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Sample records for adsorbed organic films

  1. Computer simulations of adsorbed liquid crystal films

    NASA Astrophysics Data System (ADS)

    Wall, Greg D.; Cleaver, Douglas J.

    2003-01-01

    The structures adopted by adsorbed thin films of Gay-Berne particles in the presence of a coexisting vapour phase are investigated by molecular dynamics simulation. The films are adsorbed at a flat substrate which favours planar anchoring, whereas the nematic-vapour interface favours normal alignment. On cooling, a system with a high molecule-substrate interaction strength exhibits substrate-induced planar orientational ordering and considerable stratification is observed in the density profiles. In contrast, a system with weak molecule-substrate coupling adopts a director orientation orthogonal to the substrate plane, owing to the increased influence of the nematic-vapour interface. There are significant differences between the structures adopted at the two interfaces, in contrast with the predictions of density functional treatments of such systems.

  2. Hydrophobic Porous Material Adsorbs Small Organic Molecules

    NASA Technical Reports Server (NTRS)

    Sharma, Pramod K.; Hickey, Gregory S.

    1994-01-01

    Composite molecular-sieve material has pore structure designed specifically for preferential adsorption of organic molecules for sizes ranging from 3 to 6 angstrom. Design based on principle that contaminant molecules become strongly bound to surface of adsorbent when size of contaminant molecules is nearly same as that of pores in adsorbent. Material used to remove small organic contaminant molecules from vacuum systems or from enclosed gaseous environments like closed-loop life-support systems.

  3. Performance of PF BL-13A, a vacuum ultraviolet and soft X-ray undulator beamline for studying organic thin films adsorbed on surfaces

    NASA Astrophysics Data System (ADS)

    Toyoshima, Akio; Kikuchi, Takashi; Tanaka, Hirokazu; Mase, Kazuhiko; Amemiya, Kenta; Ozawa, Kenichi

    2013-03-01

    We report on the present status of a vacuum ultraviolet and soft X-ray undulator beamline, BL-13A, located at the Photon Factory. BL-13A is mainly dedicated to the study of organic thin films adsorbed on well-defined surfaces, using angle-resolved photoelectron spectroscopy (ARPES), X-ray photoelectron spectroscopy (XPS), and X-ray absorption spectroscopy (XAS). The photon-energy resolution (E/ΔE) is estimated to be about 10000 at a photon energy of 64 eV with an exit-slit width of 30 μm. The photon intensity is estimated to be 2.9 × 1012 to 5.6 × 108 photons/s for photon energies of 30-1600 eV with an exit-slit width of 100 μm at the ring current of 450 mA. An ultrahigh vacuum (UHV) chamber equipped with an electron-energy analyzer (Gamma Data/Scienta, SES 200) is used as the main end station for ARPES, XPS, and XAS measurements. A sample can be transferred from a UHV chamber for sample preparation or from a UHV chamber for the evaporation of organic materials. The sample-holder acceptors are equipped with a heating and cooling system. The overall electron-energy resolution is estimated to be about 12 meV at a photon energy of 30 eV.

  4. Size selective hydrophobic adsorbent for organic molecules

    NASA Technical Reports Server (NTRS)

    Sharma, Pramod K. (Inventor); Hickey, Gregory S. (Inventor)

    1997-01-01

    The present invention relates to an adsorbent formed by the pyrolysis of a hydrophobic silica with a pore size greater than 5 .ANG., such as SILICALITE.TM., with a molecular sieving polymer precursor such as polyfurfuryl alcohol, polyacrylonitrile, polyvinylidene chloride, phenol-formaldehyde resin, polyvinylidene difluoride and mixtures thereof. Polyfurfuryl alcohol is the most preferred. The adsorbent produced by the pyrolysis has a silicon to carbon mole ratio of between about 10:1 and 1:3, and preferably about 2:1 to 1:2, most preferably 1:1. The pyrolysis is performed as a ramped temperature program between about 100.degree. and 800.degree. C., and preferably between about 100.degree. and 600.degree. C. The present invention also relates to a method for selectively adsorbing organic molecules having a molecular size (mean molecular diameter) of between about 3 and 6 .ANG. comprising contacting a vapor containing the small organic molecules to be adsorbed with the adsorbent composition of the present invention.

  5. Interactions of organic contaminants with mineral-adsorbed surfactants

    USGS Publications Warehouse

    Zhu, L.; Chen, B.; Tao, S.; Chiou, C.T.

    2003-01-01

    Sorption of organic contaminants (phenol, p-nitrophenol, and naphthalene) to natural solids (soils and bentonite) with and without myristylpyridinium bromide (MPB) cationic surfactant was studied to provide novel insight to interactions of contaminants with the mineral-adsorbed surfactant. Contaminant sorption coefficients with mineral-adsorbed surfactants, Kss, show a strong dependence on surfactant loading in the solid. At low surfactant levels, the Kss values increased with increasing sorbed surfactant mass, reached a maximum, and then decreased with increasing surfactant loading. The Kss values for contaminants were always higher than respective partition coefficients with surfactant micelles (Kmc) and natural organic matter (Koc). At examined MPB concentrations in water the three organic contaminants showed little solubility enhancement by MPB. At low sorbed-surfactant levels, the resulting mineral-adsorbed surfactant via the cation-exchange process appears to form a thin organic film, which effectively "adsorbs" the contaminants, resulting in very high Kss values. At high surfactant levels, the sorbed surfactant on minerals appears to form a bulklike medium that behaves essentially as a partition phase (rather than an adsorptive surface), with the resulting Kss being significantly decreased and less dependent on the MPB loading. The results provide a reference to the use of surfactants for remediation of contaminated soils/sediments or groundwater in engineered surfactant-enhanced washing.

  6. Structure and properties of water film adsorbed on mica surfaces

    NASA Astrophysics Data System (ADS)

    Zhao, Gutian; Tan, Qiyan; Xiang, Li; Cai, Di; Zeng, Hongbo; Yi, Hong; Ni, Zhonghua; Chen, Yunfei

    2015-09-01

    The structure profiles and physical properties of the adsorbed water film on a mica surface under conditions with different degrees of relative humidity are investigated by a surface force apparatus. The first layer of the adsorbed water film shows ice-like properties, including a lattice constant similar with ice crystal, a high bearing capacity that can support normal pressure as high as 4 MPa, a creep behavior under the action of even a small normal load, and a character of hydrogen bond. Adjacent to the first layer of the adsorbed water film, the water molecules in the outer layer are liquid-like that can flow freely under the action of external loads. Experimental results demonstrate that the adsorbed water layer makes the mica surface change from hydrophilic to weak hydrophobic. The weak hydrophobic surface may induce the latter adsorbed water molecules to form water islands on a mica sheet.

  7. Hydraulic properties of adsorbed water films in unsaturated porous media

    SciTech Connect

    Tokunaga, Tetsu K.

    2009-03-01

    Adsorbed water films strongly influence residual water saturations and hydraulic conductivities in porous media at low saturations. Hydraulic properties of adsorbed water films in unsaturated porous media were investigated through combining Langmuir's film model with scaling analysis, without use of any adjustable parameters. Diffuse double layer influences are predicted to be important through the strong dependence of adsorbed water film thickness (f) on matric potential ({Psi}) and ion charge (z). Film thickness, film velocity, and unsaturated hydraulic conductivity are predicted to vary with z{sup -1}, z{sup -2}, and z{sup -3}, respectively. In monodisperse granular media, the characteristic grain size ({lambda}) controls film hydraulics through {lambda}{sup -1} scaling of (1) the perimeter length per unit cross sectional area over which films occur, (2) the critical matric potential ({Psi}{sub c}) below which films control flow, and (3) the magnitude of the unsaturated hydraulic conductivity when {Psi} < {Psi}{sub c}. While it is recognized that finer textured sediments have higher unsaturated hydraulic conductivities than coarser sands at intermediate {Psi}, the {lambda}{sup -1} scaling of hydraulic conductivity predicted here extends this understanding to very low saturations where all pores are drained. Extremely low unsaturated hydraulic conductivities are predicted under adsorbed film-controlled conditions (generally < 0.1 mm y{sup -1}). On flat surfaces, the film hydraulic diffusivity is shown to be constant (invariant with respect to {Psi}).

  8. Optical spectroscopy and scanning tunneling microscopy studies of molecular adsorbates and anisotropic ultrathin films. Final report

    SciTech Connect

    Hemminger, J.C.

    1998-09-01

    The bonding, chemistry and ordering of molecular adsorbates on well defined single crystal surfaces and in ultrathin films was to be studied in an effort to develop sufficient fundamental understanding to allow the controlled preparation of anisotropic ultrathin films of organic monolayers. In this research the authors combine the use of optical probes (Raman spectroscopy, laser induced thermal desorption with Fourier transform mass spectrometry detection) with scanning tunneling microscopy (STM) and conventional methods of UHV surface science (Auger electron spectroscopy, x-ray photoelectron spectroscopy, low energy electron diffraction, and thermal desorption spectroscopy). The conventional surface probes provide well tested methods for the preparation and characterization of single crystal substrates. The optical probes used in the experiments provide powerful methods for the molecular identification of adsorbates in monolayers and ultrathin films. Scanning tunneling microscopy provides one with the ability to determine the detailed molecular level ordering of the molecular adsorbates. The emphasis of this research is on more complex molecular absorbates some of which are monomer precursors to ultrathin polymer films. Enhanced methods of Raman spectroscopy have been developed for the study of monolayer adsorbates on surfaces in ultrahigh vacuum environments. This report gives an overview of recent research results, including the construction of UHV variable temperature STM, analysis of STM images, growth and chemistry of intermetallic single crystal ultrathin films, and electron beam induced chemistry of tetracyanoquinodimethane.

  9. Alkylammonium montmorillonites as adsorbents for organic vapors from air

    SciTech Connect

    Harper, M.; Purnell, C.J. )

    1990-01-01

    Montmorillonite clays may be modified by the exchange of the inorganic interlayer cations with alkylammonium ions, resulting in a fixed internal porosity. The pore size and shape depend on the nature of the alkylammonium ion. A number of different ions were used to prepare adsorbents with varying properties, and these were examined for their potential application to sampling organic vapors in air. Characterization involved determination of nitrogen and water contents, surface area, interlayer spacing, thermal stability, and breakthrough volumes of organic vapors. The adsorbent that showed the most promise (tetramethylammonium montmorillonite (TMA)) was further evaluated for use as an adsorbent in both thermal- and solvent-desorable sampling systems.

  10. Complexation of trace metals by adsorbed natural organic matter

    USGS Publications Warehouse

    Davis, J.A.

    1984-01-01

    The adsorption behavior and solution speciation of Cu(II) and Cd(II) were studied in model systems containing colloidal alumina particles and dissolved natural organic matter. At equilibrium a significant fraction of the alumina surface was covered by adsorbed organic matter. Cu(II) was partitioned primarily between the surface-bound organic matter and dissolved Cu-organic complexes in the aqueous phase. Complexation of Cu2+ with the functional groups of adsorbed organic matter was stronger than complexation with uncovered alumina surface hydroxyls. It is shown that the complexation of Cu(II) by adsorbed organic matter can be described by an apparent stability constant approximately equal to the value found for solution phase equilibria. In contrast, Cd(II) adsorption was not significantly affected by the presence of organic matter at the surface, due to weak complex formation with the organic ligands. The results demonstrate that general models of trace element partitioning in natural waters must consider the presence of adsorbed organic matter. ?? 1984.

  11. AQUATIC PHOTOLYSIS OF OXY-ORGANIC COMPOUNDS ADSORBED ON GOETHITE.

    USGS Publications Warehouse

    Goldberg, Marvin C.

    1985-01-01

    Organic materials that will not absorb light at wavelengths longer than 295 nanometers (the solar wavelength cutoff) may nevertheless, undergo electron transfer reactions initiated by light. These reactions occur when the organic materials are adsorbed as ligand complexes to the surface of iron oxy-hydroxide (goethite). The adsorbed materials can be either inner or outer coordination sphere complexes. Goethite was chosen as the iron oxyhydroxide surface because it has the highest thermodynamic stability of any of the oxyhydroxides in water and it can be synthesized easily, with high purity.

  12. Adsorbed Methane Film Properties in Nanoporous Carbon Monoliths

    NASA Astrophysics Data System (ADS)

    Soo, Yuchoong; Chada, Nagaraju; Beckner, Matthew; Romanos, Jimmy; Burress, Jacob; Pfeifer, Peter

    2013-03-01

    Carbon briquetting can increase methane storage capacity by reducing the useless void volume resulting in a better packing density. It is a robust and efficient space-filling form for an adsorbed natural gas vehicle storage tank. To optimize methane storage capacity, we studied three fabrication process parameters: carbon-to-binder ratio, compaction temperature, and pyrolysis temperature. We found that carbon-to-binder ratio and pyrolysis temperature both have large influences on monolith uptakes. We have been able to optimize these parameters for high methane storage. All monolith uptakes (up to 260 bar) were measured by a custom-built, volumetric, reservoir-type instrument. The saturated film density and the film thickness was determined using linear extrapolation on the high pressure excess adsorption isotherms. The saturated film density was also determined using the monolayer Ono-Kondo model. Film densities ranged from ca. 0.32 g/cm3 - 0.37 g/cm3.The Ono-Kondo model also determines the binding energy of methane. Binding energies were also determined from isosteric heats calculated from the Clausius-Clapeyron equation and compared with the Ono-Kondo model method. Binding energies from Ono-Kondo were ca. 7.8 kJ/mol - 10 kJ/mol. Work funded by California Energy Commission Contract #500-08-022.

  13. DESIGNING FIXED-BED ADSORBERS TO REMOVE MIXTURES OF ORGANICS.

    EPA Science Inventory

    A liquid-phase granular activated carbon (GAC) pilot plant and a full-scale GAC adsorber were designed, built, and operated in order to evaluate their performance for treating a groundwater contaminated with several volatile and synthetic organic chemicals. Several empty bed con...

  14. Adsorbed water and thin liquid films on Mars

    NASA Astrophysics Data System (ADS)

    Boxe, C. S.; Hand, K. P.; Nealson, K. H.; Yung, Y. L.; Yen, A. S.; Saiz-Lopez, A.

    2012-07-01

    At present, bulk liquid water on the surface and near-subsurface of Mars does not exist due to the scarcity of condensed- and gas-phase water, pressure and temperature constraints. Given that the nuclei of soil and ice, that is, the soil solid and ice lattice, respectively, are coated with adsorbed and/or thin liquid films of water well below 273 K and the availability of water limits biological activity, we quantify lower and upper limits for the thickness of such adsorbed/water films on the surface of the Martian regolith and for subsurface ice. These limits were calculated based on experimental and theoretical data for pure water ice and water ice containing impurities, where water ice containing impurities exhibit thin liquid film enhancements, ranging from 3 to 90. Close to the cold limit of water stability (i.e. 273 K), thin liquid film thicknesses at the surface of the Martian regolith is 0.06 nm (pure water ice) and ranges from 0.2 to 5 nm (water ice with impurities). An adsorbed water layer of 0.06 nm implies a dessicated surface as the thickness of one monolayer of water is 0.3 nm but represents 0.001-0.02% of the Martian atmospheric water vapour inventory. Taking into account the specific surface area (SSA) of surface-soil (i.e. top 1 mm of regolith and 0.06 nm adsorbed water layer), shows Martian surface-soil may contain interfacial water that represents 6-66% of the upper- and lower-limit atmospheric water vapour inventory and almost four times and 33%, the lower- and upper-limit Martian atmospheric water vapour inventory. Similarly, taking the SSA of Martian soil, the top 1 mm or regolith at 5 nm thin liquid water thickness, yields 1.10×1013 and 6.50×1013 litres of waters, respectively, 55-325 times larger than Mars' atmospheric water vapour inventory. Film thicknesses of 0.2 and 5 nm represent 2.3×104-1.5×106 litres of water, which is 6.0×10-7-4.0×10-4%, respectively, of a 10 pr μm water vapour column, and 3.0×10-6-4.0×10-4% and 6.0×10

  15. Selective Gas Capture Ability of Gas-Adsorbent-Incorporated Cellulose Nanofiber Films.

    PubMed

    Shah, Kinjal J; Imae, Toyoko

    2016-05-01

    The 2,2,6,6-tetramethylpiperidine-1-oxyl radical-oxidized cellulose nanofibers (TOCNF) were hybridized with cation and anion-exchange organoclays, where poly(amido amine) dendrimers were loaded to enhance the functionality of gas adsorption, since dendrimers have the high adsorbability and the enough selectivity on the gas adsorption. The thin films were prepared from the organoclay-TOCNF hybrids and supplied to the gas adsorption. The adsorption of CO2 and NH3 gases increased with an increasing amount of organoclays in TOCNF films, but the behavior of the increase depended on gases, clays, and dendrimers. The hydrotalcite organoclay-TOCNF films displayed the highest adsorption of both gases, but the desorption of CO2 gas from hydrotalcite organoclay-TOCNF films was drastically high in comparison with the other systems. While the CO2 gas is adsorbed and remained on cationic dendrimer sites in cation-exchange organoclay-TOCNF films, the CO2 gas is adsorbed on cationic clay sites in anion exchange organoclay-TOCNF films, and it is easily desorbed from the films. The NH3 adsorption is inversive to the CO2 adsorption. Then the CO2 molecules adsorbed on the cationic dendrimers and the NH3 molecules adsorbed on the anionic dendrimers are preferably captured in these adsorbents. The present research incorporated dendrimers will be contributing to the development of gas-specialized adsorbents, which are selectively storable only in particular gases. PMID:27035217

  16. Enhanced photodegradation of organic dyes adsorbed on a clay.

    PubMed

    Tani, Seiji; Yamaki, Hiroshi; Sumiyoshi, Azumi; Suzuki, Yasutaka; Hasegawa, Shinya; Yamazaki, Suzuko; Kawamata, Jun

    2009-01-01

    The interaction of three photoactive organic dyes, Rhodamine B, Rhodamine 6G and a stilbazolium derivative 4'-dimethylamino-N-methyl-4-stilbazolium with synthetic sodium-saponite has been examined by UV-visible absorption spectroscopy. In all cases, bathochromic shifts and the reduction of peak absorbance for the dyes were observed in the absorption spectra at a low dye concentration (25% adsorption of the cation exchange capacity (CEC) of the clay), although the shape and the width of their absorption bands were similar to those in aqueous solution. This absorption behavior indicates that the organic dye molecules adsorbed onto the surface of the negatively charged clay particles and the adsorbed molecules were well dispersed. The photodegradation of the organic dyes in aqueous solution and in the clay suspension has been also examined by the irradiation of a laser beam at a wavelength of 532 nm. We have found that the hybridization of the organic dyes with the exfoliated clay particles largely enhanced a photodegradation. The clay particles acted as a catalyst even at a high concentration such as approximately 300% of CEC. PMID:19441365

  17. Effects of the Adsorbed Polymer Nanolayers on the Dewetting of Polystyrene Thin Films

    NASA Astrophysics Data System (ADS)

    Cheung, Justin; Wang, Jiaxun; Jiang, Naisheng; Endoh, Maya; Koga, Tadanori

    2015-03-01

    It was previously reported that irreversibly adsorbed polymer nanolayers can be produced on solid substrates by thermal annealing. This study sought to determine the impact of the adsorbed nanolayers on film stability of ultrathin polystyrene (PS) films. A series of bilayers composed of the bottom PS adsorbed nanolayers and PS overlayers with different molecular weights were prepared as model systems. The surface structures of the bilayer films annealed above the bulk glass transition temperature were analyzed by using optical and atomic force microscopes. We will discuss the unique roles of the adsorbed polymer chains in the stability of the liquid thin films. T. K. acknowledges the partial financial support from NSF Grant No. CMMI-1332499.

  18. Aging of the nanosized photochromic WO3 films and the role of adsorbed water in the photochromism

    NASA Astrophysics Data System (ADS)

    Gavrilyuk, A. I.

    2016-02-01

    Here it has been reported on aging of the nanosized WO3 film, which is revealed is continuous reduction of the photochromic sensitivity over time. Water molecules physically adsorbed on the film surface from ambient air form donor-acceptor and hydrogen bonds, changing gradually the adsorption state to chemisorption which prevents an access of organic molecules that serve as hydrogen donors by the photochromism. The mechanism of the process has been investigated and discussed. The role of water in the photochromism has been highlighted. The difference in the efficiency for being of a hydrogen donor in the photochromic process between water and organic molecules is discussed.

  19. Direct Measurement of the Adsorbed Film Volume for Estimating Heats of Adsorption

    NASA Astrophysics Data System (ADS)

    Gillespie, Andrew; Dohnke, Elmar; Rash, Tyler; Stalla, David; Knight, Ernest; Seydel, Florian; Sweany, Mark; Pfeifer, Peter

    Compressed hydrogen and methane require extremely high pressures or low temperatures in order to compete with the energy density of conventional fossil fuels. Adsorbent materials provide a means to increase the energy density of these gasses up to 6 times that of compressed gas at the same temperature and pressure. One major concern in engineering adsorbed gas systems is thermal management during charging and discharging. Adsorption is an exothermic process, releasing heat during charging and absorbing heat during discharging. To estimate the heat of adsorption, it is common to analyze excess adsorption isotherms by converting to absolute adsorption and employ the Clausius Clapeyron relation. However, this method requires an assumed volume of the adsorbed state. It is common for researchers to assume that the adsorbed film occupies the entire pore volume of the adsorbent material. However, the adsorbed film only occupies a fraction of the total pore volume. This yields heats of adsorption that are underestimated by as much as 10kJ/mol at high coverage. In this talk, we present a method to directly measure the adsorbed film volume as a function of temperature and present the resulting heats of adsorption for both methane and hydrogen.

  20. Heat capacity measurements of atoms and molecules adsorbed on evaporated metal films

    SciTech Connect

    Kenny, T.W.

    1989-05-01

    Investigations of the properties of absorbed monolayers have received great experimental and theoretical attention recently, both because of the importance of surface processes in practical applications such as catalysis, and the importance of such systems to the understanding of the fundamentals of thermodynamics in two dimensions. We have adapted the composite bolometer technology to the construction of microcalorimeters. For these calorimeters, the adsorption substrate is an evaporated film deposited on one surface of an optically polished sapphire wafer. This approach has allowed us to make the first measurements of the heat capacity of submonolayer films of /sup 4/He adsorbed on metallic films. In contrast to measurements of /sup 4/He adsorbed on all other insulating substrates, we have shown that /sup 4/He on silver films occupies a two-dimensional gas phase over a broad range of coverages and temperatures. Our apparatus has been used to study the heat capacity of Indium flakes. CO multilayers, /sup 4/He adsorbed on sapphire and on Ag films and H/sub 2/ adsorbed on Ag films. The results are compared with appropriate theories. 68 refs., 19 figs.

  1. Elastic mediated force between nanoparticles adsorbed on smectic films under an external field.

    PubMed

    Pereira, Maria S S; Lyra, Marcelo L; de Oliveira, Italo N

    2013-02-01

    Within the harmonic approximation, we analytically determine the elastic-mediated interaction between colloidal nanoparticles adsorbed on the surface of smectic films under the influence of an external field. Both cases of free-standing films and films deposited over a solid substrate are considered. We show that the asymptotic decay (1/R in free-standing and exponential in deposited films) is not altered by the external field. However, the external field plays distinct roles according to the film configuration, the interparticle distance, the film thickness, and the surface tension at the film-gas interface. We provide a detailed discussion under the light of the distinct mechanisms controlling the undulations of the surface layer. PMID:23496530

  2. Structure and dynamics of ultrathin organic films

    NASA Astrophysics Data System (ADS)

    Kiktyeva, Tatyana A.

    Existing and newly developed nonlinear optical methods have been used to characterize molecular structure, orientation and dynamics at interfaces. Optical second harmonic generation (SHG) studies have been conducted on molecular films of the organic dyes, rhodamine 6G and malachite green, adsorbed at the fused silica/air interface. The second harmonic response from the organic dye films was found to be a non-monotonic function of the surface concentration with discontinuities corresponding to completion of successive monolayers. This behavior reflects ordering of molecular adlayers, which extends for several layers. Polarized SHG studies in conjunction with optical absorbance and fluorescence measurements were used to determine the type of interactions responsible for the adsorption in the ordered layers. The results indicate that the well-defined order within the first layer is due to the specific adsorbate-substrate interactions. Orientation in subsequent layers is teed by adsorbate-adsorbate interactions, dependent on the nature of the adsorbate and consequently on its orientation within the first layer. These results provide a direct measure of the extent of the interfacial ordering and molecular interactions at the solid/air interface and can be used to determine an adsorbate's filling factor. Time and frequency resolved vibrational spectra of a monolayer of amphiphilic molecules at the CaF2/air interface were investigated using infrared-visible sum frequency generation. Vibrational wave packet dynamics following coherent excitation of CH3 vibrational modes with broad bandwidth infrared pulses is reported. The induced macroscopic polarization displays quantum interference effects (quantum beats) and decays on a time scale dependent on the nature of the interfacial environment. These observations provide a link between the degree of structural order of the monolayer and the vibrational coherence lifetime. Monitoring interfacial wave packet dynamics represents a

  3. Adsorbate-induced demagnetization and restructuring of ultrathin magnetic films: CO chemisorbed on γ-Fe/Cu(100)

    NASA Astrophysics Data System (ADS)

    Spišák, D.; Hafner, J.

    2001-09-01

    First-principles local-spin-density (LSD) investigations of the structural, magnetic, and electronic properties of clean and CO-adsorbed ultrathin γ-iron films epitaxially grown on Cu(100) surfaces demonstrate that both the geometrical and the magnetic structures of the films are profoundly modified by the adsorption of CO. The enhanced magnetic moments of the top-layer atoms are strongly quenched by the presence of the adsorbate. Due to the pronounced magnetovolume effect, this leads also to a correlated change in the interlayer relaxations. Strikingly, the adsorbate-induced demagnetization is primarily limited to those surface atoms directly bonded to the adsorbate. This leads to the formation of an in-plane magnetic pattern in a partially adsorbate-covered film. The comparison of the calculated vibrational eigenfrequencies of the CO adsorbate with experiment confirms the picture based on the LSD calculations.

  4. Thermodynamic study of argon films adsorbed on boron nitride

    SciTech Connect

    Migone, A.D.; Alkhafaji, M.T. ); Vidali, G. ); Karimi, M. )

    1993-03-15

    We have performed a detailed adsorption isotherm study of Ar on BN for temperatures between 65 and 80 K. The isothermal compressibility of the films was obtained from adsorption data. At monolayer coverages, a small isotherm substep is present at melting. We found two isothermal compressibility peaks in the first layer: a sharp peak, corresponding to the melting substep, and a smaller, broader peak that occurs at lower pressures. At multilayer coverages we found reentrant layering occurring in the third and fourth layers of the film. We compare our layering results with predictions for the preroughening transition. We also found a series of small steps in the isotherms between the second and third layers and between the third and fourth layers of the film. These small steps are evidence of individual layer melting for the second and third layers. Our results at monolayer and at multilayer coverages are extensively compared to those found for Ar on graphite. We have also performed calculations of the rare-gas--BN interaction potentials. Our calculations indicate the substrate corrugation is smaller for the rare-gas--BN systems than it is for the same rare gases on graphite. The implications of this result for the possible existence of monolayer-commensurate solids on BN are discussed.

  5. Influence of fluoride-detergent combinations on the visco-elasticity of adsorbed salivary protein films.

    PubMed

    Veeregowda, Deepak H; van der Mei, Henny C; Busscher, Henk J; Sharma, Prashant K

    2011-02-01

    The visco-elasticity of salivary-protein films is related to mouthfeel, lubrication, biofilm formation, and protection against erosion and is influenced by the adsorption of toothpaste components. The thickness and the visco-elasticity of hydrated films (determined using a quartz crystal microbalance) of 2-h-old in vitro-adsorbed salivary-protein films were 43.5 nm and 9.4 MHz, respectively, whereas the dehydrated thickness, measured using X-ray photoelectron spectroscopy, was 2.4 nm. Treatment with toothpaste slurries decreased the thickness of the film, depending on the fluoride-detergent combination involved. Secondary exposure to saliva resulted in a regained thickness of the film to a level similar to its original thickness; however, no association was found between the thickness of hydrated and dehydrated films, indicating differences in film structure. Treatment with stannous fluoride/sodium lauryl sulphate (SnF(2)/SLS)-containing toothpaste slurries yielded a strong, immediate two-fold increase in characteristic film frequency (f(c)) with respect to untreated films, indicating cross-linking in adsorbed salivary-protein films by Sn(2+) that was absent when SLS was replaced with sodium hexametaphosphate (NaHMP). Secondary exposure to saliva of films treated with SnF(2) caused a strong, six-fold increase in f(c) compared with primary salivary-protein films, regardless of whether SLS or NaHMP was the detergent. This suggests that ionized stannous is not directly available for cross-linking in combination with highly negatively charged NaHMP, but becomes slowly available after initial treatment to cause cross-linking during secondary exposure to saliva. PMID:21244507

  6. Electron-Stimulated Oxidation of Thin Water Films Adsorbed on TiO2(110)

    SciTech Connect

    Lane, Christopher D.; Petrik, Nikolay G.; Orlando, Thomas M.; Kimmel, Greg A.

