Magnetic ionic liquid-assisted synthesis of polyaniline/AgCl nanocomposites by interface polymerization

A simple strategy for the one-step synthesis of polyaniline/AgCl nanocomposites at the water/magnetic ionic liquid interface was reported. By controlling the reactive conditions, highly dispersed polyaniline/AgCl nanocomposites with their size ranging around 50–80 nm were obtained with magnetic ionic liquid as the oxidant. Transmission electron microscopy was used to show the morphology of the nanocomposites. The nanocomposites were also characterized by Fourier transform infrared spectroscopy, X-ray diffraction, and thermogravimetric analysis. Moreover, polyaniline/AgCl nanocomposites on a glassy carbon electrode showed strong electrocatalytic activity for H₂O₂ and could be used to construct a H₂O₂ biosensor.     

Preparation and Characterization of the Polyaniline Nanocomposites with Electricity/Magnetic Properties

Three kinds of magnetic particle (water-based NiZn ferrite fluid, water-based Fe₃O₄ magnetic fluid, and silicon-oil-based Fe₃O₄ magnetic fluid)/polyaniline nanocomposites were prepared in this study. The samples, after drying and grinding, were characterized by infrared spectrometry (IR), X-ray diffraction (XRD), and UV-vis, scanning electron microscope (SEM); their electromagnetic properties were also measured. The conductivitiy of the resulting water-based NiZn ferrite/polyaniline nanocomposites (WBNiZnFe/PA) was the greatest, reaching 0.094 s/cm, while the conductivitiy for water-based Fe₃O₄ magnetic particle/polyaniline nanocomposites (WBFe₃O₄/PA) was the lowest, reaching only 0.068 s/cm. The saturation magnetization for WBFe₃O₄/PA was the greatest, being 1.5 emu/g, while the saturation magnetization for WBNiZnFe/PA was the lowest, being only 0.8 emu/g. The coercivity of all magnetic particle/polyaniline nanocomposites was about He = 200 Oe.     

Ultrasound and ionic-liquid-assisted synthesis and characterization of polyaniline/Y2O3 nanocomposite with controlled conductivity

A sonochemical method has been employed to prepare polyaniline-Y₂O₃ nanocomposite with controlled conductivity with the assistance of an ionic liquid (IL). Ultrasound energy and the IL replace conventional oxidants and metal complexes in promoting the polymerization of aniline monomer for the first time. Structural characterization has revealed that the resulting nanocomposite consists of microspheres of average diameter 3–5 μm. The products were found to consist of regular solid microspheres covered with some 40 nm nanoparticles. Under certain polymerization conditions, polyaniline nanofibers and nanosheet were obtained. The method may open a new pathway for the preparation of nanoscale conducting polymer nanocomposites with the aid of ILs. The conductivity of the product varies with the mass ratio of aniline monomer to Y₂O₃ and IL. TG curves of the products suggest that the thermal degradation process of the PANI/Y₂O₃ composites proceeds in two steps and that the composites are more thermally stable than pure PANI. The reaction conditions have been optimized by varying parameters such as the aniline/Y₂O₃ ratio and the type and amount of IL used. The effect of the ultrasonic irritation time and frequency on the morphology, conductivity and yield were discussed.     

Electrical transport and optical properties of vanadyl phosphate—polyaniline nanocomposites

The nanocomposites of conducting polyaniline and layered vanadyl phosphate, VOPO₄·2H₂O are synthesized by redox intercalation method. Water content decreases with insertion of polyaniline molecules. In scanning electron micrographs plate like structures are observed for both VOPO₄·2H₂O and intercalated nanocomposites. Protonation of polyaniline and interaction with vanadyl phosphate are observed in infrared and UV absorption spectroscopy. Intercalation improves conductivity of pristine vanadyl phosphate. Thermally activated electrical dc conductivity at low temperature shows two distinct slopes around 210 K for both the nanocomposites. The optical band gap of vanadyl phosphate decreases from 4.0 to 3.7 eV due to insertion of polyaniline.     

