Synthesis and characterization of poly(3-thiophene acetic acid)/Fe3O4 nanocomposite

Poly(3-thiophene acetic acid)/Fe₃O₄ nanocomposite is synthesized by the precipitation of Fe₃O₄ in the presence of poly(3-thiophene acetic acid) (P3TAA). Structural, surface, morphological, thermal properties and conductivity characterization/evaluation of the nanocomposite were performed by XRD, FT-IR, TEM, TGA, and conductivity measurements, respectively. The capping of P3TAA around Fe₃O₄ nanoparticles was confirmed by FT-IR spectroscopy, the interaction being via bridging oxygens of the carboxylate and the nanoparticle surface through bidentate binding. The crystallite and particle size were obtained as 9 ± 2 nm and 11 ± 1 nm from XRD line profile fitting and TEM image analysis, respectively, which reveal nearly single crystalline nature of Fe₃O₄ nanoparticles. Magnetization measurements reveal that P3TAA coated magnetite particles do not saturate at higher fields. There is no coercivity and remanence revealing superparamagnetic character. Magnetic particle size calculated from the theoretical fitting as 9.1 nm which coincides the values determined from TEM micrographs and XRD line profile fitting. The comparison to the TEM particle size reveals slightly modified magnetically dead nanoparticle surface.     

Synthesis and characterization of poly(vinyl phosphonic acid) (PVPA)-Fe3O4 nanocomposite

Poly(vinyl phosphonic acid) (PVPA)-Fe₃O₄ nanocomposite is synthesized by the precipitation of Fe₃O₄ in the presence of PVPA. Structural, surface, morphological, thermal properties and conductivity characterization/evaluation of the nanocomposite were performed by XRD, FT-IR, TEM, TGA and conductivity measurements respectively. The capping of PVPA around the Fe₃O₄ nanoparticles was confirmed by FT-IR spectroscopy, the interaction being via bridging oxygens of the phosphate and the nanoparticle surface. The crystallite and particle size were obtained as 6 ± 2 and 8.7 ± 0.1 nm from XRD line profile fitting and TEM image analysis respectively, which reveal nearly single crystalline nature of the Fe₃O₄ nanoparticles. Magnetic characterization of the bulk magnetite and (PVPA)-Fe₃O₄ nanocomposite reveals that both are in the superparamagnetic state at room temperature. The average magnetic domain size of the nanoparticles has been calculated using the Langevin function, which was fitted to the measured M-H hysteresis curves as 7.6 nm for the nanocomposite. In the nanocomposite, the reduction is due to the adsorption of PVPA onto the magnetite surface, which cancels some of the free spins at the surface causing a magnetically dead layer. Analysis of the conductivity and permittivity measurements revealed the coupling of ionic and polymer segmental motions and strong temperature dependency in the nanocomposite.     

CTAB-Mn3O4 nanocomposites: Synthesis,NMR and low temperature EPR studies

We are reporting on the synthesis of Mn₃O₄ nanoparticles and CTAB-Mn₃O₄ nanocomposites via a sonochemical route using MnCl₂, ethanol, NaOH and CTAB. The crystalline phase was identified as Mn₃O₄. The crystallite size of the CTAB-Mn₃O₄ nanocomposite was identified as 13 ± 5 nm from X-ray line profile fitting and the particle size from TEM was 107.5 ± 1.4 nm. The interaction between CTAB and the Mn₃O₄ nanoparticles was investigated by FTIR and ¹H NMR spectroscopies. Two different magnetic phase transitions were observed for both samples below the Curie temperature (43 °C) by using a low temperature Electron Paramagnetic Resonance (EPR) technique. Also we determined the effect of the capping with CTAB on the reduction in absorbed power.     

Photoluminescent BaMoO4 nanopowders prepared by complex polymerization method (CPM)

The BaMoO₄ nanopowders were prepared by the Complex Polymerization Method (CPM). The structure properties of the BaMoO₄ powders were characterized by FTIR transmittance spectra, X-ray diffraction (XRD), Raman spectra, photoluminescence spectra (PL) and high-resolution scanning electron microscopy (HR-SEM). The XRD, FTIR and Raman data showed that BaMoO₄ at 300 °C was disordered. At 400 °C and higher temperature, BaMoO₄ crystalline scheelite-type phases could be identified, without the presence of additional phases, according to the XRD, FTIR and Raman data. The calculated average crystallite sizes, calculated by XRD, around 40 nm, showed the tendency to increase with the temperature. The crystallite sizes, obtained by HR-SEM, were around of 40-50 nm. The sample that presented the highest intensity of the red emission band was the one heat treated at 400 °C for 2 h, and the sample that displayed the highest intensity of the green emission band was the one heat treated at 700 °C for 2 h. The CPM was shown to be a low cost route for the production of BaMoO₄ nanopowders, with the advantages of lower temperature, smaller time and reduced cost. The optical properties observed for BaMoO₄ nanopowders suggested that this material is a highly promising candidate for photoluminescent applications.     

