An "on-off-on" fluorescent probe for ascorbic acid based on Cu-ZnCdS quantum dots and α-MnO₂ nanorods

This work established a fluorescence approach for detecting ascorbic acid (AA) based on Cu-ZnCdS quantum dots (Cu-ZnCdS QDs) and α-MnO₂ nanorods. Cu-ZnCdS QDs and α-MnO₂ nanorods were characterized by high-resolution transmission electron microscopy (HRTEM), fluorescence spectroscopy, inductively coupled plasma optical emission spectroscopy (ICP-OES) and X-ray diffraction (XRD). In the presence of α-MnO₂ nanorods, the fluorescence of Cu-ZnCdS QDs was greatly quenched through the inner filter effect (IFE). Subsequently, AA can trigger the decomposition of the α-MnO₂ nanorods which can reduce α-MnO₂ to Mn²⁺ and recover the fluorescence. Under optimal conditions, a linear relation was obtained over the range 5.02-401.77 μM with a 31.62 μM detection limit. Through applying the fluorescent sensing system for detecting AA, a satisfactory result is obtained with recoveries ranging from 89.23% to 110.99%.