Room temperature in situ chemical synthesis of Fe3O4/graphene

A simple, cost-effective, efficient, and green approach to synthesize iron oxide/graphene (Fe₃O₄/rGO) nanocomposite using in situ deposition of Fe₃O₄ nanoparticles on reduced graphene oxide (rGO) sheets is reported. In the redox reaction, the oxidation state of iron(II) is increased to iron(III) while the graphene oxide (GO) is reduced to rGO. The GO peak is not observed in the X-ray diffraction (XRD) pattern of the nanocomposite, thus providing evidence for the reduction of the GO. The XRD spectra do have peaks that can be attributed to cubic Fe₃O_4. The field emission scanning electron microscopy (FESEM) images show Fe₃O₄ nanoparticles uniformly decorating rGO sheets. At a low concentration of Fe²⁺, there is a significant increase in the intensity of the FESEM images of the resulting rGO sheets. Elemental mapping using energy dispersive X-ray (EDX) analysis shows that these areas have a significant Fe concentration, but no morphological structure could be identified in the image. When the concentration of Fe²⁺ is increased, the Fe₃O₄ nanoparticles are formed on the rGO sheets. Separation of the Fe₃O₄/rGO nanocomposite from the solution could be achieved by applying an external magnetic field, thus demonstrating the magnetic properties of the nanocomposite. The Fe₃O₄ particle size, magnetic properties, and dispersibility of the nanocomposite could be altered by adjusting the weight ratio of GO to Fe²⁺ in the starting material.     

Chemical Synthesis of Monodisperse Magnetic Nanoparticles for Sensitive Cancer Detection

This short tutorial review highlights the advance in high temperature solution phase chemical synthesis of monodisperse magnetic nanoparticles (MNPs), especially iron oxide NPs, as contrast enhancement agents for cancer detection by magnetic resonance imaging (MRI). It introduces briefly the unique nanomagnetism of MNPs required for MRI. It then summarizes some typical methods used to prepare monodisperse Fe₃O₄ and ferrite MFe₂O₄ MNPs from high temperature organic phase reaction with controlled magnetic properties. It further outlines the chemistry used to make these MNPs biocompatible and target-specific. Finally it presents two examples to demonstrate the MNP control achieved from chemical synthesis for sensitive detection of cancer.     

Amperometric tyrosinase biosensor based on Fe3O4 nanoparticles-coated carbon nanotubes nanocomposite for rapid detection of coliforms

A tyrosinase (Tyr) biosensor was developed based on Fe₃O₄ magnetic nanoparticles (MNPs)-coated carbon nanotubes (CNTs) nanocomposite and further applied to detect the concentration of coliforms with flow injection assay (FIA) system. Negatively charged MNPs were absorbed onto the surface of CNTs which were wrapped with cationic polyelectrolyte poly(dimethyldiallylammonium chloride) (PDDA). The Fe₃O₄ MNPs-coated CNTs nanocomposite was modified on the surface of the glassy carbon electrode (GCE), and Tyr was loaded on the modified electrode by glutaraldehyde. The immobilization matrix provided a good microenvironment for retaining the bioactivity of Tyr, and CNTs incorporated into the nanocomposite led to the improved electrochemical detection of phenol. The Tyr biosensor showed broad linear response of 1.0 × 10⁻⁸-3.9 × 10⁻⁵ M, low detection limit of 5.0 × 10⁻⁹ M and high sensitivity of 516 mA/M for the determination of phenol. Moreover, the biosensor integrated with a FIA system was used to monitor coliforms, represented by Escherichia coli (E. coli). The detection principle was based on determination of phenol which was produced by enzymatic reaction in the E. coli solution. Under the optimal conditions, the current responses obtained in the FIA system were proportional to the concentration of bacteria ranging from 20 to 1 × 10⁵ cfu/mL with detection limit of 10 cfu/mL and the overall assay time of about 4 h. The developed biosensor with the FIA system was well suited for quick and automatic clinical diagnostics and water quality analysis.     

