Μg Cm-2 Research Articles

Reduced-Graphene-Oxide with Traces of Iridium or Gold as Active Support for Pt Catalyst at Low Loading during Oxygen Electroreduction

Chemically-reduced graphene-oxide-supported gold nanoparticles and traces of iridium are considered here together with loadings of platinum as catalytic materials for reduction of oxygen in alkaline and acid media, respectively. Comparison is made to the analogous systems based on conventional Vulcan carbon carriers. Gold nanoparticles are prepared by the chemical reduction method, in which the NaBH4-prereduced Keggin-type phosphomolybdate heteropolyblue acts as the reducing agent for the precursor (HAuCl4). Polyoxmetallate (PMo12O40 3-) capping ligands stabilize gold nanoparticle deposits, facilitate their dispersion and attachment to carbon supports. Indeed, it is apparent from the independent diagnostic voltammetric experiments (in 0.5 mol dm-3 H2SO4) that heteropolymolybdates form readily stable adsorbates on nanostructures of both gold and carbon (reduced graphene oxide and Vulcan). It is reasonable to expect that the polyoxometallate-assisted nucleation of gold has occurred in the proximity of oxygenated defects existing on carbon substrates. Under conditions of electrochemical diagnostic experiments (performed in 0.1 mol dm-3 KOH) the phosphomolybdate adsorbates are removed from the interface as they undergo dissolution in alkaline medium; and the Au nanoparticles (Au loading, 30 µg cm-2) remain well-dispersed on the carbon as evident from transmission electron microscopy. High electrocatalytic activity of the reduced-graphene oxide-supported Au nanoparticles toward reduction of oxygen in alkaline medium is demonstrated using cyclic and rotating ring-disk electrode (RDE) voltammetric experiments. Among important issues are possible activating interactions between gold and the support, as well as presence of structural defects existing on poorly organized graphitic structure of reduced graphene oxide (as evident from Raman spectroscopy). When using the silica or titania functionalized reduced graphene oxide as carriers for Au (or Ir) and Pt nanoparticles, the resulting systems have exhibited typically higher (certainly not lower) O2-reduction currents (relative to those recorded at conventional Vulcan-supported Pt at the same loading) in acid medium (0.5 M H2SO4). The RDE data are consistent with even lower formation of hydrogen peroxide. Furthermore, the durability of this family of catalysts was outstanding. Finally, by doping the reduced graphene oxide supported Pt with traces of Ir (<1 µg cm-2), decreases amounts of produced H2O2 (<1%) at potentials 0.6 V (vs RHE) or lower.

Reduced-Graphene-Oxide with Traces of Iridium or Gold as Active Support for Pt Catalyst at Low Loading during Oxygen Electroreduction

Chemically-reduced graphene-oxide-supported gold or iridium nanoparticles are considered here as active carriers for dispersed platinum with an ultimate goal of producing improved catalysts for electroreduction of oxygen in acid medium. Comparison is made to the analogous systems not utilizing reduced graphene oxide. High electrocatalytic activity of platinum (loading up to 30 µg cm-2) dispersed over the reduced-graphene oxide-supported Au (up to 30 µg cm-2) or Ir (up to 1.5 µg cm-2) nanoparticles toward reduction of oxygen has been demonstrated using cyclic and rotating ring-disk electrode (RRDE) voltammetric experiments. Among important issues are possible activating interactions between gold and the support, as well as presence of structural defects existing on poorly organized graphitic structure of reduced graphene oxide. The RRDE data are consistent with decreased formation of hydrogen peroxide.

DEVELOPMENT OF METHOD FOREXTRACTIVE SPECTROPHOTOMETRIC DETERMINATION OF COPPER(II) WITH N-BENZOYL THIOUREATHIOSEMICARBONZONE(MAAPHE) AS AN ANALYTICAL REAGENT

TheA simple, rapid and sensitive spectrophotometric method has been developed for the determination of Cu (II) by using N-BenzoylThioureathiosemicarbazonesynthesized and characterized by elemental and analysis. MAAPHE extractsCu(II) quantitatively(99.5%) into chloroform from an aq. solution of pH range 5.5-6.5 . The chloroform extract shows an intense peak 450nm (max). Beer’s law is obeyed over the Cu(II) concentration range 0.1-4.2 μg/ml. The Sandell’s sensitively and molar absorpitivity for Cu-MAAPHE system is 0.00252μg cm-2 and 25700 L/mol/ cm respectively. The composition of extracted species are found is 1:2 (Cu:MAAPHE) by Job’scontinuous variation and mole ratio method. Interference by various ions has been studied. The proposed method hasbeen successfully applied for determination of Cu(II) in alloy

EFFECT OF FLUBENDIAMIDE ON MORPHOLOGY, AVOIDANCE BEHAVIOUR AND ACETYLCHOLINESTERASE ACTIVITY IN EARTHWORM EUDRILUS EUGENIAE

