From Two, to Three, to Multi-Color Switches: Developing AIEgen-Based Mechanochromic Materials

A multi-color switching mechanochromic aggregation-induced emission luminogen (AIEgen) whose fluorescence spectra nearly covers the whole visible region was obtained from attaching spiropyran (SP) moiety on tetraphenyl-ethylene (TPE). The covalent attachment of SP to TPE is crucial. It enables the tuning of the fluorescence of SP-TPE dyads from no color change, to two-color switching, to three-color switching under grinding, based on the amorphization of TPE moiety and isomerization of spiropyran moiety. Under quantifiable hydrostatic pressures, the multi-color switch with wide spectral response region was obtained resulting from distinct pressure thresholds for supramolecular and chemical structural changes. The attached spiropyran helped to enhance the response of the mechanochromic AIEgens to show more fantastic and obvious responses. The multi-color changes and obvious responses in a wider visible region and an enhancement of fluorescence intensity give this molecule great potential for applications in visual pressure sensors, pressure calibration, etc.National Natural Science Foundation [91227202, 51573002]; Ministry of Science and Technology of China [2013CB933501]SCI(E)ARTICLE8569-574