A defect-induced emission material with turn-on mechanoresponsive luminescence serving as a data storage

Abstract Most of the mechanoresponsive luminescent (MRL) materials function based on phase transition (crystalline-to-amorphous or crystalline-to-crystalline) or solid-state chemical reaction of the organic solid emitters. However, it is difficult to enable a turn-on type mechanoresponsive luminescence using such strategy. In this work, the defect-induced emission (DIE) of (E)-(4-((2-hydroxy-4-methoxybenzylidene)amino)phenyl)(phenyl) methanone (HMPM) was disclosed, which endows the resulting material with reversible turn-on MRL. The crystalline powder of HMPM is non-emissive, but the emission intensity can be greatly enhanced by external mechanical stimuli, showing high contrast. In the semiquantitative experiment, pressure up to 1.78 N would generate crystal defects, and further induces DIE. Crystallographic data demonstrate that the dark-state stems from the closely-connected plane-style aggregation of neighboring molecules, which allows the intermolecular orbital-overlapping to the disadvantage of radiative transition. Mechanical stimuli would destroy the plane-style aggregation to block intermolecular orbital overlap and the possible energy transfer, resulting in emission-enhancement. Taking advantage of the DIE nature, an information storage film is fabricated, capable of data-writing via mechanical force and data-erasing by fumigation treatment, showing rewritability as well as high signal contrast.