Objective: Flubendiamide is extensively used in agriculture practices as foliar application pesticide. Due to long persistency in the soil, flubendiamide pose serious health concern in non-target organisms. Our main objective was to examine flubendiamide impact on burrowing animal Eudrilus eugeniae with special emphasis on avoidance behaviour and neurotoxicity.Methods: Acute toxicity study of flubendiamide (Diamide pesticide) was conducted on earthworm, Eudrilus eugeniae through direct paper contact method and artificial soil method. Median lethal concentration (LC50) of flubendiamide was calculated by following probit analysis. The neurotoxic potential of flubendiamide was studied with marker enzyme Acetyl cholinesterase (AChE) levels in both In vivo and In vitro experiments.Results: LC50 in earthworms was found to be 94.4 µg cm-2 at 48h paper contact test and 332.21 mg kg-1and 238.31 mg kg-1 respectively at 7 and 14 d artificial soil exposure. Morphological and physiological alterations in earthworms attribute to inhibition of AChE levels. The kinetic study of AChE activity in presence and absence of inhibitor suggests the enzyme reaction is competitive in nature.Conclusion: Present study establishes concentration-dependent flubendiamide toxicity in earthworm E. eugeniae. No clear conclusive remarks were made on earthworm avoidance behaviour as the worms were located both in toxic and control soil after 48h of exposure. Further studies may be needed in this aspect to establish clear understanding on avoidance nature of E. eugeniae in different soil types.

Effect of IL-1β, TNF-α and IGF-1 on trans-endothelial passage of synthetic vectors through an in vitro vascular endothelial barrier of striated muscle.

When administrated in the blood circulation, plasmid DNA (pDNA) complexed with synthetic vectors must pass through a vascular endothelium to transfect underlying tissues. Under inflammatory condition, cytokines can modify the endothelium integrity. Here, the trans-endothelial passage (TEP) of DNA complexes including polyplexes, lipoplexes and lipopolyplexes was investigated in the presence of tumor necrosis factor-α (TNF-α), interleukin-1β (IL-1β) or insulin-like growth factor-1 (IGF-1). The experiments were performed by using an in vitro model comprising a monolayer of mouse cardiac endothelial cells (MCEC) seeded on a trans-well insert and the transfection of C2C12 myoblasts cultured on the lower chamber as read out of TEP. We report that polyplexes made with a histidinylated derivative of lPEI (His-lPEI) exhibit the highest capacity (10.5 μg cm-2 h versus 0.324 μg cm-2 h) to cross TNF-α-induced inflamed endothelium model, but this positive effect is counterbalanced by the presence of IL-1β. His-lPEI polyplex TEP is also increased in the presence of IGF-1 (2.58 μg cm-2 h). TEP of lipid-based DNA complexes including lipoplexes and lipopolyplexes was lowest compared with polymer-based DNA complexes. Overall, the results indicate that under inflammation, His-lPEI polyplexes have a good profile to cross a vascular endothelium of striated muscle with low cytotoxicity and high transfection efficiency of C2C12 myoblasts. These data provide insights concerning the endothelial passage of vectors in inflammatory conditions and can serve as a basis towards in vivo studies.

The wax bloom on blueberry: Application of luster sensor technology to assess glossiness and the effect of polishing as a fruit quality parameter

The wax bloom of the fruit is responsible for the visible quality of blueberries. This study aimed to investigate a new technology using the effect of polishing on micromorphology, wax content and weight loss of blueberries. Luster sensor (type CZ-H72, Keyence, Japan) technology was used to assess glossiness of polished blueberries compared with berries with a natural (unpolished) wax layer during 9 days after harvest. Blueberries were rubbed twice by hand within a soft microfibre tissue to obtain polished fruit. Unpolished blueberries contained ca. 120 μg wax cm-2, which was reduced by ca. 22% to ca. 95 μg cm-2 by polishing. This reduction was associated with an increase in luster levels from ca. 65 to 80 a.u.. Weight loss was larger from polished than from unpolished blueberries with a concomitant 40% increase in luster levels from 60 to 85 a.u. in polished fruit. Luster levels sharply decreased from 85 a.u. in the first 5 days after harvest and then leveled off to remain almost constant at ca. 20 a.u. with significantly larger values for polished blueberries of ca. 30 a.u. with a larger magnitude of glossiness. Overall, luster sensor technology may offer a new effective, affordable, possibly portable, non-destructive technique to assess glossiness or other surface features in real time for classifying not only blueberry, but also other waxy fruit such as aubergine/eggplant, plum, Juniperus, blue grape berry etc..

