Selective Synthesis of Fe<Subscript>2</Subscript>O<Subscript>3</Subscript> and Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> Nanowires Via a Single Precursor: A General Method for Metal Oxide Nanowires

Hematite (α-Fe₂O₃) and magnetite (Fe₃O₄) nanowires with the diameter of about 100 nm and the length of tens of micrometers have been selectively synthesized by a microemulsion-based method in combination of the calcinations under different atmosphere. The effects of the precursors, annealing temperature, and atmosphere on the morphology and the structure of the products have been investigated. Moreover, Co₃O₄ nanowires have been fabricated to confirm the versatility of the method for metal oxide nanowires.     

Preparation of stable magnetic nanofluids containing Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>@PPy nanoparticles by a novel one-pot route

Stable magnetic nanofluids containing Fe₃O₄@Polypyrrole (PPy) nanoparticles (NPs) were prepared by using a facile and novel method, in which one-pot route was used. FeCl₃·6H₂O was applied as the iron source, and the oxidizing agent to produce PPy. Trisodium citrate (Na₃cit) was used as the reducing reagent to form Fe₃O₄ NPs. The as-prepared nanofluid can keep long-term stability. The Fe₃O₄@PPy NPs can still keep dispersing well after the nanofluid has been standing for 1 month and no sedimentation is found. The polymerization reaction of the pyrrole monomers took place with Fe³⁺ ions as the initiator, in which these Fe³⁺ ions remained in the solution adsorbed on the surface of the Fe₃O₄ NPs. Thus, the core-shell NPs of Fe₃O₄@PPy were obtained. The particle size of the as-prepared Fe₃O₄@PPy can be easily controlled from 7 to 30 nm by the polymerization reaction of the pyrrole monomers. The steric stabilization and weight of the NPs affect the stability of the nanofluids. The as-prepared Fe₃O₄@PPy NPs exhibit superparamagnetic behavior.     

Synthesis and optical property of one-dimensional spinel ZnMn<Subscript>2</Subscript>O<Subscript>4</Subscript> nanorods

Spinel zinc manganese oxide (ZnMn₂O₄) nanorods were successfully prepared using the previously synthesized α-MnO₂ nanorods by a hydrothermal method as template. The nanorods were characterized by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, UV-Vis absorption, X-ray photoelectron spectroscopy, surface photovoltage spectroscopy, and Fourier transform infrared spectroscopy. The ZnMn₂O₄ nanorods in well-formed crystallinity and phase purity appeared with the width in 50-100 nm and the length in 1.5-2 μm. They exhibited strong absorption below 500 nm with the threshold edges around 700 nm. A significant photovoltage response in the region below 400 nm could be observed for the nanorods calcined at 650 and 800°C.     

Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>@SiO<Subscript>2</Subscript>@TiO<Subscript>2</Subscript>-OSO<Subscript>3</Subscript>H: an efficient hierarchical nanocatalyst for the organic quinazolines syntheses

A sulfonic acid functionalized titanium dioxide quasi-superparamagnetic nanocatalyst Fe₃O₄@SiO₂@TiO₂-OSO₃H with average size of 61 nm and semispherical shape with surface area about 97 m² g^?1 with saturation magnetization 17.7 emu g^?1 and the coercivity 9.84 Oe was successfully synthesized. The structure and morphology of the nanocatalyst was characterized by Fourier transform infrared spectroscopy (FT-IR), energy-dispersive X-ray spectroscopy, X-ray diffraction pattern, transmission electron microscopy, field-emission scanning electron microscopy, vibrating sample magnetometer and Brunauer–Emmett–Teller surface area analysis. The catalytic usage of the nanocatalyst was exemplified in synthesis of 2,3-dihydroquinazolin-4(1H)-one and spiroquinazolin-4(3H)-one derivatives in deep eutectic solvents (DESs) based on choline chloride and urea. We suggest that the synergistic effects in catalytic activities of titanium dioxide, organic acid and the CO₂ capture property of DES are the main reasons for the improvement of catalytic activity. The synthesized spiroquinazolinones and dihydroquinazolinones derivatives were characterized by FT-IR, ¹H and ¹³C nuclear magnetic resonance spectroscopy. The magnetic nanocatalyst exhibit high catalytic activity and can be simply separated from reaction media by an external magnet in a few seconds and could be reused for six cycles without significant loos in activity, which indicates the good immobilization of sulfonic acid on the magnetic titanium dioxide support. Furthermore, the solvent which has been used in this work can be readily isolated and reused for several times.     

