Synthesis of the RGO/Al2O3 core–shell nanocomposite flakes and characterization of their unique electrostatic properties using zeta potential measurements

•We successfully synthesized the RGO/Al2O3 core–shell nanocomposite flakes using sol–gel method.•Al2O3 nanoparticles were covalently bonded to GO surface.•Al2O3 nanoparticles fully covered RGO surface (forming the core–shell system) and acted as a spreader between individual flakes.•Al2O3 nanoparticles modified the electrostatic properties of GO.•CO species of GO were not taking part in the formation of electrostatic surface charge. The aim of this study was to describe the influence of the modification of electrostatic properties of RGO/Al2O3 core–shell nanocomposite flakes. The amount of crystalline form of aluminum oxide was very small. It existed mostly in amorphous phase in the form of covalently bonded to GO surface. The morphological, structural and physicochemical investigations results showed that spherical Al2O3 nanoparticles (ca. 41nm) in gamma phase completely covered the surface of curly-shaped RGO flakes and acted as a spreader between individual flakes. The high BET specific surface area of the analyzed composite (119.71m2/g) together with very low open porosity (0.479cm3/g) indicated that RGO/Al2O3 nanocomposite flakes showed low tendency to agglomeration. The zeta potential curves obtained for RGO/Al2O3 core–shell nanocomposite flakes were differing from curves obtained for GO and Al2O3 suspensions in distilled water and neutral environment. The specific electrostatic properties of the core–shell system of RGO/Al2O3 flakes had an influence on its surface charge (zeta potential) which was measured by applying an external electric field. The FTIR and Raman investigations results also confirmed that the CO species were not taking part in the surface amphoteric reactions resulting in the formation of electrostatic surface charge.