Synthesis and characterization of magnetite particles covered with α-trietoxysilil-polydimethylsiloxane

New silicon magnetite ferrofluids were prepared by dispersing siloxane-coated magnetite particles in polydimethylsiloxane with low or high molecular weights. Ferrofluids are stable colloidal dispersions of ultra fine covered magnetite particles, which may be selected for a specific application. We demonstrated new methods of stabilizing the magnetic particles by reacting the hydroxyl groups on the surface of magnetite particles with terminal ethoxy groups of polydimethylsiloxane, followed by their dispersion in silicon fluids. The new silicon ferrofluids were tested from the morphology, magnetic properties/losses, and rheological properties point of view.     

Synthesis and characterization of nanostructured strontium hexaferrite thin films by the sol–gel method

Nanostructured single phase strontium hexaferrite, SrFe₁₂O₁₉, thin films have been synthesized on the (100) silicon substrate using a spin coating sol–gel process. The thin films with various Fe/Sr molar ratios of 8–12 were calcined at different temperatures from 500 to 900 °C. The composition, microstructure and magnetic properties of the SrFe₁₂O₁₉ thin films were characterized using Fourier transform infrared spectroscopy, differential thermal analysis, thermogravimetry, X-ray diffraction, electron microscopy and vibrating sample magnetometer. The results showed that the optimum molar ratio for Fe/Sr was 10 at which the lowest calcination temperature to obtain the single phase strontium hexaferrite thin film was 800 °C. The magnetic measurements revealed that the sample with Fe/Sr molar ratio of 10, exhibited higher saturation magnetization (267.5 emu/cm³) and coercivity (4290 Oe) in comparison with those synthesized under other Fe/Sr molar ratios.     

Synthesis and characterization of cobalt–manganese oxides

Cobalt doped/un-doped manganese oxides materials were synthesized at various doping rates by soft chemical reactions, oxidation-reduction method, which allows generating a metal-mixed oxide. The synthesized materials were characterized using several techniques including chemical analysis, X-rays diffraction (XRD), scanning electron microscopy (SEM), thermogravimetric analysis (TGA), and vibrating sample magnetometer (VSM). The chemical analysis confirmed the presence of cobalt in the samples. XRD patterns reveal mainly a spinel-like structure and SEM micrographs exhibited morphology with fine aggregate of particles. TGA profiles showed weight loss due to loss of water in a first step, followed by a loss of oxygen from the lattice associated with partial reduction of Mn⁴⁺ to Mn³⁺. VSM was used to measure the magnetization as a function of the applied magnetic field at temperatures T=50 and 300 K. Different magnetic behaviors were observed when cobalt percentage changed in the samples. These behaviors are considered to be related to the size of the particles and composition of the materials. Higher coercive field and lesser magnetization were observed for the sample with higher cobalt content.     

Synthesis,vibrational and UV–visible studies of sodium cadmium orthophosphate

In this paper, NaCdPO₄ orthophosphate was prepared by solid-state reaction technique at high temperature. Structural, vibrational and optical properties have been investigated. X-ray powder diffraction analysis revealed that the titled compound crystallizes in the orthorhombic system with Pmnb space group. Vibrational study by means of Raman and FTIR spectroscopies confirms the existence of the (PO₄)^3? functional group. Optical properties were recorded at room temperature using UV–visible spectroscopy in the spectral range (200–800) nm. The UV–Vis absorption bands are attributed to the charge transfer from the oxygen ligands to the central phosphate atom inside the PO₄ ^3? groups. The optical absorbance was measured also to determinate the optical band gap using Kubelka–Munk function. The dispersion parameters (E₀ and E_d) of this compound were estimated using the Wemple Di-Domenico model.     

Synthesis and characterization of Cd1−xZnxS nanopowder and its nanostructured thin films

The effect of the current on the pinching process of Xe plasma columns pumped by capillary discharge has been studied theoretically and experimentally. An extreme ultraviolet emission monitor (E-Mon, 13.5 nm in 2% bandwidth) was applied to record the temporal evolution of the 13.5 nm (2% bandwidth) emission. According to real current waveforms, the pinching processes were simulated with the snow-plow model. Both the experimental and the simulation results showed that intensity of the 13.5 nm emission reached the maximum when the plasma was pinched to the minimum radius. The E-Mon signals and the simulations indicated that under different amplitudes of the currents the plasma could be pinched more times and faster with higher discharge current.     

