Magnetoresistive polyaniline-magnetite nanocomposites with negative dielectrical properties

Tumor necrosis factor-alpha antibody labeled-polyethylene glycol-coated nanoparticles: A mesenchymal stem cells-based drug delivery system in the rat model of cisplatin-induced nephrotoxicity

Background and Aim: A delivery system consisting of bone marrow mesenchymal stem cells (MSCs) loaded with polyethylene glycol (PEG) coated superparamagnetic iron oxide nanoparticles (SPIONs) was constructed to treat a rat model of cisplatin (Cis)-induced nephrotoxicity with 1/10 of the common dose of anti-tumor necrosis factor-alpha (TNF-α) antibodies (infliximab). Materials and Methods: Morphology, size, crystallinity, molecular structure, and magnetic properties of uncoated and PEG-coated SPIONs were analyzed. A delivery system consisting of MSCs containing infliximab-labeled PEG-coated SPIONs (Infliximab-PEG-SPIONs-MSCs) was generated and optimized before treatment. Fifty female Wistar rats were divided into five equal groups: Group 1: Untreated control; Group 2 (Cis): Rats were administered Cis through intraperitoneal (i.p.) injection (8 mg/kg) once a week for 4 weeks; Group 3 (Infliximab): Rats were injected once with infliximab (5 mg/kg), i.p. 3 days before Cis administration; Group 4 (Cis + MSCs): Rats were injected with Cis followed by an injection of 2 × 106 MSCs into the tail vein twice at a 1-week interval; and Group 5 (Cis + Infliximab (500 μg/kg)-PEG-SPIONs-MSCs): Rats were injected with the delivery system into the tail vein twice at a 1-week interval. Besides histological examination of the kidney, the Doppler ultrasound scanner was used to scan the kidney with the Gray-color-spectral mode. Results: In vivo, intra-renal iron uptake indicates the traffic of the delivery system from venous blood to renal tissues. Cis-induced nephrotoxicity resulted in a significant increase in TNF-α and malondialdehyde (MDA) (p < 0.05), bilirubin, creatinine, and uric acid (p < 0.01) levels compared with the untreated control group. The different treatments used in this study resulted in the amelioration of some renal parameters. However, TNF-α levels significantly decreased in Cis + Infliximab and Cis + MSCs (p < 0.05) groups. The serum levels of MDA significantly decreased in Cis + Infliximab (p < 0.05), Cis + MSCs (p < 0.05), and Cis + Infliximab-PEG-SPIONs-MSCs (p < 0.01). Furthermore, the serum activities of antioxidant enzymes were significantly elevated in the Cis + MSCs and Cis + Infliximab-PEG-SPIONs-MSCs groups (p < 0.05) compared to the Cis-induced nephrotoxicity rat model. Conclusion: With the support of the constructed MSCs-SPIONs infliximab delivery system, it will be possible to track and monitor cell homing after therapeutic application. This infliximab-loading system may help overcome some challenges regarding drug delivery to the target organ, optimize therapeutics' efficacy, and reduce the dose. The outcomes of the current study provide a better understanding of the potential of combining MSCs and antibodies-linked nanoparticles for the treatment of nephrotoxicity. However, further investigation is recommended using different types of other drugs. For new approaches development, we should evaluate whether existing toxicity analysis and risk evaluation strategies are reliable and enough for the variety and complexity of nanoparticles.

