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Sample records for langmuir-blodgett films based

  1. Synthesis and photoreaction of Schiff bases derived from p-nitro cinnamaldehyde and diamines in Langmuir and Langmuir Blodgett films

    NASA Astrophysics Data System (ADS)

    Kanthimathi, Mookandi; Dhathathreyan, Aruna

    2003-01-01

    Monolayers of Schiff bases derived from ethylene diamine and o-phenylene diamine with p-nitro cinnamaldehyde, (compounds 1 and 2) at air/water interface have been studied. Photolysis of 1 in chloroform solution undergoes cis- trans isomerization on irradiation of white light while compound 2 does not undergo isomerization under photolytic conditions. The photolysis of 1 and 2 in Langmuir-Blodgett films (LB films) transferred to quartz plates form dimers. The change in product distribution is attributed to the influence of bridging group of the cinnamaldehyde moieties, molecular configuration and mobility of the compounds in solution, solid state and the aggregation of molecules in monolayer assemblies.

  2. Polyheterocycle Langmuir-Blodgett Films

    DTIC Science & Technology

    1989-05-29

    3-alkyl thiophene) and Stearic acid LB films. Thc oricntation of single- and Multi-laycr films on platinum substrates have bccn studicd by Ncar Edgc...not surface active. The LB films were obtained by spreading a mixture of the poly(3-alkvl thiophenes) and stearic acid (C,71-5 COOH ) onto the water

  3. Polyoxometalate monolayers in Langmuir-Blodgett films.

    PubMed

    Clemente-León, Miguel; Coronado, Eugenio; Gómez-García, Carlos J; Mingotaud, Christophe; Ravaine, Serge; Romualdo-Torres, Gemma; Delhaès, Pierre

    2005-06-20

    Langmuir and Langmuir-Blodgett (LB) films of a variety of polyoxometalates of different shapes, sizes, and charges were prepared by taking advantage of the adsorption properties of these polyanions on a positively charged monolayer of an organic surfactant spread on water. Three different aspects were investigated. 1) The electrochemical and electrochromic properties of LB films containing the easily reducible polyoxoanion [P2Mo18O62]6-. Absorbance changes of these LB films deposited onto an ITO substrate have been induced by repeated switching of the applied potential. These changes are due to the formation of the colored reduced forms of the polyanion. Coloration and bleaching of the LB film occur very quickly and are reversible. 2) The preparation of LB films based on magnetic polyoxometalates, such as the Keggin anions, [CoW12O40]6- and [SiMn(OH2)W11O39]6-, or containing magnetic clusters of increasing nuclearities such as [Co4(H2O)2(PW9O34)2]10- and [Co4(H2O)2(P2W15O62)2]16- based on a Co4O16 ferromagnetic cluster, and the polyoxometalates [Co9(OH)3(H2O)6(HPO4)2(PW9O34)3]16- and [Ni9(OH)3-(H2O)6(HPO4)2(PW9O34)3]16- based on a nonanuclear M9O36 cluster. 3) The preparation of LB films of the giant heteropolyoxomolybdate, [Na3(NH4)12][Mo57Fe6(NO)6O174(OH)3-(H2O)24]76 H2O.

  4. Tribology of Langmuir-Blodgett Films

    DTIC Science & Technology

    1992-03-01

    the 1970" s . used a three-term model . The frictional force and hence the friction coefficient were modeled as the sum of three terms: adhesion between...N/A N/A 4. TITLE (and Subtitle) S . TyPE OF REPORT & PERIOD COVERED Tribology of Langmuir-Blodgett Films Interim Technical Report 6. PERFORMING ORO...AOORESS 12. REPORT OATE U. S . Army Research Office March 1992 Post Office Box 12211 I. NUMREROF PAGES R~~Arrh Tr npl= n D, ift’ n 25 14. MONITORING

  5. Stable Ordering in Langmuir-Blodgett Films

    NASA Astrophysics Data System (ADS)

    Takamoto, Dawn Y.; Aydil, Eray; Zasadzinski, Joseph A.; Ivanova, Ani T.; Schwartz, Daniel K.; Yang, Tinglu; Cremer, Paul S.

    2001-08-01

    Defects in the layering of Langmuir-Blodgett (LB) films can be eliminated by depositing from the appropriate monolayer phase at the air-water interface. LB films deposited from the hexagonal phase of cadmium arachidate (CdA2) at pH 7 spontaneously transform into the bulk soap structure, a centrosymmetric bilayer with an orthorhombic herringbone packing. A large wavelength folding mechanism accelerates the conversion between the two structures, leading to a disruption of the desired layering. At pH > 8.5, though it is more difficult to draw LB films, almost perfect layering is obtained due to the inability to convert from the as-deposited structure to the equilibrium one.

  6. Surface acoustic wave devices including Langmuir-Blodgett films (Review)

    NASA Astrophysics Data System (ADS)

    Plesskii, V. P.

    1991-06-01

    Recent theoretical and experimental research related to the use of Langmuir-Blodgett (LB) films in surface acoustic wave (SAW) devices is reviewed. The sensitivity of the different cuts of quartz and lithium niobate to inertial loading is investigated, and it is shown that some cuts in lithium niobate are twice as sensitive to mass loading than the commonly used YZ-cut. The large variety of organic compounds suitable for the production of LB films makes it possible to create SAW sensors reacting selectively to certain substances. The existing SAW sensors based on LB films are characterized by high sensitivity and fast response.

  7. 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.

  8. Langmuir Blodgett films of hydrophobins HFBI and HFBII

    NASA Astrophysics Data System (ADS)

    Kisko, Kaisa; Torkkeli, Mika; Vuorimaa, Elina; Lemmetyinen, Helge; Seeck, Oliver H.; Linder, Markus; Serimaa, Ritva

    2005-06-01

    Hydrophobins are small fungal proteins, which have remarkable surface-chemical properties. They self-assemble at hydrophobic/hydrophilic interfaces and work as adhesive agents and coatings. Sixteen layer Langmuir-Blodgett films of hydrophobins HFBI and HFBII from the fungus Trichoderma reesei were prepared and studied using grazing-incidence X-ray diffraction and reflectivity techniques. Both kind of films contain hexagonally ordered crystallites on the substrate with unit cell parameters of a = b = 54 Å (HFBI) and a = b = 55 Å (HFBII). The structure is similar to the structure of monolayer Langmuir-Blodgett films.

  9. Thermal conductance of nanoscale Langmuir-Blodgett films

    NASA Astrophysics Data System (ADS)

    Ziade, Elbara; Goni, Miguel; Sato, Toshiyuki; Czubarow, Pawel; Schmidt, Aaron J.

    2015-11-01

    Thermal transport across organic-inorganic interfaces is fundamental to understanding heat transfer in polymer-based composites, microelectronics, and energy conversion systems. We used the Langmuir-Blodgett (LB) technique to deposit nanometer-thick films of poly(vinyl acetate) (PVAc) on silicon and gold substrates in two distinct states: Liquid condensed (Lc) and Liquid expanded (Le). We used frequency domain thermoreflectance to measure the thermal conductivity of the PVAc film and its thermal interface conductance to the substrate. We found that PVAc films prepared through the LB process have a higher thermal conductivity when compared to bulk. We measured the thermal interface conductance between PVAc and gold to be approximately 90 MW/m2 K for both the Le and Lc states, and the thermal interface conductance between PVAc and silicon to be approximately 70 MW/m2 K for both the Le and Lc states.

  10. Langmuir-Blodgett films of salophen-based metallosurfactants as surface pretreatment coatings for corrosion mitigation.

    PubMed

    Gonawala, Sunalee; Leopoldino, Verônica R; Kpogo, Kenneth; Verani, Cláudio N

    2016-09-25

    Salophen-based metallosurfactants are successfully used as pretreatment LB films for corrosion mitigation in acidic and saline media. Passivation of electron transfer is clearly demonstrated in gold electrodes, while 99.5% iron substrates treated with such films show up to an impressive 30% corrosion mitigation.

  11. Photoresponsive behavior and switchable nonlinear optical properties of Langmuir-Blodgett film based on azobenzene derivatives.

    PubMed

    Li, Qiuyue; Chi, Zhen; Li, Tianfeng; Ran, Xia; Guo, Lijun

    2017-05-15

    Here, we present the investigations of photo-isomerization behavior and the nonlinear optical properties of azobenzene derivative LB films. The few-layer LB films of AOB-t4 and BNB-t4 exhibit positive nonlinear refraction and two-photon absorption properties as revealed by picosecond Z-scan. The increased conjugation by introducing an oxadiazole group improves the photo-isomerization rate and the nonlinear optical properties, due to a weaker intermolecular interaction and the formation of J-aggregates within AOB-t4 LB film. The third-order susceptibility of cis-AOB-t4 9-layer LB film reaches 1.866 × 10(-9) esu and the two-photon absorption coefficient is on the order of 10(-8) m/W. Interestingly, the 15-layer AOB-t4 LB film shows negative nonlinear refraction and saturable absorption. Taken together, we have demonstrated the switchable nonlinear optical absorption and refraction properties of AOB-t4 LB film with changing film thickness, which is of significance for nonlinear optics and photonics applications.

  12. A low-symmetrical zinc phthalocyanine-based Langmuir-Blodgett thin films forNO2 gas sensor applications

    NASA Astrophysics Data System (ADS)

    Krichevsky, D. M.; Zasedatelev, A. V.; Tolbin, A. Yu; Zelenskiy, Yu M.; Krasovskii, V. I.; Karpo, A. B.; Tomilova, L. G.

    2016-08-01

    For many years effective detection of hazardous substances such as nitrogen oxides has remained a crucial task for environmental safety. In this article, we demonstrate high promising NO2-sensitive Langmuir-Blodgett monolayer structures based on 2-((2'- hydroxymethyl)-benzyloxy)-9(10),16(17),23(24)-tri-/re/-butyl- substituted low symmetrical zinc phthalocyanine complex bearing hydroxyl group on the periphery (compound 1). Amphiphilic arrangement of macrocycles was demonstrated to eliminate disordered molecular aggregation, resulting in a marked NO2 gas sensing effect under real atmospheric conditions. The optical response of monolayers was at room temperature, with the significant spectral changes being caused by the specific charge transfer process in phthalocyanine n-conjugated electronic system.

  13. Size and molecular configuration of dye aggregates in mixed Langmuir-Blodgett films based on merocyanine dye

    NASA Astrophysics Data System (ADS)

    Hirano, Yoshiaki; Okada, Takuya M.; Miura, Yasuhiro F.; Sugi, Michio; Ishii, Toshio

    2000-11-01

    We have studied the blue-shifted and the red-shifted bands formed in mixed Langmuir-Blodgett films of the merocyanine dye (MS)-arachidic acid (C20)-n-octadecane (AL18) ternary system with the molar mixing ratio [MS]:[C20]:[AL18]=1:2:x(0.5≦x≦5.0). The formation of the blue-shifted and the red-shifted bands depends on the AL18 content, and shows that the aggregation state can be modulated by changing the AL18 content. The observed overlapping spectra of the blue-shifted and the red-shifted bands are deconvoluted into two original bands. The extended dipole model has been applied to examine the aggregation state of MS referring to the deconvoluted spectra. Thus the estimated minimum aggregation number Nmin and the slip angle α between the long axis of the aggregate and the transition dipole moment are Nmin=40 and α=30° and Nmin=40 and α=50° for fully-developed J- and H-aggregates, respectively, seen for x≦1.5, and Nmin tends to decrease with increasing x.

  14. Second-harmonic generation in a polymer Langmuir - Blodgett film

    SciTech Connect

    Ivanova, V N; Kudryavtsev, V V; Lebedeva, G K; Maslyanitsyn, I A; Shigorin, V D; Chudinova, G K

    1998-09-30

    Second-harmonic generation was used to investigate nonlinear optical properties and the structure of multilayer Langmuir - Blodgett films of a copolymer of fluoroalkylmethacrylate with methacrylates containing an azo dye and a cinnamoyl group inside a chain. Quantum-chemical calculations were made of the components of the molecular hyperpolarisability tensor in which the intermolecular interactions were taken into account. The orientation of nonlinear optical fragments of a polymer chain relative to the substrate and components of the quadratic optical susceptibility tensor of the film were determined. (nonlinear optical phenomena)

  15. Langmuir-Blodgett films - From micron to angstrom

    NASA Astrophysics Data System (ADS)

    Bourdieu, L.; Silberzan, P.; Chatenay, D.

    1991-10-01

    Combining optical microscopy and atomic force microscopy, a complete characterization of Langmuir-Blodgett bilayers made of arachidic acid has been performed. At macroscopic scales, both techniques can be used to control the homogeneity of the transferred films. By atomic force microscopy, roughness and thickness of the bilayers could be determined. These are compatible with a normal orientation of the fully extended aliphatic chains with respect to the substrate. Molecular-resolution images give the first direct experimental evidence for the presence of pairs of dislocations in those systems.

  16. 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.

  17. Photochemical switching in conductive Langmuir-Blodgett films

    SciTech Connect

    Tachibana, Hiroaki; Nakamura, Takayoshi; Matsuboto, Mutsuyoshi; Komizu, Hideo; Manda, Eiichiro; Niino, Hiroyuki; Yabe, Akira; Kawabata, Yasujiro )

    1989-04-12

    Conductive Langmuir-Blodgett (LB) films have recently attracted much interest from the viewpoint of ultrathin film conductors at the molecular level. We have reported that the structure of the TCNQ (7,7,8,8-tetracyanoquinodimethane) column in the LB film of N-docosylpyridinium 7,7,8,8-tetracyanoquinodimethane is changed by the variation of the subphase temperature. In addition, a partial charge transfer state of N-docosylpyridinium bis(7,7,8,8-tetracyanoquinodimethane) is stable at the air-water interface and the as-deposited LB film is highly conductive without doping or any other treatments. It will open up a wide scope of applications of the functions of the LB films can be controlled by external stimuli such as light, heat, or chemical treatments. One of the most promising candidates for this purpose is to introduce a switching unit into an amphiphilic molecule. When the switching unit is triggered by an external stimulus, the signal is conveyed through the transmission unit to the working unit and induces a change in the structure and functions of the working unit. In this paper, we use the azobenzene as the switching unit, the alkyl chain as the transmission unit, and the charge-transfer complex of TCNQ as the working unit. In this arrangement, the photoisomerization of the azobenzene induces the reversible change in the lateral conductivity of the LB film.

  18. An applied science perspective of Langmuir-Blodgett films

    NASA Astrophysics Data System (ADS)

    Roberts, G. G.

    1985-11-01

    Langmuir-Blodgett (LB) films are prepared by transferring floating organic monolayers onto solid substrates. A combination of innovative chemistry and a carefully engineered instrument (a Langmuir trough) can result in high quality monomolecular assemblies displaying a high degree of structural order. The technique was first reported about fifty years ago and since then, LB films have been widely used as model systems in fundamental research. However, it is only during the past decade that the extensive applied potential has been recognised. Their precise thickness, coupled with the degree of control over the molecular architecture, has now firmly established a role for these layers in thin film technology.Following a historical introduction, this review describes the preparation and characterization of LB films and summarizes their importance in basic science. Particular emphasis is then placed on their potential applications, especially in fields related to electronics. The article concludes with a summary of the possible future role of ordered monomolecular films in the general field of molecular electronics.

  19. Langmuir-Blodgett films of amphiphilic push-pull porphyrins

    SciTech Connect

    Chou, H.; Chen, C.T.; Stork, K.F.; Bohn, P.W.; Suslick, K.S. )

    1994-01-13

    A series of nitrophenyl-amidophenyl-substituted porphyrins with n-C[sub 17]H[sub 35] tails have been synthesized and fully characterized. Good Langmuir-Blodgett films of these materials can be prepared on water and transferred successfully to glass slides. Mean molecular areas for the series were measured and found to increase from 80 to 230 A[sup 2] as the number of aliphatic chains increased from one to four. As determined by linear dichroic measurements, this change in area does not correspond to a change in the orientation of the porphyrin with respect to the surface. In the absence of the steric constraints of multiple aliphatic chains, porphyrin-porphyrin stacking permits close packing of the rings. As the number of aliphatic chains on the porphyrin periphery increases, however, the porphyrin planes must pack more loosely. Thus, the porphyrin macrocycle orientation is determined by interactions between porphyrin rings and between porphyrins and the aqueous (or polar glass) surface. In contrast, the differences in the observed mean molecular area are determined independently by packing constraints imposed by the pendant hydrocarbon chains. 13 refs., 3 figs., 1 tab.

  20. Langmuir and Langmuir-Blodgett films containing a porphyrin-ruthenium complex.

    PubMed

    Wohnrath, Karen; Dinelli, Luis R; Mello, Sarita V; Constantino, Carlos J L; Leblanc, Roger M; Batista, Alzir A; Oliveira, Osvaldo N

    2005-06-01

    The fabrication of supramolecular structures from the tetraruthenated porphyrin-containing phosphines, {TPyP[RuCl3(dppb)]4}, RuTPyP, is demonstrated with Langmuir and Langmuir-Blodgett films. The surface pressure-molecular area isotherms (pi-A) point to an edge-on arrangement for the RuTPyP molecules in the condensed state. Weak aggregation in the Langmuir films was indicated by non-zero surface potentials at large areas per molecule and a slight red shift in the ultraviolet-visible absorption spectrum in comparison to the spectrum in solution. Further aggregation occurs in the Z-type Langmuir-Blodgett films, which was confirmed with ultraviolet-visible spectroscopy of the deposited films. Fourier transform infrared and Raman spectroscopic data for powder and Langmuir-Blodgett films indicate that the RuTPyP molecules are chemically stable in Langmuir-Blodgett films regardless of the contact with water during film fabrication. The nanostructured nature of the Langmuir-Blodgett films was manifested in cyclic voltammetry due to the high sensitivity of the metallic centers in RuTPyP. Electrodes modified with Langmuir-Blodgett films exhibit an anodic peak at 100 mV and a cathodic peak at 7 mV, which is assigned to RuIII/RuII redox processes. Furthermore, Langmuir-Blodgett films from RuTPyP showed electrocatalytic activity for oxidation of benzyl alcohol, illustrated by a large shift of 100 mV in the anodic peak at 400 mV, while electropolymerized and cast films of the same compound displayed smaller and no activities, respectively.

  1. Surface wettability and platelet adhesion studies on Langmuir Blodgett films

    NASA Astrophysics Data System (ADS)

    Lee, Yuh-Lang; Chen, Chi-Yun

    2003-02-01

    Because Langmuir-Blodgett (LB) deposition technique is known to be capable of preparing highly ordered monomolecular films with densely packed structure, LB technique is used to prepare films of DPPC, DMPC, cholesterol, octadecylamine (ODA), and stearic acid, with thickness of one molecular layer. The film surfaces were characterized by dynamic contact angle measurement and the interaction between blood and these materials were investigated. The properties of LB films were also compared with the results obtained on continuous films prepared by solution dipping. The results show that the contact angles of water on LB films of the five compounds decreases as the following order: ODA> DMPC≈ DPPC> stearic acid > cholesterol. The hydrophobic property reflects the highest organization of ODA molecules on the substrate, which is related to its interaction between the molecule and substrate. The advancing contact angle of ODA is equivalent to that of a methyl-terminated SAM, but its receding contact angle is smaller which implies the exposing of hydrophilic pole or glass substrate on LB film. The irregular orientation of molecules on LB film increases with decreasing of contact angle and is especially significant on LB film of cholesterol which has highest hydrophilic property. The plate adhesion experiments on the continuous films show that the hemocompatibility of the five materials decreases as the order: DPPC≈ DMPC> ODA> cholesterol> stearic acid ≈ glass. This result implies that the lipid has highest blood compatibility, and then -NH 2, and then -OH functionality. On the contrary, the glass surface, -COOH and -CH 3 functionalities have high reactivity to platelet. Due to the possibility of glass exposure on LB films, as estimated from the surface wettability, the LB films have higher platelet reactivity, especially for the cholesterol, compared with the continuous films. Because the interaction of the LB film to the substrate is physical force, the deposited

  2. Langmuir-Blodgett film of phycobilisomes from blue-green alga Spirulina platensis.

    PubMed

    Chen, Chao; Zhang, Yu-Zhong; Chen, Xiu-Lan; Zhou, Bai-Cheng; Gao, Hong-Jun

    2003-10-01

    The phycobilisomes were isolated from blue-green alga Spirulina platensis, and could form monolayer film at air/water interface. The monolayer film of phycobilisomes was transferred to newly cleaved mica, and coated with gold. Scanning tunneling microscope was used to investigate the structure of the Langmuir-Blodgett film of phycobilisomes. It was shown that phycobilisomes in the monolayer arrayed in rows with core attaching on the substrate surface and rods radiating towards the air phase, this phenomenon was similar to the arrangement of phycobilisomes on cytoplasmic surface of thylakoid membrane in vivo. The possible applications of the Langmuir-Blodgett film of phycobilisomes were also discussed.

  3. Enzyme activity of catalase immobilized in Langmuir-Blodgett films of phospholipids.

    PubMed

    Goto, Thiago E; Lopez, Ricardo F; Oliveira, Osvaldo N; Caseli, Luciano

    2010-07-06

    A major challenge for producing low cost biosensors based on nanostructured films with control of molecular architectures is to preserve the catalytic activity of the immobilized biomolecules. In this study, we show that catalase (HRP) keeps its activity if immobilized in Langmuir-Blodgett (LB) films of dipalmitoyl phosphatidylglycerol (DPPG). The incorporation of catalase into a DPPG monolayer at the air-water interface was demonstrated with surface pressure and surface potential isotherms, in addition to polarization-modulated infrared reflection absorption spectroscopy (PM-IRRAS). According to the PM-IRRAS data, catalase was not denatured upon adsorption on a preformed DPPG monolayer and could be transferred onto a solid substrate. The catalytic activity of catalase in a mixed LB film with DPPG was ca. 13% higher than in solution. The control of molecular architecture and choice of a suitable phospholipid matrix allows catalase-containing LB films to be used in sensing hydrogen peroxide.

  4. Structure and physicochemical properties of cation polymethine dyes in Langmuir-Blodgett films

    NASA Astrophysics Data System (ADS)

    Ibrayev, N. Kh.; Seliverstova, E. V.; Tenchurina, A. R.; Ishchenko, A. A.; Shargaeva, A. Yu.

    2013-12-01

    The physicochemical properties of monomolecular layers of amphiphilic cation polymethine dyes (i.e., thia- and oxacarbocyanines) on the surface of a water subphase are studied along with the conditions of Langmuir-Blodgett (LB) film preparation. The area occupied by one dye molecule in the liquid-stretched and liquid-condensed states of a monolayer is determined. Based on a comparison of experimental and theoretically calculated areas, the nature of dye packing in monolayers is studied by means of molecular mechanics using data from conformation analysis. The spectral and luminescent properties of cationic polymethine dyes in various media are investigated. Excimer fluorescence is observed in LB films. The excimers in LB films are found to arise not from monomers but from dye dimers. A possible mechanism of their formation is considered.

  5. 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.

  6. Analysis of organic acids and phenols of interest in the wine industry using Langmuir-Blodgett films based on functionalized nanoparticles.

    PubMed

    Medina-Plaza, C; García-Cabezón, C; García-Hernández, C; Bramorski, C; Blanco-Val, Y; Martín-Pedrosa, F; Kawai, T; de Saja, J A; Rodríguez-Méndez, M L

    2015-01-01

    A chemically modified electrode consisting of Langmuir-Blodgett (LB) films of n-dodecanethiol functionalized gold nanoparticles (SDODAuNP-LB), was investigated as a voltammetric sensor of organic and phenolic acids of interest in the wine industry. The nanostructured films demonstrated interfacial properties being able to detect the main organic acids present in grapes and wines (tartaric, malic, lactic and citric). Compared to a bare ITO electrode, the modified electrodes exhibited a shift of the reduction potential in the less positive direction and a marked enhancement in the current response. Moreover, the increased electrocatalytic properties made it possible to distinguish between the different dissociable protons of polyprotic acids. The SDODAuNP-LB sensor was also able to provide enhanced responses toward aqueous solutions of phenolic acids commonly found in wines (caffeic and gallic acids). The presence of nanoparticles increased drastically the sensitivity toward organic acids and phenolic compounds. Limits of detection as low as 10(-6) mol L(-1) were achieved. Efficient catalytic activity was also observed in mixtures of phenolic acid/tartaric in the range of pHs typically found in wines. In such mixtures, the electrode was able to provide simultaneous information about the acid and the phenol concentrations with a complete absence of interferences. The excellent sensing properties shown by these sensors could be attributed to the electrocatalytic properties of the nanoparticles combined with the high surface to volume ratio and homogeneity provided by the LB technique used for the immobilization. Moreover, the LB technique also provided an accurate method to immobilize the gold nanoparticles giving rise to stable and reproducible sensors showing repeatability lower than 2% and reproducibility lower than 4% for all the compounds analyzed. Copyright © 2014. Published by Elsevier B.V.

  7. All-Carbon Electrode Molecular Electronic Devices Based on Langmuir-Blodgett Monolayers.

    PubMed

    Sangiao, Soraya; Martín, Santiago; González-Orive, Alejandro; Magén, César; Low, Paul J; De Teresa, José M; Cea, Pilar

    2017-02-01

    Nascent molecular electronic devices, based on monolayer Langmuir-Blodgett films sandwiched between two carbonaceous electrodes, have been prepared. Tightly packed monolayers of 4-((4-((4-ethynylphenyl)ethynyl)phenyl)ethynyl)benzoic acid are deposited onto a highly oriented pyrolytic graphite electrode. An amorphous carbon top contact electrode is formed on top of the monolayer from a naphthalene precursor using the focused electron beam induced deposition technique. This allows the deposition of a carbon top-contact electrode with well-defined shape, thickness, and precise positioning on the film with nm resolution. These results represent a substantial step toward the realization of integrated molecular electronic devices based on monolayers and carbon electrodes. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. Energy dependence of the electron attenuation length in lead arachidate Langmuir-Blodgett films

    NASA Astrophysics Data System (ADS)

    Sastry, Murali; Badrinarayanan, S.; Ganguly, P.

    1992-04-01

    The attenuation lengths for electrons in the kinetic-energy range 1350-550 eV in lead arachidate [(C19H39COO)2Pb] Langmuir-Blodgett films have been determined from measurements of the x-ray photoemission intensity variation with electron takeoff angle. Attenuation lengths are determined from an elementary layer model proposed in the paper. The layer model increases the kinetic-energy range over which attenuation lengths can be determined and is thus more versatile than the overlayer method. The Bethe equation for inelastic scattering of electrons is found to describe the energy dependence of the measured attenuation lengths quite well. The material dependence of the Bethe parameters determined by Tanuma, Powell, and Penn [Surf. Interface Anal. 11, 577 (1988)] for some metals, oxides, and insulators does not exist in the case of lead arachidate Langmuir-Blodgett films.

  9. 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.

  10. 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.

  11. Molecular positional order in langmuir-blodgett films by atomic force microscopy.

    PubMed

    Bourdieu, L; Ronsin, O; Chatenay, D

    1993-02-05

    Langmuir-Blodgett films of barium arachidate have been studied on both macroscopic and microscopic scales by atomic force microscopy. As prepared, the films exhibit a disordered hexagonal structure; molecularly resolved images in direct space establish a connection between the extent of the positional order and the presence of defects such as dislocations. Upon heating, the films reorganize into a more condensed state with a centered rectangular crystallographic arrangement; in this new state the films exhibit long-range positional order and unusual structural features, such as a height modulation of the arachidic acid molecules.

  12. Molecular Positional Order in Langmuir-Blodgett Films by Atomic Force Microscopy

    NASA Astrophysics Data System (ADS)

    Bourdieu, L.; Ronsin, O.; Chatenay, D.

    1993-02-01

    Langmuir-Blodgett films of barium arachidate have been studied on both macroscopic and microscopic scales by atomic force microscopy. As prepared, the films exhibit a disordered hexagonal structure; molecularly resolved images in direct space establish a connection between the extent of the positional order and the presence of defects such as dislocations. Upon heating, the films reorganize into a more condensed state with a centered rectangular crystallographic arrangement; in this new state the films exhibit long-range positional order and unusual structural features, such as a height modulation of the arachidic acid molecules.

  13. 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.

  14. Matrix dependent changes in metachromasy of crystal violet in Langmuir-Blodgett films

    NASA Astrophysics Data System (ADS)

    Shil, Ashis; Saha, Mitu; Debnath, Chandan; Hussain, S. A.; Bhattacharjee, D.

    2016-11-01

    This communication reports the effect of building matrices and nano clay platelets on the aggregation pattern of a water soluble cationic fluorescent dye Crystal Violet (CV) in Langmuir-Blodgett (LB) Films. When stearic acid (SA) was used as a building matrix, pressure induced changes in metachromasy was observed in the SA-CV complex LB films with a characteristic J-band formed at the longer wavelength side. On the other hand, clay incorporated hybrid LB films showed high degree of control over H-dimeric band. Isotherm characteristics, Brewster Angle Microscopic (BAM) images, UV-vis absorption and fluorescence characteristic studies were employed to investigate this result.

  15. Langmuir and Langmuir-Blodgett films of a maleic anhydride derivative: effect of subphase divalent cations.

    PubMed

    Martín-García, B; Velázquez, M Mercedes; Pérez-Hernández, J A; Hernández-Toro, J

    2010-09-21

    We report the study of the equilibrium and dynamic properties of Langmuir monolayers of poly(styrene-co-maleic anhydride) partial 2-buthoxyethyl ester cumene terminated polymer and the effect of the Mg(NO(3))(2) addition in the water subphase on the film properties. Results show that the polymer monolayer becomes more expanded when the electrolyte concentration in the subphase increases. Dense polymer films aggregate at the interface. The aggregates are transferred onto silicon wafers using the Langmuir-Blodgett methodology and the morphology is observed by AFM. The structure of aggregates depends on the subphase composition of the Langmuir film transferred onto the silicon wafer.

  16. Magnetic ordering in nickel-zinc nanoferrite thin film formed by Langmuir Blodgett technique

    NASA Astrophysics Data System (ADS)

    Thakur, Sangeeta; Pandit, Pallavi; Sharma, S. K.; Katyal, S. C.; Singh, Mahavir; Gupta, Ajay

    2013-12-01

    Nickel-zinc nanoferrite thin films, which reveal application for magnetic materials, were prepared by Langmuir-Blodgett technique. X-ray reflectivity fitting was done using three layer model. Thickness of a monolayer of nanoparticles is obtained as 23.5 Å. Surface roughness increases as the thickness of the film increases. Fourier transform infrared spectra confirmed that the structure remains cubic spinel after thin film formation. We have measured zero-field cooled and field cooled magnetization and discussed the behavior in three parts: the ferromagnetic part, transition region, and the superparamagnetic part.

  17. 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.

  18. 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.

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

    PubMed

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

    2013-12-21

    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.

  20. 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.

  1. A multiscale structural study of nanoparticle films prepared by the Langmuir-Blodgett technique

    NASA Astrophysics Data System (ADS)

    Dochter, Alexandre; Pichon, Benoit P.; Fleutot, Solenne; Medard, Nicolas; Begin-Colin, Sylvie

    2013-02-01

    Arrays of magnetic nanoparticles (NPs) represent a very interesting challenge toward the development of new devices for magnetic applications such as data storage and spintronic. The final properties of such assemblies depending essentially on the spatial arrangement of NPs, it is of first importance to investigate precisely their structure. Here, the structure of monolayer and multilayer films of magnetic iron oxide NPs assembled by the Langmuir-Blodgett (LB) technique has been studied by usual techniques such as SEM, AFM and ellipsometry and by a new and an easy to process enhanced optical technique: the Surface Enhancement Ellipsometry Contrast (SEEC) microscopy. This technique is based on the use of a new generation of microscope slides used as substrates which allow the strong enhancement of the sample contrast to a point where it becomes possible to visualize the structure of monolayer and multilayer films at the nanoscale with a conventional optical microscope. The SEEC microscopy is demonstrated to be complementary to usual characterization techniques to study the structure of NPs films, especially for films containing very small nanosized NPs which are more difficult to analyze by usual techniques. While the film structure is investigated with lateral resolution of microns, the layer thickness is analyzed at the nanoscale (with a precision of 0.3 nm) with a close fit to the experimental measurements on local (AFM) and on larger (ellipsometry) areas. This technique presents the advantage to visualize directly the topography of NPs assemblies on very large areas by extracting information such as the height profile, the film roughness and generating 3D images.

  2. Langmuir-Blodgett films of cellulose nanocrystals: preparation and characterization.

    PubMed

    Habibi, Youssef; Foulon, Laurence; Aguié-Béghin, Véronique; Molinari, Michaël; Douillard, Roger

    2007-12-15

    The goal of this work is the preparation of monolayers of cellulose I nanocrystals providing flat crystalline cellulose surfaces. Suspensions of cellulose nanocrystals were prepared by hydrolyzing ramie and tunicin fibers with sulfuric acid. Due to surface grafted sulfate groups, the negatively charged, rod-like cellulose nanocrystals were found to form stable layers at the air-water interface in the presence of a cationic amphiphilic molecule such as dioctadecyldimethylammonium (DODA) used in this work. These layers were formed at different cellulose-DODA weight ratios, compressed and analyzed by tensiometry, ellipsometry and Brewster angle microscopy. At low cellulose concentrations the layers are discontinuous, becoming dense and homogeneous upon reaching a critical weight ratio, which depends on the aspect ratio of the cellulose nanocrystals. After transfer onto silicon wafers, the surface composition and morphology as well as the thickness of the films were examined by X-ray photoelectron spectroscopy, ellipsometry and atomic force microscopy. The results indicate that they are monolayer films, well structured, relatively smooth and pure. These films offer a crystalline and easily reproducible model cellulose surface.

  3. Oriented polyvinylidene fluoride-trifluoroethylene (P(VDF-TrFE)) films by Langmuir-Blodgett deposition: a synchrotron X-ray diffraction study.

    PubMed

    Lindemann, W R; Philiph, R L; Chan, D W W; Ayers, C T; Perez, E M; Beckman, S P; Strzalka, J; Chaudhary, S; Vaknin, D

    2015-11-21

    Langmuir-Blodgett films of polyvinylidene fluoride trifluoroethylene - P(VDF-TrFE)-copolymers possess substantially improved electrocaloric and pyroelectric properties, when compared with conventionally spin-cast films. In order to rationalize this, we prepared single-layered films of P(VDF-TrFE) (70 : 30) using both deposition techniques. Grazing incidence wide-angle X-ray scattering (GIWAXS), reveals that Langmuir-Blodgett deposited films have a higher concentration of the ferroelectric β-phase crystals, and that these films are highly oriented with respect to the substrate. Based on these observations, we suggest alternative means of deposition, which may substantially enhance the electrocaloric effect in P(VDF-TrFE) films. This development has significant implications for the potential use of P(VDF-TrFE) in solid-state refrigeration.

  4. 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.

  5. Using phospholipid Langmuir and Langmuir-Blodgett films as matrix for urease immobilization.

    PubMed

    Caseli, Luciano; Crespilho, Frank N; Nobre, Thatyane M; Zaniquelli, Maria Elisabete D; Zucolotto, Valtencir; Oliveira, Osvaldo N

    2008-03-01

    The immobilization of enzymes in organized two-dimensional matrices is a key requirement for many biotechnological applications. In this paper, we used the Langmuir-Blodgett (LB) technique to obtain controlled architectures of urease immobilized in solid supports, whose physicochemical properties were investigated in detail. Urease molecules were adsorbed at the air-water interface and incorporated into Langmuir monolayers of the phospholipid dipalmitoyl phosphatidyl glycerol (DPPG). Incorporation of urease made DPPG monolayers more flexible and caused the reduction of the equilibrium and dynamic elasticity of the film. Urease and DPPG-urease mixed monolayers could be transferred onto solid substrates, forming LB films. A close packing arrangement of urease was obtained, especially in the mixed LB films, which was inferred with nanogravimetry and electrochemistry measurements. From the blocking effect of the LB films deposited onto indium tin oxide (ITO) substrates, the electrochemical properties of the LB films pointed to a charge transport controlled by the lipid architecture.

  6. Langmuir-Blodgett film and nonlinear optical property of C 60-glycine ester derivative

    NASA Astrophysics Data System (ADS)

    Zhou, Dejian; Gan, Liangbing; Luo, Chuping; Tan, Haisong; Huang, Chunhui; Liu, Zhongfan; Wu, Zhongyun; Zhao, Xinsheng; Xia, Xiaohua; Zhang, Songbin; Sun, Fengqing; Xia, Zongju; Zou, Yinghua

    1995-03-01

    Both the Langmuir and Langmuir-Blodgett films of two C 60-glycine ester derivatives, C 60(C 6H 9NO 4) ( 1) and C 60(C 8H 13NO 4) ( 2), have been prepared at the air/water interface. The Langmuir films can be readily transferred onto hydrophilic quartz substrates in Z type to form LB films. The LB film of 1 has good vertical homogeneity as indicated by UV-VIS spectra and a SHG study. The second- and third-order molecular hyperpolarizabilities β and γ have been determined to be (2.3 ± 1.0) × 10 -29, 3.4 × 10 -31 esu for 1 and (1.9 ± 0.8) × 10 -29, 3.3 × 10 -31 esu for 2, respectively.

  7. 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.

  8. 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

  9. Preparation of hierarchically aligned carbon nanotube films using the Langmuir-Blodgett technique.

    PubMed

    Lee, Jae-Hyeok; Kang, Won-Seok; Nam, Gwang-Hyeon; Choi, Sung-Wook; Kim, Jae-Ho

    2009-12-01

    Hierarchically-aligned single-walled carbon nanotube (SWNT) films over large areas were fabricated by using Langmuir-Blodgett (LB) technique. Thiophenyl-modified SWNTs spreading solution in chloroform was prepared through amidation reaction of oxidized SWNTs. The resulting SWNTs were found to form stable colloidal suspensions in organic solvents, such as chloroform, which is a suitable solvent for the LB application. The compression of the thiophenyl-modified SWNTs spread onto the water surface of an LB trough leading to a uniform SWNT Langmuir monolayer, where SWNTs were aligned parallel to the trough barrier. Optical anisotropy of SWNTs LB films on quartz substrate was confirmed by polarized UV-Vis/NIR spectroscopic measurement. Moreover, the electrical conductivity of the resulting SWNT films, which were parallel to the tube axis, was found to be approximately 15 times higher than those that were perpendicular to the axis, reflecting anisotropic electrical properties due to the uniaxial alignment of individual SWNT bundles.

  10. Supramolecular architectures of iron phthalocyanine Langmuir-Blodgett films: The role played by the solution solvents

    NASA Astrophysics Data System (ADS)

    Rubira, Rafael Jesus Gonçalves; Aoki, Pedro Henrique Benites; Constantino, Carlos José Leopoldo; Alessio, Priscila

    2017-09-01

    The developing of organic-based devices has been widely explored using ultrathin films as the transducer element, whose supramolecular architecture plays a central role in the device performance. Here, Langmuir and Langmuir-Blodgett (LB) ultrathin films were fabricated from iron phthalocyanine (FePc) solutions in chloroform (CHCl3), dichloromethane (CH2Cl2), dimethylformamide (DMF), and tetrahydrofuran (THF) to determine the influence of different solvents on the supramolecular architecture of the ultrathin films. The UV-vis absorption spectroscopy shows a strong dependence of the FePc aggregation on these solvents. As a consequence, the surface pressure vs. mean molecular area (π-A) isotherms and Brewster angle microscopy (BAM) reveal a more homogeneous (surface morphology) Langmuir film at the air/water interface for FePc in DMF. The same morphological pattern observed for the Langmuir films is preserved upon LB deposition onto solid substrates. The Raman and FTIR analyses indicate the DMF-FePc interaction relies on coordination bonds between N atom (from DMF) and Fe atom (from FePc). Besides, the FePc molecular organization was also found to be affected by the DMF-FePc chemical interaction. It is interesting to note that, if the DMF-FePc leads to less aggregated FePc either in solution or ultrathin films (Langmuir and LB), with time (one week) the opposite trend is found. Taking into account the N-Fe interaction, the performance of the FePc ultrathin films with distinct supramolecular architectures composing sensing units was explored as proof-of-principle in the detection of trace amounts of atrazine herbicide in water using impedance spectroscopy. Further statistical and computational analysis reveal not only the role played by FePc supramolecular architecture but also the sensitivity of the system to detect atrazine solutions down to 10-10 mol/L, which is sufficient to monitor the quality of drinking water even according to the most stringent international

  11. Experimental analysis of the thermodynamic mechanism of Langmuir-Blodgett film transfer

    SciTech Connect

    Egusa, Syun; Gemma, Nobuhiro, Azuma, Makoto )

    1990-03-22

    An experimental investigation was made on the mechanism for the transfer of a Langmuir-Blodgett (LB) film. The transfer ratio ({rho}) and the interfacial force (f) were observed for stearyl alcohol and cadmium stearate monolayers on silicon substrates, by systematically varying both the surface pressures ({pi}) of the monolayer and the hydrophilicities of the substrate characterized by contact angle ({theta}{sub 0}). It was found that the ratios {rho} observed both for up- and down-stroke depositions changed discretely within zero and unity, divided at the critical values of {pi} and {theta}{sub 0}. To examine the film-transfer characteristics, on the basis of thermodynamics, the interfacial forces applied to the moving substrate were measured during the deposition process.

  12. Thin nanocomposite films of polyaniline/Au nanoparticles by the Langmuir-Blodgett technique.

    PubMed

    Tanami, Golan; Gutkin, Vitaly; Mandler, Daniel

    2010-03-16

    The Langmuir-Blodgett (LB) method was used to deposit multilayers of polyaniline (PANI)- and mercaptoethanesulfonate (MES)-stabilized Au nanoparticles. The electrostatic interaction between the negatively charged nanoparticles in the subphase and the positively charged PANI at the air-water interface assisted the deposition of the nanocomposite film onto a solid support. These PANI/Au-NPs films were characterized using cyclic voltammetry, copper under potential deposition, scanning electron microscopy, atomic force microscopy, and X-ray photoelectron spectroscopy. We found that the nanocomposite layers were uniform and reproducible. The density of Au-NPs in the monolayer depended on the acidity of the subphase as well as on the nanoparticles concentration. Moreover, the Au-NPs extrude above the PANI and therefore could be used as nanoelectrodes for the underpotential deposition (UPD) of copper.

  13. Correlations in the interface structure of Langmuir-Blodgett films observed by x-ray scattering

    NASA Astrophysics Data System (ADS)

    Nitz, V.; Tolan, M.; Schlomka, J.-P.; Seeck, O. H.; Stettner, J.; Press, W.; Stelzle, M.; Sackmann, E.

    1996-08-01

    X-ray scattering experiments within the region of total external reflection as well as grazing-incidence-diffraction measurements from Langmuir-Blodgett films are shown. All measurements are explained quantitatively using the distorted-wave Born approximation (small qz regions) or a simple kinematic scattering theory (large qz regions) for layered systems. Since rather imperfect systems are investigated, strong vertical correlations between the roughnesses of the organic layer interfaces were found for two samples consisting of 9 and 11 layers, respectively, of cadmium-arachidate on silicon (100) surfaces. This conformal roughness does not stem from the substrate but from defects and holes of the first transferred layer. The model of self-affine rough interfaces yields consistent parameters compared with grazing incidence diffraction experiments and no hints towards a cadmium-arachidate island formation are observed.

  14. 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.

  15. 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

  16. Epifluorescence imaging of electrochemically switchable Langmuir-Blodgett films of Nafion.

    PubMed

    Moretto, Ligia Maria; Kohls, Thiago; Chovin, Arnaud; Sojic, Neso; Ugo, Paolo

    2008-06-17

    A combination of electrochemistry and luminescence methods was exploited to obtain information on the electrochemical activity and homogeneity of Nafion Langmuir-Blodgett films. The redox behavior of the Ru(bpy)3(2+) probe incorporated in the Nafion film was monitored by epifluorescence microscopy. The photoluminescent images, recorded by a charge-coupled device (CCD) camera, reflect the distribution of the probe in the film, which resulted as very uniform, particularly in comparison with spin-coated films. Apparent diffusion coefficients (Dapp) determined by cyclic voltammetry for films of less than 10 layers are in the range of 1 x 10(-12) to 8 x 10(-12) cm(2) s(-1), that is, 2 orders of magnitude lower than values reported in the literature for spin-coated Nafion films. The application to the electrode of a potential able to oxidize the luminescent Ru(bpy)3(2+) to the nonluminescent Ru(bpy)3(3+) switched off the photoluminescence with a response time that for the LB films was much shorter than that for the spin-coated ones. Experimental evidence and calculations indicate that lowering of the film thickness down to the nanometric level is very effective in shortening the switching time, notwithstanding the lowering of the Dapp value in LB films.

  17. Yield strength of glued Langmuir-Blodgett films determined by friction force microscopy.

    PubMed

    Wagner, Kyle C; Wang, Yao; Regen, Steven L; Vezenov, Dmitri V

    2013-09-07

    We used friction force microscopy measurements to determine the yield strength of several structurally similar Langmuir-Blodgett (LB) bilayer films deposited on a hydrophobic substrate. Film failure was initiated by increasing the load applied by the probe of the atomic force microscope in the course of continuous scanning at nominally the same location on the sample. This film failure was readily detected in friction versus load curves, as well as by imaging of trenches created due to removal of the film. The depths of the trenches formed in the course of these yield strength experiments were consistent with complete removal of these bilayer films, as evidenced by comparisons to film thicknesses measured by ellipsometry. The structure of the LB bilayer was modified by replacing a tetra-chain amphiphile bearing four quaternary ammonium groups with a polymeric surfactant resulting in little change in the yield strength. On the other hand, the addition of a polyanionic gluing layer at the central interface of the bilayers almost doubled the yield strength of the films. To uncover any possible structural effects created by changes in the terminal functionality, the hydrocarbon top layer of the bilayer was replaced with a perfluorinated capping layer. In spite of the changes in frictional properties, the yield strength of this film also appeared to be dominated by the presence of the glued interface.

  18. Redox-active cellulose Langmuir-Blodgett films containing beta-carotene as a molecular wire.

    PubMed

    Sakakibara, Keita; Kamitakahara, Hiroshi; Takano, Toshiyuki; Nakatsubo, Fumiaki

    2007-05-01

    Redox-active Langmuir-Blodgett (LB) films containing dihydrophytyl ferrocenoate (DFc) and beta-carotene (betaC) were fabricated by use of 6-O-dihydrophytylcellulose (DHPC) as a matrix. A mixture of DFc-DHPC formed a stable monolayer. Atomic force microscopy images revealed that the DFc molecules were dispersed uniformly throughout the surface in the ratio DFc:DHPC = 2:8 at 30 mN m-1. The DFc-DHPC monolayer was transferred successfully onto a substrate, yielding Y-type LB films. Cyclic voltammograms for the DFc-DHPC LB films on an indium tin oxide (ITO) electrode exhibited a well-defined surface wave. The voltammograms of the DFc-DHPC LB films exhibited 60-40% redox-active ferrocene moieties, whereas those of the DFc-DHPC-betaC LB films exhibited 90-70%. X-ray diffraction patterns indicated that the distance between layers was independent of betaC molecules incorporated into the LB films. Consequently, these results suggested that betaC can function as a molecular wire.

  19. 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.

  20. Immobilization of alcohol dehydrogenase in phospholipid Langmuir-Blodgett films to detect ethanol.

    PubMed

    Caseli, Luciano; Perinotto, Angelo C; Viitala, Tapani; Zucolotto, Valtencir; Oliveira, Osvaldo N

    2009-03-03

    Enzyme immobilization in nanostructured films may be useful for a number of biomimetic systems, particularly if suitable matrixes are identified. Here we show that alcohol dehydrogenase (ADH) has high affinity toward a negatively charged phospholipid, dimyristoylphosphatidic acid (DMPA), which forms a Langmuir monolayer at an air-water interface. Incorporation of ADH into the DMPA monolayer was monitored with surface pressure measurements and polarization-modulation infrared reflection absorption spectroscopy, with the alpha-helices from ADH being mainly oriented parallel to the water surface. ADH remained at the interface even at high surface pressures, thus allowing deposition of Langmuir-Blodgett (LB) films from the DMPA-ADH film. Indeed, interaction with DMPA enhances the transfer of ADH, where the mass transferred onto a solid support increased from 134 ng for ADH on a Gibbs monolayer to 178 ng for an LB film with DMPA. With fluorescence spectroscopy it was possible to confirm that the ADH structure was preserved even after one month of the LB deposition. ADH-containing films deposited onto gold-interdigitated electrodes were employed in a sensor array capable of detecting ethanol at concentrations down to 10 ppb (in volume), using impedance spectroscopy as the method of detection.

