Green emitting N, P-doped carbon dots as efficient fluorescent nanoprobes for determination of Cr(VI) in water and soil samples

Abstract

The doping of carbon dots (CDs) with non-metallic elements has been a strategy to improve their optical properties and application fields. In the present work, nitrogen and phosphorus-doped CDs (N, P-CDs) were prepared through one-pot hydrothermal synthesis using phytic acid (PA) and L-arginine (Arg) as precursors. The synthesized N, P-CDs were characterized using transmission electron microscopy, FTIR, Raman, UV–vis, and fluorescence spectroscopies. The N, P-CDs exhibited green fluorescence (λem = 515 nm) that can be quenched sensitively and selectively in the presence of Cr(VI), combining static quenching, electron transfer, and an inner filter effect. Consequently, a new fluorescence sensing method applied to Cr(VI) determination was developed using the presently synthesized fluorescent CDs. Under optimized conditions, a linear range from 0.05 to 3 µM in Cr(VI)) was obtained, with a limit of detection of 26 nM. Additionally, the N, P-CDs were selective toward Cr(VI) in the presence of Cr(III) and twenty other species, indicating its potential use to monitor Cr(VI) in environmental samples. Then, Cr(VI) was successfully determined, with recoveries from 85 to 107% in water and soil samples. The method, combining high sensitivity and selectivity, is easy to implement and promotes the use and valorization of eco-friendly materials.