Experimental Investigation of the Effect of Graphene Nanosheets on the Optical-Electrical Properties of Vanadium Oxide Nanocomposites

We report the structural, optical and electrical properties of Graphene-Vanadium oxide nanoparticles (rGO/VO-NPs) nanocomposites prepared via a hydrothermal method on glass substrates. The samples have been characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (ATR-FTIR), Raman spectroscopy, ultraviolet-visible spectra (Uv-Vis) (absorbance/reflectance) and electrical conductivity. Our results are revealing a remarkable effect on the morphology and structure of vanadium oxide nanoparticles. Hence, the graphene layers improved their electrical conductivity and highly influenced their optical properties. Therefore, the obtained results may lead to better performance for a large field of applications.

Biosynthesized metallic nanoparticles as fertilizers:An emerging precision agriculture strategy

Nanofertilizers increase efficiency and sustainability of agricultural crop production.Due to their nanosize properties,they have been shown to increase productivity through target delivery or slow release of nutrients,thereby limiting the rate of fertilizer application required.Nanofertilizers can be synthesized via different approaches ranging from physical and chemical to green(biological)synthesis.The green approach is preferable because it makes use of less chemicals,thereby producing less chemical contamination and it is safer in comparison to physicochemical approaches.Hence,discussion on the use of green synthesized nanoparticles as nanofertilizers is pertinent for a sustainable approach in agriculture.This review discusses recent developments and applications of biologically synthesized metallic nanoparticles that can also be used as nanofertilizers,as well as their uptake mechanisms for plant growth.Toxicity concerns of nanoparticle applications in agriculture are also discussed.

The charge state distribution of B, C, Si, Ni, Cu and Au ions on 5 MV pelletron accelerator

Stripper gas and terminal potential play a key role for the charge state distribution in a tandem pelletron accelerator. The knowledge of this distribution is important for experiments performed on tandem accelerators. The charge state distribution of B, C, Si, Ni, Cu and Au beams is measured by using Ar as stripper gas, and terminal potential is varied from 0.3 to 3.0 MV on 5UDH-2 tandem pelletron accelerator installed at the National Centre for Physics, Islamabad. The individual charge state is measured after the switching magnet at 15° in high-energy portion. It is observed that the higher charge states are stable in the range of lower and middle atomic masses of periodic table, whereas higher atomic mass(Au) shows beam current instability in higher charge states. For carbon,the charge distribution at 1.7 MV terminal potential by varying stripper gas pressure is also studied, which resulted in decreased overall transmission with good current value for higher charge states.

Synthesis of Co-Cr-Mo Fluorapatite Nano-Composite Coatings by Pulsed Laser Deposition for Dental Applications

Aim: The study was to fabricate FA nanopowder/Co-Cr-Mo dental alloy nanocomposite using pulsed laser deposition (PLD), and to evaluate bioactivity properties on simulated body fluid. Methods: In this work, the FA nanopowder was prepared by mixing calcium hydroxide (Ca(OH)2), phosphorouspent oxide (P2O5) and calcium fluoride (CaF2) in a planetary high energy ball mill using zirconium vial. Fluorapatite (FA) nanopowder was processed in the form of pellet for pulsed laser deposition process. The Co-Cr-Mo alloy was coated with FA nanopowder which was approximately 35 - 65 nm at various laser energy, pressure and time. The X-ray diffraction (XRD) was used to analyze phase, crystallinity and size distribution of Co-Cr-Mo/FA nanocomposite. The surface analysis was by scanning electron microscopy (SEM), Atomic Force microscopy (AFM) and Energy dispersive spectroscopy (EDS). Results: From the results obtained, It was shown that FA nanopowder deposited on Co-Cr-Mo alloy was stable during 14 days of incubation on simulated body fluid. It was also observed that the FA nanopowder coated on the surface of the alloy was still intact after the deposition process, which indicated the bioactivity and biocompatibility of the material. Conclusions: The fabrication of FA nanocomposite based dental alloys (Co-Cr-Mo) using PLD was done successfully. This was confirmed by various characterization techniques, which included XRD, AFM, SEM and EDS.

