Assembly film method

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). 

Beginning with a discussion of the necessary basic physics and chemistry, the book proceeds to a description of the main topics of current research in this field. The Langmuir-Blodgett technique, self-assembly, and methods of film deposition exploiting the ordered structure of mesophases are discussed. Separate chapters are devoted to the properties and computer modelling of both liquid crystals and films at the air/water interface. Order in biomemebranes is also discussed. 

Evaporation Induced Self-Assembly (EISA) Method of Film Growth... 

Recent studies have been performed on alternative electrode materials. Nano-sonic has developed low modulus, highly conducting thin film electrodes by molecular level self-assembly processing methods capable of maintaining conductivity up to strains of 100% [217, 218]. Recent developments have enabled the reduction of the modulus to less than 1 MPa and an increase in the strain to rupture to 1000% [219]. A version of the material is commercially available under the name Metal Rubber . Delille et al. have developed novel compliant electrodes based on a platinum salt reduction [220]. The platinum salt is dispersed into a host elastomer and immersed in a reducing agent. A maximum conductivity of 1 S cm was observed and conductivity was maintained for strains up to 40%. 

Muller and coworkers prepared disc-like polymer Janus particles from assembled films of the triblock copolymer SBM and, after hydrolysis of the ester groups into methacrylic acid units, used these as Pickering stabilizer in the soap-free emulsion polymerization of styrene and butyl acrylate [111]. Armes and coworkers described the synthesis of PMMA/siUca nanocomposite particles in aqueous alcoholic media using silica nanoparticles as stabilizer [112], extending this method to operate in water with a glycerol-modified silica sol [113, 114]. Sacanna showed that methacryloxypropyltrimethoxysilane [115] in the presence of nanosized silica led to spontaneous emulsification in water, which upon a two-step polymerization procedure afforded armored particles with an outer shell of PMMA [116]. Bon and coworkers demonstrated the preparation of armored hybrid polymer latex particles via emulsion polymerization of methyl methacrylate and ethyl methacrylate stabilized by unmodified silica nanoparticles (Ludox TM O) [117]. Performance of an additional conventional seeded emulsion polymerization step provided a straightforward route to more complex multilayered nanocomposite polymer colloids (see Fig. 14). 

The planar order of nanostructures deposited by chemical routes has become an important issue, because of the competition with solid-state nanotechnology cap>able of the fabrication of fine two-dimensional structures. The main concern is with the layers of nanopartides produced by chemical self-assembly, because methods of electrostatic self-assembly and LB is not capable of producing two-dimensional ordered arrays of nanopartides. The features of the lateral arrangement of particles, which are buried under layers of either closely packed amphiphilic compounds or polymers, are usually smeared and difficult to observe. In the case of relatively thick (quasi-3D) films, produced by electrodeposition and sol-gel techniques, the morphology study usually reveals polycrystallites. Therefore, the quality of these materials can be assessed by the size of the crystallites and by the presence of preferential orientation, which may cause anisotropy of the electrical and optical prop>erties of materials. 

For the proposed unimolecular devices, the problem of assembly and device interrogation or control is a very serious one. If one cannot talk to a single molecule, one can perhaps talk to a monolayer of identical molecules transferred to a suitable (metal) substrate by the Langmuir-Blodgett film method [70] then, many identical molecules can be addressed electrically, provided that electrical short circuits through defects do not occur. However, LB... 

During the last decade the field of electrochemistry has witnessed a very fast progress on the modification of electrode surfaces. From the predominant use of random polymeric structures, prevalent in the electrode modification efforts of the late 70s and early 80s, electrochemists have learnt to control the molecular architecture of the electrode-solution interface to a degree that was clearly out of reach a decade ago. Many electrode modification methods developed recently rely on the use of thiolate self-assembled monolayers (SAMs) [1-3]. These systems offer unparalleled ease of preparation and levels of molecular organization close to those that can be reached with Langmuir-Blodgett film methods. Therefore, electrodes derivatized with unfunctionalized or functionalized alkanethiolate monolayers have been the subject of extensive research work during the last few years [4, 5]. 

In turn, Gao et al. studied thin films of CdSe/PPV nanocomposites that were prepared from a water-soluble precursor of pre-PPV and CdSe nanoparticles using a self-assembly deposition method [299]. The pre-PPV was converted to PPV by heating the whole sample at 130°C under 10 bar for at least lOh. EL diodes were prepared from 20 double layers of PPV/CdSe deposited onto ITO glass and covered by Al electrodes. EL devices exhibited stable EL with a turn-on voltage below 5 V, and the emission of EL was only from CdSe nanoparticles. The current-voltage curves show inversion symmetry, but light emission was observed only under forward bias. The broad emission spectra are related to exciton trapping at the particle surface, which was confirmed by femperafure-dependenf measurements of PL [299]. 

The term self-assembly is also often applied to the deposition of thin films on surfaces (i.e., self-assembled monolayers, SAMs) and is more often used in this sense in the field of nanotechnology. The formation of self-assembled films may involve a variety of interactions, such as electrostatics, van der Waals forces, or even a chemical bond (Figure 1.11). For example, we can compare two different methods for depositing a molecular pattern on a surface. In method 1, the surface is coated with a positively charged ion in a certain area. Next, the surface is immersed in a solution containing a negatively charged polymer. The polymer will self-assemble... 

The discussion now moves from ordered films and monolayers to films that are formed by dropcasting or some other method that yields a disordered film structure. Interparticle distance is likely to be less uniform in dropcast films than in self-assembled films. Dropcasting is simpler than self-assembly methods and therefore more attractive for use in device fabrication, but variability of interparticle spacing likely contributes to the fact that quantized charging features are typically not observed. Another important difference to note is that for sufficiently thick dropcast films, currents passed through the film tend to plateau, whereas in films of distinct monolayers, electron transport rate increases with each deposition layer." This has important implications for devices that aim at quantitatively utilizing electronic conductivity of MFCs. 

As an example of SAMs, eorrosion inhibition by self-assembled films formed by adipic acid (AA) molecules on caibon steel surfaces is discussed below. SAMs of AA were formed on iron oxide/caibon steel surfaces by the immersion coating method. The metal was immersed in an aqueous solution containing 60 ppm of Cl (to initiate the corrosion process and the formation of iron oxide) in the absence and presenee of adipic acid. The formation, uniformity, ordering and bonding of the monolayers accompUshed by the immersion method have been evaluated by FTIR and AFM. The electrochemical properties of the unmodified and modified caibon steel surfaces were characterized by polarization study and EIS analysis to test the abiUty of the monolayer to reduce the corrosion of the surface. 

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