Enhancement of Electrochemical Detection of Gluten with Surface Modification Based on Molecularly Imprinted Polymers Combined with Superparamagnetic Iron Oxide Nanoparticles

Novel molecularly imprinted polymers (MIPs) represent a selectively recognized technique for electrochemical detection design. This rapid and simple method prepared via chemical synthesis consists of a monomer crosslinked with an initiator, whereas low sensitivity remains a drawback. Nanomaterials can improve charge transfer for MIP surface modification in order to overcome this problem. SPIONs have semiconductor and superparamagnetic properties that can enhance carrier mobility, causing high sensitivity of electrochemical detection. In this work, surface modification was achieved with a combination of MIP and SPIONs for gluten detection. The SPIONs were synthesized via the chemical co-precipitation method and mixed with MIPs by polymerizing gluten and methyl methacrylate (MMA), presented as a template and a monomer. Magnetic MIP (MMIP) was modified on a carbon-plate electrode. The morphology of modified electrode surfaces was determined by scanning electron microscopy-energy-dispersive X-ray spectrometry. The performance of the MMIP electrode was confirmed by cyclic voltammetry, amperometry, and electrochemical impedance spectroscopy. The MMIP electrode for gluten detection shows a dynamic linear range of 5-50 ppm, with a correlation coefficient of 0.994 and a low detection limit of 1.50 ppm, which is less than the U.S. Food and Drug Administration requirements (20 ppm); moreover, it exhibits excellent selectivity, sensitivity, stability, and reproducibility.

MWCNT Decorated Rich N-Doped Porous Carbon with Tunable Porosity for CO2 Capture

Designing of porous carbon system for CO2 uptake has attracted a plenty of interest due to the ever-increasing concerns about climate change and global warming. Herein, a novel N rich porous carbon is prepared by in-situ chemical oxidation polyaniline (PANI) on a surface of multi-walled carbon nanotubes (MWCNTs), and then activated with KOH. The porosity of such carbon materials can be tuned by rational introduction of MWCNTs, adjusting the amount of KOH, and controlling the pyrolysis temperature. The obtained M/P-0.1-600-2 adsorbent possesses a high surface area of 1017 m2 g-1 and a high N content of 3.11 at%. Such M/P-0.1-600-2 adsorbent delivers an enhanced CO2 capture capability of 2.63 mmol g-1 at 298.15 K and five bars, which is 14 times higher than that of pristine MWCNTs (0.18 mmol g-1). In addition, such M/P-0.1-600-2 adsorbent performs with a good stability, with almost no decay in a successive five adsorption-desorption cycles.

Magnetic Nanocomposite Hydrogels for Tissue Engineering: Design Concepts and Remote Actuation Strategies to Control Cell Fate

Most tissues of the human body are characterized by highly anisotropic physical properties and biological organization. Hydrogels have been proposed as scaffolding materials to construct artificial tissues due to their water-rich composition, biocompatibility, and tunable properties. However, unmodified hydrogels are typically composed of randomly oriented polymer networks, resulting in homogeneous structures with isotropic properties different from those observed in biological systems. Magnetic materials have been proposed as potential agents to provide hydrogels with the anisotropy required for their use on tissue engineering. Moreover, the intrinsic properties of magnetic nanoparticles enable their use as magnetomechanic remote actuators to control the behavior of the cells encapsulated within the hydrogels under the application of external magnetic fields. In this review, we combine a detailed summary of the main strategies to prepare magnetic nanoparticles showing controlled properties with an analysis of the different approaches available to their incorporation into hydrogels. The application of magnetically responsive nanocomposite hydrogels in the engineering of different tissues is also reviewed.

Experimental and DFT Study of Metal-Free Catalyst for Selective Oxidation of Biomass-Derived Molecule (HMF)

Catalytic conversion of biomass or biomass-derived intermediate to value-added chemicals is important for both biomass waste management and production of industrially important chemicals. Oxidation of 5-hydroximethyl furfural (HMF) is considered one of the most important biomass conversion processes, which resulted in many value-added products such as 2,5-diformylfuran (DFF), 2,5-furandicarboxylic acid (FDCA), 5-hydroxymethyl-2-furancarboxylic acid (HMFCA), and 5-formyl-2-furancarboxylic acid (FFCA). In this study, the three morphologies of CdS catalyst (nanorod, nanosheet, and nanosphere) with two different crystalline structures are synthesized and characterized by SEM, TEM, and XRD analysis. The oxidation of HMF to FFCA is performed using the synthesized catalysts in the presence of different solvents and oxidizing agents. We find that CdS nanorod provides the selective oxidation of HMF to FFCA in the presence of dimethyl sulfoxide solvent and tert-butyl hydrogen peroxide oxidizing agent. The density functional theory (DFT) simulations are carried out to explain the catalytic activity of the CdS catalyst for oxidation of HMF to FFCA. The DFT simulations show that CdS is an excellent catalyst for binding HMF on the CdS surface. Our findings provide the way of effective oxidation of biomass into value-added products using the cheap CdS catalyst.

