Photochromism based on reversible proton transfer

Photochromism based on reversible proton transfer between metastable-state photoacids and acidochromic dyes is studied. Metastable-state photoacids reversibly produce a large proton concentration under moderate irradiation, protonate the acidochromic dyes and induce color change. This mechanism is different from that of conventional photochromic materials based on photoinduced structural change. The color change and the stimulating wavelength can be controlled by choosing different acidochromic dyes and photoacids. Reversible changes of various colors under sunshine or visible lights of different wavelengths were demonstrated in both solutions and polymer matrix. (C) 2014 Elsevier B.V. All rights reserved.