We present the electrical and supercapacitive performance of graphene nanoplatelets in polymer nanocomposites and flexible solid state electrical double layer capacitors (EDLC) respectively. Graphene-doped poly (3,4-ethylenedioxythiophene) (PEDOT) coated polyethylene terephthalate (PET) and glass exhibited transmittance above 95% and electrical conductivity of 2.70 × 10ˉ1 S·cmˉ1 and 9.01 × 10ˉ1 S·cmˉ1 respectively. Graphene loaded polymethyl methacrylate (PMMA) and polystyrene (PS) nanocomposites showed electrical conductivity as high as 2.11 × 10ˉ1 S·cmˉ1 at low loadings of 2 wt%. The use of graphene was necessitated by the need to increase the EDLC capacitance and energy density since it provides high effective surface area. The polymer gel membrane made from polyvinylidene fluoride-co-hexafluoropropylene (PVDF-co-HFP) and the Ionic Liquid (IL) 1-butyl-3-methylimidazolium hexafluorophosphate exhibited high porosity which made it suitable for use as separator in the EDLC. The highest recorded specific capacitance was 133.82 F/g which can be attributed to the porosity of the IL containing PVDF-co-HFP membrane and the large surface area of the graphene electrodes. At an operating voltage of 3.5 V the energy density was found to be 56.92 Wh·Kgˉ1. All chemicals were research grade and were obtained from Sigma Aldrich.

Composite porous supercapacitor electrodes were prepared by growing poly(3,4-ethylenedioxythiophene) (PEDOT) on graphite nanoplatelet- or graphene nanoplatelet-deposited open-cell polyurethane (PU) sponges via a vapor phase polymerization (VPP) method. The resulting composite supercapacitor electrodes exhibited great capacitive performance, with PEDOT acting as both the conductive binder and the active material. The chemical composition was characterized by Raman spectroscopy and the surface morphology was characterized by scanning electron microscopy (SEM). Cyclic voltammetry (CV), charge-discharge (CD) tests and electrochemical impedance spectroscopy were utilized to study the electrical performance of the composite electrodes produced in symmetrically configured supercapacitor cells. The carbon material deposited on PU substrates and the polymerization temperature of PEDOT affected significantly the PEDOT morphology and the electrical properties of the resulting composite sponges. The highest areal specific capacitance 798.2 mF cm−2 was obtained with the composite sponge fabricated by VPP of PEDOT at 110 °C with graphene nanoplatelet-deposited PU sponge substrate. The capacitance retention of this composite electrode was 101.0% after 10,000 charging–discharging cycles. The high flexibility, high areal specific capacitance, excellent long-term cycling stability and low cost make these composite sponges promising electrode materials for supercapacitors.

Functionalization of a carbon electrode through the electrochemical reduction of ruthenium tris-bipyridine diazonium salts prepared in situ allows determination of the nature of the anions often present in commonly used lithium and sodium battery electrolyte (i.e. PF6− and ClO4−) and also the presence of fluoride anions arising from PF6− degradation. Surprisingly, although these “battery” anions are supposed to exhibit poor coordination ability, their interaction with the electrogenerated RuIII complex is sufficiently strong and reversible to selectively discriminate between the anions ClO4− and PF6− through the observed shift in E°. This study examined the impact of any fluoride present and found a linear relationship between the current response and the F− concentration. This has been applied to ageing LP30 battery electrolyte, confirming the low solubility of LiF in battery electrolyte. This overall behavior could help in the analysis of electrolytes from the recycling sector.

A flexible solid-state supercapacitor based on vapor phase polymerized (VPP) PEDOT into cellulose paper matrix (PEDOT/CP) was successfully fabricated. The PEDOT/CP composite material worked as both current collector and electrode in constructed test cells. It had a low sheet resistance of 14 Omega/square and survived the Scotch tape test for adhesion. It also showed excellent stability with no significant conductivity drop after 1000 cycles of bending. The PEDOT from electrode obtained the mass specific capacitance of 179 F/g at scan rate of 10 mV/s, which was among the highest specific capacitances ever reported. This high capacitance was attributed to the combination of the VPP technique and the porous fibrous structure of the cellulose matrix. The EDOT vapor penetrated and polymerized through the CP matrix made of nanometer to micrometer level CP fibers. The highest electrode volumetric capacitance achieved was 13.7 F/cm(3). The whole device achieved an energy density of 0.76 mWh/cm(3) and a power density of 0.01 W/cm(3). Bending the supercapacitor to 90 degrees or rotating to 45 degrees caused no major change in capacitance. Owing to the all nonmetallic materials used to construct the supercapacitor, it can be easily disposed. The incineration of the supercapacitor does not release significant hazardous exhaust.