    2007-11-08

    Electron-stimulated reactions in thin (< 3 monolayer, ML) water films adsorbed on TiO2(110) are investigated. For electron fluences less than ~1×1016 e-/cm2, irradiation with 100 eV electrons results in electron-stimulated desorption (ESD) of atomic and molecular hydrogen, but no measurable O2. The ESD leaves adsorbed hydroxyls which oxidize the TiO2(110) surface and change the post-irradiation TPD spectra of the remaining water in characteristic ways. The species remaining on the TiO2(110) after irradiation of adsorbed water films are apparently similar to those produced without irradiation by co-dosing water and O2. Annealing above ~600 K reduces the oxidized surfaces, and water TPD spectra characteristic of ion sputtered and annealed TiO2(110) are recovered. The rate of electron-stimulated “oxidation” of the water films is proportional to the coverage of water in the first layer for coverages less than 1 ML. However, higher coverages suppress this reaction. When thin water films are irradiated, the rate of electron-stimulated oxidation is independent of the initial oxygen vacancy concentration, as is the final oxidized state achieved at high electron fluences. To explain the results, we propose that electron excitation of water molecules adsorbed on Ti4+ sites leads to desorption of hydrogen atoms and leaves an OH adsorbed at the site. If hydroxyls are present in the bridging oxygen rows, these react with the OH’s on the Ti4+ sites to reform water and heal the oxygen vacancy associated with the bridging OH. Once the bridge bonded hydroxyls have been eliminated, further irradiation increases the concentration of OH’s in the Ti4+ rows leading to the creation of species which block sites in the Ti4+ rows, perhaps H2O2 and/or HO2.

  7. RADIOLYSIS OF ORGANIC COMPOUNDS IN THE ADSORBED STATE

    DOEpatents

    Sutherland, J.W.; Allen, A.O.

    1961-10-01

    >A method of forming branch chained hydrocarbons by means of energetic penetrating radiation is described. A solid zeolite substrate is admixed with a cobalt ion and is irradiated with a hydrocarbon adsorbed therein. Upon irradiation with gamma rays, there is an increased yield of branched and lower molecular straight chain compounds. (AEC)

  8. 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.

  9. Unusual Morphologies of Poly(vinyl alcohol) Thin Films Adsorbed on Poly(dimethylsiloxane) Substrates.

    PubMed

    Karki, Akchheta; Nguyen, Lien; Sharma, Bhanushee; Yan, Yan; Chen, Wei

    2016-04-01

    Adsorption of poly(vinyl alcohol) (PVOH), 99% and 88% hydrolyzed poly(vinyl acetate), to poly(dimethylsiloxane) (PDMS) substrates was studied. The substrates were prepared by covalently attaching linear PDMS polymers of 2, 9, 17, 49, and 116 kDa onto silicon wafers. As the PDMS molecular weight/thickness increases, the adsorbed PVOH thin films progressively transition from continuous to discontinuous morphologies, including honeycomb and fractal/droplet. The structures are the result of thin film dewetting that occurs upon exposure to air. The PVOH film thickness does not vary significantly on these PDMS substrates, implicating the PDMS thickness as the cause for the morphology differences. The adsorbed PVOH thin films are less stable and have a stronger tendency to dewet on thicker, more liquid-like PDMS layers. When PVOH(99%) and PVOH(88%) thin films are compared, fractal and droplet morphologies are observed on high molecular weight PDMS substrates, respectively. The formation of the unique fractal features in the PVOH(99%) thin films as well as other crystalline and semicrystalline thin films is most likely driven by crystallization during the dehydration process in a diffusion-limited aggregation fashion. The only significant enhancement in hydrophilicity via PVOH adsorption was obtained on PDMS(2k), which is completely covered with a PVOH thin film. To mimic the lower receding contact angle and less liquid-like character of the PDMS(2k) substrate, light plasma treatment of the higher molecular weight PDMS substrates was carried out. On the treated PDMS substrates, the adsorbed PVOH thin films are in the more continuous honeycomb morphology, giving rise to significantly enhanced wettability. Furthermore, hydrophobic recovery of the hydrophilized PDMS substrates was not observed during a 1 week period. Thus, light plasma oxidation and subsequent PVOH adsorption can be utilized as a means to effectively hydrophilize conventional PDMS substrates. This study

  10. EVALUATION OF SOLID ADSORBENTS FOR THE COLLECTION AND ANALYSES OF AMBIENT BIOGENIC VOLATILE ORGANICS

    EPA Science Inventory

    Micrometeorological flux measurements of biogenic volatile organic compounds (BVOCs) usually require that large volumes of air be collected (whole air samples) or focused during the sampling process (cryogenic trapping or gas-solid partitioning on adsorbents) in order to achiev...

  11. Structural investigations of adsorbed films of Methyl Halides on Boron Nitride

    NASA Astrophysics Data System (ADS)

    Sprung, Michael; Freitag, Andrea; Hanson, Jonathan; Larese, John

    2000-03-01

    The Methyl Halides are a group of molecules whose properties of thin adsorbed films on Graphite have been well characterized. Boron Nitride forms a hexagonal structure with a slightly larger (about 2% ) unit cell than Graphite. The study of thin films of Methyl Halides (CH_3R, R=Cl, Br and I) on Boron Nitride is motivated by the hope to gain a better understanding of adsorbate-substrate interaction. High resolution adsorption isotherms and x-ray powder diffraction have been used to investigate the monolayer structures of CH_3R adsorbed on Boron Nitride. The experiments were carried out at the Beamline X7B of the NSLS. The gases were dosed onto the sample with an automated gas handling system, and a Mar345 image plate detector was used to collect the data. The measurements were performed in a temperature range between 50 and 175 K. All three adsorbates form a solid monolayer structure on Boron Nitride at low temperature. The structure of Methyl Chloride and Methyl Bromide is very similar to the high-density structure of CH_3Cl on Graphite. This is surprising for CH_3Br because it forms a different structure on Graphite. Methyl Iodide forms similar structures on both substrates.

  12. Inhomogeneous distribution of organic molecules adsorbed in sol gel glasses

    NASA Astrophysics Data System (ADS)

    Meneses-Nava, M. A.; Chávez-Cerda, S.; Sánchez-Villicaña, V.; Sánchez-Mondragón, J. J.; King, T. A.

    1999-09-01

    The effects of the porous matrix upon the radiative characteristics of quinine sulphate doped sol-gel glasses are investigated. The broadenings of the absorption and fluorescence spectra are explained by the attachment of the molecules on distorted sites or in a non-planar fashion, creating an inhomogeneous distribution of adsorbed molecules. For this reason, each emitting center relaxes with its own characteristics. This inhomogeneous distribution is also supported by the non-exponential and the wavelength dependence of the fluorescence decay.

  13. Aggregate formation of eosin-Y adsorbed on nanocrystalline TiO2 films

    NASA Astrophysics Data System (ADS)

    Yaguchi, Kaori; Furube, Akihiro; Katoh, Ryuzi

    2012-11-01

    We have studied the adsorption of eosin-Y on nanocrystalline TiO2 films with two different solvents namely acetonitrile (ACN) and ethanol (EtOH). A Langmuir-type adsorption isotherm was observed with ACN. In contrast, a Freundlich-type adsorption isotherm was observed with EtOH, suggesting that EtOH molecules co-adsorbed on TiO2 surface. Absorption spectra of the dye adsorbed films clearly show aggregate formation at high concentrations of dye in the solutions. From the analysis of the spectra, we conclude that head-to-tail type aggregates are observed with ACN, whereas various types of aggregates, including H-type and head-to-tail type aggregates, are observed with EtOH.

  14. Scandium-Triflate/Metal-Organic Frameworks: Remarkable Adsorbents for Desulfurization and Denitrogenation.

    PubMed

    Khan, Nazmul Abedin; Jhung, Sung Hwa

    2015-12-01

    Scandium-triflate (Sc(OTf)3) was introduced for the first time on metal-organic frameworks (MOFs), to utilize acidic Sc(OTf)3 for adsorptive desulfurization and denitrogenation of fuel containing benzothiophene (BT), dibenzothiophene (DBT), quinoline (QUI), and indole (IND). A remarkable improvement in the adsorption capacity (about 65% based on the weight of adsorbents; 90% based on the surface area of the adsorbents) was observed with the Sc(OTf)3/MOFs as compared to the virgin MOFs for the adsorption of BT from liquid fuel. The basic QUI was also adsorbed preferentially onto the acidic Sc(OTf)3/MOFs. However, nonsupported Sc(OTf)3 showed negligible adsorption capacities. The improved adsorptive performance for BT, DBT, and QUI might be derived from acid-base interactions between the acidic Sc(OTf)3 and basic adsorbates. On the other hand, the Sc(OTf)3, loaded on MOFs, reduced the adsorption capacity for neutral IND due to lack of interaction between the neutral adsorbate and acidic adsorbent and the reduced porosities of the modified adsorbents. The reusability of the adsorbents was found satisfactory up to the fourth run. On the basis of the result, it is suggested that metal-triflates, such as Sc(OTf)3, can be prospective materials for adsorptive desulfurization/denitrogenation of fuels when supported on porous materials such as MOFs. PMID:26575418

  15. Metallo-organic decomposition films

    NASA Technical Reports Server (NTRS)

    Gallagher, B. D.

    1985-01-01

    A summary of metallo-organic deposition (MOD) films for solar cells was presented. The MOD materials are metal ions compounded with organic radicals. The technology is evolving quickly for solar cell metallization. Silver compounds, especially silver neodecanoate, were developed which can be applied by thick-film screening, ink-jet printing, spin-on, spray, or dip methods. Some of the advantages of MOD are: high uniform metal content, lower firing temperatures, decomposition without leaving a carbon deposit or toxic materials, and a film that is stable under ambient conditions. Molecular design criteria were explained along with compounds formulated to date, and the accompanying reactions for these compounds. Phase stability and the other experimental and analytic results of MOD films were presented.

  16. Heat capacity of quantum adsorbates: Hydrogen and helium on evaporated gold films

    SciTech Connect

    Birmingham, J.T. |

    1996-06-01

    The author has constructed an apparatus to make specific heat measurements of quantum gases adsorbed on metallic films at temperatures between 0.3 and 4 K. He has used this apparatus to study quench-condensed hydrogen films between 4 and 923 layers thick with J = 1 concentrations between 0.28 and 0.75 deposited on an evaporated gold surface. He has observed that the orientational ordering of the J = 1 molecules depends on the substrate temperature during deposition of the hydrogen film. He has inferred that the density of the films condensed at the lowest temperatures is 25% higher than in bulk H{sub 2} crystals and have observed that the structure of those films is affected by annealing at 3.4 K. The author has measured the J = 1 to J = 0 conversion rate to be comparable to that of the bulk for thick films; however, he found evidence that the gold surface catalyzes conversion in the first two to four layers. He has also used this apparatus to study films of {sup 4}He less than one layer thick adsorbed on an evaporated gold surface. He shows that the phase diagram of the system is similar to that for {sup 4}He/graphite although not as rich in structure, and the phase boundaries occur at different coverages and temperatures. At coverages below about half a layer and at sufficiently high temperatures, the {sup 4}He behaves like a two-dimensional noninteracting Bose gas. At lower temperatures and higher coverages, liquidlike and solidlike behavior is observed. The Appendix shows measurements of the far-infrared absorptivity of the high-{Tc} superconductor La{sub 1.87}Sr{sub 0.13}CuO{sub 4}.

  17. Extra adsorption and adsorbate superlattice formation in metal-organic frameworks

    NASA Astrophysics Data System (ADS)

    Sung Cho, Hae; Deng, Hexiang; Miyasaka, Keiichi; Dong, Zhiyue; Cho, Minhyung; Neimark, Alexander V.; Ku Kang, Jeung; Yaghi, Omar M.; Terasaki, Osamu

    2015-11-01

    Metal-organic frameworks (MOFs) have a high internal surface area and widely tunable composition, which make them useful for applications involving adsorption, such as hydrogen, methane or carbon dioxide storage. The selectivity and uptake capacity of the adsorption process are determined by interactions involving the adsorbates and their porous host materials. But, although the interactions of adsorbate molecules with the internal MOF surface and also amongst themselves within individual pores have been extensively studied, adsorbate-adsorbate interactions across pore walls have not been explored. Here we show that local strain in the MOF, induced by pore filling, can give rise to collective and long-range adsorbate-adsorbate interactions and the formation of adsorbate superlattices that extend beyond an original MOF unit cell. Specifically, we use in situ small-angle X-ray scattering to track and map the distribution and ordering of adsorbate molecules in five members of the mesoporous MOF-74 series along entire adsorption-desorption isotherms. We find in all cases that the capillary condensation that fills the pores gives rise to the formation of ‘extra adsorption domains’—that is, domains spanning several neighbouring pores, which have a higher adsorbate density than non-domain pores. In the case of one MOF, IRMOF-74-V-hex, these domains form a superlattice structure that is difficult to reconcile with the prevailing view of pore-filling as a stochastic process. The visualization of the adsorption process provided by our data, with clear evidence for initial adsorbate aggregation in distinct domains and ordering before an even distribution is finally reached, should help to improve our understanding of this process and may thereby improve our ability to exploit it practically.

  18. AC microcalorimetry of adsorbates on evaporated metal films: Orientational ordering of H{sub 2} multilayers

    SciTech Connect

    Phelps, R.B.

    1991-11-01

    We have improved and extended a novel ac calorimetric technique for measuring the heat capacity of adsorbates on evaporated metal films. Metallic substrates are of particular interest in current studies of the thermodynamics of adsorbed molecules. The method described in the present work is only calorimetric technique which allows measurements of molecules on simple metallic surfaces. Among other improvements, we have achieved significant progress in the preparation and characterization of the evaporated metal film. We have applied this novel technique to a study of hydrogen multilayers on gold and sapphire substrates. We have shown that samples of normal-hydrogen with a nominal coverage n of approximately 25 monolayers (ML) undergo a bulk-like orientational ordering transition. The transition is suppressed as the coverage is decreased, and no sign of the transition remains above 1.6 K for n {approx} 1 ML. For n {approx_lt} 8 ML, the peak in the heat capacity exhibits signs of finite-size effects. At higher coverages, finite-size effects are not observed, and the shape of the peak depends strongly on the substrate. We conclude that the peak is inhomogeneously broadened for n {approx_lt} 8 ML. This work represents the first measurements of the heat capacity due to orientational ordering in adsorbed hydrogen. The results of an earlier experiment involving vibrational spectroscopy of adsorbed molecules are included in the Appendix. In this work, we have used infrared emission spectroscopy to study the spectral region in the vicinity of the C=O stretch vibration of bridge-bonded CO on Pt(111).

  19. AC microcalorimetry of adsorbates on evaporated metal films: Orientational ordering of H sub 2 multilayers

    SciTech Connect

    Phelps, R.B.

    1991-11-01

    We have improved and extended a novel ac calorimetric technique for measuring the heat capacity of adsorbates on evaporated metal films. Metallic substrates are of particular interest in current studies of the thermodynamics of adsorbed molecules. The method described in the present work is only calorimetric technique which allows measurements of molecules on simple metallic surfaces. Among other improvements, we have achieved significant progress in the preparation and characterization of the evaporated metal film. We have applied this novel technique to a study of hydrogen multilayers on gold and sapphire substrates. We have shown that samples of normal-hydrogen with a nominal coverage n of approximately 25 monolayers (ML) undergo a bulk-like orientational ordering transition. The transition is suppressed as the coverage is decreased, and no sign of the transition remains above 1.6 K for n {approx} 1 ML. For n {approx lt} 8 ML, the peak in the heat capacity exhibits signs of finite-size effects. At higher coverages, finite-size effects are not observed, and the shape of the peak depends strongly on the substrate. We conclude that the peak is inhomogeneously broadened for n {approx lt} 8 ML. This work represents the first measurements of the heat capacity due to orientational ordering in adsorbed hydrogen. The results of an earlier experiment involving vibrational spectroscopy of adsorbed molecules are included in the Appendix. In this work, we have used infrared emission spectroscopy to study the spectral region in the vicinity of the C=O stretch vibration of bridge-bonded CO on Pt(111).

  20. Atomic force microscopy of AgBr crystals and adsorbed gelatin films

    SciTech Connect

    Haugstad, G.; Gladfelter, W.L.; Keyes, M.P.; Weberg, E.B.

    1993-06-01

    Atomic force microscopy of the (111) surface of macroscopic AgBr crystals revealed steps ranging in height from two atomic layers up to 10 nm, lying predominantly along the (110) and (112) families of crystal directions. Rods of elemental Ag, formed via photoreduction, were observed along the (110) family of directions. Images of adsorbed gelatin films revealed circular pores with diameters of order 10-100 nm, extending to the AgBr surface. The length of deposition time, the pH and concentration of the gelatin solution, and the presence of steps on the AgBr surface were observed to affect the size, number, and location of pores in the gelatin films. 12 refs., 7 figs.

  1. Nanotribological properties of water films adsorbing atop, and absorbing below, graphene layers supported by metal substrates

    NASA Astrophysics Data System (ADS)

    Liu, Zijian; Curtis, C. K.; Stine, R.; Sheehan, P.; Krim, J.

    The tribological properties of graphite, a common lubricant with known sensitivity to the presence of water, have been studied extensively at the macroscopic and microscopic scales. Although far less attention has been devoted to the tribological properties of graphene, it has been established that the tribological response to the presence of water is dissimilar from that of graphite. We report here a quartz crystal microbalance study of the nanotribological properties of water films adsorbed/absorbed on graphene layers prepared by either chemical decomposition on nickel(111) substrates or transfer of freestanding graphene layers to aluminum substrates. Sliding friction levels of the water films were also measured for metal surfaces in the absence of a graphene layer. We observe very high friction levels for water adsorbed atop graphene on Ni(111) and very low levels for water on aluminum. For the case of graphene/aluminum, the data indicate that the water is absorbing between the graphene layer and the aluminum. Dissipation levels moreover indicate the presence of an interstitial water increases sliding friction between the graphene and the aluminum substrate Work supported by NSF and NRL.

  2. Atomic Motion in Low-Coverage Helium Films Adsorbed in FSM Nanochannels

    NASA Astrophysics Data System (ADS)

    Matsushita, Taku; Kuze, Atsushi; Kawai, Ryosuke; Hieda, Mitsunori; Wada, Nobuo

    2013-06-01

    4He and 3He films adsorbed in nanoporous silicates have shown similar heat capacities until the quantum-fluid layer appears at coverages over the first-layer completion n 1. To obtain information on dynamics of adatoms at low coverages below the quantum fluid region, we have done pulsed-NMR experiment at 3.3 MHz for 3He films adsorbed in straight 2.4 nm nanochannels of FSM silicates. The spin-lattice and spin-spin relaxation times T 1 and T 2 observed at 0.54-7 K were well described by the two-dimensional version of the Bloembergen-Purcell-Pound model. At coverages 0.4-1.7 n 1, minima of T 1, indicating the spin correlation time τ c of 4.8×10-8 sec, were observed at temperatures between 6 and 3 K. With decreasing temperature, changes in T 1 and T 2 become small below about 1.5 K, suggesting crossover from thermally-activated motion to quantum tunneling. In contrast to large variations below n 1, both relaxation times above n 1 are almost independent of coverage, which is likely to indicate that τ c is determined by interlayer exchange of adatoms. Below n 1, onsets for localization of adatoms were suggested by a decrease in T 2.

  3. Covalent organic frameworks: Potential adsorbent for carbon dioxide adsorption

    NASA Astrophysics Data System (ADS)

    Xie, Yinhuan

    A series of covalent organic frameworks (COFs) based on propeller shaped hexaphenylbenzene derivatives were obtained under solvothermal conditions via Schiff base reaction. The relationship between the geometry parameters of monomers and gas absorption behaviors of planar COFs was investigated. The FT-IR spectroscopy confirms the formation of imine double bond in the obtained COFs by showing a peak around 1620 cm-1. The resulting frameworks have high BET surface areas approaching 700 m2/g and CO2 uptake up to 14% at 273 K and 1 bar, which are better than most of the 2-D porous aromatic frameworks. The thermogravimetric analysis shows those frameworks are stable until 773 K, allowing for the practical application of the post-combustion CO2 technology. Moreover, a novel synthetic strategy for the trigonal pyramidal hydrozide monomers was established. It provides an efficient way to synthesize the hydrozide monomers at multi-gram scale, promising for the synthesis of hydrozane porous organic cages.

  4. COMPARISON OF SOLID ADSORBENT SAMPLING TECHNIQUES FOR VOLATILE ORGANIC COMPOUNDS IN AMBIENT AIR

    EPA Science Inventory

    The specific objective of the study was to compare the performance of three solid adsorbents (Tenax, an experimental polyimide resin, and Spherocarb) as well as cryogenic trapping/gas chromatography for sampling and analysis of a target list of volatile organic compounds in ambie...

  5. Influences of Dilute Organic Adsorbates on the Hydration of Low-Surface-Area Silicates.

    PubMed

    Sangodkar, Rahul P; Smith, Benjamin J; Gajan, David; Rossini, Aaron J; Roberts, Lawrence R; Funkhouser, Gary P; Lesage, Anne; Emsley, Lyndon; Chmelka, Bradley F

    2015-07-01

    Competitive adsorption of dilute quantities of certain organic molecules and water at silicate surfaces strongly influence the rates of silicate dissolution, hydration, and crystallization. Here, we determine the molecular-level structures, compositions, and site-specific interactions of adsorbed organic molecules at low absolute bulk concentrations on heterogeneous silicate particle surfaces at early stages of hydration. Specifically, dilute quantities (∼0.1% by weight of solids) of the disaccharide sucrose or industrially important phosphonic acid species slow dramatically the hydration of low-surface-area (∼1 m(2)/g) silicate particles. Here, the physicochemically distinct adsorption interactions of these organic species are established by using dynamic nuclear polarization (DNP) surface-enhanced solid-state NMR techniques. These measurements provide significantly improved signal sensitivity for near-surface species that is crucial for the detection and analysis of dilute adsorbed organic molecules and silicate species on low-surface-area particles, which until now have been infeasible to characterize. DNP-enhanced 2D (29)Si{(1)H}, (13)C{(1)H}, and (31)P{(1)H} heteronuclear correlation and 1D (29)Si{(13)C} rotational-echo double-resonance NMR measurements establish hydrogen-bond-mediated adsorption of sucrose at distinct nonhydrated and hydrated silicate surface sites and electrostatic interactions with surface Ca(2+) cations. By comparison, phosphonic acid molecules are found to adsorb electrostatically at or near cationic calcium surface sites to form Ca(2+)-phosphonate complexes. Although dilute quantities of both types of organic molecules effectively inhibit hydration, they do so by adsorbing in distinct ways that depend on their specific architectures and physicochemical interactions. The results demonstrate the feasibility of using DNP-enhanced NMR techniques to measure and assess dilute adsorbed molecules and their molecular interactions on low

  6. Transient magnetization of core excited organic molecules adsorbed on graphene

    NASA Astrophysics Data System (ADS)

    Ravikumar, Abhilash; Baby, Anu; Lin, He; Brivio, Gian Paolo; Fratesi, Guido

    This work presents a density functional theory based computational investigation of electronic and magnetic properties of physisorbed and chemisorbed organic molecules on graphene in the ground state and core excited one at low molecular coverage. For physisorbed molecules, where the interaction with graphene is dominated by van der Waals forces and the system is non-magnetic in the ground state, it is found that the valence electrons relax towards a spin polarized configuration upon excitation of a core-level electron. The magnetism depends on efficient electron transfer from graphene on the femtosecond time scale. On the contrary, when graphene is covalently functionalized, the system is magnetic in the ground state presenting two spin dependent mid gap states localized around the adsorption site. At variance with the physisorbed case upon core-level excitation, the LUMO of the molecule and the mid gap states of graphene hybridize and the relaxed valence shell is not magnetic anymore. This project has received funding from the European Union Seventh Framework Programme under grant agreement n∘ 607232 [THINFACE].

  7. Dissociative electron attachment and charging of SF6 adsorbed on rare-gas films

    NASA Astrophysics Data System (ADS)

    Weik, Fritz; Illenberger, Eugen

    1998-10-01

    Electron stimulated desorption (ESD) of fragment ions in the energy range between 0 and 18 eV from SF6 adsorbed on rare-gas films (Kr, Xe) is reported. The ESD results are compared with previous experiments on dissociative electron attachment (DA) to gas-phase SF6. At energies characteristic for the respective rare-gas substrate strong resonant enhancements in the ESD yield of F- are observed. This enhancement is explained by the appearance of an "electron-exciton complex" in the rare-gas film (the analogue to the anionic Feshbach resonances in single atoms) which couples to the first dipole allowed excitation of the SF6 molecule. After electron and energy transfer, the highly excited SF6*- ion dissociates at the surface resulting in the desorption of F- fragments. At low electron energies (in the range from 0 to 0.6 eV) charging of the rare-gas film covered with SF6 is observed. From these experiments a charging cross section of 2.1(±1.8)×10-15 cm2 is derived.

  8. Thermodynamic and dynamic characteristics of hydroxypropylmethylcellulose adsorbed films at the air-water interface.

    PubMed

    Pérez, Oscar E; Sánchez, Cecilio Carrera; Rodríguez Patino, Juan M; Pilosof, Ana M R

    2006-01-01

    Surface pressure isotherms and structural and surface dilatational properties of three hydroxypropylmethycelluloses (HPMCs, called E4M, E50LV, and F4M) adsorbed films at the air-water interface were determined. In this work we present evidence that HPMC molecules are able to diffuse and saturate the air-water interface at very low concentrations in the bulk phase. As bulk concentration increased, structural changes at a molecular level occurred at the interface. These changes corresponded to transition from an expanded structure (structure I) to a condensed one (structure II). When the surface concentration of HPMC was high enough, the collapse of the monolayer was observed. The three HPMCs formed very elastic films at the air-water interface, even at low surface pressures. E4M showed features that make it unique. For instance it showed the highest surface activity, mainly at low bulk concentrations (<10(-4) wt %). The differences observed in surface activity may be attributed to differences in the hydroxypropyl molar substitution and molecular weight of HPMC. All three HPMCs formed films of similar viscoelasticity and elastic dilatational modulus, which can be accounted for by their similar degree of methyl substitution. PMID:16398540

  9. Electrospun polystyrene nanofibers as a novel adsorbent to transfer an organic phase from an aqueous phase.

    PubMed

    Liu, Feilong; Song, Dandan; Huang, Xueying; Xu, Hui

    2016-04-01

    The aim of this work is to develop a simple phase-transfer method for dispersive liquid-liquid microextraction. For this purpose, a polystyrene nanofiber was prepared by a facile electrospinning strategy and used for the first time as an adsorbent to transfer the organic phase in dispersive liquid-liquid microextraction procedure. The fiber was characterized and its chemical stability and excellent hydrophobicity enable it to selectively adsorb the organic solvent in an aqueous sample. High porosity and specific surface area provide a large adsorption capacity. Under the optimal conditions, the developed dispersive liquid-liquid microextraction with high-performance liquid chromatography method was successfully applied to the analysis of aldehydes in environmental water samples. The merits of this approach are that it is easy-to-operate, low-cost, time-saving, and has satisfactory sensitivity. It provides an alternative way for fast and convenient phase transfer of the hydrophobic organic solvent from the aqueous phase. PMID:26841974

  10. Sputtering and secondary ion emission properties of alkali metal films and adsorbed monolayers

    SciTech Connect

    Krauss, A R; Gruen, D M

    1980-01-01

    The secondary ion emission of alkali metal adsorbed monlayer and multilayer films has been studied. Profiling with sub-monolayer resolution has been performed by Auger, x-ray photoemission and secondary ion mass spectroscopy. Characteristic differences in the sputtering yields, and ion fraction have been observed which are associated with both the surface bonding properties and the mechanism leading to the formation of secondary ions. By sputtering with a negative bias applied to the sample, positive secondary ions are returned to the surface, resulting in a reduced sputter-induced erosion rate. Comparison with the results obtained with K and Li overlayers sputtered without sample bias provides an experimental value of both the total and secondary ion sputtering yields. The first and second monolayers can be readily identified and the first monolayer exhibits a lower sputtering yield and higher secondary ion fraction. This result is related to adsorption theory and measured values are compared with those obtained by thermal desorption measurements.

  11. Mesoscopic Hamiltonian for the fluctuations of adsorbed Lennard-Jones liquid films.

    PubMed

    Fernández, Eva M; Chacón, Enrique; MacDowell, Luis G; Tarazona, Pedro

    2015-06-01

    We use Monte Carlo simulations of a Lennard-Jones fluid adsorbed on a short-range planar wall substrate to study the fluctuations in the thickness of the wetting layer, and we get a quantitative and consistent characterization of their mesoscopic Hamiltonian, H[ξ]. We have observed important finite-size effects, which were hampering the analysis of previous results obtained with smaller systems. The results presented here support an appealing simple functional form for H[ξ], close but not exactly equal to the theoretical nonlocal proposal made on the basis a generic density-functional analysis by Parry and coworkers. We have analyzed systems under different wetting conditions, as a proof of principle for a method that provides a quantitative bridge between the molecular interactions and the phenomenology of wetting films at mesoscopic scales. PMID:26172722

  12. Low cost adsorbents for the removal of organic pollutants from wastewater.

    PubMed

    Ali, Imran; Asim, Mohd; Khan, Tabrez A

    2012-12-30

    Water pollution due to organic contaminants is a serious issue because of acute toxicities and carcinogenic nature of the pollutants. Among various water treatment methods, adsorption is supposed as the best one due to its inexpensiveness, universal nature and ease of operation. Many waste materials used include fruit wastes, coconut shell, scrap tyres, bark and other tannin-rich materials, sawdust and other wood type materials, rice husk, petroleum wastes, fertilizer wastes, fly ash, sugar industry wastes blast furnace slag, chitosan and seafood processing wastes, seaweed and algae, peat moss, clays, red mud, zeolites, sediment and soil, ore minerals etc. These adsorbents have been found to remove various organic pollutants ranging from 80 to 99.9%. The present article describes the conversion of waste products into effective adsorbents and their application for water treatment. The possible mechanism of adsorption on these adsorbents has also been included in this article. Besides, attempts have been made to discuss the future perspectives of low cost adsorbents in water treatment. PMID:23023039

  13. Friction and transfer of copper, silver, and gold to iron in the presence of various adsorbed surface films

    NASA Technical Reports Server (NTRS)

    Buckley, D. H.

