Terje Skotheim
Stony Brook University
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Featured researches published by Terje Skotheim.
Solid State Ionics | 1993
L. Boguslavsky; P.D. Hale; Lin Geng; Terje Skotheim; Hong-Sui Lee
Abstract Polymers containing covalently attached redox molecules can be highly effective electron transfer mediators for flavin adenine dinucleotide redox centers of many oxidases. Highly flexible siloxane and ethylene oxide polymers containing covalently attached ferrocene molecules are shown to be capable of mediating electron transfer between enzymes and an electrode. The construction and response of bienzyme cholesterol biosensor, acetylcholine and glucose biosensor are described and discussed. Our data showed that the flexibility, hydrophilicity of the polymer, the density of redox centers in the polymer matrices and the self-exchange reaction rate of the redox molecules control the efficiency of the electron transfer mediation.
Biosensors and Bioelectronics | 1993
Elena Domínguez; H.L. Lan; Yoshiyuki Okamoto; P.D. Hale; Terje Skotheim; Lo Gorton; B. Hahn-Hägerdal
Amperometric biosensors for ethanol were constructed by immobilizing yeast alcohol dehydrogenase (ADH) on carbon paste (graphite powder: paraffin oil) chemically modified with a polymer to which a necessary mediator for electrocatalytic NADH oxidation had been covalently attached. Three different approaches were tested: adsorption of ADH on the electrode surface and adding NAD+ to the contacting buffer; having both ADH and NAD+ mixed into the paste; and co-immobilizing ADH and NAD+ in the paste by adding polyethylenimine to the reaction mixture. The last approach resulted in the highest and fastest response. When inserted into a flow injection system, the biosensor responded linearly to ethanol between 2 μm and 3 mm. The biosensor operates at +100 mV vs. Ag/AgCl.
Journal of The Electrochemical Society | 1982
Jiri Prejza; Ingemar Lundström; Terje Skotheim
The formation of polypyrrole on some metallic films (Pt,Pd,Ti,Au,Ni,Cr,In,Al,Fe,Ag, etc.) has been studied under potentiostatic and galvanostatic conditions. The role of pyrrole and the fluoborate ion in the polymerization process has been investigated at room temperature. From the analysis of galvanostatic current-potential curves it has been possible to distinguish the particular processes: initiator formation, polymerization, polymer degradation, and gas evolution. The polymerization in acetonitrile is indirectly initiated with a reaction order of /approximately equals/1 with respect to the BF/sub 4//sup -/ concentration. There are at least two different kinds of polypyrrole, depending on polymerization potential, that differ structurally. The formation of polymers on nonpolarized electrodes has also been observed. This work is pertinent to solar cells. 23 refs.
Applied Physics Letters | 1991
Junji Kido; Katsutoshi Nagai; Yoshiyuki Okamoto; Terje Skotheim
Electroluminescent devices were fabricated using poly(methylphenylsilane) and 8‐hydroxyquinoline aluminum complex as the hole transport layer and the emitting layer, respectively. The cell structure of glass substrate/indium‐tin‐oxide/hole transport layer/emitting layer/Mg/Ag was employed. Smooth hole injection from the electrode through the polymer layer and concomitant efficient electroluminescence from the emitting layer were observed. Green emission with a luminance of over 1000 cd/m2 was achieved at a current density of 100 mA/cm2.
Journal of The Electrochemical Society | 1994
H. S. Lee; X. Q. Yang; James McBreen; Z. S. Xu; Terje Skotheim; Yoshiyuki Okamoto
A new type of plasticizer, a modified carbonate (MC3) made by attaching three ethylene oxide units to the 4-position of ethylene carbonate, has been synthesized. The ionic conductivity of a polymer electrolyte using this type of plasticizer in a poly(ethylene oxide) (PEO)-LiCF[sub 3]SO[sub 3] complex has been studied. Adding 50% of this plasticizer by weight of PEO to the PEO-LiCF[sub 3]SO[sub 3] complex, yielded an ionic conductivity of 5 [times] 10[sup [minus]5] S/cm at 25 C, which is two orders of magnitude higher than that found for a PEO-LiCF[sub 3]SO[sub 3] electrolyte without a plasticizer, and one order of magnitude higher than that found when using propylene carbonate (PC) as a plasticizer. The temperature dependence of the conductivity and thermal analysis results indicate that this new plasticizer increases the ionic conductivity throughout the entire complex system, whereas conventional plasticizers, like PC, simply create a high conductivity pathway through the plasticizer itself. The new plasticizer also enhances the ion pair dissociation which in turn improves the ionic conductivity.
