Organic thermoelectric materials would be ideally suited for wearable thermoelectric devices but currently are not efficient enough for practical applications. Previous research efforts have tailored the composition, oxidation status, or doping levels of organic thin-film thermoelectrics to maximize their thermoelectric performance typically measured by the thermoelectric figure of merit (ZT). This study demonstrates that the thermoelectric ZT of the organic thin-films can be significantly boosted by increasing the surface roughness of the films. A simple soft-templating method that can produce nanorough thin films of organic thermoelectrics was developed and used to fabricate nanorough poly(3,4-ethylenedioxythiophene):Tosylate (PEDOT:Tos) thin films. The performance of the nanorough PEDOT:Tos films was compared to that of the smooth PEDOT:Tos films. The ZT value of the nanorough films was estimated to be 0.99, which is 83% higher than that of the smooth films and one of the highest ever reported for organic thermoelectrics. The flexibility and durability of the nanorough PEDOT:Tos films were also proved. A proof-of-concept thermoelectric device that used 5 strips of nanorough films, as the p-type thermoelectric elements, and five strips of bismuth thin films, as the n-type elements, produced 118.7 nW when ΔT = 50 K.

efficient on-site detection of pesticides such as methyl parathion (MP) is crucial to ensure public health. This study introduces the first disposable electrochemically reduced graphene oxide (ErGO) modified electrode for rapid MP detection. A square wave anodic stripping voltammetry method for the detection of MP was developed using these ErGO-modified carbon screen-printed electrodes. Based on this study, graphene's high electric conductivity and unique structure enhanced the sensitivity of the electrode for MP detection. Following optimization of the pH, equilibrium period, deposition potential, and period, the methodology demonstrated high sensitivity and reproducibility. Using the enhanced experiment conditions, calibration experiments were performed with a concentration range of 0 to 150 mu g L-1 of MP. A consistent oxidation peak was observed at-0.180 V. The calibration data showed the increase in the peak height was linearly correlated to the increase in MP concentration, with a correlation coefficient of 0.9854. The sensitivity of the developed methodology was 0.0887 mu A (mu g L-1)-1, and the limit of detection was 9.06 mu g L-1. The methodology was successfully applied to multiple water samples, specifically river water, groundwater, and General Test Water, with recovery rates of 106.01% (standard deviation = 1.46%), 109.51% (standard deviation=0.44%), and 97.69% (standard deviation=1.49%), respectively.

CuBiW2O8 (CBTO), with a band gap of 1.9–2.0 eV, responds to a wide region of the electromagnetic spectrum has been demonstrated as a photocatalyst with high activity for Cr(vi) reduction.

Hydrogen is largely produced via natural gas reforming or electrochemical water-splitting, leaving organic solid feedstocks under-utilized. Plasma technology powered by renewable electricity can lead to the sustainable upcycling of plastic waste and production of green hydrogen. In this work, low-temperature atmospheric pressure plasma reactors based on transferred arc (transarc) and gliding arc (glidarc) discharges are designed, built, and characterized to produce hydrogen from low-density polyethylene (LDPE) as a model plastic waste. Experimental results show that hydrogen production rate and efficiency increase monotonically with increasing voltage level in both reactors, with the maximum hydrogen production of 0.33 and 0.42 mmol/g LDPE for transarc and glidarc reactors, respectively. For the transarc reactor, smaller electrode-feedstock spacing favors greater hydrogen production, whereas, for the glidarc reactor, greater hydrogen production is obtained at intermediate flow rates. The hydrogen production from LDPE is comparable despite the markedly different modes of operation between the two reactors.