Novel Anti‐Biofouling Soft Contact Lens: l‐Cysteine Conjugated Amphiphilic Conetworks via RAFT and Thiol–Ene Click Chemistry

A unique l-cysteine conjugated antifouling amphiphilic conetwork (APCN) is synthesized through end-crosslinking of well-defined triblock copolymers poly(allyl methacrylate)-b-poly(ethylene glycol)-b-poly(allyl methacrylate) via a combination of reversible addition-fragmentation chain transfer (RAFT) polymerization and thiol-ene "click" chemistry. The synthesized poly(ethylene glycol) macro-RAFT agent initiates the polymerization of allyl methacrylate in a controlled manner. The vinyl pendant groups of the precursor partially conjugate with l-cysteine and the rest fully crosslink with mercaptopropyl-containing siloxane via thiol-ene click chemistry under UV irradiation into APCNs, which show distinguished properties, that is, excellent biocompatibility, more than 39.6% water content, 101 barrers oxygen permeability, optimized mechanical properties, and more than 93% visible light transmittance. What's more, the resultant APCNs exhibit eminent resistance to protein adsorption, where the bovine serum albumin and lysozyme adsorption are decreased to 12 and 21 µg cm-2 , respectively. The outstanding properties of APCNs depend on the RAFT controlled method, which precisely designs the hydrophilic/hydrophobic segments and eventually greatly improves the crosslinking efficiency and homogeneity. Meantime, the l-cysteine monolayer can effectively reduce the surface hydrophobicity and prevent protein adsorption, which exhibits the viability for antifouling surface over and under ophthalmic devices, suggesting a promising soft contact lens.

Organosilane-Based Coating of Quartz Species from the Traditional Ceramics Industry: Evidence of Hazard Reduction Using In Vitro and In Vivo Tests.

The exposure to respirable crystalline silica (RCS), e.g. quartz, in industrial settings can induce silicosis and may cause tumours in chronic periods. Consequently, RCS in the form of quartz and cristobalite has been classified as human lung carcinogen category 1 by the International Agency for Research on Cancer in 1997, acknowledging differences in hazardous potential depending on source as well as chemical, thermal, and mechanical history. The physico-chemical determinants of quartz toxicity are well understood and are linked to density and abundance of surface silanol groups/radicals. Hence, poly-2-vinylpyridine-N-oxide and aluminium lactate, which effectively block highly reactive silanol groups at the quartz surface, have formerly been introduced as therapeutic approaches in the occupational field. In the traditional ceramics industry, quartz-containing raw materials are indispensable for the manufacturing process, and workers are potentially at risk of developing quartz-related lung diseases. Therefore, in the present study, two organosilanes, i.e. Dynasylan® PTMO and Dynasylan® SIVO 160, were tested as preventive, covalent quartz-coating agents to render ceramics production safer without loss in product quality. Coating effectiveness and coating stability (up to 1 week) in artificial alveolar and lysosomal fluids were first analysed in vitro, using the industrially relevant quartz Q1 as RCS model, quartz DQ12 as a positive control, primary rat alveolar macrophages as cellular model system (75 µg cm−2; 4 h of incubation ± aluminium lactate to verify quartz-related effects), and lactate dehydrogenase release and DNA strand break induction (alkaline comet assay) as biological endpoints. In vitro results with coated quartz were confirmed in a 90-day intratracheal instillation study in rats with inflammatory parameters as most relevant readouts. The results of the present study indicate that in particular Dynasylan® SIVO 160 (0.2% w/w of quartz) was able to effectively and stably block toxicity of biologically active quartz species without interfering with technical process quality of certain ceramic products. In conclusion, covalent organosilane coatings of quartz might represent a promising strategy to increase workers’ safety in the traditional ceramics industry.

In situ data supporting remote sensing estimation of spruce forest parameters at the ecosystem station Bílý Kříž

Remote sensing offers an effective way of mapping vegetation parameters in a spatially continuous manner, at larger spatial scales and repeatedly in time compared to traditional in situ mapping approaches that are typically accurate, but limited to a few distributed location and few repetitions. In case of forest ecosystems, remote sensing allow to assess quantitative parameters or indicators related to forest health status such as leaf area index, leaf pigment content, chlorophyll fluorescence, etc. Development, calibration and validation of remote sensing-based methods, however, still rely on supportive in situ data. The aim of this contribution is to introduce the individual in situ components in the framework for the retrieval of forest quantitative parameters from airborne imaging spectroscopy data. All measurements were acquired during an extensive in situ/flight campaign that took place at the Norway spruce dominated study site Bílý Kříž (Moravian-Silesian Beskydy Mts., Czech Republic) during August 2016. In addition to airborne remote sensing data acquisition, the in situ activities included terrestrial laser scanning for tree 3D modelling, measurements of needle biochemical and optical properties, leaf area index measurements and spectral measurements of various natural and artificial surfaces. Leaf pigments varied between 25.2 and 49.1 µg cm-2 for chlorophyll a+b content, 4.9 – 10.6 µg cm-2 for carotenoid content depending on needle age and its adaptation to sun illumination, whereas ratio between the two pigments was stable around 4.6 – 5. 3. Specific leaf area of spruce needles varied between 49.3 and 105.8 cm2 g-1, being the highest for the shade adapted needles of the current year. Leaf area index of spruce stands of various age and densities varied between 5.3 and 9. 3.

