Green-synthesized porous g-C3N4@ZnHCC nanocomposite for the on–off fluorescence detection and elimination of toxic chromium(vi) metal ions

Abstract

Chromium(VI) is a significant environmental pollutant because of its highly hazardous and cancer-causing properties. Consequently, there is a great need for inexpensive, extremely sensitive Cr(VI) detection systems. In this regard, the successful application of highly luminous graphitic carbon nitride (g-C₃N₄) as pH-detecting fluorescent nanosensors, molecular compounds, and ions have been reported. g-C₃N₄ exhibits potential for use in the environmental detection of Cr(VI) owing to its apparent advantages of simplicity, ease of use, short reaction time, high selectivity, sensitivity, and ease of use. In this study, we developed a linked g-C₃N₄ nanocomposite for the on–off fluorescence detection and removal of Cr(VI). Essential characterization techniques such as PXRD, FE-SEM, XPS, UV-vis, and fluorescence spectroscopy were employed to investigate its properties. It was observed that the composite is pH-independent and generates blue light when exposed to UV irradiation (496 nm wavelength). Moreover, the resultant nanocomposite responds incredibly strongly to Cr(VI) ions, quenches fluorescence, and has a quantum yield of 14.21%. To detect Cr(VI) ions, a fluorescence-based solitary probe system with good selectivity and sensitivity was developed. Under ideal fluorescent conditions for the experiment, the linear range of Cr(VI) ions was found to be 0–20 M, with 0.184 M as the threshold for the detection limit (R² = 0.99). When exposed to Cr(VI) ions, g-C₃N₄@ZnHCC produced a significant response that quenches fluorescence. At an optimal catalytic dose of 25 mg and under neutral pH conditions, a distinct color change from orange to green visually confirmed the conversion of 2 mg L⁻¹ of Cr(VI) to Cr(III). The highest removal of Cr(VI) (92%) by the g-C₃N₄@ZnHCC nanocomposite indicated its superior activity over bare ones.