  1. 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.

  2. Colloidal interactions between Langmuir-Blodgett bitumen films and fine solid particles.

    PubMed

    Long, Jun; Zhang, Liyan; Xu, Zhenghe; Masliyah, Jacob H

    2006-10-10

    In oil sand processing, accumulation of surface-active compounds at various interfaces imposes a significant impact on bitumen recovery and bitumen froth cleaning (i.e., froth treatment) by altering the interfacial properties and colloidal interactions among various oil sand components. In the present study, bitumen films were prepared at toluene/water interfaces using a Langmuir-Blodgett (LB) upstroke deposition technique. The surface of the prepared LB bitumen films was found to be hydrophobic, comprised of wormlike aggregates containing a relatively high content of oxygen, sulfur, and nitrogen, indicating an accumulation of surface-active compounds in the films. Using an atomic force microscope, colloidal interactions between the LB bitumen films and fine solids (model silica particles and clay particles chosen directly from an oil sand tailing stream) were measured in industrial plant process water and compared with those measured in simple electrolyte solutions of controlled pH and divalent cation concentrations. The results show a stronger long-range repulsive force and weaker adhesion force in solutions of higher pH and lower divalent cation concentration. In plant process water, a moderate long-range repulsive force and weak adhesion were measured despite its high electrolyte content. These findings provide more insight into the mechanisms of bitumen extraction and froth treatment.

  3. Magnetic Langmuir-Blodgett films of ferritin with different iron contents.

    PubMed

    Clemente-León, Miguel; Coronado, Eugenio; Soriano-Portillo, Alejandra; Colacio, Enrique; Domínguez-Vera, José M; Galvez, Natividad; Madueño, Rafael; Martín-Romero, María T

    2006-08-01

    Magnetic Langmuir-Blodgett films of four ferritin derivatives with different iron contents containing 4220, 3062, 2200, and 1200 iron atoms, respectively, have been prepared by using the adsorption properties of a 6/1 mixed monolayer of methyl stearate (SME) and dioctadecyldimethylammonium bromide (DODA). The molecular organization of the mixed SME/DODA monolayer is strongly affected by the presence of the water-soluble protein in the subphase as shown by pi-A isotherms, BAM images, and imaging ellipsometry at the water-air interface. BAM images reveal the heterogeneity of this mixed monolayer at the air-water interface. We propose that the ferritin is located under the mixed matrix in those regions where the reflectivity is higher whereas the dark regions correspond to the matrix. Ellipsometric angle measurements performed in zones of different brightness of the mixed monolayer confirm such a heterogeneous distribution of the protein under the lipid matrix. Transfer of the monolayer onto different substrates allowed the preparation of multilayer LB films of ferritin. Both infrared and UV-vis spectroscopy indicate that ferritin molecules are incorporated within the LB films. AFM measurements show that the heterogeneous distribution of the ferritin at the water-air interface is maintained when it is transferred onto solid substrates. Magnetic measurements show that the superparamagnetic properties of these molecules are preserved. Thus, marked hysteresis loops of magnetization are obtained below 20 K with coercive fields that depend on the number of iron atoms of the ferritin derivative.

  4. Studies on Mixed Monolayers and Langmuir-Blodgett Films of Schiff-Base Complex Cu(SBC(18))(2) and Calix

    PubMed

    Pang, Shufeng; Ye, Zhifeng; Li, Chun; Liang, Yingqiu

    2001-08-15

    Mixed monolayers of Schiff-base complex Cu(SBC(18))(2) with an octadecyl hydrocarbon chain and Calix[4]arene without a long alkyl chain at an air/water interface were studied in ultrapure water at different temperatures. Interface behavior and thermodynamic estimation of the mixed monolayer indicate that a strong intermolecular interaction exists between the mixed components (Cu(SBC(18))(2) and calix[4]arene) and the two-dimensional miscibility decreases with the molar fraction of Cu(SBC(18))(2). It is noticeable that the calix[4]arene monolayer can be transferred successfully onto solid substrates due to the introduction of Cu(SBC(18))(2). FTIR transmission and UV-Vis absorption spectra of mixed LB films provide further evidence of molecular interaction between the headgroups. Copyright 2001 Academic Press.

  5. 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.

  6. Carbon nanotube growth from films of Langmuir-Blodgett deposited Fe nanoparticles with filler molecules

    NASA Astrophysics Data System (ADS)

    Kuriyama, Naoki; Takezawa, Akihiro; Kanasugi, Osamu; Nara, Ryuta; Kushida, Masahito

    2014-02-01

    Independently controlling the number density and diameter of Fe nanoparticles (FeNPs) used as a catalyst for vertically aligned carbon nanotube (VA-CNT) growth is difficult by conventional methods. In this study, mixed solutions of FeNPs and palmitic acid (C16) used as filler molecules were prepared to prevent the thermal aggregation of FeNPs and control the number density of VA-CNTs. FeNPs mixed with C16 monolayer films were prepared on the water surface and deposited on SiO2/Si substrates by the Langmuir-Blodgett (LB) technique. VA-CNTs were synthesized by a thermal chemical vapor deposition method using acetylene gas. Furthermore, we studied the optimum hydrogen reduction temperature and time of FeNPs used as a catalyst to encourage VA-CNT growth. By controlling the ratio of FeNP catalyst to C16 as a filler molecule in the LB film and optimizing hydrogen reduction condition, we were able to control the number density and diameter of FeNPs independently.

  7. Ionic channels in Langmuir-Blodgett films imaged by a scanning tunneling microscope.

    PubMed Central

    Kolomytkin, O V; Golubok, A O; Davydov, D N; Timofeev, V A; Vinogradova, S A; Tipisev SYa

    1991-01-01

    The molecular structure of channels formed by gramicidin A in a lipid membrane was imaged by a scanning tunneling microscope operating in air. The mono- and bimolecular films of lipid with gramicidin A were deposited onto a highly oriented pyrolitic graphite substrate by the Langmuir-Blodgett technique. It has been shown that under high concentration gramicidin A molecules can form in lipid films a quasi-regular, densely packed structure. Single gramicidin A molecules were imaged for the first time as well. The cavity of 0.4 +/- 0.05 nm in halfwidth was found on the scanning tunneling microscopy image of the gramicidin A molecule. The results of direct observation obtained by means of scanning tunneling microscope are in good agreement with the known molecular model of gramicidin A. It was shown that gramicidin A molecules can exist in a lipid monolayer as individual molecules or combined into clusters. The results demonstrate that scanning tunneling microscope can be used for high spatial resolution study of ionic channel structure. Images FIGURE 1 FIGURE 2 FIGURE 4 FIGURE 5 PMID:1712239

  8. Amphiphilic Organic-Inorganic Hybrid Zeotype Aluminosilicate like a Nanoporous Crystallized Langmuir-Blodgett Film.

    PubMed

    Ikeda, Takuji; Hiyoshi, Norihito; Matsuura, Shun-ichi; Kodaira, Tetsuya; Nakaoka, Takuma; Irisa, Ami; Kawano, Miki; Yamamoto, Katsutoshi

    2015-06-26

    A new organic-inorganic hybrid zeotype compound with amphiphilic one-dimensional nanopore and aluminosilicate composition was developed. The framework structure is composed of double aluminosilicate layers and 12-ring nanopores; a hydrophilic layer pillared by Q(2) silicon atom species and a lipophilic layer pillared by phenylene groups are alternately stacked, and 12-ring nanopores perpendicularly penetrate the layers. The framework topology looks similar to that of an AFI-type zeolite but possesses a quasi-multidimensional pore structure consisting of a 12-ring channel and intersecting small pores equivalent to 8-rings. The hybrid material with alternately laminated lipophilic and hydrophilic nanospaces can be assumed as a crystallized Langmuir-Blodgett film. It demonstrates microporous adsorption for both hydrophilic and lipophilic adsorptives, and its outer surface tightly adsorbs lysozyme whose molecular size is much larger than its micropore opening. Our results suggest the possibility of designing porous adsorbent with high amphipathicity. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  9. FABRICATION AND OPTOELECTRONIC PROPERTIES OF MgxZn1-xO ULTRATHIN FILMS BY LANGMUIR-BLODGETT TECHNOLOGY

    NASA Astrophysics Data System (ADS)

    Tang, Dongyan; Feng, Qian; Jiang, Enying; He, Baozhu

    2012-08-01

    By transferring MgxZn1-xO sol and stearic acid onto a hydrophilic silicon wafer or glass plate, the Langmuir-Blodgett (LB) multilayers of MgxZn1-xO (x:0, 0.2, 0.4) were deposited. After calcinations at 350°C for 0.5 h and at 500°C for 3 h, MgxZn1-xO ultrathin films were fabricated. The optimized parameters for monolayer formation and multilayer deposition were determined by the surface pressure-surface (Π-A) area and the transfer coefficient, respectively. The expended areas of stearic acid with MgxZn1-xO sols under Π-A isotherms inferred the interaction of stearic acid with MgxZn1-xO sols during the formation of monolayer at air-water interface. X-ray diffraction (XRD) was used to determine the crystal structures of MgxZn1-xO nanoparticles and ultrathin films. The surface morphologies of MgxZn1-xO ultrathin films were observed by scanning probe microscopy (AFM). And the optoelectronic properties of MgxZn1-xO were detected and discussed based on photoluminescence (PL) spectra.

  10. Preparation of TiO2 thin films using octadecylamine Langmuir-Blodgett films and evaluation of their photocatalytic activity.

    PubMed

    Takahashi, Masashi; Sendoh, Mitsuyuki; Kobayashi, Koichi; Tajima, Kazuo

    2011-01-01

    A study was conducted to demonstrate that nanometer-thick titanium dioxide (TiO(2)) thin films could be prepared by the hydrolysis of titanium potassium oxalate using octadecylamine (ODA) Langmuir-Blodgett (LB) films as templates. The amount of TiO(2) generated in the LB film was found to be proportional to the number of deposited ODA layers, which enables precise control of the TiO(2) film thickness. After heat treatment of the LB films at 300-600°C, the photocatalytic activities of the resulting TiO(2) films were determined from the decomposition of stearic acid cast films when irradiated with UV light for different time periods. Higher photocatalytic activity was observed in TiO(2) films heat treated at lower temperatures.

  11. Formation and structure of Langmuir-Blodgett films of organo-modified aluminosilicate with high surface coverage.

    PubMed

    Fujimori, Atsuhiro; Arai, Shuntaro; Kusaka, Jun-ichi; Kubota, Munehiro; Kurosaka, Kei-ichi

    2013-02-15

    We have developed an effective organo-modification method at the organic solvent/distilled water interface of natural aluminosilicate clay surfaces. We also investigated the molecular arrangement of organo-modified aluminosilicate with high surface coverage in Langmuir-Blodgett films (LB) by performing out-of-plane and in-plane X-ray diffraction (XRD) measurements. In addition, the surface morphology of mixed monolayers of organo-modified aluminosilicate and several biodegradable polymers (e.g., poly(L-lactide), PLLA) was also characterized by atomic force microscopy (AFM). The in-plane XRD results of multilayers of organo-modified aluminosilicate formed by the LB method indicate the formation of a two-dimensional lattice of hydrocarbons on the aluminosilicate surface. These hydrocarbons of organo-modified reagents packed hexagonal or orthorhombic in films. Based on our experimental findings, the LB technique enabled the formation of a densely packed organo-modified aluminosilicate monolayer at the water surface. Furthermore, for mixed monolayer systems comprising an organo-modified clay with high surface coverage and biodegradable polymers, a miscible surface was observed by AFM on a mesoscopic scale, whereas those with low surface coverage formed phase-separated structures.

  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)).

  13. Molecular Interaction between Merocyanine Dye and Several Kinds of Triphenyl Methane Derivatives in Langmuir-Blodgett Films

    NASA Astrophysics Data System (ADS)

    Okazaki, Choichiro; Kuniyoshi, Shigekazu; Kudo, Kazuhiro; Tanaka, Kuniaki

    1990-11-01

    Several triphenyl methane derivatives (TPMs) having different substituents can be adsorbed from an aqueous solution to Langmuir films consisting of arachidic acid (AR) or a mixture of AR and merocyanine dye (MC). The substituent dependence of the adsorption phenomenon shows that the adsorption mechanisms of TPM to AR and MC are mainly due to charge-charge and dipole-dipole interactions, respectively. Moreover, a peculiar property such as a negative photoelectric effect was obtained in the dye-adsorbed Langmuir-Blodgett films.

  14. Langmuir-Blodgett films of cholesterol oxidase and S-layer proteins onto screen-printed electrodes

    NASA Astrophysics Data System (ADS)

    Guimarães, Juliana Aguilar; Ferraz, Helen Conceição; Alves, Tito Lívio Moitinho

    2014-04-01

    Stable Langmuir monolayers of cholesterol oxidase (ChOx) and S-layer proteins were produced at the water-air interface and subsequently transferred onto the surface of screen-printed carbon electrodes by the Langmuir-Blodgett (LB) technique. The modified electrode surface was characterized by atomic force microscopy (AFM) and cyclic voltammetry (CV). AFM indicated the presence of deposited layers, showing reduction of surface roughness (RMS and Rt parameters). Significant changes in the shape of CVs were observed in modified electrodes compared to bare electrodes. The anodic peaks could be observed in cyclic voltammograms (CV), at a scan rate equal to 25 mV s-1, using electrodes with Z-type LB deposition. The presence of S-layer proteins in the ChOx LB film increases the oxidation peak intensity and reduces the oxidation potential. Altogether, these results demonstrate the feasibility of producing a cholesterol biosensor based on the immobilization of ChOx and S-layer proteins by LB technique.

  15. 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.

  16. Magnetic properties of Langmuir-Blodgett (LB) films: a theoretical study. III. LB films consisting of different types of stable π-monoradicals.

    PubMed

    Drebov, Nedko; Tyutyulkov, Nikolai; Dietz, Fritz

    2013-01-22

    We present theoretical results for the magnetic properties of modeled two-dimensional (2-D) Langmuir-Blodgett films consisting of different types of stable organic π-monoradicals. Their energy spectra and magnetic characteristics are investigated using the many-body band theory of magnetism in π-electron approximation. The main factors which determine the magnitude and character of the magnetic interaction in the 2-D molecular arrangements are thoroughly studied. Semiempirical electronic structure calculations have been also carried out for molecular clusters to gain further insight into their magnetic properties. The proposed models for LB films are potential candidates for new 2-D ferromagnetic materials which are characterized by a substantial increase of the critical temperatures up to 250 K in comparison to only about 5 K for the now existing magnetic LB films based on organometallic systems.

  17. Fabrication of Metal Oxide Thin Films Using the Langmuir-Blodgett Deposition Technique.

    NASA Astrophysics Data System (ADS)

    Johnson, David John

    The Langmuir Blodgett (LB) deposition of metal arachidates was investigated as a technique for fabrication of metal oxides with emphasis placed on the lanthanide arachidates. Traditionally, these materials are difficult to deposit via the LB process, due to the rigidity of the floating monolayer. Studies on yttrium arachidate have shown that the quality of deposition of these materials is highly dependent on the concentration of the metal salt and the pH of the subphase. Yttrium arachidate was thus deposited at 10^{-5} M YCl_3 over a pH range of 4.0 to 6.9. Uniform multilayer films were produced with films at the higher pH's showing 100% yttrium arachidate. A pK_{rm a} value of 4.9 +/- 0.2 was obtained under these conditions. Fourier transform infrared spectroscopy, Rutherford backscattering spectrometry and x-ray photoelectron spectroscopy data indicate that the metal is being incorporated into the arachidic acid predominantly as Y(OH) ^{2+}. A saturation areal density of (2.0 +/- 0.1) times 10^{14} Y/cm ^2 was measured for one layer of yttrium arachidate. Ellipsometric measurements were performed on films of yttrium arachidate to study order-disorder transitions. Upon heating the films were observed to undergo two transitions at 65^circC and 100 ^circC. At room temperature, the as -deposited films were found to be anisotropic with indices of refraction of N_{rm x} = 1.503 +/- 0.005 and N _{rm z} = 1.554 +/- 0.005 and a monolayer spacing of 2.73 +/- 0.03 nm. Above 100^ circC the films were isotropic with N = 1.440 +/- 0.005 and a thickness of 3.13 +/- 0.03 nm per original layer. The films showed no desorption below 100^circ C. In contrast to films of cadium arachidate, the yttrium arachidate films were observed to undergo supercooling by 35^circC. This may point to a lack of nucleation sites in the yttrium arachidate films explaining why they maintain areal integrity at high temperature while cadmium arachidate films do not. The decomposition of LB films was

  18. Langmuir-Blodgett films of immunoglobulin G and direct immunochemical sensing

    NASA Astrophysics Data System (ADS)

    Turko, Illarion V.; Pikuleva, Irene A.; Yurkevich, Igor S.; Chashchin, Vadim L.

    1991-09-01

    Langmuir-Blodgett technique is shown to be a suitable method for construction of the functionally-oriented layers of immunoglobulin G (IgG) which bind antigen better than in the case of chemical immobilization of IgG on the same substrate. It is assumed that the fluorescent detection of the conformational changes in the molecule of IgG or in the regular structures of IgG molecules after the interaction with antigen can be used for the development of the new type of immunosensors.

  19. Formation of crystalline heteroepitaxial SiC films on Si by carbonization of polyimide Langmuir-Blodgett films

    NASA Astrophysics Data System (ADS)

    Luchinin, Viktor V.; Goloudina, Svetlana I.; Pasyuta, Vyacheslav M.; Panov, Mikhail F.; Smirnov, Alexander N.; Kirilenko, Demid A.; Semenova, Tatyana F.; Sklizkova, Valentina P.; Gofman, Iosif V.; Svetlichnyi, Valentin M.; Kudryavtsev, Vladislav V.

    2017-06-01

    High-quality crystalline nano-thin SiC films on Si substrates were prepared by carbonization of polyimide (PI) Langmuir-Blodgett (LB) films. The obtained films were characterized by Fourier transform-infrared (FTIR) spectroscopy, X-ray diffraction (XRD) analysis, Raman spectroscopy, transmission electon microscopy (TEM), transmission electron diffraction (TED), and scanning electron microscopy (SEM). We demonstrated that the carbonization of a PI film on a Si substrate at 1000 °C leads to the formation of a carbon film and SiC nanocrystals on the Si substrate. It was found that five planes in the 3C-SiC(111) film are aligned with four Si(111) planes. As a result of repeated annealing of PI films containing 121 layers at 1200 °C crystalline SiC films were formed on the Si substrate. It was shown that the SiC films (35 nm) grown on Si(111) at 1200 °C have a mainly cubic 3C-SiC structure with small amount of hexagonal polytypes. Only 3C-SiC films (30 nm) were formed on the Si(100) substrate at the same temperature. It was shown that the SiC films (30-35 nm) can cover the voids with size up to 10 µm in the Si substrate. The current-voltage (I-V) characteristics of the n-Si/n-SiC heterostructure were obtained by conductive atomic force microscopy.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

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

    DOE PAGES

    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

  5. Elastic properties of unpolymerized and polymerized cadmium octadecyl/fumarate and cadmium octadecyl/maleate Langmuir-Blodgett films determined by Brillouin scattering

    NASA Astrophysics Data System (ADS)

    Lee, S.; Hillebrands, B.; Stegeman, G. I.; Laxhuber, L. A.; Swalen, J. D.

    1989-08-01

    We have measured the elastic properties of saturated ODF, and of unpolymerized and polymerized regular ODF, ODF/ODM, and ω-ODF Langmuir-Blodgett films by means of Brillouin spectroscopy. Whereas the ODF/ODM films show a slight increase in the elastic constants, the regular ODF and ω-ODF films exhibit elastic constants which are significantly softer in the polymerized films due to the formation of microcracks on polymerization.

  6. 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

    2016-07-06

    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.

  7. International Conference on Langmuir-Blodgett Films (5th) Held in Paris, France on 26-30 August 1991, Abstracts Booklet

    DTIC Science & Technology

    1991-08-01

    microstructures. AP5 ORIENTATION OF POLYIMIDE LB FILMS IN PLANE DIRECTION Masa-aki Kakimoto, Yasunari Nishikata, Ken Komatsu, and Yoshio Imai Department...AND PROPERTIES OF POLYAMINE LB FILMS Toshihiro Suwa, Yasunari Nishikata, Hasa-aki Kakimoto, and Yoshio Imai Department of Organic and Polymeric...working Resists Using a Polyimide Langmuir-Blodgett Film System Mitsumasa Iwamoto*, Sige asba , Keiji Iriyama-, Yasunari Nishikata++ , Masaaki Kakimoto

  8. Langmuir-Blodgett films of random copolymers of fluoroalkyl(meth)acrylate and methacrylic acid: Fabrication and X-ray diffraction study

    SciTech Connect

    Safronov, V.; Feigin, L.A.; Budovskaya, L.D.; Ivanova, V.N.

    1994-12-31

    Langmuir-Blodgett films of amphiphilic fluorinated copolymers were fabricated and studied by X-ray diffraction. Although these films show poor interlayer periodicity, they possess a uniform thickness even in the case of very thin films of one bilayer (22 {angstrom}). This feature was used to obtain complex LB structures (superlattices) with alteration of copolymer and fatty acid bilayers. X-ray diffraction data proved the regular periodical organization of these structures and allowed to calculate electron density distribution across the superlattices.

  9. Controlling the molecular architecture of lactase immobilized in Langmuir-Blodgett films of phospholipids to modulate the enzyme activity.

    PubMed

    Ayoub, Fábio de Paula; Caseli, Luciano

    2017-02-01

    In this present work, the adsorption of the enzyme lactase onto Langmuir monolayers of the phospholipid dimyristoylphosphatidic acid (DMPA) was investigated and characterized with surface pressure-area isotherms, surface potential-area isotherms and polarization-modulated infrared reflection-absorption spectroscopy (PM-IRRAS). The adsorption of the enzyme at the air-water interface expanded the lipid monolayer and increased the film compressibility at high surface pressures. Amide bands in the PM-IRRAS spectra were identified, with the CN and CO dipole moments lying parallel to the monolayer plane, revealing that the structuring of the enzyme into β-sheets was kept in the mixed monolayer. The enzyme-lipid films were transferred from the floating monolayer to solid supports as Langmuir-Blodgett (LB) films and characterized with fluorescence spectroscopy and atomic force microscopy. The catalytic activity of the films was measured and compared to the homogenous medium. The enzyme accommodated in the LB films preserved more than 80% of the enzyme activity after 20days, in contrast for the homogeneous medium, which preserved less than 60% of the enzyme activity. The method presented in this present work not only allows for an enhanced catalytic activity toward lactose, but also can help explain why certain film architectures exhibit better performance.

  10. Modeling and characterization of molecular structures in self assembled and Langmuir-Blodgett films for controlled fabrication

    SciTech Connect

    Cesarano, J. III

    1997-10-01

    Self Assembled (SA) thin films and Langmuir-Blodgett (LB) thin films are emerging technologies for the development of chemical and bio-chemical sensors, electrooptic films, second harmonic generators (frequency doublers), templates for biomimetic growth etc. One of the goals of this project was to extend Sandia`s characterization techniques and molecular modeling capabilities for these complex two-dimensional geometries with the objective of improving the control of the fabrication of these structures for specific applications. Achieving this requires understanding both the structure throughout the thickness of the films and the in-plane lattice of the amphiphilic molecules. To meet these objectives they used atomic force microscopy (AFM), X-ray reflectivity, and molecular modeling. While developing these capabilities, three different materials systems were fabricated and characterized: (1) Self Assembled Monolayers (SAMs) of octadecyltrichlorosilane (OTS) and LB films of arachidic acid on silicon wafers; (2) SAMs on PZT substrates; and (3) electrochemical deposition of CdS on LB film templates.

  11. 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.

  12. Architecture effects of glucose oxidase/Au nanoparticle composite Langmuir-Blodgett films on glucose sensing performance

    NASA Astrophysics Data System (ADS)

    Wang, Ke-Hsuan; Wu, Jau-Yann; Chen, Liang-Huei; Lee, Yuh-Lang

    2016-03-01

    The Langmuir-Blodgett (LB) deposition technique is employed to prepare nano-composite films consisting of glucose oxidase (GOx) and gold nanoparticles (AuNPs) for glucose sensing applications. The GOx and AuNPs are co-adsorbed from an aqueous solution onto an air/liquid interface in the presence of an octadecylamine (ODA) template monolayer, forming a mixed (GOx-AuNP) monolayer. Alternatively, a composite film with a cascade architecture (AuNP/GOx) is also prepared by sequentially depositing monolayers of AuNPs and GOx. The architecture effects of the composite LB films on the glucose sensing are studied. The results show that the presence of AuNPs in the co-adsorption system does not affect the adsorption amount and preferred conformation (α-helix) of GOx. Furthermore, the incorporation of AuNPs in both composite films can significantly improve the sensing performance. However, the enhancement effects of the AuNPs in the two architectures are distinct. The major effect of the AuNPs is on the facilitation of charge-transfer in the (GOx-AuNP) film, but on the increase of catalytic activity in the (AuNP/GOx) one. Therefore, the sensing performance can be greatly improved by utilizing a film combining both architectures (AuNP/GOx-AuNP).

  13. 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.

  14. 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.

  15. The long-period fiber grating coated with Langmuir-Blodgett thin film for applications on biochemistry sensors

    NASA Astrophysics Data System (ADS)

    Wang, Liwei; Zhang, Min; Liao, Yanbiao; Zhu, Jing

    2005-11-01

    The resonant wavelength of long-period fiber gratings (LPFGs) is very sensitive to the ambient refractive index. LPFGs will have many potential applications on biochemistry sensors and environment monitor system. At present, LPFGs chemical sensors can only measure the medium, which has lower refractive index than that of the fiber cladding, however, the detecting range can be greatly enlarged if the LPFGs coated with Langmuir-Blodgett thin film are used. LPFGs will have more extensive applications with the mature of the L-B thin film technology. In this paper, the spectrum performance of the resonant wavelength of LPFGs varying with the changes of the ambient refractive index (1< n < 1.8) is theoretically analyzed. As the ambient index is increased, each resonance wavelength first shifts toward the shorter-wavelength direction and then disappears where the value of n is about 1.45. When the ambient index is larger than that of the cladding (~1.45), the resonance wavelengths reappear at slightly longer wavelength than those measured in ambient air. According to the mode coupling method, the theoretical four-layered fiber model is developed on the relationships among the resonant wavelengths of LPFGs coated with L-B thin film, the refractive index and thickness of the L-B thin film, and ambient refractive index. The shift of the resonant wavelength is calculated through numeric method and is presented graphically.

  16. Langmuir-Blodgett films incorporating molecular wire candidates of ester-substituted oligo(phenylene-ethynylene) derivatives

    NASA Astrophysics Data System (ADS)

    Villares, Ana; Lydon, Donocadh P.; Robinson, Benjamin J.; Ashwell, Geoffrey J.; Royo, Félix M.; Low, Paul J.; Cea, Pilar

    2008-12-01

    Langmuir and Langmuir-Blodgett (LB) films of two "wire-like" oligo(phenylene-ethynylene) methyl ester derivatives, namely methyl-4-[(4″-(nonyloxyphenylethynyl)-4'-(phenylethynyl)]-benzoate and methyl-4-[(4″-hexadecyloxyphenylethynyl)-4'-(phenylethynyl]-benzoate (abbreviated as C9BPEB and C16BPEB), have been prepared and characterized. Surface pressure isotherms for both materials have been obtained, with C9BPEB showing more expanded monolayers. An analysis of the reflection spectra of monolayer films at the air-water interface suggests the formation of H-aggregates, and supports an organizational model in which tilt angles of C16BPEB and C9BPEB molecules with respect to the water surface are approximately 70° and 60°, respectively. The sequential transfer of monolayers of these BPEB ester derivatives onto solid substrates results in a Z-type deposition in the case of C9BPEB and Y-type for C16BPEB. The current-voltage ( I- V) characteristics of LB monolayers are relatively symmetrical for both films, with the asymmetric contacts more evident in the I- V C16BPEB characteristics.

  17. Langmuir-Blodgett film of p-tert-butylthiacalix[4]arene modified glassy carbon electrode as voltammetric sensor for the determination of Hg(II).

    PubMed

    Wang, Fei; Wei, Xiaohan; Wang, Chenbin; Zhang, Shusheng; Ye, Baoxian

    2010-01-15

    The pi-A isotherms and UV-vis spectra of the transferred films suggested that the monolayer of p-tert-butylthiacalix[4]arene can coordinate with Hg(2+) at the air-water surface. From these observations, a glassy carbon electrode coated with Langmuir-Blodgett film of p-tert-butylthiacalix[4] arene as a new voltammetric sensor is designed for the determination of trace amounts of Hg(2+). Compared with bare glassy carbon electrode and modified glassy carbon electrode using direct coating method, the Langmuir-Blodgett film-modified electrode can greatly improve the measuring sensitivity of Hg(2+). Under the selected conditions, the Langmuir-Blodgett film-modified electrode in 0.1molL(-1) H(2)SO(4)+0.01molL(-1) KCl solution shows a linear voltammetric response for Hg(2+) in the range of 5.0x10(-10) to 1.5x10(-7)molL(-1), with a detection limit of 2.0x10(-10)molL(-1). The proposed method was also applied to determine Hg(2+) in water samples (tap, lake and river water). In addition, the fabricated electrode exhibited a distinct advantage of simple preparation, non-toxicity, good reproducibility and good stability.

  18. 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. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Fabrication, structural characterization, and applications of langmuir and langmuir-blodgett films of a poly(azo)urethane.

    PubMed

    Alessio, Priscila; Ferreira, Daniele M; Job, Aldo E; Aroca, Ricardo F; Riul, Antonio; Constantino, Carlos J L; Gonzalez, Eduardo R Pérez

    2008-05-06

    The synthesis of a poly(azo)urethane by fixing CO(2) in bis-epoxide followed by a polymerization reaction with an azodiamine is presented. Since isocyanate is not used in the process, it is termed "clean method" and the polymers obtained are named "NIPUs" (non-isocyanate polyurethanes). Langmuir films were formed at the air-water interface and were characterized by surface pressure vs mean molecular area per mer unit (Pi-A) isotherms. The Langmuir monolayers were further studied by running stability tests and cycles of compression/expansion (possible hysteresis) and by varying the compression speed of the monolayer formation, the subphase temperature, and the solvents used to prepare the spreading polymer solutions. The Langmuir-Blodgett (LB) technique was used to fabricate ultrathin films of a particular polymer (PAzoU). It is possible to grow homogeneous LB films of up to 15 layers as monitored using UV-vis absorption spectroscopy. Higher number of layers can be deposited when PAzoU is mixed with stearic acid, producing mixed LB films. Fourier transform infrared (FTIR) absorption spectroscopy and Raman scattering showed that the materials do not interact chemically in the mixed LB films. The atomic force microscopy (AFM) and micro-Raman technique (optical microscopy coupled to Raman spectrograph) revealed that mixed LB films present a phase separation distinguishable at micrometer or nanometer scale. Finally, mixed and neat LB films were successfully characterized using impedance spectroscopy at different temperatures, a property that may lead to future application as temperature sensors. Principal component analysis (PCA) was used to correlate the data.

  20. Highly oriented Langmuir-Blodgett film of silver cuboctahedra as an effective matrix-free sample plate for surface-assisted laser desorption/ionization mass spectrometry.

    PubMed

    Kuo, Tsung-Rong; Chen, Yin-Chien; Wang, Chiung-I; Shen, Tzu-Hau; Wang, Hong-Yi; Pan, Xi-Yu; Wang, Di-Yan; Liou, Chien-Chung; Chang, Yi-Hsuan; Chen, Yi-Chia; Wu, Yueh-Hsiu; Liu, Yun-Ru; Lin, Yun-Ho; Hu, Cho-Chun; Chen, Chia-Chun

    2017-08-10

    The design of a homogeneous sample plate to solve the sweet heating spot issues is the key step to expand the applicability of surface-assisted laser desorption/ionization mass spectrometry (SALDI MS). Herein, large-scale and highly oriented Langmuir-Blodgett (LB) films of uniform silver nanocrystals have been fabricated as a highly efficient and matrix-free sample plate for SALDI MS. Three individual silver nanocrystals (cubes, cuboctahedra and octahedra) assembled LB films have been applied as the sample plates for glucose detection by SALDI MS without an additional matrix. The results show that the signal intensity, background noise, signal-to-noise ratio and reproducibility have been significantly improved using LB films as the sample plate in comparison with commercial matrixes of CHCA and DHB. In particular, a relative signal of 5.7% was obtained for LB films of silver cuboctahedra. The significant improvement in the SALDI MS measurement could be attributed to the homogenous dissipation of laser irradiation energy to create a large area of the sweet heating spot on well-oriented silver cuboctahedra-based LB film. This ready-to-use sample plate has the potential for widespread commercial applications in SALDI MS.

  1. Immobilization of biomaterials to nano-assembled films (self-assembled monolayers, Langmuir-Blodgett films, and layer-by-layer assemblies) and their related functions.

    PubMed

    Ariga, Katsuhiko; Nakanishi, Takashi; Michinobu, Tsuyoshi

    2006-08-01

    For utilization of highly sophisticated functions of biomaterials in nano-scale functional systems, immobilization of biomaterials on artificial devices such as electrodes via thin film technology is one of the most powerful strategies. In this review, we focus on three major organic ultrathin films, self-assembled monolayers (SAM), Langmuir-Blodgett (LB) films, and layer-by-layer (LBL) assemblies, and from the viewpoints of biomaterial immobilization, typical examples and recent progresses in these film technologies are described. The SAM method allows facile contact between biomaterials and man-made devices, and well used for bio-related sensors. In addition, recent micro-fabrication techniques such as micro-contact printing and dip-pen nanolithography were successfully applied to preparation of biomaterial patterning. A monolayer at the air-water interface, which is a unit structure of LB films, provides a unique environment for recognition of aqueous biomaterials. Recognition and immobilization of various biomaterials including nucleotides, nucleic acid bases, amino acids, sugars, and peptides were widely investigated. The LB film can be also used for immobilization of enzymes in an ultrathin film on an electrode, resulting in sensor application. The LBL assembling method is available for wide range of biomaterials and provides great freedom in designs of layered structures. These advantages are reflected in preparation of thin-film bio-reactors where multiple kinds of enzymes sequentially operate. LBL assemblies were also utilized for sensors and drug delivery systems. This kind of assembling structures can be prepared on micro-size particle and very useful for preparation of hollow capsules with biological functions.

  2. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

    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 me and 0.065 me, respectively. These parameters are important in the design of molecular electronic devices.

  4. TECHNICAL NOTE: New photosensitive ultrathin films fabricated by the Langmuir Blodgett technique

    NASA Astrophysics Data System (ADS)

    Hafiz, H. R.

    2004-08-01

    A new hybrid LB film composed of an azobenzene-based photochromic layer (the host) and a p-phenylenediacrylic acid-based photosensitive layer (the guest) has been fabricated. The host was demonstrated to regulate the photoreaction kinetics of the guest during UV illumination. The photoresponses of the relevant guest chromophores were verified to be very sensitive to the intermolecular bonding state during the course of the illumination. Both the conversion factor (and its sensitivity) and the insoluble fraction were determined; they imply that such hybrid LB film has a photoresist fingerprint. The photoreactivity of the LB film was explained in terms of a model structure.

  5. 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.

  6. 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.

  7. Cellulase and alcohol dehydrogenase immobilized in Langmuir and Langmuir-Blodgett films and their molecular-level effects upon contact with cellulose and ethanol.

    PubMed

    Rodrigues, Dilmer; Camilo, Fernanda Ferraz; Caseli, Luciano

    2014-02-25

    The key challenges for producing devices based on nanostructured films with control over the molecular architecture are to preserve the catalytic activity of the immobilized biomolecules and to provide a reliable method for determining the intermolecular interactions and the accommodation of molecules at very small scales. In this work, the enzymes cellulase and alcohol dehydrogenase (ADH) were coimmobilized with dipalmitoylphosphatidylcholine (DPPC) as Langmuir-Blodgett (LB) films, and their biological activities were assayed by accommodating the structure formed in contact with cellulose. For this purpose, the polysaccharide was dissolved in an ionic liquid, 1-buthyl-3-methylimidazolium chloride (BMImCl), and dropped on the top of the hybrid cellulase-ADH-DPPC LB film. The interactions between cellulose and ethanol, which are the catalytic substrates of the enzymes as well as important elements in the production of second-generation fuels, were then investigated using polarization-modulation infrared reflection-absorption spectroscopy (PM-IRRAS). Investigation of the secondary structures of the enzymes was performed using PM-IRRAS, through which the presence of ethanol and cellulose was observed to highly affect the structures of ADH and cellulase, respectively. The detection of products formed from the catalyzed reactions as well as the changes of secondary structure of the enzymes immobilization could be carried out, which opens the possibility to produce a means for producing second-generation ethanol using nanoscale arrangements.

  8. Chemically derived graphene sheets top assembled over multi-walled carbon nanotube thin film by Langmuir Blodgett method for improved dual field emission.

    PubMed

    Roy, Rajarshi; Jha, Arunava; Chattopadhyay, Kalyan K

    2013-01-01

    Graphene and carbon nanotubes are very much known as effective field emitter materials. However field emission applications with hybrid carbon nanostructures have mostly remained elusive so far. Here we report, top assembly of very thin layer of reduced graphene oxide (RGO) by Langmuir Blodgett method over a multi-walled carbon nanotubes (MWCNTs) thin film/ITO substrate to investigate the dual field emission property of the hybrid structure. The non-functionalized type of attachment in between the hybrid carbon nanostructures mainly due to van der Waals force of attraction ensured easy fabrication procedure. Evidence of uniform distribution of web like networks of very thin transparent RGO sheets top assembled over densely packed MWCNTs thin film was found from the field emission scanning electron microscopy analysis. The base layer conductivity was enhanced due to the incorporation of MWCNTs bottom layer over ITO and the former also additionally facilitated as emitter site pockets in between RGO planes. Finally, the RGO top assembly resulted in achieving significant improvement in current density and turn-on field in tandem with MWCNTs bottom layer bed making this hybrid system a much feasible candidate for future field emission (FE) based device applications.

  9. Molecular-level interactions of an azopolymer and poly(dodecylmethacrylate) in mixed Langmuir and Langmuir-Blodgett films for optical storage.

    PubMed

    Ceridório, Lucinéia F; Balogh, Débora T; Caseli, Luciano; Cardoso, Marcos R; Viitala, Tapani; Mendonça, Cleber R; Oliveira, Osvaldo N

    2010-06-01

    The applicability of azopolymers in optical storage can be extended through the use of nanostructured films produced with the Langmuir-Blodgett (LB) technique, but the film properties need to be optimized since these polymers generally do not form stable Langmuir films to be transferred onto solid substrates. Here, photoinduced birefringence was investigated for mixed Langmuir-Blodgett films from the homopolymers 4-[N-ethyl-N-(2-methacryloxyethyl)]-4'-nitroazobenzene (HPDR1-MA) and poly(dodecylmethacrylate) (HPDod-MA). The interactions between these polymers were studied in Langmuir and LB films. Surface pressure-area isotherms pointed to molecular-level interactions for proportions of 51 mf%, 41 mf% and 31 mf% of HPDR1-MA. Phase segregation was not apparent in the BAM images, in which the morphology of the blend film was clearly different from that of the Langmuir films of neat homopolymers. Through PM-IRRAS, we noted that the interaction between the azopolymer and HPDod-MA affected the orientation of carbonyl groups. Strong interactions for the mixture with 41 mf% of poly(dodecylmethacrylate) led to stable Langmuir films that were transferred onto solid supports as LB films. The photoinduced birefringence of 101-layer mixed LB films show features that make these films useful for optical storage, with the advantage of short writing times in comparison to other azopolymer films.

  10. Langmuir-Blodgett and Langmuir-Schaefer films of homoleptic and heteroleptic phthalocyanine complexes as voltammetric sensors:. Applications to the study of antioxidants

    NASA Astrophysics Data System (ADS)

    Casilli, Serena; De Luca, Mariangela; Apetrei, Constantin; Parra, Vicente; Arrieta, Álvaro A.; Valli, Ludovico; Jiang, Jianzhuang; Rodríguez-Méndez, María L.; De Saja, José A.

    2005-06-01

    Double- and triple-decker phthalocyanine derivatives have been successfully used as the sensitive materials for liquid electrochemical sensors. The materials include homoleptic and heteroleptic phthalocyanine complexes formed by phthalocyanine, porphyrin and naphthalocyanine rings. A high degree of cross-selectiviy towards antioxidant compounds (including vannilic acid, pyrogallol, ascorbic acid and catechin) has been attained by using different phthalocyanine complexes. The features observed in the cyclic voltammograms reflect the rich electrochemistry of either the phthalocyanine molecules or the studied solutions. In consequence, each sensor shows a selective response to the antioxidant analysed. The obtained voltammograms from by using highly ordered electrodes prepared using the Langmuir-Blodgett (LB) or the Langmuir-Schaefer (LS) techniques show better resolution and stability than those of disordered electrodes prepared by casting. For this reason, ordered films have been chosen to construct an array of liquid sensors. The principal component analysis (PCA) of the obtained signals has allowed that a clear discrimination of the antioxidant solutions be achieved. The rich and varied responses produced by antioxidant molecules evidences that voltammetric electrodes based on phthalocyanines, are especially suitable for the analysis of compounds with electrochemical activity.

  11. Photocatalytic decomposition of an alkylammonium cation in a Langmuir-Blodgett film of a titania nanosheet.

    PubMed

    Umemura, Yasushi; Shinohara, Emi; Koura, Akihiro; Nishioka, Terumichi; Sasaki, Takayoshi

    2006-04-11

    The formation of inorganic-organic hybrid films of a titania nanosheet and an amphiphilic alkylammonium cation has been investigated, and the photocatalytic decomposition of the alkylammonium cation in the film has been pursued. When a solution of the amphiphilic alkylammonium salt (octadecylammonium chloride: ODAH+ Cl-) was spread on an interface between the air and a titania nanosheet suspension, the negatively charged nanosheets were adsorbed onto the floating monolayer of ODAH+ to form a hybrid monolayer. The hybridization was confirmed by pi-A isotherm measurements, atomic force microscopy, and X-ray photoelectron spectroscopy. Multilayered films were fabricated in a layer-by-layer way by transferring the hybrid monolayers onto glass plates. Areas per ODAH+ cation in the films were estimated from the infrared (IR) spectra of the films, but these areas were smaller than those estimated from the pi-A isotherm curves. The orientation of the alkyl chain of ODAH+ in the hybrid film was determined by means of polarized IR spectroscopy. The alkyl chains were tilted 41 +/- 1 degrees and 47 +/- 1 degrees from the surface normal for the films prepared from the 8 and 20 ppm (ppm = mg dm(-3)) suspensions, respectively. Together with X-ray diffraction data of the films, the structure of the hybrid film was discussed. When the films were illuminated with a UV light, the absorption intensities due to the alkyl chain of ODAH+ decreased exponentially, indicating the photocatalytic decomposition of ODAH+ by the titania nanosheets in the films. Deviation from the exponential trend in the decomposition rate was observed in the initial period for the hybrid films prepared from the suspensions at low concentrations. Interestingly, the layered structure of the hybrid film was disturbed significantly after the ODAH+ cations were decomposed.

  12. Thickness and energy dependence of secondary ion emissions from Langmuir Blodgett films

    NASA Astrophysics Data System (ADS)

    Hoshi, T.; Yoshida, S.; Watanabe, T.; Ichinohe, Y.; Kudo, M.

    1999-04-01

    Using Cd arachidate films formed on Ag and Si substrates, secondary ion intensities were investigated by TOF-SIMS. The intensities of [M+H] +, [M+Cd] + and Ag cationized ions from samples on the Ag and Si substrates were found to change as a function of LB film thickness, as well as the primary beam energy. The intensities of [M+H] + and [M+Cd] + were seen to be (1) the highest at a one-layer LB film, (2) to decrease as the LB film becomes thicker, (3) change slightly with the primary ion beam energy. On the other hand, the intensities of Ag cationized secondary ions were almost constant with the changes of LB thickness and the energy of the primary ion beam, after normalized by Ag + intensity. The results were discussed in terms of the energy transfer of the primary beam to the LB films, the property of the substrate materials, and the strength of chemical bondings.

  13. A Langmuir Blodgett film presenting a ferromagnetic state below 25 K

    NASA Astrophysics Data System (ADS)

    Lafuente, C.; Mingotaud, C.; Delhaes, P.

    1999-03-01

    A positively charged monolayer spread on a sub-phase containing copper hexacyanoferrate leads to hybrid inorganic-organic LB films. Those multilayers present a spin ordering below 25 K. The Curie temperature of the LB films is found to be independent of the multilayer thickness. Their magnetization is clearly proportional to the number of transferred layers, demonstrating that the deposition process is perfectly regular. These results show that a bulk ferromagnetic behavior can be observed in this hybrid material, even if the distance between magnetic layers is considered as large.

  14. JPRS Report, Science & Technology, Japan, 4th International Conference on Langmuir-Blodgett Films

    DTIC Science & Technology

    1989-08-23

    Nakamura, H. Tanaka, et al. ] 23 Preparation and Properties of Poly(p-phenylene vinylene) LB Films [ Yasunari Nishikata, Masa-aki Kakimoto, et...2k Preparation and Properties of Poly(p-phenylene vinylene) i-jD Yasunari Nishikata, Masa-aki Kakimoto and Yoshio Imai Department of Organic

  15. 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.

  16. 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.

  17. 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.

  18. Langmuir-Blodgett films of fluorinated glycolipids and polymerizable lipids and their phase separating behavior.

    PubMed

    Scheibe, Patrick; Schoenhentz, Jerome; Platen, Tobias; Hoffmann-Röder, Anja; Zentel, Rudolf

    2010-12-07

    This paper describes the phase separating behavior of Langmuir monolayers from mixtures of different lipids that (i) either carry already a glycopeptide recognition site or can be easily modified to carry one and (ii) polymerizable lipids. To ensure demixing during compression, we used fluorinated lipids for the biological headgroups and hydrocarbon based lipids as polymerizable lipids. As a representative for a lipid monomer, which can be polymerized in the hydrophilic headgroup, a methacrylic monomer was used. As a monomer, which can be polymerized in the hydrophobic tail, a lipid with a diacetylene unit was used (pentacosadiynoic acid, PDA). The fluorinated lipids were on the one hand a perfluorinated lipid with three chains and on the other hand a partially fluorinated lipid with a T(N)-antigen headgroup. The macroscopic phase separation was observed by Brewster angle microscopy, whereas the phase separation on the nanoscale level was observed by atomic force microscopy. It turned out that all lipid mixtures showed (at least) a partial miscibility of the hydrocarbon compounds in the fluorinated compounds. This is positive for pattern formation, as it allows the formation of small demixed 2D patterned structures during crystallization from the homogeneous phase. For miscibility especially a liquid analogue phase proved to be advantageous. As lipid 3 with three fluorinated lipid chains (very stable monolayer) is miscible with the polymerizable lipids 1 and 2, it was mostly used for further investigations. For all three lipid mixtures, a phase separation on both the micrometer and the nanometer level was observed. The size of the crystalline domains could be controlled not only by varying the surface pressure but also by varying the molar composition of the mixtures. Furthermore, we showed that the binary mixture can be stabilized via UV polymerization. After polymerization and subsequent expansion of the barriers, the locked-in polymerized structures are stable

  19. Immbolization of uricase enzyme in Langmuir and Langmuir-Blodgett films of fatty acids: possible use as a uric acid sensor.