Novel polyurethane rigid foam/organically modified iron oxide nanocomposites

Magnetic polyurethane rigid foam nanocomposites were synthesized by incorporation of surface functionalized iron oxide nanoparticles with 3‐aminopropyltriethoxysilane (APTS). Magnetite nanoparticles (MNPs) and Fe₃O₄@APTS were synthesized via co‐precipitation and sol–gel methods, respectively. The main purpose of the surface modification of MNPs was the formation of hydrogen bond between amino groups of Fe₃O₄@APTS with the urethane groups to improve magnetic and thermal properties of the nanocomposites. The effect of different amounts of Fe₃O₄@APTS on the thermal and magnetic behavior of resultant nanocomposite was investigated and the optimum percentage of nanostructure in foam formulation was defined. POLYM. COMPOS., 38:877–883, 2017. © 2015 Society of Plastics Engineers     

The intercalation of C60-containing PEO into layered MnPS3

This paper reports the synthesis and magnetism of a new polymer-inorganic intercalation nanocomposite based on a C₆₀-containing poly(ethylene oxide) (C₆₀-PEO) into layered MnPS₃, which is characterized by XRD, IR and thermal analyses. The lattice expansion (Δd) of the intercalation nanocomposite is about 9.3 Å indicating the successful intercalation. And the charge balance is maintained by K⁺ ions coordinating with PEO chain of C₆₀-PEO polymer, which come from the pre-intercalation compound Mn_1−xPS₃[K_2x(H₂O)_y]. Magnetic measurements indicate that the intercalation nanocomposite (C₆₀-PEO/MnPS₃) exhibits a magnetic phase transition from paramagnetism to ferrimagnetism at about 40 K. And the distinctive hysteresis of M-H relationship further confirms that it is a low temperature ferrimagnetic nanocomposite.     

Preparation of electrospun magnetic polyvinyl butyral/Fe2O3 nanofibrous membranes for effective removal of iron ions from groundwater

Removing iron ions from groundwater to purify, it is a challenge faced by countries across the globe, which is why developing polymeric microfiltration membranes has garnered much attention. The authors of this study set out to develop nanofibrous membranes by embedding magnetic Fe₂O₃ nanoparticles (MNPs) into polyvinylbutyral (PVB) nanofibers via the electrospinning process. Investigation was made into the effects of the concentration of the PVB and MNPs on the morphology of the nanofibers, their magnetic properties, and capacity for filtration to remove iron ions. The fabrication and presence of well-incorporated MNPs in the PVB nanofibers were confirmed by scanning electron microscopy and transmission electron microscopy. Depending on the concentration of the MNPs, the membranes exhibited magnetization to the extent of 45.5 emu g⁻¹; hence, they exceeded the performance of related nanofibrous membranes in the literature. The magnetic membranes possessed significantly higher efficiency for filtration compared to their nonmagnetic analogues, revealing their potential for groundwater treatment applications.     

Establishment of a method to determine the magnetic particles in mouse tissues

This work is aimed to evaluate a method to detect the residual magnetic nanoparticles (MNPs) in animal tissues. Ferric ions released from MNPs through acidification with hydrochloric acid can be measured by complexation with potassium thiocyanate. MNPs in saline could be well detected by this chemical colorimetric method, whereas the detected sensitivity decreased significantly when MNPs were mixed with mouse tissue homogenates. In order to check the MNPs in animal tissues accurately, three improvements have been made. Firstly, proteinase K was used to digest the proteins that might bind with iron, and secondly, ferrosoferric oxide (Fe₃O₄) was collected by a magnetic field which could capture MNPs and leave the bio-iron in the supernatant. Finally, the collected MNPs were carbonized in the muffle furnace at 420°C before acidification to ruin the groups that might bind with ferric ions such as porphyrin. Using this method, MNPs in animal tissues could be well measured while avoiding the disturbance of endogenous iron and iron-binding groups.     

