Abstract: Nest-like Bi2WO6 microspheres were successfully synthesized through a simple one step template-free approach employing a hydrothermal process, and it is found that citrate and NaHCO3 played multifold roles in the formation process of the nest-like microspheres. A formation mechanism of nested Bi2WO6 hierarchical microspheres was proposed based on XRD analysis and SEM observation of the products of different reaction conditions. The UV-vis diffuse reflectance spectra indicated that the as-synthesized microspheres have a significantly enhanced optical absorbance in the UV-vis region and red-shift phenomenon compared to that of Bi2WO6 powder prepared by the surfactant reaction method. The nest-like Bi2WO6 microspheres exhibited good photocatalytic activity in the degradation of Rhodamine-B (RhB) under 500 W Xe lamp light irradiation.
Abstract: Synthesis of Si quantum dots (QDs), useful for multi-junction crystalline Si solar cells, using porous Silicon (PS) is presented in this paper. Four types of freestanding PS structures are fabricated by anodization method with modulation of current density between two levels. The level-1 current density is kept constant at 20 mA/cm2 (for reference monolayer structure - sample A) and 10 mA/cm2 (for all multilayer structures samples B, C, D). The level-2 is varied between 0 to 50 mA/cm2 (0, 20, 30, 50 mA/cm2 as sample A, B, C and D respectively). In order to obtain Si QDs from PS films, the films are subjected to sonication (120 W, 42 kHz) for 6 hours. HRTEM images confirm presence of Si nanoparticles in the range of 2 to 8 nm. Various spectroscopic analyses of Si nanoparticles are performed in order to evaluate quantum confinement behavior and surface modification observed during sonication. Analysis of de-convoluted Raman peaks shows frequency downshift and increase in full width half maximum due to formation of QDs. After sonication, PL spectroscopy indicates blue shift from 2.54 eV (sample A) to 2.85 eV (sample D_6HR), similar to the observations made by UV-Vis spectroscopy. FTIR spectra show oxidation of Si QDs during sonication. Spectroscopic and microscopic results are explained using quantum confinement and surface modification phenomenon.
Abstract: Au nanoparticles of average size 3.0 nm have been deposited on SWCNT surfaces following a very lucid wet chemical process. The SWCNT/Au nanohybrid material has been characterized using field emission scanning electron microscopy (FESEM), energy dispersive x-ray analysis (EDAX), X-ray diffraction (XRD) study and Raman spectroscopy. Both optical and electrical characteristics of the hybrid sample have been studied. The PL emission intensity of the nanohybrid structure has been found to decrease on increasing the excitation wavelength in the plasmon absorption region. High temperature DC conductivity has increased appreciably when pristine SWCNT is treated with Au NPs. Such SWCNT- supported gold nanoparticles can serve as efficient catalysts in chemical industry. Also the tendency of gold-based nanoparticles to attach with biological molecules may make them useful in medical diagnostics. Increase in conductivity of SWCNT on decorating with Au NPs can find practical application as conducting filler in polymer composites.
Abstract: Recent Experiments on Nano-Crystalline Materials Show an Increase of Strain-Rate Sensitivity in Contrast to the Conventional Coarse-Grained Materials. these Materials Also Show a Different Grain Size Dependency as Compared to Coarse-Grained Materials. to Explain these Issues, a Constitutive Equation Is Proposed which Considers Dominant Deformation Mechanisms Including Grain Interior Plasticity, Grain Boundary Diffusion and Grain Boundary Sliding. the Stresses Obtained from these Constitutive Equations Match Well with the Experimental Data for Nanocrystalline Copper at Different Strains and Strain Rates. the Model Also Well Predicts Variation of Strain Rate Sensitivity Parameter. this Variation Can Be Explained with Regard to the above Mentioned Effective Deformation Mechanisms. Deviation from the Hall-Petch Law and Inverse Hall-Petch Effect Are Also Well Illustrated by the Model.
Abstract: Nanoparticles based on tin compounds and alloys have been prepared by using the polyol and/or sonochemical methods. Thus, nanoparticulated Fe1-xCoxSn2 solid solutions were prepared by using the polyol method or, alternatively, a combination of the polyol and the sonochemical methods, and the Rietveld refinements of the XRD patterns confirm the formation of the solid solutions solutions. Pure or pyrolyzed polyacrylonitrile (PAN) can be used to create a matrix that encapsulate the metallic particles and improve the electrochemical cycling behavior. Thus, MSn2@PAN (where M=Fe or Co) have been prepared by using dimethylformamide like solvent of PAN and applying high-intensity ultrasonication to achieve small particle size, poor crystallinity and high dispersion. The very small particles of MSn2 exhibit higher tendency to be oxidized in air atmosphere than the larger particles. The very small particle size of the alloy and the organic phase (PAN) contribute to stabilize the interfaces and the contacts in the electrode, as is evidenced by the electrochemical cycling and the impedance spectra. A model is proposed for the electrochemical behavior of the MSn2@PAN electrode materials. MSn2@C materials can be prepared throughout the pyrolysis of the PAN molecules matrix.
