A cotton swab platform for fluorescent detection of aluminum ion in food samples based on aggregation-induced emission of carbon dots.

A novel portable cotton swab based on nitrogen-doped carbon dots (NCDs) for Al detection was constructed for the first time. NCDs with bright green fluorescence were prepared by hydrothermal method with phenylhydrazine hydrochloride and 3-hydroxy-2-naphthoic acid hydrazide as precursors. The surface of NCDs was exposed to abundant functional groups (such as amino, carboxyl, hydroxyl, etc.), which was helpful for the formation of complexes between NCDs and Al. In the presence of Al, the aggregation of NCDs obviously induced their fluorescence enhancement due to the aggregation-induced emission (AIE) of NCDs. Furthermore, the quantum yield (QY) of NCDs was enhanced by 12 times with Al, and the fluorescence lifetime was increased by 7.54 ns. The fluorescence intensity was linearly correlated with the concentration of Al (2.5-300 μM), and the limit of detection was 0.76 μM. Moreover, for the portable way, cotton swabs were successfully employed to construct the sensors for the detection of Al in food samples. This proposal has potential for the application in food analysis.