Synthesis of Electromagnetic Functionalized Barium Ferrite Nanoparticles Embedded in Polypyrrole

Preparation and Characterization of Magnetic Polypyrrole Composite Microspheres Decorated with Copper (II) As A Sensing Platform for Electrochemical Detection of Carbamazepine

With a facile solvothermal technique, synthesis and application of Fe₃O₄@PPy–Cu^IIcomposite microspheres in the carbon ionic liquid matrix have been reported as highly sensitive sensors for voltammetric determination of Carbamazepine (CBZ). The morphology, crystal phase, and structure of synthesized nanocomposite were confirmed by routine methods, such as transmission electron microscopy (TEM), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), Fourier translation infrared spectroscopy (FT-IR), thermal gravimetric analysis (TGA), and inductively coupled plasma atomic emission spectroscopy (ICP-AES). Under the optimized conditions, differential pulse voltammetric (DPV) peak current was proportional to the CBZ concentration in the range of 0.05 to 25 μM with the detection limit (S/N = 3) of 32 nM. The storage stability of the modified electrode was also investigated which shows that the current responses remain about 95.2% of their initial values, indicating the appreciable storage stability of this sensor.The proposed electrode displayed excellent repeatability and it was satisfactorily used for determination of CBZ in real samples (urine, and serum samples) with high recovery.

Sustainable Double-Network Structural Materials for Electromagnetic Shielding

Electromagnetic interference (EMI) shielding materials with excellent EMI shielding efficiency (SE), lightweight property, and superb mechanical performance are vitally important for modern society, but it is still a challenge to realize these performances simultaneously on one material. Here, we report a sustainable bioinspired double-network structural material with excellent specific strength (146 MPa g^-1 cm³) and remarkable EMI SE (100 dB) from cellulose nanofiber (CNF) and carbon nanotubes (CNTs), which demonstrates remarkable and outstanding performance to both typical metal materials and reported polymer composites. In particular, the bioinspired double-network structure design simultaneously achieves an extremely high electrical conductivity and mechanical strength, which makes it a lightweight, high shielding efficiency, and sustainable structural material for real-life electromagnetic wave shielding applications.

Synthesis of Multifunctional Electrically Tunable Fluorine-Doped Reduced Graphene Oxide at Low Temperatures

Doping with heteroatoms is a well-established method to tune the electronic properties and surface chemistry of graphene. Herein, we demonstrate the synthesis of a fluorine-doped reduced graphene oxide (FrGO) at low temperatures that offers multiple opportunities in applied fields. The as-synthesized FrGO product shows a better electrical conductivity of 750 S m^-1 than that of undoped rGO with an electrical conductivity of 195 S m^-1. To demonstrate the multifunctional applications of the as-synthesized FrGO, it was examined for electromagnetic interference shielding and electrochemical sensing of histamine as an important food biomarker. A laminate of FrGO delivered an EMI shielding effectiveness value of 22 dB in Ku band as compared with 11.2 dB for an rGO laminate with similar thickness. On the other hand, an FrGO modified sensor offered an excellent sensitivity (∼7 nM), wide detection range, and good selectivity in the presence of similar biomarkers. This performance originates from the better catalytic ability of FrGO as compared with rGO, where fluorine atoms play the role of catalytic active sites owing to their high electronegativity. The fluorination reaction also helps to improve the reduction degree of the chemically synthesized graphene, consequently enhancing the electrical conductivity, which is a prime requirement for increasing the electromagnetic and electrochemical properties of graphene.

Electromagnetic interference shielding with 2D transition metal carbides (MXenes)

Materials with good flexibility and high conductivity that can provide electromagnetic interference (EMI) shielding with minimal thickness are highly desirable, especially if they can be easily processed into films. Two-dimensional metal carbides and nitrides, known as MXenes, combine metallic conductivity and hydrophilic surfaces. Here, we demonstrate the potential of several MXenes and their polymer composites for EMI shielding. A 45-micrometer-thick Ti3C2Tx film exhibited EMI shielding effectiveness of 92 decibels (>50 decibels for a 2.5-micrometer film), which is the highest among synthetic materials of comparable thickness produced to date. This performance originates from the excellent electrical conductivity of Ti3C2Tx films (4600 Siemens per centimeter) and multiple internal reflections from Ti3C2Tx flakes in free-standing films. The mechanical flexibility and easy coating capability offered by MXenes and their composites enable them to shield surfaces of any shape while providing high EMI shielding efficiency.

