Pankaj Chamoli

Enhanced photocatalytic degradation of methylene blue and adsorption of arsenic(III) by reduced graphene oxide (rGO)–metal oxide (TiO2/Fe3O4) based nanocomposites

Reduced graphene oxide (rGO) and metal oxide based binary (rGO–TiO2/rGO–Fe3O4) and ternary (rGO–Fe3O4–TiO2) nanocomposites with enhanced photocatalytic and adsorption properties are successfully synthesized by a simple one-step solvothermal process. The microscopy images of the nanocomposites show that the ferric oxide (Fe3O4) and titania (TiO2) nanoparticles are firmly anchored over rGO, which enhances the surface area of the resultant nanocomposites. The as-synthesized nanocomposites are evaluated for the removal of methylene blue dye under UV and visible light irradiation as well as for the adsorption of As(III) from aqueous solution. Compared to binary, the ternary (rGO–Fe3O4–TiO2) nanocomposite exhibits the highest dye degradation efficiency (∼100% within 5 minutes). This enhancement is attributed to the synergetic interaction and increase in the surface area of rGO–Fe3O4–TiO2. For As(III) adsorption, the adsorption data are obtained by Langmuir and Freundlich adsorption isotherms. Compared to binary nanocomposites, the maximum monolayer adsorption capacity (147.05 mg g−1) is observed for rGO–Fe3O4–TiO2. These results reveal that the rGO–Fe3O4–TiO2 nanocomposite has potential application in water/wastewater treatment.

Mangifera indica, Ficus religiosa and Polyalthia longifolia leaf extract-assisted green synthesis of graphene for transparent highly conductive film

A green approach to synthesize graphene nanosheets (Gns) by reduction of graphene oxide (GO) using Mangifera indica, Ficus religiosa or Polyalthia longifolia leaf extract as reducing agent has been demonstrated. Further, transparent conducting films (TCFs) have been fabricated by spray coating of the synthesized Gns and the optoelectrical properties of the TCFs have been investigated. Of the three leaf extracts, Mangifera indica offers the best alternative reducing agent for the green synthesis of Gns at large scale. Raman spectroscopy reveals that GO has been deoxygenated significantly, with a Raman D to G band intensity ratio of ∼1.21, while the attainment of a C/O ratio of ∼4.58 in the synthesized Gns has been confirmed by elemental analysis. The TCF fabricated after thermal graphitization (900 °C for 1 h) of the spray coated Gns film shows a sheet resistance of ∼2.08 kΩ □−1 and transmittance of ∼57.31% at 550 nm. The study suggests significant potential for the application of plant leaf extracts as non-toxic reducing agents in large-scale production of Gns. Apart from providing an alternative to hazardous reducing agents, this approach opens the possibility of preparation of Gns at large scale by using more accessible natural resources with mild synthesis conditions.

Structural, optical, and electrical characteristics of graphene nanosheets synthesized from microwave-assisted exfoliated graphite

In the present study, low defect density graphene nanosheets (GNs) have been synthesized via chemical reduction of exfoliated graphite (EG) in the presence of a green reducing agent, oxalic acid. EG has been synthesized via chemical intercalation of natural flake graphite followed by exfoliation through microwave irradiation at 800 W for 50 s. 50 mg/mL concentration of oxalic acid helps to extract low defect density GNs from EG. As-synthesized GNs have been characterized by X-ray diffraction, Raman spectroscopy, Fourier transform infrared spectroscopy, UV-Visible spectroscopy, field emission scanning electron microscopy, and X-ray photon spectroscopy. Raman analysis confirms the removal of oxygen functional groups from EG and achieved an ID/IG ratio of ∼0.10 with low defect density (∼1.12 × 1010 cm−2). Elemental analysis supports the Raman signature of the removal of oxygen functionalities from EG, and a high C/O ratio of ∼15.97 is obtained. Further, transparent conducting films (TCFs) have been fabricate...