Self-healing, tough, red-to-near-infrared (NIR) luminescent organohydrogels derived from supramolecular assemblies of common aggregation-induced emissive luminogens

Abstract

Luminescent polymeric gels (LPGs) are promising for wide high-tech applications due to their hydrated state, tunable emission and similarity to bio-tissues. However, most LPGs only exhibit visible luminescence below 630 nm and cannot emit the preferred near-infrared (NIR) luminescence (650 ∼ 900 nm). Herein, we report red-to-NIR aggregation-induced emissive LPGs based on supramolecular co-assemblies of cationic terpyridine platinum(II) luminogen (TPY-Pt) and anionic alginate (Alg) with unexpected large red emission shift (∼100 nm). Combined analyses of UV–Vis/emission spectra, transmission electron microscopy (TEM), dynamic light scattering (DLS), zeta potential results, and density functional theory (DFT) calculations suggested that such large red-shifted emission derived from coupling of the dyes’ transition dipole moments in TPY-Pt/Alg co-assemblies. Interestingly, red-to-NIR luminescence was well-preserved after TPY-Pt/Alg co-assemblies were physically incorporated into crosslinked poly(vinyl alcohol) (PVA) networks. Consequently, PVA organohydrogels and hydrogels with red-to-NIR emission bands respectively centered at 698 nm and 708 nm were obtained. After further mechanical training to induce anisotropic orientational structures, these PVA organohydrogels were able to bear a high stress of 1.4 MPa. They also had pH-responsive emission, self-healing and remolding capacities, and biocompatibility. The developed red-to-NIR luminescent organohydrogels with these integrated merits have been seldom reported and are expected to find many potential applications.