Advances in Natural Sciences: Nanoscience and Nanotechnology

The optical extinction spectra of single metal nano-objects measured by the spatial modulation spectroscopy technique were correlated with their image obtained by scanning electron microscopy. The results show a large influence of both the object shape and the presence of the substrate on the measured optical spectra

The antimicrobial and anticancer efficiencies of green synthesized silver nanoparticles (AgNPs) through biogenic extracts were assessed on three bacterial strains and two cancer cell lines. Bio-synthesized AgNPs were achieved through domestic microwave generator for obtaining extracts from Asian nuts and Egyptian blackberry fruits. Surface plasmon resonance (SPR) ~435 nm demonstrated AgNPs earlier formation by the fruit extract. Capping by triglycerides/almond and phenols/berry extracts were responsible for the reduction proved by FTIR. XRD calculated particle sizes were 18 and 42 nm while TEM sizes are 24.5 and 21.5 nm for AgNPs from almond nut and blackberry fruits extracts (Alm.N.Ext. and BB.F.Ext.), respectively. Ag 3d5/2 was recorded at 368.12 eV for both samples through XPS. The monodispersed AgNPs recorded 0.727 and 0.5 polydispersity indices (PdI) for almond/Ag and berry/Ag, respectively. Zeta potential ~ −31 and −13.2 for the same sequence confirmed the higher stability of the former. Reaction kinetics confirmed the advantage of fruit extract consuming only six minutes compared to nuts, consuming twice. Bactericidal effect of the extracts seldomly presented remarkable inhibition compared to extracts/Ag against the three species. In addition, Alm.N.Ext. showed the highest inhibition against staphylococcus aureus (S. aureus) at 4 mM. The anti-cancerous effect of Ag/berry against HepG2 is stronger than Ag/almond, and similarly for MCF7

In this work the thermal behavior with the glass transition of phenyl-C61-butyric acid methyl ester (PCBM), poly(3-hexylthiophene) (P3HT) and their blends was investigated by thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). Both TGA and DSC measurements show that PCBM contains around 1% residual solvent in the crystalline structure. The glass transition of PCBM, P3HT and their blends was determined by quenching techniques. The quenched state of the materials has a strong effect on the glass transition of the materials, especially in the case of PCBM. In all blend compositions only one glass transition temperature was found. These results indicate that PCBM and P3HT are thermodynamically miscible in all blend compositions

We show the possibility of directional guided superradiance from a linear array of distant atoms separated by one or several wavelengths in a line parallel to the axis of a nanofiber. We find that the rate and efficiency of channeling of emission from the atoms into the fiber are cooperatively enhanced by the guided modes

High-performance permanent magnets are indispensable in the production of high-efficiency motors and generators and ultimately for sustaining the green earth. The central issue of modern permanent magnetism is to realize high coercivity near and above room temperature on marginally hard magnetic materials without relying upon the critical elements such as heavy rare earths by means of nanostructure engineering. Recent investigations based on advanced nanostructure analysis and large-scale first principles calculations have led to significant paradigm shifts in the understandings of coercivity mechanism in Nd–Fe–B permanent magnets, which includes the discovery of the ferromagnetism of the thin (2 nm) intergranular phase surrounding the Nd2Fe14B grains, the occurrence of negative (in-plane) magnetocrystalline anisotropy of Nd ions and some Fe atoms at the interface which degrades coercivity, and visualization of the stochastic behaviors of magnetization in the magnetization reversal process at high temperatures. A major change may occur also in the motor topologies, which is currently overwhelmed by the magnetic flux weakening interior permanent magnet motor type, to other types with variable flux permanent magnet type in some applications to open up a niche for new permanent magnet materials

abstractYVO4:Er3+ and YVO4:Er3+, Yb3+ nanomaterials were prepared via combustion synthesis using urea as fuel and metal nitrates as precursor. The morphology and the structure of the prepared samples were characterized by x-ray diffraction, scanning electron microscopy and transmission electron microscopy. The average size of the prepared materials ranged from 20 to 30 nm in diameter. The effects of Er3+ and Yb3+ doping concentrations on structure and optical properties have been investigated. Optical properties of YVO4:Er3+ and YVO4:Er3+, Yb3+ nanoparticles were measured by photoluminescent excitation and emission spectroscopies. For the YVO4:Er3+ and YVO4:Er3+, Yb3+samples, two strong green emissions centered at 524 and 552 nm are found, corresponding to the 2H11/2—4I15/2 and 4S11/2—4I15/2 transitions of Er3+ ions, respectively. Upconversion emission in the green region of the YVO4:Er3+ nanoparticles under 980 nm excitation was also investigated. Strong emission from these materials is promising for luminescent biolabeling applications

Thiram is a fungicide belonging to the dithiocarbamate family of pesticides that is widely used for fruits, vegetables and mature crops to control fungal diseases. The residue of thiram in food could pose a threat to human health. At present the surface-enhanced Raman scattering (SERS) is emerging as an ultrasensitive method for detection of thiram traces. In this report we show that by using home-made arrays of silver nanodendrites grown on silicon (AgNDs@Si) as SERS substrates, we can detect thiram to very low concentrations, with the limit of detection (LOD) of 1.2 ppb

The present study reports the synthesis of antibacterial biodegradable nanocomposite film of poly (vinyl alcohol)-biogenic silver. The biosynthesized silver nanoparticles were used for development of nanocomposite film. Ficus benghalensis leaf extract was used to synthesize silver nanoparticles which are cost effective, environmental friendly and rapid method. The PVA-biogenic silver nanocomposite film was characterized by AFM to determine the morphology of the film surface and confirm the incorporation of silver nanoparticles. The antibacterial activity of the nanocomposite film was investigated against Salmonella typhimurium by means of disk diffusion method. PVA-biogenic silver nanocomposite film shows excellent antibacterial activity against Salmonella typhimurium. This nanocomposite film can be a prominent material for food packaging

This study compared the fundamental properties of cellulose nanocrystals (CNC) and cellulose nanofibrils (CNF) extracted from sugarcane bagasse. Conventional hydrolysis was used to extract CNC while ball milling was used to extract CNF. Images generated by scanning electron microscope and transmission electron microscope showed CNC was needle-like with relatively lower aspect ratio and CNF was rope-like in structure with higher aspect ratio. Fourier-transformed infrared spectra showed that the chemical composition of nanocellulose and extracted cellulose were identical and quite different from bagasse. Dynamic light scattering studies showed that CNC had uniform particle size distribution with a median size of 148 nm while CNF had a bimodal size distribution with median size 240 ± 12 nm and 10 μm. X-ray diffraction showed that the amorphous portion was removed during hydrolysis; this resulted in an increase in the crystalline portion of CNC compared to CNF. Thermal degradation of cellulose initiated at a much lower temperature, in the case of the nanocrystals while the CNF prepared by ball milling were not affected, indicating higher thermal stability