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The worldwide pollution of water bodies by potential contaminants such as heavy metals, dyes, and pesticides etc. have severely affected the entire eco-system due to their toxic mobility and tough degradation in water. Consequently, there is a requirement to develop cost-competitive and easily handleable sensing materials which can detect targets sensitively and with selectivity. Among the low-cost sensory materials, carbon dots (CDs) constitute an important class of carbon nanomaterial with unique photostability, electronic and fluorescent properties. This review is an effort to comprehend the recent improvements in the sensing applications of CDs with prominence on synthetic routes, the effect of various synthesis parameters on physical properties (quantum yield, size range), detection mechanisms, and detection parameters (limit of detection, interference etc.). Particularly, the scope and progress for the detection of potential water contaminants using CDs have been explored and a holistic view of mechanisms of their detection has been included. Holistic view of mechanisms for different types of signals generated by CDs. [ABSTRACT FROM AUTHOR]

• Facile and simple synthesis of S, N-GQDs using solid state carbonization. • Synthesized QDs shows excellent water stability, photoluminescence. • Photoluminescence is independent to the excitation wavelength. • Sensor shows high selectivity and sensitivity for Ag and Hg ions. Facile and simple sulfur and nitrogen co-doped graphene Quantum Dots (S, N-GQDs) were fabricated via. calcination. UV–vis. spectrum reveals two peaks originates due to the transition from n and π to π* of the luminescent material. The photoluminescence emission of S, N-GQDs has been quenched upon addition of Hg and Ag ions. The higher affinity of sulfur for Hg and Ag ions assigned selectivity to the sensing protocol which was confirmed from the absence of any interference of the competitive ions. The S, N-GQDs could sense Hg and Ag ions as low as 9.14 µM and 12.90 µM respectively. [ABSTRACT FROM AUTHOR]

A facile method has been proposed for the determination of Ferrous (Fe(II)) and Ferric (Fe(III)) ions using phosphate functionalized graphitic carbon nitride quantum dots (Ph-g-CNQDs) in an aqueous medium. The easy solvothermal procedure using oleic acid as the solvent yielded the Ph-g-CNQDs in less than 30 min. The communication among the Fe(II) and Fe(III) with Ph-g-CNQDs caused quenching of the blue Ph-g-CNQDs fluorescence signals. The Ph-g-CNQDs have been successfully characterized using X-ray diffractometry (XRD), X-ray Photoelectron spectroscopy (XPS), Transmission electron microscopy (TEM), Fourier Transform Infrared (FT-IR) spectroscopy, UV–vis absorption and photoluminescence spectrophotometry. The temperature dependent behavior of the Ph-g-CNQDs was also observed and various thermodynamic parameters have also been evaluated. The Ph-g-CNQDs displayed an excellent quantum yield of 60.54% using quinine sulfate as the standard reference. The developed method has been applied to water samples collected from different sources and good recoveries were observed which entitles this method as apt for real time monitoring. Unlabelled Image • Easy synthesis of Ph-gCNQDs • Catalysis of energy from gCN QDs to Fe ions via phosphate group • Thermodynamic aspect of energy transfer • Sensor works efficiently for real samples. [ABSTRACT FROM AUTHOR]