Defects and band gap shrinkage in ZnO/rGO composite nano-pebbles prepared by solid-state reaction

In the present investigation, ZnO/rGO nanocomposites were prepared using conventional solid-state reaction method. Raman, XRD, FTIR, UV-Vis, PL and FESEM characterization tools were used to analyze the synthesized materials. Raman analysis reveals the formation of rGO with prominent D and G-band peaks. XRD patterns confirm the crystalline and hexagonal wurtzite structure with P6(3)mc space group of all the samples. Rietveld refinement demonstrates the size variation (33 nm-56 nm) and strain profile. FESEM micrographs of ZnO/rGO composites have established the formation of densely packed hexagonal nano-pebbles. UV-Vis and room temperature PL measurements indicate that the optical properties of ZnO and ZnO/rGO nanocomposites are affected by the rGO concentration. It also confirms a band gap shrinkage during nanocomposite preparation compared to the pure ZnO structure. Urbach energy is found to increase with increase in rGO content and the strength of electron-phonon interaction enhances. It also affects the PL emission in the UV region. FTIR spectra confirm the presence of different functional groups. Present investigation shows that ZnO/rGO materials are potential candidates for design and development of sensors for detecting gases.