Phototunable phosphorescence energy transfer based on photodimerization of coumarin-12-crown-4 accelerated by γ-cyclodextrin

Abstract

Herein, we designed and synthesized water-soluble coumarin-12-crown-4 (C12C4) which can be encapsulated by γ-cyclodextrin (γ-CD) with 2:1 ratio forming psuedorotaxane, accompanying the morphology from nanotubes to regular nanosheets with a range of edge lengths (2–10 μm) and a range of thicknesses (200–500 nm). With α-CD, β-CD as references, the encapsulation by γ-CD could promote the photodimerization process of C12C4 after irradiation with 365 nm light. Meanwhile, the morphology of pseudorotaxane C12C4⊂γ-CD changed into a chapped surface. By virtue of this, the pseudorotaxane C12C4⊂γ-CD was doped into poly (vinyl alcohol) (PVA) and a phosphorescence emission at 515 nm (τ = 458.80 ms) appeared and showed green afterglow for 3 s. Further doping commercial dye rhodamine B (RhB) into C12C4⊂γ-CD@PVA, a highly efficient triplet-to-singlet Förster-resonance energy transfer (TS-FRET) system was obtained with multicolor afterglows. More interestingly, both the phosphorescence of C12C4⊂γ-CD@PVA and the delayed fluorescence of C12C4⊂γ-CD + RhB@PVA could be tuned by 365 nm light irradiation. Finally, the photo-controlled phosphorescence smart materials were used to constructed INHIBIT logic gate, logic operation of INHIBIT + AND and time resolved anti-counterfeiting.