    1979-01-01

    Sliding friction experiments were conducted with the noble metals copper, silver, and gold and two binary alloys of these metals contacting iron in the presence of various adsorbates including, oxygen, methyl mercaptan, and methyl chloride. A pin on disk specimen configuration was used with a load of 100 grams, sliding velocity of 60 mm/min; at 25 C with the surfaces saturated with the adsorbates. Auger emission spectroscopy was used to monitor surface films. Results of the experiments indicate that friction and transfer characteristics are highly specific with respect to both the noble metal and surface film present. With all three metals and films transfer of the noble metal to iron occurred very rapidly. With all metals and films transfer of the noble metal to iron continuously increased with repeated passes except for silver and copper sliding on iron sulfide.

  14. Vibrational spectra of CO adsorbed on oxide thin films: A tool to probe the surface defects and phase changes of oxide thin films

    SciTech Connect

    Savara, Aditya

    2014-03-15

    Thin films of iron oxide were grown on Pt(111) single crystals using cycles of physical vapor deposition of iron followed by oxidative annealing in an ultrahigh vacuum apparatus. Two procedures were utilized for film growth of ∼15–30 ML thick films, where both procedures involved sequential deposition+oxidation cycles. In procedure 1, the iron oxide film was fully grown via sequential deposition+oxidation cycles, and then the fully grown film was exposed to a CO flux equivalent to 8 × 10{sup −7} millibars, and a vibrational spectrum of adsorbed CO was obtained using infrared reflection-absorption spectroscopy. The vibrational spectra of adsorbed CO from multiple preparations using procedure 1 show changes in the film termination structure and/or chemical nature of the surface defects—some of which are correlated with another phase that forms (“phase B”), even before enough of phase B has formed to be easily detected using low energy electron diffraction (LEED). During procedure 2, CO vibrational spectra were obtained between deposition+oxidation cycles, and these spectra show that the film termination structure and/or chemical nature of the surface defects changed as a function of sequential deposition+oxidation cycles. The authors conclude that measurement of vibrational spectra of adsorbed CO on oxide thin films provides a sensitive tool to probe chemical changes of defects on the surface and can thus complement LEED techniques by probing changes not visible by LEED. Increased use of vibrational spectra of adsorbed CO on thin films would enable better comparisons between films grown with different procedures and by different groups.

  15. Direct Measurement of Adsorbed Gas Redistribution in Metal–Organic Frameworks

    SciTech Connect

    Chen, Ying-Pin; Liu, Yangyang; Liu, Dahuan; Bosch, Mathieu; Zhou, Hong-Cai

    2015-03-04

    Knowledge about the interactions between gas molecules and adsorption sites is essential to customize metal-organic frameworks (MOFs) as adsorbents. The dynamic interactions occurring during adsorption/desorption working cycles with several states are especially complicated. Even so, the gas dynamics based upon experimental observations and the distribution of guest molecules under various conditions in MOFs have not been extensively studied yet. In this work, a direct time-resolved diffraction structure envelope (TRDSE) method using sequential measurements by in situ synchrotron powder X-ray diffraction has been developed to monitor several gas dynamic processes taking place in MOFs: infusion, desorption, and gas redistribution upon temperature change. The electron density maps indicate that gas molecules prefer to redistribute over heterogeneous types of sites rather than to exclusively occupy the primary binding sites. We found that the gas molecules are entropically driven from open metal sites to larger neighboring spaces during the gas infusion period, matching the localized-to-mobile mechanism. In addition, the partitioning ratio of molecules adsorbed at each site varies with different temperatures, as opposed to an invariant distribution mode. Equally important, the gas adsorption in MOFs is intensely influenced by the gas–gas interactions, which might induce more molecules to be accommodated in an orderly compact arrangement. This sequential TRDSE method is generally applicable to most crystalline adsorbents, yielding information on distribution ratios of adsorbates at each type of site.

  16. 4-Mercaptopyridine adsorbed on pure palladium island films: A combined SERS and DFT investigation

    NASA Astrophysics Data System (ADS)

    Guo, Hao; Ding, Li; Zhang, Tianjie; Mo, Yujun

    2013-03-01

    Surface-enhanced Raman scattering (SERS) can provide vibrational information with molecular specificity and potential single-molecule sensitivity. SERS studies on pure transition metals, however, remain challenging due to the weak SERS activity of transition metals compared to coinage metals. Here we fabricated alumina-supported Pd island films by depositing laser-ablated Pd colloids onto an Al substrate. Robust SERS signal employing 4-mercaptopyridine (4-Mpy) as a probe was registered from the as-prepared films. The adsorption information of 4-Mpy molecules such as orientation and coordinating site was discussed in detail based on SERS data. It was inferred that 4-Mpy adsorbs via its sulfur atom to Pd surface with a tilted binding configuration. The Raman wavenumber and intensity of an adsorption model including one 4-Mpy and Pd atom were computed using density functional theory (DFT) at the Beck's three-parameter Lee-Yang-Parr (B3LYP) level with the LANL2DZ basis set. The simulated Raman spectrum was in good agreement with the experimental one except for the relative intensity. The current investigation could be helpful to gain a comprehensive understanding of SERS.

  17. O the Transition from - to Three-Dimensional Behavior in Adsorbed Films

    NASA Astrophysics Data System (ADS)

    Day, Peter Kenneth

    1993-01-01

    Argon and krypton films adsorbed on graphite foam have been studied in detail using vapor pressure and high resolution, heat capacity measurements. Heat capacity features near the bulk triple point temperature, previously associated with the surface melting of the uniform film, are shown to be due to the melting of bulk material condensed in pores in the substrate. The melting curve of the capillary condensate agrees with the prediction of a modified Clausius -Claperon equation. The second and third layers in argon and the second layer in krypton have a triple point at which two-dimensional solid, liquid, and gas phases coexist atop a solid lower layer. Commensurate-incommensurate transitions are found in the first two layers of argon and in the second layer of krypton, so that monolayer argon melts from a registered phase, but the second layers of both systems melt from incommensurate bilayer phases. The melting of the second and third layers in both systems are likely to be first order, but the data are not conclusive. At coverages starting with 3{1over 2} layers, heat capacity features that are due to reentrant layering-transitions are seen in both systems, confirming the result of recent ellipsometry studies. Further heat capacity peaks suggest phase transitions that join the newly observed reentrant layering-transitions with the well studied layering-transitions at low temperature. These heat capacity peaks may be related to the recently proposed preroughening transition. A mean field theory is developed that reproduced the reentrant layering behavior for ratios of nearest and next nearest neighbor interaction energies greater than a critical value. The mean field theory gives an explanation for the appearance of reentrant layering -transitions at different film thicknesses depending on the substrate-adsorbate interaction parameter. Multilayer phase diagrams are drawn from the data that suggest a crossover from two-dimensional behavior in the second layer to

  18. Preparation of dye-adsorbing ZnO thin films by electroless deposition and their photoelectrochemical properties.

    PubMed

    Nagaya, Satoshi; Nishikiori, Hiromasa

    2013-09-25

    Dye-adsorbing ZnO thin films were prepared on ITO films by electroless deposition. The films were formed in an aqueous solution containing zinc nitrate, dimethylamine-borane, and eosin Y at 328 K. The film thickness was 1.2-2.0 μm. Thinner and larger-plane hexagonal columns were produced from the solution containing a higher concentration of eosin Y. A photocurrent was observed in the electrodes containing such ZnO films during light irradiation. The photoelectrochemical performance of the film was improved by increasing the concentration of eosin Y because of increases in the amount of absorbed photons and the electronic conductivity of ZnO. PMID:24020721

  19. Mercury removal from incineration flue gas by organic and inorganic adsorbents.

    PubMed

    Jurng, Jongsoo; Lee, Tai Gyu; Lee, Gyo Woo; Lee, Sung-Jun; Kim, Byung Hwa; Seier, Jochen

    2002-06-01

    Experiments were performed to investigate various adsorbents for their mercury removal capabilities from incineration flue gases. Four different materials were tested; Zeolite, Bentonite, activated carbon (AC), and wood char. Real incineration off-gas and in-lab simulated combustion flue gases (N2 + Hg) were used. Three cylindrical-shaped sorbent columns with 5 cm in diameter and 20 cm in length were used. The gas flow rate was fixed at 660 l/h at all times. Concentrations of NO, CO, O2, CO2, SO2, H2O, HCl, and mercury were continuously monitored. Mercury removal efficiencies of natural Zeolite and Bentonite were found to be much lower than those of the referenced AC. Amount of Hg removed were 9.2 and 7.4 microg/g of Zeolite and Bentonite, respectively. Removal efficiencies of each layer consisted of inorganic adsorbents were no higher than 7%. No significant improvement was observed with sulfur impregnation onto the inorganic adsorbents. Organic adsorbents (wood char and AC) showed much higher mercury removal efficiencies than those of inorganic ones (Zeolite and Bentonite). Mercury removal efficiency of wood char reached over 95% in the first layer, showing almost same effectiveness as AC which currently may be the most effective adsorbents for mercury. Amount of mercury captured by wood char was approximately 0.6 mg/g of wood char, close to the amount captured by AC tested in this study. Hence, wood char, made from the waste woods through a gasification process, should be considered as a possible alternative to relatively expensive AC. PMID:12108697

  20. Removal of organic pollutants from aqueous solutions by adsorbents prepared from an agroalimentary by-product.

    PubMed

    Delval, Franck; Crini, Grégorio; Vebrel, Joël

    2006-11-01

    Two series of crosslinked starch polymers were tested for their ability to adsorb organic pollutants in aqueous solutions. The polymers were prepared by a crosslinking reaction of starch-enriched flour using epichlorohydrin as the crosslinking agent, without and in the presence of NH(4)OH. These polymers were used as sorbent materials for the removal of phenolic derivatives from wastewater. The influence of several parameters (kinetics, pH and polymer structure) on the sorption capacity was evaluated using the batch and the open column methods. Results of adsorption experiments showed that the starch-based materials exhibited high sorption capacities toward phenolic derivatives. The study of the kinetics of pollutant uptake revealed that the adsorbents presented a relatively fast rate of adsorption. The experimental data were examined using the Langmuir and Freundlich models and it was found that the Freundlich model appeared to fit the isotherm data better than the Langmuir model. PMID:16275061

  1. Comparison of Gas and Adsorbed Phase X-ray Photoemission Spectra of Oxidized Organics on Ice

    NASA Astrophysics Data System (ADS)

    Newberg, J. T.; Bluhm, H.

    2011-12-01

    Most uptake studies of small chain organics on ice surfaces at near ambient conditions have been performed using flow tube and other methods which monitor the disappearance of the gas phase. We will present results using synchrotron based, ambient pressure X-ray photoemission spectroscopy which allows for the probing of the ice surface directly at near ambient conditions. C 1s XPS and C K-edge NEXAFS gas phase and adsorbed phase spectra will be compared for 2-propanol, acetone, and 1-propanal on ice at -45 C. Uptake experiments give rise to first order Langmuirian isotherms. Acetone and 2-propanol show little difference in the photoemission spectra between the gas phase and adsorbed phase, suggesting that adsorption occurs molecularly. However, adsorption of 1-propanal shows evidence of chemical transformation (oxidation) at the interface of ice. Further studies are underway to better understand this adsorption behavior.

  2. Adsorbed films of three-patch colloids: continuous and discontinuous transitions between thick and thin films.

    PubMed

    Dias, C S; Araújo, N A M; Telo da Gama, M M

    2014-09-01

    We investigate numerically the role of spatial arrangement of the patches on the irreversible adsorption of patchy colloids on a substrate. We consider spherical three-patch colloids and study the dependence of the kinetics on the opening angle between patches. We show that growth is suppressed below and above minimum and maximum opening angles, revealing two absorbing phase transitions between thick and thin film regimes. While the transition at the minimum angle is continuous, in the directed percolation class, that at the maximum angle is clearly discontinuous. For intermediate values of the opening angle, a rough colloidal network in the Kardar-Parisi-Zhang universality class grows indefinitely. The nature of the transitions was analyzed in detail by considering bond flexibility, defined as the dispersion of the angle between the bond and the center of the patch. For the range of flexibilities considered we always observe two phase transitions. However, the range of opening angles where growth is sustained increases with flexibility. At a tricritical flexibility, the discontinuous transition becomes continuous. The practical implications of our findings and the relation to other nonequilibrium transitions are discussed. PMID:25314441

  3. Microcrystalline organic thin-film solar cells.

    PubMed

    Verreet, Bregt; Heremans, Paul; Stesmans, Andre; Rand, Barry P

    2013-10-11

    Microcrystalline organic films with tunable thickness are produced directly on an indium-tin-oxide substrate, by crystallizing a thin amorphous rubrene film followed by its use as a template for subsequent homoepitaxial growth. These films, with exciton diffusion lengths exceeding 200 nm, produce solar cells with increasing photocurrents at thicknesses up to 400 nm with a fill factor >65%, demonstrating significant potential for microcrystalline organic electronic devices. PMID:23939936

  4. Third Sound in Superfluid 4He Films Adsorbed on Packed Multiwall Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Menachekanian, Emin

    Third sound is studied for superfluid films of 4He adsorbed on multiwall carbon nanotubes packed into an annular resonator. The third sound is generated with mechanical oscillation of the cell, and detected with carbon bolometers. A filling curve at temperatures near 250 mK shows oscillations in the third sound velocity, with maxima at the completion of the 4th and 5th atomic layers. Sharp changes in the Q factor of the third sound are found at partial layer fillings. Temperature sweeps at a number of fill points show strong broadening effects on the Kosterlitz-Thouless (KT) transition, and rapidly increasing dissipation, in qualitative agreement with the predictions of Machta and Guyer. At the 4th layer completion there is a sudden reduction of the transition temperature TKT , and then a recovery back to linear variation with fill, although the slope is considerably smaller than the KT prediction. These effects might be related to changes in the gas-liquid coexistence regions.

  5. Development of adsorbent for the simultaneous removal of organic and inorganic contaminants from aqueous solution.

    PubMed

    Choi, J W; Chung, S G; Hong, S W; Kim, D J; Lee, S H

    2011-01-01

    In this study, a modified adsorbent, alginate complex beads, was prepared and applied to the removal of mixed contaminants from wastewater. The alginate complex beads were generated by the immobilization of powdered activated carbon and synthetic zeolites onto alginate gel beads, which were then dried at 110 °C for 20 h until the diameter had been reduced to 1 mm. This dry technique increased the hardness of the adsorbent to assure its durability and application. The adsorption onto the alginate complex beads of organic and inorganic compounds, as target contaminants, was investigated by performing both equilibrium and kinetic batch experiments. From the adsorption isotherms, according to the Langmuir equation, the alginate complex bead was capable of effectively removing benzene, toluene, zinc and cadmium. From kinetic batch experiments, the removal efficiencies of benzene, toluene, zinc and cadmium were found to be 66.5, 92.4, 74.1 and 76.7%, respectively, for initial solution concentrations of 100 mg L(-1). The results indicated that the adsorbent developed in this study has the potential to be a promising material for the removal of mixed pollutants from industrial wastewater or contaminated groundwater. PMID:22020474

  6. Polyethyleneimine Incorporated Metal-Organic Frameworks Adsorbent for Highly Selective CO2 Capture

    PubMed Central

    Lin, Yichao; Yan, Qiuju; Kong, Chunlong; Chen, Liang

    2013-01-01

    A series of polyethyleneimine (PEI) incorporated MIL-101 adsorbents with different PEI loadings were reported for the first time in the present work. Although the surface area and pore volume of MIL-101 decreased significantly after loading PEI, all the resulting composites exhibited dramatically enhanced CO2 adsorption capacity at low pressures. At 100 wt% PEI loading, the CO2 adsorption capacity at 0.15 bar reached a very competitive value of 4.2 mmol g−1 at 25°C, and 3.4 mmol g−1 at 50°C. More importantly, the resulting adsorbents displayed rapid adsorption kinetics and ultrahigh selectivity for CO2 over N2 in the designed flue gas with 0.15 bar CO2 and 0.75 bar N2. The CO2 over N2 selectivity was up to 770 at 25°C, and 1200 at 50°C. We believe that the PEI based metal-organic frameworks is an attractive adsorbent for CO2 capture. PMID:23681218

  7. The effects of adsorbing organic pollutants from super heavy oil wastewater by lignite activated coke.

    PubMed

    Tong, Kun; Lin, Aiguo; Ji, Guodong; Wang, Dong; Wang, Xinghui

    2016-05-01

    The adsorption of organic pollutants from super heavy oil wastewater (SHOW) by lignite activated coke (LAC) was investigated. Specifically, the effects of LAC adsorption on pH, BOD5/COD(Cr)(B/C), and the main pollutants before and after adsorption were examined. The removed organic pollutants were characterized by Fourier transform infrared spectroscopy (FTIR), Boehm titrations, gas chromatography-mass spectrometry (GC-MS), and liquid chromatography with organic carbon detection (LC-OCD). FTIR spectra indicated that organic pollutants containing -COOH and -NH2 functional groups were adsorbed from the SHOW. Boehm titrations further demonstrated that carboxyl, phenolic hydroxyl, and lactonic groups on the surface of the LAC increased. GC-MS showed that the removed main organic compounds are difficult to be degraded or extremely toxics to aquatic organisms. According to the results of LC-OCD, 30.37 mg/L of dissolved organic carbons were removed by LAC adsorption. Among these, hydrophobic organic contaminants accounted for 25.03 mg/L. Furthermore, LAC adsorption was found to increase pH and B/C ratio of the SHOW. The mechanisms of adsorption were found to involve between the hydrogen bonding and the functional groups of carboxylic, phenolic, and lactonic on the LAC surface. In summary, all these results demonstrated that LAC adsorption can remove bio-refractory DOCs, which is beneficial for biodegradation. PMID:26808249

  8. Orientation and order of aqueous organic ions adsorbed to a solid surface

    SciTech Connect

    Sukhishvili, S.A.; Granick, S.

    1999-01-21

    The adsorption and orientation of an aqueous organic ion with anisotropic shape (1,4-dimethylpyridinium, P{sup +}) at the surface of oxidized silicon carrying opposite charge (produced by conditions of high pH) were studied using polarized infrared spectroscopy in attenuated total reflection (FTIR-ATR). Orientation relative to the surface was quantified from the dichroic ratio of in-plane skeletal vibrations of the pyridinium ring (1643 and 1523 cm{sup {minus}1}), and the adsorbed amount was inferred from the intensity of these bands. The sticking energy of the organic ion was slightly larger than that of small inorganic ions of the same charge (Li{sup +}, Na{sup +}, Cs{sup +}). From relative quantities adsorbed in competitive adsorption, the relative sticking energy was quantified ({approximately}7k{sub B}T relative to Na{sup +} at pH = 9.2 and varying in the order Cs{sup +} > Na{sup +} > Li{sup +} by the total amount of 0.6k{sub B}T). At low ionic strength (no inorganic ions present except those in the buffer solution), P{sup +} stood preferably parallel to the surface when the surface coverage was low but more nearly upright both as its surface coverage increased and as the concentration of coadsorbed small ions increased. This shows the influence of steric packing on the orientation of this ion of asymmetric shape. The larger the hydrated diameter of the coadsorbed ion, the more the P{sup +} ion tilted away from the surface (H{sup +} < Li{sup +}, Na{sup +}, Cs{sup +} < Mg{sup 2+}). Furthermore, if the mass adsorbed exceeded a critical level, both the tilt and the amount adsorbed jumped in response to increasing P{sup +} concentration in bulk solution, with hysteresis upon dilution. This jump, together with the measured ellipsometric thickness and contact angle, suggests that the discontinuity involved structural change within a single monolayer. The organic ion thus behaved at the surface as an embryonic amphiphile, although in the bulk, micelle formation has

  9. Influence of Chemical Composition on the Reaction Products Observed During Electron Stimulated Decomposition of Organohalides Adsorbed in Water (Ice) Films

    NASA Astrophysics Data System (ADS)

    Fairbrother, Howard; Perry, Christopher; Faradzhev, Nadir; Madey, Theodore

    2004-03-01

    We report on the reactions of CF_2Cl2 and other organohalides codeposited_ in water (ice) films (≈100 nm thick on Au) at ˜ 100K during X-ray or electron beam irradiation. X-ray irradiation produces a distribution of low energy secondary electrons that in CF_2Cl_2/H_2O(ice) films produce H_3O^+, CO2 and COF2 (carbonyl fluoride). Chloride and fluoride anions are also produced and solvated (trapped) within the ice film during X-ray or electron irradiation. Product partitioning is dependent on the film's chemical composition; in water rich films, CO2 and COF2 production is favored, while a thermally stable partially halogenated CF_xCly film is detected in CF_2Cl2 rich films. During the early stages of irradiation, the dominance of Cl^- anions indicates that DEA of CF_2Cl2 via C-Cl cleavage (CF_2Cl2 + e^- → ot CF_2Cl + Cl^-) is the primary initial process. These results obtained for CF_2Cl2 are compared with electron stimulated reactions of other organohalides (CCl_4, CDCl_3, CD_2Cl2 and CH_3I) adsorbed in water(ice)films.

  10. Investigation of organic, inorganic and synthetic adsorbents for the pretreatment of landfill leachate.

    PubMed

    Shahriari, H; Fernandes, L; Tezel, F H

    2008-05-01

    An investigation into the use of organic, inorganic and synthetic adsorbents for the pretreatment of landfill leachate, generated by the City of Ottawa Trail Road Landfill, was carried out. The purpose of this project was to reduce the concentration of contaminants in order to meet the local Sewer Use By-Laws, prior to transporting the leachate from the generating site to the local municipal sewage treatment plant, and thereby reducing the disposal fees. Peat moss, compost, clinoptilolite, basalt and two types of activated carbon (DSR-A and F400) were investigated to determine the adsorption capacity for contaminants from leachate. Kinetic studies were also performed. The results based on batch adsorption isotherms show that peat moss has the highest adsorption capacity for boron (B) and barium (Ba), compared with the other adsorbents. Also peat moss has good removals of Total Kjeldahl Nitrogen (TKN), Total Organic Carbon (TOC), and benzene, toluene, ethylbenzene and xylene (BTEX), but these are lower than the removals obtained with activated carbon. Because of its relatively low cost and higher adsorption of B and Ba, peat moss was selected as the filter media for the column studies. The treated leachate was tested for B, Ba, TKN, carbonaceous biological oxygen demand (CBOD5) and hydrogen sulfide (H2S). The breakthrough curves for B and Ba showed the effectiveness of peat moss in removing these contaminants. PMID:18661738

  11. Metallo-Organic Decomposition (MOD) film development

    NASA Technical Reports Server (NTRS)

    Parker, J.

    1986-01-01

    The processing techniques and problems encountered in formulating metallo-organic decomposition (MOD) films used in contracting structures for thin solar cells are described. The use of thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) techniques performed at Jet Propulsion Laboratory (JPL) in understanding the decomposition reactions lead to improvements in process procedures. The characteristics of the available MOD films were described in detail.

  12. Hollow Co@C prepared from a Co-ZIF@microporous organic network: magnetic adsorbents for aromatic pollutants in water.

    PubMed

    Hong, Seokjo; Yoo, Jin; Park, Nojin; Lee, Sang Moon; Park, Je-Geun; Park, Ji Hoon; Son, Seung Uk

    2015-12-28

    This work shows the new engineering strategy of magnetic adsorbents by the combination of zeolitic imidazolate framework (ZIF) and microporous organic network (MON) chemistry. ZIF-67 nanoparticles containing Co(2+) ions were coated with MON. The thermolysis of ZIF-67@MON under argon resulted in hollow carbon materials bearing cobalt nanoparticles which showed promising performance as magnetic adsorbents for aromatic pollutants in water. PMID:26490193

  13. Properties of Organic Films on Aqueous Subphases

    NASA Astrophysics Data System (ADS)

    Gilman, J.; Vaida, V.

    2003-12-01

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

  14. Influence of structural fluctuations on lifetimes of adsorbate states at hybrid organic-semiconductor interfaces

    NASA Astrophysics Data System (ADS)

    Müller, M.; Sánchez-Portal, D.; Lin, H.; Fratesi, G.; Brivio, G. P.; Selloni, A.

    On the road towards a more realistic description of charge transfer processes at hybrid organic-semiconductor interfaces for photovoltaic applications we extend our first-principles scheme for the extraction of elastic linewidths to include the effects of structural fluctuations. Based on snapshots obtained from Car-Parinello molecular dynamics simulations at room temperature, we set up geometries in which dye molecules at interfaces are attached to a semi-infinite TiO2 substrate. The elastic linewidths are computed using a Green's function method. This effectively introduces the coupling to a continuum of states in the substrate. In particular we investigate catechol and isonicotinic acid on rutile(110) and anatase(101) at the level of semi-local density functional theory. We perform multiple calculations of linewidths and peak-positions associated with the adsorbate's frontier orbitals for different geometric configurations to obtain a time-averaged analysis of such physical properties. We compare the results from the considered systems to understand the effects of dynamics onto interfacial charge transfer and systematically assess the dependence of the extracted elastic lifetimes on the relative alignment between adsorbate and substrate states. This project has received funding from the European Union Seventh Framework Programme under Grant Agreement No. 607323 [THINFACE].

  15. Controlling the spatial arrangement of organic magnetic anions adsorbed on epitaxial graphene on Ru(0001).

    PubMed

    Stradi, Daniele; Garnica, Manuela; Díaz, Cristina; Calleja, Fabián; Barja, Sara; Martín, Nazario; Alcamí, Manuel; Vazquez de Parga, Amadeo L; Miranda, Rodolfo; Martín, Fernando

    2014-12-21

    Achieving control over the self-organization of functional molecules on graphene is critical for the development of graphene technology in organic electronic and spintronic. Here, by using a scanning tunneling microscope (STM), we show that the electron acceptor molecule 7,7',8,8'-tetracyano-p-quinodimethane (TCNQ) and its fluorinated derivative 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyano-p-quinodimethane (F4-TCNQ), co-deposited on the surface of epitaxial graphene on Ru(0001), transform spontaneously into their corresponding magnetic anions and self-organize in two remarkably different structures. TCNQ forms densely packed linear magnetic arrays, while F4-TCNQ molecules remain as isolated non interacting magnets. With the help of density functional theory (DFT) calculations, we trace back the origin of this behavior in the competition between the intermolecular repulsion experienced by the individual charged anions, which tends to separate the molecules, and the delocalization of the electrons transferred from the surface to the molecules, which promotes the formation of molecular oligomers. Our results demonstrate that it is possible to control the spatial arrangement of organic magnetic anions co-adsorbed on a surface by means of chemical substitution, paving the way for the design of two-dimensional fully organic magnetic structures on graphene and on other surfaces. PMID:25382549

  16. Influence of ionic strength changes on the structure of pre-adsorbed salivary films. A response of a natural multi-component layer.

    PubMed

    Macakova, Lubica; Yakubov, Gleb E; Plunkett, Mark A; Stokes, Jason R

    2010-05-01

    Salivary films coating oral surfaces are critically important for oral health. This study focuses on determining the underlying nature of this adsorbed film and how it responds to departures from physiological conditions due to changes in ionic strength. Under physiological conditions, it is found that pre-adsorbed in vitro salivary film on hydrophobic surfaces is present as a highly hydrated viscoelastic layer. We follow the evolution of this film in terms of its effective thickness, hydration and viscoelastic properties, as well as adsorbed mass of proteins, using complementary surface characterisation methods: a Surface Plasmon Resonance (SPR) and a Quartz Crystal Microbalance with Dissipation Monitoring (QCM-D). Our results support a heterogeneous model for the structure of the salivary film with an inner dense anchoring layer and an outer highly extended hydrated layer. Further swelling of the film was observed upon decreasing the salt concentration down to 1mM NaCl. However, upon exposure to deionised water, a collapse of the film occurs that was associated with the loss of water contained within the adsorbed layer. We suggest that the collapse in deionised water is driven by an onset of electrostatic attraction between different parts of the multi-component salivary film. It is anticipated that such changes could also occur when the oral cavity is exposed to food, beverage, oral care and pharmaceutical formulations where drastic changes to the structural integrity of the film is likely to have implications on oral health, sensory perception and product performance. PMID:20133111

  17. Structure and friction of stearic acid and oleic acid films adsorbed on iron oxide surfaces in squalane.

    PubMed

    Doig, Michael; Warrens, Chris P; Camp, Philip J

    2014-01-14

    The structure and friction of fatty acid surfactant films adsorbed on iron oxide surfaces lubricated by squalane are examined using large-scale molecular dynamics simulations. The structures of stearic acid and oleic acid films under static and shear conditions, and at various surface coverages, are described in detail, and the effects of unsaturation in the tail group are highlighted. At high surface coverage, the measured properties of stearic acid and oleic acid films are seen to be very similar. At low and intermediate surface coverages, the presence of a double bond, as in oleic acid, is seen to give rise to less penetration of lubricant in to the surfactant film and less layering of the lubricant near to the film. The kinetic friction coefficient is measured as a function of shear rate within the hydrodynamic (high shear rate) lubrication regime. Lubricant penetration and layering are observed to be correlated with friction coefficient. The friction coefficient with oleic acid depends only weakly on surface coverage, while stearic acid admits more lubricant penetration, and its friction coefficient increases significantly with decreasing surface coverage. Connections between film structure and friction are discussed. PMID:24364665

  18. Selective Ni-P electroless plating on photopatterned cationic adsorption films influenced by alkyl chain lengths of polyelectrolyte adsorbates and additive surfactants.

