Stearic Acid Langmuir-Blodgett Films Research Articles

The photovoltage signals of bacteriorhodopsin in Langmuir–Blodgett films with different molecular orientations

AbstractThe photoresponse of bacteriorhodopsin (bR) has been studied in Langmuir–Blodgett (LB) films bR was deposited by vertical dipping as x‐ or z‐type monolayers and as z‐type multi layers between stearic acid LB films. The electrodes used were a transparent vacuum‐deposited ITO on a quartz substrate and an InGa metal alloy. The signals were observed from samples containing a single bR layer or five bR layers both at room humidity and in water‐saturated conditions. The photoelectric signals of x‐ and z‐type monolayers had opposite polarities and both had two exponential kinetics on a microsecond time scale with time constants of about 10 and 70 μs. The amplitude of the fast negative component of the signal of a bR monolayer was 0.4 mV, in the opposite direction to that in which protons were pumped. The amplitude due to five layers was five times as high as that due to a monolayer. The ratio between the amplitudes of the fast negative component and the slow positive part of the signal, in the proton‐pumping direction, was 1:3. The photoresponse signal saturated with a light intensity of about 1.7 mJ cm−2, which is equivalent to a photon density of 0.5 Å−2. The activation energy of the bR photovoltage was 75 ± 5 kJ mol−1 in the temperature range between 17 and 35°C.

Sum Frequency Spectra in the C-H Stretch Region of Adsorbates on Iron

Infrared-visible sum frequency generation (SFG) was used to record vibrational spectra in the C-H stretch region of single monolayer Langmuir-Blodgett films of stearic acid, octadecylamine, and p-octadecylphenyl acetic acid on iron oxide, demonstrating the sensitivity of SFG to about 0.1 monolayer. Within our present signal-to-noise limitations, it was not possible to obtain SFG spectra of the aromatic C-H stretch in p-octadecylphenyl acetic acid or the N-H stretch in octadecylamine. Vibrational spectra in the C-H stretch region have also been obtained for chemically adsorbed monolayers of stearic acid and oleic imidazoline on iron oxide; however an undetermined fraction of these spectra result from hydrocarbon contamination. Finally, an SFG spectrum was obtained at a buried interface, that of p-octadecylphenyl acetic acid on iron oxide under water. The potential of SFG as a surface analytical tool is discussed.

Dark-field electron microscopy of Langmuir-Blodgett films of fatty acids and their barium salts

Monolayers of fatty acids and their barium salts on water were transferred onto supporting films of carbon or silicon dioxide by horizontal attachment, down-stroke or up-stroke modes at various stages of surface-pressure-area (π− A) isotherms. Dark-field electron microscope images and electron diffraction patterns were used to determine the structure and molecular ordering of one-layer Langmuir-Blodgett (LB) films without any presurface treatment such as shadow casting and replication. The observations revealed the polycrystalline powder structure of one-layer LB films of stearic acid, arachidic acid and barium arachidate prepared by the horizontal attachment mode at no compression. With monolayer compression the LB films tended to form a structure consisting of growing island films which included a number of scattered small holes. A dark-field electron micrograph and electron diffraction pattern taken with an electron cryomicroscope led us to conclude that the presence of these scattered small holes in the LB films was due neither to the sublimation of LB film molecules in vacuum nor to electron radiation damage. Similar porous structures were found when the monolayers of barium arachidate with flexible alkyl chains of an intermediate length were transferred by the down-stroke mode onto supporting films of carbon or silicon dioxide. Arachidic acid and its barium salt formed LB films of a rather homogeneous structure with a few large holes by the up-stroke mode. Because the cohesive force increased with the length of alkyl chains, the one-layer LB films of melissic acid (C 30) showed a similar porous structure, irrespective of the mode of transfer of the monolayers.

Infrared study of electron‐beam‐induced reactions in Langmuir–Blodgett films of stearic acid

To investigate the mechanisms of carbon enhanced vapor etching of silicon oxide, electron‐beam‐induced reactions in stearic acid Langmuir–Blodgett (LB) films were studied as a model system. Stearic acid LB films were deposited on silicon, and characterized using multiple internal reflection infrared spectroscopy. Spectra of these films exposed to an electron beam show changes in both peak shape and intensity. The changes are shown to result from both electron‐beam‐induced evaporation, and from carbon–carbon bond dissociation within the films.

X-ray photoelectron spectroscopy of non-stoichiometric lead sulfide monolayers in stearic acid Langmuir-Blodgett films

The chemical state, composition and stability in air of monolayers of lead sulfide synthesized in stearic acid LB films at a H 2S pressure of 1 Torr were studied mainly by X-ray photoelectron spectroscopy (XPS). Its S/Pb ratio is about 1.5:1. In air, the lead sulfide monolayer slowly decomposes to PbSt 2, elemental sulfur and other sulfur compounds which escape in air in the form of H 2S or SO 2. After exposure to air for 77 days, the lead sulfide monolayer had decomposed about 90%, of which elemental sulfur is 62%.