    PubMed

    Zanon, Nathaly C M; Oliveira, Osvaldo N; Caseli, Luciano

    2012-05-01

    Preserving the enzyme structure in solid films is key for producing various bioelectronic devices, including biosensors, which has normally been performed with nanostructured films that allow for control of molecular architectures. In this paper, we investigate the adsorption of uricase onto Langmuir monolayers of stearic acid (SA), and their transfer to solid supports as Langmuir-Blodgett (LB) films. Structuring of the enzyme in β-sheets was preserved in the form of 1-layer LB film, which was corroborated with a higher catalytic activity than for other uricase-containing LB film architectures where the β-sheets structuring was not preserved. The optimized architecture was also used to detect uric acid within a range covering typical concentrations in the human blood. The approach presented here not only allows for an optimized catalytic activity toward uric acid but also permits one to explain why some film architectures exhibit a superior performance. Copyright © 2011 Elsevier Inc. All rights reserved.

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

    SciTech Connect

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

    2016-05-06

    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.

  1. Comparative Study of the Behavior of Bathophenanthroline in the Restricted Geometry of Langmuir-Blodgett Film with Two Different Fatty Acids

    NASA Astrophysics Data System (ADS)

    Nath, Jayasree; Deb, Subrata; Chakrabarti, Adrita; Pal, Ajitesh; Nath, Ranendu Kumar

    2014-12-01

    This communication reports the successful fabrication and the comparative study of Langmuir and Langmuir-Blodgett (LB) films of nonamphiphilic phenanthrene derivative, 1, 10 phenanthroline (bathophenanthroline) (BATH), when incorporated to a long chain fatty acid viz. heptadecanoic acid and stearic acid. Measurements of compressibility modulus from the surface pressure versus area per molecule isotherm indicate that the mixed film of BATH and SA is harder than that with HA. The plot of area per molecule versus mole fraction is the indication of some repulsive interactions between binary components of the mixed monolayer which facilitates the formation of aggregates. UV-Vis absorption spectroscopy and steady-state fluorescence spectroscopy confirms the formation of microcrystalline aggregates in the mixed LB films. Scanning electron microscopic study supports this observation. The dependence of various LB parameters in the mixed films such as mole fraction, number of layers and surface pressure of lifting have also been investigated in the light of electronic absorption spectroscopy.

  2. Preparation of pillar[5]arene-quinoline Langmuir-Blodgett thin films for detection of volatile organic compounds with host-guest principles.

    PubMed

    Kursunlu, Ahmed Nuri; Acikbas, Yaser; Ozmen, Mustafa; Erdogan, Matem; Capan, Rifat

    2017-10-07

    In this study, a novel pillar[5]arene-quinoline (P5-Q) as an organic material is used to fabricate Langmuir-Blodgett (LB) thin films and its organic vapor sensing properties have been investigated. The LB deposition process is characterized by UV-visible spectroscopy, atomic force microscopy (AFM), scanning electron microscopy (SEM) and quartz crystal microbalance (QCM) techniques. The typical frequency shift per layer is obtained as 31.75 Hz per layer and the deposited mass onto a quartz crystal is calculated to be 539.69 ng per layer (2.03 ng mm(-2)). The fitted surface plasmon resonance (SPR) data were utilized to calculate the film thickness of this material. The thickness of a single layer is calculated to be 1.26 ± 0.09 nm. QCM and SPR systems are used to investigate gas sensing performance of macrocyclic LB films during exposure to Volatile Organic Compounds (VOCs). The macrocyclic LB thin films are more sensitive to dichloromethane than that of other vapors used in this study. The sensitivity and detection limit performance of the P5-Q QCM sensor to dichloromethane vapor were calculated to be 14.751 Hz ppm(-1) and 0.203 ppm, respectively. These results demonstrated that the P5-Q material is promising as an organic vapor sensing device at room temperature. Despite Langmuir-Blodgett being a traditional technique in colloid and interface science, this study presents the first gas sensor application for pillararene LB films. Because of the unique symmetric pillar architecture of P5-Q, self-assembly of pillar[5]arene molecules should afford various characteristic nanometer-scale architectures such as micelles, vesicles, and tubes.

  3. Immobilization of urease on poly(N-vinyl carbazole)/stearic acid Langmuir-Blodgett films for application to urea biosensor.

    PubMed

    Singhal, Rahul; Gambhir, Anamika; Pandey, M K; Annapoorni, S; Malhotra, B D

    2002-08-01

    Urease was immobilized in mixed monolayers of poly(N-vinyl carbazole) (PNVK) and stearic acid (SA) formed at an air-water interface. The monolayers were transferred onto indium-tin-oxide (ITO) coated glass plates using Langmuir-Blodgett (LB) film deposition technique. Urease immobilized on PNVK/SA LB films, characterized using FTIR and UV-visible spectroscopy, was found to exhibit increased stability over a wide pH (6.5-8.5) and temperature (25-50 degrees C) range. Potentiometric measurements on these urease electrodes were carried out using an ammonium ion analyzer. Two values for K(m)(app) were obtained at lower and higher concentrations of substrate urea.

  4. 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.

  5. Understanding and controlling morphology formation in Langmuir-Blodgett block copolymer films using PS-P4VP and PS-P4VP/PDP.

    PubMed

    Perepichka, Iryna I; Lu, Qing; Badia, Antonella; Bazuin, C Geraldine

    2013-04-09

    This contribution offers a comprehensive understanding of the factors that govern the morphologies of Langmuir-Blodgett (LB) monolayers of amphiphilic diblock copolymers (BCs). This is achieved by a detailed investigation of a wide range of polystyrene-poly(4-vinyl pyridine) (PS-P4VP) block copolymers, in contrast to much more limited ranges in previous studies. Parameters that are varied include the block ratios (mainly for similar total molecular weights, occasionally other total molecular weights), the presence or not of 3-n-pentadecylphenol (PDP, usually equimolar with VP, with which it hydrogen bonds), the spreading solution concentration ("low" and "high"), and the LB technique (standard vs "solvent-assisted"). Our observations are compared with previously published results on other amphiphilic diblock copolymers, which had given rise to contradictory interpretations of morphology formation. Based on the accumulated results, we re-establish early literature conclusions that three main categories of LB block copolymer morphologies are obtained depending on the block ratio, termed planar, strand, and dot regimes. The block composition boundaries in terms of mol % block content are shown to be similar for all BCs having alkyl chain substituents on the hydrophilic block (such as PS-P4VP/PDP) and are shifted to higher values for BCs with no alkyl chain substituents (such as PS-P4VP). This is attributed to the higher surface area per repeat unit of the hydrophilic block monolayer on the water surface for the former, as supported by the onset and limiting areas of the Langmuir isotherms for the BCs in the dot regime. 2D phase diagrams are discussed in terms of relative effective surface areas of the two blocks. We identify and discuss how kinetic effects on morphology formation, which have been highlighted in more recent literature, are superposed on the compositional effects. The kinetic effects are shown to depend on the morphology regime, most strongly

  6. 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.

  7. Carbon Nanotubes Arranged As Smart Interfaces in Lipid Langmuir-Blodgett Films Enhancing the Enzymatic Properties of Penicillinase for Biosensing Applications.

    PubMed

    Scholl, Fabio A; Morais, Paulo V; Gabriel, Rayla C; Schöning, Michael J; Siqueira, José R; Caseli, Luciano

    2017-09-13

    In this paper, carbon nanotubes (CNTs) were incorporated in penicillinase-phospholipid Langmuir and Langmuir-Blodgett (LB) films to enhance the enzyme catalytic properties. Adsorption of the penicillinase and CNTs at dimyristoylphosphatidic acid (DMPA) monolayers at the air-water interface was investigated by surface pressure-area isotherms, vibrational spectroscopy, and Brewster angle microscopy. The floating monolayers were transferred to solid supports through the LB technique, forming mixed DMPA-CNTs-PEN films, which were investigated by quartz crystal microbalance, vibrational spectroscopy, and atomic force microscopy. Enzyme activity was studied with UV-vis spectroscopy and the feasibility of the supramolecular device nanostructured as ultrathin films were essayed in a capacitive electrolyte-insulator-semiconductor (EIS) sensor device. The presence of CNTs in the enzyme-lipid LB film not only tuned the catalytic activity of penicillinase but also helped conserve its enzyme activity after weeks, showing increased values of activity. Viability as penicillin sensor was demonstrated with capacitance/voltage and constant capacitance measurements, exhibiting regular and distinctive output signals over all concentrations used in this work. These results may be related not only to the nanostructured system provided by the film, but also to the synergism between the compounds on the active layer, leading to a surface morphology that allowed a fast analyte diffusion because of an adequate molecular accommodation, which also preserved the penicillinase activity. This work therefore demonstrates the feasibility of employing LB films composed of lipids, CNTs, and enzymes as EIS devices for biosensing applications.

  8. 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.

  9. The effects of chain number and state of lipid derivatives of nucleosides on hydrogen bonding and self-assembly through the investigation of Langmuir Blodgett films

    NASA Astrophysics Data System (ADS)

    Jin, Yiguang; Qiao, Yingxin; Hou, Xinpu

    2006-09-01

    The long-chain lipid derivatives of acyclovir—a nucleoside analogue were used to prepare Langmuir-Blodgett (LB) films, including the single-chained derivative (SGSA) and the double-chained derivative (DASA). The bilayer LB film of DASA or the SGSA/cholesterol (SGSA/Chol) mixture (1:1, mol/mol) on quartz plates was investigated with ultraviolet absorption spectroscopy, and the blue-shifted absorption with 4 nm (DASA) or 18 nm (SGSA/Chol) wavelength changes was observed in comparison with their solutions in chloroform. The rigid double chains of DASA prevented adjacent molecules from approach, while the flexible single chains of SGSA did not. Then the strength of intermolecular hydrogen bonding between the nucleoside moieties of DASA was much more weaker than one of SGSA, and their blue-shifted wavelength in LB films was different. DASA and SGSA/Chol also showed the different bilayer LB films on mica according to the atomic force microscopic observation. The former was prone to tilting on solid supports while the latter would like to stand vertically with the help of cholesterol that could insert into the flexible single chains of SGSA. The chain number (one or two) and state (flexible or rigid) of lipid derivatives of nucleosides strongly impact intermolecular hydrogen bonding and self-assembly behavior.

  10. 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.

  11. Microstructure and Ion Exchange in Stearic Acid Langmuir-Blodgett Films Studied by Fourier Transform Infrared-Attenuated Total Reflection Spectroscopy.

    PubMed

    Li, Chun; Zhao, Bing; Lu, Yiqing; Liang, Yingqiu

    2001-03-01

    Fourier transform infrared-attenuated total reflection (FTIR-ATR) spectra have been recorded of 11-layer Langmuir-Blodgett (LB) films of stearic acid deposited at various surface pressures (0.1, 15, and 35 mN/m), and the molecular orientation angles were evaluated quantitatively, which supplied insight into the molecular order with the alkyl chains tightly packed like crystal in the LB films deposited at the zero and higher surface pressures. These experimental results indicate that, in the Langmuir film as the precursor of LB films, stearic acid molecules self-aggregate to form two-dimensional crystalline domains already even at the zero surface pressure, which results in the inhomogeneity of monolayer. The analysis of dependence of nu(C=O) intensity on the surface pressure, surface density, and subphase temperature leads to the conclusion that the defects in LB films originate from the Langmuir film and be conserved upon deposition. Annealing below 50 degrees C and cooling could improve the monolayer homogeneity, and thus a defect-free or low-defect LB films can be deposited. Furthermore, ion exchange conducted in the LB films, on the other hand, confirms the existence of structure defects in LB films of stearic acid. The polar plane microstructure, lateral transport along the polar planes and the coordination types of stearic acid/cation system may be the rate-limiting process. The results have implication on the possible uses of stearic acid LB films as ion-exchange materials or sensors. Copyright 2001 Academic Press.

  12. Electromagnetic model and calculations of the surface-enhanced Raman-shifted emission from Langmuir-Blodgett films on metal nanostructures

    NASA Astrophysics Data System (ADS)

    Giannini, V.; Sánchez-Gil, J. A.; García-Ramos, J. V.; Méndez, E. R.

    2007-07-01

    We present a theoretical study of the electromagnetic contribution to surface-enhanced Raman scattering (SERS) from a Langmuir-Blodgett film close to a metal surface. This macroscopic dipolar model fully accounts for the Raman-shifted emission so that meaningful SERS (electromagnetic) enhancement factors that do not depend only on the local electromagnetic field enhancement at the pump frequency are defined. For a plane metal surface, analytical SERS enhancement factors that are consistent for all pump beam polarization and molecular orientation are obtained. In order to investigate SERS on complex nanostructured metal surfaces, we introduce this model into the formally exact, Green's theorem surface integral equation formulation of the scattered electromagnetic field. This formulation is thus employed to calculate numerically the near-field and far-field emissions at the Raman-shifted frequency for very rough, random nanostructured surfaces, with emphasis on the impact of collective processes for varying pump frequency and Raman shift. Our results reveal that the widely used ∣E∣4 approximation tends to overestimate average SERS enhancement factors.

  13. 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.

  14. 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.

  15. Long-range excitation energy transfer in Langmuir-Blodgett multilayer systems

    NASA Astrophysics Data System (ADS)

    Draxler, Sonja; Lippitsch, Max E.; Aussenegg, Franz R.

    1989-07-01

    In Langmuir-Blodgett films containing organic dyes, efficient energy transfer over distances exceeding 100 nm is observed. This exceptionally long-range transfer is interpreted as due to special mutual orientation of the dye molecules.

  16. 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

  17. Thermal behavior of J-aggregates in a Langmuir-Blodgett film of pure merocyanine dye investigated by UV-visible and IR absorption spectroscopy.

    PubMed

    Hirano, Yoshiaki; Tateno, Shinsuke; Maio, Ari; Ozaki, Yukihiro

    2009-03-05

    We have characterized the structure of J-aggregate in a Langmuir-Blodgett film of pure merocyanine dye (MS18) fabricated under an aqueous subphase containing a cadmium ion (Cd2+) and have investigated its thermal behavior by UV-visible and IR absorption spectroscopy in the range from 25 to 250 degrees C with a continuous scan. The results of both UV-visible and IR absorption spectra indicate that temperature-dependent changes in the MS18 aggregation state in the pure MS18 system are closely and mildly linked with the MS18 intramolecular charge transfer and the behavior of the packing, orientation, conformation, and thermal mobility of MS18 hydrocarbon chain, respectively. The J-aggregate in the pure MS18 system dissociates from 25 to 150 degrees C, and the dissociation temperature at 150 degrees C is higher by 50 degrees C than that in the previous MS18- arachidic acid (C20) binary system. The lower dissociation temperature in the binary system originates from the fact that temperature-dependent structural disorder of cadmium arachidate (CdC20), being phase-separated from MS18, has an influence on the dissociation of J-aggregate. From 160 to 180 degrees C, thermally induced blue-shifted bands, caused by the oligomeric MS18 aggregation, appear at around 520 nm in the pure MS18 system by contraries, regardless of the lack of driving force by the melting phenomenon of CdC20. The temperature at which the 520 nm bands occur is in good agreement with the melting point (160 degrees C) of hydrocarbon chain in MS18 with Cd2+, whereas its chromophore part is clearly observed to melt near 205 degrees C by UV-visible spectra. Therefore, it is suggested that the driving force that induces the 520 nm band in the pure MS18 system arises from the partial melting of hydrocarbon chain in MS18 with Cd2+.

  18. External electric field effect on interlayer vectorial electron transfer from photoexcited oxacarbocyanine to viologen in Langmuir-Blodgett films

    NASA Astrophysics Data System (ADS)

    Ito, Takashi; Yamazaki, Iwao; Ohta, Nobuhiro

    1997-10-01

    Photoinduced interlayer electron transfer from the excited state of oxacarbocyanine (OCC) to viologen (VIO) is depressed or enhanced by an external electric field, depending on the direction of applied electric fields, in a donor-acceptor system composed of mixed monolayers of OCC and mixed monolayers of VIO separated by a spacer layer of fatty acid. As a result, field-induced increase and decrease of the quantum yield of OCC fluorescence are observed in the molecular assemblies of LB films.

  19. Formation and characterization of Langmuir and Langmuir-Blodgett films of Newkome-type dendrons in presence and absence of a therapeutic compound, for the development of surface mediated drug delivery systems.

    PubMed

    Dib, Nahir; Reviglio, Ana Lucia; Fernández, Luciana; Morales, Gustavo; Santo, Marisa; Otero, Luis; Alustiza, Fabrisio; Liaudat, Ana Cecilia; Bosch, Pablo; Calderón, Marcelo; Martinelli, Marisa; Strumia, Miriam

    2017-06-15

    Organic macromolecules with dendrimeric architectures are polymeric materials potentially useful as nanocarriers for therapeutic drugs. In this work, we evaluate a series of Newkome-type dendrons in Langmuir and Langmuir-Blodgett films as platforms capable of interacting with a potential antitumoral agent. The nanocomposite is proposed as model for the development of surface mediated drug delivery systems. We were successful in the formation and characterization of pure (dendrons) and composite (drug-dendron) stable and reproducible monolayers, and their transfer to solid substrates. A detailed study of topographic characteristics of the generated surfaces by atomic force microscopy was conducted. Furthermore, we probed dendron monolayer films as anchorage surfaces for mammalian cells. Normal cell attachment and proliferation on the surfaces were observed. No evident cytotoxic effects were detected, demonstrating the adequate biocompatibility of the surfaces.

  20. Fabrication and spectroscopic characterization of Langmuir-Blodgett films with luminescent rare earth complexes of long chain double functional ligands mono-L phthalate (L = hexadecyl, octadecyl and eicosyl).

    PubMed

    Yan, Bing; Xu, Bing

    2009-07-01

    In this paper, some novel long chain amphiphillic monoester molecules were designed to afford double functions: film-formation ability and luminescent sensitization ability. Subsequently organized molecular films of rare earth complexes with these functional ligands formulated as ML2NO3 were fabricated by the Langmuir-Blodgett film (LB) technology, where RE denotes rare earth ions Eu3+, Tb3+ and Dy3+; L denotes the long chain carboxylic ligands monohexadecyl phthalate (16-Phth), monooctadecyl phthalate (18-Phth) and monoeicosyl phthalate (20-Phth). The average molecular area was obtained according to the pi-A isotherms. The layer structure of the LB films was demonstrated by low-angle X-ray diffraction and the average layer spacing was determined from the Bragg equation. UV absorption intensity increases linearly with the number of LB films layers, which indicates that the LB films are homogeneously deposited. The fluorescence spectra of these LB films were quite different from those of their solid complexes. It reveals that the long chain ester ligands are suitable for the excited states of Tb3+ and Dy3+ in the LB films as well as in the solid complexes, but not match with the europium ion in the LB films.

  1. 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.

  2. An Observation of Diamond-Shaped Particle Structure in a Soya Phosphatidylcohline and Bacteriorhodopsin Composite Langmuir Blodgett Film Fabricated by Multilayer Molecular Thin Film Method

    NASA Astrophysics Data System (ADS)

    Tsujiuchi, Y.; Makino, Y.

    A composite film of soya phosphatidylcohline (soya PC) and bacteriorhodopsin (BR) was fabricated by the multilayer molecular thin film method using fatty acid and lipid on a quartz substrate. Direct Force Microscopy (DFM), UV absorption spectra and IR absorption spectra of the film were characterized on the detail of surface structure of the film. The DFM data revealed that many rhombus (diamond-shaped) particles were observed in the film. The spectroscopic data exhibited the yield of M-intermediate of BR in the film. On our modelling of molecular configuration indicate that the coexistence of the strong inter-molecular interaction and the strong inter-molecular interaction between BR trimmers attributed to form the particles.

  3. Thermal behavior of H-aggregate in a mixed Langmuir-Blodgett film of merocyanine dye, arachidic acid, and n-octadecane ternary system investigated by UV-visible and IR absorption spectroscopy.

    PubMed

    Hirano, Yoshiaki; Tateno, Shinsuke; Yamashita, Yoshihide; Ozaki, Yukihiro

    2008-11-13

    We have investigated the thermal behavior of H-aggregate in a mixed Langmuir-Blodgett (LB) film of the merocyanine dye (MS18)-arachidic acid (C20)- n-octadecane (AL18) ternary system by means of UV-visible and IR absorption spectroscopy in the range from 25 to 250 degrees C with a continuous scan. The results of both UV-visible and IR spectra indicate that the temperature-dependent variation in MS 18 aggregation state is linked not only with the degree of intramolecular charge transfer and the behavior of packing, orientation, conformation, and thermal mobility of the MS18 hydrocarbon chain but also with the presence and absence of AL18. The H-aggregate dissociates from 25 up to 50 degrees C, which is caused by the AL18 evaporation from the mixed LB film and the increment of thermal mobility of the MS18 hydrocarbon chain. From 110 to 160 degrees C, blue-shifted bands, attributed to the oligomeric MS18 aggregation, appear near 515 nm in the MS18-C 20-AL18 ternary system as well. The temperature at which the 515 nm band occurs is identical for both present ternary system and previously investigated MS18-deuterated arachidic acid (C20- d) binary system, and it is in good agreement with the melting point (110 degrees C) of cadmium arachidate (CdC20). Therefore, it is indicated that the driving force which induces the 515 nm band comes from the melting phenomenon of CdC20 molecules which are phase-separated from MS 18 molecules in as-deposited LB films.

  4. Supramolecular assembly and nanostructures of a series of luminol derivatives with aromatic/alkyl substituted groups in Langmuir-Blodgett films.

    PubMed

    Jiao, Tifeng; Xing, Yuanyuan; Zhang, Qingrui; Zhang, Li; Liu, Minghua; Zhou, Jingxin; Gao, Faming

    2014-06-01

    A series of functional luminol derivatives with aromatic and alkyl substituted groups has been designed and synthesized from the reaction of the corresponding chloride precursors with luminol. These compounds can be spread on water surface to form stable Langmuir films at the air-water interface. It has been found that UV and IR spectra confirmed the characteristic aromatic segment, imide group, and aromatic/alkyl substituted groups. In addition, for the interfacial assembly process of compounds with alkyl substituted groups, there are obvious spectral changes for the alkyl chains. AFM results indicated that various different aggregated domains may be fabricated in the transferred LB films. For all cases, the substituted groups in molecular structures have an important effect in regulating the aggregation mode and spectral changes in organized molecular films. The present results showed that the modified luminol derivatives may have potential application in functional material fields such as ECL sensor, which may give some insight to study the relationship between the molecular structures and supramolecular aggregation of amphiphiles in organized molecular films.

  5. Influence of heat treatment in air, and subsequent hydrothermal treatment in the liquid phase or water treatment in the liquid phase on a mixed Langmuir-Blodgett film of merocyanine dye-arachidic acid- n-octadecane ternary system

    NASA Astrophysics Data System (ADS)

    Hirano, Yoshiaki; Maio, Ari; Fukuda, Akira; Kitahama, Yasutaka; Ozaki, Yukihiro

    2010-07-01

    We have investigated the influence of heat treatment in air (HT), and subsequent hydrothermal treatment in the liquid phase (HTTL) or water treatment in the liquid phase (WTL) on the H-aggregate of mixed Langmuir-Blodgett (LB) films of merocyanine dye (MS 18)-arachidic acid (C 20)- n-octadecane (AL 18) ternary system by means of polarized visible and IR absorption spectroscopy. The MS 18 monomer is obtained from the first application of HT to the H-aggregate, and the monomer rapidly changes into the J-aggregate upon subsequent HTTL. This demonstrates variation via the monomer for reorganization of the MS 18 chromophore from H- to J-aggregates induced by directly performing HTTL to the H-aggregate in our previous study. While the number of gauche conformers in the MS 18 hydrocarbon chain increases by initial HT, the hydrocarbon chain adopts an all- trans conformation after subsequent HTTL. In addition, the degree of orientation of the MS 18 hydrocarbon chain after HT also approximates to that before HT. The C 20 hexagonal packing after HT turns to orthorhombic one with subsequent HTTL, and the orientation disorder of C 20 hydrocarbon chain caused by HT is renovated as well. The structural changes in the MS 18 and C 20 hydrocarbon chains resulting from latter HTTL arise from the hydrophobic effect in the presence of warm water. Moreover, it has been verified that the AL 18 evaporation strongly relates to the dissociation of H-aggregate, but is not responsible for the variation from the monomer to J-aggregate. Comparing the results obtained upon application of HT/HTTL and HT/WTL, it has been concluded that both large relative permittivity and thermal energy inherent in warm water are quite essential in inducing the rapid reconstitution of MS 18 aggregation state from the monomer to J-aggregate. These also promote the restoration of conformation and orientation changes in the MS 18 hydrocarbon chain, and the modification of subcell packing and orientation disorder in

  6. Dynamics Simulation of Langmuir-Blodgett Films

    DTIC Science & Technology

    1990-04-01

    of water. During the dynamics simulation, theposition of the water molecules are frozen. A 1515 edge effect as shown in Fig. 4: the tilts for...temperature, I.e. 300K, by gradually assigning random understand. The strong edge effect makes it necessary to iintroduce periodic boundaries In future

  7. Calorimetry and Langmuir-Blodgett studies on the interaction of a lipophilic prodrug of LHRH with biomembrane models.

    PubMed

    Sarpietro, Maria G; Accolla, Maria L; Santoro, Nancy; Mansfeld, Friederike M; Pignatello, Rosario; Toth, Istvan; Castelli, Francesco

    2014-05-01

    The interaction between an amphiphilic luteinizing hormone-releasing hormone (LHRH) prodrug that incorporated a lipoamino acid moiety (C12-LAA) with biological membrane models that consisted of multilamellar liposomes (MLVs) and phospholipid monolayers, was studied using Differential Scanning Calorimetry (DSC) and Langmuir-Blodgett film techniques. The effect of the prodrug C12[Q1]LHRH on the lipid layers was compared with the results obtained with the pure precursors, LHRH and C12-LAA. Conjugation of LHRH with a LAA promoiety showed to improve the peptide interaction with biomembrane models. Basing on the calorimetric findings, the LAA moiety aided the transfer of the prodrug from an aqueous solution to the biomembrane model.

  8. Large Area Fabrication of Semiconducting Phosphorene by Langmuir-Blodgett Assembly

    PubMed Central

    Kaur, Harneet; Yadav, Sandeep; Srivastava, Avanish. K.; Singh, Nidhi; Schneider, Jörg J.; Sinha, Om. P.; Agrawal, Ved V.; Srivastava, Ritu

    2016-01-01

    Phosphorene is a recently new member of the family of two dimensional (2D) inorganic materials. Besides its synthesis it is of utmost importance to deposit this material as thin film in a way that represents a general applicability for 2D materials. Although a considerable number of solvent based methodologies have been developed for exfoliating black phosphorus, so far there are no reports on controlled organization of these exfoliated nanosheets on substrates. Here, for the first time to the best of our knowledge, a mixture of N-methyl-2-pyrrolidone and deoxygenated water is employed as a subphase in Langmuir-Blodgett trough for assembling the nanosheets followed by their deposition on substrates and studied its field-effect transistor characteristics. Electron microscopy reveals the presence of densely aligned, crystalline, ultra-thin sheets of pristine phosphorene having lateral dimensions larger than hundred of microns. Furthermore, these assembled nanosheets retain their electronic properties and show a high current modulation of 104 at room temperature in field-effect transistor devices. The proposed technique provides semiconducting phosphorene thin films that are amenable for large area applications. PMID:27671093

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

    PubMed Central

    Osborn, T D; Yager, P

    1995-01-01

    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. Images FIGURE 4 FIGURE 5 PMID:7540429

  10. Distance dependence of surface-enhanced resonance raman enhancement in Langmuir-Blodgett dye multilayers

    SciTech Connect

    Cotton, T.M.; Uphaus, R.A.; Moebius, D.

    1986-11-06

    Monolayers of a surface-active dye incorporated into inert matrix material were transferred onto structurally defined silver island films by the Langmuir-Blodgett technique. The dye-containing monolayers were spaced from the surface by accurately known increments by deposition of inert spacer monolayers. Surface-enhanced resonance Raman spectra were observed from dye molecules spaced as distant as six spacer increments (ca. 16 nm) from the silver surface. These results indicate an electromagnetic mechanism is operative in this system in contradiction to a chemical mechanism which would require direct contact between the Raman-active species and the metal surface.

  11. Structural characterization of a mixed Langmuir-Blodgett film of a merocyanine dye derivative-deuterated arachidic acid binary system and the influence of successive hydrothermal treatment in the liquid phase on the film as investigated by polarized UV-visible and IR absorption spectroscopy.

    PubMed

    Hirano, Yoshiaki; Yamazaki, Asuka; Maio, Ari; Kitahama, Yasutaka; Ozaki, Yukihiro

    2010-08-26

    We have investigated the structure of the mixed Langmuir-Blodgett (LB) film of a merocyanine dye derivative (MO(18))-deuterated arachidic acid (C(20)-d) binary system and the influence of successive hydrothermal treatment in the liquid phase (HTTL) on the mixed LB film by means of polarized UV-visible and IR absorption spectroscopy. The visible absorption band with in-plane anisotropy at 503 nm before HTTL transforms into an absorption band with in-plane isotropy at 557 nm after HTTL for 16-18 min through a peak maximum near 520 nm after HTTL for 2-12 min. The degree of total MO(18) intramolecular charge transfer for the 503 nm band is the largest among those for all of the bands. Therefore, the 503 nm band is ascribed to the MO(18) H-like aggregation, based on its shape, peak height, and in-plane anisotropy, the subsequent change to two kinds of visible peaks by successive HTTL, and the most degree of MO(18) intramolecular charge transfer among all of the aggregation states. While the MO(18) hydrocarbon chain takes the all-trans conformation before HTTL, its conformation and orientation are most disarranged after HTTL for 2 min. Subsequently, the original conformation and orientation are recovered by degrees with successive HTTL, except after final HTTL for 18 min, when the orientation is again changed. On the other hand, the C(20)-d hydrocarbon chain maintains the all-trans conformation before and after HTTL. The orientation of the C(20)-d hydrocarbon chain after HTTL for 2 min is more ordered than that before HTTL, with the nature of the C(20)-d subcell packing changing from hexagonal to orthorhombic. During successive HTTL from 2 to 18 min, the C(20)-d orientation is gradually disorganized but with the orthorhombic nature remaining constant. Thus, the variations in the conformation and orientation of the MS(18) hydrocarbon chain and in the orientation of the C(20)-d hydrocarbon chain tend to change from ordered and disordered structures and turn to more

  12. The Shear Properties of Langmuir-Blodgett Layers

    NASA Astrophysics Data System (ADS)

    Briscoe, B. J.; Evans, D. C. B.

    1982-04-01

    The sliding friction between two highly oriented monolayers has been studied by using molecularly smooth mica substrates in the form of contacting orthogonal cylinders. The monolayers in the form of various normal alipathic carboxylic acids and their soaps were deposited with the aid of the Langmuir-Blodgett technique by transfer from aqueous substrates. The normal alkyl group has been varied in length from 14 to 22 methylene repeat units. Data are reported also on the influence of partial saponification of the carboxylic acid and fluorination of the alkyl chain. Most of the investigation has been confined to two contacting single monolayers although a limited amount of data is presented for multilayers sliding over one another. The character of the sliding motion depends not only on the machine but also on the monolayers, particularly their chemistry. Most of the monolayers studied provide a continuous rate of energy dissipation. However, a small number, such as certain soaps, show discontinuous or stick-slip motion. The experimental arrangement allows simultaneous measurement of the sliding frictional force, contact area and film thickness to be made during sliding. In some experiments this friction is the monotonic sliding friction but in others it is the mean maximum value during the stick phase. The film thickness measurement is accurate to 0.2 mm which allows a precise assessment of the shear plane during sliding. In all cases the monolayers and multilayers were found to be extremely durable and shear invariably occurred at the original interface between the monolayers. The sliding friction data are presented as the dynamic specific friction force or interface shear strength, and a number of contact variables have been examined. These include the applied normal load per unit contact area or mean contact pressure, the temperature and the sliding velocity. The interface shear strength is found, to a good approximation, to increase linearly with mean contact

  13. Phase behaviour in binary mixed Langmuir Blodgett monolayers of triglycerides

    NASA Astrophysics Data System (ADS)

    Zdravkova, Aneliya N.; van der Eerden, J. P. J. M.

    2007-09-01

    Binary mixed monolayers of the triglycerides (TAGs)-tripalmitin (PPP), tristearin (SSS) and triarachidin (AAA) at the air-water interface are investigated with the Langmuir method. Langmuir-Blodgett (LB) layers obtained by deposition on mica are investigated by Atomic Force Microscopy. Combining Langmuir and AFM results the relation between the phase behaviour of binary mixed TAGs and their chain length is established. TAG mixtures form monolayers with molecules in trident conformation at the air-water interface, like pure TAGs. The area Acond=63 Å 2 and the pressure πcond=8-10 mN/m that separate "gas" and "condensed" film structures are the same for all mixtures and pure systems. In the π- A isotherms the sharpness of the transition from "gas" to "condensed" phase decreases with the average chain length for all systems. Using AFM data the monolayer thicknesses for mixtures and pure systems is found to be linearly dependent on the average chain length of the TAG molecules. A linear relation between film thickness and applied AFM force is established. The corresponding coefficient K˜ is higher for mixed monolayers ( K˜=0.08±0.01 nN) than for pure systems ( K˜=0.07±0.01 nN). AFM images show phase separation in the systems PPP-SSS and PPP-AAA. The solubility of the shorter PPP molecules in the "long" (SSS- and AAA-rich) phase is significant. For the mixture SSS-AAA, phase separation is not observed. In that mixture the monolayer thickness varies linearly with composition, supporting the conclusion that SSS and AAA mix almost ideally. The main driving force for phase separation is the difference in the alkyl chain length. Indeed PPP-AAA (length difference 4 C atoms) shows the most clear phase separation. The relatively weak phase separation in PPP-SSS and the absence of phase separation in SSS-AAA show that the influence of chain length difference decreases with increasing average chain length. In air PPP-SSS and PPP-AAA mixed monolayers are unstable and

  14. Potential Well Generated in Langmuir-Blodgett Heterofilm Consisting of Polar and Nonpolar Layers

    NASA Astrophysics Data System (ADS)

    Hino, Taro

    1991-06-01

    Voltage is applied in the surface direction of Langmuir-Blodgett (LB) heterofilms consisting of arachidic acid (C20, Y type, nonpolar) LB film and TCNQ-derivative (2-pentadecyl-7,7',8,8'-tetracyanoquinodimethane, C15\\cdotTCNQ, Z type, polar) or protoporphyrin IX dimethyl ester (PPDM, Z type, polar) LB film, and the voltage drop in the heterofilm is measured. As a result, a potential well is generated in the heterofilm of [nonpolar LB film/polar LB film], but no potential well is observed in the heterofilm of [polar LB film/nonpolar LB film] where the polar and the nonpolar LB films are deposited in reverse order of the former heterofilm.

  15. 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.

  16. Hierarchically structured superhydrophobic coatings fabricated by successive Langmuir-Blodgett deposition of micro-/nano-sized particles and surface silanization.

    PubMed

    Tsai, Ping-Szu; Yang, Yu-Min; Lee, Yuh-Lang

    2007-11-21

    The present study demonstrates the creation of a stable, superhydrophobic surface by coupling of successive Langmuir-Blodgett (LB) depositions of micro- and nano-sized (1.5 µm/50 nm, 1.0 µm/50 nm, and 0.5 µm/50 nm) silica particles on a glass substrate with the formation of a self-assembled monolayer of dodecyltrichlorosilane on the surface of the particulate film. Particulate films, in which one layer of 50 nm particles was deposited over one to five sublayers of larger micro-sized particles, with hierarchical surface roughness and superhydrophobicity, were successfully fabricated. Furthermore, the present 'two-scale' (micro- and nano-sized particles) approach is superior to the previous 'one-scale' (micro-sized particles) approach in that both higher advancing contact angle and lower contact angle hysteresis can be realized. Experimental results revealed that the superhydrophobicity exhibited by as-fabricated particulate films with different sublayer particle diameters increases in the order of 0.5 µm>1.0 µm>1.5 µm. However, no clear trend between sublayer number and surface superhydrophobicity could be discerned. An explanation of superhydrophobicity based on the surface roughness introduced by two-scale particles is also proposed.

  17. Fullerene nanowires: self-assembled structures of a low-molecular-weight organogelator fabricated by the Langmuir-Blodgett method.

    PubMed

    Tsunashima, Ryo; Noro, Shin-ichiro; Akutagawa, Tomoyuki; Nakamura, Takayoshi; Kawakami, Hiroko; Toma, Kazunori

    2008-01-01

    Fullerene derivative C60TT, which is substituted with the low-molecular-weight organogelator tris(dodecyloxy)benzamide, formed nanowire structures on application of the Langmuir-Blodgett (LB) method. The surface morphology of the C60TT LB film was dependent on the holding time before deposition at a surface pressure of 5 mN m(-1); it changed from a homogeneous monolayer to a bilayer fibrous structure via a fibrous monolayer structure, which was estimated to have dimensions of 1.2 nm in height, 8 nm in width, and 5-10 microm in length. From the structural and spectroscopic data, it is inferred that close packing of the fullerene moiety occurs along with intermolecular hydrogen bonding within the monolayer fibrous structure. The morphological changes in the LB film are explained kinetically by the Avrami theory, based on the decrease in the surface area of the monolayer at the air/water interface. The growth of the quasi-one-dimensional fibrous monolayer structures at holding times from 0 to 0.2 h is considered to be an interface-controlled process, whereas the growth of the quasi-one-dimensional bilayer fibrous structures from 0.2 to 18 h is thought to be a diffusion-controlled process.

  18. Nanopatterned cadmium selenide Langmuir-Blodgett platform for leukemia detection.

    PubMed

    Sharma, Aditya; Pandey, Chandra M; Matharu, Zimple; Soni, Udit; Sapra, Sameer; Sumana, Gajjala; Pandey, Manoj K; Chatterjee, Tathagat; Malhotra, Bansi D

    2012-04-03

    We present results of the studies relating to preparation of Langmuir-Blodgett (LB) monolayers of tri-n-octylphosphine oxide-capped cadmium selenide quantum dots (QCdSe) onto indium-tin oxide (ITO) coated glass substrate. The monolayer behavior has been studied at the air-water interface under various subphase conditions. This nanopatterned platform has been explored to fabricate an electrochemical DNA biosensor for detection of chronic myelogenous leukemia (CML) by covalently immobilizing the thiol-terminated oligonucleotide probe sequence via a displacement reaction. The results of electrochemical response studies reveal that this biosensor can detect target DNA in the range of 10(-6) to 10(-14) M within 120 s, has a shelf life of 2 months, and can be used about 8 times. Further, this nucleic acid sensor has been found to distinguish the CML-positive and the control negative clinical patient samples.

  19. 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.

  20. Formation of silver nanoparticle at phospholipid template using Langmuir-Blodgett technique and its Surface-enhanced Raman Spectroscopy application

    NASA Astrophysics Data System (ADS)

    Mahato, M.; Sarkar, R.; Pal, P.; Talapatra, G. B.

    2015-10-01

    The biosynthesis of metal nanoparticle and their suitable assembly has recently gained tremendous interest for its application in biomedical arena such as substrates for surface-enhanced Raman scattering and others. In this article, an easy, low-cost, fast, bio-friendly and toxic-reducing agent free protocol has been described for the preparation of silver nanoparticle film using biocompatible 1,2-dipalmitoyl-sn-glycero-3-phosphocholine phospholipid Langmuir monolayer template. Interactions, docking and attachment of silver ions to the above-mentioned phospholipid monolayer have been studied by surface pressure-area isotherm and compressibility analysis at the air-water interface. We have deposited the Langmuir-Blodgett monolayer/multilayer containing silver nanoparticle onto glass/SiO2/quartz substrates. The formation of phospholipid-silver nanoparticle complex in Langmuir-Blodgett film has been characterized by field emission-scanning electron microscopy and high-resolution tunneling electron microscopy images. We have applied this deposited film as a substrate for surface-enhanced Raman scattering application using rhodamine 123 to understand the existence of the surface plasmon activity of silver nanoparticle.

  1. Average orientation of a molecular rotor embedded in a Langmuir-Blodgett monolayer.

    PubMed

    Casher, Deborah L; Kobr, Lukáš; Michl, Josef

    2012-01-17

    A molecular rotor in which a naphthalene rotator is attached through a silicon atom to three fatty acid chains has been synthesized, and Langmuir-Blodgett techniques were used to deposit on silica surfaces monolayers of its calcium salt, both neat and diluted with stearic acid salts. The monolayer films have been characterized by ellipsometry and Fourier transform infrared (FT-IR) grazing-incidence attenuated total internal reflection (GATR) spectroscopy on Si-SiO(2) and by UV-vis absorption spectroscopy on SiO(2). The measurements were combined with calculations of the electronic (INDO/S) and vibrational (DFT) transition moment directions to deduce the average orientation of the rotor molecules, including the naphthalene ring, relative to the surface. In both neat and mixed films, the naphthalene ring is found to preferentially tilt toward the surface, enough that its rotation is most likely hindered. A comparable picture was obtained from molecular mechanics calculations on a mixed film of the naphthalene rotor and stearic acid. © 2011 American Chemical Society

  2. Control of indium tin oxide anode work function modified using Langmuir-Blodgett monolayer for high-efficiency organic photovoltaics

    NASA Astrophysics Data System (ADS)

    Yokokura, Yuya; Dogase, Tomomichi; Shinbo, Tatsuki; Nakayashiki, Yuya; Takagi, Yusuke; Ueda, Kazuyoshi; Sarangerel, Khayankhyarvaa; Delgertsetseg, Byambasuren; Ganzorig, Chimed; Sakomura, Masaru

    2017-08-01

    The use of Langmuir-Blodgett (LB) monolayers to modify the indium tin oxide (ITO) work function and thus improve the performance of zinc phthalocyanine (ZnPc)/fullerene (C60)-based and boron subphthalocyanine chloride (SubPc)/C60-based small molecule organic photovoltaic devices (OPVs) was examined. In general, LB precursor compounds contain one or more long alkyl chain substituents that can act as spacers to prevent electrical contact with adjoining electrode surfaces. As one example of such a compound, arachidic acid (CH3(CH2)18COOH) was inserted in the forms of one-layer, three-layer or five-layer LB films between the anode ITO layer and the p-type layer in ZnPc-C60-based OPVs to investigate the effects of the long alkyl chain group when it acts as an electrically insulating spacer. The short-circuit current density (Jsc) values of the OPVs with the three- and five-layer inserts (1.78 mA.cm-2 and 0.61 mA.cm-2, respectively) were reduced dramatically, whereas the Jsc value for the OPV with the single-layer insertion (2.88 mA.cm-2) was comparable to that of the OPV without any insert (3.14 mA.cm-2). The ITO work function was shifted positively by LB deposition of a surfactant compound, C9F19C2H4-O-C2H4-COOH (PFECA), which contained a fluorinated head group. This positive effect was maintained even after formation of an upper p-type organic layer. The Jsc and open-circuit voltage (Voc) of the SubPc-C60-based OPV with the LB-modified ITO layers were effectively enhanced. As a result, a 42% increase in device efficiency was achieved.

  3. Hooking horseradish peroxidase by using the affinity Langmuir-Blodgett technique for an oriented immobilization

    NASA Astrophysics Data System (ADS)

    Peng, Ye; Ling-Ling, Hu; Yu-Zhi, Du; Yong-Juan, Xu; Hua-Gang, Ni; Cong, Chen; Xiao-Lin, Lu; Xiao-Jun, Huang

    2017-05-01

    A novel method of oriented immobilization was presented: affinity Langmuir-Blodgett (LB) technique. Firstly, a long carbon chain was bond to a ligand of Horseradish Peroxidase (HRP). The ligand derivative appears surface activity with the hydrophobic carbon chain oriented to air and the hydrophilic ligand faced to water. Then, this derivative was put onto the water/air surface to assemble a LB film and formed the affinity interaction with the active site of HRP. After that, the affinity LB film with the enzyme was transferred onto the support to obtain the oriented immobilized HRP. The specific activity of HRP immobilized by affinity LB (182.1 ± 14 U/mg) was higher than that by adsorption (40.5 ± 5 U/mg). HRP immobilized by affinity LB could maintain a more native conformation, compared to that by adsorption. This method could be effectively used to immobilize protein with orientation and show widely promising applications in many fields including biosensor and bioreactor.

  4. Surface Patterns of Tetragonal Phase FePt Thin Films from Pt{at}Fe2O3 Core-Shell Nanoparticles Using Combined Langmuir-Blodgett and Soft Lithographic Techniques

    SciTech Connect

    Guo, Q.; Teng, X.; Yang, H.

    2003-09-30

    OAK B204 We present the fabrication of micron-sized patterns of FePt thin films from Pt{at}Fe2O3 core-shell nanoparticles. In a typical procedure, Pt@Fe2O3 core-shell nanoparticles were spread and formed a Langmuir film using water as the subphase. This film was lifted onto polydimethylsiloxane (PDMS) stamps with micron-sized patterns of lines, dots and wells, and transferred onto silicon wafers using microcontact printing (u-CP). The patterns of Pt@Fe2O3 core-shell nanoparticles were converted into face-centered tetragonal phase FePt alloy at enhanced temperatures in the presence of 5% hydrogen. Scanning electron microscopy (SEM), atomic force microscopy (AFM), powder X-ray diffraction (PXRD) and superconducting quantum interference device (SQUID) magnetometer were used to characterize the patterns and the properties of the final FePt alloy films.

  5. Wrinkling and Periodic Folding of Graphene Oxide Monolayers by Langmuir-Blodgett Compression.

    PubMed

    Silverberg, Gregory J; Vecitis, Chad D

    2017-09-26

    Crumples, wrinkles, and other three-dimensional topographical features in graphene oxide (GO) have been of recent interest as these features have improved material performance for a variety of applications. However, wrinkling of monolayer GO films has yet to be reported. Herein, we demonstrate wrinkling and folding of monolayer GO using the Langmuir-Blodgett technique for the first time. First, cetyltrimethylammonium bromide (CTAB) and GO are deposited on the air-water interface and uniaxially compressed to form a monolayer. CTAB enhances in-plane rigidity of the monolayer through hydrophobic tail aggregation, preventing GO-GO in-plane sliding behavior. Overcompression of the GO monolayer results in the out-of-plane periodic nanoscale wrinkling and in turn generates folds that are stable during deposition onto a substrate and GO chemical reduction. Furthermore, we investigate one potential application of this material by constructing a 3D electrode of the stacked nanofolded GO-CTAB layers that exhibits superior volumetric capacitance compared to commercial devices and comparable volumetric capacitance compared to high-performing recently reported devices. The high volumetric capacitance is attributed to the electrolyte-accessible channels generated by the nanofolds which are similar in size to the hydrated ions.

  6. Conversion of Langmuir-Blodgett monolayers and bilayers of poly(amic acid) through polyimide to graphene

    NASA Astrophysics Data System (ADS)

    Jo, Hye Jin; Lyu, Ji Hong; Ruoff, Rodney S.; Lim, Hyunseob; In Yoon, Seong; Jeong, Hu Young; Shin, Tae Joo; Bielawski, Christopher W.; Shin, Hyeon Suk

    2017-03-01

    Various solid carbon sources, particularly poly(methyl methacrylate), have been used as precursors to graphene. The corresponding growth process generally involves the decomposition of the solids to hydrocarbon gases followed by their adsorption on metallic substrates (e.g., Cu). We report a different approach that uses a thermally-resistant polyimide (PI) as a carbon precursor. Langmuir-Blodgett films of poly(amic acid) (PAA) were transferred to copper foils and then converted to graphene via a PI intermediate. The Cu foil substrate was also discovered to facilitate the orientation of aromatic moieties upon carbonization process of the PI. As approximately 50% of the initial quantity of the PAA was found to remain at 1000 °C, thermally-stable polymers may reduce the quantity of starting material required to prepare high quality films of graphene. Graphene grown using this method featured a relatively large domain size and an absence of adventitious adlayers.

  7. 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.

  8. Dip-coating with prestructured substrates: transfer of simple liquids and Langmuir-Blodgett monolayers

    NASA Astrophysics Data System (ADS)

    Wilczek, Markus; Zhu, Juan; Chi, Lifeng; Thiele, Uwe; Gurevich, Svetlana V.

