Search Results (251)

The practical application of inorganic ferroelectric fillers in flexible piezoelectric composites is critically constrained by low polarization efficiency and severe interfacial incompatibility with polymer matrices. Herein, we report a multi-level in situ surface modification strategy that simultaneously addresses both limitations. High-purity one-dimensional tetragonal barium titanate nanofibers (BTO NFs) are first synthesized via sol–gel electrospinning combined with a two-step gradient annealing process, which precisely controls phase evolution and preserves structural continuity. To overcome the detrimental acid-induced degradation of BTO NFs during functionalization, a polydopamine (PDA) buffer layer is first conformally coated, followed by the liquid-phase deposition of a conductive polypyrrole (PPy) shell, forming a robust core–shell PPy@PBT NFs architecture. Incorporating only 4 wt% of these multifunctional fillers into a poly(vinylidene fluoride) (PVDF) matrix yields a dramatic enhancement in electromechanical performance. The resulting flexible piezoelectric energy harvesters achieve a piezoelectric coefficient (d₃₃) of 28.7 pC/N, an output voltage of 13 V, and an output current of 0.7 μA, representing substantial improvements over unmodified filler systems. This synergistic enhancement originates from the PDA-mediated interfacial stress transfer and the PPy-induced Maxwell–Wagner polarization intensification, establishing a robust and generalizable paradigm for high-performance flexible piezoelectric composites in self-powered wearable electronics. Full article

Escherichia coli (E. coli) is a microorganism commonly found in water and food matrices, and its rapid and accurate detection is crucial for maintaining public health and ensuring food safety. However, traditional molecularly imprinted polymer (MIP) sensors often face challenges such as tedious template removal and prolonged sensing times. This study develops a label-free bacterial molecularly imprinted sensor that utilizes the synergistic effect of polypyrrole (PPy) and multi-walled carbon nanotubes (MWCNTs) to achieve highly sensitive detection of E. coli. Based on the large specific surface area and superior conductivity of MWCNTs, as well as the favorable electrochemical polymerization properties of PPy, a PPy/MWCNTs composite film was fabricated via a one-step electropolymerization process. The prepared sensor exhibited excellent kinetic characteristics, with a template removal time of only 15 min, and could be regenerated and used for subsequent detection within 30 min. Under optimized conditions, the biosensor showed a satisfactory linear response over the concentration range of 10²–10⁸ CFU/mL, with a low detection limit of 65 CFU/mL (3σ/S). Furthermore, recovery experiments conducted in tap water and lemon juice samples yielded satisfactory recoveries ranging from 87.1% to 114.8%, demonstrating the reliability and practical applicability of the proposed sensor for bacterial detection in real samples. This sensor offers advantages such as simple preparation, low material cost, and high sensitivity, providing a reliable and practical analytical platform for the rapid and reliable detection of bacteria. Full article

Developing efficient and durable electrocatalysts for the alkaline hydrogen evolution reaction (HER) remains challenging due to intrinsically sluggish reaction kinetics and the limited long-term stability of many non-noble metal catalysts under continuous operation. Herein, a nickel-doped polypyrrole/chitosan composite electrode on stainless steel (PPy/Chi/Ni) was fabricated via electrodeposition as a low-cost and scalable method. Benefiting from the combined effects of Ni incorporation and the conductive polymer–biopolymer composite framework, the optimized PPy/Chi/Ni electrode exhibits enhanced HER activity in alkaline environment, delivering a low overpotential of η₁₀ = 78 mV at a current density of 10 mA·cm⁻² and a reduced Tafel slope of 93 mV·dec⁻¹, indicative of accelerated reaction kinetics. Structural and morphological characterizations by XRD, FTIR, and FESEM indicate the formation of the composite structure. FESEM images suggest that the deposited layer forms a relatively uniform coating on the stainless steel substrate. EIS further reveals improved interfacial charge-transfer characteristics upon Ni doping. Additionally, long-term stability tests confirm the structural integrity of the composite electrode and its electrochemical stability under HER conditions by demonstrating stable HER performance for 15 h with only a 22 mV potential change at a constant current density. By providing a conductive interface and numerous catalytic sites, the Ni-doped electrocatalyst coating activates the stainless steel substrate, leading to a 79% reduction in overpotential compared to bare stainless steel and thereby significantly improving its HER performance. Full article

