Nitrogenous carbon dot decorated natural microcline: an ameliorative dual fluorometric probe for Fe3+ and Cr6+ detection

Abstract

In the modern era, the escalation of heavy metal discharges, especially from the industrial sector, is causing an enormous threat to nature. This article explores the dual sensing of heavy metals (Cr⁶⁺ and Fe³⁺) using a naturally formed microcline based sensor. A nano-sized microcline (M) was obtained via a facile top-down synthesis. In order to enhance the fluorescence property of the material, nitrogenous carbon-dots were loaded into the porous structure of the microcline (MCD) causing a bright blue fluorescence with remarkable stability. Detailed analysis of the composition and structure of the natural nano-sensor was carried out using X-ray diffraction, X-ray photoelectron spectroscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, and BET analysis. This sensor material is highly selective towards Cr⁶⁺ and Fe³⁺, demonstrating a “turn-off” response in aqueous Fe³⁺ and a radical red shift of the fluorescence maxima for aqueous Cr⁶⁺. Density functional studies suggest that photoinduced electron transfer (PET) based quenching of fluorescence is responsible for these types of fluorescence alteration mechanisms. Efficient sensing of both Cr⁶⁺ and Fe³⁺ in various real-life water samples along with a real wastewater sample is also reported herein. A few studies have previously reported on efficient, natural material-based sensors, but they lack real-life applications due to their complicated synthesis and restricted functionalities. This work manages to overcome those drawbacks in its own fashion, providing a tremendously selective and sensitive (4 μM for Cr⁶⁺ and 19 μM for Fe³⁺) dual fluorescent probe.