Self assembly of monolayers

Self assembly of monolayers on gold electrodes provided a viable approach to sensor construction (see below), as well as permitted electrochemical characterization of the mechanism involved in chemisorption [233,236-239]. Electrochemical investigation of the spontaneous adsorption of n-alkanethiols onto a gold electrode and the subsequent desorption of the monolayer were rationalized in terms of oxidation and reduction of the sulfur atom [233]. More intimate details concerning the chemical fate of all species involved in the chemisorption process have not yet been elucidated. 

In order to improve synthesis of TM/3CDLA, the self-assembly of monolayers on a gold electrode based on a protected cyclodextrin-LA derivative, viz. mono-6-lipoyl-amido-2,3,6-0-peracetyl-)3-cyclodextrin, has also been performed involving the deacetylation step on the electrode surface after monolayer formation <2003ANC5687>. Applying the same methodology, immobilization of the /3-cyclodextrin-LA derivative, mono-6-deoxy-lipoyl-amido-per-2,3,6-0-acetyl-/3-cyclodextrin on the solid surface was employed for the preparation of cyclodextrin-modified gold electrodes. 

The formation of two- and three-dimensional phases on electrode surfaces is a topic of central importance in interfacial electrochemistry. It is of relevance not only to hmdamental problems, such as the formation of ionic and molecular adsorbate films, but also to areas of great technological interest, such as thin-film deposition, self-assembly of monolayers, and passivation. So far, phase formation in electrochemical systems has been studied predominantly by kinetic measurements using electrochemical or spectroscopic techniques. In order to understand and control these processes as well as the resulting interface structure better, however, improved... 

Tlie potential of electronics with organic molecules and the technologies employed in then production, such as soft hthography and self-assembly of monolayers,> the feasibility of micro- and nano-devices for biomedical applications. 

In several studies on the adhesion of self-assembled monolayers, Chaudhury modified the surface of a crosslinked PDMS by corona-treatment following self-assembly of monolayers of varying chemistries. In a similar manner, Mangipudi et al. [55] coated thin film of high molecular weight polymer from a solvent on to the oxidized surface of a PDMS cap. These studies are discussed in Section 4.2. 

Rizza, R., Fitzmaurice, D., Heame, S., Hughes, G., Spoto, G., Cihberto, E., Kerp, H. and Schropp, R. 1997. Self-assembly of monolayers of semiconductor nanocrystalhtes. Chem. Mater. 9(12) 2969-2982. 

The hydroquinone derivative 191 was esterified by thioctic acid 192 in the presence of 4-dicyclohexylcarbodiimide (DCC) and (N,N-dimethylamino)pyri-dine (DMAP) to give thiolane substituted perfluorinated BSubPc 193 (Scheme 49) which exhibited an enhance ability for self-assembling of monolayers on gold-substrates [107]. 

Scheme 1 Self-Assembly of Monolayer and Multilayered Films at the Zirconated Template Layer.

Giancarlo L C and Flynn G W 1988 Scanning tunneling and atomic force microscopy probes of self-assembled, physisorbed monolayers A/ / . Rev. Phys. Chem. 49 297... 

Prime K L and Whitesides G M 1991 Self-assembled organio monolayers—model systems for studying adsorption of proteins at surfaoes Science 252 1164-7... 

Li W, Virtanen J A and Penner R M 1995 Self-assembly of n-alkanethiolate monolayers on silver nanostructures protective encapsulations Langmu/r 11 4361... 

Using this strategy, constmction of multilayer films of - O. fim thickness by self-assembly of methyl 23-ttichlorosilyltticosanoate (MTST) on siUcon substrates has been demonstrated (Fig. 9) (165). The linear relationship between the film thickness and the layer number showed a slope of 3.5 nm /layer. Filipsometry data, absorbance intensities, and dichroic ratios for the multilayers all suggest that the samples were composed of distinct monolayers. However, ir data indicated that there maybe more tilting or disordering of the alkyl chains in the seven-layer sample than for the monolayer samples. 

Random interface models for ternary systems share the feature with the Widom model and the one-order-parameter Ginzburg-Landau theory (19) that the density of amphiphiles is not allowed to fluctuate independently, but is entirely determined by the distribution of oil and water. However, in contrast to the Ginzburg-Landau approach, they concentrate on the amphiphilic sheets. Self-assembly of amphiphiles into monolayers of given optimal density is premised, and the free energy of the system is reduced to effective free energies of its internal interfaces. In the same spirit, random interface models for binary systems postulate self-assembly into bilayers and intro-... 

Therefore, the following method was suggested and realized (the scheme is shown in Fig. 17). A 1.5 M solution of KCl or NaCl (the effect of preventing BR solubility of these salts is practically the same) was used as a subphase. A platinum electrode was placed in the subphase. A flat metal electrode, with an area of about 70% of the open barriered area, was placed about 1.5-2 mm above the subphase surface. A positive potential of +50 -60 V was applied to this electrode with respect to the platinum one. Then BR solution was injected with a syringe into the water subphase in dark conditions. The system was left in the same conditions for electric field-induced self-assembly of the membrane fragments for 1 hour. After this, the monolayer was compressed to 25 mN/m surface pressure and transferred onto the substrate (porous membrane). The residual salt was washed with water. The water was removed with a nitrogen jet. 

Under deposition of cobalt nanocrystals, self-assemblies of particles are observed and the nanocrystals are organized in a hexagonal network (Fig. 2). However, it can be seen that the grid is not totally covered. We do not have a simple explanation for such behavior. In fact, the size distribution, which is one of the major parameters in controlling monolayer formation, is similar to that observed with the other nanocrystals, such as silver and silver sulfide. One of the reasons could be that the nanocrystals have magnetic properties, but there is at present no evidence for such an assumption. 

The use of tetraoctylammonium salt as phase transfer reagent has been introduced by Brust [199] for the preparation of gold colloids in the size domain of 1-3 nm. This one-step method consists of a two-phase reduction coupled with ion extraction and self-assembly using mono-layers of alkane thiols. The two-phase redox reaction controls the growth of the metallic nuclei via the simultaneous attachment of self-assembled thiol monolayers on the growing clusters. The overall reaction is summarized in Equation (5). 

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