Polyacrylonitrile Films Research Articles

Optical fiber sensing probe for detecting a carcinoembryonic antigen using a composite sensitive film of PAN nanofiber membrane and gold nanomembrane

An optical fiber sensing probe using a composite sensitive film of polyacrylonitrile (PAN) nanofiber membrane and gold nanomembrane is presented for the detection of a carcinoembryonic antigen (CEA), a biomarker associated with colorectal cancer and other diseases. The probe is based on a tilted fiber Bragg grating (TFBG) with a surface plasmon resonance (SPR) gold nanomembrane and a functionalized polyacrylonitrile (PAN) PAN nanofiber coating that selectively binds to CEA molecules. The performance of the probe is evaluated by measuring the spectral shift of the TFBG resonances as a function of CEA concentration in buffer. The probe exhibits a sensitivity of 0.46 dB/(µg/ml), a low limit of detection of 505.4 ng/mL in buffer, and a good selectivity and reproducibility. The proposed probe offers a simple, cost-effective, and a novel method for CEA detection that can be potentially applied for clinical diagnosis and monitoring of CEA-related diseases.

Three-dimensional nitrogen and oxygen co-doped hierarchical porous carbons prepared from polyacrylonitrile/polyamic acid composite films for supercapacitors

Porous carbon materials are widely used in energy storage, adsorption, catalysis, and wastewater treatment. Polymer composite films of polyacrylonitrile (PAN) and polyamic acid (PAA) were firstly prepared by phase separation with modulation of coagulation bath composition. Using these composite films as precursors, nitrogen and oxygen co-doped porous carbon materials were successfully fabricated by preoxidation, carbonization, and subsequent NaOH activation. The porous carbons had a three-dimensional interconnected structure with a specific surface area of 450–737 m2 g−1. The pore volume was 0.245–0.508 m3 g−1 and the pore size mainly located between 1 and 5 nm. The activated porous carbon obtained from PAN/PAA coagulated at a DMSO to water ratio of 3 showed a high oxygen content of 28.0 wt% and nitrogen content of 3.3 wt%. The resultant porous carbon exhibited a good mass-specific capacitance of 407.7 F g−1 at a current density of 0.5 A g−1, an excellent rate capability (237.7 F g−1 at 20 A g−1) and cyclic stability. Using the material as the electrode, a coin-cell symmetric supercapacitor (CR2032) was assembled, which provided a specific capacitance of 156 F g−1 at 0.1 A g−1 and a maximum energy density of 10.9 Wh kg−1 at a power density of 50 W kg−1. The high number of heteroatoms as well as the textural properties could be beneficial for the improvement of electrochemical performance of the carbon-based supercapacitors.

Porous Carbons Prepared from Polyacrylonitrile Doped with Graphitic Carbon Nitride or Melamine for Supercapacitor Applications

AbstractMelamine and graphitic carbon nitride (g‐C3N4) obtained by thermal condensation of melamine were doped in polyacrylonitrile (PAN) films. Nitrogen‐doped porous carbons were then prepared by pyrolysis of the composite films. Though all the porous carbons had a high nitrogen content of at least 10 %, g‐C3N4 was more efficient than melamine in nitrogen doping. The nitrogen content was elevated with the increase of the amount of each dopant, the highest value of 19.0 % was achieved by g‐3 (porous carbon obtained from the PAN/g‐C3N4 composite film with a mass ratio of 3). Amongst the nitrogen functionalities, pyridinic‐N and pyrrolic‐N held a percentage of at least 80 %. Compared with the carbon materials obtained from melamine doped PAN films, those from g‐C3N4 doped ones exhibited larger surface area and average pore size, and higher pore volume. The difference mainly resulted from the thermostability and size of the dopants. The g‐C3N4 doped materials thus presented more excellent electrochemical properties. The specific capacitance of g‐3 electrode was 135.3 F/g at a current density of 0.5 A/g. Rather than melamine, g‐C3N4 could improve the chemical composition and textural properties of the carbon materials, thus enhancing their supercapacitor performance.

Coregulation of Li/Li+ Spatial Distribution by Electric Field Gradient with Homogenized Li-Ion Flux for Dendrite-Free Li Metal Anodes.

