Ratiometric fluorometric and colorimetric dual-mode sensing of glucose based on gold-platinum bimetallic nanoclusters

The synthesis of highly sensitive and selective luminescent probes provides a vital and efficient approach for diagnosing and preventing clinical diseases. In this work, gold-platinum bimetallic nanoclusters (Au − PtNCs-GMP) were synthesized with guanosine monophosphate (GMP) as the capping agent, which possessed strong fluorescent emission at 418 nm, and also exhibited great peroxidase-like mimetic activity. Glucose can be catalyzed to generate H2O2 by glucose oxidase, in the presence of H2O2, o-phenylenediamine (OPD) regarded as a representative non-fluorescent substance was catalyzed by Au-PtNCs-GMP and produced fluorescent 2,3-diaminophenazine (DAP) with an emission wavelength of 560 nm. Furthermore, the colorless OPD was oxidized to yellow DAP with UV–vis absorption peak at 420 nm. The generation of DAP can efficiently quench the fluorescence signal of Au-PtNCs-GMP at 418 nm on account of inner filter effect (IFE). The decrease of Au-PtNCs-GMP fluorescence and the increase of DAP fluorescence made it possible to detect glucose via ratiometric fluorometric intensity. Thus, a ratiometric fluorescent and colorimetric dual-mode sensing was achieved for glucose detection. The linear ranges of ratiometric fluorescence method and colorimetric method toward glucose were in the range of 0.01–0.4 mM and 0.05–0.4 mM, with the low limits of detection (LOD) of 7 μM and 11 μM, respectively. In addition, this dual-mode sensing method can be used for detecting glucose concentration in real biological samples with satisfying results, which provided a valuable and reliable strategy for glucose-related detections.