L-cysteine modified N-doped carbon quantum dots derived from peach palm ( Bactris gasipaes ) peels for detection of mercury ions

Establishing an effective strategy for Hg 2 + determination with good sensitivity and high selectivity is of particular concern. In this work, N-doped carbon quantum dots (N - CQDs) were obtained for the first time from peels of peach palm fruit ( Bactris gasipaes ) through microwave-assisted one -pot synthesis. Surface N - CQDs was modified with l-cysteine (N - CQDs/CYS) by a chemical reaction (known as amide coupling) between the nitrogen-containing groups (amine group) of l-cysteine ligand and the carboxyl groups of N - CQDs. The chemical bonding was examined by Fourier Transform Infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). N - CQDs/CYS nanoparticles exhibited a quantum yield of fluorescence ( Phi FL ) of 25.4%, high solubility in water, and a surface with thiol groups from l-cysteine. Mercury ions induced quenching of fluorescence of N - CQDs/CYS at low concentrations (Limit of Detection, LOD = 0.19 mu M) with great sensitivity. A significant preference for Hg 2 + ions was found because of the high affinity between the thiolate groups of N - CQDs/CYS and the analyte. Time-resolved fluorescence measurements were done to study the way that led to fluorescence quenching when Hg 2 + ions were present, evidencing a static quenching fluorescence mechanism. The new N - CQDs/CYS material could be applied to accurately measure the concentration of Hg 2 + ions in water samples in a fast and cost-effective way.