    2017-01-01

    When a plate is withdrawn from a liquid bath, either a static meniscus forms in the transition region between the bath and the substrate or a liquid film of finite thickness (a Landau-Levich film) is transferred onto the moving substrate. If the substrate is inhomogeneous, e.g. has a prestructure consisting of stripes of different wettabilities, the meniscus can be deformed or show a complex dynamic behavior. Here we study the free surface shape and dynamics of a dragged meniscus occurring for striped prestructures with two orientations, parallel and perpendicular to the transfer direction. A thin film model is employed that accounts for capillarity through a Laplace pressure and for the spatially varying wettability through a Derjaguin (or disjoining) pressure. Numerical continuation is used to obtain steady free surface profiles and corresponding bifurcation diagrams in the case of substrates with different homogeneous wettabilities. Direct numerical simulations are employed in the case of the various striped prestructures. The final part illustrates the importance of our findings for particular applications that involve complex liquids by modeling a Langmuir-Blodgett transfer experiment. There, one transfers a monolayer of an insoluble surfactant that covers the surface of the bath onto the moving substrate. The resulting pattern formation phenomena can be crucially influenced by the hydrodynamics of the liquid meniscus that itself depends on the prestructure on the substrate. In particular, we show how prestructure stripes parallel to the transfer direction lead to the formation of bent stripes in the surfactant coverage after transfer and present similar experimental results.

  9. 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

  10. 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.

  11. Near infrared (NIR) lanthanide emissive Langmuir-Blodgett monolayers formed using Nd(III) directed self-assembly synthesis of chiral amphiphilic ligands.

    PubMed

    Barry, Dawn E; Kitchen, Jonathan A; Albrecht, Martin; Faulkner, Stephen; Gunnlaugsson, Thorfinnur

    2013-09-10

    The incorporation of chiral amphiphilic lanthanide-directed self-assembled Nd(III) complexes (Nd.13 and Nd.23) into stable Langmuir monolayers, and the subsequent Langmuir-Blodgett film formation of these, is described. The photophysical properties of the enantiomeric pair of ligands 1 and 2 in the presence of Nd(CF3SO3)3 were also investigated in CH3CN solutions using UV-vis, fluorescence, and lanthanide luminescence spectroscopies. Analysis of the resulting self-assembly processes revealed that two main species were formed in solution,1:1 and 1:3 Nd:L self-assembly complexes, with the latter being the dominant species upon the addition of 0.33 equivalents of Nd(III). Excited state lifetime measurements of Nd.13 and Nd.23 in CH3OH and CD3OD and CH3CN were also evaluated. The formation of the self-assembly in solution was also monitored by observing the changes in the circular dichroism (CD) spectra; and large differences were observed between the 1:3 and other stoichiometries in the spectra, allowing for correlation to be made with that seen in the emission studies of these systems. Surface pressure-area and surface pressure-time isotherms evidenced the formation of stable Langmuir monolayers of Nd.13 and Nd.23 at an air-water interface, and the deposition of these monolayers onto a quartz solid substrate (Langmuir-Blodgett films) gave rise to immobilized chiral monomolecular films which exhibited Nd(III) NIR luminescence upon excitation of the ligand chromophore, demonstrating efficient energy transfer to the Nd(III) excided state (sensitized) with concomitant emission centered at 800 and 1334 nm.

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

    PubMed

    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.

  13. 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.

  14. Atomic force microscopy and Langmuir-Blodgett monolayer technique to assess contact lens deposits and human meibum extracts.

    PubMed

    Hagedorn, Sarah; Drolle, Elizabeth; Lorentz, Holly; Srinivasan, Sruthi; Leonenko, Zoya; Jones, Lyndon

    2015-01-01

    The purpose of this exploratory study was to investigate the differences in meibomian gland secretions, contact lens (CL) lipid extracts, and CL surface topography between participants with and without meibomian gland dysfunction (MGD). Meibum study: Meibum was collected from all participants and studied via Langmuir-Blodgett (LB) deposition with subsequent Atomic Force Microscopy (AFM) visualization and surface roughness analysis. CL Study: Participants with and without MGD wore both etafilcon A and balafilcon A CLs in two different phases. CL lipid deposits were extracted and analyzed using pressure-area isotherms with the LB trough and CL surface topographies and roughness values were visualized using AFM. Meibum study: Non-MGD participant meibum samples showed larger, circular aggregates with lower surface roughness, whereas meibum samples from participants with MGD showed more lipid aggregates, greater size variability and higher surface roughness. CL Study: Worn CLs from participants with MGD had a few large tear film deposits with lower surface roughness, whereas non-MGD participant-worn lenses had many small lens deposits with higher surface roughness. Balafilcon A pore depths were shallower in MGD participant worn lenses when compared to non-MGD participant lenses. Isotherms of CL lipid extracts from MGD and non-MGD participants showed a seamless rise in surface pressure as area decreased; however, extracts from the two different lens materials produced different isotherms. MGD and non-MGD participant-worn CL deposition were found to differ in type, amount, and pattern of lens deposits. Lipids from MGD participants deposited irregularly whereas lipids from non-MGD participants showed more uniformity. Copyright © 2014 Spanish General Council of Optometry. Published by Elsevier Espana. All rights reserved.

  15. Polymerization of Conducting Polymers Confined to Free Surfaces: A comparison of the Langmuir-Blodgett Polymerization of 3-Alkyl Pyrroles and 2- Alkyl Anilines

    DTIC Science & Technology

    1992-05-19

    Confined to Free Surfaces: A Comparison of the Langmuir-Blodgett Polymerization of 3- Alkyl Pyrroles and 2- Alkyl Anilines Submitted for Publication in...Surfaces: A Comparison of the Langmuir Blodgett Polymerizations of 3- alkyl pyrroles and 2- alkyl anilines R. S. Duran and H.C. Zhou Dept. of Chemistry...polymerization reactions in more detail and compare them. To do this, the polymerization reactions were run under two conditions. In the first case

  16. Evaluation of the interaction of coumarins with biomembrane models studied by differential scanning calorimetry and Langmuir-Blodgett techniques.

    PubMed

    Sarpietro, Maria Grazia; Giuffrida, Maria Chiara; Ottimo, Sara; Micieli, Dorotea; Castelli, Francesco

    2011-04-25

    Three coumarins, scopoletin (1), esculetin (2), and esculin (3), were investigated by differential scanning calorimetry and Langmuir-Blodgett techniques to gain information about the interaction of these compounds with cellular membranes. Phospholipids assembled as multilamellar vesicles or monolayers (at the air-water interface) were used as biomembrane models. Differential scanning calorimetry was employed to study the interaction of these coumarins with multilamellar vesicles and to evaluate their absorption by multilamellar vesicles. These experiments indicated that 1-3 interact in this manner to different extents. The Langmuir-Blodgett technique was used to study the effect of these coumarins on the organization of phospholipids assembled as a monolayer. The data obtained were in agreement with those obtained in the calorimetric experiments.

  17. Development of New Amperometric Biosensors based on Organic-inorganic Hybrid Ultra-thin Films

    NASA Astrophysics Data System (ADS)

    Ohnuki, Hitoshi; Endo, Hideaki; Imakubo, Tatsuro; Izumi, Mitsuru

    The hybrid ultra-thin films composed of cationic long-alkyl chain molecules and nano-size Prussian Blue clusters were obtained by the Langmuir-Blodgett (LB) technique. It was found that the LB films are quite useful as the starting material for building the high performance biosensors based on oxidative enzymes. The biosensors were easily prepared by a simple immersion of the LB films into enzyme solution, then they work under a very low potential range avoiding the interferent current. We demonstrated that the process is applicable to prepare many types of biosensors just by changing the immobilized enzymes.

  18. Atomic-force and fluorescence microscopy of Langmuir-Blodgett monolayers of [ital L]-[alpha]-dimyristoylphosphatidic acid

    SciTech Connect

    Mikrut, J.M. ); Dutta, P.; Ketterson, J.B. ); MacDonald, R.C. )

    1993-11-15

    We have obtained fluorescence and atomic-force-microscopy images of the liquid and solid phases of Langmuir-Blodgett monolayers of [ital L]-[alpha]-dimyristoylphosphatidic acid, some containing [similar to]1 mol % of [ital L]-[alpha]-phosphatidylethanolamine-[ital N]-4-nitrobenzo-2-oxa-1,3-diazole. The fluorescence microscopy images are similar to those of monolayers at the air-water interface, but slight differences indicate that changes occur in the monolayers as a result of the deposition process. The atomic-force-microscopy images show the clean glass substrates to be very much rougher than when the monolayers are deposited on them. We propose that a water layer provides a smooth surface on which the Langmuir-Blodgett monolayers rest. We measured a [similar to]25-A height difference between the liquid and solid phase region, one explanation being that the alkyl chains of the molecule are standing up in the solid phase and lying down in the liquid phase. This result is consistent with the fluorescence and atomic-force-microscopy images which show an increase in the amount of solid phase domains as a result of the deposition process. Further, the atomic-force-microscopy images of the monolayers show features which have not been described before and which could not be attributed to the presence of the dye. Finally, we showed that if the Langmuir-Blodgett monolayers are not stored in a humid environment, they begin to collapse into multilayers.

  19. 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.

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

    PubMed

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

    2006-07-04

    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.

  1. Accelerated protein crystal growth by protein thin film template

    NASA Astrophysics Data System (ADS)

    Pechkova, Eugenia; Nicolini, Claudio

    2001-11-01

    A new method based on Langmuir-Blodgett (LB) technology is presented for the template stimulation of protein crystal growth. The new approach allows the acceleration of the hen egg white lysozyme (HEWL) crystal growth rate in comparison with such a classical vapour diffusion method as hanging drop. Protein thin films were coated on the cover slide of the common crystallization plates. Lysozyme crystal growth was observed on the LB thin films of HEWL.

  2. 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

    2013-12-03

    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. © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. 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.

  4. Structural characterization and plasmonic properties of two-dimensional arrays of hydrophobic large gold nanoparticles fabricated by Langmuir-Blodgett technique

    NASA Astrophysics Data System (ADS)

    Ishida, Takuya; Tachikiri, Yuki; Sako, Takayuki; Takahashi, Yukina; Yamada, Sunao

    2017-05-01

    We have succeeded in fabricating two-dimensional (2D) arrays of larger gold nanoparticles (AuNPs) (diameters 17, 28, and 48 nm) by Langmuir-Blodgett (LB) method. Although the particle size of AuNPs is one of the most important factors in order to control the optical properties of 2D arrays, there have been reported only the size of less than ∼20 nm. This is a first report on the bottom-up fabrication of 2D arrays consisting of hydrophobic AuNP with the diameter of ∼50 nm, of which the size is expected to obtain maximum near-field effects. Octadecylthiolate-capped AuNPs (ODT-AuNPs) which were prepared by our method could be re-dispersed in chloroform even after drying completely, realizing the spreading of the colloidal chloroform solution onto the water surface. Accordingly, densely-packed 2D LB films of ODT-AuNPs could be fabricated on an indium-tin-oxide substrate, when water as the subphase and polyethylene glycol (PEG) as an amphiphilic agent were used. PEG played an important role to form densely-packed film uniformly due to increasing affinity between hydrophobic AuNP and water. Absorption spectra of the films revealed that the resonance wavelengths of plasmon oscillation through interparticle plasmon coupling were clearly correlated with the particle sizes rather than deposition densities.

  5. Phase behavior of stratum corneum lipids in mixed Langmuir-Blodgett monolayers.

    PubMed Central

    ten Grotenhuis, E; Demel, R A; Ponec, M; Boer, D R; van Miltenburg, J C; Bouwstra, J A

    1996-01-01

    The lipids found in the bilayers of the stratum corneum fulfill the vital barrier role of mammalian bodies. The main classes of lipids found in stratum corneum are ceramides, cholesterol, and free fatty acids. For an investigation of their phase behavior, mixed Langmuir-Blodgett monolayers of these lipids were prepared. Atomic force microscopy was used to investigate the structure of the monolayers as a function of the monolayer composition. Three different types of ceramide were used: ceramide extracted from pigskin, a commercially available ceramide with several fatty acid chain lengths, and two synthetic ceramides that have only one fatty acid chain length. In pigskin ceramide-cholesterol mixed monolayers phase separation was observed. This phase separation was also found for the commercially available type III Sigma ceramide-cholesterol mixed monolayers with molar ratios ranging from 1:0.1 to 1:1. These monolayers separated into two phases, one composed of the long fatty acid chain fraction of Sigma ceramide III and the other of the short fatty acid chain fraction of Sigma ceramide III mixed with cholesterol. Mixtures with a higher cholesterol content consisted of only one phase. These observations were confirmed by the results obtained with synthetic ceramides, which have only one fatty acid chain length. The synthetic ceramide with a palmitic acid (16:0) chain mixed with cholesterol, and the synthetic ceramide with a lignoceric acid (24:0) chain did not. Free fatty acids showed a preference to mix with one of these phases, depending on their fatty acid chain lengths. The results of this investigation suggest that the model system used in this study is in good agreement with those of other studies concerning the phase behavior of the stratum corneum lipids. By varying the composition of the monolayers one can study the role of each lipid class in detail. Images FIGURE 2 FIGURE 3 FIGURE 4 FIGURE 5 FIGURE 6 PMID:8874014

  6. 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.

  7. The use of surface tension to predict the formation of 2D arrays of latex spheres formed via the Langmuir-Blodgett-like technique.

    PubMed

    Marquez, Maricel; Grady, Brian P

    2004-12-07

    Highly ordered hexagonal arrays of latex spheres on highly ordered pyrolytic graphite (HOPG) have been prepared from a Langmuir-Blodgett-like (LB-like) technique using both polymers and surfactants as spreading agents. The role of spreading agent concentration in forming a well-ordered, stable monolayer at the air-liquid interface was studied by means of atomic force microscopy, scanning electron microscopy, optical microscopy, and surface tension measurements for three different systems: a nonionic surfactant, octylphenoxy poly(ethyleneoxy)ethanol (Igepal CO 630); an anionic surfactant, sodium dodecyl sulfate; and a low-molecular-weight, water-soluble polymer, polyacrylamide. For both the anionic surfactant and the water soluble polymer, a correlation was found between a unique feature in surface tension measurements of the latex-spreading agent mixture and the concentrations at which hexagonal arrays of latex spheres form on the surface of HOPG. For the nonionic surfactant, no ordered structures were found on HOPG for any surfactant concentration, consistent with no appearance of the unique feature in surface tension measurements. These results show that a tensiometer can be used to determine the conditions under which well-ordered latex films have the possibility of forming on a substrate using the LB-like technique; however, other factors, such as pulling speed and surface chemistry, play a role as well.

  8. 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.

  9. How Langmuir-Blodgett trilayers act as templates for directed self-assembly of nanoparticles

    NASA Astrophysics Data System (ADS)

    Mukherjee, Smita; Datta, Alokmay; Biswas, Nupur; Giglia, Angelo; Nannarone, Stefano

    2014-04-01

    Atomic force microscopy (AFM) shows that Langmuir-Blodgett (LB) deposition of dissimilar metal stearates (MSt, M = Co, Zn, Cd) on templates of Co-stearate (Co-T) and Cd-stearate (Cd-T) results in self-assembly of MSts into nanocrystalline grains having clear and consistent morphological habits. The grains are better formed and well separated on Cd-T than on Co-T. Fourier transform infrared spectroscopy (FTIR) results show that the headgroup coordination of the overlayer is tuned by the coordination of the Cd-T template and remains unaffected by that of the Co-T template. They also indicate co-existence of a different kind of headgroup structure that is close to the undissociated fatty acid headgroup but differing more in the two types of carbon-oxygen bonds, suggesting an inter-headgroup bonding such as hydrogen bond that may exist on a nanocrystal surface. Results of synchrotron x-ray diffraction at C K-edge, of ZnSt on Cd-T (ZnSt/Cd-T) and Co-T (ZnSt/Co-T), point to a non-closed packed structure for ZnSt/Cd-T and a closed-packed structure for ZnSt/Co-T, with significant superlattice order in the former. The presence of crystalline phases of ZnSt in the nanometer scale, on LB templates, in contrast to the the presence of lamellar phase in bulk ZnSt, is attributed to the the presence of unidentate metal-carboxylate coordination in the former and absence of it in the latter, creating different gradients of dipolar forces at template overlayer interface. Relative strength of this long-range force over short-range intermolecular forces in the templates qualitatively explains better crystallinity and higher ordering in ZnSt/Cd-T compared to ZnSt/Co-T. We propose that the role of dipole moment gradient between template and overlayer in tuning of these metal-organic nanoparticles may be somewhat similar to structural and optical tunability of semiconductor nanocrystals by thermal and self-equilibrium strain.

  10. 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

  11. Silica nanoparticle sols. Part 3: Monitoring the state of agglomeration at the air/water interface using the Langmuir-Blodgett technique.

    PubMed

    Blute, Irena; Pugh, Robert J; van de Pas, John; Callaghan, Ian

    2009-08-15

    Langmuir-Blodgett films were prepared at the air/water interface from dispersions of hydrophilic and partially, hydrophobically modified industrially manufactured silica nanoparticles. The hydrophilic particles featured expanded, fairly easily compressible, surface pressure (pi)-area (A) isotherms with well defined collapse pressures which appeared to be caused by the formation of loosely structured agglomerates which exhibited elastic behavior at low surface pressure and inelastic behavior at high surface pressure. Lateral electrostatic interparticle interactions seemingly played an important role in this hydrophilic system. This contrasted with the hydrophobically modified particles which were more difficult to disperse in the ethanol/chloroform spreading solvent and appeared to be in the semi-agglomerated state at low surface pressures and exhibited a more difficult to compress compacted film. Both types of particulate films were shown to be sensitive to the spreading environment and changes in pH were found to increase particle agglomeration which drastically reduced the particulate area for the hydrophilic sol but less so, in the case of the moderately hydrophobically modified sol. In general, the LB technique proved to be a useful method to monitor changes in the state of aggregation of nanosized silica particles at the air/water interface. These results also appear to give some support of our ideas, presented in earlier publications in which it was suggested that the major role of the hydrophobically modified hydrophilic particles in foaming was to produce an aggregated particulate film surrounding the air/water interface which provides a physical barrier preventing coalescence of bubbles.

  12. 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.

  13. Second-harmonic generation studies of Langmuir-Blodgett monolayers of indodicarbocyanine and hemicyanine dyes and stilbazium salts

    NASA Astrophysics Data System (ADS)

    Wijekoon, W. M. K.; Park, Chi-Kyun; Prasad, Paras N.

    1994-09-01

    Second harmonic generation and UV-visible spectroscopic measurements have been performed on a series of Z-type Langmuir-Blodgett monolayer of indodicarbocyanine, hemicyanine and stilbazium salts. Optical spectra of these monolayer indicate the presence of hypsochromically shifted aggregates on the silica surface. The extent of aggregation is found to be largely dependent on the nature of the counter-ion as well as on the conditions of the monolayer preparation. The SHG intensity of dye aggregates are much smaller compared to that of monomeric dye molecules. In the case of amphiphillic counter-ion containing stilbazium salt compression speed of the monolayer has very little effect on the second harmonic signal and on the absorption spectrum, presumably due to the suppression of aggregation. It seems that the contribution from nonlinear optically active amphiphillic counter-ion to the SHG intensity is not that significant.

  14. Polyelectrolyte multilayers on PTMSP as asymmetric membranes for gas separations: Langmuir-Blodgett versus self-assembly methods of anchoring.

    PubMed

    Lin, Cen; Chen, Qibin; Yi, Song; Wang, Minghui; Regen, Steven L

    2014-01-28

    Polyelectrolyte multilayers derived from poly(diallyldimethylamonium chloride) and poly(sodium 4-styrenesulfonate) have been deposited onto poly[1-(trimethylsilyl)-1-propyne] (PTMSP) with anchoring layers formed by Langmuir-Blodgett and self-assembly methods. Using gas permeation selectivity as a basis for judging the efficacy of each anchoring method, we have found that similar CO2/N2 selectivities (ranging from 110 to 140) could be achieved by both methods and that their permeances were also similar. Although LB anchors require fewer layers of polyelectrolyte to reach this level of selectivity, the greater ease associated with self-assembly and its applicability to curved, high-surface-area supports (e.g., PTMSP-coated hollow fibers) encourage its use with PTMSP in creating new membrane materials for the practical separation of gases.

  15. Langmuir-Blodgett assembly of visible light responsive TiO2 nanotube arrays/graphene oxide heterostructure

    NASA Astrophysics Data System (ADS)

    Chen, Ying; Gao, Hongyan; Wei, Danming; Dong, Xinju; Cao, Yan

    2017-01-01

    The hybrid nanocomposites of titanium dioxide (TiO2) with graphene oxide (GO) have recently garnered much attention as electronic devices, energy conversion devices, photocatalysts and other applications. In this study, Langmuir-Blodgett (LB) assembly method was firstly reported to prepare a TiO2 nanotube arrays (TNA)-GO heterostructure. The as-prepared TNA-GO sample was characterized by X-ray diffraction, Raman spectra, scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. The promising characteristics of this TNA-GO material, the inexpensive, nontoxic and highly visible-light responsiveness, may raise the potential uses in many, various photocatalytic applications.

  16. Applications of Piezoelectric and Pyroelectric Thin Films: Opportunities for Langmuir-Blodgett Technology.

    DTIC Science & Technology

    1984-12-31

    currently employed to improve resolution and con, ast in pyroelectric vidicons is known as target reticulation . The idea is to - 19 - F- rr-r .-_- T 7 7... Reticulation was mentioned as a means to further improve performance by lowering lateral thermal diffusivity. Research in the photoresist area has... reticulation . Optical Applications The modulation and deflection of guided optical waves was discussed with respect to SAW devices. Actual optical

  17. Two-dimensional folded chain crystals of a synthetic polymer in a Langmuir-Blodgett film.

    PubMed

    Kumaki, Jiro; Kawauchi, Takehiro; Yashima, Eiji

    2005-04-27

    Isotactic poly(methyl methacrylate) monolayers deposited from a water surface onto mica at different surface pressures were studied by atomic force microscopy, and their structure formation from single chains to two-dimensional folded chain crystals was clearly observed. Furthermore, gentle crystallization of the monolayer by slow compression on the water surface enabled the observation of crystals at a molecular level, thus visualizing the chain foldings and tie-chains for the first time. The resulting molecular level information will provide an important clue toward the understanding of polymer crystals not only in two dimensions but also in three dimensions.

  18. Langmuir and langmuir-blodgett films of metallosupramolecular polyelectrolyte-amphiphile complexes.

    PubMed

    Lehmann, Pit; Symietz, Christian; Brezesinski, Gerald; Krass, Henning; Kurth, Dirk G

    2005-06-21

    A detailed analysis of a metallosupramolecular polyelectrolyte-amphiphile complex (PAC) at the air-water interface is presented. Langmuir isotherms, Brewster angle microscopy, and X-ray reflectance and diffraction methods are employed to investigate the structure of the Langmuir monolayers. The PAC is self-assembled from 1,3-bis[4'-oxa-(2,2':6',2' '-terpyridinyl)]propane, iron acetate, and dihexadecyl phosphate (DHP). Spreading the PAC at the air-water interface results in a monolayer that consists of two strata. DHP forms a monolayer at the top of the interface, while the metallosupramolecular polyelectrolyte is immersed in the aqueous subphase. Both strata are coupled to each other through electrostatic interactions. The monolayers can be transferred onto solid substrates, resulting in well-ordered multilayers. Such multilayers are model systems for well-ordered metal ions in two dimensions.

  19. Nanomagnetism study of highly-ordered iron oxide nanocrystal assemblies fabricated by the Langmuir-Blodgett technique.

    PubMed

    Zhang, HaiTao; Bao, NiNa; Yuan, Du; Ding, Jun

    2013-09-21

    Iron oxide nanocrystals are ideal building blocks for the construction of flexible nanodevices whose performance can be modulated by controlling the morphology of isolated particles and their organizational form. This work demonstrates the fabrication of high quality Langmuir-Blodgett (LB) nanocrystal assemblies with limited overlapping and higher coverage by systemically and combinatorially optimizing the parameters of compression pressure and quantity of spread nanocrystals. Monodispersed iron oxide nanocrystals with a diameter of 11.8 nm were synthesized by thermal decomposition of Fe(CO)5 in trioctylamine with the presence of oleic acid. Multilayer nanocrystal assemblies were obtained through a layer-by-layer (LBL) process by repeating the transfer procedure after their hydrophilicity had been improved via treatment in a UV-ozone oven. The quality of nanocrystal assemblies was investigated by UV-vis spectrometry and scanning electron microscopy. The nanomagnetism for the nanostructures of different combination manners was studied systemically by a superconducting quantum interference device (SQUID). A lower superparamagnetic blocking temperature was found in the monolayer Fe3O4 nanocrystal assembly. The superparamagnetic blocking temperature in magnetic nanocrystal assemblies could be tuned through modifying the interparticle interactions among the interlayer and intralayers by controlling the layer number of the assemblies.

  20. Controllable assembly of diverse rare-earth nanocrystals via the Langmuir-Blodgett technique and the underlying size- and symmetry-dependent assembly kinetics.

    PubMed

    Zhou, Huan-Ping; Zhang, Chao; Yan, Chun-Hua

    2009-11-17

    The Langmuir-Blodgett (LB) technique provides a facile and robust method for the formation of large-area films of various nanoparticles (NPs), including 24.9 nm NaYF(4):Yb,Er nanospheres, 12.0 nm LiYF(4) nanopolyhedra, 14.1 x 1.8 nm triagonal-shaped LaF(3), 12.6 nm square CaF(2), 9.5 x 2.0 nm hexagonal EuF(3), and so forth. The assembly patterns of the deposited films were studied in accordance with the pi-A isotherms. Combined with the TEM observations, several representative stages of assembly process can be distinguished. The scrutiny of the self-assembly process by means of their pi-A isotherms elucidates that the concentration, size, and symmetry of nanoparticles play crucial roles in this process. The concept of "effective concentration", which is defined as the amount of nanoblocks in the "gas phase" rather than the actual number of nanoparticles at the air-water interface, was first proposed as a control parameter to elucidate the possible assembly kinetics. The similarly shaped 12.0 nm LiYF(4) and the 24.9 nm NaYF(4):Yb,Er were selected as the size-dependent examples. The smaller nanoparticles show a strong tendency of congregation to lower the surface energy. Three representative samples, namely, 24.9 nm NaYF(4):Yb,Er nanospheres (O(h)), 14.1 x 1.8 nm oblate triagonal LaF(3) nanosheets (D(3h)), and 41.3 nm x 24.6 nm NaYF(4) rods (D(6h)), were selected as the shape-dependent samples, which showed that the assembly patterns were contributed by the stability arising from the geometry of the nanoparticles, the tendency of aggregation of nanoparticles, and the probable rotation energy during the compression. More importantly, guided by the above assembly kinetics, for the 9.5 x 2.0 nm hexagonal EuF(3), we can effectively acquire the desirable assembly pattern.

  1. The production of PEO polymer brushes via Langmuir-Blodgett and Langmuir-Schaeffer methods: incomplete transfer and its consequences.

    PubMed

    de Vos, Wiebe M; de Keizer, Arie; Kleijn, J Mieke; Cohen Stuart, Martien A

    2009-04-21

    Using fixed-angle ellipsometry, we investigate the degree of mass transfer upon vertically dipping a polystyrene surface through a layer of a polystyrene-poly(ethylene oxide) (PS-PEO) block copolymer at the air water interface (Langmuir-Blodgett or LB transfer). The transferred mass is proportional to the PS-PEO grafting density at the air-water interface, but the transferred mass is not equal to the mass at the air-water interface. We find that depending on the chain length of the PEO block only a certain fraction of the polymers at the air-water interface is transferred to the solid surface. For the shortest PEO chain length (PS36-PEO148), the mass transfer amounts to 94%, while for longer chain lengths (PS36-PEO370 and PS38-PEO770), a transfer of, respectively 57% and 19%, is obtained. We attribute this reduced mass transfer to a competition for the PS surface between the PEO block and the PS block. Atomic force microscopy shows that after transfer the material is evenly spread over the surface. However, upon a short heating of these transferred layers (95 degrees C, 5 min) a dewetting of the PS-PEO layer takes place. These results have a significant impact on the interpretation of the results in a number of papers in which the above-described transfer method was used to produce PEO polymer brushes, in a few cases in combination with heating. We briefly review these papers and discuss their main results in light of this new information. Furthermore, we show that, by using Langmuir-Schaeffer (LS, horizontal) dipping, much higher mass transfers can be reached than with the LB method. When the LB or LS methods are carefully applied, it is a very powerful technique to produce PEO brushes, as it gives full control over both the grafting density and the chain length.

  2. Studies on ultrathin films of tricycloquinazoline (TCQ) based discotic liquid crystal molecules

    NASA Astrophysics Data System (ADS)

    Gupta, Raj Kumar; V, Manjuladevi; Karthik, C.; Kumar, Sandeep

    2013-03-01

    The assembly of disk-shaped molecules on surfaces has drawn considerable attention because of their unique electro-optical properties. We have studied the monolayer of the tricycloquinazoline based disk-shaped (TCQCB) molecules at air-water and air-solid interfaces. The TCQCB molecules form a stable Langmuir monolayer at the air-water interface. The monolayer exhibits gas, low density liquid (L1), and high density liquid (L2) phases. In L1 and L2 phases, the molecules prefer edge-on conformation. The atomic force microscope study on the Langmuir-Blodgett films of the molecules reveals a structural transformation. The elongated domains in the film deposited in L1 phase transformed to a compact grainy texture in the film deposited in the L2 phase.

  3. Langmuir films of amphiphilic schiff base of O-Vaniline and its metal complexes

    NASA Astrophysics Data System (ADS)

    Hemakanthi, G.; Unni Nair, Balachandran; Dhathathreyan, Aruna

    2001-06-01

    Stable monolayers of the Schiff base of O-Vaniline have been formed at the air/water interface and on a subphase containing Cu 2+, Ni 2+ and Zn 2+ ions. Polarized UV-Visible spectra of the Langmuir-Blodgett (LB) films of the pure Schiff base and those of the metal complexes on solid substrates have been studied. The LB films indicate that the aromatic rings in the polar plane are oriented slightly out of plane to the solid substrate and the orientation remains nearly the same for the ligand and for the complexes. Low angle XRD shows that the copper complex and the ligand stack into multimeric structures as the monolayer is compressed on the water surface.

  4. Structure and Sensor Properties of Thin Ordered Solid Films

    PubMed Central

    Sołoducho, Jadwiga; Cabaj, Joanna; Świst, Agnieszka

    2009-01-01

    Miniaturized gas sensors and biosensors based on nanostructured sensing elements have attracted considerable interest because these nanostructured materials can be used to significantly improve sensor sensitivity and the response time. We report here on a generic, reversible sensing platform based on hybrid nanofilms. Thin ordered Langmuir-Blodgett (LB) films built of fluorene derivatives were used as effective gas sensors for both oxidative and reductive analytes. A novel immobilization method based on thin LB films as a matrix has been developed for construction of sensing protein layers. Biomolecules can often be incorporated into and immobilized on Langmuir-Blodgett films using adsorption methods or by covalent immobilization of proteins. The sensor sensitisation was achieved by an amphiphilic N-alkyl-bis(thiophene)arylenes admixed into the film. The interlaced derivative was expected to facilitate the electron transfer, thereby enhancing the sensor sensitivity. The results suggest that this may be very promising approach for exploring the interactions between proteins and high throughput detection of phenol derivatives in wastewater. PMID:22408477

  5. Distributions of ionic concentrations and electric field around the three-phase contact at high rates of Langmuir-Blodgett deposition.

    PubMed

    Bondarenko, M P; Zholkovskiy, E K; Kovalchuk, V I; Vollhardt, D

    2006-02-02

    A mathematical problem is formulated and numerically solved for addressing the electric field and ionic concentration distributions developing around the three-phase contact line during the Langmuir-Blodgett deposition of charged monolayers. Compared to a previous paper dealing with the same effect (J. Phys. Chem. B 2004, 108, 13449), the present analysis is not restricted to the case of low deposition rates and small concentration changes. The obtained results show that, for sufficiently high deposition rates, the subphase composition substantially changes in the immediate vicinity of the three-phase contact line. It is shown that the predicted changes in the subphase composition can drastically affect the adhesion work and the dynamic contact angle. On this basis, the influence of the concentration polarization effect on meniscus behavior is discussed.

  6. Conjugation Length Distribution in Poly(p-phenylenevinylene) (PPV) Films.

    PubMed

    da Silva, Marcelo C; Cassemiro, Sandra de M; Machado, Angelita M; Alves, Joniel C F; Nogueira, Sandra L; Jarrosson, Thibault; Serein-Spirau, Françoise; Akcelrud, Leni; Tozoni, José R; Silva, Raigna A; Freire, José A; Marletta, Alexandre

    2016-12-15

    We studied the absorption line-shape of poly(p-phenylenevinylene) (PPV) films deposited via spin coating and Langmuir-Blodgett techniques with the intent of identifying the conjugation length distribution in these two types of films, a key morphological aspect of conjugated polymer films. We treated the excitons in the polymer as independent oligomer excitons and modeled the absorption spectra of the individual oligomers using simple expressions for the oligomer size dependence of the gap energy, the line-broadening factor, the transition dipole moment and the Huang-Rhys parameter. We validated these expressions by independent measurements on phenyl-based oligomers and Density Functional Theory calculations. Our results show clear evidence that, for both types of PPV films, the conjugation length distribution depends exponentially on the segment size. Our results also set a lower limit, of about ten repeat units, for the maximum exciton length of three different phenyl-based oligomers.

  7. 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. Copyright © 2015 Elsevier B.V. All rights reserved.

  8. Single molecule magnets: from thin films to nano-patterns.

    PubMed

    Cavallini, Massimiliano; Facchini, Massimo; Albonetti, Cristiano; Biscarini, Fabio

    2008-02-14

    Single molecule magnets (SMM) are a class of molecules exhibiting magnetic properties similar to those observed in conventional bulk magnets, but of molecular origin. SMMs have been proposed as potential candidates for several technological applications that require highly controlled thin films and patterns. Here we present an overview of the most important approaches for thin film growth and micro(nano)-patterning of SMM, giving special attention to Mn(12) based molecules. We present both conventional approaches to thin film growth (Langmuir-Blodgett, chemical approach, dip and dry, laser evaporation), patterning (micro-contact printing, deposition on patterned surface, moulding of homogeneous films) and new methods specifically developed for SMM (lithographically controlled wetting, lithographically controlled de-mixing).

  9. 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.

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

    PubMed

    Jurak, Małgorzata

    2013-04-04

    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.

  11. Optical properties and recording characteristics of phthalocyanine-derivative LB films

    NASA Astrophysics Data System (ADS)

    Gan, Fuxi; Luo, Tao

    1993-08-01

    Langmuir-Blodgett (LB) films of tetra-neopentoxy phthalocyanine zinc and tetra-nonyl phthalocyanine copper are prepared. Their structures, optical properties, and temperature dependencies are investigated. Static optical recording tests by He-Ne laser are done in these LB films and the experimental results demonstrate that phthalocyanine derivates are useful for phase change type erasable data storage media.

  12. Effect of cadmium arachidate layers on the growth of pentacene and the performance of pentacene-based thin film transistors.

    PubMed

    Nayak, Pradipta K; Kim, Jinwoo; Cho, Junhee; Lee, Changhee; Hong, Yongtaek

    2009-06-02

    The effect of cadmium arachidate (CdA) layers deposited by Langmuir-Blodgett technique on the growth of pentacene thin films and the performance of pentacene-based thin film transistors has been investigated. The hydrophobicity of the SiO2 gate dielectric surface was increased (surface energy reduced) with the deposition of CdA layers as a result of the presence of long hydrophobic alkyl chains attached to the cadmium atoms. The change in surface wetting properties of SiO2 strongly influenced the growth mechanism of pentacene thin films. The grain size and root-mean-square surface roughness of pentacene was decreased with an increase in the number of CdA layers compared to the pentacene deposited on a bare SiO2 surface. Organic thin film transistors (OTFTs) with seven layers of CdA on SiO2 showed the highest mobility of 0.27 cm2/Vs and the lowest subthreshold slope of 2.4 V/dec. The enhanced electrical properties of the OTFTs with SiO2/CdA as the dielectric is attributed to the better intermolecular connection, tight packing, and improved surface quality of the pentacene, as evident from the X-ray diffraction (XRD) and atomic force microscopy (AFM) results.

  13. Graphene oxide thin films: influence of chemical structure and deposition methodology.

    PubMed

    Hidalgo, R S; López-Díaz, D; Velázquez, M Mercedes

    2015-03-10

    We synthesized graphene oxide sheets of different functionalization by oxidation of two different starting materials, graphite and GANF nanofibers, followed by purification based on alkaline washing. The chemical structure of graphene oxide materials was determined by X-ray photoelectron spectroscopy (XPS), and the nanoplatelets were characterized by ζ potential and dynamic light scattering (DLS) measurements. The XPS results indicated that the chemical structure depends on the starting material. Two different deposition methodologies, Langmuir-Blodgett (LB) and Langmuir-Schaefer (LS), were employed to build the graphene oxide thin films. The film morphology was analyzed by scanning electron microscopy (SEM). The SEM images allow us to conclude that the LB methodology provides the highest coverage. This coverage is almost independent of the chemical composition of sheets. Conversely, the coverage obtained by the LS methodology increases with the percentage of C-O groups attached to sheets. Surface-pressure isotherms of these materials were interpreted according to the Volmer model.

  14. Gel-to-fluid phase transformations in solid-supported phospholipid bilayers assembled by the Langmuir-Blodgett technique: effect of the Langmuir monolayer phase state and molecular density.

    PubMed

    Ramkaran, Mohini; Badia, Antonella

    2014-08-14

    Planar-supported phospholipid bilayers are increasingly used as synthetic membranes for scientific and practical applications. The thermotropic phase properties of supported bilayers are important for recreating biologically relevant situations. Unlike free-standing lipid membranes that undergo one gel-to-fluid or main phase transition, mica-supported single bilayers have been found to undergo two separate leaflet transitions. Although the distinctive nature of the main transition in mica-supported bilayers has been attributed to different effects, determining their relevance has been problematic because vesicle fusion, the technique most widely used to prepare solid-supported bilayer membranes, does not allow one to readily control the lipid surface coverage and molecular density. To circumvent the limitations of the vesicle fusion method and systematically investigate the effects on the individual leaflet transitions of the lipid phase state and molecular density before deposition on the substrate, mica-supported single bilayers of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) were prepared using the Langmuir-Blodgett technique. The gel-to-fluid transitions of the bilayer leaflets were tracked by controlled-temperature atomic force microscopy to determine the relative fractions of the gel and fluid phases as a function of temperature. The fraction of solid versus temperature data was fit to the van't Hoff equation to determine the leaflet melting temperatures and transition enthalpies. The phase state and molecular density of the Langmuir monolayer precursor at the transfer pressure of 35 mN m(-1) was found to have a greater effect on the main transition temperature and width of the distal (upper) leaflet than that of the proximal (lower) one. The contributions of substrate-mediated condensation, asymmetric lipid densities, and surface area available for thermal expansion of the bilayer are addressed

  15. A wearable, highly stable, strain and bending sensor based on high aspect ratio graphite nanobelts

    NASA Astrophysics Data System (ADS)

    Alaferdov, A. V.; Savu, R.; Rackauskas, T. A.; Rackauskas, S.; Canesqui, M. A.; de Lara, D. S.; Setti, G. O.; Joanni, E.; de Trindade, G. M.; Lima, U. B.; de Souza, A. S.; Moshkalev, S. A.

    2016-09-01

    A simple and scalable method was developed for the fabrication of wearable strain and bending sensors, based on high aspect ratio (length/thickness ˜103) graphite nanobelt thin films deposited by a modified Langmuir-Blodgett technique onto flexible polymer substrates. The sensing mechanism is based on the changes in contact resistance between individual nanobelts upon substrate deformation. Very high sensor response stability for more than 5000 strain-release cycles and a device power consumption as low as 1 nW were achieved. The device maximum stretchability is limited by the metal electrodes and the polymer substrate; the maximum strain that could be applied to the polymer used in this work was 40%. Bending tests carried out for various radii of curvature demonstrated distinct sensor responses for positive and negative curvatures. The graphite nanobelt thin flexible films were successfully tested for acoustic vibration and heartbeat sensing.

  16. A wearable, highly stable, strain and bending sensor based on high aspect ratio graphite nanobelts.

    PubMed

    Alaferdov, A V; Savu, R; Rackauskas, T A; Rackauskas, S; Canesqui, M A; de Lara, D S; Setti, G O; Joanni, E; de Trindade, G M; Lima, U B; de Souza, A S; Moshkalev, S A

    2016-09-16

    A simple and scalable method was developed for the fabrication of wearable strain and bending sensors, based on high aspect ratio (length/thickness ∼10(3)) graphite nanobelt thin films deposited by a modified Langmuir-Blodgett technique onto flexible polymer substrates. The sensing mechanism is based on the changes in contact resistance between individual nanobelts upon substrate deformation. Very high sensor response stability for more than 5000 strain-release cycles and a device power consumption as low as 1 nW were achieved. The device maximum stretchability is limited by the metal electrodes and the polymer substrate; the maximum strain that could be applied to the polymer used in this work was 40%. Bending tests carried out for various radii of curvature demonstrated distinct sensor responses for positive and negative curvatures. The graphite nanobelt thin flexible films were successfully tested for acoustic vibration and heartbeat sensing.

  17. Thin Film Assembly of Spider Silk-like Block Copolymers

    DTIC Science & Technology

    2011-01-01

    Film Assembly of Spider Silk -like Block Copolymers Sreevidhya T. Krishnaji,†,‡ Wenwen Huang,§ Olena Rabotyagova,†,‡ Eugenia Kharlampieva, ) Ikjun Choi...Received November 26, 2010 We report the self-assembly of monolayers of spider silk -like block copolymers. Langmuir isotherms were obtained for a series of...bioengineered variants of the spider silks , and stable monolayers were generated. Langmuir-Blodgett films were prepared by transferring the monolayers

  18. Magnetic Thin Films of Inorganic Nanosheets

    NASA Astrophysics Data System (ADS)

    Yamamoto, Takashi; Namba, Hiroaki; Einaga, Yasuaki

    2012-02-01

    Molecule-based magnets have been fascinating materials because of the potential applications in information storage, electronic and spintronic devices. However, such applications would require arraying the active materials on a substrate or interfacing with other components. Here, we focus on fabricating multi-functional magnetic films using inorganic nanosheets as a building block. The thin films could be prepared by the modified Langmuir-Blodgett, LB, technique or the layer-by-layer, LbL, method, which are representative wet-processings for film preparation. As the magnetic LB film, we chose semiconductive titania nanosheets and magnetic Prussian Blue. Upon band gap excitation of titania nanosheets, electron injection into Prussian Blue was achieved with scavenging interlayer water molecules, leading to photoreduction to Prussian White. As the magnetic LbL film, we chose magnetic layered double hydroxide, LDH, nanosheets and non-magnetic smectite nanosheets. In powdered LDH, a coercivity increased with expanding the interlayer spacing. On the other hand, despite the larger interlayer spacing for the LbL film, a coercivity was less than that of the comparative powdered LDH. It is indicated LDH nanosheets are integrated in an anisotropic manner in the LbL films.

  19. Determination of molecular anisotropy in thin films of discotic assemblies using attenuated total reflectance UV-visible spectroscopy.

    PubMed

    Flora, Ware H; Mendes, Sergio B; Doherty, Walter J; Saavedra, S Scott; Armstrong, Neal R

    2005-01-04

    We report here an investigation of absorbance anisotropy in highly ordered, single bilayer (ca. 5.6 nm) Langmuir-Blodgett (LB) thin films of discotic liquid-crystalline phthalocyanines, using a recently introduced broad-band attenuated total reflectance (ATR) spectroscopic technique, capable of measuring dichroism in such films in the UV--visible optical region down to absorbances of ca. 0.003 absorbance units. On the basis of the ATR measurements of LB-deposited films, a thorough treatment was established to determine the ensemble average of the Cartesian components and the associated optical anisotropy of transition dipoles in the molecular film. In an effort to recover order parameters of molecular orientation, those results were interpreted with a circular dipole model, which is the expected model for the isolated molecule based on symmetry properties. We measured a strong dipole component normal to the film plane that cannot be explained in terms of a truly circular model, indicating that the molecular transition dipoles were perturbed upon aggregation. The utility of the experimental approach was further demonstrated by (a) investigating the effect of substrate modifiers (methyl- and phenyl-terminated silanes) on the ordering within the phthalocyanine film and (b) the effect of water immersion and re-annealing of the thin film on molecular ordering and optical anisotropy.

  20. Controlling Piezoelectric Responses in Pb(Zr0.52Ti0.48)O3 Films through Deposition Conditions and Nanosheet Buffer Layers on Glass.

    PubMed

    Nguyen, Minh D; Houwman, Evert P; Yuan, Huiyu; Wylie-van Eerd, Ben J; Dekkers, Matthijn; Koster, Gertjan; Ten Elshof, Johan E; Rijnders, Guus

    2017-10-04

    Nanosheet Ca2Nb3O10 (CNOns) layers were deposited on ultralow expansion glass substrates by the Langmuir-Blodgett method to obtain preferential (001)-oriented growth of Pb(Zr0.52Ti0.48)O3 (PZT) thin films using pulsed laser deposition (PLD) to enhance the ferroelectric and piezoelectric properties of the films. The PLD deposition temperature and repetition frequency used for the deposition of the PZT films were found to play a key role in the precise control of the microstructure and therefore of the ferroelectric and piezoelectric properties. A film deposited at a high repetition frequency has a columnar grain structure, which helps to increase the longitudinal piezoelectric coefficient (d33f). An enhanced d33f value of 356 pm V(-1) was obtained for 2-μm-thick PZT films on CNOns/glass substrates. This high value is ascribed to the preferential alignment of the crystalline [001] axis normal to the substrate surface and the open columnar structure. Large displacement actuators based on such PZT films grown on CNOns/glass substrates should be useful in smart X-ray optics applications.

  1. 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.

  2. 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.

  3. Phase-separation of mixed surfactant monolayers: a comparison of film morphology at the solid-air and liquid-air interfaces.

    PubMed

    Eftaiha, Ala'a F; Paige, Matthew F

    2012-08-15

    The morphologies of phase-separated monolayer films prepared from two different binary mixtures of perfluorocarbons and hydrocarbons have been examined and compared, for the first time, at the solid-air and liquid-air interfaces. Films were comprised of binary mixtures of arachidic acid (C(19)H(39)COOH) with perfluorotetradecanoic acid (C(13)F(27)COOH) and of palmitic acid (C(15)H(31)COOH) with perfluorooctadecanoic acid (C(17)F(35)COOH). For both mixed systems, Langmuir Blodgett films on mica substrates consisted of polygonal domains of one surfactant dispersed in a continuous matrix of the other (arachidic acid in perfluorotetradecanoic acid or perfluorooctadecanoic acid in palmitic acid, respectively), consistent with previous reports. Real-time imaging of the air-water interface via Brewster angle microscopy revealed that comparable film morphology was present at the air-water interface and the solid-air interface over a wide range of surface pressures, and that for the arachidic acid-based mixture, domain growth dynamics at the air-water interface is consistent with that inferred from sequential "static" atomic force microscope images collected at the solid-air interface. Copyright © 2012 Elsevier Inc. All rights reserved.

  4. Development of Pressure Sensitive Molecular Film as a Measurement Technique for Micro-Flows

    NASA Astrophysics Data System (ADS)

    Matsuda, Y.; Mori, H.; Sakazaki, Y.; Uchida, T.; Suzuki, S.; Yamaguchi, H.; Niimi, T.

    2008-12-01

    The pressure-sensitive paint (PSP) has potential as a diagnostic tool for pressure measurement in the high Knudsen number regime because it works as a so-called "molecular sensor." However, there are few reports concerning application of the PSP to micro devices, because the conventional PSP is too thick owing to the use of polymer binder. In our previous work, we have adopted Langmuir-Blodgett (LB) technique to fabricate pressure sensitive molecular films (PSMFs) using Pd(II) Mesoporphyrin IX (PdMP). The PSMF based on PdMP has pressure sensitivity only at low pressure range (below 3 kPa). In this study, we have constructed PSMF composed of Pt(II) Mesoporphyrin IX (PtMP) to be applied to pressure measurement near atmospheric pressure. The pressure sensitivity of PSMF based on PtMP has been tested, and it is clarified that the PSMF of PtMP has equivalent pressure sensitivity of polymer PSP. Moreover, we have applied PSMF to measurement of pressure distribution of micro-channel gas flow, showing its usefulness.