Optically transparent and highly conductive poly(3,4-ethylenedioxythiophene) (PEDOT) thin films were grown through vapor phase polymerization on (3-Mercaptopropyl)trimethoxysilane functionalized 3,4-Ethylenedioxythiophene (MPTMS functionalized EDOT) grafted glass substrates. Compared to bare glass, the EDOT grafted surface led to enhancements in both electrical conductivity and adhesion of PEDOT thin films. A quinoid-rich structure with increased crystallinity and a further enhanced conductivity was induced by post-deposition sulfuric acid doping. X-ray diffraction showed different orientations of the PEDOT crystals grown on substrates with and without EDOT grafting. The highest conductivity of 2690 S/cm, with an average optical transmittance of 95.4 % in the visible range, was achieved when PEDOT was vapor phase polymerized on EDOT grafted substrates and doped with 98 % sulfuric acid. Photostability was tested using a xenon arc light source and characterized by attenuated total reflection Fourier-transform infrared spectroscopy, showing that photoinduced degradation is associated with a decrease in C=C double bond content.

The commercial viability of solar power will depend on a careful balance of reliability, efficiency, and overall cost. A systematic approach to the optimization of the latter two for the case of organic solar cells is outlined. This relies among other on the development of a detailed understanding of the charge generation process and the systematic application of analytical tools such as UV-vis, photoluminescence, lifetime measurements, and current-voltage (I-V) curves.

Good wettability of separators in batteries and capacitors is crucial for performance. Titanium hydroxide (Ti(OH)(x)) has been shown to greatly improve the wettability of polyvinylidene fluoride (PVDF) nanofibers (NFs). In this work, PVDF/Ti(OH)(x) NFs were evaluated for their potential use as separators. Results show that PVDF NFs incorporated with Ti(OH)(x) have improved electrolyte uptake (EU) between 550 and 1200 EU% compared to untreated PVDF with less than 100 EU%. Significant improvements in capacitance are seen from capacitors utilizing PVDF/Ti(OH)(x) NF separators with the best performing PVDF/Ti(OH)(x) NF at 15 wt% Ti(OH)(x) with 446.8 mF/cm(2) compared to untreated PVDF NF separator with 262.7 mF/cm(2). (c) 2020 Elsevier B.V. All rights reserved.

Fluorine doped metal oxides have shown great promise for use in many applications including Li-ion batteries (LiBs), photocatalysis and dye-sensitized solar cells. Both F-TiO2 and TiOF2 have been studied extensively for this purpose. However, fabrication of fluorine doped titanium oxide requires the use of dangerous fluorinated chemicals such as trifluoroacetic acid, hydrofluoric acid and fluorine gas which are both difficult to handle and create significant waste detrimental for the environment. Additionally, current procedures for fabrication of FTiO2 and TiOF2 require long heating times which are inefficient, wasting large amounts of energy. Because of these factors, fabrication of F-TiO2, TiOF2 and of other important fluorine doped metal oxides is expensive and dangerous to make. In this work, two new methods were used to greatly improve the safety and efficiency of synthesis. First, the fluorinated waste was eliminated by using the safe and inert polymer, polyvinylidene fluoride (PVDF), as the fluorine source. Second, microwave (MW) irradiation was used to reduce the time and energy required for synthesis by addition of the MW absorber, graphene, into the precursor material. The results show that when using the PVDF fluorine source with conventional oven heating it results in low levels of F-TiO2 which are dependent on heating temperatures. However, when using microwave irradiation high levels of doping were achieved creating both F-TiO2 and TiOF2 in as little as 6 min compared to several hours. This work has shown that by combining both PVDF and microwave irradiation fabrication of F-TiO2 and TiOF2 can now be done safely and efficiently with greatly reduced environmental impact.