Cubic Anisotropic Co- and Zn-Substituted Ferrite Nanoparticles as Multimodal Magnetic Agents

The use of magnetic nanoparticles as theranostic agents for the detection and treatment of cancer diseases has been extensively analyzed in the last few years. In this work, cubic-shaped cobalt and zinc-doped iron oxide nanoparticles with edge lengths in the range from 28 to 94 nm are proposed as negative contrast agents for magnetic resonance imaging and to generate localized heat by magnetic hyperthermia, obtaining high values of transverse relaxation coefficients and specific adsorption rates. The applied magnetic fields presented suitable characteristics for the potential validation of the results into the clinical practice in all cases. Pure iron oxide and cobalt- and zinc-substituted ferrites have been structurally and magnetically characterized, observing magnetite as the predominant phase and weak ferrimagnetic behavior at room temperature, with saturation values even larger than those of bulk magnetite. The coercive force increased due to the incorporation of cobalt ions, while zinc substitution promotes a significant increase in saturation magnetization. After their transfer to aqueous solution, those particles showing the best properties were chosen for evaluation in in vitro cell models, exhibiting high critical cytotoxic concentrations and high internalization degrees in several cell lines. The magnetic behavior of the nanocubes after their successful cell internalization was analyzed, detecting negligible variations on their magnetic hysteresis loops and a significant decrease in the specific adsorption rate values.

An optical-magnetic Material as a toxic gas filter and sensing device

The objective of this work is the development of a toxic gas detector/filter based on the production of porous polyaniline composites filled with magnetic nanoparticles. The composite produced was subjected to hydrogen sulfide gas as a preliminary test of its detection and sorption capacity, which were proven by gravimetric analysis. Analysis by light scattering and TEM indicated that magnetic nanoparticles with a size of approximately 5 nm were obtained through the proposed methodology. FTIR spectroscopy, UV-vis spectroscopy, TGA, and DSC were performed to prove the successful synthesis of the composite. To identify the specific properties of each constituent of the composite, the conductivity and magnetic force of the material were determined. The SEM results showed that the morphology was useful for the sorption process with the formation of pores in the polymer matrix, allowing the percolation of the gas for splicing by the nanoparticles. TGA, electrical conductivity, magnetic force, UV-vis spectroscopy, and EDS analyses were also performed after the detection/sorption tests to demonstrate the functioning of the material.

The objective of this work is the development of a toxic gas detector/filter based on the production of porous polyaniline composites filled with magnetic nanoparticles.

AlN-SWCNT Metacomposites Having Tunable Negative Permittivity in Radio and Microwave Frequencies

Discovery of plasmon resonance and negative permittivity in carbon allotropes at much lower frequencies than those of metals has evoked interest to develop random metacomposites by suitable means of addition of these dispersoids in an overall dielectric matrix. Random metacomposites have always the advantage for their easy preparation techniques over those of their regular arrayed artificial counterpart. However, thermal management during the heat generation by electromagnetic attenuation in metamaterials is not yet studied well. The present communication discusses the dielectric permittivities and loss parameters of aluminum nitride-single-wall carbon nanotube (AlN-SWCNT) composites considering high thermal conductivities of both materials. The composites are dense and have been prepared by a standard powder technological method using hot pressing at 1850 °C under a nitrogen atmosphere. Increase in the negative permittivity value with SWCNT concentration (1, 3, and 6 vol %) in the composites had been observed at low frequencies. Characterization of the materials with Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, and microstructure analysis by scanning and transmission electron microscopy (TEM) revealed the survivability of the SWCNTs and the nature of the matrix-filler interface. Plasmonic resonance following Drude's law could be observed at much lower plasma frequencies than that of pure SWCNT and for very little SWCNT addition. Exhibition of the negative permittivity has been explained with relation to the microstructure of the composites observed from field emission scanning electron micrographs (FESEM), TEM images, and the equivalent circuit model. High energy conversion efficiency is expected in these composites due to the possession of dual functionalities like high thermal conductivity as well as high negative permittivity, which should ensure the application of these materials in wave filter, cloaking device, supercapacitors, and wireless communication.