Thermoelectric composites of organic and inorganic materials exhibit significantly enhanced thermoelectric properties compared with pristine organic thermoelectrics so they might be better suited as core materials of wearable thermoelectric devices. This study describes the development of three-dimensional (3D) paper PEDOT:tosylate/CuI composites that could be shaped as 3 mm thick blocks to convert a temperature difference between their bottom and top sides into power; the majority of organic thermoelectric materials are shaped as thin strips usually on a planar substrate and convert a temperature difference between the opposite edges of the strips into power. The 3D paper PEDOT:tosylate/CuI composites can produce a power density equal to 4.8 nW/cm2 (ΔΤ = 6 Κ) that is 10 times higher than that of the pristine paper PEDOT:Tos composites. The enhanced thermoelectric properties of the paper PEDOT:tosylate/CuI composites are attributed to the CuI nanocrystals entrapped inside the composite that increases the Seebeck coefficient of the composite to 225 μV K-1; the Seebeck coefficient of paper PEDOT:Tos is 65 μV K-1. A proof-of-concept wearable thermoelectric device that uses 36 blocks of the paper PEDOT:tosylate/CuI composites (as p-type elements) and 36 wires of monel (as n-type elements) can produce up to 4.7 μW of power at ΔΤ = 20 K. The device has a footprint of 64 cm2 and can be placed directly over the skin or can be embedded into clothing.

Hydrogen, due to its high energy density and sustainability potential, is considered a leading chemical energy storage alternative to fossil fuels. Given the absence of natural sources of hydrogen, hydrogen has to be procured from substances such as water, fossil fuels, biomass, or plastics. Nonthermal plasma-based hydrogen production approaches have the potential to be more energy efficient, selective, and environmentally-benign than thermochemical methods. In this study, gliding arc and transferred arc nonthermal plasma reactors have been designed, built, and characterized through the production of hydrogen from low-density polyethylene (LDPE) using nitrogen as auxiliary gas at atmospheric pressure and temperature conditions. These reactors have complementary operational characteristics, making their parallel evaluation compelling to reveal the mechanisms by which nonthermal plasma enables the extraction of hydrogen from solid feedstock. In both reactors, the dynamic characteristics of the plasma affect its interaction with the solid LDPE feedstock, and hence the production of hydrogen. Concurrently, the interaction between the hydrogen emanating from LDPE and the impinging nitrogen flow can significantly affect the plasma dynamics, affecting its stability and the gas and particulate flows throughout the reactors. Visualization of the plasma and gas flow are conducted using long-exposure photography, high-speed photography, and high-speed Schlieren imaging. Visualization results together with current and voltage signals and gas chromotography analyses are used to correlate the plasma and flow dynamics to the production of hydrogen as function of the reactors’ main operation parameters, namely inflow rate, driving voltage, and electrode-feedstock spacing. The experimental diagnostics are complemented with Computational Fluid Dynamics simulations to assess flow and thermal characteristics across the reactors. Residence time, arc stability, gliding velocity, plasma volume, and plasma-feedstock interaction area as function of the operational parameters are also determined and analyzed.

Fabric-based thermoelectrics can be seamlessly integrated into clothing so they would be ideal to power devices embedded into smart clothing. This study describes the development of thermoelectric fabrics that have their fibers covered with PEDOT:Tosylate and CuI nanocrystals. Several types of fabrics (e.g., cotton, nylon, NYCO, polyester, nomex, modacrylic etc.) have been used in the fabrication of different fabrics PEDOT:Tosylate composites and it was concluded that NYCO (a fabric composed of 50% cotton, 50% nylon) provided the highest thermoelectric performance. The integration of CuI nanocrystals in the NYCO/PEDOT:Tos/CuI composites boosted the thermoelectric power of the composites, almost 8 times compared to NYCO/PEDOT:Tos, to reach a power density equal to 3.68 nW cm(-2) (Delta T = 12 K). A proof-of-concept wearable thermoelectric device that uses four strips of NYCO/PEDOT:Tos/CuI and four monel wires was able to produce up to 70 nW of power when Delta T = 25 K. The device was folded and attached at the edge of an armband (so that one end of each fabric PEDOT:Tos/CuI composite to be in contact with the skin and the other open to environment) and was able to produce 12.4 nW when the armband is worn by a person and the difference between the surface of the skin and the outer side of the device was 8 K. (C) 2021 Elsevier Ltd. All rights reserved.