Sonochemical synthesis and anchoring of zinc oxide on hemin-mediated multiwalled carbon nanotubes-cellulose nanocomposite for ultra-sensitive biosensing of H2O2

In this work, the metal oxide and biopolymer nanocomposites on multiwalled carbon nanotubes (MWCNT) were prepared using a simple sonochemical method. The hexagonal nanorods of zinc oxide (ZnO NR) were synthesized by probe sonication (frequency = 20 kHz, amplitude = 50) method and were integrated on ultrasonically functionalized MWCNT-cellulose nanocrystals (MWCNT-CNC) for the first time. The stable hemin bio-composites also were prepared using the bath sonication (37 kHz of frequency, 150 W of power) method, and was used for the selective and ultrasensitive electrochemical detection of H₂O₂. The UV–Vis spectroscopy studies confirmed the presence of native hemin on MWCNT-CNC/ZnO NR nanocomposite. Cyclic voltammetry studies revealed that an enhanced redox electrochemical behaviour of hemin was observed on hemin immobilised MWCNT-CNC/ZnO NR nanocomposite than that of other hemin modified electrodes. Also, the MWCNT-CNC/ZnO NR/hemin modified SPCE showed 2.3 folds higher electrocatalytic activity with a lower reduction potential (−0.2 V) towards H₂O₂ than that of other investigated hemin modified electrodes including hemin/MWCNT and hemin/CNC-ZnO. The fabricated biosensor displayed a stable amperometric response (-0.2 V vs Ag/AgCl) in the linear concentration of H₂O₂ ranging up to 4183.3 µM with a lower detection limit of 4.0 nM.     

Synthesis and characterization of Fe3O4@C@Ag nanocomposites and their antibacterial performance

We synthesized Fe₃O₄@C@Ag nanocomposites through a combination of solvothermal, hydrothermal, and chemical redox reactions. Characterization of the resulting samples by X-ray diffraction, Fourier-transform infrared spectroscopy, field-emission scanning and transmission electron microscopy, and magnetic measurement is reported. Compared to Fe₃O₄@Ag nanocomposites, the Fe₃O₄@C@Ag nanocomposites showed enhanced antibacterial activity. The Fe₃O₄@C@Ag nanocomposites were able to almost entirely prevent growth of Escherichia coli when the concentration of Ag nanoparticles was 10 μg/mL. Antibacterial activity of the Fe₃O₄@C@Ag nanocomposites was maintained for more than 40 h at 37 °C. The intermediate carbon layer not only protects magnetic core, but also improves the dispersion and antibacterial activity of the silver nanoparticles. The magnetic core can be used to control the specific location of the antibacterial agent (via external magnetic field) and to recycle the residual silver nanoparticles. The Fe₃O₄@C@Ag nanocomposites will have potential uses in many fields as catalysts, absorbents, and bifunctional magnetic-optical materials.     

Effect of ferrofluid concentration on electrical and magnetic properties of the Fe3O4/PANI nanocomposites

Magnetic nanocomposites can be controlled and tailored to provide the desired mechanical, physical, chemical, and biomedical properties depending on the final applications. The coating of ferrite nanoparticles with polymers affords the possibility of minimizing agglomeration in large-scale commercial synthesis of nanocomposite materials. The process of coating not only provides effective encapsulation of individual nanoparticles, but also controls the growth in size, thus, yielding a better overall size distribution. In this paper, in-situ polymerization of aniline was carried out in different concentration of the ferrofluid with the aim to obtain agglomerate free nanocomposites. The role of the ferrite concentration was investigated by the spectral, morphological, conductivity, and magnetic properties of Fe₃O₄/polyaniline (PANI) nanocomposites. XRD revealed the presence of spinel phase of Fe₃O₄ and the particle size was calculated to be 14.3 nm. Spectral analysis confirmed the formation of PANI encapsulated Fe₃O₄ nanocomposite. Conductivity of the nanocomposites was found to be in the range of 0.001–0.003 S/cm. Higher saturation magnetization of 3.2 emu/g was observed at 300 K, revealing a super paramagnetic behavior of this nanocomposite.     

