Self-assembly-induced luminescence of zwitterionic pyrene derivatives driven by anionic surfactants

Pyrene-imidazole-based novel zwitterionic fluorogens (X-IMP: X = H, Cl, and F) have been developed to form self-assembled nanostructures in aqueous media, driven by anionic surfactants such as sodium dodecyl sulfate and sodium dodecylbenzene sulphonate (SDBS). Surfactants facilitate electrostatic interactions with organic fluorogens, promoting solubility and formation of well-defined molecular self-assemblies. Upon the formation of these assemblies, significant fluorescence and extended excited-state lifetimes are achieved due to the effective restriction of intramolecular rotations within the organized microenvironment. This study highlights how the electron affinity nature of halogen substituents such as Cl and F on fluorogens modulate the photophysical response upon self-assembly. Furthermore, the aromatic head group and the resulting specific probe-surfactant interactions play important roles in stabilizing rigid assemblies and amplifying emission efficiency. Notably, the high electron affinity fluorogen F-IMP in combination with SDBS system enables the highest life time of 30.3 ns, demonstrating efficient suppression of non-radiative decay pathways. This work proposes new surfactant-driven strategy to regulate the self-assembly and photo-physics of zwitterionic fluorogens in water medium.