Spectrophotometric Assay of Diethylcarbamazine Citrate in Pharmaceuticals and Human Urine via Ion-Pair Reaction Using Methyl Orange Dye

Two simple and moderately selective spectrophotometric methods are described for the determination of Diethylcarbamazine Citrate (DEC) in bulk drug, dosage forms and spiked human urine. The first method (method A) is based on the formation of yellow colored ion-pair complex between DEC and Methyl Orange (MO) dye, at pH 4.95 ± 0.05, which was extracted into chloroform and measured at 420 nm. The second method (method B) involved the breaking of yellow ion-pair complex in acid medium followed by the measurement of the free dye at 520 nm. Experimental parameters influencing the formation and extraction of the ion-pair complex in method A and breaking of the complex in method B were scrupulously examined and optimized. Beer’s law is obeyed over the concentration ranges of 10-90 and 5-100 μg mL-1 DEC with corresponding molar absorptivity values of 2.90×103 and 3.54×103 L mol-1 cm-1 for method A and method B, respectively. The Sandell’s sensitivity values were 0.1351 and 0.1106 μg cm-2 for method A and method B, respectively. The Limits of Detection (LOD) and Quantification (LOQ) were calculated to be 0.36 and 1.09 μg mL-1 (method A) and 0.34 and 1.02 μg mL-1 (method B). The composition of drug-dye ion-pair complex used in method A was found to be 1:1 by Job’s method of continuous variations. The proposed methods were validated for robustness, ruggedness and selectivity, and applied to the determination of DEC in tablet, syrup formulations and spiked human urine samples. The results demonstrated that the proposed methods are as accurate and precise as the reference method. The accuracy of the methods was further ascertained by recovery study via standard-addition method.

Oriented Pt Nanoparticles Supported on Few-Layers Graphene as Highly Active Catalyst for Aqueous-Phase Reforming of Ethylene Glycol.

Pt nanoparticles (NPs) strongly grafted on few-layers graphene (G) have been prepared by pyrolysis under inert atmosphere at 900 °C of chitosan films (70-120 nm thickness) containing adsorbed H2PtCl6. Preferential orientation of exposed Pt facets was assessed by X-ray diffraction of films having high Pt loading where the 111 and 222 diffraction lines were observed and also by SEM imaging comparing elemental Pt mapping with the image of the 111 oriented particles. Characterization techniques allow determination of the Pt content (from 45 ng to 1 μg cm-2, depending on the preparation conditions), particle size distribution (9 ± 2 nm), and thickness of the films (12-20 nm). Oriented Pt NPs on G exhibit at least 2 orders of magnitude higher catalytic activity for aqueous-phase reforming of ethylene glycol to H2 and CO2 compared to analogous samples of randomly oriented Pt NPs supported on preformed graphene. Oriented [Formula: see text]/fl-G undergoes deactivation upon reuse, the most probable cause being Pt particle growth, probably due to the presence of high concentrations of carboxylic acids acting as mobilizing agents during the course of the reaction.

New Spectrophotometric Method for the Assay of Sulfadiazine Drug Based on Diazotization Coupling Reaction

Abstract A sensitive, simple and rapid spectrophotometric procedure for the assay of trace quantities of sulfadiazine (SDZ) drug as bulk and in diluted solution is characterized. The procedure depends on the diazotization reaction which is produced by coupling SDZ with (4-amino-2-hydroxy acetophenon) (AHA) to produce an intense colored complex spectrophotometrically determined at 410 nm. Beer’s law was applied in the range of concentration 0.5 - 15 ppm; the molar absorptivity and Sandell’s sensitivity were 2.8484 × 104 L mol-1 cm-1 and 0.008 μg cm-2 respectively. The method limit of detection (LOD) was 0.443 μg mL-1 and LOQ (the method limit of quantitation) was 0.249 μg mL-1. The procedure is not based on solvent extraction and the additives and excipients do not significantly influence the developed procedure.

Reproductive toxicity induced by nickel nanoparticles in Caenorhabditis elegans.

