Synthesis of nanocomposite materials in the SnO<Subscript>2</Subscript>-NiO system

The SnO₂-NiO nanocomposites with the specific surface area on the order of 100 m²/g and the particle size of both phases of less than 10 nm have been synthesized by the sol-gel method with the subsequent annealing in the temperature interval 200–1000°C. It has been shown that, with an increase in the annealing temperature to 900°C, the specific surface area of the nanocomposites increases. This effect has been explained by the increase in the porosity due to the destruction of the aggregates of primary amorphous particles. The electrical conductivity has been measured and the parameters of the surface defects have been determined.     

L10 FePt Nanoparticles Processing with Applied Magnetic Field

Due to the strong magnetic anisotropy energy, the L1₀ FePt nanocrystals are considered as one of promising candidates for magnetic recording media with ultrahigh densities. The surfaces of Si and SiO₂ wafers have been covered by FePt nanoparticles (NPs) and heated at 600 °C for 1 h to form the L1₀ phase. Bonding of NPs with the SiO₂ surface in the presence of magnetic field during annealing process controls the L1₀ FePt NPs size and their uniform surface distribution. In the presence of perpendicular magnetic field to the surface, the size of NPs obtains up to 30 nm with coercivity of 5.8 kOe and in parallel magnetic field, the NPs size reaches to 45 nm with coercivity of 2.9 kOe. These results and the easy axis ordering of samples have been determined by energy-dispersive X-ray spectroscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, field emission scanning electron microscopy, X-ray diffraction, and vibrating sample magnetometer analyses.     

Microstructure,Tuning of Band Gap,Enhanced Green Band Emission and Antibacterial Studies of Cu,Cr Dual Doped ZnO Nanoparticles by Annealing Temperature

Zn_0.94Cu_0.04Cr_0.02O nanoparticles have been synthesized by sol–gel method and annealed at 400, 600 and 800 °C. Hexagonal wurtzite structure was not affected by the temperature but single phase was altered by high temperature (800 °C). The reduced crystallite size (19.9 nm) at 600 °C was due to the proper substitution of doping element. The enhanced crystallite size at 800 °C was due to the formation secondary phase like CuO and defect states. The broad absorption peak at 800 °C around visible region represented the oxygen related defects and Cu/Cr interstitials. The red shift of band gap and enhanced visible light absorption are useful for solar applications. Better antibacterial efficiency of nanoparticles annealed at 600 °C was due to increase of surface area by reduced particle size and modification in morphology.     

多元醇还原法制备FePt纳米颗粒

以乙酰丙酮铁和氯铂酸作为Fe源和Pt源,1,2-十二烷二醇为还原剂,通过多元醇还原法制备出单分散的FePt纳米颗粒,研究了表面活性剂油酸和油胺对FePt纳米颗粒形貌和分散性的影响。结果显示,未使用表面活性剂制得的FePt纳米颗粒粒度范围是1.0～6.0 nm,平均粒径为3.4 nm;使用油酸和油胺制得的FePt纳米颗粒粒度范围是2.5～5.5 nm,平均粒径4.1 nm。通过XRD、TEM和VSM分析表明,油酸和油胺修饰的FePt纳米颗粒为面心立方结构,形状近似球形,分散性良好,粒径分布较未使用表面活性剂时变窄;VSM显示其矫顽力趋近于0,呈现超顺磁性。     

Synthesis of polyvinyl alcohol hydrogel grafted by modified Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanoparticles: characterization and doxorubicin delivery studies

During the last two decades, serious efforts have been directed towards the synthesis and coating magnetic nanoparticles for biomedical applications. Among many different types of polymeric coating materials that have been utilized in previous studies, we have selected polyvinyl alcohol (PVA). In this study, we report a novel type of magnetite nanocomposite-based PVA hydrogel. For this purpose, first, Fe₃O₄ nanoparticles were modified through hexamethylene diisocyanate (HMDI) and then PVA was modified by bromoacetyl bromide to produce bromoacetylated PVA. The modified PVA was cross-linked through various diamines such as ethylene-diamine, propylene-diamine and hexamethylenediamine. The prepared weak tridimensional PVA hydrogels were further reacted through unreacted hydroxyl groups with Fe₃O₄, modified by HMDI to form magnetite hard tridimensional hydrogels. The swelling behavior of the prepared magnetite nanocomposites were investigated and showed a fast initial swelling followed by a mild increase until attaining equilibrium. The structural, morphological, thermal and magnetic properties of the synthesized magnetite nanocomposites were confirmed by FTIR, thermal gravimetric analysis, vibrating sample magnetometer and scanning electron microscopy. The doxorubicin anti-tumor drug was loaded on a selected synthesized magnetic hydrogel and in vitro drug release studies were done in phosphate buffer solution in 37 °C.     

