Wearable Sensor Based on a Tough Conductive Gel for Real-Time and Remote Human Motion Monitoring.

The usage of a conductive hydrogel in wearable sensors has been thoroughly researched recently. Nonetheless, hydrogel-based sensors cannot simultaneously have excellent mechanical property, high sensitivity, comfortable wearability, and rapid self-healing performance, which result in poor durability and reusability. Herein, a robust conductive hydrogel derived from one-pot polymerization and subsequent solvent replacement is developed as a wearable sensor. Owing to the reversible hydrogen bonds cross-linked between polymer chains and clay nanosheets, the resulting conductive hydrogel-based sensor exhibits outstanding flexibility, self-repairing, and fatigue resistance performances. The embedding of graphene oxide nanosheets offers an enhanced hydrogel network and easy release of wearable sensor from the target position through remote irradiation, while Li+ ions incorporated by solvent replacement endow the wearable sensor with low detection limit (sensing strain: 1%), high conductivity (4.3 S m-1) and sensitivity (gauge factor: 3.04), good freezing resistance, and water retention. Therefore, the fabricated wearable sensor is suitable to monitor small and large human motions on the site and remotely under subzero (-54 °C) or room temperature, indicating lots of promising applications in human-motion monitoring, information encryption and identification, and electronic skins.

Application of Self-Assembled Polyarylether Substrate in Flexible Organic Light-Emitting Diodes.

The structure used in this study is as follows: substrate/PMMA/ZnS/Ag/MoO3/NPB/Alq3/LiF/Al. Here, PMMA serves as the surface flattening layer, ZnS/Ag/MoO3 as the anode, NPB as the hole injection layer, Alq3 as the emitting layer, LiF as the electron injection layer, and aluminum as the cathode. The properties of the devices with different substrates were investigated using P4 and glass, developed in the laboratory, as well as commercially available PET. After film formation, P4 creates holes on the surface. The light field distribution of the device was calculated at wavelengths of 480 nm, 550 nm, and 620 nm using optical simulation. It was found that this microstructure contributes to light extraction. The maximum brightness, external quantum efficiency, and current efficiency of the device at a P4 thickness of 2.6 µm were 72,500 cd/m2, 1.69%, and 5.68 cd/A, respectively. However, the maximum brightness of the same structure with PET (130 µm) was 9500 cd/m2. The microstructure of the P4 substrate was found to contribute to the excellent device performance through analysis of the AFM surface morphology, film resistance, and optical simulation results. The holes formed by the P4 substrate were created solely by spin-coating the material and then placing it on a heating plate to dry, without any special processing. To confirm the reproducibility of the naturally formed holes, devices were fabricated again with three different emitting layer thicknesses. The maximum brightness, external quantum efficiency, and current efficiency of the device at an Alq3 thickness of 55 nm were 93,400 cd/m2, 1.7%, and 5.6 cd/A, respectively.

Efficiency Analysis of Fuel Cell Components with Ionic Poly-Arylether Composite Membrane.

We use polyethylene glycol as an additive to explore how the hydrogen bonding of this additive changes the properties of SA8 blended sulfonated polyetheretherketone (SPEEK) composite films. We mixed a 5%wt polyethylene glycol solution into a 12.5%wt SA8 solution, and then prepared a film with a total weight of 40 g at a ratio of 1:99. The SA8 (PEG) solution was prepared and then mixed with 5%wt SPEEK solution, and a film-forming solution with a total weight of 8g in different mixing ratios was created. Polyethylene glycol (PEG) was mixed into the sulfonated polyarylether polymer SA8 to form physical cross-linking. Therefore, the sulfonated polyether ether ketone SPEEK was mixed in, and it exhibited good thermal stability and dimensional stability. However, there was some decrease in proton conductivity as the proportion of SPEEK increased. Although SPEEK mixed with sulfonated polymer reduces the proton conductivity, the physical cross-linking of PEG can improve the proton conductivity of the composite membrane, and adding SPEEK can not only solve the problem of the high sulfonation film swelling phenomenon, it can also improve the dimensional stability of the film through the hydrogen bonding force of PEG and obtain a composite film with excellent properties.