To investigate the reproductive toxicity and underlying mechanism of nickel nanoparticles (Ni NPs), Caenorhabditis elegans (C. elegans) were treated with/without 1.0, 2.5, and 5.0 μgcm-2 of Ni NPs or nickel microparticles (Ni MPs). Generation time, fertilized egg numbers, spermatide activation and motility were detected. Results indicated, under the same treatment doses, that Ni NPs induced higher reproductive toxicity to C. elegans than Ni MPs. Reproductive toxicities observed in C. elegans included a decrease in brood size, fertilized egg and spermatide activation, but an increase in generation time and out-of-round spermatids. The reproductive toxicity of Ni NPs on C. elegans may be induced by oxidative stress. The reproductive toxicity in C. elegans induced by Ni NPs is consistent with our previous results in the rats. Therefore, C. elegans can be used as an alternative model to detect the early reproductive toxicity of Ni NPs exposure. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 1530-1538, 2017.

Influence of Surface Oxygen Non-Stoichiometry on Oxygen Electrochemical Properties of Perovskite-Type Oxides

Introduction Much attention has been paid to oxygen electrochemical reactions in alkaline electrolytes such as alkaline fuel cell, alkaline rechargeable metal-air battery and water-splitting devices. Many researchers have been exploring highly-active and cost-effective oxygen electrode catalysts, and one example of good oxygen electrocatalysts is perovskite-type oxide with the general formula of ABO3. Our group focuses on observing intrinsic electrochemical properties of perovskite when used as an oxygen electrode catalyst, using a carbon-free and binder-free perovskite electrode.1, 2 One of our research findings was that whereas oxygen evolution reaction activity of model electrodes were as high as that of composite electrodes consisting of perovskite powder, carbon and binder, oxygen reduction reaction activity of model electrodes was much lower than that of composite electrodes. This contrasting behavior motivated us to conduct further experiments such as hydrogen peroxide reduction reaction activity and cyclic characteristics of oxygen electrochemical reactions by using the model electrode and the composite electrode in terms of surface oxygen non-stoichiometry, which is our present research topic. Experimental section Synthesis and fabrication of La0.8Sr0.2CoO3 (LSCO) crystal electrodes were described in our previous literature.2 Perovskite powders were also synthesized by hydroxide-acid aided process3 and solid state process. The resultant oxide crystals and powders were characterized by using X-ray diffraction (XRD), energy-dispersive X-ray (EDX) spectroscopy, Brunauer-Emmett-Teller for oxide powders, and iodometry for oxide powders. Electrochemical measurements were conducted by using a rotating disk electrode (RDE) in a three-electrode cell. For a working electrode, RDE of LSCO crystal electrodes were assembled by mounting a LSCO crystal in a Teflon disk holder. As for composite electrodes, a catalyst layer consisting of 250 μg cm-2 perovskite powder, 50 μg cm-2 Vulcan XC-72 (Cabot), and 50 μg cm-2 anion conductive ionomer (AS-4, Tokuyama) was formed on glassy carbon (GC) RDE. 50 μg cm-2 Pt(40wt%)/Vulcan (E-TEK) and 50 μg cm-2 anion conductive ionomer on GC RDE was also used as benchmarking of oxygen electrochemical reactions. Pt wire and reversible hydrogen electrode (RHE) were used as counter and reference electrodes, respectively. Oxygen electrochemical activity measurements were conducted using a solution of oxygen-saturated 1.0 mol dm-3 KOH for oxygen reduction reaction (ORR) and oxygen evolution reaction (OER), and argon-purged 1 mol dm-3 KOH containing ca. 5 mmol dm-3 H2O2 for hydrogen peroxide reduction reaction (PRR). For qualitative electronic conductivity measurement, ferricyanide reduction reaction (FRR) was observed in a solution of argon-purged 1.0 mol dm-3 KOH containing 20 mmol dm-3 K3[Fe(CN)6]. Results and discussions XRD and EDX measurements confirmed that resultant LSCO crystals and perovskite powders had perovskite structure and the atomic compositions were quite similar as the desired composition. Figure 1 shows PRR activity on LSCO crystal. In the initial cycles, it shows clear rotation dependence indicating that LSCO crystal was active toward PRR. However, as the cycle number of cyclic voltammetry increased, reduction currents were decreased and finally showed no dependence on rotation. Similar results were observed for solid-state-synthesized LSCO composite electrode suggesting that obtained results by model electrodes were universal for practical electrodes. The decrease in activities was also observed for ORR, while the decrease in OER activity on LSCO crystal was not observed. FRR after PRR and ORR showed that electronic conductivity of LSCO crystal was decreased. The reason of activity decrease in ORR and PRR, and the influence of B-site cation in ORR and PRR in terms of surface oxygen non-stoichiometry will be discussed in the conference.

