Electrodes sandwich

Figure 9. Schematic diagrams of (A) parallel-band electrode,141 142 (B) sandwiched electrode,139 140 and (C) rotating-disk voltammetry60 143 methods for making in situ electron transport measurements on polymer films.

Figure 11. Cyclic votammetry (top) and in situ electronic conductivity from rotating-disk voltammetry [ , Fig. 9(C)] and sandwich electrode voltammetry [ , Fig. 9(B)] for poly(3-methylthiophene) in acetonitrile containing 0.1 M BU4CIO4.60 (Reprinted from J. Ochmanska and P. G. Pickup, In situ conductivity of poly-(3-methylthiophene) and (3-methylthiophene)x,-[Ru(2,2 -bipyridine)2 (3- pyrrol-l-ylmethyl pyridine)2]2+ copolymers, J. Electroanal. Chem. 297, 211-224, 1991, with kind permission from Elsevier Sciences S.A.)...

At a Pt-[0s(bipy)2(4-vinylpyridine)2](C10J -Au sandwich electrode (see Sect. 5.2.1) plateau-like voltammograms are observed in the dry, solvent-free state when... 

Flood R, Enright B, Allen M, Barry S, Dalton A, Doyle H, Tynan D, Eitzmaurice D (1995) Determination of band edge energies for transparent nanocrystaUine TiOa-CdS sandwich electrodes prepared by electrodeposition. Sol Energy Mater Sol Cells 39 83-98... 

In the present case, the electron hopping chemistry in the polymeric porphyrins is an especially rich topic because we can manipulate the axial coordination of the porphyrin, to learn how electron self exchange rates respond to axial coordination, and because we can compare the self exchange rates of the different redox couples of a given metallotetraphenylporphyrin polymer. To measure these chemical effects, and avoid potentially competing kinetic phenomena associated with mobilities of the electroneutrality-required counterions in the polymers, we chose a steady state measurement technique based on the sandwich electrode microstructure (19). 

Figure 3 illustrates the construction of a sandwich electrode, which is a delicately assembled yet powerful experimental tool. The porosity of the Au electrode evaporated... 

Fig. 4. Voltammograms in 0.1M Eti+NClOi+ZCH CNj rT = 1.2X1 O 8 mol/cm. Curve As Cyclic voltammetry of Pt/poly-Co -NI TPP at 20 mv/s = 200pA/cm. Curve B Four-electrode voltammetry of Pt/poly-Co( -NHi(,)TPP/Au sandwich electrode with E u = 0.0 Vj Ep scanned negatively at 5 mV/s = 400pA/cm. Curve Ci Surface profilometry of a poly-Co(o-NH2)TPP film on Sn02/glassj Tt = 7.6X10 9 mol/cm. (Reproduced from Ref. 6. Copyright 1987 American Chemical Society.)...

Figure 4. Plot of poly-I conductivity as a function of potential. A series of potential step of 20mV were employed on a sandwich electrode. Each potential was held until Faradaic current ceased, where upon a DC conductivity measurement, AE = 60MV, was taken, before proceding with the next potential. The results are for 0.05 M II electrolyte in acetonitrile vs. Ag+/Ag.

Figure 14.2.4 More complex modified electrode structures based on electroactive polymers, (a) Sandwich electrode (b) array electrode (c) microelectrode d, e) bilayer electrodes if) ion-gate electrode. [Reprinted with permission from C. E. D. Chidsey and R. W. Murray, Science, 231, 25 (1986), copyright 1986, American Association for the Advancement of Science.]...

Figure 24. Temperature dependence and aging effects in KF ice grown without shunt. Notice invariance o/ slope (apparent activation energy). (One sandwich electrode, prepared with 1 X 10 M HF. Sample stored one day at —20°C. before measurements)...

Figure 25, Temperature dependence and reproducibility of conductivity of HCl ice. Upper curve One sandwich electrode (IX 10 M HF) sample stored one day at —20 C. before measurements. Measurements extended over three days. Lower curve One sandwich electrode (5 X I0" M HF) sample stored three days at —20°C, before measurements. Measurements extended over nine days...

Figure 26. Conductivity at —15°C. and highest value of the freezing potential as a function of concentration (melted ice, room temperature) for ice grown from dilute ammonium-fluoride solutions. Curve of HF ice for comparison (67). The ammonium-fluoride samples were prepared in pairs, with one sandwich electrode made from 5 X 10 M HF, and stored from two to 27 days at —20 C. before measurements. No effects of diffusion from sandwich electrodes into the samples were observed...

Electrical measurements of ice are diflBcult to interpret because of polarization effects, surface conductivity, injection of defects and/or impurity atoms from sandwich electrodes, diffusion effects, differential ion incorporation, and concentration gradients due to nonsteady state impurity distribution. Theories formulated for pure ice and for ice doped with HF (KF and CsF) in terms of ion states and valence defects, qualitatively account for experimental data, although the problem of the majority and minority carriers in doped ice, as a function of concentration and temperature, requires further examination. The measurements on ice prepared from ionic solutes other than HF, KF, and CsF are largely unexplained. An alternative approach that treats ice as a protonic semiconductor accounts for results obtained for both the before-named impurities as well as ammonia and ammonium fluoride. 

Figure 21. Log photocurrent response from a single crystal of PbNe using a sandwich electrode geometry.

FIGURE 1.97. Typical voltammetric responses observed for a 1 1 mixed-valent poly-[0s(bpy)2(vpy)2](C104) film in a two-electrode sandwich electrode configuration subjected to slow (---) and fast (---) potential sweeps, surface coverage, 1.3 X 10 molcm. Both the potential bias A and the intersite potential are shown in Fig. 1.97. The curve at fast sweep rates is well-described by Eqn. 450. (Adapted from Ref. 149.)... 

---