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Sample records for langmuir-blodgett films based

  1. Effect of bovine serum albumin on the structure and properties of Langmuir Blodgett films based phosphocholine and cholesterol

    NASA Astrophysics Data System (ADS)

    Dubatovka, K. I.; Zhavnerko, G. K.; Agabekov, V. E.

    2014-02-01

    Mono- and bilayer Langmuir-Blodgett films based on phosphocholine and cholesterol and prepared by horizontal and vertical deposition are investigated by atomic force microscopy. It was found that bovine serum albumin (BSA) included at the stage of film formation. At the same time, isolation has a considerable effect on their structure. It was shown that the globular formation of nanostructures with heights of 4-7 nm occurs as a result of transferring lipids to a hydrophobic surface from a subphase containing BSA, indicating the reorganization of monolayers during protein isolation and inclusion in its composition.

  2. Organic field-effect transistors based on Langmuir-Blodgett films of an extended porphyrin analogue - Cyclo[6]pyrrole

    NASA Astrophysics Data System (ADS)

    Xu, Hai; Wang, Ying; Yu, Gui; Xu, Wei; Song, Yabin; Zhang, Deqing; Liu, Yunqi; Zhu, Daoben

    2005-10-01

    Field-effect transistors using cyclo[6]pyrrole as active layers were prepared by Langmuir-Blodgett (LB) method. Cyclo[6]pyrrole is a porphyrin analogue with an extended π-system(22-π-electron). It could form a stable, reproducible monolayer at the air-water interface, which could be transferred onto a substrate with nearly unity transfer ratio and resulted in multilayer structure with the cyclo[6]pyrrole molecules stacking in a face-to-face configuration due to strong intermolecular π-π interactions. An un-optimized device based on this LB films displayed a mobility of 0.014 cm 2 V -1 s -1, which is higher than the highest value of the devices based on typical porphyrins reported.

  3. Second-order nonlinear optical Langmuir-Blodgett films based on a series of azo rare-earth coordination compounds

    SciTech Connect

    Gao, L.H.; Wang, K.Z.; Huang, C.H.

    1995-06-01

    A series of novel azo dyes composed of a lanthanide complex anion and an azo cation, in which strongly electron-donating (dihexadecylamino)phenyl and electron-accepting pyridinium groups are separated by an azo group, was designed as second-order nonlinear optical Langmuir-Blodgett (LB) film materials. The compounds are of good film-forming properties. The values of second-order molecular hyperpolarizability {beta} were determined to be (1.20-3.03) x 10{sup {minus}27} esu, comparable to the largest value known for azo LB materials. The compounds studied may be attactive in the application in future optical devices. 13 refs., 5 figs., 1 tab.

  4. Structural and Other Studies of Langmuir-Blodgett Films.

    NASA Astrophysics Data System (ADS)

    Prakash, Maneesha

    Certain organic materials comprised of ampiphilic molecules will spread on the surface of water to form monolayer films known as Langmuir films. These films can be transferred to solid substrates by dipping the substrates in and out of the water. The films transfer to the substrates monolayer by monolayer and the resulting built-up films are known as Langmuir-Blodgett films. Langmuir-Blodgett films are very regular, with the planes aligned parallel to a high degree. This technique has potential for building structures that may exhibit unusual mechanical, optical, magnetic or electronic properties. Because the proposed uses of Langmuir-Blodgett films depend in a fundamental way on their structure, structural studies of Langmuir-Blodgett films are of great relevance. We have made Langmuir and Langmuir-Blodgett films of simple materials for the purpose of x-ray diffraction characterization. We have looked for differences between the structure of the materials in bulk form as compared with the structure in Langmuir -Blodgett film form. We have studied the in-plane structure of films of the lead salts of various fatty acids using both an external reflection geometry for samples made on glass slide substrates, and a transmission geometry for samples made on thin single crystal mica substrates. Information concerning the in-plane structure and correlations between the layers has been obtained. For the samples made on single crystal mica substrates, epitaxial growth has been observed, whereas on glass substrates the samples have been found to be powders in the plane. An anomalous intensity pattern has been observed for the in-plane and out-of-the -plane peaks. We have proposed a positioning of the hydrocarbon chans that nicely explains the data. We have investigated the conditions for transfer of films on the lipid dipalmitoylphosphatidylcholine, a primary consituent of cell membranes. We have succeeded in forming Langmuir-Blodgett films of this material by the addition of

  5. Langmuir-Blodgett Films of the Metal-Organic Framework MIL-101(Cr): Preparation, Characterization, and CO2 Adsorption Study Using a QCM-Based Setup.

    PubMed

    Benito, Javier; Sorribas, Sara; Lucas, Irene; Coronas, Joaquin; Gascon, Ignacio

    2016-06-29

    This work reports the fabrication and characterization of Langmuir-Blodgett films of nanoparticles (size 51 ± 10 nm) of the metal organic framework MIL-101(Cr). LB film characterization by SEM, UV-vis, GIXRD, and QCM has shown that the addition of 1 wt % of behenic acid to MOF dispersion allows obtaining dense monolayers at the air-water interface that can be deposited onto solid substrates of different nature with transfer ratios close to 1. Moreover, a QCM-based setup has been built and used for the first time to measure CO2 adsorption isotherms at 303 K on MOF LB films, proving that LB films with MOF masses between 1.2 (1 layer) and 2.3 (2 layers) μg can be used to obtain accurate adsorption values at 100 kPa, similar to those obtained by conventional adsorption methods that require much larger MOF quantities (tens of milligrams). PMID:27268426

  6. Study of Langmuir and Langmuir-Blodgett Thin films

    NASA Astrophysics Data System (ADS)

    Goodwin, Ross; Prayaga, Chandra; Wade, Aaron

    Arachidic Acid, Cholesterol, and Stearic Acid thin films were created and studied utilizing the Langmuir method in order to obtain a single molecule or monomolecular layer out of a desired substance at an air-water interface. The phase transitions are observed by measuring the surface pressure vs. area isotherms. Langmuir-Blodgett (LB) films were created on a prepared substrate. The LB film structures were then studied using X-ray Diffraction, and Raman Spectroscopy. UWF Office of Undergraduate Research Project Award, UWF ITEP-Technology Fee Project Award, UWF Quality Enhancement Plan Award.

  7. Hole burning on porphyrin centers in langmuir-blodgett films

    NASA Astrophysics Data System (ADS)

    Bernard, J.; Orrit, M.; Personov, R. I.; Samoilenko, A. D.

    1989-12-01

    Spectral holes were burnt in the excitation spectra of porphyrin centers imbedded in a multilayer assembly of poly-heptyl-cyanoacrylate Langmuir-Blodgett films. We found a strong dependence of the hole width on the burning wavelength and attributed it to energy transfer to lower energy centers in our concentrated sample. The temperature dependence of the hole width was measured between 1.7 and 10 K for two wavelengths and found steeper than in glasses but weaker than in most crystals. The holes were shallower and broader in a monolayer sample.

  8. Photovoltaic Effects of Retinal-Related Materials in Langmuir-Blodgett Films

    NASA Astrophysics Data System (ADS)

    Okazaki, Choichiro

    1998-03-01

    Multilayer films consisting of retinal, retinoic acid, and retinol were fabricated using the Langmuir-Blodgett method. It was found for the first time that these three materials in Langmuir-Blodgett films exhibit different photovoltaic characteristics. To study this difference of photovoltaic characteristics, the surface pressure vs area isotherms of these materials were measured and the dipole moment of the materials were calculated.

  9. Optimization of π-A isotherms to give highly efficient SHG from Langmuir-Blodgett films

    NASA Astrophysics Data System (ADS)

    Schwartz, Hanna; Krief, P.; Becker, J. Y.; Shapiro, Lev; Khodorkovsky, Vladimir; Klug, Jacob T.; Kovalev, E.; Meshulam, Guilia; Berkovic, Garry; Kotler, Zvi; Efrima, Schlomo

    2002-12-01

    Langmuir-Blodgett films have been prepared from amphiphilc molecules containing an indandione-based nonlinear chromophore. Study of the pressure-area (π-A) isotherm enabled us to find optimal conditions for monolayer transfer to a glass substrate. The multilayer films thus formed exhibited strong optical second harmonic generation with a bulk nonlinear co-efficient equal to the ideal value predicted by the product of the chromophore density and its known molecular hyperpolarizability.

  10. Highly conducting graphene sheets and Langmuir-Blodgett films

    NASA Astrophysics Data System (ADS)

    Li, Xiaolin; Zhang, Guangyu; Bai, Xuedong; Sun, Xiaoming; Wang, Xinran; Wang, Enge; Dai, Hongjie

    2008-09-01

    Graphene is an intriguing material with properties that are distinct from those of other graphitic systems. The first samples of pristine graphene were obtained by `peeling off' and epitaxial growth. Recently, the chemical reduction of graphite oxide was used to produce covalently functionalized single-layer graphene oxide. However, chemical approaches for the large-scale production of highly conducting graphene sheets remain elusive. Here, we report that the exfoliation-reintercalation-expansion of graphite can produce high-quality single-layer graphene sheets stably suspended in organic solvents. The graphene sheets exhibit high electrical conductance at room and cryogenic temperatures. Large amounts of graphene sheets in organic solvents are made into large transparent conducting films by Langmuir-Blodgett assembly in a layer-by-layer manner. The chemically derived, high-quality graphene sheets could lead to future scalable graphene devices.

  11. Ferroelectric nanomesa formation from polymer Langmuir-Blodgett films

    NASA Astrophysics Data System (ADS)

    Bai, Mengjun; Ducharme, Stephen

    2004-10-01

    We report the fabrication and characterization of nanoscale ferroelectric structures consisting of disk-shaped nanomesas averaging 8.7±0.4nm in height and 95±22nm in diameter, and nanowells 9.8±3.3nm in depth and 128±37nm in diameter, formed from Langmuir-Blodgett films of vinylidene fluoride copolymers after annealing in the paraelectric phase. The nanomesas retain the ferroelectric properties of the bulk material and so may be suitable for use in high-density nonvolatile random-access memories, acoustic transducer arrays, or infrared imaging arrays. The nanomesa and nanowell patterns may provide useful templates for nanoscale molding or contact-printing.

  12. Photoelectric Properties Based on Electric Field Modulation of Photoinduced Electron Transfer Processes in Flavin-Porphyrin Hetero-type Langmuir-Blodgett Films

    NASA Astrophysics Data System (ADS)

    Isoda, Satoru; Hanazato, Yoshio; Ueyama, Satoshi; Nishikawa, Satoshi; Akiyama, Kouich

    2004-05-01

    Metal-insulator-meal devices composed of flavin-porphyrin hetero-type Langmuir-Blodgett films showed highly efficient photoelectric properties mainly attributable to the fast charge separation process at a molecular heterojunction (MHJ) between flavin and porphyrin. The photoelectric properties of the MHJ devices showed different characteristics depending on the redox state of the central metal of porphyrin, i.e., Ru(III) or Ru(II). The rectifying behavior of the photocurrent was observed for the Ru(III)-MHJ device, whereas the Ru(II)-MHJ device did not show the rectifying behavior. We concluded that the rectifying behavior was mainly controlled by the electric field dependence of the charge recombination process. Furthermore, a bell-shaped photocurrent-voltage curve was observed for the Ru(II)-MHJ device. The mechanism underlying the negative resistance might be based on the electric field dependence of the charge shift process in flavin monolayers controlled by the inverted region mechanism of the Marcus electron transfer theory.

  13. Photophysics of rhodamine dimers in Langmuir-Blodgett films

    NASA Astrophysics Data System (ADS)

    Vuorimaa, E.; Ikonen, M.; Lemmetyinen, H.

    1994-11-01

    Temperature dependent dimerization processes of octadecylrhodamine B (RB) and octadecylrhodamine 6G (R6G) in Langmuir-Blodgett (LB) films were studied by steady-state and time-resolved fluorescence methods. The geometry of the dimers in LB films is equal for both dyes, but different to the geometry of the dimers found in solutions. The sandwich-type dimers with lifetimes of 710 ps for RB and 620 ps for R6G have their fluorescence maxima at 635 and 620 nm for RB and R6G, respectively. The dimer with an oblique geometry has its fluorescence maximum at 675 nm for both dyes, and its fluorescence lifetime is 4.6 ns for RB and 4.9 ns for R6G. The proportion of fluorescent dimers increases with decreasing temperature, when the nonfluorescent H dimers reorganize to fluorescent J dimers. The activation energy for this temperature induced process is 1.4 and 2.6 kJ mol -1 for RB and R6G, respectively.

  14. Photophysics of rhodamine dimers in Langmuir-Blodgett films

    NASA Astrophysics Data System (ADS)

    Vuorimaa, E.; Ikonen, M.; Lemmetyinen, H.

    1994-11-01

    Temperature dependent dimerization processes of octadecylrhodamine B (RB) and octadecylrhodamine 6G (R6G) in Langmuir-Blodgett (LB) films were studied by steady-state and time-resolved fluorescence methods. The geometry of the dimers in LB films is equal for both dyes, but different to the geometry of the dimers found in solutions. The sandwich-type dimers with lifetimes of 710 ps for RB and 620 ps for R6G have their fluorescence maxima at 635 and 620 nm for RB and R6G, respectively. The dimer with an oblique geometry has its fluorescence maximum at 675 nm for both dyes, and its fluorescence lifetime is 4.6 ns for RB and 4.9 ns for R6G. The proportion of fluorescent dimers increases with decreasing temperature, when the nonfluorescent H dimers reorganize to fluorescent J dimers. The activation energy for this temperature induced process is 1.4 and 2.6 kJ/mol for RB and R6G, respectively.

  15. Preparation, Characterization and Microelectronic Applications of Langmuir Blodgett Films.

    NASA Astrophysics Data System (ADS)

    Maccagno, Pierre Luigi

    This thesis evaluates the use of ultrathin Langmuir Blodgett (LB) films in semiconductor technology. Three different applications are explored: electron-beam resists, dielectric films, and tunneling dimension insulators. Deposition processes are established for LB films of cadmium brassidate, and Poly-Methyl-Methacrylate (PMMA). Film are characterized on the water subphase of the LB trough with a Wilhelmy balance and on various substrates with X-ray diffraction, Grazing Incidence Reflection Fourier Transform Infrared Spectroscopy (GIR FTIR), Scanning Electron Microscopy (SEM), Ellipsometry, Scanning Tunnelling Microscopy (STM) and electrical conduction and admittance measurements. Ultrathin PMMA LB films are shown to behave as excellent e-beam resists. PMMA LB films 10.5nm thick (13 monolayers) have pinhole densities (10/cm^2 ) three orders of magnitude smaller than those spin cast films of the same thickness. Furthermore, the same PMMA LB film thickness is able to protect a 50nm Cr underlayer for well over 13 minutes from chemical etchants. Low energy e-beam exposure of ultrathin PMMA LB films was demonstrated with the STM. The advantages of the STM as a lithography tool is that small diameter (<50nm) low energy (20eV to 100eV) e-beams may be used with LB resist films to obtain submicron resolution and reduced proximity effects due to less scattering of electrons within the ultrathin LB resist. Electrical conduction and admittance of metal/insulator/metal capacitors are studied for various thickness LB PMMA films, and electrode materials. Capacitors with Au electrodes were shorted due to pinholes in the LB film. Shorts were not observed with Al electrodes as a result of the native alumina. The thickness and dielectric constant of PMMA monolayers and Al_2O_3 are obtained. Diverse conduction mechanisms are proposed for Al electrode capacitors separated by no PMMA film; one monolayer; and three or more monolayers. Electrical properties of Au/PMMA/n-Si diodes with

  16. Switching dynamics of ferroelectric Langmuir-Blodgett copolymer films

    NASA Astrophysics Data System (ADS)

    Othon, Christina M.

    Ferroelectric switching dynamics in ferroelectric copolymer films of poly(vinylidene fluoride-trifluoroethylene) can vary over nine orders of magnitude; 100 seconds for the slowest ultrathin (1-50 nm) Langmuir-Blodgett films to 100 ns for the fastest polymorphous spin-coat films (˜50 mum thick). These ultra-thin films share many of the same ferroelectric properties of bulk films such as polarization, phase transition temperatures, crystalline structure, and high electrical resistance (>10 MO). The slow nature of switching in ultrathin films is believed to be caused by the intrinsic nature of the switching. The polarization is no longer switching by nucleation and domain wall growth enabled by defects and nanostructures in the polymorphous samples. We investigate this hypothesis by the introduction of defects in the form of nucleation sites and/or grain boundaries by electron irradiation, production of individual ferroelectric nano-crystals, and the introduction of domain wall boundaries through Direct Laser Interference Patterning (DLIP). Electron-irradiation was performed for a large range of doses from 16 to 110 Mrad, on ultra thin films 36 nm thick. It was thought that the defects introduced by electron irradiation could act as nucleation sites, promoting faster switching. However, the primary effect of electron irradiation was the decrease in crystallinity and therefore the fraction of ferroelectric material. Even for lower doses the increase in switching speed was negligible in comparison to the loss of ferroelectricity. The introduction of false domain walls through laser annealing was used to produce more complex and controlled shapes than given by the nanomesas. We investigated patterning by continuous-wave direct write, and by pulsed laser irradiation DLIP. We have demonstrated the ability to pattern films reversibly into films of ferroelectric regions surrounded by paraelectric phase, as well as irreversibly ferroelectric regions surrounded by melted

  17. Study of nonlinear optical properties of multilayer Langmuir-Blodgett films containing bacteriorhodopsin.

    PubMed

    Barmenkov Yu, O; Kir'yanov, A V; Starodumov, A N; Maslyanitsyn, I A; Shigorin, V D; Lemmetyinen, H

    2000-08-01

    Multilayer oriented Langmuir-Blodgett films of bacteriorhodopsin were prepared and their nonlinear optical properties, including second harmonic generation and photoresponse at a two phase-modulated beams mixing, were investigated. The nonlinear component of refractive index of the films was measured. PMID:10946566

  18. Investigation on single walled carbon nanotube thin films deposited by Langmuir Blodgett method

    SciTech Connect

    Vishalli, Dharamvir, Keya; Kaur, Ramneek; Raina, K. K.

    2015-05-15

    Langmuir Blodgett is a technique to deposit a homogeneous film with a fine control over thickness and molecular organization. Thin films of functionalized SWCNTs have been prepared by Langmuir Blodgett method. The good surface spreading properties of SWCNTs at air/water interface are indicated by surface pressure-area isotherm and the monolayer formed on water surface is transferred onto the quartz substrate by vertical dipping. A multilayer film is thus obtained in a layer by layer manner. The film is characterized by Atomic Force Microscope (AFM), UV-Vis-NIR spectroscopy and FTIR.AFM shows the surface morphology of the deposited film. UV-Vis-NIR spectroscopy shows the characteristic peaks of semiconducting SWCNTs. The uniformity of LB film can be used further in understanding the optical and electrical behavior of these materials.

  19. Thermochromism and optical absorption in Langmuir-Blodgett films of alkyl-substituted polythiophenes

    NASA Astrophysics Data System (ADS)

    Ahlskog, M.; Paloheimo, J.; Stubb, H.; Dyreklev, P.; Fahlman, M.; Inganas, O.; Andersson, M. R.

    1994-07-01

    Thermochromism and optical absorption in mono- and multilayers of Langmuir-Blodgett films of poly(3-alkylthiophenes), poly(3-octyl-2,2-bithiophene), and poly(3-octyl-2,2;5,2(double prime)-terthiophene) were studied. In sparsely alkylated polythiophenes the magnitude of the thermochromic shift was smaller than in poly(3-alkylthiophenes) and roughly proportional to the sidechain concentration. Results of valence Effective Hamiltonian calculations were compared with the experimental results of thermochromism. A vibronic structure was found in the absorption spectra of Langmuir-Blodgett films at room temperature. The vibronic splitting in poly(3-hexylthiophene) was approximately 0.18 eV as previously has been observed in poly(3-alkylthiophenes) but in poly(3-octyl-2,2;5,2(double prime)-terthiophene) it was 0.20-0.25 eV. The vibronic peaks stay approximately at constant energies and vanish at elevated temperatures.

  20. Effects of Langmuir-Blodgett-film gas sensors with integrated optical interferometers

    NASA Astrophysics Data System (ADS)

    Fushen, Chen; Yunqi, Liu; Yu, Xu; Qu, Liang

    1996-10-01

    Novel Langmuir-Blodgett-film toxic-gas sensors that have a Ti:LiNbO 3 integrated optical Mach-Zehnder interferometer structure are experimentally investigated. The gas-sensing properties of the sensors are obtained for NO 2, Cl2, NH3, and H2S by means of the detection of optical output changes. All the optical connections are made with optical fiber pigtails.

  1. Surface-acoustic-wave device incorporating conducting Langmuir-Blodgett films

    NASA Astrophysics Data System (ADS)

    Holcroft, B.; Roberts, G. G.; Barraud, A.; Richard, J.

    1987-04-01

    Surface-acoustic-wave devices incorporating conducting Langmuir-Blodgett films are reported for the first time. Excellent characteristics have been obtained using a mixed valence charge transfer salt of a substituted pyridinium tetracyanoquinodimethane. The control afforded by the deposition technique has enabled the fractional change in surface wave velocity due to the electrical effects to be distinguished from those due to mass loading. The resistivity of the organic surface layer is measured to be 2 ohm-cm.

  2. Langmuir-Blodgett films of micron-sized organic and inorganic colloids.

    PubMed

    Reculusa, Stéphane; Perrier-Cornet, Romain; Agricole, Béatrice; Héroguez, Valérie; Buffeteau, Thierry; Ravaine, Serge

    2007-12-28

    Multilayered films starting with silica or polymer particles in the micron-size range have been prepared using the Langmuir-Blodgett technique. The polymer particles made of highly cross-linked cores and hydrophilic shells were elaborated through a precipitation polymerization method that allows formation of particles with a low polydispersity. The influence of the surface function, the differences between organic and inorganic systems, and the characterization of these materials by means of reflectance infrared spectroscopy are also discussed. PMID:18060168

  3. Enhanced sheet conductivity of Langmuir-Blodgett assembled graphene thin films by chemical doping

    NASA Astrophysics Data System (ADS)

    Matković, Aleksandar; Milošević, Ivana; Milićević, Marijana; Tomašević-Ilić, Tijana; Pešić, Jelena; Musić, Milenko; Spasenović, Marko; Jovanović, Djordje; Vasić, Borislav; Deeks, Christopher; Panajotović, Radmila; Belić, Milivoj R.; Gajić, Radoš

    2016-03-01

    We demonstrate a facile fabrication technique for highly conductive and transparent thin graphene films. Sheet conductivity of Langmuir-Blodgett assembled multi-layer graphene films is enhanced through doping with nitric acid, leading to a fivefold improvement while retaining the same transparency as un-doped films. Sheet resistivity of such chemically improved films reaches 10 {{k}}{{Ω }}/\\square , with optical transmittance 78% in the visible. When the films are encapsulated, the enhanced sheet conductivity effect is stable in time. In addition, stacking of multiple layers, as well as the dependence of the sheet resistivity upon axial strain have been investigated.

  4. Langmuir-Blodgett films of conjugated polymers and their applications on optoelectronic devices

    NASA Astrophysics Data System (ADS)

    Tseng, Chin-Jen

    1998-11-01

    Langmuir-Blodgett technique has been well known to produce ultra-thin films with controlled thickness and preferred orientation. In this research, this technique was used to produce conjugated polymer films and apply these films on optoelectronic devices such as the alignment layers for twisted nematic liquid crystal displays (TNLCDs) and the luminescent materials for light emitting diodes (LEDs). In the twisted nematic liquid crystal displays, oriented Langmuir-Blodgett films behave as alignment layers and provide required pretilt orientation. Poly(para- phenylene) (PPP) ultra thin films prepared by Langmuir- Blodgett technique were applied as homogeneous alignment layers. 10,12-nonacosadiynoic acid (16-8 DA) Langmuir- Blodgett films were applied as homeotropic alignment layers. In the light emitting diode, oriented PPP LB films perform as charge transfer complexes and emit polarized light without external polarizer. A precursor method was developed for the preparation of these PPP LB films. A salt (briefed as PDCP-NIII) formed with poly(2,5-dicarboxyl-1,4-phenelene) (PDCP) and o,o',o' - Trihexadecanoyltriethanolamine (NIII) was used as the precursor materials and transformed into PPP LB films via pyrolysis. Pretilt angle of 0.2o was measured via crystal rotation method on the antiparallel liquid crystal cells with PPP LB films as the homogeneous alignment layers. 10,12-nonacosadiynoic acid was synthesized via Cadiot- chodkiewicz reaction developed by Steven Walsh. Lithium salts of 16-8DA LB films were polymerized by UV lamp and used to behave as homeotropic alignment layers. Thermodynamic properties of these Langmuir films at the air-water interface such as isotherms and creep test were studied. Surface morphology was studied with Brewster Angle Microscopy (BAM) and surface rheology was studied with the Surface Light Scattering Spectroscopy (SLSS). These LB films were characterized by UV-Visible Spectroscopy (UV-Vis), Fourier Transform Infrared Spectroscopy (FTIR

  5. Synthesis of novel electrically conducting polymers: Potential conducting Langmuir-Blodgett films and conducting polymers on defined surfaces

    NASA Technical Reports Server (NTRS)

    Zimmer, Hans

    1993-01-01

    Based on previous results involving thiophene derived electrically conducting polymers in which it was shown that thiophene, 3-substituted thiophenes, furans, and certain oligomers of these compounds showed electrical conductivity after polymerization. The conductivity was in the order of up to 500 S/cm. In addition, these polymers showed conductivity without being doped and most of all they were practically inert toward ambient conditions. They even could be used in aqueous media. With these findings as a guide, a number of 3-long-chain-substituted thiophenes and 1-substituted-3-long-chain substituted pyrrols were synthesized as monomers for potential polymeric electrically conducting Langmuir-Blodgett films.

  6. Formation of Electrically Conducting Polypyrrole Fine Lines in Arachidic Acid Langmuir-Blodgett Films

    NASA Astrophysics Data System (ADS)

    Sha, Seimei; Hirata, Nobuaki; Ikezaki, Kazuo; Kaihatu, Minoru; Moriizumi, Toyosaka

    1995-07-01

    A new method is proposed for preparing electrically conducting fine lines in Langmuir-Blodgett films: during transference of arachidic acid L film containing pyrrole monomers to an indium-tin-oxide (ITO)-coated glass substrate, a voltage was applied between the ITO and the platinum counterelectrode dipped in the water subphase. From microscopic observations and conductivity measurements, it was confirmed that conducting filaments of polypyrrole were formed by this new method along the contact line between the substrate and the water surface by electrochemical polymerization of pyrrole monomers in an arachidic L film.

  7. Influence of magnetic field on delayed fluorescence of coumarin dye in Langmuir-Blodgett films

    NASA Astrophysics Data System (ADS)

    Ibrayev, N. Kh.; Afanasyev, D. A.

    2012-06-01

    The triplet-triplet annihilation (TTA) was studied in mixed Langmuir-Blodgett films of 7-decyloxy-3 (4'-ethoxyphenyl)-coumarin molecules and palmitic acid. The thermal activation of the TTA process is observed due to the inhomogeneous broadening of triplet energy levels. Modulation of the TTA rate constant in the external magnetic field for the multilayer films shows the dependence that is characteristic of crystals. Only negative magnetic effect is observed for the monolayers. Time dependence of the magnetic effect in conditions of high rate constant of triplet excitons migration is connected with the dominating contribution of ordered clusters or randomly oriented molecule clusters into the TTA process.

  8. Supramolecular structure formation of Langmuir-Blodgett films of comblike precursor and polyimide

    SciTech Connect

    Goloudina, S. I. Luchinin, V. V.; Rozanov, V. V.; Pasyuta, V. M.; Gofman, I. V.; Sklizkova, V. P.; Kudryavtsev, V. V.

    2013-03-15

    The surface structure of Langmuir-Blodgett films of a comblike polyimide precursor-a rigid-chain polyamic acid alkylamine salt bearing multichains of tertiary amine-and films of the corresponding polyimide were studied by atomic force microscopy (AFM). An analysis of the images of the surface of three-layer films revealed a domain structure. It was found that the Langmuir-Blodgett film formation of the precursor occurs as a result of the layer-by-layer deposition of two-dimensional domains (composed of polyamic acid salt molecules on the water surface) onto a substrate. The formation of domains in a monolayer is associated with the chemical structure of the precursor, to be more precise, with the rigidity of the main chain and the presence of closely spaced aliphatic side chains in the polymer chain, whose total cross-section area is close to the surface area of the projection onto the plane of the repeating unit of the main chain. Polyimide films inherit the domain structure of the precursor films; the inhomogeneity of the film thickness substantially decreases, whereas the domain size and character of their distribution in the film remain unchanged.

  9. Bulk organisation and alignment in Langmuir and Langmuir-Blodgett films of tetrachloroperylene tetracarboxylic acid esters

    NASA Astrophysics Data System (ADS)

    Modlińska, Anna; Filipowicz, Marek; Martyński, Tomasz

    2016-12-01

    Perylene derivatives with chlorine atoms attached at the bay position to the dye core are expected to affect organisation and tendency to aggregation in Langmuir and Langmuir-Blodgett (LB) films. Therefore, newly synthesized core-twisted homologous series of tetrachloroperylene tetracarboxylic acid esters with n = 1,4,5,6,9 carbon atoms in terminal alkyl chains were studied. Phase transitions and crystalline structures were specified by differential scanning calorimetry (DSC) and single crystal X-ray diffraction (XRD), respectively. Intermolecular interactions and organisation of the dyes in monomolecular films were investigated by means of Brewster angle microscope (BAM), UV-Vis absorption and emission spectroscopy, fluorescence microscopy and atomic force microscopy (AFM). The dyes investigated do not form thermotropic mesogenic phases in bulk. The crystalline triclinic elementary cell with P-1 symmetry is revealed from X-ray experiments. In Langmuir and Langmuir-Blodgett films molecular tilted head-on alignment is postulated. Spectroscopic research confirmed by AFM texture images of the LB films show that in the Langmuir and LB films the dyes, depending on length of terminal chains, have a tendency to create H or I molecular aggregates. The impact of the twisted core on the molecular behavior in a bulk and thin films is discussed.

  10. Langmuir-Blodgett film of hydrophobin protein from Pleurotus ostreatus at the air-water interface.

    PubMed

    Houmadi, S; Ciuchi, F; De Santo, M P; De Stefano, L; Rea, I; Giardina, P; Armenante, A; Lacaze, E; Giocondo, M

    2008-11-18

    We present results concerning the formation of Langmuir-Blodgett (LB) films of a class I hydrophobin from Pleurotus ostreatus at the air-water interface, and their structure as Langmuir-Blodgett (LB) films when deposited on silicon substrates. LB films of the hydrophobin were investigated by atomic force microscopy (AFM). We observed that the compressed film at the air-water interface exhibits a molecular depletion even at low surface pressure. In order to estimate the surface molecular concentration, we fit the experimental isotherm with Volmer's equation describing the equation of state for molecular monolayers. We found that about (1)/ 10 of the molecules contribute to the surface film formation. When transferred on silicon substrates, compact and uniform monomolecular layers about 2.5 nm thick, comparable to a typical molecular size, were observed. The monolayers coexist with protein aggregates, under the typical rodlet form with a uniform thickness of about 5.0 nm. The observed rodlets appear to be a hydrophilic bilayer and can then be responsible for the surface molecular depletion. PMID:18925762

  11. Optical storage in azobenzene-containing epoxy polymers processed as Langmuir Blodgett films.

    PubMed

    Fernández, Raquel; Mondragon, Iñaki; Sanfelice, Rafaela C; Pavinatto, Felippe J; Oliveira, Osvaldo N; Oyanguren, Patricia; Galante, María J

    2013-04-01

    In this study, azocopolymers containing different main-chain segments have been synthesized with diglycidyl ether of bisphenol A (DGEBA, DER 332, n=0.03) and the azochromophore Disperse Orange 3 (DO3) cured with two monoamines, viz. benzylamine (BA) and m-toluidine (MT). The photoinduced birefringence was investigated in films produced with these azopolymers using the spin coating (SC) and Langmuir Blodgett (LB) techniques. In the LB films, birefringence increased with the content of azochromophore and the film thickness, as expected. The nanostructured nature of the LB films led to an enhanced birefringence and faster dynamics in the writing process, compared to the SC films. In summary, the combination of azocopolymers and the LB method may allow materials with tuned properties for various optical applications, including in biological systems were photoisomerization may be used to trigger actions such as drug delivery. PMID:23827588

  12. Langmuir-Blodgett films of a pyrrole and ferrocene mixed surfactant system

    SciTech Connect

    Samuelson, L.; Rahman, A.K.M.; Clough, S.; Tripathy, S.; Hale, P.D.; Inagaki, T.; Skotheim, T.A.; Okamoto, Y. . Dept. of Chemistry; Brookhaven National Lab., Upton, NY; Polytechnic Univ., Brooklyn, NY . Dept. of Chemistry)

    1989-01-01

    The Langmuir-Blodgett technique was used to study the molecular organization of a mixed 3-hexadecyl pyrrole (3HDP) and ferrocene-derivatized pyrrole (Fc-Py) surfactant system. It has been determined that stable monolayer films of the mixed system could be formed at the air-water interface. The growth and assembly process led to polypyrrole 2-D lattices with heretofore unsurpassed order. In fact, the process of template polymerization, it appears, leads to a new crystal phase for the polypyrrole component of the thin film structure. Various monolayer and multilayer films were prepared on platinum coated substrates for surface spectroscopic characterization. Near Edge X-Ray Absorption Fine Structure (NEXAFS) studies revealed that highly ordered multilayer structures are being formed. Electrochemical studies have been initiated to determine the feasibility of these films in molecular electronic device applications. 13 refs., 6 figs., 1 tab.

  13. Optoelectronic properties of graphene thin films deposited by a Langmuir-Blodgett assembly

    NASA Astrophysics Data System (ADS)

    Kim, Hokwon; Mattevi, Cecilia; Kim, Hyun Jun; Mittal, Anudha; Mkhoyan, K. Andre; Riman, Richard E.; Chhowalla, Manish

    2013-11-01

    Large area thin films of few-layered unfunctionalized graphene platelets are developed with fine control over the thickness. The thin films are obtained by a Langmuir-Blodgett assembly at the interface of graphene solution in N-methyl-2-pyrrolidone (NMP) and water, and their optoelectronic properties and conduction mechanism are investigated in relation to lateral flake size and thin film thickness. The electrical conductivity and carrier mobility are affected by the flake size (200 nm to 1 μm) and by the packing of the nanostructure platelet network. General effective medium theory is used to explain the thickness dependent conductivity and to determine the percolation threshold film thickness which was found to be about 10 nm (at a volume fraction of ~39%) for a Langmuir-Blodgett film of an average platelet lateral size of 170 +/- 40 nm. The electronic behaviour of the material shows more similarities with polycrystalline turbostratic graphite than thin films of reduced graphene oxide, carbon nanotubes, or disordered conducting polymers. While in these systems the conduction mechanism is often dominated by the presence of an energy barrier between conductive and non-conductive regions in the network, in the exfoliated graphene networks the conduction mechanism can be explained by the simple two-band model which is characteristic of polycrystalline graphite.Large area thin films of few-layered unfunctionalized graphene platelets are developed with fine control over the thickness. The thin films are obtained by a Langmuir-Blodgett assembly at the interface of graphene solution in N-methyl-2-pyrrolidone (NMP) and water, and their optoelectronic properties and conduction mechanism are investigated in relation to lateral flake size and thin film thickness. The electrical conductivity and carrier mobility are affected by the flake size (200 nm to 1 μm) and by the packing of the nanostructure platelet network. General effective medium theory is used to explain the

  14. Preparation of Lead Titanate Ultrathin Film Using Langmuir-Blodgett Film as Precursor

    NASA Astrophysics Data System (ADS)

    Sugai, Hiroshi; Iijima, Takashi; Masumoto, Hiroshi

    1999-09-01

    The Langmuir-Blodgett (LB) method is investigated as a process for the fabrication of ultrathin films of oxides such as lead titanate. LB film was fabricated by depositing a monolayer prepared from a fatty acid such as stearic acid (C17H35COOH) and a subphase containing lead chloride (PbCl2) and titanium potassium oxalate (K2TiO (C2O4)2). For converting from an LB film containing lead and titanium to an inorganic film, ultraviolet/ozone (UVO) treatment was applied. Subsequent thermal annealing resulted in a dense oxide ultrathin film. The crystallographic orientation of lead titanate thin films was controlled by conditions of precursor preparation such as the molecular ratio of lead and titanium, pH value and/or temperature in the subphase and the surface pressure. An X-ray diffraction pattern of the thin film indicating a well-defined perovskite structure was observed. Moreover, the results demonstrated the potential application of LB deposition for controlling the crystallographic orientation of lead titanate ultrathin films, particularly in the (111) or (101)(110) planes.

  15. Electronic structure of nitrogen square planar copper complexes in Langmuir-Blodgett films

    SciTech Connect

    Carniato, S.; Roulet, H.; Dufour, G.

    1992-08-20

    The Cu 2p and N is X-ray photoelectron spectra of nitrogen square planar copper(II) complex, derived from copper phthalocyanine and especially substituted to produce Langmuir-Blodgett (LB) films, are reported and compared with those of commercial copper phthalocyanine (CuPc) and selected porphyrin compounds. Although the copper atom is found primarily in the Cu(II) state, the authors observe the presence of the reduced Cu(I) form, with a great variety of relative intensities, because of a concomitant ability to reduction. In contrast, in the LB films, the copper atom remains in the Cu(II) state. The authors discuss this different behavior in terms of the reduction degree of the molecule, the localization of the additional electrons on the metal or the macrocycle, and a different nitrogen geometry around copper. 25 refs., 4 figs., 1 tab.

  16. Second-harmonic generation in mixed stilbazium salt/arachidic acid Langmuir-Blodgett films

    NASA Astrophysics Data System (ADS)

    Liu, Liying; Zheng, Jiabiao; Wang, Wencheng; Zhang, Zhiming; Tao, Fenggang; Xu, Linxiao; Hu, Jiacong

    1992-10-01

    A stilbazium salt was synthesized and its second-order molecular polarizability was deduced to be 1.2×10 -27 esu. Measurements of second-harmonic generation and small-angle X-ray diffraction on Langmuir-Blodgett films of the stilbazium salt/arachide acid mixtures showed that the mixed compounds with molar ratios of 1:2 and 1:5 could form multilayers with large second- order optical nonlinearity. Second harmonic generation study on the alternate multilayers of stilbazium salt/arachide acid and arachidic acid showed that the second-harmonic signals were increasing monotonously up to 80 bilayers, but the increment was lower than the value predicted theoretically by the quadratic law. Possible reasons are discussed.

  17. Inhomogeneous translational diffusion of monoclonal antibodies on phospholipid Langmuir-Blodgett films.

    PubMed Central

    Wright, L L; Palmer, A G; Thompson, N L

    1988-01-01

    The translational mobility of fluorescent-labeled monoclonal antibodies specifically bound to supported phospholipid bilayers containing hapten-conjugated phospholipids has been measured as a function of the surface concentration of bound antibodies using fluorescence recovery after photobleaching. Fluorescence recovery curves are fit well by a model that assumes the presence of two populations of antibodies with different lateral diffusion coefficients. The larger diffusion coefficient equals 3.5 x 10(-9) cm2/s, the smaller diffusion coefficient ranges from 1.5 x 10(-9) cm2/s to 2.5 x 10(-10) cm2/s, and the fractional fluorescence recovery associated with the smaller coefficient increases from approximately 0 to approximately 0.7 with increasing concentration of bound antibody. These results suggest that complexes of haptenated phospholipids and antibodies in phospholipid Langmuir-Blodgett films form clusters or domains in a concentration-dependent fashion. PMID:3207834

  18. Electronic Properties and Langmuir-Blodgett Films of Discotic Organic Semiconductors

    NASA Astrophysics Data System (ADS)

    Ahmida, Mohamed M.

    Columnar mesophases of discotic liquid crystals (DLCs) are an emerging class of organic semiconductors that have several advantages over widely applied organic semiconductors based on conductive polymers and glasses of small molecules, such as high charge carrier mobility of >1 cm2 V-1s-1 and charge carrier diffusion length of 70 nm. Two important deficiencies that hamper the application of DLCs in organic electronic devices are an insufficient control over their frontier orbital energies and the alignment of their columnar stacks. This dissertation reports a first systematic study on the control of frontier orbital energies, along with other electronic properties, by alterations of molecular structure and two new approaches towards monomolecular alignment layers for columnar discotic mesophases. Solution cyclic voltammetry and UV-Vis absorption spectroscopy as well as computational studies at the DFT level were employed to measure and predict electronic properties of DLCs based on triphenylene and phthalocyanine derivatives (Chapters 2-4). These are the first reported studies that systematically compare changes of the molecular structures of DLCs with changes of their frontier orbital energies and mesomorphism. Our comparative studies on electron acceptor DLCs provide the first ranking of electron withdrawing groups based on their potential of lowering the energy of the lowest unoccupied molecular orbital (LUMO) of the discotic core. Unexpected was the large dependence of the frontier orbital energies on the symmetry of the substitution patterns. Symmetric patterns give higher LUMO energies mainly because of degenerated frontier orbitals. Objective of the investigation of octa-carboxylic acid and octa-alcohol substituted tetraazaporphyrin (TAP) dyes in Langmuir-Blodgett (LB) monolayers (Chapter 5) is the generation of self-assembled monolayers with the elusive face-on orientation of the TAP macrocycles. Monolayers are formed only by the TAP derivatives with the

  19. Preparation of Lead Titanate Thin Films Using Langmuir-Blodgett Method

    NASA Astrophysics Data System (ADS)

    Sugai, Hiroshi; Hoshi, Nobuo; Iijima, Takashi; Masumoto, Hiroshi

    1998-09-01

    The Langmuir-Blodgett (LB) method is investigated as a process in thefabrication of ferroelectric thin films such as lead titanate. LB film was fabricated bydepositing a monolayer prepared by stearic acid (C17H35COOH), lead chlorides (PbCl2)and titanium bis(ammonium lactato)([CH3CH(O )CO2NH4]2Ti(OH)2). As a conversionprocess from the LB film containing lead and titanium to an inorganic film, ultraviolet/ozone (UVO) treatment was found to be extremely applicable at a rate of about 4 min per monolayer. Subsequent rapid thermal annealing (RTA) resulted in a dense oxidethin film. The thickness of an oxide thin film converted from the LB film consisting of301 layers was approximately 30 nm. Hence, it is considered that approximately 0.1 nmof the oxide layer is equivalent to the thickness of the film deposited by each cycle.From an X-ray diffraction pattern of the oxide specimen, a well-defined perovskitepeak structure was observed. These results demonstrate the potential application of LBdeposition for the preparation of an inorganic oxide film such as lead titanate.

  20. Langmuir-Blodgett (LB) films of tris(2-phenylpyridine)iridium(III)

    SciTech Connect

    Samha, H.A.; Martinez, T.J.; De Armond, M.K. ); Garces, F.O.; Watts, R.J. )

    1993-05-26

    Monolayer and multilayer Langmuir-Blodgett (LB) films of the neutral hydrophobic Ir(ppy)[sub 3] (1) (ppy = 2-Phenylpyridine) have been produced on the water surface when mixed with a fatty acid (stearic acid). The molecular area of the complex in the close-packed film is 55 [angstrom][sup 2]. The homogeneity of the films was verified by measuring the absorbance vs the number of layers on a substrate (quartz) and also by comparing the relative emission intensity of multilayer mixed LB films of different molar ratios. The films are stable and capable of being transferred from the water surface onto a substrate with a transfer ratio very close to unity. A blue shift in the maxima of the emission, as the complex concentration is decreased, occurs for both room-temperature fluid solution and a rigid matrix at 77 K. In-trough cyclic voltammetry (horizontal touch) of the mixed film is also reported and compared to the cyclic voltammetry of a film transferred to an indium-tin oxide plate (vertical dip).

  1. Supramolecular architecture in Langmuir and Langmuir-Blodgett films incorporating a chiral azobenzene.

    PubMed

    Haro, Marta; del Barrio, Jesús; Villares, Ana; Oriol, Luis; Cea, Pilar; López, M Carmen

    2008-09-16

    This article describes the synthesis and fabrication of Langmuir and Langmuir-Blodgett (LB) films incorporating a chiral azobenzene derivative, namely, ( S)-4- sec-butyloxy-4'-[5''-(methyloxycarbonyl)pentyl-1''-oxy]azobenzene, abbreviated as AZO-C4(S). Appropriate conditions for the fabrication of monolayers of AZO-C4(S) at the air-water interface have been established, and the resulting Langmuir films have been characterized by a combination of surface pressure and surface potential versus area per molecule isotherms, Brewster angle microscopy, and UV-vis reflection spectroscopy. The results indicate the formation of an ordered trilayer at the air-water interface with UV-vis reflection spectroscopy showing a new supramolecular architecture for multilayered films as well as the formation of J aggregates. Films were transferred onto solid substrates, with AFM revealing well-ordered multilayered films without 3D defects. Infrared and UV-vis absorption spectroscopy indicate that the supramolecular architecture may be favored by the formation of H bonds between acid groups in neighboring layers and pi-pi intermolecular interactions. Circular dichroism spectra reveal chiro-optical activity in multilayered LB films. PMID:18686982

  2. Preparation of ordered films containing a phenylene ethynylene oligomer by the Langmuir-Blodgett technique.

    PubMed

    Villares, Ana; Lydon, Donocadh P; Porrès, Laurent; Beeby, Andrew; Low, Paul J; Cea, Pilar; Royo, Fèlix M

    2007-06-28

    This paper reports the fabrication and characterization of Langmuir and Langmuir-Blodgett (LB) films incorporating an oligo(phenylene-ethynylene) (OPE) derivative, namely, 4-[4-(4-hexyloxyphenylethynyl)-phenylethynyl]-benzoic acid (HBPEB). Conditions appropriate for deposition of monolayers of HBPEB at the air-water interface have been established and the resulting Langmuir films characterized by a combination of surface pressure and surface potential versus area per molecule isotherms, Brewster angle microscopy, and ultraviolet reflection spectroscopy. The Langmuir films are readily transferred onto solid substrates, and one-layer LB films transferred at several surface pressures onto mica substrates have been analyzed by means of atomic force microscopy, from which it can be concluded that 14 mN/m is an optimum surface pressure of transference, giving well-ordered homogeneous films without three-dimensional defects and a low surface roughness. The optical and emissive properties of the LB films have been determined with significant blue-shifted absorption spectra indicating formation of two-dimensional H aggregates and a Stokes shift illustrating the effects of the solid-like environment on the molecular chromophore. PMID:17552562

  3. J-aggregation and its characterization in Langmuir-Blodgett films of merocyanine dyes.

    PubMed

    Kuroda, Shin-ichi

    2004-12-13

    Langmuir-Blodgett (LB) films are constructed by successively transferring monomolecular layers formed at the air-water interface onto solid substrates. One of the advantages of the LB technique in fabricating molecular aggregates lies in the fact that it can employ various kinds of molecules by mixing them at the air-water interface. The mixed system may exhibit new properties that are not observed for individual components. This method would be useful, for example, in the studies of the formation and control of the J-aggregates of functional dyes that attract attention both in science and technology. In this paper, I review this subject mainly based on our recent results in merocyanines. LB films of merocyanine dyes, mixed with arachidic acid (C(20)), exhibit J-aggregate formation and have been serving as typical systems in revealing the physical and structural aspects of nanosized molecular aggregates constructed as monolayers. In the case of LB films of a merocyanine dye having benzothiazole as donor nucleus (abbreviated as DS), electron spin resonance (ESR) spectroscopy has been successful in determining the characteristic in-plane orientation of dye molecules with respect to the dipping direction, which led to the discovery of the flow orientation effect during the dipping process of LB films as the origin of optical dichroism often observed in LB films. In this article, after an introduction of ESR spectroscopy, three major topics on the merocyanine J-aggregation and its characterization in mixed films are discussed. The first topic is the observation and control of the size of J-aggregates in the dilution limit of dyes in arachidic acid matrix for a methyl-substituted DS (6-Me-DS). Dependence of atomic force microscopy (AFM) patterns on the molar ratio allows the identification of dye domains. J-band optical peak analysis based on the Kuhn's extended dipole model, supplemented by a novel application of femtosecond pump-probe optical spectroscopy, yields the

  4. Electrochromic and gas adsorption properties of Langmuir-Blodgett films of lutetium bisphthalocyanine complexes

    SciTech Connect

    Rodriguez-Mendez, M.L.; Aroca, R. ); DeSaja, J.A. )

    1993-07-01

    The electrochromic behaviour, spectroscopic properties and gas chemisorption of ultra thin films of lutetium octa-4-phenyldiphthalocyanine (LuPc[sub 2][sup Ph]), and the lutetium octa-3-bromo-octa-5-tert-butylphthalocyanine (LuPc[sub 2][sup tBr]) are reported. Electrochromism was observed for Langmuir-Blodgett (LB) and films cast onto indium tin oxide (ITO) coated glass electrodes in aqueous KClO[sub 4] solution. Mixed LB films supported on ITO glass electrodes were more stable to repetitive cycling than cast films. Films of LuPc[sub 2][sup Ph] and LuPc[sub 2][sup tBr] were sensitive to electron-acceptor gases as observed by the changes in the electronic absorption spectra and the surface-enhanced resonance Raman scattering (SERRS) spectra. The presence of electron-withdrawing bromine atoms in the phthalocyanine ring increased the rate of desorption for chemisorbed electron-acceptor molecules. 10 refs., 8 figs., 3 tabs.

  5. Formation of nanoscale aggregates of a coumarin derivative in Langmuir-Blodgett film

    NASA Astrophysics Data System (ADS)

    Chakraborty, Santanu; Bhattacharjee, D.; Hussain, Syed Arshad

    2013-06-01

    In the present communication, we report the formation of organized nanoscale aggregates of a coumarin derivative 7 Hydroxy-N-Octadecyl Coumarin-3-Carboxamide (7HNO3C) at the air-water interface and in Langmuir-Blodgett (LB) films in the presence and absence of stearic acid (SA). A pressure-area isotherm reveals that the 7HNO3C form stable monolayer at the air-water interface. However, the stability can be improved by mixing it with a fatty acid stearic acid (SA). The miscibility study shows that the nature of interaction is strongly dependent on the mixing ratio and surface pressure. At a mole fraction of 0.4 of 7HNO3C in SA, the attractive and repulsive interaction between these two molecules balance each other forming a stable film with nanoscale aggregates. UV-Vis absorption spectroscopic studies reveal the nature of the aggregates in LB films. Scanning electron microscopy gives compelling visual evidence of formation of nanoscale aggregates in the mixed LB films.

  6. Anomalous conformational transitions in cytochrome C adsorbing to Langmuir-Blodgett films

    NASA Astrophysics Data System (ADS)

    Sankaranarayanan, Kamatchi; Nair, B. U.; Dhathathreyan, A.

    2013-05-01

    Helix to beta conformational transitions in proteins has attracted much attention due to their relevance to fibril formation which is implicated in many neurological diseases. This study reports on unusual conformational transition of cytochrome C adsorbing to hydrophilic surface containing pure cationic lipid and mixed Langmuir-Blodgett films (LB films) of cationic and neutral lipids. Evidence for conformational changes of the protein from its native helical state to beta sheet comes from Circular dichroic spectroscopy (CD spectroscopy). Analysis of these samples using High resolution TEM (HRTEM) shows a typical fibrillar pattern with each strand spacing of about 0.41 nm across which can be attributed to the repeat distance of interdigitated neighboring hydrogen-bonded ribbons in a beta sheet. Changes in contact angles of protein adsorbing to the LB films together with the increased mass uptake of water using quartz crystal microbalance (QCM) confirm the role of positive charges in the conformational transition. Dehydration of the protein resulting from the excess water entrainment in the polar planes of the cationic lipid in hydrophilic surface seems to trigger the refolding of the protein to beta sheet while it retains its native conformation in hydrophobic films. The results suggest that drastic conformational changes in CytC adsorbing to cationic lipids may be of significance in its role as a peripheral membrane protein.

  7. Thermally induced conformational changes of Ca-arachidate Langmuir-Blodgett Films at different compression

    NASA Astrophysics Data System (ADS)

    Weber, Jan; Beier, Andre; Hasselbrink, Eckart; Balgar, Thorsten

    2014-07-01

    The conformational order in Ca-arachidate Langmuir-Blodgett films on solid glass supports is investigated by means of vibrational sum-frequency generation spectroscopy (VSFG). The symmetric C-H stretching vibrations of both the terminal methyl and the methylene groups are utilized to monitor the chain conformation at various sample temperatures under ambient conditions. At room temperature the film is well-ordered consisting almost entirely of all-trans configured chains. Between 340 and 430 K we observe a marked increase in gauche-defects before oxidative degeneration starts at sample temperatures above 470 K. The temperature dependence of the data is well represented by apparent enthalpy changes for the formation of gauche-defects, sharply increasing with packing density from 29 to 62 kJ/mol; values, which are an order of magnitude larger than those of the gas phase molecule. These large apparent enthalpies do not prevent the formation of a high degree of conformational disorder at elevated temperatures.

  8. Lattice and defect structures of polymerizable diacetylene Langmuir-Blodgett films studied by scanning force microscopy

    NASA Astrophysics Data System (ADS)

    Vithana, Hemasiri; Johnson, David; Shih, Raymond; Mann, J. A., Jr.; Lando, Jerome

    The Scanning Force Microscope has been used to study the lattice and defect structures of multilayers of the unsaturated fatty acid, 12-8- diacetylene (10,12-Pentacosadiynoic Acid) in ambient conditions. Films were prepared by the Langmuir-Blodgett technique on ordinary microscope glass and Indium Tin Oxide coated glass. Lattice structures were deduced from the well resolved molecular images and before polymerization found to be nearly centered rectangular with lattice parameters (0.88 +/- 0.06)nm and (0.51 +/- 0.04)nm. After exposing to UV radiation for polymerization the lattice structure changed to an oblique lattice with lattice parameters (0.466 +/- 0.008)nm and (0.55 +/- 0.01)nm. Molecular level defects such as dislocations and grain boundaries were resolved in these films very clearly. Observation of these kind of defects implies that it is possible to reliably image the real surface molecules under ambient conditions. Polymerization was found to take place in one of the lattice directions and the modulation perpendicular to that direction was more pronounced than along the polymer backbone.

  9. Preparation, characterization, and second-harmonic generation of a Langmuir-Blodgett film based on a rare-earth coordination compound

    SciTech Connect

    Wang, K.Z.; Huang, C.H.; Xu, G.X.; Zhao, X.S.; Xie, X.M.; Wu, N.Z.; Xu, Y.; Liu, Y.Q.; Zhu, D.B.

    1994-11-01

    The rare-earth coordination compound (E)-N-hexadecyl-4-(2-(4-(dimethylamino)phenyl)-ethenyl)pyridinium tetrakis(1-phenyl-3-methyl-4-benzoyl-5-pyrazolonato)dysprosium(III) was synthesized. The LB films were prepared and characterized by UV-vis, IR, X-ray photoelectron spectroscopy, and low-angle X-ray diffraction. High-quality LB films up to 50 layers on the hydrophilic substrates of quartz, calcium fluoride, and glass were obtained. From the second-harmonic generation measurement, second-order molecular hyperpolarizability {beta} of the dysprosium complex was estimated to be about (6.6-9.3) x 10{sup {minus}28} esu. 14 refs., 6 figs., 1 tab.

  10. Langmuir-Blodgett Films with Bilayer Alternation of Hemicyanine Dye and Cadmium Stearate

    NASA Astrophysics Data System (ADS)

    J, Y. Fang; Z, M. Sun; S, J. Xiao; Z, H. Lu; Y, Wei; P, Stroeve

    1991-11-01

    Multilayers consisting of bilayer alternation of hemicyanine dye and cadmium stearate have been prepared by the Langmuir-Blodgett technique. x-ray diffraction and optical absorption spectra are used to characterize their periodic structures and optical properties. The results show that a well ordered superlattice is produced and the hemicyanine dye is in non-aggregated formation in the alternating multilayers.

  11. Highly ordered thin films of polyheterocycles: A synchrotron radiation study of polypyrrole and polythiophene Langmuir-Blodgett films

    SciTech Connect

    Skotheim, T.A.; Yang, X.Q.; Chen, J.; Hale, P.D.; Inagaki, T.; Samuelson, L.; Tripathy, S.; Hong, K.; Rubner, M.F.; den Boer, M.L.

    1988-01-01

    Langmuir-Blodgett films have been made with 3-n-hexadecylpyrrole and 3-n-octadecylpyrrole monomers and copolymers with unsubstituted pyrrole made by chemical polymerization at the air-water interface on a subphase containing FeCl/sub 3/. Langmuir-Blodgett films consisting of mixtures of stearic acid and alkylsubstituted polythiophenes have also been made as bilayer films. The orientation of single and multilayer films on platinum substrates have been studied by Near Edge X-ray Absorption Fine Structure Spectroscopy which also gives information about charge transfer interactions between the aromatic groups and the metallic substrates. The alkylsubstituted pyrroles form highly ordered two-dimensional structures. FeCl/sub 3/ initiated copolymerization with unsubstituted pyrrole leads to a more disordered system. In the case of polythiophene-stearic acid bilayers, the stearic acid layers are highly ordered. The poly(alkyl thiophene) layers sandwiched between stearic acid layers, on the other hand, exhibit random orientation of the thiophene moieties. 15 refs., 3 figs., 3 tabs.

  12. White light-emitting electrochemical cells based on the Langmuir-Blodgett technique.

    PubMed

    Fernández-Hernández, Jesús M; De Cola, Luisa; Bolink, Henk J; Clemente-León, Miguel; Coronado, Eugenio; Forment-Aliaga, Alicia; López-Muñoz, Angel; Repetto, Diego

    2014-11-25

    Light-emitting electrochemical cells (LECs) showing a white emission have been prepared with Langmuir-Blodgett (LB) films of the metallosurfactant bis[2-(2,4-difluorophenyl)pyridine][2-(1-hexadecyl-1H-1,2,3-triazol-4-yl)pyridine]iridium(III) chloride (1), which work with an air-stable Al electrode. They were prepared by depositing a LB film of 1 on top of a layer of poly(N,N'-diphenyl-N,N'-bis(4-hexylphenyl)-[1,1'-biphenyl]-4,4'-diamine (pTPD) spin-coated on indium tin oxide (ITO). The white color of the electroluminescence of the device contrasts with the blue color of the photoluminescence of 1 in solution and within the LB films. Furthermore, the crystal structure of 1 is reported together with the preparation and characterization of the Langmuir monolayers (π-A compression isotherms and Brewster angle microscopy (BAM)) and LB films of 1 (IR, UV-vis and emission spectroscopy, X-ray photoelectron spectroscopy (XPS), specular X-ray reflectivity (SXR), and atomic force microscopy (AFM)). PMID:25347390

  13. Polycrystalline TiO2 (B) Nanosheet Films Deposited via Langmuir-Blodgett Method

    NASA Astrophysics Data System (ADS)

    Biedermann, Laura; Kotula, Paul; Beechem, Thomas; Dylla, Anthony; Stevenson, Keith; Chan, Calvin

    2014-03-01

    As an energy storage material, TiO2 offers higher Li+ capacities and smaller volume changes with lithiation than graphite electrodes. In particular, the bronze phase, TiO2(B) has a higher lithiation capacity (1.0 Li+/Ti) and faster lithiation kinetics due to its larger lattice parameters than other TiO2 polymorphs. Direct observation of lithiation will require TiO2(B) monolayers, such as those prepared via Langmuir-Blodgett deposition of the nanosheets (NS). Optical microscopy of the TiO2(B)-NS Langmuir monolayer at the air/water interface shows that these nanosheets assemble into large (>1 mm) islands. These elastic TiO2(B)-NS monolayers are deposited on diverse substrates for further characterization. Electron diffraction in both transmission electron microscopy (TEM) and low-energy electron microscopy (LEEM) of these films confirm that their polycrystalline structure is predominately composed of TiO2(B) nanocrystals, ~10s nm across. Discrimination of monolayer and bilayer TiO2(B) is evident in LEEM. Thermal stability of these nanosheets is investigated via in-situ TEM and ex-situ Raman spectroscopy. This monolayer TiO2(B) deposition will allow future observations of lithiation and phase changes. Sandia is managed by Sandia Corp., a subsidiary Lockheed Martin, for the U.S. DOE NNSA (DE-AC04-94AL85000). Work was supported by an U.S. DOE BES EFRC (DE-SC0001091).

  14. Complexes of carbon nanotubes with oligonucleotides in thin Langmuir-Blodgett films to detect electrochemically hybridization

    NASA Astrophysics Data System (ADS)

    Egorov, A. S.; Egorova, V. P.; Krylova, H. V.; Lipnevich, I. V.; Orekhovskaya, T. I.; Veligura, A. A.; Govorov, M. I.; Shulitsky, B. G.

    2014-10-01

    Self-assembled complexes consisting of thin multi-walled carbon nanotubes (MWCNTs) and DNA-oligonucleotides which are able to a cooperative binding to complementary oligonucleotides have been investigated. It was establised a high-performance charge transport in nanostructured Langmuir-Blodgett complexes thin MWCNTs/DNA. A method to electrochemically detect DNA hybridization on the self-organized structures has been proposed.

  15. Deactivation of excitation energy in bacterial photosynthetic reaction centres in Langmuir-Blodgett films

    NASA Astrophysics Data System (ADS)

    Miyake, J.; Hara, M.; Goc, J.; Planner, A.; Wróbel, D.

    1997-08-01

    Absorption, photoacoustic and time-resolved in μs time range delayed luminescence spectra have been measured in order to follow the interaction among chromophores when Rhodobacter sphaeroides and Rhodopseudomonas viridis reaction centres are closely packed in a form of Langmuir-Blodgett multilayers. Two types of Langmuir-Blodgett samples have been prepared and investigated: multilayers consist of one type of reaction centre ( Rhodobacter sphaeroides or Rhodopseudomonas viridis) and multilayers composed of mixed reaction centres ( Rhodobacter sphaeroides mixed with Rhodopseudomonas viridis). Using the Langmuir-Blodgett multilayers composed of two types of bacteria reaction centres mixture, we were able to extend the spectral region of the light/solar energy absorbed by the system. It was shown that each form of pigment participates in thermal dissipation but to a different degree. A special pair (bacteriochlorophyll dimer) does not contribute to delayed luminescence. Delayed luminescence in Rhodopseudomonas viridis and Rhodobacter sphaeroides differs very significantly from each other. Bacteriopheophytin as well as dihydromesochlorophyll contribute to delayed luminescence but the degree of their participation in this radiative process depends strongly on the type of reaction centre. Delayed luminescence and thermal processes have been indicated as important processes of deactivation of the photoexcited chromophores in reaction centres.

  16. Growth, Morphology, and Electrical Characterization of Polyaniline-ZnO Nano-composite Langmuir-Blodgett Thin Films

    NASA Astrophysics Data System (ADS)

    Bhullar, Gurpreet Kaur; Kaur, Ramneek; Raina, K. K.

    2015-10-01

    Polyaniline (PANi)-zinc oxide (ZnO) nano-composites were prepared by chemical polymerization of aniline doped with ZnO nanoparticles. Surface pressure-area ( π-A) isotherms for the PANi-ZnO nano-composite revealed phase transformations of the monolayer during compression. Langmuir-Blodgett (LB) films of PANi and PANi-ZnO nano-composite were characterized by use of UV-visible (UV-Vis) and Fourier-transform infrared spectroscopy, atomic force microscopy, and conductive atomic force microscopy (C-AFM). Local current-voltage ( I- V) characteristics revealed the current range for PANi-ZnO nano-composite LB films was larger than that for PANi LB films. Conductive data images were recorded to investigate charge-transport current inhomogeneities in the LB films.

  17. Substitution of spreading solvent by a less hazardous one for the fabrication of the Au(dmit)2 Langmuir-Blodgett films

    NASA Astrophysics Data System (ADS)

    Miura, Yasuhiro F.

    2016-03-01

    The Langmuir-Blodgett (LB) film based on the ditetradecyldimethylammonium-Au(dmit)2 [2C14N+Me2-Au(dmit)2] salt shows a high room-temperature conductivity of 40 S/cm with a metallic temperature dependence. However, the solvent for spreading the material at the air/water interface is a 1:1 mixture of benzene and acetonitrile, which should be substituted by a less hazardous solvent considering the health effects. Here, we report on the substitution of the solvent by a less hazardous one — a 1:1 mixture of toluene and acetone; the 2C14N+Me2-Au(dmit)2 LB film fabricated using the mixture also exhibits a high room-temperature conductivity together with a metallic temperature dependence.

  18. Spectroscopic characterization of selected fullerene-organic chromophore Langmuir-Blodgett films

    NASA Astrophysics Data System (ADS)

    Lewandowska, Kornelia; Wróbel, Danuta; Graja, Andrzej

    2012-08-01

    Electronic absorption in polarized and unpolarized light and steady-state fluorescence emission and excitation spectra of zinc porphyrins, their dimers and dyads with a fullerene as well as perylene-derived molecular systems containing a fullerene were investigated. In particular, dyads of the fullerene covalently bonded to perylene- and porphyrin-derived dyes were comprehensively studied in chloroform solution and in a form of Langmuir-Blodgett layers on solid inorganic substrates. The spectroscopic examination of the samples allowed us to analysis charge redistribution after the chromophore-fullerene dyads formation - this effect was detected as changes of the band wavelengths and shape of the lines. The layer organization, in particular the dye molecule orientation, was estimated from. Usefulness of the investigated dyads in photovoltaic devices was signaled.

  19. Optical properties of Langmuir-Blodgett film of hemicyanine containing the rare earth complex anion Dy(BPMPHD) (-2)

    NASA Astrophysics Data System (ADS)

    Wang, Kezhi; Huang, Chunhui; Xu, Guangxian; Zhao, Xinsheng; Xia, Xiaohua; Wu, Nianzu; Xu, Lingge; Li, Tiankai

    1994-12-01

    (E)-N-hexadecyl-4-(2-(4-dimethylaminophnyl) ethenyl) pyridinium bis(1,6-bis (1'-phenyl-3'-methyl-5'-pyrazolone-4') hexanedio-nato-(1,5)) dysprosium(III) was synthesized. The monolayers formed on a pure water subphase (pH 5.6,C) were transferred onto hydrophilic quartz, calcium fluoride, and glass substrates successively with a transfer ratio of around unity. From second-harmonic generation (SHG) experiments, the second-order molecular hyperpolarizability beta was evaluated to be about 4.8 x 10(exp -48) C cu m/sq V. The results of UV-visible, IR and X-ray photoelectron spectroscopy of the Langmuir-Blodgett films are also reported.

  20. Effects of nanoparticle doping on the phase transitional behaviour of ferroelectric liquid crystal Langmuir-Blodgett composite films

    NASA Astrophysics Data System (ADS)

    Kaur, Ramneek; Raina, K. K.

    2015-12-01

    Langmuir-Blodgett films of ferroelectric liquid crystals (FLCs) doped with a low concentration of functionalized Al: ZnO (AZO) nanoparticles were prepared and characterized. Pressure-area isotherms show that the nanoparticles as well as FLC composite systems have the capability to form stable monolayers at the air-water interface. The molecular interaction between nanoparticles and FLC molecules increased during barrier compression, which resulted in increased surface pressure. We observed various phases in isotherms with increasing concentration of nanoparticles in the FLC matrix. An X-ray diffraction profile at a low angle confirmed that FLCs retain their layer structure at a low concentration doping of AZO nanoparticles in the FLC matrix. Atomic force microscopy images indicate that low wt% composites are uniformly deposited without disturbing the translation behaviour of SmC* liquid crystals.

  1. Glued Langmuir-Blodgett bilayers from calix[n]arenes: Influence of calix[n]arene size on ionic cross-linking, film thickness, and permeation selectivity

    DOE PAGESBeta

    Wang, Minghui; Janout, Vaclav; Regen, Steven L.

    2010-07-12

    A homologous series of calix[4]arene-, calix[5]arene- and calix[6]arene-based surfactants, containing pendant trimethylammonium and n-hexadecyl groups, have been compared with respect to their ability (i) to undergo ionic crosslinking at the air/water interface, (ii) to incorporate poly(4-styrenesulfonate) (PSS) in Langmuir-Blodgett (LB) bilayers, and (iii) to act as barriers towards He, N2 and CO2 when assembled into crosslinked LB bilayers. As these calix[n]arenes increase in size, their ability to undergo ionic crosslinking has been found to increase, the thickness of corresponding glued LB bilayers has been found to decrease, and their barrier properties and permeation selectivities have been found to increase. Inmore » conclusion, the likely origin for these effects and the probable mechanism by which He, N2 and CO2 cross these ultrathin films are discussed.« less

  2. Efficient optical nonlinear Langmuir-Blodgett films: roles of matrix molecules

    NASA Astrophysics Data System (ADS)

    Ma, Shihong; Lu, Xingze; Liu, Liying; Han, Kui; Wang, Wencheng; Zhang, Zhi-Ming

    1996-10-01

    A novel bifat-chain amphiphilic molecule nitrogencrown (NC) was adopted as an inert material for fabrication of optical nonlinear Langmuir-Blodgett (LB) multilayers. Structural improvement in the Z-type mixed fullerene derivative (C60-Be)/NC LB multilayers samples was realized by insertion of the C60-Be molecules between two hydrophobic chains of the NC molecules. The relatively large third-order susceptibility (chi) (3)xxxx(- 3(omega) ;(omega) ,(omega) ,(omega) ) equals 2.9 multiplied by 10-19 M2V-2 (or 2.1 multiplied by 10-11 esu) was deduced by measuring third harmonic generation (THG) from the C60-Be samples. The second harmonic generation (SHG) intensity increased quadratically with the bilayer number (up to 116 bilayers) in Y-type hemicyanine (HEM)/NC interleaving LB multilayers due to improvement of the structural properties by insertion of the long hydrophobic tail of HEM molecules between two chains of NC molecules. The second-order susceptibility (chi) (2)zxx(-2(omega) ;(omega) ,(omega) ) equals 18 pM V-1 (or 4.35 multiplied by 10-8 esu) was obtained by measuring SHG from the HEM samples. The NC molecule has attractive features as a matrix material in fabrications of LB multilayers made from optically nonlinear materials with hydrophobic long tails or ball-like molecules.

  3. Nanostructured PdO Thin Film from Langmuir-Blodgett Precursor for Room-Temperature H2 Gas Sensing.

    PubMed

    Choudhury, Sipra; Betty, C A; Bhattacharyya, Kaustava; Saxena, Vibha; Bhattacharya, Debarati

    2016-07-01

    Nanoparticulate thin films of PdO were prepared using the Langmuir-Blodgett (LB) technique by thermal decomposition of a multilayer film of octadecylamine (ODA)-chloropalladate complex. The stable complex formation of ODA with chloropalladate ions (present in subphase) at the air-water interface was confirmed by the surface pressure-area isotherm and Brewster angle microscopy. The formation of nanocrystalline PdO thin film after thermal decomposition of as-deposited LB film was confirmed by X-ray diffraction and Raman spectroscopy. Nanocrystalline PdO thin films were further characterized by using UV-vis and X-ray photoelectron spectroscopic (XPS) measurements. The XPS study revealed the presence of prominent Pd(2+) with a small quantity (18%) of reduced PdO (Pd(0)) in nanocrystalline PdO thin film. From the absorption spectroscopic measurement, the band gap energy of PdO was estimated to be 2 eV, which was very close to that obtained from specular reflectance measurements. Surface morphology studies of these films using atomic force microscopy and field-emission scanning electron microscopy indicated formation of nanoparticles of size 20-30 nm. These PdO film when employed as a chemiresistive sensor showed H2 sensitivity in the range of 30-4000 ppm at room temperature. In addition, PdO films showed photosensitivity with increase in current upon shining of visible light. PMID:27299704

  4. Preparation of porous monolayer film by immersing the stearic acid Langmuir-Blodgett monolayer on mica in salt solution

    NASA Astrophysics Data System (ADS)

    Wang, S.; Li, Y. L.; Zhao, H. L.; Liang, H.; Liu, B.; Pan, S.

    2012-11-01

    Porous materials have drawn attention from scientists in many fields such as life sciences, catalysis and photonics since they can be used to induce some materials growth as expected. Especially, porous Langmuir-Blodgett (LB) film is an ideal material with controlled thickness and flat surface. In this paper, stearic acid (SA), which has been extensively explored in LB film technique, is chosen as the template material with known parameters to prepare the LB film, and then the porous SA monolayer film is obtained by means of etching in salt solution. The main etching mechanism is suggested that the cations in the solution block the electrostatic interaction between the polar carboxyl group of SA and the electronegative mica surface. The influencing factors (such as concentration of salt solution, valence of cation and surface pressure) of the porous SA film are systematically studied in this work. The novel method proposed in this paper makes it convenient to prepare porous monolayer film for designed material growth or cell culture.

  5. Growth and stability of Langmuir-Blodgett films on OH-, H-, or Br-terminated Si(001)

    NASA Astrophysics Data System (ADS)

    Bal, J. K.; Kundu, S.; Hazra, S.

    2010-01-01

    Growth of Langmuir-Blodgett (LB) films of nickel arachidate (NiA) on differently terminated (OH-, H-, or Br-terminated) Si(001) substrates and their structural evolution with time have been investigated by x-ray reflectivity technique and complemented by atomic force microscopy. Stable and strongly attached asymmetric monolayer (AML) of NiA is found to grow on freshly prepared oxide-covered Si substrate while unstable and weakly attached symmetric monolayer (SML) of NiA grows on H-terminated Si substrate, corresponding to stable hydrophilic and unstable hydrophobic natures of the substrates, respectively. The structure of LB film on Br-terminated Si substrate, however, shows intermediate behavior, namely, both AML and SML are present on the substrate, indicative of coexisting (hydrophilic and hydrophobic) nature of this terminated surface. Such coexisting nature of the substrate shows unusual growth behavior of LB films: (i) hydrophilic and hydrophobic attachments of NiA molecules in single up stroke of deposition and (ii) growth of few ring-shaped large-heights islands in subsequent deposition. These probably occur due to the presence of substrate-induced perturbation in the Langmuir monolayer and release of initially accumulated strain in the film structures near hydrophilic/hydrophobic interface, respectively, and provide the possibility to grow desired structures (AML or SML) of LB films by passivation-selective surface engineering.

