Self-assembled monolayers stability

Clegg, R. S., Reed, S. M., Hutchison, J. E. (1998). Self-assembled monolayers stabilized by three-dimensional networks of hydrogen bonds, J. Am. Chem. Soc., 120 2486. 

Salmeron M, Liu G-Y and Ogletree D F 1995 Molecular arrangement and mechanical stability of self-assembled monolayers on Au(111) under applied load Force in Scanning Probe Methods ed H-J Guntherodt et al (Amsterdam Kluwer)... 

Aronoff Y G, Chen B, Lu G, Seto C, Schwartz J and Bernasek S L 1997 Stabilization of self-assembled monolayers of carboxylic acids on native oxides of metals J. Am. Chem. Soc. 119 259-62... 

For transition and precious metals, thiols have been successfully employed as the stabilizing reagent (capping reagent) of metal nanoparticles [6]. In such cases, various functionalities can be added to the particles and the obtained nanoparticles may be very unique. It is well known that thiols provide good self-assembled monolayers (SAM) on various metal surfaces. When this SAM technique is applied to the nanoparticle preparation, nanoparticles can be covered constantly by functionalized moieties, which are connected to the terminal of thiol compounds. 

In order to prevent the irrevisible adhesion of MEMS microstructures, several studies have been performed to alter the surface of MEMS, either chemically or physically. Chemical alterations have focused on the use of organosilane self-assembled monolayers (SAMs), which prevent the adsorption of ambient moisture and also reduce the inherent attractive forces between the microstructures. Although SAMs are very effective at reducing irreversible adhesion in MEMs, drawbacks include irreproducibility, excess solvent use, and thermal stability. More recent efforts have shifted towards physical alterations in order to increase the surface roughness of MEMS devices. 

A Au-coated substrate is another model surface, to which many surface characterization methods can be applied. To achieve surface-initiated ATRP on Au-coated substrates, some haloester compounds with thiol or disulflde group were developed [80-84]. Self-assembled monolayers (SAM) of these compounds were successfully prepared on a Au-coated substrate and used for ATRP graft polymerization. Because of the limited thermal stability of the S - Au bond, the ATRP was carried out at a relatively low temperature, mostly at room temperature, by using a highly active catalyst system and water as a (co)solvent (water-accelerated ATRP). 

Finally, self-assembled monolayers (SAMs) on gold electrodes constitute electrochemical interfaces of supramolecular structures that efficiently connect catalytic reactions, substrate and product diffusion and heterogeneous electron transfer step when enzymes are immobilised on them. Resulting enzyme-SAM electrodes have demonstrated to exhibit good performance and long-term enzyme stability. 

Ionically self-assembled monolayers possessing exceptional temporal and thermal stability of % relative to poled polymers were prepared [45], Molecules of non-polymeric azo dyes (Mordant Orange 10) form pseudorotaxanes with /i-cyclodcxtrin in... 

Fig. 1 An ideal self-assembled monolayer of alkanethiolates supported on a gold surface. The terminal groups are amenable to synthesis, providing a means to immobilize and present ligands from the surface the alkyl chain spacer promotes tight, regular packing, and the gold-sulfur interface stabilizes surface atoms and alkane chains during packing...

The HBM consists of two differing leaves normally generated on a gold or silica surface. The lower leaf is a fixed long chain alkyl self-assembled monolayer covalently bound to a solid support while the upper leaf is a phospholipid mono-layer [82, 83]. This type of bilayer may show increased stability due to the covalent nature of the lower leaf fixation however it would present a system further removed in structure from the biological condition given this fixed nature and more limited fluidity [84]. 

If stabilizers or polymers are added post sonication or during sonication, then metal colloids result. These stabilizers could be alkyl thiols, PVP, oleic acid, and SDS. If the sonication is done in the presence of oxygen then oxides are formed. The size of the self-assembled monolayer-coated nanoparticles is determined by the surfactant concentration in the coating solution. 

Self-assembled monolayers have recently attracted much attention as a new methodology for molecular assembly [249, 342]. They enable highly organized chemical binding of molecules of interest to the surfaces of, e.g., metals, semiconductors, and insulators. The well-ordered structure of self-assembled monolayers is in sharp contrast with conventional Langmuir-Blodgett films and lipid bilayer membranes in terms of stability, uniformity, and manipulation. Functional molecules can be arranged unidirectionally at the molecular level on substrates when substituents which will self-assemble on the substrates are attached to a terminal of the molecules. The wide variety of examples reported to date include porphyrins and metalloporphyrins in self-assembled monolayers [299-339]. 

Scanning probe lithography on metal or silicon substrates is a well known technique and can be supported by a self-assembled monolayer (SAM) [1,2], Such monolayers are of great interest e.g. for passivation of silicon surfaces [3]. Covalently bound monolayers by Si-C bonds that are formed by the reaction of 1-alkenes and a hydrogen terminated silicon surface [4,5], are known to show high thermal [6] as well as chemical stability [3,7]. 

Langmuir monolayers play some part in the preparation of multi-layer systems, now mostly referred to as self-assembled monolayers or multilayers (SAM s). However, this role is modest because it is difficult to make Langmuir-Blodgett layers sufficiently perfect and stable to function in new materials, such as electronic and bio-mimetic devices. One approach of stabilizing LB films is by working with molecules having double bonds that, after deposition, are polymerized. Such layers are stable enough to serve as a substrate for protein adsorption ). 

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