Engineered nanostructures: A review of their synthesis, characterization and toxic hazard considerations

Research work on the synthesis, designing and characterization of nanostructures has been extensively documented in the last decades. This in-depth documentation not only enabled researchers to understand the relationship between the nanostructure properties, size, shape, and composition but also have given them immense control over their manufacturing. This enhanced knowledge, cemented the switching of academic nanotechnology research into industrial products. However; despite the recent accomplishment in synthesis, characterization and application of the nanostructure materials, a complete knowledge/information of their interactions with biological systems is still not available. Hence, it is difficult to forecast the injurious biological responses of these novel nanostructures to humans, animals, insects and plants. Due to this hesitancy, safety regulatory authorities and general public have raised their concerns to the manufacturing and use of nanostructure-based products. Consequently, it is vital for the researchers to concentrate more on safe designing, manufacturing and characterization of nanostructures before these could meet human and communal needs. This review is taking an overview of the increasing investments in nanotechnology, designing, synthesis and characterization of nanostructures and their in vitro and in vivo toxicities

RKKY magnetic interactions in chemically synthesized Zn0.95−xFe0.05AlxO (x = 0, 0.03, 0.05, 0.07) nanocrystallites

Chemically derived auto-combustion technique is employed to synthesize the Zn0.95−xFe0.05AlxO (x = 0, 0.03, 0.05, 0.07) nano-crystallites. The salient similarities between variations in lattice parameters, crystallite size, morphology, electrical resistivity and saturation magnetization designated a strong association between these properties. X-ray diffraction studies of all compositions revealed the phase pure wurtzite crystal structure with space group P63mc. The lattice parameters and crystallite size are changed with doping of Al attributed to the diversity in the size of ionic radii. Scanning electron micrographs revealed that Al doping affects the size and shape of grains in synthesized compositions. Temperature dependent electrical resistivity shows a decreased trend with the rise of temperature, confirming the semiconducting nature of compositions. The lower resistivity and enhanced saturation magnetization values in Al doped compositions correspond to the increase in density of carriers. Carrier mediated RKKY interactions are found to enhance magnetization

Enhanced Magnetization of Sol-Gel Synthesized Pb-Doped Strontium Hexaferrites Nanocrystallites at Low Temperature

Effect of Pb doping on the structural and low temperature magnetic properties of SrPbxFe12-xO19 (x=0,0.1,0.2,0.3,and  0.4), synthesized by sol-gel autocombustion technique, has been investigated. The powder samples were sintered at 800°C for 2 h in order to develop the stable hexagonal phase, characteristic of the SrFe12O19 structure. The consequences of Pb substitution (at iron sites) on various structural parameters like lattice constants, unit cell volume, crystallite size, and porosity have been discussed. Fourier transform infrared frequency bands were utilized to determine the formation of tetrahedral and octahedral clusters of M-type ferrites. Hexagonal texture of the grains, a characteristic of the hexagonal crystal structure of SrFe12O19, was refined by Pb substitution. The magnetic properties, determined using a vibrating sample magnetometer, revealed that saturation magnetization decreased, while coercivity was increased with the increase of Pb contents. However, the increased squareness ratio and hence the energy product motivate the utilization of these ferrite compositions where hard magnetic characteristics are required. The increased values of saturation magnetization were observed at reduced temperature of 200 K, attributable to the better spin alignments of individual magnetic moments at low temperature