Electric Field-Assisted Filling of Sulfonated Polymers in ePTFE Backing Material for Fuel Cell.

This study fabricated a composite ePTFE-backed proton-exchange membrane by filling the pores on the ePTFE backing with sulfonated polyarylene ethers through an externally supplied electric field. The morphology changes were observed under an SEM. The results suggested that the application of an electric field had led to the effective filling of pores by polymers. In addition, the composite membrane featured good dimensional stability and swelling ratio, and its water uptake, proton conductivity and component efficiency increased with voltage. It is found in this study that the external application of an electric field resulted in the effective filling of pores in the ePTFE by sulfonated polyarylene ether polymers and, thus, an improved composite membrane performance.

Ionomer Membranes Produced from Hexaarylbenzene-Based Partially Fluorinated Poly(arylene ether) Blends for Proton Exchange Membrane Fuel Cells.

In this study, a series of high molecular weight ionomers of hexaarylbenzene- and fluorene-based poly(arylene ether)s were synthesized conveniently through condensation and post-sulfonation modification. The use a of blending method might increase the stacking density of chains and affect the formation both of interchain and intrachain proton transfer clusters. Multiscale phase separation caused by the dissolution and compatibility differences of blend ionomer in high-boiling-point solvents was examined through analysis and simulations. The blend membranes produced in this study exhibited a high proton conductivity of 206.4 mS cm−1 at 80 °C (increased from 182.6 mS cm−1 for precursor membranes), excellent thermal resistance (decomposition temperature > 200 °C), and suitable mechanical properties with a tensile strength of 73.8−77.4 MPa. As a proton exchange membrane for fuel cell applications, it exhibits an excellent power efficiency of approximately 1.3 W cm−2. Thus, the ionomer membranes have strong potential for use in proton exchange membrane fuel cells and other electrochemical applications.

Fe, N-Doped Metal Organic Framework Prepared by the Calcination of Iron Chelated Polyimines as the Cathode-Catalyst of Proton Exchange Membrane Fuel Cells.

Aromatic polyimine (PIM) was prepared through condensation polymerization between p-phenylene diamine and terephthalaldehyde via Schiff reactions. PIM can be physically crosslinked with ferrous ions into gel. The gel-composites, calcined at two consecutive stages, with temperatures ranging from 600 to 1000 °C, became Fe- and N-doped carbonaceous organic frameworks (FeNC), which demonstrated both graphene- and carbon nanotube-like morphologies and behaved as an electron-conducting medium. After the two-stage calcination, one at 1000 °C in N2 and the other at 900 °C in a mixture of N2 and NH3, an FeNC composite (FeNC-1000A900) was obtained, which demonstrated a significant O2 reduction peak in its current-voltage curve in the O2 atmosphere, and thus, qualified as a catalyst for the oxygen reduction reaction. It also produced a higher reduction current than that of commercial Pt/C in a linear scanning voltage test, and the calculated e-transferred number reached 3.85. The max. power density reached 400 mW·cm-2 for the single cell using FeNC-1000A900 as the cathode catalyst, which was superior to other FeNC catalysts that were calcined at lower temperatures. The FeNC demonstrated only 10% loss of the reduction current at 1600 rpm after 1000 redox cycles, as compared to be 25% loss for the commercial Pt/C catalyst in the durability test.

Highly Proton-Conducting Membranes Based on Poly(arylene ether)s with Densely Sulfonated and Partially Fluorinated Multiphenyl for Fuel Cell Applications.