Lithium (Li) metal batteries are highly sought after for their exceptional energy density. However, their practical implementation is impeded by the formation of dendrites and significant volume fluctuations in Li, which stem from the uneven distribution of Li-ions and uncontrolled deposition of Li on the current collector. Here, an amino-functionalized reduced graphene oxide covered with polyacrylonitrile (PrGN) film with an electric field gradient structure is prepared to deal with such difficulties. This novel current collector serves to stabilize Li-metal anodes by regulating Li-ion flux through vertically aligned channels formed by porous polyacrylonitrile (PAN). Moreover, the amino-functionalized reduced graphene oxide (rGN) acts as a three-dimensional (3D) host, reducing nucleation overpotential and accommodating volume expansion during cycling. The combination of the insulating PAN and conducting rGN creates an electric field gradient that promotes a bottom-up mode of Li electrodeposition and safeguards the anode from interfacial parasitic reactions. Consequently, the electrodes exhibit exceptional cycle life with stable voltage profiles and minimal hysteresis under high current densities and large areal capacities.

Interfacial Photopolymerization: A Method for Light-Based Printing of Thermoplastics.

Ultraviolet (UV) printing of photopolymers is a widely adopted manufacturing method because of its high resolution and throughput. However, available printable photopolymers are typically thermosets, resulting in challenges in postprocessing and recycling of printed structures. Here, we present a new process called interfacial photopolymerization (IPP) which enables photopolymerization printing of linear chain polymers. In IPP, a polymer film is formed at the interface between two immiscible liquids, one containing a chain-growth monomer and the other containing a photoinitiator. We demonstrate the integration of IPP in a proof-of-concept projection system for printing of polyacrylonitrile (PAN) films and rudimentary multi-layer shapes . IPP shows in-plane and out-of-plane resolutions comparable to conventional photoprinting methods. Cohesive PAN films with number-average molecular weights greater than 15 kg mol-1 are obtained, and to our knowledge this is the first report of photopolymerization printing of PAN. A macrokinetics model of IPP is developed to elucidate the transport and reaction rates involved and evaluate how reaction parameters affect film thickness and print speed. Last, demonstration of IPP in a multilayer scheme suggests its suitabiliy for three-dimensional printing of linear-chain polymers.

Electrochemically Stable Rechargeable Lithium-Sulfur Batteries Equipped with an Electrospun Polyacrylonitrile Nanofiber Film.

The high theoretical charge-storage capacity and energy density of lithium-sulfur batteries make them a promising next-generation energy-storage system. However, liquid polysulfides are highly soluble in the electrolytes used in lithium-sulfur batteries, which results in irreversible loss of their active materials and rapid capacity degradation. In this study, we adopt the widely applied electrospinning method to fabricate an electrospun polyacrylonitrile film containing non-nanoporous fibers bearing continuous electrolyte tunnels and demonstrate that this serves as an effective separator in lithium-sulfur batteries. This polyacrylonitrile film exhibits high mechanical strength and supports a stable lithium stripping and plating reaction that persists for 1000 h, thereby protecting a lithium-metal electrode. The polyacrylonitrile film also enables a polysulfide cathode to attain high sulfur loadings (4-16 mg cm-2) and superior performance from C/20 to 1C with a long cycle life (200 cycles). The high reaction capability and stability of the polysulfide cathode result from the high polysulfide retention and smooth lithium-ion diffusion of the polyacrylonitrile film, which endows the lithium-sulfur cells with high areal capacities (7.0-8.6 mA·h cm-2) and energy densities (14.7-18.1 mW·h cm-2).

Formation and structure of iodine complex of polyacrylonitrile studied by vibrational spectroscopy

It has been reported that polyacrylonitrile (PAN) can form a complex with polyiodide ions, which can give some interesting thermal and electronic properties to PAN. However, the formation process and structure characteristics of the PAN-iodine complex interpreted from the molecular level are still unclear. The present research is devoted to clarifying the above problems by studying the PAN film immersed in the iodine aqueous solution with different concentrations and counter cations based on IR and Raman spectroscopy in detail. We have found that the PAN-iodine complex can form through the intermolecular interaction between PAN chains and I 5 − ions by immersing the PAN film into the iodine aqueous solution with an iodine concentration higher than 0.1 mol/L. The ν (CN) and δ (CH 2 ) modes in the IR spectra of PAN showed a remarkable shift through forming the complex in the 1 mol/L iodine solution. Moreover, the PAN-iodine complex formed in the iodine solutions containing the different types of counter ions (K + , Na + , Li + ) may have different structures based on different band positions of ν (CN), δ (CH 2 ), and ν (CH 2 ) mode in their IR spectra. More interestingly, we found that during the formation of the complex, the content of planer zigzag conformation along the atactic PAN chain increased obviously. The present study results may inspire to further develop PAN as a functional polymer material. • The formation process and structure characteristics of the PAN-iodine complex were investigated. • PAN-iodine complex is formed by the intermolecular interactions between PAN chains and I 5 − ions. • Content of the planer zigzag conformation along the PAN chain increases obviously through the complex formation.

