An Aggregation-Induced Change in the Fluorescence of Carbon Dots: Naked Eye Water Detection in a Selective Organic Solvent

In this study, newly synthesized crystalline carbon dots shows the concentration and solvent-dependent multicolor emission. The carbon dots have been characterized by several techniques like Fourier transformed infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), UV-visible and fluorescence spectroscopy, and field emission gun transmission electron microscopy (FEG-TEM). The high polarity of the solvents and the high concentration of the carbon dots help it to aggregate which opens up a new red-shifted emission band. It has been revealed that the Forster resonance energy transfer (FRET) between the dispersed and aggregated state of the carbon dots becomes the actual cause behind this change. These carbon dots selectively shows the white light emission in the dioxane. The particular polarity of the dioxane selectively helps for the coexistence of the blue and greenish-yellow emission bands with the same intensity which eventually turns the emission very much near to white light. It has been found that the very minute amount of water present in dioxane (0.1 % V/V) can change the emission nature of the carbon dots. This observation has finally helped these carbon dots for highly selective and perceptible water detection in dioxane.