Structural, electrical and magnetic properties of cadmium substituted nickel-copper ferrites

Polycrystalline ferrites with the general formula Ni_0.95−xCd_xCu_0.05Fe₂O₄ in which x varies from 0.1 to 0.3 were synthesized by standard double sintering ceramic technique. The existence of single phase cubic spinel structure of ferrites was confirmed from XRD measurement. Surface morphology and compositional features were studied by SEM and EDX measurements. Absorption bands observed in FTIR spectra at 600 cm⁻¹ (υ₁) and 410 cm⁻¹ (υ₂) corresponds to vibrations of tetrahedral and octahedral complexes respectively. In the dc conductivity measurements the decrease of dc resistivity with increase of temperature indicates the semiconducting nature of ferrites. The dielectric measurement of the samples at room temperature studied in the frequency range 20 Hz to 1 MHz shows dispersion in the low frequency region and remains constant at high frequency region. However, the small polaron hoping type of conduction mechanism was inferred from the linear increase of ac conductivity. The magnetic properties of ferrites such as saturation magnetization, magnetic moment and Y-K angles was estimated as a function of cadmium content by VSM technique. The smaller value of Mr/Ms reveals the existence of multidomain (MD) particles in the ferrite samples.     

Chemical functionalization of graphene enabled by phage displayed peptides

The development of a general approach for the nondestructive chemical and biological functionalization of graphene could expand opportunities for graphene in both fundamental studies and a variety of device platforms. Graphene is a delicate single-layer, two-dimensional network of carbon atoms whose properties can be affected by covalent modification. One method for functionalizing materials without fundamentally changing their inherent structure is using biorecognition moieties. In particular, oligopeptides are molecules containing a broad chemical diversity that can be achieved within a relatively compact size. Phage display is a dominant method for identifying peptides that possess enhanced selectivity toward a particular target. Here, we demonstrate a powerful yet benign approach for chemical functionalization of graphene via comprehensively screened phage displayed peptides. Our results show that graphene can be selectively recognized even in nanometer-defined strips. Further, modification of graphene with bifunctional peptides reveals both the ability to impart selective recognition of gold nanoparticles and the development of an ultrasensitive graphene-based TNT sensor. We anticipate that these results could open exciting opportunities in the use of graphene in fundamental biochemical recognition studies, as well as applications ranging from sensors to energy storage devices.     

Antifungal activity of Azotobacter nigricans against trichothecene-producing Fusarium species associated with cereals

Food Science and Biotechnology - Antifungal efficacy of Azotobacter nigricans on Fusarium infection, total seedlings mass, root and shoot length, and seed germination in maize, sorghum, and wheat...     

Effect of Sintering on Magnetic Properties of Ni0.55Zn0.45Fe2O4

Bulk Ni_0.55Zn_0.45Fe₂O₄ samples were obtained by sintering their nanopowder at 1100 ^°C, 1200 ^°C, and 1300 ^°C. Improvement in crystallinity on sintering was identified from increase in intensity of the XRD peaks and grain development in SEM micrographs. Saturation magnetization increased from 81.7 emu/g to 85.3 emu/g as the sintering temperature increased from 1100 ^°C to 1300 ^°C. Initial permeability increases whereas the relative loss factor, resonance frequency, and DC resistivity decreases with increasing the sintering temperature. Curie temperatures obtained from low field AC normalized susceptibility and permeability measurements are in good agreement. The DC resistivity of the samples in the present case is two orders higher than the reported values of samples prepared using conventional ceramic method.     

Utilization of green seed canola oil for in situ epoxidation

Green seed canola oil is underutilized for edible purposes due to its high chlorophyll content, which makes it more susceptible to photo‐oxidation and ultimately reduces the oxidation stability. The present work is an attempt to compare the kinetics of epoxidation of crude green seed canola oil (CGSCO) and treated green seed canola oil (TGSCO) with peroxyacids generated in situ in presence of an Amberlite IR‐120 acidic ion exchange resin (AIER) as catalyst. Among the two oxygen carrier studied, acetic acid was found to be a better carrier than the formic acid, as it gives 8% more conversion of double bond than the formic acid. A detailed process developmental study was then performed with the acetic acid/AIER combination. For the oils under investigation parameters optimized were temperature (55°C), hydrogen peroxide to double bond molar ratio (2.0), acetic acid to double bond molar ratio (0.5), and AIER loading (15%). An iodine conversion of 90.33, 90.20%, and a relative epoxide yield of 90, 88.8% were obtained at the optimum reaction conditions for CGSCO and TGSCO, respectively. The formation of the epoxide product of CGSCO and TGSCO was confirmed by Fourier Transform IR Spectroscopy (FTIR) and NMR (1H NMR) spectral analysis.     