Simple and low-temperature synthesis of NiO nanoparticles through solid-state thermal decomposition of the hexa(ammine)Ni(II) nitrate, [Ni(NH3)6](NO3)2, complex

NiO nanoparticles with an average size of about 12 nm were easily prepared via the thermal decomposition of hexa(ammine)Ni(II) nitrate complex, [Ni(NH₃)₆](NO₃)₂, at low temperature of 250 °C. The product was characterized by thermal analysis (TGA/DTA), X-ray diffraction (XRD), Fourier-transformed infrared spectroscopy (FT-IR), UV-Vis spectroscopy, BET specific surface area measurement, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), and magnetic measurement. The magnetic measurement revealed a small hysteresis loop at room temperature, confirming a superparamagnetic (weak ferromagnetic) nature of the synthesized NiO nanoparticles. Indeed, the NiO nanoparticles prepared by this method could be an appropriate semiconductor material due to the optical band gap of 3.35 eV which shows a red shift in comparison with the previous reports. This method is simple, fast, safe, low-cost and also suitable for industrial production of high purity NiO nanoparticles for applied purposes.     

Alpha-particle-induced luminescence of rare-earth-doped Y2O3 nanophosphors

The feasibility of utilizing Y₂O₃:Tb³⁺ and Y₂O₃:Eu³⁺ as radioluminescent nanophosphors under alpha-particle excitation is investigated. Materials synthesized by the urea homogeneous precipitation method were characterized using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray diffraction (XRD). The XRD analysis of as-produced precipitates and nanophosphors fired at temperatures ranging from 950 to 1100 °C indicated the presence of highly crystalline cubic Y₂O₃ with crystallite sizes of ∼40 nm. SEM and TEM analysis revealed that particles with average diameters of ∼200 nm and comprised of ∼40 nm grains were obtained. High-resolution radioluminescence and photoluminescence spectra were used to investigate the unwanted radioluminescence saturation effects associated with the high ionization rate of alpha-particles. Additionally, the radioluminescence intensity as a function of rare-earth ion dopant concentration is investigated for these materials under alpha-particle excitation. The prospect for utilizing these materials as intermediate absorbers in indirect-conversion radioisotope batteries is discussed.     

Nanocomposites of poly(l-lactide) and surface-grafted TiO2 nanoparticles: Synthesis and characterization

A new method of surface modification of TiO₂ nanoparticles by surface-grafting l-lactic acid oligomer was developed. The surface-grafting reaction was evaluated by Fourier transformation infrared (FTIR) and thermal gravimetric analysis (TGA). The results showed that l-lactic acid oligomer could be easily grafted onto the TiO₂ nanoparticles surface in the presence of stannous octanoate and the highest amount of grafted polymer was about 8.5% in weight. Transmission electron microscopy (TEM) and scanning electron microscopy (SEM) results showed that grafted TiO₂ (g-TiO₂) in chloroform or PLLA matrix approximated to uniform, while unmodified TiO₂ nanoparticles tended to aggregate. The tensile strength of this material was greatly improved by the addition of g-TiO₂ nanoparticles in poly(l-lactide) (PLLA) matrix. The tensile strength of the g-TiO₂/PLLA nanocomposite containing 5 wt.% of g-TiO₂ was 72 MPa, which was 23.1% higher than that of pure PLLA. Even though the incorporation of the TiO₂ nanoparticles into PLLA led to the deterioration of its elongation at break, the g-TiO₂/PLLA nanocomposite also exhibited better ductility than that of TiO₂/PLLA nanocomposite.     

Preparation and characterization of NiO nanoparticles from thermal decomposition of the [Ni(en)3](NO3)2 complex: A facile and low-temperature route

NiO nanoparticles with an average size of 15 nm were easily prepared via the thermal decomposition of the tris(ethylenediamine)Ni(II) nitrate complex [Ni(en)₃](NO₃)₂ as a new precursor at low temperature, and the nanoparticles were characterized by thermal analysis (TGA/DTA), X-ray diffraction (XRD), Fourier-transformed infrared spectroscopy (FT-IR), UV-Vis spectroscopy, BET specific surface area measurement, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM) and magnetic measurements. The magnetic measurements confirm that the product shows a ferromagnetic behavior at room temperature, which may be ascribed to a size confinement effect. The NiO nanoparticles prepared by this method could be an appropriate photocatalytic material due to a strong absorption band at 325 nm. This method is simple, fast, safe, low-cost and also suitable for industrial production of high purity NiO nanoparticles for applied purposes.     