Comparative Study of Electroless Platinum Deposition Using Multivalent Metal Ions or Hydrazine As Reducing Agents

Two new type electroless plating processes for deposition of continuous platinum layer are proposed and compared with known process of electroless platinum daeposition using hydrazine as reducing agent. In this study investigation of the kinetics of electroless Pt deposition, using reducing agents such as Co(II)/Co(III) and Ti(III)/Ti(IV) redox systems, is presented. The Pt layers were deposited on the copper or nickel surfaces. The morphology of Pt layers deposited using different reducing agents was investigated by means of Field Emission Scanning Electron Microscopy (FESEM). Kinetics of deposition rate of Pt was investigated by means of the Electrochemical Quartz Crystal Microgravimetry (EQCM). It was found that the deaeration of the electroless Pt plating solutions with argon, using Co(II)/Co(III) or Ti(III)/Ti(IV) redox systems as reducing agents, results in higher deposition rates of Pt. When using Co(II)/Co(III) redox system as a reducing agent, the rate of electroless deposition of Pt is ca. 0.3 µg cm-2 min-1 when using Ar-deaerated plating solution, whereas the one in non-deaerated plating solution is significantly lower, e.g. 0.02 µg cm-2 min-1. When, using the Ti(III)/Ti(IV) redox system as reducing agent, the Pt deposition rate in Ar-deaerated plating solution is higher compared with that using CoII)/Co(III) redox couple. It should be noted that the obtained Pt layers deposited on the surface of Cu using Co(II)/Co(III) or Ti(III)/Ti(IV) redox pairs as reducing agents are continuous and compact. The kinetic data of the mentioned reactions is discussed and compared with that obtained using hydrazine as reducing agent. Acknowledgment This research was funded by a Grant (No. TEC-06/2015) from the Research Council of Lithuania.

Dual Electrolyte Hybrid Supercapacitor Using Liquid-Liquid Interface

Hybrid supercapacitors utilzing a supercapacitive electrode and a battery-type electrode exhibit enhanced capacitor performance compared to conventional symmetric supercapacitors. The authors have denonstrated high energy density (>700 Wh kg-1) and high cell voltage (4.3 V) by combining metal oxides positive electrode that have high capacitance in aqeuous electrolytes and a Li negative electrode with low standard electrode potential.1,2 This hybrid supercapacitor ( Li | polymer electrolyte | solid electrolyte | 1.0 M Li2SO4 | RuO2×nH2O) utilizes a LISICON-type glass ceramic as a water-stable solid electrolyte to separate the aqueous and non-aqueous electrolytes and prevent penetration of water to Li. The conductivity of the Li-conducting glass ceramic used (~10-4 S cm-2 at 25°C) is not sufficent enough to afford the power performance characteristic of supercapacitors. In this study, a dual-electrolyte hybrid supercapacitor without solid electrolyte was investigated by utilizing a liquid/liquid interface was developed with aqueous electrolyte/ionic liquid-based electrolyte and its capacitive behavior was investigated. For the aqueous electrolyte, 1.0 M Li2SO4 was used and a 0.5 M LiTFSI/N-methyl-N-propylpiperidinium bis(trifluoromethanesulfonyl)imide (PP13TFSI) were used as the ionic liquid-based electrolyte. RuO2×nH2O deposited on a glassy carbon surface was used as the positive electrodes (204 µg cm-2). Li foil negative electrode (5 mm x 5 mm) was placed into the 0.5 M LiTFSI/PP13TFSI electrolyte. RuO2×nH2O positive electrode was placed into 1.0 M Li2SO4. Charge/discharge test was carried out in two-electrode configuration with RuO2×nH2O positive electrode and Li negative electrode at 25 °C. The higher and lower cut-off voltages were 3.8 and 2.8 V, respectively. The resistance of Li | 0.5 M LiTFSI/PP13TFSI | 1.0 M Li2SO4 | Pt cell with liquid-liquid interface was 491 W cm2 based on EIS measurement, which is ~1/3 of our best data of 1360 W cm2 when a solid electrolye is used (Li | alginate gel-0.5 M LiTFSI/PP13TFSI | LISICON | Li2SO4 | Pt ). Charge/discharge curves of the dual-electrolyte hybrid supercapacitor without solid electrolyte consisting of Li | 0.5 M LiTFSI/PP13TFSI | 1.0 M Li2SO4 | RuO2×nH2O at 0.141 mA cm-2 is shown in Fig. 1. The cell voltage profile exhibited capacitive behavior between 2.8 and 3.8 V, similar to our previously research.4 The potential of the Li negative electrode was nearly constant around -2.45 V vs RHE during charge/discharge. The specific capacity and specific capacitance calculated from discharge at 0.141 mA cm-2 was 51.1 mAh (g-RuO2)-1 and 188 F (g-RuO2)-1, respectively. The IR drop of the negative electrode was 0.194 V (Fig. 2a). An equivalent series resistance (ESR) was 535 W cm2, smaller than that of the Li | alginate gel impregnated with 0.5 M LiTFSI/PP13TFSI | LISICON | Li2SO4 | activated carbon (AC) cell of 1350 W cm2)at 0.255 mA cm-2 (Fig. 2b), and agrees well with the results estimated from EIS. Dual-electrolyte hybrid supercapacitor using liquid-liquid interface (without solid electrolyte) may be considered as a post Li-ion capacitor device. 1. S. Makino, Y. Shinohara, T. Ban, W. Shimizu, K. Takahashi, N. Imanishi, and W. Sugimoto, RSC Adv., 2, 12144 (2012). 2. S. Makino, T. Ban and W. Sugimoto, J. Electrochem. Soc., 162, A5001 (2015). 3. S. Chou, Y. Wang, J. Xu, J. Wang, H. Liu and S. Dou, Electrochem. Commun., 31, 35 (2013). 4. M. Yamagata, K. Soeda, S. Yamazaki, and M. Ishikawa, Electrochem. Solid-State Lett., 14, A165 (2011). Figure 1

