B.M. Mothudi

Microwave-assisted synthesis of simonkolleite nanoplatelets on nickel foam-graphene with enhanced surface area for high-performance supercapacitors

Simonkolleite (Zn5(OH)8Cl2·H2O) nanoplatelets has been deposited on nickel foam-supported graphene by using an efficient microwave-assisted hydrothermal method. The three-dimensional (3D) porous microstructure of the as-fabricated nickel foam-graphene/simonkolleite (NiF-G/SimonK) composite is beneficial to electrolyte penetration and ions exchange, whereas graphene provide improved electronic conductivity. Structural and morphological characterizations confirmed the presence of highly crystalline hexagonal-shaped nanoplatelets of simonkolleite. Field emission scanning electron microscope (FE-SEM) of the NiF-G/SimonK composite revealed that the SimonK nanoplatelets were evenly distributed on the surface of NiF-G and interlaced with each other, resulting in a higher specific surface area of 35.69 m(2) g(-1) compared to SimonK deposited directly on NiF 17.2 m(2) g(-1). Electrochemical measurements demonstrated that the NiF-G/SimonK composite exhibit a high specific capacitance of 836 F g(-1) at a current density of 1 A g(-1), and excellent rate capability and cycling stability with capacitance retention of 92% after 5000 charge/discharge cycles.

Rapid microwave-assisted growth of silver nanoparticles on 3D graphene networks for supercapacitor application

Silver nanoparticles (AgNPs) grown on a three dimensional (3d) graphene networks (GNs) has been successfully prepared by an efficient and rapid microwave-assisted growth process to form GNs/AgNPs nanocomposite electrode materials for supercapacitor application. The 3d nature of the used GNs offers a unique architecture, which creates an efficient conduction networks and maximum utilization of space and interface, and acts as a conductive layer for the deposited AgNPs. The electrochemical performances of the fabricated electrode were evaluated by cyclic voltammetry (CV), galvanostatic charge/discharge and electrochemical impedance spectroscopy (EIS) tests. Specifically, the optimal GNs/AgNPs nanocomposite exhibits remarkable performances with a high specific capacitance of 528Fg-1 at a current density of 1Ag-1 and excellent capacitance retention of ∼93% after 3000cycles. Moreover, this microwave-assisted growth strategy of AgNPs is simple and effective, which could be extended to the construction of other three dimensional graphene based metallic composites for energy storage and conversion applications.

Preparation and characterization of regenerated cellulose films using borassus fruit fibers and an ionic liquid

In this study, we successfully extracted cellulose from borassus fruit fibers by chemical process. The extracted cellulose was dissolved in an ionic liquid 1-allyl-3-methylimidazolium chloride (AmimCl). Using this solution, regenerated cellulose films were prepared with water as the non solvent. The raw fruit fibers and extracted cellulose were characterized by chemical analysis. The results indicated that the content of the components other than cellulose was significantly decreased during the cellulose extraction process. Further, FTIR, 13CP-MAS NMR, wide-angle X-ray diffraction (XRD), thermo gravimetric analysis (TGA) and scanning electron microscopy (SEM) were used to provide structural characterization of raw fibers, extracted cellulose and regenerated cellulose films. The average tensile strength, modulus and elongation at break of the regenerated cellulose films were found to be 111±19MPa, 6149±603MPa and 3.1±0.8%, respectively. The notable properties of regenerated cellulose films advocate their effectiveness for various industrial applications.

Luminescent Eu2O3 nanocrystals by Aspalathus linearis’ extract: structural and optical properties

Abstract. This contribution reports on the synthesis and the main physical properties of europium oxide nanocrystals synthesized for the first time by a completely green physical–chemistry process using Aspalathus linearis’ leaves natural extract as an effective chelating agent. The structural and optical properties of such biosynthesized nanocrystals were investigated by electron microscopy, selective electron diffraction, energy dispersive spectroscopy, x-rays diffraction, Raman and x-rays photoelectron spectroscopies, as well as room-temperature photoluminescence. The luminescence properties of such cubic nanocrystals with a 16.5 nm average size were characterized by an intense red emission centered at 614.8 nm (D05−F37) with an average time decay of 7.808  μs.