Metal-free activation of H<Subscript>2</Subscript>O<Subscript>2</Subscript> by synergic effect of ionic liquid and microwave: chemoselective oxidation of benzylic alcohols to carbonyls and unexpected formation of anthraquinone in aqueous condition

H₂O₂ mediated oxidation of alcohols in ionic liquid is revisited, wherein, ionic liquids under the influence of microwave irradiation have been found to facilitate activation of H₂O₂ without any metal catalyst in aqueous condition. The method utilizes a neutral ionic liquid [hmim]Br both as catalyst and solvent for efficient and chemoselective oxidation of benzyl alcohol derivatives on aromatic (β, γ) alcohols, cyclic and aliphatic analogues, which can be a useful synthetic approach in total synthesis of complex organic compounds/natural products. Moreover, an unexpected oxidation of 9-anthracenyl propanol, a polyaromatic benzyl alcohol, resulting in the formation of 9,10-anthraquinone by the loss of propyl side chain was observed. Plausible mechanism and further exploration of this method on various other related substrates are discussed in detail.     

Synthesis and characterization of Sr(ZnZr)x Fe12−2xO19-PANI composites

Strontium zinc zirconium hexaferrites/polyaniline (Sr(ZnZr)_xFe_12−2xO₁₉-PANI, x=0, 0.5, 1.0) composites were synthesized by oxidative chemical polymerization of aniline in the presence of ammonium peroxydisulfate (APS). The structure and morphology of the product was characterized by FTIR, TGA and SEM. The particle size of the core material was found to be about 250-500 nm. After coating with polyaniline, the particle size of Sr(ZnZr)_0.5Fe₁₁O₁₉-PANI composites grew upto 0.5-1.0 μm. XRD of the ferrites indicated that the structure of the core materials is hexagonal, with lattice constants around 5.886-5.885 Å. It was found that the saturation magnetization (M_S) and coercivity (H_C) for Sr(ZnZr)_xFe_12−2xO₁₉-PANI composites decreased after polyaniline coating. The composite under applied magnetic field, exhibited ferromagnetic hysteretic loops with high saturation magnetization (M_S=18.9-3.8 emu/g) and coercivity (H_C=3850.0-583.91 Oe).     

Microemulsion-mediated in-situ synthesis and magnetic characterization of polyaniline/Zn<Subscript>0.5</Subscript>Cu<Subscript>0.5</Subscript>Fe<Subscript>2</Subscript>O<Subscript>4</Subscript> nanocomposite

Polyaniline/Zn_0.5Cu_0.5Fe₂O₄ nanocomposite was synthesized by a simple, general and inexpensive in-situ polymerization method in w/o microemulsion. The effects of polyaniline coating on the magnetic properties of Zn_0.5Cu_0.5Fe₂O₄ nanoparticles were investigated. The structural, morphological and magnetic properties of as-prepared samples were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectra, scanning electron microscopy (SEM) and magnetic measurements. The morphology analysis confirmed that polyaniline was deposited on the porous surface of magnetic Zn_0.5Cu_0.5Fe₂O₄. It was shown that the saturation magnetization and coercivity of Zn_0.5Cu_0.5Fe₂O₄ decreased after polyaniline coating, which can be interpreted by the interparticle dipole–dipole interactions that contributed to magnetic anisotropy and changed the magnetic properties of the nanoparticles. PACS  74.25.Ha; 81.05.-t; 81.05.Lg     

Preparation and characterization of multi-functional CoFe2O4-ZnO nanocomposites

Multi-functional magnetic, photoluminescent and photocatalytic CoFe₂O₄-ZnO nanocomposites were successfully synthesized by a collosol method. The average diameter of the prepared CoFe₂O₄-ZnO nanocomposites was 30±5 nm, and a diffusion layer was formed to link CoFe₂O₄ and ZnO. The saturation magnetization of the CoFe₂O₄-ZnO nanocomposites was 8.99 emu/g. Generation of ZnO from Zn(OH)₂ collosol was nearly complete after thermal decomposition at about 380 °C. A photoluminescence emission peak was observed at 443 nm when excitated at 350 nm. Degradation of methyl orange is performed by CoFe₂O₄-ZnO nanocomposites under ultraviolet radiation, with a degradation rate of up to 93.9%.     