Series of partially fluorinated sulfonated poly(arylene ether)s were synthesized through nucleophilic substitution polycondensation from three types of diols and superhydrophobic tetra-trifluoromethyl-substituted difluoro monomers with postsulfonation to obtain densely sulfonated ionomers. The membranes had similar ion exchange capacities of 2.92 ± 0.20 mmol g-1 and favorable mechanical properties (Young's moduli of 1.60-1.83 GPa). The membranes exhibited considerable dimensional stability (43.1-122.3% change in area and 42.1-61.5% change in thickness at 80 °C) and oxidative stability (~55.5%). The proton conductivity of the membranes, higher (174.3-301.8 mS cm-1) than that of Nafion 211 (123.8 mS cm-1), was the percent conducting volume corresponding to the water uptake. The membranes were observed to comprise isolated to tailed ionic clusters of size 15-45 nm and 3-8 nm, respectively, in transmission electron microscopy images. A fuel cell containing one such material exhibited high single-cell performance-a maximum power density of 1.32 W cm2 and current density of >1600 mA cm-2 at 0.6 V. The results indicate that the material is a candidate for proton exchange membranes in fuel cell applications.

Superparamagnetic, High Magnetic α-Fe & α″-Fe16N2 Mixture Prepared from Inverse Suspension-Polymerized Fe3O4@polyaniline Composite.

Oleic acid (OA)-modified Fe3O4 nanoparticles were successfully covered with polyanilines (PANIs) via inverse suspension polymerization in accordance with SEM and TEM micrographs. The obtained nanoparticles were able to develop into a ferrite (α-Fe) and α″-Fe16N2 mixture with a superparamagnetic property and high saturated magnetization (SM) of 245 emu g-1 at 950 °C calcination under the protection of carbonization materials (calcined PANI) and other iron-compounds (α″-Fe16N2). The SM of the calcined iron-composites slightly decreases to 232 emu g-1 after staying in the open air for 3 months. The calcined mixture composite can be ground into homogeneous powders without the segregation of the iron and carbon phases in the mortar without significantly losing magnetic activities.

Calcined Co(II)-Triethylenetetramine, Co(II)- Polyaniline-Thiourea as the Cathode Catalyst of Proton Exchanged Membrane Fuel Cell.

Triethylenetetramine (TETA) and thiourea complexed Cobalt(II) (Co(II)) ions are used as cathode catalysts for proton exchanged membrane fuel cells (PEMFCs) under the protection of polyaniline (PANI) which can become a conducting medium after calcination. Fourier-transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS) spectra clearly reveal the presence of typical carbon nitride and sulfide bonds of the calcined Nitrogen (N)- or Sulfur (S)-doped co-catalysts. Clear (002) and (100) planes of carbon-related X-ray diffraction patterns are found for co-catalysts after calcination, related to the formation of a conducting medium after the calcination of PANI. An increasing intensity ratio of the D to G band of the Raman spectra reveal the doping of N and S elements. More porous surfaces of co-catalysts are found in scanning electronic microscopy (SEM) micropictures when prepared in the presence of both TETA and thiourea (CoNxSyC). Linear sweep voltammetry (LSV) curves show the highest reducing current to be 4 mAcm-2 at 1600 rpm for CoNxSyC, indicating the necessity for both N- and S-doping. The membrane electrode assemblies (MEA) prepared with the cathode made of CoNxSyC produces the highest maximum power density, close to 180 mW cm-2.

Melting and Recrystallization of Copper Nanoparticles Prepared by Microwave-Assisted Reduction in the Presence of Triethylenetetramine.

The small sized copper nanoparticles (Cu-NPs), prepared in the presence of triethylene tetramine (TETA) and assisted with microwave irradiation, have an extremely low melting temperature. Melting of the small sizezd Cu-NPs can be triggered by the heat generated from the e-beam irradiation during SEM and TEM image construction. The dispersed Cu atoms around the agglomerated big Cu particles can undergo recrystallization immediately due to the strong driving force of the huge temperature difference to normal melting temperature (Tm = 1085 °C). Some of the Cu-NPs with bigger sizes also recrystallize and agglomerate into dense, big particles. According to X-ray diffraction patterns, these particles can agglomerate into compact, ordered Cu crystals in less than five minutes at 60 °C. The melting and recrystallization related endothermic and exothermic phase transitions of Cu-NPs can be found from differential scanning calorimeter (DSC) thermograms and optical microscopic pictures.