To enhance the functionality of collagen (Coll)-based scaffolds, we developed a double-crosslinking strategy incorporating an electroconductive chitosan (Ch) and polypyrrole (Ppy) composite. Successful pre-crosslinking of Ch and Ppy was achieved using glutaraldehyde (GTA) at 100 µM. This facilitated imine linkage formation, confirmed by FTIR, enabling synergistic integration with Coll and successful nanofiber scaffold fabrication via electrospinning. While increasing the Ch-Ppy-GTA ratio affected the spinning process and higher GTA concentrations compromised fiber homogeneity, all other measured properties generally improved with increasing ratios. Crucially, this methodology allowed the membranes to maintain their morphology and significantly extended their degradation profile up to 20–30 days in PBS medium at 37 °C. Furthermore, the scaffolds exhibited electroactivity characterized by pseudocapacitance in the presence of Na⁺ and Ca²⁺ ions. These findings demonstrate a robust, tunable method for creating electroactive and structurally stable nanofiber scaffolds suitable for advanced tissue engineering. Full article

Early intervention is pivotal for mitigating the progression of Alzheimer’s disease (AD). This study presents an electrochemical immunosensor targeting synaptic vesicle glycoprotein 2A (SV2A) to facilitate early AD diagnosis. A sensing interface was engineered using a nanocomposite of graphene oxide (GO) and 3-carboxyl polypyrrole (3-COOH-PPy). Leveraging the synergistic effects between the large specific surface area of GO and the superior conductivity of 3-COOH-PPy, the composite established an efficient electron transport network. This architecture provided abundant active sites for capture antibody immobilization while significantly enhancing interfacial electron transfer kinetics. Coupling this interface with an enzyme-mediated signal amplification strategy based on the horseradish peroxidase (HRP)-catalyzed TMB/H₂O₂ system, the immunosensor achieved high sensitivity. It exhibited a wide linear range of 2 ng/mL to 16 μg/mL with a low limit of detection (LOD) of 0.15 ng/mL. Furthermore, successful detection in C57 mouse serum samples validated the method’s reliability and potential for clinical application. In conclusion, this immunosensor offers a sensitive and robust platform for the early diagnosis of AD. Full article

Flexible electrode materials with tailored electrical and mechanical properties are essential for reliable electrocardiographic (ECG) sensing. In this work, p-toluenesulfonic-acid-doped polypyrrole (PPy–TSA) films were modified using polymeric and inorganic fillers, as well as their combinations (polyethylene glycol, graphene, carbon nanotubes, and zeolite), to tune their functional performance. The reference PPy–TSA film exhibits typical morphological and chemical characteristics of doped polypyrrole and serves as a reliable baseline for comparison. All composite films retain electrical conductivity within the range required for ECG applications while showing improved mechanical compliance (i.e., enhanced ability to conform to the skin and sustain deformation). Based on the optimized balance between electrical and mechanical properties, flexible ECG electrodes were fabricated using the TSA-doped PPy-based composite film. ECG recordings obtained with the several proposed electrodes show good agreement with those acquired using a commercial ECG electrode, demonstrating the potential of PPy-based composite films for flexible bioelectronic sensing applications. Full article

Polypyrrole-based functional composites are increasingly explored and extensively adopted for energy storage, sensing, and environmental applications due to their tunable electronic properties, chemical versatility, and mechanical stability. However, rational optimization of these composites requires a unified understanding of electronic, mechanical, thermal, and chemical behavior at the atomic scale, which underlies their multifunctional behavior, and remains fragmented. Notably, Density Functional Theory (DFT) provides indispensable atomistic insight into the electronic, mechanical, thermal, and chemical interactions that govern the performance of multifunctional materials. To bridge these gaps, this review presents a comprehensive assessment of recent DFT and time-dependent DFT (TD-DFT) studies that elucidate the electronic, mechanical, thermal, and chemical characteristics of polypyrrole and its hybrid composites. Key theoretical descriptors, including electronic structure modulation, charge transfer behavior, adsorption energetics, interfacial binding energies, hydrogen bond formation, and charge redistribution, are critically assessed to establish structure–property relationships across diverse functional systems. Considerable attention is given to interfacial interactions, doping strategies, and composite architectures that govern durability, conductivity, and chemical stability. By consolidating current atomistic insights and identifying existing limitations, this review provides a coherent framework for rational material design. Notably, it presents the first systematic quantification of dopant steric effects in PPy multifunctional composites, linking atomistic-scale modifications to the optimization of functional properties in next-generation applications. Full article

