Alternate Langmuir-Blodgett Films Research Articles

A modular multifunctional Langmuir–Blodgett trough

A review of Langmuir–Blodgett (LB) trough designs is given. A modular design of Langmuir–Blodgett trough is presented. This trough can be used for monolayer analysis, conventional deposition of LB films, and deposition of alternating LB films by adding different combination of pressure sensors and dipper mechanisms. Research results produced with this trough are referenced.

Photochemical modulation of second order nonlinear optical properties of alternate Langmuir-Blodgett films containing Ru II-bipyridine complexes

A monolayer of a 1:4 mixture of ( N,N'-dioctadecyl-4,4′-dicarboxamide-2,2′-bipyridine)-bis (2,2′-bipyridine)ruthenium(II) perchlorate (RuC18B) and dioctadecyldimethylammonium bromide (2C18NB) was deposited alternately with a monolayer of 2C18NB alone. A second harmonic signal from alternate Langmuir-Blodgett (LB) films was observed upon irradiation with an Nd:YAG laser at 1064 nm. When alternate LB films were excited with the third harmonic (355 nm, 0.1–10 mJ cm −2) of an Nd:YAG laser before irradiation of a 1064 nm pulse, the intensity of second harmonic light (SHL) from the LB films decreased depending on the intensity of the 355 nm pulse. The intensity of SHL was varied reversibly many times. Such photochemical modulation of SHL was most probably attributed to the difference of second order nonlinear coefficients between the ground and the excited state of the Ru-complex.

Relationship between pyroelectricity and molecular orientation in alternate Langmuir-Blodgett films

The relationship between pyroelectricity and molecular orientation in alternate Langmuir-Blodgett (LB) films consisting of 5-(p-dodecyloxyphenyl)pyrazine-2-carboxylic acid and deuterated stearic acid was investigated. The same studies were also performed for alternate LB films of their barium salts. Pyroelectricity of the alternate film was measured by a static method in the temperature range from −30 to 80 o C

Characterization of Ultrathin Organic Membranes by Vibrational Spectroscopy

We first deal with a new method for quantitative evaluation of the molecular orientation in thin Langmuir-Blodgett (LB) films by Fourier transform infrared (FT-IR) transmission and reflection-absorption (RA) spectroscopy. The method was applied to the study of the 7-monolayer LB film of cadmium stearate. The orientation angle of the hydrocarbon chain axis around the surface normal was found to be 7°, being in good agreement with the average of the previous data obtained by other investigators. Then, we applied the same method to the study of temperature dependence of the molecular orientation in alternate LB films consisting of a phenylpyrazine-containing long-chain fatty acid and deuterated stearic acid, and in the corresponding alternate LB films of their barium salts. At the same time, pyroelectricity of these films was measured on heating the sample, and the results are discussed in connection with the molecular structure and orientation. It was concluded that the pyroelectricity is ascribed to changes of spontaneous polarization due to a structure modification of the polar groups of the constituent molecules with the highly oriented all-trans hydrocarbon chains.

Structural control and characterization in mixed and alternate Langmuir-Blodgett films of simple long-chain compounds

Several kinds of mixed and alternate Langmuir-Blodgett (LB) films of esters and salts of long-chain fatty acids have been prepared. Molecular arrangements in these LB films have been estimated from their X-ray Weissenberg photographs. Structural control of some functional molecules in LB films can be achieved by mixing with matrix simple long-chain compounds. A criterion for the use of long-chain esters as matrix materials in fabricating functional monolayer assemblies has been designated in this study.

Fourier transform IR studies of alternate layer acid-amine Langmuir-Blodgett films with pyroelectric properties

The effects of heating acid-amine alternate Langmuir-Blodgett films on the molecular arrangement and head group interactions have been studied in relation to pyroelectric activity. We have shown how changes in the extent of proton transfer and head group rearrangements might lead to the necessary changes in polarization with temperature. Fourier transform IR methods are demonstrated to have the sensitivity and power needed to gather valuable information about the fundamental modes of operation of molecular electronic devices.

An example of molecular building: Alternate Langmuir-Blodgett films of cobalto- meso-porphyrins designed to bind dioxygen

Alternate Langmuir-Blodgett films of amphiphilic cobalto-porphyrins and imidazole are built up to mimic haemoglobin as an oxygen carrier. The reactivity towards dioxygen is shown to be strongly dependent on the self-assembling properties of the molecules. The effects of substitution on the imidazole ring are discussed.

Second harmonic generation from alternating langmuir-blodgett films

We report here the investigation of the second harmonic generation from a non-centrosymmetric alternating Langmuir-Blodgett film of ω-tricosenoic acid and highly polarisable merocyanine dye. Results for films containing one, two and three layers of the merocyanine dye are described.