CdTe@Cu(OH)2 nanocomposite: Aqueous synthesis and characterization

CdTe@Cu(OH)₂ nanocomposites were synthesized in aqueous solution by a seed-mediated growth approach. The effect of refluxing time and the concentration of Cu²⁺ on the preparation of these samples were measured using UV-visible absorption and photoluminescence analysis. The emission peak of the synthesized nanocomposites (CdTe@Cu(OH)₂) was shifted from 605 (CdTe seed) to 621 nm. The size of CdTe nanoparticles were averaged about 3.22 nm, and the CdTe@Cu(OH)₂ nanocomposites were averaged as 5.19 nm. The synthesized CdTe@Cu(OH)₂ nanocomposite were characterized with XRD, EDAX, TEM, FT-IR, EPR, and thermal analysis (TG/DTG curves). The results indicate that as-prepared nanoparticles with core/shell structure exhibit interesting optical properties.     

Magnetic and dielectric characterization of alginic acid-Fe3O4 nanocomposite

We have reported the synthesis of water dispersible alginic acid (AA)-Fe₃O₄ nanocomposites. The crystallite size was obtained as 9 ± 2 nm from X-ray line profile fitting. As compared to the particle size of 9.2 nm obtained from TEM analysis, these particles show dominantly single crystalline nature. Dielectric analysis show that the real and imaginary parts of the permittivity of both pure AA and AA-Fe₃O₄ nanocomposite obey the ionic polarization mechanism comprised of ionic conductivity and interfacial or space charge polarization. Magnetization measurements show that the saturation magnetization of AA-capped magnetite is significantly lower than the theoretical bulk value, partly due to the structural distortions on the surface of the particles. Moreover, magnetite does not saturate and exhibits no coercivity above a certain temperature, revealing superparamagnetic behavior of the nanocomposite above a blocking temperature, T_B, of ∼175 K. The magnetic core size, determined by theoretical fitting to the magnetization data at room temperature, is 9.55 nm.     

Ultrasonic-assisted synthesis of PMMA/Ni0.5Zn0.5Fe2O4 nanocomposite in mixed surfactant system

PMMA/Ni_0.5Zn_0.5Fe₂O₄ nanocomposite with superparamagnetic behavior was synthesized by in situ emulsion polymerization of methylmethacrylate (MMA) monomer in the presence of Ni_0.5Zn_0.5Fe₂O₄ colloidal suspension assisted by ultrasonic irradiation. The obtained samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectra (FT-IR), transmission electron microscopy (TEM) and vibrating sample magnetometer (VSM). XRD and FT-IR spectra confirmed the formation of PMMA/Ni_0.5Zn_0.5Fe₂O₄ nanocomposite. TEM images showed that Ni_0.5Zn_0.5Fe₂O₄ nanoparticles with the particle sizes of about 12 nm were well dispersed in the polymer matrix. The nanocomposite at room temperature exhibited superparamagnetic behavior under applied magnetic field. The formation mechanism of PMMA/Ni_0.5Zn_0.5Fe₂O₄ nanocomposite was proposed as well.     

Preparation and characterization of pure single-phase BiFeO3 nanoparticles through thermal decomposition of the heteronuclear Bi[Fe(CN)6]·5H2O complex

The heteronuclear Bi[Fe(CN)₆]·5H₂O complex was synthesized and single-phase perovskite-type BiFeO₃ nanoparticles with an average size of 30 nm were obtained by its decomposition at 600 °C. The complex and its decomposition products were analyzed using elemental analysis, thermal analysis (TGA/DTA/DSC), X-ray diffraction (XRD), Fourier-transformed infrared spectroscopy (FT-IR), UV–Vis spectroscopy, BET specific surface area measurement, scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and magnetic measurements. The magnetic measurement confirms that the product shows a ferromagnetic order at room temperature, which may be ascribed to the size confinement effect. The DTA and DSC results confirm the multiferroic nature of the BiFeO₃ nanoparticles with Neel and Curie points at 372 and 825 °C, respectively. The BiFeO₃ prepared by this method could be an appropriate visible-light photocatalytic material due to its strong absorption band in the visible region. This method is simple, low-cost, safe and also suitable for industrial production of high purity perovskite-type BiFeO₃ nanoparticles for electromagnetic applications.     

