Yellow Fluorescent Carbon Dots for Selective Recognition of As³⁺ and Fe³⁺ Ions

Measurement levels of As3+ and Fe3+ ions have attracted considerable research attention for environmental and living being’s health safety issues. Herein, we report a green synthetic approach to prepare bright yellow fluorescent carbon dots (C-dots) from a o-phenylenediamine and pyrazole mixture. A large Stokes shift of up to 145 nm was observed under an excitation wavelength of 415 nm. The metal ion sensing study affirmed that the C-dots’ aqueous dispersion underwent a strong fluorescence quenching for selective As3+ and Fe3+ ion sensing with detection limits of 24.4 and 63.4 nM, respectively. In addition, a red shift of the C-dots’ emission was noticed in the case of Fe3+ ion incubation. Furthermore, the C-dots were coated on a simple paper strip and embedded in a solid silica aerogel porous matrix in which detection was carried out through the visible and fluorescence color changes. The quenching of the C-dots’ fluorescence was ascribed to the static quenching effect, which was proved by UV–vis absorbance and time-resolved fluorescence spectroscopy techniques. In addition, this method was successfully used to detect these ions in real water samples in the presence of other contaminants. Moreover, intracellular detection of the ions has been successfully performed in living cells at a lower concentration. The methodology reported here opens a new window in real and on-site applications.