Recent Advances in Conjugated Polymer-Based Microwave Absorbing Materials

Microwave absorbing materials (MAMs) are paving the way for exciting applications in electromagnetic (EM) pollution precaution and national defense security, as they offer an advanced alternative to conventional reflection principles to fundamentally eliminate the EM waves. Conjugated polymer (CP)-based composites appear as a promising kind of MAM with the desirable features of low density and high performance. In this review, we introduce the theory of microwave absorption and summarize recent advances in the fabrication of CP-based MAMs, including rational design of the microstructure of pure conjugated polymers and tunable chemical integration with magnetic ferrites, magnetic metals, transition metal oxides, and carbon materials. The key point of enhancing microwave absorption in CP-based MAMs is to regulate their EM properties, improve matching of characteristic impedance, and create diversified loss mechanisms. The examples presented in this review will provide new insights into the design and preparation of CP-based composites that can satisfy the high demands of the oncoming generation of MAMs.

Uniform core–shell PPy@carbon microsphere composites with a tunable shell thickness: the synthesis and their excellent microwave absorption performances in the X-band

Highly uniform core–shell polypyrrole@carbon microspheres (PPy@CM) have been successfully constructed by oxidation polymerization of pyrrole as the shell on the core of carbon microspheres.

Novel environmentally friendly waterborne polyurethane/hollow Ni0.3Zn0.5Fe2O4 nanocomposite films: superior magnetic and mechanical properties

Superparamagnetic nanocomposite films based on waterborne polyurethane and hollow Ni_0.3Zn_0.5Fe₂O₄ nanospheres (WPU/h-NZFO) were synthesized via an in situ polymerization technique.

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.

Excellent microwave-absorption performances by matched magnetic–dielectric properties in double-shelled Co/C/polyaniline nanocomposites

Double-shelled Co/C/polyaniline (Co/C/PA) nanocomposites were prepared by combining the arc-discharge process and in situ chemical oxidative polymerization reaction.

Barium ferrite decorated reduced graphene oxide nanocomposite for effective electromagnetic interference shielding

There is an increased interest in the development of high performance microwave shielding materials against electromagnetic pollution in recent years. Barium ferrite decorated reduced graphene oxide (BaFe12O19@RGO) nanocomposite was synthesized by a high energy ball milling technique and its electromagnetic properties were investigated in the frequency range of 12.4-18 GHz (Ku band). The results showed that barium ferrite (BaFe12O19) nanoparticles with an average particle size of 20-30 nm were well distributed and firmly anchored onto the surface of the reduced graphene oxide sheets. The obtained nanocomposite exhibited a saturation magnetization of 18.1 emu g(-1) at room temperature. The presence of BaFe12O19 nanoparticles in the nanocomposite enhances the space charge polarization, natural resonance, multiple scattering and the effective anisotropy energy leading to a high electromagnetic interference shielding effectiveness of 32 dB (∼99.9% attenuation) at a critical thickness of 3 mm. The results suggested that the as-prepared BaFe12O19@RGO nanocomposite showed great potential as an effective candidate for a new type of microwave absorbing material.

