A New Strategy to Enhance Room Temperature Phosphorescence Performance in Physical Doping Polymer System

Physical doping is a general and effective strategy to fabricate host-guest room temperature phosphorescence (RTP) polymer materials. However, some aggregates of phosphors will appear due to their limited solubility and phase separation in polymer matrix, resulting in unstable and/or poor RTP property. In this work, a new strategy, the utilization of cyclodextrins with fit cavity size, is proposed to improve the dispersion of phosphors and enhance RTP performance both in covalent and ionic bond system. The resultant high Förster resonance energy transfer (FRET) efficiency (Φ_FRET) and outstanding RTP performance confirmed that the added cyclodextrins can effectively disperse fluorescence dye (guest) in covalently modified sodium alginate (SA-R) matrix. Thanks to the introduced “ FRET ruler”, the distance between energy donor and acceptor can be measured, accompanying with the afterglow color of SA-R films changing from green to red. For SA-NpC@RhB, the introduction of β-CD can enhance the Φ_FRET up to 57.4%, with corresponding photoluminescence quantum yield (Φ_PL) as high as 21.15%. The Φ_FRET for SA-NpC/γ-CD@SR101 is ≈8.5 times enhanced, with the corresponding Φ_PL rising from 0.87% to 19.13%. Besides, this strategy is also successfully applied into ionic bond system (SA/R), and the Φ_PL for SA/BDA/γ-CD@RhB can reach 24.05%. Furthermore, these materials with good RTP performance are applied in multiple information encryption, optical information storage, and anti-counterfeiting.