Understanding the role of π-π stacking from red carbon for selective, high stable and anti-external interference detecting ferric ions and cellular imaging

The subcarboxylated carbon (C3O2) is a unique molecule that spontaneously polymerizes into highly conjugated fluorescence structures p(C3O2)n, named "red carbon". This unique property, combined with its role as aggregation-induced emission luminogens, has allowed for a deeper exploration of their emission mechanism. Herein, both density functional theory calculations and experimental approaches to elucidate the crystal structure of π–π stacking in red carbon, thereby enhancing the fluorescence properties of p(C3O2)n polymer in its aggregated state. The time-dependent density functional theory calculations and experimental observations indicate that the fluorescence of red carbon can be quenched by ferric ions (Fe3+) and subsequently restored by ethylenediaminetetraaceticacid (EDTA). This quenching process follows first-order reaction kinetics. On the basis of the coordination to metal ions from abundant heteroatoms on red carbon, the high sensitivity, quick responsive (1 min), sensitive detection (the lowest detection limit is 0.97 μM) for the Fe3+ were realized in red carbon, which provides inspirations for the design of new turn-on probes with high stability in detecting the Fe3+ in aqueous solution. Crucially, the red carbon as a light-up fluorescence probe can be employed for the Fe3+ sensing in living cells, which enlighten a new perspective for designing non-conjugated fluorescent polymers. This innovative approach opens up new avenues for developing probes that can detect Fe3+ with high precision and reliability in complex biological environments.