Langmuir-Blodgett films methods

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]. 

Interferometry is based on the fact that light reflected from the front and back interfaces of a film travels different distances, producing interference effects. The method has been applied to Langmuir-Blodgett films (Section XV-7) and to soap films (Section XrV-8) [147-149]. 

Improved chemisorption methods ( self-assembled monolayers ) and physi-sorption methods (Langmuir-Blodgett films). 

Langmuir-Blodgett films were prepared by spreading a 2 x 1(T4 M solution of the enantiomerically pure helicenebisquinone in chloroform onto a water surface. After evaporation of the solvent, the monolayer was compressed to a surface pressure of 20 mN/m. After stabilization for 30 min, the monolayers were transferred by the horizontal dipping method onto glass substrates, treated with octadecyltrichlorosilane to make them hydrophobic. 

The most convenient method for the evaluation of fullerene molecules aggregation is the comparison of UV-VIS absorption spectra in various solvents and for Langmuir-Blodgett films (Bensasson et al., 1994). Some preliminary conclusions about the state of aggregation can be made basing only the absorption maximum of fullerene C60 in the region of 3 30-340 nm concern. 

Geiger E, Hug P, Keller BA. Chromatic transitions in polydiacetylene Langmuir-Blodgett films due to molecular recognition at the film surface studied by spectroscopic methods and surface analysis. Macromol Chem Phys 2002 203 2422-2431. 

When some NC particles are surface treated to make them hydrophobic by, e.g., silylation and floated on the surface of water, a nanoparticle layer can be made on a solid substrate by a method similar to Langmuir-Blodgett film formation. Interparticle separation is well controlled by choosing an appropriate surface pressure prior to making LB film, as discussed next. 

The results illustrated above show that the CFT method is suitable for making chemical-sensor measurements using both bulk polymers and, in particular, thin film materials that are intrinsically weak conductors. Therefore, the CFT looks premising for such materials as poly(phenylacetylene) derivatives 24., for which carefully shielded electrometer measurements have been required in the past because of current levels at the threshold of detectability. Furthermore, the fact that the CFT always makes AC measurements reduces the problem of DC polarization of electrodes. In addition, the CFT approach should be suitable for other "chemiresistor" applications, such as the metal-substituted phthalocyanines proposed by Jarvis et. al. 2 and for Langmuir—Blodgett films 26. which, because they are so thin, may prove impossible to use in parallel-plate form, but which can be routinely used with the high-sensitivity interdigi-tated-electrode approach provided by the CFT. 

Two methods have been proposed for the preparation of organosilane monolayers. One is chemisorption from organosilane solution [4-6], and the other one is Langmuir-Blodgett (LB) method or water-cast method [7-23], Fig. 1 shows the film formation mechanism of the organosilane by LB method (a) and chemisorption method (b). In the case of LB method (Fig. 1(a)), the toluene solution of organotrichlorosilane was spread on the water surface (pH 5.8) at a controlled subphase temperature. To attain quasi-equilibrium state of the monolayer, the monolayer was kept on the water subphase under a given... 

Y. Okahata, K. Ariga, K. Tanaka, Evaluation of a Horizontal Lifting Method of Langmuir-Blodgett Films Using a Quartz-Crystal Microbalance , Thin Solid Films, 210,702(1992)... 

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