Polyaniline Based Pt-Electrocatalyst for a Proton Exchanged Membrane Fuel Cell.

Calcination reduction reaction is used to prepare Pt/EB (emeraldine base)-XC72 (Vulcan carbon black) composites as the cathode material of a proton exchange membrane fuel cell (PEMFC). The EB-XC72 core-shell composite obtained from directly polymerizing aniline on XC72 particles is able to chelate and capture the Pt-ions before calcination. X-ray diffraction spectra demonstrate Pt particles are successfully obtained on the EB-XC72 when the calcined temperature is higher than 600 °C. Micrographs of TEM and SEM illustrate the affluent, Pt nanoparticles are uniformly distributed on EB-XC72 at 800 °C (Pt/EB-XC72/800). More Pt is deposited on Pt/EB-XC72 composite as temperatures are higher than 600 °C. The Pt/EB-XC72/800 catalyst demonstrates typical type of a cyclic voltammograms (C-V) curve of a Pt-catalyst with clear Pt-H oxidation and Pt-O reduction peaks. The highest number of transferred electrons during ORR approaches 3.88 for Pt/EB-XC72/800. The maximum power density of the single cell based on Pt/EB-XC72/800 reaches 550 mW cm-2.

FeNxC Based Catalysts Prepared by the Calcination of Iron-Ethylenediamine@Polyaniline as the Cathode-Catalyst of Proton Exchange Membrane Fuel Cell.

Calcinated tris(ethylenediamine)iron(III) chloride was used as a non-precious metal catalyst (NPMCs) for a proton exchanged membrane fuel cell (PEMFC) under the protection of polyaniline (PANI), which behaves as both nitrogen source and carbon supporter. The optimal ratio of FeCl3/EDA was found to be close to 1/3 under the consideration of the electrocatalytic performance, such as better oxygen reduction reaction (ORR) and higher power density. Two-stage calcination, one at 900 °C in N2 and the other at 800 °C in mixed gases of N2 and NH3, result in an FeNxC catalyst (FeNC-900-800-A) with pretty high specific surface area of 1098 m2·g-1 covered with both micro- and mesopores. The ORR active sites focused mainly on Fe-Nx bonding made of various pyridinic, pyrrolic, and graphitic N-s after calcination. The max. power density reaches 140 mW·cm-2 for FeNC-900-800-A, which is superior to other FeNxC catalysts, experiencing only one-stage calcination in N2. The FeNxC demonstrates only 10 mV half-wave-voltage (HWV) loss at 1600 rpm after 1000 redox cycles, as compared to be 27 mV for commercial Pt/C catalyst in the durability test.

Preparation of Pt-Catalyst by Poly(p-phenylenediamine) Nanocomposites Assisted by Microwave Radiation for Proton Exchange Membrane Fuel Cell.