    PubMed

    Nakagawa, Masaru; Nawa, Nozomi; Iyoda, Tomokazu

    2004-10-26

    We demonstrated that the photopatterned single-layer adsorption film of poly(1-dodecyl-4-pyridinium bromide) on a silica surface was available for a template of nickel-phosphorus (Ni-P) electroless plating through sensitization with a SnCl(2) aqueous solution and activation with a PdCl(2) aqueous solution. Four kinds of poly(1-alkyl-4-vinylpyridinium halide)s bearing methyl, propyl, hexyl, and dodecyl groups were prepared. The cationic polymers were adsorbed by a negatively charged silica surface from their solutions, to form single-layer adsorption films exhibiting desorption-resistance toward deionized water and ethanol. The organic adsorption films could be decomposed completely by exposure to 172 nm deep-UV light. The formation and decomposition of the single-layer films were confirmed by deep-UV absorption spectral measurement and zeta-potential measurement. Ni-P electroless plating was carried out on the photopatterned adsorption films, using three types of SnO(x) colloidal materials without and with cationic or anionic surfactant as catalyst precursors in the sensitization step. In the case of the negatively charged SnO(x) colloids surrounded by anionic surfactant, Ni-deposition took place preferentially on the cationic adsorption films remaining in unexposed regions. The Ni-deposition was accelerated significantly on the cationic adsorption film bearing dodecyl groups. It was obvious by ICP-AES analyses that the hydrophobic long-chain dodecyl groups in the adsorption film could promote the adsorption of the negative SnO(x) colloids on the film surface, followed by much nucleus formation of zerovalent Pd catalysts useful for the electroless plating. The result of our experiment clearly showed that, in addition to electrostatic interaction, van der Waals interaction generating between the hydrophobic long-chain hydrocarbons of the adsorption film and the surfactant improved significantly the adsorption stability of the SnO(x) colloids, resulting in highly

  19. Activated boron nitride as an effective adsorbent for metal ions and organic pollutants.

    PubMed

    Li, Jie; Xiao, Xing; Xu, Xuewen; Lin, Jing; Huang, Yang; Xue, Yanming; Jin, Peng; Zou, Jin; Tang, Chengchun

    2013-01-01

    Novel activated boron nitride (BN) as an effective adsorbent for pollutants in water and air has been reported in the present work. The activated BN was synthesized by a simple structure-directed method that enabled us to control the surface area, pore volume, crystal defects and surface groups. The obtained BN exhibits an super high surface area of 2078 m(2)/g, a large pore volume of 1.66 cm(3)/g and a special multimodal microporous/mesoporous structure located at ~ 1.3, ~ 2.7, and ~ 3.9 nm, respectively. More importantly, the novel activated BN exhibits an excellent adsorption performance for various metal ions (Cr(3+), Co(2+), Ni(2+), Ce(3+), Pb(2+)) and organic pollutants (tetracycline, methyl orange and congo red) in water, as well as volatile organic compounds (benzene) in air. The excellent reusability of the activated BN has also been confirmed. All the features render the activated BN a promising material suitable for environmental remediation. PMID:24220570

  20. Activated boron nitride as an effective adsorbent for metal ions and organic pollutants

    NASA Astrophysics Data System (ADS)

    Li, Jie; Xiao, Xing; Xu, Xuewen; Lin, Jing; Huang, Yang; Xue, Yanming; Jin, Peng; Zou, Jin; Tang, Chengchun

    2013-11-01

    Novel activated boron nitride (BN) as an effective adsorbent for pollutants in water and air has been reported in the present work. The activated BN was synthesized by a simple structure-directed method that enabled us to control the surface area, pore volume, crystal defects and surface groups. The obtained BN exhibits an super high surface area of 2078 m2/g, a large pore volume of 1.66 cm3/g and a special multimodal microporous/mesoporous structure located at ~ 1.3, ~ 2.7, and ~ 3.9 nm, respectively. More importantly, the novel activated BN exhibits an excellent adsorption performance for various metal ions (Cr3+, Co2+, Ni2+, Ce3+, Pb2+) and organic pollutants (tetracycline, methyl orange and congo red) in water, as well as volatile organic compounds (benzene) in air. The excellent reusability of the activated BN has also been confirmed. All the features render the activated BN a promising material suitable for environmental remediation.

  1. Activated boron nitride as an effective adsorbent for metal ions and organic pollutants

    PubMed Central

    Li, Jie; Xiao, Xing; Xu, Xuewen; Lin, Jing; Huang, Yang; Xue, Yanming; Jin, Peng; Zou, Jin; Tang, Chengchun

    2013-01-01

    Novel activated boron nitride (BN) as an effective adsorbent for pollutants in water and air has been reported in the present work. The activated BN was synthesized by a simple structure-directed method that enabled us to control the surface area, pore volume, crystal defects and surface groups. The obtained BN exhibits an super high surface area of 2078 m2/g, a large pore volume of 1.66 cm3/g and a special multimodal microporous/mesoporous structure located at ~ 1.3, ~ 2.7, and ~ 3.9 nm, respectively. More importantly, the novel activated BN exhibits an excellent adsorption performance for various metal ions (Cr3+, Co2+, Ni2+, Ce3+, Pb2+) and organic pollutants (tetracycline, methyl orange and congo red) in water, as well as volatile organic compounds (benzene) in air. The excellent reusability of the activated BN has also been confirmed. All the features render the activated BN a promising material suitable for environmental remediation. PMID:24220570

  2. Effect of alkane chain length and counterion on the freezing transition of cationic surfactant adsorbed film at alkane mixture - water interfaces.

    PubMed

    Tokiwa, Yuhei; Sakamoto, Hiroyasu; Takiue, Takanori; Aratono, Makoto; Matsubara, Hiroki

    2015-05-21

    Penetration of alkane molecules into the adsorbed film gives rise to a surface freezing transition of cationic surfactant at the alkane-water interface. To examine the effect of the alkane chain length and counterion on the surface freezing, we employed interfacial tensiometry and ellipsometry to study the interface of cetyltrimethylammonium bromide and cetyltrimethylammonium chloride aqueous solutions against dodecane, tetradecane, hexadecane, and their mixtures. Applying theoretical equations to the experimental results obtained, we found that the alkane molecules that have the same chain length as the surfactant adsorb preferentially into the surface freezing film. Furthermore, we demonstrated that the freezing transition temperature of cationic surfactant adsorbed film was independent of the kind of counterion. PMID:25932500

  3. Use of layered double hydroxides and their derivatives as adsorbents for inorganic and organic pollutants

    NASA Astrophysics Data System (ADS)

    You, Youwen

    Contamination of surface and groundwaters by hazardous inorganic and organic pollutants has become an increasing threat to the safety of drinking waters. Cleanup of contaminated surface and groundwaters has, therefore, become a major focus of environmental research. Primary objectives of this dissertation study were to examine the adsorption properties of layered double hydroxides (LDHs) and their derivatives for inorganic and organic contaminants and to identify potential technologies that utilize LDHs and their derivatives for environment remediation. Studies examined the adsorption characteristics of anionic selenium, arsenic and dicamba (3,6 dichloro-2-methoxy benzoic acid) on original LDHs and calcined-LDHs. Adsorption of selenium and arsenic on LDHs was a function of pH. Competing anions in solution strongly affected adsorption of all three contaminants, with divalent anions decreasing adsorption more intensely than monovalent anions. Adsorbed selenium, arsenic and dicamba could be released from LDHs in anion solutions. Adsorption isotherms for selenium and arsenic retention could be fitted to a simple Langmuir equation. Calcination processes significantly increased adsorption capacities of LDHs. Because of adsorption-desorpion characteristics, LDHs could be recycled. X-ray diffraction patterns revealed an increase of d-spacing coupling with adsorption of contaminants, verifying the intercalation of contaminants into layer structure of LDHs. Long chain anionic surfactants intercalated into LDHs modified their surface properties, resulting in organo-LDHs with hydrophobic surface properties. Various organo-LDHs were developed by incorporating different surfactants into LDHs via different synthesis methods. Surfactant intercalation properties were examined and the geometrical arrangements of the intercalated surfactants were characterized. Results revealed that surfactant molecules could adopt various configurations within the LDH interlayer space. Intercalation

  4. Optical and electrical characterizations of nanocomposite film of titania adsorbed onto oxidized multiwalled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Feng, Wei; Feng, Yiyu; Wu, Zigang; Fujii, Akihiko; Ozaki, Masanori; Yoshino, Katsumi

    2005-07-01

    Composite film containing titania electrostatically linked to oxidized multiwalled carbon nanotubes (TiO2-s-MWNTs) was prepared from a suspension of TiO2 nanoparticles in soluble carbon nanotubes. The structure of the film was analysed principally by Fourier transform infrared spectroscopy, scanning electron micrography and x-ray diffraction. The optical and electrical characterizations of the film were investigated by UV-vis spectrum, photoluminescence and photoconductivity. The enhancement of photocurrent in the TiO2-s-MWNT film is discussed by taking the photoinduced charge transfer between the MWNT and TiO2 into consideration.

  5. NMR Study of Phase Transitions in Pure Water and Binary H(2)O/HNO(3) Films Adsorbed on Surface of Pyrogenic Silica.

    PubMed

    Bogdan; Kulmala; Gorbunov; Kruppa

    1996-01-15

    Pyrogenic silica (aerosil) was employed as host within which the phase transitions in the adsorbed pure water and binary H(2)O/HNO(3) films have been studied with NMR spectroscopy. The median freezing temperature and freezing temperature region were shown to be highly sensitive both to the average thickness of the adsorbed films and to the amount of adsorbed nitric acid. The molar concentration of nitric acid in the adsorbed films was found to be very small, on the order of 10(-3)-10(-2) (M/liter). The concentration was found to be greater in the layers adjacent to the surface of silica and sharply decreases with distance from the surface. The difference between the median freezing temperatures for adsorbed pure water and for the binary system was found to be about 9 K for films of equal thickness. This is about 150 times greater than the difference between the freezing temperatures of bulk pure water and a solution with the same concentration of nitric acid. PMID:10479419

  6. Aquatic photolysis: photolytic redox reactions between goethite and adsorbed organic acids in aqueous solutions

    USGS Publications Warehouse

    Goldberg, M.C.; Cunningham, K.M.; Weiner, Eugene R.

    1993-01-01

    Photolysis of mono and di-carboxylic acids that are adsorbed onto the surface of the iron oxyhydroxide (goethite) results in an oxidation of the organic material and a reduction from Fe(III) to Fe(II) in the iron complex. There is a subsequent release of Fe2+ ions into solution. At constant light flux and constant solution light absorption, the factors responsible for the degree of photolytic reaction include: the number of lattice sites that are bonded by the organic acid; the rate of acid readsorption to the surface during photolysis; the conformation and structure of the organic acid; the degree of oxidation of the organic acid; the presence or absence of an ??-hydroxy group on the acid, the number of carbons in the di-acid chain and the conformation of the di-acid. The ability to liberate Fe(III) at pH 6.5 from the geothite lattice is described by the lyotropic series: tartrate>citrate> oxalate > glycolate > maleate > succinate > formate > fumarate > malonate > glutarate > benzoate = butanoate = control. Although a larger amount of iron is liberated, the series is almost the same at pH 5.5 except that oxalate > citrate and succinate > maleate. A set of rate equations are given that describe the release of iron from the goethite lattice. It was observed that the pH of the solution increases during photolysis if the solutions are not buffered. There is evidence to suggest the primary mechanism for all these reactions is an electron transfer from the organic ligand to the Fe(III) in the complex. Of all the iron-oxyhydroxide materials, crystalline goethite is the least soluble in water; yet, this study indicates that in an aqueous suspension, iron can be liberated from the goethite lattice. Further, it has been shown that photolysis can occur in a multiphase system at the sediment- water interface which results in an oxidation of the organic species and release of Fe2+ to solution where it becomes available for further reaction. ?? 1993.

  7. Adsorbable organic halogens (AOXs) in solid residues from hazardous and clinical waste incineration.

    PubMed

    Durmusoglu, Ertan; Bakoglu, Mithat; Karademir, Aykan; Kirli, Lale

    2006-01-01

    Trace concentrations of a variety of chemicals remain in solid residues following combustion even in properly designed and operated incinerators. In the present study, the adsorbable organic halogen (AOX) levels of the solid residues, i.e., bottom ash, fly ash, and filter cake, were investigated during a 82-day of continuous operation of a Hazardous and Clinical Waste Incinerator. The distribution of halogens in the waste input prior to the incineration was also determined. The AOX levels measured in bottom ash, fly ash and filter cake were in the range of 0.014-1.879, 0.012-0.263, and 0.004-0.062 mg-Cl(-)/kg, respectively. The AOX levels are significantly low in the fly ash and filter cake due to the post-combustion process in the incinerator. At the end of the 82 days, the total AOX output in the bottom ash, fly ash, and filter cake were 571, 3.71, and 6.26 g, respectively. The partitioning of the total AOX in solid residues was 98.28, 0.64, and 1.08% for the bottom ash, fly ash and filter cake, respectively. This shows that the bottom ash is more contaminated with AOX than the other two residues. PMID:16835121

  8. Organic silicon compounds anf hydrogen sulfide removal from biogas by mineral and adsorbent

    NASA Astrophysics Data System (ADS)

    Choi, J.

    2015-12-01

    Biogas utilized for energy production needs to be free from organic silicon compounds and hydrogen sulfide , as their burning has damaging effects on utilities and humans; organic silicon compounds and hydrogen sulfide can be found in biogas produced from biomass wastes, due to their massive industrial use in synthetic product,such as cosmetics, detergents and paints.Siloxanes and hydrogen sulfide removal from biogas can be carried out by various methods (Ajhar et al., 2010); aim of the present work is to find a single practical andeconomic way to drastically and simultaneously reduce both hydrogen sulfide and the siloxanes concentration to less than 1 ppm. Some commercial activated carbons previously selected (Monteleoneet al., 2011) as being effective in hydrogen sulfide up taking have been tested in an adsorption measurement apparatus, by flowing both hydrogen sulphide and volatile siloxane (Decamethycyclopentasiloxane or D5) in a nitrogen stream,typically 25-300 ppm D5 over N2, through an clay minerals, Fe oxides and Silica; the adsorption process was analyzed by varying some experimental parameters (concentration, grain size, bed height). The best silica shows an adsorption capacity of 0.2 g D5 per gram of silica. The next thermo gravimetric analysis (TGA) confirms the capacity data obtained experimentally by the breakthrough curve tests.The capacity results depend on D5 and hydrogen sulphide concentrations. A regenerative silica process is then carried out byheating the silica bed up to 200 ° C and flushing out the adsorbed D5 and hydrogen sulphide samples in a nitrogen stream in athree step heating procedure up to 200 ° C. The adsorption capacity is observed to degrade after cyclingthe samples through several adsorption-desorption cycles.

  9. Analysis of Chemical Reactions between Radical Growth Precursors Adsorbed on Plasma-Deposited Silicon Thin-Film Surfaces

    NASA Astrophysics Data System (ADS)

    Bakos, Tamas; Valipa, Mayur; Maroudas, Dimitrios

    2006-03-01

    The dominant precursor in the plasma deposition of hydrogenated amorphous silicon (a-Si:H) thin films is the SiH3 radical. In this presentation, we report results of first-principles density functional theory calculations on the crystalline Si(001)-(2x1):H surface and molecular-dynamics simulations on a-Si:H surfaces for the interactions between SiH3 radicals adsorbed on Si thin-film surfaces. The analysis reveals that two SiH3 radicals may either form disilane (Si2H6) that desorbs from the surface or undergo a disproportionation reaction producing an SiH2 radical that is incorporated in the film and a silane molecule that is released in the gas phase. The corresponding activation barriers depend on the local atomic coordination of the surface Si atoms; Si2H6 formation is barrierless if both radicals are bonded to overcoordinated surface Si atoms and exhibits barriers in excess of 1 eV for two chemisorbed SiH3 radicals.

  10. Fluorescence and photoelectrochemical behavior of chlorophyll {ital a} adsorbed on a nanocrystalline SnO{sub 2} film

    SciTech Connect

    Bedja, I.; Kamat, P.V.; Hotchandani, S.

    1996-10-01

    Fluorescence and photoelectrochemical studies of chlorophyll {ital a} (Chl {ital a}) adsorbed on nanocrystalline SnO{sub 2} film were carried out. The results of fluorescence and incident photon to current conversion efficiency (IPCE) as a function of applied bias suggest that the fluorescence quenching and the photocarrier generation are interrelated. Fluorescence quenching has thus been utilized to determine the photogeneration efficiency, {eta}({ital e}), of charges in a SnO{sub 2}/Chl {ital a} based photoelectrochemical cell. A value of 0.75 was obtained for {eta}({ital e}) for unbiased cells. With an IPCE of 13{percent}, {eta}({ital e}) of 75{percent}, and a light harvesting efficiency of 70{percent}, the charge collection efficiency of {approximately}23{percent} was evaluated. These results suggest that the losses due to the charge recombination are a major factor that limit the efficiency of the cells. {copyright} {ital 1996 American Institute of Physics.}

  11. EPR studies on the organization of self-assembled spin-labeled organic monolayers adsorbed on GaAs.

    PubMed

    Ruthstein, Sharon; Artzi, Reit; Goldfarb, Daniella; Naaman, Ron

    2005-02-01

    Characterizing the structure and dynamic properties of a single monolayer is a challenge due to the minute amount of material that is probed. Here, EPR spectroscopy is used for investigating the spatial and temporal organization of self-assembled monolayers of 5- and 16-doxyl stearic acid (5 DSA and 16 DSA, respectively) adsorbed on a GaAs substrate. The results are complemented with FTIR and ellipsometery measurements, which provide the evidence for the formation of monolayers. Moreover, a comparison with the FTIR spectrum of a monolayer of stearic acid shows that the monolayers of the spin labeled molecules are less packed due to the hindrance introduced by the labeling group. The EPR spectra provide a new insight on the ordering in the layer and more interestingly, it reveals the time dependence of the organization. For 5DSA, with the spin-label group situated close to the substrate, the EPR spectrum immediately after adsorption is poorly resolved and dominated by the spin-exchange interaction between neighboring molecules. As time increases (up to 1 week) the resolution of the 14N hyperfine coupling increases, revealing a better organized monolayer where the molecules are more homogenously spaced. Moreover, the spectrum of the layer, after reaching equilibrium, shows that there is no motional freedom near the GaAs surface. Orientation dependence measurements on the equilibrated sample show the presence of a preferred orientation of the molecules, although with a wide distribution. The spectrum of the 16DSA monolayer, where the nitroxide spin label is situated at the end of the chain, far from the surface, also showed a poorly resolved spectrum at short times, but unlike 5DSA, it did not exhibit any time dependence. Through EPR line-shape simulations and by comparison with FTIR results, the differences between 5DSA and 16DSA were attributed to difference in coverage caused by the bulky spin label near the surface in the case of 5DSA. PMID:19785139

  12. Relationship between surface viscosity and surface composition of adsorbed surfactant films

    SciTech Connect

    Djabbarah, N.F.; Wasan, D.T.

    1982-02-01

    The single-bubble foaming technique was used to determine the surface excess concentrations of aqueous solutions of sodium lauryl sulfate (SLS) and lauryl alcohol (LOH). The excess concentrations of sodium lauryl sulfate-lauryl alcohol showed that lauryl alcohol is preferentially adsorbed at the surface, but only partially displaces sodium lauryl sulfate. This causes a higher total surface concentration and, consequently, a closer packing of surfactant molecules. The total surface excess concentration increases with an increase in the bulk concentration of the 2 surfactants until the critical micelle concentration (CMC) is reached. At concentrations exceeding the CMC, the surface excess concentration of LOH remains virtually constant, while that of SLS declines. This is due to the formation of SLS micelles. The surface excess concentration data have been used to estimate the extent of molecular packing at the gas/liquid interface and to assess interactions among surfactant molecules in order to explain trends in surface viscosity of a mixed surfactant system adsorbed from an aqueous solution. 30 references.

  13. Nonequilibrium Molecular Dynamics Simulations of Organic Friction Modifiers Adsorbed on Iron Oxide Surfaces.

    PubMed

    Ewen, James P; Gattinoni, Chiara; Morgan, Neal; Spikes, Hugh A; Dini, Daniele

    2016-05-10

    For the successful development and application of lubricants, a full understanding of the nanoscale behavior of complex tribological systems is required, but this is difficult to obtain experimentally. In this study, we use nonequilibrium molecular dynamics (NEMD) simulations to examine the atomistic structure and friction properties of commercially relevant organic friction modifier (OFM) monolayers adsorbed on iron oxide surfaces and lubricated by a thin, separating layer of hexadecane. Specifically, acid, amide, and glyceride OFMs, with saturated and Z-unsaturated hydrocarbon tail groups, are simulated at various surface coverages and sliding velocities. At low and medium coverage, the OFMs form liquidlike and amorphous monolayers, respectively, which are significantly interdigitated with the hexadecane lubricant, resulting in relatively high friction coefficients. At high coverage, solidlike monolayers are formed for all of the OFMs, which, during sliding, results in slip planes between well-defined OFM and hexadecane layers, yielding a marked reduction in the friction coefficient. When present at equal surface coverage, OFMs with saturated and Z-unsaturated tail groups are found to yield similar structure and friction behavior. OFMs with glyceride head groups yield significantly lower friction coefficients than amide and particularly carboxylic acid head groups. For all of the OFMs and coverages simulated, the friction coefficient is found to increase linearly with the logarithm of sliding velocity; however, the gradient of this increase depends on the coverage. The structure and friction details obtained from these simulations agree well with experimental results and also shed light on the relative tribological performance of these OFMs through nanoscale structural variations. This has important implications in terms of the applicability of NEMD to aid the development of new formulations to control friction. PMID:27064962

  14. Screening Metal-Organic Frameworks by Analysis of Transient Breakthrough of Gas Mixtures in a Fixed Bed Adsorber

    SciTech Connect

    Krishna, Rajamani; Long, Jeffrey R.

    2011-07-07

    Metal–organic frameworks (MOFs) offer considerable potential for separating a variety of mixtures that are important in applications such as CO₂ capture and H₂ purification. In view of the vast number of MOFs that have been synthesized, there is a need for a reliable procedure for comparing screening and ranking MOFs with regard to their anticipated performance in pressure swing adsorption (PSA) units. For this purpose, the most commonly used metrics are the adsorption selectivity and the working capacity. Here, we suggest an additional metric for comparing MOFs that is based on the analysis of the transient response of an adsorber to a step input of a gaseous mixture. For a chosen purity of the gaseous mixture exiting from the adsorber, a dimensionless breakthrough time τ{sub break} can be defined and determined; this metric determines the frequency of required regeneration and influences the productivity of a PSA unit. The values of τ{sub break} are dictated both by selectivity and by capacity metrics .By performing transient adsorber calculations for separation of CO₂/H₂, CO₂/CH₄, CH₄/H₂, and CO₂/CH₄/H₂ mixtures, we compare the values of τbreak to highlight some important advantages of MOFs over conventionally used adsorbents such as zeolite NaX. For a given separation duty, such comparisons provide a more realistic ranking of MOFs than afforded by either selectivity or capacity metrics alone. We conclude that breakthrough calculations can provide an essential tool for screening MOFs.

  15. Preface: Thin films of molecular organic materials

    NASA Astrophysics Data System (ADS)

    Fraxedas, J.

    2008-03-01

    This special issue is devoted to thin films of molecular organic materials and its aim is to assemble numerous different aspects of this topic in order to reach a wide scientific audience. Under the term 'thin films', structures with thicknesses spanning from one monolayer or less up to several micrometers are included. In order to narrow down this relaxed definition (how thin is thin?) I suggest joining the stream that makes a distinction according to the length scale involved, separating nanometer-thick films from micrometer-thick films. While the physical properties of micrometer-thick films tend to mimic those of bulk materials, in the low nanometer regime new structures (e.g., crystallographic and substrate-induced phases) and properties are found. However, one has to bear in mind that some properties of micrometer-thick films are really confined to the film/substrate interface (e.g. charge injection), and are thus of nanometer nature. Supported in this dimensionality framework, this issue covers the most ideal and model 0D case, a single molecule on a surface, through to the more application-oriented 3D case, placing special emphasis on the fascinating 2D domain that is monolayer assembly. Thus, many aspects will be reviewed, such as single molecules, self-organization, monolayer regime, chirality, growth, physical properties and applications. This issue has been intentionally restricted to small molecules, thus leaving out polymers and biomolecules, because for small molecules it is easier to establish structure--property relationships. Traditionally, the preparation of thin films of molecular organic materials has been considered as a secondary, lower-ranked part of the more general field of this class of materials. The coating of diverse surfaces such as silicon, inorganic and organic single crystals, chemically modified substrates, polymers, etc., with interesting molecules was driven by the potential applications of such molecular materials

  16. Development and characterization of activated hydrochars from orange peels as potential adsorbents for emerging organic contaminants.

    PubMed

    Fernandez, M E; Ledesma, B; Román, S; Bonelli, P R; Cukierman, A L

    2015-05-01

    Activated hydrochars obtained from the hydrothermal carbonization of orange peels (Citrus sinensis) followed by various thermochemical processing were assessed as adsorbents for emerging contaminants in water. Thermal activation under flows of CO2 or air as well as chemical activation with phosphoric acid were applied to the hydrochars. Their characteristics were analyzed and related to their ability to uptake three pharmaceuticals (diclofenac sodium, salicylic acid and flurbiprofen) considered as emerging contaminants. The hydrothermal carbonization and subsequent activations promoted substantial chemical transformations which affected the surface properties of the activated hydrochars; they exhibited specific surface areas ranging from 300 to ∼620 m(2)/g. Morphological characterization showed the development of coral-like microspheres dominating the surface of most hydrochars. Their ability to adsorb the three pharmaceuticals selected was found largely dependent on whether the molecules were ionized or in their neutral form and on the porosity developed by the new adsorbents. PMID:25742754

  17. Surface-sensitive UHV dielectric studies of nanoscale organic thin films: Adsorption, crystallization, and sublimation

    NASA Astrophysics Data System (ADS)

    Underwood, Jason M.

    Nanoscale systems are small collections of atoms or molecules, which as a result of their limited extent, show measurable thermodynamic deviations from bulk samples of the same species. The deviations may result from purely finite-size effects, or may be due to an increased significance of the interaction between the nanoscale system and its container. Ultra-thin (<100 nm) films of organic molecules adsorbed on surfaces afford unique opportunities to study the interplay of forces relevant to nanoscale physics. This thesis describes the development of a novel ultra-high vacuum apparatus to study the behavior of adsorbed polar molecules via dielectric spectroscopy (UHV-DS). Ultra-thin films are grown and characterized in-situ. The use of interdigitated electrode capacitors and a ratio-transformer bridge technique yields resolutions of ˜1 aF and ˜10-5 ppm in the capacitance and loss tangent, respectively. Typical sensitivity is 10 aF per monolayer at 80 K. Results are given for studies on water, methanol, and Cp* (a synthetic molecular rotor). The desorption event in the dielectric spectra is correlated with thermal desorption spectroscopy. During growth of methanol films, we observe partial crystallization for temperatures above ≳ 100 K. Crystallization is also observed upon heating glassy films grown at 80 K. Finally, we discuss UHV-DS as a probe for solid thin-film vapor pressure measurements, and show that our data on methanol compare favorably with those in the literature.

  18. Entropy-Driven Conformational Control of α,ω-Difunctional Bidentate-Dithiol Azo-Based Adsorbates Enables the Fabrication of Thermally Stable Surface-Grafted Polymer Films.