  6. Monolayers and Langmuir-Blodgett films of luminescent 1,3,5-triazine derivatives containing naphthalene or anthracene chromophores

    NASA Astrophysics Data System (ADS)

    Cai, Ya-Qi; Wu, Wei; Wang, Hua; Miyake, Jun; Qian, Dong-Jin

    2011-02-01

    Monolayer behaviors and Langmuir-Blodgett (LB) films of three luminescent aryl triazines, 2,4,6-tri(naphthalen-1-yl)-1,3,5-triazine (TN 1Ta), 2,4,6-tri(naphthalen-2-yl)-1,3,5-triazine (TN 2Ta), and 2,4,6-tri(anthracen-9-yl)-1,3,5-triazine (TATa) have been investigated. Surface pressure-area isotherms indicated that pure aryl triazines were difficult to form stable monolayers, while their mixtures with arachidic acid (AA) could be stabilized at the air-water interface. The mixed LB films of triazine-AA were deposited on substrate surfaces and analyzed by using UV-vis and infrared absorption spectra, X-ray photoelectron spectra, as well as scanning electron microscopy. Morphologies of the LB films and molecular aggregates were closely dependent on the structure of triazines and the surface pressures of deposition. Under UV radiation, TN 1Ta and TN 2Ta emitted at 410-460 nm while TATa emitted at 500-510 nm, with the emission lifetime falling into the range of 0.29 to 10.8 ns. Compared with those in solutions, the emissions of aryl triazines were red shifted in the LB films, especially for the TN 1Ta-AA and TN 2Ta-AA, which was attributed to the closely packed arrangement for the molecules in the LB films.

  7. Side-chain effect on Langmuir and Langmuir-Blodgett film properties of poly(N-alkylmethacrylamide)-coated magnetic nanoparticle.

    PubMed

    Parvin, Salina; Matsui, Jun; Sato, Eriko; Miyashita, Tokuji

    2007-09-01

    We report the fabrication of a Langmuir-Blodgett (LB) film of magnetic nanoparticles (iron oxide) coated by poly(N-alkylmethacrylamide)s with various alkyl chain lengths. The iron oxide nanoparticle (nP) was first modified with a reactive polymer, poly(N-hydroxysuccinimide methacrylate) (pSucMA) by applying surface initiated atom transfer radical polymerization (ATRP) technique. Then the succinimide group was replaced by various amine derivatives. The monolayer behaviors of the resultant nanoparticles, as modified by various poly(N-alkylmethacrylamide)s, such as poly(octylmethacrylamide) (pOMA), poly(dodecylmethacrylamide) (pDDMA), polytetradecylmethacrylamide (pTDMA), and poly(hexadecylmethacrylamide) (pHDMA) were elucidated using surface pressure-area isotherm measurements. Results show that pTDMA-modified nanoparticles (nP-pTDMA) exhibit the highest collapse pressure with a steeply rising surface pressure. The monolayer of nP-pTDMA on the water surface was transferred onto a solid substrate using the LB technique. Atomic force microscopy (AFM) images of the transferred LB film show that nP-pTDMA particles form a uniform nanoparticle monolayer. The LB film of nP-pTDMA with multilayers was fabricated through sequential transfer of the particles monolayer onto the substrate surface. The resultant LB film of nanoparticles shows a superparamagnetic behavior at room temperature. PMID:17511997

  8. A new family of Langmuir-Blodgett films of tetracyanoquinodimethane charge transfer salts: Pristine and iodine doped conducting films

    NASA Astrophysics Data System (ADS)

    Vandevyer, M.; Richard, J.; Barraud, A.; Ruaudel-Teixier, A.; Lequan, M.; Lequan, R. M.

    1987-12-01

    A new family of semiamphiphilic tetracyanoquinodimethane (TCNQ) ionic salts of nonconjugated cations, namely octadecyl-dimethylsulfonium, octadecyl-methyl-ethyl-sulfonium, and octadecyl-trimethylphosphonium labeled a, b, and c, respectively, has been synthetized. Langmuir-Blodgett (LB) films are built up from these three compounds, which are mixed with octadecylurea in a molar ratio 1/1, in order to improve the stability of the film at the water surface. The structural properties of the transferred films are thoroughly investigated by linear dichroism in the IR and UV-visible ranges, together with ESR spectroscopy. In the films of the three compounds, the polar sheets contain (TCNQ- • )2 dimers, which are the largely prevalent species. The molecular planes of these dimers are found to be roughly parallel to the substrate. Moreover, a strong in-plane orientation of the dimers is found in films of compound c. This phenomenon is thought to be related to an overall flow orientation of rod-shaped crystallites in the floating film, during the high speed downstroke of the substrate across the film. Advantage is taken from the high and well-controlled thinness of LB films to make iodine vapor diffuse into the films and convert the precursor films into conducting ones. The iodination process leads for the three salts to a stable ternary conducting compound located in the polar planes of the LB assembly. Correlatively, it induces a strong molecular reorganization in the films: the TCNQ molecules stand on edge with their long molecular axis perpendicular to the substrate. In spite of this considerable rearrangement arising from iodination, we notice that the strong in-plane anisotropy observed in pristine films of c is retained in conducting films of the iodinated c compound. Beside these structural results, the IR spectra of conducting films are reminiscent of these of highly conducting, but not metallic-like, organic conductors. The conductivity of the films is estimated

  9. Nonlinear optical anisotropy and molecular orientational distribution in poly(p-phenylene benzobisthiazole) Langmuir-Blodgett films

    NASA Astrophysics Data System (ADS)

    Wang, Liming; Wada, Tatsuo; Yuba, Tomoyuki; Kakimoto, Masaaki; Imai, Yoshio; Sasabe, Hiroyuki

    1996-06-01

    The orientational distribution and packing of polymer chains were investigated in poly(p-phenylene benzobisthiazole) (PBT) Langmuir-Blodgett (LB) films by nonresonant third-harmonic generation measurement at a wavelength of 1907 nm. The tensor components of the third-harmonic susceptibility on the PBT LB film with a surface pressure of 50 mN/m were determined to be χ(3)XXXX=(16.6±2.5)×10-12 and χ(3)YYYY=(2.0±0.3)×10-12. The large nonlinear optical anisotropy can be explained as a result of highly oriented packing of the polymer chains induced by a flow orientation. A Gaussian distribution function with a standard deviation of σ=0.40 gives a practical description of the orientational distribution of PBT polymer chains. A maximum χ(3) value of (26.8±4.4)×10-12 esu is predicted assuming a perfect alignment of polymer chains. The χ(3)XXXX value increased by factor of 2 with the surface pressure from 30 to 50 mN/m mainly due to the packing density of the polymer chains, while the orientational degree did not change.

  10. Three-component Langmuir-Blodgett films consisting of surfactant, clay mineral, and lysozyme: construction and characterization.

    PubMed

    Miao, Shiding; Leeman, Hugo; De Feyter, Steven; Schoonheydt, Robert A

    2010-02-22

    The Langmuir-Blodgett (L-B) technique has been employed for the construction of hybrid films consisting of three components: surfactant, clay, and lysozyme (Lys). The surfactants are octadecylammonium chloride (ODAH) and octadecyl ester of rhodamine B (RhB18). The clays include saponite and laponite. Surface pressure versus area isotherms indicate that lysozyme is adsorbed by the surfactant-clay L-B film at the air-water interface without phase transition. The UV-visible spectra of the hybrid film ODAH-saponite-Lys show that the amount of immobilized lysozyme in the hybrid film is (1.3+/-0.2) ng mm(-2). The average surface area (Omega) per molecule of lysozyme is approximately 18.2 nm(2) in the saponite layer. For the multilayer film (ODAH-saponite-Lys)(n), the average amount of lysozyme per layer is (1.0+/-0.1) ng mm(-2). The amount of lysozyme found in the hybrid films of ODAH-laponite-Lys is at the detection limit of about 0.4 ng mm(-2). Attenuated total reflectance (ATR) FTIR spectra give evidence for clay layers, ODAH, lysozyme, and water in the hybrid film. The octadecylammonium cations are partially oxidized to the corresponding carbamate. A weak 1620 cm(-1) band of lysozyme in the hybrid films is reminiscent of the presence of lysozyme aggregates. AFM reveals evidence of randomly oriented saponite layers of various sizes and shapes. Individual lysozyme molecules are not resolved, but aggregates of about 20 nm in diameter are clearly seen. Some aggregates are in contact with the clay mineral layers, others are not. These aggregates are aligned in films deposited at a surface pressure of 20 mN m(-1). PMID:20104549

  11. Molecular orientation of asphaltenes and PAH model compounds in Langmuir-Blodgett films using sum frequency generation spectroscopy.

    PubMed

    Andrews, A Ballard; McClelland, Arthur; Korkeila, Oona; Demidov, Alexander; Krummel, Amber; Mullins, Oliver C; Chen, Zhan

    2011-05-17

    Asphaltenes are an important class of compounds in crude oil whose surface activity is important for establishing reservoir rock wettability which impacts reservoir drainage. While many phenomenological interfacial studies with crude oils and asphaltenes have been reported, there is very little known about the molecular level interactions between asphaltenes and mineral surfaces. In this study, we analyze Langmuir-Blodgett films of asphaltenes and related model compounds with sum frequency generation (SFG) vibrational spectroscopy. In SFG, the polarization of the input (vis, IR) and output (SFG) beams can be varied, which allows the orientation of different functional groups at the interface to be determined. SFG clearly indicates that asphaltene polycyclic aromatic hydrocarbons (PAHs) are highly oriented in the plane of the interface and that the peripheral alkanes are transverse to the interface. In contrast, model compounds with oxygen functionality have PAHs oriented transverse to the interface. Computational quantum chemistry is used to support corresponding band assignments, enabling robust determination of functional group orientations. PMID:21491945

  12. Design and Synthesis of Aviram-Ratner-Type Dyads and Rectification Studies in Langmuir-Blodgett (LB) Films.

    PubMed

    Jayamurugan, Govindasamy; Gowri, Vijayendran; Hernández, David; Martin, Santiago; González-Orive, Alejandro; Dengiz, Cagatay; Dumele, Oliver; Pérez-Murano, Francesc; Gisselbrecht, Jean-Paul; Boudon, Corinne; Schweizer, W Bernd; Breiten, Benjamin; Finke, Aaron D; Jeschke, Gunnar; Bernet, Bruno; Ruhlmann, Laurent; Cea, Pilar; Diederich, François

    2016-07-18

    The design and synthesis of Aviram-Ratner-type molecular rectifiers, featuring an anilino-substituted extended tetracyanoquinodimethane (exTCNQ) acceptor, covalently linked by the σ-spacer bicyclo[2.2.2]octane (BCO) to a tetrathiafulvalene (TTF) donor moiety, are described. The rigid BCO spacer keeps the TTF donor and exTCNQ acceptor moieties apart, as demonstrated by X-ray analysis. The photophysical properties of the TTF-BCO-exTCNQ dyads were investigated by UV/Vis and EPR spectroscopy, electrochemical studies, and theoretical calculations. Langmuir-Blodgett films were prepared and used in the fabrication and electrical studies of junction devices. One dyad showed the asymmetric current-voltage (I-V) curve characteristic for rectification, unlike control compounds containing the TTF unit but not the exTCNQ moiety or comprising the exTCNQ acceptor moiety but lacking the donor TTF part, which both gave symmetric I-V curves. The direction of the observed rectification indicated that the preferred electron current flows from the exTCNQ acceptor to the TTF donor. PMID:27363287

  13. Phase-matched second harmonic generation and nonlinear phase shift in a Langmuir-Blodgett film waveguide

    NASA Astrophysics Data System (ADS)

    Schrader, Sigurd K.; Flueraru, Costel; Motschmann, Hubert; Brehmer, Ludwig

    2001-12-01

    Wave-guides have been prepared as y-type Langmuir-Blodgett multilayers from 2-docosylamino-5-nitropyridine (DCANP) on quartz glass substrates. The tensor elements of the LB-films as determined by polarization dependent second harmonic generation (SHG) are (Formula available in paper) The wave-guides were fabricated in a way that the second-order susceptibility changes sign at the nodal plane of the first-order wave-guide mode for s-polarization. In such wave-guides efficient second harmonic generation (SHG) was reached via mode conversion at a fundamental wavelength near 1064 nm. The conversion efficiency reached the extraordinary high value of 8%/W which corresponds to a normalized conversion efficiency of 3600 %/(W cm2). In addition, interferometric measurements have been carried out to study the non-linear phase-shift which the fundamental beam experiences due to non-linear interaction in the wave-guide. From these experiments an apparent intensity-dependent refractive index n2SHG of 2,6 10-13 cm2/W was calculated. This as about 400 times the intensity-dependent refractive as expected from third-order susceptibility of the isotropic material. From that it can be concluded that the main contribution of the intensity-dependent refractive index is connected to cascading of second-order processes.

  14. Synthesis of Triptycene-Based Molecular Rotors for Langmuir-Blodgett Monolayers.

    PubMed

    Kaleta, Jiří; Kaletová, Eva; Císařová, Ivana; Teat, Simon J; Michl, Josef

    2015-10-16

    We describe syntheses of six triptycene-containing molecular rotors with several single-crystal X-ray diffraction analyses. These rod-shaped molecules carrying an axial rotator are designed to interleave on an aqueous surface into Langmuir-Blodgett (LB) monolayers containing a two-dimensional trigonal array of dipoles rotatable about an axis normal to the surface. Monolayer formation was verified with the simplest of the rotor structures. On an aqueous subphase containing divalent cations (Mg(2+), Ca(2+), Zn(2+), Sr(2+), or Cd(2+)), the LB isotherm yielded an area of 53 ± 3 Å(2)/molecule (monolayer of type A), compatible with the anticipated triangular packing of axes normal to the surface. On pure water, the area is 30 ± 3 Å(2)/molecule, and it is proposed that in this monolayer (type B), the molecular axes are tilted by 40-45° to a structure similar to those observed in single crystals of related triptycenes. After transfer to a gold surface, ellipsometry and PM IRRAS yield tilt angles of 29 ± 4° (monolayers of type A) and 38 ± 4° (type B). A full-scale examination of monolayers from all the rotors on a subphase and after transfer is underway and will be reported separately. PMID:26382886

  15. Electrical conductivity in Langmuir-Blodgett films of n-alkyl cyanobiphenyls using current sensing atomic force microscope

    SciTech Connect

    Gayathri, H. N.; Suresh, K. A.

    2015-06-28

    We report our studies on the nanoscale electrical conductivity in monolayers of n-alkyl cyanobiphenyl materials deposited on solid surface. Initially, the 8CB, 9CB, and 10CB monolayer films were prepared by the Langmuir technique at air-water interface and characterized by surface manometry and Brewster angle microscopy. The monolayer films were transferred on to solid substrates by the Langmuir-Blodgett (L-B) technique. The 8CB, 9CB, and 10CB monolayer L-B films were deposited on freshly cleaved mica and studied by atomic force microscope (AFM), thereby measuring the film thickness as ∼1.5 nm. The electrical conductivity measurements were carried out on 9CB and 10CB monolayer L-B films deposited onto highly ordered pyrolytic graphite using current sensing AFM. The nanoscale current-voltage (I-V) measurements show a non-linear variation. The nature of the curve indicates electron tunneling to be the mechanism for electrical conduction. Furthermore, analysis of the I-V curve reveals a transition in the electron conduction mechanism from direct tunneling to injection tunneling. From the transition voltage, we have estimated the values of barrier height for 9CB and 10CB to be 0.71 eV and 0.37 eV, respectively. For both 9CB and 10CB, the effective mass of electron was calculated to be 0.021 m{sub e} and 0.065 m{sub e}, respectively. These parameters are important in the design of molecular electronic devices.

  16. The effect of purification of single-walled carbon nanotube bundles on the alcohol sensitivity of nanocomposite Langmuir Blodgett films for SAW sensing applications

    NASA Astrophysics Data System (ADS)

    Penza, M.; Tagliente, M. A.; Aversa, P.; Re, M.; Cassano, G.

    2007-05-01

    HiPco (high-pressure CO dissociation process) single-walled carbon nanotube (SWCNT) bundles containing Fe particles were purified in a two-step purification process by thermal annealing in oxygen and post-treatment in HCl. Nanocomposite films of pristine and purified SWCNTs embedded in an organic matrix of cadmium arachidate (CdA) were prepared by a Langmuir-Blodgett (LB) molecular engineering technique with a fixed weight filler content of 75 wt% onto a surface acoustic wave (SAW) transducer operating as an oscillator at a frequency of 433 MHz. The raw and purified samples were characterized at various stages of the purification process using thermogravimetric analysis (TGA), high-resolution transmission electron microscopy (HR-TEM), along with energy-dispersive x-ray spectroscopy (EDS), field emission scanning electron microscopy (FE-SEM) and x-ray diffraction (XRD). Functional characterizations of the SWCNT-nanocomposite-based SAW sensors were investigated towards methanol, isopropanol and ethanol, and demonstrated high sensitivity, reversibility, fast response and ppm level detection at room temperature. Results indicate that the sensitivity of the SAW sensors based on a nanocomposite film of oxygen-annealed SWCNTs is enhanced to the alcohols tested at room temperature. Purification of the SWCNTs in the nanocomposite film affects the SAW sensitivity to alcohol by modulating the sensing properties. The sensing mechanisms are analysed and discussed.

  17. Fabrication and Characterization of ZnO Langmuir-Blodgett Film and Its Use in Metal-Insulator-Metal Tunnel Diode.

    PubMed

    Azad, Ibrahim; Ram, Manoj K; Goswami, D Yogi; Stefanakos, Elias

    2016-08-23

    Metal-insulator-metal tunnel diodes have great potential for use in infrared detection and energy harvesting applications. The quantum based tunneling mechanism of electrons in MIM (metal-insulator-metal) or MIIM (metal-insulator-insulator-metal) diodes can facilitate rectification at THz frequencies. In this study, the required nanometer thin insulating layer (I) in the MIM diode structure was fabricated using the Langmuir-Blodgett technique. The zinc stearate LB film was deposited on Au/Cr coated quartz, FTO, and silicon substrates, and then heat treated by varying the temperature from 100 to 550 °C to obtain nanometer thin ZnO layers. The thin films were characterized by XRD, AFM, FTIR, and cyclic voltammetry methods. The final MIM structure was fabricated by depositing chromium/nickel over the ZnO on Au/Cr film. The current voltage (I-V) characteristics of the diode showed that the conduction mechanism is electron tunneling through the thin insulating layer. The sensitivity of the diodes was as high as 32 V(-1). The diode resistance was ∼80 Ω (at a bias voltage of 0.78 V), and the rectification ratio at that bias point was about 12 (for a voltage swing of ±200 mV). The diode response exhibited significant nonlinearity and high asymmetry at the bias point, very desirable diode performance parameters for IR detection applications. PMID:27464073

  18. Immobilized metal affinity chromatography on collapsed Langmuir-Blodgett iron(III) stearate films and iron(III) oxide nanoparticles for bottom-up phosphoproteomics.

    PubMed

    Gladilovich, Vladimir; Greifenhagen, Uta; Sukhodolov, Nikolai; Selyutin, Artem; Singer, David; Thieme, Domenika; Majovsky, Petra; Shirkin, Alexey; Hoehenwarter, Wolfgang; Bonitenko, Evgeny; Podolskaya, Ekaterina; Frolov, Andrej

    2016-04-22

    Phosphorylation is the enzymatic reaction of site-specific phosphate transfer from energy-rich donors to the side chains of serine, threonine, tyrosine, and histidine residues in proteins. In living cells, reversible phosphorylation underlies a universal mechanism of intracellular signal transduction. In this context, analysis of the phosphoproteome is a prerequisite to better understand the cellular regulatory networks. Conventionally, due to the low contents of signaling proteins, selective enrichment of proteolytic phosphopeptides by immobilized metal affinity chromatography (IMAC) is performed prior to their LC-MS or -MS/MS analysis. Unfortunately, this technique still suffers from low selectivity and compromised analyte recoveries. To overcome these limitations, we propose IMAC systems comprising stationary phases based on collapsed Langmuir-Blodgett films of iron(III) stearate (FF) or iron(III) oxide nanoparticles (FO) and mobile phases relying on ammonia, piperidine and heptadecafluorooctanesulfonic acid (PFOS). Experiments with model phosphopeptides and phosphoprotein tryptic digests showed superior binding capacity, selectivity and recovery for both systems in comparison to the existing commercial analogs. As evidenced by LC-MS/MS analysis of the HeLa phosphoproteome, these features of the phases resulted in increased phosphoproteome coverage in comparison to the analogous commercially available phases, indicating that our IMAC protocol is a promising chromatographic tool for in-depth phosphoproteomic research. PMID:27016113

  19. Optical and surface morphology study of zinc phthalocyanine Langmuir Blodgett thin film

    NASA Astrophysics Data System (ADS)

    Roy, Dhrubojyoti; Das, Nayan Mani; Gupta, M.; Ganesan, V.; Gupta, P. S.

    2014-04-01

    The UV-Vis absorption spectroscopy analysis reveals that prominent J-aggregation of ZnPc molecules was observed in the LB films while no such aggregation was found in the solution. Change in fluorescence color of ZnPc LB film from its solution confirms the appearance of new aggregation.

  20. Characterization of the fulgide-doped PMMA films and investigation of photochromic reaction of Langmuir-Blodgett films as recording materials

    NASA Astrophysics Data System (ADS)

    Lafond, Christophe; Pouraghajani, Ozra; Tork, Amir; Bolte, Michel; Ritcey, Anna-Marie R.; Lessard, Roger A.

    2001-06-01

    Photochemical characterization and holographic recording of fulgide Aberchrome 670 and 540-doped polymethyl methacrylate (PMMA) were investigated. Upon UV and visible exposure, closed-form absorbency followed first-order kinetic. The real time holographic recording in fulgides doped PMMA films were studied. The effect of dye concentration, thickness of the film and the recording intensity on diffraction efficiency was reported. We used the Langmuir-Blodgett (LB) technique in order to transferring a compact multilayer of fulgide spread on water surface between two thin films of cellulose acetate (CA). The preliminary results of the surface pressure-area isotherms obtained by LB show the transfer of the fulgide between two CA thin films. Finally, the photochromic reaction of fulgide in LB films was investigated.

  1. Optical nonlinearity of pure bacteriorhodopsin Langmuir-Blodgett films derived from multi-wave mixing

    NASA Astrophysics Data System (ADS)

    Liu, S. H.; Du, Weichong

    1993-10-01

    We report an observation of optical phase conjugate and high-order diffractions from degenerate multi-wave mixing in LB films of pure purple membrane for the first time. The saturated absorption intensity and the saturated nonlinear refractive index of the LB films have been estimated to be 0.42 W/cm2, and 5×10-2 cm2/W, respectively. The typical response time of its nonlinearity is about several milliseconds.

  2. Investigation of Epitaxial Lift-Off Gallium Arsenide and Langmuir-Blodgett Films for Optoelectronic Device Applications

    NASA Astrophysics Data System (ADS)

    Shah, Divyang Manharlal

    Epitaxial lift-off (ELO), a technique of removing an epitaxially grown GaAs layer from its growth substrate by selective etching of an AlAs sacrificial layer, is described for field-effect transistor fabrication independent of the GaAs growth substrate. Metal Semiconductor Field-Effect Transistors (MESFETs) and High Electron Mobility Transistors (HEMTs) fabricated on silicon and sapphire substrates using ELO are investigated. A 0.1 μm gate length depletion mode MESFET made on silicon exhibited a unity current gain frequency f_{ rm t} = 34 GHz. Excellent device isolation with subpicoampere leakage currents is obtained. A high input impedance amplifier has been implemented on silicon substrate using ELO GaAs MESFETs. The amplifier had an input RC time constant limited bandwidth of 500 MHz. Results of investigation of a novel source of cadmium and zinc diffusion for shallow p^ {+}-n junction fabrication in In _{0.53}Ga_{0.47 }As/InP are also presented. Langmuir-Blodgett (LB) deposited monolayers of Cadmium and Zinc arachidate have been used as a source of Cd and Zn dopants in InGaAs/InP. This new source provides precise control of the dopant dose through the number of LB film monolayers deposited and it is also a safer method of handling toxic Cd. The LB film can be patterned by lift-off for a patterned diffusion without a mask. Highly doped (N_{ rm a}= 2-4 times 10^{19} cm^ {-3}), shallow (0.1-0.4 mu m) p^{+}-n junctions have been obtained. Junction field-effect transistors (JFETs) and PIN photodetectors have been fabricated as a demonstration of the usefulness of the technique. A PIN photodetector had a 100 pA dark current at -5 V DC bias and a bandwidth of 2 GHz. A new technique for fabricating optoelectronic integrated circuit (OEIC) photoreceivers for 1.3-1.55 μm wavelength optical communication has also been proposed. The proposed OEIC uses ELO GaAs MESFETs and InGaAs/InP PIN photodetectors.

  3. Cognition and order in Langmuir-Blodgett films of a 3-hexadecyl pyrrole and ferrocene-derivatized pyrrole mixed monolayer system

    NASA Astrophysics Data System (ADS)

    Samuelson, L.; Rahman, A. K. M.; Puglia, G. P.; Clough, S.; Tripathy, S.; Inagaki, T.; Yang, X. Q.; Skotheim, T. A.; Okamoto, Y.

    Novel, self-assembled materials were designed and produced from first principle to possess unique structural hierarchy and electronic and optical properties. The Langmuir-Blodgett technique was used to study the molecular organization of a mixed 3-hexadecyl pyrrole (3HDP) and ferrocene-derivatized pyrrole (Fc-Py) surfactant system. The pyrrole moiety was chosen for its' well established electronic and optical properties when polymerized, while ferrocene, it is theorized, if properly oriented into a Langmuir-Blodgett monolayer film may show a layered array of transition metals which would be extremely valuable as a model for 2-D magnets. The ferrocene group may also provide the possibility of charge coupling between neutral ferrocene and oxidized ferricenium which could be controlled electrochemically or photochemically. It has been determined that stable monolayer films of the mixed system could be formed at the air-water interface. The growth and assembly process led to polypyrrole 2-D lattices with heretofore unsurpassed order. In fact, the process of template polymerization leads to a new crystal phase for the polypyrrole component of the thin film structure. Various monolayer and multilayer films were prepared on platinum coated substrates for surface spectroscopic characterization using synchrotron radiation. Near Edge X-Ray Absorption Fine Structure studies revealed that highly ordered multilayer structures are being formed.

  4. Cognition and order in Langmuir-Blodgett films of a 3-hexadecyl pyrrole and ferrocene-derivatized pyrrole mixed monolayer system

    SciTech Connect

    Samuelson, L.; Rahman, A.K.M.; Puglia, G.P.; Clough, S.; Tripathy, S.; Inagaki, T.; Yang, X.Q.; Skotheim, T.A.; Okamoto, Y.

    1989-01-01

    Novel, self-assembled materials have been designed and produced from first principle to possess unique structural hierarchy and electronic and optical properties. The Langmuir-Blodgett technique was used to study the molecular organization of a mixed 3-hexadecyl pyrrole (3HDP) and ferrocene-derivatized pyrrole (Fc-Py) surfactant system. The pyrrole moiety was chosen for its' well established electronic and optical properties when polymerized, while ferrocene, it is theorized, if properly oriented into a Langmuir-Blodgett monolayer film may show a layered array of transition metals which would be extremely valuable as a model for two-dimensional magnets. The ferrocene group may also provide the possibility of charge coupling between neutral ferrocene and oxidized ferricenium which could be controlled electrochemically or photochemically. It has been determined that stable monolayer films of the mixed system could be formed at the air-water interface. The growth and assembly process led to polypyrrole 2-D lattices with heretofore unsurpassed order. In fact, the process of template polymerization leads to a new crystal phase for the polypyrrole component of the thin film structure. Various monolayer and multilayer films were prepared on platinum coated substrates for surface spectroscopic characterization using synchrotron radiation. Near Edge X-Ray Absorption Fine Structure studies revealed that highly ordered multilayer structures are being formed. 8 refs., 4 figs., 1 tab.

  5. Fabrication and spectroscopic properties of Langmuir Blodgett films of novel zinc complexes with long chain mono (hexadecyl, octadecyl, eicosyl, and docosyl) phthalate

    NASA Astrophysics Data System (ADS)

    Xu, Bing; Yan, Bing

    2007-08-01

    In this paper, some novel long chain amphiphillic monoester molecules were designed to afford double functions: film-formation and luminescent sensitization. Subsequently, organized molecular films of zinc complexes with these functional ligands formulated as ZnL 2 were fabricated by the Langmuir-Blodgett film (LB) technology, where L denoted the long chain carboxylic ligands monohexadecyl phthalate (16-Phth), monooctadecyl phthalate (18-Phth), monoeicosyl phthalate (20-Phth) and monodocosyl phthalate (22-Phth). The average molecular area was obtained according to the π-A isotherms. The layer structure of the LB films was demonstrated by low-angle X-ray diffraction and the average layer spacing were obtained according to the Bragg equation. The characteristic luminescence behaviors of LB films have been discussed compared with those of their corresponding solid complexes.

  6. Studies on morphology of Langmuir-Blodgett films of stearic acid deposited with different orientation of substrates with respect to compression

    NASA Astrophysics Data System (ADS)

    Choudhary, Keerti; Manjuladevi, V.; Gupta, R. K.

    2016-05-01

    The Langmuir monolayer at an air-water interface shows remarkably different surface pressure - area isotherm, when measured with the surface normal of a Wilhemly plate parallel or perpendicular to the direction of compression of the monolayer. Such difference arises due to difference in stress exerted by the monolayer on the plate in different direction. In this article, we report the effect of changing the direction of substrate normal with respect to the compression of the monolayer during Langmuir-Blodgett (LB) film deposition on the morphology of the films. The morphology of the LB film of stearic acid was studied using an atomic force microscope (AFM). The morphology of the LB films was found to be different due to difference in the stress in different directions.

  7. Preparation of Langmuir-Blodgett thin films of calix[6]arenes and p-tert butyl group effect on their gas sensing properties

    NASA Astrophysics Data System (ADS)

    Ozmen, Mustafa; Ozbek, Zikriye; Bayrakci, Mevlut; Ertul, Seref; Ersoz, Mustafa; Capan, Rifat

    2015-12-01

    Organic vapor sensing properties of Langmuir-Blodgett (LB) thin films of p-tert-butyl calix[6]arene and calix[6]arene, and their certain characterization are reported in this work. LB films of these calixarenes have been characterized by contact angle measurement, quartz crystal microbalance (QCM), scanning electron microscopy (SEM) and atomic force microscopy (AFM). QCM system was used for the measurement of sensor response against chloroform, benzene, toluene and ethanol vapors. Forming of stable monolayers was observed at the water surface using surface pressure-area isotherm graph. The results indicate that good quality, uniform LB films can be prepared with a transfer ratio of over 0.95. Due to the adsorption of vapors into the LB film structures; they yield a response to all vapors as of large, fast, and reproducible.

  8. Synthesis of novel hybrid films of a layered silicate and alkylammonium cations on rough polymeric surfaces by Langmuir-Blodgett method.

    PubMed

    Zhou, Qi; Wang, Kean; Loo, Leslie S

    2009-12-15

    Hybrid films of a layered silicate and an amphiphilic alkylammonium (hexadecyltrimethylammonium) cation have been prepared by Langmuir-Blodgett (LB) method and transferred onto a polyamide surface by dip coating. This is the first time that stable LB hybrid monolayer and multilayer films have been formed on rough polymeric surfaces. The films were characterized by X-ray diffraction (XRD), fourier transform infrared spectroscopy (FTIR), atomic force microscopy (AFM) and water contact angle measurements. XRD and FTIR showed that the hybrid multilayer was well-organized and the thickness of one layer was calculated to be 1.6nm. Furthermore, the layered silicate was determined to be on the substrate side and the amphiphilic molecule layer was exposed to the air side. This provides a novel methodology for the surface modification of polymers. PMID:19781713

  9. Glued Langmuir-Blodgett bilayers from calix[n]arenes: Influence of calix[n]arene size on ionic cross-linking, film thickness, and permeation selectivity

    SciTech Connect

    Wang, Minghui; Janout, Vaclav; Regen, Steven L.

    2010-07-12

    A homologous series of calix[4]arene-, calix[5]arene- and calix[6]arene-based surfactants, containing pendant trimethylammonium and n-hexadecyl groups, have been compared with respect to their ability (i) to undergo ionic crosslinking at the air/water interface, (ii) to incorporate poly(4-styrenesulfonate) (PSS) in Langmuir-Blodgett (LB) bilayers, and (iii) to act as barriers towards He, N2 and CO2 when assembled into crosslinked LB bilayers. As these calix[n]arenes increase in size, their ability to undergo ionic crosslinking has been found to increase, the thickness of corresponding glued LB bilayers has been found to decrease, and their barrier properties and permeation selectivities have been found to increase. In conclusion, the likely origin for these effects and the probable mechanism by which He, N2 and CO2 cross these ultrathin films are discussed.

  10. Synergy between polyaniline and OMt clay mineral in Langmuir-Blodgett films for the simultaneous detection of traces of metal ions.

    PubMed

    de Barros, Anerise; Ferreira, Mariselma; Constantino, Carlos José Leopoldo; Bortoleto, José Roberto Ribeiro; Ferreira, Marystela

    2015-04-01

    We report on Langmuir-Blodgett (LB) films made with emeraldine salt polyaniline (PAni-ES) and organophilic montmorillonite clay mineral (OMt), where synergy between the components was reached to yield an enhanced performance in detecting trace levels of cadmium (Cd(2+)), lead (Pb(2+)) and copper (Cu(2+)). Detection was carried out using square wave anodic stripping (SWAS) voltammetry with indium tin oxide (ITO) electrodes modified with LB films of PAni-ES/OMt nanocomposite, whose data were compared to those obtained with electrodes coated with neat PAni-ES and neat OMt LB films. The enhanced performance in the nanocomposite may be attributed to the stabilizing and ordering effect promoted by OMt in PAni-ES Langmuir films, which then led to more homogeneous LB films. According to X-ray diffraction data, the stacking of OMt layers was preserved in the LB films and therefore the PAni-ES chains did not cause clay mineral exfoliation. Instead, OMt affected the polaronic state of PAni-ES as indicated in UV-vis, Raman and FTIR spectra, also consistent with the changes observed for the Langmuir films. Taken together these results do indicate that semiconducting polymers and clay minerals may be combined for enhancing the electrical properties of nanostructures for sensing and related applications. PMID:25761908

  11. Hybrid Langmuir and Langmuir-Blodgett films of a viologen derivative and TCNQ in a mixed valence state: preparation route and characterization

    NASA Astrophysics Data System (ADS)

    Martín, Santiago; Cea, Pilar; Lafuente, Carlos; Royo, Félix M.; López, María. C.

    2004-08-01

    Hybrid Langmuir and Langmuir-Blodgett (LB) films containing two moieties of great chemical and electrochemical interest, namely a viologen derivative and tetracyanoquinodimethane (TCNQ) in a mixed valence state, were fabricated. To do so, positively ionized monolayers of 1,1 '-dioctadecyl 4,4 '-bipyridilium were prepared onto aqueous solutions of tetracyanoquinodimethane in a mixed valence state. Surface pressure vs. area ( π- A), surface potential vs. area (Δ V- A), and Brewster angle microscope (BAM) images were recorded and interpreted in terms of molecular interactions as well as the incorporation of the hydrophobic anions into the monolayer. After a comprehensive study, a 10 -6 M TCNQ aqueous solution was chosen as the best one to build hybrid LB films. Thus, the floating films were transferred onto solid substrates that were characterized using several techniques including ultraviolet-visible (UV-vis), infrared (IR), scanning electron microscopy (SEM), and atomic force microscopy (AFM) proving the incorporation of the TCNQ onto the film. These films show a good optical conductivity as well as a high degree of order and layers with a constant architecture.

  12. Silver coated gold nanocolloids entrapped in organized Langmuir-Blodgett Film of stearic acid: Potential evidence of a new SERS active substrate

    NASA Astrophysics Data System (ADS)

    Saha, Somsubhra; Ghosh, Manash; Dutta, Bipan; Chowdhury, Joydeep

    2016-01-01

    SERS active substrate containing silver coated gold (Au@Ag) nanocolloids entrapped in the Langmuir-Blodgett (LB) film matrix of stearic acid (SA) has been reported. The SERS efficacy of the as prepared substrate has been tested with trace concentrations of Rhodamine 6G (R6G) molecules. Enhancement factors ranging from 104-1013 orders of magnitude have been estimated for the characteristic vibrational signatures of R6G molecule. The colossal enhancement factors also signify the superiority of the as prepared substrate in comparison to Au@Ag nanocolloids. The optical responses and the morphological features of the substrates are estimated with aid of UV-vis absorption spectra and FESEM, AFM images respectively. Correlations between the surface morphologies, fractal dimensions and roughness features of the as prepared substrates are also drawn. The electric field distributions around the aggregated nanocolloids entrapped in the SA matrix have been envisaged with the aid of three dimensional finite difference time domain (3D-FDTD) simulations. Tuning the interparticle localized surface plasmon (LSP) coupling between the aggregated nanocolloids may be achieved by lifting the LB film of SA at different surface pressures.

  13. Film fabrication of Fe or Fe3O4 nanoparticles mixed with palmitic acid for vertically aligned carbon nanotube growth using Langmuir-Blodgett technique

    NASA Astrophysics Data System (ADS)

    Nakamura, Kentaro; Kuriyama, Naoki; Takagiwa, Shota; Sato, Taiga; Kushida, Masahito

    2016-03-01

    Vertically aligned carbon nanotubes (VA-CNTs) were studied as a new catalyst support for polymer electrolyte fuel cells (PEFCs). Controlling the number density and the diameter of VA-CNTs may be necessary to optimize PEFC performance. As the catalyst for CNT growth, we fabricated Fe or Fe3O4 nanoparticle (NP) films by the Langmuir-Blodgett (LB) technique. The catalyst Fe or Fe3O4 NPs were widely separated by mixing with filler molecules [palmitic acid (C16)]. The number density of VA-CNTs was controlled by varying the ratio of catalyst NPs to C16 filler molecules. The VA-CNTs were synthesized from the catalyst NP-C16 LB films by thermal chemical vapor deposition (CVD) using acetylene gas as the carbon source. The developing solvents used in the LB technique and the hydrogen reduction conditions of CVD were optimized to improve the VA-CNT growth rate. We demonstrate that the proposed method can independently control both the density and the diameter of VA-CNTs.

  14. Optical rotation of the second harmonic radiation from retinal in bacteriorhodopsin monomers in Langmuir-Blodgett film: evidence for nonplanar retinal structure.

    PubMed Central

    Volkov, V; Svirko, Y P; Kamalov, V F; Song, L; El-Sayed, M A

    1997-01-01

    We observed optical rotation of the plane of polarization of the second harmonic (SH) radiation at 532 nm (in resonance with the retinal absorption) generated in reflection geometry in Langmuir-Blodgett film of bacteriorhodopsin (bR). The analysis of the experimental data showed that this effect arises from the nonvanishing contribution of the antisymmetrical part of the hyperpolarizability tensor. This requires that the dipole moment of the resonant electronic transition, the change of the dipole moment upon electronic excitation, and the long axis of the retinal not be coplanar. Such conditions are satisfied only if the retinal has a nonplanar geometry, a conclusion that could lend support to the heterogeneity model of the origin of the biphasic band shape of the linear CD spectrum of the retinal in bR. On the basis of our theoretical analysis, we were able to estimate the angle between the induced dipole moment and the plan that contains the long axis of the chromophore and the transition dipole moment of the retinal absorption. Images FIGURE 2 PMID:9414228

  15. Rhodanese incorporated in Langmuir and Langmuir-Blodgett films of dimyristoylphosphatidic acid: Physical chemical properties and improvement of the enzyme activity.

    PubMed

    de Araújo, Felipe Tejada; Caseli, Luciano

    2016-05-01

    Preserving the catalytic activity of enzymes immobilized in bioelectronics devices is essential for optimal performance in biosensors. Therefore, ultrathin films in which the architecture can be controlled at the molecular level are of interest. In this work, the enzyme rhodanese was adsorbed onto Langmuir monolayers of the phospholipid dimyristoylphosphatidic acid and characterized by surface pressure-area isotherms, polarization-modulated infrared reflection-absorption spectroscopy (PM-IRRAS), and Brewster angle microscopy (BAM). The incorporation of the enzyme (5% in mol) in the lipid monolayer expanded the film, providing small surface domains, as visualized by BAM. Also, amide bands could be identified in the PM-IRRAS spectra, confirming the presence of the enzyme at the air-water interface. Structuring of the enzyme into α-helices was identified in the mixed monolayer and was preserved when the film was transferred from the liquid interface to solids supports as Langmuir-Blodgett (LB) films. The enzyme-lipid LB films were then characterized by fluorescence spectroscopy, PM-IRRAS, and atomic force microscopy. Measurements of the catalytic activity towards cyanide showed that the enzyme accommodated in the LB films preserved more than 87% of the enzyme activity in relation to the homogeneous medium. After 1 month, the enzyme in the LB film maintained 85% of the activity in contrast to the homogeneous medium, which 24% of the enzyme activity was kept. The method presented in this work not only points to an enhanced catalytic activity toward cyanide, but also may explain why certain film architectures exhibit an improved performance. PMID:26836478

  16. Triggered J-aggregation in mixed Langmuir-Blodgett films of amphiphilic spiropyran having a methoxy group at the 5' position and an azobenzene derivative.

    PubMed

    Kawasaki, Hisashi; Tozawa, Shinnosuke; Matani, Takashi; Hayashi, Toshihiro; Watanabe, Satoshi; Shibata, Hirobumi; Matsumoto, Mutsuyoshi

    2014-01-01

    Here, we describe the formation of J-aggregates triggered by isomerization of an azobenzene derivative, N-[p-[(p-dodecylphenylazo)phenyloxy]dodecylpyridinium bromide (AzP), in mixed Langmuir-Blodgett (LB) films that contain an amphiphilic spiropyran with a methoxy group at the 5' position, MeO-SP1822. Pure LB films of MeO-SP1822 consist of multilayer domains embedded in a monolayer. UV irradiation of the films causes the isomerization of MeO-SP1822 to its merocyanine form, MeO-MC1822. Pure LB films of AzP comprise finger-like domains and granular domains. Irradiating mixed films of MeO-SP1822 and AzP with alternating UV and visible light causes J-aggregation of MeO-MC1822, with the amount of J-aggregates reaching a maximum at a 1:1 molar ratio. J-aggregation occurs in flat finger-like structures originating in the AzP-rich granular domains that are located on top of the MeO-MC1822-rich multilayer domains. J-aggregates are also present under the AzP-rich granular domains, though these domains do not serve as nucleation sites for the finger-like structures. We propose that granular domains serving as nucleation sites are partially buried in the multilayer domains, whereas those triggering the J-aggregation of MeO-MC1822 under the granular domains are situated on top of the multilayer domains. PMID:24919479

  17. Exploring the Effect of Ligand Structural Isomerism in Langmuir-Blodgett Films of Chiral Luminescent Eu(III) Self-Assemblies.

    PubMed

    Galanti, Agostino; Kotova, Oxana; Blasco, Salvador; Johnson, Chloe J; Peacock, Robert D; Mills, Shaun; Boland, John J; Albrecht, Martin; Gunnlaugsson, Thorfinnur

    2016-07-01

    Here we have investigated the influence of the antenna group position on both the formation of chiral amphiphilic Eu(III) -based self-assemblies in CH3 CN solution and, on the ability to form monolayers on the surface of quartz substrates using the Langmuir-Blodgett technique, by changing from the 1-naphthyl (2(R), 2(S)) to the 2-naphthyl (1(R), 1(S)) position. The evaluation of binding constants of the self- assemblies in CH3 CN solution was achieved using conventional techniques such as UV/Visible and luminescence spectroscopies along with more specific circular dichroism (CD) spectroscopy. The binding constants obtained for EuL, EuL2 and EuL3 species in the case of 2-naphthyl derivatives were comparable to those obtained for 1-naphthyl derivatives. The analysis of the changes in the CD spectra of 1(R) and 1(S) upon addition of Eu(III) not only allowed us to evaluate the values of the binding constants but the resulting recalculated spectra may also be used as fingerprints for assignment of the chiral self-assembly species formed in solution. The obtained monolayers were predominantly formed from EuL3 (≈85 %) with the minor species present in ≈15 % EuL2 . PMID:27258206

  18. Formation of 2D colloidal crystals by the Langmuir-Blodgett technique monitored in situ by Brewster angle microscopy.

    PubMed

    Gil, Alvaro; Guitián, Francisco

    2007-03-01

    We report a method that combines Brewster angle microscopy and Langmuir-Blodgett films technique to obtain highly ordered 2D colloidal crystals of nanospheres. The deposition of Langmuir-Blodgett films of silica spheres monitored by Brewster angle microscopy allows to determine with accuracy the best physical conditions to transfer highly ordered monolayers of nanoparticles. PMID:17184789

  19. Langmuir-Blodgett films of self-assembled (alkylether-derivatized Zn phthalocyanine)-(C₆₀ imidazole adduct) dyad with controlled intermolecular distance for photoelectrochemical studies.

    PubMed

    Obraztsov, Ievgen; Noworyta, Krzysztof; Hart, Aaron; Gobeze, Habtom B; Kc, Chandra B; Kutner, Wlodzimierz; D'Souza, Francis

    2014-06-11

    A multilayer Langmuir-Blodgett (LB) film of the self-assembled electron donor-acceptor dyad of Zn phthalocyanine, appended with four long-chain aliphatic ether peripheral substituents, and an imidazole adduct of C60 was prepared and applied as a photoactive material in a photoelectrochemical cell. Changes in the simultaneously recorded surface pressure and surface potential vs area per molecule compression isotherms for Langmuir films of the dyad and, separately, of its components helped to identify phase transitions and mutual interactions of molecules in films. The Brewster angle microscopy (BAM) imaging of the Langmuir films showed circular condensed phase domains of the dyad molecules. The determined area per molecule was lower than that estimated for the dyad and its components, separately. The multilayer LB films of the dyad were transferred onto hydrophobized fluorine-doped tin oxide-coated (FTO) glass slides under different conditions. The presence of both components in the dyad LB films was confirmed with the UV-vis spectroscopy measurements. For the LB films transferred at different surface pressures, the PM-IRRAS measurements revealed that the phthalocyanine macrocycle planes and ether moieties in films were tilted with respect to the FTO surface. The AFM imaging of the LB films indicated formation of relatively uniform dyad LB films. Then, the femtosecond transient absorption spectral studies evidenced photoinduced electron transfer in the LB film. The obtained transient signals corresponding to both Zn(TPPE)(•+) and C60im(•-) confirmed the occurrence of intramolecular electron transfer. The determined rate constants of charge separation, kcs = 2.6 × 10(11) s(-1), and charge recombination, kcr = 9.7 × 10(9) s(-1), indicated quite efficient electron transfer within the film. In the photoelectrochemical studies, either photoanodic or photocathodic current was generated depending on the applied bias potential when the dyad LB film-coated FTO was used

  20. Electrical characterization of single molecule and Langmuir-Blodgett monomolecular films of a pyridine-terminated oligo(phenylene-ethynylene) derivative.

    PubMed

    Osorio, Henrry Marcelo; Martín, Santiago; López, María Carmen; Marqués-González, Santiago; Higgins, Simon J; Nichols, Richard J; Low, Paul J; Cea, Pilar

    2015-01-01

    Monolayer Langmuir-Blodgett (LB) films of 1,4-bis(pyridin-4-ylethynyl)benzene (1) together with the "STM touch-to-contact" method have been used to study the nature of metal-monolayer-metal junctions in which the pyridyl group provides the contact at both molecule-surface interfaces. Surface pressure vs area per molecule isotherms and Brewster angle microscopy images indicate that 1 forms true monolayers at the air-water interface. LB films of 1 were fabricated by deposition of the Langmuir films onto solid supports resulting in monolayers with surface coverage of 0.98 × 10(-9) mol·cm(-2). The morphology of the LB films that incorporate compound 1 was studied using atomic force microscopy (AFM). AFM images indicate the formation of homogeneous, monomolecular films at a surface pressure of transference of 16 mN·m(-1). The UV-vis spectra of the Langmuir and LB films reveal that 1 forms two dimensional J-aggregates. Scanning tunneling microscopy (STM), in particular the "STM touch-to-contact" method, was used to determine the electrical properties of LB films of 1. From these STM studies symmetrical I-V curves were obtained. A junction conductance of 5.17 × 10(-5) G 0 results from the analysis of the pseudolinear (ohmic) region of the I-V curves. This value is higher than that of the conductance values of LB films of phenylene-ethynylene derivatives contacted by amines, thiols, carboxylate, trimethylsilylethynyl or acetylide groups. In addition, the single molecule I-V curve of 1 determined using the I(s) method is in good agreement with the I-V curve obtained for the LB film, and both curves fit well with the Simmons model. Together, these results not only indicate that the mechanism of transport through these metal-molecule-metal junctions is non-resonant tunneling, but that lateral interactions between molecules within the LB film do not strongly influence the molecule conductance. The results presented here complement earlier studies of single molecule

  1. Optical and electrical properties of the Langmuir-Blodgett films prepared from a rare earth coordination compound

    NASA Astrophysics Data System (ADS)

    Huang, C. H.; Wang, K. Z.; Zhu, X. Y.; Wu, N. Z.; Xu, G. X.; Xu, Y.; Liu, Y. Q.; Zhu, D. B.; Liu, Y. W.; Xue, Z. Q.

    1994-04-01

    The stable floating Langmuir film of N-hexadecylpyridinium tetrakis-(1-phenyl-3-methyl-4-benzoyl-pyrazolone-5-one) europium formed at air-water interface, could be deposited at a surface pressure of 10 mN/m onto various hydrophilic substrates of fuzed quartz, single crystal calcium floride and transparent indium tin oxide (ITO) glass successively with a transfer ratio of around unity. LB films with more than 50 layers in Z or Y type were obtained. The films were characterized by ultraviolet, fluorescent, X-ray photoelectron spectroscopy and low angle X-ray diffraction. The electric conductivity of the film is reported as well.

  2. Photoactive Langmuir-Blodgett, Freely Suspended and Free Standing Films of Carboxylate Ligand-Coated ZnO Nanocrystals.

    PubMed

    Paczesny, Jan; Wolska-Pietkiewicz, Małgorzata; Binkiewicz, Ilona; Wadowska, Monika; Wróbel, Zbigniew; Matuła, Kinga; Nogala, Wojciech; Lewiński, Janusz; Hołyst, Robert

    2016-06-01

    A new possibility for the formation of macroscopic and photoactive structures from zinc oxide nanocrystals is described. Photoactive freely suspended and free-standing films of macroscopic area (up to few square millimeters) and submicrometer thickness (up to several hundreds of nanometers) composed of carboxylate ligand-coated zinc oxide nanocrystallites (RCO2-ZnO NCs) of diameter less than 5 nm are prepared according to a modified Langmuir-Schaefer method. First, the suspension of RCO2-ZnO NCs is applied onto the air/water interface. Upon compression, the films become turbid and elastic. The integrity of such structures is ensured by interdigitation of ligands stabilizing ZnO NCs. Great elasticity allows transfer of the films onto a metal frame as a freely suspended film. Such membranes are afterward extracted from the supporting frame to form free-standing films of macroscopic area. Because the integrity of the films is maintained by ligands, no abolishment of quantum confinement occurs, and films retain spectroscopic properties of initial RCO2-ZnO NCs. The mechanism of formation of thin films of RCO2-ZnO NCs at the air/water interface is discussed in detail. PMID:27158733

  3. Synthesis of Vertically-Aligned Carbon Nanotubes from Langmuir-Blodgett Films Deposited Fe Nanoparticles on Al2O3/Al/SiO2/Si Substrate.

    PubMed

    Takagiwa, Shota; Kanasugi, Osamu; Nakamura, Kentaro; Kushida, Masahito

    2016-04-01

    In order to apply vertically-aligned carbon nanotubes (VA-CNTs) to a new Pt supporting material of polymer electrolyte fuel cell (PEFC), number density and outer diameter of CNTs must be controlled independently. So, we employed Langmuir-Blodgett (LB) technique for depositing CNT growth catalysts. A Fe nanoparticle (NP) was used as a CNT growth catalyst. In this study, we tried to thicken VA-CNT carpet height and inhibit thermal aggregation of Fe NPs by using Al2O3/Al/SiO2/Si substrate. Fe NP LB films were deposited on three typed of substrates, SiO2/Si, as-deposited Al2O3/Al/SiO2/Si and annealed Al2O3/Al/SiO2/Si at 923 K in Ar atmosphere of 16 Pa. It is known that Al2O3/Al catalyzes hydrocarbon reforming, inhibits thermal aggregation of CNT growth catalysts and reduces CNT growth catalysts. It was found that annealed Al2O3/Al/SiO2/Si exerted three effects more strongly than as-deposited Al2O3/Al/SiO2/Si. VA-CNTs were synthesized from Fe NPs-C16 LB films by thermal chemical vapor deposition (CVD) method. As a result, at the distance between two nearest CNTs 28 nm or less, VA-CNT carpet height on annealed Al2O3/Al/SiO2/Si was about twice and ten times thicker than that on SiO2/Si and that on as-deposited Al2O3/Al/SiO2/Si, respectively. Moreover, distribution of CNT outer diameter on annealed Al2O3/Al/SiO2/Si was inhibited compared to that on SiO2/Si. These results suggest that since thermal aggregation of Fe NPs is inhibited, catalyst activity increases and distribution of Fe NP size is inhibited. PMID:27451619

  4. Langmuir-Blodgett film and second harmonic generation of a series of new nonlinear optical rare earth complexes

    NASA Astrophysics Data System (ADS)

    Li, Hui; Huang, Chun-hui; Zhao, Yi-lei; Li, Tian-kai; Bai, Jie; Zhao, Xin-sheng; Xia, Xiao-hua

    1995-06-01

    Four kinds of amphiphilic rare earth complexes containing the new chromophore: 4-[(4-N,N'-diethylamino)phenyl)azo]-1-methyl-pyridinium-Tetrakis(4-benzoyl-1-phenyl-3-methyl-pyrazolone-5) Dysprosium (compound A), 4-[(4-N,N'-(diethylamino)phenyl)azo]-1-methyl-pyridinium-Tri(4-benzoyl-1-phenyl-3-methyl-pyrazolone-5)-(4-hexadecanoyl-1-phenyl-3-methyl Pyrazolone5)Dysprosium(compound B), 4-[(4-N,N'-diethylamino)phenyl)azo]-1-methyl-pyridinium-Tetrakis(2-thenoyl-trifluoroacetone)Dysprosium (compound C) and 4-[(4-N,N'-(diethylamino)phenyl)azo]-1-methyl-pyridinium-Tri(2-thenoyl-trifluoroacetone)-(4-hexadecanoyl-1-phenyl-3-methyl-pyrazolone-5 Dysprosium (compound D), and their iodide (compound E), were synthesized. The film-forming properties of compound A and B are good while compounds C, D and E cannot form stable Langmuir film. The second-order molecular hyperpolarizability β of the rare earth complexes were evaluated to be 1.3×10 -28e.s.u. and 5.9×10 -28e.s.u. for compounds A and B respectively.

  5. Pentacene organic ferroelectric transistors with [P(VDF-TrFE)] gate by Langmuir-Blodgett process

    NASA Astrophysics Data System (ADS)

    Sun, Yilin; Xie, Dan; Xu, Jianlong; Feng, Tingting; Zang, Yongyuan; Zhang, Cheng; Dai, Ruixuan; Meng, Xiangjian; Ji, Zhuoyu

    2015-09-01

    We report the fabrication and electrical properties of pentacene-based ferroelectric organic field-effect transistors (FeOFETs) with ultrathin poly(vinylidene fluoride trifluoroethylene) [P(VDF-TrFE)] gate insulators. A ultrathin and uniform P(VDF-TrFE) film was successfully deposited by Langmuir-Blodgett (LB) deposition with well-defined ferroelectric microdomains at the interface between P(VDF-TrFE) films and pentacene active layers. The P(VDF-TrFE) films derived by LB deposition significantly enhance the crystallization of the upper pentacene channel films and thus the performance of our FeOFETs. Our FeOFET device achieves a threshold voltage shift of 8.56 V induced by ferroelectric polarization under different voltage sweeping directions and such enhancement indicates a great potential for future organic nonvolatile memory applications.

  6. Raman spectroscopic investigation of the single-monolayer Langmuir-Blodgett film of C16NaphOH and C10AzoNaphC4N-SDS.

    PubMed

    Wu, Yuqing; Zhao, Bing; Xu, Weiqing; Li, Guowen; Li, Bofu

    2003-04-01

    Raman spectra were measured for Langmuir-Blodgett (LB) films of C(16)NaphOH and C(10)AzoNaphC(4)N-SDS on Calcium Fluorite substrate for the first time. In order to find out favorable excitation condition, Raman spectra of the single and multi-monolayer LB films excited at different lines at 244, 514, 633 and 778 nm are recorded and compared in the present study. Raman spectrum of the monolayer LB film of C(16)NaphOH excited by 244 nm demonstrate that excellent signal to noise is achieved even for one monolayer LB film with an extremely short integrating time as 60 s because of being resonantly enhanced, while no meaningful spectra were recorded under the same condition for the monolayer LB film of C(10)AzoNaphC(4)N-SDS because of burning. Using a HeNe 633 nm excitation the problem with strong substrate fluorescence was partially solved, since under these conditions this fluorescence is mainly outside the fingerprint region of the LB film molecules (1000-2000 cm(-1)). Therefore by using the HeNe laser excitation, Raman spectra with high signal to noise ratio of LB films of C(16)NaphOH were collected and shown in this paper. These findings stress again the necessity to define an appropriate Raman system for this special application of LB film diagnosis. PMID:12659885

  7. Second-harmonic generation from Z-type Langmuir-Blodgett films of a transparent dye and a comparison of the properties when the layers are interleaved with poly(t-butyl methacrylate)

    NASA Astrophysics Data System (ADS)

    Ashwell, Geoffrey J.; Ranjan, Rakesh

    1998-10-01

    The Langmuir-Blodgett (LB) film structure of E-4-[(N- octadecyl-6,7,8-trihydro-5-isoquinolylidene)methyl]-N,N- dibutylaniline octadecylsulfate is non-centrosymmetric when the dye is deposited on the up-stroke (Z-type) and when the layers are interleaved with poly(t-butyl methacrylate). The second-harmonic intensity increases as I(N)2(omega ) equals I(1)2(omega )N2, where N is the number of active layers, and the intensity is further enhanced when the dye is mixed in a 1 to 1 ratio with octadecanoic acid. The second-order susceptibility and repeat lattice spacing of the mixed LB films are as follows: (chi) zzz(2) equals 76 pm V-1 at 1.064 micrometers and l equals 3.15 nm layer-1 when Z-type; (chi) zzz(2) equals 52 pm V-1 and l equals 4.13 nm bilayer-1 when interleaved. The films are transparent at the fundamental wavelength and have a slight absorbance of ca. 5 X 10-4 per dye layer at 532 nm. The second-harmonic intensity is the strongest to date from such a weakly absorbing LB film and this is attributed to the close proximity of the charge-transfer band and to an optimized packing arrangement.

  8. Structural investigation of Langmuir and Langmuir-Blodgett monolayers of semifluorinated alkanes.

    PubMed

    Dynarowicz Łatka, Patrycja; Pérez-Morales, Marta; Muñoz, Eulogia; Broniatowski, Marcin; Martín-Romero, María T; Camacho, Luis

    2006-03-30

    The behavior of a semi-fluorinated alkane (C(10)F(21)C(19)H(39)) has been studied at the air-water interface by using surface pressure and surface potential-area isotherms as well as infrared spectroscopy for the Langmuir-Blodgett films. In addition, based on the quantum chemical PM3 semiempirical approach, the dimer structure was investigated, and the double helix was found to be the most stable conformation of the dimer. The obtained results allow us to imply that the phase transition observed in the course of the surface pressure/area isotherm is due to a conformational change originating from the double helix to a vertical, single helix configuration. PMID:16553421

  9. Self-assembling of C60-imidazole and C60-pyridine adducts in the Langmuir and Langmuir-Blodgett films via complex formation with water-soluble zinc porphyrins

    NASA Astrophysics Data System (ADS)

    Marczak, Renata; Noworyta, Krzysztof; Kutner, Wlodzimierz; Gadde, Suresh; D'Souza, Francis

    2003-10-01

    The C60-pyridine, C60py, and C60-imidazole, C60im, adducts were found to self-assemble in films floating onto aqueous solutions of zinc tetrakis (N-methylpyridinium)porphyrin cation, Zn(TMPyP), or zinc tetrakis (4-sulfonatophenyl)porphyrin anion, Zn(TPPS). This self assembling was due to axial ligation of the C60 adducts (acceptors) by Zn porphyrins (donors), which lead to the formation of relatively stable donor-acceptor dyads in the water-air interfaces. The films were compressed in a Langmuir trough and characterized by isotherms of surface pressure vs. area per molecule as well as by the Brewster angle microscopy imaging. All systems formed stable aggregated Langmuir films of the "expanded liquid" type. Extensive compression of the films resulted in two-dimensional phase transitions. The area per molecule at infinite dilution of the adducts in films increased in the order: water<0.1 mM Zn(TPPS)<0.1 mM Zn(TPMyP). Comparison of the determined and calculated values of area per molecule indicated that orientation of porphyrins in the complexes was parallel with respect to the interface plane. The Langmuir films were transferred, by using the Langmuir-Blodgett technique, onto quartz slides. The UV-vis spectroscopic study of these films revealed that Zn porphyrins were transferred together with the C60 adducts and that the transfer efficiency increased in the order: C60py-Zn(TPPS)

  10. Effects of Acid Vapor, Basic Vapor and Heat Treatments on the Properties of Langmuir-Blodgett Films of Divalent Metal Salts of Fatty Acids

    NASA Astrophysics Data System (ADS)

    Saito, Mitsuyoshi; Sugi, Michio; Ikegami, Keiichi; Yoneyama, Mitsuru; Iizima, Sigeru

    1986-06-01

    When LB films are exposed to the atmosphere vaporized from acid at room temperature, the X-ray diffraction peaks attributed to the lamellar structure disappear and new peaks appear depending on the metal ion species of the salt, whereas such noticeable change is not observed by basic vapor treatment and heat treatment. Diffraction patterns for LB films of free fatty acids are not influenced by these three treatments.

  11. Coulomb blockade phenomena in ultrathin Langmuir-Blodgett sandwich junctions

    NASA Astrophysics Data System (ADS)

    Burghard, M.; Mueller-Schwanneke, C.; Philipp, G.; Roth, S.

    1999-04-01

    Electrical junctions were fabricated in sandwich configuration from Langmuir-Blodgett (LB) films of two types of material, 0953-8984/11/14/015/img1-conjugated, peripherally substituted ring systems or a 0953-8984/11/14/015/img2-bonded polymer. The sandwich junctions consisted of four to ten monolayers between two micro-structured gold electrodes, corresponding to a nominal film thickness between about 8 and 20 nm. At liquid helium temperature, the current (I)/voltage (V) characteristics generally exhibited smooth exponential behaviour or irregular steps. However, for a small fraction of the LB sandwiches comprising a 0953-8984/11/14/015/img1-conjugated or 0953-8984/11/14/015/img2-bonded compound, regular staircases were observed. It was possible to fit such 0953-8984/11/14/015/img5 characteristics with curves calculated on the basis of a Coulomb blockade model. These results are accounted for by the presence of nanometre-sized gold particles formed upon evaporation of the top electrode. Single electron tunnelling is assumed to proceed through double tunnel barrier junctions consisting of a gold island asymmetrically located between the top and bottom electrode.

  12. The Langmuir-Blodgett technique as a tool for homeotropic alignment of fluorinated liquid crystals mixed with arachidic acid.

    PubMed

    Modlińska, Anna; Bauman, Danuta

    2011-01-01

    Some fluoro-substituted liquid crystals mixed with arachidic acid in monolayers formed at air-liquid (Langmuir films) and air-solid substrate (Langmuir-Blodgett films) interfaces were investigated. Molecular organization in Langmuir films was determined on the basis of the analysis of the shape of the surface pressure-mean molecular area isotherm and observations made by means of a Brewster angle microscope. It was found that in the compression process the liquid crystal molecules are pushed out towards the top of the first monolayer being in direct contact with the subphase. Langmuir films were transferred onto the quartz substrates at various surface pressures and mono- and multilayered Langmuir-Blodgett films were obtained. The films were characterized using electronic absorption measurements. The conditions for obtaining the homeotropic orientation of the liquid crystal molecules were determined. PMID:21954335

  13. The Langmuir-Blodgett Technique as a Tool for Homeotropic Alignment of Fluorinated Liquid Crystals Mixed with Arachidic Acid

    PubMed Central

    Modlińska, Anna; Bauman, Danuta

    2011-01-01

    Some fluoro-substituted liquid crystals mixed with arachidic acid in monolayers formed at air-liquid (Langmuir films) and air-solid substrate (Langmuir-Blodgett films) interfaces were investigated. Molecular organization in Langmuir films was determined on the basis of the analysis of the shape of the surface pressure-mean molecular area isotherm and observations made by means of a Brewster angle microscope. It was found that in the compression process the liquid crystal molecules are pushed out towards the top of the first monolayer being in direct contact with the subphase. Langmuir films were transferred onto the quartz substrates at various surface pressures and mono- and multilayered Langmuir-Blodgett films were obtained. The films were characterized using electronic absorption measurements. The conditions for obtaining the homeotropic orientation of the liquid crystal molecules were determined. PMID:21954335

  14. Modeling success and failure of Langmuir-Blodgett transfer of phospholipid bilayers to silicon dioxide.

    PubMed

    Osborn, T D; Yager, P

    1995-04-01

    Formation of planar phospholipid bilayers on solid and porous substrates by Langmuir-Blodgett transfer of monolayers from the air-water interface could be of much greater utility if the process were not irreproducible and poorly understood. To that end the energetics of transferring two phospholipid monolayers to a hydrophilic surface has been examined. An approximate mathematical relationship is formulated that relates the surface pressure of the precursor monolayers to the tension within the bilayer created. Data are presented that demonstrate that bilayer transfer can be carried out reproducibly even with refractory phospholipids such as phosphatidylcholine, but only over a very narrow range of precursor monolayer surface pressures. This range is related to the lysis tension of the bilayer. The morphology of films formed within and below the successful range of surface pressures are examined by fluorescence microscopy, and the observed features are discussed in terms of the relationship above. These results provide practical guidelines for successful formation of lipid bilayers on hydrophilic surfaces; these guidelines should prove useful for research into the properties of biomembranes and for development of bilayer-based biosensors. PMID:7540429

  15. Spectroscopic properties and orientation of molecules in Langmuir-Blodgett layers of selected functionalized fullerenes.

    PubMed

    Lewandowska, Kornelia; Barszcz, Boleslaw; Graja, Andrzej; Nam, Sun Young; Han, Yi-Seul; Kim, Tae-Dong; Lee, Kwang-Sup

    2014-01-24

    Vibrational properties of two fullerene derivatives: C60TZ-OT-5 (1) and C60TH-3HX (2) have been studied using infrared absorption and Raman scattering spectroscopies. Additionally, quantum chemical calculations of the equilibrium geometry and normal mode vibrations of these functionalized fullerenes were performed. It was stated that despite of distinct structural differences between the investigated molecules, their experimental spectra are quite similar and correspond well with the calculated ones. The orientation of the molecules in the Langmuir-Blodgett films was evaluated. PMID:24051291

  16. Spectroscopic properties and orientation of molecules in Langmuir-Blodgett layers of selected functionalized fullerenes

    NASA Astrophysics Data System (ADS)

    Lewandowska, Kornelia; Barszcz, Boleslaw; Graja, Andrzej; Nam, Sun Young; Han, Yi-Seul; Kim, Tae-Dong; Lee, Kwang-Sup

    2014-01-01

    Vibrational properties of two fullerene derivatives: C60TZ-OT-5 (1) and C60TH-3HX (2) have been studied using infrared absorption and Raman scattering spectroscopies. Additionally, quantum chemical calculations of the equilibrium geometry and normal mode vibrations of these functionalized fullerenes were performed. It was stated that despite of distinct structural differences between the investigated molecules, their experimental spectra are quite similar and correspond well with the calculated ones. The orientation of the molecules in the Langmuir-Blodgett films was evaluated.

  17. Organic quarter-wave stack filter fabricated by Langmuir-Blodgett deposition

    NASA Astrophysics Data System (ADS)

    Goodwin, M. J.; Carr, N.; Harrison, K.; Lewis, K.

    1991-05-01

    An optical interference filter fabricated using organic materials deposited by the Langmuir-Blodgett technique is developed. The materials chosen for this research are a side-chain polysiloxane and an hydrocarbon-based carboxylic acid. A significant refractive-index difference between these two materials was anticipated; these properties are determined by a number of techniques including ellipsometry, reflectometry, and optical waveguiding. The measured characteristics of the filter are in good agreement with the predicted response and make a more accurate assessment of the component monolayer properties possible.

  18. Linear and nonlinear optical properties in new cyanine dye Langmuir-Blodgett multilayers

    NASA Astrophysics Data System (ADS)

    Wang, Chuang; Gao, Feng; Zeng, Hao; Ma, Shihong; Liu, Wei; Liu, Liying; Wang, Wencheng; Tian, He

    2006-08-01

    We investigated on cyanine dye (HQ) in Langmuir and Langmuir-Blodgett (LB) films using UV-visible spectra and second-harmonic generation (SHG) methods. UV-visible spectra indicated a uniform film transfer. The significant SHG fringe signal as a function of angle of incidence for Z-type LB films observed respectively. The second-order susceptibility χ (2)zzz, refractive indexes at 532 nm as well as the average tilt angle ψ between the molecular (dipolar) axis and surface normal, obtained by means of fitting the SHG data, are 42 pM/V -1, 1.4841, 57° and 32 pM/V -1, 1.4775, 53° for LB films without and with Cd 2+ ions, respectively. These high nonlinearities are due to resonant enhancement resulting from the proximity of the second harmonic wavelength to the absorption band of the films.

  19. Comparison of host-guest Langmuir-Blodgett multilayer formation by two different amphiphilic cyclodextrins

    SciTech Connect

    Parazak, D.P.; Khan, A.R.; D`Souza, V.T.; Stine, K.J.

    1996-08-07

    We report here our results for Langmuir monolayers of the derivatives of cyclodextrin shown: hexakis(6-deoxy-6-dodecylamino)-{alpha}-cyclodextrin (1a), heptakis(6-deoxy-6-dodecylamino)-{beta}-cyclodextrin (1b), and heptakis(6-deoxy-6-dodecylthio)-{beta}-cyclodextrin (2b ), which was found to be partially substituted. Langmuir films of these derivatives were examined using {Pi}-A isotherm measurements and Brewster angle microscopy. Langmuir-Blodgett (LB) multilayer films of these derivatives were deposited from subphases containing p-nitrophenol to determine the extent of incorporation of the guest molecule in the LB film. The transfer ratios of the film exhibited a noteworthy evolution with the transfer pressure. The variation in the extent of guest molecule incorporation is discussed and compared with the binding behavior in solution of unmodified cyclodextrins. 29 refs., 4 figs.

  20. Oscillatory barrier-assisted Langmuir-Blodgett deposition of large-scale quantum dot monolayers

    NASA Astrophysics Data System (ADS)

    Xu, Shicheng; Dadlani, Anup L.; Acharya, Shinjita; Schindler, Peter; Prinz, Fritz B.

    2016-03-01

    Depositing continuous, large-scale quantum dot films with low pinhole density is an inevitable but nontrivial step for studying their properties for applications in catalysis, electronic devices, and optoelectronics. This rising interest in high-quality quantum dot films has provided research impetus to improve the deposition technique. We show that by incorporating oscillatory barriers in the commonly used Langmuir-Blodgett method, large-scale monolayers of quantum dots with full coverage up to several millimeters have been achieved. With assistance of perturbation provided by the oscillatory barriers, the film has been shown to relax towards thermal equilibrium, and this physical process has been supported by molecular dynamics simulation. In addition, time evolution of dilatational moduli has been shown to give a clear indication of the film morphology and its stability.

  1. Sensitive methods for estimating the anchoring strength of nematic liquid crystals on Langmuir-Blodgett monolayers of fatty acids

    SciTech Connect

    Fazio, Valentina S. U.; Nannelli, Francesca; Komitov, Lachezar

    2001-06-01

    The anchoring of the nematic liquid crystal N-(p-methoxybenzylidene)-p-butylaniline (MBBA) on Langmuir-Blodgett monolayers of fatty acids (COOHC{sub n}H{sub 2n+1}) was studied as a function of the length of the fatty acid alkyl chain n (n=15,17,19,21). The monolayers were deposited onto glass plates coated with indium tin oxide, which were used to assemble sandwich cells of various thicknesses that were filled with MBBA in the nematic phase. The mechanism of relaxation from the flow-induced quasiplanar to the surface-induced homeotropic alignment was studied for the four aligning monolayers. It was found that the speed of the relaxation decreases linearly with increasing length of the alkyl chain n, which suggests that the Langmuir-Blodgett film plays a role in the phenomenon. This fact was confirmed by a sensitive estimation of the anchoring strength of MBBA on the fatty acid monolayers after anchoring breaking, which takes place at the transition between two electric-field-induced turbulent states, denoted as DSM1 and DSM2 (where DSM indicates dynamic scattering mode). It was found that the threshold electric field for the anchoring breaking, which can be considered as a measure of the anchoring strength, also decreases linearly as n increases. Both methods thus possess a high sensitivity in resolving small differences in anchoring strength. In cells coated with mixed Langmuir-Blodgett monolayers of two fatty acids (n=15 and n=17) a maximum of the relaxation speed was observed when the two acids were present in equal amounts. This observation suggests an efficient method for controlling the anchoring strength in homeotropic cells by changing the ratio between the components of the surfactant film.