Effects of CaO on the Yield and Thermal Properties of PANI Nanofibers

The control of thermal stability of polyaniline (PANI) nanofibers is reported by systematically varying the loadings of CaO in the range from 0.005 g to 1.0 g. It was found to gradually increase the yield of synthesized PANI nanofibers with the increase of CaO addition. The highest yield, 1.103 g was obtained for 1.00 g loading of CaO. The incorporation of CaO into PANI matrix was revealed by energy-dispersive X-ray spectroscopy (EDX). Thermogravimetric analysis (TGA) data showed that the thermal stability of PANI nanofibers was greatly improved when CaO was added to the system. 1.00 g loading of CaO is favorable to obtain comparatively more thermally stable PANI. The degradation of PANI chains started at 330 °C for the PANI-CaO composites obtained at 1.00 g CaO addition, which is the highest temperature compared to PANI and the samples synthesized at other amount of CaO loadings. Furthermore, the increasing trend of thermal stability was observed with the increasing of CaO loading.

Nondegradable magnetic poly (carbonate urethane) microspheres with good shape memory as a proposed material for vascular embolization

In this study, nondegradable poly (carbonate urethane) (PCU) and poly (carbonate urethane) incorporated variable Fe₃O₄ content microspheres (PCU/Fe₃O₄) were synthesized using pre-polymerization and suspension polymerization. Synthesis was confirmed through Fourier transform infrared spectroscopy (FTIR). The effect of Fe₃O₄ incorporation was investigated on crystalline, thermal, shape memory and degradation properties by X-Ray diffraction (XRD), Differential scanning calorimetery (DSC), compression test and degradation in vitro, respectively. Otherwise, the assessment of magnetic characteristics by vibrational sample magnetometry (VSM) disclosed superparamagnetic behavior. The tunable superparamagnetic behavior depends on the amount of magnetic particles incorporated within the networks. The biological study results of as-synthesized polymers from the platelet adhesion test and the cell proliferation inhibition test indicated they were biocompatible in vitro. Fe₃O₄ incorporation was conductive to reducing platelet adhesion in blood contacting test and promotion of rat vascular smooth muscle cell proliferation and growth. These nondegradable, superparamagnetic, biocompatible polymers, combined with their good shape memory properties may allow for their future exploitation in the biomedical field, such as, in cardiovascular implants, targeted tumor treatment, tissue engineering and artificial organ's engineering.

Salt-Responsive Fe3O4 Nanocomposites and Phase Behavior in Water

The ability to achieve exquisite control over polymer building blocks within multicompartment magnetite nanocomposites (NCs) to afford predictable and ordered packing hierarchical structures remains a significant challenge for the design of NCs. Thus, there is an urgent need to develop new types of nano-dimensional assemblies that undergo responsive shape shift, size, phase, and morphological transitions, especially for processes that are triggered by biologically relevant stimuli such as ionic gradients to meet the demand for diverse applications. Accordingly, we report an unprecedented concept for the preparation of salt-responsive magnetite/polyaniline composite nanoassemblies with chemically distinct dual-compartment structures. The size, shape, and nano-dimensional phase separation of the PANI assemblies within NCs were adjusted in a facile manner with incremental changes in salt gradients using NaCl(aq). Composition effects bestow desirable diversiform shape, size, and phase behavior of the incorporated conductive polymer via dynamic H-bonding. The size, shape, and superparamagnetic character of iron oxide nanoparticles (IONPs) are unaffected by a "salting-in" process. The mechanism, gradual morphological evolution, interchangeable nanophase separation, and ion-stimulated disassembly of PANI building blocks for these magneto/ion-responsive polymer-composites at elevated ionic strength are strongly supported by DLS, Raman spectroscopy, TEM, and equilibrium dye (MB/MO) recognition studies.