Research of mica/Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> pearlescent pigment by co-precipitation

Experiments on preparation of mica/Fe₃O₄ pearlescent pigment were performed to discuss influences of several crucial parameters on final products. The samples were characterized by XRD, HRSEM, FTIR and color measurement, the content of Fe₃O₄ on the mica surface was also analyzed by XPS. It was found that the smoothness, compactness and colour deepness of the coating were influenced by different pH values and temperatures. The optimum preparation parameters of mica/Fe₃O₄ pearlescent pigment were obtained: the value of pH ≥ 9.2; the concentration of sodium hydroxide was 0.5 mol/l; the concentration ratio of Fe³⁺ to Fe²⁺ was 1.6 : 1; the velocity of magnetic stirring was 138 ≤ v ≤ 151 r/min; reaction temperature was 70–80°C; calcination temperature was 350°C and calcination time was 3 h.     

Study on the properties of Bi<Subscript>2</Subscript>O<Subscript>3</Subscript>-B<Subscript>2</Subscript>O<Subscript>3</Subscript>-BaO lead-free glass using in the electronic pastes

The Sb₂O₃ doping lead-free glass in Bi₂O₃-B₂O₃-BaO ternary system were prepared in the composition of several different subsystem, and the glass powder was produced through the process of water quenching. Glass transition temperatures (T _g ), glass soften temperatures(T _s ), the volume resistivity (ρ) in the temperature range of 80–200°C, and linear thermal coefficients of expansion in the temperatures range of 25–300°C (α_25–300) were measured for subsystems along with the different ratio of Bi₂O₃, B₂O₃ and BaO. For these subsystems, T _g ranged from 458 to 481°C, and T _s ranged from 490 to 512°C, both decreasing with the increasing of Bi₂O₃/B₂O₃ ratio, and increasing with the increasing of BaO/B₂O₃ ratio. The measured α_25–300 ranged from 65.3 to 76.3 × 10⁻⁷ K⁻¹, with values increasing with increasing Bi₂O₃/B₂O₃ and BaO/B₂O₃ ratio. The volume resistivity remains at a high standards, which may caused by it’s non-alkali composition, and it fluctuated from 10¹³ to 10¹¹ Ω cm with the temperature varied from 80–200°C. The structure of Bi₂O₃-B₂O₃-BaO ternary leadfree glass system was mearsured by FT-IR. The IR studies indicate that these glasses are made up of [BiO₆], [BO₃], and [BO₄] basic structural units, and it appears that Ba²⁺ acts as a glass-modifier in this ternary system, but the Bi³⁺ has entered the glass network when it is in relative high content so as to change the α_25–300, T _s and T _g .     

Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanoparticles coated by new functionalized tetraaza-2,3 dialdehyde micro-crystalline cellulose: synthesis,characterization, and catalytic application for degradation of Acid Yellow 17

