Asim Jilani

Facile spectroscopic approach to obtain the optoelectronic properties of few-layered graphene oxide thin films and their role in photocatalysis

Herein, we report the synthesis of few-layered graphene oxide (GO), reduced graphene oxide (rGO), and rGO/ZnO thin films on a glass substrate by the combination of spin coating, low temperature thermal annealing, and radio frequency (RF) sputtering. A spectroscopic approach was applied for the very first time to calculate the optical and dielectric properties of GO thin films. The GO thin film was characterised for structural, optical, morphological, and surface chemical state composition properties by X-ray diffraction, UV-visible spectroscopy, atomic force microscopy, field emission scanning electron microscopy, and X-ray photoelectron microscopy. The chemical state analysis of O1s and C1s spectra evidently proved the successful reduction of GO at 200–300 °C. The change in grain size, lattice strain, and dislocation density was studied after the reduction of GO to rGO, and the band gap analysis was performed through Tauc plot relation. The optical conductivity of the GO films was estimated by the UV technique. Moreover, the dielectric constant and dielectric loss of GO and rGO thin films were also studied, and the samples annealed at high temperature showed comparatively low loss. Due to the high conductivity and low band gap of few-layered rGO, its composite with RF-sputtered ZnO (rGO/ZnO) was studied for its ability to photocatalytically degrade 2-chlorophenol.

Development of Silver-Nanoparticle-Decorated Emulsion-Templated Hierarchically Porous Poly(1-vinylimidazole) Beads for Water Treatment

Water, the driver of nature, has always been polluted by the blind hurling of highly toxic contaminants, but human-friendly science has continuously been presenting better avenues to help solve these challenging issues. In this connection, the present study introduces novel nanocomposites composed of emulsion-templated hierarchically porous poly(1-vinylimidazole) beads loaded with the silver nanoparticles generated via an in situ approach. These nanocomposites have been thoroughly characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, Brunauer-Emmett-Teller, and field emission scanning electron microscopy. The appropriate surface chemistry, good thermal stability, swelling behavior, porosity, and nanodimensions contributed to achieve very good performance in water treatment. Owing to their easier handling and separation, these novel nanocomposites are highly efficient to remove arsenic and eriochrome black T with decent adsorption capacities in addition to the inactivation and killing of Escherichia coli (Gram-negative) and Staphylococcus aureus (Gram-positive) bacteria.

Correction to: Novel Control of the Synthesis and Band Gap of Zinc Aluminate (ZnAl2O4) by Using a DC/RF Sputtering Technique

Due to an oversight, the Surname of Haya Alhummiany was incorrectly spelled in the published online version. The correct surname is “Alhummiany”, instead of “Alhumminay”. The correct spelling is also shown above.

Novel Control of the Synthesis and Band Gap of Zinc Aluminate (ZnAl2O4) by Using a DC/RF Sputtering Technique

AbstractZinc aluminate (ZnAl2O4) thin films have been deposited through direct current/radio frequency (DC/RF) magnetron sputtering by varying the applied power of an Aluminum (Al) target. The X-ray diffraction (XRD) pattern showed the formation of monophase ZnAl2O4 with spinel structure. Moreover, structural analysis like grain size, dislocation density, and lattice strain was calculated through the XRD obtained data. The surface morphological analysis through field emission scanning electron microscopy (FESEM) confirmed the formation of nano-size spinel ZnAl2O4. The transmittance of the ZnAl2O4 thin film was found to be dependent on the aluminum (Al) target power. An inverse relation was noticed between the transmittance and the Al-power. The optical band gap dependent refractive index, high-frequency dielectric, and static dielectric constant were calculated. Graphical AbstractScheme of experimental work

Structural, optical, and photocatalytic investigation of nickel oxide@graphene oxide nanocomposite thin films by RF magnetron sputtering

Despite the recent advancement in graphene oxide (GO) as a host material in energy and environmental sectors, its composite thin films with metal oxides such as nickel oxide (NiO) and its optical, structural, chemical state, and photocatalytic activities have been poorly explored. Herein, we have reported the GO/NiO thin films preparation by a combination of chemical and physical deposition techniques (i.e. spin coating followed by DC/RF sputtering). The as-prepared composites thin films were characterised using Raman spectroscopy, X-ray diffraction/photoelectron spectroscopy scanning electron microscopy, and atomic force microscopy. The surface topography confirmed the uniform deposition of NiO over thin films of GO. The XPS results showed the formation of NiC along with the partial reduction in GO into graphene with their existing four constituents, i.e. NiO, NiC, GO, in the thin film composites. The classical plasmon, Wemple and Didomenico model, was first time applied for GO/NiO to compute energy loss functions, and dispersion energy parameters. The theoretical calculated values for the deposited GO/NiO thin films were found to be in very close agreement to the standard classical plasmon values. The change in spin orbital movement of Ni is considered due to the interaction between its nanoparticles and basal planes of GO. Thin films applied for the photodegradation of recalcitrant organic pollutant 2-chlorophenol (2-CP) revealed the dependence of photocatalytic efficiency on particle size and also on the interaction of GO with NiO rather than the ratio of NiO and GO in the films.

Polymer composite reinforced with nanoparticles produced from graphitic carbon-rich fly ash:

Carbon nanotubes and graphene are considered effective reinforcement materials for various polymers because of their superior properties. However, they are expensive and difficult to separate and incorporate individually into matrix systems because of their tendency to exist in clustered form. In this work, carbon nanoparticles produced from graphitic carbon-rich fly ash by high-energy ball milling are evaluated as a reinforcement in a high-performance epoxy matrix system. They were used in various weight fractions ranging from 0.1 to 2 wt.%. The obtained carbon nanoparticles have an average particle size of around 20 nm, while XPS spectrum shows active carbonyl groups on their surfaces. The mechanical tensile properties of the carbon nanoparticles/epoxy nanocomposite, including their Youngs modulus, stiffness, and load at fracture, were investigated. Moreover, the effect of ethanol as a dispersion medium was studied. The obtained results indicate that the Youngs modulus and load at fracture changed only slightly upon the addition of carbon nanoparticles to the epoxy matrix system. On the other hand, the stiffness was improved by 60% over that of the pure epoxy matrix system. This improvement was obtained at 0.6 wt.% carbon nanoparticle content. The test results indicate that ethanol is effective in modifying the nanocomposite mechanical properties. Additionally, results show that low-cost CNPs might be useful as a reinforcement material for high-stiffness products.