Dual-layer systems

To demonstrate unidirectional charge flow via electron mediation, Murray s group electrochemically polymerized complexes [Ru(bpy)2(vpy)2] " ", A, and [Ru(bpy)2(vpy)Cl]+, B, on Pt electrodes in CH3CN. (vpy is 4-vinylpyridine.) The order of deposition of the fllms is crucial of course since Eg f [Ru +z2+(a)] = +1.23 and Eg j. [Ru " " (B) ] = +.76 V vs SSCE and the inner film mediator (poly(A)) would not be expected to move electrons uphill. The results are summarized in Figure 2, where it is clear that both redox waves associated with the outer film couple (poly (B)) are missing in the dual layer system (Fig 2(b)). The (A + B) copolymerized single film electrode (Fig 2(c)) shows the electronic presence of both couples at the Pt/polymer interface. 

Dual-layer systems have the advantages of high sensitivity, long process lifetime, and a reduction in the hysteresis of latent image formation. The transport layer requires the displacement of either electrons or holes. Since most trans-... 

Fig. 6.3 presents results obtained with a dual-layer system [8, 9]. Here, the CG layer consisted of a dispersion of the triphenylamine triazo pigment AZO-3 (see Chart 6.1) in poly (vinyl butyral) in a 4 10 weight ratio, while the CT layer consisted of a mixture of bisphenol A polycarbonate and the triarylamine derivative MAPS (see Chart 6.1) in a 10 9 weight ratio. 

The dual-layer ASC system herein studied consisted of commercial state-of-the-art PGM and SCR catalysts the PGM catalyst was a Pt/Al203-based system, while an Fe-zeolite was used as the NH3-SCR catalyst component. The original ASC monolith was a dual-layer system with an SCR layer coated on top of a PGM one. For the present study, in addition to the dual-layer monolith, the SCR and PGM catalysts were supplied both in the form of precursor powders of the monolith washcoat and in the form of single washcoated monoliths (400 CPSI, wall thickness = 5 mils). 

In a similar way, electrochemistry may provide an atomic level control over the deposit, using electric potential (rather than temperature) to restrict deposition of elements. A surface electrochemical reaction limited in this manner is merely underpotential deposition (UPD see Sect. 4.3 for a detailed discussion). In ECALE, thin films of chemical compounds are formed, an atomic layer at a time, by using UPD, in a cycle thus, the formation of a binary compound involves the oxidative UPD of one element and the reductive UPD of another. The potential for the former should be negative of that used for the latter in order for the deposit to remain stable while the other component elements are being deposited. Practically, this sequential deposition is implemented by using a dual bath system or a flow cell, so as to alternately expose an electrode surface to different electrolytes. When conditions are well defined, the electrolytic layers are prone to grow two dimensionally rather than three dimensionally. ECALE requires the definition of precise experimental conditions, such as potentials, reactants, concentration, pH, charge-time, which are strictly dependent on the particular compound one wants to form, and the substrate as well. The problems with this technique are that the electrode is required to be rinsed after each UPD deposition, which may result in loss of potential control, deposit reproducibility problems, and waste of time and solution. Automated deposition systems have been developed as an attempt to overcome these problems. 

Heterogeneous tandem catalysis involving at least one of the components being supported has also been reported [178, 179]. For example, calcosilicate has recently been used as an effective carrier for simultaneous immobilisation of a dual-functional system based on a bis(imino)pyridine iron compound and a zirconocene to form a heterogeneous catalyst precursor. On activation with triethylaluminium, ethylene was converted to LLDPE the layered structure of the calcosilicate was used to account for the improved thermal stability and higher molecular weights of the LLDPE formed [179],... 

Finally, it is important to be aware of the fact that visualization systems with dual recognition such as the EnVision + Dual Link System do not discriminate between species, and thus are only suitable for multiple staining when using the sequential method. Visualization kits with amplification layers that are not well specified should be avoided since possible cross-reactivity cannot be predicted. 

Figure 5 Examples of (a) hole- and (b) electron-transporting materials for mono-and dual-layer photoconductive systems.

The parameters include the critical cracking energy G and the mode-I tensile toughness of the coating. For the dual layer and triple layer systems presented here, the parameters deduced from three experiments for each type of sample are presented in Tables 6 and 7. The strain values are measured to an accuracy of 0.02% following a prior calibration. The applied stress is known to be within 0.1%, from a force sensor and the distance between two cracks is the average of twenty or so values determined to an accuracy of one micron in the central part of the specimen. 

Fig. 6.3 Charge generation in a dual-layer photoreceptor system. The quantum yield of charge generation as a function of the wavelength of the incident light at...

Sun protection elements (aluminium and ETFE lamellae, or mobile textile membranes, cf. Fig. 6.6) can be integrated for further building-physics improvement in the clearance of dual-chamber systems with separate layers. In variants with a curved middle layer and decoupled volumes, and different pressures, the middle layer can assume the sun protection role. For this, the outer and middle foil layers display a print of inversely arranged patterns. The translucency of the cushions is controlled by adjusting the middle layer through pressure control of the two air-chambers. 

In comparison to conventional materials for building envelopes, the heat insulation of ETFE-foil cushions is only moderate. It could be improved by using a dual-chamber system with a third middle layer and separated layers at the anchoring profiles (c/ Fig. 6.5 positions 5 and 6). A three-layer ETFE-cushion with two separated chambers achieves a U-value of approximately 2.0 W/m K. Hence, with separated or more layers the U-value can be improved. 

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