    PubMed

    Lee, Han Ju; Jamison, Andrew C; Lee, T Randall

    2016-06-22

    Thermally stable radical initiator monolayers were prepared from uniquely designed α,ω-difunctional adsorbates with bidentate headgroups for the growth of nanoscale polymer films on metal surfaces. The length of the spacer separating the bidentate headgroups was varied to afford 4,4'-(diazene-1,2-diyl)bis(N-(16-(3,5-bis(mercaptomethyl)phenoxy)hexadecyl)-4-cyanopentanamide) (B16), 4,4'-(diazene-1,2-diyl)bis(N-(16-(3,5-bis(mercapto-methyl)phenoxy)decyl)-4-cyanopentanamide) (B10), and 4,4'-(diazene-1,2-diyl)bis(N-(4-(3,5-bis(mercaptomethyl)phenoxy)butyl)-4-cyanopentanamide) (B4). The structural features of the self-assembled monolayers (SAMs) derived from B16, B10, and B4 were characterized by X-ray photoelectron spectroscopy (XPS), ellipsometry, and polarization modulation infrared reflection-absorption spectroscopy (PM-IRRAS) and compared to those derived from an analogous α,ω-difunctional adsorbate with monodentate headgroups, 4,4'-(diazene-1,2-diyl)bis(4-cyano-N-(16-mercaptohexadecyl)pentanamide (M). These studies demonstrate that the conformation (i.e., hairpin vs standing up) of the bidentate initiator adsorbates on gold surfaces was easily controlled by adjusting the concentration of the adsorbates in solution. The results of solution-phase thermal desorption tests revealed that the radical initiator monolayers generated from B16, B10, and B4 exhibit an enhanced thermal stability when compared to those generated from M. Furthermore, a study of the growth of polymer films was performed to evaluate the utility of these new bidentate adsorbate SAMs as film-development platforms for new functional materials and devices. Specifically, surface-grafted polystyrene films were successfully generated from SAMs derived from B16. In contrast, attempts to grow polystyrene films from SAMs derived from M under a variety of analogous conditions were unsuccessful. PMID:27219525

  19. Organic thin films. Rational synthesis of organic thin films with exceptional long-range structural integrity.

    PubMed

    Seiki, Noriya; Shoji, Yoshiaki; Kajitani, Takashi; Ishiwari, Fumitaka; Kosaka, Atsuko; Hikima, Takaaki; Takata, Masaki; Someya, Takao; Fukushima, Takanori

    2015-06-01

    Highly oriented, domain-boundary-free organic thin films could find use in various high-performance organic materials and devices. However, even with state-of-the-art supramolecular chemistry, it is difficult to construct organic thin films with structural integrity in a size regime beyond the micrometer length scale. We show that a space-filling design, relying on the two-dimensional (2D) nested hexagonal packing of a particular type of triptycene, enables the formation of large-area molecular films with long-range 2D structural integrity up to the centimeter length scale by vacuum evaporation, spin-coating, and cooling from the isotropic liquid of the triptycene. X-ray diffraction analysis and microscopic observations reveal that triptycene molecules form a completely oriented 2D (hexagonal triptycene array) + 1D (layer stacking) structure, which is key for the long-range propagation of structural order. PMID:26045433

  20. Adsorption and oxidation of formaldehyde on a polycrystalline Pt film electrode: An in situ IR spectroscopy search for adsorbed reaction intermediates

    PubMed Central

    Behm, R Jürgen

    2014-01-01

    Summary As part of a mechanistic study of the electrooxidation of C1 molecules we have systematically investigated the dissociative adsorption/oxidation of formaldehyde on a polycrystalline Pt film electrode under experimental conditions optimizing the chance for detecting weakly adsorbed reaction intermediates. Employing in situ IR spectroscopy in an attenuated total reflection configuration (ATR-FTIRS) with p-polarized IR radiation to further improve the signal-to-noise ratio, and using low reaction temperatures (3 °C) and deuterium substitution to slow down the reaction kinetics and to stabilize weakly adsorbed reaction intermediates, we could detect an IR absorption band at 1660 cm−1 characteristic for adsorbed formyl intermediates. This assignment is supported by an isotope shift in wave number. Effects of temperature, potential and deuterium substitution on the formation and disappearance of different adsorbed species (COad, adsorbed formate, adsorbed formyl), are monitored and quantified. Consequences on the mechanism for dissociative adsorption and oxidation of formaldehyde are discussed. PMID:24991512

  1. Effect of adsorbed films on friction of Al2O3-metal systems

    NASA Technical Reports Server (NTRS)

    Pepper, S. V.

    1976-01-01

    The kinetic friction of polycrystalline Al2O3 sliding on Cu, Ni, and Fe in ultrahigh vacuum was studied as a function of the surface chemistry of the metal. Clean metal surfaces were exposed to O2, Cl2, C2H4, and C2H3Cl, and the change in friction due to the adsorbed species was observed. Auger electron spectroscopy assessed the elemental composition of the metal surface. It was found that the systems exposed to Cl2 exhibited low friction, interpreted as the van der Waals force between the Al2O3 and metal chloride. The generation of metal oxide by oxygen exposures resulted in an increase in friction, interpreted as due to strong interfacial bonds established by reaction of metal oxide with Al2O3 to form the complex oxide (spinel). The only effect of C2H4 was to increase the friction of the Fe system, but C2H3Cl exposures decreases friction in both Ni and Fe systems, indicating the dominance of the chlorine over the ethylene complex on the surface

  2. The analysis of surface-adsorbed organic molecules by alkali-assisted MIES combined with UPS(He I)

    NASA Astrophysics Data System (ADS)

    Günster, J.; Ochs, D.; Dieckhoff, S.; Kempter, V.

    1996-12-01

    Metastable impact electron spectroscopy (MIES) in combination with UPS(He I) is applied to the study of s-triazine and triethoxytriazine molecules adsorbed on Si(100) either alone or in combination with cesium atoms. It is demonstrated that the presence of the Cs atoms facilitates the identification of the adsorbed species considerably. It is concluded that (i) non-dissociative adsorption of the studied organic molecules occurs whereby the basal rings of the molecules lie flat on the silicon surface, in accordance with previous studies by Bu and Lin, (ii) the binding of the molecules to the surface is mainly via the lone pair orbitals of the nitrogen in the ring, and (iii) s-triazine reacts strongly with oxygen which bonds to the carbon atoms of the triazine ring.

  3. Thick-Film Carbon Dioxide Sensor via Anodic Adsorbate Stripping Technique and Its Structural Dependence

    PubMed Central

    Photinon, Kanokorn; Wang, Shih-Han; Liu, Chung-Chiun

    2009-01-01

    A three-electrode based CO2 sensor was fabricated using thick-film technology. The performance of this sensor was further enhanced by incorporating platinum nanoparticles onto the working electrode surface. An eight-fold increase in the signal output was obtained from the electrode with the platinum nanoparticles. The sensing output was linearly related to the CO2 presented. Stability measurements demonstrated that the decline of the active surface area and the sensitivity of the sensor were 8% and 13%, respectively, over a two week period of time. The sensor response appeared to be a structural dependence of the crystallographic orientation of platinum electrode. PMID:22399993

  4. Kosterlitz-Thouless Transition in 4He Films Adsorbed to Rough Calcium Fluoride

    SciTech Connect

    Luhman, D. R.; Hallock, R. B.

    2006-09-07

    Previous measurements in our lab have shown that the onset of superfluidity at the KT transition, typically seen as a sharp change in the frequency of a smooth-surface quartz crystal microbalance, becomes less identifiable in the presence of increasing surface roughness or disorder, while the peak in the dissipation is unchanged. Using a series of microbalances coated with increasingly rough CaF2, we have extended our measurements to lower 4He film coverages and thus lower temperatures. We find at lower 4He coverages that the presence of disorder on the substrate has a diminished effect on the frequency shift.

  5. Third Sound Generation in Superfluid 4He Films Adsorbed on Multiwall Carbon Nanotubes

    NASA Astrophysics Data System (ADS)

    Iaia, Vito; Menachekanian, Emin; Williams, Gary

    2014-03-01

    A technique is developed for generating third sound in superfluid 4He films coating the surface of multiwall carbon nanotubes. Third sound is a thickness and temperature wave of the helium film, and in our case we detect the temperature oscillations with a carbon resistance bolometer. The nanotubes are packed in an annular resonator that is vibrated with a mechanical shaker assembly consisting of a permanent magnet mounted on springs, and surrounded by a superconducting coil. The coil is driven with an oscillating current, vibrating the cell at that frequency. Sweeping the drive frequency over the range 100-200 Hz excites the resonant third sound mode of the cell, seen as a high-Q signal in the FFT analysis of the bolometer signal. A problem with our original cell was that the mechanical drive would also shake the dilution refrigerator cooling the cell to low temperatures, and increasing the drive would start to heat up the refrigerator and the cell, which were rigidly coupled together. A new configuration now suspends the cell as a pendulum on a string, with thermal contact made by copper wires. Piezo sensor measurements show this reduces the vibration reaching the refrigerator by two orders of magnitude, which should allow measurements at lower temperatures.

  6. Infrared spectroscopy of water clusters co-adsorbed with hydrogen molecules on a sodium chloride film

    NASA Astrophysics Data System (ADS)

    Yamakawa, Koichiro; Fukutani, Katsuyuki

    2016-06-01

    Hydrogen gas containing a trace of water vapor was dosed on a vacuum-evaporated sodium chloride film at 13 K, and water clusters formed on the substrate were investigated by infrared absorption spectroscopy. Absorption bands due to (H2O)n clusters with n = 3-6 and an induced absorption band due to hydrogen were clearly observed. With increasing gas dosage, the intensities of the cluster bands increased linearly while the intensity of the hydrogen band was constant. This suggests that the water clusters were formed in two-dimensional matrices of hydrogen. We found that the water clusters did exist on the surface upon heating even after the hydrogen molecules had desorbed. A further rise of the substrate temperature up to 27 K yielded the formation of larger clusters, (H2O)n with n > 6 . We also discuss the origins of the two bands of the trimer in terms of pseudorotation and a metastable isomer.

  7. Comparison between the adsorption behaviors of an organic cation and an organic anion on several reversed-phase liquid chromatography adsorbents.

    PubMed

    Gritti, Fabrice; Guiochon, Georges

    2004-09-01

    Adsorption data of an organic cation (propranololium chloride) and an organic anion (sodium 1-naphthalene sulfonate) were measured by frontal analysis on two RPLC adsorbents, Symmetry-C18 and XTerra-C18, with aqueous solutions of methanol as the mobile phases. The influence of supporting neutral salts on the adsorption behavior of these two ions are compared. The Henry constants are close (H approximately 5). The four sets of isotherm data are all well accounted for using the bi-Moreau model. However, the isotherms of the two ions behave differently at high concentrations. The initial behaviors of all the isotherms are antilangmuirian but remain so in a much wider concentration range for the cation than for the anion, due to its stronger adsorbate-adsorbate interactions on the low-energy adsorption sites. The retention times of both ions increase with increasing concentration of neutral salt in the mobile phase, suggesting the formation of ion-pair complexes, with Cl- for the cation and with Na+ for the anion. The adsorbate-adsorbate interactions vanish in the presence of salt and the bi-Moreau isotherm model tends toward a bi-Langmuir model. Differences in adsorption behavior are also observed between the cation and the anion when bivalent inorganic anions and cations, respectively, are dissolved in the mobile phase. High concentration band profiles of 1-naphthalene sulfonic acid are langmuirian, except in the presence of a trivalent cation, while those of propranolol are antilangmuirian under certain conditions even with uni- or divalent cations. PMID:15453413

  8. Dynamic interfaces in an organic thin film

    PubMed Central

    Tao, Chenggang; Liu, Qiang; Riddick, Blake C.; Cullen, William G.; Reutt-Robey, Janice; Weeks, John D.; Williams, Ellen D.

    2008-01-01

    Low-dimensional boundaries between phases and domains in organic thin films are important in charge transport and recombination. Here, fluctuations of interfacial boundaries in an organic thin film, acridine-9-carboxylic acid on Ag(111), have been visualized in real time and measured quantitatively using scanning tunneling microscopy. The boundaries fluctuate via molecular exchange with exchange time constants of 10–30 ms at room temperature, with length-mode fluctuations that should yield characteristic f−1/2 signatures for frequencies less than ≈100 Hz. Although acridine-9-carboxylic acid has highly anisotropic intermolecular interactions, it forms islands that are compact in shape with crystallographically distinct boundaries that have essentially identical thermodynamic and kinetic properties. The physical basis of the modified symmetry is shown to arise from significantly different substrate interactions induced by alternating orientations of successive molecules in the condensed phase. Incorporating this additional set of interactions in a lattice–gas model leads to effective multicomponent behavior, as in the Blume–Emery–Griffiths model, and can straightforwardly reproduce the experimentally observed isotropic behavior. The general multicomponent description allows the domain shapes and boundary fluctuations to be tuned from isotropic to highly anisotropic in terms of the balance between intermolecular interactions and molecule–substrate interactions. PMID:18765797

  9. Hybrid inorganic-organic adsorbents Part 1: Synthesis and characterization of mesoporous zirconium titanate frameworks containing coordinating organic functionalities.

    PubMed

    Griffith, Christopher S; De Los Reyes, Massey; Scales, Nicholas; Hanna, John V; Luca, Vittorio

    2010-12-01

    A series of functional hybrid inorganic-organic adsorbent materials have been prepared through postsynthetic grafting of mesoporous zirconium titanate xerogel powders using a range of synthesized and commercial mono-, bis-, and tris-phosphonic acids, many of which have never before been investigated for the preparation of hybrid phases. The hybrid materials have been characterized using thermogravimetric analysis, diffuse reflectance infrared (DRIFT) and 31P MAS NMR spectroscopic techniques and their adsorption properties studied using a 153Gd radiotracer. The highest level of surface functionalization (molecules/nm2) was observed for methylphosphonic acid (∼3 molecules/nm2). The level of functionalization decreased with an increase in the number of potential surface coordinating groups of the phosphonic acids. Spectral decomposition of the DRIFT and 31P MAS NMR spectra showed that each of the phosphonic acid molecules coordinated strongly to the metal oxide surface but that for the 1,1-bis-phosphonic acids and tris-phosphonic acids the coordination was highly variable resulting in a proportion of free or loosely coordinated phosphonic acid groups. Functionalization of a porous mixed metal oxide framework with the tris-methylenephosphonic acid (ATMP-ZrTi-0.33) resulted in a hybrid with the highest affinity for 153Gd3+ in nitric acid solutions across a wide range of acid concentrations. The ATMP-ZrTi-0.33 hybrid material extracted 153Gd3+ with a Kd value of 1×10(4) in 0.01 M HNO3 far exceeding that of the other hybrid phases. The unfunctionalized mesoporous mixed metal oxide had negligible affinity for Gd3+ (Kd<100) under identical experimental conditions. It has been shown that the presence of free or loosely coordinated phosphonic acid groups does not necessarily translate to affinity for 153Gd3+. The theoretical cation exchange capacity of the ATMP-ZrTi-0.33 hybrid phase for Gd3+ has been determined to be about 0.005 mmol/g in 0.01 M HNO3. This behavior and

  10. David Adler Lectureship Award Talk: Friction and energy dissipation mechanisms in adsorbed molecules and molecularly thin films

    NASA Astrophysics Data System (ADS)

    Krim, Jacqueline

    2015-03-01

    Studies of the fundamental origins of friction have undergone rapid progress in recent years, with the development of new experimental and computational techniques for measuring and simulating friction at atomic length and time scales. The increased interest has sparked a variety of discussions and debates concerning the nature of the atomic-scale and quantum mechanisms that dominate the dissipative process by which mechanical energy is transformed into heat. Measurements of the sliding friction of physisorbed monolayers and bilayers can provide information on the relative contributions of these various dissipative mechanisms. Adsorbed films, whether intentionally applied or present as trace levels of physisorbed contaminants, moreover are ubiquitous at virtually all surfaces. As such, they impact a wide range of applications whose progress depends on precise control and/or knowledge of surface diffusion processes. Examples include nanoscale assembly, directed transport of Brownian particles, material flow through restricted geometries such as graphene membranes and molecular sieves, passivation and edge effects in carbon-based lubricants, and the stability of granular materials associated with frictional and frictionless contacts. Work supported by NSFDMR1310456.

  11. Tribochemical synthesis of nano-lubricant films from adsorbed molecules at sliding solid interface: Tribo-polymers from α-pinene, pinane, and n-decane

    NASA Astrophysics Data System (ADS)

    He, Xin; Barthel, Anthony J.; Kim, Seong H.

    2016-06-01

    The mechanochemical reactions of adsorbed molecules at sliding interfaces were studied for α-pinene (C10H16), pinane (C10H18), and n-decane (C10H22) on a stainless steel substrate surface. During vapor phase lubrication, molecules adsorbed at the sliding interface could be activated by mechanical shear. Under the equilibrium adsorption condition of these molecules, the friction coefficient of sliding steel surfaces was about 0.2 and a polymeric film was tribochemically produced. The synthesis yield of α-pinene tribo-polymers was about twice as much as pinane tribo-polymers. In contrast to these strained bicyclic hydrocarbons, n-decane showed much weaker activity for tribo-polymerization at the same mechanical shear condition. These results suggested that the mechanical shear at tribological interfaces could induce the opening of the strained ring structure of α-pinene and pinane, which leads to polymerization of adsorbed molecules at the sliding track. On a stainless steel surface, such polymerization reactions of adsorbed molecules do not occur under typical surface reaction conditions. The mechanical properties and boundary lubrication efficiency of the produced tribo-polymer films are discussed.

  12. Structural studies of ultrathin organic films

    NASA Astrophysics Data System (ADS)

    Yim, Hyun

    1998-11-01

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

  13. Effects of molecule-insulator interaction on geometric property of a single phthalocyanine molecule adsorbed on an ultrathin NaCl film

    NASA Astrophysics Data System (ADS)

    Miwa, Kuniyuki; Imada, Hiroshi; Kawahara, Shota; Kim, Yousoo

    2016-04-01

    The adsorption structure and orientation of a metal-free phthalocyanine (H2Pc ) and a magnesium phthalocyanine (MgPc) on a bilayer of NaCl films were investigated both theoretically and experimentally by means of first-principles calculations based on density functional theory and by scanning tunneling microscopy. H2Pc is adsorbed with its center over the sodium cation, and H-N bonds in the molecule are aligned with the [100] or [010] surface direction of a bilayer (001)-terminated NaCl film. The most stable structures of MgPc on the NaCl film show two kinds of orientations corresponding to the molecule rotated by ±7∘ relative to the [110] surface direction, with the Mg cation positioned over the chlorine anion in both cases. The energetic barrier for switching between these orientations is as low as 9.0 meV, and during an STM measurement, an orientational change of MgPc can be observed. The interaction between the adsorbed molecule and the NaCl film were analyzed in terms of dispersion interaction, Mg-Cl chemical bonding, and electrostatic interaction. It is found that the small electrostatic interaction between the molecule and the film gives a dominant contribution to determining the molecular orientation. Our detailed and comprehensive studies of the molecule-insulator interaction will provide knowledge to understand and control the properties of molecules on an insulating material.

  14. Ultrathin organic semiconductor films--soft matter effect.

    PubMed

    Wang, Tong; Yan, Donghang

    2014-05-01

    The growth of organic semiconductor thin films has been a crucial issue in organic electronics, especially the growth at the early stages. The thin-film phase has been found to be a common phenomenon in many organic semiconductor thin films, which is closely related with the weak van der Waals interaction between organic molecules, the long-range interaction between organic molecules and the substrate, as well as the soft matter characteristics of ultrathin films. The growth behavior and soft matter characteristics of the thin-film phase have great effects on thin film morphology and structure, for example, the formation and coalescence of grain boundaries, which further influences the performance of organic electronic devices. The understanding of thin-film phase and its intrinsic quality is necessary for fabricating large-size, highly ordered, continuous and defect-free ultrathin films. This review will focus on the growth behavior of organic ultrathin films, i.e., the level of the first several molecular layers, and provide an overview of the soft matter characteristics. PMID:24548597

  15. Difference in Surface Properties between Insoluble Monolayer and Adsorbed Film from Kinetics of Water Evaporation and BAM Image.

    PubMed

    Moroi, Yoshikiyo; Rusdi, Muhammad; Kubo, Izumi

    2004-05-20

    The evaporation rate of water molecules across three kinds of interfaces (air/water interface (1), air/surfactant solution interface (2), and air/water interface covered by insoluble monolayer (3)) was examined using a remodeled thermogravimetric balance. There was no difference in both the evaporation rate and the activation energy for the first two interfaces for three types of surfactant solutions below and above the critical micelle concentration (cmc). This means that the molecular surface area from the Gibbs surface excess has nothing to do with the evaporation rate. In the third case, the insoluble monolayer of 1-heptadecanol decreased the evaporation rate and increased the activation energy, indicating a clear difference between an insoluble monolayer and an adsorbed film of soluble surfactant. This difference was substantiated by BAM images, too. The images of three surfactant solution interfaces were similar to that of just the water surface, while distinct structures of molecular assemblies were observed for the insoluble monolayer. The concentration profile of water molecules in an air/liquid interfacial region was derived by Fix's second law. The profile indicates that a definite layer just beneath the air/liquid interface of the surfactant solution is made mostly of water molecules and that the layer thickness is a few times the root-mean-square displacement %@mt;sys@%%@rl;;@%2%@ital@%Dt%@rsf@%%@rlx@%%@mx@% of the water molecules. The thickness was found to be more than a few nanometers, as estimated from several relaxation times derived from the other kinetics than evaporation of amphiphilic molecules in aqueous systems and a maximum evaporation rate of purified water. PMID:18950121

  16. Effect of the adsorbate kinetic diameter on the accuracy of the Dubinin-Radushkevich equation for modeling adsorption of organic vapors on activated carbon.

    PubMed

    Jahandar Lashaki, Masoud; Fayaz, Mohammadreza; Niknaddaf, Saeid; Hashisho, Zaher

    2012-11-30

    This paper investigates the effect of the kinetic diameter (KD) of the reference adsorbate on the accuracy of the Dubinin-Radushkevich (D-R) equation for predicting the adsorption isotherms of organic vapors on microporous activated carbon. Adsorption isotherms for 13 organic compounds on microporous beaded activated carbon were experimentally measured, and predicted using the D-R model and affinity coefficients. The affinity coefficients calculated based on molar volumes, molecular polarizabilities, and molecular parachors were used to predict the isotherms based on four reference compounds (4.3≤KD≤6.8 Å). The results show that the affinity coefficients are independent of the calculation method if the reference and test adsorbates are from the same organic group. Choosing a reference adsorbate with a KD similar to that of the test adsorbate results in better prediction of the adsorption isotherm. The relative error between the predicted and the measured adsorption isotherms increases as the absolute difference in the kinetic diameters of the reference and test adsorbates increases. Finally, the proposed hypothesis was used to explain reports of inconsistent findings among published articles. The results from this study are important because they allow a more accurate prediction of adsorption capacities of adsorbents which allow for better design of adsorption systems. PMID:23044198

  17. Influence of molecular structure and adsorbent properties on sorption of organic compounds to a temperature series of wood chars.

    PubMed

    Lattao, Charisma; Cao, Xiaoyan; Mao, Jingdong; Schmidt-Rohr, Klaus; Pignatello, Joseph J

    2014-05-01

    Chars from wildfires and soil amendments (biochars) are strong adsorbents that can impact the fate of organic compounds in soil, yet the effects of solute and adsorbent properties on sorption are poorly understood. We studied sorption of benzene, naphthalene, and 1,4-dinitrobenzene from water to a series of wood chars made anaerobically at different heat treatment temperatures (HTT) from 300 to 700 °C, and to graphite as a nonporous, unfunctionalized reference adsorbent. Peak suppression in the NMR spectrum by sorption of the paramagnetic relaxation probe TEMPO indicated that only a small fraction of char C atoms lie near sorption sites. Sorption intensity for all solutes maximized with the 500 °C char, but failed to trend regularly with N2 or CO2 surface area, micropore volume, mesopore volume, H/C ratio, O/C ratio, aromatic fused ring size, or HTT. A model relating sorption intensity to a weighted sum of microporosity and mesoporosity was more successful. Sorption isotherm linearity declined progressively with carbonization of the char. Application of a thermodynamic model incorporating solvent-water and char-graphite partition coefficients permitted for the first time quantification of steric (size exclusion in pores) and π-π electron donor-acceptor (EDA) free energy contributions, relative to benzene. Steric hindrance for naphthalene increases exponentially from 9 to 16 kJ/mol (∼ 1.6-2.9 log units of sorption coefficient) with the fraction of porosity in small micropores. π-π EDA interactions of dinitrobenzene contribute -17 to -19 kJ/mol (3-3.4 log units of sorption coefficient) to sorption on graphite, but less on chars. π-π EDA interaction of naphthalene on graphite is small (-2 to 2 kJ/mol). The results show that sorption is a complex function of char properties and solute molecular structure, and not very predictable on the basis of readily determined char properties. PMID:24758543

  18. CORRELATIONS FOR THE DETERMINATION OF SURFACE DIFFUSIVITIES OF ORGANIC CHEMICALS ADSORBED ONTO GRANULAR ACTIVATED CARBON

    EPA Science Inventory

    Differential column batch reactor (DCBR) experiments in organic-free water were conducted for the following volatile organic compounds (VOCs): trichloroethene, tetrachloroethene, cis-1,2 dichlorethene, and toluene. Surface diffusion was required to explain the rate of uptake for ...

  19. In-plane conductance of thin films as a probe of surface chemical environment: Adsorbate effects on film electronic properties of indium tin oxide and gold

    NASA Astrophysics Data System (ADS)

    Swint, Amy Lynn

    Changes in the in-plane conductance of conductive thin films are observed as a result of chemical adsorption at the surface. Reaction of the indium tin oxide (ITO) surface with Bronsted acids (bases) leads to increases (decreases) in its in-plane conductance as measured by a four-point probe configuration. The conductance varies monotonically with pH suggesting that the degree of surface protonation or hydroxylation controls the surface charge density, which in turn affects the width of the n-type depletion layer, and ultimately the in-plane conductance. Measurements at constant pH with a series of tetraalkylammonium hydroxide species of varying cation size indicate that surface dipoles also affect ITO conductance by modulating the magnitude of the surface polarization. Modulating the double layer with varying aqueous salt solutions also affects ITO conductance, though not to the same degree as strong Bronsted acids and bases. Solvents of varying dielectric constant and proton donating ability (ethanol, dimethylformamide) decrease ITO conductance relative to H2O. In addition, changing solvent gives rise to thermally-derived conductance transients, which result from exothermic solvent mixing. The self-assembly of alkanethiols at the surface increases the conductance of ITO films, most likely through carrier population effects. In all cases examined the combined effects of surface charge, adsorbed dipole layer magnitude and carrier injection are responsible for altering the ITO conductance. Besides being directly applicable to the control of electronic properties, these results also point to the use of four-point probe resistance measurements in condensed phase sensing applications. Ultrasensitive conductance-based gas phase sensing of organothiol adsorption to gold nanowires is accomplished with a limit of detection in the 105 molecule range. Further refinement of the inherently low noise resistance measurement may lead to observation of single adsorption events at

  20. Removing organic contaminants with bifunctional iron modified rectorite as efficient adsorbent and visible light photo-Fenton catalyst.

    PubMed

    Zhao, Xiaorong; Zhu, Lihua; Zhang, Yingying; Yan, Jingchun; Lu, Xiaohua; Huang, Yingping; Tang, Heqing

    2012-05-15

    Iron-modified rectorite (FeR) was prepared as both adsorbent and catalyst. The iron modification increased layer-to-layer spacing and surface area of rectorite, leading to much increased adsorption of Rhodamine B (RhB) on rectorite. The maximum adsorption capacity of RhB on FeR reached 101mgg(-1) at pH 4.5, being 11 folds of that on the unmodified one. The iron modification also enabled rectorite to have efficient visible light photocatalytic ability. The apparent rate constant for the degradation of RhB (80μM) at 298K and pH 4.5 in the presence of H(2)O(2) (6.0mM) and FeR (0.4gL(-1)) was evaluated to be 0.0413min(-1) under visible light and 0.122min(-1) under sunlight, respectively. The analysis with electron spin resonance spin-trapping technique supported that the iron modified rectorite effectively catalyzed the decomposition of H(2)O(2) into hydroxyl radicals. On the basis of the characterization and analysis, the new bifunctional material was well clarified as both adsorbent and photocatalyst in the removing of organic pollutants. PMID:22410720

  1. A model to predict the adsorber thermal behavior during treatment of volatile organic compounds onto wet activated carbon.

    PubMed

    Pré, P; Delage, F; Le Cloirec, P

    2002-11-01

    A model for adsorption of volatile organic compounds (VOCs) onto a wet activated carbon bed was proposed in this study. This model accounts for temperature changes induced by the reversed and coupled mass-transfer processes of both organic species adsorption and water desorption. Indeed, it was experimentally pointed out that temperature rises, which result from the exothermal nature of the energetic interactions between the organic molecule and the activated carbon surface, are notably reduced when the adsorbent contains an initial moisture of approximately 10% in weight. Moreover, it was shown that water rate desorption was enhanced in the presence of organic vapor. This phenomenon may be explained by the displacement of sorbed water bythe organic molecules, owing to more intensive interactions with the activated carbon surface. The model proposed was elaborated from a previous comprehensive analysis of the diffusion mechanisms governing VOC adsorption at high concentrations onto a dry activated carbon bed. In a similar way, a theoretical approach was developed to model water desorption during drying of a wet activated carbon bed under pure flowing air. At last, a theoretical depiction of both competitive and reverse processes was outlined. The final model fits reasonably with experimental data relative to both breakthrough curves and thermal wave shape along the bed, even if local temperature change calculation may require some further improvement. PMID:12433182

  2. Resin pellets from beaches of the Portuguese coast and adsorbed persistent organic pollutants

    NASA Astrophysics Data System (ADS)

    Antunes, J. C.; Frias, J. G. L.; Micaelo, A. C.; Sobral, P.

    2013-09-01

    The occurrence of stranded plastic marine debris along the Portuguese coastline was investigated. Number of items m-2 and size range of resin pellets were recorded, corresponding to 53% of total marine debris collected items. In addition, concentrations of adsorbed persistent bioaccumulative and toxic chemicals (PBTC) were determined, PAH - polycyclic aromatic hydrocarbons; PCB - polychlorinated biphenyls and DDT - dichlorodiphenyltrichloroethane. Matosinhos (Mt) and Vieira de Leiria (VL) presented the highest number of items m-2 (362 and 332, respectively). Resin pellets with 4 mm diameter were the most abundant (50%). Contaminants concentration was variable. PAH concentrations recorded values between 53 and 44800 ng g-1, PCB ranged from 2 to 223 ng g-1 and DDT between 0.42 and 41 ng g-1. In general, aged and black pellets recorded higher concentrations for all contaminants. Matosinhos (Mt), Vieira de Leiria (VL) and Sines (Si), near industrial areas and port facilities, were the most contaminated beaches. Research efforts are needed to assess the points of entry of industrial plastic pellets in order to take action and minimize impacts on the ecosystems, in particular, points of transfer during transportation from plastic manufacturers to plastic converters should be identified and controlled so that virgin pellets are contained and will not enter rivers and be carried to the oceans where they can remain for a long time and travel great distances.

  3. Comparison of nutshell granular activated carbons to commercial adsorbents for the purge-and-trap gas chromatographic analysis of volatile organic compounds.

