Photochromic switching of excited-state intramolecular proton-transfer (ESIPT) fluorescence: A unique route to high-contrast memory switching and nondestructive readout

Aiming at the high-contrast photochromic switching of fluorescence emission and its perfect nondestructive readout, a polymer film highly loaded with a specific photochromic compound, 1,2-bis(2'-methyl-5'-phenyl-3'-thienyl)perfluorocyclopentene (BP-BTE), and an excited-state intramolecular proton-transfer (ESIPT)-active compound, 2,5-bis(5'-tert-butyl-benzooxazol-2'-yl) hydroquinone (DHBO), was employed in this work. The special class of photochrome, BP-BTE, has negligible absorbance at 415 nm both in the open form and in the 365 nm photostationary state (PSS), and the ESIPT fluorophore, DHBO, emits large Stokes' shifted (175 nm; lambda(abs)(max) = 415 nm, lambda(em)(max) = 590 nm) and enhanced fluorescence (Phi(powder)(F) = 10%, Phi(soln)(F) = 2%). Bistability, high-contrast switching (on/ off fluorescence switching ratio > 290), nondestructive readout (over 125000 shots), and erasability were all together accomplished in this novel recording medium.