The catalyst in methanol oxidation plays a pivotal role in direct fuel cell reaction. The aim of this work is to study the influence of polypyrrole polymer (PPy) added in the carbon Vulcan support for the methanol oxidation reaction. The catalytic active phase synthesized was nickel-based materials, which have been demonstrated to exhibit remarkable chemical stability in alkaline solutions. The metallic-active phase was supported at the PPy-carbon Vulcan matrix. PPy is a conductor polymer and the research of electric conduction in synergy with a carbon Vulcan and a Ni catalyst is scarcely reported. The morphology characterization of composite catalytic material was carried out by XRD, XPS, and TEM techniques. In turn, the catalytic activity of the composite is characterized by means of cyclic voltammetry (CV). Electrochemical impedance spectroscopy (EIS) showed the influence of PPy on the charge transfer resistance (Rch. t.). The results indicate that a decrease in the Rch. t. was associated with an increase in methanol oxidation; therefore, higher amounts of charge transfer is produced. Furthermore, the DEMS technique corroborates the EIS results, confirming elevated conversion toward oxidation products. In turn, the selectivity of the composite-catalytic support on the methanol oxidation was elucidated using in situ Raman spectroscopy. Full article

Conductive hydrogels that simultaneously exhibit high mechanical robustness, reliable electrical conductivity, and interfacial adhesion are highly desirable for flexible sensing applications; however, achieving these properties in a single system remains challenging due to intrinsic structure–property trade-offs. Herein, a multifunctional conductive hydrogel (ASP hydrogel) is developed based on a polyacrylamide (PAM)/sodium alginate (SA) double-network architecture using a gallic acid (GA)–Fe³⁺–pyrrole (Py) coupling strategy. In this design, GA provides metal-coordination sites for Fe³⁺, while Fe³⁺ simultaneously serves as an oxidant to trigger the in situ polymerization of pyrrole, enabling the homogeneous integration of polypyrrole (PPy) conductive networks within the hydrogel matrix. The resulting ASP hydrogel exhibits a markedly enhanced fracture strength of 2.95 MPa compared with PAM (0.26 MPa) and PAM–SA (0.22 MPa) hydrogels, together with stable electrical conductivity and reproducible strain-dependent electrical responses. Moreover, the introduction of dynamic metal–phenolic coordination and hydrogen-bonding interactions endows the hydrogel with intrinsic self-healing capability and strong adhesion to diverse substrates. Rather than relying on simple filler incorporation, this work demonstrates an integrated network design that balances mechanical strength, conductivity, and adhesion, providing a versatile material platform for flexible strain sensors and wearable electronics. Full article

Conductive polymers (CPs), such as polypyrrole (PPy), have shown promising properties for use as electro-responsive bioactive scaffolds for tissue regeneration. PPy can be synthesized by chemical electrosynthesis and doped with biomolecules such as hyaluronic acid (HA). Taking advantage of the electrochemical synthesis versatility, nanofibers for surface-modified indium tin oxide (ITO) electrodes can be used as templates to produce tridimensional HA-doped PPy scaffolds. In this study, polyvinyl alcohol/chitosan (PVA/CTS) electrospun nanofibers deposited on ITO electrodes were used as a 3D template for the in situ electrosynthesis of HA-doped PPy to produce a bioactive scaffold for tissue engineering. The final material gathers the advantages of each biopolymer, the porous morphology of the nanofiber, and the conductivity of the electrosynthetized polymer. Furthermore, the biological activity of the NF-PVA/CTS@PPy:HA composite was evaluated in NIH-3T3 fibroblasts by MTT, resulting in a cell viability of 146 ± 40% and wound-healing capacity of 97 ± 1.9% at 24 h of culture. Full article

At present, composite phase change materials are widely studied for battery thermal management. However, to ensure the battery’s thermal safety, it is necessary not only to control the temperature during regular operation, but also to prevent sudden thermal runaway. This basic function depends on the flame-retardant properties of the composite phase change materials. In this study, a hexagonal double-layer hollow nanocage S2 with defect orientation was prepared and combined with carbon nanotubes (PNT) derived from polypyrrole (PPy) tubes to form a high adsorption mixture. Multifunctional composite phase change material PNT/S2@PEG/TEP was prepared by adsorbing and coating polyethylene glycol 8000 (PEG-8000) and triethyl phosphate (TEP) with microfibrillated cellulose nanofibers (CNF) as the skeleton. The characterization shows that its thermal conductivity is 0.65 W/m·K and its phase transition enthalpy is 146.1 J/g, demonstrating its excellent thermal regulation. Microcalorimetric testing (MCC) confirmed its flame-retardant ability, attributed to the strong adsorption of PNT/S2 on PEG-8000 and TEP, the improvement in PNT’s thermal conductivity, and the contribution of CNF to flexibility. This composite phase change material, with excellent comprehensive properties, has broad application prospects in thermal safety for electronic equipment, significantly expanding its practical scope. Full article