Size dependent electron-phonon coupling in Li0.5Co0.1Fe2.4O4 nanoparticles investigated by Raman spectroscopy

The Raman spectra of Li_0.5Co_0.1Fe_2.4O₄ nanoparticles have been recorded in the spectral range, 400-800 cm⁻¹ at four different particle sizes. X-ray and TEM measurements were done to determine crystal structure and size of the nanoparticles. X-ray diffraction (XRD) shows that the Li_0.5Co_0.1Fe_2.4O₄ nanoparticles have an order phase spinel structure without any impurity. The size of the nanocrystal was calculated through XRD patterns and TEM micrographs and it turns out to be 34-42 nm. The Raman spectra of each size nanoparticles show five Raman bands. The most intense Raman band shows a noticeable asymmetrical feature towards lower wavenumber side. A line shape analysis was performed to get the exact spectral parameters of the Raman bands. The intensity of asymmetrical feature keeps on increasing with decreasing the particle size from 42 nm to 34 nm and finally evolved as a new Raman band. The appearance of new band and its intensity response relative to the intensity of the main Raman band as a function of particle size has been explained in terms of electron-phonon coupling. It was observed that the strength of electron-phonon coupling goes on increasing with reducing the particle size. The red shifting of the Raman bands upon reducing the crystalline size is explained in terms of the lattice expansion, which is well supported by the XRD data.     

Preparation and characterization of novel alkylviologens-intercalated vanadyl-vanadate (RV)V3O8

Various n-alkylviologens-intercalated vanadyl-vanadate (RV)V₃O₈ were synthesized with the combination of redox and ions-exchange methods. The derivative compounds were characterized by X-ray diffraction (XRD), FT infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and UV-vis diffuse reflectance spectroscopy (UV-vis DRS). The XRD results indicate that the interlayer spacing increases with the alkyl chain length of the alkylviologen cations. The FTIR data shows that alkylviologens were inserted into the interlayers of V₃O₈²⁻. XPS data reveals that the vanadium ions in the intercalation compounds are mostly in a pentavalent V⁵⁺ state with some partially reduced to the V⁴⁺ state. The intercalation compounds have the strong absorption character in the ultraviolet and visible light region. Magnetic susceptibility indicates that the (ethylviologen) V₃O₈ (EV3) is antiferromagnetic and possesses an ordered magnetic structure below 15 K. Above 15 K, EV3 exhibits paramagnetic behavior and a disordered magnetic structure.     

Hydrophilic and hydrophobic nano-sized Mn3O4 particles

Mn₃O₄ Hausmanite nanoparticles were prepared in aqueous solution by using metallic salt and hydrazine as precursor and reducing agent, respectively. The crystallite sizes ranged from 10 to 20 nm and the particle diameter distribution was very narrow and estimated between 20 and 30 nm. Influence of some parameters such as temperature, time of reaction, surfactant nature was studied for a synthesis in an aqueous medium. The as-made manganese oxides particles could be dispersed in an organic solvent containing stabilizing agents, according to perform the synthesis in an H₂O/n-hexan two-phase medium. These nanoparticles were characterized by X-ray diffraction, infrared spectroscopy, scanning and transmission electron microscopies and nitrogen absorption measurements.     

Sol-gel synthesized semiconducting LaCo0.8Fe0.2O3-based powder for thick film NH3 gas sensor

Perovskite type LaCo_xFe_1−xO₃ nanoparticles was synthesized by a sol-gel citrate method. The structural, electrical and sensing characteristics of the LaCo_xFe_1−xO₃ system were investigated. The structural characteristics were performed by using X-ray diffraction (XRD) and transmission electron microscopy (TEM) to examine the phase and morphology of the resultant powder. The XRD pattern shows nanocrystalline solid solution of LaCo_xFe_1−xO₃ with perovskite phase. Electrical properties of synthesized nanoparticles are studied by DC conductivity measurement. The sensor shows high response towards ammonia gas in spite of other reducing gases when x = 0.8. The effect of 0.3 wt.% Pd-doped LaCo_0.8Fe_0.2O₃ on the response and a recovery time was also addressed.     

