LbL deposition method

Besides ruthenium complexes, rhenium complexes were also used as the photosensitizers in photovoltaic cells. Bulk heterojunction photovoltaic cells fabricated from sublimable rhenium complexes exhibited a power conversion efficiency of 1.7%.75,76 The same rhenium complex moiety was incorporated into conjugated polymer chains such as polymer 16a c (Scheme 9). Fabrication of devices based on conjugated rhenium containing polymers 17a c and SPAN by the LbL deposition method was reported.77 The efficiencies of the devices are on the order of 10 4%. 

A final important motif for self-assembly of CPEs is by LbL deposition of polyelectrolyte multilayer films. The LbL multilayer film deposition method was first introduced by Decher [37,38], and since then it has been used to fabricate nanostructured films using a wide variety of synthetic and naturally occurring polyelectrolytes [39]. Deposition of LbL films involves a very simple sequence of alternately dipping a substrate into solutions that contain a cationic polyelectrolyte and an anionic polyelectrolyte. The sequential LbL deposition method leads to formation of polymer multilayer film structures. A single... 

Layer-by-layer (LBL) assembly technique has been proven as a well-established approach to build composites or function-specific multilayer assemblies. Mamedov et al. fabricated isotropic polymer/SWNT composites by LBL deposition method to preserve SWNT dispersion [98]. Zhang et al. prepared PVA/poly(vinyl pyrolidone)/SDS (sodium dodecyl sulfate)/SWNT composite films by LBL technique with good nanotube dispersion and load transfer from polymer matrix to the carbon nanotubes [99]. With the aid of a surfactant, super-tough PVA/SWNT fibers were also fabricated by LBL method with SWNT loading as high as 60 wt% [100]. 

In another work using static LbL deposition method (Li et al. 2008a), it was observed that membranes with rougher surfaces could be obtained by increasing the number of deposited layers (refer Figure 4.13). The rougher membrane surfaces found in this work were one of the weaknesses that had to be overcome to avoid the fouling tendency of the membrane. 

Selection of polyelectrolyte materials plays a key role in producing membranes with good performance stability. For instance, CA NF membranes were used as the support membranes during the static LbL deposition method in 2004 (Lajimi et al. 2004). The... 

Sonochemical methods have been used by the Cordoba de Torresi group to prepare Ni(OH)2, Co(OH)2 and mixed Ni/Co hydroxide NPs [33, 34]. For the sonochemical synthesis, the appropriate metal nitrate was mixed with ammonium hydroxide solutions and then sonochemically irradiated for various times. This produced about 5-nm diameter metal-hydroxide NPs that were then immobilized at ITO surfaces using a LbL approach with poly(allylamine) hydrochloride (PAH). In one study, the electrochromic behavior of the LbL deposits was compared with that of bulk deposits... 

Towards fabrication of SWNT-based molecular electronic devices, two methods have been used to assemble the 03-SWNTs on functionalized SAMs of OPEs, as shown in Figure 5.10. The first, termed chemical assembly , is based on a condensation reaction between the carboxylic acid functionalities of O3-SWNTs and the amine functionalities of SAMs to form amides. The results show that O3 -SWNTs coat the amino-terminated SAM with a high degree of surface coverage. The second method is based on physical adsorption via layer-by-layer (LBL) deposition with bridging of metal cations, i.e., Fe3+ on carboxylate terminated SAMs or Cu2+ on thiol-terminated SAMs. The oxidatively shortened 03 -SWNTs are shown to be perpendicular to the surface with random adsorption of longer tubes. The patterned nanotube assemblies may be useful in hybridized electronic devices, where device functions can be modified by the orientation and stacking of SWNTs, and the properties of the SAM. 

Apart from the formation of ultrathin surface-attached PEL-PEL complexes it is very interesting whether the PEL brushes can be also used for the formation of PEL multilayer assemblies. The so-called layer-by-layer (LBL) technique is a simple and powerful method to form well-defined multilayered structures [80]. For the formation of such multilayer assemblies the brushes are dipped alternately into polyelectrolyte solutions, one consisting of a positively charged polyelectrolyte, the other of a negatively charged polyelectrolyte. It is usually assumed that in this LBL deposition process the driving force for each monolayer formation is charge overcompensation [81, 82]. The stability of the multilayered system formed by LBL process in different environments is one of the limitations of this process. Since the attachment of the first layer depends solely on the interaction of... 

Other methods Layer-by-layer (LBL) deposition and solid reaction are used to prepare graphene-MNPs sometimes. Zhu and Dong et al. reported a LBL self-assembly method for constructing a graphene/platinum NPs three-dimensional hybrids base on the... 

LbL deposition is a thin film fabrication technique in which films are formed by depositing alternating layers of oppositely charged materials. Wash steps are added between the different depositing layers. The first implementation of this LbL deposition technique was mentioned in a research by Kirkl and Iler. They carried it out in 1966 using microparticles. The method was later revitalized by Decher by the discovery of its applicability to a wide range of polyelectrolytes."... 

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