Synthesis and characterization of Co@Ag core–shell nanoparticles

Journal of Nanoparticle Research - A micellar method has been used to prepare silver-coated cobalt (Co@Ag) nanoparticles. The synthesized particles have been deeply characterized by several...     

Synthesis and luminescent characterization of sol-gel derived zirconia–alumina

Luminescence and sintering characteristics of α-Al₂O₃-tetragonal zirconia [t-ZrO₂(Y₂O₃)] mixtures have been investigated. The pseudoboehmite is one of the main precursors of the α-alumina. In this investigation pseudoboehmite has been synthesized through a desulphatation of the commercial Al₂(SO₄)₃ using an ammonia solution. Tetragonal zirconia powders were added in adequate proportion for each composition. The mixture constituted by Al₂O₃ (pseudoboehmite) and t-ZrO₂ has been annealed at different temperatures to obtain the crystalline phases. XRD and SEM techniques measurements have been used to structural characterization. Photoluminescence (PL) emission spectra of Al₂O₃–ZrO₂ composites were performed at room temperature. Thermoluminescent emission spectrum of the samples was obtained and analyzed.     

Synthesis and characterization of highly textured Pt–Bi thin films

Pt–Bi films were synthesized on glass and thermally oxidized silicon substrates by e-beam evaporation and annealing. The structures were characterized using X-ray diffraction (XRD) and transmission electron microscopy/selected area electron diffraction (TEM/SAED) techniques. Single-phase PtBi was obtained at an annealing temperature of 300°C, whereas a higher annealing temperature of 400°C was required to obtain the highly textured γ-PtBi₂ phase. TEM/SAED analysis showed that the films annealed at 400°C contain a dominant γ-PtBi₂ phase with a small amount of β-PtBi₂ and α-PtBi₂ phases. Both the PtBi and γ-PtBi₂ phases are highly textured in these two kinds of film: the c-axis of the hexagonal PtBi phase is mostly in the film plane, whereas the c-axis of the trigonal γ-PtBi₂ phase is perpendicular to the film plane. The electrical resistivity of the film with the γ-PtBi₂ phase was smaller by one order of magnitude than that of the film with the PtBi phase.     

Synthesis and characterization of CdS nanocrystals in Maleic anhydride–Octene-1–Vinylbutyl Ether terpolymer matrix

A Maleic anhydride–Octene-1–Vinylbutyl Ether terpolymer was synthesized via the radical terpolymerization method in order to prepare a new matrix for CdS nanocrystal synthesis. CdS nanocrystals were synthesized through the reaction of thiourea with cadmium chloride. The synthesized terpolymer/CdS nanocrystal composites were characterized by several methods. Energy Dispersive X-ray analysis, Raman spectroscopy and powder X-ray diffraction methods. The room temperature UV–visible absorption spectra show a shift of the absorption edge towards higher energies. The band gap of the CdS nanocomposite is bigger than that of bulk CdS. Raman spectrum exhibits characteristic peaks of CdS. Images of the nanocomposite obtained with Atomic Force Microscopy and Transmission Electron Microscopy are the evidences of CdS nanocrystal formation in the terpolymer. Thermal investigation shows that the nanocomposite is more thermostable than the terpolymer which could be useful for application in thermo aggressive medium.     

Graphene oxide–gellan gum–sodium alginate nanocomposites: synthesis,characterization, and mechanical behavior

This paper reports the preparation and characterization of graphene oxide–gellan gum–sodium alginate nanocomposites (GO–GG–Alg). The nanocomposites were prepared by a simple solution mixing-evaporation method. Fourier transform infrared spectroscopy, X-ray diffractions, Raman spectroscopy, scanning electron microscopy, transmission electron microscopy, thermal gravimetric analysis, and mechanical testing were conducted to study the structure and properties of the nanocomposites. The obtained findings reveal that gellan gum, sodium alginate, and graphene oxide are able to form a homogeneous mixture. Small amount of GO loading on GO–GG–Alg drastically improves its tensile strength and Young’s modulus. Detailed material characteristics of the nanocomposites are addressed.     