Magnetoelectric characterization of xNi0.75Co0.25Fe2O4-(1−x)BiFeO3 nanocomposites

Magnetoelectric (ME) nanocomposites containing Ni_0.75Co_0.25Fe₂O₄-BiFeO₃ phases were prepared by citrate sol-gel process. X-ray diffraction (XRD) analysis showed phase formation of xNi_0.75Co_0.25Fe₂O₄-(1−x)BiFeO₃ (x=0.1, 0.2, 0.3 and 0.4) composites on heating at 700 °C. Transmission electron microscopy revealed the formation of powders of nano order size and the crystal size was found to vary from 30 to 85 nm. Dispersion in dielectric constant (ε) and dielectric loss (tan δ) in the low-frequency range have been observed. It is seen that nanocomposites exhibit strong magnetic properties and a large ME effect. On increasing Ni_0.75Co_0.25Fe₂O₄ contents in the nanocomposites, the saturation magnetization (M_S) and coercivity (H_C) increased after annealing at 700 °C. The large ME output in the nanocomposites exhibits strong dependence on magnetic bias and magnetic field frequency. The large value of ME output can be attributed to small grain size of ferrite phase of nanocomposite being prepared by citrate precursor process.     

Synthesis of Fe3O4/CNTs magnetic nanocomposites at the liquid-liquid interface using oleate as surfactant and reactant

Carbon nanotubes (CNTs)-based magnetic nanocomposites have attracted significant research interest owing to their great potentialities in various technological fields. In this investigation, a kind of novel Fe₃O₄/CNTs magnetic nanocomposites were prepared by in situ chemical precipitation using oleate as reactant and surfactant at the liquid-liquid interface of cyclohexane/ethanol/water mixture solvent. The as-prepared samples were characterized via transmission electron microscopy (TEM), X-ray diffractometry (XRD), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared (FTIR) and vibration sample magnetometry (VSM). Results indicated that the Fe₃O₄/CNTs magnetic nanocomposites dispersed well in organic medium were prepared organic medium, were prepared. The magnetic nanocomposites were proved to be superparamagnetic with coercive force of 3.69 Oe. A mechanism scheme was proposed to illustrate the formation process of the magnetic nanocomposites.     

Preparation of chitosan–ethylenediaminetetraacetate-enwrapped magnetic CoFe2O4 nanoparticles via zero-length emulsion crosslinking method

A kind of magnetic multiple functional groups nanocomposites, chitosan–ethylenediaminetetraacetate (EDTA)-enwrapped CoFe₂O₄ nanoparticles, i.e. CoFe₂O₄@chitosan–EDTA nanocomposites were synthesized by a facile zero-length emulsion crosslinking process. In this method, CoFe₂O₄ was used as magnetic core, and 1-ethyl-3-(3-dimethylminopropyl) carbodiimide hydrochloride (EDAC) was used as a crosslinker, integrating amino group of chitosan and carboxyl group of EDTA. Determination of amino groups in chitosan modified by EDAC-activated EDTA was carried out through the trinitrobenzenesulfonic acid (TNBS) method. The as-prepared magnetic nanocomposites were characterized by XRD, FT-IR, XPS, SEM, EDS, TEM, SAED and vibrating sample magnetometer (VSM), and the results showed that the as-prepared CoFe₂O₄@chitosan–EDTA nanocomposites have good dispersibility, spherical shape and enough magnetization. The method proposed can be extended to fabricate other magnetic nanocomposites possessed amino and carboxyl groups.     

