Fig. 2. (a) Illustration of the working mechanisms for TTET induced visible light photochromism with a narrow ΔEST sensitizer (left) and for photochromism of direct excitation (right). (b) The absorption of both DAE (grey) and 4CzIPN sensitizer (grey dash) in micelles (D@M and S@M), respectively. The photochromic performance of DS@M in PBS buffer solution (2.5 × 10−5 M, 2 mL) under alternate 475/560 nm irradiation. DS@M before (black) and after 475 nm irradiation (red, PSS), and photo-decoloration upon 560 nm irradiation (blue). Inset: repetitive switching cycles of DS@M in PBS buffer solution (2.5 × 10−5 M, 2 mL) via alternate 475/560 nm irradiation. (c) Photocyclization performances of DS@M (2.5 × 10−5 M, 2 mL) in de-aerated (argon bubbled) PBS buffer (magenta), PBS buffer without argon bubbling (blue); DAE/4CzIPN (2.5 × 10−5 M, 2 mL) in de-aerated (argon bubbled) THF solution (red) and without argon bubbling (black). (d) Transient absorption decays of 4CzIPN (1.0 × 10−4 M in 3 mL THF, top, black line), DAE-o/4CzIPN (1.0 × 10−4 M in 3 mL THF, top, red line), S@M (1.0 × 10−4 M in 3 mL PBS buffer, bottom, black line) and DS@M (1.0 × 10−4 M in 3 mL PBS buffer, bottom, red line) at 477 nm (LP-980 laser flash photolysis spectrometer setup). (e) The delayed luminescence lifetime spectra of 4CzIPN (1.0 × 10−4 M in 3 mL THF, black), DAE-o/4CzIPN (1.0 × 10−4 M in 3 mL THF, red), S@M (1.0 × 10−4 M in 3 mL PBS buffer, blue) and DS@M (1.0 × 10−4 M in 3 mL PBS buffer, magenta) at 540 nm (FLS 1000 spectrofluorometer). (f) ABDA (9,10-anthracenediyl-bis (methylene)dimalonic acid) absorption at 398 nm as a function of time, induced by ROS generated from RB (Rose Bengal, black), 4CzIPN (magenta), S@M (blue) and DS@M (red) upon white light irradiation. (g) Solvent-dependent photochromic performance of DAE/4CzIPN (red column) and the emission wavelength of DAE/4CzIPN in different de-aerated solvents (THF: tetrahydrofuran; ACN: acetonitrile; DMSO: dimethylsulfoxide; DS@M: in PBS buffer) (λex = 365 nm, gray column), 2.5 × 10−5 M, 2 mL.
