Polyaniline Nanofibers Research Articles

A Novel Method to Enhance the Mechanical Properties of Polyacrylonitrile Nanofiber Mats: An Experimental and Numerical Investigation.

This study addresses the challenge of enhancing the transverse mechanical properties of oriented polyacrylonitrile (PAN) nanofibers, which are known for their excellent longitudinal tensile strength, without significantly compromising their inherent porosity, which is essential for effective filtration. This study explores the effects of doping PAN nanofiber composites with varying concentrations of polyvinyl alcohol (PVA) (0.5%, 1%, and 2%), introduced into the PAN matrix via a dip-coating method. This approach ensured a random distribution of PVA within the nanofiber mat, aiming to leverage the synergistic interactions between PAN fibers and PVA to improve the composite's overall performance. This synergy is primarily manifested in the structural and functional augmentation of the PAN nanofiber mats through localized PVA agglomerations, thin films between fibers, and coatings on the fibers themselves. Comprehensive evaluation techniques were employed, including scanning electron microscopy (SEM) for morphological insights; transverse and longitudinal mechanical testing; a thermogravimetric analysis (TGA) for thermal stability; and differential scanning calorimetry (DSC) for thermal behavior analyses. Additionally, a finite element method (FEM) analysis was conducted on a numerical simulation of the composite. Using our novel method, the results demonstrated that a minimal concentration of the PVA solution effectively preserved the porosity of the PAN matrix while significantly enhancing its mechanical strength. Moreover, the numerical simulations showed strong agreement with the experimental results, validating the effectiveness of PVA doping in enhancing the mechanical properties of PAN nanofiber mats without sacrificing their functional porosity.

Highly conductive and transparent metal microfiber networks as front electrodes of flexible thin-film photovoltaics

Simultaneously enhancing the optical transmittance and electrical conductivity of transparent conductors (TCs) applicable in various optoelectronic devices is a long-standing challenge. Herein, we present an innovative approach for fabricating electroplated Ni and Cu microfiber networks (NiMF and CuMF) as highly conductive TCs to realize high efficiency and desired aesthetics in thin-film solar cells and modules. The metal microfibers (MFs) are fabricated using electrospun polyacrylonitrile nanofibers as the template. The large cross-sectional aspect ratio of the metal MF networks remarkably and concurrently improves their electrical conductivity and optical transmittance. Between the NiMF and CuMF TCs, the CuMF sample exhibits a superior figure of merit owing to its exceptionally low electrical resistivity. The metal MF TC is a promising alternative to conventional patterned grids used in flexible Cu(In,Ga)Se2 thin-film solar cells, because it effectively reduces the series resistance, which is advantageous for large-area cells. The CuMF can be successfully employed as a ribbon to maintain the solar cell performance in centimeter-scale cells connected in series. The outstanding performance of the metal MF TCs indicates their potential to eliminate complicated monolithic integration processes or front grids and ribbons in flexible thin-film solar cells and modules.

Electrospun synthesis of polyaniline and titanium dioxide nanofibers as potential electrode materials in electrochemical hydrogen storage

To meet the imperative of advancing sustainable energy, prioritizing storage systems for clean energy, such as hydrogen, is crucial. However, challenges exist in hydrogen storage, and focusing on nanofibers that incorporate appropriate nanoparticles emerges as a promising approach to enhance storage capacity. In this study, polyaniline/polyvinyl alcohol (PANI/PVA) nanofibers and polyaniline/polyvinyl alcohol/titanium dioxide (PANI/PVA/TiO2) nanofibers were synthesized using the electrospinning method under constant conditions. After characterization of the nanofibers by various techniques, the nanocomposites were used as novel electrode materials for a first time for electrochemical hydrogen energy. Electrochemical tests were conducted on the synthesized nanofibers, and an optimal current of 1.5 mA was determined. The electrochemical analyses obtained revealed a significant improvement in the maximum hydrogen storage capacity with the presence of TiO2 nanoparticles. It increased from 654.8 mAh/g for PANI/PVA nanofibers to 1250 mAh/g for PANI/PVA/TiO2 nanofibers. The difference in storage capacity is attributed to the addition of TiO2 nanoparticles.

