Boron‐Doped Carbon Dots Derived From Herbal Mixture for Selective Fluorimetric Sensing of Cr ^{<i>6</i> +} and Their Environmental Applications

Abstract

ABSTRACT 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 Cr 6+ ions through a visual color change from colorless to yellow. Selective quenching of BCDs' emission by Cr 6+ was identified as an efficient analytical tool based on complexation between BCDs and Cr 6+ . BCDs were able to detect Cr 6+ within the linear range of 0–500 μM, and the limit of detection was 0.29 μM. Rapid, label‐free, and selective detection of Cr 6+ by BCDs was further used for quantitative analysis of toxic Cr 6+ in real water samples.