Smart polydiacetylene nanowire paper with tunable colorimetric response

We report the synthesis of mesostructured conjugated nanowires and fabrication of their freestanding papers. The nanowires are formed through non-covalent self-assembly of conjugated diacetylene precursor 5,7-octadecadiynoic acid via hydrogen bonding and pi-pi stacking in a simple sol-gel process. Resultant nanowires exhibit lamellar mesostructure and can be dispersed uniformly in aqueous solutions. The nanowire papers are fabricated through filtration of nanowire solutions. The papers exhibit mechanical robustness allowing them to be freely folded and cut like regular printer papers, and show rapid sensitivity to different ions, solvents, and UV irradiation, as well as reversible blue <-> red chromatic switching induced by UV irradiation and solvatochromic transition.