Curves illuminated

Figure 10.30. (a) Action spectra of perylene XXa in a bilayer photoreceptor device, (upper curve) illumination through the CTL, (lower curve) illumination through the semi-transparent aluminium substrate (b) absorption spectrum of an evaporated film of XXa ( 1700 A) (Reproduced from ref 247, Copyright 1988, North-Holland). 

Fig. 2. Curves 1, 2, and 3 show the spectral radiance factor for equivalent coatings of separate toluenesulfonamide—melamine—formaldehyde Day-Glo pigments containing 0.5% of a dye, either Alberta Yellow, Rhodamine F5G, or Rhodamine B Extra. Curve 4 is for a bright nonfluorescent red-orange printing ink. The illuminant was Source C. A magnesium oxide-coated block was used as a comparison white.

An illuminating example is the effect of Ostwald ripening on pore size distribution in a sintered body, resulting from vacancy transfer from the smaller to the larger pores, where the decrease in the number and die increase in average diameter of the pores can be clearly seen. The disnibutioii curve for... 

Figure 15-34. t/V curves of Al/PVK-MDMO-PPV-PCBM/1TO photocells. The concentration of the conventional polymer PVK in the blend is denoted in the ligurc. Tlie devices were illuminated through the ITO side by 41) iiiWA.nr at 4Kb inn. 

The indirect methods discussed thus far have dealt with measurement of color only as it can be correlated with physical characteristics of materials and the effect of these materials on radiant energy. As has been pointed out, the reflectance spectro-photometric curve describes a property of the material. A change in the reflectance spectrophotometric properties may not always result in a change in visual color. The reason is that color of the object is not an unchangeable characteristic of the object itself, dependent only upon these reflectance properties, but is also dependent upon the quality of the illuminating light and the sensitivity of the observer s eye. Thus the measurement and description of visual color are psychophysical problems... 

Objective Evaluation of Color. In recent years a method has been devised and internationally adopted (International Commission on Illumination, I.C.I.) that makes possible objective specification of color in terms of equivalent stimuli. It provides a common language for description of the color of an object illuminated by a standard illuminant and viewed by a standard observer (H). Reflectance spectro-photometric curves, such as those described above, provide the necessary data. The results are expressed in one of two systems the tristimulus system in which the equivalent stimulus is a mixture of three standard primaries, or the heterogeneous-homogeneous system in which the equivalent stimulus is a mixture of light from a standard heterogeneous illuminant and a pure spectrum color (dominant wave-length-purity system). These systems provide a means of expressing the objective time-constant spectrophotometric results in numerical form, more suitable for tabulation and correlation studies. In the application to food work, the necessary experimental data have been obtained with spectrophotometers or certain photoelectric colorimeters. 

ZnO instead of T1O2 because ZnO provides a 220 times higher mobility for photoinjected electrons, which would allow reduction of the exciting laser intensity. The slow PMC decay of TiOrbased nanostructured sensitization solar cells (the Ru complex as sensitizer), which cannot be matched by a single exponential curve and is influenced by a bias illumination, is strongly affected by the concentration of iodide in the electrolyte (Fig. 38). On the basis of PMC transients and their dependence on the iodide concentration, a kinetic mechanism for the reaction of photoinjected electrons could be elaborated.40... 

Figure 41. PMC potential curves for a ZnO single crystal measured in contact with propylene carbonate (0.1 M TRAP) containing 10 mM ferrocene (curve 1), and with increasing concentrations (5,10, and 20%) of water (curves 2-4). Illumination with He-Cd U V laser. 5 mW.

When Munsell devised his color space, he did so on the basis of minimum observable color perception steps. But the problem with the Munsell System was one of reproducibility, which the CIE Standard Observer cured. In formulating a color match, one wants to be able to predict the correct concentration of colorants required, whose scattering and absorption properties are known, i.e.- the lightness, so as to match the sample submitted, starting with their spectrophotometric curves. In practice, this is not so simple, since two colors must have identical spectrophotometric curves to be exactly equal. It turns out that the human eye will identify the two colors to be equal if their spectrophotometric reflectances are reasonably close. Two colors may appear to be equal under Daylight illumination, but quite different under incandescent lamp illumination. These colors are known zus "metamers" and the phenomenon "metamerism". 