Free-Green Synthesis and Dynamics of Reduced Graphene Sheets via Sun Light Irradiation

It is universally known that the preparation of high quality graphene on a large scale and in a cost-effective manner is essential for many technological applications. Graphene oxide (GO) has emerged as the precursor of choice for bulk production of graphene-based materials, as it can be synthesized from inexpensive graphite powders. In this paper, a simple method is described for reduction of GO solution by a free and green irradiation based technique. The majority of oxygen-containing functional groups of GO are removed by sun light. This methodology provides an effective way to quantitatively produce high quality graphene sheets. This paper presents irradiation by sun light of synthesized graphene oxide nano-flakes prepared by Hummer’s method. These nano-flakes have been successfully reduced while the dynamic of this irradiation process is discussed. The irradiated nano-flakes of graphene oxide have been investigated using X-Ray diffraction, ATR-FTIR and UV-Vis-NIR.

Synthesis and Characterization of Mass Produced High Quality Few Layered Graphene Sheets via a Chemical Method

Graphene is a two-dimensional crystal of carbon atoms arranged in a honeycomb lattice. It is a zero band gap semimetal with very unique physical and chemical properties which make it useful for many applications such as ultra-high-speed field-effect transistors, p-n junction diodes, terahertz oscillators, and low-noise electronic, NEMS and sensors. When the high quality mass production of this nanomaterial is still a big challenge, we developed a process which will be an important step to achieve this goal. Atomic Force Microscopy, Scanning Electron Microscopy, Scanning tunneling microscopy, High Resolution Transmission Electron Microscopy, X-Ray Diffraction, Raman spectroscopy, Energy Dispersive X-ray system were investigated to characterize and examine the quality of this product.

Antibacterial and cytotoxicity activity of green synthesized silver nanoparticles using aqueous extract of naartjie(Citrus unshiu)fruit peels

The application of plant extracts in the green synthesis of silver nanoparticles(AgNPs)has attracted significant attention owing to their eco-friendliness and cost-effective features.However,nanoparticles synthesized from plant materials may also display unique physicochemical properties.This study described an improved synthesis process for silver nanoparticles(AgNPs)from the peel of the Citrus unshiu fruit,an agricultural waste product.In addition to evaluating the produced AgNPs'physico-chemical characteristics,the research also examines their antibacterial and cytotoxic/anticancer capa-bilities.The color change from yellow to dark brown was observed immediately when 20 ml of Citrus unshiu fruit peel extract was added to 0.5 g of silver nitrate.A surface plasmon resonance band at 424 nm revealed by ultra-violet spectroscopy was used as additional confirmation that AgNP had formed.The scanning electron microscope(SEM),and the transmission electron microscope(TEM),revealed spherical-shaped NPs with a mean size of 23 nm.Furthermore,X-ray diffraction(XRD)confirmed the high crystallinity of the obtained NPs while Fourier transform infrared spectroscopy(FTIR)confirmed the bioreducing capacity of the Citrus unshiu fruit peel extract.The minimum inhibitory concentration(MIC)(31.25 mg/mL)of AgNPs significantly revealed a strong dose-dependent antibacterial effect on Staphy-lococcus aureus and Bacillus cereus.In contrast,their impact on gram-negative bacteria,such as Escher-ichia coli and Salmonella typhimurium,displayed an MIC of 250 mg/mL.The assessment of cytotoxicity on human embryonic kidney cells(HEK293)and lung cancer cells(A549)through a 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide assay revealed no detectable cytotoxic effects.The IC 50 values were determined as 37.73±0.34 mg/mL for HEK293 and 56.37±0.73 mg/mL for A549,indicating the absence of significant adverse impacts on these cell lines.The anticancer drug doxorubicin was used as a reference standard,and had an IC 50 value of 1.22±0.09 and 0.76±0.12 mg/mL against HEK293 and A549 cells,respectively.The results show that AgNPs synthesized from Citrus unshiu fruit peel could serve as antibacterial agents that may in the future be optimized for us in for example nanofiltration systems.