Polyvinylidene Fluoride-graphene Oxide Research Articles

Study of Electrospun PVDF/GO Nanofibers as a Conductive Piezoelectric Heart Patch for Potential Support of Myocardial Regeneration

AbstractHeart patches are currently being utilized to repair damaged myocardium and are a promising way to address the limitations of current therapeutic strategies. Given the electromechanical nature of cardiac tissue, conductive or piezoelectric materials are of interest to researchers. An electrospinning method is used to synthesize and evaluate polyvinylidene fluoride/graphene oxide (PVDF/GO) nanocomposites. Effects of GO concentration (0, 0.1, 0.3, 0.5, 0.7, and 1 wt%) on the main physical‐mechanical characteristics of the patch are studied. Results show nanofibers containing 0.7 wt% GO with a diameter of 857 ± 168 nm, provide excellent tensile strength (0.51 ± 10.34 MPa). Fourier transform infrared and X‐ray diffraction analysis confirm the increase of the β‐polymer phase by adding 1 wt% of GO from 63% to 86%. However, the highest output voltage in the piezoelectric shock test is recorded at 9.44 V for a concentration of 0.5 wt%, which is increased by 8.2 times compared to the neat PVDF. In addition, human umbilical vein endothelial cell culture on the electrospun patches confirmed no toxicity as well as increased cell growth and proliferation (3.4 times) over 7 d. The developed material has the potential to be utilized as a heart patch due to its promising characteristics.

Conduction mechanism in hot-pressed Poly(vinylidene fluoride)/Graphene Oxide composites

Poly(vinylidene fluoride)/Graphene Oxide (PVDF/GO) composites were prepared by solvent casting and processed by hot pressing. Filler GO is synthesized by the improved Hummers method and purified by centrifuging. GO is characterized by XRD, FTIR, RAMAN, SEM, and TEM. XRD, FTIR, and DSC techniques were employed to characterize composites. AC conductivity data of PVDF and PVDF/GO composites with varying GO content were fitted with Jonscher’s power law at different temperatures, and the obtained DC conductivity was used to find the activation energy of the samples. The frequency exponent in power law is analyzed to identify the conduction mechanism in the composites. The frequency and temperature dependence of the exponent value and the nature of the frequency exponent with temperature confirm the overlapping large polaron tunneling as the responsible mechanism of conduction in PVDF/GO composites.

Effects of Film Confinement on Dielectric and Electrical Properties of Graphene Oxide and Reduced Graphene Oxide-Based Polymer Nanocomposites: Implications for Energy Storage

2D nanofillers such as graphene oxide (GO) and reduced GO (rGO)-based polymer nanocomposites have emerged as crucial materials for various applications, from flexible solid-state capacitors to electromagnetic interference (EMI) shielding devices. Specifically, the dielectric breakdown strength (EBD) and dielectric constant of polymer nanocomposite capacitors determine their ability to store energy, whereas frequency-dependent loss is crucial for EMI shielding applications. The miniaturization of energy storage and electronic devices demands a detailed understanding of the behavior of these polymer nanocomposites in the thin-film regime (micron to sub-micron thicknesses). In this work, we demonstrate the effect of confinement on the dielectric, electrical, and capacitive energy storage properties of the polyvinylidene fluoride (PVDF)–GO and PVDF–rGO films. We show that the dielectric permittivity is significantly impacted by the nanofiller confinement in thin (≈1 μm) PVDF polymer films, which is comparable to the lateral dimension of these 2D nanofillers. In thin PVDF–GO films, the nanofillers (and associated surface dipoles) become oriented quasi-parallel to the film interfaces, affecting the relative projected area to the applied electric field. The conductivity and loss tangent values increased as a function of frequency with reduced film thickness, which is beneficial to EMI shielding application. The EBD of the confined GO-based films was found to be relatively independent of the filler fraction, whereas rGO-based films increased with the filler fraction after an initial decrease. These results provide fundamental insights into rational design principles for using ultrathin GO and rGO-based polymer nanocomposite films in next-generation flexible electronic and energy storage devices.