  2. Sensitive methods for estimating the anchoring strength of nematic liquid crystals on Langmuir-Blodgett monolayers of fatty acids

    NASA Astrophysics Data System (ADS)

    Fazio, Valentina S.; Nannelli, Francesca; Komitov, Lachezar

    2001-06-01

    The anchoring of the nematic liquid crystal N-(p-methoxybenzylidene)-p-butylaniline (MBBA) on Langmuir-Blodgett monolayers of fatty acids (COOHCnH2n+1) was studied as a function of the length of the fatty acid alkyl chain n (n=15,17,19,21). The monolayers were deposited onto glass plates coated with indium tin oxide, which were used to assemble sandwich cells of various thicknesses that were filled with MBBA in the nematic phase. The mechanism of relaxation from the flow-induced quasiplanar to the surface-induced homeotropic alignment was studied for the four aligning monolayers. It was found that the speed of the relaxation decreases linearly with increasing length of the alkyl chain n, which suggests that the Langmuir-Blodgett film plays a role in the phenomenon. This fact was confirmed by a sensitive estimation of the anchoring strength of MBBA on the fatty acid monolayers after anchoring breaking, which takes place at the transition between two electric-field-induced turbulent states, denoted as DSM1 and DSM2 (where DSM indicates dynamic scattering mode). It was found that the threshold electric field for the anchoring breaking, which can be considered as a measure of the anchoring strength, also decreases linearly as n increases. Both methods thus possess a high sensitivity in resolving small differences in anchoring strength. In cells coated with mixed Langmuir-Blodgett monolayers of two fatty acids (n=15 and n=17) a maximum of the relaxation speed was observed when the two acids were present in equal amounts. This observation suggests an efficient method for controlling the anchoring strength in homeotropic cells by changing the ratio between the components of the surfactant film.

  3. Naked-eye cadmium sensor: using chromoionophore arrays of Langmuir-Blodgett molecular assemblies.

    PubMed

    Prabhakaran, Deivasigamani; Yuehong, Ma; Nanjo, Hiroshi; Matsunaga, Hideyuki

    2007-06-01

    This study demonstrates the possibility of a reversible naked-eye detection method for submicromolar levels of cadmium(II) using the Langmuir-Blodgett (L-B) technique. Molecular assemblies of 4-n-dodecyl-6-(2-thiazolylazo)resorcinol are transferred on precleaned microscopic glass slides, to act as a sensing probe. Isotherm (pi-A) measurements were performed to ensure the films' structural rigidity and homogeneity during sensor fabrication. The sensor surface morphology was characterized using atomic force microscopy and scanning electron microscopy. The probe membrane exhibits visual color transition, forming a series of reddish-orange to pinkish-purple complexes with cadmium, over a wide concentration range (0.04-44.5 microM). Cadmium response kinetics and the changes in the sensors' intrinsic optical properties were monitored using absorption spectroscopy and further confirmed using X-ray photoelectron spectroscopy. A hybrid L-B film composite of poly(vinyl stearate) and poly(vinyl-N-octadecylcarbamate) were investigated for enhancing sensor performance. The sensor was tested for its practical approach to prove its cadmium selectivity and sensitivity amid common matrix constituents using synthetic mixtures and real water samples. Using the sensor strips, the respective lower limits of cadmium detection and quantification are 0.039 and 0.050 microM, as estimated from a normalized linear calibration plot. PMID:17447727

  4. Atomic force microscopy for the study of specially prepared surfaces including transferred Langmuir-Blodgett layers. Final report

    SciTech Connect

    Dr. J. D. Miller

    1999-06-02

    During the past four years a major number of surface science research programs in the Department of Metallurgical Engineering at the University of Utah have involved the use of the Atomic Force Microscope (AFM) and the Langmuir-Blodgett (LB) film balance procured with financial assistance from DOE under grant number DE-FG03-96ER76049. These instruments have been used for research in the areas of nonsulfide flotation chemistry, mineral processing, waste paper deinking, water treatment, treatment of contaminated soil, coal preparation, and plastics recycling. In addition, the AFM and LB film balance have been of great help to university researchers in other departments at the University of Utah and elsewhere, as well as researchers from industry.

  5. High-Yield Spreading of Water-Miscible Solvents on Water for Langmuir-Blodgett Assembly.

    PubMed

    Nie, Hua-Li; Dou, Xuan; Tang, Zhihong; Jang, Hee Dong; Huang, Jiaxing

    2015-08-26

    Langmuir-Blodgett (LB) assembly is a classical molecular thin-film processing technique, in which the material is spread onto water surface from a volatile, water-immiscible solvent to create floating monolayers that can be later transferred to solid substrates. LB has also been applied to prepare colloidal thin films with an unparalleled level of microstructural control and thickness, which has enabled the discovery of many exciting collective properties of nanoparticles and the construction of bulk nanostructured materials. To maximize the benefits of LB assembly, the nanoparticles should be well dispersed in both the spreading solvent and on water. This is quite challenging since colloids usually need contrasting surface properties in order to be stable in the water-hating organic solvents and on water surface. In addition, many organic and polymeric nanostructures dissolve in those organic solvents and cannot be processed directly. Using water-liking spreading solvents can avoid this dilemma. However, spreading of water-miscible solvents on water surface is fundamentally challenging due to extensive mixing, which results in significant material loss. Here we report a conceptually simple strategy and a general technique that allows nearly exclusive spreading of such solvents on water surface using electrospray. Since the volume of these aerosolized droplets is reduced by many orders of magnitude, they are readily depleted during the initial spreading step before any significant mixing could occur. The new strategy drastically reduces the burden of material processing prior to assembly and broadens the scope of LB assembly to previously hard-to-process materials. It also avoids the use of toxic volatile organic spreading solvents, improves the reproducibility, and can be readily automated, making LB assembly a more robust tool for colloidal assembly and thin-film fabrication. PMID:26272701

  6. Molecular dynamics simulations of sputtering of Langmuir-Blodgett multilayers by keV C60 projectiles

    PubMed Central

    Paruch, R.; Rzeznik, L.; Czerwinski, B.; Garrison, B. J.; Winograd, N.; Postawa, Z.

    2009-01-01

    Coarse-grained molecular dynamics computer simulations are applied to investigate fundamental processes induced by an impact of keV C60 projectile at an organic overlayer composed of long, well-organized linear molecules. The energy transfer pathways, sputtering yields, and the damage induced in the irradiated system, represented by a Langmuir-Blodgett (LB) multilayers composed from molecules of bariated arachidic acid, are investigated as a function of the kinetic energy and impact angle of the projectile and the thickness of the organic system. In particular, the unique challenges of depth profiling through a LB film vs. a more isotropic solid are discussed. The results indicate that the trajectories of projectile fragments and, consequently, the primary energy can be channeled by the geometrical structure of the overlayer. Although, a similar process is known from sputtering of single crystals by atomic projectiles, it has not been anticipated to occur during C60 bombardment due to the large size of the projectile. An open and ordered molecular structure of LB films is responsible for such behavior. Both the extent of damage and the efficiency of sputtering depend on the kinetic energy, the impact angle, and the layer thickness. The results indicate that the best depth profiling conditions can be achieved with low-energy cluster projectiles irradiating the organic overlayer at large off-normal angles. PMID:20174461

  7. Polar Glass Structure for Second-Order Nonlinear Optics Prepared by the Langmuir-Blodgett Method Using Amorphous Polymers with an Azo-Dye

    NASA Astrophysics Data System (ADS)

    Okada, Shuji; Matsuda, Hiro; Masaki, Atsushi; Nakanishi, Hachiro; Abe, Takashi; Ito, Hiroshi

    1992-02-01

    In order to obtain Langmuir-Blodgett (LB) films for second-order nonlinear optics, LB films of the amorphous copolymers synthesized from methyl methacrylate and 2-(N-ethyl-N-(4-(4-nitrophenyl)azo)phenyl)aminoethyl acrylate were investigated. From the measurement of F-A isotherms and UV and visible spectra of the Langmuir (L) film, it was estimated that the azo-dye moiety was squeezed out from the air-water interface into the subphase, and the dipoles of azo-dye align uniaxially in the direction perpendicular to the interface. The L film could be deposited into X-type multilayers by the horizontal lifting method, resulting in the formation of “polar glass.”

  8. Wetting characteristics and stability of Langmuir-Blodgett carboxylate monolayers at the surfaces of calcite and fluorite

    SciTech Connect

    Jang, W.H.; Drelich, J.; Miller, J.D.

    1995-09-01

    Although surface chemistry fundamentals of semisoluble minerals have been studied by many researchers, detailed understanding of these systems is still incomplete. In situ Fourier transform infrared internal reflection spectroscopy (FT-IR/IRS) techniques have recently been used to successfully describe the adsorption of carboxylates at semisoluble mineral surfaces. The wetting characteristics of these adsorbed films, however, require further consideration. In this regard, the hydrophobicity and stability of transferred Langmuir-Blodgett (LB) monolayers of fatty acids at fluorite and calcite surfaces have been studied by contact angle measurements with water and diiodomethane. Generally, it was found that the transferred LB monolayers of fatty acids at a calcite surface are unstable whereas such monolayers transferred onto a fluorite surface are stable, as revealed from advancing and receding contact angle measurements. These results are believed to be due to incomplete reaction of the fatty acid monolayer at the calcite surface. In addition it was found that a closely packed well-ordered stearate monolayer similar to that of a transferred LB monolayer can be formed at fluorite surfaces by spontaneous adsorption and self-assembly from aqueous solutions. 41 refs., 13 figs., 1 tab.

  9. Simple solutions for relativistic generalizations of the Child-Langmuir law and the Langmuir-Blodgett law

    SciTech Connect

    Zhang Yongpeng; Liu Guozhi; Yang Zhanfeng; Shao Hao; Xiao Renzhen; Xing Qingzi; Zhong Huaqiang; Lin Yuzheng

    2009-04-15

    In this paper, the Child-Langmuir law and Langmuir-Blodgett law are generalized to the relativistic regime by a simple method. Two classical laws suitable for the nonrelativistic regime are modified to simple approximate expressions applicable for calculating the space-charge-limited currents of one-dimensional steady-state planar diodes and coaxial diodes under the relativistic regime. The simple approximate expressions, extending the Child-Langmuir law and Langmuir-Blodgett law to fit the full range of voltage, have small relative errors less than 1% for one-dimensional planar diodes and less than 5% for coaxial diodes.

  10. Crossover from layering to island formation in Langmuir-Blodgett growth: Role of long-range intermolecular forces

    NASA Astrophysics Data System (ADS)

    Mukherjee, Smita; Datta, Alokmay

    2011-04-01

    Combined studies by atomic force microscopy, x-ray reflectivity, and Fourier transform infrared spectroscopy on transition-metal stearate (M-St, M = Mn, Co, Zn, and Cd) Langmuir-Blodgett films clearly indicate association of bidentate coordination of the metal-carboxylate head group to layer-by-layer growth as observed in MnSt and CoSt and partially in ZnSt. Crossover to islandlike growth, as observed in CdSt and ZnSt, is associated with the presence of unidentate coordination in the head group. Morphological evolutions as obtained from one, three, and nine monolayers (MLs) of M-St films are consistent with Frank van der Merwe, Stranski-Krastanov, and Volmer Weber growth modes for M=Mn/Co, Zn, and Cd, respectively, as previously assigned, and are found to vary with number (n) of metal atoms per head group, viz. n=1 (Mn/Co), n=0.75 (Zn), and n=0.5 (Cd). The parameter n is found to decide head-group coordination such that n=1.0 corresponds to bidentate and n=0.5 corresponds to unidentate coordination; the intermediate value in Zn corresponds to a mixture of both. The dependence of the growth mode on head-group structure is explained by the fact that in bidentate head groups, with the in-plane dipole moment being zero, intermolecular forces between adjacent molecules are absent and hence growth proceeds via layering. On the other hand, in unidentate head groups, the existence of a nonzero in-plane dipole moment results in the development of weak in-plane intermolecular forces between adjacent molecules causing in-plane clustering leading to islandlike growth.

  11. Healing of Defects at the Interface of Nematic Liquid Crystals and Structured Langmuir-Blodgett Monolayers

    NASA Astrophysics Data System (ADS)

    Petit-Garrido, Núria; Trivedi, Rahul P.; Ignés-Mullol, Jordi; Claret, Josep; Lapointe, Clayton; Sagués, Francesc; Smalyukh, Ivan I.

    2011-10-01

    We use Langmuir-Blodgett molecular monolayers and nematic liquid crystals as model two- and three-dimensional orientationally ordered systems to study the stability and healing of topological defects at their contact interfaces. Integer-strength defects at the monolayer induce disclinations of similar strength in the nematic that, however, do not propagate deep into the bulk, but rather form single- or double-split arch-shaped loops pinned to the interface. This behavior is qualitatively independent of the far-field director orientation and involves either half-integer singular or twist-escaped unity-strength nonsingular nematic disclinations. These two defect configurations can be selected by varying sample preparation given their comparable free energy, consistently with direct probing by use of laser tweezers.

  12. Photoluminescence kinetics in CdS nanoclusters formed by the Langmuir-Blodgett technique

    SciTech Connect

    Zarubanov, A. A. Zhuravlev, K. S.

    2015-03-15

    The photoluminescence kinetics in CdS nanocrystals produced by the Langmuir-Blodgett technique is studied at a temperature of 5 K. The photoluminescence kinetics is described by the sum of two exponential functions, with characteristic times of about 30 and 160 ns. It is found that the fast and slow decay times become longer, as the nanocrystal size increases. Analysis of the data shows that the fast decay time is controlled by trion recombination in nanocrystals with defects, whereas the slow decay time is controlled by the annihilation of optically inactive excitons in nanocrystals without defects. It is established that, as the nanocrystal size is decreased, the fraction of imperfect nanocrystals is reduced because of an increase in the energy of defect formation.

  13. Self-Assembled Monolayers Get Their Final Finish via a Quasi-Langmuir-Blodgett Transfer.

    PubMed

    Meltzer, Christian; Dietrich, Hanno; Zahn, Dirk; Peukert, Wolfgang; Braunschweig, Björn

    2015-04-28

    The growth of self-assembled monolayers (SAMs) of octadecylphosphonic acid (ODPA) molecules on α-Al2O3(0001) and subsequent dewetting of the SAMs were studied with a combination of in situ sum-frequency generation (SFG) and molecular dynamics (MD) simulations. Although SAM growth after deposition times >8 h reduces to nearly negligible values, the resultant ODPA SAMs in solution are still not in a well-ordered state with the alkyl chains in all-trans configurations. In fact, in situ SFG spectroscopy revealed a comparatively high concentration of gauche defects of the SAM in the ODPA 2-propanol solution even after a growth time of 16 h. Here, results of the MD simulations strongly suggest that defects can be caused by ODPA molecules which are not attached to the substrate but are incorporated into the SAM layer with the polar headgroup oriented into the 2-propanol solvent. This inverted adsorption geometry of additional ODPA molecules blocks adsorption sites and thus stabilizes the SAM without improving ordering to an extent that all molecules are in the all-trans configuration. While persistent in solution, the observed defects can be healed out when the SAMs are transferred from the solvent to a gas phase. During this process, a quasi-Langmuir-Blodgett transfer of molecules takes place which drives the SAM into a higher conformational state and significantly improves its quality. PMID:25835342

  14. Growth of CdS nanocrystallites on graphene oxide Langmuir-Blodgett monolayers

    NASA Astrophysics Data System (ADS)

    Narayanam, Pavan K.; Singh, Gulbagh; Divakar Botcha, V.; Sutar, D. S.; Talwar, S. S.; Srinivasa, R. S.; Major, S. S.

    2012-08-01

    Large area GO-Cd composite Langmuir-Blodgett monolayers were transferred onto Si substrate by introducing Cd2+ ions into the subphase. The changes in the behaviour of the Langmuir monolayer isotherm in the presence of Cd2+ ions are attributed to changes in the microstructure and density of the GO sheets on the subphase surface. The uptake of Cd onto the GO monolayers and the effect of subsequent sulphidation were investigated by AFM, FTIR, Raman, XPS and HRTEM techniques. The incorporation of Cd into the GO monolayers causes some overlapping of sheets and extensive formation of wrinkles. Sulphidation of the GO-Cd sheets results in the formation of uniformly distributed CdS nanocrystallites on the entire basal plane of the GO monolayers. The de-bonding of Cd with oxygen functional groups results in a reduction of the wrinkles. The GO sheets function primarily as a platform for the interaction of metal ions with oxygen functionalities and their structure and characteristic features are not affected by either uptake of Cd or formation of CdS.

  15. Growth of CdS nanocrystallites on graphene oxide Langmuir-Blodgett monolayers.

    PubMed

    Narayanam, Pavan K; Singh, Gulbagh; Botcha, V Divakar; Sutar, D S; Talwar, S S; Srinivasa, R S; Major, S S

    2012-08-17

    Large area GO-Cd composite Langmuir-Blodgett monolayers were transferred onto Si substrate by introducing Cd(2+) ions into the subphase. The changes in the behaviour of the Langmuir monolayer isotherm in the presence of Cd(2+) ions are attributed to changes in the microstructure and density of the GO sheets on the subphase surface. The uptake of Cd onto the GO monolayers and the effect of subsequent sulphidation were investigated by AFM, FTIR, Raman, XPS and HRTEM techniques. The incorporation of Cd into the GO monolayers causes some overlapping of sheets and extensive formation of wrinkles. Sulphidation of the GO-Cd sheets results in the formation of uniformly distributed CdS nanocrystallites on the entire basal plane of the GO monolayers. The de-bonding of Cd with oxygen functional groups results in a reduction of the wrinkles. The GO sheets function primarily as a platform for the interaction of metal ions with oxygen functionalities and their structure and characteristic features are not affected by either uptake of Cd or formation of CdS. PMID:22828441

  16. Emergence of the bifurcation structure of a Langmuir-Blodgett transfer model

    NASA Astrophysics Data System (ADS)

    Köpf, Michael H.; Thiele, Uwe

    2014-11-01

    We explore the bifurcation structure of a modified Cahn-Hilliard equation that describes a system that may undergo a first-order phase transition and is kept permanently out of equilibrium by a lateral driving. This forms a simple model, e.g., for the deposition of stripe patterns of different phases of surfactant molecules through Langmuir-Blodgett transfer. Employing continuation techniques the bifurcation structure is numerically investigated using the non-dimensional transfer velocity as the main control parameter. It is found that the snaking structure of steady front states is intertwined with a large number of branches of time-periodic solutions that emerge from Hopf or period-doubling bifurcations and end in global bifurcations (sniper and homoclinic). Overall the bifurcation diagram has a harp-like appearance. This is complemented by a two-parameter study in non-dimensional transfer velocity and domain size (as a measure of the distance to the phase transition threshold) that elucidates through which local and global codimension 2 bifurcations the entire harp-like structure emerges.

  17. Surface morphologies of Langmuir-Blodgett monolayers of PEOnPSn multiarm star copolymers.

    PubMed

    Gunawidjaja, Ray; Peleshanko, Sergiy; Genson, Kirsten L; Tsitsilianis, Constantinos; Tsukruk, Vladimir V

    2006-07-01

    Star polymers composed of equal numbers of poly(ethylene oxide) (PEO) and polystyrene (PS) arms with variable lengths and a large (up to 38 total) number of arms, PEO(n)PS(n), have been examined for their ability to form domain nanostructures at the air-water and air-solid interfaces. All PEO(n)PS(n) star polymers formed stable Langmuir-Blodgett (LB) monolayers transferable to a solid substrate. A range of nanoscale surface morphologies have been observed, ranging from cylindrical to circular domains to bicontinuous structures as the weight fraction of the PEO block varied from 19% to 88% and n from 8 to 19. For the PS-rich stars and at elevated surface pressure, a two-dimensional supramolecular netlike nanostructure was formed. In contrast, in the PEO-rich star polymer with the highest PEO content, we observed peculiar dendritic superstructures caused by intramolecular segregation of nonspherical core-shell micellar structures. On the basis of Langmuir isotherms and observed monolayer morphologies, three different models of possible surface behavior of the star polymers at the interfaces were proposed. PMID:16800672

  18. 25th anniversary article: what can be done with the Langmuir-Blodgett method? Recent developments and its critical role in materials science.

    PubMed

    Ariga, Katsuhiko; Yamauchi, Yusuke; Mori, Taizo; Hill, Jonathan P

    2013-12-01

    The Langmuir-Blodgett (LB) technique is known as an elegant method for fabrication of well-defined layered structures with molecular level precision. Since its discovery the LB method has made an indispensable contribution to surface science, physical chemistry, materials chemistry and nanotechnology. However, recent trends in research might suggest the decline of the LB method as alternate methods for film fabrication such as layer-by-layer (LbL) assembly have emerged. Is LB film technology obsolete? This review is presented in order to challenge this preposterous question. In this review, we summarize recent research on LB and related methods including (i) advanced design for LB films, (ii) LB film as a medium for supramolecular chemistry, (iii) LB technique for nanofabrication and (iv) LB involving advanced nanomaterials. Finally, a comparison between LB and LbL techniques is made. The latter reveals the crucial role played by LB techniques in basic surface science, current advanced material sciences and nanotechnologies. PMID:24302266

  19. Large Area 2D and 3D Colloidal Photonic Crystals Fabricated by a Roll-to-Roll Langmuir-Blodgett Method.

    PubMed

    Parchine, Mikhail; McGrath, Joe; Bardosova, Maria; Pemble, Martyn E

    2016-06-14

    We present our results on the fabrication of large area colloidal photonic crystals on flexible poly(ethylene terephthalate) (PET) film using a roll-to-roll Langmuir-Blodgett technique. Two-dimensional (2D) and three-dimensional (3D) colloidal photonic crystals from silica nanospheres (250 and 550 nm diameter) with a total area of up to 340 cm(2) have been fabricated in a continuous manner compatible with high volume manufacturing. In addition, the antireflective properties and structural integrity of the films have been enhanced via the use of a second roll-to-roll process, employing a slot-die coating of an optical adhesive over the photonic crystal films. Scanning electron microscopy images, atomic force microscopy images, and UV-vis optical transmission and reflection spectra of the fabricated photonic crystals are analyzed. This analysis confirms the high quality of the 2D and 3D photonic crystals fabricated by the roll-to-roll LB technique. Potential device applications of the large area 2D and 3D colloidal photonic crystals on flexible PET film are briefly reviewed. PMID:27218474

  20. Diffusion barrier characteristics of co monolayer prepared by Langmuir Blodgett technique

    NASA Astrophysics Data System (ADS)

    Sharma, Sumit; Kumar, Mukesh; Rani, Sumita; Kumar, Dinesh

    2016-04-01

    Monolayers of Co over SiO2/Si substrate were deposited using Langmuir Blodgett (LB) technique. The diffusion barrier capability of Co layer was evaluated against copper diffusion. The structure of the deposited Co layer was analyzed using X-ray photoelectron spectroscopy (XPS), Energy Dispersive X-ray Spectroscopy (EDS) and Atomic force microscopy (AFM) techniques. Thermal stability of Cu/SiO2/Si and Cu/Co/SiO2/Si test structures was studied and compared using X-ray diffraction (XRD), scanning electron microscope (SEM) and four probe techniques. The samples were annealed at different temperatures starting from 200 °C up to 700 °C in vacuum for 30 min. XRD results indicated that combination of Co/SiO2 worked as diffusion barrier up to 550 °C whereas SiO2 alone could work as barrier only up to 300 °C. Sheet resistance of these samples was measured as a function of annealing temperature which also supports XRD results. C-V curves of these structures under the influence of Biased Thermal Stress (BTS) were analyzed. BTS was applied at 2.5 MV cm-1 at 150 °C. Results showed that in the presence of Co barrier layer there was no shift in the C-V curve even after 90 min of BTS while in the absence of barrier there was a significant shift in the C-V curve even after 30 min of BTS. Further these test structures were examined for leakage current density (jL) at same BTS conditions and leakage current density (jL) was plotted against the BTS duration. It was found that the Cu/Co/SiO2/Si test structure could survive about one and half time more than the Cu/SiO2/Si test structure.

  1. Distinguishing individual vibrational fingerprints: single-molecule surface-enhanced resonance raman scattering from one-to-one binary mixtures in Langmuir-Blodgett monolayers.

    PubMed

    Goulet, Paul J G; Aroca, Ricardo F

    2007-04-01

    Here, it is demonstrated that similar chemical species within a multicomponent sample can be distinguished, down to the single-molecule level, by means of their surface-enhanced vibrational fingerprints. Surface-enhanced resonance Raman scattering spectra and 2D spatial intensity maps are recorded from thin Ag nanoparticle films coated with fatty acid Langmuir-Blodgett monolayers containing one-to-one binary mixtures, at varying concentrations, of two dye molecules of similar absorption and scattering cross section (n-pentyl-5-salicylimidoperylene and octadecylrhodamine B). The results reveal the change in the distribution of the two dyes within the monolayer, and the breakdown of ensemble spectral averaging, which occur as the single-molecule regime is approached. It is found that the unimolecular level is reached when 1-10 molecules of each dye occupy the 1-microm2 scattering areas probed by the laser. These signals are attributed to the rare spatial coincidence of isolated target analyte molecules and localized electromagnetic hot spots in the nanostructured metal film. The bianalyte nature of the samples provides strong corroborative support for the attribution of spectra to single molecules at high dilution, while the effect of domain formation/aggregation is found to be important at higher concentrations. PMID:17311464

  2. Angle-resolved X-ray photoelectron spectroscopy study of poly(vinylidene fluoride)/poly(N-dodecylacrylamide) Langmuir-Blodgett nanofilms

    NASA Astrophysics Data System (ADS)

    Zhu, Huie; Gao, Yu; Yamamoto, Shunsuke; Miyashita, Tokuji; Mitsuishi, Masaya

    2016-03-01

    Our earlier research prepared ferroelectric poly(vinylidene fluoride) (PVDF) homopolymer monolayers at the air-water interface using amphiphilic poly(N-dodecylacrylamide) (pDDA) nanosheets with Langmuir-Blodgett (LB) technique. However, the miscibility of solvent for PVDF with the water sub-phase in the Langmuir trough makes the film composition unclear in spite of the feeding ratio of \\text{PVDF}:\\text{pDDA} (50:1). In this study, angle-resolved X-ray photoelectron spectroscopy (AR-XPS) was used to investigate the surface chemical composition and the depth profile of the PVDF/pDDA LB nanofilms. The X-ray photoelectron spectroscopy (XPS) spectra confirmed by the detection of fluorine atoms that PVDF molecules were deposited successfully onto the substrate. The constant chemical composition with increasing takeoff angle from 15 to 75° reflects a well-regular layer structure of the PVDF LB nanofilm. The mixing ratio of \\text{PVDF}:\\text{pDDA} is 33:1, which contributes 89.8 wt % PVDF and 10.2 wt % in the PVDF/pDDA LB nanofilms.

  3. Au/Cr-ZnO-Ni structured metal-insulator-metal diode fabrication using Langmuir-Blodgett technique for infrared sensing

    NASA Astrophysics Data System (ADS)

    Azad, Ibrahim; Ram, Manoj K.; Goswami, D. Yogi; Stefanakos, Elias

    2016-05-01

    The thin nanolayer film of ZnO was synthesized through Langmuir-Blodgett (LB) organic precursor film. The zinc stearate monolayer was formed at air-water interface using zinc acetate as a subphase. The zinc stearate monolayers were deposited on silicon (Si), glass, and gold (Au)/chromium (Cr) plated Silicon (Si) substrates using LB technique. Later, the zinc stearate multilayers LB films on various substrates were annealed at two different temperatures (300oC and 550oC) for the fabrication of zinc oxide (ZnO) nanolayer film. The zinc stearate monolayers as well zinc oxide (ZnO) nanolayer films were characterized using atomic force microscopy (AFM) and X-ray diffraction techniques. The X-ray diffraction measurement has shown the hexagonal wurtzite structure of the ZnO nanolayer on the substrate. The average surface roughness was estimated to be 1.076 nm using AFM technique. The metal-insulator-metal (MIM) diode structure was realized by sandwiching ZnO nanolayer film between thin layer of Gold (Au)/Chromium (Cr) and Nickel (Ni) on silicon substrates. The electron tunneling conduction mechanism is understood through the current-voltage (I-V) characteristics of MIM diode. The highest measured sensitivity magnitude of 20 in inverse of voltage (V-1) with rectification ratio of nearly 10 at +/-400 mV in MIM diode is an indicative of its potential application in infrared sensing applications. However, the thin film of ZnO synthesized using LB film as an insulating layer in metal-insulator-metal diode structure was studied for the first time.

  4. Construction of highly ordered lamellar nanostructures through Langmuir-Blodgett deposition of molecularly thin titania nanosheets tens of micrometers wide and their excellent dielectric properties.

    PubMed

    Akatsuka, Kosho; Haga, Masa-aki; Ebina, Yasuo; Osada, Minoru; Fukuda, Katsutoshi; Sasaki, Takayoshi

    2009-05-26

    Exfoliated unilamellar titania nanosheets of Ti(0.87)O(2) with a lateral size of 10-30 microm were deposited layer-by-layer onto various substrates by Langmuir-Blodgett procedure to produce a highly ordered lamellar nanofilms. The nanosheets dispersed in an aqueous suspension containing quaternary ammonium ions as a supporting electrolyte floated spontaneously at the air/liquid interface, and they were successfully transferred onto the substrate after surface compression. Neat tiling of the nanosheets could be realized at an optimized surface pressure. The film thus obtained was exposed to UV light to turn the substrate surface hydrophilic, which was helpful for stable repetition of monolayer deposition. Layer-by-layer growth was confirmed by UV-visible absorption spectra, which showed progressive enhancement of an absorption band due to the nanosheet. Cross-sectional transmission electron microscopy images visualized the ultrathin film homogeneously deposited on the substrate surface and a lamellar fringe of the layer-by-layer assembled nanosheets was clearly resolved at a higher magnification. X-ray diffraction data on the films showed sharp basal reflections up to the seventh order, and Williamson-Hall analysis of the pattern indicated that the film was coherent across the total thickness with respect to X-ray and that the lattice strain was extremely small. In addition, the first basal reflection was accompanied by small satellite peaks, which are accounted for by the Laue interference function. All these features clearly indicate the formation of a highly ordered lamellar nanostructure of the titania nanosheets comparable to artificial lattice films produced via modern vapor-phase deposition processes. The obtained films showed superior dielectric and insulating properties as a reflection of the highly organized film nanoarchitecture. PMID:19402657

  5. New effects in Langmuir and Langmuir-Blodgett monolayers from fluorescently labelled phospholipids and their possible use for water quality control

    NASA Astrophysics Data System (ADS)

    Ivanov, G. R.; Geshev, N. I.

    2016-02-01

    Secondary water contamination poses significant challenges to the sensitivity and selectivity of sensors used for its detection and monitoring. Currently only lab tests can detect these contaminants and by the time this happens the contaminated water has entered the city water supply system. Fluorescent chromophore NitroBenzoxaDiazole (NBD) is very suitable and had been successfully used in biosensor applications due to its high sensitivity to close proximity polarity of the medium. Over the years we have discovered 3 new effects in NBD- labelled phospholipids which can significantly improve the performance of biosensors. The phospholipid matrix provides flexible biocompatible environment for immobilization of selectively reacting enzymes, microorganisms, DNA, immunoagents, whole cells. Use of single layer (3.1 nm thickness) films at the air-water interface (Langmuir films) or deposited on solid support as Langmuir-Blodgett (LB) film gives fast response times for real time monitoring (no slow diffusion processes) and precise molecule ordering and orientation. The first new effect was fluorescence self-quenching in Langmuir and LB films. In the liquid phase films exhibit normal fluorescence. Upon transition to solid phase fluorescence intensity is almost completely self-quenched and fluorescence lifetimes in the nanosecond region decrease 2 times. This is easily measured. Usually large heavy metal atoms quench fluorescence. We observed the opposite new effect when LB film is deposited in the solid phase from a subphase containing heavy metals. The third new effect is the obtaining of nanosized cylinders with bilayer thickness, which remain stable at least for months, when LB monolayer is deposited in the phase coexistence region at thermodynamic equilibrium. This greatly increases reacting surface and sensitivity of possible sensors. Almost all possible optical experimental methods were used for this research. This includes polarized ATR FTIR and polarized UV

  6. Indium-chlorine and gallium-chlorine tetrasubstituted phthalocyanines in a bulk system, Langmuir monolayers and Langmuir-Blodgett nanolayers--spectroscopic investigations.

    PubMed

    Bursa, B; Wróbel, D; Biadasz, A; Kędzierski, K; Lewandowska, K; Graja, A; Szybowicz, M; Durmuş, M

    2014-07-15

    The paper deals with spectroscopic characterization of metallic phthalocyanines (Pc's) (indium and gallium) complexed with chlorine and substituted with four benzyloxyphenoxy peripheral groups in bulk systems, 2D Langmuir monolayers and Langmuir-Blodgett nanolayers. An influence of the molecular structure of dyes (the presence of metal and of substitutes attached to the phthalocyanine macroring) on the in situ measurements of light absorption is reported. Molecular arrangement of the phthalocyanine molecular skeleton in the Langmuir monolayers on water substrate and in the Langmuir-Blodgett nanolayers is evaluated. A comparison of the light absorption spectra of the phthalocyanine monolayers with the spectra of the dyes in solution supports the existence of dye aggregates in the monolayer. It was shown that the type of dye aggregates (oblique and H types) depends markedly on the dye molecular structures. The NIR-IR, IR reflection-absorption and Raman spectra are also monitored for Langmuir-Blodgett nanolayers in non-polarized and polarized light. It was shown that the dye molecules in the Langmuir-Blodgett layers are oriented nearly vertically with respect to a gold substrate. PMID:24682066

  7. Indium-chlorine and gallium-chlorine tetrasubstituted phthalocyanines in a bulk system, Langmuir monolayers and Langmuir-Blodgett nanolayers - Spectroscopic investigations

    NASA Astrophysics Data System (ADS)

    Bursa, B.; Wróbel, D.; Biadasz, A.; Kędzierski, K.; Lewandowska, K.; Graja, A.; Szybowicz, M.; Durmuş, M.

    2014-07-01

    The paper deals with spectroscopic characterization of metallic phthalocyanines (Pc's) (indium and gallium) complexed with chlorine and substituted with four benzyloxyphenoxy peripheral groups in bulk systems, 2D Langmuir monolayers and Langmuir-Blodgett nanolayers. An influence of the molecular structure of dyes (the presence of metal and of substitutes attached to the phthalocyanine macroring) on the in situ measurements of light absorption is reported. Molecular arrangement of the phthalocyanine molecular skeleton in the Langmuir monolayers on water substrate and in the Langmuir-Blodgett nanolayers is evaluated. A comparison of the light absorption spectra of the phthalocyanine monolayers with the spectra of the dyes in solution supports the existence of dye aggregates in the monolayer. It was shown that the type of dye aggregates (oblique and H types) depends markedly on the dye molecular structures. The NIR-IR, IR reflection-absorption and Raman spectra are also monitored for Langmuir-Blodgett nanolayers in non-polarized and polarized light. It was shown that the dye molecules in the Langmuir-Blodgett layers are oriented nearly vertically with respect to a gold substrate.

  8. Single molecular detection of a perylene dye dispersed in a Langmuir-Blodgett fatty acid monolayer using surface-enhanced resonance Raman scattering

    NASA Astrophysics Data System (ADS)

    Constantino, C. J. L.; Lemma, T.; Antunes, P. A.; Aroca, R.

    2002-02-01

    The Langmuir-Blodgett (LB) monolayer technique was used to fabricate single molecule LB monolayer containing bis(phenethylimido)perylene (PhPTCD), a red dye dispersed in arachidic acid (AA) with an average doping of 1 molecule per μm 2. The monolayer was transferred onto Ag island films to obtain spatially resolved surface-enhanced resonance Raman scattering (SERRS) spectra. The mixed LB monolayers were fabricated with a concentration, on average, of 1, 6, 19 and 118 PhPTCD molecules per μm 2 in AA. The AA provides a two-dimensional host matrix whose background signal does not interfere with the detection of the probe molecule's SERRS signal. The properties of the single molecule detection were investigated using micro-Raman with a 514.5-nm laser line. The Ag island surfaces coated with the LB monolayer were mapped with spatial steps of 3 μm and global chemical imaging of the most intense SERRS band in the spectrum was also recorded. The SERRS and surface-enhanced fluorescence (SEF) of the neat and single molecule LB monolayer were recorded in a temperature range from liquid nitrogen to +200°C. Neat PhPTCD LB monolayer spectra served as reference for the identification of characteristic signatures of the single molecule behavior. The spatial resolution of Raman-microscopy experiments, the multiplicative effect of resonance Raman and SERRS, and the high sensitivity of the new dispersive Raman instruments, allow SERRS to be part of the family of single molecular spectroscopies.

  9. Charge storage phenomena and I-V characteristics observed in ultrathin polyimide Langmuir-Blodgett films

    NASA Astrophysics Data System (ADS)

    Iwamoto, Mitsumasa; Fukuda, Atsushi

    1992-04-01

    Au/PI/Al junctions were fabricated and the charge storage phenomena in polyimide (PI) layers were examined. The current-voltage (I-V) characteristics of the junctions were examined in connection with charge storage phenomena. It was found that numerous excess charges were injected into PI multilayers from electrodes by the application of biasing voltages. Therefore, the space charge field formed in as-deposited PI layers was distorted by the excess charges injected. It was also found that asymmetric I-V characteristics observed for Au/PI/Al junctions depended on the biasing voltages, because the space charge field formed in PI layers influenced the I-V characteristics.

  10. Characterization of Langmuir-Blodgett Organclay Films using X-ray Reflectivity and Atomic Fore Microscopy

    SciTech Connect

    Koo,J.; Park, S.; Satija, S.; Tikhonov, A.; Sokolov, J.; Rafailovich, M.; Koga, T.

    2008-01-01

    Monolayers of organoclay platelets were formed at the air/water interface using the Langmuir technique and were then investigated either by in situ or lifted onto Si wafers and studied ex situ, using X-ray reflectivity (XR) methods. The XR data showed that the surfactant molecules on the clay platelets formed a dense, self-assembled monolayer where the molecules were tilted at an angle of 35 {+-}6 from the normal to the dry clay surface. The surfactant layers only covered a fraction of the clay platelet surface area, where the fractional surface coverage for the three clays studied (C6A, C15A, and C20A) was found to be 0.90, 0.86, and 0.73, respectively. These values were significantly higher than those estimated from the cation exchange capacity (CEC) values. Rather than being uniformly distributed, the surfactant was clustered in patchy regions, indicating that the surface of the clay platelets had both polar and non-polar segments. This heterogeneity confirmed the hypothesis which was previously invoked to explain the distribution of the clay platelets in melt mixed homopolymer and polymer blend nanocomposites.

  11. Order in phospholipid Langmuir-Blodgett layers and the effect of the electrical potential of the substrate.

    PubMed Central

    Yang, J; Kleijn, J M

    1999-01-01

    The ordering in dipalmitoylphosphatidylcholine (DPPC) Langmuir-Blodgett monolayers and bilayers on a semiconducting indium tin oxide (ITO) surface has been investigated at the equilibrium potential of the interface and at various externally applied potentials. Second- and fourth-rank order parameters of a diphenylhexatriene (DPH) containing phospholipid probe were derived from total internal reflection fluorescence measurements, and orientation distributions were calculated using the maximum-entropy method. Generally, bimodal orientation distributions were obtained, suggesting that only part of the probes is aligned with the DPPC molecules. The effect of applied potentials is small for DPPC layers on unmodified (hydrophilic) ITO; with decreasing potential the ordering changes slightly to more random distributions, possibly because of the onset of hydrogen evolution at the substrate surface. For monolayers on hydrophobized ITO, where the phospholipids are initially with their tails directed toward the surface, the changes are more significant. At the highest positive potential applied, the derived order parameters indicate that nearly all probes are flat on the surface. This can be understood as a result of enhanced competition between headgroups and tails for access to the surface as it becomes more polarized. On unmodified ITO the electrochemistry of Fe(CN)6(3-/4-) and Ru(bipyridyl)3(2+/3+) is hardly hindered by the presence of DPPC monolayers or bilayers. On hydrophobized ITO a DPPC monolayer enhances the redox reactions. PMID:9876144

  12. A Raft-Associated Species of Phosphatidylethanolamine Interacts with Cholesterol Comparably to Sphingomyelin. A Langmuir-Blodgett Monolayer Study

    PubMed Central

    Grzybek, Michal; Kubiak, Jakub; Łach, Agnieszka; Przybyło, Magdalena; Sikorski, Aleksander F.

    2009-01-01

    Background Specific interactions between sphingomyelin (SM) and cholesterol (Ch) are commonly believed to play a key role in the formation of rafts in the biological membranes. A weakness of this model is the implication that these microdomains are confined to the outer bilayer leaflet. The cytoplasmic leaflet, which contains the bulk of phosphatidylethanolamine (PE), phosphatidylserine (PS) and phosphatidylinositol (PI), is thought also to harbour half of the membrane cholesterol. Moreover, SLPE (1-stearoyl-2-linoleoyl-sn-glycero-3-phosphatidyl-ethanolamine) has recently been shown to be enriched in isolated detergent-resistant membranes (DRM), and this enrichment was independent of the method of isolation of DRM. Methodology/Principal Findings Here we present quantitative evidence coming from Langmuir-Blodgett monolayer experiments that SLPE forms complex with Ch similar to that between SM and Ch. The energies of these interactions as calculated form the monolayer studies are highly negative. FRAP analysis showed that NBD-Ch recovery was similar in liposomes composed of DOPC/Ch SM or SLPE but not DPPE, providing further evidence that SLPE may form an lo phase in the presence of high Ch concentration. Experiments on the solubility of DOPC liposomes containing DPPE/Ch (1∶1), SM/Ch (1∶1) or SLPE/Ch (1∶1) showed the presence of Triton X-100 insoluble floating fraction (TIFF) in the case of SM/Ch or SLPE/Ch but not in DPPE/Ch containing liposomes. Quantitative determination of particular lipid species in the TIFF fraction confirms the conclusion that SLPE (or similar PE species) could be an important constituent of the inner leaflet raft. Conclusion Such interactions suggest a possible existence of inner-leaflet nanoscale assemblies composed of cholesterol complexes with SLPE or similar unsaturated PE species. PMID:19330037

  13. Preparation of NiO Monolayer by Langmuir-Blodgett Technique and Its Characterization as Diffusion Barrier for Copper Metallization

    NASA Astrophysics Data System (ADS)

    Sharma, Sumit; Kumar, Mukesh; Rani, Sumita; Kumar, Dinesh; Tripathi, C. C.

    2015-07-01

    Langmuir-Blodgett (LB) technique was used to prepare monolayers of NiO over SiO2/Si substrate. Diffusion barrier capability of NiO layer against the diffusion of copper into the dielectric was evaluated. Deposition and structure of the NiO layer were analyzed using X-ray photoelectron spectroscopy, energy-dispersive X-ray spectroscopy, and atomic force microscopy (AFM) techniques. Thermal stability of Cu/SiO2/Si and Cu/NiO/SiO2/Si test structures was compared using X-ray diffraction (XRD), scanning electron microscope (SEM), and four probe techniques. The samples were annealed at different temperatures starting from 473 K up to 873 K (200 °C up to 600 °C) in vacuum for 30 minutes each. XRD and SEM results indicated that combination of NiO/SiO2 worked as diffusion barrier up to 773 K (500 °C), whereas SiO2 alone could work as barrier only up to 573 K (300 °C). Sheet resistance of these samples was measured as a function of annealing temperature which also supports XRD results. Capacitance-voltage ( C- V) curves of these structures under the influence of biased thermal stress (BTS) were analyzed. BTS was applied at 2.5 MV cm-1 at 423 K (150 °C). Results showed that in the presence of NiO barrier layer, there was no shift in the C- V curve even after 45 minutes of BTS. Little shift was observed after 60 minutes of BTS while in the absence of barrier there was a significant shift in the C- V curve even after 30 minutes of BTS. For the structure with NiO barrier, the threshold voltage ( V t) was almost unchanged up to 60 minutes under BTS while Vt of structure without barrier changed significantly even after 15 minutes of stress. Further, these test structures were examined for leakage current density ( j L) at same BTS conditions. It was found that the Cu/NiO/SiO2/Si test structure could survive about one and half time more than the Cu/SiO2/Si test structure.

  14. Reversible response to NO of copper phthalocyanine-based sensor at low temperature

    SciTech Connect

    Emelyanov, Yu.L.; Khatko, V.V.; Tomchenko, A.A.

    1996-12-31

    Recently, it have been reported that the NO{sub x} adsorption resulted in marked in the semiconducting properties of copper tetra-tert-butyl phthalocyanine Langmuir-Blodgett films (CuTTBPc LB films). However, the recovery time of these chemiresistors after NO{sub x} exposure was very long at room temperature. Because of this, the heating up to 150{degrees}C was needed for reasons of a reversibility. In the present paper, the authors report on the development of CuTTBPc-based sensor reversibly operating at low temperature (<50{degrees}C).

  15. Immunosensor systems with the Langmuir-film-based fluorescence detection

    SciTech Connect

    Chudinova, G K; Nagovitsyn, I A; Savranskii, V V; Karpov, R E

    2003-09-30

    A method is developed for detecting protein antigens for fluorescent immunoassay using a model system based on the technique for preparation of Langmuir films. Fluorescein isothiocyanate and donor-acceptor energy-transfer pairs of markers (the Yb complex of tetraphenyl porphyrin - benzoyl trifluoroacetoneisothiocyanate and derivatives of tetra(carboxyphenyl) porphyrin - cyanine dye containing a five-membered polyene chain), which were nor studied earlier, were used as markers for detecting the binding of an antigen on the surface of Langmuir films of antibodies. Fluorescence was detected in the near-IR region (for the first pair) and in the visible spectral range (for the second pair). To reduce the nonspecific sorption of a protein (antigen), a method was proposed for the preparation of a nonpolar surface by applying an even number of layers of stearic acid as a substrate for the Langmuir - Blodgett film. A high sensitivity of model systems to a protein antigen in solution was achieved ({approx}10{sup -11} M), the assay time being 6 - 8 min. The model system with the first donor - acceptor pair was tested in analysis of the blood plasma. The fluorescence of the Dy{sup 3+}, Tm{sup 3+}, and Yb{sup 3+} complexes of tetraphenyl porphyrin sensitised by diketonate complexes of lanthanides was studied for the first time and the enhancement of the IR fluorescence of these complexes in a Langmuir film was demonstrated. (papers devoted to the memory of academician a m prokhorov)

  16. Thermal Response of Langmuir-Blodgett Films of Dipalmitoylphosphatidylcholine Studied by Atomic Force Microscopy and Force Spectroscopy

    PubMed Central

    Oncins, Gerard; Picas, Laura; Hernández-Borrell, Jordi; Garcia-Manyes, Sergi; Sanz, Fausto

    2007-01-01

    The topographic evolution of supported dipalmitoylphosphatidylcholine (DPPC) monolayers with temperature has been followed by atomic force microscopy in liquid environment, revealing the presence of only one phase transition event at ∼46°C. This finding is a direct experimental proof that the two phase transitions observed in the corresponding bilayers correspond to the individual phase transition of the two leaflets composing the bilayer. The transition temperature and its dependency on the measuring medium (liquid saline solution or air) is discussed in terms of changes in van der Waals, hydration, and hydrophobic/hydrophilic interactions, and it is directly compared with the transition temperatures observed in the related bilayers under the same experimental conditions. Force spectroscopy allows us to probe the nanomechanical properties of such monolayers as a function of temperature. These measurements show that the force needed to puncture the monolayers is highly dependent on the temperature and on the phospholipid phase, ranging from 120 ± 4 pN at room temperature (liquid condensed phase) to 49 ± 2 pN at 65°C (liquid expanded phase), which represents a two orders-of-magnitude decrease respective to the forces needed to puncture DPPC bilayers. The topographic study of the monolayers in air around the transition temperature revealed the presence of boundary domains in the monolayer surface forming 120° angles between them, thus suggesting that the cooling process from the liquid-expanded to the liquid-condensed phase follows a nucleation and growth mechanism. PMID:17586574

  17. Development of a Taste Sensor Based on a Carbon Nanotube-Polymer Composite Material

    NASA Astrophysics Data System (ADS)

    Hirata, Takamichi; Takagi, Keisuke; Akiya, Masahiro

    2007-04-01

    A taste sensor consisting of a back-gate type field effect transistor (FET) chip based on carbon nanotube compound materials [poly(ethylene glycol) (PEG)-grafted single-walled carbon nanotubes (PEG-SWNTs)] was developed. The results of impedance measurements for five tastes (sourness, saltiness, bitterness, sweetness, and umami), are shown much difference for specific tastes which are difficult to identify by using Langmuir-Blodgett (LB) film. Moreover, the sensor is able to distinguish most of the experimental taste materials with a short response time (˜60 s).

  18. Unexpected luminescent and quenching properties of metalloporphyrins in Langmuir-Blodgett structures: application to relative air-humidity sensing

    NASA Astrophysics Data System (ADS)

    Papkovsky, Dmitry B.; Ponomarev, Gely V.; Chernov, Sergey F.; Kurochkin, Ilya N.

    1993-05-01

    Monomolecular thin solid films containing water-soluble Pt- and Pd-porphyrins were prepared and transferred onto solid supports. Surface active charged polymer on the basis of alkylated polyethyleneimine was used to improve extraction of the dye from aqueous solution to the interface. The solid-state materials obtained which showed intense long-decay luminescence were studied by optical methods with emphasis to luminescence quenching and lifetime measurements. The results were applied to quenched-luminescence lifetime-based sensing of relative air humidity. A corresponding fiber-optic prototype device was developed.

  19. High performance NH 3 gas sensor based on ordered conducting polymer ultrathin film

    NASA Astrophysics Data System (ADS)

    Xu, Jianhua; Jiang, Yadong; Yu, Junsheng; Yang, Yajie; Ying, Zhihua

    2008-02-01

    Conducting polymer ultrathin film shows promising future for gas sensor application due to their high conductivity and excellent doping/dedoping performance. In this work, based on an modified Langmuir-Blodgett film method, ultrathin conducting poly(3,4-ethylene dioxythiophene) (PEDOT) film was fabricated. The PEDOT ultathin film was characterized by UV-Vis absorption spectrum, X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) techniques. The results showed small PEDOT grains distributed in polymer LB films after the polymerization of monomer. This ultrathin film exhibited an electrical conductivity about 1.2 Scm -1, and the conductivity increased and decreased to 16.8 and 0.03 Scm -1 after doping and dedoping treatment. The interaction or response of films coated QCM to NH 3 have been tested and it has been found that sensitivity of the composite films on QCM showed better sensitivity than bulk material. To the same analyte concentration, it increased with the increasing number of LB layers coated onto QCMS before 80 layers, and then a decrease of sensitivity of QCM was observed after the layer number exceeded 80 layers. The interaction mechanisms between the ultrathin film and analyte vapor were also included.

  20. The behavior of the adsorption of cytochrome C on lipid monolayers: A study by the Langmuir-Blodgett technique and theoretical analysis.

    PubMed

    Li, Junhua; Sun, Runguang; Hao, Changchun; He, Guangxiao; Zhang, Lei; Wang, Juan

    2015-10-01

    Cytochrome c (Cyt c) is an essential component of the inner mitochondrial respiratory chain because of its function of transferring electrons. The feature is closely related to the interaction between Cyt c and membrane lipids. We used Langmuir-Blodgett monolayer technique combined with AFM to study the interaction of Cyt c with lipid monolayers at air-buffer interface. In our work, by comparing the mixed Cyt c-anionic (DPPS) and Cyt c-zwitterionic (DPPC/DPPE) monolayers, the adsorption capacity of Cyt c on lipid monolayers is DPPS>DPPE>DPPC, which is attributed to their different headgroup structures. π-A isothermal data show that Cyt c (v=2.5 μL) molecules are at maximum adsorption quantity on lipid monolayer. Moreover, Cyt c molecules would form aggregations and drag some lipids with them into subphase if the protein exceeds the maximum adsorption quantity. π-T curve indicates that it takes more time for Cyt c molecular conformation to rearrange on DPPE monolayer than on DPPC. The compressibility study reveals that the adsorption or intermolecular aggregation of Cyt c molecules on lipid monolayer will change the membrane fluidization. In order to quantitatively estimate Cyt c molecular adsorption properties on lipid monolayers, we fit the experimental isotherm with a simple surface state equation. A theoretical model is also introduced to analyze the liquid expanded (LE) to liquid condensed (LC) phase transition of DPPC monolayer. The results of theoretical analysis are in good agreement with the experiment. PMID:26071844

  1. A new approach to the deposition of nanostructured biocatalytic films

    NASA Astrophysics Data System (ADS)

    Troitsky, V. I.; Berzina, T. S.; Pastorino, L.; Bernasconi, E.; Nicolini, C.

    2003-06-01

    In the present work, monolayer engineering was used to fabricate biocatalytic nanostructured thin films based on the enzyme penicillin G acylase. The biocatalytic films with enhanced characteristics were produced by the deposition of alternate-layer assemblies with a predetermined structure using a combination of Langmuir-Blodgett and adsorption techniques. The value of enzyme activity and the level of protein detachment were measured in dependence on the variation of film composition and on the sequence of layer alternation. As a result, highly active and stable structures were found, which could be promising candidates for practical applications. The method of modification of the deposition method to provide continuous film formation on large-area supports is discussed.

  2. Synchrotron FTIR microscopy of Langmuir-Blodgett monolayers and polyelectrolyte multilayers at the solid-solid interface.

    PubMed

    Beattie, David A; Beaussart, Audrey; Mierczynska-Vasilev, Agnieszka; Harmer, Sarah L; Thierry, Benjamin; Puskar, Ljiljana; Tobin, Mark

    2012-01-24

    Synchrotron FTIR microscopy has been used to probe the structure of model boundary lubricant layers confined at the solid-solid interface. The combination of high brightness of the IR source and a novel contact geometry that uses a hemispherical internal reflection element as the means for light delivery has enabled the detection of <2.5 nm thin monolayer lubricant layers in the solid-solid contact, in addition to allowing for spectral acquisition from specific regions of the contact. Spectra of hydration water from within a confined polyelectrolyte multilayer film have also been acquired, highlighting the altered hydrogen bonding environment within the polymer layer. PMID:22225512

  3. Thermodynamic aspects of cholesterol effect on properties of phospholipid monolayers: Langmuir and Langmuir-Blodgett monolayer study.

    PubMed

    Jurak, Małgorzata

    2013-04-01

    Cholesterol is an important component of lipid rafts in mammalian cell membranes. Studies of phospholipid monolayers containing cholesterol provide insight into the role of cholesterol in regulating the properties of animal cells, raft stability, and organization. In this contribution, a study of the characteristics of binary Langmuir monolayers consisting of phospholipids, 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC), 2-oleoyl-1-palmitoyl-sn-glycero-3-phosphocholine (POPC), 1,2-dipalmitoyl-sn-glycero-3-phospho-rac-(1-glycerol) (DPPG), and cholesterol (Chol), was conducted on the basis of the surface pressure-area per molecule (π-A) isotherms. Analysis of the results obtained provided information on the mean molecular area, the excess Gibbs energy of mixing, and condensation in the monolayer. The mixed monolayers were also deposited onto the mica plates and investigated by the contact angle measurements of water, formamide, and diiodomethane. The contact angles allowed calculating surface free energy of the films from the van Oss et al. approach. It was found that cholesterol determines the molecular packing and ordering of the monolayers closely connected with the kind of phospholipid. This is reflected in the values of surface free energy of the model membranes. From the thermodynamic analysis of phospholipid/cholesterol/liquid interactions, one may draw conclusions about the most favorable composition (stoichiometry) of the binary film which is especially important in view of the lipid rafts formation. PMID:23470025

  4. Phase-modulated beams technique for thin photorefractive films characterization

    NASA Astrophysics Data System (ADS)

    Barmenkov, Yu. O.; Kir'yanov, A. V.; Starodumov, A. N.; Kozhevnikov, N. M.; Lemmetyinen, H.

    2000-04-01

    The phase-modulated beams technique is developed for nonlinear thin photorefractive films characterization. In the Raman-Nath diffraction approximation, the formulas are deduced, allowing us to measure the amplitude of phase grating recorded in a film and its nonlinear refractive index n2. The method is applied for studying Langmuir-Blodgett multilayer thin (˜0.6 μm) films of Bacteriorhodopsin at wavelength 633 nm.

  5. A Taste Sensor Based on a Carbon Nanotube

    NASA Astrophysics Data System (ADS)

    Takagi, Keisuke; Hirata, Takamichi; Akiya, Masahiro

    A taste sensor consisting of a back-gate type field effect transistor(FET) chip based on carbon nanotube compound materials[poly(ethylene glycol)(PEG)-grafted single-walled carbon nanotubes(PEG-SWNTs)] was developed. The results of impedance measurements for five tastes (sourness, saltiness, bitterness, sweetness, and umami), are shown much difference for specific tastes which are difficult to identify by using Langmuir-Blodgett(LB)film. Moreover, the sensor is able to distinguish most of the experimental taste materials with a short response time. Characteristics of the sensor involve in taste material concentration , initial impedance and frequency characteristics. A clear difference is observed over five basic taste materials.

  6. Photoluminescence quenching in a polymer thin-film field-effect luministor

    NASA Astrophysics Data System (ADS)

    Dyreklev, P.; Inganas, O.; Paloheimo, J.; Stubb, H.

    1992-03-01

    Photoluminescence quenching is observed in thin films of poly(3-hexylthiophene) and Langmuir-Blodgett films of poly(3-hexylthiophene)/arachidic acid due to the injection of positive charges in the polymer. Charge injection was made in a polymer field-effect transistor. The quenching is discussed in terms of polarons/bipolarons acting as recombination centra for the excitons and suppress the photoluminescence. The inverse phenomenon, luminescence enhancement by depletion of charges, is also achieved.

  7. Study of polymorphism of ZnPc LB thin film on annealing

    NASA Astrophysics Data System (ADS)

    Roy, Dhrubojyoti; Das, Nayan Mani; Gupta, Mukul; Gupta, P. S.

    2016-05-01

    The average molecular orientation in the as-deposited Zinc Phthalocyanine (ZnPc) Langmuir-Blodgett (LB) film has been obtained to be 47° w.r.t to substrate surface from polarized Raman spectroscopy analysis. Absorption spectroscopy confirms the phase transition of ZnPc thin film from α-phase to β-phase on annealinghowever, such confirmation could not get established from Raman spectroscopy.

  8. Fabrication Of Nano-Silver Thin Films Using Self Assembly And Its Interaction With Proteins

    SciTech Connect

    Verma, Gunjan; Choudhury, Sipra; Hassan, P. A.

    2010-12-01

    The silver nanoparticle thin films were prepared with an aim to use them for sensing of biomolecules. The monolayers of arachidic acid were deposited on glass plates by Langmuir Blodgett (LB) technique and silver nanoparticles thin films were deposited within the arachidic acid films. Small angle XRD studies confirm the formation of ordered array of nanoparticles. These thin films were treated with a model protein, bovine serum albumin (BSA a natural protein). From the optical absorption spectra a shift in the intensity as well as lambda max ({lambda}max) could be observed when silver thin films were treated with BSA.

  9. Composite films of poly(allylamine)-capped polydopamine nanoparticles and P8W48 polyoxometalates with electroactive properties.

    PubMed

    Ball, Vincent; Haider, Ali; Kortz, Ulrich

    2016-11-01

    Polyoxometalates (POMs) are often used to functionalize surfaces with photochromic or electroactive compounds. Among the common deposition methods, besides the Langmuir-Blodgett deposition, the layer-by-layer (LBL) deposition method has become more and more popular due to its facility and versatility combined with the polyanionic character of POMs. The LBL deposition of POMs and oppositely charged nanoparticles is however poorly described in the literature. Using polydopamine nanoparticles (PDA) produced in the presence of poly(allylamine) and displaying a hydrodynamic diameter of 25nm, we show that LBL films containing the large, cyclic P8W48 polyanion and the PDA@PAH nanoparticles display reduction currents which are proportional to the number of deposition steps and hence to the film thickness. In addition the obtained films display not only the electrochemical properties of the POM but also that of PDA nanoparticles. Hence we demonstrate the feasibility to build up films based on particles only with the electrochemical behavior of each kind of particles being conserved. PMID:27474813

  10. Self-assembly of ferromagnetic organic-inorganic perovskite-like films.

    PubMed

    Akhtar, Naureen; Polyakov, Alexey O; Aqeel, Aisha; Gordiichuk, Pavlo; Blake, Graeme R; Baas, Jacob; Amenitsch, Heinz; Herrmann, Andreas; Rudolf, Petra; Palstra, Thomas T M

    2014-12-10

    Perovskite-based organic-inorganic hybrids hold great potential as active layers in electronics or optoelectronics or as components of biosensors. However, many of these applications require thin films grown with good control over structure and thickness--a major challenge that needs to be addressed. The work presented here is an effort towards this goal and concerns the layer-by-layer deposition at ambient conditions of ferromagnetic organic-inorganic hybrids consisting of alternating CuCl4-octahedra and organic layers. The Langmuir-Blodgett technique used to assemble these structures provides intrinsic control over the molecular organization and film thickness down to the molecular level. Magnetic characterization reveals that the coercive field for these thin films is larger than that for solution-grown layered bulk crystals. The strategy presented here suggests a promising cost effective route to facilitate the excellently controlled growth of sophisticated materials on a wide variety of substrates that have properties relevant for the high density storage media and spintronic devices. PMID:25059565

  11. Self-assembly of rigid macromolecules to create ordered thin films

    SciTech Connect

    Enriquez, E.P.; Samulski, E.T.

    1993-12-31

    Poly({gamma}-benzyl-L-glutamate) (PBLG) derivatized at its N-terminus with lipoic acid, a disulfide-containing moiety, self-assembles on gold from helicogenic solvents to give a thin film with the polypetide {alpha}-helices orientation distribution different from the planar orientation in the unlabeled, physisorbed PBLG films (control) and Langmuir-Blodgett monolayers. These films were studied by angle-dependent XPS, reflection-absorption FTIR spectroscopy, ellipsometry, and contact angle measurements. The IR dichroic properties of the amide vibrational frequencies, in particular, were used to infer the orientational distribution of the helices in the self-assembled film.

  12. Gas sensitivity measurements on NO{sub 2} sensors based on copper(II) tetrakis(n-butylaminocarbonyl)phthalocyanine LB films

    SciTech Connect

    Capone, S.; Rella, R.; Siciliano, P.; Mongelli, S.; Valli, L.

    1999-03-02

    The NO{sub 2} gas-sensing characteristics of chemiresistors in the form of multilayered Langmuir-Blodgett films of a symmetrically substituted phthalocyanine, containing on the periphery four amidic groups -CONH-, have been studied. Floating layers were spread onto the water surface from a chloroform solution and were transferred onto both hydrophilic and hydrophobic quartz substrates using the vertical lifting method. Response and recovery times have been measured for different working temperatures at a fixed NO{sub 2} concentration. Dynamic response characteristics of the electrical conductance of the LB films to different NO{sub 2} concentrations, carried out in dry air, have shown a high sensitivity to concentrations of nitrogen dioxide smaller than 20 ppm at room temperature. All measurements have been carried out using coplanar configurations of the devices.

  13. Temperature dependence of electronic transport property in ferroelectric polymer films

    NASA Astrophysics Data System (ADS)

    Zhao, X. L.; Wang, J. L.; Tian, B. B.; Liu, B. L.; Zou, Y. H.; Wang, X. D.; Sun, S.; Sun, J. L.; Meng, X. J.; Chu, J. H.

    2014-10-01

    The leakage current mechanism of ferroelectric copolymer of polyvinylidene fluoride with trifluoroethylene prepared by Langmuir-Blodgett was investigated in the temperature range from 100 K to 350 K. The electron as the dominant injected carrier was observed in the ferroelectric copolymer films. The transport mechanisms in copolymer strongly depend on the temperature and applied voltage. From 100 K to 200 K, Schottky emission dominates the conduction. With temperature increasing, the Frenkel-Poole emission instead of the Schottky emission to conduct the carrier transport. When the temperature gets to 260 K, the leakage current becomes independent of temperature, and the space charge limited current conduction was observed.

  14. Surface excitons on a ZnO (000-1) thin film

    SciTech Connect

    Kuehn, S. Friede, S.; Elsaesser, T.; Sadofev, S.; Blumstengel, S.; Henneberger, F.

    2013-11-04

    Elementary excitations at the polar (000-1) surface of a 20 nm pseudomorphically grown ZnO thin film are examined by steady state and time-resolved photoluminescence spectroscopy at low temperature. We control the density of emission centers through the deposition of prototypical organic molecules with a carboxylic acid anchor group by the Langmuir-Blodgett technique. Knowledge of the precise film thickness, defect concentrations and number density of deposited molecules leads us to associate the surface exciton emission to defect-related localization centers that are generated through a photochemical process.

  15. How does spacer length of imidazolium gemini surfactants control the fabrication of 2D-Langmuir films of silver-nanoparticles at the air-water interface?

    PubMed

    Datta, Sougata; Biswas, Joydeep; Bhattacharya, Santanu

    2014-09-15

    A series of gemini surfactants based on cationic imidazolium ring as polar headgroup, abbreviated as [Im-n-Im], 2Br(-) (n=2, 5, 6 and 12), was synthesized. Their ability to stabilize silver nanoparticles in aqueous media was investigated. The resulting suspensions were characterized by UV-Vis spectroscopy and transmission electron microscopy (TEM). They exhibit specific morphologies by adopting different supramolecular assemblies in aqueous media depending on the internal packing arrangements and on the number of spacer methylene units [-(CH2)n-]. Individual colloids were extracted from the aqueous to chloroform layer and spread at the air/water interface to allow the formation of well-defined Langmuir films. By analysis of the surface pressure-area isotherms, the details about the packing behavior and orientation of the imidazolium gemini surfactant capped silver nanoparticles were obtained. Morphological features of the dynamic process of monolayer compression at the air-water interface were elucidated using Brewster angle microscopy (BAM). These monolayers were further transferred on mica sheets by the Langmuir-Blodgett technique at their associated collapse pressure and the morphology of these monolayers was investigated by atomic force microscopy (AFM). The number of spacer methylene units [-(CH2)n-] of the gemini surfactants exerted critical influence in modulating the characteristics of the resulting Langmuir films. PMID:24998058

  16. Characteristic Fragmentation of Polysiloxane Monolayer Films by Bombardment with Monatomic and Polyatomic Primary Ions in TOF-SIMS

    NASA Astrophysics Data System (ADS)

    Moon, Hye Kyoung; Wells, David D.; Gardella, Joseph A.

    2012-01-01

    This study reports the characteristic fragmentation patterns from two polysiloxane polymers that form ordered overlayer on silver substrates. Results are compared for the bombardment of various monatomic and polyatomic projectiles of Cs+, C{60/+} (10 keV), Bi{1/+}, and Bi{3/+} (25 keV) in the high mass range time-of-flight secondary ion mass spectrometry (TOF-SIMS) spectra. Results are reported from sub-monolayer (solution cast) coverages of poly(dimethylsiloxane)s with the number average molecular weights (Mn) of 2200 and 6140 Da, respectively, and Langmuir-Blodgett monolayers of poly(methylphenylsiloxane) with molecular weights (MW) from 600 and 1000 Da. For each film, Bi projectiles resulted in the emission of positive silver cluster ions from the substrate under the polymer overlayer and peaks corresponding to silver cluster ions with larger mass were observed by impact of polyatomic 25 keV Bi{3/+} projectiles. In addition, depending on the change of energy of Bi{3/+}, a different pattern of fragments was observed. With Cs+ and C{60/+} impact, however, the emission of silver cluster ions was not detected. In the case of C{60/+} impact for PDMS-6140, peaks corresponding to silver-cationized intact oligomers were not observed. In this paper, these results are explained by the possible bombardment mechanism for each projectile, based on its mass, energy, and split trajectories of the component atoms under the polyatomic impact.

  17. Electrocatalytic (Bio)Nanostructures Based on Polymer-Grafted Platinum Nanoparticles for Analytical Purpose.

    PubMed

    Gal, François; Challier, Lylian; Cousin, Fabrice; Perez, Henri; Noel, Vincent; Carrot, Geraldine

    2016-06-15

    Functionalized platinum nanoparticles (PtNPs) possess electrocatalytic properties toward H2O2 oxidation, which are of great interest for the construction of electrochemical oxidoreductase-based sensors. In this context, we have shown that polymer-grafted PtNPs could efficiently be used as building bricks for electroactive structures. In the present work, we prepared different 2D-nanostructures based on these elementary bricks, followed by the subsequent grafting of enzymes. The aim was to provide well-defined architectures to establish a correlation between their electrocatalytic properties and the arrangement of building bricks. Two different nanostructures have been elaborated via the smart combination of surface initiated-atom transfer radical polymerization (SI-ATRP), functionalized PtNPs (Br-PtNPs) and Langmuir-Blodgett (LB) technique. The first nanostructure (A) has been elaborated from LB films of poly(methacrylic acid)-grafted PtNPs (PMAA-PtNPs). The second nanostructure (B) consisted in the elaboration of polymer brushes (PMAA brushes) from Br-PtNPs LB films. In both systems, grafting of the glucose oxidase (GOx) has been performed directly to nanostructures, via peptide bonding. Structural features of nanostructures have been carefully characterized (compression isotherms, neutron reflectivity, and profilometry) and correlated to their electrocatalytic properties toward H2O2 oxidation or glucose sensing. PMID:27192083

  18. Synergistic electrocatalytic effect of nanostructured mixed films formed by functionalised gold nanoparticles and bisphthalocyanines.

    PubMed

    Medina-Plaza, C; Furini, L N; Constantino, C J L; de Saja, J A; Rodri Guez-Mendez, M L

    2014-12-01

    A synergistic electrocatalytic effect was observed in sensors where two electrocatalytic materials (functionalized gold nanoparticles and lutetium bisphthalocyanine) were co-deposited using the Langmuir-Blodgett technique. Films were prepared using a novel method where water soluble functionalised gold nanoparticles [(11-mercaptoundecyl)tetra(ethylene glycol)] (SAuNPs) were inserted in floating films of lutetium bisphthalocyanine (LuPc2) and dimethyldioctadecylammonium bromide (DODAB) as the amphiphilic matrix. The formation of stable and homogeneous mixed films was confirmed by π-A isotherms, BAM, UV-vis and Raman spectroscopy, as well as by SEM and TEM microscopy. The synergistic effect towards hydroquinone of the electrodes modified with LuPc2:DODAB/SAuNP was characterised by an increase in the intensity of the redox peaks and a reduction of the overpotential. This synergistic electrocatalytic effect arose from the interaction between the SAuNPs and the phthalocyanines that occur in the Langmuir-Blodgett films and from the high surface area provided by the nanostructured films. The sensitivity increased with the amount of LuPc2 and SAuNPs inserted in the films and limits of detection in the range of 10(-7)molL(-1) were attained. PMID:25440670

  19. Impedimetric and amperometric bifunctional glucose biosensor based on hybrid organic-inorganic thin films.

    PubMed

    Wang, Huihui; Ohnuki, Hitoshi; Endo, Hideaki; Izumi, Mitsuru

    2015-02-01

    A novel glucose biosensor with an immobilized mediator was studied using electrochemical impedance spectroscopy (EIS) and amperometry measurements. The biosensor has a characteristic ultrathin form and is composed of a self-assembled monolayer anchoring glucose oxidase (GOx) covered with Langmuir-Blodgett (LB) films of Prussian blue (PB). The immobilized PB in the LB films acts as a mediator and enables the biosensor to work under a low potential (0.0V vs. Ag/AgCl). In the EIS measurements, a dramatic decrease in charge transfer resistance (Rct) was observed with sequential addition of glucose, which can be attributed to enzymatic activity. The linearity of the biosensor response was observed by the variation of the sensor response (1/Rct) as a function of glucose concentration in the range 0 to 25mM. The sensor also showed linear amperometric response below 130mM glucose. The organic-inorganic system of GOx and PB nanoclusters demonstrated bifunctional sensing action, both amperometry and EIS modes, as well as long sensing stability for 4 days. PMID:25014167

  20. Synthesis, Characterization, and Electrochemical Properties of Polyaniline Thin Films

    NASA Astrophysics Data System (ADS)

    Rami, Soukaina

    Conjugated polymers have been used in various applications (battery, supercapacitor, electromagnetic shielding, chemical sensor, biosensor, nanocomposite, light-emitting-diode, electrochromic display etc.) due to their excellent conductivity, electrochemical and optical properties, and low cost. Polyaniline has attracted the researchers from all disciplines of science, engineering, and industry due to its redox properties, environmental stability, conductivity, and optical properties. Moreover, it is a polymer with fast electroactive switching and reversible properties displayed at low potential, which is an important feature in many applications. The thin oriented polyaniline films have been fabricated using self-assembly, Langmuir-Blodgett, in-situ self-assembly, layer-by-layer, and electrochemical technique. The focus of this thesis is to synthesize and characterize polyaniline thin films with and without dyes. Also, the purpose of this thesis is to find the fastest electroactive switching PANI electrode in different electrolytic medium by studying their electrochemical properties. These films were fabricated using two deposition techniques: in-situ self-assembly and electrochemical deposition. The characterization of these films was done using techniques such as Fourier Transform Infrared Spectroscopy (FTIR), UV-spectroscopy, Scanning Electron Microscope (SEM), and X-Ray Diffraction (XRD). FTIR and UV-spectroscopy showed similar results in the structure of the polyaniline films. However, for the dye incorporated films, since there was an addition in the synthesis of the material, peak locations shifted, and new peaks corresponding to these materials appeared. The 1 layer PANI showed compact film morphology, comparing to other PANI films, which displayed a fiber-like structure. Finally, the electrochemical properties of these thin films were studied using cyclic voltammetry (CV), chronoamperometry (CA), and electrochemical impedance spectroscopy (EIS) in

  1. Solution-Based Fabrication of Perovskite Multilayers and Superlattices Using Nanosheet Process

    NASA Astrophysics Data System (ADS)

    Li, Bao-Wen; Osada, Minoru; Akatsuka, Kosho; Ebina, Yasuo; Ozawa, Tadashi C.; Sasaki, Takayoshi

    2011-09-01

    We report a solution-based fabrication of perovskite multilayers and superlattices using perovskite nanosheets. Perovskite nanosheets (LaNb2O7, Ca2Nb3O10, and Sr2Nb3O10) were prepared by delaminating layered perovskites. A layer-by-layer approach using Langmuir-Blodgett deposition was effective for fabricating high-quality nanofilms of perovskite nanosheets on various substrates, such as quartz glass, Si, and SrRuO3. Structural characterizations by X-ray diffraction, transmission electron microscopy, and hard X-ray photoelectron spectroscopy revealed that these perovskite nanofilms are composed of a well-ordered lamellar structure with an atomically sharp interface. The multilayer films exhibited a stable dielectric response inherent to the perovskite nanosheet. We also found that the superlattices of (LaNb2O7/Ca2Nb3O10)5 and (Sr2Nb3O10/Ca2Nb3O10)5 possess strong interface coupling, which gives rise to enhanced dielectric constant.