Abstract: Biosensors’ research filed has clearly been changing towards the production of multifunctional and innovative design concepts to address the needs related with sensitivity and selectivity of the devices. More recently, waveguide biosensors, that do not require any label procedure to detect biomolecules adsorbed on its surface, have been pointed out as one of the most promising technologies for the production of biosensing devices with enhanced performance. Moreover the combination of optical and electrochemical measurements through the integration of transparent and conducting oxides in the multilayer structures can greatly enhance the biosensors’ sensitivity. Furthermore, the integration of polymeric substrates may bring powerful advantages in comparison with silicon based ones. The biosensors will have a lower production costs being possible to disposable them after use (“one use sensor chip”). This research work represents a preliminary study about the influence of substrate temperature on the overall properties of ITO thin films deposited by DC magnetron sputtering onto 0,5 mm thick PMMA sheets.
Abstract: The Polymorphic Er2Si2O7 Is Synthesized by Solid State Double Sintering Method. Structural and Morphological Characterizations Have Been Performed Using X-Ray Diffraction (XRD) and Scanning Electron Microscopy (SEM). The Electrical Characterization Has Been Performed by Two Probe Method as a Function of Temperature. the Dielectric Spectroscopic Measurements of Polymorphic Er2Si2O7 Are Performed in the Temperature Range 300-555 K and Frequency Range 3 kHz to 1 MHz. the dc Electrical Transport Data Are Analyzed According to Mott’s Variable-Range Hopping. The ac Conductivity σac(ω) Is Obtained through the Dielectric Spectroscopic Measurements. the ac Conductivity Obeys Power Law which Can Be Expressed as σac (ω) = B ωs, where S Is Slope and it Determines the ac Electrical Transport Phenomenon. the ac Electrical Transport Data and its Variation with Temperature in this Rare Earth Formulation Are Well Discussed. the Magnetic Behavior of Synthesized Material Is Analyzed and Confirmed that Material Have Non-Magnetic Behavior with Coercivity (Hc) 842 Oe. while the Values of Magnetic Saturation (MS) and Remanace (Mr) Were Found in Range 3.90emu/g and 1.07emu/g.
Abstract: Spinel Nanoferrites of Composition Mg0.50Cu0.5-XNixFe2O4 (0.00≤x≤0.50) Were Synthesized by Chemical Co-Precipitation Method. the Structural, Morphological and Magnetically Changes due to Varying Concentrations of Metal Ions of Cu and Ni in the Prepared Nanoferrites Were Studied. XRD Confirmed the Formation of Single Phase Spinel Ferrite with Crystalline Sizes in between 16-29 Nm, and the Lattice Parameter (a) Found to Decreases with Increase of Ni Concentration. Electrical Resistivity of the Prepared Nanoferrites with Varying Nickel and Copper Concentrations X Observed to Follow Arrhenius Relation and Also Exhibited the Semiconductor Behavior. the Magnetic Hysteresis Curves Clearly Indicate the Soft Nature of the Prepared Samples. Saturation Magnetization (Ms) Increases with Ni Content. This Effect Is Related to the Magnetic Moments of Ni+2 Ions. the Y-K Angles Increase with Increasing Ni Content, and Suggest a Non Collinearity Néel Type of Ordering of the Y-K Type. the Increase in the Y-K Angles Also Suggests the Increase in Triangular Spin Arrangements on B Sites, which Subsequently Lead to Increment in A-B Interactions.