Highly stable mesoporous CeO2/CeS2 nanocomposite as electrode material with improved supercapacitor electrochemical performance

The performance of a pseudocapacitor electrode relies largely on the conductivity, cyclic stability, specific surface area and the mesoporosity of the nanomaterials. The CeO₂ is highly stable oxide but poor conductor, on the other hand, CeS₂ is highly conductive but its stability is questionable. Herein, we report the synthesis of CeO₂/CeS₂ nanocomposite, and exploit the properties of both the constituent materials and demonstrates that CeO₂/CeS₂ nanocomposite electrode exhibits an improved capacitance and energy density than CeO₂ nanomaterial. It encompasses large number of pores with a mean size of ～17?nm. The mesoporous nature of the CeO₂/CeS₂ nanocomposite electrode increases its activity, rapid diffusion and transportation of ions and facilitates surface-dependent reversible redox reactions. The nanocomposite electrode demonstrates high stability and its specific capacitance increases almost linearly up to 1000 cyclic voltammetry (CV) cycles. At a current density of 1?A/g it achieves a specific capacitance of 420?F/g. These findings evidently suggest the practical use of CeO₂/CeS₂ nanocomposite as electrode material for future supercapacitors.     

Self-propagating high-temperature synthesis of advanced ceramics MoSi2–HfB2–MoB

This study focuses on the investigation of the macrokinetic features of SHS (combustion synthesis) of elemental mixtures Mo–Hf–Si–B, in particular the mechanisms of structure and phase formation in the combustion front as well as the structure and properties of consolidated ceramics. Two routes for the fabrication of the composite SHS powder in system MoSi₂–HfB₂–MoB were used: (1) synthesis using Mo–Si–B and Hf–B mixtures followed by mixing of the combustion products and (2) synthesis using the four-component Mo–Hf–Si–B mixture. Dense ceramic samples with a homogeneous structure and low residual porosity (0.8–3.6%) were prepared by hot pressing of SHS powders. Although the particles size distribution and phase composition of SHS powders are similar for both synthesis routes, the structure and properties of both the composite SHS powders and hot-pressed ceramics differ considerably. Synthesis using the four-component Mo–Hf–Si–B mixture allows one to produce hierarchically ordered nanocomposite material with improved mechanical properties: hardness up to 17.6?GPa and fracture toughness up to 7.16?MPa?m^1/2.     

A comparative study of NiO-Ce0.9Gd0.1O1.95 nanocomposite powders synthesized by hydroxide and oxalate co-precipitation methods

In this study, NiO-Ce_0.9Gd_0.1O_1.95 (NiO-GDC) nanocomposite powders, which were applied as anode materials of low temperature solid oxide fuel cells (SOFCs), were synthesized by hydroxide and oxalate reverse co-precipitation methods, respectively. The crystal phases, crystallite size, particle size, particle size distribution, and sintering characteristics of the synthesized NiO-GDC nanocomposite powders were investigated and compared. Results showed that the different co-precipitation methods affected strongly the synthesis and characteristics of the NiO-GDC nanocomposite powders. The NiO-GDC nanocomposite powders could be synthesized at lower temperature by the hydroxide reverse co-precipitation method, and the synthesized NiO-GDC nanocomposite powders had better sinterability. The NiO-GDC nanocomposite powders synthesized by the oxalate reverse co-precipitation method had smaller particle size and uniform particle size distribution and, however, were easy to result in crack formation in the sintered disks.     

ZrO2/聚甲基丙烯酸甲酯纳米复合物:制备及其在聚合物阵列中的分散（英文）

ZrO2/PMMA nanocomposite particles are synthesized through an in-situ free radical emulsion polymerization based on the silane coupling agent (Z-6030) modified ZrO2 nanoparticles, and the morphology, size and its distribution of nanocomposite particles are investigated. Scanning electron microscopy (SEM) images demonstrate that the methyl methacrylate (MMA) feeding rate has a significant effect on the particle size and morphology. When the MMA feeding rate decreases from 0.42ml·min-1 to 0.08ml·min-1 , large particles (about 200-550nm) will not form, and the size distribution become narrow (36-54nm). The average nanocomposite particles size increases from 34nm to 55nm, as the MMA/ZrO2 nanoparticles mass ratio increased from 4:1 to 16:1. Regular spherical ZrO2/PMMA nanocomposite particles are synthesized when the emulsifier OP-10 concentration is 2mg·ml-1. The nanocomposite particles could be mixed with VAc-VeoVa10 polymer matrix just by magnetic stirring to prepare the ZrO2 /PMMA/VAc-VeoVa10 hybrid coatings. SEM and atomic force microscopy (AFM) photos reveal that the distribution of the ZrO2 /PMMA nanocomposite particles in the VAc-VeoVa10 polymer matrix is homogenous and stable. Here, the grafted-PMMA polymer on ZrO2 nanoparticles plays as a bridge which effectively connects the ZrO2 nanoparticles and the VAc-VeoVa10 polymer matrix with improved comparability. In consequence, the hybrid coating with good dispersion stability is obtained.     