  2. Molecular-based electronically switchable tunnel junction devices.

    PubMed

    Collier, C P; Jeppesen, J O; Luo, Y; Perkins, J; Wong, E W; Heath, J R; Stoddart, J F

    2001-12-19

    Solid-state tunnel junction devices were fabricated from Langmuir Blodgett molecular monolayers of a bistable [2]catenane, a bistable [2]pseudorotaxane, and a single-station [2]rotaxane. All devices exhibited a (noncapacitive) hysteretic current-voltage response that switched the device between high- and low-conductivity states, although control devices exhibited no such response. Correlations between the structure and solution-phase dynamics of the molecular and supramolecular systems, the crystallographic domain structure of the monolayer film, and the room-temperature device performance characteristics are reported. PMID:11741428

  3. Visible Absorption Properties of Retinoic Acid Controlled on Hydrogenated Amorphous Silicon Thin Film

    NASA Astrophysics Data System (ADS)

    Tsujiuchi, Yutaka; Masumoto, Hiroshi; Goto, Takashi

    2008-02-01

    Langmuir-Blodgett (LB) films of retinoic acid and LB films of retinoic acid mixed with a peptide that contains an alanine-lysine-valine (AKV) amino acid sequence deposited on a hydrogenated amorphous silicon (a-Si:H) film prepared by electron cyclotron resonance (ECR) plasma sputtering were fabricated, and their light absorption spectrums were compared. A specific visible light absorption at approximately 500 nm occurred in a film that had a film thickness of more than 80 nm and a hydrogen concentration of more than 20% in the sputtering process gas. Mixing the AKV sequence peptide with retinoic acid caused a 6 nm blueshift, from 363 to 357 nm, of the absorption maximum of the composite LB film on a SiO2 substrate. Using the same peptide, a large 30 nm blueshift, from 500 to 470 nm, was induced in the composite LB film on the a-Si:H film.

  4. Highly ordered thin films prepared with octabutoxy copper phthalocyanine complexes.

    PubMed

    Stevenson, Kelly; Miyashita, Naoko; Smieja, Joanne; Mazur, Ursula

    2003-01-01

    Langmuir-Blodgett (LB) films of copper (II) 1,4,8,11,15,18,22,25-octabutoxyphthalocyanine, nCuPc(OBu)(8), (non-peripheral substitution) and copper (II) 2,3,9,10,16,17,23,24-octabutoxyphthalocyanine, pCuPc(OBu)(8), (peripheral substitution), were fabricated and characterized by optical spectroscopy and scanning probe microscopy. The LB films were transferred onto hydrophilic substrates by vertical dipping. Although they posses relatively short polar substituents both compounds form smooth, uniform, dense, and highly stable LB monolayers composed of linear arrays of cofacial oligomers. The long range discotic assemblies of LB and spun cast films of pCuPc(OBu)(8) and nCuPc(OBu)(8) posses physical and chemical properties favorable for molecular electronic device application. PMID:12801680

  5. The influence of the preparation conditions on structure and optical properties of solid films of graphene oxide

    NASA Astrophysics Data System (ADS)

    Seliverstova, E.; Ibrayev, N.; Dzhanabekova, R.; Gladkova, V.

    2016-02-01

    In this study, we investigated the physico-chemical properties of graphene oxide monolayers at the interface water-air. Monolayers were formed by the spreading of dispersion of graphene oxide in acetone and THF. It was found than graphene monolayers are in the “liquid” state on the surface of subphase. Monolayers were transferred onto solid substrates according to Langmuir-Blodgett (LB) method. SEM images show that the films have an island structure. The films obtained from acetone solutions are more uniform, which makes them more promising in terms of their use as conductive coatings. Absorption spectrum of graphene LB films exhibits a broad band in the ultraviolet and visible region of the spectrum. The optical density of the film obtained from acetone solution is greater than the optical density of the film prepared from THF. In the visible region of the spectrum both films have high transparency.

  6. Zinc Oxide LB Films with Improved Antireflective, Photoactive and Mechanical Properties

    NASA Astrophysics Data System (ADS)

    Naszályi Nagy, Lívia; Ábrahám, Nóra; Kovács, Attila L.; van der Lee, Arie; Rouessac, Vincent; Cot, Didier; Ayral, André; Hórvölgyi, Z.

    Multifunctional Langmuir-Blodgett films were prepared using sol-gel derived ZnO and silica nanoparticles synthesized by the procedure of Seelig et al. [1] and Stöber et al. [2], respectively. High inherent porosity was observed for ZnO particles (30-40%) by pycnometry, scanning angle reflectometry, N2 adsorption-desorption and ellipsometric porosimetry methods. Water contact angle of ZnO nanoparticles was determined from the non-dissipative part of the obtained surface pressure-surface area isotherms, and by scanning angle reflectometry measurements in a Wilhelmy film balance. Antireflective and photocatalytically active coatings of ZnO particles were deposited on glass, conductive glass and silicon substrates. The antireflectivity of ZnO LB films was improved by the integration of silica nanoparticles in the LB film. The photocatalytic activity and the mechanical stability of the samples were enhanced by means of surface modification with 3-methacryloxypropyl(trimethoxy)silane.

  7. Magneto-optical investigations of molecular nanomagnet monolayers.

    PubMed

    Rozbořil, J; Rechkemmer, Y; Bloos, D; Münz, F; Wang, C N; Neugebauer, P; Čechal, J; Novák, J; van Slageren, J

    2016-05-01

    We report field-dependent magnetization measurements on monolayers of [Dy(Pc)2] on quartz, prepared by the Langmuir-Blodgett technique. The films are thoroughly characterized by means of X-ray reflectivity and atomic force microscopy. The magnetisation of the sample is measured through the magnetic circular dichroism of a ligand-based electronic transition. PMID:27080152

  8. Periodic large-area metallic split-ring resonator metamaterial fabrication based on shadow nanosphere lithography.

    PubMed

    Gwinner, Michael Christian; Koroknay, Elisabeth; Fu, Liwei; Patoka, Piotr; Kandulski, Witold; Giersig, Michael; Giessen, Harald

    2009-03-01

    A fast and cheap, large-area (>1 cm(2)), high-coverage fabrication technique for periodic metallic split-ring resonator metamaterials is presented, which allows control of inner- and outer-ring diameters, gap angles, as well as thickness and periodicity. This method, based on shadow nanosphere lithography, uses tilted-angle-rotation thermal evaporation onto Langmuir-Blodgett-type monolayers of close-packed polystyrene nanospheres. Excellent agreement of the process parameters with a simplified model is demonstrated. Pronounced, tunable optical metamaterial resonances in the range of 100 THz are consistent with simulations. PMID:19148886

  9. Artificial biomembrane based on DPPC--Investigation into phase transition and thermal behavior through ellipsometric techniques.

    PubMed

    González, Carmen M; Pizarro-Guerra, Guadalupe; Droguett, Felipe; Sarabia, Mauricio

    2015-10-01

    Organic thin film deposition presents a multiplicity of challenges. Most notably, layer thickness control, homogeneity and subsequent characterization have been not cleared yet. Phospholipid bilayers are frequently used to model cell membranes. Bilayers can be disrupted by changes in mechanical stress, pH and temperature. The strategy presented in this article is based on thermal study of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) through analysis of slight changes in material thickness. The sample was prepared by depositing X- or Y-type DPPC bilayers using Langmuir-Blodgett technique over silicon wafer. Thus, molecular inclination degree, mobility and stability of phases and their respective phase transitions were observed and analyzed through ellipsometric techniques during heating cycles and corroborated by Grazing Incidence X-ray Diffraction and Atomic Force Microcopy measurements. DPPC functional group vibrations were detected by Raman spectra analysis. Scanning Electron Microscope with Field Emission gun (FE-SEM) and conventional SEM micrographs were also used to characterize sample morphology, demonstrating that homogenous bilayer formations coexist with some vesicles or micelles at surface level. Contact angle measurements corroborate DPPC surface wettability, which is mainly related to surface treatment methods of silicon wafer used to create either hydrophilic or hydrophobic nature regarding the substrate surface. Also, shifting and intensity changes of certain functional groups into Raman spectra confirm water presence between DPPC layers. Signal analysis detects certain interdigitation between aliphatic chains. These studies correspond to the base of future biosensors based on proteins or antimicrobial peptides stabilized into phospholipid bilayers over thin hydrogel films as moist scaffold. PMID:26150275

  10. Towards Organized Hybrid Nanomaterials at the Air/Water Interface Based on Liquid-Crystal/ZnO Nanocrystals.

    PubMed

    Paczesny, Jan; Wolska-Pietkiewicz, Małgorzata; Binkiewicz, Ilona; Wróbel, Zbigniew; Wadowska, Monika; Matuła, Kinga; Dzięcielewski, Igor; Pociecha, Damian; Smalc-Koziorowska, Julita; Lewiński, Janusz; Hołyst, Robert

    2015-11-16

    The ability to self-assemble nanosized ligand-stabilized metal oxide or semiconductor materials offers an intriguing route to engineer nanomaterials with new tailored properties from the disparate components. We describe a novel one-pot two-step organometallic approach to prepare ZnO nanocrystals (NCs) coated with deprotonated 4-(dodecyloxy)benzoic acid (i.e., an X-type liquid-crystalline ligand) as a model LC system (termed ZnO-LC1 NCs). Langmuir and Langmuir-Blodgett films of the resulting hybrids are investigated. The observed behavior of the ZnO NCs at the air/water interface is rationalized by invoking a ZnO-interdigitation process mediated by the anchored liquid-crystalline shell. The ordered superstructures form according to mechanism based on a ZnO-interdigitation process mediated by liquid crystals (termed ZIP-LC). The external and directed force applied upon compression at the air/water interface and the packing of the ligands that stabilize the ZnO cores drives the formation of nanorods of ordered internal structure. To study the process in detail, we follow a nontraditional protocol of thin-film investigation. We collect the films from the air/water interface in powder form (ZnO-LC1 LB), resuspend the powder in organic solvents and utilize otherwise unavailable experimental techniques. The structural and physical properties of the resulting superlattices were studied by using electron microscopy, atomic force microscopy, X-ray studies, dynamic light scattering, thermogravimetric analysis, UV/Vis absorption, and photoluminescence spectroscopy. PMID:26427916

  11. Investigation of ferroelectric domains in thin films of vinylidene fluoride oligomers

    SciTech Connect

    Sharma, Pankaj Poddar, Shashi; Ducharme, Stephen; Gruverman, Alexei; Korlacki, Rafal

    2014-07-14

    High-resolution vector piezoresponse force microscopy (PFM) has been used to investigate ferroelectric domains in thin vinylidene fluoride oligomer films fabricated by the Langmuir-Blodgett deposition technique. Molecular chains are found to be preferentially oriented normal to the substrate, and PFM imaging shows that the films are in ferroelectric β-phase with a predominantly in-plane polarization, in agreement with infrared spectroscopic ellipsometry and X-ray diffraction measurements. The fractal analysis of domain structure has yielded the Hausdorff dimension (D) in the range of ∼1.3–1.5 indicating a random-bond nature of the disorder potential, with domain size exhibiting Landau-Lifshitz-Kittel scaling.

  12. Swift heavy ion induced modifications of single walled carbon nanotube thin films

    NASA Astrophysics Data System (ADS)

    Vishalli; Raina, K. K.; Avasthi, D. K.; Srivastava, Alok; Dharamvir, Keya

    2016-04-01

    Thin films of single walled carbon nanotubes (SWCNTs) were prepared by Langmuir-Blodgett method and irradiated with swift heavy ions, carbon and nickel each of energy 60 MeV. The ion beams have different electronic energy loss (Se) values and the samples were exposed to various irradiation doses. The irradiated films were characterized using Raman and optical absorption spectroscopy. Raman spectroscopy results indicate the competing processes of defect creation and healing (annealing) of SWCNTs at lower fluences, while at higher fluences defect creation or damage dominates. In UV-Vis-NIR spectroscopy we find that there is decrease in the intensity of characteristic peaks with every increasing fluence, indicating decrease in the optically active states with irradiation.

  13. (Thin films under chemical stress)

    SciTech Connect

    Not Available

    1990-01-01

    As stated above the purpose of this research is to enable workers in a variety of fields to understand the chemical and physical changes which take place when thin films (primarily organic films) are placed under chemical stress. This stress may occur because the film is being swelled by penetrant entrained in solvent, because interfacial reactions are occurring at one or more boundaries within the film structure, or because some component of the film is responding to an external stimulus (e.g. pH, temperature, electric field, or radiation). These questions are important within the context of our long-term goal of understanding the behavior of composite structures, composed of thin organic polymer films interspersed with Langmuir-Blodgett (LB) and self-assembled monolayers, which might have unique functional properties. In the past year we have concentrated on the following objectives: (1) understanding how the two possible diffusion mechanisms contribute to the swelling of thin films of organic polymers place in solution, (2) identifying systems which are appropriate polymer media for the construction of composite membranes for use in aqueous environments, and (3) understanding the self-assembly process for long chain fatty acids at model surfaces. Progress in meeting each of these objectives will be described in this report. 4 figs.

  14. Multimodal underwater adsorption of oxide nanoparticles on catechol-based polymer nanosheets

    NASA Astrophysics Data System (ADS)

    Yamamoto, Shunsuke; Uchiyama, Shun; Miyashita, Tokuji; Mitsuishi, Masaya

    2016-03-01

    Multimodal underwater adsorption behaviour of catechol units was demonstrated by examining the adsorption of different oxide nanoparticles on nanoscale-integrated polymer nanosheets. Catechol-based polymer nanosheets were fabricated using the Langmuir-Blodgett (LB) technique with random copolymers (p(DDA/DMA)s) of N-dodecylacrylamide (DDA) and dopamine methacrylamide (DMA). The p(DDA/DMA) nanosheets were immersed into water dispersions of SiO2, Al2O3, and WO3 nanoparticles (NPs) respectively. The results show that the adsorption properties can be altered by varying the NP type: SiO2 NP adsorption was observed only below pH = 6, at which the o-quinone form in p(DDA/DMA) nanosheets transforms into the catechol form or vice versa. However, their transition point for Al2O3 NP adsorption was found at approximately pH 10, at which the surface potential of Al2O3 NPs changes the charge polarity, indicating that the electrostatic interaction is predominant. For WO3 NPs, adsorption was observed when citric acid, which modifies the surface of WO3 NPs by complex formation, was used as a pH-controlling agent, but no adsorption was found for hydrochloric acid used as a pH controlling agent. FT-IR measurements proved that miniscule amounts of water molecules were trapped in p(DDA/DMA) nanosheets and that they acquired hydrogen bonding network formations, which might assist nanoparticle adsorption underwater and make the catechol units adjustable. The results indicate that the nanoscale spatial arrangements of catechol units in films are crucially important for the application of multimodal adsorption of oxide nanoparticles on catechol-based polymer materials.Multimodal underwater adsorption behaviour of catechol units was demonstrated by examining the adsorption of different oxide nanoparticles on nanoscale-integrated polymer nanosheets. Catechol-based polymer nanosheets were fabricated using the Langmuir-Blodgett (LB) technique with random copolymers (p(DDA/DMA)s) of N

  15. Ordered and ultrathin reduced graphene oxide LB films as hole injection layers for organic light-emitting diode

    PubMed Central

    2014-01-01

    In this paper, we demonstrated the utilization of reduced graphene oxide (RGO) Langmuir-Blodgett (LB) films as high performance hole injection layer in organic light-emitting diode (OLED). By using LB technique, the well-ordered and thickness-controlled RGO sheets are incorporated between the organic active layer and the transparent conducting indium tin oxide (ITO), leading to an increase of recombination between electrons and holes. Due to the dramatic increase of hole carrier injection efficiency in RGO LB layer, the device luminance performance is greatly enhanced comparable to devices fabricated with spin-coating RGO and a commercial conducting polymer PEDOT:PSS as the hole transport layer. Furthermore, our results indicate that RGO LB films could be an excellent alternative to commercial PEDOT:PSS as the effective hole transport and electron blocking layer in light-emitting diode devices. PMID:25298757

  16. Ordered and ultrathin reduced graphene oxide LB films as hole injection layers for organic light-emitting diode.

    PubMed

    Yang, Yajie; Yang, Xiaojie; Yang, Wenyao; Li, Shibin; Xu, Jianhua; Jiang, Yadong

    2014-01-01

    In this paper, we demonstrated the utilization of reduced graphene oxide (RGO) Langmuir-Blodgett (LB) films as high performance hole injection layer in organic light-emitting diode (OLED). By using LB technique, the well-ordered and thickness-controlled RGO sheets are incorporated between the organic active layer and the transparent conducting indium tin oxide (ITO), leading to an increase of recombination between electrons and holes. Due to the dramatic increase of hole carrier injection efficiency in RGO LB layer, the device luminance performance is greatly enhanced comparable to devices fabricated with spin-coating RGO and a commercial conducting polymer PEDOT:PSS as the hole transport layer. Furthermore, our results indicate that RGO LB films could be an excellent alternative to commercial PEDOT:PSS as the effective hole transport and electron blocking layer in light-emitting diode devices. PMID:25298757

  17. Large-scale recrystallization of the S-layer of Bacillus coagulans E38-66 at the air/water interface and on lipid films.

    PubMed Central

    Pum, D; Weinhandl, M; Hödl, C; Sleytr, U B

    1993-01-01

    S-layer protein isolated from Bacillus coagulans E38-66 could be recrystallized into large-scale coherent monolayers at an air/water interface and on phospholipid films spread on a Langmuir-Blodgett trough. Because of the asymmetry in the physiochemical surface properties of the S-layer protein, the subunits were associated with their more hydrophobic outer face with the air/water interface and oriented with their negatively charged inner face to the zwitterionic head groups of the dipalmitoylphosphatidylcholine and dipalmitoylphosphatidylethanolamine (DPPE) monolayer films. The dynamic crystal growth at both types of interfaces was first initiated at several distant nucleation points. The individual monocrystalline areas grew isotropically in all directions until the front edge of neighboring crystals was met. The recrystallized S-layer protein and the S-layer-DPPE layer could be chemically cross-linked from the subphase with glutaraldehyde. Images PMID:8478338

  18. Interfacial Assembly of Graphene Oxide Films

    NASA Astrophysics Data System (ADS)

    Valtierrez, Cain; Ismail, Issam; Macosko, Christopher; Stottrup, Benjamin

    Controlled assembly of monolayer graphene-oxide (GO) films at the air/water interface is of interest for the development of transparent conductive thin films of chemically-derived graphene. We present experimental results from investigations of the assembly of polydisperse GO sheets at the air-water interface. GO nanosheets with lateral dimensions of greater than 10 microns were created using a modified Tour synthesis (Dimiev and Tour, 2014). GO films were generated with conventional Langmuir trough techniques to control lateral packing density. Film morphology was characterized in situ with Brewster angle microscopy. Films were transferred unto a substrate via the Langmuir-Blodgett deposition technique and imaged with fluorescence quenching microscopy. Through pH modulation of the aqueous subphase, it was found that GO's intrinsic surface activity to the interface increased with increasing subphase acidity. Finally, we found a dominant elastic contribution during uniaxial film deformation as measured by anisotropic pressure measurements. A. M. Dimiev, and J. M. Tour, ``Mechanism of GO Formation,'' ACS Nano, 8, (2014)

  19. Preparation of Amperometric Glucose Biosensor Based on 4-Mercaptobenzoic Acid

    NASA Astrophysics Data System (ADS)

    Wang, Huihui; Ohnuki, Hitoshi; Endo, Hideaki; Izumi, Mitsuru

    A novel glucose biosensor was fabricated by a combination of a self-assembled monolayer (SAM) of 4-mercaptobenzoic acid and the Langmuir-Blodgett (LB) technique. Because of the catalysis of Prussian Blue contained in the LB film layers, the prepared amperometric biosensor worked at a very low potential range around 0.0 V vs. Ag/AgCl. The optimum operating conditions for glucose biosensor were investigated by varying the glucose oxidase immobilization time, the applied potential and the pH of buffer solution. The steady-state current responses of the glucose biosensor showed a good linear relationship to glucose concentrations from 0.1 mM to 154 mM.

  20. Measurement of optical anisotropy in ultrathin films using surface plasmon resonance

    NASA Astrophysics Data System (ADS)

    Devanarayanan, V. P.; Manjuladevi, V.; Poonia, Monika; Gupta, R. K.; Gupta, Sanjeev K.; Akhtar, Jamil

    2016-01-01

    The optical phenomenon, surface plasmon resonance (SPR) is employed for the measurement of optical anisotropy in the ultrathin films fabricated through Langmuir-Blodgett (LB) and self-assembled monolayer (SAM) techniques onto 50 nm gold film supported on BK7 glass substrates. The resonance angle (RA) is measured using a home built setup in Kretschmann configuration. The LB films and SAM can provide a single layer of highly ordered and organized molecules on the two dimensional surface. If the film forming molecules are anisotropic, their organization in the LB films and SAM can yield an anisotropic film due to tilt of the molecules with respect to the surface normal. The SPR spectra are recorded for the two orthogonal directions of the film with respect to the plane of incidence. The spectra are simulated by modeling the Fresnel's reflection from 4-layers viz., prism, gold, ultrathin films and air; and the real and imaginary parts of refractive index are estimated. Our study shows the metallic and dielectric nature of the LB films of bundles of single walled carbon nanotubes (SWCNTs) when the long axis of SWCNTs are aligned parallel and perpendicular to plane of incidence, respectively. The optical anisotropy was estimated from the change in real part of refractive index (Δnr) of the ultrathin films measured in the orthogonal directions. In addition, we have also studied such optical anisotropy in the LB film of cadmium-stearate and self-assembled monolayer of octadecanethiol.

  1. Quantitative determination of molecular structure in multilayered thin films of biaxial and lower symmetry from photon spectroscopies. I. Reflection infrared vibrational spectroscopy

    NASA Astrophysics Data System (ADS)

    Parikh, Atul N.; Allara, David L.

    1992-01-01

    appropriate rotation matrix operation. To test the viability of this approach, three sets of experimentally derived infrared spectra of oriented monolayer assemblies on quite distinctively different substrates were chosen for simulation: (1) n-alkanethiols self- assembled onto gold, (2) n-alkanoic acid salt Langmuir-Blodgett (LB) monolayers on carbon, and (3) n-alkanoic acid salt LB monolayers on silica glass. The formalism developed was used to simulate the spectral response and to derive structural features of the monolayers. Good agreement was found where comparisons with independent studies could be made and, in general, the method appears quite useful for structural studies of highly organized thin films.

  2. Tracing the 4000 year history of organic thin films: From monolayers on liquids to multilayers on solids

    SciTech Connect

    Greene, J. E.

    2015-03-15

    The recorded history of organic monolayer and multilayer thin films spans approximately 4000 years. Fatty-acid-based monolayers were deposited on water by the ancients for applications ranging from fortune telling in King Hammurabi's time (∼1800 BC, Mesopotamia) to stilling choppy waters for sailors and divers as reported by the Roman philosopher Pliny the Elder in ∼78 AD, and then much later (1774) by the peripatetic American statesman and natural philosopher Benjamin Franklin, to Japanese “floating-ink” art (suminagashi) developed ∼1000 years ago. The modern science of organic monolayers began in the late-1800s/early-1900s with experiments by Lord Rayleigh and the important development by Agnes Pockels, followed two decades later by Irving Langmuir, of the tools and technology to measure the surface tension of liquids, the surface pressure of organic monolayers deposited on water, interfacial properties, molecular conformation of the organic layers, and phase transitions which occur upon compressing the monolayers. In 1935, Katherine Blodgett published a landmark paper showing that multilayers can be synthesized on solid substrates, with controlled thickness and composition, using an apparatus now known as the Langmuir-Blodgett (L-B) trough. A disadvantage of LB films for some applications is that they form weak physisorbed bonds to the substrate. In 1946, Bigelow, Pickett, and Zisman demonstrated, in another seminal paper, the growth of organic self-assembled monolayers (SAMs) via spontaneous adsorption from solution, rather than from the water/air interface, onto SiO{sub 2} and metal substrates. SAMs are close-packed two-dimensional organic crystals which exhibit strong covalent bonding to the substrate. The first multicomponent adsorbed monolayers and multilayer SAMs were produced in the early 1980s. Langmuir monolayers, L-B multilayers, and self-assembled mono- and multilayers have found an extraordinarily broad range of applications including

  3. Tracing the 4000 year history of organic thin films: From monolayers on liquids to multilayers on solidsa)

    NASA Astrophysics Data System (ADS)

    Greene, J. E.

    2015-03-01

    The recorded history of organic monolayer and multilayer thin films spans approximately 4000 years. Fatty-acid-based monolayers were deposited on water by the ancients for applications ranging from fortune telling in King Hammurabi's time (˜1800 BC, Mesopotamia) to stilling choppy waters for sailors and divers as reported by the Roman philosopher Pliny the Elder in ˜78 AD, and then much later (1774) by the peripatetic American statesman and natural philosopher Benjamin Franklin, to Japanese "floating-ink" art (suminagashi) developed ˜1000 years ago. The modern science of organic monolayers began in the late-1800s/early-1900s with experiments by Lord Rayleigh and the important development by Agnes Pockels, followed two decades later by Irving Langmuir, of the tools and technology to measure the surface tension of liquids, the surface pressure of organic monolayers deposited on water, interfacial properties, molecular conformation of the organic layers, and phase transitions which occur upon compressing the monolayers. In 1935, Katherine Blodgett published a landmark paper showing that multilayers can be synthesized on solid substrates, with controlled thickness and composition, using an apparatus now known as the Langmuir-Blodgett (L-B) trough. A disadvantage of LB films for some applications is that they form weak physisorbed bonds to the substrate. In 1946, Bigelow, Pickett, and Zisman demonstrated, in another seminal paper, the growth of organic self-assembled monolayers (SAMs) via spontaneous adsorption from solution, rather than from the water/air interface, onto SiO2 and metal substrates. SAMs are close-packed two-dimensional organic crystals which exhibit strong covalent bonding to the substrate. The first multicomponent adsorbed monolayers and multilayer SAMs were produced in the early 1980s. Langmuir monolayers, L-B multilayers, and self-assembled mono- and multilayers have found an extraordinarily broad range of applications including controlled wetting

  4. Thin films under chemical stress

    SciTech Connect

    Not Available

    1991-01-01

    The goal of work on this project has been develop a set of experimental tools to allow investigators interested in transport, binding, and segregation phenomena in composite thin film structures to study these phenomena in situ. Work to-date has focuses on combining novel spatially-directed optical excitation phenomena, e.g. waveguide eigenmodes in thin dielectric slabs, surface plasmon excitations at metal-dielectric interfaces, with standard spectroscopies to understand dynamic processes in thin films and at interfaces. There have been two main scientific thrusts in the work and an additional technical project. In one thrust we have sought to develop experimental tools which will allow us to understand the chemical and physical changes which take place when thin polymer films are placed under chemical stress. In principle this stress may occur because the film is being swelled by a penetrant entrained in solvent, because interfacial reactions are occurring at one or more boundaries within the film structure, or because some component of the film is responding to an external stimulus (e.g. pH, temperature, electric field, or radiation). However all work to-date has focused on obtaining a clearer understanding penetrant transport phenomena. The other thrust has addressed the kinetics of adsorption of model n-alkanoic acids from organic solvents. Both of these thrusts are important within the context of our long-term goal of understanding the behavior of composite structures, composed of thin organic polymer films interspersed with Langmuir-Blodgett (LB) and self-assembled monolayers. In addition there has been a good deal of work to develop the local technical capability to fabricate grating couplers for optical waveguide excitation. This work, which is subsidiary to the main scientific goals of the project, has been successfully completed and will be detailed as well. 41 refs., 10 figs.

  5. A trilayer film approach to multicolor electrochromism.

    PubMed

    Matsui, Jun; Kikuchi, Rie; Miyashita, Tokuji

    2014-01-22

    Development of multicolored electrochromic materials is important to realize their applications in electronic devices such as full color electronic paper. One method to increase the number of colors in an electrochromic device is by color mixing. A simple method for color mixing involves two electrochromes deposited at different working electrodes. Selective control of the redox state of each electrochrome allows the generation of both the individual electrochrome colors and a mixture of the two colors. In this paper we report a new strategy that enables color mixing using a single working electrode. A trilayer film composed of an ultrathin layer of a ruthenium complex sandwiched between two layers of Prussian blue (PB) nanoparticles was prepared on an ITO electrode using the Langmuir-Blodgett technique. Cyclic voltammetry and spectroelectrochemistry of the films indicate that the redox state of PB located at the top and bottom layer can be independently controlled using a single working electrode. In this way a mixture of the colors of PB and Prussian yellow could be produced without the necessity for multiple electrodes. PMID:24380502

  6. Langmuir films of asphaltene model compounds and their fluorescent properties.

    PubMed

    Nordgård, Erland L; Landsem, Eva; Sjöblom, Johan

    2008-08-19

    The relationship between the physicochemical properties of asphaltenes and asphaltene structure is an issue of increasing focus. Surface pressure-area isotherms of asphaltene model compounds have been investigated to gain more knowledge of their arrangement at an aqueous surface. Variations in interfacial activity have been correlated to proposed arrangements. The presence of a carboxylic acid has shown to be crucial for their interfacial activity and film properties. The acid group directs the molecules normal to the surface, forming a stable monolayer film. The high stability was absent when no acidic groups were present. Fluorescence spectra of deposited Langmuir-Blodgett films showed only the presence of the excimer emission for thin films of acidic model compounds, indicating a close face-to-face arrangement of the molecules. Time-correlated single photon counting (TCSPC) of the model compounds in toluene indicated the presence of aggregates for two of four compounds at low concentrations. However, a sudden drop of interfacial tension observed could not be correlated to the aggregation. Instead, aggregation induced by addition of a "poor" solvent showed decreased interfacial activity when aggregated due to decrease of monomers in bulk. The findings regarding these asphaltene model compounds and their structural differences show the great effect an acidic group has on their physicochemical properties. PMID:18652499

  7. Structural hierarchy in molecular films of two class II hydrophobins.

    PubMed

    Paananen, Arja; Vuorimaa, Elina; Torkkeli, Mika; Penttilä, Merja; Kauranen, Martti; Ikkala, Olli; Lemmetyinen, Helge; Serimaa, Ritva; Linder, Markus B

    2003-05-13

    Hydrophobins are highly surface-active proteins that are specific to filamentous fungi. They function as coatings on various fungal structures, enable aerial growth of hyphae, and facilitate attachment to surfaces. Little is known about their structures and structure-function relationships. In this work we show highly organized surface layers of hydrophobins, representing the most detailed structural study of hydrophobin films so far. Langmuir-Blodgett films of class II hydrophobins HFBI and HFBII from Trichoderma reesei were prepared and analyzed by atomic force microscopy. The films showed highly ordered two-dimensional crystalline structures. By combining our recent results on small-angle X-ray scattering of hydrophobin solutions, we found that the unit cells in the films have dimensions similar to those of tetrameric aggregates found in solutions. Further analysis leads to a model in which the building blocks of the two-dimensional crystals are shape-persistent supramolecules consisting of four hydrophobin molecules. The results also indicate functional and structural differences between HFBI and HFBII that help to explain differences in their properties. The possibility that the highly organized surface assemblies of hydrophobins could allow a route for manufacturing functional surfaces is suggested. PMID:12731866

  8. Tensile testing of ultra-thin films on water surface

    NASA Astrophysics Data System (ADS)

    Kim, Jae-Han; Nizami, Adeel; Hwangbo, Yun; Jang, Bongkyun; Lee, Hak-Joo; Woo, Chang-Su; Hyun, Seungmin; Kim, Taek-Soo

    2013-10-01

    The surface of water provides an excellent environment for gliding movement, in both nature and modern technology, from surface living animals such as the water strider, to Langmuir-Blodgett films. The high surface tension of water keeps the contacting objects afloat, and its low viscosity enables almost frictionless sliding on the surface. Here we utilize the water surface as a nearly ideal underlying support for free-standing ultra-thin films and develop a novel tensile testing method for the precise measurement of mechanical properties of the films. In this method, namely, the pseudo free-standing tensile test, all specimen preparation and testing procedures are performed on the water surface, resulting in easy handling and almost frictionless sliding without specimen damage or substrate effects. We further utilize van der Waals adhesion for the damage-free gripping of an ultra-thin film specimen. Our approach can potentially be used to explore the mechanical properties of emerging two-dimensional materials.

  9. Characteristics of Intramolecular Charge Transfer by J-Aggregates in Merocyanine Dye LB Films.

    PubMed

    Yang, Chang Heon; Kwon, Young-Soo; Shin, Hoon-Kyu

    2016-06-01

    In this study, for the development of future molecular electronic devices, we have investigated the characteristics of the aggregates of Langmuir-Blodgett films. The characteristics of intramolecular charge transfer by J-aggregates in merocyanine dye LB films have been studied experimentally by using UV irradiation and heat treatment. In addition to intramolecular charge transfer, we also studied the conjugation and energy changes of the molecules. In case a dye is thinned by LB method, the alkyl chain is often displaced in order to form a mono-molecular film with ease. Since the molecular association form is often made by self-organization of molecules themselves, in case the dye and the alkyl chain are strongly bonded by the covalent bond, it may be said that the properties of the LB film to be built up are almost determined at the time of synthesis of film-forming molecules. Meanwhile, since, in case LB film is fabricated by the diffusion absorption method, the cohesive force between the water-soluble dye and the surface-active mono-molecular film is electrostatic, the dye molecule can move relatively freely on the air/water interface, which may be regarded as a two-dimensional crystal growth process. PMID:27427711

  10. Ordered organic thin films self-assembled from the vapor phase

    NASA Technical Reports Server (NTRS)

    Debe, M. K.

    1993-01-01

    Organic films self-assembled from a liquid phase, as in Langmuir-Blodgett or adsorption from solution, have received much attention in the past decade as techniques to achieve highly oriented-ordered polymeric thin films. Many organic compounds including some of the same fatty acids have been vapor deposited as well. However, organic pigments and dyes comprise a major class of important materials which have very low solubilities yet excellent thermal stabilities, making them ideally suited for film deposition from the vapor phase. Surprisingly, such molecular systems exhibit a significant propensity to self order, a high sensitivity to deposition parameters, and a range of microstructural forms that cannot be duplicated by the less energetic mechanisms associated with solution adsorption processes. Molecular solids such as heterocyclic polynuclear aromatics are excellent candidates for film formation by vacuum deposition means. Over the past decade, our work and that of others investigating a wide variety of perylene and phthalocyanine derivatives identified five deposition parameters that can significantly affect film morphology, physical microstructure, and type and extent of ordering developed in vacuum and vapor transport grown films. These parameters are substrate temperature, deposition rate, substrate chemistry and epitaxy, ambient gas convective flows, and post deposition annealing. Examples of how each of these conditions manifest themselves in the film structure and ordering, most frequently revealed by scanning electron microscopy, reflection absorption infrared spectroscopy (RAIR), and grazing incidence x-ray diffraction (GIX), are presented.

  11. Properties of Organic Films on Aqueous Subphases

    NASA Astrophysics Data System (ADS)

    Gilman, J.; Vaida, V.

    2003-12-01

    Recently, it has been determined that organics represent a significant percentage of the composition of certain atmospheric aerosols. The air/aqueous interface of such an aerosol has the ability to act as a concentrator and selector of organic surfactants. Amphiphilic organics, such as fatty acids and alcohols, have been found to partition to the interface of aerosols thus creating a hydrophobic organic coating on an aqueous core. The selectivity of the interface was studied by monitoring the composition of various films, via GC-MS, as a function of exposure time. A Langmuir-Blodgett trough was used to contain and collect the self-assembled films that were produced from the addition of binary solutions of surfactants to the surface of an aqueous subphase. Surfactants with differing carbon number and head group functionalities were studied. The stability of the films was examined by varying the thickness of the organic films and the pH of the subphase. For a multilayer film containing equimolar stearic acid and lauric acid on a distilled water subphase, it was found that the acid with the longer hydrocarbon tail (stearic acid) remained at the interface much longer that the shorter acid. Films containing 1-octadecanol and stearic acid, both of which have identical carbon numbers, showed similar lifetimes at the air/water interface. Octadecane was found to have a longer lifetime at the interface when dissolved in equimolar stearic acid than when in a homogeneous film. Multilayer films and films formed on acidic subphases were found to be the most stable for both fatty acids studied. The relevance of these findings as they relate to organic aerosol content and structure as well as atmospheric processing and transport will be discussed.

  12. Electric Transport Phenomena of Nanocomposite Organic Polymer Thin Films

    NASA Astrophysics Data System (ADS)

    Jira, Nicholas C.; Sabirianov, Ildar; Ilie, Carolina C.

    We discuss herein the nanocomposite organic thin film diodes for the use of plasmonic solar cells. This experimental work follows the theoretical calculations done for plasmonic solar cells using the MNPBEM toolbox for MatLab. These calculations include dispersion curves and amount of light scattering cross sections for different metallic nanoparticles. This study gives us clear ideas on what to expect from different metals, allowing us to make the best choice on what to use to obtain the best results. One specific technique for light trapping in thin films solar cells utilizes metal nanoparticles on the surface of the semiconductor. The characteristics of the metal, semiconductor interface allows for light to be guided in between them causing it to be scattered, allowing for more chances of absorption. The samples were fabricated using organic thin films made from polymers and metallic nanoparticles, more specifically Poly(1-vinylpyrrolidone-co-2-dimethylaminoethyl methacrylate) copolymer and silver or gold nanoparticles. The two fabrication methods applied include spin coating and Langmuir-Blodgett technique. The transport properties are obtained by analyzing the I-V curves. We will also discuss the resistance, resistivity, conductance, density of charge carriers. SUNY Oswego SCAC Grant.

  13. Ordered conducting polymer multilayer films and its application for hole injection layers in organic light-emitting devices

    NASA Astrophysics Data System (ADS)

    Xu, Jianhua; Yang, Yajie; Yu, Junsheng; Jiang, Yadong

    2009-01-01

    We reported a controlled architecture growth of layer-ordered multilayer film of poly(3,4-ethylene dioxythiophene) (PEDOT) via a modified Langmuir-Blodgett (LB) method. An in situ polymerization of 3,4-ethylene dioxythiophene (EDOT) monomer in multilayer LB film occurred for the formation of ordered conducting polymer embedded multilayer film. The well-distribution of conducting polymer particles was characterized by secondary-ion mass spectrometry (SIMS). The conducting film consisting of ordered PEDOT ultrathin layers was investigated as a hole injection layer for organic light-emitting diodes (OLEDs). The results showed that, compared to conventional spin-coating PEDOT film and electrostatic self-assembly (ESA) film, the improved performance of OLEDs was obtained after using ordered PEDOT LB film as hole injection layer. It also indicated that well-ordered structure of hole injection layer was attributed to the improvement of OLED performance, leading to the increase of charged carrier mobility in hole injection layer and the recombination rate of electrons and holes in the electroluminescent layer.

  14. Photosensitive organized organic films in the light of bound electromagnetic waves

    NASA Astrophysics Data System (ADS)

    Sekkat, Zouheir; Knoll, Wolfgang

    1997-01-01

    This paper describes recent advances in the field of photochromic polymeric structures for optical data storage. In particular, we discuss photo-induced effects in supramolecular assemblies containing azobenzene molecules (e.g. Langmuir-Blodgett-Kuhn structures and ultrathin silane layers). Reorientation of azobenzenes in these structures is compared to that observed in spin-cast films. Photoisomerization and photo-induced orientation of azobenzene molecules is studied at the molecular level by means of azosilane molecules chemisorbed on silicon oxide substrates. The study of the thermal back isomerization reaction of the azobenzene molecules in these layers reveals steric hindrance at the molecular level. These ultra-thin photochromic self-assembled monolayers (SAMs) exhibit persistent dichroism upon linearly polarized light irradiation. This dichroism could be both written and erased by irradiation with light of an appropriate wavelength. In addition, the sign of this dichroism can be inverted by choosing the appropriate polarization of the irradiating light, thus showing a 'smart communication' between the light polarization and the ultra-thin photochromic layers. Photoisomerization also induces reversible changes in the optical thickness of these molecularly thin SAMs. Langmuir- Blodgett-Kuhn (LBK) multilayer assemblies of 'hairy-rod' polyglutamates with stiff main chains and flexible side chains containing photochromic azo units exhibit a highly optically anisotropic structure when the azo molecules are in the trans form, and a nearly optically isotropic structure when the azo molecules are in the cis form. The trans $ARLR cis photoisomerization of the azo molecules switches them between a highly oriented trans configuration and a bend cis configuration, thus turning the anisotropy 'on' and 'off.' In contrast to spin-cast polymer films containing azobenzene units, photoselection under polarized light irradiation does not occur in these LBK structures. The

  15. Aggregation of quantum dots in hybrid structures based on TiO2 nanoparticles

    NASA Astrophysics Data System (ADS)

    Kolesova, Ekaterina P.; Orlova, Anna O.; Maslov, Vladimir G.; Gun'ko, Yurii K.; Cleary, Olan; Baranov, Aleksander V.; Fedorov, Anatoly V.

    2016-04-01

    A morphology and photoinduced changes of luminescence properties of two types of hybrid structures based on TiO2 nanoparticles and CdSe/ZnS QDs were examined. A spin-coating method and a modified Langmuir- Blodgett technique have been applied to form the multilayer hybrid structures on glass slides. It was demonstrated that uniformity of QD surface concentration in hybrid structures depends on the method of structure formation. A photodegradation of luminescence properties of the structures is associated with the formation of QD aggregates. The QD aggregate concentration and their size depend on the method of the structure formation and the concentration of TiO2 nanoparticles. A decay of luminescence of QD aggregates in hybrid structures contains a microsecond components. An exposure of the hybrid structures with uniform QD surface concentration by visible light resulted in a photopassivation of their surface, which is accompanied by significant increase of luminescence quantum yield of QDs.

  16. 70 Years of Built-Up Films: Katharine Blodgett's Scientific Legacy

    NASA Astrophysics Data System (ADS)

    Schwartz, Daniel

    2004-03-01

    While working at the General Electric Research Laboratories in 1934, Katharine Blodgett published a brief account (in JACS) of her success at transferring layers of fatty acids from the water surface to a glass plate layer-by-layer; creating what was arguably the first rationally-designed nanostructured material. These structures would come bear her name along with that of her mentor, Irving Langmuir. Although various commercial applications have been proposed, ranging from anti-reflection coatings to soft X-ray monochromators, Langmuir-Blodgett (LB) films have never truly found their way into the marketplace in a significant way. Nevertheless, the scientific interest in LB films remains strong after 70 years because the technique offers a controlled method for building supermolecular assemblies with well-defined molecular arrangement and orientation. LB films have proven extremely useful as a research tool in order to explore fundamental interactions of amphiphilic molecules, chemical reactions in confined geometries, and to create model systems to calibrate and challenge new experimental techniques. From a statistical physics standpoint, LB films offer the possibility of studying the evolution of structure and phase transitions as a molecular system evolves from two to three dimensions. LB methods are also frequently used to create model biological membranes of known composition as well as molecular (or nanoparticle) layers for studies of potential nanoscale optoelectronic devices.

  17. Atomically Defined Templates for Epitaxial Growth of Complex Oxide Thin Films

    PubMed Central

    Dral, A. Petra; Dubbink, David; Nijland, Maarten; ten Elshof, Johan E.; Rijnders, Guus; Koster, Gertjan

    2014-01-01

    Atomically defined substrate surfaces are prerequisite for the epitaxial growth of complex oxide thin films. In this protocol, two approaches to obtain such surfaces are described. The first approach is the preparation of single terminated perovskite SrTiO3 (001) and DyScO3 (110) substrates. Wet etching was used to selectively remove one of the two possible surface terminations, while an annealing step was used to increase the smoothness of the surface. The resulting single terminated surfaces allow for the heteroepitaxial growth of perovskite oxide thin films with high crystalline quality and well-defined interfaces between substrate and film. In the second approach, seed layers for epitaxial film growth on arbitrary substrates were created by Langmuir-Blodgett (LB) deposition of nanosheets. As model system Ca2Nb3O10- nanosheets were used, prepared by delamination of their layered parent compound HCa2Nb3O10. A key advantage of creating seed layers with nanosheets is that relatively expensive and size-limited single crystalline substrates can be replaced by virtually any substrate material. PMID:25549000

  18. Effects of plasmonic field due to gold nanoparticles and magnetic field on photocurrents of zinc porphyrin-viologen linked compound-gold nanoparticle composite films

    NASA Astrophysics Data System (ADS)

    Yonemura, Hiroaki; Niimi, Tomoki; Yamada, Sunao

    2016-03-01

    Composite films of zinc-porphyrin-viologen (ZnP-V2+) linked compound containing six methylene group [ZnP(6)V]-gold nanoparticles (AuNP) were fabricated by combining electrostatic layer-by-layer adsorption and the Langmuir-Blodgett method. The anodic photocurrents of the ZnP(6)V-AuNP composite films are higher than those of the ZnP(6)V films. The large photocurrents in ZnP(6)V-AuNP composite films are most likely attributable to the combination of localized surface plasmon resonance due to AuNP and photoinduced intramolecular electron transfer from excited state of ZnP to V2+. The photocurrents of the ZnP(6)V-AuNP composite films increase in the presence of magnetic field. The photocurrents increase with low magnetic fields (B ≤ 150 mT) and are almost constant under high magnetic fields (B ≥ 150 mT). Magnetic field effects (MFEs) were clearly observed for both ZnP(6)V-AuNP composite films and ZnP(6)V films. The MFEs can be explained by a radical pair mechanism.

  19. Cellulose antibody films for highly specific evanescent wave immunosensors

    NASA Astrophysics Data System (ADS)

    Hartmann, Andreas; Bock, Daniel; Jaworek, Thomas; Kaul, Sepp; Schulze, Matthais; Tebbe, H.; Wegner, Gerhard; Seeger, Stefan

    1996-01-01

    For the production of recognition elements for evanescent wave immunosensors optical waveguides have to be coated with ultrathin stable antibody films. In the present work non amphiphilic alkylated cellulose and copolyglutamate films are tested as monolayer matrices for the antibody immobilization using the Langmuir-Blodgett technique. These films are transferred onto optical waveguides and serve as excellent matrices for the immobilization of antibodies in high density and specificity. In addition to the multi-step immobilization of immunoglobulin G(IgG) on photochemically crosslinked and oxidized polymer films, the direct one-step transfer of mixed antibody-polymer films is performed. Both planar waveguides and optical fibers are suitable substrates for the immobilization. The activity and specificity of immobilized antibodies is controlled by the enzyme-linked immunosorbent assay (ELISA) technique. As a result reduced non-specific interactions between antigens and the substrate surface are observed if cinnamoylbutyether-cellulose is used as the film matrix for the antibody immobilization. Using the evanescent wave senor (EWS) technology immunosensor assays are performed in order to determine both the non-specific adsorption of different coated polymethylmethacrylat (PMMA) fibers and the long-term stability of the antibody films. Specificities of one-step transferred IgG-cellulose films are drastically enhanced compared to IgG-copolyglutamate films. Cellulose IgG films are used in enzymatic sandwich assays using mucine as a clinical relevant antigen that is recognized by the antibodies BM2 and BM7. A mucine calibration measurement is recorded. So far the observed detection limit for mucine is about 8 ng/ml.

  20. Oriented inorganic thin film channel structures with uni-directional monosize micropores

    SciTech Connect

    Cesarano, J. III; Sasaki, D.Y.; Singh, S.; Brinker, C.J.

    1997-10-01

    The goal of this project was to develop a novel technology that may be used to eventually manufacture a new generation of inorganic membranes and sensors with oriented, unidirectional monosized pores. The premise is that very thin membranes with oriented channels as pores will have a high flux in addition to being highly selective. Applications include: (1) gas separation membranes for oxygen enrichment, partial oxidation, dehydrogenation, and purification of natural gas; (2) refractory catalytic membrane reactors; and (3) molecular recognition sensors. The methodology for making such membranes was to combine Langmuir - Blodgett (LB) technology with sol-gel chemistry to engineer pore channels within the range 3 to 20 K The channel structure was fabricated of amorphous SiO{sub 2} because of its good thermal, chemical, and mechanical stability. Our approach was to use LB techniques to uniformly place organic molecular spacers throughout a thin silica precursor matrix and apply this film to a substrate. LB films of solid solutions of commercially available silane amphiphiles and organic amphiphiles were fabricated. The siloxane groups were then hydrolyzed to form silica and the organic portions of the amphiphiles removed by thermal decomposition. With the completely fugitive organic spacer amphiphiles removed, a thin silica film with micropores resulted. The pore size was in the range of 6 - 8 {angstrom} and in an ultra-thin configuration. With further development this technique may be useful for fabrication of inorganic membranes which satisfy all the criteria of the ideal membrane.

  1. Characterisation of thin films of graphene-surfactant composites produced through a novel semi-automated method.

    PubMed

    Walch, Nik J; Nabok, Alexei; Davis, Frank; Higson, Séamus P J

    2016-01-01

    In this paper we detail a novel semi-automated method for the production of graphene by sonochemical exfoliation of graphite in the presence of ionic surfactants, e.g., sodium dodecyl sulfate (SDS) and cetyltrimethylammonium bromide (CTAB). The formation of individual graphene flakes was confirmed by Raman spectroscopy, while the interaction of graphene with surfactants was proven by NMR spectroscopy. The resulting graphene-surfactant composite material formed a stable suspension in water and some organic solvents, such as chloroform. Graphene thin films were then produced using Langmuir-Blodgett (LB) or electrostatic layer-by-layer (LbL) deposition techniques. The composition and morphology of the films produced was studied with SEM/EDX and AFM. The best results in terms of adhesion and surface coverage were achieved using LbL deposition of graphene(-)SDS alternated with polyethyleneimine (PEI). The optical study of graphene thin films deposited on different substrates was carried out using UV-vis absorption spectroscopy and spectroscopic ellipsometry. A particular focus was on studying graphene layers deposited on gold-coated glass using a method of total internal reflection ellipsometry (TIRE) which revealed the enhancement of the surface plasmon resonance in thin gold films by depositing graphene layers. PMID:26977378

  2. Electrical and Optical Properties of Organic Thin Films

    NASA Astrophysics Data System (ADS)

    Buckner, Spencer Lewis

    The purpose of this research was to examine the applicability of organic thin films as electrical insulators in metal-insulator-semiconductor (MIS) and metal-insulator -metal (MIM) devices and an anti-reflective (A-R) coatings for solar cells. Films of anthracene, stearic acid and diacetylene alcohol were examined for their electrical and optical properties. Two techniques were used to deposit the films for these studies. Thermal evaporation in vacuum was used to deposit aluminum as electrodes and contacts in MIS and MIM devices. The organic films were deposited by either thermal evaporation or the Langmuir-Blodgett (L-B) dipping technique. Several vacuum systems and an L-B trough were fabricated for these studies and their design and construction are outlined. Several types of measurements were used to examine the properties of the organic films. Optical reflectance measurements of the diacetylene alcohol and stearic acid, both deposited by the L-B technique, on commercial silicon solar cells were used to study the potential use of these types of films as A-R and protective coatings. Electrical breakdown studies of the MIM devices were conducted to determine the maximum electric fields the insulators could withstand without destruction. Capacitance versus voltage (C-V) measurements of the organic films in MIS devices were used to determine surface defect densities at the semicondcutor/insulator interface. For each type of measurements made on the devices, theories are outlined to analyze the data obtained. The optical reflectance data are analyzed using standard electromagnetic theory. The electrical breakdown data are examined using the theories of Forlani and Minnaja (F-M) and Klein. The C-V data are examined using several different theories to determine charge and defect densities and to analyze the effects of thermal stressing and annealing. Finally, conclusions are drawn as to the applicability of these types of organic materials as insulators and coatings

  3. Photochemistry and photophysics of stilbene and diphenylpolyene surfactants in supported multilayer films

    NASA Astrophysics Data System (ADS)

    Spooner, Susan P.; Whitten, David G.

    1991-03-01

    A number of surfactant trans-stilbene derivatives have been synthesized and investigated in supported Langmuir-Blodgett assemblies. Layers of pure stilbene surfactants or mixtures with fatty acids show 'H' aggregate characteristics including relatively low oscillator strengths for the lowest excited singlet state. Consequently these exhibit relatively low ability, individually, to donate excitation energy or transfer electrons over long ranges. Mixtures of these stilbenes, layered together to form mixed films, also show 'H' aggregate characteristics but give evidence for delocalization which can effectively span the width of an entire monolayer and result in efficient energy and electron transfer processes over distances spanning several monolayers. The extension to 'H' aggregated and dilute (monomer) diphenylbutadiene and diphenylhexatriene layers results in assemblies in which vectorial energy transfer and redox processes can occur. One of the molecules used as an energy transfer and electron transfer quencher is the cobalt (III) complex of 8S1A. Although this molecule undergoes photochemical intramolecular-electron transfer-induced fragmentation in solution and microheterogeneous media, it show net photostability in the films but serves a highly effective trap.

  4. Electrochemistry of LB films of mixed MGDG:UQ on ITO.

    PubMed

    Hoyo, Javier; Guaus, Ester; Torrent-Burgués, Juan; Sanz, Fausto

    2015-08-01

    The electrochemical behaviour of biomimetic monolayers of monogalactosyldiacylglycerol (MGDG) incorporating ubiquinone-10 (UQ) has been investigated. MGDG is the principal component in the thylakoid membrane and UQ seems a good substitute for plastoquinone-9, involved in photosynthesis chain. The monolayers have been performed using the Langmuir and Langmuir-Blodgett (LB) techniques and the redox behaviour of the LB films, transferred at several surface pressures on a glass covered with indium-tin oxide (ITO), has been characterized by cyclic voltammetry. The cyclic voltammograms show that UQ molecules present two redox processes (I and II) at high UQ content and high surface pressures, and only one redox process (I) at low UQ content and low surface pressures. The apparent rate constants calculated for processes I and II indicate a different kinetic control for the reduction and the oxidation of UQ/UQH2 redox couple, being k(Rapp)(I) = 2.2 · 10(-5) s(-1), k(Rapp)(II) = 5.1 · 10(-14) k(Oapp)(I) = 3.3 · 10(-3) s(-1) and k(Oapp)(II) = 6.1 · 10(-6) s(-1), respectively. The correlation of the redox response with the physical states of the LB films allows determining the positions of the UQ molecules in the biomimetic monolayer, which change with the surface pressure and the UQ content. These positions are known as diving and swimming. PMID:25725477

  5. Modifying surface properties of diamond-like carbon films via nanotexturing

    NASA Astrophysics Data System (ADS)

    Corbella, C.; Portal-Marco, S.; Rubio-Roy, M.; Bertran, E.; Oncins, G.; Vallvé, M. A.; Ignés-Mullol, J.; Andújar, J. L.

    2011-10-01

    Diamond-like amorphous carbon (DLC) films have been grown by pulsed-dc plasma-enhanced chemical vapour deposition on silicon wafers, which were previously patterned by means of colloidal lithography. The substrate conditioning comprised two steps: first, deposition of a self-assembled monolayer of silica sub-micrometre spheres (~300 nm) on monocrystalline silicon (~5 cm2) by Langmuir-Blodgett technique, which acted as lithography template; second, substrate patterning via ion beam etching (argon) of the colloid samples (550 eV) at different incidence angles. The plasma deposition of a DLC thin film on the nanotextured substrates resulted in hard coatings with distinctly different surface properties compared with planar DLC. Also, in-plane anisotropy was generated depending on the etching angle. The samples were morphologically characterized by scanning electron microscopy and atomic force microscopy. The anisotropy introduced by the texture was evidenced in the surface properties, as shown by the directional dependences of wettability (water contact angle) and friction coefficient. The latter was measured using a nanotribometer and a lateral force microscope. These two techniques showed how the nanopatterns influenced the tribological properties at different scales of load and contact area. This fabrication technique finds applications in the industry of microelectromechanical systems, anisotropic tribological coatings, nanoimprint lithography, microfluidics, photonic crystals, and patterned surfaces for biomedicine.

  6. Time-resolved grazing-incidence diffraction studies of thin films using an imaging-plate camera and focusing monochromator.

    PubMed

    Foran, G J; Gentle, I R; Garrett, R F; Creagh, D C; Peng, J B; Barnes, G T

    1998-03-01

    A multiple imaging-plate (IP) detector system and focusing monochromator have been developed and successfully applied to the time-resolved study of phase transitions in Langmuir-Blodgett (LB) films by grazing-incidence X-ray diffraction (GIXD). The first reported application of imaging plates to a GIXD study was carried out by our group and proved to be very successful in the determination of thin-film structure [Foran, Peng, Steitz, Barnes & Gentle (1996). Langmuir, 12, 774-777]. To extend the capabilities of this system, an IP camera was designed and built which can accommodate up to 13 IPs (40 x 20 cm) inside the vacuum chamber of the main diffractometer at the Australian Beamline at the Photon Factory. The camera allows the enclosed IPs to be successively exposed and stored inside the diffractometer for later scanning. The focusing monochromator employed in this technique combines fixed exit-beam height with sagittal focusing of the second crystal and delivers a gain in flux of >/=20 times when measured through a 0.1 x 0.1 mm aperture. The utility of the system incorporating the IP camera and the focusing monochromator has been demonstrated through the study of temperature-dependent phase transitions in LB films of metal fatty acids. PMID:16687811

  7. Biomimetic collagen I and IV double layer Langmuir-Schaefer films as microenvironment for human pluripotent stem cell derived retinal pigment epithelial cells.

    PubMed

    Sorkio, Anni E; Vuorimaa-Laukkanen, Elina P; Hakola, Hanna M; Liang, Huamin; Ujula, Tiina A; Valle-Delgado, Juan José; Österberg, Monika; Yliperttula, Marjo L; Skottman, Heli

    2015-05-01

    The environmental cues received by the cells from synthetic substrates in vitro are very different from those they receive in vivo. In this study, we applied the Langmuir-Schaefer (LS) deposition, a variant of Langmuir-Blodgett technique, to fabricate a biomimetic microenvironment mimicking the structure and organization of native Bruch's membrane for the production of the functional human embryonic stem cell derived retinal pigment epithelial (hESC-RPE) cells. Surface pressure-area isotherms were measured simultaneously with Brewster angle microscopy to investigate the self-assembly of human collagens type I and IV on air-subphase interface. Furthermore, the structure of the prepared collagen LS films was characterized with scanning electron microscopy, atomic force microscopy, surface plasmon resonance measurements and immunofluorescent staining. The integrity of hESC-RPE on double layer LS films was investigated by measuring transepithelial resistance and permeability of small molecular weight substance. Maturation and functionality of hESC-RPE cells on double layer collagen LS films was further assessed by RPE-specific gene and protein expression, growth factor secretion, and phagocytic activity. Here, we demonstrated that the prepared collagen LS films have layered structure with oriented fibers corresponding to architecture of the uppermost layers of Bruch's membrane and result in increased barrier properties and functionality of hESC-RPE cells as compared to the commonly used dip-coated controls. PMID:25771016

  8. Photoconductive properties of organic-inorganic hybrid films of layered perovskite-type niobate.

    PubMed

    Saruwatari, Kazuko; Sato, Hisako; Idei, Tomochika; Kameda, Jun; Yamagishi, Akihiko; Takagaki, Atsushi; Domen, Kazunari

    2005-06-30

    A hybrid film of layered niobate and an organic amphiphile was prepared by the Langmuir-Blodgett (LB) method. Trimethylammonium-exchanged perovskite-type niobates ((CH(3))(3)NHSr(2)Nb(3)O(10)) were exfoliative to form an aqueous suspension. A monolayer of octadecylamine was produced on such an aqueous dispersion as a template for a hybrid film. A hybrid film was transferred as a Y-type LB film onto a hydrophilic glass plate or an ITO substrate. The structure of a deposited film was investigated with X-ray diffraction (XRD), Fourier transform infrared (FT-IR), and atomic force microscopy (AFM) measurements, indicating a layer-by-layer structure with a single or double sheet of niobate as an inorganic composite. From the cyclic voltammogram on an ITO electrode modified with the Y-type 10 layered film, the lower edge of the conduction band of a niobate layer was determined to be - 0.6 V (vs Ag/AgCl). ac impedance and dc measurements were carried out on 1, 5, and 10-layered LB films (2 mm (electrode spacing) x 8 mm (width)) with aluminum electrodes. The freshly deposited samples behaved as an insulator under the illumination of 280 nm light (2.04 x 10(16) quanta s(-1)). Photoconductivities appeared, however, when they were preirradiated with a 150 W Xe lamp (ca. 2 x 10(18) quanta s(-1)) for 0.5-8.5 h. The process was denoted as photomodification. From the FT-IR and XRD results, it was deduced that the photomodification of LB films caused the decomposition of organic templates (octadecylammonium) accompanied by the collapse of layer-by-layer structures. dc analyses on the 5- and 10-layered films after photomodification also showed that they behaved as a photosemiconductor under UV light illumination. PMID:16852536

  9. Structural and electrochemical properties of lutetium bis-octachloro-phthalocyaninate nanostructured films. Application as voltammetric sensors.

    PubMed

    Alessio, P; Apetrei, C; Rubira, R J G; Constantino, C J L; Medina-Plazal, C; De Saja, J A; Rodríguez-Méndez, M L

    2014-09-01

    Thin films of the bis[2,3,9,10,16,17,23,24-octachlorophthalocyaninate] lutetium(III) complex (LuPc2Cl32) have been prepared by the Langmuir-Blodgett and the Langmuir-Schaefer (LS) techniques. The influence of the chlorine substituents in the structure of the films and in their spectroscopic, electrochemical and sensing properties has been evaluated. The π-A isotherms exhibit a monolayer stability greater than the observed in the unsubstituted analogue (LuPc2), being easily transferred to solid substrates, also in contrast to LuPc2. The LB and LS films present a linear growth forming stratified layers, monitored by UV-VIS absorption spectroscopy. The latter also revealed the presence of LuPc2Cl32 in the form of monomers and aggregates in both films. The FTIR data showed that the LuPc2Cl32 molecules present a non-preferential arrangement in both films. Monolayers of LB and LS were deposited onto 6 nm Ag island films to record surface-enhanced resonance Raman scattering (SERRS), leading to enhancement factors close to 2 x 10(3). Finally, LB and LS films deposited onto ITO glass have been successfully used as voltammetric sensors for the detection of catechol. The improved electroactivity of the LB and LS films has been confirmed by the reduction of the overpotential of the oxidation of catechol. The enhancement of the electrocatalytic effect observed in LB and LS films is the result of the nanostructured arrangement of the surface which increases the number of active sites. The sensors show a limit of detection in the range of 10(-5) mol/L. PMID:25924327

  10. Acylated Carrageenan Changes the Physicochemical Properties of Mixed Enzyme-Lipid Ultrathin Films and Enhances the Catalytic Properties of Sucrose Phosphorylase Nanostructured as Smart Surfaces.

    PubMed

    Rocha, Jefferson M; Pavinatto, Adriana; Nobre, Thatyane M; Caseli, Luciano

    2016-06-23

    Control over the catalytic activity of enzymes is important to construct biosensors with a wide range of detectability and higher stability. For this, immobilization of enzymes on solid supports as nanostructured films is a current approach that permits easy control of the molecular architecture as well as tuning of the properties. In this article, we employed acylated carrageenan (AC) mixed with phospholipids at the air-water interface to facilitate the adsorption of the enzyme sucrose phosphorylase (SP). AC stabilized the adsorption of SP at the phospholipid monolayer, as detected by tensiometry, by which thermodynamic parameters could be inferred from the surface pressure-area isotherm. Also, infrared spectroscopy applied in situ over the monolayer showed that the AC-phospholipid system not only permitted the enzyme to be adsorbed but also helped conserve its secondary structure. The mixed monolayers were then transferred onto solid supports as Langmuir-Blodgett (LB) films and investigated with transfer ratio, quartz crystal microbalance, fluorescence spectroscopy, and atomic force microscopy. The enzyme activity of the LB film was then determined, revealing that although there was an expected reduction in activity in relation to the homogeneous environment the activity could be better preserved after 1 month, revealing enhanced stability. PMID:27249064

  11. Lamellar versus compact self-assembly of lipoguanosine derivatives in thin surface films.

    PubMed

    Čoga, Lucija; Masiero, Stefano; Drevenšek-Olenik, Irena

    2014-09-01

    We performed a comparative study on the self-assembling properties of four guanosine derivatives with one and two lipophilic chains of two different lengths at the air-water interface and after Langmuir-Blodgett (LB) deposition onto various solid supports (mica, silicon wafer, graphite). At the air-water interface the derivatives with one lipophilic chain exhibit surface compression behaviour with a profound first order phase transition from the liquid-expanded to the liquid-condensed phase. They assemble into lamellar surface formations, whose structural characteristics remain practically unmodified after their transfer onto the solid substrates. Domain regions with orientationally aligned lamellar formations of sizes up to 150μm(2) can be obtained. The compression behaviour of double-chain derivatives is more diverse. While the derivative with two decanoyl chains exhibits the liquid-expanded as well as the liquid-condensed phase, the derivative with two hexadecanoyl chains reveals only the condensed-analogous phase with a relatively high collapse pressure. LB films of double chain derivatives show formation of very homogeneous and compact surface structures with high surface coverage. PMID:24956505

  12. Thin films under chemical stress. [Final Report], September 1, 1988--April 1, 1991

    SciTech Connect

    Not Available

    1991-12-01

    The goal of work on this project has been develop a set of experimental tools to allow investigators interested in transport, binding, and segregation phenomena in composite thin film structures to study these phenomena in situ. Work to-date has focuses on combining novel spatially-directed optical excitation phenomena, e.g. waveguide eigenmodes in thin dielectric slabs, surface plasmon excitations at metal-dielectric interfaces, with standard spectroscopies to understand dynamic processes in thin films and at interfaces. There have been two main scientific thrusts in the work and an additional technical project. In one thrust we have sought to develop experimental tools which will allow us to understand the chemical and physical changes which take place when thin polymer films are placed under chemical stress. In principle this stress may occur because the film is being swelled by a penetrant entrained in solvent, because interfacial reactions are occurring at one or more boundaries within the film structure, or because some component of the film is responding to an external stimulus (e.g. pH, temperature, electric field, or radiation). However all work to-date has focused on obtaining a clearer understanding penetrant transport phenomena. The other thrust has addressed the kinetics of adsorption of model n-alkanoic acids from organic solvents. Both of these thrusts are important within the context of our long-term goal of understanding the behavior of composite structures, composed of thin organic polymer films interspersed with Langmuir-Blodgett (LB) and self-assembled monolayers. In addition there has been a good deal of work to develop the local technical capability to fabricate grating couplers for optical waveguide excitation. This work, which is subsidiary to the main scientific goals of the project, has been successfully completed and will be detailed as well. 41 refs., 10 figs.

  13. Functional properties of chitosan-based films.

    PubMed

    Leceta, I; Guerrero, P; de la Caba, K

    2013-03-01

    Chitosan-based films plasticized with glycerol were prepared by casting with the aim to obtain environmentally friendly materials for packaging applications. Different contents of glycerol were incorporated into chitosan solutions to improve mechanical properties and all films obtained were flexible and transparent. It was observed that the transparency and good behaviour of the films against UV radiation were not affected by chitosan molecular weight or glycerol content. Moreover, chitosan-based films exhibited excellent barrier properties against water vapour and oxygen, even with the addition of glycerol. The effect of the plasticizer on the properties has been explained using Fourier transform infrared (FTIR) spectroscopic analysis. The changes observed in the intensity of the bands showed that glycerol interacts with chitosan, which could be confirmed by total soluble matter (TSM). PMID:23465939

  14. Effect of annealing on the growth dynamics of ZnPc LB thin film and its surface morphology

    NASA Astrophysics Data System (ADS)

    Roy, Dhrubojyoti; Das, Nayan Mani; Gupta, P. S.

    2014-07-01

    The ZnPc molecules in the thin film prepared by Langmuir-Blodgett (LB) process in asdeposited state has been found to have an edge on orientation with average tilt angle of 64.3 ° as confirmed from the Pressure-Area (π-A) isotherm and X-ray diffraction (XRD) study. The ZnPc LB thin film has been observed to have abnormal growth mode at higher annealing temperature and it is mainly driven by minimization of surface free energy which lead to large increase in crystallinity of the film. Kinetically favored orientational and structural transitions of ZnPc thin film during annealing and their effect on the surface morphology of the thin film has been studied using scaling concepts. The scaling exponents 1) root mean square (RMS) roughness σ, 2) roughness exponent α and, 3) in plane correlation length ξ are calculated from the HDCF g(r) and ACF C(r). The RMS surface roughness σ is found to be dependent on the as defined short wavelength undulations (ρ) and long wavelength undulations (χ). Both ρ and χ are the function of all the three scaling exponents. σ has been observed to be maximum for the ZnPc thin film annealed at 290 °C, since the χ shoot to maximum value at this temperature due to the formation of small domains of ZnPc nanorods. The self affinity of the ZnPc thin film is found to decrease on annealing as obtained from both power spectral density (PSD) and HDCF g(R) & ACF C(R) study, which confirms that the dimension of surface morphology of the ZnPc LB thin film transform towards 2D with increase in annealing temperature.

  15. Effect of annealing on the growth dynamics of ZnPc LB thin film and its surface morphology

    SciTech Connect

    Roy, Dhrubojyoti Das, Nayan Mani; Gupta, P. S.

    2014-07-15

    The ZnPc molecules in the thin film prepared by Langmuir-Blodgett (LB) process in asdeposited state has been found to have an edge on orientation with average tilt angle of 64.3 ° as confirmed from the Pressure-Area (π-A) isotherm and X-ray diffraction (XRD) study. The ZnPc LB thin film has been observed to have abnormal growth mode at higher annealing temperature and it is mainly driven by minimization of surface free energy which lead to large increase in crystallinity of the film. Kinetically favored orientational and structural transitions of ZnPc thin film during annealing and their effect on the surface morphology of the thin film has been studied using scaling concepts. The scaling exponents 1) root mean square (RMS) roughness σ, 2) roughness exponent α and, 3) in plane correlation length ξ are calculated from the HDCF g(r) and ACF C(r). The RMS surface roughness σ is found to be dependent on the as defined short wavelength undulations (ρ) and long wavelength undulations (χ). Both ρ and χ are the function of all the three scaling exponents. σ has been observed to be maximum for the ZnPc thin film annealed at 290 °C, since the χ shoot to maximum value at this temperature due to the formation of small domains of ZnPc nanorods. The self affinity of the ZnPc thin film is found to decrease on annealing as obtained from both power spectral density (PSD) and HDCF g(R) and ACF C(R) study, which confirms that the dimension of surface morphology of the ZnPc LB thin film transform towards 2D with increase in annealing temperature.

  16. 49 CFR 173.183 - Nitrocellulose base film.

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... 49 Transportation 2 2014-10-01 2014-10-01 false Nitrocellulose base film. 173.183 Section 173.183... Nitrocellulose base film. Films, nitrocellulose base, must be packaged in packagings conforming to the... tape or paper; authorized only for not over 600 m (1969 feet) of film....

  17. 49 CFR 173.183 - Nitrocellulose base film.

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... 49 Transportation 2 2013-10-01 2013-10-01 false Nitrocellulose base film. 173.183 Section 173.183... Nitrocellulose base film. Films, nitrocellulose base, must be packaged in packagings conforming to the... tape or paper; authorized only for not over 600 m (1969 feet) of film....

  18. 49 CFR 173.183 - Nitrocellulose base film.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... 49 Transportation 2 2012-10-01 2012-10-01 false Nitrocellulose base film. 173.183 Section 173.183... Nitrocellulose base film. Films, nitrocellulose base, must be packaged in packagings conforming to the... tape or paper; authorized only for not over 600 m (1969 feet) of film....

  19. Thin film based plasmon nanorulers

    NASA Astrophysics Data System (ADS)

    Taylor, Alexander D.; Lu, Chang; Geyer, Scott; Carroll, D. L.

    2016-07-01

    In this work, isolated metal nanoparticles are supported on a dielectric thin film that is placed on a conducting plane. The optical scattering characteristics of these metal nanoparticles are directly correlated with the localized surface plasmon states of the nanoparticle—image particle dimer, formed in the conducting plane below. Quantification of plasmon resonance shifts can be directly correlated with the application of the plasmon nanoruler equation. This simple geometry shows that direct optical techniques can be used to resolve thickness variations in dielectrics of only a few nanometers.