Modification of electrospun polyacrylonitrile nanofiber membranes with curcumin quantum dots for enhanced self-cleaning, antifouling and photocatalytic performance for water treatment

This work presents the fabrication of electrospun PAN-CMQD nanofiber membranes by blending laser ablated curcumin quantum dots (CMQD) with polyacrylonitrile (PAN) for water treatment application. The electrospinning process conditions were optimized using TOPSIS-Taguchi L9 (33) approach to develop membranes with superior membrane performance. The PAN-CMQD nanofiber membranes were of average fibre diameter 85.89 nm and exhibited increased hydrophilicity and improved membrane performance with 53.01 %, 36.74 %, 58.03 %, 37.68 % and 57.33 % increase in porosity, solute rejection, fouling rejection ratio, tensile strength and pure water flux respectively in contrast to the pristine PAN membrane. The PAN-CMQD nanofiber membrane possessed enhanced recyclability, self-cleaning ability, antibacterial activity and also showed good heavy metal ion removal efficiency towards Pb2+, Fe2+, Cr6+, Cd2+ and Mn2+. The PAN-CMQD membrane also showed 98.80 % photocatalytic degradation efficiency towards methylene blue dye under visible light irradiation. This study proves that PAN-CMQD nanofiber membrane is efficient in treating contaminated water with improved photocatalytic and self-regeneration capacity and the developed membrane could possibly be deployed for the mitigation of heavy metals and dyes from industrial waste water.

Polyaniline- nanofibers (PANI) / titanium dioxide (TiO2) for Cr(III) and Cr(VI) detection in aqueos solution by using surface plasmon resonance

Polyaniline- nanofibers (PANI) / titanium dioxide (TiO2) for Cr(III) and Cr(VI) detection in aqueos solution by using surface plasmon resonance

Zr-UiO-66, ionic liquid (HMIM+TFSI−), and electrospun nanofibers (polyacrylonitrile): All in one as a piezo-photocatalyst for degradation of organic dye

The synergistic effect provided by combining piezocatalysis and photocatalysis can assure the future of water cleaning. The Zr-UiO-66 (ZrU) piezo-photocatalyst was first synthesized through the solvothermal process and then followed by the incorporation with the liquid-based piezocatalyst of HMIM+TFSI− at three different concentrations to provide ZrU@ILs, which were subsequently incorporated into the piezocatalytic matrix of polyacrylonitrile (PAN). The solution of ZrU@IL/PAN was then subjected to electrospinning to fabricate the ZrU@IL/PAN nanofibers (NFs). Among the three dye models, Rhodamine B (RhB) was more degraded and the order of ZrU@IL/PAN NFs > ZrU/PAN NFs > ZrU@IL > IL/PAN NFs > pure PAN NFs > ZrU > HMIM+TFSI− was observed for its degradation in exposure to both ultrasonic (US) vibration and light radiation, approving the boosted influence of the three catalytic components of ZrU, HMIM+TFSI−, and PAN NFs in the degradation of RhB and more effectiveness of the fibrous form of catalysts compared to their corresponding catalytic powders. A synergistic effect was detected in the piezo-photodegradation efficiencies of RhB (2.2 %-95.4 %) compared to the individual photodegradation (0.0 %-21.3 %) and individual piezodegradation efficiencies (2.3 %-84.2 %). The ZrU@IL-1/PAN NFs as the optimal piezo-photocatalyst displayed high recycling after four cycles of usage, RhB mineralization percentage of 67 % within 40 min, and a pseudo-first-order kinetic rate constant being 1.67 and 12.8 times higher than that of individual piezocatalysis and individual photocatalysis. Tauc plots and Mott-Schottky measurements in agreement with the radical trapping experiments suggested the main role of O2•- and HO• species in the RhB degradation mechanism. LC-MS-MS was applied to clarify the intermediates generated during the RhB piezo-photodegradation process.

Highly sensitive flexible pressure sensor based on a 1D/2D hybrid aerogel

Wearable pressure sensors with highly sensitive and wide detection ranges are essential for human motion monitoring. In this work, a self-assembled hybrid aerogel was obtained by polyacrylonitrile nanofibers, polyaniline, and reduced graphene oxide. Based on the complementation of 1D and 2D nanomaterials, the aerogel acted like a spring under lower pressure and a membrane under higher pressure, showing great potential in human motion monitoring. According to the wide detection range of the aerogel, an artificial hand was designed to recognize different spatial pressures such as grasping a pen, holding a bottle, and shaking hands. These signal outputs could be precisely reflected by voltage change and further converted to RGB values. Meanwhile, a shoe pad was prepared to monitor foot pressure and the resistance change could be converted to color scale signals. This work provides a new strategy for 1D/2D hybrid nanomaterials-based aerogel with wide pressure ranges in flexible electronics.