Preparation and characterization of shuttle-like α-Fe2O3 nanoparticles by supermolecular template

Shuttle-like α-Fe₂O₃ nanoparticles have been successfully synthesized via a new soft-template route using polyethylene glycol (PEG) as polymer, cetyltrimethylammonium bromide (CTAB) as surfactant and FeCl₃·6H₂O as iron source materials. Meanwhile, spherical α-Fe₂O₃ nanoparticles are also fabricated under the similar conditions without surfactant and polymer. The resultant products are characterized by means of thermalgravimetric analysis (TGA), powder X-ray diffraction (XRD), infrared (IR) spectroscopy, transmission electron micrograph (TEM), X-ray photoelectron spectra (XPS) and magnetization measurements. The homogeneous α-Fe₂O₃ nanoparticles with shuttle-like shape have an average length of 120 nm and a mean diameter of about 50 nm in the middle part (an average aspect ratio of about 2.5) whereas spherical α-Fe₂O₃ nanoparticles have a mean particle diameter of about 35 nm. Magnetic hysteresis measurements reveal that shuttle-like α-Fe₂O₃ nanoparticles display normal ferromagnetic behaviors while spherical α-Fe₂O₃ nanoparticles exhibit weak ferromagnetic behaviors at room temperature. The two types of α-Fe₂O₃ exhibit hysteretic features with the remanence and coercivity of 0.156 emu/g and 664 Oe, 0.048 emu/g and 110 Oe, respectively. The higher remanent magnetization and coercivity of shuttle-like α-Fe₂O₃ nanoparticles may be associated with the aspect ratio of α-Fe₂O₃ since shape anisotropy would exert a tremendous influence on their magnetic properties.     

Ionic transport in P(VDF-HFP)-PMMA-LiCF3SO3-(PC + DEC)-SiO2 composite gel polymer electrolyte

Composite gel polymer electrolytes composed of poly(vinylidene fluoride-co-hexafluoropropylene) P(VDF-HFP) and polymethylmethacrylate PMMA polymers, PC + DEC as plasticizer and LiCF₃SO₃ as salt and fumed silica as filler have been synthesized by solvent casting technique with varying plasticizer-filler ratio systematically. Films of thickness in the range of 40-70 μm were characterized by a.c. impedance measurements in the temperature range 303 K to 373 K. Addition of filler to the polymer electrolyte was found to result in an enhancement of the ionic conductivity. A maximum electrical conductivity of ∼1 × 10⁻³ S/cm at 303 K and ∼2.1 × 10⁻³ S/cm at 373 K has been achieved with the dispersion of the SiO₂. FTIR spectral studies confirmed the polymer-salt interaction. XRD patterns exhibit the increased amorphicity in the blended composite gel polymer electrolytes. Scanning electron micrograph shows the dispersion of SiO₂ particle in the polymer electrolyte.     

Thermo-Raman spectroscopy in situ monitoring study of solid-state synthesis of NiO-Al2O3 nanoparticles and its characterization

Hyphenation of thermogravimetric analyzer (TGA) and thermo-Raman spectrophotometer for in situ monitoring of solid-state reaction in oxygen atmosphere forming NiO-Al₂O₃ catalyst nanoparticles is investigated. In situ thermo-Raman spectra in the range from 200 to 1400 cm⁻¹ were recorded at every degree interval from 25 to 800 °C. Thermo-Raman spectroscopic studies reveal that, although the onset of formation is around 600 °C, the bulk NiAl₂O₄ forms at temperatures above 800 °C. The X-ray diffraction (XRD) spectra and the scanning electron microscopy (SEM) images of the reaction mixtures were recorded at regular temperature intervals of 100 °C, in the temperature range from 400 to 1000 °C, which could provide information on structural and morphological evolution of NiO-Al₂O₃. Slow controlled heating of the sample enabled better control over morphology and particle size distribution (∼20-30 nm diameter). The observed results were supported by complementary characterizations using TGA, XRD, SEM, transmission electron microscopy, and energy dispersive X-ray analysis.     

In situ formation of Ni nanoparticles supported on NiFe2O4 by calcination

Ni/NiFe₂O₄ composites have been successfully prepared by calcination at 400°C in air of the mixture K₃[Fe(ox)₃]·2.5H₂O and NiCl₂·6H₂O with a molar ratio of 0.7-2. The products are featured by the Ni crystallite size of 15-34 nm, BET surface area of 23-41 m²/g and variable Ni loadings. TGA and FTIR results indicate in situ generation of CO molecules from decomposition of K₃[Fe(ox)₃]·2.5H₂O. These in situ generated CO molecules account for the formation of Ni nanoparticles by reduction of Ni(II) ions.