3D hierarchical flower-like nickel ferrite/manganese dioxide toward lead (II) removal from aqueous water

A functionalized magnetic nickel ferrite/manganese dioxide (NiFe₂O₄/MnO₂) with 3D hierarchical flower-like and core-shell structure was synthesized by a facile hydrothermal approach and applied for the removal of Pb(II) ions from aqueous solutions. Batch adsorption experiments were conducted to study the effect of solution pH, initial Pb(II) concentration, and dose of absorbents on the Pb(II) removal by NiFe₂O₄/MnO₂. The NiFe₂O₄/MnO₂ nanocomposites showed the fast Pb(II) adsorption performance with the maximum adsorption capacity of 85.78mgg^-1. The adsorption kinetics of Pb(II) onto NiFe₂O₄/MnO₂ obeyed a pseudo-second-order model. The isothermal experimental results indicated that the Langmuir model was fitted better than the Freundlich model, illustrating a monolayer adsorption process for Pb(II) onto NiFe₂O₄/MnO₂. Meanwhile, the NiFe₂O₄/MnO₂ was easily separated from the solution by an external magnet within a short period of time and still exhibited almost 80% removal capacity after six regenerations. The NiFe₂O₄/MnO₂ is expected to be a new promising adsorbent for heavy metal removal.

Removal of elevated level of chromium in groundwater by the fabricated PANI/Fe3O4 nanocomposites

In this work, we report the reduction of chromium concentration in the polluted groundwater samples from Madurai Kamaraj University area, India, where the dissolved salts in groundwater are reported as serious health hazards for its inhabitants. The water samples have intolerable amounts of total dissolved solids (TDS) and chromium is a prominent pollutant among them. Chromium reduction was achieved by treating the polluted groundwater with PANI/Fe₃O₄ nanocomposites synthesized by in situ polymerization method. Further experimentation showed that the nanocomposites exhibit better chromium removal characteristics upon increasing the aniline concentration during the synthesis. We were able to reduce chromium concentration in the samples from 0.295 mg L^-1 to a tolerable amount of 0.144 mg L^-1. This work is expected to open doors for chromium-free groundwater in various regions of India, when improved to an industrial scale.

Preparation and Application of Water-in-Oil Emulsions Stabilized by Modified Graphene Oxide

A series of alkyl chain modified graphene oxides (AmGO) with different alkyl chain length and content was fabricated using a reducing reaction between graphene oxide (GO) and alkyl amine. Then AmGO was used as a graphene-based particle emulsifier to stabilize Pickering emulsion. Compared with the emulsion stabilized by GO, which was oil-in-water type, all the emulsions stabilized by AmGO were water-in-oil type. The effects of alkyl chain length and alkyl chain content on the emulsion properties of AmGO were investigated. The emulsions stabilized by AmGO showed good stability within a wide range of pH (from pH = 1 to pH = 13) and salt concentrations (from 0.1 to 1000 mM). In addition, the application of water-in-oil emulsions stabilized by AmGO was investigated. AmGO/polyaniline nanocomposite (AmGO/PANi) was prepared through an emulsion approach, and its supercapacitor performance was investigated. This research broadens the application of AmGO as a water-in-oil type emulsion stabilizer and in preparing graphene-based functional materials.

