Self-Assembly Method

The self-assembly method has attracted much attention because it can form monomolecular films on the surface of many matrixes, such as silicon oxide and titanium oxide. Considering potassium titanate whiskers as an example, the similar surface structure (Ti-O) between potassium titanate whiskers and titanium oxide means there is some comparability between them. 

Wang et al. surface modified potassium titanate whiskers (PTW) using the self-assembly of octadecyl trichloro silane (OTS). The process is as follows. Add 0.5 mL of OTS to the suspension liquid of whiskers (10 g) and heptane (200 ml) with stirring and continue stirring for 20 minutes after the whiskers are evenly dispersed in the solution. Then the mixture is filtered and washed several times to remove dissociative OTS and dried in a vacuum. 

After surface modification, whiskers have much better lipophilic and hydrophobic properties, and the alkyl chains of OTS absorbed on the whisker surface are inclined while OTS usually is distributed unequally on the matrix surface. The self-assembly mechanism of OTS is as follows. First, Si-Cl bonds are changed to Si-OH bonds when OTS and trace water on the whisker surface are hydrolyzed. Then, Si-OH 

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With the complex where L = pyridine an optical nanosensor was developed [135-137], the method used to fix the vapochromic material to the optical fiber was the electrostatic self assembling method (ESA) and the light source used was an 850 nm LED. The sensor was tested for two different alcohols (ethanol and methanol) and it was possible to distinguish between different concentrations. It was also possible to discriminate between the two different alcohols. 

Self-assembly methods have been used to form zinc bisquinoline assemblies with high refractive index and film uniformity.287... 

A huge number of transition metal-sulfur clusters have been synthesized,36 most of which have been obtained based on the self-assembly methods. On the other hand, to construct the cluster cores with the desired metal-sulfur compositions and connecting schemes, rational pathways leading to the high-yield syntheses of tailored metal-sulfur clusters have recently been explored. Fragment condensations have been demonstrated to be the powerful methods to obtain such clusters numerously,37 some examples of which are shown below. 

In order to prepare and isolate solid-state, crystalline, oxygenated iron-heme model complexes, chemists learned to synthesize (by self-assembly methods) and oxygenate many types of hindered porphyrins. For instance, capped porphyrins were synthesized by direct condensation of a suitable tetraaldehyde with four pyrrole molecules.37 Picket-fence porphyrins such as I e(TPP)((V-MeIm) (where TPP = meso-tetraphenylporphyrin and /V-Melm = (V-methylimidazole)... 

Redox enzymes have been assembled in a monolayer on the solid surface by a potential-assisted self-assembling method as well as a thiol-gold selfassembling method. These enzymes are electronically communicated with the solid substrate through a molecular interface of conducting polymer and a covalently bound mediator. Electron transfer type of enzyme sensors have been fabricated by the self-assembling methods. 

An ordered antibody array has also been assembled on the solid surface by a combination of Langmuir Blodgett (LB) film method and self-assembling method. An ordered monolayer of protein A is deposited on the solid surface by LB method, which is followed by self-assembling of antibody. Individual antigen molecules which are complexed with the antibody array have been quantitated selectively by atomic force microscopy (AFM). 

There have been several methods for assembling protein molecules on the surfaces of various matrices. These include (1) covalent, (2) Langmuir-Blodgett, and (3) self-assembling methods. The protein assembling by these methods are mostly accompanied by appreciable loss of biological activity. 

In the past several years, we have used the SAAP method to prepare different long multiblock copolymers. Generalities about the preparation and characterization of different end-functionalized triblock copolymers are first outlined. Then, the micellization of triblock copolymer as well as coupling efficiency with and without self-assembly method are discussed. 

An orthogonally self-assembling method can be achieved by tailoring different functionalities on predefined regions of surfaces. Xu et al. (2006) demonstrated... 

Yin W, Zhang MS (2003) Characterization of nanosized Tb-MCM-41 synthesized by the sol-gel-assisted self-assembly method. J Alloys Compounds 360 231-235... 

Landon, P., Glosser, R. Zakhidov, A. Self-assembly methods for photonic crystals. Trends Opt. Photon. 91, 52-54 (2003). 

