Carbon Dot-Stabilized Hydrogel Composite: A New Adsorbent for Efficient and Sustainable Pb(II) Removal.

In this paper, a carbon dot hydrogel composite (CDs-Hy) capable of efficiently removing Pb(II) was prepared by hydrogen bonding self-assembly in combination with carbon dots and a hydrogel. CDs-Hy was characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS), and the effect of the adsorption conditions on the adsorption efficiency of CDs-Hy was studied. The results of the study showed that the incorporation of carbon dots, on the one hand, significantly increased the adsorption capacity of the material. On the other hand, it can increase the stability of hydrogels in aqueous solution. The possible adsorption mechanisms were further verified as ion exchange and coordination. CDs-Hy is a novel adsorbent material capable of removing Pb2+ efficiently, which can be reused several times with high stability.

One step synthesis of highly photoluminescent red light-emitting carbon dots from O-phenylenediamine and 2,4-diaminophenol as fluorescent probes for the detection of pH and Cr(VI).

In this study, new red light-emitting carbon dots (R-CDs) that can selectively recognize Cr(VI) were prepared using a strategy that utilizes 2,4-diaminophenol to enhance the fluorescence of O-phenylenediamine based carbon dots. The results showed that 2,4-diaminophenol increased the quantum yield (QY) of the carbon quantum dots (CDs), and that the QY of the CDs increased from their original value of 8.7% to 20.1% (R-CDs). The R-CDs show sensitivity to acidic conditions and maintain good linearity between pH = 1.00-4.00, making them useful as pH probes. Furthermore, the prepared R-CDs possess good solubility in water and are responsive to changes in Cr(VI) concentrations in aqueous environments. The quenching of the R-CDs fluorescence was linearly correlated with the Cr(VI) concentration within a range of 0-20 µM, with a lower detection limit of 66 nM. The detection mechanism is attributed to the formation of hydrogen bonds between Cr(VI) and the R-CDs, resulting in the fluorescence quenching of the R-CDs. The R-CDs can be considered effective multifunctional fluorescent probes for both pH and Cr(VI) in aqueous environments. This study will provide new R-CD design strategies for probes that selectively identify specific target substances.