Graphene as a nanotemplating auxiliary on the polypyrrole pigment for anticorrosion coatings

In this article, we report on the exceptional application of polypyrrole/graphene composites (Ppy/G) for the corrosion protection of steel. Well-dispersed Ppy/G composites were successfully prepared using in situ solution polymerization. The prepared nanocomposites exhibited superior anticorrosion properties compared with the bare and epoxy, in which the corrosion protection efficiency increased 50–100 times with the Ppy(97)@G(3) pigment. The rheological and dielectric properties of the nanocomposites were superior to those of pure Ppy/epoxy. Ppy(97)@G(3) increased the thermal curing temperature from approximately 100°C to 110°C and considerably decreased the volume resistivity. The substantially improved properties of the nanocomposites were attributed to their high dispersions, which greatly enhanced the corrosion factors and barrier properties.

Electrically conductive strain sensing polyurethane nanocomposites with synergistic carbon nanotubes and graphene bifillers

Thermoplastic polyurethane (TPU) based conductive polymer composites (CPCs) with a reduced percolation threshold and tunable resistance-strain sensing behavior were obtained through the addition of synergistic carbon nanotubes (CNT) and graphene bifillers. The percolation threshold of graphene was about 0.006 vol% when the CNT content was fixed at 0.255 vol% that is below the percolation threshold of CNT/TPU nanocomposites. The synergistic effect between graphene and CNT was identified using the excluded volume theory. Graphene acted as a 'spacer' to separate the entangled CNTs from each other and the CNT bridged the broad gap between individual graphene sheets, which was beneficial for the dispersion of CNT and formation of effective conductive paths, leading to better electrical conductivity at a lower conductive filler content. Compared with the dual-peak response pattern of the CNT/TPU based strain sensors, the CPCs with hybrid conductive fillers displayed single-peak response patterns under small strain, indicating good tunability with the synergistic effect of CNT and graphene. Under larger strain, prestraining was adopted to regulate the conductive network, and better tunable single-peak response patterns were also obtained. The CPCs also showed good reversibility and reproductivity under cyclic extension. This study paves the way for the fabrication of CPC based strain sensors with good tunability.

Significantly enhanced mechanical and electrical properties of epoxy nanocomposites reinforced with low loading of polyaniline nanoparticles

Enhanced mechanical and electrical properties were observed in the polyaniline–epoxy nanocomposites prepared by three different techniques.

Polystyrene controlled growth of zerovalent nanoiron/magnetite on a sponge-like carbon matrix towards effective Cr(vi) removal from polluted water

Epoxide functionalized polystyrene controlled growth of zerovalent nanoiron/magnetite on a sponge-like carbon matrix (nZVI/Fe₃O₄@C) nanocomposites show a unique Cr(vi) removal performance over a wide pH range.

Thermal, mechanical and magnetic properties of functionalized magnetite/vinyl ester nanocomposites

Thiol functionalized magnetite nanoparticles increased the mechanical properties of the polymer matrix while introducing magnetic properties.

The generation mechanism of negative permittivity in multi-walled carbon nanotubes/polyaniline composites

Conductive polymers filled with carbon nanotubes have been proved to have negative permittivity but the mechanism of its strange properties has not been intensively studied.

Synergistic effect of graphene and polypyrrole to enhance the SnO2 anode performance in lithium-ion batteries

The cycling performances for hollow SnO₂ microspheres, core–shell structured hollow SnO₂/21 wt% PPy nanocomposites, hollow SnO₂/21.5 wt% rGO nanocomposites and core–shell structured hollow SnO₂/21.5 wt% rGO/16.5 wt% PPy nanocomposites.

Tunable negative permittivity behavior of random carbon/alumina composites in the radio frequency band

As carbon content increases, the composites undergo a capacitive–inductive transition, and a weakly negative permittivity behavior is observed.

A highly sensitive chlorine gas sensor and enhanced thermal DC electrical conductivity from polypyrrole/silicon carbide nanocomposites

We report the synthesis of polypyrrole (PPy) and polypyrrole/silicon carbide nanocomposites (PPy/SiC) and PPy/SiC/dodecylbenzenesulfonic acid (DBSA) by in situ chemical polymerization and their application as sensors for the detection of highly toxic chlorine gas.