Multifunctional liposomal drug delivery with dual probes of magnetic resonance and fluorescence imaging

Many liposomal drug carriers have shown great promise in the clinic. To ensure the efficient preclinical development of drug-loaded liposomes, the drug retention and circulation properties of these systems should be characterized. Iron oxide (Fe₃O₄) magnetic nanoparticles (MNPs) are used as T2 contrast agents in magnetic resonance imaging (MRI). Gold nanoclusters (GNCs) contain tens of atoms with subnanometer dimensions; they have very low cytotoxicity and possess superb red emitting fluorescent properties, which prevents in vivo background autofluorescence. The aim of this study was to develop dual imaging, nanocomposite, multifunctional liposome drug carriers (Fe₃O₄-GNCs) comprising MNPs of iron oxide and GNCs. First, MNPs of iron oxide were synthesized by co-precipitation. The MNP surfaces were modified with amine groups using 3-aminopropyltriethoxysilane (APTES). Second, GNCs were synthesized by reducing HAuCl₄·3H₂O with NaBH4 in the presence of lipoic acid (as a stabilizer and nanosynthetic template). The GNCs were grown by adsorption onto particles to control the size and stability of the resultant colloids. Subsequently, dual Fe₃O₄-GNCs imaging probes were fabricated by conjugating the iron oxide MNPs with the GNCs via amide bonds. Finally, liposome nanocarriers were used to enclose the Fe₃O₄-GNCs in an inner phase (liposome@Fe₃O₄-GNCs) by reverse phase evaporation. These nanocarriers were characterized by dynamic light scattering (DLS), fluorescence spectroscopy, X-ray diffraction (XRD), transmission electron microscopy (TEM), Fourier transform infrared (FT-IR) spectrophotometry, superconducting quantum interference device (SQUID), nuclear magnetic resonance (NMR) imaging and in vivo imaging systems (IVIS). These multifunctional liposomal drug delivery systems with dual probes are expected to prove useful in preclinical trials for cancer diagnosis and therapy.     

Toughening of MgAl2O4 spinel/ Si3N4 nanocomposite fabricated by spark plasma sintering

The main objective of this work is to compare the hardness, fracture toughness, and optical transparency of MgAl₂O₄ spinel (magnesium aluminate), MgAl₂O₄ spinel/ Si₃N₄ nanocomposite, and the heat-treated spinel/Si₃N₄ nanocomposite. For this purpose, the commercial spinel nanopowder and the laboratory-made spinel/ Si₃N₄ nanocomposite powder were sintered using spark plasma sintering (SPS). A heat treatment at 1000?°C for 4?h was carried out on the as-sintered nanocomposite. The field emission scanning electron microscopy (FESEM), Energy dispersive X-ray (EDX) mapping, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Nanoindentation, and Vickers microhardness analyses were used to determine microstructure, elemental analysis, functional group, hardness, and indentation toughness of the samples. The results showed that the hardness and toughness of the heat-treated sample are more than those of the as-SPSed nanocomposite as much as 15.7% and 25.7%, respectively. Also, the values of optical transmission of the nanocomposite sample in the visible range (400–800?nm) and infrared region (800–2000?nm) were lower than those of pure spinel.     

