Langmuir—Blodgett deposition self-assembled monolayers

Industrial Applications Characterizing inverted micelles electrooptical displays electronic systems for optical information processing (organic photoconductors) " Langmuir-Blodgett films self-assembled monolayer films nano-stmctured silica films vacuum-deposited films Safety/Toxicity No data available... 

Deposited Langmuir-Blodgett films take on many of the same stmctures as the Langmuir monolayers discussed in Section IV-4C, and they are often compared to the self-assembling monolayers described in Section XI-IB. The area... 

Langmuir-Blodgett films (LB) and self assembled monolayers (SAM) deposited on metal surfaces have been studied by SERS spectroscopy in several investigations. For example, mono- and bilayers of phospholipids and cholesterol deposited on a rutile prism with a silver coating have been analyzed in contact with water. The study showed that in these models of biological membranes the second layer modified the fluidity of the first monolayer, and revealed the conformation of the polar head close to the silver [4.300]. 

Self-assembled monolayers of amphiphilic molecules have been deposited at surfaces since Langmuir and Blodgett developed their dip coating deposition method in 1937.4 These were briefly discussed in Chapter 10 in relation to thiol... 

The focus in this chapter is on the scientific issues and challenges in the application of vapor deposited top metal contacts to devices fabricated from self-assembled monolayers (SAMs) and related films such as Langmuir Blodgett (LB) monolayers. Specifically the chapter will review the types of possible interactions... 

Several examples of catenanes and rotaxanes have been constructed and investigated on solid surfaces.1 la,d f 12 13 26 If the interlocked molecular components contain electroactive units and the surface is that of an electrode, electrochemical techniques represent a powerful tool to study the behavior of the surface-immobilized ensemble. Catenanes and rotaxanes are usually deposited on solid surfaces by employing the Langmuir-Blodgett technique27 or the self-assembled monolayer (SAM) approach.28 The molecular components can either be already interlocked prior to attachment to the surface or become so in consequence of surface immobilization in the latter setting, the solid surface plays the dual role of a stopper and an interface (electrode). In most instances, the investigated compounds are deposited on macroscopic surfaces, such as those of metal or semiconductor electrodes 26 less common is the case of systems anchored on nanocrystals.29... 

Bryce and co-workers reported that the crown-annulated TTF derivatives 98 and 99 were used for UV-Vis spectroscopic and electrochemical studies of metal complexation <1996J(P2)1587>. Solution electrochemical studies showed that metal complexation to the crown unit leads to a small anodic shift in the first oxidation potential of the TTF system. Langmuir-Blodgett films of amphiphilic 99 have been assembled on solid substrates by Y-type deposition. Compounds 100-104 were used to prepare self-assembled monolayers on gold and platinum surfaces <1998AM395, 2000JOC8269>. The self-assembled monolayers of 104 were the most stable in this series of TTF-crowns. Electrochemical data for the self-assembled monolayers of 100-104 in MeCN showed two reversible one-electron waves, typical of the TTF system. The self-assembled monolayers of 102-104 exhibited an electrochemical response in aqueous electrolyes, which was observed between 50 and 100 cycles. 

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 ). 

SEIRA and SERS are powerful techniques for stmctural characterization of ultra thin films and well-ordered monolayer on metal surfaces. Thin films at interfaces are prepared by different procedures and developed for various applications. The fabrication and characterization of ultra thin films is a permanent area of research where some of the most interesting subjects are (a) bilayers and monolayers at liquid-liquid interface, (b) adsorption monolayers and Langmuir (water-insoluble) monolayers at air-water interface, (c) adsorption films and self-assembled monolayers (SAMs) at liquid-solid interface and Langmuir-Blodgett Alms, cast (deposit) films and spin-coat films at air-solid interface. Studies about molecular organization of monolayers of porphyrins derivatives, of azamacrocy-cles and their metallic derivatives among the many SEIRA applications to films and interfaces, were published . 

Monolayers as modifiers on electrode surfaces are prepared by sorption techniques. Self-assembled monolayer s (SAMs) form by spontaneous adsorption of precursors on the electrode substrate with an ordered orientation by interaction of certain molecule areas protruding from the sorption plane [109—112] most popular are SAMs prepared by thiol compounds on gold surfaces, but also SAM formation on CPEs is possible. Langmuir-Blodgett layers (LBLs) are monolayers made by surfactants by adsorption from the surface of a solution [113]. Highly ordered multistacked structures from polyelectrolytes can be obtained by layer-by-layer deposition, where the ensuing plane of the stack can be immobilized by sorption of a countercharged polyelectrolyte [114-116]. 

This chapter deals primarily with monolayers of surfactants at fluid interfaces, but some attention is also given to (nano) coatings such as Langmuir-Blodgett (LB) and Langmuir-Schaefer (LS) films, self-assembled monolayers (SAMs), and layers obtained by alternating polyelectrolyte deposition. Such coatings may be applied for the functionalization of surfaces, for instance, to achieve biocompatibility of biomaterials, improve specificity and selectivity of biosensors and membranes, and control immobilization of enzymes or cells in bioreactors. 

In order to determine the effect of chemical modification on the friction and pull-off forces, self-assembled monolayers (SAMs) and Langmuir-Blodgett (LB) films were formed on the silicon surface. Films were formed on the asperity arrays having various groove depths, where the distance between the adjacent peaks was about 240 mn for each asperity array. The SAM and LB films were deposited as follows. 

With this feature in mind, numerous organized macromolec-ular architectures have been deposited on electrode surfaces. Accordingly, self-assembled monolayers [387] and Langmuir-Blodgett-type [388] multilayers have been used to attach numerous functional moieties to electrode surfaces, e.g., crown ethers [389-391] and other complexing macrocyclic cavities (cal-ixarene [392], cyclodextrin [393], and cyclophane [394-396]), vio-logens [397], porphyrins [398, 399], and enzymes [400-402]. 

The combination of XPS with another technique (AFM and, or radiolabeling) to characterize adsorbed phases is further illustrated for adsorption of proteins on polymers and on self-assembled monolayers,and for mixed Langmuir-Blodgett films of DPPC and surfactin deposited on mica. ... 

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