In this study, we developed an original approach for preparing cellulose-coated magnetite nanoparticles (NPs). Two novel Schiff bases (PDA-g-DAC) and [Bz-(PDA-g-DAC)] were synthesized via condensation reactions of periodate oxidized micro-crystalline cellulose (DAC) with o-phenylene diamine (PDA) to obtain its azomethine derivative with 85% yield. Subsequently, the functionalization of (PDA-g-DAC) with benzil (Bz) yields the tetraaza macrocycle [Bz-(PDA-g-DAC)]. The physicochemical characterization of the condensation products was performed using ¹³CNMR, FTIR, ATG, DSC, and X-ray diffraction techniques. Magnetic nanomaterial-based Schiff base cellulose was successfully prepared using in situ chemical co-precipitation of coordinated ferric and ferrous ions in cellulose Schiff base matrix under optimized conditions, and then, its magnetic properties were characterized. The results demonstrated that the Fe₃O₄ NPs coated with [Bz-(PDA-g-DAC)] were homogeneously coated in the matrix under ultrasonic irradiation with the saturation magnetization of 69.50 emu g^?1. In addition, XRD line broadening analysis showed that the average particle size of the NPs was 37.3 nm. Furthermore, FTIR spectra demonstrated that [Bz-(PDA-g-DAC)] concavity was anchored to magnetite Fe₃O₄ NPs through azomethine groups. Vibrating sample magnetometry (VSM) of [Bz-(PDA-g-DAC)@Fe₃O₄] magnetic nanocomposite samples showed the typical behavior of ferromagnetism. This study provided a green and facile method to inhibit magnetic nanoparticle aggregation. Activity results revealed that the prepared [Bz-(PDA-g-DAC)@Fe₃O₄] catalyst shows the maximum activity for degradation of Acid Yellow 17 (AY17) compared to other prepared catalysts. After degradation reaction, the [Bz-(PDA-g-DAC)@Fe₃O₄] catalyst was recovered from the reaction mixture via an external magnet and used for further five consecutive cycles with excellent catalytic activity, successively, which was comparable to the fresh catalyst. The catalyst degradation efficiency and its easy separation exhibited that [Bz-(PDA-g-DAC)@Fe₃O₄] catalyst is a promising material for the removal of AY17 from aqueous solutions in green chemistry perspectives.     

Preparation and properties of Co<Subscript>3</Subscript>O<Subscript>4</Subscript> nanorods as supercapacitor material

Co₃O₄ nanorods have been successfully synthesized by thermal decomposition of the precursor prepared via a facile and efficient microwave-assisted hydrothermal method, using cetyltrimethylammonium bromide (CTAB) with ordered chain structures as soft template for the first time. The obtained Co₃O₄ was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and electrochemical measurements. The results demonstrate that the as-synthesized nanorods are single crystalline with an average diameter of about 20 to 50 nm and length up to several micrometers. Preliminary electrochemical studies, including cyclic voltammetry (CV), galvanostatic charge–discharge, and electrochemical impedance spectroscopy (EIS) measurements, are carried out in 6 M KOH electrolyte. Specific capacitance of 456 F g⁻¹ for a single electrode could be achieved even after 500 cycles, suggesting its potential application in electrochemical capacitors. This promising method could provide a universal green chemistry approach to synthesize other low-cost and environmentally friendly transition metal hydroxide or oxide.     

One-pot method fabrication of superparamagnetic sulfonated polystyrene/Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>/graphene oxide micro-nano composites

In this work, using monodispersed sulfonated polystyrene (SPS) microspheres as carriers, FeCl₃·6H₂O and FeSO₄·7H₂O as precursors, NaOH as precipitant in the presence of graphene oxide (GO), SPS/Fe₃O₄/GO micro-nano composites were fabricated by a simple one-pot method employing an inverse coprecipitation in-situ compound technology. The SPS/Fe₃O₄/GO micro-nano composites were characterized by scanning electron microscopy, transmission electron microscopy, X-ray powder diffractometer, Fourier transform infrared spectroscopy, nitrogen adsorption/desorption isotherms and vibrating sample magnetometer. The results show that the SPS/Fe₃O₄/GO micro-nano composites were fabricated with SPS as core, GO and Fe₃O₄ nanoparticles as shell. The SPS/Fe₃O₄/GO micro-nano composites had larger BET specific surface area, average pore width and micropore volume than the pure SPS microspheres. Meanwhile, the SPS/Fe₃O₄/GO micro-nano composites had superparamagnetism and hydrophilic property. The saturation magnetization (M_s) of the SPS/Fe₃O₄/GO micro-nano composites was 10.86 emu/g, which was enough to ensure the convenient magnetic separation of solid and liquid phase.     

