Boron-Doped Carbon Dots Derived From Herbal Mixture for Selective Fluorimetric Sensing of Cr6+ and Their Environmental Applications.

Carbon dots prepared from natural resources are presently being used as chemosensors of different metal ions. In the present work, highly fluorescent and photostable boron-doped carbon dots (BCDs) with an average size of 10.7 nm were prepared from a powder mixture of Azadirachta indica, Momordica charantia, and Syzygium cumini in the presence of boric acid using a hydrothermal process. BCDs were characterized using HRTEM, XRD, XPS, Fourier transform infrared spectra (FTIR), UV-Vis, and fluorescence techniques. Maximum emission intensity of BCDs was recorded at 420 nm on excitation at 330 nm. The quantum yield of BCDs was ~12%. BCDs selectively detected Cr6+ ions through a visual color change from colorless to yellow. Selective quenching of BCDs' emission by Cr6+ was identified as an efficient analytical tool based on complexation between BCDs and Cr6+. BCDs were able to detect Cr6+ within the linear range of 0-500 μM, and the limit of detection was 0.29 μM. Rapid, label-free, and selective detection of Cr6+ by BCDs was further used for quantitative analysis of toxic Cr6+ in real water samples.