| 1. |
- Qvarford, M., et al.
(författare)
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Polarisation-dependent X-ray absorption in high- and low-Tc Bi2Sr2Can-1CunO4+2n superconductors
- 1993
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Ingår i: Physica C: Superconductivity and its Applications. - : Elsevier BV. - 0921-4534. ; 214:1-2, s. 119-126
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Tidskriftsartikel (refereegranskat)abstract
- Taking advantage of the linear polarisation of synchrotron radiation, the polarisation dependence of the O K and Cu L3 X-ray absorption edges has been compared for in situ cleaved Bi2Sr2CaCu2O8 and Bi2Sr2CuO6 single crystals. The X-ray absorption spectra were measured by means of total electron yield detection. The spectra show for both crystals that the lowest unoccupied Cu 3d and O 2p orbitals are dominantly oriented parallel to the a-b plane, but also the presence of a small amount of unoccupied orbitals oriented perpendicular to the a-b plane can be deduced from both the O K and Cu L3 absorption spectra. A shift of the order of 0.5 eV between absorption into the in-plane and the out-of-plane Cu 3d orbitals was measured for the Bi2Sr2CaCu2O8 crystal, but no such shift was found for the Bi2Sr2CuO6 crystal.
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| 2. |
- ROGELET, T, et al.
(författare)
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ELECTRONIC-STRUCTURE OF NIO(1 0 0) WITH ADSORBED NA
- 1993
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Ingår i: Solid State Communications. - 0038-1098 .- 1879-2766. ; 85:7, s. 657-660
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Tidskriftsartikel (refereegranskat)abstract
- Adsorption of Na on single crystals of NiO(1 0 0) at room temperature has been investigated via angle-resolved photoemission spectroscopy and measurements of work-function changes. The drastic changes in the valence band spectra upon Na deposition are assigned to a chemical reaction between Na and O where metallic Ni is left as by-product. At short deposition times, Na mainly acts as an inert electron donor, and at these coverages no dispersion is observed in the angle-resolved photoemission spectra which indicates that the electronic states are localized. The measurements were performed both for a polished and an in-situ cleaved NiO crystal.
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| 3. |
- SAINI, S, et al.
(författare)
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BIOSENSORS IN ORGANIC PHASES
- 1991
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Ingår i: Biochemical Society Transactions. - : Portland Press. - 0300-5127 .- 1470-8752. ; 19:1, s. 28-31
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Tidskriftsartikel (refereegranskat)abstract
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| 4. |
- SAINI, S, et al.
(författare)
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ORGANIC-PHASE ENZYME ELECTRODES
- 1991
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Ingår i: Analytica Chimica Acta. - : Elsevier Science B.V., Amsterdam.. - 0003-2670 .- 1873-4324. ; 249:1
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Tidskriftsartikel (refereegranskat)abstract
- Organic phase enzyme electrodes (OPEEs) offer new possibilities both for the design of biosensors for use in organic solvents and in the construction of devices incorporating an organic phase for use with aqueous samples. The advantages that accrue from performing biocatalytic and electrochemical reactions in non-aqueous systems are discussed in relation to possible applications in medicine. pharmaceuticals, petrochemicals, the food industry, environmental monitoring and defence. This critical but speculative review considers the detailed implications of operating enzyme electrodes in organic solvents and briefly examines the broader issues of optical, calorimetric and piezoelectric transduction coupled with both catalytic and affinity systems, such as nucleic acid probes and antibodies.
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| 5. |
- SCHUBERT, F, et al.
(författare)
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MEDIATED AMPEROMETRIC ENZYME ELECTRODE INCORPORATING PEROXIDASE FOR THE DETERMINATION OF HYDROGEN-PEROXIDE IN ORGANIC-SOLVENTS
- 1991
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Ingår i: Analytica Chimica Acta. - : Elsevier Science B.V., Amsterdam.. - 0003-2670 .- 1873-4324. ; 245:2, s. 133-138
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Tidskriftsartikel (refereegranskat)abstract
- An amperometric enzyme electrode incorporating horseradish peroxidase is described for the determination of hydrogen peroxide in organic solvents. The enzyme was co-adsorbed with an electron mediator, potassium hexacyanoferrate(II), on the surface of a graphite foil electrode, making reagentless measurement possible. The electrochemical reduction of the enzymatically oxidized mediator was utilized as the analytical signal. Studies in different solvent systems revealed that the electrode could be operated in dioxane, chloroform and chlorobenzene, the last two providing approximately double the sensitivity of the former. The presence of a small amount of aqueous buffer was essential for sensor activity. During 2 weeks of intermittent use, the sensitivity of the electrode decreased to 40% of its initial value. At least 50 assays could be performed with a single sensor.
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| 6. |
- SCHUBERT, F, et al.
(författare)
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ORGANIC-PHASE ENZYME ELECTRODES FOR THE DETERMINATION OF HYDROGEN-PEROXIDE AND PHENOL
- 1992
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Ingår i: Sensors and actuators. B, Chemical. - : Elsevier Science B.V., Amsterdam.. - 0925-4005 .- 1873-3077. ; 7:03-jan, s. 408-411
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Tidskriftsartikel (refereegranskat)abstract
- An amperometric horseradish peroxidase electrode is described for the determination of hydrogen peroxide in organic solvents. The enzyme was co-adsorbed with an electron mediator, hexacyanoferrate(II), to the surface of a graphite foil electrode making reagentless measurement possible. The electrochemical reduction of the enzymatically oxidized mediator was utilized as the analytical signal. The electrode can be operated in dioxane, chloroform and chlorobenzene, the presence of a small quantity of aqueous buffer being essential for activity. On this basis a small, probe-type sensor has been assembled the response of which is linearly related to hydrogen peroxide concentration between 0.05 and 1 mM. A tyrosinase sensor has been constructed by combining a Clark-type oxygen electrode with a membrane bearing adsorbed enzyme. The sensor is capable of measuring between 0.1 and 5 mM phenol in chloroform saturated with aqueous buffer.
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