Electrospun graphene oxide–polyvinylidene fluoride composite film preparation and application for air filtration

In this work, polyvinylidene fluoride (PVDF) and graphene oxide (GO) composite membranes were fabricated using electrospinning technology for particulate matter (PM) filtration. The preparation conditions like GO oxidation time, electrospinning solution composition, and GO content in the composite film, and the basic properties and filtration performance of PVDF–GO films were systematically analyzed. It was found that GO with lamellar structure was of great benefit to endow the membrane with excellent mechanical properties and particle capture capacity. The as-prepared PVDF–GO membranes with GO addition of 0.6 wt.% exhibited the highest tensile strength and PM filtration efficiency. This work demonstrated that blending GO in PVDF is a feasible modification to fabricate an effective PM filtration membrane.

High flux and complete dyes removal from water by reduced graphene oxide laminate on Poly Vinylidene Fluoride/graphene oxide membranes

Dyes molecules are the most common pollutants of wastewater in the environment from the textile industry to numbers of technologies include dyeing, printing, and painting procedures. Among membrane-based separation approaches as established methods in the water treatment industry, polymers attracted massive attention in the production of membranes due to their low cost and high-performance filtration of pollutants. However, hydrophobicity and low speed of filtration along with limited decontamination performance against some of the dyes, demand new approaches and membranes to overcome drawbacks points. Herein, a new design introduced including a support layer made by Poly Vinylidene Fluoride (PVDF)/Graphene Oxide (PGO) composite membrane via immersion precipitation process and a thin layer (≤100 nm) of reduced graphene oxide (rGO) deposited (as an active layer) through a simple vacuum filtration method. It has been observed that the presence of the GO sheets in the PGO composite improved the hydrophilicity of the membrane, water flux (from ~90 L m−2 h−1 bar−1 in pristine PVDF to ~1690 L m−2 h−1 bar−1 in PGO), and anti-fouling property. By deposition of rGO laminate on PGO support, dyes separation as high as ~99% can be achieved for most of the cationic and anionic dyes due to electrostatic adsorption, π−π interactions and molecular sieving. This approach opens new insight on hybrid designs for graphene-polymers based membrane toward efficient and fast removal of pollutants from wastewater.

Fabrication of tight GO/PVDF hollow fiber membranes with improved permeability for efficient fractionation of dyes and salts in textile wastewater

In this study, a graphene oxide/polyvinylidene fluoride (GO/PVDF) tight hollow fiber membrane (HFM) with improved permeability was fabricated via one-step direct spinning process to fractionate the dyes and salts (NaCl and Na2SO4) in textile wastewater. Scanning electron microscopy (SEM) indicated that the GO/PVDF HFM possessed a smooth and tight outer selective layer and a relatively porous and loose inner surface. The optimized HFM not only possesses a small mean pore radius of 1.14 nm, but also has a high pure water flux of 24.8 L/m2·h·bar. The stronger negative charge (− 40 mV at pH = 7) was obtained by the GO/PVDF HFM. Due to the synergistic effects of size exclusion and charge repulsion, the resultant HFM exhibited excellent rejection for dyes (i.e., close to 100% for Congo red and Methyl blue, 98.9% for Eriochrome black T) and low salts rejection (i.e., 1% for NaCl, 11% for Na2SO4). Besides, with appropriate addition of hydrophilic GO to the doped solution, the resultant membrane exhibited good hydrophilicity, antifouling property and excellent stability. The newly developed tight HFM would be of great significance for effective fractionation and treatment of textile wastewater.

Mixed matrix membranes for rubidium-dependent recognition and separation: A synergistic recombination design based on electrostatic interactions

Exposure and distribution of recognition sites are critical for membrane separation materials to enhance adsorption and separation efficiency toward rubidium ion. Herein, we prepared the rubidium (Rb) ion separation membranes (Rb-ISMs) through a delayed phase inversion method taking advantage of the different polarities between ethanol and water. Fabrication process was conducted through immersion of a poly (vinylidene fluoride)/graphene oxide (PVDF/GO) casting solution into coagulating bath containing 18-crown-6 (18C6) grafted mesoporous silica, ethanol and water. After phase inversion process, the as-prepared adsorbent materials were immobilized on membrane surface by strong electrostatic interaction force. The method could effectively avoid the embedding and aggregation recognition sites, and the coagulating bath only required the ethanol and water that was relatively healthy and environmental. The Rb-ISMs prepared at optimal conditions showed enhanced rebinding capacity (49.344 mg g−1) towards Rb±, with a superior rebinding selectivity (11.8, 6.82, 9.08 for Rb±/Ca2+, Rb±/Cs±, Rb±/Mg2+, respectively). Importantly, Rb-ISMs showed remarkable perm-selectivity and regeneration performance, which further demonstrated its potentials in the rapid and effective separation field of Rb ions.