The Pt elements are prepared via the redox reaction with microwave (MW) irradiation in the presence of poly(p-phenylenediamine) (PpPD) which is polymerized on XC72 carbon matrix (PpPD/XC72), behaving as reducing agent. The free primary amines of PpPD are actually converted (oxidized) to secondary ones (5,10-dihydrophenazine) after MW irradiation. Transmission electronic microscopy (TEM) micrographs reveal the prepared Pt nanoparticles are well-dispersed on the carbon matrix like commercial Pt-implanted carbon nanocomposite (Pt/C). From the residue weights of thermogravimetric analysis (TGA) thermograms of Pt-loaded PpPD/XC72 (PpPD/XC72-Pt-MW), more Pt (18.49 wt %) nanoparticles are implanted on PpPD/XC72 composite. The Pt-implanted wt % on PpPD/XC72 matrix is just slightly lower than that of commercial Pt/C (22.30 wt %). The Pt-catalyst supports of PpPD/XC72-Pt-MW illustrate typical cyclic voltammograms (C-V) of Pt-catalyst, including significant Pt⁻H oxidation and Pt⁻O reduction peaks. The electrochemical active surface area of PpPD/XC72-Pt-MW is found to be as high as 60.1 m² g-1. Max. number of electron transfer during oxygen reduction reaction (ORR) approaches 3.83 for PpPD/XC72-Pt-MW, higher than that of commercial Pt/C (3.62). Single cell based on PpPD/XC72-Pt-MW demonstrates much higher specific max. power density to be 34.6 mW cm-2 Pt, higher than that single cell prepared with commercial Pt/C electrode (30.6 mW cm-2 Pt).

Epigenetics regulates gene expression patterns of skeletal muscle induced by physical exercise.

As it is well known, proper exercise benefits our mind and body, especially the skeletal muscle. Exercise increases the capacity of muscle metabolism, enhances the biological function of mitochondria, regulates the transformation of muscle fiber types and increases the muscle power. In recent years, more and more researches show that epigenetic regulation plays an important role in strengthening the muscle, and these studies mainly include DNA methylation, histone modification, and regulation of miRNA expression. In order to adapt to the body movement, these three epigenetic patterns change the metabolic capacity of skeletal muscle, mitochondrial biological function and muscle fiber types by regulating the gene expression of skeletal muscle. In this review, we summarize research progresses of exercise-induced epigenetic regulation of gene expression of skeletal muscle, in order to provide a reference for further studies of how sports improve our body health.

Measurement uncertainty assessment of magnesium trisilicate column for determination of Sudan colorants in food by HPLC using C8 column.

This study aimed to conduct measurement uncertainty assessment of a new method for determination of Sudan colorants (Sudan I, II, III and IV) in food by high performance liquid chromatography (HPLC). Samples were extracted with organic solvents (hexane, 20% acetone) and first purified by magnesium trisilicate (2MgO·3SiO2). The Sudan colorants (Sudan I-IV) were also initially separated on C8 by gradient elution using acetonitrile and 0.1% (v/v) formic acid aqueous solution as the mobile phases and detected with diode-array detector (DAD). The uncertainty of mathematical model of Sudan I, II, III and IV is based on EURACHEM guidelines. The sources and components of uncertainty were calculated. The experiment gave a good linear relationship over the concentration from 0.4 to 4.0 µg/mL and spiked recoveries were from 74.0% to 97.5%. The limits of determination (LOD) were 48, 61, 36, 58 µg/kg for the four analytes, respectively. The total uncertainty of Sudan colorants (Sudan I, II, III and IV) was 810±30.8, 790±28.4, 750±27.0, 730±50.0 µg/kg, respectively. The recovery uncertainty was the most significant factor contributing to the total uncertainty. The developed method is simple, rapid, and highly sensitive. It can be used for the determination of trace Sudan dyes in food samples. The sources of uncertainty have been identified and uncertainty components have been simplified and considered.

Preparation of insulating SiO2 nanostructured thin films by the sol-gel process.

Organic dispersion agents can effectively decrease the surface roughness of films. Here, films containing organic dispersion agents are used to produce metal-insulator-metal structures. It was found that addition of Triton caused films to become denser, and thicker, and the leak current of devices to decrease by 10 times compared with that without Triton because of its uniform dispersion in the films. The resulting films were used as the insulator layer of thin film transistors containing a semiconductor layer of evaporated pentacene. The interface between the insulator and semiconductor layers was found to affect the arrangement of pentacene, and O2 plasma was used to improve the interface activity to increase the order of the pentacene molecules and enhance the carrier mobility of the devices.

