Polyethylenimine-Mediated Assembly of Dual-Emissive CsPbBr3@SiO2@EuW10 Composite Nanospheres for Ratiometric Detection of 2,6-Dipicolinic Acid.

Bacillus anthracis, a highly pathogenic bacterium that causes anthrax, poses a bioterrorism threat to both wildlife and human health. Consequently, as a key biomarker for anthrax spores, quantitative and visual detection of 2,6-dipicolinic acid (DPA) is critical for biodefense and public health security. Herein, a dual-emissive CsPbBr3@SiO2@EuW10 (CPB@SiO2@EuW10) composite nanospheres were successfully prepared through the confinement effect of SiO2 on CsPbBr3 perovskite quantum dots (PQDs), followed by a polyethylenimine (PEI)-mediated ionic self-assembly (ISA) of EuW10 on the exterior surface of CsPbBr3@SiO2. The resultant CPB@SiO2@EuW10 composite nanospheres exhibit a selective response to DPA with exceptional luminescent stability and good sensitivity. The green-emitting CsPbBr3 PQDs centered in the composite nanospheres can be quenched by DPA via the inner filter effect (IFE), while the antenna effect of DPA enhances the red fluorescence of Eu3+. The contrasting fluorescence response behaviors of CsPbBr3 and Eu3+ centers endow the CPB@SiO2@EuW10 composite nanospheres with a self-calibrated sensing mechanism for reliable DPA detection. The low detection limit (LOD) is 0.052 μM within a linear range of 10-120 μM. The ratiometric sensing of DPA based on the CPB@SiO2@EuW10 fluorescent probe also shows a color shift from green to yellow, enabling visual detection and efficient identification of DPA in aqueous solutions.