Preparation and characterization of mesoporous TiO<Subscript>2</Subscript> thin film

Ordered hexagonal mesoporous TiO₂ thin film was prepared by the evaporation-induced self-assembly (EISA) method using triblock copolymer (Pluronic P123) and tetrabutyl orthotitanate (Ti(OBu ⁿ )₄, TBOT) in 1-methoxy-2-propanol (C₄H₁₀O₂, PGME) solvent. The arrangement of mesopores was identified by small-angle X-ray diffraction and transmission electron microscopy (TEM). The well-ordered hexagonal mesoporous TiO₂ had a high specific surface area of 239 m²/g and an average pore size of 6.3 nm. The structure of mesoporous TiO₂ thin film was anatase with a 5.1 nm crystallite. The absorption band shift of the mesoporous TiO₂ toward longer wavelengths as calcined at 350 °C due to the residual carbon.     

Preparation and properties of poly(acrylic acid-co-styrene)/Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanocomposites

Poly(acrylic acid-co-styrene)/Fe₃O₄ nanocomposites were prepared using poly(acrylic acid-co-styrene) (P(AA-co-St)) and nano-Fe₃O₄ particles. The resultant materials were characterized by transmission electron microscope (TEM), Fourier transform infrared (FTIR), thermogravimetric analysis (TGA), advanced rheology expand system and superconducting quantum interference device (SQUID) magnetometer. The diameter of the magnetic particles was around 3–14 nm. The experimental results reveal that the acrylic acid segment of P(AA-co-St) can react with nano-Fe₃O₄. With increasing reaction time the storage modulus, loss modulus, complex viscosity and shear stress of the P(AA-co-St)/Fe₃O₄ ethanol suspension were increased, and the suspension changed from liquid-like behavior to gel-like behavior for the reaction between P(AA-co-St) and Fe₃O₄, as found during the rheology measurements. The thermal stability of P(AA-co-St) decreased with the addition of nano-Fe₃O₄, and the nanocomposites exhibited superparamagnetic properties above the blocking temperature.     

Icosahedral quasicrystalline Fe<Subscript>10</Subscript>Cu<Subscript>20</Subscript>Al<Subscript>70</Subscript> by electrothermal explosion: Structural and magnetic properties

A systematic study on the formation and stability of the icosahedral quasicrystalline (IQC) Al₇₀Cu₂₀Fe₁₀ alloy has been carried out using electrothermal explosion (ETE) reaction as a preparation method. The influence of added elements on the formation of icosahedral phase has been investigated by Mössbauer spectroscopy, XRD, and field emission scanning electron microscopy (FESEM). Combined ball milling and ETE reaction (BM-ETE) of Al₆₃Cu₂₅Fe₁₂ composition resulted in the formation of the ICQ Fe₁₀Cu₂₀Al₇₀ phase with a face-centered structure. In all cases, an Al(Cu, Fe) solid solution and β-Fe₃Al have been detected along with the ICQ phase. The icosahedral phase appears to form in a peritectoid-type reaction between Fe₃Al and Al₂Cu. A mechanism for formation of the IQC phase in the Al-Cu-Fe system was suggested. VSM measurements showed the ferromagnetic behavior of the alloy. The Mössbauer measurements in transmission and XRD data showed that the reaction product contained 65% Fe₁₀Cu₂₀Al₇₀ with an admixture of β-Fe₃Al and Al₂Cu.     

Combustion synthesis of some compounds in the Li<Subscript>2</Subscript>O-Al<Subscript>2</Subscript>O<Subscript>3</Subscript> system

At least four compounds, viz. LiAlO₂, LiAl₅O₈, Li₅AlO₄ and Li₂Al₄O₇, are known in the Li₂O-Al₂O₃ system. These compounds are important for several technological applications. Combustion synthesis of these compounds using urea as a fuel was attempted. LiAlO₂ and LiAl₅O₈ could be successfully prepared by choosing the starting materials in required stoichiometric ratios. Li₂Al₄O₇ was not obtained as a pure phase; γ-LiAlO₂ was formed as an impurity phase. Li₅AlO₄ could not be prepared by combustion process. Some phosphors based on these aluminates could also be prepared. Activation of these aluminates with Fe³⁺, Mn⁴⁺, Cu⁺, etc. was successfully achieved. Excitation and emission spectra for LiAl₅O₈: Fe³⁺, LiAl₅O₈: Mn²⁺, and Li₂Al₄O₇: Cu⁺ are reported.     

