Guided Self-Assembly

Recently, LB techniques have also been used to fabricate ordered 2-D structures of metal nanoparticles, with several approaches having been identified using particles in the size range of 3 to 5 nm [61-67]. For example. Heath et al. reported [62] that success in the organization of alkanethiolate-protected nanoparticles vfith LB techniques depends characteristically on the ratio of ligand length and the surface pressure. 

Self-assembled structures are quite suitable for studying the electronic behavior of ordered monomolecular films, and have contributed considerably to the provision of a better understanding of the quantum size nature of metal nanoparticles. On the other hand, it is quite clear that metal particles in future nanoelectronic devices should be in structures in which the QDs should not be self-arranged, but rather are 

Notably, gold is by no means the only material that can be incorporated into block copolymer micelles. Indeed, other metals such as palladium, silver, and cobalt have been successfully applied, and even nanoparticles of CdS and PbS have been 

Other diblock copolymers and metal compounds such as H2PtCl6, Pd(Ac)2, TiCU or FeCls have been used successfully in this process. In this case, the less-noble metals Ti and Fe are deposited as oxides following plasma treatment. 

The use of so-called S-layers is a combination of self-organization and spatial patterning [88]. S-layers consist of 2-D protein crystals that are formed naturally as the outermost cell surface layer (S-layer) of prokaryotic organisms. The subunits can recrystallize into nanoporous monolayers in suspension, at liquid-surface interfaces, on lipid films, or on solid substrates. The S-layers of Bacillus sphaericus CCM 2177 have been used to generate ordered arrays of 4—5 nm gold particles, with a 13.1 nm repeat distance, from AuCr ions [89]. The spontaneous self-assembly of 5 nm AuN Ps was shown to occur at the S-layer of Deinococcus radiodurans, to produce micrometersized ordered domains [90]. Arrays of 1.9 nm platinum particles were achieved from Pt salts in the S-layer of Sporosarcina ureae [90] these were of square symmetry and had a lattice constant of 13.2 nm. 

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D self-assembly of metal nanoparticles requires special conditions since 3D growth of any kind of material is preferred. Two principal strategies to generate 2D organizations of metal nanoparticles have been developed during the last 1-2 decades true self-assembly, guided self-assembly and aimed structures. 

However, with the expanding spectrum of complexity and functionality of new polymer-based hybrid materials, no general routes and recipes for processing polymer-assisted materials should be expected. The effort to establish new approaches for guiding self-assembly of complex functional materials is the key to further technological application. 

Figure 12. Dual-Patterning or guided self-assembly approaches to SOMA disks. The array ordering length scale of 1-10 pm is replicated around the circumference of a disk by topographic or chemical guide patterns.

A guided self-assembly of gold nanoparticles succeeded also on patterned GaAs surfaces. Stmctured Be-doped GaAs surfaces were first decorated with a monolayer of xylyl dithiol molecules. A uniform monolayer of dodecanethiol stabilized 5 nm Au particles, generated by spreading a hexane solntion... 

Once such method of controlling the surface undulations is through stress-guided self-assembly. Stress-driven self-assembly is a promising route to either induce ripples in a desired pattern [12] or guide undulation growth such that a specific corrugation is produced [4]. 

G. A. Buxton and N. Clarke, Stress-guided self-assembly in Dutcher films. Phys. Rev. E 73, 041801 (2006). 

The generation of 2-D and 1-D structures of metal nanoparticles can be achieved using very different techniques of (i) self assembly, (ii) guided self-assembly and (iii) aimed structures. Examples of these three principal routes are presented and discussed in the following subsections. 

This work will also have implications for future experimental work. Surface-guided self-assembly of proteins is growing in interest the observed effects on... 

Peptide amphiphUes (PAs) are well known to form functirmal supramolecular materials [68]. PAs consists of (i) a short hydrophobic domain, often an alkyl chain, linked to (ii) an oligopeptide that induces and guides self-assembly by the formatiOTi of P-sheets, and (iii) an oligopeptide containing a bioactive domain [69]. In water, these molecules assemble into high-aspect-ratio nanofibers, which entangle and... 

Unguided self-assembly has little control on domain orientation, rendering the fabrication of ordered nanostructure difficult. To overcome this problem, templates can be utihzed to guide self-assembly and to obtain better controls of regularity or orders of resultant nanostructures. The template can be either smaller or larger than the final self-assembly. For patterning purposes, the template (i.e., substrate with guidance) is... 

S. T. Liu, R. Maoz, G. Schmid, and). Sagiv, Template guided self-assembly of [Auss] clusters on nanolithographically defined monolayer patterns. Nano Lett, 2,1055-1060 (2002). 

C) Block copolymer thin film. (D) Guided self-assembly in registration with the underlying chemical pattern. (Reproduced with permission from R. Ruiz, H. King, F.A. Detcheverry et al., Density multiplication and improved lithography by directed block copolymer assembly, Science, 321, 936-939, 2008. 2008 American Association for the Advancement of Science.)... 

Yang, X.M., Peters, R.D. et al. (2000) Guided self-assembly of symmetric diblock copolymer films on chemically nanopatterned substrates. Macromolecules, 33(26), 9575-9582. 

Recently, researchers paid more attention to the guided self-assembly of block copolymer thin films on a patterned surface. The patterned surface means the surface of a constrained situation is chemically or physically modified to form a pattern with specific property and size. A series of exquisite structures are found in the microphase separation of block copolymer under the patterned surface. In the theoretic work of Wu and Dzenis [43], they designed two kinds of patterned surface to direct the block copolymer self-assembly (Fig. 15.7). The self-assembled structures are found strongly influenced by the commensurability of polymer bulk period and pattern period. With mismatched patterns on two surfaces, both MC simulation [44] and SCFT researching [45] predicted the titled lamellae and perforated lamellae structures for symmetric diblock copolymers. Petrus et al. carried out a detailed investigation on the microphase separation of symmetric and asymmetric diblock copolymers confined between two planar surfaces using DPD simulation [46,47]. It is found that various nonbulk nanostructures can be fabricated by the nanopatterns on the surfaces. 

Wu X-F, Dzenis YA. Guided self-assembly of diblock copolymer thin films on chemically patterned substrates J Chem Phys 2006 125 174707. 

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