  20. Single Molecular Film for Recognizing Biological Molecular Interaction: DNA-Protein Interaction and Enzyme Reaction

    NASA Astrophysics Data System (ADS)

    Kurihara, Kazue

    Protein-protein and protein-substrate interactions play essential roles in biological functions. Surface forces measurement and atomic force microscopy, which directly measure the interaction forces as a function of the surface separation, enable us to quantitatively evaluate these interactions [1-3]. We have employed the surface forces measurement [4] and colloidal probe atomic force microscopy [5] to study interactions involved in specific molecular recognition of DNA-protein and enzyme-substrate reaction. Studied are interactions between nucleic acid bases (adenine and thymine) [6], Spo0A-DB (the DNA-binding site of a transcription factor Spo0A), and DNA [7,8], those between subunits I and II of heptaprenyl diphosphate (HepPP) synthase in the presence of a substrate ((E,E)-farnesyl diphosphate, FPP) and a cofactor (Mg2+) [9-11], and the selectivity of the substrates in this enzymatic reaction [12]. Keys of our approach are the preparation of well-defined samples and the appropriate analysis. We have modified he substrate surfaces with these proteins using the Langmuir-Blodgett (LB) method. This chapter reviews the LB modification method and subsequent demonstrations of biological specific interactions employing this approach.

  1. Functional Materials for Microsystems: Smart Self-Assembled Photochromic Films: Final Report

    SciTech Connect

    BURNS, ALAN R.; SASAKI, DARRYL Y.; CARPICK, R.W.; SHELNUTT, JOHN A.; BRINKER, C. JEFFREY

    2001-11-01

    This project set out to scientifically-tailor ''smart'' interfacial films and 3-D composite nanostructures to exhibit photochromic responses to specific, highly-localized chemical and/or mechanical stimuli, and to integrate them into optical microsystems. The project involved the design of functionalized chromophoric self-assembled materials that possessed intense and environmentally-sensitive optical properties (absorbance, fluorescence) enabling their use as detectors of specific stimuli and transducers when interfaced with optical probes. The conjugated polymer polydiacetylene (PDA) proved to be the most promising material in many respects, although it had some drawbacks concerning reversibility. Throughout his work we used multi-task scanning probes (AFM, NSOM), offering simultaneous optical and interfacial force capabilities, to actuate and characterize the PDA with localized and specific interactions for detailed characterization of physical mechanisms and parameters. In addition to forming high quality mono-, bi-, and tri-layers of PDA via Langmuir-Blodgett deposition, we were successful in using the diacetylene monomer precursor as a surfactant that directed the self-assembly of an ordered, mesostructured inorganic host matrix. Remarkably, the diacetylene was polymerized in the matrix, thus providing a PDA-silica composite. The inorganic matrix serves as a perm-selective barrier to chemical and biological agents and provides structural support for improved material durability in microsystems. Our original goal was to use the composite films as a direct interface with microscale devices as optical elements (e.g., intracavity mirrors, diffraction gratings), taking advantage of the very high sensitivity of device performance to real-time dielectric changes in the films. However, our optical physics colleagues (M. Crawford and S. Kemme) were unsuccessful in these efforts, mainly due to the poor optical quality of the composite films.

  2. Kaolin-based particle films for arthropod control

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Particle film technology was conceived by ARS scientists in the mid-1990's as an alternative to chemical pesticides. This technology was based on coating plant parts with mineral films that were chemically inert, could be formulated to spread and create a uniform film, formed a porous film that doe...

  3. Molecular self assembly on optical fiber-based fluorescence sensor

    NASA Astrophysics Data System (ADS)

    Ayyagari, Madhu S. R.; Gao, Harry H.; Bihari, Bipin; Chittibabu, Kethinni G.; Kumar, Jayant; Marx, Kenneth A.; Kaplan, David L.; Tripathy, Sukant K.

    1994-03-01

    We discuss the molecular self-assembly on optical fibers in which a novel method for protein attachment to the sensing tip of the fiber is used. Our objective is to assemble a conjugated polythiophene copolymer as an attachment vehicle. Subsequent attachment of the photodynamic phycobiliprotein serves as the fluorescence probe element. Following our earlier experiments from Langmuir-Blodgett deposition of these polymeric materials as thin films on glass substrates, we extended the technique to optical fibers. First, the bare fiber surface is silanized with a C18 silane compound. The copolymer (3-undecylthiophene-co-3- methanolthiophene, biotinylated at the methanol moiety) assembly on the fiber is carried out presumable through van der Waals interactions between the hydrophobic fiber surface and the undecyl alkyl chains on the polymer backbone. A conjugated Str-PE (streptavidin covalently attached to phycoerythrin) complex is then attached to the copolymer via the conventional biotin-streptavidin interaction. The conjugated polymer not only supports the protein but, in principle, may help to transduce the signal generated by phycoerythrin to the fiber. Our results from fluorescence intensity measurements proved the efficacy of this system. An improved methodology is also sought to more strongly attach the conjugated copolymer to the fiber surface, and a covalent scheme is developed to polymerize and biotinylate polythiophene in situ on the fiber surface.

  4. Lignin and silicate based hydrogels for biosensor applications

    NASA Astrophysics Data System (ADS)

    Burrs, S. L.; Jairam, S.; Vanegas, D. C.; Tong, Z.; McLamore, E. S.

    2013-05-01

    Advances in biocompatible materials and electrocatalytic nanomaterials have extended and enhanced the field of biosensors. Immobilization of biorecognition elements on nanomaterial platforms is an efficient technique for developing high fidelity biosensors. Single layer (i.e., Langmuir-Blodgett) protein films are efficient, but disadvantages of this approach include high cost, mass transfer limitations, and Vromer competition for surface binding sites. There is a need for simple, user friendly protein-nanomaterial sensing membranes that can be developed in laboratories or classrooms (i.e., outside of the clean room). In this research, we develop high fidelity nanomaterial platforms for developing electrochemical biosensors using sustainable biomaterials and user-friendly deposition techniques. Catalytic nanomaterial platforms are developed using a combination of self assembled monolayer chemistry and electrodeposition. High performance biomaterials (e.g., nanolignin) are recovered from paper pulp waste and combined with proteins and nanomaterials to form active sensor membranes. These methods are being used to develop electrochemical biosensors for studying physiological transport in biomedical, agricultural, and environmental applications.

  5. Structural studies of ultrathin organic films

    NASA Astrophysics Data System (ADS)

    Yim, Hyun

    1998-11-01

    Ultrathin organic films have been a focus of research due to the growing interest in optoelectronics and molecular electronics. In both areas, it is believed that self-assembled (SA) films and Langmuir-Blodgett (LB) films may provide the desired control of order at the molecular level. The tethering of polyglutamate molecules to surfaces is of special interest due to nonlinear optical properties which can be achieved when the molecules are oriented. The tethering of poly(benzyl-L-glutamate) to silicon has been done by polymerization of benzyl-L-glutamate-N-carboxyanhydride using self-assembled monolayers with various concentrations of amino end groups as initiating layers. X-ray reflectivity results show that a minimum concentration of initiator sites on the surface is required. The second tethering system is a polystyrene brush. The polystyrene brush is expected to give strong sensitivity to solvent swelling. The structure of the polystyrene brush, which was chemically grafted to a substrate, in poor solvent and its change at different temperatures were investigated by neutron reflectometry. When temperature increases up to 30sp°C, both the thickness and roughness increase greatly, which indicates that the polystyrene brush changes from a collapsed state to a theta state. Hairy-rod polyimide molecules are of interest due to their interesting physical properties. Multilayer films of preformed polyimide molecules (6FDA-C18) have been obtained for the first time by the LB technique. The multilayer films do not display a distinctively periodic structure. Upon annealing for a few hours at 180sp°C, the structure relaxes slightly. The alkyl side chain substituted polyimides (BACBF/BPDA) can form metastable monolayers for which the pressure-area isotherms vary markedly with side chain length. For the polyimide with octadecyl side chains, a sharp reduction in zero pressure area occurs between 20 and 24sp°C, suggesting an important change in side chain mobility

  6. Thin and ordered hydrogel films deposited through electrospinning technique; a simple and efficient support for organic bilayers.

    PubMed

    González-Henríquez, Carmen M; del C Pizarro, Guadalupe; Sarabia-Vallejos, Mauricio A; Terraza, Claudio A

    2015-10-01

    Thermal behavior of Dipalmitoylphosphatidylcholine (DPPC) bilayers deposited over hydrogel fibers was examined. Thus, membrane stability, water absorption-release, phase transitions and phase transition temperatures were studied through different methods during heating cycles. Hydrogel films were realized using an oligomer mixture (HEMA-PEGDA575/photo-initiator) with adequate viscosity. Then, the fibers were deposited over silicon wafers (hydrophilic substrate) through electrospinning technique using four different voltages: 15, 20, 25 and 30 kV. The films were then exposed to UV light, favoring polymer chain crosslinking and interactions between hydrogel and substrate. For samples deposited at 20 and 25 kV, hierarchical wrinkle folds were observed at surface level, their arrangement distribution depends directly on thickness and associated point defects. DPPC bilayers were then placed over hydrogel scaffold using Langmuir-Blodgett technique. Field emission scanning electron microscopy (FE-SEM) analysis were used to investigate sample surface, micrographies show homogeneous layer formation with chain polymer order/disorder related to applied voltage during hydrogel deposition process, among other parameters. According to the results obtained, it is possible to conclude that the oligomer deposited at 20 kV produce thin homogenous films (~40 nm) with enhanced ability to absorb water and release it in a controlled way during heating cycles. These scaffold properties confer to DPPC membrane thermal stability, which allow an easy detection of phase(s) and phase transitions. Thermal behavior was also studied via Atomic Force Microscopy (roughness analysis). Contact angle measurements corroborate system wettability, supporting the theory that hydrogel thin films act as DPPC membrane enhancers for thermal stability against external stimuli. PMID:26129642

  7. Polarization of poly(vinylidene fluoride) and poly(vinylidene fluoride-trifluoroethylene) thin films revealed by emission spectroscopy with computational simulation during phase transition

    NASA Astrophysics Data System (ADS)

    Bystrov, Vladimir S.; Paramonova, Ekaterina V.; Dekhtyar, Yuri; Pullar, Robert C.; Katashev, Aleksey; Polyaka, Natalie; Bystrova, Anna V.; Sapronova, Alla V.; Fridkin, Vladimir M.; Kliem, Herbert; Kholkin, Andrei L.

    2012-05-01

    The electronic structure and self-polarization of P(VDF-TrFE) Langmuir-Blodgett nanofilms were analyzed under temperature-driven phase transitions, according to their thickness, composition, and structural conformation. Both thermo-stimulated exoelectron emission (TSEE) spectroscopy and computational simulation, including quantum-chemical calculations from first principles, were carried out. PVDF and composite P(VDF-TrFE) (70:30) molecular chains as Trans and Gauche conformers, as well as crystal cells, were modeled for these TSEE analyses. The quantum-chemical calculations and the computational simulation were based on the density functional theory (DFT) as well as semi-empirical (PM3) methods. It was demonstrated that the energy of electron states, as well as the total energies of the studied P(VDF-TrFE) molecular clusters during phase transformation, is influenced by electron work function and electron affinity. Analysis was performed by combining TSEE experimental data with the computational data of the molecular models, demonstrating the effectiveness of this joint approach. For the first time, TSEE was used for contactless measurements of nanofilm polarization, and characterization of the phase transition. The proposed new method can be widely applied in nanobiomedicine, particularly in development of new bone bio-implants, including built-in sensors (new smart nanotechnology).

  8. Synthesis of KCa₂Nb₃O₁₀ Crystals with Varying Grain Sizes and Their Nanosheet Monolayer Films As Seed Layers for PiezoMEMS Applications.

    PubMed

    Yuan, Huiyu; Nguyen, Minh; Hammer, Tom; Koster, Gertjan; Rijnders, Guus; ten Elshof, Johan E

    2015-12-16

    The layered perovskite-type niobate KCa2Nb3O10 and its derivatives show advantages in several fields, such as templated film growth and (photo)catalysis. Conventional synthesis routes generally yield crystal size smaller than 2 μm. We report a flux synthesis method to obtain KCa2Nb3O10 crystals with significantly larger sizes. By using different flux materials (K2SO4 and K2MoO4), crystals with average sizes of 8 and 20 μm, respectively, were obtained. The KCa2Nb3O10 crystals from K2SO4 and K2MoO4 assisted synthesis were protonated and exfoliated into monolayer nanosheets, and the optimal exfoliation conditions were determined. Using pulsed laser deposition, highly (001)-oriented piezoelectric stacks (SrRuO3/PbZr0.52Ti0.48O3/SrRuO3, SRO/PZT/SRO) were deposited onto Langmuir-Blodgett films of Ca2Nb3O10(-) (CNO) nanosheets with varying lateral nanosheet sizes on Si substrates. The resulting PZT thin films showed high crystallinity irrespective of nanosheet size. The small sized nanosheets yielded a high longitudinal piezoelectric coefficient d33 of 100 pm/V, while the larger sized sheets had a d33 of 72 pm/V. An enhanced transverse piezoelectric coefficient d31 of -107 pm/V, an important input parameter for the actuation of active structures in microelectromechanical systems (MEMS) devices, was obtained for PZT films grown on CNO nanosheets with large lateral size, while the corresponding value on small sized sheets was -96 pm/V. PMID:26583282

  9. Tuning the peak position of subwavelength silica nanosphere broadband antireflection coatings

    PubMed Central

    2014-01-01

    Subwavelength nanostructures are considered as promising building blocks for antireflection and light trapping applications. In this study, we demonstrate excellent broadband antireflection effect from thin films of monolayer silica nanospheres with a diameter of 100 nm prepared by Langmuir-Blodgett method on glass substrates. With a single layer of compact silica nanosphere thin film coated on both sides of a glass, we achieved maximum transmittance of 99% at 560 nm. Furthermore, the optical transmission peak of the nanosphere thin films can be tuned over the UV-visible range by changing processing parameters during Langmuir-Blodgett deposition. The tunable optical transmission peaks of the Langmuir-Blodgett films were correlated with deposition parameters such as surface pressure, surfactant concentration, ageing of suspensions and annealing effect. Such peak-tunable broadband antireflection coating has wide applications in diversified industries such as solar cells, windows, displays and lenses. PMID:25136278

  10. Tuning the peak position of subwavelength silica nanosphere broadband antireflection coatings.

    PubMed

    Tao, Fei; Hiralal, Pritesh; Ren, Lianbing; Wang, Yong; Dai, Qing; Amaratunga, Gehan Aj; Zhou, Hang

    2014-01-01

    Subwavelength nanostructures are considered as promising building blocks for antireflection and light trapping applications. In this study, we demonstrate excellent broadband antireflection effect from thin films of monolayer silica nanospheres with a diameter of 100 nm prepared by Langmuir-Blodgett method on glass substrates. With a single layer of compact silica nanosphere thin film coated on both sides of a glass, we achieved maximum transmittance of 99% at 560 nm. Furthermore, the optical transmission peak of the nanosphere thin films can be tuned over the UV-visible range by changing processing parameters during Langmuir-Blodgett deposition. The tunable optical transmission peaks of the Langmuir-Blodgett films were correlated with deposition parameters such as surface pressure, surfactant concentration, ageing of suspensions and annealing effect. Such peak-tunable broadband antireflection coating has wide applications in diversified industries such as solar cells, windows, displays and lenses. PMID:25136278

  11. Quantum dot-based microfluidic biosensor for cancer detection

    NASA Astrophysics Data System (ADS)

    Ghrera, Aditya Sharma; Pandey, Chandra Mouli; Ali, Md. Azahar; Malhotra, Bansi Dhar

    2015-05-01

    We report results of the studies relating to fabrication of an impedimetric microfluidic-based nucleic acid sensor for quantification of DNA sequences specific to chronic myelogenous leukemia (CML). The sensor chip is prepared by patterning an indium-tin-oxide (ITO) coated glass substrate via wet chemical etching method followed by sealing with polydimethylsiloxane (PDMS) microchannel for fluid control. The fabricated microfluidic chip comprising of a patterned ITO substrate is modified by depositing cadmium selenide quantum dots (QCdSe) via Langmuir-Blodgett technique. Further, the QCdSe surface has been functionalized with specific DNA probe for CML detection. The probe DNA functionalized QCdSe integrated miniaturized system has been used to monitor target complementary DNA concentration by measuring the interfacial charge transfer resistance via hybridization. The presence of complementary DNA in buffer solution significantly results in decreased electro-conductivity of the interface due to presence of a charge barrier for transport of the redox probe ions. The microfluidic DNA biosensor exhibits improved linearity in the concentration range of 10-15 M to 10-11 M.

  12. Cationic copper(II)-containing surfactants: molecular structures, film morphology, and influence on the alignment of nematic mesogens.

    PubMed

    Verani, Cláudio N; Driscoll, Jeffery; Keyes, Paul H; Heeg, Mary Jane

    2014-06-01

    We discuss the synthesis and amphiphilic behavior of the cationic metallosurfactants [(L(Py14))2Cu(II)ClO4]ClO4 (1), [(L(Py16))2Cu(II)ClO4]ClO4 (2), [(L(Py18))2Cu(II)ClO4]ClO4 (3), [(L(Py18))2Cu(II)NO3]NO3 (4), [(L(Py18))2Cu(II)Cl]Cl (5), and [(L(Py18))2Cu(II)Br]Br (6) obtained by treatment of the appropriate alkylaminemethyl-2-pyridine ligand containing tetra-, hexa-, or octadecyl chains with copper salts. These metallosurfactants show excellent agreement between infrared spectroscopic bands, spectrometric masses with isotopic patterns, and elemental composition. Single-crystal X-ray data available for 1, 2, 5 and the previously published 3 reveal a trigonal bipyramidal copper(II) ion bound at the basal plane to the amine and pyridine of each alkylaminemethylpyridine ligand and an anionic coligand to the apical position. Except for the surfactant with the shortest tetradecyl (C14) chain, these species yield Langmuir films with collapse pressures of 45-55 mN·m(-1) and average areas of ca. 50 Å(2). A plateau around 15 mN·m(-1) is observed for 3, 4, and 5 and associated with the formation of dendritic domains about 50 μm in size. Species 2 and 6 lack this plateau and show domains of ca. 5 μm. Once transferred onto solid substrates, the resulting Langmuir-Blodgett film of 3 at 18 mN·m(-1) influences the alignment of the nematic liquid crystal N-(4-methoxybenzylidene)-4-butylaniline. PMID:24813105

  13. Study on aluminium-based single films.

    PubMed

    Vinod Kumar, G S; García-Moreno, F; Babcsán, N; Brothers, A H; Murty, B S; Banhart, J

    2007-12-28

    In the present paper the authors studied isolated metallic films made from the same material used for making metallic foams, and then characterised their properties. Metal films were made from a liquid aluminium alloy reinforced with ceramic particles of known concentration. Melts without such particles were also investigated. It is shown that stable films could not be made from Al-Si alloy having no particles, and just extremely thin and fragile films could be made from commercially-pure Al. In contrast, aluminium alloys containing particles such as SiC and TiB(2) allowed pulling thin, stable films, which did not rupture. Significant thinning of films was observed when the particle concentration in the melt decreased. By in situ X-ray monitoring of liquid films during pulling, film thickness and drainage effects within the liquid film could be studied. The morphology and microstructure of films was characterised after solidification. Our work shows that the question of how foams are stabilised can be studied using a simplified system such as a film, instead of having to deal with the multitude of different structural elements present in a foam. PMID:18060172

  14. Photochemical arrays formed by spatial compartmentalization of colloidal nanoparticles in a polymer-based hydrogel

    SciTech Connect

    Firestone, M. A.; Rajh, T.; Makarova, O. V.; Seifert, S.; Tiede, D. M.; Thurnauer, M. C.

    2000-01-13

    The development of practical strategies for the assembly of semiconductor and metal colloid nanoparticles into ordered architectures is an area of considerable current interest, since it offers an opportunity for exploiting the optical and electronic properties of these colloids for device development. Prior research has explored creating such organized nanoparticle assemblies by Langmuir-Blodgett techniques or controlled solvent evaporation on suitable substrates. These approaches suffer from several limitations, however, most notably the generation of relatively simple structures and the lack of structural tailorability, preventing full exploitation of these materials. More recently, directed assembly using chemisorption of streptavidin-biotin or thiol-derivatized gold nanoparticles onto substrates has been described. Alternative approaches to achieving two-dimensional confinement of nanoparticles that do not involve substrate-supported materials, but rather organize the nanoparticles into mesoscopically-ordered soft condensed matter, may offer the advantage of enhanced processability and may permit construction of nanocomposite structures based on functional nanoparticles embedded in a processable, polymer-based matrix. This work describes the development of an alternative strategy for constructing 2-D arrays of functional metal and semiconductor nanoparticles. The approach involves directing the organization of nanocrystals into a processable (i.e., by externally applied magnetic and electric fields) polymer-grafted lipid-based complex fluid. By altering the surface chemistry of the nanoparticles, they can be selectively placed into defined regions encapsulating matrix.

  15. Sensitivity of linear CCD array based film scanners used for film dosimetry

    SciTech Connect

    Devic, Slobodan; Wang Yizhen; Tomic, Nada; Podgorsak, Ervin B.

    2006-11-15

    Film dosimetry is commonly performed by using linear CCD array transmission optical densitometers. However, these devices suffer from a variation in response along the detector array. If not properly corrected for, this nonuniformity may lead to significant overestimations of the measured dose as one approaches regions close to the edges of the scanning region. In this note, we present measurements of the spatial response of an AGFA Arcus II document scanner used for radiochromic film dosimetry. Results and methods presented in this work can be generalized to other CCD based transmission scanners used for film dosimetry employing either radiochromic or radiographic films.

  16. Sensitivity of linear CCD array based film scanners used for film dosimetry.

    PubMed

    Devic, Slobodan; Wang, Yi-Zhen; Tomic, Nada; Podgorsak, Ervin B

    2006-11-01

    Film dosimetry is commonly performed by using linear CCD array transmission optical densitometers. However, these devices suffer from a variation in response along the detector array. If not properly corrected for, this nonuniformity may lead to significant overestimations of the measured dose as one approaches regions close to the edges of the scanning region. In this note, we present measurements of the spatial response of an AGFA Arcus II document scanner used for radiochromic film dosimetry. Results and methods presented in this work can be generalized to other CCD based transmission scanners used for film dosimetry employing either radiochromic or radiographic films. PMID:17153378

  17. DNA-Based Synthesis and Assembly of Organized Iron Oxide Nanostructures

    NASA Astrophysics Data System (ADS)

    Khomutov, Gennady B.

    Organized bio-inorganic and hybrid bio-organic-inorganic nanostructures consisting of iron oxide nanoparticles and DNA complexes have been formed using methods based on biomineralization, interfacial and bulk phase assembly, ligand exchange and substitution, Langmuir-Blodgett technique, DNA templating and scaffolding. Interfacially formed planar DNA complexes with water-insoluble amphiphilic polycation or intercalator Langmuir monolayers were prepared and deposited on solid substrates to form immobilized DNA complexes. Those complexes were then used for the synthesis of organized DNA-based iron oxide nanostructures. Planar net-like and circular nanostructures of magnetic Fe3O4 nanoparticles were obtained via interaction of cationic colloid magnetite nanoparticles with preformed immobilized DNA/amphiphilic polycation complexes of net-like and toroidal morphologies. The processes of the generation of iron oxide nanoparticles in immobilized DNA complexes via redox synthesis with various iron sources of biological (ferritin) and artificial (FeCl3) nature have been studied. Bulk-phase complexes of magnetite nanoparticles with biomolecular ligands (DNA, spermine) were formed and studied. Novel nano-scale organized bio-inorganic nanostructures - free-floating sheet-like spermine/magnetite nanoparticle complexes and DNA/spermine/magnetite nanoparticle complexes were synthesized in bulk aqueous phase and the effect of DNA molecules on the structure of complexes was discovered.

  18. Dynamic Properties of Langmuir Films by Laser Light Scattering

    NASA Astrophysics Data System (ADS)

    Sanders, John Newell

    A technique and instrumentation for measuring visco-elastic properties of Langmuir film organic monolayers has been developed. This technique is used to characterize certain films used in the manufacture of Langmuir-Blodgett solid films. Furthermore a comparison of the dynamic viscous and elastic moduli determined by this technique is made with static values determined from the Pressure versus Area Isotherm. Briefly, a Langmuir film consists of amphiphilic organic molecules spread in a trough filled with pure water. The hydrophobic ends of the molecules trap them on the water surface. When spread at a dilute concentration the molecules exhibit two dimensional ideal gas behavior. By increasing the surface concentration one obtains two dimensional liquid and finally two dimensional solid behavior. The measurement is performed by electrodynamically driving the liquid surface with the electric field from a razor blade brought to within less than 1 mm of the surface. A sinusoidally varying electric field induces dipoles in the water subphase and generates waves at twice the driving frequency (Attractive dipoles are generated whether the field is positive or negative). The space propagation and damping of these waves is measured by laser light scattering. A focused laser beam incident on the surface is reflected at an angle due to the slope of the waves on the surface. By observing the movement of the beam the amplitude and phase of the oscillation with respect to the driving function may be determined (via a Lock-In amplifier) at various distances from the razor blade. One may directly profile the waves by translating the profiler, or one may observe the variation in amplitude and phase while scanning the frequency or surface pressure. In the latter cases one uses a known reference state to determine the wavelength and damping from the amplitude and phase change. This data is fit by a non-linear least squares curve fitting program to determine the wavelength and space

  19. Antimicrobial and physicochemical properties of chitosan-HPMC-based films.

    PubMed

    Möller, Heike; Grelier, Stéphane; Pardon, Patrick; Coma, Véronique

    2004-10-20

    To prepare composite films from biopolymers with anti-listerial activity and moisture barrier properties, the antimicrobial efficiency of chitosan-hydroxy propyl methyl cellulose (HPMC) films, chitosan-HPMC films associated with lipid, and chitosan-HPMC films chemically modified by cross-linking were evaluated. In addition, the physicochemical properties of composite films were evaluated to determine their potential for food applications. The incorporation of stearic acid into the composite chitosan-HPMC film formulation decreased water sensitivity such as initial solubility in water and water drop angle. Thus, cross-linking of composite chitosan-HPMC, using citric acid as the cross-linking agent, led to a 40% reduction in solubility in water. The water vapor transfer rate of HPMC film, approximately 270 g x m(-2) x day(-1) x atm(-1), was improved by incorporating chitosan and was further reduced 40% by the addition of stearic acid and/or cross-linking. Anti-listerial activity of films was determined on solid medium by a numeration technique. Chitosan-HPMC-based films, with and without stearic acid, inhibited the growth of Listeria monocytogenes completely. On the other hand, a loss of antimicrobial activity after chemical cross-linking modification was observed. FTIR and 13C NMR analyses were then conducted in order to study a potential chemical modification of biopolymers such as a chemical reaction with the amino group of chitosan. To complete the study, the mechanical properties of composite films were determined from tensile strength assays. PMID:15479027

  20. Crystallization of zirconia based thin films.

    PubMed

    Stender, D; Frison, R; Conder, K; Rupp, J L M; Scherrer, B; Martynczuk, J M; Gauckler, L J; Schneider, C W; Lippert, T; Wokaun, A

    2015-07-28

    The crystallization kinetics of amorphous 3 and 8 mol% yttria stabilized zirconia (3YSZ and 8YSZ) thin films grown by pulsed laser deposition (PLD), spray pyrolysis and dc-magnetron sputtering are explored. The deposited films were heat treated up to 1000 °C ex situ and in situ in an X-ray diffractometer. A minimum temperature of 275 °C was determined at which as-deposited amorphous PLD grown 3YSZ films fully crystallize within five hours. Above 325 °C these films transform nearly instantaneously with a high degree of micro-strain when crystallized below 500 °C. In these films the t'' phase crystallizes which transforms at T > 600 °C to the t' phase upon relaxation of the micro-strain. Furthermore, the crystallization of 8YSZ thin films grown by PLD, spray pyrolysis and dc-sputtering are characterized by in situ XRD measurements. At a constant heating rate of 2.4 K min(-1) crystallization is accomplished after reaching 800 °C, while PLD grown thin films were completely crystallized already at ca. 300 °C. PMID:26119755

  1. Piezoresistivity of graphene-based thin films

    NASA Astrophysics Data System (ADS)

    Raveendran Nair, Rahul; Navoselov, K. S.; Jiang, Da; Neubeck, Soren; Ponomarenko, Leonid; Geim, A. K.

    2009-03-01

    Large-scale production of graphene films is of particular interest because of graphene's extraordinary electronic, mechanical and optical properties. We report the properties of graphene films produced by spraying or spinning of a graphene suspension obtained by ultrasound cleavage of graphite in organic solvents, the route that does not involve graphene oxide [1]. Wafer-scale uniform films of overlapping submicron graphene crystallites were made on transparent substrates and exhibited sheet resistivity of a few kφ with more than 80% transmission with respect to white light. Electric measurements and Raman studies suggest that the films are p-doped. In particular, we have investigated the piezoresistive effect in such films by depositing them on flexible plastic substrates. Fully reversible changes in the resistance were observed as a function of strain that could exceed 8% before the films started loosing their continuity. The piezoresistive gauge factor was up to ˜30 for our films. [1] Peter Blake et al., Nano Lett. 2008, 8,1704-1708.

  2. Electrocaloric devices based on thini-film heat switches

    SciTech Connect

    Epstein, Richard I; Malloy, Kevin J

    2009-01-01

    We describe a new approach to refrigeration and electrical generation that exploits the attractive properties of thin films of electrocaloric materials. Layers of electrocaloric material coupled with thin-film heat switches can work as either refrigerators or electrical generators, depending on the phasing of the applied voltages and heat switching. With heat switches based on thin layers of liquid crystals, the efficiency of these thin-film heat engines can be at least as high as that of current thermoelectric devices. Advanced heat switches would enable thin-film heat engines to outperform conventional vaporcompression devices.

  3. Ion beam-based characterization of multicomponent oxide thin films and thin film layered structures

    SciTech Connect

    Krauss, A.R.; Rangaswamy, M.; Lin, Yuping; Gruen, D.M.; Schultz, J.A.; Schmidt, H.K.; Chang, R.P.H.

    1992-11-01

    Fabrication of thin film layered structures of multi-component materials such as high temperature superconductors, ferroelectric and electro-optic materials, and alloy semiconductors, and the development of hybrid materials requires understanding of film growth and interface properties. For High Temperature Superconductors, the superconducting coherence length is extremely short (5--15 {Angstrom}), and fabrication of reliable devices will require control of film properties at extremely sharp interfaces; it will be necessary to verify the integrity of thin layers and layered structure devices over thicknesses comparable to the atomic layer spacing. Analytical techniques which probe the first 1--2 atomic layers are therefore necessary for in-situ characterization of relevant thin film growth processes. However, most surface-analytical techniques are sensitive to a region within 10--40 {Angstrom} of the surface and are physically incompatible with thin film deposition and are typically restricted to ultra high vacuum conditions. A review of ion beam-based analytical methods for the characterization of thin film and multi-layered thin film structures incorporating layers of multicomponent oxides is presented. Particular attention will be paid to the use of time-of-flight techniques based on the use of 1- 15 key ion beams which show potential for use as nondestructive, real-time, in-situ surface diagnostics for the growth of multicomponent metal and metal oxide thin films.

  4. Orientation and lateral mobility of cytochrome c on the surface of ultrathin lipid multilayer films.

    PubMed Central

    Pachence, J M; Amador, S; Maniara, G; Vanderkooi, J; Dutton, P L; Blasie, J K

    1990-01-01

    We have previously shown that cytochrome c can be electrostatically bound to an ultrathin multilayer film having a negatively charged hydrophilic surface; furthermore, x-ray diffraction and absorption spectroscopy techniques indicated that the cytochrome c was bound to the surface of these ultrathin multilayer films as a molecular monolayer. The ultrathin fatty acid multilayers were formed on alkylated glass, using the Langmuir-Blodgett method. In this study, optical linear dichroism was used to determine the average orientation of the heme group within cytochrome c relative to the multilayer surface plane. The cytochrome c was either electrostatically or covalently bound to the surface of an ultrathin multilayer film. Horse heart cytochrome c was electrostatically bound to the hydrophilic surface of fatty acid multilayer films having an odd number of monolayers. Ultrathin multilayer films having an even number of monolayers would not bind cytochrome c, as expected for such hydrophobic surfaces. Yeast cytochrome c was covalently bound to the surface of a multilayer film having an even number of fatty acid monolayers plus a surface monolayer of thioethyl stearate. After washing extensively with buffer, the multilayer films with either electrostatically or covalently bound cytochrome c were analyzed for bound protein by optical absorption spectroscopy; the orientation of the cytochrome c heme was then investigated via optical linear dichroism. Polarized optical absorption spectra were measured from 450 to 600 nm at angles of 0 degrees, 30 degrees, and 45 degrees between the incident light beam and the normal to the surface plane of the multilayer. The dichroic ratio for the heme alpha-band at 550 nm as a function of incidence angle indicated that the heme of the electrostatically-bound monolayer of cytochrome c lies, on average, nearly parallel to the surface plane of the ultrathin multilayer. Similar results were obtained for the covalently-bound yeast cytochrome c

  5. Processing and characterization of extruded zein-based biodegradable films

    NASA Astrophysics Data System (ADS)

    Wang, Ying

    The objectives of this study were to prepare biodegradable zein films by extrusion processing and to evaluate relevant physical properties of resulting films with respect to their potential as packaging materials. The manufacture of protein-based packaging films by extrusion has remained a challenge. In this study, a zein resin was prepared by combining zein and oleic acid. This resin was formed into films by blown extrusion at the bench-top scale. Resin moisture content and extruder barrel temperature profile were identified as major parameters controlling the process. The optimum temperature of the blowing head was determined to be 40--45°C, while optimum moisture at film collection was 14--15%. Physico-chemical properties of the extruded products were characterized. Extruded products exhibited plastic behavior and ductility. Morphology characterization by SEM showed micro voids in extruded zein sheets, caused by entrapped air bubbles or water droplets. DSC characterization showed that zein was effectively plasticized by oleic acid as evidenced by the lowered glass transition temperature of zein films. X-ray scattering was used to investigate changes in zein molecular aggregation during processing. It was observed that higher mechanical energy treatment progressively disrupted zein molecular aggregates, resulting in a more uniform distribution of individual zein molecules. With the incorporation of oleic acid as plasticizer and monoglycerides as emulsifier, zein formed structures with long-range periodicity which varied depending on the formulation and processing methods. Processing methods for film formation affected the binding of oleic acid to zein with higher mechanical energy treatment resulting in better interaction between the two components. The moisture sorption capacity of extruded zein films was reduced due to the compact morphology caused by extrusion. Plasticization with oleic acid further reduced moisture sorption of zein films. The overall

  6. The location of cytochrome c on the surface of ultrathin lipid multilayer films using x-ray diffraction.

    PubMed Central

    Pachence, J M; Blasie, J K

    1987-01-01

    X-ray diffraction and spectroscopic techniques were used to characterize ultrathin fatty acid multilayers having a bound surface layer of cytochrome c. Three to six monolayers of arachidic acid were deposited onto an alkylated glass surface, using the Langmuir-Blodgett method. These fatty acid multilayer films were stored either in a 1 mM NaHCO3 pH 7.5 solution or a buffered 10 microM cytochrome c solution, pH 7.5. After washing extensively with buffer, these multilayer films were assayed for bound cytochrome c by optical spectroscopy. It was found that the cytochrome c bound only to the odd-numbered monolayer films (which have hydrophilic surfaces). The theoretical number of cytochrome c molecules bound to the ultrathin multilayer films having three or five monolayers was calculated as N = 1.2 x 10(13)/cm2 (assuming a hexagonally close-packed monolayer of protein), which would produce an optical density of 0.002 at a wavelength of 550 nm; for a three or five monolayer ultrathin film that was incubated with cytochrome c, OD550 approximately equal to 0.002. The protein was released from the film when treated with greater than 100 mM KCl solution, as would be expected for an electrostatic interaction. Meridional x-ray diffraction data were collected from the arachidic acid films with and without a bound cytochrome c layer. A box refinement technique, previously shown to be effective in deriving the profile structures of nonperiodic ultrathin films, was used to determine the multilayer electron density profiles. The electron density profiles and their autocorrelation functions showed that bound cytochrome c resulted in an additional electron dense feature on the multilayer surface, consistent with a bound cytochrome c monolayer. The position of the bound protein relative to the multilayer surface was independent of the number of fatty acid monolayers in the multilayer. Future studies will use these methods to investigate the structures of membrane protein complexes

  7. Antimicrobial nanostructured starch based films for packaging.

    PubMed

    Abreu, Ana S; Oliveira, M; de Sá, Arsénio; Rodrigues, Rui M; Cerqueira, Miguel A; Vicente, António A; Machado, A V

    2015-09-20

    Montmorillonite modified with a quaternary ammonium salt C30B/starch nanocomposite (C30B/ST-NC), silver nanoparticles/starch nanocomposite (Ag-NPs/ST-NC) and both silver nanoparticles/C30B/starch nanocomposites (Ag-NPs/C30B/ST-NC) films were produced. The nanoclay (C30B) was dispersed in a starch solution using an ultrasonic probe. Different concentrations of Ag-NPs (0.3, 0.5, 0.8 and 1.0mM) were synthesized directly in starch and in clay/starch solutions via chemical reduction method. Dispersion of C30B silicate layers and Ag-NPs in ST films characterized by X-ray and scanning electron microscopy showed that the presence of Ag-NPs enhanced clay dispersion. Color and opacity measurements, barrier properties (water vapor and oxygen permeabilities), dynamic mechanical analysis and contact angle were evaluated and related with the incorporation of C30B and Ag-NPs. Films presented antimicrobial activity against Staphylococcus aureus, Escherichia coli and Candida albicans without significant differences between Ag-NPs concentrations. The migration of components from the nanostructured starch films, assessed by food contact tests, was minor and under the legal limits. These results indicated that the starch films incorporated with C30B and Ag-NPs have potential to be used as packaging nanostructured material. PMID:26050897

  8. Nanocrystalline silicon based thin film solar cells

    NASA Astrophysics Data System (ADS)

    Ray, Swati

    2012-06-01

    Amorphous silicon solar cells and panels on glass and flexible substrate are commercially available. Since last few years nanocrystalline silicon thin film has attracted remarkable attention due to its stability under light and ability to absorb longer wavelength portion of solar spectrum. For amorphous silicon/ nanocrystalline silicon double junction solar cell 14.7% efficiency has been achieved in small area and 13.5% for large area modules internationally. The device quality nanocrystalline silicon films have been fabricated by RF and VHF PECVD methods at IACS. Detailed characterizations of the materials have been done. Nanocrystalline films with low defect density and high stability have been developed and used as absorber layer of solar cells.

  9. Methods for preparing colloidal nanocrystal-based thin films

    DOEpatents

    Kagan, Cherie R.; Fafarman, Aaron T.; Choi, Ji-Hyuk; Koh, Weon-kyu; Kim, David K.; Oh, Soong Ju; Lai, Yuming; Hong, Sung-Hoon; Saudari, Sangameshwar Rao; Murray, Christopher B.

    2016-05-10

    Methods of exchanging ligands to form colloidal nanocrystals (NCs) with chalcogenocyanate (xCN)-based ligands and apparatuses using the same are disclosed. The ligands may be exchanged by assembling NCs into a thin film and immersing the thin film in a solution containing xCN-based ligands. The ligands may also be exchanged by mixing a xCN-based solution with a dispersion of NCs, flocculating the mixture, centrifuging the mixture, discarding the supernatant, adding a solvent to the pellet, and dispersing the solvent and pellet to form dispersed NCs with exchanged xCN-ligands. The NCs with xCN-based ligands may be used to form thin film devices and/or other electronic, optoelectronic, and photonic devices. Devices comprising nanocrystal-based thin films and methods for forming such devices are also disclosed. These devices may be constructed by depositing NCs on to a substrate to form an NC thin film and then doping the thin film by evaporation and thermal diffusion.

  10. Neutron Reflectivity Measurement for Polymer Dynamics near Graphene Oxide Monolayers

    NASA Astrophysics Data System (ADS)

    Koo, Jaseung

    We investigated the diffusion dynamics of polymer chains confined between graphene oxide layers using neutron reflectivity (NR). The bilayers of polymethylmetacrylate (PMMA)/ deuterated PMMA (d-PMMA) films and polystyrene (PS)/d-PS films with various film thickness sandwiched between Langmuir-Blodgett (LB) monolayers of graphene oxide (GO) were prepared. From the NR results, we found that PMMA diffusion dynamics was reduced near the GO surface while the PS diffusion was not significantly changed. This is due to the different strength of GO-polymer interaction. In this talk, these diffusion results will be compared with dewetting dynamics of polymer thin films on the GO monolayers. This has given us the basis for development of graphene-based nanoelectronics with high efficiency, such as heterojunction devices for polymer photovoltaic (OPV) applications.

  11. Integrated thick-film nanostructures based on spinel ceramics

    PubMed Central

    2014-01-01

    Integrated temperature-humidity-sensitive thick-film structures based on spinel-type semiconducting ceramics of different chemical compositions and magnesium aluminate ceramics were prepared and studied. It is shown that temperature-sensitive thick-film structures possess good electrophysical characteristics in the region from 298 to 358 K. The change of electrical resistance in integrated thick-film structures is 1 order, but these elements are stable in time and can be successfully used for sensor applications. PMID:24670141

  12. Integrated thick-film nanostructures based on spinel ceramics.

    PubMed

    Klym, Halyna; Hadzaman, Ivan; Shpotyuk, Oleh; Brunner, Michael

    2014-01-01

    Integrated temperature-humidity-sensitive thick-film structures based on spinel-type semiconducting ceramics of different chemical compositions and magnesium aluminate ceramics were prepared and studied. It is shown that temperature-sensitive thick-film structures possess good electrophysical characteristics in the region from 298 to 358 K. The change of electrical resistance in integrated thick-film structures is 1 order, but these elements are stable in time and can be successfully used for sensor applications. PMID:24670141

  13. Linear Microbolometric Array Based on VOx Thin Film

    NASA Astrophysics Data System (ADS)

    Chen, Xi-Qu

    2010-05-01

    In this paper, a linear microbolometric array based on VOx thin film is proposed. The linear microbolometric array is fabricated by using micromachining technology, and its thermo-sensitive VOx thin film has excellent infrared response spectrum and TCR characteristics. Integrated with CMOS circuit, an experimentally prototypical monolithic linear microbolometric array is designed and fabricated. The testing results of the experimental linear array show that the responsivity of linear array can approach 18KV/W and is potential for infrared image systems.

  14. Surface Detection in a STXM Microscope

    SciTech Connect

    Behyan, S.; Haines, B.; Urquhart, S. G.; Karanukaran, C.; Wang, J.; Obst, M.; Tyliszczak, T.

    2011-09-09

    We have modified scanning transmission x-ray microscopes (STXM) at the Canadian Light Source and the Advanced Light Source with total electron yield (TEY) detection (TEY-STXM). This provides improved surface-sensitive detection, simultaneous with existing bulk-sensitive transmission detection in the STXM microscopes. We have explored sample-current and channeltron-based electron yield detection. Both approaches provide improved surface sensitive imaging and spectroscopy, although channeltron-based detection is superior. TEY-STXM provides surface sensitive imaging of ultrathin films such as phase-separated Langmuir-Blodgett monolayer films, as well as differentiation of surface and bulk oxides of patterned metallic thin films. This paper will outline the experimental challenges of this method and the opportunities for correlative surface and bulk measurements of complex samples.

  15. Development and Evaluation of Cefadroxil Drug Loaded Biopolymeric Films Based on Chitosan-Furfural Schiff Base

    PubMed Central

    Dixit, Ritu B.; Uplana, Rahul A.; Patel, Vishnu A.; Dixit, Bharat C.; Patel, Tarosh S.

    2010-01-01

    Cefadroxil drug loaded biopolymeric films of chitosan-furfural schiff base were prepared by reacting chitosan with furfural in presence of acetic acid and perchloric acid respectively for the external use. Prepared films were evaluated for their strength, swelling index, thickness, drug content, uniformity, tensile strength, percent elongation, FTIR spectral analysis and SEM. The results of in vitro diffusion studies revealed that the films exhibited enhanced drug diffusion as compared to the films prepared using untreated chitosan. The films also demonstrated good to moderate antibacterial activities against selective gram positive and gram negative bacteria. PMID:21179325

  16. ZnS-nanocrystals/polypyrrole nanocomposite film based immunosensor

    NASA Astrophysics Data System (ADS)

    Mishra, Sujeet K.; Pasricha, Renu; Biradar, Ashok M.; Rajesh

    2012-01-01

    We report an electrochemically synthesized ZnS nanocrystals modified polypyrrole (PPy) nanocomposite film based immunosensor for the detection of C-reactive protein (αCRP). The ZnS-PPy composite film was characterized by transmission electron microscopy (TEM), atomic force microscopy (AFM) and electrochemical techniques. The modified film showed good biocompatibility with efficient binding to protein antibody (αCRP-Ab) molecules through ZnS nanocrystals, exhibited an attractive platform for immunosensor fabrication. The electrical and sensing properties of the polymer composite film of different thickness towards protein antigen (αCRP-Ag) were delineated. The immunosensor exhibited an impedance response to αCRP-Ag concentration in a linear range from 10 ng to 10 μg mL-1.

  17. SUBTLEX-ESP: Spanish Word Frequencies Based on Film Subtitles

    ERIC Educational Resources Information Center

    Cuetos, Fernando; Glez-Nosti, Maria; Barbon, Analia; Brysbaert, Marc

    2011-01-01

    Recent studies have shown that word frequency estimates obtained from films and television subtitles are better to predict performance in word recognition experiments than the traditional word frequency estimates based on books and newspapers. In this study, we present a subtitle-based word frequency list for Spanish, one of the most widely spoken…

  18. Size fractionation of graphene oxide sheets by pH-assisted selective sedimentation.

    PubMed

    Wang, Xiluan; Bai, Hua; Shi, Gaoquan

    2011-04-27

    Graphene oxide (GO) sheets prepared by Hummers' method have been separated into two portions with large (f1) or small (f2) lateral dimensions from their aqueous dispersion. This method is based on the selective precipitation of GO sheets with lateral dimensions mostly (>90%) larger than 40 μm(2) at a pH value of 4.0 because of their larger hydrophobic planes and fewer hydrophilic oxygenated groups. The hydrazine reduced Langmuir-Blodgett (LB) films of f1 showed much higher conductivities than those of f2. Furthermore, the thin film of f1 prepared by filtration exhibited a smaller d-space and much higher tensile strength and modulus than those of f2 films. The one-step size fractionation method reported here is simple, cheap, efficient, and environmentally friendly, which can be used for the size fractionation of GO sheets in large scale. PMID:21449601

  19. Gadolinium nitride films deposited using a PEALD based process

    NASA Astrophysics Data System (ADS)

    Fang, Ziwen; Williams, Paul A.; Odedra, Rajesh; Jeon, Hyeongtag; Potter, Richard J.

    2012-01-01

    Gadolinium nitride films have been deposited on Si(100) using a plasma-enhanced ALD (PEALD) based process. The deposition was carried out using tris(methylcyclopentadienyl)gadolinium {Gd(MeCp) 3} and remote nitrogen plasma, separated by argon pulses. Films were deposited at temperatures between 150 and 300 °C and capped with tantalum nitride to prevent post-deposition oxidation. Film composition was initially assessed using EDX and selected samples were subsequently depth profiled using medium energy ion scattering (MEIS) or AES. X-ray diffraction appears to show that the films are effectively amorphous. Films deposited at 200 °C were found to have a Gd:N ratio close to 1:1 and a low oxygen incorporation (˜5%). Although the growth was affected by partial thermal decomposition of the Gd(MeCp) 3, it was still possible to obtain smooth (Ra.=˜0.7 nm) films with good thickness uniformity (97%). Less successful attempts to deposit gadolinium nitride using thermal ALD with ammonia or mono-methyl-hydrazine are also reported.

  20. MEMS-based microstructures for nanomechanical characterization of thin films

    NASA Astrophysics Data System (ADS)

    Boé, A.; Safi, A.; Coulombier, M.; Fabrègue, D.; Pardoen, T.; Raskin, J.-P.

    2009-11-01

    The measurement of mechanical properties of thin films is a major issue for the design of reliable microelectronic devices, microsensors or thin coatings. New simple microstructures actuated through the release of internally stressed long beams made of high temperature, low pressure chemical vapour deposition silicon nitride have been developed to test under uniaxial tension submicron thin film material specimens. The relative displacement between a fixed and a moving cursor is used to determine the strain applied to the specimen. The stress is inferred based on the mismatch strain and Young's modulus of the silicon nitride actuator beam. By multiplying the tensile test microstructures with different lengths, the full stress-strain curve characterizing the thin material sample is generated from which the elastic stiffness, yield strength, ductility and fracture stress can be extracted. The potential of the method is demonstrated through applications on both brittle and ductile thin films. The Young's modulus of 238 GPa for a 373 nm thick silicon nitride film is extracted and size effects are observed for the yield strength of pure aluminium with a value of 220 and 550 MPa, respectively, for 373 and 205 nm thick films. An original variant of the procedure based on this new test microstructure for measuring Young's modulus is also presented.

  1. Ferroelectric memory element based on thin film field effect transistor

    NASA Astrophysics Data System (ADS)

    Poghosyan, A. R.; Aghamalyan, N. R.; Elbakyan, E. Y.; Guo, R.; Hovsepyan, R. K.

    2013-09-01

    We report the preparation and investigation of ferroelectric field effect transistors (FET) using ZnO:Li films with high field mobility of the charge carriers as a FET channel and as a ferroelectric active element simultaneously. The possibility for using of ferroelectric FET based on the ZnO:Li films in the ZnO:Li/LaB6 heterostructure as a bi-stable memory element for information recording is shown. The proposed ferroelectric memory structure does not manifest a fatigue after multiple readout of once recorded information.

  2. Diffractive Optical Elements based in Diamond Like Carbon (DLC) films

    NASA Astrophysics Data System (ADS)

    Sparvoli, M. Marina; Mansano, Ronaldo D.

    2008-04-01

    In this work was developed a Diffractive Optical Elements (DOEs) based in amorphous hydrogenated carbon (Diamond Like Carbon) films. DOEs can be built in large scale with high reproducibility and eliminating almost stages used in optical elements tradicional fabrication, as abrasion and burnishing. These devices had been built by the etching of DLC deposited by sputtering process. The characterizations of these devices are realized by optical analyzes with a 633 nm HeNe laser. The DLC films roughness and etch rate after process were measured by high step meter.

  3. Bimorph micro heat engines based on carbon nanotube freestanding films

    NASA Astrophysics Data System (ADS)

    Ikuno, Takashi; Fukano, Tatsuo; Higuchi, Kazuo; Takeda, Yasuhiko

    2015-11-01

    We have found that lightweight bimorph strips consisting of multiwalled carbon nanotube freestanding films (MWNT-FSFs) and Ni thin films exhibit a continuous bending-stretching motion on a hot plate even below the temperature of 100 °C in an environment at room temperature. In fact, the Ni/MWNT-FSFs exhibited this motion at a temperature difference of as small as 5 °C. The requirements of this motion have been qualitatively elucidated by a simulation based on a relaxation time approximation.

  4. Switchable mirrors based on nickel-magnesium films

    SciTech Connect

    Richardson,Thomas J.; Slack, Jonathan L.; Armitage, Robert D.; Kostecki, Robert; Farangis, Baker; Rubin, Michael D.

    2001-01-16

    A new type of electrochromic mirror electrode based on reversible uptake of hydrogen in nickel magnesium alloy films is reported. Thin,magnesium-rich Ni-Mg films prepared on glass substrates by cosputtering from Ni and Mg targets are mirror-like in appearance and have low visible transmittance. Upon exposure to hydrogen gas or on reduction in alkaline electrolyte, the films take up hydrogen and become transparent. When hydrogen is removed, the mirror properties are recovered. The transition is believed to result from reversible formation of Mg2NiH4 and MgH2. A thin overlayer of palladium was found to enhance the kinetics of hydrogen insertion and extraction,and to protect the metal surface against oxidation.

  5. Switchable mirrors based on nickel-magnesium films

    NASA Astrophysics Data System (ADS)

    Richardson, T. J.; Slack, J. L.; Armitage, R. D.; Kostecki, R.; Farangis, B.; Rubin, M. D.

    2001-05-01

    An electrochromic mirror electrode based on reversible uptake of hydrogen in nickel magnesium alloy films is reported. Thin, magnesium-rich Ni-Mg films prepared on glass substrates by co-sputtering from Ni and Mg targets are mirror-like in appearance and have low visible transmittance. Upon exposure to hydrogen gas or on cathodic polarization in alkaline electrolyte, the films take up hydrogen and become transparent. When hydrogen is removed, the mirror properties are recovered. The transition is believed to result from reversible formation of Mg2NiH4 and MgH2. A thin overlayer of palladium was found to enhance the kinetics of hydrogen insertion and extraction, and to protect the metal surface against oxidation.

  6. 36 CFR 1237.30 - How do agencies manage records on nitrocellulose-base and cellulose-acetate base film?

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... film as specified in Department of Transportation regulations (49 CFR 172.101, Hazardous materials... records on nitrocellulose-base and cellulose-acetate base film? 1237.30 Section 1237.30 Parks, Forests... and cellulose-acetate base film? (a) The nitrocellulose base, a substance akin to gun cotton,...

  7. 36 CFR 1237.30 - How do agencies manage records on nitrocellulose-base and cellulose-acetate base film?

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... film as specified in Department of Transportation regulations (49 CFR 172.101, Hazardous materials... records on nitrocellulose-base and cellulose-acetate base film? 1237.30 Section 1237.30 Parks, Forests... and cellulose-acetate base film? (a) The nitrocellulose base, a substance akin to gun cotton,...

  8. 36 CFR 1237.30 - How do agencies manage records on nitrocellulose-base and cellulose-acetate base film?

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... film as specified in Department of Transportation regulations (49 CFR 172.101, Hazardous materials... records on nitrocellulose-base and cellulose-acetate base film? 1237.30 Section 1237.30 Parks, Forests... and cellulose-acetate base film? (a) The nitrocellulose base, a substance akin to gun cotton,...

  9. 36 CFR 1237.30 - How do agencies manage records on nitrocellulose-base and cellulose-acetate base film?

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... film as specified in Department of Transportation regulations (49 CFR 172.101, Hazardous materials... records on nitrocellulose-base and cellulose-acetate base film? 1237.30 Section 1237.30 Parks, Forests... and cellulose-acetate base film? (a) The nitrocellulose base, a substance akin to gun cotton,...

  10. Femtosecond laser micromachining of polyvinylidene fluoride (PVDF) based piezo films

    NASA Astrophysics Data System (ADS)

    Lee, Seongkuk; Bordatchev, Evgueni V.; Zeman, Marco J. F.

    2008-04-01

    Piezoelectric polymers have been known to exist for more than 40 years, but in recent years they have been recognized as smart materials for the fabrication of microsensors, microactuators and other micro-electro-mechanical systems (MEMS). In this work, femtosecond laser micromachining of a polyvinylidene fluoride (PVDF) film, coated with NiCu on both sides, has been studied to understand selective patterning mechanisms of NiCu layers and ablation characteristics of PVDF films. A detailed characterization of morphological changes of the laser-irradiated areas has been investigated using scanning electron microscopy. Through morphological analysis, the multiple shot damage thresholds of a 28 µm thick PVDF film and 40 nm thick NiCu layer have been determined. Surface morphology examination indicates that NiCu layers are removed from the PVDF film through a sequence of cracking-peeling off-curling. In addition, the NiCu layer on the rear side was also removed by the partially transmitted laser energy. The PVDF film was removed in forms of bundles of filaments and solid fragments by a combination of pure ablation and explosive removal of material by bursting of bubbles; the role of the explosive removal becomes more dominant with the increase of laser fluence. Optimal process conditions for cutting of the PVDF film and patterning of the NiCu coating without damaging the PVDF polymer have been established and applied to fabricate a vibration microsensor prototype that shows significant potential in using PVDF-based functional microdevices for telecommunications, transportation and biomedical applications.

  11. Design, Fabrication and Characterization of MIM Diodes and Frequency Selective Thermal Emitters for Solar Energy Harvesting and Detection Devices

    NASA Astrophysics Data System (ADS)

    Sharma, Saumya

    Energy harvesting using rectennas for infrared radiation continues to be a challenge due to the lack of fast switching diodes capable of rectification at THz frequencies. Metal insulator metal diodes which may be used at 30 THz must show adequate nonlinearity for small signal rectification such as 30 mV. In a rectenna assembly, the voltage signal received as an output from a single nanoantenna can be as small as ~30microV. Thus, only a hybrid array of nanoantennas can be sufficient to provide a signal in the ~30mV range for the diode to be able to rectify around 30THz. A metal-insulator-metal diode with highly nonlinear I-V characteristics is required in order for such small signal rectification to be possible. Such diode fabrication was found to be faced with two major fabrication challenges. The first one being the lack of a precisely controlled deposition process to allow a pinhole free insulator deposition less than 3nm in thickness. Another major challenge is the deposition of a top metal contact on the underlying insulating thin film. As a part of this research study, most of the MIM diodes were fabricated using Langmuir Blodgett monolayers deposited on a thin Ni film that was sputter coated on a silicon wafer. UV induced polymerization of the Langmuir Blodgett thin film was used to allow intermolecular crosslinking. A metal top contact was sputtered onto the underlying Langmuir Blodgett film assembly. In addition to material characterization of all the individual films using IR, UV-VIS spectroscopy, electron microscopy and atomic force microscopy, the I-V characteristics, resistance, current density, rectification ratio and responsivity with respect to the bias voltage were also measured for the electrical characterization of these MIM diodes. Further improvement in the diode rectification ratio and responsivity was obtained with Langmuir Blodgett films grown by the use of horizontally oriented organic molecules, due to a smaller tunneling distance that

  12. Fabrication, Characterization, and Applications of Graphene-based Flexible Films

    NASA Astrophysics Data System (ADS)

    Naik, Gautam

    Scientific interest in the field of nanotechnology has increased multifold since the discovery of multi-walled carbon nanotubes in the early 1990s. This further received a tremendous boost with the isolation of graphene, a single layer of sp2-hybridized carbon atoms, in 2004. Graphene has exceptional mechanical and electrical properties, which makes it an attractive candidate for electronics and composites. In order to realize the implementation of graphene for such applications, scalable production of graphene-based materials needs to be accomplished. Graphene oxide, the product of oxidation and exfoliation of graphite, is a promising precursor for bulk-production of graphene and graphene-like materials. The oxidation of graphite to synthesize graphene oxide results in the decoration of the basal plane of graphene with oxygen-containing functional groups. The presence of these functional groups makes graphene oxide strongly hydrophilic, making it soluble in water and a good candidate for solution-based processing. This hydrophilic nature of graphene oxide can also be utilized to fabricate highly sensitive and flexible humidity sensors, the results of which are included in this research. The fabricated humidity sensors show high sensitivity and a fast response time. A difference in response is observed at low and high humidity, with hysteresis observed at high humidity levels. A method to "reset" the sensor and a mechanism to explain the response is also proposed. Although the hydrophilic nature of graphene oxide makes it suitable for bulk processing, the presence of functional groups makes it defective and insulating. Graphene oxide needs to be reduced to make it electrically active. Numerous methodologies proposed for reduction of graphene oxide result in the simultaneous reduction and exfoliation of graphene oxide films. But for instances where flexible graphene films are required for certain applications, a method for reduction of graphene oxide flexible films

  13. Bacteria counting method based on polyaniline/bacteria thin film.

    PubMed

    Zhihua, Li; Xuetao, Hu; Jiyong, Shi; Xiaobo, Zou; Xiaowei, Huang; Xucheng, Zhou; Tahir, Haroon Elrasheid; Holmes, Mel; Povey, Malcolm

    2016-07-15

    A simple and rapid bacteria counting method based on polyaniline (PANI)/bacteria thin film was proposed. Since the negative effects of immobilized bacteria on the deposition of PANI on glass carbon electrode (GCE), PANI/bacteria thin films containing decreased amount of PANI would be obtained when increasing the bacteria concentration. The prepared PANI/bacteria film was characterized with cyclic voltammetry (CV) technique to provide quantitative index for the determination of the bacteria count, and electrochemical impedance spectroscopy (EIS) was also performed to further investigate the difference in the PANI/bacteria films. Good linear relationship of the peak currents of the CVs and the log total count of bacteria (Bacillus subtilis) could be established using the equation Y=-30.413X+272.560 (R(2)=0.982) over the range of 5.3×10(4) to 5.3×10(8)CFUmL(-1), which also showed acceptable stability, reproducibility and switchable ability. The proposed method was feasible for simple and rapid counting of bacteria. PMID:26921555

  14. Films and components from holographic recording based on bacteriorhodopsin

    NASA Astrophysics Data System (ADS)

    Hampp, Norbert A.; Sanio, Markus; Anderle, Klaus

    2000-03-01

    Since more than ten years films and cubes made from the halobacterial photochromic retinal protein bacteriorhodopsin (BR) are discussed as storage media for short-term and long- term data storage. The efficient photochemistry of BR, the stability towards chemical and thermal degradation, the reversibility and the polarization recording capability of bacteriorhodopsin films are attractive. The limited storage time of the recorded information implies some restrictions in the use of this material. Because bacteriorhodopsin returns also through a thermal pathway to its initial state recorded information decays with a characteristic time constant which is related to the lifetime of the M-state of the material. By genetic methods and by suitable film compositions this value can be extended up to several minutes which is more than enough for all real-time applications. In some cases a longer storage time is desired, among them optical data storage. Optical modules and components based on bacteriorhodopsin films, which can be thermostated to different temperatures, are presented. They allow very sensitive optical recording and can be photochemically or thermally erased. These bacteriorhodopsin containing modules may be used for high resolution optical recording with extended storage time.

  15. Quantification of ecotoxicological tests based on bioluminescence using Polaroid film.

    PubMed

    Tamminen, Manu V; Virta, Marko P J

    2007-01-01

    Assays based on the measurement of bacterial luminescence are widely used in ecotoxicology. Bacterial strains responding either to general toxicity or specific pollutants are rapid, cost-effective and easy to use. However, quantification of the signal requires relatively expensive instrumentation. We show here that the detection of luminescence of BioTox, a Vibrio fischeri-based toxicity test, and of a specific recombinant bacterial strain for arsenic determination, is possible using common Polaroid film. The exposed films can be used for visual or computer-assisted quantification of the signal. Qualitative visual comparison to standards can be used in the rapid and relatively accurate estimation of toxicity or pollutant concentration. The computer-assisted method significantly improves the accuracy and quantification of the results. The results obtained by computer-assisted quantification were in good agreement with the values obtained with a luminometer. PMID:16949132

  16. Superconducting thin film cavities and base electrode planarization

    NASA Astrophysics Data System (ADS)

    Thomas, Christopher Doyle

    1997-11-01

    This study concerns two separate projects. The first deals with a new technique to improve superconducting tunnel junction fabrication technology through the use of planarized base electrodes. Planarization, resulting in smooth film surfaces, is realized by coating a conventional niobium base electrode with a multilayer of niobium and aluminum. Very low leakage tunnel junctions were made using this method. The second project involves electromagnetic coupling to a superconducting thin film cavity. A novel device, potentially useful as an x-ray detector, has been fabricated and characterized. The theory of operation of this closed superconducting cavity, or "Fiske Cavity", is presented along with experimental results. Current - voltage measurements reveal current steps at selected voltages that are predicted theoretically and indicate electromagnetic coupling in this system. This form of coupling motivates new devices with arrays of phase locked junctions that interact through an underlying resonant waveguide and with no external microwave source.

  17. Real-time DNA detection using Pt nanoparticle-decorated reduced graphene oxide field-effect transistors.

    PubMed

    Yin, Zongyou; He, Qiyuan; Huang, Xiao; Zhang, Juan; Wu, Shixin; Chen, Peng; Lu, Gang; Chen, Peng; Zhang, Qichun; Yan, Qingyu; Zhang, Hua

    2012-01-01

    A large-area, continuous, few-layer reduced graphene oxide (rGO) thin film has been fabricated on a Si/SiO(2) wafer using the Langmuir-Blodgett (LB) method followed by thermal reduction. After photochemical reduction of Pt nanoparticles (PtNPs) on rGO, the obtained PtNPs/rGO composite is employed as the conductive channel in a solution-gated field effect transistor (FET), which is then used for real-time detection of hybridization of single-stranded DNA (ssDNA) with high sensitivity (2.4 nM). Such a simple, but effective method for fabrication of rGO-based transistors shows great potential for mass-production of graphene-based electronic biosensors. PMID:22089471

  18. Cobalt-Based Hard Magnets, Thin Films and Multilayers

    NASA Astrophysics Data System (ADS)

    Gao, Chuan

    1991-02-01

    Co-based magnetic materials including bulk, thin film and magnetic multilayers have been studied. The purpose of the first part of this work is to study a Co -based transition metal alloy to be processed to result in significant enhancement of its magnetic properties (coercivity, magnetization, and energy product) in the absence rare earths. CoZr(Hf)BSi alloys have been studied. Rapidly quenched Co_ {78}Zr_{16}B_3Si_3 and Co_{76}Hf_ {76}B_3Si_3 showed the highest coercivity (6.7 kOe and 6.5 kOe respectively). This is the highest room temperature coercivity reported in a non -rare-earth containing magnet up to now. This system has excellent thermal stability. Co-based thin film alloys were also studied and we obtain coercivities as high as 700 Oe for sputtered thin films. This lies in between the maximum value obtained for as-cast bulk alloys (50 Oe) and rapidly quenched alloys (6.7 kOe). Multilayers were studied with the objective of determining the effect of interfaces on the magnetic properties of Co alloys. Multilayers of the form Co/Cu, Co_{95}B _5/Cu and Co/Al were studied and the interface anisotropy was found to favor a magnetization perpendicular to the film. Very thin magnetic layers led to very small coercivities since the size of magnetic domains was restricted. We also noted some interesting layer-layer magnetic interactions. Finally some unusual magnetization reversal behavior was noted in which the magnetic moment goes to zero and reverses before the applied field goes to zero.

  19. MEMS-based thin-film fuel cells

    DOEpatents

    Jankowksi, Alan F.; Morse, Jeffrey D.

    2003-10-28

    A micro-electro-mechanical systems (MEMS) based thin-film fuel cells for electrical power applications. The MEMS-based fuel cell may be of a solid oxide type (SOFC), a solid polymer type (SPFC), or a proton exchange membrane type (PEMFC), and each fuel cell basically consists of an anode and a cathode separated by an electrolyte layer. Additionally catalyst layers can also separate the electrodes (cathode and anode) from the electrolyte. Gas manifolds are utilized to transport the fuel and oxidant to each cell and provide a path for exhaust gases. The electrical current generated from each cell is drawn away with an interconnect and support structure integrated with the gas manifold. The fuel cells utilize integrated resistive heaters for efficient heating of the materials. By combining MEMS technology with thin-film deposition technology, thin-film fuel cells having microflow channels and full-integrated circuitry can be produced that will lower the operating temperature an will yield an order of magnitude greater power density than the currently known fuel cells.

  20. Preparation and Properties of Silver Nanowire-Based Transparent Conductive Composite Films

    NASA Astrophysics Data System (ADS)

    Tian, Ji-Li; Zhang, Hua-Yu; Wang, Hai-Jun

    2016-06-01

    Silver nanowire-based transparent conductive composite films with different structures were successfully prepared using various methods, including liquid polyol, magnetron sputtering and spin coating. The experimental results revealed that the optical transmittance of all different structural composite films decreased slightly (1-3%) compared to pure films. However, the electrical conductivity of all composite films had a great improvement. Under the condition that the optical transmittance was greater than 78% over the wavelength range of 400-800 nm, the AgNW/PVA/AgNW film became a conductor, while the AZO/AgNW/AZO film and the ITO/AgNW/ITO film showed 88.9% and 94% reductions, respectively, for the sheet resistance compared with pure films. In addition, applying a suitable mechanical pressure can improve the conductivity of AgNW-based composite films.

  1. Hydrogen Microsensor Based on NiO Thin Films

    NASA Astrophysics Data System (ADS)

    Fasaki, I.; Antoniadou, M.; Giannoudakos, A.; Stamataki, M.; Kompitsas, M.; Roubani-Kalantzopoulou, F.; Hotovy, I.; Rehacek, V.

    A multitude of industries use H2 either as part of their process or as a fuel. All these applications motivate nowadays the development of hydrogen sensor devices which enable its safe and controlled use. Since H2 is explosive above the lower explosion limit at 40,000 ppm, devices which permit the detection of its presence and measure its concentration become indispensable. In this work, we present a microsensor based on NiO thin films produced with dc reactive magnetron sputtering on GaAs, with an incorporated Pt heater, all on a DO-8 package ready for use. The microsensor was tested to H2 concentrations 5,000 and 10,000 ppm at different working temperatures. The change of the electrical resistance of NiO thin films was the signal for hydrogen sensing. The response of the sensor was not proportional to concentration of the gas neither to the working temperature.

  2. Large displacement vertical translational actuator based on piezoelectric thin films

    PubMed Central

    Qiu, Zhen; Pulskamp, Jeffrey S; Lin, Xianke; Rhee, Choong-Ho; Wang, Thomas; Polcawich, Ronald G; Oldham, Kenn

    2014-01-01

    A novel vertical translational microactuator based on thin-film piezoelectric actuation is presented, using a set of four compound bend-up/bend-down unimorphs to produce translational motion of a moving platform or stage. The actuation material is a chemical-solution deposited lead–zirconate–titanate (PZT) thin film. Prototype designs have shown as much as 120 μm of static displacement, with 80–90 μm displacements being typical, using four 920 μm long by 70 μm legs. Analytical models are presented that accurately describe nonlinear behavior in both static and dynamic operation of prototype stages when the dependence of piezoelectric coefficients on voltage is known. Resonance of the system is observed at a frequency of 200 Hz. The large displacement and high bandwidth of the actuators at low-voltage and low-power levels should make them useful to a variety of optical applications, including endoscopic microscopy. PMID:25506130

  3. Identification and annotation of erotic film based on content analysis

    NASA Astrophysics Data System (ADS)

    Wang, Donghui; Zhu, Miaoliang; Yuan, Xin; Qian, Hui

    2005-02-01

    The paper brings forward a new method for identifying and annotating erotic films based on content analysis. First, the film is decomposed to video and audio stream. Then, the video stream is segmented into shots and key frames are extracted from each shot. We filter the shots that include potential erotic content by finding the nude human body in key frames. A Gaussian model in YCbCr color space for detecting skin region is presented. An external polygon that covered the skin regions is used for the approximation of the human body. Last, we give the degree of the nudity by calculating the ratio of skin area to whole body area with weighted parameters. The result of the experiment shows the effectiveness of our method.

  4. Dendritic wideband metamaterial absorber based on resistance film

    NASA Astrophysics Data System (ADS)

    Wang, Bing; Gong, Bo Yi; Wang, Mei; Weng, Bin; Zhao, Xiaopeng

    2015-03-01

    A type of dendritic wideband metamaterial absorber was designed and constructed from resistance film composed of indium-tin oxide conductive film having a dendritic metamaterial structure, dielectric layer made of polymethacrylimide foam, and metallic sheet based on the equivalent circuit model. In terms of normal incidence, the simulation using the absorber yielded operating absorption rates >80 % in the frequency range of 8-27.9 GHz. In addition, the experimental measurements verified 8-17 GHz range of more than 80 % absorption rate, whereas its relative bandwidth reached 72 %. Moreover, this reasonable absorption performance was maintained for oblique incidences of <60°. The effects of dielectric layer thickness on absorption properties were verified.

  5. Antimicrobial and physical-mechanical properties of agar-based films incorporated with grapefruit seed extract.

    PubMed

    Kanmani, Paulraj; Rhim, Jong-Whan

    2014-02-15

    The use of synthetic petroleum based packaging films caused serious environmental problems due to their difficulty in recycling and poor biodegradability. Therefore, present study was aimed to develop natural biopolymer-based antimicrobial packaging films as an alternative for the synthetic packaging films. As a natural antimicrobial agent, grapefruit seed extract (GSE) has been incorporated into agar to prepare antimicrobial packaging film. The films with different concentrations of GSE were prepared by a solvent casting method and the resulting composite films were examined physically and mechanically. In addition, the films were characterized by FE-SEM, XRD, FT-IR and TGA. The incorporation of GSE caused increase in color, UV barrier, moisture content, water solubility and water vapor permeability, while decrease in surface hydrophobicity, tensile strength and elastic modulus of the films. As the concentration of GSE increased from 0.6 to 13.3 μg/mL, the physical and mechanical properties of the films were affected significantly. The addition of GSE changed film microstructure of the film, but did not influence the crystallinity of agar and thermal stability of the agar-based films. The agar/GSE films exhibited distinctive antimicrobial activity against three test food pathogens, such as Listeria monocytogenes, Bacillus cereus and Escherichia coli. These results suggest that agar/GSE films have potential to be used in an active food packaging systems for maintaining food safety and extending the shelf-life of the packaged food. PMID:24507339

  6. Direct Colorimetric Detection of a Receptor-Ligand Interaction by a Polymerized Bilayer Assembly

    NASA Astrophysics Data System (ADS)

    Charych, Deborah H.; Nagy, Jon O.; Spevak, Wayne; Bednarski, Mark D.

    1993-07-01

    Detection of receptor-ligand interactions is generally accomplished by indirect assays such as enzyme-linked immunosorbent assay. A direct colorimetric detection method based on a polydiacetylene bilayer assembled on glass microscope slides has been developed. The bilayer is composed of a self-assembled monolayer of octadecylsilane and a Langmuir-Blodgett monolayer of polydiacetylene. The polydiacetylene layer is functionalized with an analog of sialic acid, the receptor-specific ligand for the influenza virus hemagglutinin. The sialic acid ligand serves as a molecular recognition element and the conjugated polymer backbone signals binding at the surface by a chromatic transition. The color transition is readily visible to the naked eye as a blue to red color change and can be quantified by visible absorption spectroscopy. Direct colorimetric detection by polydiacetylene films offers new possibilities for diagnostic applications and screening for new drug candidates or binding ligands.