The current research presents the synthesis, characterization, and application of a novel gas sensor based on polypyrrole/strontium titanate (PPy/STO) nanocomposites for the selective detection of CO₂. Utilizing chemical oxidative polymerization, PPy and PPy/STO nanocomposites with varying STO (10–50) wt.% were synthesized and characterized. The structural and morphological analysis confirms the formation of spherical structure and well-dispersed PPy nanoparticles with increasing crystallinity and interaction of STO in PPy chain particle compactness as the STO content increases. The integration of perovskite STO within the conducting polymer matrix enhances the electronic structure, porosity, and surface area of the composite, promoting improved gas sensing performance. Electrical impedance spectroscopy reveals that the composites exhibit a frequency-dependent dielectric response and conduction attributed to charge carrier mobility and interfacial polarization effects. PPy/STO 20% exhibits highest conductivity and dielectric constants of 0.03604 Scm⁻¹ and 1.074 × 10⁴, respectively. Real-time CO₂ sensing experiments conducted at 50 °C demonstrate good sensitivity, stability, and rapid response/recovery characteristics, particularly for the PPy/STO 10% and 40% composites. These findings highlight the potential of PPy/STO nanocomposites as flexible, lightweight, and efficient materials for portable CO₂ gas sensors, addressing the growing needs for environmental and health monitoring. Full article

The rapid advancement of flexible electronics has propelled the development of lightweight, wearable piezoresistive sensors that integrate high sensitivity, excellent mechanical properties, and multifunctionality, making them a research hotspot. This work presents a flexible and lightweight multifunctional polyvinyl alcohol (PVA) composite hydrogel film, which is constructed based on a synergistic conductive network of cuttlefish ink-derived carbon nanospheres (CNPs) and polypyrrole (PPy). Within this composite, the CNPs and PPy form an interpenetrating conductive network throughout the PVA matrix, where PPy effectively suppresses the agglomeration of CNPs, thereby significantly enhancing the electron transport efficiency. This unique structure endows the material with improved flame retardancy and hydrophobicity while maintaining its lightweight characteristic. Consequently, the sensor demonstrates fast response (64 ms) and recovery times (66 ms) and a high sensitivity factor of 4.34 kPa⁻¹ within a pressure range of 11.2–16.8 kPa. Excellent stability is retained after nearly 6000 loading–unloading cycles, primarily attributed to the efficient response of the contact points and conductive pathways within the synergistic network under stress. Furthermore, this flexible sensor can not only reliably monitor human physiological activities (such as finger joint bending and facial expression changes) but also generate distinct current responses to subtle mouse-clicking actions, enabling tactile handwriting input. This study provides a novel strategy for constructing high-performance sensing materials by utilizing natural biomass-derived carbon materials and conductive polymers, highlighting the significant application potential of such lightweight, multifunctional hydrogel films in next-generation flexible electronic devices. Full article

The remarkable growth of high-frequency electronic systems has raised concerns about electromagnetic interference (EMI), emphasizing the need for lightweight and efficient shielding materials. In this study, ternary composites based on polypyrrole (PPy), graphene oxide (GO), and silver nanowires (AgNWs) were synthesized through chemical oxidative polymerization of pyrrole monomer and embedded into polycaprolactone (PCL) matrices to create flexible films. Structural and morphological analyses confirmed the successful incorporation of all components, with scanning electron microscopy showing granular PPy, sheet-like GO, and fibrous AgNWs, while spectroscopic studies indicated strong interfacial interactions without damaging the PPy backbone. Thermomechanical analysis revealed that GO increased stiffness and defined the glass transition, whereas AgNWs improved toughness and energy dissipation; their combined use resulted in balanced properties. EMI shielding effectiveness (SE) was tested in the X-band (8–12 GHz). Pure PPy exhibited poor shielding ability, while the addition of GO and AgNWs significantly enhanced performance. The highest EMI SE values were observed in PPy/GO–AgNWs composites, with an average SE of 16.05 dB at 20 wt% of the composite in the PCL matrix, equivalent to about 84.4% attenuation of incident waves. These results demonstrate that the synergistic integration of GO and AgNWs into PPy matrices enables the creation of lightweight, flexible films with advanced EMI shielding properties, showing great potential for next-generation electronic and aerospace applications. Full article

Electrodes and electrolytes are critical components for the performance of supercapacitors. In this study, supercapacitors with different interfaces were assembled using polypyrrole (PPy) or a polypyrrole–carbon nanotube (PPy-CNT) composite as active materials, and dimethyl sulfoxide (DMSO) and sodium chloride (NaCl) were used as electrolytes. Electrochemical measurements were obtained by cyclic voltammetry (CV) at a scan rate of 20 mV/s and galvanostatic charge–discharge (GCD) measurements at a scan rate of 50 µA/s. The results suggest that the supercapacitor with a PPy-CNT composite and NaCl electrolyte has promising electrochemical characteristics. Full article