Low-Temperature Preparation of Superparamagnetic CoFe<Subscript>2</Subscript>O<Subscript>4</Subscript> Microspheres with High Saturation Magnetization

Based on a low-temperature route, monodispersed CoFe₂O₄ microspheres (MSs) were fabricated through aggregation of primary nanoparticles. The microstructural and magnetic characteristics of the as-prepared MSs were characterized by X-ray diffraction/photoelectron spectroscopy, scanning/transmitting electron microscopy, and vibrating sample magnetometer. The results indicate that the diameters of CoFe₂O₄ MSs with narrow size distribution can be tuned from over 200 to ~330 nm. Magnetic measurements reveal these MSs exhibit superparamagnetic behavior at room temperature with high saturation magnetization. Furthermore, the mechanism of formation of the monodispersed CoFe₂O₄ MSs was discussed on the basis of time-dependent experiments, in which hydrophilic PVP plays a crucial role.     

Thermochemical modification of Mg<Subscript>3</Subscript>Si<Subscript>2</Subscript>O<Subscript>5</Subscript>(OH)<Subscript>4</Subscript> hydrosilicate nanotubes by silver nitrate solutions

The interaction of an aqueous solution of silver nitrate with Mg₃Si₂O₅(OH)₄ hydrosilicate nanotubes under atmospheric conditions at 50 and 80°C and under dynamic conditions with subsequent annealing at 300°C has been investigated. The intercalation of AgNO₃ solutions into the internal channel and interlayer spaces of the nanotube structure and the crystallization of the silver particles of the spherical shapes on the nanotube surface have been established.     

Synthesis and characterization of monodisperse hollow SnO<Subscript>2</Subscript> microspheres and their enhanced sensing properties to ethanol

The monodisperse hollow SnO₂ (H-SnO₂) microspheres were successfully synthesized by the ion exchange method using sulfonated PS microspheres as a template. The structure and morphology were characterized by X-ray diffraction, transmission electron microscopy and high-resolution transmission electron microscopy, which confirms the hollow structure of the products. The H-SnO₂ microspheres are composed of numerous SnO₂ nanoparticles with a shell thickness of about 13 nm. The monodisperse H-SnO₂ microspheres have a high specific surface area of 55.54 m²/g, which improves the gas sensing properties toward ethanol. Gas-sensing measurement results indicate that H-SnO₂ microspheres exhibit an excellent sensitivity (103.1) toward 200 ppm ethanol at 260 °C, which is much higher than that (65.8) of SnO₂ nanoparticles.     

Facile fabrication approach for a novel multifunctional superamphiphobic coating based on chemically grafted montmorillonite/Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-polydimethylsiloxane binary nanocomposite

In this paper, a novel multifunctional superamphiphobic coating for anticorrosion was successfully prepared on aluminum substrate via a simple spraying technique. Al₂O₃ nanoparticles were chemically grafted onto montmorillonite (MMT) nanosheets via coupling effect of NH₂-C₃H₆-Si(OC₂H₅)₃ (KH-550) and then modified by low surface energy material polydimethylsiloxane (PDMS). The ethylene tetrafluoroethylene (ETFE) composite coating with 25 wt% MMT/Al₂O₃-PDMS binary nanocomposite exhibited well-designed nano/μ structures and possessed superamphiphobicity with high contact angles towards water (164°), glycerol (158°) and ethylene glycol (155°). This coating demonstrated outstanding self-cleaning ability and strong adhesive ability (Grade 1 according to the GB/T 9286). The superhydrophobicity could be maintained after 8000 times abrasion or annealing treatment for 2 h under 350 °C. The coating still retained high water-repellence after immersion in 1 mol/L HCl (146°), 1 mol/L NaOH (144°) and 3.5 wt% NaCl (151°) solutions for 30 d. It should be noted that this superamphiphobic coating revealed excellent long-term corrosion protection with extremely low corrosion rate (4.3 × 10^?3 μm/year) and high protection performance (99.999%) after 30 d immersion in 3.5 wt% NaCl solutions based on electrochemical corrosion measurements. It is believed that such integrated functional coating could pave new way for self-cleaning and anticorrosion applications under corrosive/abrasive environment.     