A novel method for fabricating bioinspired layered nanocomposites using aligned graphene oxide/PVDF and their micromechanical modeling

Graphene and graphene derivatives are among the extensively studied materials as multifunctional reinforcement for polymeric materials. This is due to their relative ease of synthesis, interface engineering and wide range of property tailoring. In this study, we present a novel method for the fabrication of aligned graphene oxide/polyvinylidene fluoride (GO/PVDF) nanocomposite inspired by nacre-like materials. The process is based on the electrospinning of GO/PVDF solution on a rotating collecting drum to produce aligned fiber mats. The GO particles are forced to align in the direction of the fibers axis through the induced shear forces and the electric field resulting from the electrospinning process. Layered films can then be produced by successive folding and hot pressing. Microstructural analysis showed that the GO particles are well distributed and aligned with respect to the fiber axis. Mechanical testing showed enhancement in modulus and strength up to 0.3 wt%. However, fracture strain increased at 0.1 wt% and then decreased gradually for 0.2 and 0.3 wt%. Finite element modeling revealed the activation of crack deflection and excessive plastic deformation for 0.1 wt%, while cracks tend for coalesce forming a fracture plane and brittle fracture with further increase of GO content.

A Membrane Modified with Nitrogen-Doped TiO2/Graphene Oxide for Improved Photocatalytic Performance

An improved photocatalytic microfiltration membrane was successfully prepared by the impregnation method with nitrogen-doped TiO2/graphene oxide (GO) (NTG). By utilizing the unique role of N and GO, the photocatalytic activity of the membrane in UV and sunlight was improved. Compared with the Polyvinylidene Fluoride (PVDF) microfiltration membrane which was modified by TiO2, N-TiO2 (NT) and TiO2-GO (TG), the NTG/PVDF membrane exhibited high photocatalytic efficiency and significantly improved photodegradation power to the methylene blue (MB) solution under ultraviolet light and sunlight, with the photocatalytic efficiency reaching 86.5% and 80.6%, respectively. Scanning electron microscopy (SEM), X-ray diffractometry (XRD) and Fourier transform infrared spectroscopy (FT-IR) were used to analyze the morphology, crystal structure and chemical bonds of the membrane surface. The hydrophilicity of the modified PVDF microfiltration membrane was significantly improved, the flux of the pure water membrane reached 1672 Lm−2h−1, the flux of the MB solution was also significantly improved due to photodegradation. Therefore, the nitrogen-doped titanium dioxide graphene oxide PVDF microfiltration membrane (NTG/PVDF membrane) has great development prospects in sustainable water treatment.

In vitro osteogenic differentiation potential of the human induced pluripotent stem cells augments when grown on Graphene oxide-modified nanofibers

Due to the several limitations that surgeons are faced during bone tissue implantation there are daily increases in introducing new cell-co-polymer composites for use in bone tissue engineering approaches. In this study tried to develop a suitable nanostructured bio-composite for enhancing osteogenic differentiation of the human induced pluripotent stem cells (iPSCs). Polyvinylidene fluoride-Graphene oxide (PVDF-GO) nanofibers was fabricated by electrospinning and then characterized using scanning electron microscope, tensile and viability assays. After that osteogenic differentiation of the iPSCs was investigated in three groups, including PVDF, PVDF-GO and tissue culture plate as a control group. Alkaline phosphatase activity and calcium content of the iPSCs cultured on PVDF-GO were significantly higher than those cultured on other groups. In addition, Runx2, osteocalcin and osteonectin genes were up regulated in iPSCs cultured on PVDF-GO significantly higher than those cells cultured on PVDF and control. Finally, osteocalcin and osteopontin proteins expression evaluated and the results confirmed higher osteoinductivity of the PVDF-GO nanofibers in comparison with the PVDF nanofibers. According to the results, it was demonstrated that PVDF-GO nanofibers have a great osteoinductive potential and taking together iPSCs-PVDF-GO nanofibrous construct can be an appropriate bio-implant to use for bone tissue engineering applications.

