Reduced graphene oxide (rGO) was synthesized by chemically reducing graphene oxide (GO) using a reducing agent. The product, rGO, showed excellent hydrophobicity, as indicated by its high-water contact angle, which was greater than 150°. Characterizations using Fourier-transform infrared (FTIR) spectroscopy, Raman spectroscopy, and X-ray diffraction (XRD) were used to analyze the composition and structural differences between GO and the superhydrophobic rGO material. Scanning electron microscopy (SEM) showed that GO particles exhibited a plate-like morphology with layers of stacked plates, while rGO displayed fewer stacks that show a more separated structure of layers. The increasing demand for superhydrophobic materials in advanced materials industries, due to their potential to enhance performance, durability, and safety, makes rGO a promising candidate for use in composite materials.

The development of a fluorescent sensor has attracted much attention for the detection of various toxic pollutants in the environment. In this work, fluorescent carbon dots (N,Zn-CDs) doped with nitrogen and zinc were synthesized using citric acid monohydrate and 4-pyridinecarboxyaldehyde as carbon and nitrogen sources, respectively. The synthesized N,Zn-CDs served as an “off” fluorescence detector for the rapid and sensitive detection of hexavalent chromium ions (Cr(VI)). The zinc metal integrated into the heteroatomic fluorescent carbon dot played a functional role by creating a coordination site for the hydrogen ions that were displaced after the addition of Cr to the solution matrix. The stepwise addition of Cr(VI) effectively quenched the fluorescence intensity of the N,Zn-CDs, and this phenomenon was attributed to the internal filter effect. A low detection limit of 0.47 nmol/L for Cr(VI) was achieved in the fluorescence experiments. Real water samples were used to evaluate the practical application of N,Zn-CDs for the quantification of Cr(VI). The results show acceptable recoveries and agreement with ion chromatography-ultraviolet spectrometry results. These good recoveries indicate that the fluorescence probe is very well suited for environmental measurements.