Preparation and Support Effect of Graphdiyne Nanotubes with Abundant Cu Quantum Dots.

Graphdiyne (GDY) is considered a very attractive support for metal nanocatalysts due to its unique structure and superior properties. The metal-GDY interaction can significantly affect the performance of catalysts. Herein, GDY nanotubes abundant in in situ formed Cu quantum dots (QDs) (Cu-GDYNT) are prepared using the electrospun polyacrylonitrile nanofibers collected on the surface of electrolytic Cu foil as templates. The diameter of the Cu-GDYNT is controllable and the uniform size of the embedded Cu QDs is about 2.2 nm. And then, the uniformly dispersed and highly active supported catalysts of ruthenium nanoparticles (Rux/Cu-GDYNT) are produced using the Cu-GDYNT as the support. Among them, the Ru3/Cu-GDYNT exhibit outstanding HER performance at all pH levels. Only 17, 67 and 83 mV overpotential is required to reach a current density of 10 mA cm-2 in 1.0 M KOH, 0.5 M H2SO4 and 1.0 M neutral PBS solutions, respectively. The sample exhibits 3000 CV cycle stability and 20 h continuous electrolysis without performance degradation in an alkaline medium. This work provides a new idea for constructing the GDY-supported metal nanocatalysts.

A Finite Element Method for Determining the Mechanical Properties of Electrospun Nanofibrous Mats.

This study focuses on the mechanical properties of electrospun nanofibrous mats, highlighting the importance of the characteristics of single nanofibers in determining the overall mechanical behavior of the mats. Recognizing the significant impacts of the diameter and structural properties of the nanofibers, this research introduces a novel methodology for deriving the effects of the mechanical properties of single nanofibers on the aggregate mechanical performance of electrospun oriented nanofiber mats. For this purpose, a finite element method (FEM) model is developed to simulate the elastoplastic response of the mats, incorporating the influence of structural parameters on mechanical properties. The validation of the FEM model against experimental data from electrospun polyacrylonitrile (PAN) nanofibers with different orientations demonstrates its effectiveness in capturing the elastic-plastic tensile behaviors of the material and confirms its accuracy in terms of reflecting the complex mechanical interactions within the nanofibrous mats. Through a detailed analysis of how nanofiber diameter, orientation of fibers, length-to-width ratio, and porosity affect the mechanical properties of the mats, this research provides valuable insights for the engineering of nanofibrous materials to meet specific mechanical requirements. These findings improve our understanding of nanofibrous mat structures, allowing for better performance in diverse applications as well as highlighting the critical importance of identifying the properties of single nanofibers and their associated impacts on material design.

Electroactive nanofibrous membrane with antibacterial and deodorizing properties for air filtration

Water vapor from respiration can severely accelerate the charge dissipation of the face mask, reducing filtration efficiency. Moreover, the foul odor from prolonged mask wear tends to make people remove their masks, leading to the risk of infection. In this study, an electro-blown spinning electroactive nanofibrous membrane (Zn/CB@PAN) with antibacterial and deodorization properties was prepared by adding zinc (Zn) and carbon black (CB) nanoparticles to the polyacrylonitrile (PAN) nanofibers, respectively. The filtration efficiency of Zn/CB@PAN for PM0.3 was > 99% and could still maintain excellent durability within 4 h in a high-humidity environment (25 ℃ and RH = 95%). Moreover, the bacterial interception rate of the Zn/CB@PAN could reach 99.99%, and it can kill intercepted bacteria. In addition, the deodorization rate of Zn/CB@PAN in the moist state for acetic acid was 93.75% and ammonia was 95.23%, respectively. The excellent filtering, antibacterial, and deodorizing performance of Zn/CB@PAN can be attributed to the synergistic effect of breath-induced Zn/CB galvanic couples’ electroactivity, released metal ions, and generated reactive oxygen species. The developed Zn/CB@PAN could capture and kill airborne environmental pathogens under humid environments and deodorize odors from prolonged wear, holding promise for broad applications as personal protective masks.