On‐Chip Direct Laser Writing of PAN‐Based Carbon Supercapacitor Electrodes

Back Cover: Article number 2100731 describes the fabrication of a micro-supercapacitor on a printed circuit board. Volker Strauss, Alexander J. C. Kuehne, and co-workers develop a laser-carbonization process for polyacrylonitrile films, leading to patterned, interdigitated carbon electrodes. The unexposed, non-carbonized areas of the film can be peeled-off to fully expose the carbonized electrodes to an electrolyte. Specific capacities as high as 260 µF cm–2 can be achieved.

On-Chip Direct Laser Writing of PAN-Based Carbon Supercapacitor Electrodes.

The carbonization of polyacrylonitrile (PAN) by direct laser writing to produce microsupercapacitors directly on-chip is reported. The process is demonstrated by producing interdigitated carbon finger electrodes directly on a printed circuit board (PCB), which is then employed to characterize the supercapacitor electrodes. By varying the laser power, the process can be tuned from carbonization to material ablation. This allows to not only convert pristine PAN films into carbon electrodes, but also to pattern and cut away non-carbonized material to produce completely freestanding carbon electrodes. While the carbon electrodes adhere well to the printed circuit board, non-carbonized PAN is peeled off the substrate. Specific capacities as high as 260 µF cm⁻2 are achieved in a supercapacitor with 16 fingers.

Non-homogeneous dispersion of graphene in polyacrylonitrile substrates induces a migrastatic response and epithelial-like differentiation in MCF7 breast cancer cells

BackgroundRecent advances from studies of graphene and graphene-based derivatives have highlighted the great potential of these nanomaterials as migrastatic agents with the ability to modulate tumor microenvironments. Nevertheless, the administration of graphene nanomaterials in suspensions in vivo is controversial. As an alternative approach, herein, we report the immobilization of high concentrations of graphene nanoplatelets in polyacrylonitrile film substrates (named PAN/G10) and evaluate their potential use as migrastatic agents on cancer cells.ResultsBreast cancer MCF7 cells cultured on PAN/G10 substrates presented features resembling mesenchymal-to-epithelial transition, e.g., (i) inhibition of migratory activity; (ii) activation of the expression of E-cadherin, cytokeratin 18, ZO-1 and EpCAM, four key molecular markers of epithelial differentiation; (iii) formation of adherens junctions with clustering and adhesion of cancer cells in aggregates or islets, and (iv) reorganization of the actin cytoskeleton resulting in a polygonal cell shape. Remarkably, assessment with Raman spectroscopy revealed that the above-mentioned events were produced when MCF7 cells were preferentially located on top of graphene-rich regions of the PAN/G10 substrates.ConclusionsThe present data demonstrate the capacity of these composite substrates to induce an epithelial-like differentiation in MCF7 breast cancer cells, resulting in a migrastatic effect without any chemical agent-mediated signaling. Future works will aim to thoroughly evaluate the mechanisms of how PAN/G10 substrates trigger these responses in cancer cells and their potential use as antimetastatics for the treatment of solid cancers.Graphical

Selective Removal of Cesium Ion from Water by Ferro-hexacyanoferrate Immobilized Polyacrylonitrile Film

After the accident at Fukushima Nuclear Power Plant, the removal of cesium from water became an emerging issue. In this study, ferro hexacyanoferrate-polyacrylonitrile (FeHCF-PAN) film was prepared and used as a adsorbent for the removal of cesium from water. A batch adsorption experiments were systematically carried out to assess the effect of different parameters such as presence of competing cations, contact time, initial cesium concentration and temperature on the adsorption of cesium on FeHCF-PAN film. The presence of competing cations showed no adverse effect on cesium removal. Langmuir, Freundlich and Dubinin-Radushkevich isotherm models were fitted to the obtained experimental adsorption data and it was observed that the adsorption of cesium on the FeHCF-PAN film was better represented by the Langmuir model. The maximum monolayer adsorption capacity was found to be 76.92 mg/g at DIW and 100.0 mg/g at seawater, respectively. The pseudo-second-order kinetic model described well the kinetic data, and resulted in the activation energy of 24.02 kJ/mol, which indicate that the adsorption mechanism was chemisorption. Adsorption thermodynamic parameters such as ΔG°, ΔH° and ΔS° were calculated and showed that the adsorption of cesium is endothermic process and spontaneous in nature.