Abstract: This Paper Describes the Synthesis of Cobalt Ferrite (CoFe2O4) Nanoparticles and their Application in Enhanced Oil Recovery. Cobalt Ferrite (CoFe2O4) Nanoparticles Were Used as Ferrite Magnetic Feeders with Antenna to Improve the Magnetic Field Strength and Cobalt Ferrite Nanofluid to Improve Oil Recovery. Cobalt Ferrite (CoFe2O4) Nanoparticles Were Synthesized by Sol-Gel Method. these Nanoparticles Were then Characterized by Using X-Ray Diffractometer (XRD) and Field Emission Scanning Electron Microscope (FESEM). Cobalt Ferrite Nanoparticles Annealed at 600oC, the Particle Size Is 51.17nm and 26nm as Determined by XRD and FESEM, Respectively while for the Sample Annealed at 800oC, the Particle Size Is 62nm as Determined by XRD and 60 Nm as Determined by FESEM. Magnetic Measurement Results Show that Initial Permeability of Cobalt Ferrite Powder Increased and Relative Loss Factor Decreased at High Frequency. in Order to Improve the Oil Recovery, Nanoparticles Were Used in Two Different Experiments. in the First Experiment, Nanoparticles Were Used as Magnetic Feeders with an Antenna to Improve the Magnetic Field Strength. in the Second Experiment, Nanoparticles Were Used as Nanofluids. Results Show that the Antenna with Magnetic Feeders Increases the Magnetic Field Strength by 0.94% as Compared to Antenna without Magnetic Feeders in the Water, and by 5.90% in the Air. Magnitude versus Offset (MVO) Study of Antenna with Magnetic Feeders Shows an Increase in Magnetic Field Strength of 275% as Compared to Antenna without Magnetic Feeders. it Is Found that Antenna with Magnetic Feeders Was Able to Recover 29.50% and 20.82% of Original Oil in Place (OOIP) in Core Rock Samples A-1 and A-2 Respectively. the Use of Cobalt Ferrite Nanoparticles as a Nanofluid with Electromagnetic Waves Yielded a Higher Recovery of Residual Oil in Place (ROIP) which Is 31.58% as Compared to 8.70% when it Was Used as Nanofluid Alone. it Is Investigated that due to Absorption of Electromagnetic Waves by Cobalt Ferrite Nanoparticles the Oil Viscosity Reduces which Increase the Oil Recovery. it Can Be Concluded that the Synthesised Cobalt Ferrite (CoFe2O4) Nanoparticles Can Be Potentially Used for Enhanced Oil Recovery in Future.
Abstract: Many Modern Technologies, such as High Density Data Storage, Require Monodispersed Magnetic Nanoparticles (MNPs), which Have a Consistent Magnetic Behavior, Specifically Immobilized onto a Patterned Surface. Current Methods for Synthesizing Uniform Mnps Require High Temperatures and Harsh Chemicals, which Is Not Environmentally Friendly. Also, the Particles Are Expensive to Make and Expensive to Pattern Using Conventional Lithography Methods. Magnetic Bacteria Are Able to Synthesize Consistent Mnps in Vivo Using Biomineralization Proteins inside Magnetosome Vesicles to Control Particle Size and Shape and Make Single Domain Mnps. Mms6 Is a Biomineralization Protein that Is Able to Template Cubo-Octahedral MNP Formation in Vitro. it Is Thought the N-Terminus Helps Integrate the Protein into the Magnetosome Membrane, and the C-Terminus Interacts with Magnetite during Nucleation and/or MNP Growth. by Selectively Attaching Mms6 to a Patterned Self Assembled Monolayer via the N-Terminus, Patterns of Uniform Magnetite Mnps Are Templated in Situ. this Also Requires Careful Selection of the Mineralization Solution Used to Mineralize the Patterned Mms6. here we Evaluate some Low Temperature (room Temperature to < 100°C) Methods of Magnetite Formation to Produce Monodispersed Magnetite Mnps onto Immobilized Mms6. Room Temperature Co-Precipitation (RTCP) Was Found to Be Unsuitable, as the Magnetite Does Not Form on the Immobilized Mms6, but Appears to Form Rapidly as Base Is Added. Partial Oxidation of Ferrous Hydroxide (POFH) Was Found to Be Able to Form Consistent Magnetite Mnps on the Immobilized Mms6, as the Reactants Gradually Mature to Form Magnetite over a few Hours (at 80°C) or a few Days (room Temperature). by Carefully Controlling the Type of Base Used, the Ratio of the Reactants and the Temperature and Duration of the POFH Mineralization Reaction, this System Was Optimized to Produce Consistent Mnps (340 ± 54 Nm, Coercivity 109 Oe) on the Immobilized Mms6, with Scarcely any Mineralization on the Anti-Biofouling Background. the Mnps Are Ferrimagnetic, and Appear to Be Exchange Coupled across Multiple Particles in MFM Measurements. the Specificity of this Method towards Precise Magnetite Mineralization under Relatively Mild Conditions May Be Adapted to Nanoscale Patterning of Multiple Biotemplated Materials, by Using other Biomineralization Proteins or Peptides. this Would Allow the Fabrication of Cheaper, More Environmentally Friendly Components for Devices of the Future.