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

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 (A430 nm/A360 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.