Synergy of Fe dopant and graphite oxide in ZnO based nanocomposites for efficient photocatalytic degradation of indigo carmine dye

In order to remove the organic dye 'indigo carmine' (IC) from aqueous solution, this work report the facile synthesis using sol-gel method and structural, morphological, elemental composition, vibrational and optical characterization of the as synthesized samples ZnO Nanorods (NRs), Fe doped ZnO (Zn1-xFexO) NRs and its nanocomposite (NCs) with graphite oxide (GO). X-ray diffraction (XRD) analysis reveals the polycrystalline nature of the synthesized materials whereas, Field emission scanning electron microscopy (FE-SEM) analysis shows the hexagonal rod shaped morphology of undoped ZnO and Fe doped ZnO, Whereas, spherical shaped NPs like morphology of GO. Energy dispersive spectra (EDS) has been used for the elemental composition identification of the synthesized samples. The coexistence of ZnO and GO in the as-prepared nanocomposites is confirmed by the functional group analysis, obtained from FT-IR spectra. The UV-Vis characterisation shows the 374 nm characteristics peak of ZnO and also shows the significantly improved optical characteristics of the as synthesized Zn(1-x)Fe(x)ONRs and Zn1-xFexO/GO NCs. Raman analysis confirms the existence of carbonaceous material in the as synthesized Zn1-xFexO/GO NCs sample. Photoluminescence (PL) analysis used in the evaluation of the lifetime of the electron-hole pairs generated in the degradation process of photocatalysis. Dynamic Light Scattering (DLS) analysis used to evaluate the hydrodynamic sizes and Zeta potential was used to analyze the surface charge and stability of the synthesized material. The presence of a high negative charge shows the well- stabilized nature of the synthesized materials throughout the fluid. The obtained results show that both Zn1-x FexO and Fe doped ZnO/GO nanocomposite (Zn1-xFexO/GO NCs) have a better potential for the removal of IC as compared with pristine ZnO NRs and GO NPs. The enhanced percentage removal ability of the Zn1-xFexO/GO NCs shows that the lattice-based deposition of Fe and the distribution of both Fe and GO over ZnO NRs increase the number of active catalytic sites and facilitate interactions between the Zn1-xFexO/GO NCs sample with the IC dye through p-p, hydrogen bonding, anion exchange, and other mechanisms. A variation in the catalyst dosage has also been used to assess the parameterized photocatalytic behavior. The outcome demonstrates that 40 mg/100 mL is the optimum dose for successfully removing 50 ppm of IC dye from an aqueous solution. The removal efficiency achieved to similar to 95.17 % and 96.34 % by using 40 mg optimum dose of Zn(1-x)Fe(x)ONRs and Zn1-xFexO/GO NCs samples with their rate of degradation (k) values 0.0713, 0.0778 min(-1), respectively. Reusability has also been tested to assess the photostability of the synthesized samples for the five consecutive cycles of degradation process. On the basis of synergistic analysis, it can be inferred that both Zn(1-x)Fe(x)ONRs and Zn1-xFexO/GO NCs appear to be promising materials for IC dye removal from aqueous solution and also can be employed in various energy and environmental based applications.