Journal of Applied Physics | 1996
R. A. Campos; I. P. Kovalev; Y. Guo; N. Wakili; Terje Skotheim
We investigate the performance of organic electroluminescence devices employing a fluorinated diketone complex of europium (ETP) as the emitter material. The architecture of our devices isolates the emitter from the injecting contacts by sandwiching a thin layer of ETP between a hole‐transporting diamine layer and an electron‐transporting aluminum complex layer. The organic layers are deposited in high vacuum with rate‐controlled sources onto glass substrates coated with indium–tin–oxide, and the cell is completed by evaporation of aluminum or calcium–aluminum cathodes. By varying the thickness of ETP layer in increments of 6 A we demonstrate spatial confinement of the electroluminescence emission zone and optimal performance for an ETP thickness of 50 A. Both the optical and electrical characteristics of these cells follow steep power‐law relationships with voltage, which are indicative of trap‐modified, space‐charge‐limited conduction. With aluminum cathodes we routinely achieve luminances up to 10 cd/m...
Biosensors and Bioelectronics | 1993
Björn Persson; H.L. Lan; Lo Gorton; Yoshiyuki Okamoto; P.D. Hale; L. Boguslavsky; Terje Skotheim
Abstract Amperometric biosensors based on redox polymer-mediated electron transfer from NADH to carbon paste electrodes, regenerating the NAD + needed for the dehydrogenase-catalysed reaction, are described. These sensors, operating around 0 mV vs SCE, can drive an unfavourable equilibrium of a dehydrogenase-catalysed reaction to the product side, and are reagentless in that NAD + need not be added to the analyte solution. By covering the sensor with an additional polymer, protection of the electrode surface, inclusion of water soluble components, exclusion of interferents and a diffusion controlled linear response current can be obtained.
Journal of The Electrochemical Society | 1982
Terje Skotheim; L. ‐G. Petersson; Olle Inganäs; Ingemar Lundström
Highly stable photoanodes based on single crystal n-Si protected with a thin coating of Pt and electrochemically grown polypyrrole films have been studied. A power conversion efficiency of 5.5% under illumination of 55 mW/cm/sup 2/ tungsten-halogen light is reported with an iodide/triiodide electrolyte. The cells exhibit long-term stability over a time period of weeks. The operating characteristics of the junctions yield high fill factors and rapid electron transfer kinetics at the interface. Values of the junction quality factor as low as 1.1 have been achieved showing almost ideal Schottky junction behavior. The open-circuit voltage as a function of the redox potential of the electrolyte shows substantial Fermi level pinning at the interface. The physical structure of the junctions has been studied with AES sputter profiling techniques. The main factor limiting the power conversion efficiency of the present devices is low short-circuit photocurrent due to light absorption in the concentrated iodide/triiodide electrolyte. 11 refs.
Journal of Applied Physics | 1983
Olle Inganäs; Terje Skotheim; Ingemar Lundström
Junctions between polypyrrole, a conducting polymer formed by electrooxidation, and n‐type semiconductors have been studied. Cadmium sulphide and titanium dioxide were chosen as substrates as a complement to earlier studies on silicon. The junctions behave as Schottky barriers on these semiconductors. The series resistance of the polypyrrole film is large and was taken into account in the evaluation of the data. The barrier heights of the junctions are compared with those found with ordinary metals. It is deduced that the work function of polypyrrole must be close to 5 eV.
Biosensors and Bioelectronics | 1995
L. Boguslavsky; Lin Geng; I.P. Kovalev; S.K. Sahni; Z. Xu; Terje Skotheim; V. Laurinavicius; Björn Persson; Lo Gorton
Amperometric glucose sensors were constructed based on solid graphite electrodes, surface-modified with NAD+ dependent glucose dehydrogenase (GDH), Toluidine Blue O (TBO), and protective ionic polymers. The electrocatalytic oxidation of NADH was evaluated from cyclic voltammetry with TBO dissolved, adsorbed, and electrostatically or covalently bound to polymers. The NADH and glucose sensors constructed were investigated and operated at 0 mV vs. Ag/AgCl using single potential step chronoamperometry. The operational stability of the glucose sensors was limited by leakage of NAD+. A glucose sensitivity much higher than carbon paste electrode was found. A sensitivity as high as 25 microA cm-2 mM-1 was achieved.