  7. Smooth surface roughness of silanized CdSe(ZnS) quantum dots.

    PubMed

    Xu, Jianmin; Wang, Chengshan; Wang, Jinhai; Huo, Qun; Crawford, Nicholas F; Véliz, Eduardo A; Leblanc, Roger M

    2013-03-01

    The interparticle distance of CdSe(ZnS) quantum dots was accurately controlled by polymerization at the air-water interface which provided an increased homogeneity of the Langmuir-Blodgett film leading to a surface smoothness comparable to mica. The choice of a silane derivative is based on the fact that silicon is semiconductor, and the compound CdSe being the core of the quantum dot is also semiconductor. The combination of the two semiconductors could bring some unusual conduction properties as a polymeric silanized network. But first, it is most important to characterize the smoothness of the surface, which might be correlated to the formation of "trap" states, i.e. the photo-excited electron can fall, or the photo-excited hole can "float". One will focus our research strategy, as a pilot study, to characterize the surface of the new polymeric material. PMID:23273542

  8. Direct colorimetric detection of a receptor-ligand interaction by a polymerized bilayer assembly

    SciTech Connect

    Charych, D.H.; Nagy, J.O.; Bednarski, M.D. ); Spevak, W. )

    1993-07-30

    Detection of receptor-ligand interactions is generally accomplished by indirect assays such as enzyme-linked immunosorbent assay. A direct colorimetric detection method based on a polydiacetylene bilayer assembled on glass microscope slides has been developed. The bilayer is composed of a self-assembled monolayer of octadecylsilane and a Langmuir-Blodgett monolayer of polydiacetylene. The polydiacetylene layer is functionalized with an analog of sialic acid, the receptor-specific ligand for the influenza virus hemagglutinin. The sialic acid ligand serves as a molecular recognition element and the conjugated polymer backbone signals binding at the surface by a chromatic transition. The color transition is readily visible to the naked eye as a blue to red color change and can be quantified by visible absorption spectroscopy. Direct colorimetric detection by polydiacetylene films offers new possibilities for diagnostic applications and screening for new drug candidates or binding ligands.

  9. Synthesis, characterization and antibacterial activity of biodegradable films prepared from Schiff bases of zein.

    PubMed

    Soliman, E A; Khalil, A A; Deraz, S F; El-Fawal, G; Elrahman, S Abd

    2014-10-01

    Pure zein is known to be very hydrophobic, but is still inappropriate for coating and film applications because of their brittle nature. In an attempt to improve the flexibility and the antimicrobial activity of these coatings and films, Chemical modification of zein through forming Schiff bases with different phenolic aldhydes was tried. Influence of this modifications on mechanical, topographical, wetting properties and antimicrobial activity of zein films were evaluated. The chemical structure of the Schiff bases films were characterized by ATR-FTIR spectroscopy. The results indicate an improvement in mechanical properties with chemically modification of zein to form Schiff bases leading to a reduction in the elastic modulus. An increase in the elongation at break has been observed, but with slight influence on tensile strength. Plasticized zein films have similar initial contact angle (∼40°). An increase in reaction temperature and time increases film's affinity towards water. As shown by contact angle measurements, a noticeable relation was found between film composition and the hydrophilicity. Surface topography also varied by forming Schiff bases, becoming rougher than zein-based films. The antibacterial activities of zein and Schiff bases of zein-based films were investigated against gram-positive bacteria (Listeria innocua, Listeria monocytogenes, Bacillus cereus and Clostridium sporogenes) and gram-negative bacteria (Escherichia coli, Yersinia enterocolitica and Salmonella enterica). It was found that the antibacterial activity of the Schiff bases-based films was more effective than that of zein-based films. PMID:25328181

  10. Bismuth pyrochlore-based thin films for dielectric energy storage

    NASA Astrophysics Data System (ADS)

    Michael, Elizabeth K.

    The drive towards the miniaturization of electronic devices has created a need for dielectric materials with large energy storage densities. These materials, which are used in capacitors, are a critical component in many electrical systems. Here, the development of dielectric energy storage materials for pulsed power applications, which require materials with the ability to accumulate a large amount of energy and then deliver it to the system rapidly, is explored. The amount of electrostatic energy that can be stored by a material is a function of the induced polarization and the dielectric breakdown strength of the material. An ideal energy storage dielectric would possess a high relative permittivity, high dielectric breakdown strength, and low loss tangent under high applied electric fields. The bismuth pyrochlores are a compositionally tunable family of materials that meet these requirements. Thin films of cubic pyrochlore bismuth zinc niobate, bismuth zinc tantalate, and bismuth zinc niobate tantalate, were fabricated using a novel solution chemistry based upon the Pechini method. This solution preparation is advantageous because it avoids the use of teratogenic solvents, such as 2-methoxyethanol. Crystalline films fabricated using this solution chemistry had very small grains that were approximately 27 nm in lateral size and 35 nm through the film thickness. Impedance measurements found that the resistivity of the grain boundaries was two orders of magnitude higher than the resistivity of the grain interior. The presence of many resistive grain boundaries impeded conduction through the films, resulting in high breakdown strengths for these materials. In addition to high breakdown strengths, this family of materials exhibited moderate relative permittivities of between 55 +/- 2 and 145 +/- 5, for bismuth zinc tantalate and bismuth zinc niobate, respectively, and low loss tangents on the order of 0.0008 +/- 0.0001. Increases in the concentration of the tantalum

  11. Enhanced optical discrimination system based on switchable retroreflective films

    NASA Astrophysics Data System (ADS)

    Schultz, Phillip; Heikenfeld, Jason

    2016-04-01

    Reported herein is the design, characterization, and demonstration of a laser interrogation and response optical discrimination system based on large-area corner-cube retroreflective films. The switchable retroreflective films use light-scattering liquid crystal to modulate retroreflected intensity. The system can operate with multiple wavelengths (visible to infrared) and includes variable divergence optics for irradiance adjustments and ease of system alignment. The electronic receiver and switchable retroreflector offer low-power operation (<4 mW standby) on coin cell batteries with rapid interrogation to retroreflected signal reception response times (<15 ms). The entire switchable retroreflector film is <1 mm thick and is flexible for optimal placement and increased angular response. The system was demonstrated in high ambient lighting conditions (daylight, 18k lux) with a visible 10-mW output 635-nm source out to a distance of 400 m (naked eye detection). Nighttime demonstrations were performed using a 1.5-mW, 850-nm infrared laser diode out to a distance of 400 m using a night vision camera. This system could have tagging and conspicuity applications in commercial or military settings.

  12. Thin-film transistors based on organic conjugated semiconductors

    NASA Astrophysics Data System (ADS)

    Garnier, Francis

    1998-02-01

    The use of organic semiconductors as active layers in thin-film transistors has raised in the recent years a large interest, both for the fundamental understanding of the charge transport processes in organic materials, and also for the potential applications of these devices in the new field of flexible electronics. Short conjugated oligomers have been shown to possess much higher field-effect mobilities than their parent conjugated polymers. The origin of such increase in the efficiency of charge transport is mainly attributed to the close-packing and long-range structural organization displayed in thin films of conjugated oligomers. The various routes for controlling this organization are described, which allow to realize liquid crystal-like two-dimensional structures for these semiconductors, whose carrier mobility has now become equivalent to that of amorphous silicon. It is also shown that the effect of conjugation length on carrier mobility is not as critical as previously thought, but the associated increase of the band gap energy effects the efficiency of charge injection at the metal/semiconductor interface. This problem can be answered by realizing a local doping of the semiconductor, which allows the injection of charge to operate through an efficient tunneling mechanism. Organic-based thin-film transistors have now become viable devices.

  13. A biomimetic tactile sensing system based on polyvinylidene fluoride film.

    PubMed

    Xin, Yi; Tian, Hongying; Guo, Chao; Li, Xiang; Sun, Hongshuai; Wang, Peiyuan; Qian, Chenghui; Wang, Shuhong; Wang, Cheng

    2016-02-01

    Polyvinylidene fluoride (PVDF) film has been widely investigated as a sensing material due to its outstanding properties such as biocompatibility, high thermal stability, good chemical resistance, high piezo-, pyro- and ferro-electric properties. This paper reports on the design, test, and analysis of a biomimetic tactile sensor based on PVDF film. This sensor consists of a PVDF film with aluminum electrodes, a pair of insulating layers, and a "handprint" friction layer with a copper foil. It is designed for easy fabrication and high reliability in outputting signals. In bionics, the fingerprint of the glabrous skin plays an important role during object handling. Therefore, in order to enhance friction and to provide better manipulation, the ridges of the fingertips were introduced into the design of the proposed tactile sensor. And, a basic experimental study on the selection of the high sensitivity fingerprint type for the biomimetic sensor was performed. In addition, we proposed a texture distinguish experiment to verify the sensor sensitivity. The experiment's results show that the novel biomimetic sensor is effective in discriminating object surface characteristics. Furthermore, an efficient visual application program (LabVIEW) and a quantitative evaluation method were proposed for the verification of the biomimetic sensor. The proposed tactile sensor shows great potential for contact force and slip measurements. PMID:26931883

  14. A biomimetic tactile sensing system based on polyvinylidene fluoride film

    NASA Astrophysics Data System (ADS)

    Xin, Yi; Tian, Hongying; Guo, Chao; Li, Xiang; Sun, Hongshuai; Wang, Peiyuan; Qian, Chenghui; Wang, Shuhong; Wang, Cheng

    2016-02-01

    Polyvinylidene fluoride (PVDF) film has been widely investigated as a sensing material due to its outstanding properties such as biocompatibility, high thermal stability, good chemical resistance, high piezo-, pyro- and ferro-electric properties. This paper reports on the design, test, and analysis of a biomimetic tactile sensor based on PVDF film. This sensor consists of a PVDF film with aluminum electrodes, a pair of insulating layers, and a "handprint" friction layer with a copper foil. It is designed for easy fabrication and high reliability in outputting signals. In bionics, the fingerprint of the glabrous skin plays an important role during object handling. Therefore, in order to enhance friction and to provide better manipulation, the ridges of the fingertips were introduced into the design of the proposed tactile sensor. And, a basic experimental study on the selection of the high sensitivity fingerprint type for the biomimetic sensor was performed. In addition, we proposed a texture distinguish experiment to verify the sensor sensitivity. The experiment's results show that the novel biomimetic sensor is effective in discriminating object surface characteristics. Furthermore, an efficient visual application program (LabVIEW) and a quantitative evaluation method were proposed for the verification of the biomimetic sensor. The proposed tactile sensor shows great potential for contact force and slip measurements.

  15. Engineered pigments based on iridescent cellulose nanocrystal films.

    PubMed

    Bardet, Raphael; Roussel, Francine; Coindeau, Stéphane; Belgacem, Naceur; Bras, Julien

    2015-05-20

    A simple method to produce biobased iridescent pigments from cellulose nanocrystal (CNC) films is reported. The process consists of forming nanostructured films from a CNC liquid-crystalline suspension and an appropriate dry grinding. The features of the iridescent pigments are described; they have a flake-like morphology with a thickness of 25 μm. However, because of the presence of sulfate groups, thermal degradation and high redispersion in water occur, which affect the iridescent property of these biobased pigments. To overcome such limitations, two post-treatments are proposed. The sulfate ester groups are removed from the iridescent pigments with vacuum overdrying. The mass loss of iridescent pigment in water is reduced with an increase of the ionic strength in the aqueous medium by NaCl addition. These post-treatments have proven to be efficient and engineered pigments based on CNC films can be used to add anticounterfeiting features to packaging manufactured by classical paper techniques or extrusion. PMID:25817681

  16. Optimal grid-based methods for thin film micromagnetics simulations

    NASA Astrophysics Data System (ADS)

    Muratov, C. B.; Osipov, V. V.

    2006-08-01

    Thin film micromagnetics are a broad class of materials with many technological applications, primarily in magnetic memory. The dynamics of the magnetization distribution in these materials is traditionally modeled by the Landau-Lifshitz-Gilbert (LLG) equation. Numerical simulations of the LLG equation are complicated by the need to compute the stray field due to the inhomogeneities in the magnetization which presents the chief bottleneck for the simulation speed. Here, we introduce a new method for computing the stray field in a sample for a reduced model of ultra-thin film micromagnetics. The method uses a recently proposed idea of optimal finite difference grids for approximating Neumann-to-Dirichlet maps and has an advantage of being able to use non-uniform discretization in the film plane, as well as an efficient way of dealing with the boundary conditions at infinity for the stray field. We present several examples of the method's implementation and give a detailed comparison of its performance for studying domain wall structures compared to the conventional FFT-based methods.

  17. Tantalum-based thin film coatings for wear resistant arthroprostheses.

    PubMed

    Balagna, C; Faga, M G; Spriano, S

    2011-10-01

    Cobalt-chromium-molybdenum alloys with high carbon content (HC-CoCrMo) are widely used as materials for arthroprosthesis, in particular in metal-on-metal (MoM) hip joints. In spite of their good wear and corrosion resistance, production of metallic wear particles and metal ion release will occur on a large time-scale. An enhancement of the metal ion level in the patient's blood and urine is often reported in clinical data. Hypersensitivity, inflammatory response and cell necrosis can occur as consequence. So implants on young patients and women on childbearing age are not so widespread. The aim of this research is the realization of a thin film coating in order to improve the biocompatibility of Co-based alloys and to reduce debris production, ion release and citotoxicity. The innovative process consists of a thermal treatment in molten salts, in order to obtain a tantalum enriched thin film coating. Tantalum is chosen because it is considered a biocompatible metal with high corrosion resistance and low ion release. Three HC-CoCrMo alloys, produced by different manufacturing processes, are tested as substrates. The coating is a thin film of TaC or it can be composed by a multilayer of two tantalum carbides and metallic tantalum, depending on the temperature of the treatment and on the carbon content of the substrate. The thin films as well the substrates are characterized from the structural, chemical and morphological point of view. Moreover mechanical behaviour of treated and untreated materials is analyzed by means of nanohardness, scratch and ball-on-disc wear tests. The coating increases the mechanical and tribological properties of HC-CoCrMo. PMID:22400292

  18. Photopolymerization-based fabrication of chemical sensing films

    DOEpatents

    Yang, Xiaoguang; Swanson, Basil I.; Du, Xian-Xian

    2003-12-30

    A photopolymerization method is disclosed for attaching a chemical microsensor film to an oxide surface including the steps of pretreating the oxide surface to form a functionalized surface, coating the functionalized surface with a prepolymer solution, and polymerizing the prepolymer solution with ultraviolet light to form the chemical microsensor film. The method also allows the formation of molecular imprinted films by photopolymerization. Formation of multilayer sensing films and patterned films is allowed by the use of photomasking techniques to allow patterning of multiple regions of a selected sensing film, or creating a sensor surface containing several films designed to detect different compounds.

  19. Novel surface-based methodologies for investigating GH11 xylanase-lignin derivative interactions.

    PubMed

    Zeder-Lutz, G; Renau-Ferrer, S; Aguié-Béghin, V; Rakotoarivonina, H; Chabbert, B; Altschuh, D; Rémond, C

    2013-11-21

    The recalcitrance of lignocellulose to bioprocessing represents the core problem and remains the limiting factor in creating an economy based on lignocellulosic ethanol production. Lignin is responsible for unproductive interactions with enzymes, and understanding how lignin impairs the susceptibility of biomass to enzymatic hydrolysis represents a significant aim in optimising the biological deconstruction of lignocellulose. The objective of this study was to develop methodologies based on surface plasmon resonance (SPR), which provide novel insights into the interactions between xylanase (Tx-xyn11) and phenolic compounds or lignin oligomers. In a first approach, Tx-xyn11 was fixed onto sensor surfaces, and phenolic molecules were applied in the liquid phase. The results demonstrated weak affinity and over-stoichiometric binding, as several phenolic molecules bound to each xylanase molecule. This approach, requiring the use of soluble molecules in the liquid phase, is not applicable to insoluble lignin oligomers, such as the dehydrogenation polymer (DHP). An alternative approach was developed in which a lignin oligomer was fixed onto a sensor surface. Due to their hydrophobic properties, the preparation of stable lignin layers on the sensor surfaces represented a considerable challenge. Among the various chemical and physico-chemical approaches assayed, two approaches (physisorption via the Langmuir-Blodgett technique onto self-assembled monolayer (SAM)-modified gold and covalent coupling to a carboxylated dextran matrix) led to stable lignin layers, which allowed the study of its interactions with Tx-xyn11 in the liquid phase. Our results indicated the presence of weak and non-specific interactions between Tx-xyn11 and DHP. PMID:24071685

  20. Optical switch based on nanocrystalline VOx thin film

    NASA Astrophysics Data System (ADS)

    Chen, Xiqu; Dai, Jun

    2009-11-01

    An optical switch is fabricated based on nanocrystalline vanadium oxide (VOx) thin film using micromachining technology. An "on" state with semiconducting phase to an "off" state with metallic phase is controlled by applying a DC power to Aurum electrodes of the optical switch. The optical switching performance for the fabricated device is investigated at optical communication wavelength of 1.55μm. The heater power requires to achieve switching action is about 15mW. The testing results show that the extinction ratio and switching response time are 14dB and 2ms, respectively.

  1. Functional chitosan-based grapefruit seed extract composite films for applications in food packaging technology

    SciTech Connect

    Tan, Y.M.; Lim, S.H.; Tay, B.Y.; Lee, M.W.; Thian, E.S.

    2015-09-15

    Highlights: • Chitosan-based grapefruit seed extract (GFSE) films were solution casted. • GFSE was uniformly dispersed within all chitosan film matrices. • All chitosan-based composite films showed remarkable transparency. • Increasing amounts of GFSE incorporated increased the elongation at break of films. • Chitosan-based GFSE composite films inhibited the proliferation of fungal growth. - Abstract: Chitosan-based composite films with different amounts of grapefruit seed extract (GFSE) (0.5, 1.0 and 1.5% v/v) were fabricated via solution casting technique. Experimental results showed that GFSE was uniformly dispersed within all chitosan film matrices. The presence of GFSE made the films more amorphous and tensile strength decreased, while elongation at break values increased as GFSE content increased. Results from the measurement of light transmission revealed that increasing amounts of GFSE (from 0.5 to 1.5% v/v) did not affect transparency of the films. Furthermore, packaging of bread samples with chitosan-based GFSE composite films inhibited the proliferation of fungal growth as compared to control samples. Hence, chitosan-based GFSE composite films have the potential to be a useful material in the area of food technology.

  2. 36 CFR 1237.30 - How do agencies manage records on nitrocellulose-base and cellulose-acetate base film?

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... Department of Transportation regulations (49 CFR 172.101, Hazardous materials table; 172.504, Transportation... on nitrocellulose-base and cellulose-acetate base film? 1237.30 Section 1237.30 Parks, Forests, and... cellulose-acetate base film? (a) The nitrocellulose base, a substance akin to gun cotton, is...

  3. PET based nanocomposite films for microwave packaging applications

    NASA Astrophysics Data System (ADS)

    Galdi, M. R.; Olivieri, R.; Liguori, L.; Albanese, D.; Di Matteo, M.; Di Maio, L.

    2015-12-01

    In recent years, changes in life standards have promoted the diffusion of Ready to Cook (RTC) and Ready to Eat (RTE) products for microwave ovens. However, the main limits in microwave (MW) ovens usage are often related to the proper choice of packaging materials suitable for such technology. In fact, packages for microwaveable RTC and RTE foods should ensure adequate preservation of the product before cooking/heating such as high barriers to gases and aromas and adequate control of water vapor transmission. In addition, microwaveable packaging material must be transparent to MW, thermally stable and resistant to the mechanical stress induced by the accumulation in the head space of volatile substances produced during the cooking. Polymeric materials are good candidates for microwaveable packaging thanks to their transparency to MW. In the last years a great interest is devoted to developing innovative solution based on the use of additives or systems that act as susceptors or heating enhancers for improving the characteristics of polymers in cooking/heating in MW ovens. The present work was focused on the production and characterization of nanocomposite copolyester based films suitable for microwaveable food packaging applications. The matrices selected consist in two PET copolymers modified with carbon black (ULTRA STD) and with titanium oxide (ULTRA NA). Nanocomposite co-extruded multilayer films were produced using different percentages (0%, 2% and 4%wt/wt) of Cloisite 20A (C20A). Films were analyzed for evaluating the effect of nanofiller on the morphology and barrier properties. Moreover, to verify the effectiveness of the designed systems in reducing the cooking times of meat products, MW heating tests were carried out on pork meat hamburgers in MW oven at varying supplied powers. The cooking tests have pointed out that the selected matrices are efficient in reducing cooking times and that even low concentration of C20A acts as heating enhancers of PET.

  4. PET based nanocomposite films for microwave packaging applications

    SciTech Connect

    Galdi, M. R. Olivieri, R.; Liguori, L.; Albanese, D. Di Matteo, M.; Di Maio, L.

    2015-12-17

    In recent years, changes in life standards have promoted the diffusion of Ready to Cook (RTC) and Ready to Eat (RTE) products for microwave ovens. However, the main limits in microwave (MW) ovens usage are often related to the proper choice of packaging materials suitable for such technology. In fact, packages for microwaveable RTC and RTE foods should ensure adequate preservation of the product before cooking/heating such as high barriers to gases and aromas and adequate control of water vapor transmission. In addition, microwaveable packaging material must be transparent to MW, thermally stable and resistant to the mechanical stress induced by the accumulation in the head space of volatile substances produced during the cooking. Polymeric materials are good candidates for microwaveable packaging thanks to their transparency to MW. In the last years a great interest is devoted to developing innovative solution based on the use of additives or systems that act as susceptors or heating enhancers for improving the characteristics of polymers in cooking/heating in MW ovens. The present work was focused on the production and characterization of nanocomposite copolyester based films suitable for microwaveable food packaging applications. The matrices selected consist in two PET copolymers modified with carbon black (ULTRA STD) and with titanium oxide (ULTRA NA). Nanocomposite co-extruded multilayer films were produced using different percentages (0%, 2% and 4%wt/wt) of Cloisite 20A (C20A). Films were analyzed for evaluating the effect of nanofiller on the morphology and barrier properties. Moreover, to verify the effectiveness of the designed systems in reducing the cooking times of meat products, MW heating tests were carried out on pork meat hamburgers in MW oven at varying supplied powers. The cooking tests have pointed out that the selected matrices are efficient in reducing cooking times and that even low concentration of C20A acts as heating enhancers of PET.

  5. Multilevel Ge-Se Film Based Resist Systems

    NASA Astrophysics Data System (ADS)

    Tai, K. L.; Vadimsky, R. G.; Ong, E.

    1982-06-01

    Multilevel resist systems based on Ge-Se films make possible the use of optical projection printers for printing 0.5-1.0μm features. The four multilevel resist systems considered employ either a photosensitive or a photopassive polymer layer for planarization. In bilevel schemes the surface of the Ge-Se film is reacted in a Ag(CN)i- containing solution to form a Ag2Se imaging layer. No reacted Ge-Se is used as a sacrificial layer in trilevel schemes. Ge-Se films are resistant to attack by oxygen plasma and therefore make good masks for pattern transfer by dry (reactive ion) etching, to a thick underlying photopassive polymer layer. Because of their high absorbance (a 105cm-1) in the ultraviolet and violet, Ge-Se patterns can also be used as exposure masks for transferring images to a thick underlying photosensitive polymer layer. The latter is "flood" exposed through the Ge-Se mask and wet developed. Both dry and wet processes provide steep wall-profile patterns in the polymer layer. The dry process provides superior feature size control while the wet process offers reduced processing cost. The exceptional lithographic performance exhibited by Ge-Se resist systems is attributed to a unique edge-sharpening effect; diffraction is compensated for by lateral silver diffusion in the Ag2Se layer. Patterns having 0.6μm lines and spaces are obtained over lcmXlcm fields with a defocus tolerance of 2.5μm using a standard Zeiss 10:1 reduction lens (N.A.=0.28, λ=436nm). Results indicate that optical lithography can practically print features in the size regime previously reserved for a-beam or x-ray based lithographic technologies.

  6. Fast-response humidity-sensing films based on methylene blue aggregates formed on nanoporous semiconductor films

    NASA Astrophysics Data System (ADS)

    Ishizaki, Ryota; Katoh, Ryuzi

    2016-05-01

    We prepared fast-response colorimetric humidity-sensing (vapochromic) films based on methylene blue adsorption onto nanoporous semiconductor (TiO2, Al2O3) films. Color changes caused by changes of humidity could be easily identified visually. A characteristic feature of the vapochromic films was their fast response to changes of humidity. We found that the response began to occur within 10 ms. The response was rapid because all the methylene blue molecules attached to the nanoporous semiconductor surface were directly exposed to the environment. We also deduced that the color changes were caused by structural changes of the methylene blue aggregates on the surface.

  7. Solution-Processed Indium Oxide Based Thin-Film Transistors

    NASA Astrophysics Data System (ADS)

    Xu, Wangying

    Oxide thin-film transistors (TFTs) have attracted considerable attention over the past decade due to their high carrier mobility and excellent uniformity. However, most of these oxide TFTs are usually fabricated using costly vacuum-based techniques. Recently, the solution processes have been developed due to the possibility of low-cost and large-area fabrication. In this thesis, we have carried out a detailed and systematic study of solution-processed oxide thin films and TFTs. At first, we demonstrated a passivation method to overcome the water susceptibility of solution-processed InZnO TFTs by utilizing octadecylphosphonic acid (ODPA) self-assembled monolayers (SAMs). The unpassivated InZnO TFTs exhibited large hysteresis in their electrical characteristics due to the adsorbed water at the semiconductor surface. Formation of a SAM of ODPA on the top of InZnO removed water molecules weakly absorbed at the back channel and prevented water diffusion from the surroundings. Therefore the passivated devices exhibited significantly reduced hysteretic characteristics. Secondly, we developed a simple spin-coating approach for high- k dielectrics (Al2O3, ZrO2, Y 2O3 and TiO2). These materials were used as gate dielectrics for solution-processed In2O3 or InZnO TFTs. Among the high-k dielectrics, the Al2O3-based devices showed the best performance, which is attributed to the smooth dielectric/semiconductor interface and the low interface trap density besides its good insulating property. Thirdly, the formation and properties of Al2O3 thin films under various annealing temperatures were intensively studied, revealing that the sol-gel-derived Al2O3 thin film undergoes the decomposition of organic residuals and nitrate groups, as well as conversion of aluminum hydroxides to form aluminum oxide. Besides, the Al2O 3 film was used as gate dielectric for solution-processed oxide TFTs, resulting in high mobility and low operating voltage. Finally, we proposed a green route for

  8. Tribological behaviors of lanthanum-based phosphonate 3-aminopropyltriethoxysilane self-assembled films

    NASA Astrophysics Data System (ADS)

    Gu, Qinlin; Cheng, Xianhua

    2007-06-01

    Lanthanum-based thin films deposited on the phosphonate 3-aminopropyltriethoxysilane (APTES) self-assembled monolayer (SAM) were prepared on the hydroxylated glass substrate by a self-assembling process from specially formulated solution. Chemical compositions of the films and chemical state of the elements were detected by X-ray photoelectron spectrometry (XPS). The thickness of the films was determined with an ellipsometer, while the morphologies of the original and worn surfaces of the samples were analyzed by means of atomic force microscopy (AFM) and scanning electron microscopy (SEM), respectively. The tribological properties of the films sliding against GCr15 steel ball were evaluated on a UMT-2MT reciprocating friction and wear tester. As the results, the target film was obtained and reaction may have taken place between the film and the glass substrate. The tribological results show that lanthanum-based thin films are superior in reducing friction and resisting wear compared with APTES-SAM and phosphorylated APTES-SAM. SEM observation of the morphologies of worn surfaces indicates that the wear of APTES-SAM and the phosphorylated APTES-SAM is characteristic of brittle fracture and severe abrasion. Differently, slight abrasion and micro-crack dominate the wear of lanthanum-based thin films. The superior friction reduction and wear resistance of lanthanum-based thin films are attributed to the enhanced load-carrying capacity of the inorganic lanthanum particles in the lanthanum-based thin films as well as good adhesion of the films to the substrate.

  9. Release behavior and stability of encapsulated D-limonene from emulsion-based edible films.

    PubMed

    Marcuzzo, Eva; Debeaufort, Frédéric; Sensidoni, Alessandro; Tat, Lara; Beney, Laurent; Hambleton, Alicia; Peressini, Donatella; Voilley, Andrée

    2012-12-12

    Edible films may act as carriers of active molecules, such as flavors. This possibility confers to them the status of active packaging. Two different film-forming biopolymers, gluten and ι-carrageenans, have been compared. D-Limonene was added to the two film formulations, and its release kinetics from emulsion-based edible films was assessed with HS-SPME. Results obtained for edible films were compared with D-limonene released from the fatty matrix called Grindsted Barrier System 2000 (GBS). Comparing ι-carrageenans with gluten-emulsified film, the latter showed more interesting encapsulating properties: in fact, D-limonene was retained by gluten film during the process needed for film preparation, and it was released gradually during analysis time. D-Limonene did not show great affinity to ι-carrageenans film, maybe due to high aroma compound hydrophobicity. Carvone release from the three different matrices was also measured to verify the effect of oxygen barrier performances of edible films to prevent D-limonene oxidation. Further investigations were carried out by FT-IR and liquid permeability measurements. Gluten film seemed to better protect D-limonene from oxidation. Gluten-based edible films represent an interesting opportunity as active packaging: they could retain and release aroma compounds gradually, showing different mechanical and nutritional properties from those of lipid-based ingredients. PMID:23163743

  10. Elements of adaptive optics based on metallized polymer films

    NASA Astrophysics Data System (ADS)

    Voliak, T. B.; Krasiuk, I. K.; Pashinin, P. P.

    Results of an experimental study of the stability of metallized polymer films exposed to laser radiation at wavelengths of 1.06 and 10.6 microns are reported, and methods for fabricating variable-curvature mirrors from these films are discussed. Formulas are presented for calculating the shape of film mirrors as a function of the pressure acting on the film, mounting contour, and film properties. The performance of film mirrors is investigated experimentally in a pulsed CO2 laser with stable and unstable resonators.

  11. A facile route to prepare cellulose-based films.

    PubMed

    Xu, Qin; Chen, Chen; Rosswurm, Katelyn; Yao, Tianming; Janaswamy, Srinivas

    2016-09-20

    Cellulose is the most abundant renewable and biodegradable material available in nature. Its insoluble character in water as well as common organic and inorganic liquids, however, curtails the wholesome utility. The continuous rise for biodegradable products based on cellulose coupled with its intrinsic ability to form a viable substitute for the petroleum-based materials necessitates the critical need for solubilizing the cellulose. Herein, we demonstrate the feasibility of ZnCl2 solutions, especially the 64-72% concentrations, to dissolve cellulose. FTIR results suggest that Zn(2+) ions promote Zn⋯O3H interactions, which in-turn weaken the intrinsic O3H⋯O5 hydrogen bonds that are responsible for strengthening the cellulose chains. Interestingly, Ca(2+) ions promote interactions among the Zn-cellulose chains leading to the formation of nano fibrils and yield gelling solutions. The tensile strength of the Ca(2+) added Zn-cellulose films increases by around 250% compared to the Zn-cellulose films. Overall, utilization of inorganic salt solutions to solubilize and crosslink cellulose is cost-effective, recyclable and certainly stands out tall among the other available systems. More importantly, the proposed protocol is simple and is a "green" process, and thus its large-scale adaptability is quite feasible. We strongly believe that the outcome opens up a new window of opportunities for cellulose in the biomedical, pharmaceutical, food and non-food applications. PMID:27261751

  12. Fabrication of graphene-based films using remote plasma CVD

    NASA Astrophysics Data System (ADS)

    Hiramatsu, Mineo; Tsukada, Ryosuke; Kashima, Yohei; Naito, Masateru; Kondo, Hiroki; Hori, Masaru

    2012-10-01

    Plasma-enhanced CVD (PECVD) employing methane/hydrogen gases has been used to grow diamond, diamond-like carbon, and carbon nanotubes. In the case of microwave PECVD with methane/hydrogen system without catalyst nanoparticles at temperatures of 700--850 ^oC, where the substrate is exposed to the plasma, vertical nano-graphenes and carbon nanoflakes have been easily grown even on Cu substrate due to the ion bombardment and local electric field forces. In this work, we demonstrate the synthesis of planar few-layer graphene-based film using PECVD with remote plasma configuration. In the case using microwave plasma of cylindrical resonant cavity type, by simply installing grounded grid over the substrate plate for obtaining remote plasma configuration, we have successfully fabricated graphene-based films on Cu substrate, which was confirmed by the Raman spectrum and SEM image of deposit. Similar method will be applied to other plasmas such as low-pressure inductively coupled plasma, in order to verify the effectiveness of remote plasma configuration for the growth of planar graphene using PECVD technique. We will discuss the planar graphene growth mechanism in terms of precursors and their surface reaction.

  13. Explanation of the photocurrent quantum efficiency (Φ) enhancements through the CAN's model equation for the p-CuI sensitized methylviolet-C18 LB films in the photoelectrochemical cells (PECs) and Cu/n-Cu2O/M-C18/p-CuI solid-state photovoltaic cells

    NASA Astrophysics Data System (ADS)

    Fernando, C. A. N.; Liyanaarachchi, U. S.; AARajapaksha, R. D.

    2013-04-01

    Photocurrent enhancements in a dye sensitized photoelectrochemical cell (PEC) with a Cu/p-CuI/M-C18 photoelectrode and a dye sensitized solid state photovoltaic cell (DSSC) with Cu/n-Cu2O/M-C18/p-CuI are studied by controlling the formation of dye aggregates of M-C18 Langmuir-Blodgett (LB) films on the p-CuI layer. LB films of M-C18 are deposited under biasing conditions during the LB deposition process on Cu/p-CuI, Cu/n-Cu2O/p-CuI and conductive glass plates with the three-electrode configuration setup coupling to the LB trough. LB films prepared under positive biasing conditions enhance the photocurrent quantum efficiencies for both PECs and DSSCs controlling and minimizing the formation of dye aggregates. The electrolyte used for LB deposition and photocurrent measurements is (10-2 M) Fe2+ + Fe3+ (10-2 M) and (10-2 M) NaH2PO4-Na2HPO4, pH = 6 buffer solution. Maximum photocurrent quantum efficiencies (Фmax%) obtained are ≈22% for PEC and ≈20% for DSSCs, where the M-C18 LB film deposition applied potentials +0.3 V versus Ag/AgCl. The mechanism of the photocurrent enhancement is discussed through the CAN's model equation, Ф = AD0-BD02, where A = k1k2/F, B = I k12 k2[2k6/F3 + k2k4/k32 X2F2], F = k2 + k5Y + k7 + k1 I [1 + k2/k3 X], presented from our previous study [1]. Experimental evidence for the formation of the aggregates of M-C18 LB films for the negative applied potentials and suppression of the aggregates with positive applied potentials are presented from absorption spectra, AFM pictures and fluorescence measurements of the samples. Conversion efficiency obtained is ≈2.5%, Voc ≈750 mV and Isc ≈ 5.8 mA cm-2 for DSSC fabricated with +0.3 V versus Ag/AgCl applied deposition potential of M-C18 LB films.

  14. Ion permeability of polydopamine films revealed using a Prussian blue-based electrochemical method.

    PubMed

    Gao, Bowen; Su, Lei; Tong, Ying; Guan, Miao; Zhang, Xueji

    2014-11-01

    Polydopamine (PDA) is fast becoming a popular surface modification technique. Detailed understanding of the ion permeability properties of PDA films will improve their applications. Herein, we report for the first time the thickness-independent ion permeability of PDA films using a Prussian blue (PB)-based electrochemical method. In this method, PDA films are deposited via ammonium persulfate-induced dopamine polymerization onto a PB electrode. The ion permeability of the PDA films can thus be detected by observing the changes in electrochemical behaviors of the PB coated by PDA films. On the basis of this method, it was unexpectedly found that the PDA films with thickness greater than 45 nm (e.g., ~60 and ~113 nm) can exhibit pH-switchable but thickness-insensitive permeability to monovalent cations such as potassium and sodium ions. These observations clearly indicate the presence of a continuous network of interconnected intermolecular voids within PDA films, regardless of film thickness. PMID:25317484

  15. Physicochemical properties of alginate/polycaprolactone-based films containing essential oils.

    PubMed

    Salmieri, Stéphane; Lacroix, Monique

    2006-12-27

    Oregano, savory, and cinnamon essential oils (EOs) 1% (w/v) were separately incorporated as natural antioxidant agents in alginate/polycaprolactone-based films. Films were then treated in 2 or 20% (w/v) CaCl2 solutions in order to generate insoluble films. The mechanical properties and the insoluble matter of films were determined. Intermolecular interactions between film components and alginate cross-linkage were characterized by Fourier transform infrared (FTIR) spectroscopy. Surface morphology of the polymer membrane was determined by scanning electron microscopy (SEM) analysis. Antiradical properties of films were also evaluated following a modified colorimetric method using the N,N-diethyl-p-phenylenediamine (DPPD) discoloration test. Results showed that films treatment with CaCl2 (20%) solution increased the percentage of insoluble matter in films but did not enhance their mechanical properties. FTIR analysis showed higher interactions in films treated in CaCl2 solutions despite the concentration used (2 vs 20%). The SEM observations of films showed a smoother surface with a higher density when films were treated in CaCl2 (20%) solution. The DPPD test showed that the oregano-based films had the highest antiradical properties. PMID:17177561

  16. Large area radiation detectors based on II VI thin films

    NASA Astrophysics Data System (ADS)

    Quevedo-Lopez, Manuel

    2015-03-01

    The development of low temperature device technologies that have enabled flexible displays also present opportunities for flexible electronics and flexible integrated systems. Of particular interest are possible applications in flexible, low metal content, sensor systems for unattended ground sensors, smart medical bandages, electronic ID tags for geo-location, conformal antennas, neutron/gamma-ray/x-ray detectors, etc. In this talk, our efforts to develop novel CMOS integration schemes, circuits, memory, sensors as well as novel contacts, dielectrics and semiconductors for flexible electronics are presented. In particular, in this presentation we discuss fundamental materials properties including crystalline structure, interfacial reactions, doping, etc. defining performance and reliability of II-VI-based radiation sensors. We investigate the optimal thickness of a semiconductor diode for thin-film solid state thermal neutron detectors. Besides II-VI materials, we also evaluated several diode materials, Si, CdTe,GaAs, C (diamond), and ZnO, and two neutron converter materials,10B and 6LiF. We determine the minimum semiconductor thickness needed to achieve maximum neutron detection efficiency. By keeping the semiconductor thickness to a minimum, gamma rejection is kept as high as possible. In this way, we optimize detector performance for different thin-film semiconductor materials.

  17. Crack width monitoring of concrete structures based on smart film

    NASA Astrophysics Data System (ADS)

    Zhang, Benniu; Wang, Shuliang; Li, Xingxing; Zhang, Xu; Yang, Guang; Qiu, Minfeng

    2014-04-01

    Due to its direct link to structural security, crack width is thought to be one of the most important parameters reflecting damage conditions of concrete structures. However, the width problem is difficult to solve with the existing structural health monitoring methods. In this paper, crack width monitoring by means of adhering enameled copper wires with different ultimate strains on the surface of structures is proposed, based on smart film crack monitoring put forward by the present authors. The basic idea of the proposed method is related to a proportional relationship between the crack width and ultimate strain of the broken wire. Namely, when a certain width of crack passes through the wire, some low ultimate strain wires will be broken and higher ultimate strain wires may stay non-broken until the crack extends to a larger scale. Detection of the copper wire condition as broken or non-broken may indicate the width of the structural crack. Thereafter, a multi-layered stress transfer model and specimen experiment are performed to quantify the relationship. A practical smart film is then redesigned with this idea and applied to Chongqing Jiangjin Yangtze River Bridge.

  18. Electrical and Mechanical Properties of the Dielectric Capacitor Film Based on Polyvinylidene Fluoride and Aromatic Polythiourea

    NASA Astrophysics Data System (ADS)

    Li, Ya; Fu, Qiong; Li, Lili; Li, Weiping

    2016-06-01

    To obtain the flexible dielectric material suitable for mass produced supercapacitor, blend films based on polyvinylidene fluoride (PVDF) and aromatic polythiourea (ArPTU) were prepared by solution casting. We found that the PVDF/ArPTU blend film is a good energy storage material for capacitors with high breakdown strength and low loss at high filed. The breakdown field of PVDF/ArPTU (90/10) film is more than 700 MV/m, and the maximum released energy density is up to 11 J/cm3 with discharging efficiency above 80%. We also proved that the mechanical property of blend films is much better than that of pure ArPTU film, and the toughness and softness are close to the level of PVDF film. The blend film based on PVDF and ArPTU is a flexible dielectric material in the manufacture of supercapacitor.

  19. Bamboo (Neosinocalamus affinis)-based thin film, a novel biomass material with high performances.

    PubMed

    Song, Fei; Xu, Chen; Bao, Wen-Yi; Wang, Xiu-Li; Wang, Yu-Zhong

    2015-03-30

    Exploration of biomass based materials to replace conventional petroleum based ones has been a trend in recent decades. In this work, bamboo (Neosinocalamus affinis) with abundant resources was used for the first time to prepare films in the presence of cellulose. The effects of weight ratio of bamboo/cellulose on the appearances and properties of the films were investigated. It was confirmed there existed strong interactions between bamboo and cellulose, which were favorable to formation of homogeneous structure of blend films. Particularly, the presence of bamboo could improve the surface hydrophobicity, water resistance and thermal stability of blend films, and the films possessed an excellent oxygen barrier property, compared with generally used commercial packaging films. The bamboo biomass, therefore, is successfully used to create a new film material with a good application prospect in the fields of packaging, coating, and food industry. PMID:25563957

  20. Printed organic thin-film transistor-based integrated circuits

    NASA Astrophysics Data System (ADS)

    Mandal, Saumen; Noh, Yong-Young

    2015-06-01

    Organic electronics is moving ahead on its journey towards reality. However, this technology will only be possible when it is able to meet specific criteria including flexibility, transparency, disposability and low cost. Printing is one of the conventional techniques to deposit thin films from solution-based ink. It is used worldwide for visual modes of information, and it is now poised to enter into the manufacturing processes of various consumer electronics. The continuous progress made in the field of functional organic semiconductors has achieved high solubility in common solvents as well as high charge carrier mobility, which offers ample opportunity for organic-based printed integrated circuits. In this paper, we present a comprehensive review of all-printed organic thin-film transistor-based integrated circuits, mainly ring oscillators. First, the necessity of all-printed organic integrated circuits is discussed; we consider how the gap between printed electronics and real applications can be bridged. Next, various materials for printed organic integrated circuits are discussed. The features of these circuits and their suitability for electronics using different printing and coating techniques follow. Interconnection technology is equally important to make this product industrially viable; much attention in this review is placed here. For high-frequency operation, channel length should be sufficiently small; this could be achievable with a combination of surface treatment-assisted printing or laser writing. Registration is also an important issue related to printing; the printed gate should be perfectly aligned with the source and drain to minimize parasitic capacitances. All-printed organic inverters and ring oscillators are discussed here, along with their importance. Finally, future applications of all-printed organic integrated circuits are highlighted.

  1. Tungsten oxide proton conducting films for low-voltage transparent oxide-based thin-film transistors

    SciTech Connect

    Zhang, Hongliang; Wan, Qing; Wan, Changjin; Wu, Guodong; Zhu, Liqiang

    2013-02-04

    Tungsten oxide (WO{sub x}) electrolyte films deposited by reactive magnetron sputtering showed a high room temperature proton conductivity of 1.38 Multiplication-Sign 10{sup -4} S/cm with a relative humidity of 60%. Low-voltage transparent W-doped indium-zinc-oxide thin-film transistors gated by WO{sub x}-based electrolytes were self-assembled on glass substrates by one mask diffraction method. Enhancement mode operation with a large current on/off ratio of 4.7 Multiplication-Sign 10{sup 6}, a low subthreshold swing of 108 mV/decade, and a high field-effect mobility 42.6 cm{sup 2}/V s was realized. Our results demonstrated that WO{sub x}-based proton conducting films were promising gate dielectric candidates for portable low-voltage oxide-based devices.

  2. Tungsten oxide proton conducting films for low-voltage transparent oxide-based thin-film transistors

    NASA Astrophysics Data System (ADS)

    Zhang, Hongliang; Wan, Qing; Wan, Changjin; Wu, Guodong; Zhu, Liqiang

    2013-02-01

    Tungsten oxide (WOx) electrolyte films deposited by reactive magnetron sputtering showed a high room temperature proton conductivity of 1.38 × 10-4 S/cm with a relative humidity of 60%. Low-voltage transparent W-doped indium-zinc-oxide thin-film transistors gated by WOx-based electrolytes were self-assembled on glass substrates by one mask diffraction method. Enhancement mode operation with a large current on/off ratio of 4.7 × 106, a low subthreshold swing of 108 mV/decade, and a high field-effect mobility 42.6 cm2/V s was realized. Our results demonstrated that WOx-based proton conducting films were promising gate dielectric candidates for portable low-voltage oxide-based devices.

  3. A micromachined carbon nanotube film cantilever-based energy cell.

    PubMed

    Gong, Zhongcheng; He, Yuan; Tseng, Yi-Hsuan; O'Neal, Chad; Que, Long

    2012-08-24

    This paper reports a new type of energy cell based on micromachined carbon nanotube film (CNF)-lead zirconate titanate cantilevers that is fabricated on silicon substrates. Measurements found that this type of micro-energy cell generates both AC voltages due to the self-reciprocation of the microcantilevers and DC voltages due to the thermoelectric effect upon exposure to light and thermal radiation, resulting from the unique optical and thermal properties of the CNF. Typically the measured power density of the micro-energy cell can be from 4 to 300 μW cm(-2) when it is exposed to sunlight under different operational conditions. It is anticipated that hundreds of integrated micro-energy cells can generate power in the range of milliwatts, paving the way for the construction of self-powered micro- or nanosystems. PMID:22842491

  4. LTCC Phase Shifters Based on Tunable Ferroelectric Composite Thick Films

    NASA Astrophysics Data System (ADS)

    Nikfalazar, M.; Kohler, C.; Heunisch, A.; Wiens, A.; Zheng, Y.; Schulz, B.; Mikolajek, M.; Sohrabi, M.; Rabe, T.; Binder, J. R.; Jakoby, R.

    2015-11-01

    This paper presents, the investigation of tunable components based on LTCC technology, implementing ferroelectric tunable thick-film dielectric. The tunable loaded line phase shifters are fabricated with metal-insulator-metal (MIM) varactors to demonstrate the capabilities of this method for packaging of the tunable components. The MIM varactors consist of one tunable dielectric paste layer that is printed between two silver layers. The tunable ferroelectric paste is optimized for LTCC sintering temperature around 850°C. The phase shifters are fabricated in two different process. They were achieved a figure of merit of 24°/dB (phase shift 192°) at 3 GHz and 18°/dB (phase shift 98°) at 4.4 GHz by using seven unit cells that each unit cell consisting of two MIM varactors.

  5. Graphene-based electrodes for enhanced organic thin film transistors based on pentacene.

    PubMed

    Basu, Sarbani; Lee, Mu Chen; Wang, Yeong-Her

    2014-08-21

    This paper presents 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-pentacene) and pentacene-based organic thin film transistors (OTFTs) with monolayer graphene source-drain (S-D) electrodes. The electrodes are patterned using conventional photolithographic techniques combined with reactive ion etching. The monolayer graphene film grown by chemical vapor deposition on Cu foil was transferred on a Si dioxide surface using a polymer-supported transfer method to fabricate bottom-gate, bottom-contact OTFTs. The pentacene OTFTs with graphene S-D contacts exhibited superior performance with a mobility of 0.1 cm(2) V(-1) s(-1) and an on-off ratio of 10(5) compared with OTFTs with Au-based S-D contacts, which had a mobility of 0.01 cm(2) V(-1) s(-1) and an on-off ratio of 10(3). The crystallinity, grain size, and microscopic defects (or the number of layers of graphene films) of the TIPS-pentacene/pentacene films were analyzed by X-ray diffraction spectroscopy, atomic force microscopy, and Raman spectroscopy, respectively. The feasibility of using graphene as an S-D electrode in OTFTs provides an alternative material with high carrier injection efficiency, chemical stability, and excellent interface properties with organic semiconductors, thus exhibiting improved device performance of C-based electronic OTFTs at a reduced cost. PMID:25000388

  6. Analysis of the permeation and mechanical characteristics of some aqueous-based film coating systems.

    PubMed

    Okhamafe, A O; York, P

    1983-07-01

    The moisture permeability and mechanical properties of some aqueous-based free films have been evaluated using sorption-desorption and stress-strain techniques, respectively. These properties for blends of two film-formers--hydroxypropyl methylcellulose and polyvinyl alcohol--have been compared with those of hydroxypropyl methylcellulose films plasticized with polyethylene glycols. The polyethylene glycols generally increased the moisture permeability of hydroxypropyl methylcellulose films while polyvinyl alcohol decreased it. Both polyvinyl alcohol and the polyethylene glycols lowered tensile strength at break and Young's modulus but the effects of the polyethylene glycols were more pronounced. These results are discussed in terms of structural interactions between film components. All film systems evaluated, except that containing hydroxypropyl methylcellulose alone, exhibited a degree of anisotropy, a phenomenon with potentially adverse consequences in tablet film coating. PMID:6136580

  7. Ultrasmooth and thermally stable silver-based thin films with subnanometer roughness by aluminum doping.

    PubMed

    Gu, Deen; Zhang, Cheng; Wu, Yi-Kuei; Guo, L Jay

    2014-10-28

    Rough surface and poor stability of ultrathin Ag films limit their applications in nanophotonic and optoelectronic devices. Here, we report an approach for fabricating ultrasmooth and thermally stable Ag-based thin films on SiO2/Si substrates by Al-doping. The effect of Al-doping on the surface morphology and stability of ultrathin Ag films at room temperature and elevated temperature was investigated. The 15 nm Al-doped Ag films with an Al atomic concentration of 4% have a root-mean-square roughness as low as 0.4 nm. The smooth surface morphology is maintained even after 300 °C annealing in N2. Al-doping enhances the nuclei density of films. Moreover, a capping layer spontaneously formed over the Al-doped Ag films restrains the surface diffusion and mass transportation of Ag atoms. Therefore, Al-doping induces ultrathin Ag films with highly stable and ultrasmooth surface morphology. PMID:25211394

  8. Transmission enhancement based on strong interference in metal-semiconductor layered film for energy harvesting

    NASA Astrophysics Data System (ADS)

    Li, Qiang; Du, Kaikai; Mao, Kening; Fang, Xu; Zhao, Ding; Ye, Hui; Qiu, Min

    2016-07-01

    A fundamental strategy to enhance optical transmission through a continuous metallic film based on strong interference dominated by interface phase shift is developed. In a metallic film coated with a thin semiconductor film, both transmission and absorption are simultaneously enhanced as a result of dramatically reduced reflection. For a 50-nm-thick Ag film, experimental transmission enhancement factors of 4.5 and 9.5 are realized by exploiting Ag/Si non-symmetric and Si/Ag/Si symmetric geometries, respectively. These planar layered films for transmission enhancement feature ultrathin thickness, broadband and wide-angle operation, and reduced resistance. Considering one of their potential applications as transparent metal electrodes in solar cells, a calculated 182% enhancement in the total transmission efficiency relative to a single metallic film is expected. This strategy relies on no patterned nanostructures and thereby may power up a wide spectrum of energy-harvesting applications such as thin-film photovoltaics and surface photocatalysis.

  9. Effectiveness of silane monomer and gamma radiation on chitosan films and PCL-based composites

    NASA Astrophysics Data System (ADS)

    Sharmin, Nusrat; Khan, Ruhul A.; Dussault, Dominic; Salmieri, Stephane; Akter, Nousin; Lacroix, Monique

    2012-08-01

    Chitosan films were prepared by casting from its 1% (w/w) solution. Tensile strength (TS) and tensile modulus (TM) of chitosan films were found to be 30 MPa and 450 MPa, respectively. Silane monomer (3-aminopropyl tri-methoxysilane) (0.25%, w/w) was added into the chitosan solution (1%, w/w) and films were casted. Then films were exposed to gamma radiation (5-25 kGy) and mechanical properties were investigated. It was found that at 10 kGy, the values of TS and TM were improved significantly. Silane grafted chitosan film reinforced poly(caprolactone) (PCL)-based tri-layer composites were prepared by compression molding. Silane improved interfacial adhesion between chitosan and PCL in composites. Surface of the films was investigated by scanning electron microscope (SEM) and found better morphology for silane grafted films.

  10. Optical properties of porous-silicon-based structures with modified nanodiamond films

    NASA Astrophysics Data System (ADS)

    Yuzova, V. A.; Korets, A. Ya.; Merkushev, F. F.; Semenova, O. V.

    2015-02-01

    We have studied the optical properties of silicon-based sandwich structures with diamond-like films deposited by electrophoresis from aqueous suspensions of modified detonation nanodiamonds. It is shown that these films can be used as antireflection and protective coatings for silicon-based solar cells.

  11. Moving beyond "Bookish Knowledge": Using Film-Based Assignments to Promote Deep Learning

    ERIC Educational Resources Information Center

    Olson, Joann S.; Autry, Linda; Moe, Jeffry

    2016-01-01

    This article investigates the effectiveness of a film-based assignment given to adult learners in a graduate-level group counseling class. Semi-structured interviews were conducted with four students; data analysis suggested film-based assignments may promote deep approaches to learning (DALs). Participants indicated the assignment helped them…

  12. Optical Sensors Based on Single Arm Thin Film Waveguide Interferometer

    NASA Technical Reports Server (NTRS)

    Sarkisov, S. S.; Diggs, D.; Curley, M.; Adamovsky, Grigory (Technical Monitor)

    2001-01-01

    Single-arm double-mode double-order optical waveguide interferometer utilizes interference between two propagating modes of different orders. Sensing effect results from the change in propagation conditions of the modes caused by the environment. The waveguide is made as an open asymmetric slab structure containing a dye-doped polymer film onto a fused quartz substrate. It is more sensitive to the change of environment than its conventional polarimetric analog using orthogonal modes (TE and TM) of the same order. The sensor still preserves the option of operating in polarimetric regime using a variety of mode combinations such as TE(sub 0)/TM(sub 0) (conventional), TE(sub 0)/TM(sub 1), TE(sub 1)/TM(sub 0), or TE(sub 1)/TM(sub 1) but can also work in nonpolarimetric regime using combinations TE(sub 0)/TM(sub 1) or TE(sub 0)/TM(sub 1). Utilization of different mode combinations simultaneously makes the device more versatile. Application of the sensor to gas sensing is based on doping polymer film with an organic indicator dye sensitive to a particular gas. Change of optical absorption spectrum of the dye caused by the gaseous pollutant results change of the reactive index of the dye-doped polymer film that can be detected by the sensor. As an indicator dyes, we utilize Bromocresol Purple doped into polymer poly(methyl) methacrylate, which shows a reversible growth of the absorption peak neat 600 nm after exposure to wet ammonia. We have built a breadboard prototype of the sensor with He-Ne laser as a light source and with a single mode fiber input and a multimode fiber output. The prototype showed sensitivity to temperature change of the order of 2 C per one full oscillation of the signal. The sensitivity of the sensor to the presence of wet ammonia is 200 ppm per one full oscillation of the signal. The further improvements include switching to a longer wavelength laser source (750-nm semiconductor laser), substitution of poly(methyl) methacrylate with hydrophilic

  13. Organic Solar Cells Based on Electrodeposited Polyaniline Films

    NASA Astrophysics Data System (ADS)

    Inoue, Kei; Akiyama, Tsuyoshi; Suzuki, Atsushi; Oku, Takeo

    2012-04-01

    Polyaniline thin films as hole transporting layers were fabricated on transparent indium-tin-oxide electrodes by electrodeposition of aniline in an aqueous H2SO4 electrolyte solution. Emerald-green polyaniline films were obtained, which showed stable redox waves. A mixed solution of polythiophene and fullerene derivative was spin-coated onto the electrodeposited polyaniline film. After the modification of titanium oxide film on the surface of the polythiophene/fullerene layer, an aluminum electrode was fabricated by vacuum deposition. The obtained solar cells generated stable photocurrent and photovoltage under light illumination.

  14. Films based on oxidized starch and cellulose from barley.

    PubMed

    El Halal, Shanise Lisie Mello; Colussi, Rosana; Deon, Vinícius Gonçalves; Pinto, Vânia Zanella; Villanova, Franciene Almeida; Carreño, Neftali Lenin Villarreal; Dias, Alvaro Renato Guerra; Zavareze, Elessandra da Rosa

    2015-11-20

    Starch and cellulose fibers were isolated from grains and the husk from barley, respectively. Biodegradable films of native starch or oxidized starches and glycerol with different concentrations of cellulose fibers (0%, 10% and 20%) were prepared. The films were characterized by morphological, mechanical, barrier, and thermal properties. Cellulose fibers isolated from the barley husk were obtained with 75% purity and high crystallinity. The morphology of the films of the oxidized starches, regardless of the fiber addition, was more homogeneous as compared to the film of the native starch. The addition of cellulose fibers in the films increased the tensile strength and decreased elongation. The water vapor permeability of the film of oxidized starch with 20% of cellulose fibers was lower than the without fibers. However the films with cellulose fibers had the highest decomposition with the initial temperature and thermal stability. The oxidized starch and cellulose fibers from barley have a good potential for use in packaging. The addition of cellulose fibers in starch films can contribute to the development of films more resistant that can be applied in food systems to maintain its integrity. PMID:26344323

  15. Polyester-based thin films with high photosensitivity

    SciTech Connect

    POTTER,KELLY SIMMONS; POTTER JR.,BARRETT G.; WHEELER,DAVID R.; JAMISON,GREGORY M.

    2000-02-29

    A great deal of research has been done to understand the photosensitive optical response of inorganic glasses, which exhibit a permanent, photo-induced refractive index change due to the presence of optically active point defects in the glass structure. In the present work, the authors have performed a preliminary study of the intrinsic photosensitivity of a polyester containing a cinnamylindene malonate group (CPE, a photo- and thermal-crosslinkable group) for use in photonic waveguide devices. Thin films of CPE (approximately 0.5 microns thick) were spun onto fused silica substrates. Optical absorption in the thin films was evaluated both before and after exposure to UV radiation sources. It was found that the polyester exhibits two dominant UV absorption bands centered about 240 nm and 330 nm. Under exposure to 337 nm radiation (nitrogen laser) a marked bleaching of the 330 nm band was observed. This band bleaching is a direct result of the photo-induced crosslinking in the cinnamylindene malonate group. Exposure to 248 nm radiation (excimer laser), conversely, resulted in similar bleaching of the 330 nm band but was accompanied by nearly complete bleaching of the higher energy 240 nm band. Based on a Kramers-Kronig analysis of the absorption changes, refractive index changes on the order of {minus}10{sup {minus}2} are estimated. Confirmation of this calculation has been provided via ellipsometry which estimates a refractive index change at 632 nm of {minus}0.061 {+-} 0.002. Thus, the results of this investigation confirm the photosensitive potential of this type of material.

  16. Molecular Interactions in Monolayers οf Azo Dye/Liquid Crystal Mixtures at Interfaces

    NASA Astrophysics Data System (ADS)

    Bauman, D.; Płóciennik, A.; Inglot, K.

    2009-08-01

    Full Text PDF A study of azo dye/liquid crystal mixtures in monolayers formed at an air-water interface (the Langmuir films) and at a solid surface (the Langmuir-Blodgett films) has been performed. Five azo dyes with various molecular structure and the liquid crystal 4-octyl-4' cyanobiphenyl (8CB) have been used. The dyes have been added to the liquid crystal at various molar fractions. Surface pressure and surface potential versus mean molecular area isotherms for the Langmuir films have been recorded and information about intermolecular interactions at the air-water interface has been obtained. On the basis of electronic absorption measurements for the Langmuir and Langmuir-Blodgett films the conclusions about the ability of dyes molecules to form self aggregates at the interfaces have been drawn. The influence of the dye molecular structure and its concentration on aggregates' geometry has been found.

  17. Investigation of thin films of organic-based magnets grown by physical vapor deposition

    SciTech Connect

    Kao, C. Y.; Lu, Y.; Li, B.; Yoo, J.-W.; Epstein, A. J.

    2014-10-06

    Thin films of organic-based magnet, V[TCNE]{sub x} (TCNE: tetracyanoethylene), were deposited by physical vapor deposition (PVD) based reactive evaporation. The growth conditions were studied in detail. A saturated composition of V[TCNE]{sub ∼1.9} was determined by optimizing the growth condition. Two sets of films with different V to TCNE ratios were characterized. Both films were magnetic ordered up to 400 K and held coercive field of 60 Oe at room temperature. With the presence of excess vanadium within the film, the increase of defects created by PVD results in significant change in electronic property.

  18. Room-temperature ferromagnetic and ferroelectric behavior in polycrystalline ZnO-based thin films

    NASA Astrophysics Data System (ADS)

    Lin, Yuan-Hua; Ying, Minghao; Li, Ming; Wang, Xiaohui; Nan, Ce-Wen

    2007-05-01

    Polycrystalline ZnO-based thin films with Li and/or Co doping have been prepared by a sol-gel spin-coating method on silicon substrates. Magnetization measurements reveal that Li-doped ZnO film shows paramagnetic behavior. However, the Co-doped ZnO thin films show obvious room-temperature ferromagnetic properties, and ferromagnetic properties can be enhanced by the Li codoping, which may be ascribed to indirect exchange via Li-related defects. All ZnO-based films exhibit ferroelectric behavior, and ferroelectric properties can be tuned by the dopants.

  19. Composite edible films based on hydroxypropyl methylcellulose reinforced with microcrystalline cellulose nanoparticles.

    PubMed

    Bilbao-Sáinz, Cristina; Avena-Bustillos, Roberto J; Wood, Delilah F; Williams, Tina G; McHugh, Tara H

    2010-03-24

    It has been stated that hydroxypropyl methyl cellulose (HPMC) based films have promising applications in the food industry because of their environmental appeal, low cost, flexibility and transparency. Nevertheless, their mechanical and moisture barrier properties should be improved. The aim of this work was to enhance these properties by reinforcing the films with microcrystalline cellulose (MCC) at the nano scale level. Three sizes of MCC nanoparticles were incorporated into HPMC edible films at different concentrations. Identical MCC nanoparticles were lipid coated (LC) prior to casting into HPMC/LC-MCC composite films. The films were examined for mechanical and moisture barrier properties verifying how the addition of cellulose nanoparticles affected the water affinities (water adsorption/desorption isotherms) and the diffusion coefficients. The expected reinforcing effect of the MCC was observed: HPMC/MCC and HPMC/LC-MCC films showed up to 53% and 48% increase, respectively, in tensile strength values in comparison with unfilled HPMC films. Furthermore, addition of unmodified MCC nanoparticles reduced the moisture permeability up to 40% and use of LC-MCC reduced this value up to 50%. Water vapor permeability was mainly influenced by the differences in water solubility of different composite films since, in spite of the increase in water diffusivity values with the incorporation of MCC to HPMC films, better moisture barrier properties were achieved for HPMC/MCC and HPMC/LC-MCC composite films than for HPMC films. PMID:20187652

  20. Soil burial biodegradation studies of palm oil-based UV-curable films

    NASA Astrophysics Data System (ADS)

    Tajau, Rida; Salleh, Mek Zah; Salleh, Nik Ghazali Nik; Abdurahman, Mohamad Norahiman; Salih, Ashraf Mohammed; Fathy, Siti Farhana; Azman, Anis Asmi; Hamidi, Nur Amira

    2016-01-01

    The palm oil-based ultraviolet (uv)-curable films were subjected to an outdoor soil burial test to investigate the biodegradation under natural environment. The films were burial in the soil experiment plot at the Nuclear Malaysia's Dengkil complex. The uv-curable films were synthesized from the epoxidized palm oil acrylated (EPOLA) resin and the polyurethane palm oil (POBUA) resin, respectively. Biodegradation tests are more specific to burial film in soil experiments for 12 months under natural conditions. The biodegradability of palm oil resin based uv-curable films were investigated and compared with the petrochemical resin based film. The films properties were compared with respect to properties of the thermal characteristic, the crystallinity, the morphology and the weight loss which are analyzed using the thermogravimetric analysis (TGA), the differential scanning calorimetry (DSC), the scanning electron microscope (SEM), an optical microscope and the weight loss of film calculation. These findings suggested that the palm oil-based uv-curable films show quite satisfactory biodegradation levels.

  1. Planting Healthy Roots: Using Documentary Film to Evaluate and Disseminate Community-Based Participatory Research.

    PubMed

    Brandt, Heather M; Freedman, Darcy A; Friedman, Daniela B; Choi, Seul Ki; Seel, Jessica S; Guest, M Aaron; Khang, Leepao

    2016-01-01

    Documentary filmmaking approaches incorporating community engagement and awareness raising strategies may be a promising approach to evaluate community-based participatory research. The study purpose was 2-fold: (1) to evaluate a documentary film featuring the formation and implementation of a farmers' market and (2) to assess whether the film affected awareness regarding food access issues in a food-desert community with high rates of obesity. The coalition model of filmmaking, a model consistent with a community-based participatory research (CBPR) approach, and personal stories, community profiles, and expert interviews were used to develop a documentary film (Planting Healthy Roots). The evaluation demonstrated high levels of approval and satisfaction with the film and CBPR essence of the film. The documentary film aligned with a CBPR approach to document, evaluate, and disseminate research processes and outcomes. PMID:27536929

  2. Reduced graphene oxide based silver sulfide hybrid films formed at a liquid/liquid interface

    SciTech Connect

    Bramhaiah, K. John, Neena S.

    2014-04-24

    Free-standing, ultra-thin films of silver sulfide and reduced graphene oxide (RGO) based silver sulfide hybrids are prepared at a liquid/liquid interface employing in situ chemical reaction strategy. Ag{sub 2}S and RGO−Ag{sub 2}S hybrid films are characterized by various techniques such as UV-visible and photo luminescence spectroscopy, X-ray diffraction and scanning electron microscopy. The morphology of hybrid films consists of Ag{sub 2}S nanocrystals on RGO surface while Ag{sub 2}S films contains branched network of dendritic structures. RGO−Ag{sub 2}S exhibit interesting optical and electrical properties. The hybrid films absorb in the region 500–650 nm and show emission in the red region. A higher conductance is observed for the hybrid films arising from the RGO component. This simple low cost method can be extended to prepare other RGO based metal sulfides.

  3. Optical position detectors based on thin film amorphous silicon

    NASA Astrophysics Data System (ADS)

    Henry, Jasmine; Livingstone, John

    2001-10-01

    Thin film optical position sensitive detectors (PSDs) based on novel hydrogenated amorphous silicon Schottky barrier (SB) structures are compared in this work. The three structures reported here have been tested under different light sources to measure their linear properties and wavelength response characteristics. The sputtered a-Si sensors were configured as layered structures of platinum, a-Si and indium tin oxide, forming SB-i-n devices and exhibited linear properties similar to multi-layer a-Si p-i- n devices produced by complex chemical vapor deposition procedures, which involve flammable and toxic gases. All structures were test4ed as possible configurations for 2D sensors. The devices were tested under white light, filtered white light and also a red diode laser. Each of the three structures responded quite differently to each of the sources. Results, based on the correlation coefficient, which measures the linearity of output and which has a maximum value of 1, produced r values ranging between 0.992 to 0.999, in the best performances.

  4. Thin-film chemical sensors based on electron tunneling

    NASA Technical Reports Server (NTRS)

    Khanna, S. K.; Lambe, J.; Leduc, H. G.; Thakoor, A. P.

    1985-01-01

    The physical mechanisms underlying a novel chemical sensor based on electron tunneling in metal-insulator-metal (MIM) tunnel junctions were studied. Chemical sensors based on electron tunneling were shown to be sensitive to a variety of substances that include iodine, mercury, bismuth, ethylenedibromide, and ethylenedichloride. A sensitivity of 13 parts per billion of iodine dissolved in hexane was demonstrated. The physical mechanisms involved in the chemical sensitivity of these devices were determined to be the chemical alteration of the surface electronic structure of the top metal electrode in the MIM structure. In addition, electroreflectance spectroscopy (ERS) was studied as a complementary surface-sensitive technique. ERS was shown to be sensitive to both iodine and mercury. Electrolyte electroreflectance and solid-state MIM electroreflectance revealed qualitatively the same chemical response. A modified thin-film structure was also studied in which a chemically active layer was introduced at the top Metal-Insulator interface of the MIM devices. Cobalt phthalocyanine was used for the chemically active layer in this study. Devices modified in this way were shown to be sensitive to iodine and nitrogen dioxide. The chemical sensitivity of the modified structure was due to conductance changes in the active layer.

  5. Photo-Sensitivities of Immobilized Retinoids

    NASA Astrophysics Data System (ADS)

    Tsuchida, Yosuke; Ikeda, Yasukazu; Kobayashi, Naohiro; Arakawa, Takamasa; Yamano, Shinichiro; Mitachi, Seiko

    2009-03-01

    Optical absorption of retinoids, retinal and retinoic acid, in immobilized thin films were measured and evaluated using films fabricated by spin coating, Langmuir-Blodgett (LB), and layer-by-layer self-assembly methods. We succeeded in forming thin films of immobilized retinoids fabricated by self-assembly methods for the first time. Based on measurements with an atomic force microscope (AFM), it is estimated that film thickness was about 30 nm, with a total of sixteen layers. The photoisomerization reaction rate of the self-assembled film was found to be much more suppressed than that of LB films. Photoreceptive devices were built around films produced using a chitosan sol and immobilized retinoids in a self-assembled film, and the photocurrent responses of these devices were measured. Photoreceptive biophotonic devices using a self-assembled film showed photocurrent response by irradiation of ultraviolet light of 254 nm. Photocurrent response of the self-assembled films was faster than that of sol-based films. These nanoscale photoreceptive devices may be applied to bio-functional optical sensing or to future visual information processing devices.

  6. High efficiency THz-wave modulators based on conjugated polymer-based organic films

    NASA Astrophysics Data System (ADS)

    He, Ting; Zhang, Bo; Wang, Guo-cui; Zang, Meng-di; Hou, Yan-bing; Shen, Jing-ling

    2016-02-01

    A study of the modulation mechanisms of conjugated polymer-based organic films and high-efficiency, broadband and all-optically controlled terahertz modulators based on these films is presented in this paper. Under very low-level external laser excitation, modulation efficiency of more than 99% is achieved using MEH-PPV/Si, PFO/Si and F8BT/Si bilayers. By analyzing the changes in the photo-excited carrier density and photoconductivity with changes in the external laser intensity, we introduce a nonlinear photo-induced absorption process to explain the strong attenuation mechanism for the transmitted terahertz waves. Finally, a simple THz communication test is carried out to demonstrate the potential future applications of the high-efficiency all-optically controlled terahertz modulator.

  7. Adsorption of a water soluble cationic dye into a cationic Langmuir monolayer

    NASA Astrophysics Data System (ADS)

    Shil, Ashis; Hussain, S. A.; Bhattacharjee, D.

    2015-05-01

    This communication reports the successful adsorption of a water soluble cationic fluorescent dye Rhodamine B (RhB) into a cationic Langmuir monolayer of Octadecylamine (ODA). Anionic nano clay platelets Hectorite played an important role in the process of adsorption. Surface pressure vs. area per molecule (π-A) isotherms were studied to monitor the adsorption process. In-situ fluorescence Imaging Microscopic (FIM) technique was employed to visualize the domain structures formed at the air-water interface. Atomic Force Microscopic (AFM) image of the monolayer Langmuir-Blodgett (LB) films were taken to study the morphology and ultrastructure of the film. Detailed spectroscopic investigations were carried out on the mono- and multilayer Langmuir-Blodgett (LB) films.

  8. Antimicrobial and in vitro wound healing properties of novel clay based bionanocomposite films.

    PubMed

    Mishra, R K; Ramasamy, K; Lim, S M; Ismail, M F; Majeed, A B A

    2014-08-01

    The present study investigates the development of methyl cellulose (MC)-sodium alginate (SA)-montmorillonite (MMT) clay based bionanocomposite films with interesting wound healing properties. The differential scanning calorimetry analysis of the composite films revealed presence of single glass transition temperature (Tg) confirming the miscible nature of the ternary blended films. The increase in MMT ratio in the composite films reduced the mobility of biopolymer chains (MC/SA) which increased the Tg of the film. Thermogravimetric analysis showed that dispersion of clay (MMT) at nano level significantly delayed the weight loss that correlated with higher thermal stability of the composite films. It was observed that the developed films were able to exhibit antimicrobial activity against four typical pathogenic bacteria found in the presence of wound. The developed films were able to significantly inhibit (10 mg/ml) the growth of Enterococcus faecium and Pseudomonas aeruginosa. In vitro scratch assay indicated potential wound closure activities of MC-2-4 bionanocomposite films at their respective highest subtoxic doses. In conclusion, these ternary bionanocomposite films were found to be promising systems for wound healing applications. PMID:24831081

  9. Elastohydrodynamic film thickness formula based on X-ray measurements with a synthetic paraffinic oil

    NASA Technical Reports Server (NTRS)

    Loewenthal, S. H.; Parker, R. J.; Zaretsky, E. V.

    1973-01-01

    An empirical elastohydrodynamic film thickness formula for heavily loaded contacts based upon X-ray film thickness measurements made with a synthetic paraffinic oil is presented. The deduced relation was found to adequately reflect the high load dependence exhibited by the measured minimum film thickness data at high Hertizian contact stresses, that is, above 1.04 x 10 to the ninth N/sq m (150,000 psi). Comparisons were made with the numerical results from a theoretical isothermal film thickness formula. The effects of changes in contact geometry, material, and lubricant properties on the form of the empirical model are also discussed.

  10. Thickness microscopy based on photothermal radiometry for the measurement of thin films.

    PubMed

    Wang, Liping; Prekel, Helmut; Liu, Hengbiao; Deng, Yanzhuo; Hu, Jiming; Goch, Gert

    2009-03-01

    The photothermal detection technique is an innovative and non-contact method to investigate the properties of films on workpieces. This paper describes a novel experimental set-up for thickness microscopy based on photothermal radiometry. The correlation between the thermal wave signal and the film thickness is deduced and evaluated to determine the film thickness with a lateral resolution of less than 1mm. Results indicate that the thickness microscopy is a useful method to characterize thin films and has the potential to be applied in-process. PMID:19046925

  11. AFM and XPA data on structural features and properties of films and powders based on naphthalocyanines

    NASA Astrophysics Data System (ADS)

    Ramonova, A. G.; Nakusov, A. T.; Sozanov, V. G.; Bliev, A. P.; Magkoev, T. T.

