties of both components remains a significant challenge. In this study, we introduce a novel composite material formed by covalently conjugating NaYF 4 : Yb 3 + /Er 3 + UCNPs with NDs. Subsequent controlled near-infrared (NIR) laser processing generates a high-phonon-energy, sp 2 -hybridized carbon interface on the NDs while preserving the intrinsic nitrogen vacancy (NV) centers. This leads to the selective quenching of the Er 3 + red emission ( 4 F 9 / 2 → 4 I 15 / 2 ), resulting in green-dominant luminescence and a shortened fluorescence lifetime. The laser-processed composite demonstrates enhanced temperature-sensing performance by utilizing non-thermally coupled levels (NTCLs) of Er 3 + , specifically the 2 H 11 / 2 and 4 F 9 / 2 levels. The composite achieves a maximum relative sensitivity of 4.89% K −1 over a temperature range of 173–523 K. This work establishes laser processing as a powerful strategy for tailoring interfacial properties in hybrid nanomaterials, thereby opening new possibilities for high-performance temperature sensors and multifunctional platforms in quantum sensing and bioimaging.