Polymer-mediated vacancy defects of graphene sheets as high-performance cathode materials for aqueous zinc-ion hybrid supercapacitors

The electrochemical behavior of graphene sheets in energy storage system is closely related to its electronic structures. Specifically, structural vacancy defects can expose more active sites and enhance the electrochemical performance. However, it is still a challenging problem to realize valid defect regulation on improving the reaction kinetics of electrode materials. Herein, vacancy-defective graphene sheets were constructed through the thermal mediated method via intercalation of polyacrylonitrile nanofibers. The vacancy defects were generated from the NH3 gas resulting from polymer decomposition at gradient carbonization temperature. The obtained composites of the graphene sheets and carbon nanofibers demonstrate that the vacancy defects benefit to charge transport, allowing more electrons to pass through the interlayered structure, and enhance the adsorption capacitance during the reversible electrochemical process. In addition, the as-assembled Zn ion hybrid supercapacitors exhibit a high energy density of 129.9 Wh kg−1 and outstanding cyclic stability (99.8 % after 10,000 cycling). The confined polymer-mediated thermal modification strategy can afford abundant vacancy defective sites and exhibit promising outlook for constructing high-performance graphene-based electrode materials for Zn ion hybrid supercapacitors.

Flexible and freestanding temperature sensors based on laser carbonization of carbon nanofibers

A new single-step, low-cost method for producing a wearable, flexible temperature sensor has been developed using laser writing technology. The process involves carbonizing and patterning polymeric nanofibers to create a standalone laser-carbonized nanofibers (LCNFs) substrate. A large-area polyacrylonitrile nanofibers mat is first prepared using electrospinning and then carbonized with a high-power CO2 laser beam. The resulting LCNFs are highly conductive and retain their fibrous structure. The near-complete disappearance of polyacrylonitrile peaks in the FTIR measurements and the high-intensity characteristic peaks of carbon materials obtained in the Raman scattering measurements of the LCNFs confirm their complete carbonization. SEM microscopy showed that the fibrous structure of the LCNFs remained intact after the laser carbonization process with no significant damage. Additionally, TEM microscopy revealed that the LCNFs are made up of axially ordered graphene sheets, which form their unique fibrous structure. LCNFs' temperature sensor exhibits >87% higher temperature coefficient of resistance (TCR) than laser-induced graphene (LIG) temperature sensor on a polyamide substrate when tested under the same experimental conditions. The LCNFs sensor also boasts excellent resistance stability, mechanical stability, and flexibility. To fit various wearable applications and enhance the temperature-sensing capabilities, three different sensor patterns of LCNFs were created: square, serpentine, and heater. Among these patterns, the heater design exhibited superior TCR and temperature response. However, it also had a higher thermal mass compared to the other patterns.

CdBi2S4-Decorated Aminated Polyacrylonitrile Nanofiber for Photocatalytic Treatment of Cr(VI) and Tetracycline Wastewater.

The significant threat posed by the high toxicity of heavy metals and antibiotics in water pollutants has prompted a growing emphasis on the development of highly efficient removal methods for these pollutants. In this paper, flexible electrospinning polyacrylonitrile (PAN) nanofiber-supported CdBi2S4 was synthesized via a hydrothermal method, followed by amination treatment with diethylenetriamine (DETA). The as-prepared CdBi2S4/NH2-PAN nanofiber, enriched with sulfur vacancies, demonstrated outstanding visible-light trapping ability and a suitable band gap, leading to efficient separation and transport of photogenerated carriers, ultimately resulting in exceptional photocatalytic capability. The optimal 3-CdBi2S4/NH2-PAN nanofiber achieved impressive reduction rates of 92.26% for Cr(VI) and 96.45% for tetracycline hydrochloride (TCH) within 120 min, which were much higher than those for CdS/NH2-PAN, Bi2S3/NH2-PAN, and CdBi2S4/PAN nanofibers. After five cycles, the removal rate of the CdBi2S4/NH2-PAN nanofiber consistently remained above 90%. Their ease of separation and recovery from the application environment contributes to their practicality. Additionally, compared with conventional suspended particle catalyzers, the composite nanofiber exhibited remarkable flexibility and self-supporting properties.

