Cyclodextrin‐Based Functional Materials and Surfaces

Phase transitions and morphology control of Langmuir Blodget (LB) films of graphene oxide.

A set of covalently linked phenyl-amidophenyl-substituted porphyrin amphiphiles with n-C15H31 tails have been synthesized and completely characterized. These amphiphiles form good Langmuir-Blodgett (LB) films at the air/water interface. Mean molecular areas for the series were measured from the isotherms and found to increase as the number of aliphatic chains increased from one to four. No influence of the subphase pH was observed on the isotherms. LB films can be transferred successfully onto different solid surfaces. The LB films were characterized using tapping mode atomic force microscopy (AFM). Bis-, tris-, and tetra-substituted porphyrins were found to be fairly good film-forming amphiphiles, whereas irregular aggregates were seen in the case of the monosubstituted porphyrin amphiphile. Multilayers were also formed with tetra-substituted amphiphiles on mica. Detailed AFM studies of tetra-substituted amphiphiles have been carried out to investigate the effect of preparation procedure and solid substrates on film formation and transfer. The absorption and fluorescence spectra for the amphiphiles in solution and LB films deposited onto mica and glass were recorded, which demonstrated the successful transfer of LB films onto the substrates and provided more information about the arrangement of porphyrin molecules within the LB films. For comparison, self-assembled monolayers (SAMs) and the cast thin films of the amphiphiles were prepared and characterized.

Photopolymerization of monomolecular films with diacetylene bonds on an aqueous subphase

Template-assisted electrochemical deposition of ultrathin films of cadmium sulfide

A study is reported on Langmuir and Langmuir-Blodgett (LB) films obtained by adding different percentages of stearic acid (SA) to poly(3-octylhiophene) (P3OT). Surface pressure - mean molecular area (π - A) isotherms, ultraviolet-visible (UV-Vis) absorption spectrum, atomic force microscope (AFM) and dc electrical measurements have been used for characterization. From π - A isotherms, the area per monomer for condensed films (of SA) increased according to P3OT amount. Good transfer ratios were obtained for LB deposition from P3OT/SA films with higher percentage of SA. LB films revealed linear growth as monitored by UV-Vis absorption spectra. Electrical characterization showed higher conductivity for LB film with 54 wt.% of SA. AFM images of the same film revealed high roughness and presence of large size agglomerates. Finally, interdigitated electrodes (IDE) coated with P3OT/SA LB films showed to be sensitive to the presence of volatile organic compounds.

Thin films of polyimide which exhibit enhanced resistance to moisture have been fabricated using the Langmuir-Blodgett (LB) technique. LB films are ultrathin organic coatings of thicknesses ranging from tens of angstroms to a micrometer, characterized by high molecular density and a high degree of structural order. The adhesion strength of both LB and spin-coated films of several different polyimides, deposited on fused silica, has been measured by subjecting these films to steam or water, followed by a tape test, and monitoring changes in their UV spectra. The results demonstrate that LB films of polyimide adhere better to fused silica than the spin-coated films. In addition, measurements of water vapor transmission rate through Kapton sheet coated by a monolayer of any of the polyimides show that a monolayer forms a moisture barrier, decreasing the water vapor transmission through the Kapton. Based on these results, the electrical performance of polyimide films has been tested at 85 degrees C, 85% humidity, by measuring leakage current between conducting paths under 180-V bias, on samples which are coated with various combinations of LB and spin-coated polyimide films. Composite films of polyimide consisting of an LB monolayer either underneath or on top of a thick, spin-coated film exhibit superior electrical performance to either a spin-coated or LB film by itself. This may be explained by the improved adhesion and/or decreased water permeability of polyimide LB films. >

Adsorption of cyanine dyes and optical properties of phosphatidic acid Langmuir monolayers and Langmuir-Blodgett films

Ultrathin Langmuir-Blodgett film of functionalized single-walled carbon nanotubes for enhanced acetone sensing

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

A new series of organometallic/inorganic hybrid Langmuir-Blodgett (LB) films containing an organometallic gold(i) aryleneethynylene metal complex (OMA) as the p-conjugated organometallic molecule and a polyoxometalate (POM, POM = H3BW12O40, H6As2W18O62, or H6P2Mo18O62) of the Keggin and Dawson structure as the inorganic composite, were prepared and characterized by p–A isotherms, UV-vis absorption spectra, photoluminescence spectra, atomic force microscopy imaging, scanning tunnelling microscopy, and surface photovoltage spectroscopy. Our experimental results indicate that stable, well defined and well organized Langmuir and LB films are formed in pure water and polyoxometalate subphases. There is a quenching effect in the luminescence of the gold(i) complex when it is made into the LB films. The OMA/POM hybrid LB films display strong photovoltage effect in the UV-vis region. The photovoltage response of OMA/H6As2W18O62 can be as high as 3338 µV. OMA/POM monolayer films show good electrical conductivity, and the tunnelling current for a OMA/H3BW12O40 monolayer film amounts to 50 to approximately –100 nA when the voltage is set at ±9 V.

A new family of organometallic/inorganic hybrid Langmuir-Blodgett (LB) films, consisting of organometallic mercury acetylide (OMA) as the π-conjugated organometallic molecule and polyoxometallate (POM, POM = K5BW12O40 or Na5IMo6O24) of the Keggin and Anderson structures as the inorganic composite and docosanoic acid (DA) as the auxiliary film-forming agent, were prepared and well characterized by π–A isotherms, UV-vis absorption and photoluminescence spectra, atomic force microscopy imaging, scanning tunnelling microscopy, and low-angle X-ray diffraction. Our experimental results indicate that stable and well defined monolayer Langmuir and LB films are formed in pure water and POM subphases. There is a quenching effect in the luminescence intensity of the mercury complex when it is made into the LB films due to the enhanced aggregation phenomenon. These alkynylmercury(ii) based LB films exhibit interesting electrical conductivity behaviour, dependent of the characteristics of the POM used. They all reveal decent electrical conductivity, and the tunnelling current can reach ±100 nA when the voltage is set at –5 to +5 V.

Thermal stability of nano-structure in polymeric Langmuir-Blodgett films studied by the energy transfer method

Development of a Schottky barrier diode using molecular network of 1-alkyl-2-(arylazo) imidazole prepared by Langmuir–Blodgett technique

We report a versatile method to confine metal thin films in micro- and nanopatterns using directed self-assembly on the templates fabricated from phase-separated mixed Langmuir-Blodgett (LB) films. The pattern of the mixed LB films can be tuned by adjusting intermolecular interaction between the film-forming molecules in the LB films and by varying the fabrication conditions of the films such as the mixing ratio, subphase temperature, and surface pressure. We use the patterned LB films for templates to confine metal in patterned regions, taking advantage of the difference between the surface free energy of the patterned regions and that of the self-assembled monolayer of the silane coupling agent. Au nanoparticles are confined onto the patterned films as a catalyst for the succeeding Cu electroless deposition. The atomic force microscopic images, Auger electron spectra, and scanning Auger electron maps of a Cu-deposited film show that Cu is selectively deposited on the patterns of phase separation of the original mixed LB films.

Molecular arrangement characteristics of a pyrrole-containing arachidic acid LB film