  5. Exfoliation of non-oxidized graphene flakes for scalable conductive film.

    PubMed

    Park, Kwang Hyun; Kim, Bo Hyun; Song, Sung Ho; Kwon, Jiyoung; Kong, Byung Seon; Kang, Kisuk; Jeon, Seokwoo

    2012-06-13

    The increasing demand for graphene has required a new route for its mass production without causing extreme damages. Here we demonstrate a simple and cost-effective intercalation based exfoliation method for preparing high quality graphene flakes, which form a stable dispersion in organic solvents without any functionalization and surfactant. Successful intercalation of alkali metal between graphite interlayers through liquid-state diffusion from ternary KCl-NaCl-ZnCl(2) eutectic system is confirmed by X-ray diffraction and X-ray photoelectric spectroscopy. Chemical composition and morphology analyses prove that the graphene flakes preserve their intrinsic properties without any degradation. The graphene flakes remain dispersed in a mixture of pyridine and salts for more than 6 months. We apply these results to produce transparent conducting (∼930 Ω/□ at ∼75% transmission) graphene films using the modified Langmuir-Blodgett method. The overall results suggest that our method can be a scalable (>1 g/batch) and economical route for the synthesis of nonoxidized graphene flakes.

  6. Phosphorescence lifetime-based sensing of SO{sub 2} in the gas phase

    SciTech Connect

    Papkovsky, D.B.; Desyaterik, I.V.; Ponomarev, G.V.

    1995-08-01

    Two different types of solid-state coatings based on the phosphorescent metalloporphyrins - polymer film compositions or Langmuir-Blodgett films - were studied comparatively with respect to their application to sensing of SO{sub 2}. While the polymer films were only slightly sensitive to SO{sub 2}, LB-coatings appeared to be highly suitable for analyzing SO{sub 2} in the air in the range 0.01-2% (v/v). Performance characteristics of the new phosphorescence lifetime-based sensor for SO{sub 2} were studied. Interferences by a number important species on sensing of SO{sub 2} in gas phase were studied. The new SO{sub 2} sensor was shown to be rather inert to quenching with molecular oxygen and interference by such species, as CO{sub 2}, CO, NH{sub 3}, CH{sub 4} gases. On the other hand, NOx interfere with SO{sub 2} sensing and vapors of water (i.e. high relative air humidity); alcohols, acids at concentrations close to saturated also cause interference by enhancing quenching with environmental oxygen.

  7. 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.

  8. Characteristic fragmentation of polysiloxane monolayer films by bombardment with monatomic and polyatomic primary ions in TOF-SIMS.

    PubMed

    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 (M(n)) 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.

  9. REVIEW ARTICLE: Trends in interfacial design for surface plasmon resonance based immunoassays

    NASA Astrophysics Data System (ADS)

    Shankaran, Dhesingh Ravi; Miura, Norio

    2007-12-01

    Immunosensors based on surface plasmon resonance (SPR) have become a promising tool in sensor technology for biomedical, food, environmental, industrial and homeland security applications. SPR is a surface sensitive optical technique, suitable for real-time and label-free analysis of biorecognition events at functional transducer surfaces. Fabrication of highly active and robust sensing surfaces is an important part in immunoassays because the quality, quantity, chemistry and topography of the interfacial biomembranes play a major role in immunosensor performance. Eventually, a variety of immobilization methods such as physical adsorption, covalent coupling, Langmuir Blodgett film, polymer thin film, self-assembly, sol gel, etc, have been introduced over the years for the immobilization of biomolecules (antibody or antigen) on the transducer surfaces. The selection of an immobilization method for an immunoassay is governed by several factors such as nature and stability of the biomolecules, target analyte, application, detection principle, mode of signal transduction, matrix complexity, etc. This paper provides an overview of the various surface modification methods for SPR based immunosensor fabrication. The preparation, structure and application of different functional interfacial surfaces have been discussed along with a brief introduction to the SPR technology, biomolecules and detection principles.

  10. 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

  11. 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.

  12. Ultrathin oligonucleotide layers for fluorescence-based DNA sensors

    NASA Astrophysics Data System (ADS)

    Furch, M.; Ueberfeld, J.; Hartmann, Andreas; Bock, Daniel; Seeger, Stefan

    1996-11-01

    Preliminary investigations into the design of an affinity sensor using evanescent wave technology concentrate upon the means of immobilization of the receptor molecules. In this work DNA served as the selective recognition element. The molecular principle of a sequence-selective biosensor for DNA is based on a sandwich-hybridization assay wherein the analyte, a single-stranded (ss)DNA, bound specifically to both an immobilized capture probe and a dye-labeled oligonucleotide in free solution. The efficiency of the capture array depends on the density of highly organized oligonucleotides on the waveguide surface and correlates therefore directly with the specificity and the sensitivity of the sensor. In the present approach using the Langmuir- Blodgett technique cinnamoylbutylether-cellulose monolayers were transferred onto optical fibers or planar waveguides. These films served as matrices for the immobilization of biotinylated oligonucleotides via streptavidin. For the first time streptavidin was immobilized by that manner. The specificity of the streptavidin layer or the following bounded nucleic acid molecules were controlled by an enzyme- linked immunosorbent assay (ELISA). Finally, this application has also shown to be suitable for the detection of Salmonella, which is an important pathogen associated with acute gastroenteritidis and food borne diseases.

  13. The preparation, characterization, and application of thin film devices

    NASA Astrophysics Data System (ADS)

    Berno, Bob

    This thesis deals with the preparation of two thin film devices, in particular a nitrogen dioxide (NOsb2) gas sensor and a rechargeable lithium battery. A number of different thin film preparation techniques were used for a variety of applications and the resultant films were characterized by spectroscopic and electrochemical methods. The NOsb2 gas sensor was based on Langmuir-Blodgett (LB) monolayer films of the sandwich molecule europium bisphthalocyanine (EuPcsb2). The intense UV-visible absorption spectrum of a monolayer of the EuPcsb2 dye molecules was recorded before and after exposure to NOsb2 gas. It was noted that with time the film spectrum returned to its original colour, thus indicating the process to be reversible. The powerful spectroscopic technique of surface enhanced Raman scattering (SERS) was also utilized for film characterization. As with the absorption spectroscopy, the SERS experiments also indicated a reversible NOsb2 adsorption-desorption process. An interdigitated gold electrode was used to measure the electrical conductivity of LB monolayers of EuPcsb2. The activation energy for conduction for this molecular semiconductor was determined to be 0.27 eV from thermal conductivity experiments. Upon exposure to NOsb2 gas, the conductivity of the film increases considerably until it reaches saturation. Kinetics studies indicated that the conductivity changes resulted from two sources: the adsorption of NOsb2 molecules on the surface, and the absorption of the molecules into the film. While the spectroscopic experiments suggested this process to be completely reversible, the electrical measurements indicated that heating was required to remove the residual absorbed NOsb2. Thin film cathodes for a rechargeable lithium battery were fabricated by the magnetron sputtering technique. The cathodes were deposited from a sample of the LiMnsb2Osb4 pure spinel material. The Li-Mn-O film was characterized by grazing angle x-ray diffraction, Raman and

  14. Surface acoustic wave vapor sensors based on resonator devices

    NASA Astrophysics Data System (ADS)

    Grate, Jay W.; Klusty, Mark

    1991-05-01

    Surface acoustic wave (SAW) devices fabricated in the resonator configuration have been used as organic vapor sensors and compared with delay line devices more commonly used. The experimentally determined mass sensitivities of 200, 300, and 400 MHz resonators and 158 MHz delay lines coated with Langmuir-Blodgett films of poly(vinyl tetradecanal) are in excellent agreement with theoretical predictions. The response of LB- and spray-coated sensors to various organic vapors were determined, and scaling laws for mass sensitivities, vapor sensitivities, and detection limits are discussed. The 200 MHz resonators provide the lowest noise levels and detection limits of all the devices examined.

  15. Oriented bacteriorhodopsin film biomolecular devices and their photoelectric dynamics

    NASA Astrophysics Data System (ADS)

    Yao, Baoli; Xu, Dalun; Hou, Xun

    1997-05-01

    Thin oriented bacteriorhodopsin films isolated from the Halobacterium halobium R1M1 strain are made on transparent conductive ITO glass and stainless sheet respectively by the use of electrophoretic sedimentation method and Langmuir-Blodgett technique. To construct photoelectric devices, another Cu or Al electrode is applied, and electrolytes or insulant films are sandwiched between the electrodes. A Q-switched double frequency Nd:YAG laser and a pulsed dye laser are used to stimulate the bacteriorhodopsin films. The photoelectric response signals are directly measured by a 300 MHz digitizing oscilloscope. Experimental curves are fitted through the use of Marquardt's algorithm least square method, and at least five exponential decay components are found in the whole process. A theory on the bacteriorhodopsin film photoelectric dynamics is proposed and the dynamic equations are mathematically derived. Comparison between the theoretical and experimental results gives the parameters of time constants and charge displacements in the bacteriorhodopsin photocycle.

  16. Aggregation of gramicidin A in phospholipid Langmuir-Blodgett monolayers.

    PubMed Central

    Diociaiuti, Marco; Bordi, Federico; Motta, Annelisa; Carosi, Alessandra; Molinari, Agnese; Arancia, Giuseppe; Coluzza, Carlo

    2002-01-01

    The aggregation of Gramicidin A (gA) in dipalmitoylphosphatidylcoline (DPPC) monolayers is investigated by both thermodynamic and structural methods. Compression isotherm analysis and atomic force microscopy (AFM) observations are performed. Our experimental results indicate that gA aggregation does occur in DPPC monolayers even at very low gA concentration (about 8 x 10(-4) mol%). At the low gA concentration limit, the aggregation process seems to be mainly horizontal (i.e., side-by-side, into the monolayer plane), following a fractal pattern growth producing the formation of typical, flat (0.5 nm height) "doughnut" structures, with a diameter of approximately 150 nm. These structures appear to be composed of smaller subunits (about 70 nm diameter) showing the same doughnut structure. At a molar fraction of approximately 3.8 mol%, the big doughnuts start to disaggregate and only small doughnuts appear. Above a gA concentration of approximately 4.4 mol%, all doughnuts (large and small) disappear, and the morphology assumes the appearance of a patchwork of two distinct phases: one that, being very flat, can be associated with a gA-free or gA-poor DPPC phase, and a second one, characterized by a more corrugated surface, associated with a gA-rich DPPC phase. At gA concentration of approximately 5 mol%, a percolation transition in the gA-rich DPPC phase occurs. Thermodynamic data indicate that the maximum of miscibility between gA and DPPC molecules occurs at approximately 28 mol%, suggesting that gA could aggregate in hexamers that are, on average, bound to 16 DPPC molecules. At the same concentration, AFM images show a network of small gA aggregation units of a size compatible with gA hexamers. PMID:12023244

  17. Nanoscale domain patterns in ultrathin polymer ferroelectric films.

    PubMed

    Sharma, P; Reece, T; Wu, D; Fridkin, V M; Ducharme, S; Gruverman, A

    2009-12-02

    High-resolution studies of domain configurations in Langmuir-Blodgett films of ferroelectric polymer poly(vinylidene fluoride-trifluoroethylene), P(VDF-TrFE), have been carried out by means of piezoresponse force microscopy (PFM). Changes in film thickness and morphology cause significant variations in polarization patterns. In continuous films and nanomesas with relatively low thickness/grain aspect ratio (<1/10), the relationship between the average domain size and thickness follows the Kittel law. Nanomesas with high aspect ratio (>1/5) exhibit significant deviations from this law, suggesting additional surface-energy-related mechanisms affecting the domain patterns. Polarization reversal within a single crystallite has been demonstrated and local switching parameters (coercive voltage and remnant piezoresponse) have been measured by monitoring the local hysteresis loops. Reliable control of polarization at the sub-grain level demonstrates a possibility of studying the mechanism of the intrinsic switching behavior down to the molecular scale.

  18. Monolayer-Mediated Growth of Organic Semiconductor Films with Improved Device Performance.

    PubMed

    Huang, Lizhen; Hu, Xiaorong; Chi, Lifeng

    2015-09-15

    Increased interest in wearable and smart electronics is driving numerous research works on organic electronics. The control of film growth and patterning is of great importance when targeting high-performance organic semiconductor devices. In this Feature Article, we summarize our recent work focusing on the growth, crystallization, and device operation of organic semiconductors intermediated by ultrathin organic films (in most cases, only a monolayer). The site-selective growth, modified crystallization and morphology, and improved device performance of organic semiconductor films are demonstrated with the help of the inducing layers, including patterned and uniform Langmuir-Blodgett monolayers, crystalline ultrathin organic films, and self-assembled polymer brush films. The introduction of the inducing layers could dramatically change the diffusion of the organic semiconductors on the surface and the interactions between the active layer with the inducing layer, leading to improved aggregation/crystallization behavior and device performance.

  19. Polarization dependence of Raman scattering from a thin film involving optical anisotropy theorized for molecular orientation analysis.

    PubMed

    Itoh, Yuki; Hasegawa, Takeshi

    2012-06-14

    Polarized Raman scattering from a thin film involving uniaxial optical anisotropy deposited on a dielectric substrate has analytically been theorized. The analyte film is modeled as a three-phase system (air/film/substrate) to calculate the electromagnetic fields of the incident and scattered light propagating across the system with an aid of the transfer matrix method to exactly take the optical anisotropy of the film into account. On the new theory, a methodology for molecular orientation analysis of an extended polymethylene chain in the film is proposed, which is employed for determination of the tilt angles of the chains in single- and five-monolayer Langmuir-Blodgett (LB) films of cadmium stearate deposited on a glass plate. The results agree well with those obtained by infrared spectroscopy, which confirms reliability of the present method.

  20. 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.

  1. Biocatalysts Immobilized in Ultrathin Ordered Films

    PubMed Central

    Sołoducho, Jadwiga; Cabaj, Joanna

    2010-01-01

    The immobilization of enzymes and other proteins into ordered thin materials has attracted considerable attention over the past few years. This research has demonstrated that biomolecules immobilized in different [Langmuir-Blodgett (LB)/Langmuir-Schaefer (LS)] matrixes retain their functional characteristics to a large extent. These new materials are of interest for applications as biosensors and biocatalysts. We review the growing field of oxidases immobilized onto ordered Langmiur-Blodgett and Langmuir-Schaefer films. Strategies for the preparation of solid supports and the essential properties of the resulting materials with respect to the envisaged applications are presented. Basic effects of the nature of the adsorption and various aspects of the application of these materials as biosensors, biocatalysts are discussed. Outlook of potential applications and further challenges are also provided. PMID:22163470

  2. How electrolyte and polyelectrolyte affect the adsorption of the anionic surfactant SDS onto the surface of a cellulose thin film and the structure of the cellulose film. 1. Hydrophobic cellulose.

    PubMed

    Tucker, Ian M; Petkov, Jordan T; Penfold, Jeffrey; Thomas, Robert K

    2012-07-24

    The nature of hydrophobic thin cellulose films, formed by Langmuir-Blodgett (LB) deposition on silica, has been studied using neutron reflectivity (NR). The impact of electrolyte and a polyelectrolyte, poly(dimethyldiallylammonium chloride) (polydmdaac), on the adsorption of the anionic surfactant sodium dodecyl sulfate (SDS) onto the surface of the hydrophobic cellulose film and upon the structure of the cellulose film has been investigated. The results show how a combination of polyelectrolytes and electrolyte can be used to manipulate surfactant adsorption onto hydrophobic cellulose surfaces and modify the structure of the cellulose film by swelling and penetration. The results illustrate how polyelectrolytes can be used to reverse adsorption and swelling of cellulose films which are not reversible simply by dilution in solvent.

  3. Polymeric Materials for Electro-Optic Testing.

    DTIC Science & Technology

    1987-07-01

    what Langmuir Blodgett films are, how they are grown and deposited on a material, and the electro - optic effects in Langmuir/Blodgett films. Stephen...Kowel has experimented with several different types of organic dyes mixed in the films to increase the electro - optic effect in the films. The bulk of his...test integrated circuits. Keywords: Langmuir Blodgett films, Electro - optic testing, Integrated circuits, Linear electro - optic effect.

  4. J-aggregates of thiacyanine dye organized in LB films: Effect of irradiation of light

    NASA Astrophysics Data System (ADS)

    Hussain, Syed Arshad; Dey, Dibyendu; Chakraborty, S.; Bhattacharjee, D.

    2011-08-01

    In the present communication we report the preparation and characterizations of Langmuir and Langmuir-Blodgett films of a thiacyanine dye-dioctadecyl thiacyanine perchlorate (NK) mixed with Octadecyl trimethyl ammonium bromide (OTAB). The relationship between the molar ratio of OTAB and NK and the orientation of molecules at the air-water interface was investigated using surface pressure - area per molecule ({\\pi}-A) isotherm. UV-Vis absorption and fluorescence spectroscopic investigations reveal that prominent J-aggregation of NK molecule was observed in the LB films lifted at higher surface pressure. This J-aggregation can be controlled by diluting the NK molecules with OTAB. It was observed that the J-aggregates of NK decayed to monomer and H-aggregates when the NK-LB film was exposed to a monochromatic light of wavelength 460 nm (Lambda max of J - aggregates).

  5. Effect of the conditions of transfer on the structure and optical properties of Langmuir graphene oxide films during deposition on a substrate

    NASA Astrophysics Data System (ADS)

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

    2017-09-01

    The effect the solvent and transfer pressure of graphene oxide (SLGO) Langmuir-Blodgett films on the physicochemical properties of monolayers, and on their structural and optical properties, is studied. Examination of the physicochemical properties of SLGO monolayers on subphase surfaces that are formed from SLGO dispersions in different organic solvents reveals that monolayer behavior is virtually independent of the solvent. Electron microscope and optical studies show that the monolayers formed from SLGO dispersions in DMF and acetone have the highest transfer coefficients. It is concluded that the structural heterogeneity of the surfaces of graphene oxide films results from simultaneous effect of electrostatic interactions between graphene oxide particles and Van der Waals interactions with the solvation shell of the particles. Studies focusing on the effect the pressure of transferring a graphene oxide monolayer onto the surface of a solid substrate has on structural features of LB films show that films produced at low surface pressures have more homogeneous structures.

  6. Surface chemistry and spectroscopy of UG8 asphaltene Langmuir film, part 1.

    PubMed

    Orbulescu, Jhony; Mullins, Oliver C; Leblanc, Roger M

    2010-10-05

    This research focuses on a systematic investigation of UG8 asphaltene Langmuir films at the air-water interface using toluene as the spreading solvent. From the surface pressure-area isotherms, it was concluded that small-sized aggregates are spread on the water surface and the compression of the film leads to formation of large aggregates. Our methods provide a stringent test and confirmation for the formation of corresponding asphaltene nanoaggregates that have recently been proposed for bulk solutions. These results were confirmed by compression-decompression isotherms, Brewster angle microscopy, and p-polarized infrared reflection-absorption spectroscopy. The transfer of a single layer using both the Langmuir-Schaefer and Langmuir-Blodgett deposition techniques shows different aggregate shapes depending on the technique used as imaged using atomic force microscopy. The films reveal the existence of nanoaggregates spread on the water surface that coexist with large aggregates formed during compression. For the nanoaggregate, the thickness of the Langmuir-Schaefer and Langmuir-Blodgett films determined by AFM is consistent with small aggregation numbers of nanoaggregates determined by Langmuir film compression. In addition to these findings, the spreading solvent, toluene, was found to be trapped within the aggregates as confirmed by in situ UV-vis spectroscopy at the air-water interface. This result was possible only after waiting a time period of 1 h to allow the complete evaporation of the spreading solvent. This is the only study that reveals the presence of the in situ toluene within the UG8 aggregates directly at the air-water interface.

  7. 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. Copyright © 2015 Elsevier B.V. All rights reserved.

  8. 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.

  9. 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.

  10. Bioelectronic tongue based on lipidic nanostructured layers containing phenol oxidases and lutetium bisphthalocyanine for the analysis of grapes.

    PubMed

    Medina-Plaza, C; de Saja, J A; Rodriguez-Mendez, M L

    2014-07-15

    In this work, a multisensor system formed by nanostructured voltammetric biosensors based on phenol oxidases (tyrosinase and laccase) has been developed. The enzymes have been incorporated into a biomimetic environment provided by a Langmuir-Blodgett (LB) film of arachidic acid (AA). Lutetium bisphthalocyanine (LuPc2) has also been introduced in the films to act as electron mediator. The incorporation of the enzymes to the floating layers to form Tyr/AA/LuPc2 and Lac/AA/LuPc2 films has been confirmed by the expansion in the surface pressure isotherms and by the AFM images. The voltammetric response towards six phenolic compounds demonstrates the enhanced performance of the biosensors that resulted from a preserved activity of the tyrosinase and laccase combined with the electron transfer activity of LuPc2. Biosensors show improved detection limits in the range of 10(-7)-10(-8) mol L(-1). An array formed by three sensors AA/LuPc2, Tyr/AA/LuPc2 and Lac/AA/LuPc2 has been employed to discriminate phenolic antioxidants of interest in the food industry. The Principal Component Analysis scores plot has demonstrated that the multisensor system is able to discriminate phenols according to the number of phenolic groups attached to the structure. The system has also been able to discriminate grapes of different varieties according to their phenolic content. This good performance is due to the combination of four factors: the high functionality of the enzyme obtained using a biomimetic immobilization, the signal enhancement caused by the LuPc2 mediator, the improvement in the selectivity induced by the enzymes and the complementary activity of the enzymatic sensors demonstrated in the loading plots. Copyright © 2014 Elsevier B.V. All rights reserved.

  11. (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.

  12. Microcavity Laser Based on a Single Molecule Thick High Gain Layer.

    PubMed

    Palatnik, Alexander; Aviv, Hagit; Tischler, Yaakov R

    2017-04-05

    The ability to confine excitons within monolayers has led to fundamental investigations of non-radiative energy transfer, super-radiance, strong light-matter coupling, high-efficiency LEDs, and recently lasers in lateral resonator architectures. Vertical Cavity Surface Emitting Lasers (VCSELs), in which lasing occurs perpendicular to the device plane, are critical for telecommunications and large-scale photonics integration, however strong optical self-absorption and low fluorescence quantum yields have thus far prevented coherent emission from a monolayer microcavity device. Here we show lasing from a monolayer VCSEL using a single molecule thick film of amphiphilic fluorescent dye, assembled via Langmuir-Blodgett deposition, as the gain layer. Threshold was observed when 5% of the molecules were excited (4.4 μJ/cm(2)). At this level of excitation, the optical gain in the monolayer exceeds 1056 cm(-1). High localization of the excitons in the VCSEL gain layer can enhance their collective emission properties with Langmuir-Blodgett deposition presenting a paradigm for engineering the high gain layers on the molecular level.

  13. 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

  14. 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.

  15. PM IRRAS investigation of thin silica films deposited on gold. Part 1. Theory and proof of concept.

    PubMed

    Zawisza, Izabella; Wittstock, Gunther; Boukherroub, Rabah; Szunerits, Sabine

    2007-08-28

    Polarization modulation infrared reflection absorption spectroscopy (PM IRRAS) was successfully used for the first time to characterize an optically transparent thin oxide film. SiO2 layers of 7 nm thickness were synthesized by plasma enhanced chemical vapor deposition (PECVD) on 200 nm thick gold covered glass slides. Despite the fact that silica is transparent and absorptive to IR radiation when deposited in the form of thin films on a gold surface, it preserves the high metallic reflectivity for the IR light. At grazing angles of incidence of the IR beam, the enhancement of the normal component of the electric field at the interface is comparable to that of Au alone. In addition, the analysis of the structure of a 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) lipid monolayer deposited using the Langmuir-Blodgett technique is demonstrated.

  16. 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

  17. Enzymatic modification and X-ray photoelectron spectroscopy analysis of a functionalized polydiacetylene thin film

    SciTech Connect

    Wilson, T.E.; Spevak, W.; Bednarski, M.D. Lawrence Berkeley Lab., CA ); Charych, D.H. )

    1994-05-01

    The mild conditions and specificity of biological catalysts are attractive incentives for their use in the formation of surfaces with well-defined chemical functionality. Herein, we describe the synthesis, characterization, and enzymatic modification of a functionalized polymeric bilayer assembly. The assembly is composed of a self-assembled monolayer of octadecylsilane and a Langmuir-Blodgett monolayer of polydiacetylene functionalized with the dipeptide phenylalanine-alanine (Phe-Ala). We demonstrate via X-ray photoelectron spectroscopy surface analysis that the surface-bound Phe-Ala dipeptide is a substrate for specific cleavage by the enzyme subtilisin BPN[prime]. In-situ surface transformations via enzymatic synthesis or cleavage offer an alternative to chemical treatments of organic thin films. 28 refs., 4 figs.

  18. Free-standing lipid films stabilized by Annexin-A5.

    PubMed

    Simon, Anne; Gounou, Céline; Tan, Sisareuth; Tiefenauer, Louis; Di Berardino, Marco; Brisson, Alain R

    2013-11-01

    Free-standing lipid bilayers in nano- and micro-pores are interesting membrane models and attractive for biotechnological applications. We describe here the controlled preparation of proteo-lipid mono- and bilayers using the Langmuir-Schaefer transfer or Langmuir-Blodgett technique, respectively on hydrophobic and hydrophilic surfaces. We demonstrate the formation of suspended proteo-lipid layers by Transmission Electron Microscopy (TEM) and in situ Atomic Force Microscopy (AFM) imaging. Using Annexin-A5 as a membrane-associated protein, continuous proteo-lipid mono- and bilayers were formed, which span pore arrays over areas of several square-micrometers. The 2D organization of proteins associated to lipid monolayer is well preserved during the transfer process and the protein association is Ca(2+)-dependent and therefore reversible. The simple formation and reliable transfer of stabilized free-standing lipid films is a first crucial step to create biomimetic membranes for biotechnological applications and membrane protein research.

  19. Attenuation Lengths of Photoelectrons in Hydrocarbon Films

    DTIC Science & Technology

    1988-10-01

    lower than those obtained by Ringsdorf7 for polymerized , Langmuir-Blodgett cadmium diacetylene multilayers, by King 8 for Langmuir- Blodgett barium...Sci., Po’ . Chem. Ed. 1977, i5, 2843. 7 Hupfer, B.; Schupp, H.; Andrade, J. D.; Ringsdorf, H. J. Electron Spectrosc. 1981, 23, 103. 8 Cartier , E...Warren T. Ford Dr. J.C.H. Chien Department of Chemistry Department of Polymer Science and Oklahoma State University Engineering Stillwater, OK 74078

  20. Thin films and assemblies of photosensitive membrane proteins and colloidal nanocrystals for engineering of hybrid materials with advanced properties.

    PubMed

    Zaitsev, Sergei Yu; Solovyeva, Daria O; Nabiev, Igor

    2012-11-15

    The development and study of nano-bio hybrid materials engineered from membrane proteins (the key functional elements of various biomembranes) and nanoheterostructures (inorganic colloidal nanoparticles, transparent electrodes, and films) is a rapidly growing field at the interface of materials and life sciences. The mainspring of the development of bioinspired materials and devices is the fact that biological evolution has solved many problems similar to those that humans are attempting to solve in the field of light-harvesting and energy-transferring inorganic compounds. Along this way, bioelectronics and biophotonics have shown considerable promise. A number of proteins have been explored in terms of bioelectronic device applications, but bacteriorhodopsin (bR, a photosensitive membrane protein from purple membranes of the bacterium Halobacterium salinarum) and bacterial photosynthetic reaction centres have received the most attention. The energy harvesting in plants has a maximum efficiency of 5%, whereas bR, in the absence of a specific light-harvesting system, allows bacteria to utilize only 0.1-0.5% of the solar light. Recent nano-bioengineering approaches employing colloidal semiconductor and metal nanoparticles conjugated with biosystems permit the enhancement of the light-harvesting capacity of photosensitive proteins, thus providing a strong impetus to protein-based device optimisation. Fabrication of ultrathin and highly oriented films from biological membranes and photosensitive proteins is the key task for prospective bioelectronic and biophotonic applications. In this review, the main advances in techniques of preparation of such films are analyzed. Comparison of the techniques for obtaining thin films leads to the conclusion that the homogeneity and orientation of biomembrane fragments or proteins in these films depend on the method of their fabrication and increase in the following order: electrophoretic sedimentation < Langmuir-Blodgett and

  1. The cis-bis(decanoate)tin phthalocyanine/DPPC film at the air/water interface.

    PubMed

    Ramos, Salvador; Garza, Cristina; Beltran, Hiram I; Campos-Terán, José; Arenas-Alatorre, Jesús; Castillo, Rolando

    2012-03-01

    Films made of cis-bis-decanoate-tin(IV) phthalocyanine (PcSn10) and racemic dipalmitoylphosphatidylcholine (DPPC) are studied with compression isotherms and Brewster angle microscopy (BAM) at the air/water interface. Films enriched in PcSn10 present phase separation elliptical-shaped domains. These domains present optical anisotropy and molecular order. They are enriched in PcSn10, and the film outside these domains is enriched in DPPC, as shown in by high-angle annular dark-field transmission electron microscopy on Langmuir-Blodgett (LB) transferred films. Film collapse area and atomic force microscopy images of LB transferred films on mica indicate that the films are actually multilayers. A computational survey was performed to determine how the PcSn10 molecules prefer to self-assemble, in films basically made of PcSn10. The relative energetic stability for several dimeric assemblies was obtained, and a crystal model of the film was developed through packing and repeating the PcSn10 molecules, along the crystallographic directions of the unit cell. Our results contribute to understanding the strong interaction between PcSn10 and DPPC at the air/water interface, where even small quantities of DPPC (~1-2%) can modify the film in an important way.

  2. 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.

  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. 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

  5. Evolution of Nanoflowers and Nanospheres of Zinc Bisporphyrinate Tweezers at the Air/water Interface.

    PubMed

    Xie, Fan; Zhuo, Congcong; Hu, Chuanjiang; Liu, Ming Hua

    2017-03-22

    While the sophisticated Langmuir and Langmuir-Blodgett technique facilitates the fabrication of uniform ultrathin monolayer and films, it is also revealed as a powerful tool for the bottom-up constructions of the nanostructures through the air/water interface. In this paper, unique nanoflowers or nanospheres were constructed based on the synthesized m-phthalic diamide-linked Zinc bis-porphyrinate tweezers using the Langmuir and Langmuir-Blodgett (LB) technique. It was found that both the two tweezer type Zinc bisporphyrinates could form stable two-dimensional spreading films at the air/water interface, which could be subsequently transferred onto solid substrates by the vertical lifting method. The atomic force microscope (AFM) revealed that at the initial spreading stage the compound formed flat disk-like domains and then hierarchically evolved into nanoflowers or nanospheres upon compressing the floating film. Such nanostructures have not been reported before and cannot be fabricated using the other self-assembly methods.

  6. 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.

  7. High proton conductivity in the molecular interlayer of a polymer nanosheet multilayer film.

    PubMed

    Sato, Takuma; Hayasaka, Yuta; Mitsuishi, Masaya; Miyashita, Tokuji; Nagano, Shusaku; Matsui, Jun

    2015-05-12

    High proton conductivity was achieved in a polymer multilayer film with a well-defined two-dimensional lamella structure. The multilayer film was prepared by deposition of poly(N-dodecylacryamide-co-acrylic acid) (p(DDA/AA)) monolayers onto a solid substrate using the Langmuir-Blodgett technique. Grazing-angle incidence X-ray diffraction measurement of a 30-layer film of p(DDA/AA) showed strong diffraction peaks in the out-of-plane direction at 2θ = 2.26° and 4.50°, revealing that the multilayer film had a highly uniform layered structure with a monolayer thickness of 2.0 nm. The proton conductivity of the p(DDA/AA) multilayer film parallel to the layer plane direction was 0.051 S/cm at 60 °C and 98% relative humidity with a low activation energy of 0.35 eV, which is comparable to perfluorosulfonic acid membranes. The high conductivity and low activation energy resulted from the formation of uniform two-dimensional proton-conductive nanochannels in the hydrophilic regions of the multilayer film. The proton conductivity of the multilayer film perpendicular to the layer plane was determined to be 2.1 × 10(-13) S/cm. Therefore, the multilayer film showed large anisotropic conductivity with an anisotropic ratio of 2.4 × 10(11).

  8. 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.

  9. Self-assembly of hydrophobic gold nanoparticles and adhesion property of their assembled monolayer films.

    PubMed

    Lin, Guanhua; Lu, Wensheng

    2017-09-01

    Monodispersed gold nanoparticles had been successfully fabricated and they could form highly ordered two-dimensional (2D) film beyond a critical surface pressure by using Langmuir-Blodgett (LB) technology. To study adhesion property of these AuNPs films, atomic force microscope (AFM) has been used in measuring the interaction force between AFM tip and the gold nanoparticle films deposited on the silicon wafer, and defined the force at the breaking point as the adhesive force between nanoparticle films and the substrate. It has been found that the adhesive force was an exponential function of the packing density of the AuNPs in the film. When the packing density is near to the saturated value, the adhesive force of gold nanoparticle monolayer could reach 675nN which is approximately 30-fold of that for the nanoparticles on the substrate at low surface pressure (5mN/m). It shows that the adhesive force of assembled nanoparticle films is quantitative sensitive with their packing density and our method could be used to detect defact of assembled nanoparticle films, which presents great potential application. Copyright © 2017 Elsevier Inc. All rights reserved.

  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. 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.

  12. Novel Liquid Crystals - Polymers and Monomers - As Nonlinear Optical Materials

    DTIC Science & Technology

    1987-12-31

    and pyridine N - oxides . Results of collaborative efforts in further characterization (electrooptic, dielectric, Langmuir-Blodgett films) are described...Polymalonate Liquid Crystals for Nonlinear Optics", A. C. Griffin, A. M. Bhatti and R. S. L. Hung, Mol Cryst LiS Cryst, 155, 129 (1988). " Pyridine N - oxides ... pyridine N - oxide based side chain polymers having a push-pull pi electronic structure, (d) generation of a series of copolymers involving both an nlo

  13. Structure and mechanical properties of poly(benzyl ether) monodendron Langmuir films

    NASA Astrophysics Data System (ADS)

    Kampf, James Patrick

    2000-10-01

    preliminary study of the organization and surface viscoelasticity of Langmuir-Blodgett films of the monodendrons on hydrophilic silicon substrates using ellipsometry and atomic force microscopy. These films exhibit a viscoelastic transition consistent with the behavior of monolayers at the air-water interface. Furthermore, the Langmuir-Blodgett films assume a number of morphologies that depend on film thickness and may be generated by dewetting from the solid surface.

  14. Monomolecular films of cholesterol oxidase and S-Layer proteins

    NASA Astrophysics Data System (ADS)

    Ferraz, Helen Conceição; Guimarães, Juliana Aguilar; Alves, Tito Livio Moitinho; Constantino, Carlos José Leopoldo

    2011-05-01

    Cholesterol oxidase (ChOx) is a flavoenzyme that catalyzes the oxidation of cholesterol to cholest-5-en-3-one and subsequently the isomerization to cholest-4-en-3-one. ChOx has been very commonly studied as the detection element in cholesterol biosensors. In the biosensor development field, a relatively new approach is the use of crystalline bacterial cell surface layers, known as S-Layer proteins. These proteins exhibit the ability of self-assembling at surfaces, opening a vast spectrum of applications, both in basic and applied researches. In our study, monomolecular films of ChOx and mixed films of ChOx/S-Layer proteins and DPPC/S-Layer proteins were produced using the Langmuir technique. Characterization of the films was performed by means of surface pressure-molecular area ( π- A) isotherms. Stable monolayers were obtained, which means that they can be transferred to solid substrates by Langmuir-Blodgett technique. Mixed monolayers showed an ideal like behavior.

  15. 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.

  16. Thiophene-based monolayer OFETs prepared by Langmuir techniques

    NASA Astrophysics Data System (ADS)

    Agina, Elena V.; Sizov, Alexey S.; Anisimov, Daniil S.; Trul, Askold A.; Borshchev, Oleg V.; Paraschuk, Dmitry Y.; Shcherbina, Maxim A.; Chvalun, Sergey N.; Ponomarenko, Sergey A.

    2015-08-01

    A novel fast, easily processible and highly reproducible approach to thiophene-based monolayer OFETs fabrication by Langmuir-Blodgett or Langmuir-Schaefer techniques was developed and successfully applied. It is based on selfassembly of organosilicon derivatives of oligothiophenes or benzothienobenzothiophene on the water-air interface. Influence of the conjugation length and the anchor group chemistry of the self-assembling molecules on the monolayer structure and electric performance of monolayer OFETs was systematically investigated. The efficient monolayer OFETs with the charge carrier mobilities up to 0.01 cm2/Vs and on/off ratio up to 106 were fabricated, and their functionality in integrated circuits under normal air conditions was demonstrated.

  17. Fabrication and investigation of the bionic curved visual microlens array films

    NASA Astrophysics Data System (ADS)

    Kuo, Wen-Kai; Lin, Syuan-You; Hsu, Sheng-Wei; Yu, Hsin Her

    2017-04-01

    The compound eyes of insects are smaller, lighter, and have a wider field of view and high sensitivity to moving targets. In recent years, these advantages have attracted many researchers to develop minimized optical devices. In this study, a high performance microlens was fabricated, mimicking the biological visual feature. Polystyrene (PS) microspheres were synthesized by dispersion polymerization first, and then a close-packed monolayer of PS microspheres was assembled by the Langmuir-Blodgett (LB) deposition method. Following this, a 2D polydimethylsiloxane (PDMS) concave mold was fabricated by a soft lithography technique. Different aperture sizes of poly(methyl methacrylate) (PMMA) curved microlens array replicated films were prepared using traditional Chinese medicine cupping tool with a temperature-controllable hot plate, which eliminated the need for inconvenient metal modeling. The optical performance of the curved microlens films were evaluated by a system of optical microscopy (OM) and a home-made image capture charge-coupled device (CCD). The field of view (FOV) and the light intensity distribution of the curved microlens array were also investigated. We found that a broader field of view corresponded to a smaller aperture size of the curved microlens films, as the convex heights of the films are identical. The resolution of the curved microlens films was not affected by their aperture sizes, but was determined by their interommatidial angle and the diameter of the microlens.

  18. 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.

  19. 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

  20. 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.

  1. Enzyme Catalyzed 2-D Polymerization of Phenol and Aniline Derivatives on a Langmuir-Blodgett Through

    DTIC Science & Technology

    1992-12-31

    substituted C14PP and phenol monomer (ratio 1:10 ) was initiated by the injection of 2 ml Laccase solution (10mg/ml) into the buffered (pH 7.5) subphase...no hydrogen peroxide was required for this polymerization). Laccase (Benzenediol:oxygen oxidoreductase EC 1.10.3.2),120-150 units/mg solid was used

  2. Interaction of lipophilic gemcitabine prodrugs with biomembrane models studied by Langmuir-Blodgett technique.

    PubMed

    Castelli, Francesco; Sarpietro, Maria Grazia; Rocco, Flavio; Ceruti, Maurizio; Cattel, Luigi

    2007-09-01

    The stability and bioavailability of anticancer agents, such as gemcitabine, can be increased by forming prodrugs. Gemcitabine is rapidly deaminated to the inactive metabolite (2('),2(')-difluorodeoxyuridine), thus to improve its stability a series of increasingly lipophilic gemcitabine prodrugs linked through the 4-amino group to valeroyl, lauroyl, and stearoyl acyl chains were synthesized. Studies of monolayer properties are important to improve understanding of biological phenomena involving lipid/gemcitabine or lipid/gemcitabine derivative interactions. The interfacial behavior of monolayers constituted by DMPC plus gemcitabine or lipophilic gemcitabine prodrugs at increasing molar fractions was studied at the air/water interface at temperatures below (10 degrees C) and above (37 degrees C) the lipid phase transition. The effect of the hydrophobic chain length of gemcitabine derivatives on the isotherm of pure DMPC was investigated by surface tension measurement, and the results are reported as molar fractions as a function of mean molecular area per molecule. The results show that the compounds interact with DMPC producing mixed monolayers that are subject to an expansion effect, depending on the prodrug chain length. The results give useful hints of the interaction of these prodrugs with biological membranes and increase knowledge on the incorporation site of such compounds, as a function of their lipophilicity, in a lipid carrier; they may lead to improved liposomal formulation design.

  3. The Effect of Surface Pressure on the Langmuir-Blodgett Polymerization of 2-Pentadecyl Aniline

    DTIC Science & Technology

    1992-05-19

    the mean molecular area was decreasing during the polymerization of 2-pentadecyl aniline . Also no polymer was found when the reaction was run at low...and polymer, we suppose, is the cause of Mma decrease during the polymerization of 2-pentadecyl aniline . Compared with the area of a long alkyl ...is put into changing its conformation at the surface. In the case of 2-pentadecyl aniline , the work done upon compressing the monolayer, we suppose, is

  4. Calcium carbonate particle growth depending on coupling among adjacent layers in hybrid LB/LbL films.

    PubMed

    Ramos, Ana P; Nobre, Thatyane M; Montoro, Luciano A; Zaniquelli, Maria E D

    2008-11-20

    There are practical and academic situations that justify the study of calcium carbonate crystallization and especially of systems that are associated with organic matrices and a confined medium. Despite the fact that many different matrices have been studied, the use of well-behaved, thin organic films may provide new knowledge about this system. In this work, we have studied the growth of calcium carbonate particles on well-defined organic matrices that were formed by layer-by-layer (LbL) polyelectrolyte films deposited on phospholipid Langmuir-Blodgett films (LB). We were able to change the surface electrical charge density of the LB films by changing the proportions of a negatively charged lipid, the sodium salt of dimyristoyl-sn-glycero-phosphatidyl acid (DMPA), and a zwitterionic lipid, dimyristoyl-sn-glycero-phosphatidylethanolamine (DMPE). This affects the subsequent polyelectrolyte LbL film deposition, which also changes the the nature of the bonding (electrostatic interaction or hydrogen bonding). This approach allowed for the formation of calcium carbonate particles of different final shapes, roughnesses, and sizes. The masses of deposited lipids, polyelectrolytes, and calcium cabonate were quantified by the quartz crystal microbalance technique. The structures of obtained particles were analyzed by scanning electron microscopy.

  5. 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.

  6. Influence of the type of phospholipid head and of the conformation of the polyelectrolyte on the growth of calcium carbonate thin films on LB/LbL matrices.

    PubMed

    Ramos, Ana P; Espimpolo, Daniela M; Zaniquelli, Maria Elisabete D

    2012-06-15

    Calcium carbonate is one of the most important biominerals, and it is the main constituent of pearls, seashells, and teeth. The in vitro crystallization of calcium carbonate using different organic matrices as templates has been reported. In this work, the growth of calcium carbonate thin films on special organic matrices consisting of layer-by-layer (LbL) polyelectrolyte films deposited on a pre-formed phospholipid Langmuir-Blodgett (LB) film has been studied. Two types of randomly coiled polyelectrolytes have been used: lambda-carrageenan and poly(acrylic acid). A precoating comprised of LB films has been prepared by employing a negatively charged phospholipid, the sodium salt of dimyristoilphosphatidyl acid (DMPA), or a zwitterionic phospholipid, namely dimyristoilphosphatidylethanolamine (DMPE). This approach resulted in the formation of particulate calcium carbonate continuous films with different morphologies, particle sizes, and roughness, as revealed by scanning electron microscopy (SEM) and atomic force microscopy (AFM). The crystalline structure of the calcium carbonate particles was analyzed by Raman spectroscopy. The randomly coiled conformation of the polyelectrolytes seems to be the main reason for the formation of continuous films rather than CaCO(3) isolated crystals.

  7. Nanostructured films employed as sensing units in an "electronic tongue" system.

    PubMed

    da Silva, B A; Antunes, P A; Pasquini, D; Curvelo, A A S; Aroca, R F; Riul, A Júnior; Constantino, C J L

    2007-02-01

    Nanostructured films of lignin (macromolecule extracted from sugar cane bagasse), polypyrrole (conducting polymer) and bis butylimido perylene (organic dye) were used in the detection of trace levels of fluorine (from H2SiF6), chlorine (from NaClO), Pb(+2), Cu(+2), and Cd(+2) in aqueous solutions. Langmuir monolayers on ultrapure water were characterised by surface pressure-mean molecular area (II-A) isotherms. Langmuir-Blodgett (LB) films were transferred onto gold interdigitated electrodes and used as individual sensing units of an electronic tongue system. Impedance spectroscopy measurements were taken with the sensor immersed into aqueous solutions containing the ions described above in different molar concentrations. Fourier transform infrared absorption (FTIR) was employed to identify possible interactions between the LB films and the analytes in solution, and no significant changes could be observed in the FTIR spectra of BuPTCD and Ppy. Therefore, the results for lignin point to an interaction involving the electronic cloud of the phenyl groups with the metallic ions.

  8. Effects of Ca(2+) ions on bestrophin-1 surface films.

    PubMed

    Mladenova, Kirilka; Petrova, Svetla D; Andreeva, Tonya D; Moskova-Doumanova, Veselina; Topouzova-Hristova, Tanya; Kalvachev, Yuri; Balashev, Konstantin; Bhattacharya, Shomi S; Chakarova, Christina; Lalchev, Zdravko; Doumanov, Jordan A

    2017-01-01

    Human bestrophin-1 (hBest1) is a transmembrane calcium-activated chloride channel protein - member of the bestrophin family of anion channels, predominantly expressed in the membrane of retinal pigment epithelium (RPE) cells. Mutations in the protein cause ocular diseases, named Bestrophinopathies. Here, we present the first Fourier transform infrared (FTIR) study of the secondary structure elements of hBest1, π/A isotherms and hysteresis, Brewster angle microscopy (BAM) and atomic force microscopy (AFM) visualization of the aggregation state of protein molecules dispersed as Langmuir and Langmuir-Blodgett films. The secondary structure of hBest1 consists predominantly of 310-helices (27.2%), α-helixes (16.3%), β-turns and loops (32.2%). AFM images of hBest1 suggest approximate lateral dimensions of 100×160Å and 75Å height. Binding of calcium ions (Ca(2+)) induces conformational changes in the protein secondary structure leading to assembly of protein molecules and changes in molecular and macro-organization of hBest1 in monolayers. These data provide basic information needed in pursuit of molecular mechanisms underlying retinal and other pathologies linked to this protein.

  9. Membrane-mimetic films of asymmetric phosphatidylcholine lipid bolaamphiphiles.

    PubMed

    Sun, Xue-Long; Biswas, Nilanjana; Kai, Toshitsugu; Dai, Zhifei; Dluhy, Richard A; Chaikof, Elliot L

    2006-01-31

    Membrane-spanning phospholipid bolaamphiphiles either alone or as a constituent of a multicomponent lipid membrane may prove to be facile building blocks for generating robust bioactive membrane-mimetic assemblies. We have previously reported the synthesis of asymmetric dialkyl phospholipid bolaamphiphiles that contain ester linked phosphatidylcholine and amine functionalities at opposite chain ends. In this report, we describe the synthesis of phospholipid bolaamphiphiles that are conjugated to biotin via the terminal amine with or without a poly(ethylene oxide) spacer arm of varying chain length. The behavior of biotinylated bolaamphiphiles as a self-assembled monolayer at an air-water interface was characterized by epi-fluorescence microscopy and revealed that domain structure and pi-A isotherms were substantially influenced by linker type and size. Substrate bound assemblies were produced by Langmuir-Blodgett deposition onto planar substrates coated with an avidin derivatized polyelectrolyte multilayer. Significantly, external reflectance infrared spectroscopy confirmed the fabrication of bolaamphiphile thin films that display extended stability in vitro.