Manganese Oxide/Poly(3,4-ethylenedioxythiophene) Hybrid Electrocatalysts for the Oxygen Reduction Reaction in Alkaline Fuel Cells

Manganese oxide/poly(3,4-ethylenedioxythiophene) (MnOx/PEDOT) nanostructured hybrid thin films are readily prepared using a simple anodic electrodeposition process from aqueous solution. Using this approach, MnOx/PEDOT films with thicknesses and mass loadings up to 100 nm and 40 μg cm-2 were prepared, then tested for oxygen reduction reaction (ORR) activity in alkaline electrolyte using rotating disk electrode and rotating ring disk electrode methods. MnOx/PEDOT provided improvements over MnOx-only and PEDOT-only control films, with > 0.2 V decrease in onset and half-wave overpotentials and > 1.5 times increase in current density. The MnOx/PEDOT film exhibited only a slightly lower reaction order (n = 3.86-3.92) than the 20% Pt/C benchmark electrocatalyst (n = 3.98) across all potentials. MnOx/PEDOT also displayed a more positive half-wave potential and superior electrocatalytic selectivity for the ORR upon methanol exposure than 20% Pt/C. The high activity and synergism of MnOx/PEDOT towards the ORR is attributed to effective intermixing/dispersion of the two materials, intimate substrate contact and the improved charge transfer processes attained by co-electrodepositing MnOx with PEDOT. PEDOT has previously been demonstrated in fuel cells to limit methanol crossover. PEDOT has also been used as a catalyst support in fuel cells. These facts, combined with the substantially lower cost of Mn versus Pt (Mn is ~ 17,000 times cheaper), augurs for further development and testing of MnOx/PEDOT hybrid materials as ORR electrocatalysts with application in alkaline fuel cells. This work was supported by the Laboratory Directed Research and Development program at Sandia National Laboratories, a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under contract DE-AC04-94AL85000.

Estimation of the Rate Constants for the 2x2-Electron ORR by Combining the Voltammograms of O2 and H2O2 Reduction Reactions