    PubMed

    Wartelle, L H; Marshall, W E; Toles, C A; Johns, M M

    2000-05-26

    Granular activated carbons (GACs) made from agricultural by-products were investigated as adsorbents for short path thermal desorption gas chromatographic analysis of selected polar and nonpolar organic compounds. GACs made from macadamia nut, black walnut and hazelnut shells were compared to four commercially available adsorbents, namely, Tenax TA, Carboxen 569, Carbosieve SIII and coconut charcoal for their properties in purge-and-trap analysis. Adsorption values and breakthrough volumes were calculated for compounds from C3 and C6-C10. GACs derived from macadamia nut shells were found to adsorb and desorb between 80% (benzene) and 277% (ethylbenzene) more acetone (C3), benzene (C6), toluene (C7), ethyl- (C8), n-propyl- (C9), or sec.-butylbenzenes (C10) purged from water at the 100 ppb level than the commercial adsorbents tested. PMID:10893033

  4. [Melting in adsorbed films

    SciTech Connect

    Simon, M.I.

    1992-01-01

    Over the past several years we have been developing a new approach to cloning large fragments of mammalian DNA in E. coli. which will permit detailed analysis of complex genomes. In January 1992 we began construction of an arrayed total human genomic library prepared in our BAC vector. Our goal is to create a 4-5X library which will be accessible for screening both by colony hybridization and by PCR. Our efforts in 1992 have been focused on expanding this library, characterizing specific clones isolated from the library, and demonstrating the use of BACs and Fosmids in creating physical maps. As a Model for the use of BACs in physical mapping, we have begun mapping human chromosome 22. In addition to their stability and ease of handling, BACs and Fosniids offer the advantage of permitting isolation of relatively large amounts of pure DNA which should greatly facilitate contig construction. We have created a 7X chromosome 22-specific Fosmid library consisting of clones obtained from DNA from a hybrid cell line.

  5. Removal of hexenuronic acid by xylanase to reduce adsorbable organic halides formation in chlorine dioxide bleaching of bagasse pulp.

    PubMed

    Nie, Shuangxi; Wang, Shuangfei; Qin, Chengrong; Yao, Shuangquan; Ebonka, Johnbull Friday; Song, Xueping; Li, Kecheng

    2015-11-01

    Xylanase-aided chlorine dioxide bleaching of bagasse pulp was investigated. The pulp was pretreated with xylanase and followed a chlorine dioxide bleaching stage. The ATR-FTIR and XPS were employed to determine the surface chemistry of the control pulp, xylanase treated and chlorine dioxide treated pulps. The hexenuronic acid (HexA) could obviously be reduced after xylanase pretreatment, and the adsorbable organic halides (AOX) were reduced after chlorine dioxide bleaching. Compared to the control pulp, AOX could be reduced by 21.4-26.6% with xylanase treatment. Chlorine dioxide demand could be reduced by 12.5-22% to achieve the same brightness. The ATR-FTIR and XPS results showed that lignin and hemicellulose (mainly HexA) were the main source for AOX formation. Xylanase pretreatment could remove HexA and expose more lignin, which decreased the chlorine dioxide demand and thus reduced formation of AOX. PMID:26263004

  6. Fluorescent thin gel films using organic dyes and pigments

    NASA Astrophysics Data System (ADS)

    Nakazumi, Hiroyuki; Takashi, Tarao; Taniguchi, Shin-ichi; Nanto, Hidehito

    1997-10-01

    New organic-inorganic fluorescent thin gel films included with laser dyes or fluorescent organic pigments have been prepared for display application. The florescent dyes (benzoxazolium, pyrromethene, and rhodamine dyes) and super-fine particles of fluorescent pigments (coumarin and perylene) were successfully incorporated into thin silicate gel films prepared from tetraethoxysilane (TEOS), methyltriethoxysilane (MTES), and methoxysilane oligomer (MTSO) under acid catalyzed hydrolysis. The blue, green, and red luminescence were observed from these thin films (thickness: 100 - 400 nm), respectively. Fluorescence spectra, fluorescent quantum yield and lifetime of thin gel films are examined. Fluorescent peaks for most of dyes and pigments used in gel films were similar to those in solution, and fluorescent lifetime for dyes and pigments used in gel films were 2.9 - 4.5 ns. Photostability of fluorescent gel films is dependent on fluorescent organic dyes and pigments used and/or silicate gel matrixes. Coumarin and perylene pigments have higher fluorescent quantum yield in gel film prepared from MTSO. The large Stokes shift was observed in fluorescent gel film using coumarin and benzoxazolium dyes. The coumarin and perylene pigments are significantly photo- stable in gel film prepared from MTSO, and photodegradation of perylene red after irradiation of 500 W Xi-lamp for 30 min is below 20%.

  7. Binding energy and work function of organic electrode materials phenanthraquinone, pyromellitic dianhydride and their derivatives adsorbed on graphene.

    PubMed

    Yu, Yang-Xin

    2014-09-24

    Electroactive organic compounds are a novel group of green cathode materials for rechargeable metal-ion batteries. However, the organic battery life is short because the organic compounds can be dissolved by nonaqueous electrolytes. Here a comparative investigation of phenanthraquinone (PQ), pyromellitic dianhydride (PMDA) and their derivatives, i.e., benzo[1,2-b:4,3-b']difuran-4,5-dione (BDFD), benzo[1,2-b:4,3-b']dithiophene-4,5-quinone (BDTQ), 3,8-phenanthroline-5,6-dione (PAD), pyromellitic dithioanhydride (PMDT), pyromellitic diimide (PMDI) and 1,4,5,8-anthracenetetrone (ATO), adsorbed on graphene is performed using a density functional theory (DFT) with a van der Waals (vdW) dispersion-correction. The computed results show a strong physisorption with the binding energies between 1.10 and 1.56 eV. A sequence of the calculated binding energies from weak to strong is found to be BDFD < BDTQ < PMDA ≤ PMDI < PMDT < PQ < PAD < ATO. The formation of stable organic molecule-graphene nanocomposites can prevent the dissolution of the eight organic compounds in nonaqueous electrolyte and hence improve cycling performance of batteries. In addition, the work functions for the nanocomposites are found to be strongly affected by the work function of each organic compound. To understand the DFT results, a novel simple expression is proposed to predict the work function of the nanocomposites from the interfacial dipole and the work functions of the isolated graphene nanosheet and organic molecules. The predicted work functions for the nanocomposites from the new equation agree quite well with the values calculated from the vdW dispersion-corrected DFT. PMID:25216389

  8. Prediction of capacity factors for aqueous organic solutes adsorbed on a porous acrylic resin

    USGS Publications Warehouse

    Thurman, E.M.

    1978-01-01

    The capacity factors of 20 aromatic, allphatic, and allcycllc organic solutes with carboxyl, hydroxyl, amine, and methyl functional groups were determined on Amberlite XAD-8, a porous acrylic resin. The logarithm of the capacity factor, k???, correlated inversely with the logarithm of the aqueous molar solubility with significance of less than 0.001. The log k???-log solubility relationship may be used to predict the capacity of any organic solute for XAD-8 using only the solubility of the solute. The prediction is useful as a guide for determining the proper ratio of sample to column size In the preconcentration of organic solutes from water. The inverse relationship of solubility and capacity is due to the unfavorable entropy of solution of organic solutes which affects both solubility and sorption.

  9. Porous Organic Cage Thin Films and Molecular-Sieving Membranes.

    PubMed

    Song, Qilei; Jiang, Shan; Hasell, Tom; Liu, Ming; Sun, Shijing; Cheetham, Anthony K; Sivaniah, Easan; Cooper, Andrew I

    2016-04-01

    Porous organic cage molecules are fabricated into thin films and molecular-sieving membranes. Cage molecules are solution cast on various substrates to form amorphous thin films, with the structures tuned by tailoring the cage chemistry and processing conditions. For the first time, uniform and pinhole-free microporous cage thin films are formed and demonstrated as molecular-sieving membranes for selective gas separation. PMID:26800019

  10. Growth and physical properties of molecular organic thin films

    NASA Astrophysics Data System (ADS)

    Fraxedas, J.

    2004-04-01

    Highly-oriented polycrystalline thin films of molecular organic materials consisting of small molecules can be easily obtained by physical and chemical vapour deposition methods. The crystallographic phase, orientation and morphology of the films critically depend on the interface and on the kinetics of growth and can be controlled, to a certain extent, by a judicious selection of the substrates and of the growth parameters. This article shortly explores the formation of organic-inorganic heterostructures as a function of coverage: from the most fundamental case, a single molecule on a surface, to thick films (thickness ˜ 1 μ m). The case of high-quality thick TTF-TCNQ films exemplifies the fact that the derived physical properties are essentially identical to those obtained from single crystals. Key words. Molecular organic materials thin films interfaces.

  11. Understanding Organic Film Behavior on Alloy and Metal Oxides

    PubMed Central

    Raman, Aparna; Quiñones, Rosalynn; Barriger, Lisa; Eastman, Rachel; Parsi, Arash

    2010-01-01

    Native oxide surfaces of stainless steel 316L and Nitinol alloys and their constituent metal oxides namely, nickel, chromium, molybdenum, manganese, iron and titanium were modified with long chain organic acids to better understand organic film formation. The adhesion and stability of films of octadecylphosphonic acid, octadecylhydroxamic acid, octadecylcarboxylic acid and octadecylsulfonic acid on these substrates was examined in this study. The films formed on these surfaces were analyzed by diffuse reflectance infrared Fourier transform spectroscopy, contact angle goniometry, atomic force microscopy and matrix assisted laser desorption ionization mass spectrometry. The effect of the acidity of the organic moiety and substrate composition on the film characteristics and stability is discussed. Interestingly, on the alloy surfaces, the presence of less reactive metal sites does not inhibit film formation. PMID:20039608

  12. Understanding organic film behavior on alloy and metal oxides.

    PubMed

    Raman, Aparna; Quiñones, Rosalynn; Barriger, Lisa; Eastman, Rachel; Parsi, Arash; Gawalt, Ellen S

    2010-02-01

    Native oxide surfaces of stainless steel 316L and Nitinol alloys and their constituent metal oxides, namely nickel, chromium, molybdenum, manganese, iron, and titanium, were modified with long chain organic acids to better understand organic film formation. The adhesion and stability of films of octadecylphosphonic acid, octadecylhydroxamic acid, octadecylcarboxylic acid, and octadecylsulfonic acid on these substrates were examined in this study. The films formed on these surfaces were analyzed by diffuse reflectance infrared Fourier transform spectroscopy, contact angle goniometry, atomic force microscopy, and matrix-assisted laser desorption ionization mass spectrometry. The effect of the acidity of the organic moiety and substrate composition on the film characteristics and stability is discussed. Interestingly, on the alloy surfaces, the presence of less reactive metal sites does not inhibit film formation. PMID:20039608

  13. Organic conductive films for semiconductor electrodes

    DOEpatents

    Frank, A.J.

    1984-01-01

    According to the present invention, improved electrodes overcoated with conductive polymer films and preselected catalysts are provided. The electrodes typically comprise an inorganic semiconductor over-coated with a charge conductive polymer film comprising a charge conductive polymer in or on which is a catalyst or charge-relaying agent.

  14. Organic conductive films for semiconductor electrodes

    DOEpatents

    Frank, Arthur J.

    1984-01-01

    According to the present invention, improved electrodes overcoated with conductive polymer films and preselected catalysts are provided. The electrodes typically comprise an inorganic semiconductor overcoated with a charge conductive polymer film comprising a charge conductive polymer in or on which is a catalyst or charge-relaying agent.

  15. Uptake of organic trace gases by organic films

    NASA Astrophysics Data System (ADS)

    Donaldson, D. James

    2004-03-01

    Surfaces exposed to the atmosphere, particularly in urban environments, become coated with a film whose chemical composition is similar to that of urban aerosol particles. Such films can act as reservoirs for gas phase pollutants and as media for chemical reactions (much as aerosols do). We have constructed a Knudsen effusion cell apparatus to study the non-reactive and reactive uptake of trace atmospheric gases by such urban films. We report here our first results of the uptake of three classes of compound: polycyclic aromatic hydrocarbons (PAHs), chlorinated aromatics and carboxylic acids, by films composed of fatty acids and high molecular weight hydrocarbons.

  16. AMBIENT LEVEL VOLATILE ORGANIC COMPOUND (VOC) MONITORING USING SOLID ADSORBANTS - RECENT U.S. EPA STUDIES

    EPA Science Inventory

    Ambient air spiked with 1-10 ppbv concentrations of 41 toxic volatile organic compounds (VOCs) listed in U.S. Environmental Protection Agency (EPA) Compendium Method TO-14A was monitored using solid sorbents for sample collection and a Varian Saturn 2000 ion trap mass spectrome...

  17. Composition of Organic Compounds Adsorbed on PM10 in the Air Above Maribor.

    PubMed

    Miuc, Alen; Vončina, Ernest; Lečnik, Uroš

    2015-01-01

    Organic compounds in atmospheric particulate matterabove Maribor were analysed in 120 samples of PM10 sampled according to the EN 12341:2014 reference method. Organic compounds compositions were investigated together with the primary and secondary sources of air pollution. Silylation as derivatisation method was used for the GC/MS determination of volatile and semi-volatile polar organic compounds. Distribution of fatty acids, n-alkanes and iso-alkanes, phthalate esters, siloxanes, different sterols, various sugars and sugar alcohols, compounds of lignin and resin acids, dicarboxylic acids from photochemical reactions, PAHs, organic nitrogen compounds and products from secondary oxidation of monoterpenes were determined. The use of silicone grease for the purpose of lubricating the impact surface of the air sampler caused higher values of gravimetric determination. Solid particles may have been bounced from the surface of a greasy impact plate and re-entrained within the air stream and then collected on a sample filter. The carryover of siloxanes was at least from 5% up to 15% of the accumulated particles weight, depending on ambient temperature. This was the reason that the gravimetric results for determination of PM10 according to the standard EN 12341:2014 were overestimated. PMID:26680711

  18. Design of hydrophilic metal organic framework water adsorbents for heat reallocation.

    PubMed

    Cadiau, Amandine; Lee, Ji Sun; Damasceno Borges, Daiane; Fabry, Paul; Devic, Thomas; Wharmby, Michael T; Martineau, Charlotte; Foucher, Damien; Taulelle, Francis; Jun, Chul-Ho; Hwang, Young Kyu; Stock, Norbert; De Lange, Martijn F; Kapteijn, Freek; Gascon, Jorge; Maurin, Guillaume; Chang, Jong-San; Serre, Christian

    2015-08-26

    A new hydrothermally stable Al polycarboxylate metal-organic framework (MOF) based on a heteroatom bio-derived aromatic spacer is designed through a template-free green synthesis process. It appears that in some test conditions this MOF outperforms the heat reallocation performances of commercial SAPO-34. PMID:26193346

  19. Fluorous Metal Organic Frameworks as Superhydrophobic Adsorbents for Oil Spill Cleanup and Hydrocarbons Storage

    SciTech Connect

    Yang, Chi; Mather, Qian; Wang, Xiaoping; Kaipa, Ushasree; Nesterov, Vladimir; Venero, Augustin; Omary, Mohammad A

    2011-01-01

    We demonstrate that fluorous metal-organic frameworks (FMOFs) are highly hydrophobic porous materials with a high capacity and affinity to C{sub 6}-C{sub 8} hydrocarbons of oil components. FMOF-1 exhibits reversible adsorption with a high capacity for n-hexane, cyclohexane, benzene, toluene, and p-xylene, with no detectable water adsorption even at near 100% relative humidity, drastically outperforming activated carbon and zeolite porous materials. FMOF-2, obtained from annealing FMOF-1, shows enlarged cages and channels with double toluene adsorption vs FMOF-1 based on crystal structures. The results suggest great promise for FMOFs in applications such as removal of organic pollutants from oil spills or ambient humid air, hydrocarbon storage and transportation, water purification, etc. under practical working conditions.

  20. Reduction of ferrihydrite with adsorbed and coprecipitated organic matter: microbial reduction by Geobacter bremensis vs. abiotic reduction by Na-dithionite

    NASA Astrophysics Data System (ADS)

    Eusterhues, K.; Hädrich, A.; Neidhardt, J.; Küsel, K.; Keller, T. F.; Jandt, K. D.; Totsche, K. U.

    2014-09-01

    Ferrihydrite is a widespread poorly crystalline Fe oxide which becomes easily coated by natural organic matter in the environment. This mineral-bound organic matter entirely changes the mineral surface properties and therefore the reactivity of the original mineral. Here, we investigated 2-line ferrihydrite, ferrihydrite with adsorbed organic matter, and ferrihydrite coprecipitated with organic matter for microbial and abiotic reduction of Fe(III). Ferrihydrite-organic matter associations with different organic matter loadings were reduced either by Geobacter bremensis or abiotically by Na-dithionite. Both types of experiments showed decreasing initial Fe-reduction rates and decreasing degrees of reduction with increasing amounts of mineral-bound organic matter. At similar organic matter loadings, coprecipitated ferrihydrites were more reactive than ferrihydrites with adsorbed organic matter. The difference can be explained by the smaller crystal size and poor crystallinity of such coprecipitates. At small organic matter loadings the poor crystallinity of coprecipitates led to even faster Fe-reduction rates than found for pure ferrihydrite. The amount of mineral-bound organic matter also affected the formation of secondary minerals: goethite was only found after reduction of organic matter-free ferrihydrite and siderite was only detected when ferrihydrites with relatively low amounts of mineral-bound organic matter were reduced. We conclude that direct contact of G. bremensis to the Fe oxide mineral surface was inhibited by attached organic matter. Consequently, mineral-bound organic matter shall be taken into account as a factor in slowing down reductive dissolution.

  1. Recycling of Organic Waste Sludge by Hydrothermal Dry Steam Aiming for Adsorbent

    NASA Astrophysics Data System (ADS)

    Hoshikawa, Hisahiro; Hayakawa, Tomoki; Yamasaki, Nakamichi

    2006-05-01

    Global warming becomes more serious problem today. We have to develop new technology for new energy or fixation of carbon dioxide. Biomass is considered to be one of new energies. Methane fermentation is a method to make methane from biomass, such as garbage and fecal of farm animals, by methane fermentation bacteria. It has a problem, however, that bacteria are deactivated due to ammonia, which is made by itself. And much methane fermentation residue is incinerated. Therefore recycling methane fermentation residue is important for effective use of biomass. We research hydrothermal process. Dry steam means unsaturated vapor, we call. It demands a temperature less than 400 °C. And it is expected to accelerate dehydration effect, decompose and extract the organic matter, and make porous material. Thus, we try to apply the dry steam to recycling of organic waste sludge aiming for absorbent. Experiments were conducted at 250-350 °C in nitrogen atmosphere. The carbon products are analyzed by CHNS elemental analysis, and Thermogravimetry. The extractives are analyzed by gas chromatograph.

  2. Femtomagnetism in graphene induced by core level excitation of organic adsorbates.

    PubMed

    Ravikumar, Abhilash; Baby, Anu; Lin, He; Brivio, Gian Paolo; Fratesi, Guido

    2016-01-01

    We predict the induction or suppression of magnetism in the valence shell of physisorbed and chemisorbed organic molecules on graphene occurring on the femtosecond time scale as a result of core level excitations. For physisorbed molecules, where the interaction with graphene is dominated by van der Waals forces and the system is non-magnetic in the ground state, numerical simulations based on density functional theory show that the valence electrons relax towards a spin polarized configuration upon excitation of a core-level electron. The magnetism depends on efficient electron transfer from graphene on the femtosecond time scale. On the other hand, when graphene is covalently functionalized, the system is magnetic in the ground state showing two spin dependent mid gap states localized around the adsorption site. At variance with the physisorbed case upon core-level excitation, the LUMO of the molecule and the mid gap states of graphene hybridize and the relaxed valence shell is not magnetic anymore. PMID:27089847

  3. Femtomagnetism in graphene induced by core level excitation of organic adsorbates

    PubMed Central

    Ravikumar, Abhilash; Baby, Anu; Lin, He; Brivio, Gian Paolo; Fratesi, Guido

    2016-01-01

    We predict the induction or suppression of magnetism in the valence shell of physisorbed and chemisorbed organic molecules on graphene occurring on the femtosecond time scale as a result of core level excitations. For physisorbed molecules, where the interaction with graphene is dominated by van der Waals forces and the system is non-magnetic in the ground state, numerical simulations based on density functional theory show that the valence electrons relax towards a spin polarized configuration upon excitation of a core-level electron. The magnetism depends on efficient electron transfer from graphene on the femtosecond time scale. On the other hand, when graphene is covalently functionalized, the system is magnetic in the ground state showing two spin dependent mid gap states localized around the adsorption site. At variance with the physisorbed case upon core-level excitation, the LUMO of the molecule and the mid gap states of graphene hybridize and the relaxed valence shell is not magnetic anymore. PMID:27089847

  4. Mechanisms of Heat Transfer in Porous Crystals Containing Adsorbed Gases: Applications to Metal-Organic Frameworks

    NASA Astrophysics Data System (ADS)

    Babaei, Hasan; Wilmer, Christopher E.

    2016-01-01

    We have studied the mechanisms of heat transfer in a porous crystal-gas mixture system, motivated by the not insignificant challenge of quickly dissipating heat generated in metal-organic frameworks (MOFs) due to gas adsorption. Our study reveals that the thermal conductance of the system (crystal and gas) is dominated by lattice thermal conductivity in the crystal, and that conductance is reduced as the concentration of gas in the pores increases. This mechanism was observed from classical molecular simulations of a monatomic gas in an idealized porous crystal structure. We show that the decreased conductivity associated with increased gas concentration is due to phonon scattering in the crystal due to interactions with gas molecules. Calculations of scattering rates for two phonon modes reveal that scattering of the lowest frequency mode scales linearly with gas density. This result suggests that the probability of a phonon-gas collision is simply proportional to the number of gas molecules in the pore.

  5. A Water-Stable Cationic Metal-Organic Framework as a Dual Adsorbent of Oxoanion Pollutants.

    PubMed

    Desai, Aamod V; Manna, Biplab; Karmakar, Avishek; Sahu, Amit; Ghosh, Sujit K

    2016-06-27

    A three-dimensional water-stable cationic metal-organic framework (MOF) pillared by a neutral ligand and with Ni(II)  metal nodes has been synthesized employing a rational design approach. Owing to the ordered arrangement of the uncoordinated tetrahedral sulfate (SO4 (2-) ) ions in the channels, the compound has been employed for aqueous-phase ion-exchange applications. The compound exhibits rapid and colorimetric aqueous-phase capture of environmentally toxic oxoanions (with similar geometries) in a selective manner. This system is the first example of a MOF-based system which absorbs both dichromate (Cr2 O7 (2-) ) and permanganate (MnO4 (-) ) ions, with the latter acting as a model for the radioactive contaminant pertechnetate (TcO4 (-) ). PMID:26855323

  6. Femtomagnetism in graphene induced by core level excitation of organic adsorbates

    NASA Astrophysics Data System (ADS)

    Ravikumar, Abhilash; Baby, Anu; Lin, He; Brivio, Gian Paolo; Fratesi, Guido

    2016-04-01

    We predict the induction or suppression of magnetism in the valence shell of physisorbed and chemisorbed organic molecules on graphene occurring on the femtosecond time scale as a result of core level excitations. For physisorbed molecules, where the interaction with graphene is dominated by van der Waals forces and the system is non-magnetic in the ground state, numerical simulations based on density functional theory show that the valence electrons relax towards a spin polarized configuration upon excitation of a core-level electron. The magnetism depends on efficient electron transfer from graphene on the femtosecond time scale. On the other hand, when graphene is covalently functionalized, the system is magnetic in the ground state showing two spin dependent mid gap states localized around the adsorption site. At variance with the physisorbed case upon core-level excitation, the LUMO of the molecule and the mid gap states of graphene hybridize and the relaxed valence shell is not magnetic anymore.

  7. In situ x-ray photoelectron spectroscopic and density-functional studies of Si atoms adsorbed on a C60 film.

    PubMed

    Onoe, Jun; Nakao, Aiko; Hara, Toshiki

    2004-12-01

    The interaction between C(60) and Si atoms has been investigated for Si atoms adsorbed on a C(60) film using in situ x-ray photoelectron spectroscopy (XPS) and density-functional (DFT) calculations. Analysis of the Si 2p core peak identified three kinds of Si atoms adsorbed on the film: silicon suboxides (SiO(x)), bulk Si crystal, and silicon atoms bound to C(60). Based on the atomic percent ratio of silicon to carbon, we estimated that there was approximately one Si atom bound to each C(60) molecule. The Si 2p peak due to the Si-C(60) interaction demonstrated that a charge transfer from the Si atom to the C(60) molecule takes place at room temperature, which is much lower than the temperature of 670 K at which the charge transfer was observed for C(60) adsorbed on Si(001) and (111) clean surfaces [Sakamoto et al., Phys. Rev. B 60, 2579 (1999)]. The number of electrons transferred between the C(60) molecule and Si atom was estimated to be 0.59 based on XPS results, which is in good agreement with the DFT result of 0.63 for a C(60)Si with C(2v) symmetry used as a model cluster. Furthermore, the shift in binding energy of both the Si 2p and C 1s core peaks before and after Si-atom deposition was experimentally obtained to be +2.0 and -0.4 eV, respectively. The C(60)Si model cluster provides the shift of +2.13 eV for the Si 2p core peak and of -0.28 eV for the C 1s core peak, which are well corresponding to those experimental results. The covalency of the Si-C(60) interaction was also discussed in terms of Mulliken overlap population between them. PMID:15634092

  8. Effective anchoring energy in dipolar organic film on metals surfaces

    NASA Astrophysics Data System (ADS)

    Iwamoto, Mitsumasa; Zakharov, A. V.

    2007-04-01

    The influence of electron injection from the metal electrode into organic liquid crystal dipolar film on the effective anchoring energy (EAE) of the polar organic film is discussed from the energy point of view. It is shown that the accounting for the injected carrier in organic film results in a polynomial function for the EAE expanded up to the fourth order in cos θs, where θs is the polar angle of the director nˆ at the film/metal interface. It is also shown that in a certain range of the location of centroid of the injected carrier z¯ the destabilizing surface polarization mechanism may lead to destruction of the linear anchoring strength coefficient w1. The strong influence of z¯ on the quadratic term w2 also has been demonstrated.

  9. Aluminium fumarate metal-organic framework: A super adsorbent for fluoride from water.

    PubMed

    Karmakar, Sankha; Dechnik, Janina; Janiak, Christoph; De, Sirshendu

    2016-02-13

    Potential of aluminium fumarate metal organic framework (MOF) for fluoride removal from groundwater has been explored in this work. The laboratory produced MOF exhibited characteristics similar to the commercial version. MOF was found to be micro-porous with surface area of 1156 m(2)/g and average pore size 17Å. Scanning electron micrograph of the AlFu MOF showed minute pores and texture was completely different from either of the parent materials. Change in the composition of AlFu MOF after fluoride adsorption was evident from powder X-ray diffraction analysis. Thermal stability of the AlFu MOF up to 700K was established by thermo-gravimetric analysis. Incorporation of fluoride phase after adsorption was confirmed by X-ray fluorescence analysis. As observed from FTIR study, hydroxyl ions in AlFu MOF were substituted by fluoride. 0.75 g/l AlFu MOF was good enough for complete removal of 30 mg/l fluoride concentration in feed solution. The maximum adsorption capacity for fluoride was 600, 550, 504 and 431 mg/g, respectively, at 293, 303, 313 and 333K. PMID:26513559

  10. Adsorbent phosphates

    NASA Technical Reports Server (NTRS)

    Watanabe, S.

    1983-01-01

    An adsorbent which uses as its primary ingredient phosphoric acid salts of zirconium or titanium is presented. Production methods are discussed and several examples are detailed. Measurements of separating characteristics of some gases using the salts are given.

