Well-Designed Au Nanorod-Doped CuO Core-Shell Nanocube-Embedded Reduced Graphene Oxide Composite for Efficient Removal of a Water Pollutant Dye.

To ensure environmental safety, the removal of organic pollutants has gained increasing attention globally. We have synthesized uniform Au nanorod (NR)-doped CuO core-shell nanocubes (CSNCs) via a seed-mediated route embedded on the surface of rGO sheets. The Au NRs@CuO/rGO nanocomposite was characterized using various techniques such as transmission electron microscopy (TEM), atomic force microscopy (AFM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), and Fourier-transform infrared (FT-IR) and Raman spectroscopies. The scanning TEM-energy-dispersive spectroscopy (STEM-EDS) elemental mapping of the AuNRs@CuO/rGO nanocomposite indicates that the Au NR (40 nm) is fully covered with the CuO particles (∼145 nm) as a shell. N gas sorption analysis shows that the specific surface area of the composite is 205.5 m/g with a mesoporous character. Moreover, incorporation of Au NRs@CuO CSNCs increases the nanogaps around the nanoparticles and suppresses the stacking/bundling of rGO, which significantly influences the pore size and increase the surface area. A batch adsorption experiment was carried out under various parameters, such as the effect of pH, contact time, temperature, initial dye concentration, and adsorbent dosage, for the removal of methylene blue (MB) in aqueous solution. The high surface area and mesoporosity can cause the adsorption capacity to reach equilibrium within 20 min with a 99.8% removal efficiency. Both kinetic and isotherm data were obtained and fitted very well with the pseudo-second-order kinetic and Langmuir isotherm model. The Langmuir isotherm revealed an excellent dye sorption capacity of 243.9 mg/g at 298 K. Moreover, after five adsorption cycles, the dye removal efficiency decreased from 99 to 86%. This novel route paves a new path for heterogeneous adsorbent synthesis, which is useful for catalysis and electrochemical applications.