    2015-06-01

    The template synthesis is used to produce powders and films based on naphthalocyanines and the corresponding metal complexes (Pc, CuPc, and NiPc). The atomic-force microscopy (AFM) and X-ray phase analysis (XPA) are employed in the study of structure and phase of fine powders and nanostructured films. The AFM data are used to determine the orientation and density of primary particles packed in the film. The XPA method is used to study the chemical composition and crystal structure of the synthesized samples. The regularities related to the structural features that affect the electrophysical properties of the films under study are revealed.

  12. Versatile Method for Coating Surfaces with Functional and Responsive Polymer-Based Films.

    PubMed

    Zhang, Qiang Matthew; Serpe, Michael J

    2015-12-16

    A versatile surface modification technique was developed to yield poly(N-isopropylacrylamide) (pNIPAm) microgel-based thin films on a variety of substrates, e.g., metals, nonmetals, and polymers. Because the chemistry, and hence functionality and responsivity, of the pNIPAm-based microgels is easily tuned, multifunctional and responsive thin films could be generated on many different surfaces without varying the coating conditions. In one case, we showed that fluorescent/light emitting thin films could be generated using crystal violet-modified microgels. Antibacterial films could be obtained using silver nanoparticle-modified pNIPAm-based microgels. Finally, we show that thin films fabricated via the methods here could be used as a component in optical sensors. Although we show only a few examples of the utility of this approach, we feel that the apparent universality of the technique can be extended to countless other applications. PMID:26640982

  13. Electrodeposited Fe-Co films prepared from a citric-acid-based plating bath

    NASA Astrophysics Data System (ADS)

    Yanai, T.; Uto, H.; Shimokawa, T.; Nakano, M.; Fukunaga, H.; Suzuki, K.

    2013-06-01

    Electrodeposited Fe-Co films are commonly prepared in a boric-acid-based bath. In this research, we applied citric acid instead of boric acid for the plating of Fe-Co films because boron in the waste bath is restricted by environmental-protection regulations in Japan. We evaluated the effect of citric acid on the magnetic and structural properties of the films. The saturation magnetization of the Fe-Co films slightly increased while the Fe content in the Fe-Co films decreased with increasing citric acid concentration. The lowest coercivity value of 240 A/m was obtained at a citric acid concentration of 100 g/L. The plating bath with this citric acid concentration enabled us to obtain Fe-Co films with high saturation magnetizations and smooth surface morphologies.

  14. Thin film porous membranes based on sol-gel chemistry for catalytic sensors

    SciTech Connect

    Hughes, R.C.; Patel, S.V.; Jenkins, M.W.; Boyle, T.J.; Gardner, T.J.; Brinker, C.J.

    1998-05-01

    Nanoporous sol-gel based films are finding a wide variety of uses including gas separations and supports for heterogeneous catalysts. The films can be formed by spin or dip coating, followed by relatively low temperature annealing. The authors used several types of these films as coatings on the Pd alloy thin film sensors they had previously fabricated and studied. The sol-gel films have little effect on the sensing response to H{sub 2} alone. However, in the presence of other gases, the nanoporous film modifies the sensor behavior in several beneficial ways. (1) They have shown that the sol-gel coated sensors were only slightly poisoned by high concentrations of H{sub 2}S while uncoated sensors showed moderate to severe poisoning effects. (2) For a given partial pressure of H{sub 2}, the signal from the sensor is modified by the presence of O{sub 2} and other oxidizing gases.

  15. Tunneling Nanoelectromechanical Switches Based on Compressible Molecular Thin Films.

    PubMed

    Niroui, Farnaz; Wang, Annie I; Sletten, Ellen M; Song, Yi; Kong, Jing; Yablonovitch, Eli; Swager, Timothy M; Lang, Jeffrey H; Bulović, Vladimir

    2015-08-25

    Abrupt switching behavior and near-zero leakage current of nanoelectromechanical (NEM) switches are advantageous properties through which NEMs can outperform conventional semiconductor electrical switches. To date, however, typical NEMs structures require high actuation voltages and can prematurely fail through permanent adhesion (defined as stiction) of device components. To overcome these challenges, in the present work we propose a NEM switch, termed a "squitch," which is designed to electromechanically modulate the tunneling current through a nanometer-scale gap defined by an organic molecular film sandwiched between two electrodes. When voltage is applied across the electrodes, the generated electrostatic force compresses the sandwiched molecular layer, thereby reducing the tunneling gap and causing an exponential increase in the current through the device. The presence of the molecular layer avoids direct contact of the electrodes during the switching process. Furthermore, as the layer is compressed, the increasing surface adhesion forces are balanced by the elastic restoring force of the deformed molecules which can promote zero net stiction and recoverable switching. Through numerical analysis, we demonstrate the potential of optimizing squitch design to enable large on-off ratios beyond 6 orders of magnitude with operation in the sub-1 V regime and with nanoseconds switching times. Our preliminary experimental results based on metal-molecule-graphene devices suggest the feasibility of the proposed tunneling switching mechanism. With optimization of device design and material engineering, squitches can give rise to a broad range of low-power electronic applications. PMID:26244821

  16. Hysteresis in pentacene-based organic thin-film transistors

    NASA Astrophysics Data System (ADS)

    Gu, Gong; Kane, Michael G.

    2006-08-01

    Memory effects are commonly seen in organic thin-film transistor (OTFT) characteristics. In the absence of memory effects associated with the gate dielectric, the hysteresis in p-channel pentacene-based OTFTs, as measured in air and under illumination, was found to be dominated by trapped electrons, rather than trapped holes, in the semiconductor. The responsible acceptor type traps have very long lifetime. The immobile, previously stored negative charge requires extra holes to balance it, resulting in early establishment of the channel and extra drain current. This model is unique in that it discusses the majority carrier population influenced by trapped charge opposite in sign to the majority carriers in a simple electrostatic manner, to explain history dependence. The model was supported by drain current transient decay data. This memory effect is ambient and illumination sensitive. We studied the presence or absence of this effect under various ambient and illumination conditions, and found the responsible acceptor type traps mostly extrinsic and their formation reversible. Efforts were taken in the quantitative analysis to exclude the bias stress effect from the memory effect due to the charged acceptors.

  17. Perylene Diimide Based ``Nanofabric'' Thin Films for Organic Photovoltaic Cells

    NASA Astrophysics Data System (ADS)

    Carter, Austin; Park, June Hyoung; Min, Yong; Epstein, Arthur

    2011-03-01

    We report progress in using a perylene diimide (PDI) nanofabric as an effective electron accepting nanostructure for organic photovoltaics (OPV). A key challenge in OPV continues to be the recovery of electrons after charge separation due to the relatively poor mobility of C60 and related materials. A series of PDI compounds and complexes have been synthesized and used to fabricate nanofibers and thin films using solution and vacuum deposition techniques. Overlaping PDI-based nanofibers form a fast electron-transporting ``nanofabric'' that has been characterized (AFM, PL, UV-vis, etc.) and can be blended with electron donating materials. A solution-processible OPV configuration containing a nanofabric heterojunction (FHJ) of poly(3-hexylthiophene) and the PDI nanofabric was investigated. We observed a significant improvement in power-conversion efficiency due in part to expansion of the interfacial area and the presence of high mobility electron pathways to the LiF/Al electrode. This work is supported by the Wright Center for Photovoltaic Innovation and Commercialization, the Institute for Materials Research and the Center for Affordable Nanoengineering of Polymeric Biomedical Devices.

  18. Comparative study on properties of edible films based on pinhao (Araucaria angustifolia) starch and flour

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The aim of this study was to develop and compare the properties of edible films based on pinhao starch and pinhao flour. Seven formulations were developed by casting methodology: 5% pinhao starch with 0, 1, 1.5, and 2% glycerol, and 5% pinhao flour with 1, 1.5, and 2% glycerol. The films were evalua...

  19. Potential of Kaolin-based Particle Film Barriers for Formosan Subterranean Termite (Isoptera: Rhinotermitidae) Control

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Effects of three particle film products on Formosan subterranean termites, Coptotermes formosanus Shiraki, were evaluated in feeding, tunneling, and contact assays. The particle films, hydrophobic M96-018 and hydrophilic Surround and Surround WP are based on the inert clay mineral kaolin. In 2-week ...

  20. Structure and physicochemical properties of thin film photosemiconductor cells based on porphine derivatives

    NASA Astrophysics Data System (ADS)

    Kazak, A. V.; Usol'tseva, N. V.; Smirnova, A. I.; Bodnarchuk, V. V.; Sul'yanov, S. N.; Yablonskii, S. V.

    2016-05-01

    Photosemiconductor thin films based on two organic porphine derivatives have been investigated. These compounds have different pendent groups; the film morphology, along with the specific fabrication technique, is determined to a great extent by these groups. The films have been fabricated by vacuum sputtering and using the Langmuir-Schaefer method. According to the atomic force microscopy (AFM) data, the Langmuir-Schaefer films are more homogeneous than the sputtered ones. It is shown that the sputtered films based on substituted porphine have a looser stacking than the initial analog. A spectroscopy study revealed a bathochromic shift of the Soret band in the Langmuir-Schaefer films-sputtered films series. This shift is explained by the increase in the concentration and size of molecular aggregates in sputtered films. It is shown that a polycrystalline C60 fullerene film deposited onto an amorphous substituted porphine layer improves the photoelectric characteristics of the latter. Both the time stability of the photodiode structure and its ampere‒watt sensitivity increase (by a factor of 10 in the transition regime). The steady-state current does not change. The effect of polarity reversal of the photovoltaic signal is observed in a planar C60‒substituted metalloporphine heterostructure, which is similar to the pyroelectric effect. The polarity reversal can be explained by the contribution of the trap charge and discharge current at the interface between the amorphous photosemiconductor and crystalline photosemiconductor to the resulting photoelectric current.

  1. Effect of carboxymethyl cellulose concentration on physical properties of biodegradable cassava starch-based films

    PubMed Central

    2011-01-01

    Background Cassava starch, the economically important agricultural commodity in Thailand, can readily be cast into films. However, the cassava starch film is brittle and weak, leading to inadequate mechanical properties. The properties of starch film can be improved by adding plasticizers and blending with the other biopolymers. Results Cassava starch (5%w/v) based films plasticized with glycerol (30 g/100 g starch) were characterized with respect to the effect of carboxymethyl cellulose (CMC) concentrations (0, 10, 20, 30 and 40%w/w total solid) and relative humidity (34 and 54%RH) on the mechanical properties of the films. Additionally, intermolecular interactions were determined by Fourier transform infrared spectroscopy (FT-IR), melting temperature by differential scanning calorimetry (DSC), and morphology by scanning electron microscopy (SEM). Water solubility of the films was also determined. Increasing concentration of CMC increased tensile strength, reduced elongation at break, and decreased water solubility of the blended films. FT-IR spectra indicated intermolecular interactions between cassava starch and CMC in blended films by shifting of carboxyl (C = O) and OH groups. DSC thermograms and SEM micrographs confirmed homogeneity of cassava starch-CMC films. Conclusion The addition of CMC to the cassava starch films increased tensile strength and reduced elongation at break of the blended films. This was ascribed to the good interaction between cassava starch and CMC. Cassava starch-CMC composite films have the potential to replace conventional packaging, and the films developed in this work are suggested to be suitable for low moisture food and pharmaceutical products. PMID:21306655

  2. Chitosan based edible films and coatings: a review.

    PubMed

    Elsabee, Maher Z; Abdou, Entsar S

    2013-05-01

    Chitosan is a biodegradable biocompatible polymer derived from natural renewable resources with numerous applications in various fields, and one of which is the area of edible films and coatings. Chitosan has antibacterial and antifungal properties which qualify it for food protection, however, its weak mechanical properties, gas and water vapor permeability limit its uses. This review discusses the application of chitosan and its blends with other natural polymers such as starch and other ingredients for example essential oils, and clay in the field of edible films for food protection. The mechanical behavior and the gas and water vapor permeability of the films are also discussed. References dealing with the antimicrobial behavior of these films and their impact on food protection are explored. PMID:23498203

  3. Transparent and conductive electrodes based on unpatterned, thin metal films

    NASA Astrophysics Data System (ADS)

    O'Connor, Brendan; Haughn, Chelsea; An, Kwang-Hyup; Pipe, Kevin P.; Shtein, Max

    2008-12-01

    Transparent electrodes composed of ultrathin, unpatterned metal films are investigated in planar heterojunction (PHJ) and bulk heterojunction organic photovoltaic (OPV) cells. Optimal electrode composition and thickness are deduced from electrical and optical models and experiments, enabling a PHJ-OPV cell to be realized using a silver anode, achieving power conversion efficiency parity with an analogous cell that uses an indium tin oxide anode. Beneficial aspects of smooth, unpatterned metal films as transparent electrodes in OPV cells are also discussed in the text.

  4. LiMn2O4-based cathode thin films for Li thin-film batteries

    NASA Astrophysics Data System (ADS)

    Yim, Haena; Shin, Dong-Wook; Choi, Ji-Won

    2016-01-01

    Substitution methods for Mn3+ in a spinel lithium manganese oxide with other cations have been used to prevent capacity degradation during the electrochemical charge and discharge of Li-batteries by increasing the average valence of Mn. In particular, in this review we outlin the effects of Sn substitution on the cycling performance of LiMn2O4 thin films that can be used as positive electrode in Li-batteries. The thin films were prepared by using pulsed laser deposition and solution deposition with regard to the structural and the electro-chemical characteristics.

  5. Design of camouflage material for visible and near infrared based on thin film technology

    NASA Astrophysics Data System (ADS)

    Miao, Lei; Shi, Jia-ming; Zhao, Da-peng; Liu, Hao; Wang, Chao; Xu, Yan-liang

    2015-11-01

    Visible light and near infrared based camouflage materials achieve good stealth under traditional optical detection equipment but its spectral differences with green plants can be taken advantage of by high spectrum based detection technologies. Based on the thin structure of bandpass filter, we designed an optical film with both green and near infrared spectrum. We conducted simulations using transfer matrix methods and optimized the result by simplex methods. The spectral reflectance curve of the proposed thin film matches that of green plants, and experiments show that the proposed thin film achieve good invisibility under visible light and near infrared in a wide viewing angle.

  6. Multifractal characterization of water soluble copper phthalocyanine based films surfaces

    NASA Astrophysics Data System (ADS)

    Ţălu, Ştefan; Stach, Sebastian; Mahajan, Aman; Pathak, Dinesh; Wagner, Tomas; Kumar, Anshul; Bedi, R. K.; Ţălu, Mihai

    2014-07-01

    This paper presents a multifractal approach to characterize the structural complexity of 3D surface roughness of CuTsPc films on the glass and quartz substrate, obtained with atomic force microscopy (AFM) analysis. CuTsPc films prepared by drop cast method were investigated. CuTsPc films surface roughness was studied by AFM in tapping-mode™, in an aqueous environment, on square areas of 100 μm2 and 2500 μm2. A detailed methodology for CuTsPc films surface multifractal characterization, which may be applied for AFM data, was also presented. Analysis of surface roughness revealed that CuTsPc films have a multifractal geometry at various magnifications. The generalized dimension D q and the singularity spectrum f( α) provided quantitative values that characterize the local scale properties of CuTsPc films surface morphology at nanometer scale. Multifractal analysis provides different yet complementary information to that offered by traditional surface statistical parameters.

  7. Edible antimicrobial films based on microencapsulated lemongrass oil.

    PubMed

    Bustos C, Rubén O; Alberti R, Francesca V; Matiacevich, Silvia B

    2016-01-01

    Edible films and coatings have been proposed as viable alternatives for the preservation of fresh food such as fruit, meat, fish and cheese. They can be designed to contain natural antioxidants, vitamins and antimicrobials in order to extend shelf life of the product keeping the natural sensorial properties. Essential oils have been targeted as potential active principles for edible films and coatings given their well-recognized antioxidant, antimicrobial and sensory properties. In the present work, lemongrass oil (LMO) microcapsules were prepared by the emulsification-separation method using sodium caseinate as wall material. Microcapsules had an average size of 22 μm and contained over 51 % oil in their nucleus. The release kinetics of the LMO components was studied for both, microcapsules and microcapsule containing films. Experimental data for the controlled release of LMO components showed good correlation with Peppas and Weibull models. The effect of the alginate matrix on the release parameters of the mathematical models could be detected by the modification of the b constant of the Weibull equation which changed from 0.167 for the microcapsules to 0.351 for the films. Films containing LMO at concentrations of 1250, 2500 and 5000 ppm were able to inhibit growth of Escherichia coli ATCC 25922 and Listeria monocytogenes ISP 65-08 in liquid cultures. A possible future application of these films for shelf life extension of fresh food is discussed. PMID:26788005

  8. Characterization of films based on chitosan lactate and its blends with oxidized starch and gelatin.

    PubMed

    Kowalczyk, Dariusz; Kordowska-Wiater, Monika; Nowak, Jakub; Baraniak, Barbara

    2015-01-01

    Minimal inhibitory concentration (MIC) of chitosan lactate (CHL) was tested against bacteria and phytopathogenic fungi. Then, the structural, physicochemical and antimicrobial properties of films based on CHL, oxidized potato starch (OPS), and gelatin (GEL) were investigated. With the exception of Rhizopus nigricans, CHL was effective against the target organisms. Gram-positive bacteria (Staphylococcus aureus and Bacillus cereus) were more sensitive to CHL than Gram-negative bacteria (Pectobacterium carotovorum and Escherichia coli). Cryo-SEM images showed total miscibility between the polymers in the blends and the ATR-FTIR spectra revealed that there was an interaction among the polymeric components. Pure CHL films displayed the highest moisture content (25.51%), water vapor permeability (48.78gmmm(-2)d(-1)kPa(-1)), and the lowest tensile and puncture strength (2.00 and 1.45MPa, respectively) among the studied films. CHL50/GEL50 films had lower permeability, higher mechanical strength, and lower elongation compared to CHL50/OPS50 films. Films obtained from CHL and CHL50/GEL50 were completely water-soluble and did not show sorbitol recrystallization. The incorporation of CHL into OPS and GEL films did not affect their transparency and improved UV-blocking capacity. CHL films were the only ones that exhibited antibacterial efficiency. Antifungal activities against Alternaria alternata and Monilinia fructigena were detected for CHL and CHL50/GEL50 films. PMID:25841370

  9. Influence of hydroxypropylmethylcellulose addition and homogenization conditions on properties and ageing of corn starch based films.

    PubMed

    Jiménez, Alberto; Fabra, María José; Talens, Pau; Chiralt, Amparo

    2012-06-20

    Edible films based on corn starch, hydroxypropyl methylcellulose (HPMC) and their mixtures were prepared by using two different procedures to homogenize the film forming dispersions (rotor-stator and rotor-stator plus microfluidizer). The influence of both HPMC-starch ratio and the homogenization method on the structural, optical, tensile and barrier properties of the films was analysed. The ageing of the films was also studied by characterizing them after 5 weeks' storage. Starch re-crystallization in newly prepared and stored films was analysed by means of X-ray diffraction. HPMC-corn starch films showed phase separation of polymers, which was enhanced when microfluidization was applied to the film forming dispersion. Nevertheless, HPMC addition inhibited starch re-crystallization during storage, giving rise to more flexible films at the end of the period. Water barrier properties of starch films were hardly affected by the addition of HPMC, although oxygen permeability increased due to its poorer oxygen barrier properties. PMID:24750773

  10. Oxide-based method of making compound semiconductor films and making related electronic devices

    DOEpatents

    Kapur, Vijay K.; Basol, Bulent M.; Leidholm, Craig R.; Roe, Robert A.

    2000-01-01

    A method for forming a compound film includes the steps of preparing a source material, depositing the source material on a base and forming a preparatory film from the source material, heating the preparatory film in a suitable atmosphere to form a precursor film, and providing suitable material to said precursor film to form the compound film. The source material includes oxide-containing particles including Group IB and IIIA elements. The precursor film includes non-oxide Group IB and IIIA elements. The compound film includes a Group IB-IIIA-VIA compound. The oxides may constitute greater than about 95 molar percent of the Group IB elements and greater than about 95 molar percent of the Group IIIA elements in the source material. Similarly, non-oxides may constitute greater than about 95 molar percent of the Group IB elements and greater than about 95 molar percent of the Group IIIA elements in the precursor film. The molar ratio of Group IB to Group IIIA elements in the source material may be greater than about 0.6 and less than about 1.0, or substantially greater that 1.0, in which case this ratio in the compound film may be reduced to greater than about 0.6 and less than about 1.0. The source material may be prepared as an ink from particles in powder form. The oxide-containing particles may include a dopant, as may the compound film. Compound films including a Group IIB-IVA-VA compound may be substituted using appropriate substitutions in the method. The method, also, is applicable to fabrication of solar cells and other electronic devices.

  11. Optically active multilayer films based on chitosan and an azopolymer.

    PubMed

    Fernández, Raquel; Ocando, Connie; Fernandes, Susana C M; Eceiza, Arantxa; Tercjak, Agnieszka

    2014-04-14

    The layer-by-layer technique has been widely adopted for the fabrication of nanostructures with tailored properties. In this work, photoactive multilayer films consisting of alternating layers of chitosan and an azopolymer were developed by this method. Taking into account that pH is the factor controlling the charge of weak polyelectrolytes, the influence of this parameter on the structure and properties of the multilayer films was evaluated. Thus, different films were prepared by varying pH conditions as well as bilayer number. The morphology and properties of the films were analyzed by diverse advanced techniques, such as ultraviolet-visible spectroscopy, X-ray diffraction, and atomic force microscopy equipped with PeakForce QNM (Quantitative Nanomechanical Property Mapping). It was found that the thickness, roughness and elastic modulus of the developed multilayer films increased with the decrease of the chitosan solution pH and the increase of the bilayer number. Furthermore, induced birefringence measurements revealed that a higher level of photo-orientation was attained with the decrease of pH and the increase of bilayer number. PMID:24564819

  12. Magnetic Fe-Co films electroplated in a deep-eutectic-solvent-based plating bath

    NASA Astrophysics Data System (ADS)

    Yanai, T.; Shiraishi, K.; Watanabe, Y.; Ohgai, T.; Nakano, M.; Suzuki, K.; Fukunaga, H.

    2015-05-01

    We fabricated Fe-Co films from a deep eutectic solvent (DES)-based plating bath and investigated magnetic properties of the plated films. The plating baths were obtained by stirring the mixture of choline chloride, ethylene glycol, FeCl2.4H2O, and CoCl2.6H2O. The composition of the plated films depended on the amount of FeCl2.4H2O in the plating bath, and Fe content of the films was varied from 0 to 100 at. %. Depending on the Fe content, the saturation magnetization and the coercivity of the films varied. The Fe76Co24 film shows high saturation magnetization and smooth surface, and the change in the saturation magnetization shows good agreement with the expected change by the Slater-Pauling curve. High current efficiency (>90%) could be obtained in the wide film composition. From these results, we concluded that the DES-based plating bath is one of effective baths for the Fe-Co films with high current efficiency.

  13. Thin film lithium-based batteries and electrochromic devices fabricated with nanocomposite electrode materials

    DOEpatents

    Gillaspie, Dane T; Lee, Se-Hee; Tracy, C. Edwin; Pitts, John Roland

    2014-02-04

    Thin-film lithium-based batteries and electrochromic devices (10) are fabricated with positive electrodes (12) comprising a nanocomposite material composed of lithiated metal oxide nanoparticles (40) dispersed in a matrix composed of lithium tungsten oxide.

  14. Thermal conductivity and mechanical properties of AlN-based thin films

    NASA Astrophysics Data System (ADS)

    Moraes, V.; Riedl, H.; Rachbauer, R.; Kolozsvári, S.; Ikeda, M.; Prochaska, L.; Paschen, S.; Mayrhofer, P. H.

    2016-06-01

    While many research activities concentrate on mechanical properties and thermal stabilities of protective thin films, only little is known about their thermal properties being essential for the thermal management in various industrial applications. Based on the 3ω-method, we show the influence of Al and Cr on the temperature dependent thermal conductivity of single-phase cubic structured TiN and single-phase wurtzite structured AlN thin films, respectively, and compare them with the results obtained for CrN thin films. The dc sputtered AlN thin films revealed a highly c-axis oriented growth for deposition temperatures of 250 to 700 °C. Their thermal conductivity was found to increase strongly with the film thickness, indicating progressing crystallization of the interface near amorphous regions during the sputtering process. For the 940 nm AlN film, we found a lower boundary for the thermal conductivity of 55.3 W m-1 K-1 . By the substitution of only 10 at. % Al with Cr, κ significantly reduces to ˜5.0 W m-1 K-1 , although the single-phase wurtzite structure is maintained. The single-phase face centered cubic TiN and Ti0.36Al0.64N thin films exhibit κ values of 3.1 W m-1 K-1 and 2.5 W m-1 K-1 , respectively, at room temperature. Hence, also here, the substitutional alloying reduces the thermal conductivity, although at a significantly lower level. Single-phase face centered cubic CrN thin films show κ values of 3.6 W m-1 K-1 . For all nitride based thin films investigated, the thermal conductivity slightly increases with increasing temperature between 200 and 330 K. This rather unusual behavior is based on the high defect density (especially point defects) within the thin films prepared by physical vapor deposition.

  15. Nanocomposite films based on xylan-rich hemicelluloses and cellulose nanofibers with enhanced mechanical properties.

    PubMed

    Peng, Xin-wen; Ren, Jun-li; Zhong, Lin-xin; Sun, Run-cang

    2011-09-12

    Interest in xylan-rich hemicelluloses (XH) film is growing, and efforts have been made to prepare XH films with improved mechanical properties. This work described an effective approach to produce nanocomposite films with enhanced mechanical properties by incorporation of cellulose nanofibers (CNFs) into XH. Aqueous dispersions of XH (64-75 wt %), sorbitol (16-25 wt %), and CNF (0-20 wt %) were cast at a temperature of 23 °C and 50% relative humidity. The surface morphology of the films was revealed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The thermal properties and crystal structure of the films were evaluated by thermal analysis (TG) and X-ray diffraction (XRD). The surface of XH films with and without CNF was composed primarily of nanonodules, and CNFs were embedded in the XH matrix. Freeze-dried XH powder was amorphous, whereas the films with and without CNF showed a distinct peak at around 2θ = 18°, which suggested that XH molecules aggregated or reordered in the casting solution or during water evaporation. Furthermore, the nanocomposite films had improved thermal stability. XH film with 25 wt % plasticizer (sorbitol, based on dry XH weight) showed poor mechanical properties, whereas incorporation of CNF (5-20 wt %, based on the total dry mixture) into the film resulted in enhanced mechanical properties due to the high aspect ratio and mechanical strength of CNF and strong interactions between CNF and XH matrix. This effective method makes it possible to produce hemicellulose-based biomaterials of high quality. PMID:21815695

  16. Charge carrier transport in polycrystalline organic thin film based field effect transistors

    NASA Astrophysics Data System (ADS)

    Rani, Varsha; Sharma, Akanksha; Ghosh, Subhasis

    2016-05-01

    The charge carrier transport mechanism in polycrystalline thin film based organic field effect transistors (OFETs) has been explained using two competing models, multiple trapping and releases (MTR) model and percolation model. It has been shown that MTR model is most suitable for explaining charge carrier transport in grainy polycrystalline organic thin films. The energetic distribution of traps determined independently using Mayer-Neldel rule (MNR) is in excellent agreement with the values obtained by MTR model for copper phthalocyanine and pentacene based OFETs.

  17. Experimental Evaluation of Biodegradable Film Compositions Based on Gelatin with Colchicine.

    PubMed

    Bokeriya, L A; Bokeriya, O L; Sivtsev, V S; Novikova, S P; Salokhedinova, R R; Nikolashina, L N; Samsonova, N N; Gorodkov, A Yu; Serov, R A

    2016-07-01

    Biodegradable film compositions based on natural biopolymer gelatin with immobilized colchicine were prepared and their efficiency in prevention of the adhesion process in the pericardium was evaluated on rabbit model of postoperative pericarditis. The use of gelatin-based biodegradable film compositions significantly reduced the intensity of adhesion formation in the pericardial cavity, while immobilization of anti-inflammatory drug colchicine amplified their anti-adhesion activity. PMID:27496036

  18. A Naphthalenediimide-Based Metal-Organic Framework and Thin Film Exhibiting Photochromic and Electrochromic Properties.

    PubMed

    Xie, Yi-Xin; Zhao, Wen-Na; Li, Guo-Chang; Liu, Peng-Fei; Han, Lei

    2016-01-19

    A multifunctional metal-organic framework, NBU-3, has been explored as a 2D three-connected network based on a naphthalenediimide-based ligand. The NBU-3 crystals display photochromic properties, and NBU-3 thin films on FTO substrates exhibit electrochromic properties. NBU-3 is the first example of MOF materials containing both photochromic and electrochromic properties, which can be desirable for thin film devices. PMID:26713454

  19. Physical properties of emulsion-based hydroxypropyl methylcellulose films: effect of their microstructure.

    PubMed

    Zúñiga, R N; Skurtys, O; Osorio, F; Aguilera, J M; Pedreschi, F

    2012-10-01

    The initial characteristics of emulsions and the rearrangement of the oil droplets in the film matrix during film drying, which defines its microstructure, has an important role in the physical properties of the emulsion-based films. The objective of this work was to study the effect of the microstructure (two droplet size distributions) and stability (with or without surfactant) of HPMC oil-in-water emulsions over physical properties of HPMC emulsion-based edible films. HPMC was used to prepare sunflower oil-in-water emulsions containing 0.3 or 1.0% (w/w) of oil with or without SDS, as surfactant, using an ultrasonic homogenizer. Microstructure, rheological properties and stability of emulsions (creaming) were measured. In addition, microstructure, coalescence of oil droplets, surface free energy, optical and mechanical properties and water vapor transfer of HPMC films were evaluated. Image analysis did not show differences among droplet size distributions of emulsions prepared at different oil contents; however, by using SDS the droplet size distributions were shifted to lower values. Volume mean diameters were 3.79 and 3.77 μm for emulsions containing 0.3 and 1.0% without surfactant, respectively, and 2.72 and 2.71 μm for emulsions with SDS. Emulsions formulated with 1.0% of oil presented higher stability, with almost no change during 5 and 3 days of storage, for emulsions with and without SDS, respectively. Internal and surface microstructure of emulsion-based films was influenced by the degree of coalescence and creaming of the oil droplets. No effect of microstructure over the surface free energy of films was found. The incorporation of oil impaired the optical properties of films due to light scattering of light. Addition of oil and SDS decreased the stress at break of the emulsion-based films. The replace of HPMC by oil and SDS produce a lower "amount" of network structure in the films, leading to a weakening of their structure. The oil content and SDS

  20. Modeling the mechanics of graphene-based polymer composite film measured by the bulge test

    NASA Astrophysics Data System (ADS)

    Zhang, Jian-Jun; Sun, You-yi; Li, Dian-sen; Cao, Yang; Wang, Zuo; Ma, Jing; Zhao, Gui-Zhe

    2015-10-01

    Graphene-based polymer composite films have wide-ranging potential applications, such as in sensors, electromagnetic shielding, absorbing materials, corrosion resistance and so on. In addition, the practical applications of graphene-based polymer composite films are closely related to their mechanical properties. However, the mechanical properties of graphene-based polymer composite films are difficult to characterize with tensile tests. In this paper, the bugle test was used to investigate the mechanical properties of graphene-based polymer composite films. The experimental results show that the Young’s modulus of polymer composite films increases non-linearly with an increase in the doping content of graphene, and viscoelastic deformation is induced under cyclic loading conditions. Moreover, in order to describe their mechanical behavior, an ‘Arruda-Boyce’ finite-strain constitutive model (modified BPA model), based on the strain amplification hypothesis, and a traditional ‘Arruda-Boyce’ model was proposed, which incorporated many of the features of previous theories. The numerical treatment of the modified BPA model associated with finite element analysis is also discussed. This new model is shown to be able to predict the experimentally observed mechanical behavior of graphene based polymer composite films measured by the bugle test effectively.

  1. Stress Relaxation in Sn-Based Films: Effects of Pb Alloying, Grain Size, and Microstructure

    NASA Astrophysics Data System (ADS)

    Jadhav, Nitin; Wasserman, Jacob; Pei, Fei; Chason, Eric

    2012-03-01

    Stress is believed to provide the driving force for growth of Sn whiskers, so stress relaxation in the Sn layer plays a key role in their formation. To understand and enhance stress relaxation in Sn-based films, the effects of Pb alloying and microstructure on their mechanical properties have been studied by observing the relaxation of thermal expansion-induced strain. The relaxation rate is found to increase with film thickness and grain size in pure Sn films, and it depends on the microstructure in Pb-alloyed Sn films. Measurements of multilayered structures (Sn on Pb-Sn and Pb-Sn on Sn) show that changing the surface layer alone is not sufficient to enhance the relaxation, indicating that the Pb enhances relaxation in the bulk of the film and not by surface modification. Implications of our results for whisker mitigation strategies are discussed.

  2. Mechanical and thermal properties of irradiated films based on Tilapia ( Oreochromis niloticus) proteins

    NASA Astrophysics Data System (ADS)

    Sabato, S. F.; Nakamurakare, N.; Sobral, P. J. A.

    2007-11-01

    Proteins are considered potential material in natural films as alternative to traditional packaging. When gamma radiation is applied to protein film forming solution it resulted in an improvement in mechanical properties of whey protein films. The objective of this work was the characterization of mechanical and thermal properties of irradiated films based on muscle proteins from Nile Tilapia ( Oreochromis niloticus). The films were prepared according to a casting technique with two levels of plasticizer: 25% and 45% glycerol and irradiated in electron accelerator type Radiation Dynamics, 0.550 MeV at dose range from 0 to 200 kGy. Thermal properties and mechanical properties were determined using a differential scanning calorimeter and a texture analyzer, respectively. Radiation from electron beam caused a slightly increase on its tensile strength characteristic at 100 kGy, while elongation value at this dose had no reduction.

  3. High-energy-density sol-gel thin film based on neat 2-cyanoethyltrimethoxysilane.

    PubMed

    Kim, Yunsang; Kathaperumal, Mohanalingam; Smith, O'Neil L; Pan, Ming-Jen; Cai, Ye; Sandhage, Kenneth H; Perry, Joseph W

    2013-03-13

    Hybrid organic-inorganic sol-gel dielectric thin films from a neat 2-cyanoethyltrimethoxysilane (CNETMS) precursor have been fabricated and their permittivity, dielectric strength, and energy density characterized. CNETMS sol-gel films possess compact, polar cyanoethyl groups and exhibit a relative permittivity of 20 at 1 kHz and breakdown strengths ranging from 650 V/μm to 250 V/μm for film thicknesses of 1.3 to 3.5 μm. Capacitors based on CNETMS films exhibit extractable energy densities of 7 J/cm(3) at 300 V/μm, as determined by charge-discharge and polarization-electric field measurements, as well as an energy extraction efficiency of ~91%. The large extractable energy resulting from the linear dielectric polarization behavior suggests that CNETMS films are promising sol-gel materials for pulsed power applications. PMID:23427818

  4. A silane-based electroactive film prepared in an imidazolium chloroaluminate molten salt

    SciTech Connect

    Carlin, R.T. . Frank J. Seiler Research Lab.); Osteryoung, R.A. . Dept. of Chemistry)

    1994-07-01

    Electrochemical oxidation of Ph[sub 3]SiCl (Ph = phenyl) in the room-temperature molten salt AlCl[sub 3]:EMICl (EMICl = 1-ethyl-3-methylimidazolium chloride) results in the formation of an adherent electroactive film on the surface of solid electrodes. The film is reversibly oxidized and reduced in the molten salt and is conducting when in the oxidized state. Based on x-ray photoelectron spectroscopy analysis, the film consists of both a silane and an imidazole component, and the charge storage properties of the film are localized on the heterocyclic rings. This electroactive film compares favorably to other conducting polymers currently being investigated as positive electrodes in room-temperature molten salt batteries.

  5. Atomic Oxygen Sensors Based on Nanograin ZnO Films Prepared by Pulse Laser Deposition

    SciTech Connect

    Wang Yunfei; Chen Xuekang; Li Zhonghua; Zheng Kuohai; Wang Lanxi; Feng Zhanzu; Yang Shengsheng

    2009-01-05

    High-quality nanograin ZnO thin films were deposited on c-plane sapphire (Al{sub 2}O{sub 3}) substrates by pulse laser deposition (PLD). Scanning electron microscopy (SEM) and x-ray diffraction (XRD) were used to characterize the samples. The structural and morphological properties of ZnO films under different deposition temperature have been investigated before and after atomic oxygen (AO) treatment. XRD has shown that the intensity of the (0 0 2) peak increases and its FWHM value decreases after AO treatment. The AO sensing characteristics of nano ZnO film also has been investigated in a ground-based atomic oxygen simulation facility. The results show that the electrical conductivity of nanograin ZnO films decreases with increasing AO fluence and that the conductivity of the films can be recovered by heating.

  6. POLYMERIC ACRYLATE-BASED HYBRID FILMS CONTAINING LEAD AND IRON PATTERNED BY UV PHOTO-POLYMERIZATION

    PubMed Central

    Han, Huilan; Bissell, John; Yaghmaie, Frank; Davis, Cristina E.

    2009-01-01

    The development and processing of hybrid inorganic-organic thin film materials plays a critical role in advancing interdisciplinary sciences and device manufacturing. Here we present a novel approach to synthesize and deposit acrylate-containing organic/inorganic hybrid films. The material is based on a chemical solution and includes specifically desired metal dopants that are fully-integrated into the backbone of the polymer structure. The film can be deposited by simple spin coating, and we confer photosensitive properties to the material making it directly patterned by traditional UV photolithography techniques. Film thickness, chemical characterization and wet/dry etching capability of the film are also investigated. We believe this innovative material has the potential to be used in a broad range of applications for electronic, photonic, biology and other interdisciplinary fields. PMID:19795818

  7. Photoactivated chlorophyllin-based gelatin films and coatings to prevent microbial contamination of food products.

    PubMed

    López-Carballo, G; Hernández-Muñoz, P; Gavara, R; Ocio, M J

    2008-08-15

    The aim of this work was to develop antimicrobial photosensitizer-containing edible films and coatings based on gelatin as the polymer matrix, incorporating sodium magnesium chlorophyllin (E-140) and sodium copper chlorophyllin (E-141). Chlorophyllins were incorporated into the gelatin film-forming solution and the inhibiting effect of the cast films was tested against Staphylococcus aureus and Listeria monocytogenes. The results demonstrated that water soluble sodium magnesium chlorophyllin and water soluble sodium copper chlorophyllin reduced the growth of S. aureus and L. monocytogenes by 5 log and 4 log respectively. Subsequently, the activity of self-standing films and coatings containing E-140 was assessed on cooked frankfurters inoculated with S. aureus and L. monocytogenes. These tests showed that it was possible to reduce microorganism growth in cooked frankfurters inoculated with S. aureus and L. monocytogenes by covering them with sodium magnesium chlorophyllin-gelatin films and coatings. PMID:18555550

  8. Theoretical investigation of acoustic wave devices based on different piezoelectric films deposited on silicon carbide

    NASA Astrophysics Data System (ADS)

    Fan, Li; Zhang, Shu-yi; Ge, Huan; Zhang, Hui

    2013-07-01

    Performances of acoustic wave (AW) devices based on silicon carbide (SiC) substrates are theoretically studied, in which two types of piezoelectric films of ZnO and AlN deposited on 4H-SiC and 3C-SiC substrates are adopted. The phase velocities (PV), electromechanical coupling coefficients (ECC), and temperature coefficients of frequency (TCF) for three AW modes (Rayleigh wave, A0 and S0 modes of Lamb wave) often used in AW devices are calculated based on four types of configurations of interdigital transducers (IDTs). It is found that that the ZnO piezoelectric film is proper for the AW device operating in the low-frequency range because a high ECC can be realized using a thin ZnO film. The AlN piezoelectric film is proper for the device operating in the high-frequency range in virtue of the high PV of AlN, which can increase the finger width of the IDT. Generally, in the low-frequency Lamb wave devices using ZnO piezoelectric films with small normalized thicknesses of films to wavelengths hf/λ, thin SiC substrates can increase ECCs but induce high TCFs simultaneously. In the high-frequency device with a large hf/λ, the S0 mode of Lamb wave based on the AlN piezoelectric film deposited on a thick SiC substrate exhibits high performances by simultaneously considering the PV, ECC, and TCF.

  9. Photochemical solar energy conversion utilizing semiconductors localized in membrane-mimetic systems

    SciTech Connect

    Fendler, J.H.

    1991-08-31

    Extending the frontiers of colloidal photochemistry and colloidal electrochemistry to solar photochemistry research had been the main objective of this research. More specific objectives of this proposal include the examination of semiconductor-particle-mediated photoelectron transfer and photoelectric effects in different membrane mimetic systems. Emphasis had been placed on developing bilayer lipid membranes and Langmuir-Blodgett films as new membrane-mimetic systems, as well as on the characterization and utilization of these systems.

  10. Photochemical solar energy conversion utilizing semiconductors localized in membrane-mimetic systems. Performance report, April 1, 1989--August 31, 1991

    SciTech Connect

    Fendler, J.H.

    1991-08-31

    Extending the frontiers of colloidal photochemistry and colloidal electrochemistry to solar photochemistry research had been the main objective of this research. More specific objectives of this proposal include the examination of semiconductor-particle-mediated photoelectron transfer and photoelectric effects in different membrane mimetic systems. Emphasis had been placed on developing bilayer lipid membranes and Langmuir-Blodgett films as new membrane-mimetic systems, as well as on the characterization and utilization of these systems.

  11. Gafchromic EBT2 film dosimetry in reflection mode with a novel plan-based calibration method

    SciTech Connect

    Mendez, I.; Hartman, V.; Hudej, R.; Strojnik, A.; Casar, B.

    2013-01-15

    Purpose:A dosimetric system formed by Gafchromic EBT2 radiochromic film and Epson Expression 10000XL flatbed scanner was commissioned for dosimetry. In this paper, several open questions concerning the commissioning of radiochromic films for dosimetry were addressed: (a) is it possible to employ this dosimetric system in reflection mode; (b) if so, can the methods used in transmission mode also be used in reflection mode; (c) is it possible to obtain accurate absolute dose measurements with Gafchromic EBT2 films; (d) which calibration method should be followed; (e) which calibration models should be used; and (f) does three-color channel dosimetry offer a significant improvement over single channel dosimetry. The purpose of this paper is to help clarify these questions. Methods: In this study, films were scanned in reflection mode, the effect of surrounding film was evaluated and the feasibility of EBT2 film dosimetry in reflection mode was studied. EBT2's response homogeneity has been reported to lead to excessive dose uncertainties. To overcome this problem, a new plan-based calibration method was implemented. Plan-based calibration can use every pixel and each of the three color channels of the scanned film to obtain the parameters of the calibration model. A model selection analysis was conducted to select lateral correction and sensitometric curve models. The commonly used calibration with fragments was compared with red-channel plan-based calibration and with three-channel plan-based calibration. Results: No effect of surrounding film was found in this study. The film response inhomogeneity in EBT2 films was found to be important not only due to differences in the fog but also due to differences in sensitivity. The best results for lateral corrections were obtained using absolute corrections independent of the dose. With respect to the sensitometric curves, an empirical polynomial fit of order 4 was found to obtain results equivalent to a gamma

  12. Verification of Gamma Knife extend system based fractionated treatment planning using EBT2 film

    SciTech Connect

    Natanasabapathi, Gopishankar; Bisht, Raj Kishor

    2013-12-15

    Purpose: This paper presents EBT2 film verification of fractionated treatment planning with the Gamma Knife (GK) extend system, a relocatable frame system for multiple-fraction or serial multiple-session radiosurgery.Methods: A human head shaped phantom simulated the verification process for fractionated Gamma Knife treatment. Phantom preparation for Extend Frame based treatment planning involved creating a dental impression, fitting the phantom to the frame system, and acquiring a stereotactic computed tomography (CT) scan. A CT scan (Siemens, Emotion 6) of the phantom was obtained with following parameters: Tube voltage—110 kV, tube current—280 mA, pixel size—0.5 × 0.5 and 1 mm slice thickness. A treatment plan with two 8 mm collimator shots and three sectors blocking in each shot was made. Dose prescription of 4 Gy at 100% was delivered for the first fraction out of the two fractions planned. Gafchromic EBT2 film (ISP Wayne, NJ) was used as 2D verification dosimeter in this process. Films were cut and placed inside the film insert of the phantom for treatment dose delivery. Meanwhile a set of films from the same batch were exposed from 0 to 12 Gy doses for calibration purposes. An EPSON (Expression 10000 XL) scanner was used for scanning the exposed films in transparency mode. Scanned films were analyzed with inhouse written MATLAB codes.Results: Gamma index analysis of film measurement in comparison with TPS calculated dose resulted in high pass rates >90% for tolerance criteria of 1%/1 mm. The isodose overlay and linear dose profiles of film measured and computed dose distribution on sagittal and coronal plane were in close agreement.Conclusions: Through this study, the authors propose treatment verification QA method for Extend frame based fractionated Gamma Knife radiosurgery using EBT2 film.

  13. Memory switches based on metal oxide thin films

    NASA Technical Reports Server (NTRS)

    Ramesham, Rajeshuni (Inventor); Thakoor, Anilkumar P. (Inventor); Lambe, John J. (Inventor)

    1990-01-01

    MnO.sub.2-x thin films (12) exhibit irreversible memory switching (28) with an OFF/ON resistance ratio of at least about 10.sup.3 and the tailorability of ON state (20) resistance. Such films are potentially extremely useful as a connection element in a variety of microelectronic circuits and arrays (24). Such films provide a pre-tailored, finite, non-volatile resistive element at a desired place in an electric circuit, which can be electrically turned OFF (22) or disconnected as desired, by application of an electrical pulse. Microswitch structures (10) constitute the thin film element, contacted by a pair of separate electrodes (16a, 16b) and have a finite, pre-selected ON resistance which is ideally suited, for example, as a programmable binary synaptic connection for electronic implementation of neural network architectures. The MnO.sub.2-x microswitch is non-volatile, patternable, insensitive to ultraviolet light, and adherent to a variety of insulating substrates (14), such as glass and silicon dioxide-coated silicon substrates.

  14. Short Fiction on Film: A Relational DataBase.

    ERIC Educational Resources Information Center

    May, Charles

    Short Fiction on Film is a database that was created and will run on DataRelator, a relational database manager created by Bill Finzer for the California State Department of Education in 1986. DataRelator was designed for use in teaching students database management skills and to provide teachers with examples of how a database manager might be…

  15. [Analysis of spectral characteristics of oil film on water based on wavelet transform].

    PubMed

    Li, Ying; Liu, Bing-Xin; Li, Bao-Yu; Chen, Duo

    2012-07-01

    The diagnostic features are the basis to detect and characterize the oil film on water through optical remote sensing. This work shows the results of lab spectral measurements of light diesel oil with thickness ranged 1.0 - 127 microm. A wavelet transform were performed to the reflectance, and the singularity (388-393 nm) was explored as the indicators of oil film thickness. The results indicate that the reflectance of light diesel oil film is higher than that of water in the range from 350-2 500 nm. There is a reflectance peak near 388 nm when the thickness of oil film is larger than 6 microm, however, no distinguished features could be recognized when oil films were thinner than 6 microm. The wavelet coefficients of the fifth decomposition level by applying Daubechies 4 (db4) mother wavelets proved successful for identifying the singularity of oil film's reflectance spectra and its accurate position. With the thickness lager than 6 microm, the detail coefficients performed an abrupt change within the range of 388-393 nm, and became more violent while oil films' thickness increased. This research demonstrated that oil films on water with different thickness could be distinguished based on wavelet detail coefficients, with important implications for detection of oils on water using UV and short wave optical remote sensing. PMID:23016354

  16. Bio-based barium alginate film: Preparation, flame retardancy and thermal degradation behavior.

    PubMed

    Liu, Yun; Zhang, Chuan-Jie; Zhao, Jin-Chao; Guo, Yi; Zhu, Ping; Wang, De-Yi

    2016-03-30

    A bio-based barium alginate film was prepared via a facile ionic exchange and casting approach. Its flammability, thermal degradation and pyrolysis behaviors, thermal degradation mechanism were studied systemically by limiting oxygen index (LOI), vertical burning (UL-94), microscale combustion calorimetry (MCC), thermogravimetric analysis (TGA) coupled with Fourier transform infrared analysis (FTIR) and pyrolysis-gas chromatography-mass spectrometry (Py-GC-MS). It showed that barium alginate film had much higher LOI value (52.0%) than that of sodium alginate film (24.5%). Moreover, barium alginate film passed the UL-94 V-0 rating, while the sodium alginate film showed no classification. Importantly, peak of heat release rate (PHRR) of barium alginate film in MCC test was much lower than that of sodium alginate film, suggested that introduction of barium ion into alginate film significantly decreased release of combustible gases. TG-FTIR and Py-GC-MS results indicated that barium alginate produced much less flammable products than that of sodium alginate in whole thermal degradation procedure. Finally, a possible degradation mechanism of barium alginate had been proposed. PMID:26794953

  17. Thin film transistor based on TiOx prepared by DC magnetron sputtering.

    PubMed

    Chung, Sung Mook; Shin, Jae-Heon; Hong, Chan-Hwa; Cheong, Woo-Seok

    2012-07-01

    This paper reports on the thin film transistor (TFT) based on TiOx prepared by direct current (DC) magnetron sputtering for the application of n-type channel transparent TFTs. A ceramic TiOx target was prepared for the sputtering of the TiO2 films. The structural, optical, and electrical properties of the TiO2 films were investigated after their heat treatment. It is observed from XRD measurement that the TiO2 films show anatase structure having (101), (004), and (105) planes after heat treatment. The anatase-structure TiO2 films show a band-gap energy of approximately 3.20 eV and a transmittance of approximately 91% (@550 nm). The bottom-gate TFTs fabricated with the TiO2 film as an n-type channel layer. These devices exhibit the on-off ratio, the field-effect mobility, and the threshold voltage of about 10(4), 0.002 cm2/Vs, and 6 V, respectively. These results indicate the possibility of applying TiO2 films depositied by DC magnetron sputtering to TiO2-based opto-electronic devices. PMID:22966586

  18. Electroplated Fe-Co-Ni films prepared from deep-eutectic-solvent-based plating baths

    NASA Astrophysics Data System (ADS)

    Yanai, Takeshi; Shiraishi, Kotaro; Akiyoshi, Toshiki; Azuma, Keita; Watanabe, Yoshimasa; Ohgai, Takeshi; Morimura, Takao; Nakano, Masaki; Fukunaga, Hirotoshi

    2016-05-01

    We fabricated soft magnetic films from DES-based plating baths, and investigated magnetic properties of the plated films. The plating baths were obtained by stirring the mixture of choline chloride, ethylene glycol, FeCl2 ṡ 4H2O, NiCl2 ṡ 6H2O and CoCl2 ṡ 6H2O. The composition of the electroplated film depended on the amount of the reagent in the plating bath, and we consequently obtained the films with various composition. The current efficiency of the plating process shows high values (> 88 %) in the wide composition range. The soft magnetic films with low coercivity were obtained at the Fe compositions of ≈ 30 at.% and > 80 at.%, and we found that low coercivity could be realized by the control of the film composition. We also found that the Fe-rich films prepared from DES-based plating bath have some advantages as a soft magnetic phase for a nanocomposite magnet due to their high saturation magnetization and very fine crystal structure.

  19. Single Nanoparticle-Based Heteronanojunction as a Plasmon Ruler for Measuring Dielectric Thin Films.

    PubMed

    Li, Li; Hutter, Tanya; Li, Wenwu; Mahajan, Sumeet

    2015-06-18

    Nondestructive, noninvasive and accurate measurement of thin film thicknesses on dielectric substrates is challenging. In this work a ruler for measuring thin film thicknesses utilizes the heteronanojunction construct formed between a plasmonic nanoparticle and a high refractive index nonplasmonic substrate. The high near-field sensitivity in the nanojunction renders it suitable for measuring the thickness of intervening dielectric thin films. We demonstrate this by controlling the thickness of dielectric spacer layers created by overgrowing SiO2 thin films on commercially available silicon substrates. While Rayleigh (using dark-field) scattering measurements show that the spectral response is well correlated to the thickness of SiO2 spacer layers the distance-dependence is much steeper with surface-enhanced Raman scattering (SERS). Good agreement between 3D simulations and experimental results confirm the plasmon ruler construct's sensitivity to the dielectric thin film spacing. Thus, we postulate that this single nanoparticle based heteronanojunction configuration can serve as a convenient and simple ruler in metrology of thin films as well as a platform for SERS-based detection even in cases where plasmonically active films are not a suitable substrate. PMID:26266605

  20. Investigating the nature of graphene-based films prepared by vacuum filtration of graphene dispersions.

    PubMed

    Yi, Min; Liang, Shuaishuai; Liu, Lei; Shen, Zhigang; Zheng, Yiting; Zhang, Xiaojing; Ma, Shulin

    2014-07-01

    Though the graphene-based films prepared by vacuum filtration of graphene dispersions can be well and easily prepared so far and show great prospects in conductive, transparent, and flexible devices and coatings, the nature of these films has been rarely investigated. In order to reveal how graphene flakes constitute these films, herein we prepared a thin graphene-based film by vacuum filtering graphene dispersions and characterized the film by diverse techniques. Microscopic analyses evidenced the layer structure nature of the film. Raman spectra, transmission electron microscopy, and X-ray diffraction results indicate that the film is neither graphene nor graphite, but intrinsically a graphene block constituted by numerous graphene flakes which are randomly stacked. Though aggregation of graphene flakes happens in the filtration process, the aggregation is not a process to drive graphene flakes stacked in Bernal AB style to form bulk graphite. The adjoining graphene flakes are poorly coupled, likely due to the interlayer adventitious impurities introduced from liquid-phase processing. PMID:24757968

  1. High melt strength, tear resistant blown film based on poly(lactic acid)

    NASA Astrophysics Data System (ADS)

    Edmonds, Neil R.; Plimmer, Peter N.; Tanner, Chris

    2015-05-01

    A major problem associated with the commercial manufacture of thin films from PLA is inferior processing characteristics on blown film lines compared to low density polyethylene. PLA has poor melt strength (leading to bubble instability) and develops a permanent crease in the flattened film as it exits the tower of the film line. In addition, the thin film product has poor tear strength and an unacceptable `noise' level when converted into flexible packaging. Furthermore, fabricated articles based on PLA are known to show an unattractive tendency toward dimensional instability. This behaviour is associated with `cold crystallization', a phenomenon which also causes exudation of any plasticizer added for improving flexibility. Blow moulded articles based on PLA also exhibit dimensional sensitivity above 60°C. All of these issues have been overcome by the technology described in this paper. This has been accomplished without loss of the valuable compostability characteristic of PLA; this was confirmed by evaluation of film in a commercial composting operation. These results have been achieved through novel reactive compounding technology which: (a) Creates a PLA-rich structure containing long chain crosslinks, (b) generates a low glass transition temperature phase covalently bonded to the PLA structure, and (c) provides a material which performs like LDPE in a blown film manufacturing operation. The technology developed is covered by NZ Patent 580231 (3). The patent is held by UniServices Ltd, The University of Auckland, New Zealand.

  2. Zein-based films and their usage for controlled delivery: Origin, classes and current landscape.

    PubMed

    Zhang, Yong; Cui, Lili; Che, Xiaoxia; Zhang, Heng; Shi, Nianqiu; Li, Chunlei; Chen, Yan; Kong, Wei

    2015-05-28

    Zein is a class of alcohol-soluble prolamine proteins present in maize endosperm, which was approved as a generally recognized as safe (GRAS) excipient in 1985 by the United States Food and Drug Administration (US-FDA) for film coating of pharmaceuticals, e.g., tablets. Despite its long-term application in tablet production, effects of zein coating on tablet properties are still not fully understood. Moreover, many studies have also been conducted to illustrate its potential as an active ingredient of direct compressed tablets and film-based delivery carriers. In addition, the use of zein as a functional film coating material for new biomedical applications was also widely investigated in recent reports, which involved medical devices, nanoparticles, quantum dots and nanofibers. In this review, the present status of zein in the form of a thin film and uniform layer for use as a biomedical material is discussed. In addition, studies related to the behaviors and properties of zein films are also summarized and analyzed based on published works to gain mechanistic insights into the relationship between zein film and various improved profiles. This review will benefit future prospects of the use of zein film in drug delivery and biomedical applications. PMID:25828699

  3. Ammonia gas sensors based on poly (3-hexylthiophene)-molybdenum disulfide film transistors

    NASA Astrophysics Data System (ADS)

    Xie, Tao; Xie, Guangzhong; Su, Yuanjie; Hongfei, Du; Ye, Zongbiao; Jiang, Yadong

    2016-02-01

    In this work, in order to enhance the recovery performance of organic thin film transistors (OTFTs) ammonia (NH3) sensors, poly (3-hexylthiophene) (P3HT) and molybdenum disulfide (MoS2) were combined as sensitive materials. Different sensitive film structures as active layers of OTFTs, i.e., P3HT-MoS2 composite film, P3HT/MoS2 bilayer film and MoS2/P3HT bilayer film were fabricated by spray technology. OTFT gas sensors based on P3HT-MoS2 composite film showed a shorter recovery time than others when the ammonia concentration changed from 4 to 20 ppm. Specifically, x-ray diffraction (XRD), Raman and UV-visible absorption were employed to explore the interface properties between P3HT and single-layer MoS2. Through the complementary characterization, a mechanism based on charge transfer is proposed to explain the physical originality of these OTFT gas sensors: closer interlayer d-spacing and better π-π stacking of the P3HT chains in composite film have ensured a short recovery time of OTFT gas sensors. Moreover, sensing mechanisms of OTFTs were further studied by comparing the device performance in the presence of nitrogen or dry air as a carrier gas. This work not only strengthens the fundamental understanding of the sensing mechanism, but provides a promising approach to optimizing the OTFT gas sensors.

  4. Chemical sensing employingpH sensitive emeraldine base thin film for carbon dioxide detection

    NASA Astrophysics Data System (ADS)

    Irimia-Vladu, Mihai

    Respiration, or CO2 evolution, is a universal indicator for all the biological activities. Among many potential applications, the measurement of CO2 evolution has been found to be a rapid and nondestructive means for examining microbial contamination of food. The sensor developed in this work consists of a thin emeraldine base-polyaniline (EB-PAni) film. In the first half of the project the effect of carbon dioxide over the conductivity of a composite film of emeraldine base polyaniline and poly(vinyl alcohol) in N-methyl pyrrolidone (NMP) respectively was tested. Argon gas or mixture of argon and 5% CO2 were circulated through the glass cell containing the polymer film deposited on interdigitated electrode and exposed to specific humidity levels fixed by aqueous supersaturated salt solutions. In the second half of the project, a thin emeraldine base film in NMP was directly deposited on interdigitated electrode and the respective sensor inserted in water. Carbonic acid solutions of various pHs were generated by bubbling specific mixtures of carbon dioxide and argon. Conductivity measurements were performed by impedance spectroscopy throughout the project. The sensing mechanism is based on intermediate stages of the transformation of the emeraldine base polyaniline to a conductive salt type (ES-PAni). This EB-ES transformation is the consequence of the exposure of EB-PAni to a protonic acid and is accompanied by a change in the conductivity of the polymer film. Carbonic acid, unfortunately, is a very weak acid and is unable to induce a conductivity change, but the intermediate steps that predetermine this transformation are detected by impedance spectroscopy even when the overall conductivity of the film is unchanged. The composite thin film developed in the first part of the project showed poor sensing characteristics: limited dynamic range, drift, instability and slow time response. However, the sensor design employed in the second half of this work, coupled with

  5. Correcting scan-to-scan response variability for a radiochromic film-based reference dosimetry system

    SciTech Connect

    Lewis, David; Devic, Slobodan

    2015-10-15

    Purpose: In radiochromic film dosimetry systems, measurements are usually obtained from film images acquired on a CCD-based flatbed scanner. The authors investigated factors affecting scan-to-scan response variability leading to increased dose measurement uncertainty. Methods: The authors used flatbed document scanners to repetitively scan EBT3 radiochromic films exposed to doses 0–1000 cGy, together with three neutral density filters and three blue optical filters. Scanning was performed under two conditions: scanner lid closed and scanner lid opened/closed between scans. The authors also placed a scanner in a cold room at 9 °C and later in a room at 22 °C and scanned EBT3 films to explore temperature effects. Finally, the authors investigated the effect of altering the distance between the film and the scanner’s light source. Results: Using a measurement protocol to isolate the contribution of the CCD and electronic circuitry of the scanners, the authors found that the standard deviation of response measurements for the EBT3 film model was about 0.17% for one scanner and 0.09% for the second. When the lid of the first scanner was opened and closed between scans, the average scan-to-scan difference of responses increased from 0.12% to 0.27%. Increasing the sample temperature during scanning changed the RGB response values by about −0.17, −0.14, and −0.05%/°C, respectively. Reducing the film-to-light source distance increased the RBG response values about 1.1, 1.3, and 1.4%/mm, respectively. The authors observed that films and film samples were often not flat with some areas up to 8 mm away from the scanner’s glass window. Conclusions: In the absence of measures to deal with the response irregularities, each factor the authors investigated could lead to dose uncertainty >2%. Those factors related to the film-to-light source distance could be particularly impactful since the authors observed many instances where the curl of film samples had the

  6. Brain-based decoding of mentally imagined film clips and sounds reveals experience-based information patterns in film professionals.

    PubMed

    de Borst, Aline W; Valente, Giancarlo; Jääskeläinen, Iiro P; Tikka, Pia

    2016-04-01

    In the perceptual domain, it has been shown that the human brain is strongly shaped through experience, leading to expertise in highly-skilled professionals. What has remained unclear is whether specialization also shapes brain networks underlying mental imagery. In our fMRI study, we aimed to uncover modality-specific mental imagery specialization of film experts. Using multi-voxel pattern analysis we decoded from brain activity of professional cinematographers and sound designers whether they were imagining sounds or images of particular film clips. In each expert group distinct multi-voxel patterns, specific for the modality of their expertise, were found during classification of imagery modality. These patterns were mainly localized in the occipito-temporal and parietal cortex for cinematographers and in the auditory cortex for sound designers. We also found generalized patterns across perception and imagery that were distinct for the two expert groups: they involved frontal cortex for the cinematographers and temporal cortex for the sound designers. Notably, the mental representations of film clips and sounds of cinematographers contained information that went beyond modality-specificity. We were able to successfully decode the implicit presence of film genre from brain activity during mental imagery in cinematographers. The results extend existing neuroimaging literature on expertise into the domain of mental imagery and show that experience in visual versus auditory imagery can alter the representation of information in modality-specific association cortices. PMID:26826515

  7. Predicting the optoelectronic properties of nanowire films based on control of length polydispersity.

    PubMed

    Large, Matthew J; Burn, Jake; King, Alice A; Ogilvie, Sean P; Jurewicz, Izabela; Dalton, Alan B

    2016-01-01

    We demonstrate that the optoelectronic properties of percolating thin films of silver nanowires (AgNWs) are predominantly dependent upon the length distribution of the constituent AgNWs. A generalized expression is derived to describe the dependence of both sheet resistance and optical transmission on this distribution. We experimentally validate the relationship using ultrasonication to controllably vary the length distribution. These results have major implications where nanowire-based films are a desirable material for transparent conductor applications; in particular when application-specific performance criteria must be met. It is of particular interest to have a simple method to generalize the properties of bulk films from an understanding of the base material, as this will speed up the optimisation process. It is anticipated that these results may aid in the adoption of nanowire films in industry, for applications such as touch sensors or photovoltaic electrode structures. PMID:27158132

  8. Predicting the optoelectronic properties of nanowire films based on control of length polydispersity

    NASA Astrophysics Data System (ADS)

    Large, Matthew J.; Burn, Jake; King, Alice A.; Ogilvie, Sean P.; Jurewicz, Izabela; Dalton, Alan B.

    2016-05-01

    We demonstrate that the optoelectronic properties of percolating thin films of silver nanowires (AgNWs) are predominantly dependent upon the length distribution of the constituent AgNWs. A generalized expression is derived to describe the dependence of both sheet resistance and optical transmission on this distribution. We experimentally validate the relationship using ultrasonication to controllably vary the length distribution. These results have major implications where nanowire-based films are a desirable material for transparent conductor applications; in particular when application-specific performance criteria must be met. It is of particular interest to have a simple method to generalize the properties of bulk films from an understanding of the base material, as this will speed up the optimisation process. It is anticipated that these results may aid in the adoption of nanowire films in industry, for applications such as touch sensors or photovoltaic electrode structures.

  9. Heterojunction thin films based on multifunctional metal oxides for photovoltaic application

    SciTech Connect

    Prabhu, M.; Soundararajan, N.; Ramachandran, K.; Marikkannan, M.; Mayandi, J.

    2014-04-24

    Metal oxides based multifunctional heterojunction thin films of ZnO/SnO{sub 2} and ZnO/SnO{sub 2}/CuO QDs were prepared by spin-coating technique. The crystallographic properties and the surface morphologies of the films were studied by X-ray diffraction (XRD) and scanning electron microscopy (SEM), respectively. The optical absorption studies revealed that the film thickness has considerable effect on the band gap values and is found to be in the range of 3.73–3.48 eV. The photoluminescence spectra showed several weak visible emission peaks related to the deep level defects (450-575 nm). Finally, the current density-voltage (J-V) characteristic of ZnO/SnO{sub 2}/CuO QDs (ZSCI) based heterojunction thin film coated on ITO is also reported.

  10. Hydrogen gas sensor based on palladium and yttrium alloy ultrathin film

    NASA Astrophysics Data System (ADS)

    Yi, Liu; You-ping, Chen; Han, Song; Gang, Zhang

    2012-12-01

    Compared with the other hydrogen sensors, optical fiber hydrogen sensors based on thin films exhibits inherent safety, small volume, immunity to electromagnetic interference, and distributed remote sensing capability, but slower response characteristics. To improve response and recovery rate of the sensors, a novel reflection-type optical fiber hydrogen gas sensor with a 10 nm palladium and yttrium alloy thin film is fabricated. The alloy thin film shows a good hydrogen sensing property for hydrogen-containing atmosphere and a complete restorability for dry air at room temperature. The variation in response value of the sensor linearly increases with increased natural logarithm of hydrogen concentration (ln[H2]). The shortest response time and recovery response time to 4% hydrogen are 6 and 8 s, respectively. The hydrogen sensors based on Pd0.91Y0.09 alloy ultrathin film have potential applications in hydrogen detection and measurement.

  11. Photoluminescence-based quality control for thin film absorber layers of photovoltaic devices

    DOEpatents

    Repins, Ingrid L.; Kuciauskas, Darius

    2015-07-07

    A time-resolved photoluminescence-based system providing quality control during manufacture of thin film absorber layers for photovoltaic devices. The system includes a laser generating excitation beams and an optical fiber with an end used both for directing each excitation beam onto a thin film absorber layer and for collecting photoluminescence from the absorber layer. The system includes a processor determining a quality control parameter such as minority carrier lifetime of the thin film absorber layer based on the collected photoluminescence. In some implementations, the laser is a low power, pulsed diode laser having photon energy at least great enough to excite electron hole pairs in the thin film absorber layer. The scattered light may be filterable from the collected photoluminescence, and the system may include a dichroic beam splitter and a filter that transmit the photoluminescence and remove scattered laser light prior to delivery to a photodetector and a digital oscilloscope.

  12. Predicting the optoelectronic properties of nanowire films based on control of length polydispersity

    PubMed Central

    Large, Matthew J.; Burn, Jake; King, Alice A.; Ogilvie, Sean P.; Jurewicz, Izabela; Dalton, Alan B.

    2016-01-01

    We demonstrate that the optoelectronic properties of percolating thin films of silver nanowires (AgNWs) are predominantly dependent upon the length distribution of the constituent AgNWs. A generalized expression is derived to describe the dependence of both sheet resistance and optical transmission on this distribution. We experimentally validate the relationship using ultrasonication to controllably vary the length distribution. These results have major implications where nanowire-based films are a desirable material for transparent conductor applications; in particular when application-specific performance criteria must be met. It is of particular interest to have a simple method to generalize the properties of bulk films from an understanding of the base material, as this will speed up the optimisation process. It is anticipated that these results may aid in the adoption of nanowire films in industry, for applications such as touch sensors or photovoltaic electrode structures. PMID:27158132

  13. Porous cobalt-based thin film as a bifunctional catalyst for hydrogen generation and oxygen generation.

    PubMed

    Yang, Yang; Fei, Huilong; Ruan, Gedeng; Tour, James M

    2015-05-27

    A mixed-phased Co-based catalyst composed of Co phosphide and Co phosphate is successfully fabricated for bifunctional water electrolysis. The highly porous morphology in this anodized film enables efficient catalytic activity toward water splitting in an extremely low loading mass. The mixed phases in the porous film afford an ability to generate both H2 and O2 in a single electrolyzer. PMID:25872881

  14. Study of oxygen scavenging PET-based films activated by water

    NASA Astrophysics Data System (ADS)

    Rossi, Gabriella; Scarfato, Paola; Incarnato, Loredana

    2016-05-01

    In this work an active barrier system consisting of a thin and transparent film based on polyethylene terephthalate (PET) was studied. Dynamic oxygen absorption measurements were performed at different values of relative humidity and temperature, pointing out that humidity is a key factor in activating the oxidation of the polymer sample. Moreover, the thermal and optical properties of the films were investigated and a good correlation was found between the crystallinity increase and the consequent transparency reduction occurring after the oxygen absorption.

  15. Conductivity of Thin Films Based on Single-Walled Carbon Nanotubes Grown by Chemical Vapor Deposition

    NASA Astrophysics Data System (ADS)

    Rybakov, M. S.; Kosobutsky, A. V.; Sevostyanov, O. G.; Russakov, D. M.; Lomakin, M. V.; Chirkova, I. M.; Shandakov, S. D.

    2015-03-01

    Electrical and optical properties of thin films of single-walled carbon nanotubes (SWCNT) obtained by aerosol chemical vapor deposition using ethanol, ferrocene, and sulfur are studied. Structural and geometrical characteristics of the synthesis products are determined by the methods of Raman spectroscopy and transmission electron microscopy. The effect of sulfur on the properties of the SWCNTs and thin films based on them is found.

  16. The mechanisms of plant stress mitigation by kaolin-based particle films and its applications in horticultural and agricultural crops

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Kaolin-based particle films have utility in reducing insect, heat, light, and uv stress in plants due to the reflective nature of the particles. Particle films with a residue density of 1 to 3 g/ square meter have been evaluated in a range of crops and agricultural environments. The particle film ...

  17. An Iron-based Film for Highly Efficient Electrocatalytic Oxygen Evolution from Neutral Aqueous Solution.

    PubMed

    Chen, Mingxing; Wu, Yizhen; Han, Yongzhen; Lin, Xiaohuan; Sun, Junliang; Zhang, Wei; Cao, Rui

    2015-10-01

    An ultrathin Fe-based film was prepared by electrodeposition from an Fe(II) solution through a fast and simple cyclic voltammetry method. The extremely low Fe loading of 12.3 nmol cm(-2) on indium tin oxide electrodes is crucial for high atom efficiency and transparence of the resulted film. This Fe-based film was shown to be a very efficient electrocatalyst for oxygen evolution from neutral aqueous solution with remarkable activity and stability. In a 34 h controlled potential electrolysis at 1.45 V (vs NHE) and pH 7.0, impressive turnover number of 5.2 × 10(4) and turnover frequency of 1528 h(-1) were obtained. To the best of our knowledge, these values represent one of the highest among electrodeposited catalyst films for water oxidation under comparable conditions. The morphology and the composition of the catalyst film was determined by scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray, and X-ray photoelectron spectroscopy, which all confirmed the deposition of Fe-based materials with Fe(III) oxidation state on the electrode. This study is significant because of the use of iron, the fast and simple cyclic voltammetry electrodeposition, the extremely low catalyst loading and thus the transparency of the catalyst film, the remarkable activity and stability, and the oxygen evolution in neutral aqueous media. PMID:26368828

  18. Leaching-resistant carrageenan-based colorimetric oxygen indicator films for intelligent food packaging.

    PubMed

    Vu, Chau Hai Thai; Won, Keehoon

    2014-07-23

    Visual oxygen indicators can give information on the quality and safety of packaged food in an economic and simple manner by changing color based on the amount of oxygen in the packaging, which is related to food spoilage. In particular, ultraviolet (UV)-activated oxygen indicators have the advantages of in-pack activation and irreversibility; however, these dye-based oxygen indicator films suffer from dye leaching upon contact with water. In this work, we introduce carrageenans, which are natural sulfated polysaccharides, to develop UV-activated colorimetric oxygen indicator films that are resistant to dye leakage. Carrageenan-based indicator films were fabricated using redox dyes [methylene blue (MB), azure A, and thionine], a sacrificial electron donor (glycerol), an UV-absorbing photocatalyst (TiO2), and an encapsulation polymer (carrageenan). They showed even lower dye leakage in water than conventional oxygen indicator films, owing to the electrostatic interaction of anionic carrageenan with cationic dyes. The MB/TiO2/glycerol/carrageenan oxygen indicator film was successfully bleached upon UV irradiation, and it regained color very rapidly in the presence of oxygen compared to the other waterproof oxygen indicator films. PMID:24979322

  19. Characterization of constitutional liquid film migration in nickel-base alloy 718

    NASA Astrophysics Data System (ADS)

    Acoff, V. L.; Thompson, R. G.