Multi-functional nanofibrous membrane with antibacterial property for highly effective capture of PM0.3 and hydrogen sulfide

In order to reduce the possible harm caused by air pollution, including particulate matters (PM), harmful gases and airborne pathogens, high-efficiency air filtration materials are attracting more and more attention. Therefore, multifunctional materials that can filter these pollutants and kill pathogenic bacteria simultaneously are urgently desired. Herein, a copper-coordinated nanofibrous membrane, named PAN-P-Cu, was successfully prepared based on polyacrylonitrile (PAN) nanofibers grafted polyethyleneimine (PEI) by electrospinning and coordination assembly method. The PAN-P-Cu showed high filtration efficiency (99.9%) towards PM0.3 under an airflow velocity of 5.3 cm s−1 and high filtration efficiency (99.94%) towards PM10, respectively. Importantly, used membrane could be regenerated by a simple washing process. Moreover, PAN-P-Cu possessed removal property of 60 mg g−1 for hydrogen sulfide through the occurrence of chemical reactions. Furthermore, the PAN-P-Cu also exhibited excellent antibacterial activities against Escherichia coli and Staphylococcus aureus (>99.99%). This work may provide new insights on designing high-performance and multi-functional air filtration materials for public health protection in complicated environments.

In situ growth of ZIF-8 on nanofibrous membrane for long-term ultra-high flux coalescence separation of oil-in-water emulsion

The presence of oil-in-water (O/W) emulsions poses a serious threat to the equilibrium of aquatic ecosystems, contaminates potable water resources, and disrupts the structure of soil layers. Consequently, there is an urgent need for effective and economically viable methods for removing emulsified oil droplets from water. The coalescence method has been proposed as an effective means of separating O/W emulsions. In this study, we developed an in situ growth strategy to decorate zeolitic imidazolate framework-8 (ZIF-8) on electrospun polyacrylonitrile (PAN) nanofibers for coalescence separation. The in situ growth process commenced with pretreatment to activate the PAN membrane, creating anchor sites for zinc ions, which was followed by immersion in precursors of ZIF-8 particles. The incorporation of ZIF-8 enhanced amphiphilicity, and roughness, and imparted a positive charge to the membrane, which was anticipated to effectively demulsify and coalesce oil droplets with a negative charge. The ZIF-8/PAN nanofiber membrane obtained a separation ratio exceeding 99.9 % for surfactant-free emulsions and 97.1 % for surfactant-stabilized emulsions. It also demonstrated an ultra-high permeation flux of 21,177 L m−2 h−1 and 14,118 L m−2 h−1, respectively, in a long-term continuous separation process.

All‐Nanofiber Iontronic Sensor with Multiple Sensory Capabilities for Wearable Electronics

AbstractWearable multi‐functional sensor with practical features is crucial for applications in many areas such as e‐skin, health monitoring, and human‐computer interaction. Herein, an all‐nanofiber flexible breathable iontronic sensor based on polyacrylonitrile (PAN) nanofiber membrane doped with ionic liquid (IL) is prepared by electrospinning technique. Compared to the traditional capacitor's electrode‐dielectric‐electrode sandwich structure, an undoped PAN nanofiber membrane is added between the electrode and the dielectric layer as the spacer. The iontronic sensor demonstrated an impressive linear response in pressure ranges of 0–50 and 50–300 kPa, with linearity values of R12 = 0.992, R22 = 0.998 by adjusting the thickness of the spacer. Additionally, the iontronic sensor demonstrates excellent temperature response attributed to the thermal sensitivity of the IL. It exhibits high sensitivities of 8.5, 31.8, and 71.1% °C−1, along with low detection limits of 0.5°C, across temperature ranges of 20–40, 40–55, and 55–80 °C, respectively. To validate the sensor for practical applications, its uses are demonstrated in various scenarios, such as body joint flexion, heartbeat monitoring, encrypted messaging, and temperature‐sensitive gloves. This study enables the integration of pressure and temperature sensing functions to develop diverse and integrated designs for wearable electronic devices.