Experimental and theoretical analysis of element mercury adsorption on Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>/Ag composites

A novel magnetic nano-sorbent Fe₃O₄/Ag was synthesized and applied to capture the elemental mercury from the simulated flue gas. The morphology, components and crystal phase of the sorbents were characterized by transmission electron microscope (TEM), energy dispersive spectrometry (EDS) and X-ray diffraction (XRD), respectively. The mercury removal performance of the sorbents was investigated through the fixed-bed tests. The results indicated that silver was successfully loaded on the surface of Fe₃O₄ particles, which could significantly enhance the Hg⁰ removal performance of the sorbents. Flue gas components, including CO₂, SO₂, and NO, have little impact on the Hg⁰ removal performance of Fe₃O₄/Ag sorbents, while O₂ has a slightly positive effect. The Hg⁰ removal efficiency decreased with the increasing of temperature, Hg⁰ inlet concentration and gas hourly space velocity. Only one broad mercury desorption peak at approximately 210 °C could be observed during the temperature-programmed desorption (TPD) process, which indicated that mercury species existing on the surface of Fe₃O₄/Ag sorbents might be elemental mercury instead of oxidized mercury. Furthermore, the reusability tests showed that the Fe₃O₄/Ag sorbents could be efficiently regenerated and reused. Finally, the theoretical analysis based on the DFT method showed that a weak chemisorption of Hg⁰ on Fe₃O₄ sorbents changed to a strong chemisorption when silver was loaded. The results of theoretical analysis conformed to the experiments results well.     

Soft Template Synthesis of Super Paramagnetic Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> Nanoparticles a Novel Technique

The present study reports a facile technique for the synthesis of crystalline super paramagnetic nano ferrite (Fe₃O₄) particles using diethyl amine as a soft template. The spectral properties of Fe₃O₄ nanoparticles were characterized by UV–visible and Fourier Transform Infrared (FTIR) spectroscopies while the crystalline structure and particle size was estimated using X-Ray diffraction (XRD) as well as transmission electron microscopy (TEM) techniques. The super paramagnetic behavior of Fe₃O₄ nanoparticles was determined using vibrating sample magnetometer (VSM) at 300 K. The results of the studies revealed that this technique could be adopted to synthesize agglomerate free super paramagnetic Fe₃O₄ nanoparticles which may find potential application in the filed of biosensor and corrosion protective coatings.     

Effect of surface modification of Fe<Subscript>3</Subscript>O<Subscript>4</Subscript> nanoparticles on the preparation of Fe<Subscript>3</Subscript>O<Subscript>4</Subscript>/polystyrene composite particles via miniemulsion polymerization

Fe₃O₄ nanoparticles were modified by n-octadecyltrimethoxysilane (C18TMS) and 3-trimethoxysilylpropylmethacrylate (MPS). The modified Fe₃O₄ nanoparticles were used to prepare Fe₃O₄/polystyrene composite particles by miniemulsion polymerization. The effect of surface modification of Fe₃O₄ on the preparation of Fe₃O₄/polystyrene composite particles was investigated by transmission electron microscopy, Fourier transform infrared spectrophotometer (FT-IR), contact angle, and vibrating sample magnetometer (VSM). It was found that C18TMS modified Fe₃O₄ nanoparticles with high hydrophobic property lead to the negative effect on the preparation of the Fe₃O₄/polystyrene composite particles. The obtained composite particles exhibited asymmetric phase-separated structure and wide size distribution. Furthermore, un-encapsulated Fe₃O₄ were found in composite particles solution. MPS modified Fe₃O₄ nanoparticles showed poor hydrophobic properties and resulted in the obtained Fe₃O₄/polystyrene composite particles with regular morphology and narrow size distribution because the ended C=C of MPS on the surface of Fe₃O₄ nanoparticles could copolymerize with styrene which weakened the phase separation distinctly.     