A Study on the Rheological and Magnetic Properties of Polymer-Bonded Magnets Using Polycarbonate as the Bonding Material

The effect of three metal oxides on the magnetic properties of polymer bonded magnets (PBMs) was studied. The three PBMs, using polycarbonate (PC) as binder and 5 wt% of Fe₃O₄, Fe₂O₃, or CuO nanoparticles, were prepared by melt extrusion in a twin screw extruder followed by compression molding. Transmission electron microscopic (TEM) images showed a better dispersion for the PC/Fe₃O₄ nanocomposite compared with that of the other nanocomposites. The dynamic intersection frequency (ω_c), which is related to the crossing of the G′ and G^″ curves, showed that there was more homogeneity in the PC/Fe₃O₄ and PC/Fe₂O₃ nanocomposites. The curves of saturation magnetization for the three nanocomposites showed that there was a relationship between the magnetic properties and the homogeneity of the nanoparticles studied by rheometry. Because the magnetic strength of PC/Fe₃O₄ was greater than that of the other nanocomposites, it was concluded that not only the intrinsic magnetic property of the filler was an important factor to increase the magnetic property, but also the homogeneity of the filler within the matrix had an important role.     

Microwave absorption properties of 50% SrFe12O19–50% TiO2 nanocomposites with porosity

SrFe₁₂O₁₉–TiO₂ nanocomposites are usually used for absorbing microwaves in military and civil applications. In this work, microwave absorption properties of porous SrFe₁₂O₁₉ nanocomposites with 50% weight ratio of TiO₂ have been investigated. 50% TiO₂–50% SrFe₁₂O₁₉ nanocomposites were prepared by a controlled hydrolysis of titanium tetraisopropoxide in which SrFe₁₂O₁₉ nanoparticles were synthesized by a sol–gel auto combustion route. The morphology, crystalline structure and crystallite size of SrFe₁₂O₁₉–TiO₂ nanocomposites were characterized by field emission scanning electron microscopy and X-ray powder diffraction. The magnetic measurements were carried out with a vibrating sample magnetometer. The microwave absorption was measured by a Vector Network Analyzer. The microwave absorption results indicated that the reflection losses for specimens with 52%–56% porosity and thicknesses of 1.8, 2.1 and 2.6 mm were not very low but minimum reflection loss for a specimen with 4.2 mm thickness reached upto −33 dB.     

Silane treatment of Fe3O4 and its effect on the magnetic and wear properties of Fe3O4/epoxy nanocomposites

In this study, the effect of silane treatment of Fe₃O₄ on the magnetic and wear properties of Fe₃O₄/epoxy nanocomposites was investigated. Fe₃O₄ nanopowders were prepared by coprecipitation of iron(II) chloride tetrahydrate with iron(III) chloride hexahydrate, and the surfaces of Fe₃O₄ were modified with 3-aminopropyltriethoxysilane. The magnetic properties of the powders were measured on unmodified and surface-modified Fe₃O₄/epoxy nanocomposites using SQUID magnetometer. Wear tests were performed on unmodified and surface-modified Fe₃O₄/epoxy nanocomposites under the same conditions (sliding speed: 0.18 m/s, load: 20 N).The results showed that the saturation magnetization (M_s) of surface-modified Fe₃O₄/epoxy nanocomposites was approximately 110% greater than that of unmodified Fe₃O₄/epoxy nanocomposites. This showed that the specific wear rate of surface-modified Fe₃O₄/epoxy nanocomposites was lower than that of unmodified Fe₃O₄/epoxy nanocomposites. The decrease in wear rate and the increase in magnetic properties of surface-modified Fe₃O₄/epoxy nanocomposites occurred due to the improved dispersion of Fe₃O₄ into the epoxy matrix.     

Sonochemical fabrication of gold nanoparticles–boron nitride sheets nanocomposites for enzymeless hydrogen peroxide detection

A simple sonochemical route was developed for the preparation of gold nanoparticles/boron nitride sheets (AuNPs/BNS) nanocomposites without using reducing or stabilizing agents. Transmission electron microscopy, scanning electron microscopy, X-ray diffraction, and UV–vis absorption spectra were used to characterize the structure and morphology of the nanocomposites. The experimental results showed that AuNPs with approximately 20 nm were uniformly attached onto the BNS surface. It was found that the AuNPs/BNS nanocomposites exhibited good catalytic activity for the reduction of H₂O₂. The modified electrochemical sensor showed a linear range from 0.04 to 50 mM with a detection limit of 8.3 μM at a signal-to-noise ratio of 3. The findings provide a low-cost approach to the production of stable aqueous dispersions of nanoparticles/BNS nanocomposites.     