On the Hydrogen Peroxide Sensing employing Fibres composed of Polyvinyl alcohol (PVA) and Polyaniline (PANI)

The sensitivity of an electrocatalyst depends upon the kinetics of electrochemical reactions occurring at its surface. In this work, we prepared the polyvinyl alcohol (PVA) and polyaniline (PANI) nanofibres using a facile and cost-effective electrospinning method. We observed that the fibres composed of PANI and PVA exhibited efficient sensing of hydrogen peroxide (H2O2) as compared to the fibres prepared employing PVA alone. At low concentration of H2O2, a two-fold enhancement in the sensing activity is noticed in case of the fibre prepared using PVA-PANI (as compared to PVA fibres). On the other hand, at higher concentration, the sensitivity is around five times high. The enhancement in the sensing activity for PVA-PANI nanofibres is due to the increase in conductivity and electrochemical surface area upon addition of conducting PANI. The increased conductivity enhances the surface energy of the fibre and increased electrochemical surface area enhances the number of reactive sites, which results in enhanced sensing activity. The above analysis is further supported via the impedance analysis showing lower charge transfer resistance for PVA-PANI sample.

Polyacrylonitrile-based carbon nanofiber electrode fabricated via electrospun for supercapacitor application

The versatile properties of electrospun carbon nanofibers gaining attention for electrode materials for supercapacitors. The heat treatment process of stabilization played an important role before the carbonization process in electrode fabrication. In the present study, electrospun stabilized polyacrylonitrile nanofiber (St PAN) and carbonized Polyacrylonitrile nanofiber (CNF) at minimum temperature were used as active mass for supercapacitor electrodes. Stabilized CNF nanofiber sample showed a reduction in nanofiber diameter with increased carbon percentage. XRD results showed increased crystallinity in the CNF sample as compared with the Stabilized PAN sample. Electrochemical characterization was performed to measure specific capacitance and to analyze the charge storage mechanism. The proportion of capacitive and diffusion-controlled contributions to energy storage was estimated using Dunn’s model. The results obtained demonstrated that, in comparison to the St PAN electrode, the CNF electrode exhibited a greater capacitive-controlled contribution. The CNF sample has shown an increased capacitive contribution of 82.3% as compared with the St PAN sample. This work provides a method for making electrospun carbon nanofiber-based electrodes as well as a methodical methodology for examining the charge storage process.

Polyelectrolyte electrostatically self-assembled modified porous polyacrylonitrile nanofibers as adsorbents for anionic dye removal

Herein, we chose PAN with good sunlight and weather resistance and easy surface modification as the electrospinning material to prepare the PAN nanofiber membrane. Then the surface modification of the obtained PAN fiber membrane was carried out sequentially by alkali hydrolysis and acid neutralization to make the surface of the fiber membrane negatively charged. Finally, the positively charged polyelectrolyte PAH on the surface was selected as the functional material, and a simple and environmentally friendly electrostatic self-assembly method was adopted to modify the prepared PAN nanofiber membranes labeled as PAN@PAH. This treatment effectively increased the storage space and adsorption groups of the fiber membranes, which led to a significant increase in the removal ability of anionic dyes in wastewater. In particular, the PAN@PAH nanofiber membrane adsorbed 439.66 mg/g of methyl orange and 946.83 mg/g of Congo red, which showed better adsorption capacity than many other membranes reported in the literature. Moreover, the adsorption capacity of PAN@PAH remained at 90.19 % after eight adsorption-desorption cycles. The preparation method and modification strategy of this membrane adsorbent provides new ideas and methods for the removal of other anionic dyes.

Application of vertically ordered polyaniline nanofibers in enhancing the ORR activity of Pt catalysis

Pt-based nanocatalysts supported on carbon materials have exhibited remarkable catalytic activity in the oxygen reduction reaction (ORR). However, these catalysts still encounter challenges such as low utilization efficiency, weak binding strength with substrate and proneness to detachment from it. Consequently, we explore the potential application of electron-rich polymer as carrier in high efficiency ORR catalysts, the uniformly distributed Pt-PANI catalyst is successfully synthesized by taking advantage of ion-exchange property of polyaniline (PANI). As an emerging catalyst for ORR, Pt-PANI shows excellent ORR performance in acidic solution, the vertically aligned PANI nanoarrays accelerate the ion diffusion in electrolyte and promote the charge transfer at the interface, improving the catalytic activity of low-loading Pt-based catalyst. In short, this work provides a novel alternative beyond conventional carbonaceous materials for the selection of carriers for Pt-based catalyst.