A novel turn-on fluorescent sensor for highly selective detection of Al(iii) in an aqueous solution based on simple electrochemically synthesized carbon dots

Abstract

In this study, a simple and sensitive turn on fluorescent sensor for the detection of Al³⁺ ion in an aqueous solution was developed based on carbon dots (C-dots) obtained via one-step electrolysis of graphite in sodium hydroxide aqueous solution. The as-prepared C-dots exhibit excellent photoluminescence and up-conversion photoluminescence properties and have an average size of 5.0 nm. The as-prepared C-dots showed a light green luminescence emission under 365 nm ultraviolet excitation and could be used as a novel label-free turn on fluorescent probe for the selective detection of Al³⁺; this is quite different from the case of usual quenching effects of metal ions on fluorescent C-dots. The fluorescence enhancement effect of Al³⁺ ion on the as-prepared C-dots could be attributed to the chelation-enhanced fluorescence (CHEF) mechanism. Abundant oxygen functional groups on the surface of C-dots have chelation interaction with Al³⁺ and increase the rigidity of the C-dots, leading to fluorescence enhancement. Moreover, the as-prepared C-dots are highly selective for Al³⁺ over other metal ions, with a detection limit of 0.05 μM, and the linear relationship between fluorescence intensity and concentration of Al³⁺ is in the range of 0.1–7.2 μM. In addition, the as-prepared novel fluorescent probe was successfully applied for the direct analysis of Al³⁺ in a real environmental water sample.