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American Society for Testing and Materials

Elements Of X Ray Diffraction

Multidrug resistance of the pathogenic microorganisms to the antimicrobial drugs has become a major impediment toward successful diagnosis and management of infectious diseases. Recent advancements in nanotechnology-based medicines have opened new horizons for combating multidrug resistance in microorganisms. In particular, the use of silver nanoparticles (AgNPs) as a potent antibacterial agent has received much attention. The most critical physico-chemical parameters that affect the antimicrobial potential of AgNPs include size, shape, surface charge, concentration and colloidal state. AgNPs exhibits their antimicrobial potential through multifaceted mechanisms. AgNPs adhesion to microbial cells, penetration inside the cells, ROS and free radical generation, and modulation of microbial signal transduction pathways have been recognized as the most prominent modes of antimicrobial action. On the other side, AgNPs exposure to human cells induces cytotoxicity, genotoxicity and inflammatory response in human cells in a cell-type dependent manner. This has raised concerns regarding use of AgNPs in therapeutics and drug delivery. We have summarized the emerging endeavors that address current challenges in relation to safe use of AgNPs in therapeutics and drug delivery platforms. Based on research done so far, we believe that AgNPs can be engineered so as to increase their efficacy, stability, specificity, biosafety and biocompatibility. In this regard, three perspectives research directions have been suggested that include 1) synthesizing AgNPs with controlled physico-chemical properties, 2) examining microbial development of resistance towards AgNPs, and 3) ascertaining the susceptibility of cytoxicity, genotoxicity, and inflammatory response to human cells upon AgNPs exposure.

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Mechanistic Basis of Antimicrobial Actions of Silver Nanoparticles.

Giant and isotropic magnetoresistance as huge as −53% was observed in magnetic manganese oxide La0.72Ca0.25MnOz films with an intrinsic antiferromagnetic spin structure. We ascribe this magnetoresistance to spin‐dependent electron scattering due to spin canting of the manganese oxide.

31p-S-4 Giant Magnetoresistance in Magnetic Manganese Oxide with Intrinsic Antiferromagnetic Spin Structure

Solution combustion is an exciting phenomenon, which involves propagation of self-sustained exothermic reactions along an aqueous or sol–gel media. This process allows for the synthesis of a variety of nanoscale materials, including oxides, metals, alloys, and sulfides. This Review focuses on the analysis of new approaches and results in the field of solution combustion synthesis (SCS) obtained during recent years. Thermodynamics and kinetics of reactive solutions used in different chemical routes are considered, and the role of process parameters is discussed, emphasizing the chemical mechanisms that are responsible for rapid self-sustained combustion reactions. The basic principles for controlling the composition, structure, and nanostructure of SCS products, and routes to regulate the size and morphology of the nanoscale materials are also reviewed. Recently developed systems that lead to the formation of novel materials and unique structures (e.g., thin films and two-dimensional crystals) with unusual...

Solution Combustion Synthesis of Nanoscale Materials

Effect of pH variation on structural and optical properties of Zn0.95Co0.05O nanoparticles

Polycrystalline undoped and chromium doped (2%, 4%, 6% and 8%) TiO2 nanoparticles (NPs) were synthesized using a simple acid-modified sol–gel method. Influence of chromium (Cr) doping on the microstructural, electrical, optical, and photocatalytic properties was studied using various analytical techniques viz. X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), two-probe resistivity measurement and UV–visible absorption spectroscopy. Rietveld refinement of the XRD data reveals single phase, anatase crystal structure of the NPs in tetragonal symmetry with space group I41/amd. FTIR spectra demonstrate various functional groups and ensure anatase phase of all the samples. TEM images exhibit a significant change in the shape, size and morphology of the NPs on Cr incorporation in TiO2. Temperature-dependent resistivity measurements indicate the semiconducting nature of the samples and obey Arrhenius behaviour based on the mechanism of thermally activated conduction. A red shift in the UV–visible absorption spectra is noted on Cr doping, associated with the decrease in band gap from 3.1 eV for an undoped sample to 2.5 eV for an 8% Cr doped sample. Photoluminescence spectra signify that the dopant ions alter the density of oxygen vacancies that directly influence the electron–hole recombination rate. The photocatalytic performance is studied with regard to the degradation of chromophoric dyes, namely, rhodamine B and methylene blue under visible light illumination, revealing an increase in the photocatalytic activity with 82.2% and 73.4% degradation of the dyes after 120 min for the 6% Cr doped sample. This significant enhancement in the photocatalytic activity is attributed to the ease in the electron and hole separation by trapping sites produced due to Cr ions and oxygen vacancies. These observed results suggest that the Cr doped TiO2 NPs can be considered efficient photocatalysts with the advantage to tune the electronic structure and optical properties for possible applications in waste water treatment.

Enhanced Photocatalytic Activity by Tuning of Structural and Optoelectrical Properties of Cr(III) Incorporated TiO 2 Nanoparticles

A systematic investigation of the structural and magnetic properties of La2/3Sr1/3Mn1−xNixO3 (x = 0%, 5%, 15%, and 25%) perovskite nanoparticles synthesized using mild sol-gel technique is reported. These samples were characterized using x-ray diffraction (XRD), transmission electron microscopy, Fourier transform infrared (FTIR) spectroscopy, and temperature dependent magnetoresistance (MR) measurements. XRD analysis confirmed the single phase nature of the samples, and crystallite size was found to decrease from 21.4 nm to 17.0 nm with the increase in Ni concentration. Further, maximum MR was observed for 25% Ni doped sample at low temperature (77 K), whereas at room temperature (300 K) MR decreases with increase in Ni concentration. FTIR spectra show a broad peak at 605.28 cm−1, giving an evidence for the formation of metal oxygen bond which subsequently organize into a MnO6 octahedral structure as evidenced by the appearance of a well defined spectral band. Room temperature magnetization for all sample...

Wasi Khan

Papers

Effect of pH variation on structural and optical properties of Zn0.95Co0.05O nanoparticles

Enhanced Photocatalytic Activity by Tuning of Structural and Optoelectrical Properties of Cr(III) Incorporated TiO 2 Nanoparticles

Synthesis and evolution of magnetic properties of Ni doped La2/3Sr1/3Mn1−xNixO3 nanoparticles

Investigation of alteration in physical properties of dysprosium orthochromite instigated through cobalt doping

Formation of self-assembled spherical-flower like nanostructures of cobalt doped anatase TiO2 and its optical band-gap