Sensitive and selective determining ascorbic acid and activity of alkaline phosphatase based on electrochemiluminescence of dual-stabilizers-capped CdSe quantum dots in carbon nanotube-nafion composite

Sensitive and selective determining bio-related molecule and enzyme play an important role in designing novel procedure for biological sensing and clinical diagnosis. Herein, we found that dual-stabilizers-capped CdSe quantum dots (QDs) in composite film of multi-walled carbon nanotubes (CNTs) and Nafion, displaying eye-visible monochromatic electrochemiluminescence (ECL) with fwhm of 37   nm, which offers promising ECL signal for detecting ascorbic acid (AA) as well as the activity of alkaline phosphatase (ALP) in biological samples. It was also shown that the dual-stabilizers-capped CdSe QDs can preserve their highly passivated surface states with prolonged lifetime of excited states in Nafion mixtures, and facilitate electron-transfer ability of Nafion film along with CNTs . Compared with the QDs/GCE, the ECL intensity is enhanced 1.8 times and triggering potential shifted to lower energy by 0.12   V on the CdSe-CNTs-Nafion/GCE. The ECL quenching degree increases with increasing concentration of AA in the range of 0.01–30   nM with a limit of detection (LOD) of 5   pM. The activity of ALP was determined indirectly according to the concentration of AA, generated in the hydrolysis reaction of l -ascorbic acid 2-phosphate sesquimagnesium (AA-P) in the presence of ALP as a catalyst, with an LOD of 1   μU/L. The proposed strategy is favorable for developing simple ECL sensor or device with high sensitivity, spectral resolution and less electrochemical interference.