  10. Self-Assembled, Perforated Monolayers for Enhanced Permselectivity in Membranes

    DTIC Science & Technology

    2006-11-01

    Selective Membranes. In the 1930s, Irving Langmuir and Katherine Blodgett introduced a method for fabricating monolayer and multilayer arrays of... Langmuir -Blodgett (LB) films. Here, we show how ionic cross-linking of multiply-charged surfactants (a process that we have termed, “gluing”) can yield...LB films on the order of 6 nm thick having extraordinary barrier properties, high flux, and stability. 2. Langmuir -Blodgett Films as Permeation

  11. Thin Films of Uniform Hematite Nanoparticles: Controls on Surface Hydrophobicity and Self-Assembly

    SciTech Connect

    Wang, Wei; Liang, Liyuan; Johs, Alexander; Gu, Baohua

    2008-01-01

    In this study we show that uniform hematite ( -Fe2O3) nanoparticle thin films with controlled layer thickness can be formed by Langmuir-Blodgett (LB) monolayer deposition on surface areas of several square centimeters. The technique involves synthesis of uniform hematite nanoparticles by forced hydrolysis and surface modifications for increased hydrophobicity to bring the particles to the air-water interface. Methods of thermal treatment, stepped solvent exchange, and oleate surfactant coating were studied for their effectiveness in increasing hydrophobicity by removing surface adsorbed water and OH groups and were subsequently validated by Fourier-transform infrared (FTIR) spectral analysis. Surface pressure-area ( -A) and surface pressure-time ( -t) isotherms indicate that the stability of the particle monolayer at the air-water interface depends on the method of surface modification. Thermal evaporation treatment was found to produce thin films of hematite nanoparticles with the greatest uniformity and surface coverage as characterized by UV-visible spectroscopic, scanning electron microscopic (SEM) and atomic force microscopic (AFM) analyses.

  12. 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. Copyright © 2015 Elsevier B.V. All rights reserved.

  13. Reversible Monolayer-Bilayer Transition in Supported Phospholipid LB Films under the Presence of Water: Morphological and Nanomechanical Behavior.

    PubMed

    Ruiz-Rincón, Silvia; González-Orive, Alejandro; de la Fuente, Jesús M; Cea, Pilar

    2017-08-01

    Mixed monolayer Langmuir-Blodgett (LB) films of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) and cholesterol (Chol) in the 1:1 ratio have been prepared onto solid mica substrates. Upon immersion in water or in an aqueous HEPES solution (pH 7.4) the monolayer LB films were spontaneously converted into well-organized bilayers leaving free mica areas. The process has been demonstrated to be reversible upon removal of the aqueous solution, resulting in remarkably free of defects monolayers that are homogeneously distributed onto the mica. In addition, the nanomechanical properties exhibited by the as-formed bilayers have been determined by means of AFM breakthrough force studies. The bilayers formed by immersion of the monolayer in an aqueous media exhibit nanomechanical properties and stability under compression analogous to those of DPPC:Chol supported bilayers obtained by other methods previously described in the literature. Consequently, the hydration of a monolayer LB film has been revealed as an easy method to produce well-ordered bilayers that mimic the cell membrane and that could be used as model cell membranes.

  14. Nanoscale fabrication of the ferroelectric polymer poly(vinylidene fluoride with trifluoroethylene) P(VDF-TrFE) 75:25 thin films by atomic force microscope nanolithography.

    PubMed

    Vega, Omar; Delgado, David; Wong, Freddy; Gonzalez, Rosette; Rosa, Luis G

    2012-01-01

    Thin films of an organic ferroelectric system, poly(vinylidene fluoride with trifluoroethylene) P(VDF-TrFE, Kureha Corporation, Tokyo, Japan) 75:25 layers, have been deposited on highly ordered pyrolytic graphite and silicon dioxide by the horizontal Schaefer method of Langmuir-Blodgett techniques. It is possible to "shave" or mechanically displace small regions of the polymer film by using atomic force microscope nanolithography techniques such as nanoshaving, leaving swaths of the surface cut to a depth of 4 nm and 12 nm exposing the substrate. The results of fabricating stripes by nanoshaving two holes close to each other show a limit to the material "stripe" widths of an average of 153.29 nm and 177.67 nm that can be produced. Due to the lack of adhesion between the substrates and the polymer P(VDF-TrFE) film, smaller "stripes" of P(VDF-TrFE) cannot be produced, and it can be shown by the sequencing of nanoshaved regions that "stripes" of thin films can be removed. © Wiley Periodicals, Inc.

  15. 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.

  16. Chirality Transfer and Modulation in LB Films Derived From the Diacetylene/Melamine Hydrogen-Bonded Complex.

    PubMed

    Zhu, Yu; Xu, Yangyang; Zou, Gang; Zhang, Qijin

    2015-08-01

    Introduction of hydrogen-bonding interaction into π-conjugated systems is a promising strategy, since the highly selective and directional hydrogen-bonding can increase the binding strength, provide enhanced stability to the assemblies, and position the π-conjugated molecules in a desired arrangement. The helical packing of the rigid melamine cores seems to play a dominating role in the subsequent formation of the peripheral helical PDA backbone. The polymerized Langmuir-Blodgett (LB) films exhibited reversible colorimetric and chiroptical changes during repeated heating-cooling cycles, which should be ascribed to the strong hydrogen-bonding interaction between the carboxylic acid and the melamine core. Further, the closely helical packing of the melamine cores could be destroyed upon exposure to HCl or NH(3) gas, whereas the peripheral helical polyaniline and polydiacetylene (PDA) backbone exhibited excellent stability. Although similar absorption changes could be observed for the films upon exposure to HCl or NH(3) gas, their distinct circular dichroism (CD) responses enabled us to distinguish the above two stimuli.

  17. Perforated Monolayers for Enhanced Permselectivity in Chemical Biological Barrier Membranes

    DTIC Science & Technology

    2004-12-01

    Membranes. In the 1930s, Irving Langmuir and Katherine Blodgett introduced a method for fabricating monolayer and multilayer arrays of surfactants...pass. With this goal in mind, we have been developing an ultra-thin membrane capable of blocking chemical agents, utilizing Langmuir -Blodgett (LB...order of 6 nm thick having extraordinary barrier properties, high flux, and stability. 2. Langmuir -Blodgett Films as Permeation-Selective

  18. Properties of amphiphilic oligonucleotide films at the air/water interface and after film transfer.

    PubMed

    Keller, R; Kwak, M; de Vries, J W; Sawaryn, C; Wang, J; Anaya, M; Müllen, K; Butt, H-J; Herrmann, A; Berger, R

    2013-11-01

    The self-assembly of amphiphilic hybrid materials containing an oligonucleotide sequence at the air/water interface was investigated by means of pressure-molecular area (Π-A) isotherms. In addition, films were transferred onto solid substrates and imaged using scanning force microscopy. We used oligonucleotide molecules with lipid tails, which consisted of a single stranded oligonucleotide 11 mer containing two hydrophobically modified 5-(dodec-1-ynyl)uracil nucleobases (dU11) at the 5'-end of the oligonucleotide sequence. The air/water interface was used as confinement for the self-assembling process of dU11. Scanning force microscopy of films transferred via Langmuir-Blodgett technique revealed mono-, bi- (Π ≥ 2 mN/m) and multilayer formation (Π ≥ 30 mN/m). The first layer was 1.6 ± 0.1 nm thick. It was oriented with the hydrophilic oligonucleotide moiety facing the hydrophilic substrate while the hydrophobic alkyl chains faced air. In the second layer the oligonucleotide moiety was found to face the air. The second layer was found to cover up to 95% of the sample area. Our measurements indicated that the rearrangement of the molecules into bi- and multiple bilayers happened already at the air/water interface. Similar results were obtained with a second type of oligonucleotide amphiphile, an oligonucleotide block copolymer, which was composed of an oligonucleotide 11 mer covalently attached at the terminus to polypropyleneoxide (PPO). Copyright © 2013 Elsevier B.V. All rights reserved.

  19. 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.

  20. Lignin from sugar cane bagasse: extraction, fabrication of nanostructured films, and application.

    PubMed

    Pereira, A A; Martins, G F; Antunes, P A; Conrrado, R; Pasquini, D; Job, A E; Curvelo, A A S; Ferreira, M; Riul, A; Constantino, C J L

    2007-06-05

    Four lignin samples were extracted from sugar cane bagasse using four different alcohols (methanol, ethanol, n-propanol, and 1-butanol) via the organosolv-CO2 supercritical pulping process. Langmuir films were characterized by surface pressure vs mean molecular area (Pi-A) isotherms to exploit information at the molecular level carrying out stability tests, cycles of compression/expansion (hysteresis), subphase temperature variations, and metallic ions dissolved into the water subphase at different concentrations. Briefly, it was observed that these lignins are relatively stable on the water surface when compared to those obtained via different extraction processes. Besides, the Pi-A isotherms are shifted to smaller molecular areas at higher subphase temperatures and to larger molecular areas when the metallic ions are dissolved into the subphase. The results are related to the formation of stable aggregates (domains) onto the water subphase by these lignins, as shown in the Pi-A isotherms. It was found as well that the most stable lignin monolayer onto the water subphase is that extracted with 1-butanol. Homogeneous Langmuir-Blodgett (LB) films of this lignin could be produced as confirmed by UV-vis absorption spectroscopy and the cumulative transfer parameter. In addition, FTIR analysis showed that this lignin LB film is structured in a way that the phenyl groups are organized preferentially parallel to the substrate surface. Further, these LB films were deposited onto gold interdigitated electrodes and ITO and applied in studies involving the detection of Cd+2 ions in aqueous solutions at low concentration levels through impedance spectroscopy and electrochemical measurements. FTIR spectroscopy was carried out before and after soaking the thin films into Cd+2 aqueous solutions, revealing a possible physical interaction between the lignin phenyl groups and the heavy metal ions. The importance of using nanostructured systems is demonstrated as well by comparing

  1. 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). Copyright © 2012 Elsevier Ltd. All rights reserved.

  2. 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....

  3. 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....

  4. 49 CFR 173.183 - Nitrocellulose base film.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 49 Transportation 2 2010-10-01 2010-10-01 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. [Amdt. 173-224, 55 FR 52643...

  5. 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....

  6. 49 CFR 173.183 - Nitrocellulose base film.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 49 Transportation 2 2011-10-01 2011-10-01 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....

  7. Plasmonic films based on colloidal lithography.

    PubMed

    Ai, Bin; Yu, Ye; Möhwald, Helmuth; Zhang, Gang; Yang, Bai

    2014-04-01

    This paper reviews recent advances in the field of plasmonic films fabricated by colloidal lithography. Compared with conventional lithography techniques such as electron beam lithography and focused ion beam lithography, the unconventional colloidal lithography technique with advantages of low-cost and high-throughput has made the fabrication process more efficient, and moreover brought out novel films that show remarkable surface plasmon features. These plasmonic films include those with nanohole arrays, nanovoid arrays and nanoshell arrays with precisely controlled shapes, sizes, and spacing. Based on these novel nanostructures, optical and sensing performances can be greatly enhanced. The introduction of colloidal lithography provides not only efficient fabrication processes but also plasmonic films with unique nanostructures, which are difficult to be fabricated by conventional lithography techniques. Copyright © 2013 Elsevier B.V. All rights reserved.

  8. Algal polysaccharides as matrices for the immobilization of urease in lipid ultrathin films studied with tensiometry and vibrational spectroscopy: Physical-chemical properties and implications in the enzyme activity.

    PubMed

    de Brito, Audrey Kalinouski; Nordi, Cristina S F; Caseli, Luciano

    2015-11-01

    Currently, many biological substances extracted from algae have received special attention because of their intrinsic characteristics, which can be applied to different areas of biotechnology. Therefore, in the current study, exopolysaccharides (EPS) from the microalgae Cryptomonas tetrapirenoidosa were employed as an aqueous subphase of a monolayer formed by the lipid dioctadecyldimethylammonium bromide (DODAB). The primary objective of this approach was to evaluate whether EPS could serve as a matrix for the immobilization of the enzyme urease to produce biosensors for urea. After DODAB was spread on the EPS solutions, urease was injected into the aqueous subphase, and the surface was submitted to compression using lateral barriers. The monolayers were subsequently characterized by surface pressure-area isotherms and polarization modulation infrared reflection-absorption spectroscopy (PM-IRRAS). The results indicated that EPS enhanced the adsorption of the enzyme on the lipid monolayer. The mixed films were later transferred to solid supports using the Langmuir-Blodgett (LB) technique and were characterized by transfer ratio, PM-IRRAS, quartz crystal microbalance, and atomic force microscopy. The immobilization of the enzyme on solid supports was fundamental for providing an ideal geometrical accommodation of urease because the interaction of EPS with urease in solution causes a decrease of the relative activity of urease. Therefore, these LB films are promising for the fabrication of future urea biosensors, the architecture of which can be manipulated and enhanced at the molecular level.

  9. Development of a Quantum Dot Based Luminescent Solar Concentrator

    NASA Astrophysics Data System (ADS)

    Suter, John David

    Luminescent solar concentrators (LSCs) have been proposed as a lower cost and more aesthetically pleasing alternative to traditional photovoltaic devices. The LSC presented in this thesis will use II-VI semiconducting quantum dots (QDs) as luminescent material. CdSe/ZnSe core/shell QDs; CdSe/ZnS core/shell QDs; and CdxZn1-xSe QDs can be synthesized with high quality (quantum yield >50%) using simple, reproducible methods. Furthermore, two methods of incorporating the QDs into an LSC will be discussed. In the first method, single QD thick monolayers or multilayered QD thin films can be deposited onto an optically clear medium using Langmuir-Blodgett (LB) deposition. However, these QD films have poor optical qualities making them unfit for use in a LSC. Alternatively, QDs can be incorporated into a polymer slide. These highly fluorescent QD-polymer slides act as waveguides directing the photons emitted by the QDs towards the edges of the slide.

  10. 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.

  11. Synthesis and Characterization of Thionated Reduced Graphene Oxides and Their Thin Films

    NASA Astrophysics Data System (ADS)

    Jeon, Kiwan

    Thiol functionalization is one potentially useful way to tailor physical and chemical properties of graphene oxides (GOs) and reduced graphene oxides (RGOs). Despite the ubiquitous presence of thiol functional groups in diverse chemical systems, efficient thiol functionalization has been challenging for GOs and RGOs, or for carbonaceous materials in general. In this work, thionation of GOs has been achieved in high yield through two new methods that also allow concomitant chemical reduction/thermal reduction of GOs; a solid-gas metathetical reaction method with boron sulfides (BxSy) gases and a solvothermal reaction method employing phosphorus decasulfide (P4S10). The thionation products, called "mercapto reduced graphene oxides (m-RGOs)", were characterized by employing X-ray photoelectron spectroscopy, powder X-ray diffraction, UV-Vis spectroscopy, FT-IR spectroscopy, Raman spectroscopy, electron probe analysis, scanning electron microscopy, (scanning) transmission electron microscopy, nano secondary ion mass spectrometry, Ellman assay and atomic force microscopy. The excellent dispersibility of m-RGOs in various solvents including alcohols has allowed fabrication of thin films of m-RGOs. Deposition of m-RGOs on gold substrates was achieved through solution deposition and the m-RGOs were homogeneously distributed on gold surface shown by atomic force microscopy. Langmuir-Blodgett (LB) films of m-RGOs were obtained by transferring their Langmuir films, formed by simple drop casting of m-RGOs dispersion on water surface, onto various substrates including gold, glass and indium tin oxide. The m-RGO LB films showed low sheet resistances down to about 500 kΩ/sq at 92% optical transparency. The successful results make m-RGOs promising for applications in transparent conductive coatings, biosensing, etc.

  12. Kaolin-based particle films for arthropod control

    USDA-ARS?s Scientific Manuscript database

    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...

  13. Organization of Artificial Superlattices Utilizing Nanosheets as a Building Block and Exploration of Their Advanced Functions

    NASA Astrophysics Data System (ADS)

    Ma, Renzhi; Sasaki, Takayoshi

    2015-07-01

    This review covers some of the latest developments in the organization of artificial superlattice assemblies utilizing colloidal oxide or hydroxide nanosheets bearing a negative or positive charge, respectively. Various solution-based procedures, e.g., flocculation, electrostatic sequential adsorption, and Langmuir-Blodgett deposition, have been introduced for the self-assembly of 2D nanosheets. Superlattice composites or films integrated with different nanosheets may yield concerted or synergistic modulation, e.g., soft coupling or new electronic states at interfaces. This behavior offers an unprecedented opportunity for the exploration of high-performance devices, as well as advanced or novel functions that cannot be achieved with a single-component material.

  14. Stabilized lipid film based biosensor for atenolol.

    PubMed

    Nikolelis, Dimitrios P; Mitrokotsa, Maria

    2002-06-01

    This work reports a technique for the stabilization after storage in air of a lipid film based biosensor for atenolol. Microporous filters composed of glass fibers (nominal pore sizes 0.7 and 1.0 microm) were used as supports for the formation and stabilization of these devices. The lipid film is formed on the filter by polymerization prior to its use. Methacrylic acid was the functional monomer, ethylene glycol dimethacrylate was the crosslinker and 2,2'-azobis-(2-methylpropionitrile) was the initiator. The method for preparation of stabilized lipid film biosensor is studied throughout this work. The response towards atenolol of these stabilized lipid membrane biosensor, for repetitive use, composed of phosphatidylcholine was compared with planar freely suspended bilayer lipid membranes (BLMs). The stabilized lipid membranes provided similar artificial ion gating events as BLMs in the form of transient signals and can function for repetitive uses after storage in air. This will allow the practical use of the techniques for chemical sensing based on lipid films and commercialization of these devices.

  15. 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. Copyright © 2015 Elsevier B.V. All rights reserved.

  16. 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.

  17. Preferred deposition of phospholipids onto ferroelectric P(VDF-TrFE) films via polarization patterning

    NASA Astrophysics Data System (ADS)

    Heredia, A.; Machado, M.; Bdikin, I. K.; Gracio, J.; Yudin, S.; Fridkin, V. M.; Delgadillo, I.; Kholkin, A. L.

    2010-08-01

    Ferroelectric polarization can be used to assemble various organic and inorganic species and to create nanostructures with controlled properties. In this work, we used poly(vinylidene fluoride-co-trifluoroethylene) P(VDF-TrFE), ultrathin films deposited by the Langmuir-Blodgett technique as templates for the assembly of various phospholipids, which are the essential components of cell membranes. It was observed that 1,2-di-O-hexadecyl-sn-glycero-3-phosphocholine phospholipids (DHPC) form self-assembled structures (molecular domains) on bare P(VDF-TrFE) surfaces. These were revealed by the formation of homogeneous and stable rounded blobs with diameters in the range 0.5-3 µm. Further, ferroelectric polymer films were polarized by the application of various voltages via a conducting tip using a piezoresponse force microscopy (PFM) setup and PFM images were obtained showing controlled polarization distribution. After this, the phospholipid molecules were deposited from the solution. Conventional atomic force microscopy experiments were then performed to assess the selectivity of the deposition process. It was observed that the deposition process is very sensitive to the concentration of the solution. The selective deposition was observed mainly at the polarization boundaries where the selectivity reached a maximum value of about 20-40%. In this way, the controlled assembly of organic molecules on the polymer surfaces could be achieved. In addition, the PFM tips could be functionalized by the phospholipids and switchable lines of the DHPC molecules on the P(VDF-TrFE) surface were then visualized by PFM.

  18. Pulsed Laser Deposition of the Ni-Base Superalloy Films

    NASA Astrophysics Data System (ADS)

    Shin, Joonghan; Mazumder, Jyotirmoy

    2016-03-01

    Ni-base superalloy films were deposited on single-crystal (SC) Ni-base superalloy substrates from a target with the same alloy composition by pulsed laser deposition (PLD) technique. Microstructure and growth behavior of the films deposited were investigated by X-ray diffraction and scanning electron microscopy, and atomic force microscope. The homoepitaxial growth of the SC Ni-base superalloy film occurred at the 1123 K (850 °C) substrate temperature and 2 J/cm2 pulse energy. Films generally exhibited a strong polycrystalline characteristic as the substrate temperature and pulse energy increased. The SC film had a smooth surface. The measured root mean square roughness of the SC film surface was ~6 nm. Based on the Taguchi analysis, the substrate temperature and pulse energy were the most significant process parameters influencing the structural characteristics of the films. Also, the influence of the pulse repletion rate and deposition time was not found to be significant.

  19. Biomimetic biosensor based on lipidic layers containing tyrosinase and lutetium bisphthalocyanine for the detection of antioxidants.

    PubMed

    Apetrei, C; Alessio, P; Constantino, C J L; de Saja, J A; Rodriguez-Mendez, M L; Pavinatto, F J; Ramos Fernandes, E Giuliani; Zucolotto, V; Oliveira, O N

    2011-01-15

    This paper describes the preparation of a biomimetic Langmuir-Blodgett film of tyrosinase incorporated in a lipidic layer and the use of lutetium bisphthalocyanine as an electron mediator for the voltammetric detection of phenol derivatives, which include one monophenol (vanillic acid), two diphenols (catechol and caffeic acid) and two triphenols (gallic acid and pyrogallol). The first redox process of the voltammetric responses is associated with the reduction of the enzymatically formed o-quinone and is favoured by the lutetium bisphthalocyanine because significant signal amplification is observed, while the second is associated with the electrochemical oxidation of the antioxidant and occurs at lower potentials in the presence of an electron mediator. The biosensor shows low detection limit (1.98×10(-6)-27.49×10(-6) M), good reproducibility, and high affinity to antioxidants (K(M) in the range of 62.31-144.87 μM). The excellent functionality of the enzyme obtained using a biomimetic immobilisation method, the selectivity afforded by enzyme catalysis, the signal enhancement caused by the lutetium bisphthalocyanine mediator and the increased selectivity of the curves due to the occurrence of two redox processes make these sensors exceptionally suitable for the detection of phenolic compounds. Copyright © 2010 Elsevier B.V. All rights reserved.

  20. 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.

  1. 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.

  2. The structure of oleamide films at the aluminum/oil interface and aluminum/air interface studied by Sum Frequency Generation (SFG) vibrational spectroscopy and Reflection Absorption Infrared Spectroscopy (RAIRS).

    PubMed

    Casford, Michael T L; Davies, Paul B

    2009-08-01

    The structure of oleamide (cis-9-octadecenamide) films on aluminum has been investigated by sum frequency generation vibrational spectroscopy (SFG) and reflection absorption infrared spectroscopy (RAIRS). Three different film deposition strategies were investigated: (i) films formed by equilibrium adsorption from oleamide solutions in oil, (ii) Langmuir-Blodgett films cast at 1 and 25 mN m(-1), (iii) thick spin-cast films. Both L-B and spin-cast films were examined in air and under oil. The adsorbate formed in the 1 mN m(-1) film in air showed little orientational order. For this film, the spectroscopic results and the ellipsometric thickness point to a relatively conformationally disordered monolayer that is oriented principally in the plane of the interface. Direct adsorption to the metal interface from oil results in SFG spectra of oleamide that are comparable to those observed for the 1 mN m(-1) L-B film in air. In contrast, SFG and RAIRS results for the 25 mN m(-1) film in air and SFG spectra of the spin-cast film in air both show strong conformational ordering and orientational alignment normal to the interface. The 25 mN m(-1) film has an ellipsometric thickness almost twice that of the 1 mN m(-1) L-B film. Taken in combination with the spectroscopic results, this is indicative of a well packed monolayer in air in which the hydrocarbon chain is in an essentially defect-free extended conformation with the methyl terminus oriented away from the surface. A similar structure is also deduced for the surface of the spin-cast film in air. Upon immersion of the 25 mN m(-1) L-B film in oil the SFG spectra show that this film rapidly adopts a relatively disordered structure similar to that seen for the 1 mN m(-1) L-B film in air. Immersion of the spin-cast film in oil results in the gradual disordering of the amide film over a period of several days until the observed spectra become essentially identical to those observed for direct adsorption of oleamide from oil.

  3. 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.

  4. Scale-up of water-based spider silk film casting using a film applicator.

    PubMed

    Agostini, Elisa; Winter, Gerhard; Engert, Julia

    2017-08-24

    Spider silk proteins for applications in drug delivery have attracted an increased interest during the past years. Some possible future medical applications for this biocompatible and biodegradable material are scaffolds for tissue engineering, implantable drug delivery systems and coatings for implants. Recently, we reported on the preparation of water-based spider silk films for drug delivery applications. In the current study, we describe the development of a manufacturing technique for casting larger spider silk films from aqueous solution employing a film applicator. Films were characterized in terms of morphology, water solubility, protein secondary structure, thermal stability, and mechanical properties. Different post-treatments were evaluated (phosphate ions, ethanol, steam sterilization and water vapor) to increase the content of β-sheets thereby achieving water insolubility of the films. Finally, the mechanical properties of the spider silk films were improved by incorporating 2-pyrrolidone as plasticizer. Copyright © 2017 Elsevier B.V. All rights reserved.

  5. 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.

  6. Interferometric measurement method of thin film thickness based on FFT

    NASA Astrophysics Data System (ADS)

    Shuai, Gaolong; Su, Junhong; Yang, Lihong; Xu, Junqi

    2009-05-01

    The kernel of modern interferometry is to obtain necessary surface shape and parameter by processing interferogram with reasonable algorithm. The paper studies the basic principle of interferometry involving 2-D FFT, proposes a new method for measuring thin film thickness based on FFT: by CCD receiving and acquired card collecting with the help of Twyman-Green interferometer, can a fringe interferogram of the measured thin film be obtained. Based on the interferogram processing knowledge, an algorithm processing software/program can be prepared to realize identification of the edge films, regional extension, filtering, unwrapping the wrapped phase etc. And in this way can the distribution of film information-coated surface be obtained and the thickness of thin film samples automatically measured. The findings indicate the PV value and RMS value of the measured film samples are 0.256 λ and 0.068 λ respectively and prove the new method has high precision.

  7. Temperature-controlled transparent-film heater based on silver nanowire-PMMA composite film.

    PubMed

    He, Xin; Liu, A'lei; Hu, Xuyang; Song, Mingxia; Duan, Feng; Lan, Qiuming; Xiao, Jundong; Liu, Junyan; Zhang, Mei; Chen, Yeqing; Zeng, Qingguang

    2016-11-25

    We fabricated a high-performance film heater based on a silver nanowire and polymethyl methacrylate (Ag NW-PMMA) composite film, which was synthesized with the assistance of mechanical lamination and an in situ transfer method. The films exhibit excellent conductivity, high figure of merit, and strong adhesion of percolation network to substrate. By controlling NW density, we prepared the films with a transmittance of 44.9-85.0% at 550 nm and a sheet resistance of 0.13-1.40 Ω sq(-1). A stable temperature ranging from 130 °C-40 °C was generated at 3.0 V within 10-30 s, indicating that the resulting film heaters show a rapid thermal response, low driving voltage and stable temperature recoverability. Furthermore, we demonstrated the applications of the film heater in defrosting and a physical therapeutic instrument. A fast defrosting on the composite film with a transmittance of 88% was observed by applying a 9 V driving voltage for 20 s. Meanwhile, we developed a physical therapeutic instrument with two modes of thermotherapy and electronic-pulse massage by using the composite films as two electrodes, greatly decreasing the weight and power consumption compared to a traditional instrument. Therefore, Ag NW-PMMA film can be a promising candidate for diversified heating applications.

  8. Temperature-controlled transparent-film heater based on silver nanowire-PMMA composite film

    NASA Astrophysics Data System (ADS)

    He, Xin; Liu, A.'lei; Hu, Xuyang; Song, Mingxia; Duan, Feng; Lan, Qiuming; Xiao, Jundong; Liu, Junyan; Zhang, Mei; Chen, Yeqing; Zeng, Qingguang

    2016-11-01

    We fabricated a high-performance film heater based on a silver nanowire and polymethyl methacrylate (Ag NW-PMMA) composite film, which was synthesized with the assistance of mechanical lamination and an in situ transfer method. The films exhibit excellent conductivity, high figure of merit, and strong adhesion of percolation network to substrate. By controlling NW density, we prepared the films with a transmittance of 44.9-85.0% at 550 nm and a sheet resistance of 0.13-1.40 Ω sq-1. A stable temperature ranging from 130 °C-40 °C was generated at 3.0 V within 10-30 s, indicating that the resulting film heaters show a rapid thermal response, low driving voltage and stable temperature recoverability. Furthermore, we demonstrated the applications of the film heater in defrosting and a physical therapeutic instrument. A fast defrosting on the composite film with a transmittance of 88% was observed by applying a 9 V driving voltage for 20 s. Meanwhile, we developed a physical therapeutic instrument with two modes of thermotherapy and electronic-pulse massage by using the composite films as two electrodes, greatly decreasing the weight and power consumption compared to a traditional instrument. Therefore, Ag NW-PMMA film can be a promising candidate for diversified heating applications.

  9. In Situ μGISAXS: II. Thaumatin Crystal Growth Kinetic

    PubMed Central

    Gebhardt, Ronald; Pechkova, Eugenia; Riekel, Christian; Nicolini, Claudio

    2010-01-01

    The formation of thaumatin crystals by Langmuir-Blodgett (LB) film nanotemplates was studied by the hanging-drop technique in a flow-through cell by synchrotron radiation micrograzing-incidence small-angle x-ray scattering. The kinetics of crystallization was measured directly on the interface of the LB film crystallization nanotemplate. The evolution of the micrograzing-incidence small-angle x-ray scattering patterns suggests that the increase in intensity in the Yoneda region is due to protein incorporation into the LB film. The intensity variation suggests several steps, which were modeled by system dynamics based on first-order differential equations. The kinetic data can be described by two processes that take place on the LB film, a first, fast, process, attributed to the crystal growth and its detachment from the LB film, and a second, slower process, attributed to an unordered association and conversion of protein on the LB film. PMID:20713011

  10. 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.

  11. Electrocaloric devices based on thin-film heat switches

    NASA Astrophysics Data System (ADS)

    Epstein, Richard I.; Malloy, Kevin J.

    2009-09-01

    We describe a new approach to refrigeration, heat pumping, and electrical generation that allows one to exploit the attractive properties of thin films of electrocaloric materials. Layers of electrocaloric material coupled with thin-film heat switches can work as either refrigerators and heat pumps 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 electrocaloric thin-film devices can be at least as high as that of current thermoelectric devices. Advanced heat switches that may use carbon nanotubes would enable thin-film refrigerators and generators to outperform conventional vapor-compression devices.

  12. 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.

  13. 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.

  14. 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.

  15. Conducting polymer-based multilayer films for instructive biomaterial coatings

    PubMed Central

    Hardy, John G; Li, Hetian; Chow, Jacqueline K; Geissler, Sydney A; McElroy, Austin B; Nguy, Lindsey; Hernandez, Derek S; Schmidt, Christine E

    2015-01-01

    Aim: To demonstrate the design, fabrication and testing of conformable conducting biomaterials that encourage cell alignment. Materials & methods: Thin conducting composite biomaterials based on multilayer films of poly(3.4-ethylenedioxythiophene) derivatives, chitosan and gelatin were prepared in a layer-by-layer fashion. Fibroblasts were observed with fluorescence microscopy and their alignment (relative to the dipping direction and direction of electrical current passed through the films) was determined using ImageJ. Results: Fibroblasts adhered to and proliferated on the films. Fibroblasts aligned with the dipping direction used during film preparation and this was enhanced by a DC current. Conclusion: We report the preparation of conducting polymer-based films that enhance the alignment of fibroblasts on their surface which is an important feature of a variety of tissues. PMID:28031928

  16. Metallosupramolecular coordination polyelectrolytes: potential building blocks for molecular-based devices.

    PubMed

    Kurth, Dirk G

    2002-04-01

    Metal-ion-induced self-assembly of ditopic ligands, based on bisterpyridines, and transition metal ions result in formation of metallosupramolecular coordination polyelectrolytes (MEPE). The positive charge of MEPE can be utilized in several ways to process highly ordered architectures. Alternating adsorption of MEPE and oppositely charged polyelectrolytes on solid substrates results in multilayers. The sequential nature of this process allows combining MEPEs with other functional components. This process permits nanometer thickness control, is readily adapted for automated processing, and is applicable to two-dimensional substrates as well as to colloidal templates. The surface chemical properties of MEPE are readily controlled by complexing MEPE with negatively charged amphiphiles. The resulting polyelectrolyte-amphiphile complexes (PAC) are soluble in organic solvents and form liquid crystalline phases. The PAC also spreads at the air-water interface as Langmuir monolayer, which can be transferred onto solid substrates. The resulting Langmuir-Blodgett multilayers are highly ordered and anisotropic. Materials with transition metal ions possess many interesting properties, including spin transitions, magnetism, as well as photochemical assets that are relevant for the construction of functional devices and materials. The presented approach combines principles of supramolecular and colloidal chemistry as well as surface science, is highly modular in nature, and provides extensive control of structure and function from molecular to macroscopic levels.

  17. Anatase titanium dioxide thin film based carbon monoxide gas sensor

    NASA Astrophysics Data System (ADS)

    Al-Homoudi, Ibrahim Abdullah

    2005-11-01

    Gas sensors are finding increasing number of applications in home, industrial and automotive areas. Incomplete combustion in gas and coal fired electricity plants can generate harmful gases and pollutants. The purpose of the proposed research was to develop titanium dioxide (TiO2) thin film based materials for carbon monoxide (CO) gas sensing to detect a very low concentration (20--100 ppm) of CO gas. Anatase TiO2 thin films (100--1000 nm) have been developed using pulsed DC magnetron reactive sputtering technique on glass, Si(100) and sapphire substrates. Optimum deposition parameters were determined by studying the crystalline quality of the films using X-ray diffraction. The x-ray photo-emission (XPS) studies indicated a good stoichiometric TiO 2 surface with O to Ti ratio of 1.95 +/- 0.05. Film residual stress was measured using curvature measurements of the substrates before and after deposition of the films. The anatase TiO2 thin films on sapphire showed lower stress compared to glass and Si substrates. Raman spectroscopy measurements were further used to study the correlation between the residual stress and Raman shifts of characteristic peaks to obtain a calibration factor. Anatase TiO2 thin films showed n-type electrical conductivity indicating the presence of shallow electron donors caused by oxygen vacancies. The response of films was tested for 100 ppm of CO in 100 sccm of N2 gas flow as a function of temperature, film thickness, and the substrate. The films show the highest response at 200°C. The films grown on sapphire substrates show the highest response. The response is higher for a film with 1000 nm thickness than the 250 nm thickness film. The CO sensor was tested as a function of CO concentration and as well as under different environs: The films respond to very low concentration, 20--100 ppm, of CO gas, with good reversibility. The response and recovery time were from 2 min to 1 min as the concentration increased from 20 to 100 ppm. It can be

  18. Water-based oxygen-sensor films.

    PubMed

    Habibagahi, Arezoo; Mébarki, Youssef; Sultan, Yasir; Yap, Glenn P A; Crutchley, Robert J

    2009-08-01

    The luminescent cyclometalated iridium complex [Ir(fppy)(2)(t-Bu-iCN)(2)]CF(3)SO(3), 1 (fppy = 4-(2-pyridyl)benzaldehyde, and t-Bu-iCN = tert-butyl isocyanide), was synthesized and characterized by X-ray crystallography and (1)H NMR, absorption, and emission spectroscopies. Complex 1 was quantitatively bound to the water-soluble amine-functionalized polymer Silamine D208-EDA by reductive amination, to produce 2. The quantum yield of emission and excited state lifetime of 2 (varphi(em) = 0.23 and tau = 20.6 mus) are comparable to that of the model complex [Ir(tpy)(2)(t-Bu-iCN)(2)]CF(3)SO(3), 3 (tpy = 2-(p- tolyl) pyridine) with varphi(em) = 0.28 and tau = 35.6 mus. Aqueous blends of 2 with Silamine and colloidal microcrystalline cellulose (MC) were used to prepare oxygen-sensor films. Oxygen sensitivities of these films were determined as a function of Silamine:MC ratio and obeyed Stern-Volmer kinetics. The optimum oxygen-sensor film composition was 2 in 1:1 Silamine:MC, which had an oxygen sensitivity of 0.502 over an atmospheric pressure range of 0.007-45 psi. Temperature sensitivity (percentage loss of intensity per degrees C) of this film was determined to be -1.1 and -1.4% degrees C(-1) at vacuum and 1 bar atmospheric pressure, respectively. These results were compared to those of films incorporating dispersions of 1 and 3. Luminescence microscopy of 9:1, 1:1, and 1:5 Silamine:MC films of 2 show that the charged iridium complex in 2 associates with the surface of MC and lifetime measurements of these films show an increase in lifetime with increasing MC fraction. The optimum quenching sensitivity observed for the 1:1 Silamine:MC film suggests that the diffusion of oxygen must decrease with increasing fraction of MC and thereby decrease oxygen sensitivity. These novel materials offer an environmentally friendly alternative to the preparation of oxygen-sensor films.

  19. 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. Copyright © 2015 Elsevier Ltd. All rights reserved.

  20. 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.

  1. 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.

  2. 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.

  3. 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

  4. High-temperature superconducting thin-film-based electronic devices

    SciTech Connect

    Wu, X.D; Finokoglu, A.; Hawley, M.; Jia, Q.; Mitchell, T.; Mueller, F.; Reagor, D.; Tesmer, J.

    1996-09-01

    This the final report of a one-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The project involved optimization of processing of Y123 and Tl-2212 thin films deposited on novel substrates for advanced electronic devices. The Y123 films are the basis for development of Josephson Junctions to be utilized in magnetic sensors. Microwave cavities based on the Tl-2212 films are the basis for subsequent applications as communication antennas and transmitters in satellites.

  5. Thermoforming of film-based biomedical microdevices.

    PubMed

    Truckenmüller, Roman; Giselbrecht, Stefan; Rivron, Nicolas; Gottwald, Eric; Saile, Volker; van den Berg, Albert; Wessling, Matthias; van Blitterswijk, Clemens

    2011-03-18

    For roughly ten years now, a new class of polymer micromoulding processes comes more and more into the focus both of the microtechnology and the biomedical engineering community. These processes can be subsumed under the term "microthermoforming". In microthermoforming, thin polymer films are heated to a softened, but still solid state and formed to thin-walled microdevices by three-dimensional stretching. The high material coherence during forming is in contrast to common polymer microreplication processes where the material is processed in a liquid or flowing state. It enables the preservation of premodifications of the film material. In this progress report, we review the still young state of the art of microthermoforming technology as well as its first applications. So far, the applications are mainly in the biomedical field. They benefit from the fact that thermoformed microdevices have unique properties resulting from their special, unusual morphology. The focus of this paper is on the impact of the new class of micromoulding processes and the processed film materials on the characteristics of the moulded microdevices and on their applications. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. A film pressure sensor based on optical fiber Bragg grating

    NASA Astrophysics Data System (ADS)

    Zhang, Zhichun; Deng, Gang; Dai, Yongbo; Liu, Yanju; Leng, Jinsong

    2010-03-01

    The measurement of pressure is essential for the design and flying controlling of aircraft. In order to measure the surface pressures of the aircraft, the common pressure tube method and Pressure sensitive paint measurement method have their own disadvantages, and are not applicable to all aircraft structures and real time pressure monitoring. In this paper, a novel thin film pressure sensor based on Fiber Bragg Grating (FBG) is proposed, using FBG measuring the tangential strain of the disk sensing film. Theoretical circle strain of the disk sensing film of the pressure sensor under pressure and temperature variation are analyzed, and the linear relationship between FBG center wavelength shift and pressure, temperature variation is gotten. The pressure and temperature calibration experiments prove the theoretical analysis. But the calibration sensing parameters are small than the calculating ones, which is caused by the constraint of optical fibre to the thin sensing film.

  7. 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.

  8. 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

  9. 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…

  10. Sharpness of edges at different film orientations in film based tomography

    NASA Astrophysics Data System (ADS)

    Bushlin, Y.; Notea, A.; Lindegaard-Andersen, A.; Rheinlander, J.

    A mathematical description of the intensity summation image, which contains information about the interior of an object depending on the orientation of the film in the image space, is presented. The calculated results are compared with experimental images generated for alumina test specimens. Emphasis is given to the outer boundaries of high absorption objects where the mathematical description reduces to simple analytical expressions. It is shown that in rotational film based X-ray tomography some of the image characteristics, such as the long-range degradation of edges and the position dependent on the edge response, result from the intensity summation during rotation. From the analysis of the outer edge response it is demonstrated that an edge is defined better in vertical oriented film than in horizontal.

  11. Surface chemistry and spectroscopy of UG8 asphaltene Langmuir film, part 2.

    PubMed

    Orbulescu, Jhony; Mullins, Oliver C; Leblanc, Roger M

    2010-10-05

    While there has been much focus on asphaltenes in toluene, there has been much less focus on asphaltenes in other solvents. It is important to quantify characteristics of asphaltenes in solvents besides toluene in order to better assess their molecular architecture as well as their fundamental aggregation characteristics. The present work focuses on the investigation of UG8 asphaltene Langmuir films at the air-water interface using chloroform as spreading solvent. The results are compared to the results recently obtained using toluene as spreading solvent. Surface pressure-area isotherms and UV-vis spectroscopy indicate that asphaltenes form smaller nanoaggregates in chloroform than in toluene in similar concentration ranges. Still these nanoaggreates share common features with those in toluene. From the surface pressure-area and compression-decompression isotherms, Brewster angle microscopy, and p-polarized infrared reflection-absorption spectroscopy, it was concluded that small size aggregates are spread on the water surface and the compression of the film leads to formation of large aggregates. The films (Langmuir-Schaefer and Langmuir-Blodgett) studied by atomic force microscopy reveal the existence of nanoaggregates spread on the water surface that coexist with large aggregates formed during compression. In addition to these findings, the spreading solvent, chloroform, allows the determination of asphaltene absorption bands using in situ UV-vis spectroscopy at the air-water interface after 15 min waiting time period. The absorbance data carried out after waiting a time period of 1 h shows similar features with the ones carried out after only 15 min; therefore, there is no need to wait 1 h as in the case when toluene is used as spreading solvent. A comparison of the data obtained from chloroform and toluene shows that smaller aggregate sizes are obtained from chloroform as suggested from the surface pressure-area isotherm, in situ UV-vis spectroscopy, and

  12. Field emission from graphene based composite thin films

    NASA Astrophysics Data System (ADS)

    Eda, Goki; Emrah Unalan, H.; Rupesinghe, Nalin; Amaratunga, Gehan A. J.; Chhowalla, Manish

    2008-12-01

    Field emission from graphene is challenging because the existing deposition methods lead to sheets that lay flat on the substrate surface, which limits the field enhancement. Here we describe a simple and general solution based method for the deposition of field emitting graphene/polymer composite thin films. The graphene sheets are oriented at some angles with respect to the substrate surface leading to field emission at low threshold fields (˜4Vμm-1). Our method provides a route for the deposition of graphene based thin film field emitter on different substrates, opening up avenues for a variety of applications.

  13. Nanocrystalline cellulose (NCC) reinforced alginate based biodegradable nanocomposite film.

    PubMed

    Huq, Tanzina; Salmieri, Stephane; Khan, Avik; Khan, Ruhul A; Le Tien, Canh; Riedl, Bernard; Fraschini, Carole; Bouchard, Jean; Uribe-Calderon, Jorge; Kamal, Musa R; Lacroix, Monique

    2012-11-06

    Nanocrystalline cellulose (NCC) reinforced alginate-based nanocomposite film was prepared by solution casting. The NCC content in the matrix was varied from 1 to 8% ((w/w) % dry matrix). It was found that the nanocomposite reinforced with 5 wt% NCC content exhibits the highest tensile strength which was increased by 37% compared to the control. Incorporation of NCC also significantly improved water vapor permeability (WVP) of the nanocomposite showing a 31% decrease due to 5 wt% NCC loading. Molecular interactions between alginate and NCC were supported by Fourier Transform Infrared Spectroscopy. The X-ray diffraction studies also confirmed the appearance of crystalline peaks due to the presence of NCC inside the films. Thermal stability of alginate-based nanocomposite films was improved after incorporation of NCC. Copyright © 2012 Elsevier Ltd. All rights reserved.

  14. Organic Polymeric Electro-Optic Materials: Synthesis, Processing and Device Applications

    DTIC Science & Technology

    1993-04-01

    A number of polymeric second and third order nonlinear optical materials were designed and synthesized. The materials were characterized for their...performed.... Electro-Optic Effects, Guided Wave Devices, Organic Polymers, Nonlinear Optical Materials , Langmuir-Blodgett Films, Second Harmonic Generation

  15. Films.

    ERIC Educational Resources Information Center

    Philadelphia Board of Education, PA. Div. of Instructional Materials.

    The Affective Curriculum Research Project produced five films and two records during a series of experimental summer programs. The films and records form part of a curriculum designed to teach to the concerns of students. The films were an effort to describe the Philadelphia Cooperative Schools Program, to explain its importance, and to…

  16. MBE growth of Fe-based superconducting films

    NASA Astrophysics Data System (ADS)

    Ueda, S.; Yamagishi, T.; Takeda, S.; Agatsuma, S.; Takano, S.; Mitsuda, A.; Naito, M.

    2011-11-01

    We report MBE growth of the iron-based superconductors, Sr1-xKxFe2As2, Ba1-xKxFe2As2, and SmFeAs(O,F). In the growth of Sr1-xKxFe2As2 and Ba1-xKxFe2As2 films, the key to incorporating volatile K in films is low-temperature (300-350 °C) growth in reduced As flux. The highest Tc so far obtained are Tcon (Tcend) = 33.4K (31.0 K) and 38.3 K (35.5 K) for Sr1-xKxFe2As2 and Ba1-xKxFe2As2, respectively. In the growth of superconducting SmFeAs(O,F), we have adopted two approaches. In the first approach, we first grew F-free SmFeAsO films, and subsequently introduced F to the films via F diffusion from an overlayer of SmF3 or NdF3. In the second approach, we attempted the growth of as-grown superconducting SmFeAs(O,F) films by coevaporating Sm, SmF3, Fe, and As. In both the approaches, the growth temperature was as high as 650 °C. So far better results have been obtained by the first F diffusion method. The films prepared by F diffusion showed Tcon (Tcend) = 52 K (48.6 K) whereas the as-grown films showed Tcon = 47 K but with a long transition tail.

  17. Mechanical and electrical properties of calcinated tea-based cellulose composite films

    NASA Astrophysics Data System (ADS)

    Tippabattini, Jayaramudu; Kim, Jung Woong; Ko, Hyun-U.; Kafy, Abdullahil; Li, Yaguang; Kim, Jaehwan

    2017-04-01

    In the present investigation, calcinated tea-based cellulose composite films were fabricated via solution casting technique. The fabricated films were characterized by using Fourier transform infrared spectroscopy and differential scanning calorimetry. The effect of calcinated tea loading on the properties of the calcinated tea-based cellulose composite films was studied. The results were showed that the calcinated tea composite films display better mechanical properties and dielectric constant than the pure cellulose films.

  18. Ferromagnetism in antiferromagnetic NiO-based thin films

    NASA Astrophysics Data System (ADS)

    Lin, Yuan-Hua; Zhan, Bin; Nan, Ce-Wen; Zhao, Rongjuan; Xu, Xiang; Kobayashi, M.

    2011-08-01

    Polycrystalline NiO-based thin films with Li or/and transition metal ions (V, Cr, Mn, Fe, Co, Cu, Zn) doping have been prepared by a sol-gel spin-coating method. Magnetization measurements reveal that V-, Fe-, and Mn-doped NiO thin films show obvious room-temperature ferromagnetic behaviors and ferromagnetic properties can be enhanced by the Li co-doping. Microstructure and X-ray core-level photoemission spectra analysis indicate that the ferromagnetism was not from the impurity TM metal cluster and may be ascribed to double exchange coupling effects via Li-induced holes.

  19. Nanocrystalline films of soft magnetic iron-based alloys

    NASA Astrophysics Data System (ADS)

    Sheftel', E. N.; Bannykh, O. A.

    2006-10-01

    The physicochemical and structural aspects of designing soft magnetic alloys Fe- MX (where M is a Group III V metal of the periodic table and X = C, N, O) in the form of nanocrystalline films precipitation-hardened by refractory interstitial phases are discussed and developed. The results of studying the structure and magnetic properties of Fe78Zr10N12 films are reported. The films in the amorphous state are produced by reactive magnetron sputtering. Upon annealing at 300 600°C, the amorphous films crystallize to form mainly a bcc α-Fe-based phase and the fcc ZrN phase. The grain size of the bcc phase is shown to increase from ˜3 nm to ˜30 nm as the annealing temperature increases; the grain size of the fcc phase does not exceed 2 3 nm. Films annealed at 400°C exhibit a record level of magnetic properties: H c = 5 6 A/m and B s = 1.7 1.8 T. The experimental results obtained confirm the validity of our scientific approach.