  11. Preparation of a new adsorbent from activated carbon and carbon nanofiber (AC/CNF) for manufacturing organic-vacbpour respirator cartridge

    PubMed Central

    2013-01-01

    In this study a composite of activated carbon and carbon nanofiber (AC/CNF) was prepared to improve the performance of activated carbon (AC) for adsorption of volatile organic compounds (VOCs) and its utilization for respirator cartridges. Activated carbon was impregnated with a nickel nitrate catalyst precursor and carbon nanofibers (CNF) were deposited directly on the AC surface using catalytic chemical vapor deposition. Deposited CNFs on catalyst particles in AC micropores, were activated by CO2 to recover the surface area and micropores. Surface and textural characterizations of the prepared composites were investigated using Brunauer, Emmett and Teller’s (BET) technique and electron microscopy respectively. Prepared composite adsorbent was tested for benzene, toluene and xylene (BTX) adsorption and then employed in an organic respirator cartridge in granular form. Adsorption studies were conducted by passing air samples through the adsorbents in a glass column at an adjustable flow rate. Finally, any adsorbed species not retained by the adsorbents in the column were trapped in a charcoal sorbent tube and analyzed by gas chromatography. CNFs with a very thin diameter of about 10-20 nm were formed uniformly on the AC/CNF. The breakthrough time for cartridges prepared with CO2 activated AC/CNF was 117 minutes which are significantly longer than for those cartridges prepared with walnut shell- based activated carbon with the same weight of adsorbents. This study showed that a granular form CO2 activated AC/CNF composite could be a very effective alternate adsorbent for respirator cartridges due to its larger adsorption capacities and lower weight. PMID:23369424

  12. Preparation and characterization of humic acid-carbon hybrid materials as adsorbents for organic micro-pollutants.

    PubMed

    Radwan, Emad K; Abdel Ghafar, Hany H; Moursy, Ahmed S; Langford, Cooper H; Bedair, Ahmed H; Achari, Gopal

    2015-08-01

    The present work involves the preparation of novel adsorbent materials by the insolubilization and hybridization of humic acid (HA) with carbon. The prepared materials were characterized by N2 adsorption, elemental analysis, Fourier transform infrared spectroscopy, scanning electron microscopy, transmission electron microscopy, solid-state (13)C cross polarization magic angle spinning nuclear magnetic resonance, and low-field nuclear magnetic resonance (NMR) relaxometry on wetted samples. The water solubility of these materials and the lack of effect of oxidants were also confirmed. With this background, the adsorption capacities toward phenol, 2,4,6-tricholrophenol, and atrazine were evaluated, using these as model compounds for organic micropollutants of concern in water. Experimental results show that the prepared materials are mesoporous and have a higher surface area than humic acid and even than the porous carbon in the case of carbon coating. They retain the basic features of the starting materials with lowered functional group content. Moreover, there are interesting new features. NMR relaxometry shows that equilibration of water uptake is very fast, making use in water simple. They have higher adsorption capacities than the pure materials, and they can be applied under a wide range of environmental conditions. PMID:25874433

  13. EFFECTS OF COVAPORS ON ADSORPTION RATE COEFFICIENTS OF ORGANIC VAPORS ADSORBED ONTO ACTIVATED CARBON FROM FLOWING AIR

    SciTech Connect

    G. WOOD

    2000-12-01

    Published breakthrough time, adsorption rate, and capacity data for components of organic vapor mixtures adsorbed from flows through fixed activated carbon beds have been analyzed. Capacities (as stoichiometric centers of constant pattern breakthrough curves) yielded stoichiometric times {tau}, which are useful for determining elution orders of mixture components. We also calculated adsorption rate coefficients k{sub v} of the Wheeler (or, more general Reaction Kinetic) breakthrough curve equation, when not reported, from breakthrough times and {tau}. Ninety-five k{sub v} (in mixture)/ k{sub v} (single vapor) ratios at similar vapor concentrations were calculated and averaged for elution order categories. For 43 first-eluting vapors the average ratio (1.07) was statistically no different (0.21 standard deviation) than unity, so that we recommend using the single-vapor k{sub v} for such. Forty-seven second-eluting vapor ratios averaged 0.85 (0.24 standard deviation), also not significantly different from unity; however, other evidence and considerations lead us recommend using k{sub v} (in mixture) = 0.85 k{sub v} (single vapor). Five third- and fourth-eluting vapors gave an average of 0.56 (0.16 standard deviation) for a recommended k{sub v} (in mixture) = 0.56 k{sub v} (single vapor) for such.

  14. Use of industrial by-products and natural media to adsorb nutrients, metals and organic carbon from drinking water.

    PubMed

    Grace, Maebh A; Healy, Mark G; Clifford, Eoghan

    2015-06-15

    Filtration technology is well established in the water sector but is limited by inability to remove targeted contaminants, found in surface and groundwater, which can be damaging to human health. This study optimises the design of filters by examining the efficacy of seven media (fly ash, bottom ash, Bayer residue, granular blast furnace slag (GBS), pyritic fill, granular activated carbon (GAC) and zeolite), to adsorb nitrate, ammonium, total organic carbon (TOC), aluminium, copper (Cu) and phosphorus. Each medium and contaminant was modelled to a Langmuir, Freundlich or Temkin adsorption isotherm, and the impact of pH and temperature (ranging from 10 °C to 29 °C) on their performance was quantified. As retention time within water filters is important in contaminant removal, kinetic studies were carried out to observe the adsorption behaviour over a 24h period. Fly ash and Bayer residue had good TOC, nutrient and Cu adsorption capacity. Granular blast furnace slag and pyritic fill, previously un-investigated in water treatment, showed adsorption potential for all contaminants. In general, pH or temperature adjustment was not necessary to achieve effective adsorption. Kinetic studies showed that at least 60% of adsorption had occurred after 8h for all media. These media show potential for use in a multifunctional water treatment unit for the targeted treatment of specific contaminants. PMID:25777954

  15. Organic thin film transistors: from active materials to novel applications

    NASA Astrophysics Data System (ADS)

    Torsi, L.; Cioffi, N.; Di Franco, C.; Sabbatini, L.; Zambonin, P. G.; Bleve-Zacheo, T.

    2001-08-01

    In this paper, a bird's eye view of most of the organic materials employed as n-channel and p-channel transistor active layers is given along with the relevant device performances; organic thin film transistors (OTFT) operation regimes are discussed and an interesting perspective application of OTFT as multi-parameter gas sensor is proposed.

  16. Reversible CO Scavenging via Adsorbate-Dependent Spin State Transitions in an Iron(II)-Triazolate Metal-Organic Framework.

    PubMed

    Reed, Douglas A; Xiao, Dianne J; Gonzalez, Miguel I; Darago, Lucy E; Herm, Zoey R; Grandjean, Fernande; Long, Jeffrey R

    2016-05-01

    A new metal-organic framework, Fe-BTTri (Fe3[(Fe4Cl)3(BTTri)8]2·18CH3OH, H3BTTri =1,3,5-tris(1H-1,2,3-triazol-5-yl)benzene)), is found to be highly selective in the adsorption of CO over a variety of other gas molecules, making it extremely effective, for example, in the removal of trace CO from mixtures with H2, N2, and CH4. This framework not only displays significant CO adsorption capacity at very low pressures (1.45 mmol/g at just 100 μbar), but, importantly, also exhibits readily reversible CO binding. Fe-BTTri utilizes a unique spin state change mechanism to bind CO in which the coordinatively unsaturated, high-spin Fe(II) centers of the framework convert to octahedral, low-spin Fe(II) centers upon CO coordination. Desorption of CO converts the Fe(II) sites back to a high-spin ground state, enabling the facile regeneration and recyclability of the material. This spin state change is supported by characterization via infrared spectroscopy, single crystal X-ray analysis, Mössbauer spectroscopy, and magnetic susceptibility measurements. Importantly, the spin state change is selective for CO and is not observed in the presence of other gases, such as H2, N2, CO2, CH4, or other hydrocarbons, resulting in unprecedentedly high selectivities for CO adsorption for use in CO/H2, CO/N2, and CO/CH4 separations and in preferential CO adsorption over typical strongly adsorbing gases like CO2 and ethylene. While adsorbate-induced spin state transitions are well-known in molecular chemistry, particularly for CO, to our knowledge this is the first time such behavior has been observed in a porous material suitable for use in a gas separation process. Potentially, this effect can be extended to selective separations involving other π-acids. PMID:27097297

  17. Mechanism of formation of humus coatings on mineral surfaces 3. Composition of adsorbed organic acids from compost leachate on alumina by solid-state 13C NMR

    USGS Publications Warehouse

    Wershaw, R. L.; Llaguno, E.C.; Leenheer, J.A.

    1996-01-01

    The adsorption of compost leachate DOC on alumina is used as a model for elucidation of the mechanism of formation of natural organic coatings on hydrous metal oxide surfaces in soils and sediments. Compost leachate DOC is composed mainly of organic acid molecules. The solid-state 13C NMR spectra of these organic acids indicate that they are very similar in composition to aquatic humic substances. Changes in the solid-state 13C NMR spectra of compost leachate DOC fractions adsorbed on alumina indicate that the DOC molecules are most likely adsorbed on metal oxide surfaces through a combination of polar and hydrophobic interaction mechanisms. This combination of polar and hydrophobic mechanism leads to the formation of bilayer coatings of the leachate molecules on the oxide surfaces.

  18. The effects of framework dynamics on the behavior of water adsorbed in the [Zn(l-L)(Cl)] and Co-MOF-74 metal-organic frameworks.

    PubMed

    Terranova, Zachary L; Paesani, Francesco

    2016-03-21

    The effects of framework flexibility on the structural and dynamical properties of water adsorbed in two prototypical metal-organic frameworks are investigated through molecular dynamics simulations. It is found that water molecules in the pores of a flexible model of [Zn(l-L)(Cl)] exhibit slower dynamics than when the framework is artificially held rigid in the simulations. In contrast, the water dynamics in Co-MOF-74 is predicted to be accelerated by the framework vibrations. The origin of this different behavior directly relates to how water interacts with the two frameworks, which, in turn, determines different hydrogen-bond patterns in the pores. While the first water molecules adsorbed in [Zn(l-L)(Cl)] donate a single hydrogen bond to the Zn-Cl groups and point the other hydrogen atom towards the center of the pore, water molecules adsorbed in Co-MOF-74 initially bind to the cobalt atoms of the framework via their oxygen atoms, thus leaving each molecule free to form two hydrogen bonds with additional molecules adsorbed at higher loading. The simulation results indicate that taking into account the framework flexibility in computer simulations is necessary for a quantitative modeling of adsorption and transport processes in metal-organic frameworks. PMID:26928975

  19. High Performance Airbrushed Organic Thin Film Transistors

    SciTech Connect

    Chan, C.; Richter, L; Dinardo, B; Jaye, C; Conrad, B; Ro, H; Germack, D; Fischer, D; DeLongchamp, D; Gunlach, D

    2010-01-01

    Spray-deposited poly-3-hexylthiophene (P3HT) transistors were characterized using electrical and structural methods. Thin-film transistors with octyltrichlorosilane treated gate dielectrics and spray-deposited P3HT active layers exhibited a saturation regime mobility as high as 0.1 cm{sup 2} V{sup -1} s{sup -1}, which is comparable to the best mobilities observed in high molecular mass P3HT transistors prepared using other methods. Optical and atomic force microscopy showed the presence of individual droplets with an average diameter of 20 {micro}m and appreciable large-scale film inhomogeneities. Despite these inhomogeneities, near-edge x-ray absorption fine structure spectroscopy of the device-relevant channel interface indicated excellent orientation of the P3HT.

  20. Growth and nonlinear optical characterization of organic single crystal films

    NASA Astrophysics Data System (ADS)

    Zhou, Ligui

    1997-12-01

    Organic single crystal films are important for various future applications in photonics and integrated optics. The conventional method for inorganic crystal growth is not suitable for organic materials, and the high temperature melting method is not good for most organic materials due to decomposition problems. We developed a new method-modified shear method-to grow large area organic single crystal thin films which have exceptional nonlinear optical properties and high quality surfaces. Several organic materials (NPP, PNP and DAST) were synthesized and purified before the thin film crystal growth. Organic single crystal thin films were grown from saturated organic solutions using modified shear method. The area of single crystal films were about 1.5 cm2 for PNP, 1 cm2 for NPP and 5 mm2 for DAST. The thickness of the thin films which could be controlled by the applied pressure ranged from 1μm to 10 μm. The single crystal thin films of organic materials were characterized by polarized microscopy, x-ray diffraction, polarized UV-Visible and polarized micro-FTIR spectroscopy. Polarized microscopy showed uniform birefringence and complete extinction with the rotation of the single crystal thin films under crossed- polarization, which indicated high quality single crystals with no scattering. The surface orientation of single crystal thin films was characterized by x-ray diffraction. The molecular orientation within the crystal was further studied by the polarized UV-Visible and Polarized micro-FTIR techniques combined with the x-ray and polarized microscopy results. A Nd:YAG laser with 35 picosecond pulses at 1064nm wavelength was employed to perform the nonlinear optical characterization of the organic single crystal thin films. Two measurement techniques were used to study the crystal films: second harmonic generation (SHG) and electro-optic (EO) effect. SHG results showed that the nonlinear optical coefficient of NPP was 18 times that of LiNbO3, a standard

  1. Electrical and Optical Properties of Organic Thin Films

    NASA Astrophysics Data System (ADS)

    Buckner, Spencer Lewis

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

  2. New diffusive gradients in a thin film technique for measuring inorganic arsenic and selenium(IV) using a titanium dioxide based adsorbent.

    PubMed

    Bennett, William W; Teasdale, Peter R; Panther, Jared G; Welsh, David T; Jolley, Dianne F

    2010-09-01

    A new diffusive gradients in a thin film (DGT) technique, using a titanium dioxide based adsorbent (Metsorb), has been developed and evaluated for the determination of dissolved inorganic arsenic and selenium. As(III), As(V), and Se(IV) were found to be quantitatively accumulated by the adsorbent (uptake efficiencies of 96.5-100%) and eluted in 1 M NaOH (elution efficiencies of 81.2%, 75.2%, and 88.7%). Se(VI) was not quantitatively accumulated by the adsorbent (<20%). Laboratory DGT validation experiments gave linear mass uptake over time (R(2) >or= 0.998) for As(III), As(V), and Se(IV). Consistent uptake occurred over pH (3.5-8.5) and ionic strength (0.0001-0.75 mol L(-1) NaNO(3)) ranges typical of natural waters, including seawater. Field deployments of DGT probes with various diffusive layer thicknesses confirmed the use of the technique in situ, allowing calculation of the diffusive boundary layers and an accurate measurement of inorganic arsenic. Reproducibility of the technique in field deployments was good (relative standard deviation <8%). Limits of detection (4 day deployments) were 0.01 microg L(-1) for inorganic arsenic and 0.05 microg L(-1) for Se(IV). The results of this study confirmed that DGT with Metsorb was a reliable and robust method for the measurement of inorganic arsenic and the selective measurement of Se(IV) within useful limits of accuracy. PMID:20695441

  3. Evaluation and Application of a Solid Adsorbent Method for Monitoring Exposure to Volatile Organic Compounds from Oil and Gas Operations.

    NASA Astrophysics Data System (ADS)

    Smith, K. R.; Helmig, D.; Thompson, C. R.; Wang, W.; Terrell, R. M.; Lewis, A. C.

    2014-12-01

    Residential communities are being increasingly impacted by emissions from oil and gas development and this has driven the need for simple, effective, and low-cost methods for air quality monitoring. Primary emissions from oil and gas production consist of volatile organic compounds (VOCs) ranging from the short chain alkanes and alkenes to aromatic and semi-volatile species; many of these are a concern from both an air quality and public health viewpoint, as they can lead to local ozone pollution and increased risk of cancer or respiratory illness. The fate of hydrocarbons once in the atmosphere is ultimately oxidation through to CO2 and water, adding to the greenhouse gas burden. Measurement techniques that are capable of identifying and quantifying the full range of primary emissions of concern are required to assess community exposure to air toxics and to better inform residents, as well as local and state legislators. Here, we present evaluation of a low-cost air monitoring technique using stainless steel diffusion cartridges containing multiple solid adsorbents. Over the course of a three-month period in summer of 2014, cartridges were deployed at five monitoring sites located around Boulder County in the Northern Colorado Front Range, and exposed to ambient air for periods of up to four days along with concurrent sampling using stainless steel SUMMA canisters. Samples collected with both methods were subsequently analyzed for VOCs by GC-FID and the results were compared to determine the accuracy and precision of the diffusion cartridge method. Results of this evaluation show that the diffusion cartridge method has the potential to be a simple and low-cost solution for widespread exposure monitoring in communities near oil and gas development regions. Such measurements may also provide supporting evidence on wider effects on greenhouse gas emissions from oil and gas development operations.

  4. 3He Bilayer Film Adsorbed on Graphite Plated with a Bilayer of 4He: a New Frustrated 2D Magnetic System

    NASA Astrophysics Data System (ADS)

    Neumann, Michael; Nyéki, Ján; Cowan, Brian; Saunders, John

    2006-09-01

    The heat capacity and NMR response of a 3He bilayer adsorbed on graphite plated with a bilayer of 4He have been measured over the temperature range 1-80 mK. We find that the first 3He layer requires the presence of a 3He fluid overlayer before it solidifies. Solidification is completed at a total coverage close to 9.85 nm-2, On further increasing the coverage the heat capacity maximum grows from `antiferromagnetic-like' (AFM-like) to `ferromagnetic-like' (FM-like). On the other hand, when the 3He layer first solidifies, it has a low temperature saturation magnetisation corresponding to a significant fraction of full polarisation, and this increases with increasing coverage. Furthermore the effective exchange constant inferred from the high temperature magnetisation data is always ferromagnetic. The effective exchange constants inferred from the heat capacity and magnetisation are significantly larger than those observed in the second layer of pure 3He films adsorbed on bare graphite. Otherwise there are strong similarities in the coverage dependence of the heat capacity and magnetisation, providing fresh insights into how the magnetic ground state of such 2D magnets evolves as the frustration is tuned with increasing coverage.

  5. Nanoscale confinement and interfacial effects on the dynamics and glass transition/crystallinity of thin adsorbed films on silica nanoparticles

    NASA Astrophysics Data System (ADS)

    Madathingal, Rajesh Raman

    The research investigated in this dissertation has focused on understanding the structure-property-function relationships of polymer nanocomposites. The properties of composite systems are dictated by the properties of their components, typically fillers in a polymer matrix. In nanocomposites, the polymer near an interface has significantly different properties compared with the bulk polymer, and the contribution of the adsorbed polymer to composite properties becomes increasingly important as the filler size decreases. Despite many reports of highly favorable properties, the behavior of polymer nanocomposites is not generally predictable, and thus requires a better understanding of the interfacial region. The ability to tailor the filler/matrix interaction and an understanding of the impact of the interface on macroscopic properties are keys in the design of nanocomposite properties. In this original work the surface of silica nanoparticles was tailored by: (a) Changing the number of sites for polymer attachment by varying the surface silanols and, (b) By varying the size/curvature of nanoparticles. The effect of surface tailoring on the dynamic properties after the adsorption of two model polymers, amorphous polymethyl methacrylate (PMMA) and semicrystalline polyethylene oxide (PEO) was observed. The interphase layer of polymers adsorbed to silica surfaces is affected by the surface silanol density as well as the relative size of the polymer compared with the size of the adsorbing substrate. The non-equilibrium adsorption of PMMA onto individual colloidal Stober silica (SiO2) particles, where Rparticle (100nm) > RPMMA (˜6.5nm) was compared with the adsorption onto fumed silica, where Rparticle (7nm) ˜ RPMMA (6.5nm) < Raggregate (˜1000nm), both as a function of silanol density [SiOH] and hydrophobility. In the former case, TEM images showed that the PMMA adsorbed onto individual nanoparticles, so that the number of PMMA chains/bead could be calculated, whereas

  6. Measuring Thicknesses Of Vacuum-Deposited Organic Thin Films

    NASA Technical Reports Server (NTRS)

    David, Carey E.

    1996-01-01

    Method of measuring thickness of thin organic liquid film deposited in vacuum involves use of quartz-crystal monitor (QCM) calibrated by use of witness plate that has, in turn, calibrated by measurement of absorption of infrared light in deposited material. Present procedure somewhat tedious, but once calibration accomplished, thicknesses of organic liquid deposits monitored in real time and in situ by use of QCM.

  7. Metal-organic frameworks: A thin film opening

    NASA Astrophysics Data System (ADS)

    Sumby, Christopher J.

    2016-04-01

    The properties of metal-organic frameworks -- promising for a myriad of applications -- can be commonly tuned by judicious choice of the building blocks used to prepare the material. Now, simply downsizing a rigid, non-porous MOF to a thin film has been shown to endow it with dynamic, gate-opening-type guest uptake behaviour.

  8. Remediation of Organic and Inorganic Arsenic Contaminated Groundwater using a Nonocrystalline TiO2 Based Adsorbent

    SciTech Connect

    Jing, C.; Meng, X; Calvache, E; Jiang, G

    2009-01-01

    A nanocrystalline TiO2-based adsorbent was evaluated for the simultaneous removal of As(V), As(III), monomethylarsonic acid (MMA), and dimethylarsinic acid (DMA) in contaminated groundwater. Batch experimental results show that As adsorption followed pseudo-second order rate kinetics. The competitive adsorption was described with the charge distribution multi-site surface complexation model (CD-MUSIC). The groundwater containing an average of 329 ?g L-1 As(III), 246 ?g L-1 As(V), 151 ?g L-1 MMA, and 202 ?g L-1 DMA was continuously passed through a TiO2 filter at an empty bed contact time of 6 min for 4 months. Approximately 11 000, 14 000, and 9900 bed volumes of water had been treated before the As(III), As(V), and MMA concentration in the effluent increased to 10 ?g L-1. However, very little DMA was removed. The EXAFS results demonstrate the existence of a bidentate binuclear As(V) surface complex on spent adsorbent, indicating the oxidation of adsorbed As(III). A nanocrystalline TiO2-based adsorbent could be used for the simultaneous removal of As(V), As(III), MMA, and DMA in contaminated groundwater.

  9. Sample water removal method in volatile organic compound analysis based on diffusion through poly(vinyl fluoride) film.

    PubMed

    Beghi, Sandra; Guillot, Jean-Michel

    2006-09-15

    The humidity caught during air sampling or sample storage causes various problems during volatile organic compound (VOC) analysis and gives unreliable results. In this study, water vapour diffusion capacities through poly(vinyl fluoride) Tedlar, fluoroethylene propylene Teflon and Flex foil film were compared. A new approach to humidity removal has been tested for moderately polluted atmospheres. This approach consists in using the water vapour diffusion property of Tedlar film to remove humidity from bag samples containing a mixture of ten VOCs at 500 ppbv each in a 70% relative humidity atmosphere. The sampling bags were placed in a chamber flushed by a dry air stream at less than 5% relative humidity. After a few hours in the chamber, the samples in the Tedlar bags were dry (relative humidity <5%) and did not show significant VOC loss. This sample water removal (SWR) method is especially interesting as a pretreatment before air sampling on water sensitive adsorbents. PMID:16828784

  10. Thin-film transistors based on organic conjugated semiconductors

    NASA Astrophysics Data System (ADS)

    Garnier, Francis

    1998-02-01

    The use of organic semiconductors as active layers in thin-film transistors has raised in the recent years a large interest, both for the fundamental understanding of the charge transport processes in organic materials, and also for the potential applications of these devices in the new field of flexible electronics. Short conjugated oligomers have been shown to possess much higher field-effect mobilities than their parent conjugated polymers. The origin of such increase in the efficiency of charge transport is mainly attributed to the close-packing and long-range structural organization displayed in thin films of conjugated oligomers. The various routes for controlling this organization are described, which allow to realize liquid crystal-like two-dimensional structures for these semiconductors, whose carrier mobility has now become equivalent to that of amorphous silicon. It is also shown that the effect of conjugation length on carrier mobility is not as critical as previously thought, but the associated increase of the band gap energy effects the efficiency of charge injection at the metal/semiconductor interface. This problem can be answered by realizing a local doping of the semiconductor, which allows the injection of charge to operate through an efficient tunneling mechanism. Organic-based thin-film transistors have now become viable devices.

  11. Determination of adsorbable organic fluorine from aqueous environmental samples by adsorption to polystyrene-divinylbenzene based activated carbon and combustion ion chromatography.

    PubMed

    Wagner, Andrea; Raue, Brigitte; Brauch, Heinz-Jürgen; Worch, Eckhard; Lange, Frank T

    2013-06-21

    A new method for the determination of trace levels of adsorbable organic fluorine (AOF) in water is presented. Even if the individual contributing target compounds are widely unknown, this surrogate parameter is suited to identify typical organofluorine contaminations, such as with polyfluorinated chemicals (PFCs), and represents a lower boundary of the organofluorine concentration in water bodies. It consists of the adsorption of organofluorine chemicals on a commercially available synthetic polystyrene-divinylbenzene based activated carbon (AC) followed by analysis of the loaded AC by hydropyrolysis combustion ion chromatography (CIC). Inorganic fluorine is displaced by excess nitrate during the extraction step and by washing the loaded activated carbon with an acidic sodium nitrate solution. Due to its high purity the synthetic AC had a very low and reproducible fluorine blank (0.3 μg/g) compared to natural ACs (up to approximately 9 μg/g). Using this AC, fluoride and the internal standard phosphate could be detected free of chromatographic interferences. With a sample volume of 100 mL and 2× 100 mg of AC packed into two extraction columns combined in series, a limit of quantification (LOQ), derived according to the German standard method DIN 32645, of 0.3 μg/L was achieved. The recoveries of six model PFCs were determined from tap water and a municipal wastewater treatment plant (WWTP) effluent. Except for the extremely polar perfluoroacetic acid (recovery of approximately 10%) the model substances showed fairly good (50% for perfluorobutanoic acid (PFBA)) to very good fluorine recoveries (100±20% for perfluorooctanoic acid (PFOA), perfluorobutanesulfonate (PFBS), 6:2 fluorotelomersulfonate (6:2 FTS)), both from tap water and wastewater matrix. This new analytical protocol was exemplarily applied to several surface water and groundwater samples. The obtained AOF values were compared to the fluorine content of 19 target PFCs analyzed by high performance

  12. Exploration of exciton delocalization in organic crystalline thin films

    NASA Astrophysics Data System (ADS)

    Hua, Kim; Manning, Lane; Rawat, Naveen; Ainsworth, Victoria; Furis, Madalina

    The electronic properties of organic semiconductors play a crucial role in designing new materials for specific applications. Our group recently found evidence for a rotation of molecular planes in phthalocyanines that is responsible for the disappearance of a delocalized exciton in these systems for T >150K.................()().......1 In this study, we attempt to tune the exciton delocalization of small organic molecules using strain effects and alloying different molecules in the same family. The exciton behavior is monitored using time- and polarization resolved photolumniscence (PL) spectroscopy as a function of temperature. Specifically, organic crystalline thin films of octabutoxy phthalocyanine (H2OBPc), octyloxy phthalocyanines and H-bonded semiconductors such as the quinacridone and indigo derivatives are deposited on flexible substrates (i.e. Kapton and PEN) using an in-house developed pen-writing method.........2 that results in crystalline films with macroscopic long range order. The room temperature PL studies show redshift and changes in polarization upon bending of the film. Crystalline thin films of alloyed H2OBPc and octabutoxy naphthalocyanine with ratios ranging from 1:1 to 100:1 fabricated on both sapphire and flexible substrates are also explored using the same PL spectroscopy to elucidate the behaviors of delocalized excitons. .1N. Rawat, et al., J Phys Chem Lett 6, 1834 (2015). 2R. L. Headrick, et al., Applied Physics Letters 92, 063302 (2008). NSF DMR-1056589, NSF DMR-1062966.

  13. Thin films by metal-organic precursor plasma spray

    SciTech Connect

    Schulz, Douglas L.; Sailer, Robert A.; Payne, Scott; Leach, James; Molz, Ronald J.

    2009-07-15

    While most plasma spray routes to coatings utilize solids as the precursor feedstock, metal-organic precursor plasma spray (MOPPS) is an area that the authors have investigated recently as a novel route to thin film materials. Very thin films are possible via MOPPS and the technology offers the possibility of forming graded structures by metering the liquid feed. The current work employs metal-organic compounds that are liquids at standard temperature-pressure conditions. In addition, these complexes contain chemical functionality that allows straightforward thermolytic transformation to targeted phases of interest. Toward that end, aluminum 3,5-heptanedionate (Al(hd){sub 3}), triethylsilane (HSi(C{sub 2}H{sub 5}){sub 3} or HSiEt{sub 3}), and titanium tetrakisdiethylamide (Ti(N(C{sub 2}H{sub 5}){sub 2}){sub 4} or Ti(NEt{sub 2}){sub 4}) were employed as precursors to aluminum oxide, silicon carbide, and titanium nitride, respectively. In all instances, the liquids contain metal-heteroatom bonds envisioned to provide atomic concentrations of the appropriate reagents at the film growth surface, thus promoting phase formation (e.g., Si-C bond in triethylsilane, Ti-N bond in titanium amide, etc.). Films were deposited using a Sulzer Metco TriplexPro-200 plasma spray system under various experimental conditions using design of experiment principles. Film compositions were analyzed by glazing incidence x-ray diffraction and elemental determination by x-ray spectroscopy. MOPPS films from HSiEt{sub 3} showed the formation of SiC phase but Al(hd){sub 3}-derived films were amorphous. The Ti(NEt{sub 2}){sub 4} precursor gave MOPPS films that appear to consist of nanosized splats of TiOCN with spheres of TiO{sub 2} anatase. While all films in this study suffered from poor adhesion, it is anticipated that the use of heated substrates will aid in the formation of dense, adherent films.

  14. Reference spectra of important adsorbed organic and inorganic phosphate binding forms for soil P speciation using synchrotron-based K-edge XANES spectroscopy.

