Aggregation-Induced Emission Behavior of Dual-NIR-Emissive Zinc-Doped Carbon Nanosheets for Ratiometric Anthrax Biomarker Detection

The development of near-infrared (NIR) emission nanoprobes for the ratiometric fluorescent determination of living cells in vitro/vivo is of great analytical importance. In this work, dual-NIR-emissive Zn-doped carbon-based nanosheets (Zn-CNSHs) were prepared with a beneficial and special donor-pi-acceptor-conjugated (D-pi-conjugated) spatial framework, which resulted in not only a much lower HOMO-LUMO energy level but also excellent biocompatibility and physicochemical properties. The Zn-CNSHs were prepared by simple one-pot solvothermal synthesis with zinc gluconate (ZGN) and a strong acid and exhibited two distinctive photoluminescence (PL) peaks at 620 and 720 nm with the 600 nm excitation. The 620 nm peak intensity was dependent on dipicolinic acid (DPA) owing to the aggregation-induced emission enhancement effect via the strong intersheet hydrogen bonds between Zn-CNSHs and DPA, enabling the ratiometric fluorescent determination of DPA, an important clinical anthrax biomarker. An excellent calibration curve showed linear regions over the range of 0.05-500 mu M between the ratio of PL intensity (PL620 nm/PL720 nm) and the concentrations of DPA. The detection limit was down to 21.7 nM. Based on the high stability, low cytotoxicity, high selectivity, and outstanding PL-reliant sensitivity for the DPA assay, the nanoprobe has been successfully used to monitor DPA in serum, wastewater, and cells.