Preparation and structure of Q-state lead sulfide monolayers in metastable stearic acid Langmuir-Blodgett films

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTPreparation and structure of Q-state lead sulfide monolayers in metastable stearic acid Langmuir-Blodgett filmsXiaogang Peng, Shiquan Guan, Xiangdong Chai, Yueshun Jiang, and Tiejin LiCite this: J. Phys. Chem. 1992, 96, 7, 3170–3174Publication Date (Print):April 1, 1992Publication History Published online1 May 2002Published inissue 1 April 1992https://doi.org/10.1021/j100186a072RIGHTS & PERMISSIONSArticle Views388Altmetric-Citations45LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (640 KB) Get e-Alerts

Production and growth of size-quantized cadmium sulphide in the hydrophilic interlayer of Langmuir–Blodgett films

Exposure of Langmuir–Blodgett (LB) films of cadmium stearate to H2S gas yielded size-quantized CdS in the hydrophilic interlayers of the stearic acid LB film, and the CdS formed therein could be grown by repetition of the immersion in aqueous CdCl2 and exposure to H2S gas without destroying the layered structure.

On the presence of holes in stearic acid Langmuir-Blodgett films studied by dark field electron microscopy

Transmission electron microscopy using the dark field mode of imaging has been demonstrated as a useful method for the structural characterization of Langmuir-Blodgett (LB) thin films and for revealing the presence of holes in such films. In this paper, we show that the presence of such holes may be related to the nature of the substrate used to support the LB films and that some substrates, notably amorphous carbon, may be unsuitable for this purpose. In addition, real-time electron microscopy studies reveal that holes may, in some materials at least, be created by the action of the electron beam.

Adhesion of fatty acid in Langmuir-Blodgett films

The use of Langmuir-Blodgett (LB) films in electronic devices means that the strength of the films is an important factor. To our knowledge, there are only a few reports on the strength of LB films. We have designed a testing machine suitable for organic thin films, and have measured the adhesion of stearic acid LB films to the substrates Ag 2O, InO, SnO and SiO 2 using the scratch method. From these experiments, the relationship between the adhesion and the substrate material is found to be rather complicated, and adhesion exhibits a strong dependence on surface roughness.

ステアリン酸１〜９層ＬＢ膜のフーリエ変換赤外（ＦＴＩＲ）‐減衰全反射（ＡＴＲ）スペクトルと金属蒸着膜による強度増大

Fourier transform infrared (FTIR) -attenuated total reflection (ATR) spectra have been studied of Langmuir-Blodgett (LB) films of stearic acid with 1 to 9 monolayers. Difference in the spectral features observed among respective monolayers suggests that there are changes in structure, subcell packing, and molecular orientation as a function of the number of monolayers. (1) The hydrocarbon chains of stearic acid in the first monolayer are in the hexagonal subcell packing where each chain is freely rotated around its long axis oriented perpendicular to the surface. However, the molecules in the upper monolayers crystallize with the monoclinic form where the hydrocarbon chains are packed alternately and are inclined at the angle about 30° with the surface normal. (2) Stearic acid occurs as the cis configuration for the C=O and Cα-Cβ bonds in the 1- and 2-monolayer films, but the trans configuration starts to appear in the 3-monolayer film.Band intensity enhancement of FTIR-ATR spectra of the stearic acid LB film is obtained by evaporation of thin Ag island layers. It is found that in the 1-monolayer LB film, all stearic acids react with evaporated Ag forming silver stearate and the symmetric COO- stretching band is enhanced a factor of 30. This phenomenon is ascribed to the electric field enhancement due to collective electron resonances associated with the island nature of the thin Ag layers.

界面有機薄膜の赤外ラマンスペクトル

Recent studies on infrared and Raman spectra of monolayers, bilayers, and Langmuir-Blodgett (LB) films are reviewed. Regarding infrared measurements of these films, the transmission, attenuated total reflection (ATR), reflection-absorption (R-A), and surface electromagnetic wave (SEW) techniques are outlined. For Raman measurements, on the other hand, the external reflection, optical waveguide, and total internal reflection techniques are briefly described. The advancement of these techniques and the improvement in sensitivity of infrared and Raman spectrophotometers allowed us to study the structure and molecular orientation even in single monolayers at various interfaces.The infrared ATR spectroscopy of stearic acid LB films indicates that there exists the structural and orientational heterogenity among the first few monolayers. The R-A spectroscopy of cadmium arachidate LB films suggests the almost perpendicular orientation of the molecular axis on the silver substrate as well as significant disruption of molecular conformation and lateral packing during heating and melting processes. Application, of the total internal reflection spectroscopy to the study on resonance Raman spectra of spread monolayers on water and of adsorbed monolayers at an oil-water interface indicates changes in molecular orientation and interaction with changes in the amount of molecules in the monolayers.

FTIR-ATR studies on Langmuir-Blodgett films of stearic acid with 1-9 monolayers

FTIR-ATR studies on Langmuir-Blodgett films of stearic acid with 1-9 monolayers

Polymerization and optical properties of mixed LB films of β-parinaric acid and stearic acid

The structure and the polymerization process in Langmuir-Blodgett (LB) films of mixtures of β-parinaric acid and stearic acid were studied by measuring X-ray diffraction, optical absorption and fluorescence spectroscopy. The layer structure of the mixed LB film was broken as the molar fraction of β-parinaric acid increased, as a result of increased polymerization between the β-parinaric acids. The polymerization process was determined by the decrease of the absorption band and the fluorescence band due to the β-parinaric acid. The reduction of the fluorescence intensity as a function of the square root of the molar concentration of β-parinaric acid and stearic acid was explained by superimposition of the polymerization effect and the fluorescence quenching effect based on the Förster theory.

The Structure of Langmuir-Blodgett Films of Stearic Acid

The Structure of Langmuir-Blodgett Films of Stearic Acid