Abstract  Creatinine deiminase (CD) immobilized on Nafion®-nanostructured polyaniline (nsPANi) composite film prepared by the cyclic voltammetry (CV) is used as sensing material to measuring the concentration of creatinine in the aqueous solution. The effect of cycle number, scanning rate, temperature and the concentrations of hydrochloric acid and aniline for preparing composite sensing film on the sensitivity of amperometric creatinine biosensor are systematically investigated. The surface morphologies and the properties of as-prepared Nafion®-nsPANi composite film are analyzed by FESEM and FTIR, respectively. The maximum sensitivities for monitoring NH4 + based on Nafion®-nsPANi composite film are obtained to be 1647 and 376 μA mM−1 in the concentration ranges of 0.005–0.1 and 0.1–0.4 mM, respectively. By immobilizing CD enzyme on the Nafion®-nsPANi composite film the maximum sensitivity of amperometric creatinine biosensor is 1300 μA mM−1 cm−2. © 2018 Elsevier B.V.

Abstract  Membrane electrode assembly (MEA), a common arrangement used in direct methanol fuel cells, has been employed in a fed-batch mode microbial fuel cell (MFC), using mixed microbial population. This modification has been done for analyzing the prospect of obtaining increased power productivity. In addition, the electrodes have also been configured for the purpose of better current collection. Use of MEA as a replacement of the conventionally used 'separate membrane and electrode' arrangement has evidently resulted in reducing one of the limiting factors for higher power production in MFC, that is, its internal resistance. Open circuit potentials of more than 1 volt have been obtained for two MFC setups: (a) one consisting of an MEA and (b) the other having electrodes situated 2 cm apart from each other, but having better current collectors than the first setup. Power densities of 2212.57 mW m(-2) and 1098.29 mW m(-2) have been obtained at corresponding current densities of 5028.57 mA m(-2) and 3542.86 mA m(-2), respectively. The potential and power obtained for the MFC consisting of an MEA is quite significant compared to the other systems employed in this study.

Abstract  A HPPY-N212 composite membrane was prepared by the in situ polymerization of pyrrole on Nafion (R) 212 substrate membrane, followed by sulfuric acid treatment. The proton-acid doping structure endowed the HPPY-N212 membrane with enhanced conductivity as well as reduced vanadium ion permeability. These unique properties enabled vanadium redox flow battery (VRFB) fabricated with HPPY-N212 membrane to exhibit better coulombic, voltage and energy efficiency than that with N212 membrane under current densities of 60-150 mA cm(-2). However, a gradual decay of voltage and energy efficiency occurred during the charge-discharge cycles. The efficiency decay resulted from the irreversible damage to PPY doping structure caused by the over-oxidation during chargedischarge cycles. These investigations help better understand the structure-performance relationships and open up exciting opportunities for the development of new high-performance membranes for VRFBs.

Abstract  Zn(2+)-Dependent acid phosphatase (Zn(2+)-APase) was purified to homogeneity from bovine brain. The apparent molecular weight of the enzyme was estimated to be about 62000 by gel filtration and 31000 by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulfate. The enzyme exhibited an isoelectric point of approximately 4.8. The enzyme required Zn2+ ions for catalytic activity, but other cations had little or no effect. The maximum enzyme activity was obtained in the presence of about 5 mM of Zn2+ at pH 5.5 in 50 mM 2-(N-morpholino)ethanesulfonic acid-NaOH buffer. The enzyme significantly catalyzed the hydrolysis of p-nitrophenyl phosphate, phenyl phosphate, and phosphotyrosine. The enzyme was also active for myo-inositol-2-monophosphate and adenosine 2'-monophosphate of the other common phosphate esters tested, though significantly less active than for p-nitrophenyl phosphate. The optimum activity pH of the enzyme was around 5.5 with p-nitrophenyl phosphate and myo-inositol-2-monophosphate. The enzyme was resistant to fluoride ions. Two types of Zn(2+)-APases, a high molecular weight (molecular weight, M(r)., about 110,000) and a low molecular weight (M(r), about 62,000) type, were found to exist in various tissues of rat. Brain, lung, spleen, stomach, heart, skeletal muscle, and erythrocytes contained only the lower molecular weight type. On the other hand, liver and kidney contained mainly the higher molecular weight type, and the small intestine contained significant quantities of the both types.