Co nanoparticles induced resistive switching and magnetism for the electrochemically deposited polypyrrole composite films

The resistive switching behavior of Co-nanoparticle-dispersed polypyrrole (PPy) composite films is studied. A novel design method for resistive random access memory (ReRAM) is proposed. The conducting polymer films with metal nanocrystal (NC)-dispersed carbon chains induce the spontaneous oxidization of the conducting polymer at the surface. The resistive switching behavior is achieved by an electric field controlling the oxygen ion mobility between the metal electrode and the conducting polymer film to realize the mutual transition between intrinsic conduction (low resistive state) and oxidized layer conduction (high resistive state). Furthermore, the formation process of intrinsic conductive paths can be effectively controlled in the conducting polymer ReRAM using metal NCs in films because the inner metal NCs induce electric field lines converging around them and the intensity of the electric field at the tip of NCs can greatly exceed that of the other region. Metal NCs can also bring new characteristics for ReRAM, such as magnetism by dispersing magnetic metal NCs in polymer, to obtain multifunctional electronic devices or meet some special purpose in future applications. Our works will enrich the application fields of the electromagnetic PPy composite films and present a novel material for ReRAM devices.

Synthesis and electromagnetic, microwave absorbing properties of core-shell Fe3O4-poly(3, 4-ethylenedioxythiophene) microspheres

Highly regulated core-shell Fe(3)O(4)-poly(3, 4-ethylenedioxythiophene) (PEDOT) microspheres were successfully synthesized by a two-step method in the presence of polyvinyl alcohol (PVA) and p-toluenesulfonic acid (p-TSA). And their morphology, microstructure, electromagnetic and microwave absorbing properties were subsequently characterized. By simply adjusting the molar ratio of 3, 4-ethylenedioxythiophene (EDOT) to Fe(3)O(4) (represented by (EDOT)/(Fe(3)O(4))), the thickness of the polymer shell can be tuned from tens to hundreds of nanometers. Moreover, it was found that the composite exhibited excellent microwave absorbing property with a minimum reflection loss (RL) of about -30 dB at 9.5 GHz with a (EDOT)/(Fe(3)O(4)) ratio of 20.

Field-assisted synthesis of SERS-active silver nanoparticles using conducting polymers

A gradient of novel silver nanostructures with widely varying sizes and morphologies is fabricated on a single conducting polyaniline-graphite (P-G) membrane with the assistance of an external electric field. It is believed that the formation of such a silver gradient is a synergetic consequence of the generation of a silver ion concentration gradient along with an electrokinetic flow of silver ions in the field-assisted model, which greatly influences the nucleation and growth mechanism of Ag particles on the P-G membrane. The produced silver dendrites, flowers and microspheres, with sharp edges, intersections and bifurcations, all present strong surface enhanced Raman spectroscopy (SERS) responses toward an organic target molecule, mercaptobenzoic acid (MBA). This facile field-assisted synthesis of Ag nanoparticles via chemical reduction presents an alternative approach to nanomaterial fabrication, which can yield a wide range of unique structures with enhanced optical properties that were previously inaccessible by other synthetic routes.

A mesoporous silica nanosphere-based drug delivery system using an electrically conducting polymer

In this study, a mesoporous silica nanoparticle (MSN)-based nerve growth factor (NGF) delivery system has been successfully embedded within an electroactive polypyrrol (Ppy). The spherical particles with approximately 100 nm diameter possess a large surface-to-volume ratio for the entrapment of NGF into the pores of MSNs while retaining their bioactivity. Direct incorporation of MSN-NGF within Ppy was achieved during electrochemical polymerization. The loading amount and release profile of NGF from the composite was investigated by sandwich ELISA. The NGF incorporation can be controllable by varying particle concentration or by extending electrodeposition time. The morphology and chemical composition of the Ppy/MSN-NGF composite was evaluated by atomic force microscopy (AFM), transmission electron microscopy (TEM), scanning electron microscopy (SEM), and x-ray photoelectron spectroscopy (XPS). Optical and electron microscopy revealed a characteristic attachment of PC 12 cells and the outgrowth of their neurites when grown on the Ppy/MSN-NGF composite as a result of a sustained and controlled release of NGF. In order to observe the effectiveness of electrical stimulation, neurite extension of cells cultured on unstimulated and stimulated Ppy/MSN-NGF was compared. The NGF release in the presence of electrical stimulation promoted significantly greater neurite extension.