Water-enhanced high-efficiency persistent room-temperature phosphorescence materials for temperature sensing via crystalline transformation

Organic persistent room-temperature phosphorescence (pRTP) materials have shown potential advantages in stimuli-responsive optoelectronic applications due to their long-lived lifetime and environmental sensitivity. However, the development and utilization of pRTP materials in an aqueous environment is still full of challenges. Herein, a boric acid containing compound MP with certain solubility in water is selected, and a temperature-responsive pRTP material MP-G is prepared by heating and dissolving it in water and then cooling and crystallization. Interestingly, the phosphorescence of materials is not quenched in water but greatly enhanced, as evidenced by the increased phosphorescence quantum yield from 0.5% to 12.8% and the increased lifetime from 72 ms to 880 ms. Single-crystal analysis and theoretical calculations indicate the hydrogen bonds formed by MP and water molecules in MP-G crystals, which could promote a more ordered intermolecular packing mode relative to the crystal MP, thereby improving the pRTP performance. More importantly, the crystal MP-G exhibits rapid and reversible crystalline transformation at lower temperature. And it displays excellent temperature-responsive luminescence properties, accompanied by color-tunable afterglow from 300 K to 230 K. This work provides a method to achieve high-efficiency pRTP in an aqueous environment and leads to further development for practical application in temperature sensing.