▎ 摘　　要

Graphene oxide (GO) has been widely used as a fluorescence quencher for constructing fluorescence sensing probes based on fluorescence Forster resonance energy transfer (FRET). To further improve its fluorescence quenching performance, we have introduced a water-soluble black hole quencher (BHQ-2) to be modified on the surface of carboxylated GO by chemical crosslinking method, and the fluorescence quenching properties of BHQ-2 modified GO nanocomposites (GO@BHQ-2) toward CdSe/ZnS QDs were analyzed in detail. Results show that the fluorescence quenching efficiency of GO@BHQ-2 as a dual energy acceptor, is significantly superior to that of unmodified GO. Therefore, GO@BHQ-2 can be used as a fluorescence super-quencher for designing highly sensitive biological fluorescent probes. Moreover, the GO@BHQ-2 nanocomposites were further applied to the construction of QD-based aptasensor for the quantitative detection of ricin B-chain (RTB). The established probe can detect RTB in the range of 0.05-3.0 mu g mL(-1) (R-2 = 0.991), with a detection limit of 0.037 mu g mL(-1). The proposed probe can also be used to detect RTB in real samples, and thus it has potential applications in biological analysis.