Sampling in surface-enhanced Raman and infrared spectroscopy is intimately linked to the optical enhancement induced by arrays and fractals of hot metal particles, primarily of silver and gold. The key to both techniques is preparation of the metal particles either in a suspension or as architectures on the surface of substrates. We will therefore detail the preparation and self-assembly methods used to obtain films, sols, and arrayed architectures coupled with the methods of adsorbing the species of interest on them to obtain optimal enhancement of the Raman and infrared signatures. Surface-enhanced Raman spectroscopy (SERS) has been more widely used and studied because of the relative ease of the sampling process and the ready availability of lasers in the visible range of the optical spectrum. Surface-enhanced infrared spectroscopy (SEIRA) using attenuated total reflection coupled to Fourier transform infrared spectroscopy, on the other hand, is an attractive alternative to SERS but has yet to be widely applied in analytical chemistry. 

While preparation of multilayers by the self-assembly method is less straightforward than that by the LB method, it still can be accomplished [11-13], The amphiphilic molecule should have a functionalized terminal group. In order to avoid either uncontrolled multilayer deposition or the simultaneous attachment of both head and terminal groups to the substrate, the terminal group should be protected. After the first monolayer is deposited, the sample should be removed from the solution, the terminal groups should be deprotected and the sample should be returned to the solution for deposition of the second layer. Subsequent deprotections and reimmersions allow one to coat the desired number of layers onto the substrate. 

Conventional SERS substrates typically have disordered nanoscale features, such as that found in electrochemically roughened Au or Ag surfaces.170 SERS substrates can also be rationally designed by lithography, by self-assembly, or a combination of the two. Both supramolecular and nanoscale self-assembly methods can be used to fabricate two-dimensional Au nanoparticle arrays with tunable optical properties.33 171172 For example, macrocyclic surfactants based on resorcinarenes (a subclass... 

The noncovalent self-assembly method relies on less specific types of interactions, including electrostatic, hydrogen bonding, metal ion coordination, Van der Waals forces, and/or hydrophobic attractions.8 In this approach, the template and the polymerizable monomer (i.e., an organoalkoxysilane) are judiciously chosen so that they will have complementary interactions. Removal of the template is easier than in the covalent assembly approach and often involves simply washing the materials in a suitable solvent.8... 

The motivation of all scientists to employ self-assembly methods in synthetic chemistry and materials science is the biological self-organization in Nature. Biological self-organization has been defined as the spontaneous building up of complex structures that takes place under adequate environmental conditions so-... 

Another successful approach has been to use Langmuir-Blodgett (LB) techniques, or self-assembly methods to make films. The LB approach has been used to make oriented films with excellent registry, and even multiple oppositely ordered layers. Although SHG, and even low optical losses, have been obtained by a number of researchers, the LB approach still has to be demonstrated as a cost-effective fabrication technique. 

Tsuge, Y., K. Inokuchi, K. Onozuka, O. Shingo, S. Sugi, M. Yoshikawa and S. Shiratori (2006). Fabrication of porous Ti02 films using a spongy replica prepared by layer-by-layer self-assembly method Application to dye-sensitized solar cells. Thin Solid Films, 499(1-2), 396—401. 

Hao, W. C., Pan, F. and Wang, T. M. (2005). Photocatalytic activity Ti02 granular films prepared by layer-by-layer self-assembly method. J. Mater. Sci. 40(5), 1251-1253. 

Kim, J. H., Fujita, S. and Shiratori, S. (2006). Fabrication and characterization of Ti02 thin film prepared by a layer-by-layer self-assembly method. Thin Solid Films 499(1-2), 83-89. 

A monolayer or submonolayer is formed when chemisorption or chemical reaction occurs, or when a self-assembly method is applied, however, further layers can be developed on top of the primary layer. Usually multilayer films are formed when polymers are deposited on a conductor surface by -> electropolymerization, by solvent evaporation, or other methods. Further modification of a polymer film is also often used, e.g., by incorporation of enzymes. 

Supramolecular entities are prepared either by designed or self-assembly, or by the breakdown of larger species - the so-called bottom-up and top-down approaches respectively. Most supramolecular zinc compounds have been obtained by self-assembly methods, often operating in a rather hit-and-miss way. However, controlled cleavage of coordination polymers should prove a useful route to predesigned supramolecular assemblies. An example of this approach is provided by the... 

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