LAUSR

Abstract A novel near-infrared (NIR) emitting cyanine dye, 2-[4-N,N-diphenylaminostyryl] -β-naphthothiazolium propylsulfonate (N3), has been newly developed. N3 exhibits striking size-dependent aggregation-induced emission (AIE) characteristic in DMSO/H2O mixtures with water fractions (fw) > 70%. The formation of nanoparticles is advantageous for fluorescence emission, while larger size agglomeration leads to a reduction. In solid, N3 shows crystal-induced emission enhancement (CIEE) and its NIR emissive behavior is morphology-dependent. The brightly emissive crystalline powder (λem = 687 nm) (ON state) is transformed into non-emissive amorphous state (OFF state) when grinding. The smart fluorescent ON-OFF properties can be reversibly tuned by grinding and heating or solvent fuming. Possible strategies to construct the physical sensor for pressure or temperature, chemosensor for volatile organic compounds (VOCs), as well as the technology for data storage are disclosed.