  20. 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.

  1. Monte-Carlo based prediction of radiochromic film response for hadrontherapy dosimetry

    NASA Astrophysics Data System (ADS)

    Frisson, T.; Zahra, N.; Lautesse, P.; Sarrut, D.

    2009-07-01

    A model has been developed to calculate MD-55-V2 radiochromic film response to ion irradiation. This model is based on photon film response and film saturation by high local energy deposition computed by Monte-Carlo simulation. We have studied the response of the film to photon irradiation and we proposed a calculation method for hadron beams.

  2. Supramolecular Assembly of Organic-Inorganic Hybrid Polyoxometalate Nanoclusters at Solid-liquid Interface

    NASA Astrophysics Data System (ADS)

    Qi, Na; Jing, Benxin; Zhu, Yingxi

    2013-03-01

    Polyoxometalate (POM) inorganic nanoclusters have recently emerged as building blocks for the design and synthesis of novel functional materials for broad applications ranging from catalysis to nanomedicines. Rather than taking the slow self-assembly of POMs in aqueous solutions, we have investigated the assembly of hybrid Anderson-type Mo-based POMs with organic ligands at a solid surface by Langmuir-Blodgett (LB) deposition and characterized the films by AFM, TEM, and X-ray diffraction. We have observed the formation of well-ordered monolayer or bilayer consisting of periodic arrangement of hybrid POM nanoclusters, showing a strong dependence on substrate chemistry and LB compression pressure. The controlled assembly of hybrid POM nanocluster films by LB deposition could be used as a template with stoichiometric crystalline nanostructure to the programmed assembly of novel multi-functional supramolecular complexes.

  3. Structure and Properties of Carbon Based Nanocomposite Films

    DTIC Science & Technology

    2004-03-18

    Research Institute for Technical Physics and Materials Science of the Hungarian Academy of Sciences Structure and Properties of Carbon Based...MAR 2004 2. REPORT TYPE N/A 3. DATES COVERED - 4. TITLE AND SUBTITLE Structure and Properties of Carbon Based Nanocomposite Films 5a...INTRODUCTION The theoretically predicted superhard β-C3N4 has not yet been experimentally realized, however, the different CNx structures and their

  4. Polysaccharide films at an air/liquid and a liquid/silicon interface: effect of the polysaccharide and liquid type on their physical properties.

    PubMed

    Taira, Yasunori; McNamee, Cathy E

    2014-11-14

    We investigated the effect of the polysaccharide type, the subphase on which the Langmuir monolayers were prepared, and the liquid in which the properties of the transferred monolayers were measured on the physical properties of the polysaccharide films at an air/aqueous interface and at a silicon substrate, and the forces and friction of the polysaccharide transferred films when measured in solution against a silica probe. Chitosan was modified with a silane coupling agent to make chitosan derived compounds with a low and a medium molecular weight. Chitin and the chitosan-derived compounds were used to make Langmuir monolayers at air/water and air/pH 9 buffer interfaces. The monolayers were transferred to silicon substrates via Langmuir-Blodgett deposition, and the chitosan-derived compounds subsequently chemically reacted with the silicon substrates. Atomic force microscope force and friction measurements were made in water and in the pH 9 buffer, where the water and the pH 9 buffer acted as a good and a bad solvent for the polysaccharides, respectively. The polysaccharide type affected the friction of the polysaccharide film, where the physically adsorbed chitin gave the lowest friction. The friction of L-chitosan was higher than that of M-chitosan in water, suggesting that the molecular weight of the polymer affects its lubricating ability. The forces and friction of the polysaccharide films changed when the subphase on which the Langmuir monolayers were formed was changed or when the liquid in which the properties of the films adsorbed at the silicon substrate were measured was changed. The friction increased significantly when the liquid was changed from water to the pH 9 buffer. This increase was explained by the reduced charge of the chitin and chitosan-derived materials due to the pH increase, the screening of the charges by the salts in the buffer, and the possible hardening of the monolayer caused by the adsorption of salts from the buffer.

  5. Antistaphylococcal Nanocomposite Films Based on Enzyme-Nanotube Conjugates

    PubMed Central

    Pangule, Ravindra C.; Brooks, Sarah J.; Dinu, Cerasela Zoica; Bale, Shyam Sundhar; Salmon, Sharon L.; Zhu, Guangyu; Metzger, Dennis W.; Kane, Ravi S.; Dordick, Jonathan S.

    2010-01-01

    Infection with antibiotic-resistant pathogens such as methicillin-resistant Staphylococcus aureus (MRSA) is one of the primary causes of hospitalizations and deaths. To address this issue, we have designed antimicrobial coatings incorporating carbon nanotube-enzyme conjugates that are highly effective against antibiotic–resistant pathogens. Specifically, we incorporated conjugates of carbon nanotubes with lysostaphin, a cell wall degrading enzyme, into films to impart bactericidal properties against Staphylococcus aureus and Staphylococcus epidermidis. We fabricated and characterized nanocomposites containing different conjugate formulations and enzyme loadings. These enzyme–based composites were highly efficient in killing MRSA (>99% within 2 h) without release of the enzyme into solution. Additionally, these films were reusable and stable under dry storage conditions for a month. Such enzyme–based film formulations may be used to prevent growth of pathogenic and antibiotic-resistant microorganisms on various common surfaces in hospital settings. Polymer and paint films containing such antimicrobial conjugates, in particular, could be advantageous to prevent risk of staphylococcal-specific infection and biofouling. PMID:20604574

  6. Physically based DC lifetime model for lead zirconate titanate films

    NASA Astrophysics Data System (ADS)

    Garten, Lauren M.; Hagiwara, Manabu; Ko, Song Won; Trolier-McKinstry, Susan

    2017-09-01

    Accurate lifetime predictions for Pb(Zr0.52Ti0.48)O3 thin films are critical for a number of applications, but current reliability models are not consistent with the resistance degradation mechanisms in lead zirconate titanate. In this work, the reliability and lifetime of chemical solution deposited (CSD) and sputtered Pb(Zr0.52Ti0.48)O3 thin films are characterized using highly accelerated lifetime testing (HALT) and leakage current-voltage (I-V) measurements. Temperature dependent HALT results and impedance spectroscopy show activation energies of approximately 1.2 eV for the CSD films and 0.6 eV for the sputtered films. The voltage dependent HALT results are consistent with previous reports, but do not clearly indicate what causes device failure. To understand more about the underlying physical mechanisms leading to degradation, the I-V data are fit to known conduction mechanisms, with Schottky emission having the best-fit and realistic extracted material parameters. Using the Schottky emission equation as a base, a unique model is developed to predict the lifetime under highly accelerated testing conditions based on the physical mechanisms of degradation.

  7. Antistaphylococcal nanocomposite films based on enzyme-nanotube conjugates.

    PubMed

    Pangule, Ravindra C; Brooks, Sarah J; Dinu, Cerasela Zoica; Bale, Shyam Sundhar; Salmon, Sharon L; Zhu, Guangyu; Metzger, Dennis W; Kane, Ravi S; Dordick, Jonathan S

    2010-07-27

    Infection with antibiotic-resistant pathogens such as methicillin-resistant Staphylococcus aureus (MRSA) is one of the primary causes of hospitalizations and deaths. To address this issue, we have designed antimicrobial coatings incorporating carbon nanotube-enzyme conjugates that are highly effective against antibiotic-resistant pathogens. Specifically, we incorporated conjugates of carbon nanotubes with lysostaphin, a cell wall degrading enzyme, into films to impart bactericidal properties against Staphylococcus aureus and Staphylococcus epidermidis. We fabricated and characterized nanocomposites containing different conjugate formulations and enzyme loadings. These enzyme-based composites were highly efficient in killing MRSA (>99% within 2 h) without release of the enzyme into solution. Additionally, these films were reusable and stable under dry storage conditions for a month. Such enzyme-based film formulations may be used to prevent growth of pathogenic and antibiotic-resistant microorganisms on various common surfaces in hospital settings. Polymer and paint films containing such antimicrobial conjugates, in particular, could be advantageous to prevent risk of staphylococcal-specific infection and biofouling.

  8. 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

  9. Biodegradable Films Based on Gelatin Extracted from Chrome Leather Scrap.

    PubMed

    Dang, Xugang; Shan, Zhihua; Chen, Hui

    2017-09-19

    A biodegradable film based on gelatin extracted from chrome leather scrap was studied in this paper. According to the results of a variety of characterization, the extracted gelatin contains 13 kinds of amino acid; the chrome content is 30mg/kg, mineral and salt content are both at low levels and the nitrogen content is 43.84%. Its molecular weight has been measured at about 6.5kDa ∼26.6kDa, and the average particle distribution appears to be 125nm with a narrow distribution. When the extracted gelatin was modified with the β-cyclodextrin to prepare the biodegradable films, the β-cyclodextrin and gelatin blends can build up perfect compatibility and film-forming properties. Comparing to the gelatin film without β-cyclodextrin, the viscosity, biodegradability, thermal stability and physical properties of the β-cyclodextrin and gelatin blends in the present research were significantly increased, especially when the ratio of β-cyclodextrin to gelatin was 1:2, the biodegradation rates reached 81%, elongation at break 15.74% and the tensile strength 122.34MPa. The blends show perfect swelling properties and overcome the rapid solubility drawback of extracted gelatin. Copyright © 2017 Elsevier B.V. All rights reserved.

  10. 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. Copyright © 2016 Elsevier B.V. All rights reserved.

  11. Thick-film humidity sensor based on porous ? material

    NASA Astrophysics Data System (ADS)

    Qu, Wenmin; Meyer, Jörg-Uwe

    1997-06-01

    A new compact, robust, yet fast and highly sensitive ceramic humidity sensor based on the semiconducting metal oxide 0957-0233/8/6/002/img2 has been developed using thick-film technology. The sensor element possesses a novel `sandwich' configuration with a 0957-0233/8/6/002/img3 porous 0957-0233/8/6/002/img2 ceramic layer sandwiched by two 0957-0233/8/6/002/img5 polarity-reversed interdigitated metal films. Instead of traditional glass frits, LiCl powders were used as adhesion promoters. The sintered ceramic layer exhibits a porous structure. The degree of the porosity is controlled by the amount of LiCl added and by the firing conditions for the ceramic. The surfaces of ceramic grains behave like electrolytes and easily adsorb water vapour through the pores. The novel electrode arrangement combines the advantages of humidity sensors in the form of a parallel capacitor with those in the form of an interdigital capacitor. The influence of temperature on the sensor characteristics has been compensated for by integrating a thick-film NTC resistor. The results of studies on the material processing, the fabrication and the characterization of this novel thick-film humidity sensor are described.

  12. Hybrid Thin Films Based Upon Polyoxometalates-Polymer Assembly

    NASA Astrophysics Data System (ADS)

    Qi, Na; Jing, Benxin; Zhu, Yingxi

    2014-03-01

    Block copolymers (BCPs) and polyoxometalates (POMs) have been used individually as building blocks for design and synthesis of novel functional materials. POM nanoclusters, the assemblies of transition metal oxides with well-defined atomic coordination structure, have been recently explored as novel nanomaterials... for catalysis, semiconductors, and even anti-cancer treatment due to their unique chemical, optical and electrical characteristics. We have explored the blending of inorganic POM nanocluster with BCPs into hierarchaically structured inorganic-organic hybrid nanocomposites. Using polystyrene-b-poly(ethylene oxide) (PS-b-PEO) thin films as the template, we have observed that the spatial organization of BCP thin films is modified by molybdenum based POM nanocluster to form 2D in-plane hexagonal ordered or 3D ordered network of POM-BCP assemblies, depending on the concentration ratio of POM to PS-b-PEO. The dielectric properties of such hybrid thin films can be enhanced by embedded POMs but show a strong dependence on the supramolecular structures of POM-polymer complexes. The assembly of nanoclusters in BCP-templated thin films could pave a new path to design new hybrid nanocomposites with uniquely combined functionality and material properties.

  13. 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

  14. Thin film display based on polymer waveguides.

    PubMed

    Park, Suntak; Park, Bong Je; Yun, Sungryul; Nam, Saekwang; Park, Seung Koo; Kyung, Ki-Uk

    2014-09-22

    This paper reports thin, transparent, and soft displays based on polymer waveguides that are compliant with curvilinear interfaces. In order to prove a feasibility of optical waveguide for a flexible display, we suggest the waveguide fabricated by a multi-step lithography process using two photo-curable pre-polymers with different refractive index. The displays are composed of light sources, polymer waveguides, and scatter patterns. The light signal propagating through the waveguides forms images of the scatter patterns by deflecting the light signals to outer surface. The scatter patterns are configured to a seven-segment. The seven-segment design with a switching methodology of the light sources contributes to selectively representing all decimal numbers from 0 to 9 by combination of activated segments. For a large area display based on the proposed methodology, a single light source interconnected to multi-waveguide section is integrated with a QWERTY key pad design. The display shows high transparency and flexibility without visual distortion.

  15. Filmless versus film-based systems in radiographic examination costs: an activity-based costing method.

    PubMed

    Muto, Hiroshi; Tani, Yuji; Suzuki, Shigemasa; Yokooka, Yuki; Abe, Tamotsu; Sase, Yuji; Terashita, Takayoshi; Ogasawara, Katsuhiko

    2011-09-30

    Since the shift from a radiographic film-based system to that of a filmless system, the change in radiographic examination costs and costs structure have been undetermined. The activity-based costing (ABC) method measures the cost and performance of activities, resources, and cost objects. The purpose of this study is to identify the cost structure of a radiographic examination comparing a filmless system to that of a film-based system using the ABC method. We calculated the costs of radiographic examinations for both a filmless and a film-based system, and assessed the costs or cost components by simulating radiographic examinations in a health clinic. The cost objects of the radiographic examinations included lumbar (six views), knee (three views), wrist (two views), and other. Indirect costs were allocated to cost objects using the ABC method. The costs of a radiographic examination using a filmless system are as follows: lumbar 2,085 yen; knee 1,599 yen; wrist 1,165 yen; and other 1,641 yen. The costs for a film-based system are: lumbar 3,407 yen; knee 2,257 yen; wrist 1,602 yen; and other 2,521 yen. The primary activities were "calling patient," "explanation of scan," "take photographs," and "aftercare" for both filmless and film-based systems. The cost of these activities cost represented 36.0% of the total cost for a filmless system and 23.6% of a film-based system. The costs of radiographic examinations using a filmless system and a film-based system were calculated using the ABC method. Our results provide clear evidence that the filmless system is more effective than the film-based system in providing greater value services directly to patients.

  16. Filmless versus film-based systems in radiographic examination costs: an activity-based costing method

    PubMed Central

    2011-01-01

    Background Since the shift from a radiographic film-based system to that of a filmless system, the change in radiographic examination costs and costs structure have been undetermined. The activity-based costing (ABC) method measures the cost and performance of activities, resources, and cost objects. The purpose of this study is to identify the cost structure of a radiographic examination comparing a filmless system to that of a film-based system using the ABC method. Methods We calculated the costs of radiographic examinations for both a filmless and a film-based system, and assessed the costs or cost components by simulating radiographic examinations in a health clinic. The cost objects of the radiographic examinations included lumbar (six views), knee (three views), wrist (two views), and other. Indirect costs were allocated to cost objects using the ABC method. Results The costs of a radiographic examination using a filmless system are as follows: lumbar 2,085 yen; knee 1,599 yen; wrist 1,165 yen; and other 1,641 yen. The costs for a film-based system are: lumbar 3,407 yen; knee 2,257 yen; wrist 1,602 yen; and other 2,521 yen. The primary activities were "calling patient," "explanation of scan," "take photographs," and "aftercare" for both filmless and film-based systems. The cost of these activities cost represented 36.0% of the total cost for a filmless system and 23.6% of a film-based system. Conclusions The costs of radiographic examinations using a filmless system and a film-based system were calculated using the ABC method. Our results provide clear evidence that the filmless system is more effective than the film-based system in providing greater value services directly to patients. PMID:21961846

  17. Films

    NASA Astrophysics Data System (ADS)

    Li, Ming; Zhang, Yang; Shao, Yayun; Zeng, Min; Zhang, Zhang; Gao, Xingsen; Lu, Xubing; Liu, J.-M.; Ishiwara, Hiroshi

    2014-09-01

    In this paper, we investigated the microstructure and electrical properties of Bi2SiO5 (BSO) doped SrBi2Ta2O9 (SBT) films deposited by chemical solution deposition. X-ray diffraction observation indicated that the crystalline structures of all the BSO-doped SBT films are nearly the same as those of a pure SBT film. Through BSO doping, the 2Pr and 2Ec values of SBT films were changed from 15.3 μC/cm2 and 138 kV/cm of pure SBT to 1.45 μC/cm2 and 74 kV/cm of 10 wt.% BSO-doped SBT. The dielectric constant at 1 MHz for SBT varied from 199 of pure SBT to 96 of 10 wt.% BSO-doped SBT. The doped SBT films exhibited higher leakage current than that of non-doped SBT films. Nevertheless, all the doped SBT films still had small dielectric loss and low leakage current. Our present work will provide useful insights into the BSO doping effects to the SBT films, and it will be helpful for the material design in the future nonvolatile ferroelectric memories.

  18. Team-based thin-film CIS research activities

    NASA Astrophysics Data System (ADS)

    Ullal, Harin S.

    1997-02-01

    This paper describes the team-based thin-film copper indium diselenide (CIS) research activities. The CIS team was formed in December 1994 in Kona, Hawaii. Originally, the team had two working groups: the "Junction" and the "Absorber" groups. Currently, there are four working groups the Present Junction, New Junction, Substrate/Mo Impact, and the Transient Effect groups. We have completed extensive data compilation of CIS-based films and solar cells using various techniques such as Auger, photoluminescence, scanning electron microscopy, secondary-ion mass spectrometry, X-ray photoelectron spectroscopy, X-ray diffraction, capacitance-voltage, light and dark current-voltage, and quantum efficiency. Studies are under way to understand the fundamental mechanisms that demonstrate a total-area, high efficiency of 17.7% in CuInGaSe2 devices using chemical-bath deposition (CBD) CdS. Alternate buffer layers are also being investigated to replace the CBD CdS. The impact of various Mo substrates from the various industrial partners has been investigated, and the results are reported. A study is under way to investigate the transient effects in encapsulated/laminated thin-film CIS-based devices.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  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. Naphthacene Based Organic Thin Film Transistor With Rare Earth Oxide

    SciTech Connect

    Konwar, K.; Baishya, B.

    2010-12-01

    Naphthacene based organic thin film transistors (OTFTs) have been fabricated using La{sub 2}O{sub 3}, as the gate insulator. All the OTFTs have been fabricated by the process of thermal evaporation in vacuum on perfectly cleaned glass substrates with aluminium as source-drain and gate electrodes. The naphthacene film morphology on the glass substrate has been studied by XRD and found to be polycrystalline in nature. The field effect mobility, output resistance, amplification factor, transconductance and gain bandwidth product of the OTFTs have been calculated by using theoretical TFT model. The highest value of field effect mobility is found to be 0.07x10{sup -3} cm{sup 2}V{sup -1}s{sup -1} for the devices annealed in vacuum at 90 deg. C for 5 hours.

  5. Self-assembled dual-sided hemispherical nano-dimple-structured broadband antireflection coatings

    NASA Astrophysics Data System (ADS)

    Lin, Cheng-Yen; Lin, Kun-Yi; Tsai, Hui-Ping; He, Yi-Xuan; Yang, Hongta

    2016-11-01

    A non-lithography-based approach is developed in this study for assembling monolayer close-packed hemispherical nano-dimple arrays on both sides of a PET film by a scalable Langmuir-Blodgett technology. The resulting gratings greatly suppress specular reflection and therefore enhance specular transmission for a broad range of visible wavelengths, resulting from a gradual change in the effective refractive index at air/PET interface. The experimental results reveal that the antireflection properties of the as-fabricated coatings are affected by the size of the nano-dimples. Moreover, both optical performances of single-sided and dual-sided nano-dimple-structured coatings have been investigated in this study.

  6. 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.

  7. 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.

  8. Electrochemical deposition of layered copper thin films based on the diffusion limited aggregation

    NASA Astrophysics Data System (ADS)

    Wei, Chenhuinan; Wu, Guoxing; Yang, Sanjun; Liu, Qiming

    2016-10-01

    In this work layered copper films with smooth surface were successfully fabricated onto ITO substrate by electrochemical deposition (ECD) and the thickness of the films was nearly 60 nm. The resulting films were characterized by SEM, TEM, AFM, XPS, and XRD. We have investigated the effects of potential and the concentration of additives and found that 2D dendritic-like growth process leaded the formation of films. A suitable growth mechanism based on diffusion limited aggregation (DLA) mechanism for the copper films formation is presented, which are meaningful for further designing homogeneous and functional films.

  9. Electrochemical deposition of layered copper thin films based on the diffusion limited aggregation

    PubMed Central

    Wei, Chenhuinan; Wu, Guoxing; Yang, Sanjun; Liu, Qiming

    2016-01-01

    In this work layered copper films with smooth surface were successfully fabricated onto ITO substrate by electrochemical deposition (ECD) and the thickness of the films was nearly 60 nm. The resulting films were characterized by SEM, TEM, AFM, XPS, and XRD. We have investigated the effects of potential and the concentration of additives and found that 2D dendritic-like growth process leaded the formation of films. A suitable growth mechanism based on diffusion limited aggregation (DLA) mechanism for the copper films formation is presented, which are meaningful for further designing homogeneous and functional films. PMID:27734900

  10. Development and Characterization of Novel Nonlinear Optical Ultrathin Films from Preformed Polymers

    NASA Astrophysics Data System (ADS)

    Cheong, Dong-Wook

    This thesis focuses on the fabrication of Langmuir -Blodgett (LB) films of performed polymers to achieve improved non-linear optical (NLO) properties. Two different classes of polymers have been investigated in the course of this study, which include an asymmetrically substituted polydiacetylene and a polyamic acid containing p-nitroazobenzene as NLO side group. The polyamic acid film has been subsequently imidized to obtain polyimide thin films. The hydrophilic side groups distributed at regular short intervals along the backbone of these polymers assist the formation of stable polymeric monolayers at the air-water interface, which could be transferred to solid surfaces as multilayers for further characterization. An asymmetric polydiacetylene studied here is poly-{8- ((butoxycarbonyl-methyl)urethanyl) -1- (5-pyrimidyl) octa-1,3-diyne} (P-BPOD), consisting of hetero-aromatic pyrimidyl ring at one side and flexible urethane group at the other. Multilayers of P-BPOD could be deposited on hydrophobic surfaces in a non-centrosymmetric fashion. Both linear and non-linear optical experiments have suggested that P-BPOD molecules organize in a structure having inplane anisotropy and bulk asymmetry. The second harmonic generation (SHG) studies have indicated that the p-polarized SHG signal is higher when the polarization of the fundamental beam is parallel to the dipping direction than when it is perpendicular. The preferential orientation of the backbone along the dipping direction, induced by the shear force applied to the viscous polymeric monolayer, has resulted in an enhanced _chi^{(3)} along the dipping direction, which is an order of magnitude higher as compared to that along the perpendicular direction. These preformed polymeric LB films may provide ultrathin NLO films, which can be applied towards the fabrication of thin-film waveguides and optical-switching with definite technological advantages such as negligible film shrinkage (thus less defects) and improved

  11. Carbon nanotube based transparent conductive films: progress, challenges, and perspectives

    PubMed Central

    Zhou, Ying; Azumi, Reiko

    2016-01-01

    Abstract Developments in the manufacturing technology of low-cost, high-quality carbon nanotubes (CNTs) are leading to increased industrial applications for this remarkable material. One of the most promising applications, CNT based transparent conductive films (TCFs), are an alternative technology in future electronics to replace traditional TCFs, which use indium tin oxide. Despite significant price competition among various TCFs, CNT-based TCFs have good potential for use in emerging flexible, stretchable and wearable optoelectronics. In this review, we summarize the recent progress in the fabrication, properties, stability and applications of CNT-based TCFs. The challenges of current CNT-based TCFs for industrial use, in comparison with other TCFs, are considered. We also discuss the potential of CNT-based TCFs, and give some possible strategies to reduce the production cost and improve their conductivity and transparency. PMID:27877899

  12. 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.

  13. 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. Copyright © 2015 Elsevier Ltd. All rights reserved.

  14. Study of carbon nanotubes based Polydimethylsiloxane composite films

    NASA Astrophysics Data System (ADS)

    Shahzad, M. I.; Giorcelli, M.; Shahzad, N.; Guastella, S.; Castellino, M.; Jagdale, P.; Tagliaferro, A.

    2013-06-01

    Thanks to their remarkable characteristics, carbon nanotubes (CNTs) have fields of applications which are growing every day. Among them, the use of CNTs as filler for polymers is one of the most promising. In this work we report on Polydimethylsiloxane (PDMS) composites with different weight percentages (0.0% to 3.0%) of multiwall carbon nanotubes (MWCNTs) having diameter 10-30 nm and length 20-30 μm. To achieve optimum dispersion of CNTs in PDMS matrix, high speed mechanical stirring and ultrasonication were performed. By using the doctor blade technique, 70 μm thick uniform films were produced on glass. They were subsequently thermally cured and detached from the glass to get flexible and self standing films. The surface morphological study done by FESEM, shows that CNTs are well dispersed in the PDMS. Raman spectroscopy and FTIR were used to investigate the possible structural changes in the polymer composite. To examine the optical behavior UV-VIS spectroscopy was employed in both specular and diffused modes. A linear increase in absorption coefficient is found with the increasing percentage of CNTs while the transmittance decreases exponentially. The results confirm the dependence of optical limiting effect on the quantity of MWCNTs. Based on optical study, MWCNTs/PDMS composite films can be a promising material to extend performances of optical limiters against laser pulses, which is often required in lasing systems.

  15. 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.

  16. 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.

  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.

  18. Photopolymerization-based fabrication of chemical sensing films

    SciTech Connect

    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. 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.

  20. 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.

  1. 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.

  2. 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.

  3. Preparation and characterization of bio-based hybrid film containing chitosan and silver nanowires.

    PubMed

    Shahzadi, Kiran; Wu, Lin; Ge, Xuesong; Zhao, Fuhua; Li, Hui; Pang, Shuping; Jiang, Yijun; Guan, Jing; Mu, Xindong

    2016-02-10

    A bio-based hybrid film containing chitosan (CS) and silver nanowires (AgNWs) has been prepared by a simple casting technique. X-ray diffraction (XRD), Fourier infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and UV-visible spectroscopy were employed to characterize the structure of bio-based film. The bio-based hybrid film showed unique performance compared with bare chitosan film. The incorporated nano-silver could improve the strength properly. The results revealed that AgNWs in CS film, improved its tensile strength more than 62% and Young modulus 55% compared with pure chitosan film. On the other hand tensile strength was increased 36.7% with AgNPs. Importantly, the film also exhibited conductivity and antibacterial properties, which may expand its future application. Copyright © 2015. Published by Elsevier Ltd.

  4. 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.

  5. Graphene-based flexible and stretchable thin film transistors

    NASA Astrophysics Data System (ADS)

    Yan, Chao; Cho, Jeong Ho; Ahn, Jong-Hyun

    2012-07-01

    Graphene has been attracting wide attention owing to its superb electronic, thermal and mechanical properties. These properties allow great applications in the next generation of optoelectronics, where flexibility and stretchability are essential. In this context, the recent development of graphene growth/transfer and its applications in field-effect transistors are involved. In particular, we provide a detailed review on the state-of-the-art of graphene-based flexible and stretchable thin film transistors. We address the principles of fabricating high-speed graphene analog transistors and the key issues of producing an array of graphene-based transistors on flexible and stretchable substrates. It provides a platform for future work to focus on understanding and realizing high-performance graphene-based transistors.

  6. Graphene-based flexible and stretchable thin film transistors.

    PubMed

    Yan, Chao; Cho, Jeong Ho; Ahn, Jong-Hyun

    2012-08-21

    Graphene has been attracting wide attention owing to its superb electronic, thermal and mechanical properties. These properties allow great applications in the next generation of optoelectronics, where flexibility and stretchability are essential. In this context, the recent development of graphene growth/transfer and its applications in field-effect transistors are involved. In particular, we provide a detailed review on the state-of-the-art of graphene-based flexible and stretchable thin film transistors. We address the principles of fabricating high-speed graphene analog transistors and the key issues of producing an array of graphene-based transistors on flexible and stretchable substrates. It provides a platform for future work to focus on understanding and realizing high-performance graphene-based transistors.

  7. Ion permeability of polydopamine films revealed using a Prussian blue-based electrochemical method.

    PubMed

    Gao, Bowen; Su, Lei; Tong, Ying; Guan, Miao; Zhang, Xueji

    2014-11-06

    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.

  8. Optimization of a fiber grating film sensor based on dual peak resonance

    NASA Astrophysics Data System (ADS)

    Gu, Zheng-Tian; Xu, Yan-Ping; Deng, Chuan-Lu

    2008-03-01

    Based on the dual peak resonance of long-period fiber grating(LPFG), a novel film sensor is presented, in which films sensitive to the surrounding gases are coated on the cladding of the fiber grating region, and the intervals of the dual peak resonant wavelengths change with the film refractive index. According to the coupled-mode theory, a triple-clad numerical model is developed to analyze the relation between the sensitivity S n and the thin film optical parameters (the film thickness h 3 and the refractive index n 3) and the fiber grating parameters (the grating period Λ and the core index modulation σ). By using optimization method, the optimal film optical parameters and the grating structure parameters are obtained. Numerical simulation shows that the sensitivity of this scheme to refractive index of the films is predicted to be more than 10-7. The theoretic analysis provides straightforward foundation for the actual highly sensitive film sensors.

  9. Fiber-Tip Fabry-Perot Interferometric Sensor based on a Thin Silver Film

    DTIC Science & Technology

    2012-11-01

    Engineering, Department of 11-1-2012 Fiber-Tip Fabry - Perot Interferometric Sensor based on a Thin Silver Film Fawen Guo University of Nebraska-Lincoln...administrator of DigitalCommons@University of Nebraska - Lincoln. Guo, Fawen, "Fiber-Tip Fabry - Perot Interferometric Sensor based on a Thin Silver Film...00-00-2012 to 00-00-2012 4. TITLE AND SUBTITLE Fiber-Tip Fabry - Perot Interferometric Sensor based on a Thin Silver Film 5a. CONTRACT NUMBER

  10. 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. Copyright © 2016 Elsevier Ltd. All rights reserved.

  11. 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.

  12. A novel humidity sensor based on alumina nanowire films

    NASA Astrophysics Data System (ADS)

    Feng, Zhe-sheng; Chen, Xin-Jie; Chen, Jin-ju; Hu, Jing

    2012-06-01

    Alumina nanowire (ANW) films were prepared by etching porous anodic aluminium oxide (AAO), and then humidity sensors with coplanar interdigitated electrodes based on ANWs were fabricated. The ANWs not only present tremendous surface area for water molecule adsorption but also provide efficient sites for attracting water molecules at low relative humidity (RH) levels. The sensors based on the particular morphology of ANWs with large open voids show high sensitivity and small hysteresis, and have fast response and recovery time to humidity. The capacitance rises slowly at a lower RH and increases rapidly after 70% RH, which is associated with the humidity mechanism of chemisorption at lower RH and physisorption at higher RH levels. The impendence analysis suggests that the ANWs are the main factor for sensing humidity, and AAO also contributes to humidity sensing. This study demonstrates that ANWs have promising applications in humidity monitoring.

  13. Thin-film filament-based solar cells and modules

    NASA Astrophysics Data System (ADS)

    Tuttle, J. R.; Cole, E. D.; Berens, T. A.; Alleman, J.; Keane, J.

    1997-04-01

    This concept paper describes a patented, novel photovoltaic (PV) technology that is capable of achieving near-term commercialization and profitability based upon design features that maximize product performance while minimizing initial and future manufacturing costs. DayStar Technologies plans to exploit these features and introduce a product to the market based upon these differential positions. The technology combines the demonstrated performance and reliability of existing thin-film PV product with a cell and module geometry that cuts material usage by a factor of 5, and enhances performance and manufacturability relative to standard flat-plate designs. The target product introduction price is 1.50/Watt-peak (Wp). This is approximately one-half the cost of the presently available PV product. Additional features include: increased efficiency through low-level concentration, no scribe or grid loss, simple series interconnect, high voltage, light weight, high-throughput manufacturing, large area immediate demonstration, flexibility, modularity.

  14. 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.

  15. NanoSQUIDs based on niobium nitride films

    NASA Astrophysics Data System (ADS)

    Russo, R.; Esposito, E.; Crescitelli, A.; Di Gennaro, E.; Granata, C.; Vettoliere, A.; Cristiano, R.; Lisitskiy, M.

    2017-02-01

    We present an experimental investigation of nanoSQUIDs based on niobium nitride films. Niobium nitride has a relatively high critical temperature and a large upper critical magnetic field, making it a good material for superconducting electronics working in high magnetic field. We have fabricated nanoSQUIDs using electron beam lithography lift-off technique and deposition of niobium nitride films by magnetron sputtering at room temperature. The characterization of nanoSQUIDs was performed at 4.2 K and it consists mainly of current-voltage (IV) characteristics and critical current as a function of external magnetic field (magnetic pattern). The fabricated nanoSQUIDs show a hysteretic IV characteristic and they present a multi-values magnetic pattern. We show that by reducing the critical current by ion etching it is possible to obtain nanoSQUIDs with a single value magnetic pattern suitable for magnetic particle measurements. Magnetic noise analysis has been performed and a white noise of 0.3 μΦ0 Hz-1/2 has been estimated.

  16. Research on the measurement of thin film thickness based on phaseshift interferometry

    NASA Astrophysics Data System (ADS)

    Shi, Yi-lei; Su, Jun-hong; Yang, Li-hong; Xu, Jun-qi

    2009-05-01

    Only by solving the problem of accurate measurement of thin film thickness, will it be possible to solve the problem of thin film preparation. A novel measurement method of thin film thickness based on phase-shift interferometry is presented in the paper. Taking advantage of Twyman-Green interferometer, the multi-frame interferogram measured the thin film can be obtained by receiving the interference fringes of thin film by means of CCD and using digital acquisition card to collect interferogram and with the help of computer control PZT driver and modulation piezoelectric regulator to promote reference mirror uniformly-spaced movement. After the gained interferogram were disposed of phase unwrapped, 3D wavefront containing the information of thin film thickness can be obtained. According to the characteristics between the thin film thickness and the unwrapping phase, taking advantage of the overlapping 4-frame average algorithm, corresponding relationships between the quantification phase information and thin film thickness of each point has been established to realize the thin film thickness accurate measurement. The results show that this method has the advantage of non-contact, the high accuracy, not only has testified the feasibility of film thickness measurement with phase-shift interferometry, but also has further ensured research and optimization of the thin film preparation technics. The PV and RMS value of the measured thin film thickness are 0.162μm and 0.043μm respectively.

  17. Preparation and characterization of oxadiazole based electron transporting thin films

    NASA Astrophysics Data System (ADS)

    Mahajan, Aman; Aulakh, Ramanpreet Kaur; Bedi, R. K.

    2012-08-01

    To study the effect of aggregation of the 2-(4-biphenylyl)-5-phenyl-1,3,4-oxadiazole (PBD) molecule in solid state, thin films of PBD have been prepared by the thermal evaporation technique onto glass and quartz substrates under different experimental conditions. These films have been studied for their structural, optical and electrical properties. AFM investigations of the films revealed that the films were smooth, dense and crack free with RMS roughness of 11-14 nm. XRD measurements indicate that films deposited on quartz are more crystalline than films deposited on glass substrate. Both absorption and reflectance spectra over the wavelength range 200-800 nm have been recorded to find optical parameters, namely, absorption, extinction coefficient, refractive index and dielectric constants. The inter-band transition energies are found to lie within the range 3.45-3.49 eV. Optical studies of the films indicate that PBD molecules preferred J-aggregation. A prominent single emission peak in the range of 370-390 nm has been observed which confirms that the fluorescent property of this molecule is not quenched in the thin film state. The electrical conductivity results for the evaporated films exhibited semiconductor behaviour within the investigated field and temperature range. The nature of the substrate is found to be a useful tool to modify the film morphology and for enhancing the charge transport within the films.

  18. Development of 3D Slicer based film dosimetry analysis

    NASA Astrophysics Data System (ADS)

    Alexander, K. M.; Robinson, A.; Pinter, C.; Fichtinger, G.; Schreiner, L. J.

    2017-05-01

    Radiochromic film dosimetry has been widely adopted in the clinic as it is a convenient option for dose measurement and verification. Film dosimetry analysis is typically performed using expensive commercial software, or custom made scripts in Matlab. However, common clinical film analysis software is not transparent regarding what corrections/optimizations are running behind the scenes. In this work, an extension to the open-source medical imaging platform 3D Slicer was developed and implemented in our centre for film dosimetry analysis. This extension streamlines importing treatment planning system dose and film imaging data, film calibration, registration, and comparison of 2D dose distributions, enabling greater accessibility to film analysis and higher reliability.

  19. Fennel waste-based films suitable for protecting cultivations.

    PubMed

    Mariniello, L; Giosafatto, C V L; Moschetti, G; Aponte, M; Masi, P; Sorrentino, A; Porta, R

    2007-10-01

    Biodegradable, flexible, and moisture-resistant films were obtained by recycling fennel waste and adding to fennel homogenates the bean protein phaseolin that was modified or not modified by the enzyme transglutaminase. All films were analyzed for their morphology, mechanical properties, water vapor permeability, and susceptibility to biodegradation under soil-like conditions. Our experiments showed that transglutaminase treatment of the phaseolin-containing fennel waste homogenates allowed us to obtain films comparable in their mechanical properties and water vapor permeability to the commercial films Ecoflex and Mater-Bi. Furthermore, biodegradability tests demonstrated that the presence of the enzyme in the film-casting sample significantly influences the integrity of such a product that lasts longer than films obtained either with fennel waste alone or with a mixture of fennel waste and phaseolin. These findings indicate the fennel-phaseolin film prepared in the presence of transglutaminase to be a promising candidate for a new environmentally friendly mulching bioplastic.

  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. Active biopolymer film based on carboxymethyl cellulose and ascorbic acid for food preservation

    NASA Astrophysics Data System (ADS)

    Halim, Al Luqman Abdul; Kamari, Azlan

    2017-05-01

    In the present study, an active biopolymer film based on carboxymethyl cellulose (CMC) and ascorbic acid (AA) was synthesised at an incorporation rate of 15% (w/w). Several analytical instruments such as Fourier Transform Infrared Spectrometer (FTIR), Thermogravimetry Analyser (TGA), UV-Visible Spectrophotometer (UV-Vis), Scanning Electron Microscope (SEM) and Universal Testing Machine were used to characterise the physical and chemical properties of CMC-AA film. The addition of AA significantly reduced elongation at break (322%) and tensile strength (10 MPa) of CMC-AA film. However, CMC-AA film shows a better antimicrobial property against two bacteria, namely Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) as compared to CMC film. The CMC-AA film was able to preserve cherry tomato with low weight loss and browning index. Overall, results from this study highlight the feasibility of CSAA film for food preservation.

  2. 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

    2016-07-12

    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.

  3. 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.

  4. Morphological, Mechanical and Thermal Study of ZnO Nanoparticle Reinforced Chitosan Based Transparent Biocomposite Films

    NASA Astrophysics Data System (ADS)

    Das, Kunal; Maiti, Sonakshi; Liu, Dagang

    2014-04-01

    Chitosan based biocomposite transparent films reinforced with zinc oxide (ZnO) nanoparticles at different loading i.e. 2, 4 and 6 wt% were successfully prepared by solution casting method. Shape, size and geometry of the zinc oxide nanoparticles were characterized by scanning electron microscopy (SEM). The biocomposite films were subjected to mechanical characterization, thermal analysis, morphology study and moisture uptake behaviour. The characterization tools used here include wide angle X-ray diffraction study, scanning electron microscopic analysis, differential scanning calorimetric analysis and also UV-visible transmittance behavior. SEM micrographs revealed uniformly dispersed ZnO nanoparticles in biocomposite films. Improvement of the tensile strength about 133 % was observed significantly in case of 4 wt% loaded chitosan/ZnO films with respect to the neat chitosan film. 43 % higher transparency was observed in case of 2 wt% ZnO loaded biocomposites films, thus indicating the best combination of properties of 2 wt% ZnO loaded biocomposite films.

  5. 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.

  6. 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…

  7. 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…

  8. 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.

  9. Films based on protein isolated from croaker (Micropogonias furnieri) and palm oil.

    PubMed

    Halal, Shanise Lisie Mello El; Zavareze, Elessandra da Rosa; Rocha, Meritaine da; Pinto, Vânia Zanella; Nunes, Michael Ramos; Luvielmo, Márcia de Mello; Prentice, Carlos

    2016-05-01

    The microstructure and the physical, mechanical, barrier and thermal properties of films based on different concentrations of protein isolated from croaker waste (CPI) and palm oil (PO) were analyzed. Films were elaborated by a casting technique using 2, 3 and 4 g CPI 100 g(-1) of a filmogenic solution and 0, 10 and 20 g of PO 100 g(-1) CPI. Microstructure of the film surfaces of CPI with PO showed no presence of lipid droplets dispersed in the filmogenic matrix, although a rough surface was present. Films with 3% and 4% CPI and 20% PO had the lowest rates of water vapor permeability. When there was an addition of PO to the reduced tensile strength of the films, regardless of the concentration of CPI, this addition reduced the elongation of films with 3% and 4% CPI; however, it did not influence films with 2% CPI, which did not differ from the control film (0% OP). Thermal analysis revealed that films with the highest PO percentage had a lower initial weight loss when compared with other films, due to higher hydrophobicity. The use of protein isolate obtained from fish residues of low commercial value and palm oil is viable for the production of biodegradable films because the latter constitute good barrier properties and thermal stability. © 2015 Society of Chemical Industry. © 2015 Society of Chemical Industry.

  10. 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

  11. 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

  12. 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.

  13. 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.

  14. Patterning of Tl-based superconducting films using new etching solution

    NASA Astrophysics Data System (ADS)

    Sojková, M.; Štrbík, V.; Španková, M.; Chromik, Š.

    2014-09-01

    Tl-based cuprate superconducting films were prepared in a two-step process by RF magnetron sputtering of an amorphous precursor and ex situ thallination in open system. The films prepared on LaAlO3 and CeO2 buffered R-plane sapphire substrates consisted from c-axis oriented Tl-2212 superconducting phase. The zero resistance critical temperature TC0 exhibited values up to 94 K. Subsequently, superconducting structures were prepared from the Tl-based thin films using photolithography process and wet etching. A new etchant based on potassium iodide was used for the Tl-based film patterning. The prepared structures had sharp edges, unchanged phase composition and critical temperature values. Such a way of the Tl-based film patterning is very simple, fast and easy to realize.

  15. Nonlinear polarization responses of ZrO2-based thin films fabricated by chemical solution deposition

    NASA Astrophysics Data System (ADS)

    Yoneda, Shingo; Hosokura, Tadasu; Kimura, Masahiko; Ando, Akira; Shiratsuyu, Kosuke

    2017-10-01

    The nonlinear polarization responses of ZrO2-based thin films were investigated. Y, Ce, Ti, and Sn were used as substitutes in ZrO2 thin films by chemical solution deposition. A pure ZrO2 film and the ZrO2 film with 1% Y substitution showed constricted polarization–electric field (P–E) curves. In contrast, the ZrO2 film with 5% Y substitution showed a linear P–E curve. The dielectric constants of the pure ZrO2 film and the ZrO2 film with 1% Y substitution increased by 7 and 11%, respectively, under an applied electric field of 2.5 MV/cm. The nonlinearity of the polarization responses was decreased by Ce substitution and Ti substitution. The ZrO2 films with Sn substitution showed narrow P–E curves. The dielectric constant of the ZrO2 film with 10% Sn substitution increased by 13% under an applied electric field of 3 MV/cm. These dielectric constant increases originate from electric-field-induced phase transitions of ZrO2-based thin films.

  16. Soil burial biodegradation studies of palm oil-based UV-curable films

    SciTech Connect

    Tajau, Rida Salleh, Mek Zah Salleh, Nik Ghazali Nik Abdurahman, Mohamad Norahiman; Salih, Ashraf Mohammed; Fathy, Siti Farhana; Azman, Anis Asmi Hamidi, Nur Amira

    2016-01-22

    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.

  17. Characterization and performance of carbon films deposited by plasma and ion beam based techniques

    SciTech Connect

    Walter, K C; Kung, H; Levine, T

    1994-12-31

    Plasma and ion beam based techniques have been used to deposit carbon-based films. The ion beam based method, a cathodic arc process, used a magnetically mass analyzed beam and is inherently a line-of-sight process. Two hydrocarbon plasma-based, non-line-of-sight techniques were also used and have the advantage of being capable of coating complicated geometries. The self-bias technique can produce hard carbon films, but is dependent on rf power and the surface area of the target. The pulsed-bias technique can also produce hard carbon films but has the additional advantage of being independent of rf power and target surface area. Tribological results indicated the coefficient of friction is nearly the same for carbon films from each deposition process, but the wear rate of the cathodic arc film was five times less than for the self-bias or pulsed-bias films. Although the cathodic arc film was the hardest, contained the highest fraction of sp{sup 3} bonds and exhibited the lowest wear rate, the cathodic arc film also produced the highest wear on the 440C stainless steel counterface during tribological testing. Thus, for tribological applications requiring low wear rates for both counterfaces, coating one surface with a very hard, wear resistant film may detrimentally affect the tribological behavior of the counterface.

  18. 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.

  19. 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.

  20. 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.

  1. Degradation studies of nitride-based low-e films

    NASA Astrophysics Data System (ADS)

    Andersson, Kent E.; Wahlstrom, M. K.; Roos, Arne; Ribbing, Carl-Gustaf

    1992-11-01

    Triple layer structures of TiO2/TiN/TiO2 and quadruple layer structures of TiO2/Al/TiN/TiO2 have been sputtered on glass substrates at temperatures ranging from room temperature to 300 degree(s)C. The reflectance and transmittance were measured in the visible and the near infrared wavelength regions. Accelerated degradation tests with respect to high temperature and acid exposure have been performed with these laboratory samples of low-e coatings and the degradation has been compared with that of commercial silver based window coatings. As expected the durability of the nitride based coatings is far superior to the stability of those based on noble metals. Furthermore, the nitride coatings with an aluminum sacrificial layer have been found to resist aging at elevated temperatures (as high as 350 - 400 degree(s)C) far better than similar coatings without the aluminum. It has also been shown that the aluminum layer protects the nitride film during deposition of the top oxide layer. The effects of high temperature annealing have been modeled with optical multilayer calculations. Comparison of two degradation mechanisms demonstrates that the silver layers fail by agglomeration while the nitride suffers successive oxidation. This explains the effectiveness of the aluminum layer which forms a dense oxide during the initial stages of TiO2- deposition.

  2. Evaluation of variational principle based model for LDPE large scale film blowing process

    NASA Astrophysics Data System (ADS)

    Kolarik, Roman; Zatloukal, Martin

    2013-04-01

    In this work, variational principle based film blowing model combined with Pearson and Petrie formulation, considering non-isothermal processing conditions and novel generalized Newtonian model allowing to capture steady shear and uniaxial extensional viscosities has been validated by using experimentally determined bubble shape and velocity profile for LDPE sample on large scale film blowing line. It has been revealed that the minute change in the flow activation energy can significantly influence the film stretching level.