The curve OAE in Fig. 17, calculated according to Eq. (50), shows the course of the rise in the radical concentration following the commencement of illumination when the initial radical concentration is zero, i.e. o = 0. Observation of the rate of polymerization as a function of the time during the interval preceding the steady state (i.e., for t < 2ts) would provide information suitable for the evaluation of r. ... 

The radical decay according to this equation is depicted by curve ABF in Fig. 17. Observation of the decay in the polymerization rate immediately following cessation of illumination offers an alternative method for determining r, for it follows from Eq. (53) that the slope of the ratio Rp)s/Rp plotted against t should equal 1/r,. 

Very little can be concluded form the experimental results with respwt to theoretical current-potential characteristics in the dark and under illumination derived in the previous chapter. Since in none of these cases a complete i-U-curve was pubhshed or... 

Fig. 15. Anion chromatograms of X-irradiated solutions of 0.1 M alcohol and 0.015 M COj (upper curves) and of illuminated 2 10 M ZnS sols containing 1 M alcohol and 0.015 M COj (lower curve). The latter also contained C10 anions from the preparation of the ZnS sol...

FIG. 14 On-off photocurrent responses (a) associated with the reaction in Eq. (41) at Ao0 = —0.225 V. In this figure, positive currents correspond to the transfer of a negative charge from water to DCE. The potential dependence of the photocurrent (b) was obtained under chopped illumination and lock-in detection. The maximum in the photocurrent-potential curve contrasts with the small changes in the dark current shown in (c). These responses are developed within the polarizable window described in (d). (From Ref. 49. Reproduced by permission of The Royal Society of Chemistry.)... 

Despite the potential impact of novel photosynthetic routes based on these developments, the most ambitious application remains in the conversion of solar energy into electricity. Dvorak et al. showed that photocurrent as well as photopotential response can be developed across liquid-liquid junctions during photoinduced ET reactions [157,158]. The first analysis of the output power of a porphyrin-sensitized water-DCE interface has been recently reported [87]. Characteristic photocurrent-photovoltage curves for this junction connected in series to an external load are displayed in Fig. 22. It should be mentioned that negligible photoresponses are observed when only the platinum counterelectrodes are illuminated. Considering irradiation AM 1, solar energy conversions from 0.01 to 0.1% have been estimated, with fill factors around 0.4. The low conversion... 

The photocurrent density (/ph) is proportional to the light intensity, but almost independent of the electrode potential, provided that the band bending is sufficiently large to prevent recombination. At potentials close to the flatband potential, the photocurrent density again drops to zero. A typical current density-voltage characteristics of an n-semiconductor electrode in the dark and upon illumination is shown in Fig. 5.61. If the electrode reactions are slow, and/or if the e /h+ recombination via impurities or surface states takes place, more complicated curves for /light result. 

To examine the mechanism of C02 reduction, it would be useful to detect intermediates. In this connection, FTIR techniques were applied to study an illuminated p-CdTe electrode during the photoassisted reduction of C02 in acetonitrile.58 This was the first report on IR spectroscopy applied to an illuminated electrode, and adsorbed COJ was detected (Fig. 9). The parallelism between the coverage of the intermediate and the photocurrent-potential curve was concluded to be consistent with the mechanism suggested by Amatore and Saveant53 for C02 reduction to CO [Eqs. (8) and (10)—(12)], when we take into account that COJ was adsorbed on the electrode. 

Photobioreactor [Tsygankov et al., 1994] withitt. sphaeroides RV immobilised on porous glass (125x50x0.5 mm3) with continuous medium flow (5 ml h 1 reactor 1) was illuminated from face (thickness 0.5 mm curve 1) or side position (thickness 50 mm curve 2) by halogen lamp [Tsygankov, Miyake, unpublished]. 

H2 production stage. H2 productions were determined between 10 and 3 5 min after onset of illumination. A light intensity curve of H2 production, B Energy conversion efficiency [10]. 

Figure 7.9 Current-potential characteristics for an n-type semiconductor in the dark and under illumination. The difference between the two curves is the photocurrent.

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