Magnetoresistive polyaniline–silicon carbide metacomposites: plasma frequency determination and high magnetic field sensitivity

Both negative permittivity and high magnetic field resistance sensitivity are observed in silicon carbide/polyaniline nanocomposites.

Improving Electrical Conductivity, Thermal Stability, and Solubility of Polyaniline-Polypyrrole Nanocomposite by Doping with Anionic Spherical Polyelectrolyte Brushes

The extent to which anionic spherical polyelectrolyte brushes (ASPB) as dopant improved the performance of polyaniline-polypyrrole (PANI-PPy) nanocomposite was investigated. Different characterization and analytical methods including Fourier transform infrared spectroscopy (FTIR), thermo-gravimetric analysis (TGA), scanning electron microscopy (SEM), and X-ray diffraction (XRD) confirmed that ASPB serving as dopant could improve the comprehensive properties of PANI-PPy nanocomposite. It was different from dopants such as SiO2, poly(sodium-p-styrenesulfonate) (PSS), and canonic spherical polyelectrolyte brushes (CSPB) which only enhanced the performance of PANI-PPy nanocomposite on one or two sides. The electrical conductivity of (PANI-PPy)/ASPB nanocomposite at room temperature was 8.3 S/cm, which was higher than that of PANI-PPy (2.1 S/cm), (PANI-PPy)/PSS (6.8 S/cm), (PANI-PPy)/SiO2 (7.2 S/cm), and (PANI-PPy)/CSPB (2.2 S/cm). Meanwhile, (PANI-PPy)/ASPB nanocomposite possessed enhanced thermal stability and good solubility. In addition, the effects of polymerization temperature, the molecular weight of grafted polyelectrolyte brushes, and storage time on electrical conductivity were discussed.

Strengthened Magnetoresistive Epoxy Nanocomposite Papers Derived from Synergistic Nanomagnetite-Carbon Nanofiber Nanohybrids

Novel papers based on epoxy nanocomposites with magnetite and carbon nanofiber (CNF) nanohybrids, without any surface modification to the nanofillers, show combined conductive, magnetic, and magnetoresistive properties. Negative magnetoresistance (MR) is observed in synthesized epoxy nanohybrid papers for the first time. These papers have potential applications for flexible electronics, magnetoresistive sensors, and the printing industry.

Constructing Uniform Core-Shell PPy@PANI Composites with Tunable Shell Thickness toward Enhancement in Microwave Absorption

Highly uniform core-shell composites, polypyrrole@polyaniline (PPy@PANI), have been successfully constructed by directing the polymerization of aniline on the surface of PPy microspheres. The thickness of PANI shells, from 30 to 120 nm, can be well controlled by modulating the weight ratio of aniline and PPy microspheres. PPy microspheres with abundant carbonyl groups have very strong affinity to the conjugated chains of PANI, which is responsible for the spontaneous formation of uniform core-shell microstructures. However, the strong affinity between PPy microspheres and PANI shells does not promote the diffusion or reassembly of two kinds of conjugated chains. Coating PPy microspheres with PANI shells increases the complex permittivity and creates the mechanism of interfacial polarization, where the latter plays an important role in increasing the dielectric loss of PPy@PANI composites. With a proper thickness of PANI shells, the moderate dielectric loss will produce well matched characteristic impedance, so that the microwave absorption properties of these composites can be greatly enhanced. Although PPy@PANI composites herein consume the incident electromagnetic wave by absolute dielectric loss, their performances are still superior or comparable to most PANI-based composites ever reported, indicating that they can be taken as a new kind of promising lightweight microwave absorbers. More importantly, microwave absorption of PPy@PANI composites can be simply modulated not only by the thickness of the absorbers, but also the shell thickness to satisfy the applications in different frequency bands.