1. Introduction After the major discovery of the platinum based electro-catalysts for the cathodic reduction of the oxygen in the polymer electrolyte membrane fuel cells, commercialization of PEM fuel cells begins for automobile applications. However, it is necessary to replace the platinum-based electro-catalysts due to the high cost and scarcity by using other cheap and abundant non-precious metal catalysts. Fe-containing nitrogen-doped carbon catalysts (Fe-N-C) have been demonstrated as the potential alternative for the Pt-based catalysts for the last few years. However the poor understanding of the active sites of Fe-N-C catalysts prevents the development of highly active durable catalysts. Our recent studies[1] of the ORR on the Fe-N-C and N-C catalyst demonstrates that the ORR predominantly proceeds via the step wise reduction. Though the conventional Damjanovic model[2] (as shown in Scheme 1) concludes the direct 4-electron ORR, it actually overestimates the k 1 and underestimates the k 2 and k 3. Since the metal free catalysts are very active towards the reduction of O2 to H2O2, the role of the Fe on the reduction of H2O2 to H2O is studied and the estimated rate constants for the reduction of H2O2 to H2O will be used to estimate the real current for direct 4-electron ORR (I 1), 2-electron ORR to H2O2 (I 2) and 2-electron H2O2 reduction to H2O (I 3). 2. Methodology The precursor synthesis has been already discussed in the previous papers[3,4]. Briefly, the stoichiometric amount of pyromellitic acid dianhydride and 4,4’-oxydianiline was polymerized in the presence of tris(acetylacetonato) iron (III) (Fe(acac)3) yielding polyimides/Fe(acac)3 (the size of the polymer is controlled by maintaining low temperature during polymerization). The precursor was subjected to the multi-step pyrolysis reported earlier and the resulting catalyst is designated as Fe/PI. The Fe/PI-modified GC electrode with the loading density of 100 µg cm-2, carbon cloth and reversible hydrogen electrode was used as working, counter and reference electrodes, respectively. Both oxygen reduction reaction (ORR) and H2O2 reduction reaction was measured using rotating disk and rotating ring (Pt)-disk electrode voltammetry in 0.5 M H2SO4 solution. The H2O2 reduction rate constants (k 3) with potential were estimated using Koutecký‒Levich plot. From the ORR voltammograms, the value of I 1 , I2 and I 3 were determined by the following equations; I 2=0.5*{I r/N+ [(Ir/N)2(1+4k3/(Zω0.5)]0.5} (1) I 3=0.5*{-I r/N+ [(Ir/N)2(1+4k3/(Zω0.5)]0.5} (2) I 1=I d - [(Ir/N)2(1+4k3/(Zω0.5)]0.5 (3) where I d and I r represents disk and ring current of the oxygen reduction reaction, respectively, k 3 represents the rate constant of the H2O2 reduction reaction and ω refers the rotational speed of the ORR voltammogram. The value of the Z can be estimated from the kinematic viscosity (v) and diffusion coefficient (D) of H2O2 in 0.5 M H2SO4 (Z=0.62D 2/3 v -1/6) 3. Results and Discussion The H2O2-reduction steady-state voltammograms indicates that the Fe/PI catalyst is more active for both H2O2 oxidation and reduction indicated by the sharp intersection on the potential axis around 0.8 V vs. RHE. This simple method will be helpful separate the currents of many ORR voltammograms to describe the kinetics because this does not requires any parameters to be plotted against the rotation speed. The I 2 and I 3 values estimated using this method is significantly improved than the conventional Damjanovic model currents estimated form the rate constants (Figure 1). 4. Conclusion The newly developed methodology successfully separated I 1, I 2 and I 3 for ORR over Fe/N/C cathode catalysts. 5. Acknowledgements This work was financially supported by the New Energy and Industrial Technology Development Organization (NEDO), Japan. 6.

Iontophoresis on minoxidil sulphate-loaded chitosan nanoparticles accelerates drug release, decreasing their targeting effect to hair follicles

The experiments described in this paper tested the hypothesis whether iontophoresis applied on a chitosan nanoparticle formulation could combine the enhanced drug accumulation into the follicular casts obtained using iontophoresis and the sustained drug release, reducing dermal exposure, provided by nanoparticles. Results showed that even though iontophoresis presented comparable minoxidil targeting potential to hair follicles than passive delivery of chitosan-nanoparticles (4.1 ± 0.9 and 5.3 ± 1.0 µg cm-2, respectively), it was less effective on preventing dermal exposure, since chitosan-nanoparticles presented a drug permeation in the receptor solution of 15.3 ± 4.3 µg cm-2 after 6 h of iontophoresis, while drug amounts from passive nanoparticle delivery were not detected. Drug release experiments showed particles were not able to sustain the drug release under the influence of a potential gradient. In conclusion, the application of MXS-loaded chitosan nanoparticles remains the best way to target MXS to the hair follicles while preventing dermal exposure.

Nickel Release, ROS Generation and Toxicity of Ni and NiO Micro- and Nanoparticles.

Occupational exposure to airborne nickel is associated with an elevated risk for respiratory tract diseases including lung cancer. Therefore, the increased production of Ni-containing nanoparticles necessitates a thorough assessment of their physical, chemical, as well as toxicological properties. The aim of this study was to investigate and compare the characteristics of nickel metal (Ni) and nickel oxide (NiO) particles with a focus on Ni release, reactive oxygen species (ROS) generation, cellular uptake, cytotoxicity and genotoxicity. Four Ni-containing particles of both nano-size (Ni-n and NiO-n) and micron-size (Ni-m1 and Ni-m2) were tested. The released amount of Ni in solution was notably higher in artificial lysosomal fluid (e.g. 80–100 wt% for metallic Ni) than in cell medium after 24h (ca. 1–3 wt% for all particles). Each of the particles was taken up by the cells within 4 h and they remained in the cells to a high extent after 24 h post-incubation. Thus, the high dissolution in ALF appeared not to reflect the particle dissolution in the cells. Ni-m1 showed the most pronounced effect on cell viability after 48 h (alamar blue assay) whereas all particles showed increased cytotoxicity in the highest doses (20–40 μg cm2) when assessed by colony forming efficiency (CFE). Interestingly an increased CFE, suggesting higher proliferation, was observed for all particles in low doses (0.1 or 1 μg cm-2). Ni-m1 and NiO-n were the most potent in causing acellular ROS and DNA damage. However, no intracellular ROS was detected for any of the particles. Taken together, micron-sized Ni (Ni-m1) was more reactive and toxic compared to the nano-sized Ni. Furthermore, this study underlines that the low dose effect in terms of increased proliferation observed for all particles should be further investigated in future studies.