Upconverting Nanoparticles\nand Cu(I) Complex-Based\nPlatform for Oxygen Sensing, Thermometry, and Emission Color Tuning

Multifunctional nanoplatforms\ncombine different material properties\nto meet a wide range of applications, allowing highly customizable\nsystems. In this rapidly advancing research field, we introduce a\nmultifunctional nanomaterial based on the synergy between Tm<sup>3+</sup>-doped upconverting nanoparticles (UCNPs) and a Cu(I) complex (CuCom).\nThis material is designed for oxygen sensing, optical thermometry,\nand emission color tuning. In various concentrations, the CuCom complex\nwas electrostatically integrated into a mesoporous silica shell surrounding\nthe core UCNPs (UCNP@mSiO<sub>2</sub>). The optimized system, UCNP@mSiO<sub>2</sub>@CuCom-10, was evaluated for different applications. Due to\nthe spectral overlap between the CuCom absorption and the nanoparticles\nemission, excitation at 980 nm allows most of the UV-blue emission\noutput from the UCNPs to be transferred to the CuCom via luminescent\nresonance energy transfer (LRET), producing red emission from the\nmolecule. The remaining Tm<sup>3+</sup> emission enables optical thermometry,\nwhile CuCom’s sensitivity to molecular oxygen supports its\napplication in gas sensing. In upconversion mode, the nanoplatform\nachieved a Stern–Volmer constant for O<sub>2</sub> sensing\nof 1.64 and demonstrated thermometric relative sensitivities of 0.9%\nand 1% K<sup>–1</sup> at room temperature, with a linear response\nfrom 193 to 373 K. Additionally, the emission color of UCNP@mSiO<sub>2</sub>@CuCom-10 can be tuned from blue to white and yellow, by varying\nthe excitation and temperature, adding further functionality to the\nsystem. This multifunctional platform suggests promising applications\nin biology, medicine, and environmental monitoring.