L-cysteine functionalized graphene quantum dots for sub-ppb detection of As (III)

Here, we report functionalized graphene quantum dots (GQDs) for the optical detection of arsenic at room temperature. GQDs with the fluorescence of three fundamental colors (red, green, and blue) were synthesized and functionally capped with L-cysteine (L-cys) to impart selectively towards As (III) by exploiting the affinity of L-cys towards arsenite. The optical characterization of GQDs was carried out using UV-vis absorption spectroscopy, Fourier transform infrared spectroscopy, and fluorescence spectrometry, and the structural characterizations were performed using transmission electron microscopy. The fluorescence results showed instantaneous quenching in intensity when the GQDs came in contact with As (III) for all test concentrations over a range from 0.025 to 25 ppb, which covers the permissible limit of arsenic in drinking water. The experimental results suggested excellent sensitivity and selectivity towards As (III).

Automated summary

In this study, functionalized graphene quantum dots (GQDs) were used for the optical detection of arsenic at room temperature. The GQDs were synthesized with three different fluorescence colors and functionalized with L-cysteine for selective binding to As (III). The results showed that the fluorescence intensity of GQDs decreased instantly when in contact with As (III) within a concentration range covering the permissible limit of arsenic in drinking water, indicating excellent sensitivity and selectivity towards As (III).