Ultrasound-assisted one-pot syntheses of ZnO nanoparticles that are homogeneously adsorbed on exfoliated graphite and a simplified method to determine the graphite layer thickness in such composites

The combination of zinc oxide (ZnO) and graphite provides a promising approach for technological applications, particularly in the field of gas sensors, as anode material for lithium-ion batteries and also as photocatalyst. Versatile strategies exist to combine ZnO and graphite. Here, we report on two novel, facile, and environmentally friendly one-pot synthesis routes yielding highly dispersed spherical ZnO nanoparticles with an average particle diameter of about 5 nm supported by exfoliated graphite sheets. For both preparation methods, the ultrasound-assisted synthesis does not result only in high yield but also in the opportunity for industrial scale-up. The composites are produced via a facile synthesis process and provide also a higher ZnO content and a higher surface coverage than other composites as previously reported by this group. Furthermore, we introduce a convenient simplified method to monitor and to determine the ultrasound-assisted exfoliation of graphite and its layer thickness, by taking only four parameters into account—namely the density of the substrate, the specific surface area of the initial and of the exfoliated substrate, and the concentration of the adsorbed particles. By applying tailored parameters, the here-derived equation can be applied for various composites including adsorbed particles on the substrate.