  3. Electrochemical double-layer capacitors based on functionalized graphene

    NASA Astrophysics Data System (ADS)

    Pope, Michael Allan

    Graphene is a promising electrode material for electrochemical double-layer capacitors (EDLCs) used for energy storage due to its high electrical conductivity and theoretical specific surface area. However, the intrinsic capacitance of graphene is known to be low and governed by the electronic side of the interface. Furthermore, graphene tends to aggregate and stack together when processed into thick electrode films. This significantly lowers the ion-accessible specific surface area (SSA). Maximizing both the SSA and the intrinsic capacitance are the main problems addressed in this thesis in an effort to improve the specific capacitance and energy density of EDLCs. In contrast to pristine graphene, functionalized graphene produced by the thermal exfoliation of graphite oxide contains residual functional groups and lattice defects. To study how these properties affect the double-layer capacitance, a model electrode system capable of measuring the intrinsic electrochemical properties of functionalized graphene was developed. To prevent artifacts and uncertainties related to measurements on porous electrodes, the functionalized graphene sheets (FGSs) were assembled as densely tiled monolayers using a Langmuir-Blodgett technique. In this way, charging can be studied in a well-defined 2D geometry. The possibility of measuring and isolating the intrinsic electrochemical properties of FGS monolayers was first demonstrated by comparing capacitance and redox probe measurements carried out on coatings deposited on passivated gold and single crystal graphite substrates. This monolayer system was then used to follow the double-layer capacitance of the FGS/electrolyte interface as the structure and chemistry of graphene was varied by thermal treatments ranging from 300 °C to 2100 °C. Elemental analysis and Raman spectroscopy were used to determine the resulting chemical and structural transformation upon heat treatment. It was demonstrated that intrinsically defective

  4. Physicochemical and antifungal properties of bio-nanocomposite film based on gelatin-chitin nanoparticles.

    PubMed

    Sahraee, Samar; Milani, Jafar M; Ghanbarzadeh, Babak; Hamishehkar, Hamed

    2017-04-01

    The gelatin-based nanocomposite films containing chitin nanoparticles (N-chitin) with concentrations of 0, 3, 5 and 10% were prepared and their physical, thermal and anti-microbial properties were investigated. Scanning electron microscopy (SEM) micrographs showed that N-chitin size distribution was around 60-70nm which dispersed appropriately at low concentration in gelatin matrix. The results showed that incorporation of N-chitin significantly influenced apparent color and transparency of the gelatin films. The reduced water vapor permeability (WVP) and solubility and higher surface hydrophobicity of the nanocomposite films were obtained by enhancing N-chitin concentration in film formulation. The use of N-chitin up to 5% concentration in the gelatin based nanocomposite film led to improved mechanical properties. Also, the results of differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA) confirmed improved stability of nanocomposite films against melting and degradation at high temperatures in comparison to neat gelatin film. The well compatibility of chitin nanoparticles with gelatin polymer was concluded from Fourier transform infrared (FTIR) spectra and X-ray diffraction (XRD) plots. Finally, the gelatin based nanocomposite films had anti-fungal properties against Aspergillus niger in the contact surface zone. Increasing the concentration of N-chitin up to 5% enlarged inhibition zone diameter, but the nanocomposite film containing 10% N-chitin showed smaller inhibition zone. Copyright © 2016 Elsevier B.V. All rights reserved.

  5. Raman spectra of heterogeneous nanostructures based on organosilicon films

    NASA Astrophysics Data System (ADS)

    Vlasukova, L. A.; Komarov, F. F.; Leontyev, A. V.; Parkhomenko, I. N.

    2013-01-01

    We studied the effect of ion bombardment on the structure of SOG (spin-on-glass) films. We used IR and Raman spectroscopy and plan-view transmission electron microscopy to study the characteristic features of the structural transformation in organosilicon films when bombarded by nitrogen ions. We show that they are heterogeneous and we establish the presence of inclusions of nanocrystalline graphite.

  6. Free-standing films based on silicone resins

    NASA Astrophysics Data System (ADS)

    Katsoulis, Dimitris E.; Suto, Michitaka; Kushibiki, Nobuo

    2003-07-01

    We report here the preparation of transparent, flexible films from silicone resins by solvent casting techniques. The films exhibit no birefringence, higher than 90% transparency between 350 to 1700 nm and average surface roughness below 1 nm. Thermal analysis shows that the films are stable at temperatures greater than 200 °C (depending upon the starting resin composition). The films are suitable substrates for deposition of various coatings including indium tin oxide (ITO). Transparent conducting ITO electrodes were prepared with ion plating and RF sputtering methods and characterized by microscopy, XPS, absorption spectroscopy and electrical conductivity measurements. Potential applications for silicone resin films exist in the market areas of displays, electronics and energy.

  7. 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.

  8. Multielectrocatalysis by layer-by-layer films based on pararosaniline and vanadium-substituted phosphomolybdate.

    PubMed

    Fernandes, Diana M; Teixeira, Alexandra; Freire, Cristina

    2015-02-10

    Hybrid multilayer films based on the two molecular species pararosaniline (PR) and Keggin-type polyoxometalate K5[PMo11VO40)] (PMo11V) were prepared on different substrates using the electrostatic layer-by-layer (LbL) self-assembly method. The film buildup, monitored by electronic spectroscopy, showed a regular stepwise growth, and X-ray photoelectron spectroscopy data confirmed the presence of both molecular components within the LbL films. Scanning electron microscopy images revealed a completely covered surface with a nonuniform distribution of film components, and atomic force microscopy images confirmed a rough surface. The film electrochemical responses and permeability were studied by cyclic voltammetry. Films revealed three Mo-based redox processes (Mo(VI) → Mo(V)) and one V-based redox process (V(V) → V(IV)) in the potential range between 0.8 and -0.4 V vs Ag/AgCl. Studies with the redox probes [Fe(CN)6](3-/4-) and [Ru(NH3)6](3+/2+) showed that the films maintain the permeability even after six bilayers. Furthermore, the {PR/PMo11V}n multilayer films exhibit excellent Mo-based electrocatalytic activity toward reduction of iodate and V-based electrocatalytic activity toward ascorbic acid oxidation, thus acting as a versatile multielectrocatalyst.

  9. Functional Polymers and Guest-Host Polymer Blends for Optical and Electronic Applications: A Molecular Engineering Approach

    DTIC Science & Technology

    1993-04-14

    Langmuir-Blodgett (LB) method. Ultra-thin films of poly( benzothiazole ) (PBT) containing thiophene were successfully obtained by this method...benzimidazole) (PBI), 3 poly(benzoxazole) (PBO) or poly( benzothiazole ) PBT) are highly stable at elevated temperatures above 300’C and have the fully...previously found that fabrication of poly( benzothiazole ) (PBT) as a uniform thin film can be accomplished by using the LB method at air/water interfaces. The

  10. Tungsten-rhenium thin film thermocouples for SiC-based ceramic matrix composites.

    PubMed

    Tian, Bian; Zhang, Zhongkai; Shi, Peng; Zheng, Chen; Yu, Qiuyue; Jing, Weixuan; Jiang, Zhuangde

    2017-01-01

    A tungsten-rhenium thin film thermocouple is designed and fabricated, depending on the principle of thermal-electric effect caused by the high temperature. The characteristics of thin film thermocouples in different temperatures are investigated via numerical analysis and analog simulation. The working mechanism and thermo-electric features of the thermocouples are analyzed depending on the simulation results. Then the thin film thermocouples are fabricated and calibrated. The calibration results show that the thin film thermocouples based on the tungsten-rhenium material achieve ideal static characteristics and work well in the practical applications.

  11. Designing a Self-Biased CPW Circulator Based on Strontium Hexaferrite Thick Film

    NASA Astrophysics Data System (ADS)

    Kiani, E.; poorbafrani, A.

    2017-08-01

    A 400 μm strontium hexaferrite thick film was prepared through a two-step sintering method; with the grain size diameter of the film about 0.7 μm, the relative density about ρ_{{relative}} = 0.9 , and the remanent magnetization ( M r ) 3940 G. Based on this thick film, a self-biased coplanar waveguide circulator was proposed. The calculated S-parameters indicate that by proper optimization of the structure, an isolation of 19 dB and insertion loss of 1.53 dB is attained. The effects of film porosity and thickness on the insertion losses are discussed.

  12. Structural and optical investigation of Te-based chalcogenide thin films

    NASA Astrophysics Data System (ADS)

    Sharma, Rita; Sharma, Shaveta; Chander, Ravi; Kumar, Praveen; Thangaraj, R.; Mian, M.

    2015-05-01

    We report the structural and optical properties of thermally evaporated Bi2Te3, In2Te3 and InBiTe3 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 (Eg) has been reported for In2Te3, InBiTe3 films. Raman Spectroscopy was performed to investigate the effect of Bi, In, on lattice vibration and chemical bonding in Te based chalcogenide glassy alloys.

  13. Tungsten-rhenium thin film thermocouples for SiC-based ceramic matrix composites

    NASA Astrophysics Data System (ADS)

    Tian, Bian; Zhang, Zhongkai; Shi, Peng; Zheng, Chen; Yu, Qiuyue; Jing, Weixuan; Jiang, Zhuangde

    2017-01-01

    A tungsten-rhenium thin film thermocouple is designed and fabricated, depending on the principle of thermal-electric effect caused by the high temperature. The characteristics of thin film thermocouples in different temperatures are investigated via numerical analysis and analog simulation. The working mechanism and thermo-electric features of the thermocouples are analyzed depending on the simulation results. Then the thin film thermocouples are fabricated and calibrated. The calibration results show that the thin film thermocouples based on the tungsten-rhenium material achieve ideal static characteristics and work well in the practical applications.

  14. 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.

  15. Planting Healthy Roots: Using Documentary Film to Evaluate and Disseminate Community-Based Participatory Research

    PubMed Central

    Brandt, Heather M.; Freedman, Darcy A.; Friedman, Daniela B.; Choi, Seul Ki; Seel, Jessica S.; Guest, M. Aaron; Khang, Leepao

    2016-01-01

    The study purpose was twofold: (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). 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

  16. 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.

  17. Fabrication of transparent and ultraviolet shielding composite films based on graphene oxide and cellulose acetate.

    PubMed

    de Moraes, Ana Carolina Mazarin; Andrade, Patricia Fernanda; de Faria, Andreia Fonseca; Simões, Mateus Batista; Salomão, Francisco Carlos Carneiro Soares; Barros, Eduardo Bedê; Gonçalves, Maria do Carmo; Alves, Oswaldo Luiz

    2015-06-05

    Graphene oxide (GO) has been considered a promising filler material for building polymeric nanocomposites because of its excellent dispersibility and high surface area. In this work, we present the fabrication and characterization of transparent and ultraviolet (UV) shielding composite films based on GO and cellulose acetate (CA). GO sheets were found to be well-dispersed throughout the CA matrix, providing smooth and homogeneous composite films. Moreover, the GO sheets were completely embedded within the CA matrix and no presence of this nanomaterial was found at the surface. Nevertheless, CAGO composite films offered an improved high energy light-shielding capacity when compared to pristine CA films. Particularly for UVC irradiation, the CAGO film containing 0.50wt% GO displayed a UV-shielding capacity of 57%, combined with 79% optical transparency under visible light. These CAGO composite films can be potentially applied as transparent UV-protective coatings for packing biomedical, pharmaceutical, and food products.

  18. Vacuum-vapor-deposited films based on benzo(a)phenoxazine derivatives under surface plasma fluorination

    NASA Astrophysics Data System (ADS)

    Agabekov, Vladimir E.; Ignasheva, Olga E.; Belyatsky, Vladimir N.

    1997-07-01

    Modification of vacuum vapor deposited thin films based on benzo(a)phenoxazone-5 derivatives with C3F8 and SF6 plasma were investigated. X-ray photoelectron spectroscopy (XPS) method was used to identify and study the distribution of surface functional groups of untreated and fluorinated films investigated. It was shown that fluor content in element composition of surface film layers and perfluorocarbon group content in Cls-lines of XP-spectra depended on chemical structure of the initial compounds. The more quantity and size of side substitutes were contained in the compound chemical structure the less was the content of fluor and perfluorocarbon groups in film surface fluorinated layer. The probable way of plasma active particle interaction with film surface is discussed. Using Kaelbe's method the influence of treatment conditions and initial compound chemical structure on surface properties of fluorinated films was studied.

  19. 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

  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. Versatile fluoride substrates for Fe-based superconducting thin films

    NASA Astrophysics Data System (ADS)

    Kurth, F.; Reich, E.; Hänisch, J.; Ichinose, A.; Tsukada, I.; Hühne, R.; Trommler, S.; Engelmann, J.; Schultz, L.; Holzapfel, B.; Iida, K.

    2013-04-01

    We demonstrate the growth of Co-doped BaFe2As2 (Ba-122) thin films on CaF2 (001), SrF2 (001), and BaF2 (001) single crystal substrates using pulsed laser deposition. All films are grown epitaxially despite of a large misfit of -10.6% for BaF2 substrate. For all films, a reaction layer is formed at the interface confirmed by X-ray diffraction and for the films grown on CaF2 and BaF2 additionally by transmission electron microscopy. The superconducting transition temperature of the film on CaF2 is around 27 K, whereas the corresponding values of the films on SrF2 and BaF2 are around 22 K and 21 K, respectively. The Ba-122 on CaF2 shows almost identical crystalline quality and superconducting properties as films on Fe-buffered MgO.

  2. Potential of Kaolin-based Particle Film Barriers for Formosan Subterranean Termite (Isoptera: Rhinotermitidae) Control

    USDA-ARS?s Scientific Manuscript database

    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 ...

  3. The Imagery of Rhetoric: Film and Academic Writing in the Discipline-based ESL Course.

    ERIC Educational Resources Information Center

    Kasper, Loretta F.

    2000-01-01

    Describes three reading/writing lessons on the topics of linguistics, environmental science, and anthropology used in a discipline-based college-level English as a second language course to illustrate how to use film to teach academic writing skills. Discusses how students analyze a film to help articulate the content of an essay or a book. (SR)

  4. Comparative study on properties of edible films based on pinhao (Araucaria angustifolia) starch and flour

    USDA-ARS?s Scientific Manuscript database

    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...

  5. Systematics of Permanent Magnet Film Texturing and the Limits of Film Synthesized 1-12 and 2-17 Iron Based Rare Earth Transition Metal Permanent Systems

    DTIC Science & Technology

    1998-01-21

    onto a separate substrate was used to saturate the magnetization of the Bi- YIG waveguide. The TbCu7 SmCo based film magnet was 22 urn thick in this case...structure. Microwave circulators using ferrite disks and external bulk permanent magnets are an example of such devices. Magnetoresistive heads are...tested. In a preliminary device configuration consisting of a waveguide etched into a Bi- YIG film, a SmCo based permanent magnet film deposited

  6. Properties of blend film based on cuttlefish (Sepia pharaonis) skin gelatin and mungbean protein isolate.

    PubMed

    Hoque, Md Sazedul; Benjakul, Soottawat; Prodpran, Thummanoon; Songtipya, Ponusa

    2011-11-01

    Blend films based on cuttlefish (Sepia pharaonis) ventral skin gelatin (CG) and mungbean protein isolate (MPI) at different blend ratios (CG/MPI=10:0, 8:2, 6:4, 4:6, 2:8 and 0:10, w/w) prepared at pH 11 using 50% glycerol (based on total protein) as plasticizer were characterized. CG films incorporated with MPI at increasing amounts had the decreases in tensile strength (TS) (p<0.05). The increases in elongation at break (EAB) were observed when CG/MPI ratios of 6:4 or 4:6 were used (p<0.05). Decreased water vapor permeability (WVP) was obtained for films having the increasing proportion of MPI (p<0.05). CG/MPI blend films with higher MPI proportion had lower film solubility and L*-values (lightness) but higher b*-values (yellowness) and ΔE*-values (total color difference) (p<0.05). Electrophoretic study revealed that disulfide bond was present in MPI and CG/MPI blend films. However, hydrogen bonds between CG and MPI in the film matrix were dominant, as elucidated from FTIR spectroscopic analysis. Moreover, thermal stability of CG/MPI blend film was improved as compared to that of films from respective single proteins. Differential scanning calorimetry result suggested solid-state morphology of CG/MPI (6:4) blend film that consisted of amorphous phase of partially miscible CG/MPI mixture and the coexisting two different order phases of individual CG and MPI domains. Thus, the incorporation of MPI into gelatin film could improve the properties of resulting blend film, which were governed by CG/MPI ratio. Copyright © 2011 Elsevier B.V. All rights reserved.

  7. Effect and mechanism of cellulose nanofibrils on the active functions of biopolymer-based nanocomposite films.

    PubMed

    Yu, Zhilong; Alsammarraie, Fouad K; Nayigiziki, Francois Xavier; Wang, Wei; Vardhanabhuti, Bongkosh; Mustapha, Azlin; Lin, Mengshi

    2017-09-01

    Cellulose nanofibrils (CNFs) are superfine cellulose fibrils with a nanoscale diameter and have gained increasing attention due to their great potential in the food industry. However, the applications of CNFs in active food packaging are still limited. The objectives of this study were to develop biopolymer-based edible nanocomposite films using CNFs, corn starch, and chitosan, and to investigate the effect and mechanisms of CNFs on the active functions and properties of the nanocomposite films. Important functional properties of the films were measured and the films were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and Zetasizer. The results demonstrate that CNFs increased the rigidity of the films due to more hydrogen bonds being induced by CNFs (≥60%). Incorporating a high content of CNFs (≥60%) in the film resulted in enhanced filling effect on the structure of the biopolymer films, which significantly improved the light barrier, oxygen barrier and water vapor barrier capacities. As CNF content increased to 100%, the film opacity increased by 59%, while the peroxide value of corn oil protected with edible films was reduced by 23%. Furthermore, the antimicrobial properties of the edible films with 80% and 100% CNFs were increased by up to 2logCFU/g on day 8 in a beef model, due to more positive charges in the films and improved blocking effects on oxygen. These results demonstrate that CNFs can effectively enhance the antimicrobial effect and barrier properties of biopolymer-based nanocomposite films and have great potential in applications of active packaging for food products. Copyright © 2017 Elsevier Ltd. All rights reserved.

  8. Photoelectric properties of a detector based on dried bacteriorhodopsin film.

    PubMed

    Wang, Wei Wei; Knopf, George K; Bassi, Amarjeet S

    2006-01-15

    The photoelectric response of a detector using dried bacteriorhodopsin (bR) film as the light sensing material is mathematically modeled and experimentally verified in this paper. The photocycle and proton transfer kinetics of dried bR film differ dramatically from the more commonly studied aqueous bR material because of the dehydration process. The photoelectric response of the dried film is generated by charge displacement and recombination instead of transferring a proton from the cytoplasmic side to the extracellular side of the cell membrane. In this work, the wild-type bR samples are electrophoretically deposited onto an indium tin oxide (ITO) electrode to construct a simple multiple layered photo-detector with high sensitivity to small changes in incident illumination. The light absorption characteristics of the thin bR film are mathematically represented using the kinetics of the bR photocycle and the charge displacement theorem. An electrically equivalent RC circuit is used to describe the intrinsic photoelectric properties of the film and external measurement circuitry to analyze the detector's response characteristics. Simulated studies and experimental results show that the resistance of the dried bR film is in the order of 10(11) Omega. When the input impedance of the measurement circuitry is one order of magnitude smaller than the dried film, the detector exhibits a strong differential response to the original time-varying light signal. An analytical solution of the equivalent circuit also reveals that the resistance and capacitance values exhibited by the dried bR film, in the absence of incident light, are almost twice as large as the values obtained while the material is under direct illumination. Experimental observations and a predictive model both support the notion that dried bR film can be used in simple highly sensitive photo-detector designs.

  9. In situ X-ray diffraction based investigation of crystallization in solution deposited PZT thin films

    NASA Astrophysics Data System (ADS)

    Nittala, Krishna

    Solution deposited PZT based thin films have potential applications in embedded decoupling capacitors and pulse discharge capacitors. During solution deposition, precursor solution is deposited onto a substrate to obtain an amorphous film. The film is then crystallized by heating it at a high temperature (˜600 - 700°C). Conditions during the crystallization anneal such as precursor stoichiometry in solution, heating rate and adhesion layer in the substrate are known to influence phase and texture evolution in these films. However, a mechanistic understanding of the changes taking place in these thin films during crystallization is lacking. A better understanding of the crystallization processes in these thin films could enable tailoring the properties of thin films to suit specific applications. To explore the crystallization process in solution deposited PZT thin films, high temperature in situ laboratory and synchrotron X-ray diffraction based techniques were developed. Taking advantage of the high X-ray flux available at synchrotron facilities such as beamline 6-ID-B, Advanced Photon Source, Argonne National Laboratory, crystalline phases formed in the thin films during crystallization at the high heating rates (0.5 -- 60°C/s) typically used during film processing could be measured. Using a 2-D detector for these measurements allowed the simultaneous measurement of both phase and texture information during crystallization. Analytical treatment of the unconventional diffraction geometry used during the synchrotron based measurements was performed to develop methodologies for quantitative estimation of texture components. The nominal lead content in the starting solutions and the heating rate used during crystallization was observed to influence the sequence of phases formed during crystallization of the films. In films crystallized at fast heating rates, titanium segregation, probably due to diffusion of titanium from the adhesion layer, was observed. To

  10. Physicochemical, nutritional, and antimicrobial properties of wine grape (cv. Merlot) pomace extract-based films.

    PubMed

    Deng, Qian; Zhao, Yanyun

    2011-04-01

    Wine grape pomace (WGP) (cv. Merlot) extract-based films were studied in terms of their physicochemical, mechanical, water barrier, nutritional, and antibacterial properties. Pomace extract (PE) was obtained by hot water extraction and had a total soluble solid of 3.6% and pH 3.65. Plant-based polysaccharides, low methoxyl pectin (LMP, 0.75% w/w), sodium alginate (SA, 0.3% w/w), or Ticafilm (TF, 2% w/w), was added into PE for film formation, respectively. Elongation at break and tensile strength were 23% and 4.04 MPa for TF-PE film, 25% and 1.12 MPa for SA-PE film, and 9.89% and 1.56 MPa for LMP-PE film. Water vapor permeability of LMP-PE and SA-PE films was 63 and 60 g mm m(-2) d(-1) kPa, respectively, lower than that of TF-PE film (70 g mm m(-2) d(-1) kPa) (P<0.05). LMP-PE film had higher water solubility, indicated by the haze percentage of water after 24 h of film immersion (52.8%) than that of TF-PE (25.7%) and SA-PE (15.9%) films, and also had higher amount of released phenolics (96.6%) than that of TF-PE (93.8%) and SA-PE (80.5%) films. PE films showed antibacterial activity against both Escherichia coli and Listeria innocua, in which approximate 5-log reductions in E. coli and 1.7- to 3.0-log reductions in L. innocua were observed at the end of 24 h incubation test compared with control. This study demonstrated the possibility of utilizing WGP extracts as natural, antimicrobial, and antioxidant promoting film-forming material for various food applications.   WGP extract-based edible films with the addition of a small amount of commercial polysaccharides showed attractive color and comparable mechanical and water barrier properties to other edible films. The films also demonstrated their potential antioxidant and antimicrobial functions. Hence, they may be used as colorful wraps or coatings for food, pharmaceutical, or other similar applications.

  11. Optothermal Raman Studies of Thermal Properties of Graphene Based Films

    NASA Astrophysics Data System (ADS)

    Malekpour, Hoda

    Efficient thermal management is becoming a critical issue for development of the next generation of electronics. As the size of electronic devices shrinks, the dissipated power density increases, demanding a better heat removal. The discovery of graphene's unique electrical and thermal properties stimulated interest of electronic industry to development of graphene based technologies. In this dissertation, I report the results of my investigation of thermal properties of graphene derivatives and their applications in thermal management. The dissertation consists of three parts. In the first part, I investigated thermal conductivity of graphene laminate films deposited on thermally insulating polyethylene terephthalate substrates. Graphene laminate is made of chemically derived graphene and few layer graphene flakes packed in overlapping structure. Two types of graphene laminate were studied: as deposited and compressed. The thermal conductivity of the laminate was found to be in the range from 40 W/mK to 90 W/mK at room temperature. It was established that the average size and the alignment of graphene flakes are parameters dominating the heat conduction. In the second part of this dissertation, I investigated thermal conductivity of chemically reduced freestanding graphene oxide films. It was found that the in-plane thermal conductivity of graphene oxide can be increased significantly using chemical reduction and temperature treatment. Finally, I studied the effect of defects on thermal conductivity of suspended graphene. The knowledge of the thermal conductivity dependence on the concentration of defects can shed light on the strength of the phonon - point defect scattering in two-dimensional materials. The defects were introduced to graphene in a controllable way using the low-energy electron beam irradiation. It was determined that as the defect density increases the thermal conductivity decreases down to about 400 W/mK, and then reveal saturation type behavior

  12. Metal-organic chemical vapor deposition of cadmium oxide-based transparent conductors: Precursor design, film growth, and film characterization

    NASA Astrophysics Data System (ADS)

    Metz, Andrew William

    2003-07-01

    The growing importance of cadmium containing thin films and the desire for their efficient deposition has necessitated the development of high performance MOCVD precursors. To this end, a series of low-melting, and thermally-stable cadmium MOCVD precursors has been synthesized, characterized, and implemented in the growth of highly conductive and transparent CdO-based thin films. One member of the series, bis(1,1,1,5,5,5-hexafluoro-2,4-pentanedionato)(N,N-diethyl-N ', N'-dimethyl-ethylenediamine)cadmium(II), Cd(hfa)2(N,N-DE-N' ,N'-DMEDA), represents a particularly significant improvement over previously available Cd precursors owing to its low melting point, and robust thermal stability. This precursor will allow careful control of composition and growth rates in complex cadmium-containing oxide systems owing to the elimination of sintering effects detrimental to reproducible growth with solid precursors. Materials with high electrical conductivity and optical transparency are needed for future flat panel display, solar energy, and other opto-electronic technologies. High quality Cd1-xInxO films with been deposited utilizing our new class of MOCVD precursors. The x = 0.05 film, with conductivity of 17,000 S/cm, carrier mobility of 70 cm2/V·s, and wide visible region optical transparency window considerably exceed the corresponding parameters for commercial indium-tin oxide (ITO). A detailed understanding of the fundamental aspects of charge transport in degenerate semiconductors is of great interest. In order to elucidate the importance of individual scattering mechanisms in TCO materials, high-quality CdO films were grown by MOCVD in parallel on glass and single-crystal MgO (100) between 300°C and 412°C. Enhanced mobilities observed for highly biaxially textured films grown on MgO (100) vs. glass are attributed, on the basis of DC charge transport measurements and microstructure analysis, to a reduction in neutral impurity scattering and/or to a more densely

  13. 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. Copyright © 2013 Elsevier B.V. All rights reserved.

  14. 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.

  15. Optical isolator based on mode conversion in magnetic garnet films.

    PubMed

    Hemme, H; Dötsch, H; Menzler, H P

    1987-09-15

    Calculations are presented describing a novel optical isolator which works by complete TE(0)-TM(0) mode conversion in magnetic garnet films caused by stress-induced optical anisotropy (50%) and by Faraday rotation (50%). These conversions take place along two different, perpendicular light paths in the same crystal that are connected by an integrated mirror. Possible tolerances of the film parameters are given so that a 30-dB isolation is still guaranteed.

  16. 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.

  17. Extraction of agar from Gelidium sesquipedale (Rhodopyta) and surface characterization of agar based films.

    PubMed

    Guerrero, P; Etxabide, A; Leceta, I; Peñalba, M; de la Caba, K

    2014-01-01

    The chemical structure of the agar obtained from Gelidium sesquipedale (Rhodophyta) has been determined by (13)C nuclear magnetic resonance ((13)C NMR) and Fourier transform infrared spectroscopy (FTIR). Agar (AG) films with different amounts of soy protein isolate (SPI) were prepared using a thermo-moulding method, and transparent and hydrophobic films were obtained and characterized. FTIR analysis provided a detailed description of the binding groups present in the films, such as carboxylic, hydroxyl and sulfonate groups, while the surface composition was examined using X-ray photoelectron spectroscopy (XPS). The changes observed by FTIR and XPS spectra suggested interactions between functional groups of agar and SPI. This is a novel approach to the characterization of agar-based films and provides knowledge about the compatibility of agar and soy protein for further investigation of the functional properties of biodegradable films based on these biopolymers. Copyright © 2013 Elsevier Ltd. All rights reserved.

  18. Antioxidant edible films based on chitosan and starch containing polyphenols from thyme extracts.

    PubMed

    Talón, Emma; Trifkovic, Kata T; Nedovic, Viktor A; Bugarski, Branko M; Vargas, María; Chiralt, Amparo; González-Martínez, Chelo

    2017-02-10

    The aim of this study was to analyse the antioxidant activity of different polymeric matrices based on chitosan and starch, incorporating a thyme extract (TE) rich in polyphenols. TE provided the films with remarkable antioxidant activity. When mixed with chitosan, the polyphenols interacted with the polymer chains, acting as crosslinkers and enhancing the tensile behaviour of films. The opposite effect was observed when incorporated into the starch matrix. All the films became darker, more reddish and less transparent when TE was incorporated. These colour changes were more marked in starch matrices, which suggests that TE compounds were poorly encapsulated. The use of chitosan-based matrices carrying TE polyphenols is recommended as a means of obtaining antioxidant films, on the basis of their tensile response and greater antioxidant activity, which could be associated with the development of polyphenol-chitosan interactions, contributing to a better protection of the functionality of polyphenols during film formation and conditioning.

  19. Determining the elastic modulus of thin films using a buckling-based method: computational study

    NASA Astrophysics Data System (ADS)

    Zheng, Xiu-Peng; Cao, Yan-Ping; Li, Bo; Feng, Xi-Qiao; Jiang, Hanqing; Y Huang, Yonggang

    2009-09-01

    The buckling mode of a thin film lying on a soft substrate has been used to determine the elastic modulus of thin films and one-dimensional objects (e.g. nanowires and nanotubes). In this paper, dimensional analysis and three-dimensional nonlinear finite element computations have been made to investigate the buckling of a film with finite width bonded to a compliant substrate. Our study demonstrates that the effect of Poisson's ratio of the film can be neglected when its width-thickness ratio is smaller than 20. For wider films, omitting the influence of Poisson's ratio may lead to a significant systematic error in the measurement of the Young's modulus and, therefore, the film should be treated as a plate. It is also found that the assumption of the uniform interfacial normal stress along the width of the film made in the theoretical analysis does not cause an evident error, even when its width is comparable to its thickness. Based on the computational results, we further present a simple expression to correlate the buckling wavelength with the width and thickness of the film and the material properties (Young's moduli and Poisson's ratios) of the film and substrate, which has a similar form to that in the classical plane-strain problem. The fundamental solutions reported here are not only very accurate in a broad range of geometric and material parameters but also convenient for practical use since they do not involve any complex calculation.

  20. Three-dimensional measurement of multilayer thin films based on scanning white light interferometer

    NASA Astrophysics Data System (ADS)

    Shi, Zhendong; Zhang, Lin; Ren, Huan; Yuan, Quan; Yang, Yi; Ma, Hua

    2016-09-01

    For multilayer films system, in order to obtain the thickness and surface profile in each layer of thin film, a method to measure the 3D morphology of a multilayer films system based on scanning white light interferometer has been proposed in this article. At first, the mathematical relationship between reflection phase and thickness of each film layer has been obtained by using the electromagnetic field boundary conditions. Then, a nonlinear least square algorithm has been used to fit the reflection phase which had been found through a scanning white light interferometer, in this way the linear and nonlinear terms of the reflection phase have been separated, which made it possible to measure top-layer surface profile and thickness of each thin film layer respectively and avoided the interference with each other, because the linear term is related to the top layer's surface profile but the nonlinear term is correlated to the thickness of each film layer in multilayer thin films system. Thus, the three-dimensional morphology of multilayer thin films system could be reconstructed. Experimental results showed this method was effective in the three-dimensional morphology measurement for multilayer thin films. And the measurement could be completed just using the existing commercial scanning white light interferometer, as a consequence the measurement cost is low, and the operation will be quite simple.

  1. Development and antilisterial activity of PE-based biological preservative films incorporating plantaricin BM-1.

    PubMed

    Zhang, Min; Gao, Xiuzhi; Zhang, Hongxing; Liu, Hui; Jin, Junhua; Yang, Wenge; Xie, Yuanhong

    2017-04-01

    In recent years, bacteriocin, as a natural antimicrobial compound, provides enormous promise to be used in food safety preservation. In this work, the polyethylene(PE)-based biological preservative films incorporating plantaricin BM-1, a typical IIa bacteriocin produced by Lactobacillus plantarum BM-1, were developed and characterized. The results showed that PE, low-density PE (LDPE) and high-density PE (HDPE) films soaked in plantaricin BM-1 solution had obvious antimicrobial activities against Listeria monocytogenes. And the volume of plantaricin BM-1 solution absorbed by PE, LDPE and HDPE films continued to increase and reached the maximum during exposure for up to 10, 6 and 16 h, respectively. And the maximum absorption volumes of plantaricin BM-1 solution had no significant difference (P > 0.05) between the PE, LDPE and HDPE films. When soaking in water, the release amount of plantaricin BM-1 from active PE, LDPE and HDPE films reached the maximum potency at 16, 12 and 20 h, respectively. And the maximum release amount of plantaricin BM-1 from PE and LDPE active films was dramatically more than the HDPE active film (P < 0.05). Moreover, the inhibitory effect of active films incorporating plantaricin BM-1 maintained stability for at least 120 days against L. monocytogenes stored at 25°C, which suggest a potential application of the biological preservative films on the control of foodborne pathogen L. monocytogenes. © FEMS 2016. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  2. 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.

  3. Gallic Acid as an Oxygen Scavenger in Bio-Based Multilayer Packaging Films

    PubMed Central

    Pant, Astrid F.; Sängerlaub, Sven; Müller, Kajetan

    2017-01-01

    Oxygen scavengers are used in food packaging to protect oxygen-sensitive food products. A mixture of gallic acid (GA) and sodium carbonate was used as an oxygen scavenger (OSc) in bio-based multilayer packaging films produced in a three-step process: compounding, flat film extrusion, and lamination. We investigated the film surface color as well as oxygen absorption at different relative humidities (RHs) and temperatures, and compared the oxygen absorption of OSc powder, monolayer films, and multilayer films. The films were initially brownish-red in color but changed to greenish-black during oxygen absorption under humid conditions. We observed a maximum absorption capacity of 447 mg O2/g GA at 21 °C and 100% RH. The incorporation of GA into a polymer matrix reduced the rate of oxygen absorption compared to the GA powder because the polymer acted as a barrier to oxygen and water vapor diffusion. As expected, the temperature had a significant effect on the initial absorption rate of the multilayer films; the corresponding activation energy was 75.4 kJ/mol. Higher RH significantly increased the oxygen absorption rate. These results demonstrate for the first time the production and the properties of a bio-based multilayer packaging film with GA as the oxygen scavenger. Potential applications include the packaging of food products with high water activity (aw > 0.86). PMID:28772849

  4. 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.

  5. Preparation and characterization of chitosan-based nanocomposite films with antimicrobial activity.

    PubMed

    Rhim, Jong-Whan; Hong, Seok-In; Park, Hwan-Man; Ng, Perry K W

    2006-08-09

    Four different types of chitosan-based nanocomposite films were prepared using a solvent-casting method by incorporation with four types of nanoparticles, that is, an unmodified montmorillonite (Na-MMT), an organically modified montmorillonite (Cloisite 30B), a Nano-silver, and a Ag-zeolite (Ag-Ion). X-ray diffraction patterns of the nanocomposite films indicated that a certain degree of intercalation was formed in the nanocomposite films, with the highest intercalation in the Na-MMT-incorporated films followed by films with Cloisite 30B and Ag-Ion. Scanning electron micrographs showed that in all of the nanocomposite films, except the Nano-silver-incorporated one, nanoparticles were dispersed homogeneously throughout the chitosan polymer matrix. Consequently, mechanical and barrier properties of chitosan films were affected through intercalation of nanoparticles, that is, tensile strength increased by 7-16%, whereas water vapor permeability decreased by 25-30% depending on the nanoparticle material tested. In addition, chitosan-based nanocomposite films, especially silver-containing ones, showed a promising range of antimicrobial activity.

  6. Gallic Acid as an Oxygen Scavenger in Bio-Based Multilayer Packaging Films.

    PubMed

    Pant, Astrid F; Sängerlaub, Sven; Müller, Kajetan

    2017-05-03

    Oxygen scavengers are used in food packaging to protect oxygen-sensitive food products. A mixture of gallic acid (GA) and sodium carbonate was used as an oxygen scavenger (OSc) in bio-based multilayer packaging films produced in a three-step process: compounding, flat film extrusion, and lamination. We investigated the film surface color as well as oxygen absorption at different relative humidities (RHs) and temperatures, and compared the oxygen absorption of OSc powder, monolayer films, and multilayer films. The films were initially brownish-red in color but changed to greenish-black during oxygen absorption under humid conditions. We observed a maximum absorption capacity of 447 mg O₂/g GA at 21 °C and 100% RH. The incorporation of GA into a polymer matrix reduced the rate of oxygen absorption compared to the GA powder because the polymer acted as a barrier to oxygen and water vapor diffusion. As expected, the temperature had a significant effect on the initial absorption rate of the multilayer films; the corresponding activation energy was 75.4 kJ/mol. Higher RH significantly increased the oxygen absorption rate. These results demonstrate for the first time the production and the properties of a bio-based multilayer packaging film with GA as the oxygen scavenger. Potential applications include the packaging of food products with high water activity (aw > 0.86).

  7. Physico-chemical and microstructural properties of fish gelatin/agar bio-based blend films.

    PubMed

    Mohajer, Setareh; Rezaei, Masoud; Hosseini, Seyed Fakhreddin

    2017-02-10

    This study was conducted with the aim of improving the physico-chemical properties of fish gelatin (FG) based films. For this purpose, FG was blended with agar (AG) in different compositions to acquire biodegradable films (100:0, 80:20, 60:40, 50:50 & 0:100, FG:AG). The obtained results showed that the AG addition strongly increased the film rigidity and resistance to fracture, while reducing the film stretchability, mainly at 50FG: 50AG ratio. AG incorporation greatly reduced the water vapor permeability (WVP) and solubility of gelatin films, as this decline for the blend film with a 50:50 ratio of biopolymers has been about 41% and 66%, respectively (p<0.05). Additional advantages of AG inclusion to FG films are the reduction of the UV-transmittance. Both polymers showed good compatibility, as demonstrated by scanning electron microscopy (SEM) and atomic force microscopy (AFM) images. Therefore, the blend composition influenced the properties of FG/AG bio-based films. Copyright © 2016 Elsevier Ltd. All rights reserved.

  8. Radiochromic film-based quality assurance for CT-based high-dose-rate brachytherapy.

    PubMed

    Asgharizadeh, Saeid; Bekerat, Hamed; Syme, Alasdair; Aldelaijan, Saad; DeBlois, François; Vuong, Té; Evans, Michael; Seuntjens, Jan; Devic, Slobodan

    2015-01-01

    In the past, film dosimetry was developed into a powerful tool for external beam radiotherapy treatment verification and quality assurance. The objective of this work was the development and clinical testing of the EBT3 model GafChromic film based brachytherapy quality assurance (QA) system. Retrospective dosimetry study was performed to test a patient-specific QA system for preoperative endorectal brachytherapy that uses a radiochromic film dosimetry system. A dedicated phantom for brachytherapy applicator used for rectal cancer treatment was fabricated enabling us to compare calculated-to-measured dose distributions. Starting from the same criteria used for external beam intensity-modulated radiation therapy QA (3%, 3 mm), passing criteria for high- and low-dose gradient regions were subsequently determined. Finally, we investigated the QA system's sensitivity to controlled source positional errors on selected patient plans. In low-dose gradient regions, measured dose distributions with criteria of 3%, 3 mm barely passed the test, as they showed 95% passing pixels. However, in the high-dose gradient region, a more stringent condition could be established. Both criteria of 2%, 3 mm and 3%, 2 mm with gamma function calculated using normalization to the same absolute dose value in both measured and calculated dose distributions, and matrix sizes rescaled to match each other showed more than 95% of pixels passing, on average, for 15 patient plans analyzed. Although the necessity of the patient-specific brachytherapy QA needs yet to be justified, we described a radiochromic film dosimetry-based QA system that can be a part of the brachytherapy commissioning process, as well as yearly QA program. Copyright © 2015 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.

  9. Ethanol-assisted graphene oxide-based thin film formation at pentane-water interface.

    PubMed

    Chen, Fuming; Liu, Shaobin; Shen, Jianmin; Wei, Li; Liu, Andong; Chan-Park, Mary B; Chen, Yuan

    2011-08-02

    Graphene oxide (GO) can be viewed as an amphiphilic soft material, which form thin films at organic solvent-water interfaces. However, organic solvent evaporation provides little driving force, which results in slow GO transfer in aqueous phase, thus dawdling GO film formation processes for various potential applications. We present an ethanol-assisted self-assembly method for the quick formation of GO or GO-based composite thin films with tunable composition, transmittance, and surface resistivity at pentane-water interface. The thickness of pure GO and reduced GO (rGO) films ranging from ~1 nm to more than 10 nm can be controlled by the concentration of GO in bulk solution. The transmittance of rGO films can be tuned from 72% to 97% at 550 nm while the surface resistivity changes from 8.3 to 464.6 kΩ sq(-1). Ethanol is essential for achieving quick formation of GO thin films. When ethanol is injected into GO aqueous dispersion, it serves as a nonsolvent, compromising the stability of GO and providing driving force to allow GO sheets aggregate at the water-pentane interface. On the other hand, neither the evaporation of pentane nor the mixing between ethanol and water provides sufficient driving forces to allow noteworthy amount of GO sheets to migrate from the bulk aqueous phase to the interface. This method can also be extended to prepare GO-based composites thin films with tunable composition, such as GO/single walled carbon nanotube (SWCNT) composite thin films investigated in this work. Reduced GO/SWCNT composite films show much lower surface resistivity compared to pure rGO thin films. This ethanol-assisted self-assembly method opens opportunities to design and fabricate new functional GO-based hybrid materials for various potential applications.

  10. 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.

  11. 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.

  12. Infrared Response and Optoelectronic Memory Device Fabrication Based on Epitaxial VO2 Film.

    PubMed

    Fan, Lele; Chen, Yuliang; Liu, Qianghu; Chen, Shi; Zhu, Lei; Meng, Qiangqiang; Wang, Baolin; Zhang, Qinfang; Ren, Hui; Zou, Chongwen

    2016-12-07

    In this work, high-quality VO2 epitaxial films were prepared on high-conductivity n-GaN (0001) crystal substrates via an oxide molecular beam epitaxy method. By fabricating a two-terminal VO2/GaN film device, we observed that the infrared transmittance and resistance of VO2 films could be dynamically controlled by an external bias voltage. Based on the hysteretic switching effect of VO2 in infrared range, an optoelectronic memory device was achieved. This memory device was operated under the "electrical writing-optical reading" mode, which shows promising applications in VO2-based optoelectronic device in the future.

  13. Thin-film-based sensitivity enhancement for total internal reflection fluorescence live-cell imaging.

    PubMed

    Kim, Kyujung; Cho, Eun-Jin; Huh, Yong-Min; Kim, Donghyun

    2007-11-01

    We investigated experimentally the evanescent field enhancement based on dielectric thin films in total internal reflection microscopy. The sample employed two layers of Al2O3 and SiO2 deposited on an SF10 glass substrate. Field intensity enhancement measured by fluorescent excitation of microbeads relative to that of a control sample without dielectric films was polarization dependent, determined as 4.2 and 2.4 for TE and TM polarizations, respectively, and was in good agreement with numerical results. The thin-film-based field enhancement was also applied to live-cell imaging of quantum dots, which confirmed the sensitivity enhancement qualitatively.

  14. Surface acoustic wave gas sensor based on film conductivity changes

    NASA Astrophysics Data System (ADS)

    Ricco, A. J.; Martin, S. J.; Zipperian, T. E.

    1985-12-01

    The first surfce acoustic wave (SAW) sensor that functions via changes in conductivity of a thin surface film is reported. A lead phthalocyanine (PbPc) thin film is deposted on the acoustic progagation path of a LiNbO3 SAW delay line, which serves as the feedback element of an oscillator circuit. Reaction with strongly oxidizing gases, in particular NO2, increases the conductivity of the PbPc film. Acoustoelectric coupling of the traveling electric potential wave associated with the SAW-to-charge carriers in the PbPc film slows the acoustic wave velocity, altering the oscillation frequency of the circuit. This sensor is about 1000 times more sensitive, in terms of the number of NO2 molecules that can be detected (10 to the 16th molecules/cu cm of PbPc film), than an identical SAW sensor functioning via mass loading would be. Sensitivity to a few ppm of NO2 in N2 has been demonstrated.

  15. Surface acoustic wave gas sensor based on film conductivity changes

    NASA Astrophysics Data System (ADS)

    Ricco, A. J.; Martin, S. J.; Zipperian, T. E.

    The first surface acoustic wave (SAW) sensor that functions via changes in conductivity of a thin surface film is reported. A lead phthalocyanine (PbPc) thin film is deposited on the acoustic propagation path of a LiNbO3 SAW delay line, which serves as the feedback element of an oscillator circuit. Reaction with strongly oxidizing gases, in particular NO2, increases the conductivity of the PbPc film. Acoustoelectic coupling of the traveling electric potential wave associated with the SAW-to-charge carriers in the PbPc film slows the acoustic wave velocity, altering the oscillation frequency of the circuit. This sensor is about 1000 times more sensitive, in terms of the number of NO2 molecules that can be detected (10 to the 16th molecules/cu cm of PbPc film), than an identical SAW sensor functioning via mass loading would be. Sensitivity to a few ppm of NO2 in Ne was demonstrated.

  16. Buccal delivery of acyclovir from films based on chitosan and polyacrylic acid.

    PubMed

    Rossi, Silvia; Sandri, Giuseppina; Ferrari, Franca; Bonferoni, Maria Cristina; Caramella, Carla

    2003-01-01

    The aim of the present work was to investigate the possibility of achieving buccal delivery of a problematic drug, acyclovir, from films based on chitosan hydrochloride (HCS) and polyacrylic acid sodium salt (PAA). At first, the ionic interaction between HCS and PAA in distilled water was investigated by means of rheological and turbidimetric analysis. Films containing 1 mg/cm2 of acyclovir and based on pure HCS and on HCS and PAA mixed in different ratios were prepared by casting technique. The films were subjected to hydration, rheological, mucoadhesion, drug release, "wash away," and permeation/penetration measurements. A commercial cream containing acyclovir and an aqueousacyclovir suspension were used as references. The addition of PAA to HCS produced a decrease in film hydration. Films based on HCS/PAA weight ratio close to interaction productstoichiometry were characterized by higher rigidity and better "wash away" properties with respect to the other films and the reference formulation. The worst mucoadhesive properties were shown by films based on mixing ratios close to interaction product stoichiometry. The addition of PAA to HCS produced a lowering in drug release profile. All the films examined promoted the permeation of acyclovir across porcine cheek epithelium when compared with acyclovir suspension and the commercial cream. The penetration enhancement properties were affected by the mixing ratio of the two polymers. The film based on 1/1.3 HCS/PAA weight ratio, besides possessing the best resilience properties on the mucosa, was also characterized by the highest permeation profile and, therefore, represents a promising formulation for buccal delivery of acyclovir.

  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.

  18. 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.

  19. Radiation dose dependent change in physiochemical, mechanical and barrier properties of guar gum based films.

    PubMed

    Saurabh, Chaturbhuj K; Gupta, Sumit; Bahadur, Jitendra; Mazumder, S; Variyar, Prasad S; Sharma, Arun

    2013-11-06

    Mechanical and water vapor barrier properties of biodegradable films prepared from radiation processed guar gum were investigated. Films prepared from GG irradiated up to 500 Gy demonstrated significantly higher tensile strength as compared to non-irradiated control films. This improvement in tensile strength observed was demonstrated to be due to the ordering of polymer structures as confirmed by small angle X-ray scattering analysis. Exposure to doses higher than 500 Gy, however, resulted in a dose dependent decrease in tensile strength. A dose dependent decrease in puncture strength with no significant differences in the percent elongation was also observed at all the doses studied. Water vapor barrier properties of films improved up to 15% due to radiation processing. Radiation processing at lower doses for improving mechanical and barrier properties of guar based packaging films is demonstrated here for the first time.

  20. 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.