Flexible Polyimide Nanocomposites with dc Bias Induced Excellent Dielectric Tunability and Unique Nonpercolative Negative- k toward Intrinsic Metamaterials

Ferrocene derivatives and aniline copolymers with tunable magnetoresistance and dielectric properties

Inspired by the electron-rich characteristics of ferrocene (Fc), we have strategically integrated this compound into polyaniline (PANI), aiming to modulate the magnetoresistance (MR) and dielectric properties of PANI. The copolymers (P(ANI-co-FcA)) are synthesized by copolymerization of aniline and 1,1'-bis[[(4-aminophenyl)amino]carbon]ferrocene (FcA). The resistivity and temperature-dependent resistivity are measured to unveil the charge carrier transport mechanism, aligning with the Efros-Shklovskii variable-range hopping (ES-VRH) model. Additionally, the MR and dielectric properties are tuned by alternating the FcA content in the main chain of copolymers. MR analysis reveals a positive effect, which is intensified with an increased FcA content. Notably, the MR effect of P(ANI-co-FcA)-3 containing 31.92 wt% FcA attains 1.51% under a magnetic field of 3 T. The real permittivity of copolymers is changed from negative to positive values upon the incorporation of FcA. This research proffers an approach to manipulate the electrical performance of conducting polymer materials for potential applications in electronic devices.

Polyimide-multiwalled carbon nanotubes composite as electrochemical sensing platform for the simultaneous detection of nitrophenol isomers

Developing novel electrode materials plays a crucial role in enhancing the electrochemical sensing performance of chemically modified electrodes. This research presents a composite electrode material based on polyimide incorporated with multiwalled carbon nanotubes (PI-MWCNT) for the simultaneous detection of three nitrophenol isomers (NPs). First, the composite was prepared and characterized using microscopies, spectroscopic techniques, and electrochemical experiments. The results indicated that the PI-MWCNT exhibited porosity and roughness, which facilitated the enhancement of its sensing performance. Afterward, the detection capabilities of PI-MWCNT towards NPs were evaluated through voltammetry experiments under optimal conditions. The differential pulse voltammetry (DPV) curves revealed three distinct anodic peaks in the NPs solution, with linear ranges of 1-300 μM for 2-NP, 0.25-250 μM for 3-NP, and 0.25-400 μM for 4-NP. The limits of detection (LOD) were 0.50 μM for both 2-NP and 3-NP, and 0.64 μM for 4-NP. Furthermore, the proposed electrode material was successfully applied to real samples, achieving recovery rates ranging from 92.9% to 106%. This study could contribute to the development of more efficient and sensitive electrochemical sensors.

Ultra-high dielectric tuning performance and double-set resistive switching effect achieved on the Bi2NiMnO6 thin film prepared by sol-gel method

With the development of mobile terminals, tunable capacitors for signal processing and memristors for calculation have received a lot of attention. Combining a tunable capacitor and a memristor can improve the performance of mobile terminals and reduce space requirements. In this article, we report on Bi₂NiMnO₆ (BNMO) films with high dielectric tuning and nonvolatile resistive switching (RS) effects. The BNMO films are fabricated by the sol-gel method and annealed at different temperatures. It exhibits a dielectric tunability of up to 92%. This high dielectric tunability may be attributed to the modulation of the interface dipole by the electric field. When an electric field is applied, the interface dipole of the BNMO film is far away from the interface of the BNMO, and then forms a conductive channel where anions and cations are mixed. The BNMO films are found to have a double-set type effect due to its dielectric tunability properties. This work introduces an ultra-high dielectric tuning material and a new type of RS effect on BNMO thin film, which can achieve tuning and memory behavior on a device.

Development and Characterization of Novel Conductive Sensing Fibers for In Vivo Nerve Stimulation

Advancements in electrode technologies to both stimulate and record the central nervous system's electrical activities are enabling significant improvements in both the understanding and treatment of different neurological diseases. However, the current neural recording and stimulating electrodes are metallic, requiring invasive and damaging methods to interface with neural tissue. These electrodes may also degrade, resulting in additional invasive procedures. Furthermore, metal electrodes may cause nerve damage due to their inherent rigidity. This paper demonstrates that novel electrically conductive organic fibers (ECFs) can be used for direct nerve stimulation. The ECFs were prepared using a standard polyester material as the structural base, with a carbon nanotube ink applied to the surface as the electrical conductor. We report on three experiments: the first one to characterize the conductive properties of the ECFs; the second one to investigate the fiber cytotoxic properties in vitro; and the third one to demonstrate the utility of the ECF for direct nerve stimulation in an in vivo rodent model.

Enhanced permittivity of negative permittivity middle-layer sandwich polymer matrix composites through conductive filling with flake MAX phase ceramics

Polymer matrix composites are expected to promote the development of embedded packaging technology for circuit boards, but it is still impossible to obtain polymer matrix composites with high permittivity and low loss tangent simultaneously. In this study, a laminated composite with a middle-layer possessing negative permittivity effects was prepared by hot pressing sintering using MAX phase ceramics as a conductive filler. High permittivity (170@1 kHz) and low loss tangent (0.3@1 kHz) were achieved in traditional sandwich polymer matrix composites (SPMCs). Its high permittivity can be explained by the series capacitor model and the interfacial polarization promoted by the flake structure of the MAX phase ceramics. Low loss tangent is guaranteed by the ohmic barrier effect caused by the huge resistance difference between adjacent layers in the composite material. These SPMCs with special structure are expected to provide new ideas for developing embedded capacitors.

In this study, a laminated composite with a middle-layer possessing negative permittivity effects was prepared by hot pressing sintering using MAX phase ceramics as a conductive filler.

Polypropylene-MWCNT composite degradation, release, detection, and toxicity of MWCNT during accelerated aging

Nanomaterials (NM) are incorporated into polymers to enhance their properties. However, there are a limited number of studies on the aging of these nanocomposites and the resulting potential release of NM. To characterize NM at critical points in their life cycles, polypropylene (PP) and multiwall carbon nanotube filled PP (PP-MWCNT) plates with different thicknesses (from 0.25 mm to 2 mm) underwent accelerated weathering in a chamber that simulates solar irradiation and rainfall. The physicochemical changes of the plates depended on the radiation exposure, the plate thickness, and the presence of CNT fillers. Photodegradation increased with aging time, making the exposed surface more hydrophilic, decreasing the surface hardness and creating surface stress-cracks. Aged surface and cross-section showed crazing due to the polymer bond scission and the formation of carbonyls. The degradation was higher near the UV-exposed surface as the intensity of the radiation and oxygen diffusion decreased with increasing depth of the plates, resulting in an oxidation layer directly proportional to oxygen diffusion. Thus, sample thickness determines the kinetics of the degradation reaction and the transport of reactive species. Plastic fragments, which are less than 1 mm, and free CNTs were released from weathered MWCNT-PP. The concentrations of released NM that were estimated using ICP-MS, increased with prolonged aging time. Various toxicity tests, including reactive oxygen species generation and cell activity/viability, were performed on the released CNTs. The toxicity of the released fragments and CNTs to A594 adenocarcinomic human alveolar basal epithelial cells was observed. The released polymer fragments and CNTs did not show significant toxicity under the experimental conditions in this study. This study will help manufacturers, users of consumer products with nanocomposites and policymakers in the development of testing guidelines, predictive models, and risk assessments and risk based-formulations of NM exposure.