Simultaneously facilitating dispersion and thermal reduction of graphene oxide to enhance thermal conductivity of poly(vinylidene fluoride)/graphene nanocomposites by water in continuous extrusion

Poly(vinylidene fluoride)/graphene oxide (PVDF/GO) nanocomposites were fabricated by a melt mixing extrusion especially with water injection. It was found for the first time that the injected water simultaneously facilitated the dispersion and in situ thermal reduction of the unfunctionalized GO in the PVDF matrix under environmental friendly conditions in melt extrusion. The injected water accelerated the removal of oxygen-containing groups especially CO group and the transformation of carbon sp3 into sp2 bonds of the GO through enhancing the interaction between the PVDF and GO and facilitating the hydrothermal dehydration of GO. The interfacial interaction between the GO and PVDF facilitated the nucleation of crystallites at the PVDF-GO interfaces, which can reduce the interfacial thermal resistivity. Thus, the thermal conductivity of the PVDF/GO nanocomposites prepared with water injection was significantly improved. Compared with the neat PVDF sample, the enhancements in the thermal conductivities were 64.1% and 132.5% for the nanocomposites with low loading of 1.0 wt% GO prepared without and with water injection, respectively. The results provide a scalable and environmentally benign approach for fabricating thermally conductive nanocomposites without complex dispersion and reduction processes.

Porous PVdF/GO Nanofibrous Membranes for Selective Separation and Recycling of Charged Organic Dyes from Water.

Graphene oxide (GO) membranes are robust and continue to attract great attention due to their fascinating properties, despite their potential issues regarding stability and selectivity in aqueous-phase processing. That being said, however, the functional moieties of GO could be used for membrane surface modification, while ensuring simultaneous removal and recycling of industrial organic dyes. Herein, we present a versatile porous structured polyvinylidene fluoride-graphene oxide (PVdF-GO) nanofibrous membranes (NFMs), prepared by using simple and straightforward electrospinning approach for selective separation and filtration. The GO nanosheets were distributed homogeneously throughout the PVdF nanofiber, regulating the surface morphology and performance of PVdF-GO NFM. The PVdF-GO NFMs possesses high mechanical strength and surface free energy (SFE), consequently resulting high permeation and filtration efficiency as compared to PVdF NFM. The selectivity (99%) toward positively charged dyes based on electrostatic attraction, while maintaining rejection (100%) for negatively charged dye from mixed solutions highlight the role of GO in PVdF-GO NFM, owing to uniform pores and negatively charged surface. In addition, the actual efficiency of NFMs could be recovered easily up to three consecutive filtration cycles by regeneration, thereby assuring high stability. The high permeation, purification and filtration efficiency, good stability and recycling of PVdF-GO NFMs are promising for use in practical water purification and applications, particularly for selective filtration and recycling of dyes.

Facile green fabrication of well dispersed poly(vinylidene fluoride)/graphene oxide nanocomposites with improved properties

Poly(vinylidene fluoride)/graphene oxide (PVDF/GO) nanocomposites are fabricated for the first time by one-step water-assisted mixing extrusion (WAME) via injecting GO suspension into PVDF melt. Introduced GO layers increase the crystallinities especially the β-phase fractions of the PVDF due to the special interaction between carbonyl groups at the GO surface and fluorine groups in the PVDF. The GO layers are found to reinforce the PVDF matrix, as evidenced by the increased Young's moduli and tensile strengths. Predicted aspect ratio of the GO layers using the Halpin–Tsai equation is much larger than that in the PGOs samples, which may be attributed strong interaction between the PVDF chains and GO layers. TEM micrographs demonstrate that the GO layers are well exfoliated and dispersed in the PVDF matrix, the mechanism of which is analyzed from interactions among the PVDF chains, GO layers, and water molecules during the WAME. The WAME can be an excellent method for facile, continuous and mass fabrication of polymer/graphene nanocomposites.