Synthesis and electrochemical characterization of nitrogen-doped and nitrogen–phosphorus-doped multi-walled carbon nanotubes

Nitrogen-doped and nitrogen–phosphorus-doped multi-walled carbon nanotubes (N-MWCNTs and N–P-MWCNTs, respectively) were fabricated by chemical vapor deposition and characterized using scanning electron microscopy and transmission electron microscopy in combination with energy dispersive X-ray spectroscopy and Raman spectroscopy. The electrochemical response of N-MWCNTs and N–P-MWCNTs towards ferrocyanide/ferricyanide was initially studied. The findings exhibit weakening of electrochemical response and sensitivity of nanotubes with phosphorus doping, and thus, within the composite films tested, those consist exclusively of N-MWCNTs exhibit the greatest electrocatalytic activity. N–P-MWCNT film was further applied for individual electrochemical analysis of ascorbic acid (AA), uric acid (UA), and dopamine (DA), and lower limits of detections of 11.6, 7.8, and 1.9 μM were estimated, respectively. The findings demonstrate that AA does not interfere with UA, but considerable interference of AA in analysis of DA was observed. Thus, the simultaneous analysis of AA, UA, and DA on N–P-MWCNTs appears to be restricted.     

Synthesis, characterization of the pentacene and fabrication of pentacene field-effect transistors

A comprehensive understanding of the organic semiconductor material pentacene is meaningful for organic fieldeffect transistors （OFETs）. Thin films of pentacene are the most mobile molecular films known to date. This paper reported that the pentacene sample was successfully synthesized. The purity of pentacene is up to 95%. The results of a joint experimental investigation based on a combination of infrared absorption spectra, mass spectra （MS）, element analysis, x-ray diffraction （XRD） and atom force microscopy （AFM）. The authors fabricated OFET with the synthesized pentacene. Its field effect mobility is about 1.23 cm^2/（V·s） and on-off ratio is above 10^6.     

Synthesis,characterization and mechanical properties of nylon–silver composite nanofibers prepared by electrospinning

Silver (Ag) nanoparticles (∼3 nm) were synthesized using silver nitrate as the starting precursor, ethylene glycol as solvent and poly (N-vinylpyrrolidone) (PVP) introduced as a capping agent. These nano-Ag particles were reinforced in nylon matrix by electrospinning of nylon-6/Ag solution in 2,2,2-trifluoroethanol and composite nanofibrous membranes were synthesized. The effects of solution concentration and relative humidity (RH) on the resultant fibrous membranes were studied. Scanning electron microscopy and Transmission electron microscopy was used to study the size and morphology of the fibers. It was observed that concentration and RH could be used to modulate the fiber diameter. Tensile test was used to evaluate the mechanical property of these electrospun composite membranes. The composite membranes showed higher strength (approx. 2–3 times increase in strength) compare to as synthesized nylon fibers.     

Synthesis, structural and conductivity characterization of alginic acid–Fe3O4 nanocomposite

Alginic acid–Fe₃O₄ nanocomposite is synthesized by the precipitation of Fe₃O₄ in the presence of alginic acid (AA). Structural, surface, morphological, thermal and electrical transport properties of the nanocomposite were performed by XRD, FT-IR, TEM-SEM, TGA and conductivity measurements respectively. FT-IR analysis revealed that Fe₃O₄ NPs are strongly capped with AA and TGA analysis showed that nanocomposite have 80% of Fe₃O₄ content. TEM analysis of Fe₃O₄ NPs show an average particle size of 9.5 nm, and upon nanocomposite formation with AA these particles are observed to form aggregates of ~150 nm. The frequency-dependency of the AC conductivity show electrode polarization effect. Analysis of electrical modulus and dielectric permittivity functions suggest that ionic and polymer segmental motions are strongly coupled. DC electrical conductivity is strongly temperature dependent, and is classified into three regions over a limited temperature range of up to 100 °C.     

Synthesis,characterization and mesomorphic properties of new liquid-crystalline compounds involving ester–chalcone linkages

We report the synthesis and evaluation of thermal behaviour of two novel series of chalcone-based liquid-crystalline compounds. The flexibility in these systems is provided by attaching straight alkoxy chain at one end. All the mesogens have been characterized by spectroscopic methods such as ¹H-NMR, FTIR, mass spectra, UV/Vis, and also elemental analysis. Their thermal behaviour was evaluated mainly by polarizing optical microscopic observation and DSC studies. It has been observed that the majority of the compounds display nematic and/or smectic mesophases. In both the series, compounds having C₃ to C₇ tail display only enantiotropic nematic phase, whereas C₈ and C₁₀ homologues exhibit enantiotropic smectic C and nematic phases. The higher homologues with C₁₂, C₁₄ and C₁₆ tails show the smectic C phase only.     