Formation of CoFe2O4/PVA-SiO2 nanocomposites: Effect of diol chain length on the structure and magnetic properties

The paper presents the influence of diol (1,2-ethanediol, 1,2-propanediol, 1,3-propanediol and 1,4-butanediol) on the formation of magnetic crystalline cobalt ferrite embedded in polyvinyl alcohol-silica hybrid matrix at 200?°C. Formation of crystalline oxides (CoFe₂O₄, Co₃O₄ and Co₂SiO₄) was studied by X-ray diffraction and Fourier transformed infrared spectroscopy. The effect of annealing temperature and diol chain length on the cobalt ferrite nanocrystallites size was investigated. Using transmission electron microscopy, the size and shape of particles obtained at 200?°C were recorded and compared to those obtained by annealing at 500, 800 and 1100?°C. The saturation magnetization (M_s) and coercive field were calculated from the magnetic hysteresis loops of nanocomposites. The M_s was influenced by the particle size and crystallinity only for nanocomposites annealed at 800 and 1100?°C, when the magnetic domains started to form and to be larger than the critical particle size. The diols used in the synthesis influence both the oxidic phase formation and its properties.     

Preparation and characterizations of superparamagnetic iron oxide‐embedded poly(2‐hydroxyethyl methacrylate) nanocarriers

The present study aims at formulating a novel multifunctional biocompatible superparamagnetic nanoparticles carrier system with homogeneously dispersed magnetic material in solid polymer matrix of poly(2‐hydroxyethyl methacrylate) (PHEMA). The nanocomposites were designed by modified suspension polymerization of 2‐hydroxyethyl methacrylate followed by in situ coprecipitation of iron oxide inside the nanoparticle matrix yielding magnetic PHEMA (mPHEMA) nanocomposites. The so prepared nanocomposites were characterized by Fourier transform Infrared spectroscopy, X‐ray diffraction technique, Raman spectroscopy, electron diffraction, and energy‐dispersive X‐ray spectroscopy confirming the presence of Fe₃O₄ inside the PHEMA nanoparticles. The magnetization studies of nanocomposites conducted at room temperature using vibrating sample magnetometer suggested for their superparamagnetic nature having saturation magnetization (Ms) of 20 emu/g at applied magnetic field of 5 kOe. Transmission electron microscopy, field‐emission scanning electron microscopy, and dynamic light scattering/zeta potential measurements were also performed which revealed that size of mPHEMA nanocomposites was lying in the range of 60–300 nm having zeta potential of ?93 mV. The nanocomposites showed no toxicity as revealed by cytotoxicity test performed on L‐929 fibroblast by extract method. The results indicated that the prepared superparamagnetic mPHEMA nanocomposites have enormous potential to provide a possible option for magnetically assisted targeted delivery of anticancer drugs. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40791.     

Synthesis and Characterization of FePt/NiO Core–Shell Nanoparticles

Monodisperse FePt nanoparticles were successfully synthesized using the chemical polyol process. Annealing at the high temperatures is required to achieve the hard ferromagnetic behavior with L1₀ phase. Annealing causes the surfactant surrounding particles to be decomposed. Under such circumstances, FePt particles are agglomerated, and their size increases. In this research, NiO oxide particle with a high melting point was used for the first time as the shell around FePt core particles to prevent agglomeration. As a result, coercivity, H_c, of FePt and FePt/NiO nanoparticles after annealing at 750?°C are equal to 10 and 7?kOe, respectively.     

Preparation and characterization of spindle-like Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> mesoporous nanoparticles

Magnetic spindle-like Fe₃O₄ mesoporous nanoparticles with a length of 200 nm and diameter of 60 nm were successfully synthesized by reducing the spindle-like α-Fe₂O₃ NPs which were prepared by forced hydrolysis method. The obtained samples were characterized by transmission electron microscopy, powder X-ray diffraction, attenuated total reflection fourier transform infrared spectroscopy, field emission scanning electron microscopy, vibrating sample magnetometer, and nitrogen adsorption-desorption analysis techniques. The results show that α-Fe₂O₃ phase transformed into Fe₃O₄ phase after annealing in hydrogen atmosphere at 350°C. The as-prepared spindle-like Fe₃O₄ mesoporous NPs possess high Brunauer-Emmett-Teller (BET) surface area up to ca. 7.9 m² g^-1. In addition, the Fe₃O₄ NPs present higher saturation magnetization (85.2 emu g^-1) and excellent magnetic response behaviors, which have great potential applications in magnetic separation technology.     