Effects of gas saturation and sparging on sonochemical oxidation activity in open and closed systems,Part I: H2O2 generation

Cavitational/sonochemical activity can be significantly enhanced or reduced depending on the gases dissolved in the liquid. Although many researchers have suggested the order of importance of dissolved gas conditions that affect the degree of sonoluminescence (SL), sonochemiluminescence (SCL), and compound degradation, the most suitable gas condition for sonochemical oxidation reactions is currently unknown. In this study (Part I), the effects of gas saturation and sparging on the generation of H₂O₂ were investigated in a 28-kHz sonoreactor system. Four gas modes, saturation/closed, saturation/open, sparging/closed, and sparging/open, were applied to Ar, O₂, N₂, and binary gas mixtures. The change in dissolved oxygen (DO) concentration during ultrasonic irradiation was measured and was used as an indicator of whether the gaseous exchange between liquid and air altered the gas content of the liquid. Considerable difference in the DO concentration was observed for the gas saturation/open mode, ranging from –11.5 mg/L (O₂ 100 %) to +4.3 mg/L (N₂ 100 %), while no significant difference was observed in the other gas modes. The change in the gas content significantly reduced the linearity for H₂O₂ generation, which followed pseudo-zero-order kinetics, and either positively or negatively affected H₂O₂ generation. Ar:O₂ (75:25) and Ar:O₂ (50:50) resulted in the highest and second-highest H₂O₂ generation for both gas saturation and sparging, respectively. In addition, gas sparging resulted in much higher H₂O₂ generation for all gas conditions compared to gas saturation; this was because of the significant change in the cavitational active zone and concentrated ultrasonic energy, which formed a bulb-shaped active zone, especially for the Ar/O₂ mixtures adjacent to the transducer at the bottom. The sparging flow rate and position also significantly affected H₂O₂ generation; the highest H₂O₂ generation was obtained when the sparger was placed at the bottom adjacent to the transducer, with a flow rate of 3 L/min.In Part II, the generation of nitrogen oxides, including nitrite (NO₂^–) and nitrate (NO₃^–), was investigated using the same ultrasonic system with three gas modes: saturation/open, saturation/closed, and sparging/closed.     

Transport properties and battery discharge characteristics of the Ag+ ion conducting composite electrolyte system (1−x)[0.75AgI: 0.25AgCl]: xFe2O3

Ion transport and battery discharge characteristic studies are reported for a new Ag⁺ ion conducting two-phase composite electrolyte system (1−x)[0.75AgI: 0.25AgCl]: xFe₂O₃, where 0 ≤ x ≤ 0.5 in molar weight fraction. An alternative single-phase host-matrix ‘annealed [0.75AgI: 0.25AgCl] mixed system/ solid solution’ has been used in place of the traditional host, AgI. Submicron size particles (<1 μm) of Fe₂O₃ has been used as second phase dispersoid. The composition 0.8[0.75AgI: 0.25AgCl]: 0.2Fe₂O₃, exhibiting the highest room temperature conductivity has been referred to as the optimum conducting composition (OCC). The reason for an enhancement of an order of magnitude in the conductivity from that of the pure host has been identified through direct determination of ionic mobility (μ) and mobile ion concentration (n) using transient ionic current (TIC) technique. The XRD study confirmed the coexistence of the constituent phases. The ionic transference number is found to be very close to unity. This reveals the fact that the silver ions are the sole charge carriers in the system. The results are discussed in the light of space-charge models proposed for the two-phase composite electrolyte systems. Solid state batteries, fabricated using OCC as electrolyte, Ag-metal as anode and mixtures of iodine & graphite, viz. (C+I₂), (C+KI₃), (C+(CH₃)₄NI₃), (C+(C₂H₅)₄NI₃), etc. as cathodes, were discharged under different load conditions. The battery with (C+I₂) cathode performed satisfactorily specially under low current drain states. Paper presented at the 2nd International Conference on Ionic Devices, Anna University, Chennai, India, Nov. 28–30, 2003.