Kramers–Kronig analysis of the optical constants of magnetite,pyrite, and chalcopyrite in the microwave range

The optical constants of a series of ore minerals (pyrite, magnetite, and chalcopyrite) have been analyzed in the microwave range using the Kramers–Kronig method. The spectral dependences of the reflectance of these minerals in a wide frequency range (from deep UV to microwave) have been plotted based on numerous experimental data from different sources. These dependences made it possible to calculate the optical constants of the minerals under study in a frequency range of 12–145 GHz and compare them with the results of the theoretical and laboratory studies published in different sources.     

Synthesis and characterization of aqueous MPA-capped CdS–ZnS core–shell quantum dots

The novel CdS–ZnS core–shell nanoparticles are synthesized using simple one-step aqueous chemical approach. 3-mercaptopropionic acid (MPA) was used as the capping molecule. The structural and optical properties of the prepared samples are characterized by X-ray diffraction (XRD), UV–vis absorption spectroscopy, photoluminescence (PL) spectroscopy, energy-dispersive X-ray (EDX) and transition electron microscopy (TEM). The studies show that pH contributed noticeably to the growth and optical properties of nanoparticles. The TEM results indicate that the prepared particles have core–shell structure.     

Synthesis,characterization and third-order nonlinear optical properties of polydiacetylene nanostructures,silver nanoparticles and polydiacetylene–silver nanocomposites

We have synthesized, characterized and studied the third-order nonlinear optical properties of two different nanostructures of polydiacetylene (PDA), PDA nanocrystals and PDA nanovesicles, along with silver nanoparticles-decorated PDA nanovesicles. The second molecular hyperpolarizability γ(?ω; ω, ?ω, ω) of the samples has been investigated by antiresonant ring interferometric nonlinear spectroscopic (ARINS) technique using femtosecond mode-locked Ti:sapphire laser in the spectral range of 720–820 nm. The observed spectral dispersion of γ has been explained in the framework of three-essential states model and a correlation between the electronic structure and optical nonlinearity of the samples has been established. The energy of two-photon state, transition dipole moments and linewidth of the transitions have been estimated. We have observed that the nonlinear optical properties of PDA nanocrystals and nanovesicles are different because of the influence of chain coupling effects facilitated by the chain packing geometry of the monomers. On the other hand, our investigation reveals that the spectral dispersion characteristic of γ for silver nanoparticles-coated PDA nanovesicles is qualitatively similar to that observed for the uncoated PDA nanovesicles but bears no resemblance to that observed in silver nanoparticles. The presence of silver nanoparticles increases the γ values of the coated nanovesicles slightly as compared to that of the uncoated nanovesicles, suggesting a definite but weak coupling between the free electrons of the metal nanoparticles and π electrons of the polymer in the composite system. Our comparative studies show that the arrangement of polymer chains in polydiacetylene nanocrystals is more favourable for higher nonlinearity.     

Synthesis and characterization of α-cobalt hydroxide nanobelts

α-Cobalt hydroxide was synthesized by a facile hydrothermal process from Co(Ac)₂ and NH₃·H₂O in the presence of 1,3-propanediol. The large-scale-prepared cobalt hydroxide has a uniform nanobelt morphology with a considerably high aspect-ratio more than 20 which may be advantageous for exploration of their physicochemical properties. This synthetic method is convenient, economical, and controllable. The samples were characterized by powder X-ray diffraction, energy dispersive spectrum, scanning electron microscopy, transmission electron microscopy, Fourier transform infrared spectroscopy, CHN element analysis, thermogravimetric and differential-thermogravimetric analysis, which revealed the compound is lamellar structural cobalt organic–inorganic hybrid with the chemical formula of Co(OH)_1.49(NH₃)_0.01(CO₃ ²⁻)_0.22(Ac⁻)_0.07(H₂O)_0.11 and single-crystalline.