Service life prediction of organic coatings: electrochemical impedance spectroscopy vs actual service life

Electrochemical impedance spectroscopy (EIS) is used to derive an expression for predicting the service life of organic coating in a C4-type environment (industrial and costal areas with moderate salinity) as defined in ISO 12944 standard for paints and varnishes—corrosion protection of steel structures by protective paint systems. Three coating systems with a record of 2, 5, and 10 years of durability were selected for the study. The selection was also based on proven composition and dry film thickness (DFT) of the coatings as per ISO 12944. Electrochemical impedance measurements of the paint-coated panels were carried out by exposing the coated mild steel panels without scribe in different corrosive environments such as immersion in NaCl solution, neutral salt spray, etc. Neutral salt spray exposure was found to be the most severe corrosive environment among all the three coating systems. In most of the cases, EIS gave early indication of coating failure when compared to visual defects such as blistering and over-film corrosion.     

Interrogating the catalytic mechanism of nanoparticle mediated Stille coupling reactions employing bio-inspired Pd nanocatalysts

To address issues concerning the global environmental and energy state, new catalytic technologies must be developed that translate ambient and efficient conditions to heavily used reactions. To achieve this, the structure/function relationship between model catalysts and individual reactions must be critically discerned to identify structural motifs responsible for the reactivity. This is especially true for nanoparticle-based systems where this level of information remains limited. Here we present evidence indicating that peptide-capped Pd nanoparticles drive Stille C-C coupling reactions via Pd atom leaching. Through a series of reaction studies, the materials are shown to be optimized for reactivity under ambient conditions where increases in temperature or catalyst concentration deactivate reactivity due to the leaching process. A quartz crystal microbalance analysis demonstrates that Pd leaching occurs during the initial oxidative addition step at the nanoparticle surface by aryl halides. Together, this suggests that peptide-based materials may be optimally suited for use as model systems to isolate structural motifs responsible for the generation of catalytically reactive materials under ambient synthetic conditions.     

An investigation into transition metal ion binding properties of silk fibers and particles using radioisotopes

Silk is a structural protein fiber that is stable over a wide pH range making it attractive for use in medical and environmental applications. Variation in amino acid composition has the potential for selective binding for ions under varying conditions. Here we report on the metal ion separation potential of Mulberry and Eri silk fibers and powders over a range of pH. Highly sensitive radiotracer probes, ⁶⁴Cu²⁺, ¹⁰⁹Cd²⁺, and ⁵⁷Co²⁺ were used to study the absorption of their respective stable metal ions Cu²⁺, Cd²⁺, and Co²⁺ into and from the silk sorbents. The total amount of each metal ion absorbed and time taken to reach equilibrium occurred in the following order: Cu²⁺ > Cd²⁺ > Co²⁺. In all cases the silk powders absorbed metal ions faster than their respective silk fibers. Intensive degumming of the fibers and powders significantly reduced the time to absorb respective metal ions and the time to reach equilibrium was reduced from hours to 5–15 min at pH 8. Once bound, 45–100% of the metal ions were released from the sorbents after exposure to pH 3 buffer for 30 min. The transition metal ion loading capacity for the silk sorbents was considerably higher than that found for commercial ion exchange resins (AG MP‐50 and AG 50W‐X2) under similar conditions. Interestingly, total Cu²⁺ bound was found to be higher than theoretically predicted values based on known specific Cu²⁺ binding sites (AHGGYSGY), suggesting that additional (new) sites for transition metal ion binding sites are present in silk fibers. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

Unlocking the Latent Antimicrobial Potential of Biomimetically Synthesized Inorganic Materials

Inspired by biomineralization, biomimetic approaches utilize biomolecules and synthetic analogs to produce materials of controlled chemistry, morphology, and function under relatively benign conditions. A common characteristic of biological and biomimetic mineral‐forming processes is the generation of mineral/biomolecule nanocomposites. In this work, it is demonstrated that a facile chemical reaction may be utilized to halogenate the nitrogen‐containing moieties of the organics entrapped within bio‐inorganic composites to yield halamine compounds. This process provides rapid and potent bactericidal activity to biomimetically and biologically produced materials that otherwise lack such functionality. Additionally, bio‐inorganic composites containing the chlorinated peptide protamine are effective in rapidly neutralizing Bacillus spores (≥99.97% reduction in colony forming units within 10 min). The straightforward nature of the described process, and the efficacy of halamine compounds in neutralizing biological and chemical agents, provide new applicability to biogenic and biomimetic materials.