Microstructure,mechanical properties,and high-temperature oxidation resistance of AlN/SiO<Subscript>2</Subscript> nanomultilayer coatings

The microstructure, mechanical properties, and high-temperature oxidation resistance of AlN/SiO₂ nanomultilayer coatings with various SiO₂ layer thicknesses were investigated using X-ray diffractometry, high-resolution transmission electron microscopy, scanning electron microscopy, and nanoindentation. The results revealed that SiO₂ formed wurtzite-typed hexagonal pseudo-crystal structures and grew epitaxially with AlN when its thickness was less than 0.6 nm. Meanwhile, the multilayer coatings yielded superhardness effect with a maximum hardness of 29.0 GPa. A minute increase in SiO₂ thickness from 0.6 to 0.9 nm would decrease the hardness of the nanomultilayer coatings due to the formation of amorphous SiO₂ and destruction of epitaxial structure. The high hardness of superhard coatings was sustained after high-temperature annealing treatment of up to 800°C. However, a further increase in annealing temperature to 900°C caused severe oxidation of AlN and thus degradation of coating’s hardness.     

Effect of surfactant in a modified sol on the physicochemical properties and photocatalytic activity of crystalline TiO<Subscript>2</Subscript> nanoparticles

This study describes the effect of amphiphilic organic molecules (surfactants) in a sol on the physicochemical properties and photocatalytic activity of crystalline TiO₂ nanoparticles prepared via a simple sol–gel route at high temperatures from 400 to 800 °C. Addition of polyoxyethylenesorbitan surfactant and polyethylene oxide and polypropylene oxide triblock copolymer as particle size inhibitors and pore directing agents into a stable titania sol affected the physicochemical properties of TiO₂ nanoparticles such as their crystallographic structure, morphology, and defect structure. With the addition of the surfactants, the ratio of anatase and rutile crystal phases of TiO₂ was controlled and an active anatase crystal phase was maintained during heat treatment up to 800 °C. Decrease in the sintering rate and inhibition in crystal growth were also observed, which resulted in higher surface area and inhibition of crystallite aggregation. Bulk defects in TiO₂ were reduced while surface defects were increased as a result of the addition of surfactants. These physicochemical properties of TiO₂ nanoparticles were correlated with photocatalytic degradation of 4-chlorophenol in water. The results revealed that high crystallinity, anatase crystal phase, high specific surface area, surface defects, and segregated morphology of TiO₂ nanoparticles, which were induced by the addition of surfactants, were more advantageous for enhancing photocatalytic destruction of the model organic compound tested in the study.     

Synthesis and Sintering Behavior of Ultrafine (<10 nm) Magnesium Aluminate Spinel Nanoparticles

This article reports a comparative characterization of ultrafine MgAl₂O₄ spinel nanoparticles synthesized by polymeric precursor (Pechini) and coprecipitation methods. The nanoparticles were evaluated in terms of purity and surface cleanliness, size distribution, state of agglomeration, and sintering behavior. Powders synthesized by the Pechini technique were highly agglomerated and revealed a bimodal particle size distribution centered around 12 and 27 nm. Thermal analysis and infrared spectroscopy measurements indicated that carbon species remained on the surface of the powders only to be released when temperatures exceeded 1000°C. Isothermal sintering of such nanopowders at 1300°C showed a maximum relative density of only 54%. MgAl₂O₄ synthesized via coprecipitation created small nanoparticles, around 5–6 nm after calcination at 800°C, with significantly less agglomeration. Compared with the precursor‐derived powders, excellent sinterability of the coprecipitated powders was obtained under the same sintering conditions. Relative densities above 90% were obtained after only 10 min, which further increased to greater than 95% after 20 min with no sintering aids or dopants. The results highlight the importance of purity and processing control to exploit the beneficial high sinterability of nanoparticles.     