Synthesis and properties of the composite ceramics from nanocrystalline Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-30% Y<Subscript>0.1</Subscript>Zr<Subscript>0.9</Subscript>O<Subscript>2</Subscript> prepared from a water-alcohol solution

The hydrogel of the mixed oxide Al₂O₃-30% Y_0.1Zr_0.9O₂ was prepared by precipitation of ammonia from a water-alcohol mixture (1 : 5). The Al₂O₃-30% Y_0.1Zr_0.9O₂ compound thus synthesized was characterized using differential scanning calorimetry, transmission electron microscopy, and the BET adsorption method. The obtained sample consisted of spherical particles with an average size of 16–20 nm and a specific surface area of 167 m²/g. The Al₂O₃-30% Y_0.1Zr_0.9O₂ powder was pressed at 300 MPa and then calcinated at 1600°C for 2 h in air. The topographic and structural features of the prepared ceramics were determined using atomic force microscopy and X-ray electron probe microanalysis. The porosity, the Vickers microhardness, and the tensile strength were determined by mercury porometry.     

Synthetic spinels of the system MgO-Cr<Subscript>2</Subscript>O<Subscript>3</Subscript>-Al<Subscript>2</Subscript>O<Subscript>3</Subscript>-Fe<Subscript>2</Subscript>O<Subscript>3</Subscript>

Synthetic spinels of the system MgO-Cr₂O₃-Al₂O₃-Fe₂O₃ are considered and the desirability of organizing their production for the refractory industry is demonstrated. Translated from Novye Ogneupory, No. 6, pp. 32–35, June 2008.     

Electrochemical properties of microwave-assisted reflux-synthesized Mn<Subscript>3</Subscript>O<Subscript>4</Subscript> nanoparticles in different electrolytes for supercapacitor applications

The nanosized Mn₃O₄ particles were prepared by microwave-assisted reflux synthesis method. The prepared sample was characterized using various techniques such as X-ray diffraction (XRD), Fourier transform-infrared spectroscopy (FT-IR), Raman analysis, and transmission electron microscopy (TEM). Electrochemical properties of Mn₃O₄ nanoparticles were investigated using cyclic voltammogram (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic charge–discharge analysis in different electrolytes such as 1 M KCl, 1 M Na₂SO₄, 1 M NaNO₃, and 6 M KOH electrolytes. XRD pattern reveals the formation of single-phase Mn₃O₄ nanoparticles. The FT-IR and Raman analysis also assert the formation of Mn₃O₄ nanoparticles. The TEM image shows the spherical shape particles with less than 50 nm sizes. Among all the electrolytes, the Mn₃O₄ nanoparticles possess maximum specific capacitance of 94 F g⁻¹ in 6 M KOH electrolyte calculated from CV. The order of capacitance obtained by various electrolytes is 6 M KOH > 1 M KCl > 1 M NaNO₃ > 1 M Na₂SO₄. The EIS and galvanostatic charge–discharge results further substantiate with the CV results. The cycling stability of Mn₃O₄ electrode reveals that the prepared Mn₃O₄ nanoparticles are a suitable electrode material for supercapacitor application.     

Voltammetric behavior and the determination of quercetin at a flowerlike Co<Subscript>3</Subscript>O<Subscript>4</Subscript> nanoparticles modified glassy carbon electrode

Flowerlike Co₃O₄ nanoparticles were used as a modifier on the glassy carbon electrode to fabricate a quercetin (Qu) sensor. The morphology and crystallinity of the prepared Co₃O₄ material were investigated by scanning electron microscopy and X-ray diffraction. Electrochemical behavior of Qu at the sensor was studied by cyclic voltammetry and semi-derivative voltammetry. Results suggested that the modified electrode exhibited a strong electrocatalytic activity toward the redox of Qu. The electron transfer coefficient (α), the number of electron transfer (n), and the diffusion coefficient (D) of Qu at the sensor were calculated. Under the optimum conditions, the catalytic peak currents of Qu were linearly dependent on the concentrations of Qu in the range from 5.0 × 10⁻⁷ to 3.3 × 10⁻⁴ M, with a detection limit of 1.0 × 10⁻⁷ M. This proposed method was successfully applied to determine the quercetin concentration in Ginkgo leaf tablet and human urine samples.