Synthesis of magnetic citric‐acid‐functionalized graphene oxide and its application in the removal of methylene blue from contaminated water

A magnetic nanocomposite of citric‐acid‐functionalized graphene oxide was prepared by an easy method. First, citric acid (CA) was covalently attached to acyl‐chloride‐functionalized graphene oxide (GO). Then, Fe₃O₄ magnetic nanoparticles (MNPs) were chemically deposited onto the resulting adsorbent. CA, as a good stabilizer for MNPs, was covalently attached to the GO; thus MNPs were adsorbed much more strongly to this framework and subsequent leaching decreased and less agglomeration occurred. The attachment of CA onto GO and the formation of the hybrid were confirmed by Fourier transform infrared spectroscopy, scanning electron microscopy, X‐ray diffraction spectrometry and transmission electron microscopy. The specific saturation magnetization of the magnetic CA‐grafted GO (GO‐CA‐Fe₃O₄) was 57.8 emu g^?1 and the average size of the nanoparticles was found to be 25 nm by transmission electron microscopy. The magnetic nanocomposite was employed as an adsorbent of methylene blue from contaminated water. The adsorption tests demonstrated that it took only 30 min to attain equilibrium. The adsorption capacity in the concentration range studied was 112 mg g^?1. The GO‐CA‐Fe₃O₄ nanocomposite was easily manipulated in an external magnetic field which eases the separation and leads to the removal of dyes. Thus the prepared nanocomposite has great potential in removing organic dyes. © 2014 Society of Chemical Industry     

Preparation and characterization of magnetic γ-Al2O3 ceramic nanocomposite particles with variable Fe3O4 content and modification with epoxide functional polymer

Porous γ-alumina (γ-Al₂O₃) is one of widely used ceramic materials. To maximize the application potentials attempt was made to prepare multifunctional γ-Al₂O₃ ceramic composite particles following magnetization and then seeded polymerization with epoxide functional glycidyl methacrylate (GMA). γ-Al₂O₃ particles were first prepared by a modified sol-gel approach and then doped with variable content Fe₃O₄ nanoparticles. At higher Fe₃O₄ content the magnetite nanoparticles were oriented into needle like hairy structure basically grown from the surface of γ-Al₂O₃ particles. Before the seeded polymerization the magnetic γ-Al₂O₃ particles were modified with SiO₂ layer to improve the compatibility with the PGMA layer. The produced multifunctional ceramic particles were named as γ-Al₂O₃/Fe₃O₄/SiO₂/PGMA nanocomposite because one of the phases constituting Fe₃O₄ was in nano-size range. The produced nanocomposite particles possessed superparamagnetic properties and could be isolated from the dispersion medium by external magnetic field. Fourier Transform IR (FTIR) and X-ray photoelectron spectroscopic (XPS) data revealed that final nanocomposite particles contained reactive epoxide groups on or near the surface. The produced multifunctional γ-Al₂O₃ ceramic nanocomposite particles can be useful in biotechnology, catalysis and adsorbents for pollutant removal.     

Exploiting Size-Dependent Drag and Magnetic Forces for Size-Specific Separation of Magnetic Nanoparticles

Realizing the full potential of magnetic nanoparticles (MNPs) in nanomedicine requires the optimization of their physical and chemical properties. Elucidation of the effects of these properties on clinical diagnostic or therapeutic properties, however, requires the synthesis or purification of homogenous samples, which has proved to be difficult. While initial simulations indicated that size-selective separation could be achieved by flowing magnetic nanoparticles through a magnetic field, subsequent in vitro experiments were unable to reproduce the predicted results. Magnetic field-flow fractionation, however, was found to be an effective method for the separation of polydisperse suspensions of iron oxide nanoparticles with diameters greater than 20 nm. While similar methods have been used to separate magnetic nanoparticles before, no previous work has been done with magnetic nanoparticles between 20 and 200 nm. Both transmission electron microscopy (TEM) and dynamic light scattering (DLS) analysis were used to confirm the size of the MNPs. Further development of this work could lead to MNPs with the narrow size distributions necessary for their in vitro and in vivo optimization.     