    1996-09-01

    When multiphase alloys are rapidly heated, it is possible to cause melting of the interface between phases. This is called constitutional liquation if, during melting, the bulk composition is in a nonliquid region of the phase diagram but the tie-line between the liquating phases passes through a liquid region. The liquid produced during constitutional liquation can spread along grain boundaries and promote liquid film migration (LFM). This is known as constitutional liquid film migration (CLFM), which is thermodynamically similar to liquid film migration; however, mechanistically there are significant differences. Nickel-base alloy 718 has been studied to show the features of migration that are unique to CLFM. Experimentation consisted of heat-treating rods of alloy 718 to promote the trapping of niobium carbide particles on the grain boundaries. These samples were then subjected to isothermal treatments above their constitutional-liquation temperature, which produced CLFM of the grain boundaries. The movement of the liquid films away from their centers of curvature, the formation of a new solid solution behind the migrated liquid films, and the reversals of curvature of the migrated liquid films confirmed that CLFM was the phenomenon observed. The concentration of niobium behind the migrated liquid films for isothermal treatments below the solidus temperature was shown to be greater than the niobium concentration in the matrix. Above the solidus temperature, there was no increase in niobium concentration. The validity of the coherency strain hypothesis as the driving force for CLFM in alloy 718 is discussed.

  20. Terahertz ultrathin film thickness sensor below λ/90 based on metamaterial.

    PubMed

    Chen, Meng; Fan, Fei; Shen, Si; Wang, Xianghui; Chang, Shengjiang

    2016-08-10

    The film thickness sensing based on metamaterial is investigated in the terahertz (THz) region. We fabricated the metamaterial sensor, and demonstrated its resonance by using the THz time-domain spectroscopy system. The results show that the resonant dip redshifts as the film thickness increases, which achieves reliable film sensing in the THz band. Its sensitivity is larger than 9.4 GHz/μm with a film thinner than λ/90. Meanwhile, the sensing mechanism is revealed by the simulation of near-field resonance distribution, which shows that the resonant intensity is stronger when the field is closer to the interface between the metamaterial surface and polyvinyl alcohol film. Therefore, the nonlinear type of the sensing sensitivity in our experiment can be well explained, and a higher sensitive sensing can be obtained when the film thickness is smaller. This simple and flexible method can realize the ultrathin film sensing in the THz region, and has application potential in the real-time monitoring of sample quality. PMID:27534497

  1. Temperature dependence of resistive switching behaviors in resistive random access memory based on graphene oxide film

    NASA Astrophysics Data System (ADS)

    Yi, Mingdong; Cao, Yong; Ling, Haifeng; Du, Zhuzhu; Wang, Laiyuan; Yang, Tao; Fan, Quli; Xie, Linghai; Huang, Wei

    2014-05-01

    We reported resistive switching behaviors in the resistive random access memory (RRAM) devices based on the different annealing temperatures of graphene oxide (GO) film as active layers. It was found that the resistive switching characteristics of an indium tin oxide (ITO)/GO/Ag structure have a strong dependence on the annealing temperature of GO film. When the annealing temperature of the GO film was 20 °C, the devices showed typical write-once-read-many-times (WORM) type memory behaviors, which have good memory performance with a higher ON/OFF current ratio (˜104), the higher the high resistance state (HRS)/low resistance state (LRS) ratio (˜105) and stable retention characteristics (>103 s) under lower programming voltage (-1 V and -0.5 V). With the increasing annealing temperature of GO film, the resistive switching behavior of RRAM devices gradually weakened and eventually disappeared. This phenomenon could be understood by the different energy level distributions of the charge traps in GO film, and the different charge injection ability from the Ag electrode to GO film, which is caused by the different annealing temperatures of the GO film.

  2. Development and Characterization of Edible Films Based on Fruit and Vegetable Residues.

    PubMed

    Andrade, Roberta M S; Ferreira, Mariana S L; Gonçalves, Édira C B A

    2016-02-01

    Edible films were developed from the solid residue of the processing of whole fruits and vegetables. The solid residue, processed into flour (FVR flour) was chemically and structurally characterized by microstructure, elemental composition, structural links, and moisture sorption isotherm. Films were prepared by casting using aqueous extracts of 8% and 10% of flour (w/w) and characterized in terms of thickness, water solubility, mechanical properties, water vapor permeability, and Fourier transform infrared (FTIR). The analysis of microstructure and elemental composition, performed on flour (mean particle size 350 μm), showed an essentially granular aspect, with the presence of fibrous particles having potassium as one of the most abundant elements. FTIR results showed similarity between the characteristic bands of other raw materials used in edible films. The sorption isotherm of FVR flour showed a typical profile of foods rich in soluble components, such as sugars. Dried films presented an average thickness of 0.263 ± 0.003 mm, a homogenous aspect, bright yellow color, pronounced fruit flavor, and high water solubility. The FTIR spectra of the edible films revealed that addition of potato skin flour did not change the molecular conformation. Moreover, the films presented low tensile strength at break when compared with fruit starch-based films. PMID:26766297

  3. Composite film polarizer based on the oriented assembly of electrospun nanofibers

    NASA Astrophysics Data System (ADS)

    Hu, Zhongliang; Ma, Zhijun; Peng, Mingying; He, Xin; Zhang, Hang; Li, Yang; Qiu, Jianrong

    2016-04-01

    Polarizers are widely applied in antiglare glasses, planner displays, photography filters and optical communications, etc. In this investigation, we propose a new strategy for the preparation of a flexible film polarizer based on the electrospinning technique. An aligned assembly of polyvinyl acetate (PVA) nanofibers was electrospun and collected by a fast-rotating drum, then soaked in polymethyl methacrylate (PMMA) solution and dried thoroughly to obtain a transparent PVA-PMMA composite film polarizer. The morphology, structure and optical performance of the PVA nanofibers and the film polarizers were characterized with a scanning electron microscope, UV-vis-IR spectrometer and polarized Raman spectra, etc. The PVA-PMMA film polarizer demonstrated efficient polarizing activity toward visible and near-infrared light, while keeping fair transparency in the range of 400-1400 nm. Due to the protection from the hydrophobic PMMA matrix, the PVA-PMMA film polarizers show high moisture resistance, making it applicable in a humid environment. Considering the scalability and versatility of the strategy employed here, the PVA-PMMA film polarizer prepared could replace the conventional film polarizers in a wide range of applications.

  4. Transmission enhancement based on strong interference in metal-semiconductor layered film for energy harvesting

    PubMed Central

    Li, Qiang; Du, Kaikai; Mao, Kening; Fang, Xu; Zhao, Ding; Ye, Hui; Qiu, Min

    2016-01-01

    A fundamental strategy to enhance optical transmission through a continuous metallic film based on strong interference dominated by interface phase shift is developed. In a metallic film coated with a thin semiconductor film, both transmission and absorption are simultaneously enhanced as a result of dramatically reduced reflection. For a 50-nm-thick Ag film, experimental transmission enhancement factors of 4.5 and 9.5 are realized by exploiting Ag/Si non-symmetric and Si/Ag/Si symmetric geometries, respectively. These planar layered films for transmission enhancement feature ultrathin thickness, broadband and wide-angle operation, and reduced resistance. Considering one of their potential applications as transparent metal electrodes in solar cells, a calculated 182% enhancement in the total transmission efficiency relative to a single metallic film is expected. This strategy relies on no patterned nanostructures and thereby may power up a wide spectrum of energy-harvesting applications such as thin-film photovoltaics and surface photocatalysis. PMID:27404510

  5. Facile Fabrication of Gradient Surface Based on (meth)acrylate Copolymer Films

    NASA Astrophysics Data System (ADS)

    Zhang, Y.; Yang, H.; Wen, X.-F.; Cheng, J.; Xiong, J.

    2016-08-01

    This paper describes a simple and economic approach for fabrication of surface wettability gradient on poly(butyl acrylate - methyl methacrylate) [P (BA-MMA)] and poly(butyl acrylate - methyl methacrylate - 2-hydroxyethyl methacrylate) [P (BA-MMA-HEMA)] films. The (meth)acrylate copolymer [including P (BA-MMA) and P (BA-MMA-HEMA)] films are hydrolyzed in an aqueous solution of NaOH and the transformation of surface chemical composition is achieved by hydrolysis in NaOH solution. The gradient wetting properties are generated based on different functional groups on the P (BA-MMA) and P (BA-MMA-HEMA) films. The effects of both the surface chemical and surface topography on wetting of the (meth)acrylate copolymer film are discussed. Surface chemical composition along the materials length is determined by XPS, and surface topography properties of the obtained gradient surfaces are analyzed by FESEM and AFM. Water contact angle system (WCAs) results show that the P (BA-MMA-HEMA) films provide a larger slope of the gradient wetting than P (BA-MMA). Moreover, this work demonstrates that the gradient concentration of chemical composition on the poly(meth) acrylate films is owing to the hydrolysis processes of ester group, and the hydrolysis reactions that have negligible influence on the surface morphology of the poly(meth) acrylate films coated on the glass slide. The gradient wettability surfaces may find broad applications in the field of polymer coating due to the compatibility of (meth) acrylate polymer.

  6. Polyamines as new cationic plasticizers for pectin-based edible films.

    PubMed

    Esposito, Marilena; Di Pierro, Prospero; Regalado-Gonzales, Carlos; Mariniello, Loredana; Giosafatto, C Valeria L; Porta, Raffaele

    2016-11-20

    Zeta potential and particle size were determined on pectin aqueous solutions as a function of pH and the effects of calcium ions, putrescine and spermidine on pectin film forming solutions and derived films were studied. Ca(2+) and polyamines were found to differently influence pectin zeta potential as well as thickness and mechanical and barrier properties of pectin films prepared at pH 7.5 either in the presence or absence of the plasticizer glycerol. In particular, Ca(2+) was found to increase film tensile strength and elongation at break only in the presence of glycerol and did not affect film thickness and permeability to both water vapor and CO2. Conversely, increasing polyamine concentrations progressively reduced film tensile strength and markedly enhanced film thickness, elongation at break and permeability to water vapor and CO2, both in the presence and absence of glycerol. Our findings indicate that polyamines give rise to a structural organization of the heteropolysaccharide different from that determined by calcium ions, previously described as "egg box" model, and suggest their possible application as plasticizers to produce pectin-based "bioplastics" with different features. PMID:27561490

  7. Transmission enhancement based on strong interference in metal-semiconductor layered film for energy harvesting.

    PubMed

    Li, Qiang; Du, Kaikai; Mao, Kening; Fang, Xu; Zhao, Ding; Ye, Hui; Qiu, Min

    2016-01-01

    A fundamental strategy to enhance optical transmission through a continuous metallic film based on strong interference dominated by interface phase shift is developed. In a metallic film coated with a thin semiconductor film, both transmission and absorption are simultaneously enhanced as a result of dramatically reduced reflection. For a 50-nm-thick Ag film, experimental transmission enhancement factors of 4.5 and 9.5 are realized by exploiting Ag/Si non-symmetric and Si/Ag/Si symmetric geometries, respectively. These planar layered films for transmission enhancement feature ultrathin thickness, broadband and wide-angle operation, and reduced resistance. Considering one of their potential applications as transparent metal electrodes in solar cells, a calculated 182% enhancement in the total transmission efficiency relative to a single metallic film is expected. This strategy relies on no patterned nanostructures and thereby may power up a wide spectrum of energy-harvesting applications such as thin-film photovoltaics and surface photocatalysis. PMID:27404510

  8. Composite film polarizer based on the oriented assembly of electrospun nanofibers.

    PubMed

    Hu, Zhongliang; Ma, Zhijun; Peng, Mingying; He, Xin; Zhang, Hang; Li, Yang; Qiu, Jianrong

    2016-04-01

    Polarizers are widely applied in antiglare glasses, planner displays, photography filters and optical communications, etc. In this investigation, we propose a new strategy for the preparation of a flexible film polarizer based on the electrospinning technique. An aligned assembly of polyvinyl acetate (PVA) nanofibers was electrospun and collected by a fast-rotating drum, then soaked in polymethyl methacrylate (PMMA) solution and dried thoroughly to obtain a transparent PVA-PMMA composite film polarizer. The morphology, structure and optical performance of the PVA nanofibers and the film polarizers were characterized with a scanning electron microscope, UV-vis-IR spectrometer and polarized Raman spectra, etc. The PVA-PMMA film polarizer demonstrated efficient polarizing activity toward visible and near-infrared light, while keeping fair transparency in the range of 400-1400 nm. Due to the protection from the hydrophobic PMMA matrix, the PVA-PMMA film polarizers show high moisture resistance, making it applicable in a humid environment. Considering the scalability and versatility of the strategy employed here, the PVA-PMMA film polarizer prepared could replace the conventional film polarizers in a wide range of applications. PMID:26894877

  9. Temperature dependence of resistive switching behaviors in resistive random access memory based on graphene oxide film.

    PubMed

    Yi, Mingdong; Cao, Yong; Ling, Haifeng; Du, Zhuzhu; Wang, Laiyuan; Yang, Tao; Fan, Quli; Xie, Linghai; Huang, Wei

    2014-05-01

    We reported resistive switching behaviors in the resistive random access memory (RRAM) devices based on the different annealing temperatures of graphene oxide (GO) film as active layers. It was found that the resistive switching characteristics of an indium tin oxide (ITO)/GO/Ag structure have a strong dependence on the annealing temperature of GO film. When the annealing temperature of the GO film was 20 °C, the devices showed typical write-once-read-many-times (WORM) type memory behaviors, which have good memory performance with a higher ON/OFF current ratio (∼10(4)), the higher the high resistance state (HRS)/low resistance state (LRS) ratio (∼10(5)) and stable retention characteristics (>10(3) s) under lower programming voltage (-1 V and -0.5 V). With the increasing annealing temperature of GO film, the resistive switching behavior of RRAM devices gradually weakened and eventually disappeared. This phenomenon could be understood by the different energy level distributions of the charge traps in GO film, and the different charge injection ability from the Ag electrode to GO film, which is caused by the different annealing temperatures of the GO film. PMID:24739543

  10. Antimicrobial effects of alginate-based film containing essential oils for the preservation of whole beef muscle.

    PubMed

    Oussalah, Mounia; Caillet, Stéphane; Salmiéri, Stéphane; Saucier, Linda; Lacroix, Monique

    2006-10-01

    Alginate-based edible films containing 1% (wt/vol) essential oils of Spanish oregano, Chinese cinnamon, or savory were immersed in 2% (wt/vol) or 20% (wt/vol) CaCl2 solution and then applied to beef muscle slices to control the growth of Escherichia coli O157:H7 and Salmonella Typhimurium. Whole beef muscle surfaces were inoculated with one of these strains at 10(3) CFU/cm2. During the 5 days of storage, samples of meat were obtained periodically for microbiological analysis. The availability of active compounds from essential oils present in films was evaluated by determination of total phenolic compounds for oregano- and savory-based films and of total aldehydes for cinnamon-based films during storage. After 5 days of storage, films containing oregano or cinnamon essential oils were the most effective against Salmonella Typhimurium regardless of the type of pretreatment used (2 or 20% CaCl2). During the same period, meat inoculated with E. coli O157:H7 and coated with films treated with 2% CaCl2 had significantly fewer bacteria (P < or = 0.05) when oregano-based films were used than when cinnamon- and savory-based films were used. The E. coli O157:H7 concentration was higher at the end of the storage period when films were pretreated with 20% CaCl2. Evaluation of the active compounds in films revealed that availability in oregano- and savory-based films was significantly more important (P < or = 0.05) than that in cinnamon-based films regardless of the type of pretreatment used (2 or 20% CaCl2). At the end of storage, release rates of 40, 60, and 77% were noted in oregano-, savory-, and cinnamon-based films in 2% CaCl2 and rates of 65, 62, and 90% were noted in the same films in 20% CaCl2. PMID:17066914

  11. Physical, Chemical and Biochemical Modifications of Protein-Based Films and Coatings: An Extensive Review.

    PubMed

    Zink, Joël; Wyrobnik, Tom; Prinz, Tobias; Schmid, Markus

    2016-01-01

    Protein-based films and coatings are an interesting alternative to traditional petroleum-based materials. However, their mechanical and barrier properties need to be enhanced in order to match those of the latter. Physical, chemical, and biochemical methods can be used for this purpose. The aim of this article is to provide an overview of the effects of various treatments on whey, soy, and wheat gluten protein-based films and coatings. These three protein sources have been chosen since they are among the most abundantly used and are well described in the literature. Similar behavior might be expected for other protein sources. Most of the modifications are still not fully understood at a fundamental level, but all the methods discussed change the properties of the proteins and resulting products. Mastering these modifications is an important step towards the industrial implementation of protein-based films. PMID:27563881

  12. Tunable permalloy-based films for magnonic devices

    NASA Astrophysics Data System (ADS)

    Yin, Yuli; Pan, Fan; Ahlberg, Martina; Ranjbar, Mojtaba; Dürrenfeld, Philipp; Houshang, Afshin; Haidar, Mohammad; Bergqvist, Lars; Zhai, Ya; Dumas, Randy K.; Delin, Anna; Åkerman, Johan

    2015-07-01

    Using both broadband ferromagnetic resonance (FMR) spectroscopy and ab initio calculations, we study the magnetodynamic properties of permalloy (Py,Ni80Fe20) and Py100 -xMx films with M as platinum (Pt), gold (Au), or silver (Ag). From the uniform FMR mode, we extract the saturation magnetization (MS), damping (α ), and inhomogeneous broadening (Δ H0) ; from the first perpendicular standing spin-wave (PSSW) mode, we extract the exchange stiffness (A ). MS and A are found to decrease with increasing alloying, most strongly for Au and less so for Pt. On the other hand, α increases rapidly with both Pt and Au content, while being virtually independent of Ag content. The physical origins of the observed trends in α , MS, and A are analyzed and explained using density functional theory calculations in the coherent potential approximation. The calculated trends quantitatively agree with the experimental observations. The drastically different impacts of Pt, Au, and Ag on the various fundamental magnetodynamic properties will allow for significant design freedom, where different properties can be varied independently of others through careful combinations of the Pt, Au, and Ag contents of Py100 -xMx films. By empirical approximations of each property's concentration dependence, we can dial in any desired combination of magnetodynamic properties within this parameter space. As a proof-of-principle demonstration we design a set of Py100 -x -yPtxAgy films, where the saturation magnetization stays constant throughout the set and the damping can be tuned by a factor of 4.

  13. Perpendicular Magnetic Anisotropy in Co-Based Full Heusler Alloy Thin Films

    NASA Astrophysics Data System (ADS)

    Wu, Y.; Xu, X. G.; Miao, J.; Jiang, Y.

    2015-12-01

    Half-metallic Co-based full Heusler alloys have been qualified as promising functional materials in spintronic devices due to their high spin polarization. The lack of perpendicular magnetic anisotropy (PMA) is one of the biggest obstacles restricting their application in next generation ultrahigh density storage such as magnetic random access memory (MARM). How to induce the PMA in Co-based full Heusler alloy thin films has attracted much research interest of scientists. This paper presents an overview of recent progress in this research area. We hope that this paper would provide some guidance and ideas to develop highly spin-polarized Co-based Heusler alloy thin films with PMA.

  14. Poster — Thur Eve — 20: CTDI Measurements using a Radiochromic Film-based clinical protocol

    SciTech Connect

    Quintero, C.; Bekerat, H.; DeBlois, F.; Tomic, N.; Devic, S.; Seuntjens, J.

    2014-08-15

    The purpose of the study was evaluating accuracy and reproducibility of a radiochromic film-based protocol to measure computer tomography dose index (CTDI) as a part of annual QA on CT scanners and kV-CBCT systems attached to linear accelerators. Energy dependence of Gafchromic XR-QA2 ® film model was tested over imaging beam qualities (50 – 140 kVp). Film pieces were irradiated in air to known values of air-kerma (up to 10 cGy). Calibration curves for each beam quality were created (Film reflectance change Vs. Air-kerma in air). Film responses for same air-kerma values were compared. Film strips were placed into holes of a CTDI phantom and irradiated for several clinical scanning protocols. Film reflectance change was converted into dose to water and used to calculate CTDIvol values. Measured and tabulated CTDIvol values were compared. Average variations of ±5.2% in the mean film reflectance change were observed in the energy range of 80 to 140 keV, and 11.1% between 50 and 140 keV. Measured CTDI values were in average 10% lower than tabulated CTDI values for CT-simulators, and 44% higher for CBCT systems. Results presented a mean variation for the same machine and protocol of 2.6%. Variation of film response is within ±5% resulting in ±15% systematic error in dose estimation if a single calibration curve is used. Relatively large discrepancy between measured and tabulated CTDI values strongly support the trend towards replacing CTDI value with equilibrium dose measurement in the center of cylindrical phantom, as suggested by TG- 111.

  15. Optical multilayer films based on an amorphous fluoropolymer

    SciTech Connect

    Chow, R.; Loomis, G.E.; Ward, R.L.

    1996-01-01

    Multilayered coatings were made by physical vapor deposition (PVD) of a perfluorinated amorphous polymer, Teflon AF2400, and with other optical materials. A high reflector for 1064 nm light was made with ZnS and AF2400. An all-organic 1064 nm reflector was made from AF2400 and polyethylene. Oxide (HfO{sub 2} and SiO{sub 2}) compatibility with AF2400 was also tested. The multilayer morphologies were influenced by coating stress and unintentional temperature rises from the PVD process. Analysis by liquid nuclear magnetic resonance of the thin films showed slight compositional variations between the coating and starting materials of perfluorinated amorphous polymers.

  16. Methodology for cost analysis of film-based and filmless portable chest systems

    NASA Astrophysics Data System (ADS)

    Melson, David L.; Gauvain, Karen M.; Beardslee, Brian M.; Kraitsik, Michael J.; Burton, Larry; Blaine, G. James; Brink, Gary S.

    1996-05-01

    Many studies analyzing the costs of film-based and filmless radiology have focused on multi- modality, hospital-wide solutions. Yet due to the enormous cost of converting an entire large radiology department or hospital to a filmless environment all at once, institutions often choose to eliminate film one area at a time. Narrowing the focus of cost-analysis may be useful in making such decisions. This presentation will outline a methodology for analyzing the cost per exam of film-based and filmless solutions for providing portable chest exams to Intensive Care Units (ICUs). The methodology, unlike most in the literature, is based on parallel data collection from existing filmless and film-based ICUs, and is currently being utilized at our institution. Direct costs, taken from the perspective of the hospital, for portable computed radiography chest exams in one filmless and two film-based ICUs are identified. The major cost components are labor, equipment, materials, and storage. Methods for gathering and analyzing each of the cost components are discussed, including FTE-based and time-based labor analysis, incorporation of equipment depreciation, lease, and maintenance costs, and estimation of materials costs. Extrapolation of data from three ICUs to model hypothetical, hospital-wide film-based and filmless ICU imaging systems is described. Performance of sensitivity analysis on the filmless model to assess the impact of anticipated reductions in specific labor, equipment, and archiving costs is detailed. A number of indirect costs, which are not explicitly included in the analysis, are identified and discussed.

  17. Influence of Molecular Rigidity on Interfacial Ordering in Diphenyl-Based Polysiloxane Films

    SciTech Connect

    Evmenenko,G.; Kewalramani, S.; Dutta, P.

    2007-01-01

    Synchrotron X-ray reflectivity (XRR) shows significant differences between the ordering in thin films of diphenyl-based siloxane oligomers with single versus double backbones of -Si-O- repeating groups. We show that the more restricted conformational arrangement of twofold-skeleton molecules results in a higher degree of molecular ordering indicated by 2-2.5 times higher value of intensity of the corresponding Bragg peak in thin solid films of poly(phenylsilsesquioxane) than in films of poly(diphenylsiloxane), regardless of the solvent used for film casting. In both cases, the ordered molecules are located within 40-50 Angstroms of the substrate surface. The results indicate unambiguously that the chain stiffness of siloxanes governs the degree of ordering in the restricted geometry of the interfacial region.

  18. Electroluminescent ZnS:Mn films prepared by an MOCVD method based on dithiocarbamate precursors

    NASA Astrophysics Data System (ADS)

    Zavyalova, L. V.; Beletski, A. I.; Svechnikov, G. S.

    1999-05-01

    It is shown that electroluminescent ZnS:Mn films with luminance more than 0268-1242/14/5/013/img6 and luminous efficiency 0268-1242/14/5/013/img7 can be obtained by low-temperature deposition from Mn and Zn dithiocarbamates; subsequent thermal treatment of these films is not necessary. Starting materials were deposited on the substrate heated to a temperature of 220-0268-1242/14/5/013/img8C by spraying organic solution in air at atmospheric pressure. As a result homogeneous polycrystalline layers of ZnS:Mn with a growth rate of 60-0268-1242/14/5/013/img9 have been obtained. The electroluminescent characteristics of the thin films and structures based on various preparation and excitation conditions are presented. The possibility of application of these films as a planar light source is discussed.

  19. Structural and optical investigation of Te-based chalcogenide thin films

    SciTech Connect

    Sharma, Rita Sharma, Shaveta; Thangaraj, R.; Mian, M.; Chander, Ravi; Kumar, Praveen

    2015-05-15

    We report the structural and optical properties of thermally evaporated Bi{sub 2}Te{sub 3}, In{sub 2}Te{sub 3} and InBiTe{sub 3} films by using X-ray diffraction, optical and Raman Spectroscopy techniques. The as-prepared thin films were found to be Semi-crystalline by X-ray diffraction. Particle Size and Strain has been calculated from XRD data. The optical constants, film thickness, refractive index and optical band gap (E{sub g}) has been reported for In{sub 2}Te{sub 3}, InBiTe{sub 3} films. Raman Spectroscopy was performed to investigate the effect of Bi, In, on lattice vibration and chemical bonding in Te based chalcogenide glassy alloys.

  20. Transparent sunlight conversion film based on carboxymethyl cellulose and carbon dots.

    PubMed

    You, Yaqin; Zhang, Haoran; Liu, Yingliang; Lei, Bingfu

    2016-10-20

    Transparent sunlight conversion film based on carboxymethyl cellulose (CMC) and carbon dots (CDs) has been developed for the first time through dispersion of CDs in CMC aqueous solution. Due to the hydrogen bonds interaction, CMC can effectively absorb the CDs, whose surfaces are functionalized by lots of polar groups. The results from atomic force microscopy (AFM), scanning electron microscopy (SEM) confirm that the composite film possesses a homogeneous and compact structure. Besides, the CMC matrix neither competes for absorbing excitation light nor absorbs the emissions of CDs, which reserves the inherent optical properties of the individual CDs. The composite films can efficiently convert ultraviolet light to blue light. What's more, the film is transparent and possesses excellent mechanical properties, expected to apply in the field of agricultural planting for sunlight conversion. PMID:27474564

  1. Tunable electrical conductivity in oriented thin films of tetrathiafulvalene-based covalent organic framework

    SciTech Connect

    Cai, SL; Zhang, YB; Pun, AB; He, B; Yang, JH; Toma, FM; Sharp, ID; Yaghi, OM; Fan, J; Zheng, SR; Zhang, WG; Liu, Y

    2014-09-16

    Despite the high charge-carrier mobility in covalent organic frameworks (COFs), the low intrinsic conductivity and poor solution processability still impose a great challenge for their applications in flexible electronics. We report the growth of oriented thin films of a tetrathiafulvalene-based COF (TTF-COF) and its tunable doping. The porous structure of the crystalline TTF-COF thin film allows the diffusion of dopants such as I-2 and tetracyanoquinodimethane (TCNQ) for redox reactions, while the closely packed 2D grid sheets facilitate the cross-layer delocalization of thus-formed TTF radical cations to generate more conductive mixed-valence TTF species, as is verified by UV-vis-NIR and electron paramagnetic resonance spectra. Conductivity as high as 0.28 S m(-1) is observed for the doped COF thin films, which is three orders of magnitude higher than that of the pristine film and is among the highest for COF materials.

  2. Nanometric thin polymeric films based on molecularly imprinted technology: towards electrochemical sensing applications.

    PubMed

    Ginzburg-Turgeman, Roni; Mandler, Daniel

    2010-09-28

    A new approach for assembling selective electrodes based on molecularly imprinted polymers (MIPs) is presented. The approach is based on the radical polymerization of a mixture of methacrylic acid (MAA) and ethyleneglycol dimethacrylate (EGDMA) in the presence of an initiator, benzoyl peroxide (BPO) and an activator, N,N'-dimethyl-p-toluidine (DMpT) at room temperature and atmospheric pressure. To form nanometric thin polymeric films the polymerization solution was spin-coated in the course of polymerization. The different physical and chemical parameters that affected the properties of the films, such as the spinning rate and the EGDMA:MAA ratio, were studied and optimized. A variety of techniques, e.g., rheoscopy, SEM, AFM, profilometry and electrochemistry, were used to characterize the films and the polymerization process. By optimizing the conditions very thin and reproducible films could be prepared and imprinted. The electrochemical behavior of the films showed that they were permeable to water-soluble electroactive species providing that either polyethylene glycol or template species were added to the polymerization mixture. Finally, we demonstrated that films imprinted with ferrocenylmethyl alcohol (Fc-MeOH) successfully extracted the imprinted species after their removal from MIPs. PMID:20668737

  3. Photoinduced effect in Ga Ge S based thin films

    NASA Astrophysics Data System (ADS)

    Messaddeq, S. H.; Li, M. Siu; Inoue, S.; Ribeiro, S. J. L.; Messaddeq, Y.

    2006-10-01

    Glassy films of Ga 10Ge 25S 65 with 4 μm thickness were deposited on quartz substrates by electron beam evaporation. Photoexpansion (PE) (photoinduced increase in volume) and photobleaching (PB) (blue shift of the bandgap) effects have been examined. The exposed areas have been analyzed using perfilometer and an expansion of 1.7 μm (Δ V/ V ≈ 30%) is observed for composition Ga 10Ge 25S 65 exposed during 180 min and 3 mW/cm 2 power density. The optical absorption edge measured for the film Ge 25Ga 10S 65 above and below the bandgap show that the blue shift of the gap by below bandgap photon illumination is considerable higher (Δ Eg = 440 meV) than Δ Eg induced by above bandgap illumination (Δ Eg = 190 meV). The distribution of the refraction index profile showed a negative change of the refraction index in the irradiated samples (Δ n = -0.6). The morphology was examined using a scanning electron microscopy (SEM). The chemical compositions measured using an energy dispersive analyzer (EDX) indicate an increase of the oxygen atoms into the irradiated area. Using a Lloyd's mirror setup for continuous wave holography it was possible to record holographic gratings using the photoinduced effects that occur in them. Diffraction efficiency up to 25% was achieved for the recorded gratings and atomic force microscopy images are presented.

  4. Affective Realism of Animated Films in the Development of Simulation-Based Tutoring Systems

    ERIC Educational Resources Information Center

    Ekanayake, Hiran B.; Fors, Uno; Ramberg, Robert; Ziemke, Tom; Backlund, Per; Hewagamage, Kamalanath P.

    2013-01-01

    This paper presents a study focused on comparing real actors based scenarios and animated characters based scenarios with respect to their similarity in evoking psychophysiological activity for certain events by measuring galvanic skin response (GSR). In the experiment, one group (n = 11) watched the real actors' film whereas another group (n…

  5. Collagen-Based Films Containing Liposome-Loaded Usnic Acid as Dressing for Dermal Burn Healing

    PubMed Central

    Nunes, Paula S.; Albuquerque-Júnior, Ricardo L. C.; Cavalcante, Danielle R. R.; Dantas, Marx D. M.; Cardoso, Juliana C.; Bezerra, Marília S.; Souza, Jamille C. C.; Serafini, Mairim Russo; Quitans-Jr, Lucindo J.; Bonjardim, Leonardo R.; Araújo, Adriano A. S.

    2011-01-01

    The aim of this study was assess the effect of collagen-based films containing usnic acid as a wound dressing for dermal burn healing. Second-degree burn wounds were performed in forty-five Wistar rats, assigned into nine groups: COL—animals treated with collagen-based films; PHO—animals treated with collagen films containing empty liposomes; UAL—animals treated with collagen-based films containing usnic acid incorporated into liposomes. After 7, 14, and 21 days the animals were euthanized. On 7th day there was a moderate infiltration of neutrophils, in UAL, distributed throughout the burn wounds, whereas in COL and PHO, the severity of the reaction was slighter and still limited to the margins of the burn wounds. On the 14th day, the inflammatory reaction was less intense in UAL, with remarkable plasma cells infiltration. On the 21st day, there was reduction of the inflammation, which was predominantly composed of plasma cells in all groups, particularly in UAL. The use of the usnic acid provided more rapid substitution of type-III for type-I collagen on the 14th day, and improved the collagenization density on the 21st day. It was concluded that the use of reconstituted bovine type-I collagen-based films containing usnic acid improved burn healing process in rats. PMID:21274404

  6. PEALD YSZ-based bilayer electrolyte for thin film-solid oxide fuel cells.

    PubMed

    Yu, Wonjong; Cho, Gu Young; Hong, Soonwook; Lee, Yeageun; Kim, Young Beom; An, Jihwan; Cha, Suk Won

    2016-10-14

    Yttria-stabilized zirconia (YSZ) thin film electrolyte deposited by plasma enhanced atomic layer deposition (PEALD) was investigated. PEALD YSZ-based bi-layered thin film electrolyte was employed for thin film solid oxide fuel cells on nanoporous anodic aluminum oxide substrates, whose electrochemical performance was compared to the cell with sputtered YSZ-based electrolyte. The cell with PEALD YSZ electrolyte showed higher open circuit voltage (OCV) of 1.0 V and peak power density of 182 mW cm(-2) at 450 °C compared to the one with sputtered YSZ electrolyte(0.88 V(OCV), 70 mW cm(-2)(peak power density)). High OCV and high power density of the cell with PEALD YSZ-based electrolyte is due to the reduction in ohmic and activation losses as well as the gas and electrical current tightness. PMID:27595193

  7. Second Harmonic Generation as a Nondestructive Readout of Optical (Photo(electro)chromic and Magnetic) Memories

    NASA Astrophysics Data System (ADS)

    Aktsipetrov, O.; Fedyanin, A.; Melnikov, A.; Mishina, E.; Murzina, T.

    1998-01-01

    Optical second harmonic generation (SHG) is suggested as a nonlinear-optical nondestructive readout of (thin) film-based optical memories. Systematic studies of photoinduced, electroinduced, and magnetoinduced variations in the anisotropic SHG intensity in (i) thin solid photo(electro)chromic films of bacteriorhodopsin, (ii) photosensitive Langmuir-Blodgett films of 4-nitro-4'-N-octadecylazobenzene, and (iii) rare-earth iron garnet films show sufficient modification of their nonlinear-optical properties by these external factors. These photo-, electro- and magnetomodified nonlinear-optical properties of thin films being used for recording the information can be easily distinguished by the SHG readout. The IR fundamental radiation used for the excitation of the SHG is shown not to disturb the information recorded in photo(electro)chromic memories. For, what is to our knowledge, the first time, the surface-bulk crossterms in the SHG intensity originating from the interference of the crystalline and magnetization induced second harmonic fields are observed in magnetic iron garnet films.

  8. Inverse opals of molecularly imprinted hydrogels for the detection of bisphenol A and pH sensing.

    PubMed

    Griffete, Nébéwia; Frederich, Hugo; Maître, Agnès; Ravaine, Serge; Chehimi, Mohamed M; Mangeney, Claire

    2012-01-10

    Inverse opal films of molecularly imprinted polymers (MIP) were elaborated using the colloidal crystal template method. The colloidal crystals of silica particles were built by the Langmuir-Blodgett technique, allowing a perfect control of the film thickness. Polymerization in the interspaces of the colloidal crystal in the presence of bisphenol A (BPA) and removal of the used template provides 3D-ordered macroporous methacrylic acid-based hydrogel films in which nanocavities derived from bisphenol A are distributed within the thin walls of the inverse opal hydrogel. The equilibrium swelling properties of the nonimprinted (NIPs) and molecularly imprinted polymers (MIPs) were studied as a function of pH and bisphenol A concentration, while the molecular structures of the bulk hydrogels were analyzed using a cross-linked network structure theory. This study showed an increase in nanopore (mesh) size in the MIPs after BPA extraction as compared to NIPs, in agreement with the presence of nanocavities left by the molecular imprints of the template molecule. The resulting inverse opals were found to display large responses to external stimuli (pH or BPA) with Bragg diffraction peak shifts depending upon the hydrogel film thickness. The film thickness was therefore shown to be a critical parameter for improving the sensing capacities of inverse opal hydrogel films deposited on a substrate. PMID:22088132

  9. Designed supramolecular assemblies for biosensors and photoactive devices. LDRD final report

    SciTech Connect

    Song, X.Z.; Shelnutt, J.A.; Hobbs, J.D.; Cesarano, J.

    1997-02-01

    The objective of this project is the development of a new class of supramolecular assemblies for applications in biosensors and biodevices. The supramolecular assemblies are based on membranes and Langmuir-Blodgett (LB) films composed of naturally-occurring or synthetic lipids, which contain electrically and/or photochemically active components. The LB films are deposited onto electrically-active materials (metal, semiconductors). The active components film components (lipo-porphyrins) at the surface function as molecular recognition sites for sensing proteins and other biomolecules, and the porphyrins and other components (e.g., fullerenes) incorporated into the films serve as photocatalysts and vectorial electron-transport agents. Computer-aided molecular design (CAMD) methods are used to tailor the structure of these film components to optimize function. Molecular modeling is also used to predict the location, orientation, and motion of these molecular components within the films. The result is a variety of extended, self-assembled molecular structures that serve as devices for sensing proteins and biochemicals or as other bioelectronic devices.

  10. High piezoelectricity of Pb(Zr,Ti)O{sub 3}-based ternary compound thin films on silicon substrates

    SciTech Connect

    Zhang Tao; Zhang Shuyi; Chen Zhaojiang; Zhou Fengmei; Zhang Zhongning; Yang Yuetao; Wasa, Kiyotaka

    2009-03-23

    Pb(Zr,Ti)O{sub 3} (PZT)-based ternary compound thin films, 0.06PMnN-0.94PZT(50/50) (PMnN-PZT), are deposited on Si-based heterostructures by rf magnetron sputtering system. The intrinsic PZT(50/50) thin films are also deposited on the same kind of substrates for comparison. The PMnN-PZT thin films show the similar polycrystalline structures as those of PZT with highly (111) oriented perovskite phase. The PMnN-PZT thin films show excellent piezoelectricity and ferroelectricity which are distinctly better than those of PZT thin films prepared with the same deposition conditions. Besides, the cantilevers of PMnN-PZT thin films on the heterostructure substrates also exhibit higher sensitivities than the PZT thin film cantilevers.

  11. Morphogen Electrochemically Triggered Self-Construction of Polymeric Films Based on Mussel-Inspired Chemistry.

    PubMed

    Maerten, Clément; Garnier, Tony; Lupattelli, Paolo; Chau, Nguyet Trang Thanh; Schaaf, Pierre; Jierry, Loïc; Boulmedais, Fouzia

    2015-12-15

    Inspired by the strong chemical adhesion mechanism of mussels, we designed a catechol-based electrochemically triggered self-assembly of films based on ethylene glycol molecules bearing catechol groups on both sides and denoted as bis-catechol molecules. These molecules play the role of morphogens and, in contrast to previously investigated systems, they are also one of the constituents, after reaction, of the film. Unable to interact together, commercially available poly(allylamine hydrochloride) (PAH) chains and bis-catechol molecules are mixed in an aqueous solution and brought in contact with an electrode. By application of defined potential cycles, bis-catechol molecules undergo oxidation leading to molecules bearing "reactive" quinone groups which diffuse toward the solution. In this active state, the quinones react with amino groups of PAH through Michael addition and Schiff's base condensation reaction. The application of cyclic voltammetry (CV) between 0 and 500 mV (vs Ag/AgCl, scan rate of 50 mV/s) of a PAH/bis-catechol solution results in a fast self-construction of a film that reaches a thickness of 40 nm after 60 min. The films present a spiky structure which is attributed to the use of bis-functionalized molecules as one component of the films. XPS measurements show the presence of both PAH and bis-catechol cross-linked together in a covalent way. We show that the amine/catechol ratio is an important parameter which governs the film buildup. For a given amine/catechol ratio, it does exist an optimum CV scan rate leading to a maximum of the film thickness as a function of the scan rate. PMID:26575431

  12. Electrodeposition of Zn based nanostructure thin films for photovoltaic applications

    SciTech Connect

    Al-Bat’hi, S. A. M.

    2015-03-30

    We present here a systematic study on the synthesis thin films of various ZnO, CdO, Zn{sub x}Cd{sub 1-x} (O) and ZnTe nanostructures by electrodeposition technique with ZnCl{sub 2,} CdCl{sub 2} and ZnSO{sub 4} solution as starting reactant. Several reaction parameters were examined to develop an optimal procedure for controlling the size, shape, and surface morphology of the nanostructure. The results showed that the morphology of the products can be carefully controlled through adjusting the concentration of the electrolyte. The products present well shaped Nanorods arrays at specific concentration and temperature. UV-VIS spectroscopy and X-ray diffraction results show that the product presents good crystallinity. A possible formation process has been proposed.

  13. Schottky solar cells based on colloidal nanocrystal films.

    PubMed

    Luther, Joseph M; Law, Matt; Beard, Matthew C; Song, Qing; Reese, Matthew O; Ellingson, Randy J; Nozik, Arthur J

    2008-10-01

    We describe here a simple, all-inorganic metal/NC/metal sandwich photovoltaic (PV) cell that produces an exceptionally large short-circuit photocurrent (>21 mA cm(-2)) by way of a Schottky junction at the negative electrode. The PV cell consists of a PbSe NC film, deposited via layer-by-layer (LbL) dip coating that yields an EQE of 55-65% in the visible and up to 25% in the infrared region of the solar spectrum, with a spectrally corrected AM1.5G power conversion efficiency of 2.1%. This NC device produces one of the largest short-circuit currents of any nanostructured solar cell, without the need for sintering, superlattice order or separate phases for electron and hole transport. PMID:18729414

  14. Schottky Solar Cells Based on Colloidal Nancrystal Films

    SciTech Connect

    Luther, J. M.; Law, M.; Beard, M. C.; Song, Q.; Reese, M. O.; Ellingson, R. J.; Nozik, A. J.

    2008-01-01

    We describe here a simple, all-inorganic metal/NC/metal sandwich photovoltaic (PV) cell that produces an exceptionally large short-circuit photocurrent (>21 mA cm{sup -2}) by way of a Schottky junction at the negative electrode. The PV cell consists of a PbSe NC film, deposited via layer-by-layer (LbL) dip coating that yields an EQE of 55-65% in the visible and up to 25% in the infrared region of the solar spectrum, with a spectrally corrected AM1.5G power conversion efficiency of 2.1%. This NC device produces one of the largest short-circuit currents of any nanostructured solar cell, without the need for sintering, superlattice order or separate phases for electron and hole transport.

  15. Modeling and experimental analysis of RPCVD based nitride film growth

    NASA Astrophysics Data System (ADS)

    Martin, C.; Butcher, K. S. A.; Wintrebert-Fouquet, M.; Fernandes, A.; Dabbs, T.; Chen, P. P.-T.; Carmen, R.

    2008-02-01

    The growth of group-III nitride compound films using the Remote Plasma Chemical Vapour Deposition (RPCVD) process is investigated. The scalability of the technology to larger deposition areas will be discussed. In addition, the key advantages of the RPCVD process for GaN over more conventional deposition methods (such as MOCVD), which are realized through a lower growth temperature, compatibility with glass substrates, in addition to silicon and sapphire, and the complete elimination of toxic NH 3 from the growth process will be presented. These advantages will be discussed via analysis of X-Ray diffraction, Scanning Electron Microscopy (SEM) and Optical Transmission Spectroscopy characterization methods of samples grown using the RPCVD process. In addition, subsequent downstream device processing of double heterojunction devices grown on glass and sapphire substrates will be discussed.

  16. Silver based SERS substrates fabricated from block copolymer thin film

    NASA Astrophysics Data System (ADS)

    Zhang, Xin; Lee, Wonjoo; Lee, Seung Yong; Gao, Zhenghan; Rabin, Oded; Briber, R. M.

    2013-03-01

    Poly (styrene-block-4-vinyl pyridine) (PS-b-P4VP, Mw = 47-b-10 kDa, PDI =1.10) thin films were used to form large-scale long range ordered self-assembled hexagonal patterns of vertically P4VP oriented cylinders in a PS matrix on Si substrates. The P4VP cylindrical domains were crosslinked and quaternized using 1,4-dibromobutane. Negatively charged 15nm gold nanoparticles were attached to the quaternized P4VP domains through Coulombic interactions. Silver was then grown on the gold seeds to create nanometer scale gaps between the nanoparticles. The gap between the nanoparticles was fine tuned by controlling the silver growth time. The substrates showed large enhancement factors in the Raman scattering signal for a broad range of incident wavelengths. Present address: LG Chem Ltd, Information Technology & Electronic Materials R&D, Yuseong-gu Daejeon, South Korea

  17. Copper Oxide Thin Films through Solution Based Methods for Electrical Energy Conversion and Storage

    NASA Astrophysics Data System (ADS)

    Zhu, Changqiong

    Copper oxides (Cu2O and CuO), composed of non-toxic and earth abundant elements, are promising materials for electrical energy generation and storage devices. Solution based techniques for creating thin films of these materials, such as electrodeposition, are important to understand and develop because of their potential for realizing substantial energy savings compared to traditional fabrication methods. Cuprous oxide (Cu2O), with its direct band gap, is a p-type semiconductor that is well suited for creating solution-processed photovoltaic devices (solar cells); several key advancements made toward this application are the primary focus of this thesis. Electrodeposition of single-phase, crystalline Cu2O thin films is demonstrated using previously unexplored, acidic lactate/Cu2+ solutions, which has provided additional understanding of the impacts of growth solution chemistry on film formation. The influence of pH on the resulting Cu2O thin film properties is revealed by using the same ligand (sodium lactate) at various solution pH values. Cu2O films grown from acidic lactate solutions can exhibit a distinctive flowerlike, dendritic morphology, in contrast to the faceted, dense films obtained using alkaline lactate solutions. Relative speciation distributions of the various metal complex ions present under different growth conditions are calculated using reported equilibrium association constants and experimentally supported by UV-Visible absorption spectroscopy. Dependence of thin film morphology on the lactate/Cu2+ molar ratio and applied potential is described. Cu2O/eutectic gallium-indium Schottky junction devices are formed and devices are tested under monochromatic green LED illumination. Further surface examination of the Cu2O films using X-ray photoelectron spectroscopy (XPS) reveals the fact that films grown from acidic lactate solution with a small lactate/Cu2+ molar ratio, which exhibit improved photovoltaic performance compared to films grown from

  18. AlGaInN-based light emitting diodes with a transparent p-contact based on thin ITO films

    SciTech Connect

    Smirnova, I. P. Markov, L. K.; Pavlyuchenko, A. S.; Kukushkin, M. V.

    2012-03-15

    A method for obtaining transparent conductive ITO (indium-tin oxide) films aimed for use in light emitting diodes of the blue spectral range is developed. The peak external quantum efficiency of light-emitting diodes with a p-contact based on the obtained films reaches 25%, while for similar light-emitting diodes with a standard semitransparent metal contact, it is <10%. An observed increase in the direct voltage drop from 3.15 to 3.37 V does not significantly affect the possibility of applying these films in light-emitting diodes since the optical power of light-emitting diodes with a transparent p-contact based on ITO films exceeds that of chips with metal semitransparent p-contacts with a working current of 20 mA by a factor of almost 2.5. Light-emitting diodes with p-contacts based on ITO films successfully withstand a pumping current that exceeds their calculated working current by a factor of 5 without the appearance of any signs of degradation.

  19. Thermally Sprayed Coatings as Interlayers for DLC-Based Thin Films

    NASA Astrophysics Data System (ADS)

    Bolelli, G.; Gualtieri, E.; Lusvarghi, L.; Pighetti Mantini, F.; Pitacco, F.; Valeri, S.; Volz, H.

    2009-06-01

    This article examines the usefulness of a thick thermally sprayed interlayer (plasma-sprayed Ni-50%Cr, plasma-sprayed Al2O3-13%TiO2, or high-velocity oxygen-fuel-sprayed WC-17%Co) for enhancing the wear resistance and the corrosion protectiveness of a diamond-like carbon (DLC)-based thin film deposited onto a carbon steel substrate. Scratch tests indicate that the Al2O3-13%TiO2 and WC-17%Co interlayers definitely increase the critical spallation load of the thin film, but the Al2O3-13%TiO2 interlayer itself undergoes brittle fracture under high-contact loads. Accordingly, during ball-on-disk tests at room temperature, no cracking and spallation occur in the DLC-based film deposited onto the WC-17%Co interlayer, whereas the one onto the Al2O3-13%TiO2 interlayer is rapidly removed because the interlayer itself is fractured. At 300 °C, by contrast, the DLC-based film on the Al2O3-13%TiO2 interlayer offers the best tribological performance, possibly thanks to the increased toughness of the ceramic interlayer at this temperature. Electrochemical polarization tests indicate that the thin film/WC-Co systems possess the lowest corrosion current density.

  20. Slit-based supersonic microplasma jets: Scalable sources for nanostructured thin film deposition

    NASA Astrophysics Data System (ADS)

    Koh, T.; Chiles, I.; Gordon, M.

    2013-10-01

    Slit-based, hollow cathode microplasma jets operating in under-expanded supersonic flow were investigated as spray deposition sources to realize nanostructured metal oxide thin films. Design of the slit cathode, its operation (e.g., IV characteristics, fluorescence imaging of supersonic flow shock structures, etc.), and companion CuO nanowire deposition experiments are discussed. Overall, this work demonstrates that slit-based, flow-through microplasmas are a promising way to scale up hollow cathode discharges for large area deposition of thin films at high pressures (>10 Torr).

  1. Fatigue Life Prediction Based on Local Strain Energy for Healed Copper Film by Laser Irradiation

    NASA Astrophysics Data System (ADS)

    Liu, Feng-Zhu; Shang, De-Guang; Ren, Chong-Gang; Sun, Yu-Juan

    2016-04-01

    Changes of total cyclic strain energy at the notch for copper film specimen were analyzed before and after laser irradiation treatment. The results showed that laser irradiation can increase total cyclic strain energy and the effect of increase is more evident for the damaged copper specimen. Based on the damage-healing mechanism, an enhancement parameter and a healing parameter were defined by the local cyclic strain energy. A new model based on local strain energy was proposed to predict residual fatigue life for the damaged copper film specimen after laser irradiation. The predicted results by the proposed model agree well with the experimental lives.

  2. Stability of methylcellulose-based films after being subjected to different conservation and processing temperatures.

    PubMed

    Tavera Quiroz, M J; Lecot, J; Bertola, N; Pinotti, A

    2013-07-01

    Methylcellulose films with and without sorbitol addition were developed. The major objective of this study was to attempt insights into the stability of the methylcellulose-based film properties after having been subjected to freezing, storage or a combination of both procedures. The importance of the sorbitol concentration and process temperature was also to be elucidated. As-prepared film solubility decreased at 100 °C, as a result of the methylcellulose thermogelation property when the samples were exposed to high temperatures. By analyzing the film pattern behavior and its properties 0.25% w/v sorbitol concentration turned out to be an inflexion point. The moisture content as well as the mechanical and thermal properties made this fact evident. Moreover the elastic modulus (Ec) and glass transition temperature (Tg) did not undergo significant changes for higher plasticizer concentrations. The methylcellulose film properties remained more stable in the presence of sorbitol, which would act as a protective agent due to its hydrogen bonding capacity. This stability is crucial for film and coating applications in the food industry. PMID:23623115

  3. Erasable thin-film optical diode based on a photoresponsive liquid crystal polymer.

    PubMed

    Zhang, Xinping; Zhang, Jian; Sun, Yujian; Yang, Huai; Yu, Haifeng

    2014-04-01

    We report a thin-film optical diode written into thin films of a liquid-crystalline polymer (LCP), which is based on the photoinduced LC-to-isotropic phase transition of LCPs. The interference pattern between a collimated and a focused UV laser beam is imprinted as chirped volume-phase gratings in photoresponsive LCP films and no further processing steps like development or liftoff are required for the fabrication. The resultant thin-film device not only possesses the fundamental functions of an optical lens for laser beam focusing, but also shows diode effects with the focusing/defocusing function dependent on the direction of light incidence and orientation of the device. Furthermore, this photonic thin-film lens exhibits a spatially tunable spectroscopic response, revealing a unique physics of secondary excitations of resonance modes of the single-layer LCP waveguide grating structures. This reveals the mechanisms for the focusing/defocusing of laser beams by chirped grating structures. Erasability and reconstructibility of the photoresponsive LCPs guarantee rewritability of the thin-film diode lens. PMID:24584886

  4. Novel composite films based on amidated pectin for cationic dye adsorption.

    PubMed

    Nesic, Aleksandra R; Velickovic, Sava J; Antonovic, Dusan G

    2014-04-01

    Pectin, with its tendency to gel in the presence of metal ions has become a widely used material for capturing the metal ions from wastewaters. Its dye-capturing properties have been much less investigated, and this paper is the first to show how films based on amidated pectin can be used for cationic dye adsorption. In the present study amidated pectin/montmorillonite composite films were synthesized by membrane casting, and they are stable in aqueous solution both below and above pectin pKa. FTIR, thermogravimetry and SEM-EDAX have confirmed the presence of montmorillonite in the cast films and the interactions between the two constituents. In order to evaluate the cationic dye adsorption of these films Basic Yellow 28 was used, showing that the films have higher adsorption capacity compared to the others reported in the literature. The results were fitted into Langmuir, Freundlich and Temkin isotherms indicating an exothermic process and setting the optimum amount of montmorillonite in the films to 30% of pectin mass. According to the Langmuir isotherm the maximum adsorption capacity is 571.4 mg/g. PMID:24268651

  5. Reversible potentiometric oxygen sensors based on polymeric and metallic film electrodes.

    PubMed

    Yim, H S; Meyerhoff, M E

    1992-09-01

    Various materials and sensor configurations that exhibit reversible potentiometric responses to the partial pressure of oxygen at room temperature in neutral pH solution are examined. In one arrangement, platinum electrodes are coated with plasticized poly(vinyl chloride) films doped with a cobalt(II) tetraethylene pentamine complex. For such sensors, potentiometric oxygen response is attributed to a mixed potential originating from the underlying platinum electrode surface as well as a change in redox potential of the Co(II)-tetren-doped film as the complex binds oxygen reversibly. The response due to the platinum surface is prolonged by the presence of the Co(II)-tetren/PVC film. Alternately, thin films of metallic copper, electrochemically deposited on platinum and/or sputtered or vapor deposited on a single crystal silicon substrate, may be used for reversible oxygen sensing. The long-term reversibility and potentiometric stability of such copper film-based sensors is enhanced (up to 1 month) by preventing the formation of cuprous oxide on the surfaces via the application of an external nonpolarizing cathodic current through the working electrode or by specifically using sputtered copper films that have [100] preferred crystal structures as determined by X-ray diffraction. The implications of these findings in relation to fabricating analytically useful potentiometric oxygen sensors are discussed. PMID:1416035

  6. Hydrogen storage in Ti, V and their oxides-based thin films

    NASA Astrophysics Data System (ADS)

    Tarnawski, Z.; Zakrzewska, K.; Kim-Ngan, N.-T. H.; Krupska, M.; Sowa, S.; Drogowska, K.; Havela, L.; Balogh, A. G.

    2015-03-01

    We have investigated the hydrogen storage ability and the effect of hydrogenation on structure and physical properties of Ti/V and their oxides-based thin films. A series of Ti-TiO2 and VOx-TiO2 thin films with different layer structures, geometries and thicknesses have been prepared by the sputtering technique on different (Si(111), SiO2, C) substrates. For the Ti-TiO2-Ti films up to 50 at.% of hydrogen can be stored in the Ti layers, while the hydrogen can penetrate without accumulation through the TiO2 layer. A large hydrogen storage was also found in some V2O5-TiO2 films. Hydrogen could also remove the preferential orientation in the Ti films and induce a transition of V2O5 to VO2 in the films. Invited talk at the 7th International Workshop on Advanced Materials Science and Nanotechnology IWAMSN2014, 2-6 November, 2014, Ha Long, Vietnam.

  7. Ferroelectricity and antiferroelectricity of doped thin HfO2-based films.

    PubMed

    Park, Min Hyuk; Lee, Young Hwan; Kim, Han Joon; Kim, Yu Jin; Moon, Taehwan; Kim, Keum Do; Müller, Johannes; Kersch, Alfred; Schroeder, Uwe; Mikolajick, Thomas; Hwang, Cheol Seong

    2015-03-18

    The recent progress in ferroelectricity and antiferroelectricity in HfO2-based thin films is reported. Most ferroelectric thin film research focuses on perovskite structure materials, such as Pb(Zr,Ti)O3, BaTiO3, and SrBi2Ta2O9, which are considered to be feasible candidate materials for non-volatile semiconductor memory devices. However, these conventional ferroelectrics suffer from various problems including poor Si-compatibility, environmental issues related to Pb, large physical thickness, low resistance to hydrogen, and small bandgap. In 2011, ferroelectricity in Si-doped HfO2 thin films was first reported. Various dopants, such as Si, Zr, Al, Y, Gd, Sr, and La can induce ferro-electricity or antiferroelectricity in thin HfO2 films. They have large remanent polarization of up to 45 μC cm(-2), and their coercive field (≈1-2 MV cm(-1)) is larger than conventional ferroelectric films by approximately one order of magnitude. Furthermore, they can be extremely thin (<10 nm) and have a large bandgap (>5 eV). These differences are believed to overcome the barriers of conventional ferroelectrics in memory applications, including ferroelectric field-effect-transistors and three-dimensional capacitors. Moreover, the coupling of electric and thermal properties of the antiferroelectric thin films is expected to be useful for various applications, including energy harvesting/storage, solid-state-cooling, and infrared sensors. PMID:25677113

  8. Thin film polarizer and color filter based on photo-polymerizable nematic liquid crystal

    NASA Astrophysics Data System (ADS)

    Mohammadimasoudi, Mohammad; Neyts, Kristiaan; Beeckman, Jeroen

    2015-03-01

    We present a method to fabricate a thin film color filter based on a mixture of photo-polymerizable liquid crystal and chiral dopant. A chiral nematic liquid crystal layer reflects light for a certain wavelength interval Δλ (= Δn.P) with the period and Δn the birefringence of the liquid crystal. The reflection band is determined by the chiral dopant concentration. The bandwidth is limited to 80nm and the reflectance is at most 50% for unpolarized incident light. The thin color filter is interesting for innovative applications like polarizer-free reflective displays, polarization-independent devices, stealth technologies, or smart switchable reflective windows to control solar light and heat. The reflected light has strong color saturation without absorption because of the sharp band edges. A thin film polarizer is developed by using a mixture of photo-polymerizable liquid crystal and color-neutral dye. The fabricated thin film absorbs light that is polarized parallel to the c axis of the LC. The obtained polarization ratio is 80% for a film of only 12 μm. The thin film polarizer and the color filter feature excellent film characteristics without domains and can be detached from the substrate which is useful for e.g. flexible substrates.

  9. Plasma Processing of Functional Thin Films by Sputtering Deposition Using Metal-Based Powder Target

    NASA Astrophysics Data System (ADS)

    Kawasaki, Hiroharu; Ohshima, Tamiko; Ihara, Takeshi; Arafune, Kento; Taniyama, Daichi; Yagyu, Yoshihito; Suda, Yoshiaki

    2013-11-01

    Titanium-based functional thin films were prepared by a sputtering deposition method using a metal powder target, and the electron density and temperature of the processing plasma were investigated. The electron density of the plasma, measured by a probe method, when using a powder target was higher than that when using a bulk target. The deposition rate when using a powder target was also higher than that in the case of a bulk target. These results may be due to the net-cathode area of the powder target being larger than that of the bulk target. X-ray photoelectron spectroscopy, X-ray diffraction measurements, and atomic force microscopy images of the films prepared using the Ti powder target indicated nearly the same properties as those of films prepared using a Ti bulk target, and the prepared films are oxide. These results suggest that TiO2 thin films can be prepared using a Ti powder target and that the quality is almost the same as those of films prepared using a Ti bulk target.

  10. Surface plasmon resonance biochip based on ZnO thin film for nitric oxide sensing.

    PubMed

    Feng, Wei-Yi; Chiu, Nan-Fu; Lu, Hui-Hsin; Shih, Hsueh-Ching; Yang, Dongfang; Lin, Chii-Wann

    2008-01-01

    In this study, the design of a novel optical sensor that comprises surface plasmon resonance sensing chip and zinc oxide nano-film was proposed for the detection of nitric oxide gas. The electrical and optical properties of zinc oxide film vary in the presence of nitric oxide. This effect was utilized to prepare biochemical sensors with transduction based on surface plasmon resonance. Due to the refractive index of the transparent zinc oxide film that was deposited on the gold film, however, changes will be observed in the surface plasmon resonance spectra. For this reason, the thickness of zinc oxide film will be investigated and determined in this study. The interaction of nitric oxide with a 20 nm zinc oxide layer on gold leads to the shift of the resonance angle. The analysis on the reflectance intensity of light demonstrates that such effect is caused by the variation of conductivity and permittivity of zinc oxide film. Finally, a shift in surface plasmon resonance angle was measured in 25 ppm nitric oxide at 180 C and a calibration curve of nitride oxide concentration versus response intensity was successfully obtained in the range of 250 to 1000 ppm nitric oxide at lower temperature of 150 C. Moreover, these effects are quasi-reversible. PMID:19164025

  11. Disposable urea biosensor based on nanoporous ZnO film fabricated from omissible polymeric substrate.

    PubMed

    Rahmanian, Reza; Mozaffari, Sayed Ahmad; Abedi, Mohammad

    2015-12-01

    In the present study, a facile and simple fabrication method of a semiconductor based urea biosensor was reported via three steps: (i) producing a ZnO-PVA composite film by means of a polymer assisted electrodeposition of zinc oxide (ZnO) on the F-doped SnO2 conducting glass (FTO) using water soluble polyvinyl alcohol (PVA), (ii) obtaining a nanoporous ZnO film by PVA omission via a subsequent post-treatment by annealing of the ZnO-PVA film, and (iii) preparation of a FTO/ZnO/Urs biosensor by exploiting a nanoporous ZnO film as an efficient and excellent platform area for electrostatic immobilization of urease enzyme (Urs) which was forced by the difference in their isoelectric point (IEP). The characterization techniques focused on the analysis of the ZnO-PVA film surfaces before and after annealing, which had a prominent effect on the porosity of the prepared ZnO film. The surface characterization of the nanostructured ZnO film by a field emission-scanning electron microscopy (FE-SEM), exhibited a film surface area as an effective bio-sensing matrix for enzyme immobilization. The structural characterization and monitoring of the biosensor fabrication was performed using UV-Vis, Fourier Transform Infrared (FT-IR), Raman Spectroscopy, Thermogravimetric Analysis (TGA), Cyclic Voltammetry (CV), and Electrochemical Impedance Spectroscopy (EIS) techniques. The impedimetric results of the FTO/ZnO/Urs biosensor showed a high sensitivity for urea detection within 8.0-110.0mg dL(-1) with the limit of detection as 5.0mg dL(-1). PMID:26354280

  12. CO responses of sensors based on cerium oxide thick films prepared from clustered spherical nanoparticles.

    PubMed

    Izu, Noriya; Matsubara, Ichiro; Itoh, Toshio; Akamatsu, Takafumi; Shin, Woosuck

    2013-01-01

    Various types of CO sensors based on cerium oxide (ceria) have been reported recently. It has also been reported that the response speed of CO sensors fabricated from porous ceria thick films comprising nanoparticles is extremely high. However, the response value of such sensors is not suitably high. In this study, we investigated methods of improving the response values of CO sensors based on ceria and prepared gas sensors from core-shell ceria polymer hybrid nanoparticles. These hybrid nanoparticles have been reported to have a unique structure: The core consists of a cluster of ceria crystallites several nanometers in size. We compared the characteristics of the sensors based on thick films prepared from core-shell nanoparticles with those of sensors based on thick films prepared from conventionally used precipitated nanoparticles. The sensors prepared from the core-shell nanoparticles exhibited a resistance that was ten times greater than that of the sensors prepared from the precipitated nanoparticles. The response values of the gas sensors based on the core-shell nanoparticles also was higher than that of the sensors based on the precipitated nanoparticles. Finally, improvements in sensor response were also noticed after the addition of Au nanoparticles to the thick films used to fabricate the two types of sensors. PMID:23529123

  13. Defects in solution-processed dithienylsilole-based small-molecule photovoltaic thin-films

    NASA Astrophysics Data System (ADS)

    Muntasir, Tanvir; Chaudhary, Sumit

    2016-01-01

    DTS-(FBTTh2)2 is a prominent solution-processable small-molecule donor for donor-acceptor bulk-heterojunction organic photovoltaics. Power conversion efficiency of DTS-(FBTTh2)2 based photovoltaic devices exceeds 8%. This paper reports on the distribution of sub-bandgap trap states in DTS-(FBTTh2)2. Trap states were probed using admittance spectroscopy and low-frequency capacitance-voltage profiling and analyzed using established theoretical models. Three distributions were revealed in the trap density of states energy spectra. Key observations were (1) thicker solution-processed films with higher drying time had 55% less traps than thinner films that dried relative faster (2) blending of DTS-(FBTTh2)2 with the acceptor PC70BM introduced traps at the center of the donor-acceptor interfacial bandgap. Charge carrier dynamics in DTS-(FBTTh2)2 based thin-films was also characterized using impedance spectroscopy.

  14. Tunneling-enabled spectrally selective thermal emitter based on flat metallic films

    SciTech Connect

    Wang, Zhu; Tan, Yixuan; Zhou, Ming; Yu, Zongfu; Luk, Ting Shan; Ji, Dengxin; Gan, Qiaoqiang

    2015-03-09

    Infrared thermal emission from metals has important energy applications in thermophotovoltaics, radiative cooling, and lighting. Unfortunately, the emissivity of flat metal films is close to zero because the screening effect prevents metals' fluctuating currents from emitting to the far field. As a result, metal films are often used as reflecting mirrors instead of thermal emitters. Recently, nanostructured metals, such as metamaterials, have emerged as an interesting way to enhance and to spectrally control thermal emission based on plasmonic resonant effects. However, they require sophisticated lithography. Here, we proposed and experimentally demonstrated a completely different mechanism to achieve spectrally selective metallic emitters based on a tunneling effect. This effect allows a simple flat metal film to achieve a near-unity emissivity with controlled spectral selectivity for efficient heat-to-light energy conversion.

  15. Tunneling-enabled spectrally selective thermal emitter based on flat metallic films

    SciTech Connect

    Wang, Zhu; Luk, Ting S.; Tan, Yixuan; Ji, Dengxin; Zhou, Ming; Gan, Qiaoqiang; Yu, Zongfu

    2015-03-11

    Infrared thermal emission from metals has important energy applications in thermophotovoltaics, radiative cooling, and lighting. The emissivity of flat metal films is close to zero because the screening effect prevents metals' fluctuating currents from emitting to the far field. As a result, metal films are often used as reflecting mirrors instead of thermal emitters. Recently, nanostructured metals, such as metamaterials, have emerged as an interesting way to enhance and to spectrally control thermal emission based on plasmonic resonant effects. However, they require sophisticated lithography. Here, we proposed and experimentally demonstrated a completely different mechanism to achieve spectrally selective metallic emitters based on atunneling effect. Furthermore, this effect allows a simple flat metal film to achieve a near-unity emissivity with controlled spectral selectivity for efficient heat-to-light energy conversion.

  16. On-wafer millimeter wave notch filter based on barium hexagonal ferrite thin films on platinum

    NASA Astrophysics Data System (ADS)

    Harward, Ian Roylance

    In this work, the growth of BaM and Al doped Ba M thin films on Pt templates, layered on a Si wafer, is demonstrated using a newly developed metallo-organic decomposition (MOD) process. It is shown that the BaM films are polycrystalline, with preferred perpendicular c-axis grain orientation. The magnetic properties such as anisotropy field, saturation magnetization, and remnant magnetization are studied as a function of temperature and film composition, and are shown to be correlated to the film microstructure. It is shown that these films exhibit high remnant magnetization, a property not measured in BaM single crystals, meaning a biasing magnet may not be necessary for millimeter wave device applications. Ferromagnetic resonance (FMR) studies were performed on the ferrite films using the tool developed at UCCS for the study of high frequency magnetic materials, the broadband FMR (BFMR) system. The instrument is described in great detail, and the FMR studies on BaM show that the MOD-grown films exhibit narrow FMR linewidths, on the order of 150 Oe, and are therefore of sufficient quality for use in mm wave devices. Finally, notch filters using the Pt/BaM are demonstrated. The filters are based on a microstrip design, where the Pt serves as the ground plane and the BaM is part of the dielectric. The Ba M absorbs signals at the ferromagnetic resonance frequency, which takes place in the mm wave range. The filters described were based on pure BaM, but Al doped BaM could easily be used to increase the operating frequency of the device. The operating frequency of these devices is also tunable using an externally applied magnetic field.

  17. Oxygen-scavenging coatings and films based on lignosulfonates and laccase.

    PubMed

    Johansson, Kristin; Winestrand, Sandra; Johansson, Caisa; Järnström, Lars; Jönsson, Leif J

    2012-09-15

    Laccase and lignosulfonates were included in coating colors and embedded in latex-based or starch-based films and coatings on foil or board. After 6 days at 23 °C and 100% relative humidity, the oxygen content in airtight chambers decreased from 1.0% (synthetic gas consisting of 99% N(2) and 1% O(2)) to 0.3% in the presence of board coated with lignosulfonate and laccase, while the oxygen content remained unchanged in control experiments without enzyme. The water stability of lignosulfonate-containing latex-based coatings and starch-based films was improved after laccase-catalyzed oxidation of lignosulfonates, which indicates polymerization to products with lower solubility in water. Furthermore, the E' modulus of starch-based films increased with 30%, which indicates laccase-catalyzed polymerization of lignosulfonates resulting in increased stiffness of the film. The results suggest that laccases and lignosulfonates can be used as an oxygen-scavenging system in active packaging and that enzyme-catalyzed polymerization of lignosulfonates contributes to improved water stability and mechanical properties. PMID:22721759

  18. Development and Characterization of Novel Films Based on Sulfonamide-Chitosan Derivatives for Potential Wound Dressing.

    PubMed

    Dragostin, Oana Maria; Samal, Sangram Keshari; Lupascu, Florentina; Pânzariu, Andreea; Dubruel, Peter; Lupascu, Dan; Tuchilus, Cristina; Vasile, Cornelia; Profire, Lenuta

    2015-01-01

    The objective of this study was to develop new films based on chitosan functionalized with sulfonamide drugs (sulfametoxydiazine, sulfadiazine, sulfadimetho-xine, sulfamethoxazol, sulfamerazine, sulfizoxazol) in order to enhance the biological effects of chitosan. The morphology and physical properties of functionalized chitosan films as well the antioxidant effects of sulfonamide-chitosan derivatives were investigated. The chitosan-derivative films showed a rough surface and hydrophilic properties, which are very important features for their use as a wound dressing. The film based on chitosan-sulfisoxazol (CS-S6) showed the highest swelling ratio (197%) and the highest biodegradation rate (63.04%) in comparison to chitosan film for which the swelling ratio was 190% and biodegradation rate was only 10%. Referring to the antioxidant effects the most active was chitosan-sulfamerazine (CS-S5) which was 8.3 times more active than chitosan related to DPPH (1,1-diphenyl-2-picrylhydrazyl) radical scavenging ability. This compound showed also a good ferric reducing power and improved total antioxidant capacity. PMID:26694354

  19. Development and Characterization of Novel Films Based on Sulfonamide-Chitosan Derivatives for Potential Wound Dressing

    PubMed Central

    Dragostin, Oana Maria; Samal, Sangram Keshari; Lupascu, Florentina; Pânzariu, Andreea; Dubruel, Peter; Lupascu, Dan; Tuchilus, Cristina; Vasile, Cornelia; Profire, Lenuta

    2015-01-01

    The objective of this study was to develop new films based on chitosan functionalized with sulfonamide drugs (sulfametoxydiazine, sulfadiazine, sulfadimetho-xine, sulfamethoxazol, sulfamerazine, sulfizoxazol) in order to enhance the biological effects of chitosan. The morphology and physical properties of functionalized chitosan films as well the antioxidant effects of sulfonamide-chitosan derivatives were investigated. The chitosan-derivative films showed a rough surface and hydrophilic properties, which are very important features for their use as a wound dressing. The film based on chitosan-sulfisoxazol (CS-S6) showed the highest swelling ratio (197%) and the highest biodegradation rate (63.04%) in comparison to chitosan film for which the swelling ratio was 190% and biodegradation rate was only 10%. Referring to the antioxidant effects the most active was chitosan-sulfamerazine (CS-S5) which was 8.3 times more active than chitosan related to DPPH (1,1-diphenyl-2-picrylhydrazyl) radical scavenging ability. This compound showed also a good ferric reducing power and improved total antioxidant capacity. PMID:26694354

  20. Photoacoustic microscopy based on polydimethylsiloxane thin film Fabry-Perot optical interferometer

    NASA Astrophysics Data System (ADS)

    Park, Soongho; Eom, Jonghyun; Shin, Jun Geun; Rim, Sunghwan; Lee, Byeong Ha

    2016-03-01

    We present a photoacoustic microscopy (PAM) system based on a Fabry-Perot Interferometer (FPI) consisting of a transparent Polydimethylsiloxane (PDMS) thin film. Most of the PAM systems have limitations with the system alignment because the ultrasound transducers for detection are not transparent. Therefore, the excitation laser source should avoid the opaque transducer to illuminate the sample, which makes the system difficult to build-up. Especially, the system volume is highly limited to be compact. In our experiment, to solve these difficulties, a FPI based on the PDMS film has been implemented and applied to measure the acoustic wave signal. The system uses a FPI as an acoustic wave detector instead of a conventional ultrasound transducer. A tunable laser was used to choose the quadrature-point at which the signal has the highly sensitve and linear response to the acoustic wave. Also a 20Hz pulsed Nd:YAG laser was used to generate acoustic waves from a sample. When the acoustic waves arrive at the PDMS film, one of the surfaces of the film is modulated at the detecting point, which gives the tuned FPI interference signal. From the signal arriving time, the depth location of the sample is calculated. As a primary experiment using the PDMS thin film as an ultrasound transducer, a couple of narrow black friction tapes located in a water container were used as the samples. This proposed imaging method can be used in various applications for the detection and measurement of acoustic waves.