A carbon dots/rutin system for colorimetric and fluorimetric dual mode detection of Al3+ in aqueous solution

Abstract

In this work, colorimetric and fluorimetric dual mode detection of Al³⁺ in aqueous solution was achieved using a carbon dots/rutin (CDs/rutin) coexisting system. Upon addition of Al³⁺, a yellow Al(III)–rutin complex was formed without any interaction between Al³⁺ and the carbon dots (CDs). As a result, a new absorption peak of the complex at 430 nm increased while the peak of rutin at 360 nm decreased. Therefore, a ratiometric colorimetric method for the detection of Al³⁺ was built on a good linear relationship between the absorbance ratio (A_{430 nm}/A_{360 nm}) and the concentration of Al³⁺ in a wide linear range from 2.0 to 40.0 μM, with a limit of detection (LOD) as low as 0.38 μM. More interestingly, the excitation spectrum of the CDs overlapped with the absorption band of the Al(III)–rutin complex, resulting in an inner filter effect on the fluorescence of the CDs. Accordingly, a fluorimetric approach was developed on an excellent linear relationship between (F₀ − F)/F₀ and the concentration of Al³⁺ in the range from 0.8 to 20.0 μM, with an LOD of 0.32 μM. Finally, the spiked Al³⁺ in real samples (tap water and lake water) was recovered by the as-proposed dual mode detection with high accuracy.