Discriminating and recording different types of mechanical force by distinct turn-on responses of a T-shape luminescent compound

Abstract

Smart mechano-responsive luminescent (SMRL) materials that can discriminate different types of mechanical force have attracted extensive research interest. However, the reported few SMRL materials were limited in low sensitivity (pressure ≥ GPa) and transient record. Herein, a T-shape compound (T2) combination with a flexible alkyl chain and a rigid backbone of slightly twisted conjugate has been demonstrated. It presents sensitively distinct luminescence turn-on responses to grinding (red, λem = 622 nm) and pressing (near-infrared, λem = 696 nm), with pressure threshold as low as 1 MPa. More importantly, the resulted luminescent information of mechanical forces can be maintained and recorded for several days, after removing the external stimuli. It is revealed that the loose grid-like-stack assembly formed by T2 was destroyed by grinding but pressed into compact interlaced-stack by pressing. This study paves a new way for realizing SMRL materials on the basis of T-shape compound combing rigidity and flexibility, with turn-on response for sensitively discriminating and long-term recording mechanical forces.