Artemisia herba-alba Asso eco-friendly reduced few-layered graphene oxide nanosheets: structural investigations and physical properties

ABSTRACT Nowadays graphene is universally known as a promising material. Hence, the development of eco-friendly synthesis methods for this material is of great importance. This study reports on the bio-synthesis of graphene by a green chemistry process using Artemisia herba-alba Asso (AHAA) natural extract. Moreover, this work reports on the physical properties, including surface/interface and optical and electrical properties of the obtained graphene sheets. UV–VIS, Raman, XPS spectroscopies and TEM microscopy investigations confirmed the reduction, and the conversion of graphene oxide to few-layered reduced graphene oxide as well as the efficiency of this plant extract compared with several natural extracts and chemical agents. Furthermore, it was found that the optical and electrical properties of graphene can be modulated and controlled via this eco-friendly cost-effective process. Hence, AHAA can be an effective chelating agent to produce graphene sheets. GRAPHICAL ABSTRACT

Extraction and characterization of cellulose single fibers from native african napier grass

With increasing awareness of protecting the environment, the demand for renewable and environmental materials is increasing. In this work, the cellulose single fibers (CSFs) were extracted from the African native Napier grass fibers (NGFs) by chemical process. NGFs and CSFs were characterized for their chemical composition, structure, morphology, crystallinity and thermal properties using, chemical analysis, FTIR, 13C CP/MAS NMR, SEM, XRD and TGA techniques. The resulted CSFs had higher α-cellulose content, crystallinity and thermal stability than the pristine NGFs. SEM images showed cleaner and rough surfaces for the CSFs when compared to those of NGFs. About 69% of the extracted CSFs showed a diameter range between 4 and 10 μm. FTIR and 13C CP/MAS NMR spectra confirmed the removal of lignin and hemicellulose components after chemical treatments.

Structural, optical and photocatalytic applications of biosynthesized NiO nanocrystals

ABSTRACT NiO is one of the most important candidates for semiconductors metal oxide nanocrystals by the arrangement of photocatalytic application. However, the photocatalytic performance of biosynthesized nanocrystals using Aspalathus linearis (Burm.f.) R. Dahlgren has not been investigated yet. In this contribution, we synthesize α-Ni(OH)2 using an A. linearis. A heat treatment of the α-Ni(OH)2 is carried out at 300–400°C for 2 h at normal air yields. Furthermore, we have characterized the structural, optical and photocatalytic activity of the samples. The optical results indicate that biosynthesized nanocrystals exhibit UV–visible light absorption and a narrow range distribution of intense green light (518.95 nm) emission, which decreases significantly as annealing temperature increases. The bandgap energies of the sample annealed at 300–400°C shift to lower photon energy, compared to bulk NiO (∼ 4 eV). Moreover, the photocatalytic experimental results reveal that NiO nanocrystals enable color switching of methylene blue. GRAPHICAL ABSTRACT

Structural and optical properties of hydrothermally synthesized vanadium oxides nanobelts

Nanostructured metal oxides have attracted a lot of attention recently owning to their unique structural advantages, and demonstrated promising chemical and physical properties for various applications. In this study, we report the structural and optical properties of vanadium oxide nanoparticles (VO-NPs) prepared via a hydrothermal method. Our results are revealing that the components of VO-NPs films are having a belt-like shape with a uniform size distribution. The nanobelts with very smooth and flat surfaces have a typical length of up to 1μm and a width of about 9-14 nm. Moreover, The UV-Visible spectroscopy revealed an excellent optical propertiesshowing clearly the good stoichiometry and crystallinity of our VO-NPs films. This synthesis method provides a new simple route to fabricate one-dimensional nanostructured metal oxides which is suitable for a large field of applications.

The Dynamics of Luminescence

Domestic light providing devices have always been an important component of life and continue to provide us light beyond sunset. These devices continue to be improved frequently to allow ease of use and to enhance their efficiency. The tungsten electric light bulbs are widely used, which are based on incandescence of a continuously heated tungsten element. However, their use will soon be short lived because of the increased usage of fluorescent tubes and light-emitting diode (LED) devices, which are based on luminescence emission. These emission materials that display luminescence are called phosphors, and their emission is based on electron transitions. In the following chapter, we shall look into photoluminescence from both intrinsic and extrinsic defects, covering both downand upconversion (UP). We will look into the concept of energy transfer and persistent luminescence and lastly provide related applications of luminescence in the modern days.

Structural and optical characterization of Holmium coated ZnO nanorods

One-dimensional ZnO nanostructures have been attracting growing research effort worldwide over the last few years due to their various morphologies, easy synthesis and excellent physical properties for fabricating optoelectronic devices. In this study, we have reported the synthesis of Holmium coated ZnO nanostructures. The structural, morphological and optical properties of our materials were studied using different techniques. The obtained materials show promising properties and the remarkable effects of the coated material. The experimental results obtained for our material exhibit signficant enhancement in properties, which is suitable for the optoelectronic applications.