Synthesis and characterization of novel type poly (4-chloromethyl styrene-grft-4-vinylpyridine)/TiO2 nanocomposite via nitroxide-mediated radical polymerization

This paper describes the synthesis and characterization of novel type poly (4-chloromethyl styrene-graft-4-vinylpyridine)/TiO₂ nanocomposite. Firstly, poly (4-chloromethyl styrene)/TiO₂ nanocomposite was synthesized by in situ free radical polymerizing of 4-chloromethyl styrene monomers in the presence of 3-(trimethoxysilyl) propylmethacrylate (MPS) modified nano-TiO₂. Thereafter, 1-hydroxy-2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO-OH) was synthesized by the reduction of 2,2,6,6-tetramethyl-1-piperidinyloxy (TEMPO). This functional nitroxyl compound was covalently attached to the poly (4-chloromethyl styrene)/TiO₂ with replacement of chlorine atoms in the poly (4-chloromethyl styrene) chains. The controlled graft copolymerization of 4-vinylpyridine was initiated by poly (4-chloromethyl styrene)/TiO₂ nanocomposite carrying TEMPO groups as a macroinitiators. The coupling of TEMPO with poly (4-chloromethyl styrene)/TiO₂ was verified using ¹H nuclear magnetic resonance (NMR) spectroscopy. The obtained nanocomposites were studied using transmission electron microscopy (TEM), Fourier-transform infrared (FTIR) spectra, thermogravimetric analysis (TGA), differential scanning calorimetry (DSC) and the optical properties of the nanocomposites were studied using ultraviolet-visible (UV-Vis) spectroscopy.     

Crystal structure and molecular packing of an asymmetric giant amphiphile constructed by one C60 and two POSSs

Based on our recent understanding and development of functionalized molecular nanoparticles (MNPs) as building blocks for constructing various giant molecules, we report our efforts on design and synthesis of an asymmetric giant amphiphile, diBPOSS–C₆₀, composed of one [60]fullerene (C₆₀) covalently linked with two isobutyl-functionalized polyhedral oligomeric silsesquioxane (BPOSS) MNPs. Its crystal structure and molecular packing were investigated. The compositional asymmetry between C₆₀ and BPOSS led to a “sandwich-layered” molecular packing scheme, where a single layer of C₆₀ is sandwiched between double BPOSS layers: a so-called “one-and-half-layered” structure. Within these layers, the molecules further organized into crystalline arrays. Interestingly, this compound can be viewed as size amplification of a class of atomically thin, two-dimensional layered transition metal dichalcogenides with the “one-and-half-layered” structure.     

Fabrication of highly sensitive MnO2/F-MWCNT/Ta hybrid nanocomposite sensor with different MnO2 overlayer thickness for H2O2 detection

In this work, we report the development of MnO₂/F-MWCNT/Ta hybrid nanocomposite sensor with different MnO₂ overlayer thickness for the detection of H₂O₂ in real samples. A novel two-step process using e-beam evaporation and spray pyrolysis deposition was adopted for the synthesis of hybrid MnO₂/F-MWCNT/Ta electrodes. SE morphology revealed smaller-sized, compact grains of MnO₂ infiltrated on the outermost walls of MWCNTs. Raman analysis confirmed the existence of carbon nanotubes with abundant structural defects of MnO₂ in the composite. The cyclic voltammetry results displayed a high peak current and narrowed over potential towards the reduction of H₂O₂. The sensor displayed a fast response (<5?s), wide linear range (2–1510?μM) and a low limit of detection (0.04?μM) with significant anti-interfering properties, promising for the development of highly sensitive and reproducible biosensors. The three dimensional nanocomposite sensor also exhibited good recovery (> 98%), thus providing a favourable tool for analysis of H₂O₂ in milk samples.     

Microstructural, electrical and magnetic properties of multiferroic CoFe2O4/0.68Pb(Mg1/3Nb2/3)O3-0.32PbTiO3 nanocomposite thin films

Bilayered CoFe₂O₄/0.68Pb(Mg_1/3Nb_2/3)O₃-0.32PbTiO₃ nanocomposite films are successfully prepared on Pt/Ti/SiO₂/Si substrate via simple sol-gel process. X-ray diffraction result reveals that there exists no chemical reaction or phase diffusion between the CoFe₂O₄ and 0.68Pb(Mg_1/3Nb_2/3)O₃-0.32PbTiO₃ phases. The microstructure is characterized by scanning/transmission electron microscopy (STEM). The composite thin films exhibit both strong ferroelectric and ferromagnetic responses at room temperature. The maximal magnetoelectric coupling coefficient of the nanocomposite films reaches up to 25 mV/cm Oe, occurs at a lower bias magnetic field (H_dc) of 550 Oe.