Study on acidified carbon nanotubes modified polyacrylonitrile hollow fiber membrane

In this paper, the adsorption capacity of CNT modified polyacrylonitrile (PAN) film on copper ions under different conditions was studied by the adsorption experiment of the prepared multilayer diazo resin acidified carbon nanotubes/PAN composite film. The concentration of copper ion solution before and after adsorption was measured by inductively coupled plasma (ICP). The results show that the adsorption capacity of the pan film modified by CNT increases first and then reaches the adsorption equilibrium with the increase of the adsorption time of copper ion, and the adsorption capacity of the pan film modified by CNT increases with the increase of the initial concentration of copper ion and the external temperature With the increase of solution pH, the adsorption capacity of CNT modified polyacrylonitrile membrane to copper ion increases first and then decreases; after multiple desorption/adsorption of the modified membrane which has reached adsorption equilibrium, the membrane still has CNT adsorption capacity to copper ion, indicating that the membrane has excellent recycling performance.

Direct-current piezoelectric nanogenerator based on two-layer zinc oxide nanorod arrays with equal c-axis orientation for energy harvesting

Direct current (DC) piezoelectric nanogenerators, that can harvest mechanical energy into electrical power, have been extensively studied for driving low-power electronic devices without pre-rectification. However, the output power of most developed DC generators is generally too low to satisfy the requirements of diverse micro-electronic devices. Herein, we design a high-output Schottky DC nanogenerator consisting of a top gold electrode, the piezoelectric layer of zinc oxide (ZnO) nanorod arrays grown on polarized polyacrylonitrile film, a bottom copper electrode with ZnO nanorod arrays, where the crystallographic c-axis orientation of both ZnO nanorod arrays trends to be the same. The fabricated DC nanogenerator shows the peak voltage and current density as high as 1.6 V and 7.2 μA/cm2, respectively, which are several times higher than that of a pure ZnO-based nanogenerator. It has been demonstrated to harvest ambient tiny mechanical energy, including human activity, impact/collision, and sound vibration, to power commercial microelectronics directly, and to charge a storage capacitor for driving a heath-care device. Such novel DC nanogenerator may have great application prospects in self-powered electronics, structure and human health monitoring, and many more places.

Radio Frequency Heating Response of Polyacrylonitrile (PAN) Films and Nanofiber Mats

Radio Frequency Heating Response of Polyacrylonitrile (PAN) Films and Nanofiber Mats

Cell design for the electrodeposition of polyacrylonitrile onto graphite composite electrodes for use in lithium-ion cells

Polyacrylonitrile (PAN) is among the most common polymer materials in the world thanks to its versatility in a wide range of applications. Of importance to this work is its use in electrochemical cells. PAN has seen use as a separator material and as a binder material in lithium-ion cells. Expanding upon innovations made in recent decades for electrodepositing PAN onto conductive surfaces, this work details methods used to apply PAN as a thin coating to graphite composite electrodes; the resultant films may then be used for further electrochemical analysis in a lithium-ion cell. Graphite electrodes coated with electrodeposited PAN films were produced of a practical size for electrochemical testing in Swagelok cells; optical microscopy images of the resulting PAN coated graphite electrodes were also recorded to study the morphology of the coating.

Preparation of Nanoscale Urushiol/PAN Films to Evaluate Their Acid Resistance and Protection of Functional PVP Films.

Different amounts of urushiol were added to a fixed amount of polyacrylonitrile (PAN) to make nanoscale urushiol/PAN films by the electrospinning method. Electrospinning solutions were prepared by using dimethylformamide (DMF) as the solvent. Nanoscale urushiol/PAN films and conductive Poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate)(PEDOT:PSS)/polyvinyl pyrrolidone (PVP) films were prepared by electrospinning. In order to prepare an electrospun sandwich nanoscale film, urushiol/PAN films were deposited as both the top and bottom layers and PEDOT:PSS/PVP film as the inner layer. When the PAN to urushiol ratio was 7:5, the fiber diameter ranged between 150 nm and 200 nm. The single-layer urushiol/PAN film could not be etched after being immersed into 60%, 80%, and 100% sulfuric acid (H2SO4) for 30 min, which indicated the improved acid resistance of the PAN film. The urushiol/PAN film was used to fabricate the sandwich nanoscale films. When the sandwich film was immersed into 80% and 100% H2SO4 solutions for 30 min, the structure remained intact, and the conductive PVP film retained its original properties. Thus, the working environment tolerability of the functional PVP film was increased.