One of the challenges preventing rapid, onsite voltammetric detection of arsenic(III) is the overlapping oxidation peak of copper(II). This paper describes a novel methodology for the voltammetric detection of trace levels of arsenic(III) in the presence of high copper(II) concentrations (up to the action level of 1.3 mg L-1 set by the US EPA for drinking water). Square wave stripping voltammetry tests were performed using disposable carbon screen printed electrodes modified with gold nanostars on samples buffered with Britton-Robinson buffer. The optimized parameters for accurate codetection of arsenic(III) and copper(II) were a buffer pH of 9.5, a loading of gold nanostars of 2.39(*)10(-5) nmol per electrode, a deposition voltage of -0.8 V, and a deposition time of 180 s. Based on calibration testing, the limits of detection for arsenic(III) and copper(II) were determined to be 2.9 mu g L-1 and 42.5 mu g L-1, respectively. Furthermore, the linear ranges for arsenic and copper were 0-100 mu g L-1 and 0-250 mu g L-1 with sensitivities of 0.101 mu A (mu g L-1)(-1) and 0.121 mu A (mu g L-1)(-1), respectively. Interference testing was performed with several common ionic species, sodium bicarbonate, sodium chloride, tannic acid, iron(iii) chloride, magnesium chloride, calcium nitrate, and sodium sulfate, with only sodium bicarbonate significantly affecting the response. Validation testing in real-world samples was performed by comparison with graphite furnace atomic absorption spectroscopy. The validation testing demonstrated good accuracy and precision, expressed as percent recovery and relative standard deviation (RSD), respectively, in river water and tap water, with mean percent recoveries of 87.7% (RSD = 4.20%) and 83.2% (RSD = 10.02%), respectively. (C) 2020 Elsevier B.V. All rights reserved.

A new method of characterizing the curvature change in thermally adaptive fibers is introduced in this paper. Based on the same principle as bi-metallic strips commonly found in thermostats, multi-component polymer fibers can be created to change their geometrical form in response to a temperature change. This works by creating fibers from two or more materials that have a mismatched Coefficient of Thermal Expansion (CTE). A temperature change leads to a change in curvature of these fibers. When fibers interact in an insulation batting structure, a temperature change leads to a thickness change in the insulation. While these fibers have visually been observed to function, there was no method to quantitatively characterize their curvature performance. This paper introduces a method that can be used to quantify fiber performance by tracking change in curvature over a specific temperature range. This is accomplished by suspending fibers on the surface of a liquid bath and changing the bath temperature. Digital images of the fiber are taken at different temperatures and analyzed using software to determine the radius of curvature. Absolute change in curvature was found to be as high as 0.5% per degree °C from 20 to −20°C for certain samples. A trend was also noted between higher initial curvature and lower overall performance. Digital image correlation was further used to investigate the time-dependence relationship of fiber curvature. Future experiments can be performed with this setup to characterize and compare curvature change performance of different fibers accurately.

In recent years, polymer films have found an increasing role in sensors due to their unique characteristics. It is widely accepted that the sensitivity of a film is proportional to the surface area per unit mass. Thin films with very large surface areas can be easily fabricated by electrospinning, wherein a polymer solution is exposed to a high static voltage, creating sub-micron or nanometer scale fibers collected as a non-woven membrane. Electrospun nanofibrous membranes have surface areas approximately one to two orders of the magnitude higher than those found in continuous thin films. It is expected that their sensitivities are potentially as large. In this paper, the first use of an electrospun membrane as a highly responsive fluorescence quenching-based optical sensor is reported. A new fluorescent polymer, polyacrylic acid - poly (pyrene methanol) (PAA-PM), was synthesized via covalent attachment of the fluorescent indicator, pyrene methanol (PM), onto polyacrylic acid (PAA). Optical chemical sensors were then fabricated by electrospinning PAA-PM and thermal crosslinkable polyurethane latex mixture solutions. The synthesis, characterization, electrospinning fabrication, and comparison of the sensitivities to analytes such as ferric ions, mercury, and 2, 4-dinitrotoluene between the electrospun membranes and electrostatically layer-by-layer (ELBL) assembled films are presented.