Enhanced ferroelectric and pyroelectric properties of poly(vinylidene fluoride) with addition of graphene oxides

Poly(vinylidene fluoride)/graphene oxide (PVDF/GO) nanocomposites are synthesized and their structural, ferroelectric, and pyroelectric properties are investigated. The dielectric spectrum analysis and P-E loop tests indicate that the nanocomposites exhibit enhanced ferroelectric and pyroelectric properties compared with those of poly(vinylidene fluoride) samples. The isothermal crystallization kinetics of PVDF/GO nanocomposites quantitatively determined by differential scanning calorimetry demonstrates that GOs facilitate the crystallization of the PVDF. Dynamic mechanical analyses on the PVDF/GO reveal that the amorphous and crystalline phases of PVDF are modified by the addition of GO sheets. The GO-enhanced formation of crystalline β phase in PVDF could result from the strong interaction between the –C = O groups in GO and the –CF2 groups in PVDF, and the GO-induced ordering of the microstructures of amorphous and crystalline phases. The results suggest that PVDF/GO nanocomposites could be promising dielectric materials used in sensors, transducers, and actuators.

Fabrication and characterization of highly efficient flexible energy harvesters using PVDF–graphene nanocomposites

This paper describes the development of flexible energy harvesters using PVDF–graphene nanocomposites. Nanocomposite films are prepared by simple solution casting of polyvinylidene fluoride/graphene oxide (PVDF/GO) solution. PVDF/reduced graphene oxide (PVDF/RGO) films are produced by in situ thermal reduction of PVDF/GO films. The effects of the presence of GO and RGO on the characteristics of the PVDF are examined through scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), Fourier transform infrared spectroscopy (FTIR) and x-ray diffraction (XRD) measurements. The ferroelectric behavior and dielectric constant of the nanocomposite show remarkable increase compared to those of pure PVDF for a value of 0.1 wt% of GO loading. The PVDF/RGO film-based energy harvesting (EH) device generates higher energy compared to those of PVDF and PVDF/GO films. The nanocomposite EH device scavenges a maximum power of 36 nW against a load resistance of 704 kΩ.

Improved hydrophilicity, permeability, antifouling and mechanical performance of PVDF composite ultrafiltration membranes tailored by oxidized low-dimensional carbon nanomaterials

Polyvinylidene fluoride (PVDF)–oxidized carbon nanotubes (OMWCNTs), PVDF–graphene oxide (GO) and PVDF–OMWCNTs–GO composite ultrafiltration membranes were prepared by solution-blending the ternary mixture of PVDF–oxidized low-dimensional carbon nanomaterials–dimethylacetamide in combination with the phase inversion method. The microscope images of the PVDF matrix microstructure showed that the composite membranes exhibited a bigger mean pore size and higher roughness parameters than pristine membranes. The contact angle of the membranes decreased from 78.5° (PVDF) to 66.8° (PVDF–OMWCNTs), 66.4° (PVDF–GO) and 48.5° (PVDF–OMWCNTs–GO). For the PVDF–OMWCNTs, PVDF–GO and PVDF–OMWCNTs–GO composite membranes, there was a 99.33%, 173.03% and 240.03% increase in permeation flux and a 21.71%, 17.23% and 14.29% increase in bovine serum albumin (BSA) rejection, respectively, compared with those of the pristine membranes. The newly developed composite ultrafiltration membranes demonstrate an impressive prospect for the anti-irreversible fouling performance in multi-cycle operations from BSA treatment. Additionally, the addition of OMWCNTs and GO increased the tensile strength of composite membranes from 1.866 MPa to 2.106 MPa and 2.686 MPa, respectively. Conspicuously, the PVDF composite ultrafiltration membranes endowed with oxidized low-dimensional carbon nanomaterials demonstrated fascinating hydrophilicity, permeability, antifouling and mechanical performance and promising application prospects owing to the rich oxygen-containing functional groups, high specific surface and synergistic effect of inorganic additive.

A graphene oxide–polyvinylidene fluoride mixture as a precursor for fabricating thermally reduced graphene oxide–polyvinylidene fluoride composites

A solid mixture of graphene oxide (GO) with polyvinylidene fluoride (PVDF) was investigated as the precursor material for fabricating graphene–PVDF nanocomposites. The mixture was prepared by solution mixing GO in PVDF solution followed by coagulation. Hot-pressing of the mixture led to the reduction of GO to graphene, and transformed the material to a graphene–PVDF nanocomposite. Consequently, the in situ thermally reduced graphene (TRG) sheets were found to be dispersed homogeneously in the polymer matrix. This resulted in a very low percolation threshold of 0.12 vol% TRG. In addition, hot-pressed GO–PVDF mixtures with higher filler loadings were employed as the master batches for forming conductive polymer composites by melt compounding. This processing route has great potential for scalable production of electrically conductive graphene–polymer nanocomposites.