Fulgide Derivative-Based Solid-State Reversible Fluorescent Switches for Advanced Optical Memory

Fulgide Derivative-Based Solid-State Reversible Fluorescent Switches for Advanced Optical Memory

Alignment of linear polymeric grains for highly stable N-type thin-film transistors

Summary Temperature-insensitive properties are attractive for most electronics, including polymeric semiconducting devices. Especially, polymeric field-effect transistors (FETs) with high mobility have been important research targets due to their broad applications. However, polymeric FETs with stable charge transport operating at extremely cold or hot zones are faced with enormous challenges. In this study, the polyacrylonitrile was found to significantly tune the sizes of pre-aggregates of polymers in solutions and the crystallinity of the polymeric films. The orientation of 5–25 μm linear grains in the films were prepared through the bar-coating process with polyacrylonitrile as an additive, which stabilized the electron mobility over a wide range of temperatures. The linear-grain morphology of the film contributed to reducing the holes and grain boundaries in the transport paths of carriers. Typically, the top-gate FETs based on P(NDI2OD-T2) displayed a stable electron transporting behavior from 200 to 460 K, with mobility greater than 3.5 cm2V−1s−1.

Hydrogen detection properties of palladium sputtered polyacrylonitrile nanofibrous layers

AbstractIn this research, electrospun polyacrylonitrile (PAN) nanofibrous layers are investigated as substrate for palladium‐based resistive type hydrogen sensors. The fabricated sensors showed sensitivity to hydrogen with a concentration as low as 12 ppm at room temperature. Up to 50 ppm hydrogen concentration, hydrogen induced lattice expansion (HILE) constituted the mechanism, whereas, with concentrations of 125 ppm and higher, palladium hydride formation (PdHx) mechanism ruled. For equal palladium thickness, the response of the sensors increased with increasing nanofiber diameter. With constant diameter of nanofibers, response and response time increased with thicker palladium layer. The sensor with 104 nm nanofibers and 4 nm palladium layer showed the best behavior. The sensor with nanofibrous substrate showed a higher response and lower response time in comparison to glass, PAN film, and PAN fibrous (fiber diameter: 16 μm, non‐nanofiber) substrate.

Uranium concentration using reactive polymer thin films for spectroscopic analyses

This contribution describes the development of reactive polymer films for the concentration of uranium from circumneutral pH solutions for spectroscopic analyses. These films were prepared by grafting uranium-selective polymers from polyethersulfone (PES) films via UV-initiated polymerization, and by introducing uranium-selective functional groups to polyacrylonitrile (PAN) films by chemical reaction. Ellipsometry was used to study poly(phosphoric acid 2-hydroxyethyl methacrylate ester) film growth kinetics on PES films. X-ray photoelectron spectroscopy of modified PAN films revealed conversion of nitrile groups to amidoxime groups to be as high as 40% and showed that the extent and depth of reaction could be varied precisely. Static uptake experiments with solutions of depleted uranium spiked with 233U were conducted to determine uranium binding capacities and kinetics of the modified polymer films at different pH values from 4 to 8. Sorption isotherm data were fitted to the Langmuir model, and the highest sorption capacities of 1.09 × 10−2 ± 1.03 × 10−3 mmol m−2 and 1.02 × 10−2 ± 3.00 × 10−3 mmol m−2 were obtained at pH 6 for modified PAN (M-PAN) and PES (M-PES) films. Capacities at pH 4 and 8 were lower and could be explained by differences in sorption mechanisms. Uranium batch uptake kinetics followed a pseudo-second order rate model. Equilibrium uptake was attained within 3 h for M-PAN film and 1 h for M-PES film. Alpha spectroscopy pulse height spectra were analyzed to study the role of selective layer film thickness on peak energy resolution. Full width at half maximum values from 29 to 41 keV were recorded for M-PAN film and from 26 to 45 keV for M-PES film. Whereas uranium uptake increased with selective layer film thickness and varied with polymer chemistry/extent of modification, the peak energy resolution was independent of layer thickness and polymer chemistry within the experimental measurement uncertainties. Results from this work are being used to guide the development of thin-film composite membrane-based detection methods for the rapid, fieldable analysis of radionuclides in water for nuclear forensics investigations and environmental studies.