Abstract : We have investigated phase separating immiscible polymer blends of a polymer melt and a polymer solution as a means to produce composites with features on a submicron length scale. A 2D cell dynamics code for modeling phase separation in a flow field has been modified to include features such as a boundary which favors one component and a flow profile for a power law fluid. The simulations indicate that the skin formation seen experimentally is driven by surface energy effects rather than viscosity. In pressure driven flow a power law fluid is predicted to have a more pronounced sheath core structure than a Newtonian fluid.

The phase behavior and structure development in immiscible blends of melt-extruded polycaprolactone and a viscous aqueous poly(ethylene oxide) solution were investigated. The coextrusion of an aqueous polymer solution and a molten polymer is a largely unexplored technique and offers exciting potential for creating new materials via the execution of chemical reactions in the aqueous phase. Samples were prepared both with and without a block copolymer acting as a surface-active agent. The resulting morphology was characterized with scanning electron microscopy after the removal of the watersoluble phase. Spheres, rods, fibers, and cocontinuous gyroidal structures were observed, yet the exact phase inversion was not observed, and the changes in the feature shape depended on which component composed the major phase. Significant orientation in the flow direction was observed when the less viscous poly(ethylene oxide) was the major phase, whereas orientation was minimal when polycaprolactone was the major phase. These observations indicate that control of the feature shape and orientation may be accomplished through the control of the viscosity. The spontaneous formation of an outer layer of polycaprolactone in all samples was observed, suggesting that the morphology could be induced by control of the material interaction with the extruder die wall. The inclusion of a diblock copolymer significantly reduced the feature size but did not alter the morphology type. (C) 2008 Wiley Periodicals, Inc. J Appl Polym Sci 110: 2841-2848, 2008

Lenses and other transparent optical materials suffer rapid damage when subjected to blowing abrasive particulates. The time-scale of these impact event falls between typical scratch tests (less than 1m/s) and ballistic tests (100s of m/s) and has not been studied in depth to date. Polymeric lens materials like polycarbonate are usually treated with a scratch-resistant coating, which is commonly silica-based. The coating provides some protection, yet is not sufficient at resisting abrasion from blown sand in most commercial products. We demonstrate that silicone elastomeric coatings are superior to polycarbonate and silica glass at resisting damage by blown sand particles. Sand abrasion tests were conducted using a custom-built test apparatus that exposes the sample to 400 micron diameter quartz silica moving at 16.5 m/s (approx. 38 mph). Scanning electron microscopy revealed the presence of small cracks and pits in polycarbonate, coated polycarbonate, and silica glass after sand exposure. No such damage was observed in the silicone-coated samples after an identical exposure. We speculate that the elastic tensile strain at the surface is an important predictor of the material response at the time-scale of the impact. A simple mathematical model was developed using a momentum balance pre- and post-impact, and was used to approximate the maximum deformation and impact time-scale. A semispherical interaction volume was used in the model with a radius of 1.5x the particle diameter, determined through profilometry experiments. The material’s resistance to deformation was measured experimentally through a static mechanical test using a spherical indenter to represent the particle. Tensile tests were performed on both materials to identify the maximum elastic strain.Additionally, dynamic mechanical tests were performed to confirm that the mechanical behavior at long time-scales was valid at shorter time-scales of the impacts. DMA curves were shifted using the WLF equation. Profilometry and scanning electron microscopy (SEM) imaging were used to confirm the presence or absence of blown-sand induced damage.

We propose and demonstrate the concept that a polymer−micelle complex can be used as an aid to preparing nanofibers from aqueous solutions by the electrospinning process. This is based on the recognition that a polymer−micelle complex can simultaneously contribute to an increase in solution viscosity, decrease in surface tension, and increase in electrical conductivity, all of which favor the formation of nanofibers by electrospinning. By incorporating the polymer−micelle complex as a secondary ingredient, electrospinning of sparingly soluble or low molecular weight polymers is made possible, as is illustrated here using a PEO−SDS complex to electrospin a gel forming, genetically engineered silk-elastin biopolymer. The wide choice of polymers and surfactants available to form the polymer-micelle complex with a range of viscosity, surface tension and electrical conductivity properties, potentially allows for a variety of solutions and dispersions to be electrospun from the aqueous medium.