Electrospun nanofibers (NFs) incorporated with catalytically active components have gained significant interest in chemical protective clothing. This is because of the desirable properties of the NFs combined with decontamination capability of the active component. Here, a series of metal hydroxide catalysts Ti(OH)x, Zr(OH)4, and Ce(OH)4 were incorporated into three different polymer NF systems. These new polymer/metal hydroxide composite NFs were then evaluated for their catalytic activity against a nerve agent simulant. Two methods were utilized to incorporate the metal hydroxides into the NFs. Method one used direct incorporation of Ti(OH)x, Zr(OH)4, and Ce(OH)4 catalysts, whereas method two employed incorporation of Ti(OH)x via a precursor molecule. Composite NFs prepared via method one resulted in greatly improved reaction rates over the respective pure metal hydroxides due to reduced aggregation of catalysts, with polymer/Ce(OH)4 composite NFs having the fastest reaction rates out of method one materials. Interestingly, composite samples prepared by method two yielded the fastest reaction rates overall. This is because of the homogeneous distribution of the metal hydroxide catalyst throughout the NF. This homogeneous distribution created a hydroxyl-decorated NF surface with a greater number of exposed active sites for catalysis. The hydroxyl-decorated NF surface also resulted in an unexpected highly wettable composite NF, which also was found to contribute to the observed reaction rates. These results are not only promising for applications in chemical protective clothing but also show great potential for application in areas which need highly wettable membrane materials. This includes areas such as separators, antifouling membranes, and certain medical applications.

Metal organic frameworks (MOFs), the UiO series in particular, have attracted much attention because of the high surface area and ability to capture and decontaminate chemical warfare agents. Much work has been done on incorporating these MOFs into or onto textile materials while retaining the desirable properties of the MOF. Many different techniques have been explored to achieve this. Atomic layer deposition (ALD) of TiO2 followed by solvothermal synthesis of MOF has become one of the most adaptable techniques for growing MOFs on the surface of many different polymer fabric materials. However, little work has been done with using this technique on polymer composite materials. In this work, UiO-66-NH2 was grown onto the surface of poly(methyl methacrylate) (PMMA)/Ti(OH)4 and poly(vinylidene fluoride) (PVDF)/Ti(OH)4 composite fibers by first modifying the surface with ALD of TiO2 (@TiO2) followed by solvothermal synthesis of MOF (@MOF). The catalytic activity of these materials was then evaluated using the simulant paraoxon-methyl (DMNP). These new MOF-functionalized composite fabrics were compared to polyamide-6 (PA-6)@TiO2@MOF- and polypropylene (PP)@TiO2@MOF-functionalized fabrics. PMMA/Ti(OH)4@TiO2@MOF fibers resulted in unique hollowed fibers with high surface area of 264 m2/g and fast catalytic activity. The catalytic activity of these samples was found to be related to the active MOF mass fraction on the MOF-functionalized composite fabric, with the hollowed PMMA/Ti(OH)4@TiO2@MOF having the highest weight percent of active MOF and a DMNP t1/2 of 26 min followed by PA-6@TiO2@MOF with 45 min, PVDF/Ti(OH)4@TiO2@MOF with 61 min, and PP@TiO2@MOF with 83 min.

Many small animals have evolved ultrasensitive hearing capability by detecting acoustic flow with mechanosensory hair-like structures. The highly-damped hairy structures such as the fluffy mosquito antennae are driven to move by viscous forces in the fluctuating medium, in contrast to sensing acoustic pressure with tympanal membranes. Inspired by the acoustic flow sensing of animals, the highly-damped 2D nanofiber mesh is presented here for the ultrasensitive, broadband acoustic flow detection. By evaporating 90nm Au on a freestanding electrospun Poly(methyl methacrylate) (PMMA) nanofiber mesh, we fabricate a thin layer of conductive Au-PMMA nanomesh with dimensions 8 mm x 8 mm, with thickness of approximately 3 mu m and average fiber diameter around 430nm. The nanomesh is shown to move instantaneously with broadband fluctuating airflow near maximum physical efficiency from 100 Hz to 10 000 Hz, i.e. v(m)(esh)(t)/v(air)(t) approximate to 1, surpassing the frequency response and efficiency of previously-reported microscale hairy structures. By transducing the motion of the nanomesh with electromagnetic induction, we demonstrate fluctuating airflow detection with almost full fidelity in the measured frequency range. Sensing flow with highly-damped nanomaterials will benefit miniaturized flow measurement and sound detection, and provides an important application for the diverse flourishing nanomaterials, such as 1D nanofibers, 2D nanomeshes, and 3D nanolattices.