Design of multi-porous layer for dye-sensitized solar cells by doping with TiO2 nanoparticles.

We propose a multi-layer dye-sensitized solar cell (DSSC). Conventional DSSC components use a singular TiO2 particle size and a mono-layer active layer, but we demonstrate a multi-layer and multi-scale TiO2 particle based DSSC. Doping with large TiO2 particles can produce light scattering inside the DSSC component. Light scattering effects reduce TiO2 absorption at wavelengths of 200-300 nm. The unabsorbed light zig-zags between the Pt back electrode layer and the substrate, and enhances the Ru-dye absorption. To enhance the scattering, we doped the active layer with 20 wt% of large diameter TiO2. The multi-layer DSSC increases efficiency by about 15% compared with standard DSSCs.

Hierarchical structured TiO2 photoanodes for dye-sensitized solar cells.

A novel approach has been developed to fabricate hills-like hierarchical structured TiO2 photoanodes for dye-sensitized solar cells (DSSCs). The appropriately aggregated TiO2 clusters in the photoanode layer could cause stronger light scattering and higher dye loading that increases the efficiency of photovoltaic device. For detailed light-harvesting study, different molecular weights of polyvinyl alcohol (PVA) were used as binders for TiO2 nanoparticles (P-25 Degussa) aggregation. A series of TiO2 films with dissimilar morphology, the reflection of TiO2 films, absorbance of attached dye, amount of dye loading, and performance of fabricated DSSC devices, were measured and investigated. An optimized device had energy conversion efficiency of 4.47% having a higher dye loading and good light harvesting, achieving a 23% increase of short-circuit current J(sc) in DSSCs.

A novel chromogenic peptide for prekallikrein/kallikrein determination.

OBJECTIVE: To determine the Km, Vmax, and Ki of BOC-Leu-Ser-Thr-Arg-pNA (B3644) in the determination of kallikrein, and then to establish the procedure for plasma prekallikrein/kallikrein determination. Method Chromogenic substrate assays on a semi-auto spectrophotometer were employed. RESULTS: The apparent activities of seven substrates: B3644, S2238, S2251, ChromozymPCa, T6140, ChromozymPK, and T1637, for porcine kallikrein were 0.788, 0.691, 0.659, 0.636, 0.438, 0.396, and 0.145, respectively, that of B3644 being the highest. Amidolysis caused by kaolin activated human normal plasma was independent of coagulation factors II, X, XI, and protein C, but dependent on prekallikrein and to some extent on factor XII. The kallikrein's, thrombin's, and plasmin's Km and Vmax for the B3644 were determined and calculated to be 235 micromol/L and 337 nmol x s(-1) x U(-1), 469 micromol/L and 63 nmol x s(-1) x U(-1), and 70 micromol/L and 358 nmol x s(-1) x U(-1), respectively. At the same time, the kallikrein, thrombin, and plasmin Ki values for antithrombin III (AT-III) or limabean trypsin inhibitor (LBTI) were detected to be 840 or 2.50. 32 or 0.32, and, 108 or 1.55 U/L, [d1] respectively. With B3644, the recovery percentages of kallikrein and kaolin activated plasma were 100%. Intra-assay CV values ranged from 2.3% to 4.6%. By using B3644 and introducing AT-III or LBLI into the determination system, an optimized procedure for prekallikrein/kallikrein determination was obtained. With this procedure, the mean percentage values of plasma prekallikrein in normal subjects, pregnant women (gestation > or =24 weeks), and in patients with hypertension, hepatic failure, or with advanced cancers were determined to be 113.5, 151.6 (P<0.01), 173.2 (P<0.01), 43.5 (P<0.005), and 88.7 (P<0.05), respectively. CONCLUSION: B3644 was identified as a suitable substrate for the determination of plasma prekallkrein/kallikrein activity. A sensitive and reliable chromogenic substrate assay for human plasma prekallikrein was developed by using this novel substrate.