Nanocasting Synthesis of Ultrafine WO<Subscript>3</Subscript> Nanoparticles for Gas Sensing Applications

Ultrafine WO₃ nanoparticles were synthesized by nanocasting route, using mesoporous SiO₂ as a template. BET measurements showed a specific surface area of 700 m²/gr for synthesized SiO_2, while after impregnation and template removal, this area was reduced to 43 m²/gr for WO3 nanoparticles. HRTEM results showed single crystalline nanoparticles with average particle size of about 5 nm possessing a monoclinic structure, which is the favorite crystal structure for gas sensing applications. Gas sensor was fabricated by deposition of WO₃ nanoparticles between electrodes via low frequency AC electrophoretic deposition. Gas sensing measurements showed that this material has a high sensitivity to very low concentrations of NO₂ at 250°C and 300°C.     

Low-temperature fabrication of TiO<Subscript>2</Subscript> film on flexible substrate by atmospheric roll-to-roll CVD

Titanium dioxide (TiO₂) thin film was fabricated using titanium isopropoxide as a precursor through an atmospheric low-temperature roll-to-roll chemical vapor deposition method. TiO₂ was deposited on the PET substrate in the temperature range of room temperature to 100°C, and the working pressure was 740 Torr. The surface morphology of TiO₂ thin film was analyzed by field emission scanning electron microscopy and a 2D surface profiler. The results revealed that the growth rate of TiO₂ film was 31 nm/min at 100°C, and it also showed that the surface is uniform and smooth. Moreover, the lowest root mean square roughness (R _q) value of 1.87 nm was obtained for TiO₂ film prepared at 100°C. The composition of TiO₂ film was confirmed by X-ray photoelectron spectroscopy (XPS) analysis. The film showed very good chemical and optical properties while increasing the substrate deposition temperature. The UV–Vis spectroscopy analysis revealed that TiO₂ films exhibited excellent optical transmittance, more than 91% observed in the visible region.     

Synthesis and Electrochemical Properties of LaCr<Subscript>1−x</Subscript>Co<Subscript>x</Subscript>O<Subscript>3</Subscript> (0 ≤ x ≤ 0.5) via Co-precipitation Method

Perovskite LaCr_1?xCo_xO₃ (0 ≤ x ≤ 0.5) oxides synthesized by co precipitation method were investigated. X-ray diffraction, thermo gravimetric and differential thermal analysis, Fourier transform infrared spectroscopy, scanning electron microscopy (SEM) and electrochemical measurements, were used to characterize the structure, morphology, electrochemical properties of the samples. The studied compounds have orthorhombic and rhombohedral systems in the ranges (0 ≤ x ≤ 0.2) and (0.3 ≤ x ≤ 0.5) respectively. Thermal analysis results indicate that the pure phase was obtained at temperature above 800 °C. The structure and morphology of the samples characterized by SEM measurements indicate that particles have nearly spherical shapes and are agglomerated. The electrochemical measurements indicate that the catalytic activity is strongly influenced by cobalt doping. The highest electrode performance is achieved with large cobalt content.     

Natural fuel assisted synthesis of Mg–Cu ferrite nanoparticles: Evaluation of structural,dielectric, magnetic and humidity sensing properties

The effects of lemon juice and annealing treatment on phase composition, vibrational modes, microstructural and dielectric behavior of Mg doped copper ferrite nanoparticles have been synthesized and analyzed in detail in this present work. The various characterization techniques are used to examine the phase, microstructural, vibrational and dielectric nature of the samples at different annealing temperatures (600 °C and 900 °C). The phase and microstructure of Mg substituted CuFe₂O₄ nanoparticles have been analyzed by XRD, SEM and TEM. The secondary phase peaks free XRD spectra revealed that the as burst and the annealed Mg–CuFe₂O₄ nanoparticles have single phase cubic spinel structure. The average crystallite size of the as burnt, annealed 600 °C and annealed 900 °C of as prepared nanoparticles are calculated as 8.9 nm, 12.8 nm and 31.6 nm respectively. Another verification of the spherical shaped particle's size was confirmed by TEM analysis and it found as average size of 28.7 nm, this result is well matched with XRD analysis. The effect of size with impact of annealing treatment on magnetic and dielectric properties also analyzed. The size-dependent Mg–CuFe₂O₄ nanostructures exhibit promising sensing properties which ensure them as a potential candidate for humidity sensor applications. The as-burnt and annealed samples both show a humidity response over the humid range of 10–95 %RH. The sample annealed at 900 °C has the highest average sensor response (6.02 MΩ/%RH) among the as-burnt sample (6.38 MΩ/%RH) and annealed sample at 600 °C (7.11 MΩ/%RH).