    PubMed

    Prietzel, Jörg; Harrington, Gertraud; Häusler, Werner; Heister, Katja; Werner, Florian; Klysubun, Wantana

    2016-03-01

    Direct speciation of soil phosphorus (P) by linear combination fitting (LCF) of P K-edge XANES spectra requires a standard set of spectra representing all major P species supposed to be present in the investigated soil. Here, available spectra of free- and cation-bound inositol hexakisphosphate (IHP), representing organic P, and of Fe, Al and Ca phosphate minerals are supplemented with spectra of adsorbed P binding forms. First, various soil constituents assumed to be potentially relevant for P sorption were compared with respect to their retention efficiency for orthophosphate and IHP at P levels typical for soils. Then, P K-edge XANES spectra for orthophosphate and IHP retained by the most relevant constituents were acquired. The spectra were compared with each other as well as with spectra of Ca, Al or Fe orthophosphate and IHP precipitates. Orthophosphate and IHP were retained particularly efficiently by ferrihydrite, boehmite, Al-saturated montmorillonite and Al-saturated soil organic matter (SOM), but far less efficiently by hematite, Ca-saturated montmorillonite and Ca-saturated SOM. P retention by dolomite was negligible. Calcite retained a large portion of the applied IHP, but no orthophosphate. The respective P K-edge XANES spectra of orthophosphate and IHP adsorbed to ferrihydrite, boehmite, Al-saturated montmorillonite and Al-saturated SOM differ from each other. They also are different from the spectra of amorphous FePO4, amorphous or crystalline AlPO4, Ca phosphates and free IHP. Inclusion of reference spectra of orthophosphate as well as IHP adsorbed to P-retaining soil minerals in addition to spectra of free or cation-bound IHP, AlPO4, FePO4 and Ca phosphate minerals in linear combination fitting exercises results in improved fit quality and a more realistic soil P speciation. A standard set of P K-edge XANES spectra of the most relevant adsorbed P binding forms in soils is presented. PMID:26917141

  15. Direct observation of epitaxial organic film growth: temperature-dependent growth mechanisms and metastability.

    PubMed

    Marchetto, Helder; Schmidt, Thomas; Groh, Ullrich; Maier, Florian C; Lévesque, Pierre L; Fink, Rainer H; Freund, Hans-Joachim; Umbach, Eberhard

    2015-11-21

    The growth of the first ten layers of organic thin films on a smooth metallic substrate has been investigated in real-time using the model system PTCDA on Ag(111). The complex behaviour is comprehensively studied by electron microscopy, spectroscopy and diffraction in a combined PEEM/LEEM instrument revealing several new phenomena and yielding a consistent picture of this layer growth. PTCDA grows above room temperature in a Stranski-Krastanov mode, forming three-dimensional islands on a stable bi-layer, in competition with metastable 3rd and 4th layers. Around room temperature this growth mode changes into a quasi layer-by-layer growth, while at temperatures below about 250 K a Vollmer-Weber-like behaviour is observed. By means of laterally resolved soft X-ray absorption spectroscopy the orientation of all adsorbed molecules is found to be homogeneously flat lying on the surface, even during the growth process. The films grow epitaxially, showing long-range order with rotational domains. For the monolayer these domains could be directly analysed, showing an average size of several micrometers extending over substrate steps. PMID:26462749

  16. Graphene nanosheets as novel adsorbents in adsorption, preconcentration and removal of gases, organic compounds and metal ions.

    PubMed

    Yu, Jin-Gang; Yu, Lin-Yan; Yang, Hua; Liu, Qi; Chen, Xiao-Hong; Jiang, Xin-Yu; Chen, Xiao-Qing; Jiao, Fei-Peng

    2015-01-01

    Due to their high adsorption capacities, carbon-based nanomaterials such as carbon nanotubes, activated carbons, fullerene and graphene are widely used as the currently most promising functional materials. Since its discovery in 2004, graphene has exhibited great potential in many technological fields, such as energy storage materials, supercapacitors, resonators, quantum dots, solar cells, electronics, and sensors. The large theoretical specific surface area of graphene nanosheets (2630 m(2)·g(-1)) makes them excellent candidates for adsorption technologies. Further, graphene nanosheets could be used as substrates for decorating the surfaces of nanoparticles, and the corresponding nanocomposites could be applied as novel adsorbents for the removal of low concentrated contaminants from aqueous solutions. Therefore, graphene nanosheets will challenge the current existing adsorbents, including other types of carbon-based nanomaterials. PMID:25244035

  17. Remediation of organic and inorganic arsenic contaminated groundwater using a nanocrystalline TiO2-based adsorbent.

    PubMed

    Jing, Chuanyong; Meng, Xiaoguang; Calvache, Edwin; Jiang, Guibin

    2009-01-01

    A nanocrystalline TiO2-based adsorbent was evaluated for the simultaneous removal of As(V), As(III), monomethylarsonic acid (MMA), and dimethylarsinic acid (DMA) in contaminated groundwater. Batch experimental results show that As adsorption followed pseudo-second order rate kinetics. The competitive adsorption was described with the charge distribution multi-site surface complexation model (CD-MUSIC). The groundwater containing an average of 329 microg L(-1) As(III), 246 microg L(-1) As(V), 151 microg L(-1) MMA, and 202 microg L(-1) DMA was continuously passed through a TiO2 filter at an empty bed contact time of 6 min for 4 months. Approximately 11,000, 14,000, and 9900 bed volumes of water had been treated before the As(III), As(V), and MMA concentration in the effluent increased to 10 microg L(-1). However, very little DMA was removed. The EXAFS results demonstrate the existence of a bidentate binuclear As(V) surface complex on spent adsorbent, indicating the oxidation of adsorbed As(III). PMID:19339086

  18. Temperature and layer thickness dependent in situ investigations on epindolidione organic thin-film transistors

    PubMed Central

    Lassnig, R.; Striedinger, B.; Jones, A.O.F.; Scherwitzl, B.; Fian, A.; Głowacl, E.D.; Stadlober, B.; Winkler, A.

    2016-01-01

    We report on in situ performance evaluations as a function of layer thickness and substrate temperature for bottom-gate, bottom-gold contact epindolidione organic thin-film transistors on various gate dielectrics. Experiments were carried out under ultra-high vacuum conditions, enabling quasi-simultaneous electrical and surface analysis. Auger electron spectroscopy and thermal desorption spectroscopy (TDS) were applied to characterize the quality of the substrate surface and the thermal stability of the organic films. Ex situ atomic force microscopy (AFM) was used to gain additional information on the layer formation and surface morphology of the hydrogen-bonded organic pigment. The examined gate dielectrics included SiO2, in its untreated and sputtered forms, as well as the spin-coated organic capping layers poly(vinyl-cinnamate) (PVCi) and poly((±)endo,exo-bicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic acid, diphenylester) (PNDPE, from the class of polynorbornenes). TDS and AFM revealed Volmer-Weber island growth dominated film formation with no evidence of a subjacent wetting layer. This growth mode is responsible for the comparably high coverage required for transistor behavior at 90–95% of a monolayer composed of standing molecules. Surface sputtering and an increased sample temperature during epindolidione deposition augmented the surface diffusion of adsorbing molecules and therefore led to a lower number of better-ordered islands. Consequently, while the onset of charge transport was delayed, higher saturation mobility was obtained. The highest, bottom-contact configuration, mobilities of approximately 2.5 × 10−3cm2/Vs were found for high coverages (50 nm) on sputtered samples. The coverage dependence of the mobility showed very different characteristics for the different gate dielectrics, while the change of the threshold voltage with coverage was approximately the same for all systems. An apparent decrease of the mobility with increasing coverage on the

  19. Liquid crystals for organic thin-film transistors

    NASA Astrophysics Data System (ADS)

    Iino, Hiroaki; Usui, Takayuki; Hanna, Jun-Ichi

    2015-04-01

    Crystalline thin films of organic semiconductors are a good candidate for field effect transistor (FET) materials in printed electronics. However, there are currently two main problems, which are associated with inhomogeneity and poor thermal durability of these films. Here we report that liquid crystalline materials exhibiting a highly ordered liquid crystal phase of smectic E (SmE) can solve both these problems. We design a SmE liquid crystalline material, 2-decyl-7-phenyl-[1]benzothieno[3,2-b][1]benzothiophene (Ph-BTBT-10), for FETs and synthesize it. This material provides uniform and molecularly flat polycrystalline thin films reproducibly when SmE precursor thin films are crystallized, and also exhibits high durability of films up to 200 °C. In addition, the mobility of FETs is dramatically enhanced by about one order of magnitude (over 10 cm2 V-1 s-1) after thermal annealing at 120 °C in bottom-gate-bottom-contact FETs. We anticipate the use of SmE liquid crystals in solution-processed FETs may help overcome upcoming difficulties with novel technologies for printed electronics.

  20. Effects of dissolved organic matter on adsorbed Fe(II) reactivity for the reduction of 2-nitrophenol in TiO2 suspensions.

    PubMed

    Zhu, Zhenke; Tao, Liang; Li, Fangbai

    2013-09-01

    Dissolved organic matter (DOM) is widespread in aquatic and terrestrial environments. Iron is the most abundant transition metal in the Earth's crust. The biogeochemistry of iron and the strength of Fe(II) as a reducing agent while adsorbed on minerals are affected by DOM. This study investigated the effects of Fe(II)/DOM interactions on the reduction of 2-nitrophenol (2-NP) in TiO2 suspensions. Kinetic measurements demonstrated that rates (k) of 2-NP reduction by adsorbed Fe(II) species are affected by adding DOM (denoted O-DOM), and the obtained k values under the impact of the Fe(II)/DOM interaction with different molecular weight DOM fractions [including MW<3500Da (L-DOM), 350014000Da (H-DOM)] showed significant differences. The enhanced rates of 2-NP reduction contributed to increases in the amount of adsorbed Fe(II) species and negative shifts in peak oxidation potential values (EP) in CV tests. For different molecular weight DOM fractions, increases in k (O-DOMadsorbed Fe(II) and the lower EP values. In addition, the ETC values were slightly higher in the TiO2 suspension containing the H-DOM fraction as compared the other two DOM fractions, which would further enhance the reduction rate of 2-NP. These findings promote a general understanding of Fe(II)/DOM interactions and their impact on the fate of contaminants in actual subsurface environments. PMID:23796307

  1. Polycrystalline organic thin film transistors for advanced chemical sensing

    NASA Astrophysics Data System (ADS)

    Torsi, Luisa; Tanese, Maria C.; Cioffi, Nicola; Sabbatini, Luigia; Zambonin, Pier G.

    2003-11-01

    Organic thin-film transistors have seen a dramatic improvement of their performance in the last decade. They have been also proposed as gas sensors. This paper deals with the interesting new aspects that polycrystalline based conducting polymer transistors present when operated as chemical sensors. Such devices are capable to deliver multi-parameter responses that are also extremely repeatable and fast at room temperature. Interesting are also the perspectives for their use as chemically selective devices in array type sensing systems.

  2. Magnetic field effect in organic films and devices

    NASA Astrophysics Data System (ADS)

    Gautam, Bhoj Raj

    In this work, we focused on the magnetic field effect in organic films and devices, including organic light emitting diodes (OLEDs) and organic photovoltaic (OPV) cells. We measured magnetic field effect (MFE) such as magnetoconductance (MC) and magneto-electroluminescence (MEL) in OLEDs based on several pi- conjugated polymers and small molecules for fields |B|<100 mT. We found that both MC(B) and MEL(B) responses in bipolar devices and MC(B) response in unipolar devices are composed of two B-regions: (i) an 'ultra-small' region at |B| < 1-2 mT, and (ii) a monotonic response region at |B| >˜2mT. Magnetic field effect (MFE) measured on three isotopes of Poly (dioctyloxy) phenylenevinylene (DOO-PPV) showed that both regular and ultra-small effects are isotope dependent. This indicates that MFE response in OLED is mainly due to the hyperfine interaction (HFI). We also performed spectroscopy of the MFE including magneto-photoinduced absorption (MPA) and magneto-photoluminescence (MPL) at steady state conditions in several systems. This includes pristine Poly[2-methoxy-5-(2-ethylhexyl-oxy)-1,4-phenylene-vinylene] (MEH-PPV) films, MEH-PPV films subjected to prolonged illumination, and MEH-PPV/[6,6]-Phenyl C61 butyric acid methyl ester (PCBM) blend, as well as annealed and pristine C60 thin films. For comparison, we also measured MC and MEL in organic diodes based on the same materials. By directly comparing the MPA and MPL responses in films to MC and MEL in organic diodes based on the same active layers, we are able to relate the MFE in organic diodes to the spin densities of the excitations formed in the device, regardless of whether they are formed by photon absorption or carrier injection from the electrodes. We also studied magneto-photocurrent (MPC) and power conversion efficiency (PCE) of a 'standard' Poly (3-hexylthiophene)/PCBM device at various Galvinoxyl radical wt%. We found that the MPC reduction with Galvinoxyl wt% follows the same trend as that of the

  3. Rate of organic film formation and oxidation on aqueous drops

    NASA Astrophysics Data System (ADS)

    Aumann, E.; Tabazadeh, A.

    2008-12-01

    Previous studies suggest that saturated fatty acids or other lipids, which are known to be strong film-forming agents, form condensed films on aqueous drops. Specifically, stearic acid (SA) has been used in laboratory and modeling studies to mimic the surface composition of some particles in the atmosphere. In this study, laboratory measurements were used to determine the rate of SA spreading from a solid on aqueous surfaces,ranging in composition from ammonium sulfate to highly acidic sulfuric acid. Maximum spreading rates were measured on neutral electrolyte solutions, while spreading was not observed on aqueous sulfuric and hydrochloric acids (pH < 0). Also, the spreading rates on water and electrolyte surfaces declined sharply as the solution pH was lowered from 7 to 3. Spreading rates are reported with a dependence on the length of solid-aqueous-air boundary (triple interface perimeter). Spreading rates measured on bulk solutions were modeled on atmospheric particles to determine the time constant of organic film formation on aqueous drops. The time required for a saturated fatty acid to spread and coat a submicron salt particle or a cloud drop is on the order of seconds to minutes or minutes to hours, respectively. In conclusion, lipid coatings can form quickly on neutral or slightly acidic salt drops if a sufficient amount of lipid is present in the drop and the lipid is in direct contact with the aqueous solution surface. Rapid film formation and fast heterogeneous oxidation can provide an efficient way of converting water-insoluble organic films into more water-soluble components in aerosols or cloud drops.

  4. Organic thin-film transistors for chemical and biological sensing.

    PubMed

    Lin, Peng; Yan, Feng

    2012-01-01

    Organic thin-film transistors (OTFTs) show promising applications in various chemical and biological sensors. The advantages of OTFT-based sensors include high sensitivity, low cost, easy fabrication, flexibility and biocompatibility. In this paper, we review the chemical sensors and biosensors based on two types of OTFTs, including organic field-effect transistors (OFETs) and organic electrochemical transistors (OECTs), mainly focusing on the papers published in the past 10 years. Various types of OTFT-based sensors, including pH, ion, glucose, DNA, enzyme, antibody-antigen, cell-based sensors, dopamine sensor, etc., are classified and described in the paper in sequence. The sensing mechanisms and the detection limits of the devices are described in details. It is expected that OTFTs may have more important applications in chemical and biological sensing with the development of organic electronics. PMID:22102447

  5. Novel solutions for thin film layer deposition for organic materials

    NASA Astrophysics Data System (ADS)

    Keiper, Dietmar; Long, Michael; Schwambera, Markus; Gersdorff, Markus; Kreis, Juergen; Heuken, Michael

    2011-03-01

    Innovative systems for carrier-gas enhanced vapor phase deposition of organic layers offer advanced methods for the precise deposition of complex thin-film layer stacks. The approach inherently avoids potential short-comings from solvent-based polymer deposition and offers new opportunities. The process operates at low pressure (thus avoiding complex vacuum setups), and, by employing AIXTRON's extensive experience in freely scalable solutions, can be adapted to virtually any production process and allows for R&D and production systems alike. Deposition of organic layers and stacks recommends the approach for a wide range of organic small molecule and polymer materials (including layers with gradual change of the composition), for conductive layers, for dielectric layers, for barrier systems, for OLED materials, and surface treatments such as oleophobic / hydrophobic coatings. With the combination of other vapor phase deposition solutions, hybrid systems combining organic and inorganic materials and other advanced stacks can be realized.

  6. 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.

  7. Effects of feed-borne Fusarium mycotoxins with or without yeast cell wall adsorbent on organ weight, serum biochemistry, and immunological parameters of broiler chickens.

    PubMed

    Li, Z; Yang, Z B; Yang, W R; Wang, S J; Jiang, S Z; Wu, Y B

    2012-10-01

    The objectives of the present study were to investigate the toxicity of feed-borne Fusarium mycotoxins on organ weight, serum biochemistry, and immunological parameters of broiler chickens and to evaluate the efficacy of yeast cell wall adsorbent in preventing mycotoxin-induced adverse effects. In total, 300 one-day-old vaccinated (Marek's disease and infectious bronchitis) Arbor Acres broiler chickens (mixed sex) were randomly divided into 3 treatments (5 repetitions per treatment) and fed basal diet and naturally contaminated diets with or without yeast cell wall adsorbent. Treatments were control, naturally contaminated diet (NCD; aflatoxin, 102.08 mg/kg; zearalenone, 281.92 mg/kg; fumonisin, 5,874.38 mg/kg; deoxynivalenol, 2,038.96 mg/kg), and NCD + 2 g/kg of yeast cell wall adsorbent (NCDD). The test included 2 phases: d 0-21 and d 22-42. At 42 d, broilers fed contaminated diets without yeast cell wall adsorbent had higher (P < 0.05) serum albumin and higher relative weight of liver, bursa of Fabricius, and thymus, and greater splenic mRNA expression of IL-1β and IL-6 at 42 d compared with the control, but lower (P < 0.05) serum globulin at 42 d, IgA at 21 d, relative weight of spleen at 21 d, antibody titers of Newcastle disease at both 28 d and 42 d, and splenic mRNA expression of IFN-γ at 42 d were observed in the NCD treatment compared with control. Dietary addition of yeast cell wall adsorbent in the NCD treatment showed a positive protection effect on the relative weight of the liver and spleen at 21 d, relative weight of the bursa of Fabricius and thymus at 42 d, antibody titers of Newcastle disease at both 28 d and 42 d, and splenic mRNA expression of IL-1β, IL-6, and IFN-γ at 42 d. It is suggested that feeding a naturally contaminated diet for 42 d might result in a deleterious effect in broiler chickens, and addition of 2 g/kg of yeast cell wall enterosorbent can partly neutralize the detrimental effects of the naturally contaminated feed. PMID

  8. Ion-imprinted silica adsorbent modified diffusive gradients in thin films technique: Tool for speciation analysis of free lead species.

    PubMed

    Sui, Dian-Peng; Chen, Hua-Xia; Liu, Lin; Liu, Ming-Xuan; Huang, Cong-Cong; Fan, Hong-Tao

    2016-02-01

    A new diffusive gradients in thin films (DGT) device, using Pb(II) ion-imprinted silica (IIS) as the binding agents and commercial cellulose acetate dialysis (CAD) membrane as the diffusion layer (CAD/IIS-DGT), has been developed and evaluated for sampling and measurement of free Pb(II) species. The CAD/IIS-DGT devices were successfully applied to the measurement of free Pb(II) species in synthetic solutions, in natural freshwaters and in industrial wastewaters. The CAD/IIS-DGT provides reliable results over pH range of 4.5-6.5 and a wide range of ionic strength from 1.0×10(-3) to 0.7 mol L(-1). The concentrations of the free Pb(II) species in synthetic solution containing different concentrations of ligands measured by CAD/IIS-DGT showed a good agreement with the value measured by Pb-ion selective electrode. Field deployments of the CAD/IIS-DGT devices allowed accurate measurements of the concentrations of free Pb(II) species. PMID:26653451

  9. Oriented Thin Films of a Benzodithiophene Covalent Organic Framework

    PubMed Central

    2014-01-01

    A mesoporous electron-donor covalent organic framework based on a benzodithiophene core, BDT-COF, was obtained through condensation of a benzodithiophene-containing diboronic acid and hexahydroxytriphenylene (HHTP). BDT-COF is a highly porous, crystalline, and thermally stable material, which can be handled in air. Highly porous, crystalline oriented thin BDT-COF films were synthesized from solution on different polycrystalline surfaces, indicating the generality of the synthetic strategy. The favorable orientation, crystallinity, porosity, and the growth mode of the thin BDT-COF films were studied by means of X-ray diffraction (XRD), 2D grazing incidence diffraction (GID), transmission and scanning electron microscopy (TEM, SEM), and krypton sorption. The highly porous thin BDT-COF films were infiltrated with soluble fullerene derivatives, such as [6,6]-phenyl C61 butyric acid methyl ester (PCBM), to obtain an interpenetrated electron-donor/acceptor host–guest system. Light-induced charge transfer from the BDT-framework to PCBM acceptor molecules was indicated by efficient photoluminescence quenching. Moreover, we monitored the dynamics of photogenerated hole-polarons via transient absorption spectroscopy. This work represents a combined study of the structural and optical properties of highly oriented mesoporous thin COF films serving as host for the generation of periodic interpenetrated electron-donor and electron-acceptor systems. PMID:24559375

  10. Robust absolute magnetometry with organic thin-film devices

    PubMed Central

    Baker, W.J.; Ambal, K.; Waters, D.P.; Baarda, R.; Morishita, H.; van Schooten, K.; McCamey, D.R.; Lupton, J.M.; Boehme, C.

    2012-01-01

    Magnetic field sensors based on organic thin-film materials have attracted considerable interest in recent years as they can be manufactured at very low cost and on flexible substrates. However, the technological relevance of such magnetoresistive sensors is limited owing to their narrow magnetic field ranges (∼30 mT) and the continuous calibration required to compensate temperature fluctuations and material degradation. Conversely, magnetic resonance (MR)-based sensors, which utilize fundamental physical relationships for extremely precise measurements of fields, are usually large and expensive. Here we demonstrate an organic magnetic resonance-based magnetometer, employing spin-dependent electronic transitions in an organic diode, which combines the low-cost thin-film fabrication and integration properties of organic electronics with the precision of a MR-based sensor. We show that the device never requires calibration, operates over large temperature and magnetic field ranges, is robust against materials degradation and allows for absolute sensitivities of <50 nT Hz−1/2. PMID:22692541

  11. 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.

  12. Multifunctional organic thin films and their electronic/optical properties

    NASA Astrophysics Data System (ADS)

    Shao, Yan

    The concept of multifunctional organic thin films and their electronic/optical properties has been applied to organic functional device design, fabrication, and characterization. The organic devices involve organic light-emitting diodes (OLEDs) and organic photovoltaic devices (OPV) in this dissertation. In the research of graded junction structure of OLEDs, two kinds of naturally-formed graded junction (NFGJ) structures, sharp and shallow graded junctions, can be formed using single thermal evaporation boat loaded with uniformly mixed charge transport and light-emitting materials. OLEDs with NFGJ have been demonstrated in Chapter 3; the performance is comparable to the heterojunction OLEDs, but with better device lifetime. A novel method to prepare highly uniform mixed organic solid solutions through a high temperature and high-pressure fusion process has been demonstrated in Chapter 4. A series of fused organic solid solution (FOSS) compounds with NPD doped with different organic emitting dopants were prepared and DSC technique was utilized to determine the thermal characteristics. For the first time, the schematic phase diagram for this binary system has been obtained. High performance OLEDs of single color and white emission were fabricated and the device properties were characterized. In Chapter 5, an efficient photovoltaic heterojunction of tetracene and fullerene has been investigated and high performance organic solar cells have been demonstrated by thermal deposition and successive heat treatment. The preliminary conclusion for this enhancement is discussed and supported by atomic force microscopy images, absorption spectra and x-ray diffraction analysis. Additionally, an effective organic photovoltaic heterojunction based on the typical triplet material PtOEP was demonstrated. It is believed that introducing appropriate organic materials with long exciton lifetime is a very promising way to improve photovoltaic performance.

  13. Sense or no-sense of the sum parameter for water soluble "adsorbable organic halogens" (AOX) and "absorbed organic halogens" (AOX-S18) for the assessment of organohalogens in sludges and sediments.

    PubMed

    Müller, German

    2003-07-01

    "AOX" is the abbreviation of the sum parameter for water soluble "adsorbable organic halogens" in which 'A' stands for adsorbable, 'O' for organic and 'X' for the halogens chlorine, bromine and iodine. After the introduction of the AOX in 1976, this parameter has been correctly used for "real" AOX constituents (DDT and its metabolites, PCBs, etc.) but also misused for non-adsorbable adsorbed OX-compounds, mostly high molecular organohalogens in plants and even to inorganic compounds being neither organic nor adsorbable. The question of natural "Adsorbable Organic Halogens" (AOX) formed by living organisms and/or during natural abiogenic processes has been definitively solved by the known existence of already more than 3650 organohalogen compounds, amongst them the highly reactive, cancerogenic vinyl chloride (VC). The extension of the AOX to AOX-S18 for Sludges and Sediments, in which A stands for adsorbed (not for adsorbable) is questionable. It includes the most important water insoluble technical organochlorine product: polyvinyl chloride, PVC. In addition to organic halogens it also includes inorganic, mineralogenic halides, incorporated mainly in the crystal lattice of fine grained phyllosilicates, the typical clay minerals (kaolinite, montmorillonite, illite and chlorite) which are main constituents of sediments and sedimentary rocks representing the major part of the sedimentary cover of the earth. Other phyllosilicates, biotite and muscovite, major constituents of granites and many metamorphic rocks (gneiss and mica schist) will also contribute to the AOX-S18 especially in soils as result of weathering processes. Since chlorine is incorporated into the mineral structure and, as a consequence, not soluble by the nitric acid analytical step (pH 0.5) of the S18 determination, it will account to the AOX-S18 in the final charcoal combustion step at temperatures >950 degrees C. After heavy rainfalls sewage sludge composition is strongly influenced by

  14. Thin film solar cells grown by organic vapor phase deposition

    NASA Astrophysics Data System (ADS)

    Yang, Fan

    Organic solar cells have the potential to provide low-cost photovoltaic devices as a clean and renewable energy resource. In this thesis, we focus on understanding the energy conversion process in organic solar cells, and improving the power conversion efficiencies via controlled growth of organic nanostructures. First, we explain the unique optical and electrical properties of organic materials used for photovoltaics, and the excitonic energy conversion process in donor-acceptor heterojunction solar cells that place several limiting factors of their power conversion efficiency. Then, strategies for improving exciton diffusion and carrier collection are analyzed using dynamical Monte Carlo models for several nanostructure morphologies. Organic vapor phase deposition is used for controlling materials crystallization and film morphology. We improve the exciton diffusion efficiency while maintaining good carrier conduction in a bulk heterojunction solar cell. Further efficiency improvement is obtained in a novel nanocrystalline network structure with a thick absorbing layer, leading to the demonstration of an organic solar cell with 4.6% efficiency. In addition, solar cells using simultaneously active heterojunctions with broad spectral response are presented. We also analyze the efficiency limits of single and multiple junction organic solar cells, and discuss the challenges facing their practical implementations.

  15. Surface vibrational spectroscopy. A comparison of the EELS spectra of organic adsorbates at Pt(111) with IR and Raman spectra of the unadsorbed organics

    NASA Astrophysics Data System (ADS)

    Kahn, Bruce E.; Chaffins, Scott A.; Gui, John Y.; Lu, Frank; Stern, Donald A.; Hubbard, Arthur T.

    1990-02-01

    In this study EELS spectra obtained for the adsorbed species formed from aqueous electrolytes at Pt(111) electrode surfaces are compared with the IR and Raman spectra of the unadsorbed compounds in order to reveal the changes in vibrational spectra resulting from chemisorption of various important functional groups, and to explore the differences in vibrational absorptivities between EELS spectra of adsorbed species and IR and Raman spectra of the corresponding unadsorbed compounds. Of particular interest are the variations in EELS vibrational frequency, bandwidth and absorptivity due to bonding with the surface, intermolecular interactions of adsorbed molecules and changes in adsorbate molecular orientation. The influence of surface bonding on the EELS spectrum of a functional group was explored through studies of phenol (PL), phenol- d6 (PLD6), benzyl alcohol (BZOH), catechol (CT), benzoic acid (BA), 2-picolinic acid (PA), 2,6-pyridine dicarboxylic acid (26PDCA), and propenoic acid (PPEA). The aromatic ring of adsorbed PL, PLD6, BZA, CT, BA, PA and 26PDCA is oriented parallel to the Pt(111) surface. The resulting strong interactions affect the frequencies and relative intensities of the EELS bands: weak CH stretching modes; a large CC stretching band (1600-1650 cm -1), and weak CH bending (700-800 cm -1). The carboxylic acid moieties of BA and PA interact strongly with the Pt surface, while those of 26PDCA do so only when adsorbed at relatively positive electrode potentials. OH stretching and bending are absent from the EELS spectra of adsorbed PL, BZOH and CT, perhaps due to dissociation of the hydroxyl hydrogen during adsorption of the molecule. Adsorption of alkenes at Pt(111) from solution preserves the characteristic CC stretching band near 1650 cm -1; examples are: PPEA; 1-hexene (HXE); propenol (PPEOH); 4-pentenol (PTEOH); and cis-2-butene-1,4-diol (CBED); adsorption of ethene, propene and butene from vacuum at room temperature has been reported to

  16. Two-Dimensional Organic-Inorganic Hybrid Perovskite Photonic Films.

    PubMed

    Meng, Ke; Gao, Shanshan; Wu, Longlong; Wang, Geng; Liu, Xin; Chen, Gang; Liu, Zhou; Chen, Gang

    2016-07-13

    Organic-inorganic hybrid perovskites have created enormous expectations for low-cost and high-performance optoelectronic devices. In prospect, future advancements may derive from reaping novel electrical and optical properties beyond pristine perovskites through microscopic structure design and engineering. Herein, we report the successful preparation of two-dimensional inverse-opal perovskite (IOP) photonic films, featuring unique nanostructures and vivid colors. Further compositional and structural managements promise optical property and energy level tunability of the IOP films. They are further functionalized in solar cells, resulting in colorful devices with respectable power conversion efficiency. Such concept has not been previously applied for perovskite-based solar cells, which could open a route for more versatile optoelectronic devices. PMID:27267266

  17. Orbital tomography for highly symmetric adsorbate systems

    NASA Astrophysics Data System (ADS)

    Stadtmüller, B.; Willenbockel, M.; Reinisch, E. M.; Ules, T.; Bocquet, F. C.; Soubatch, S.; Puschnig, P.; Koller, G.; Ramsey, M. G.; Tautz, F. S.; Kumpf, C.

    2012-10-01

    Orbital tomography is a new and very powerful tool to analyze the angular distribution of a photoemission spectroscopy experiment. It was successfully used for organic adsorbate systems to identify (and consequently deconvolute) the contributions of specific molecular orbitals to the photoemission data. The technique was so far limited to surfaces with low symmetry like fcc(110) oriented surfaces, owing to the small number of rotational domains that occur on such surfaces. In this letter we overcome this limitation and present an orbital tomography study of a 3,4,9,10-perylene-tetra-carboxylic-dianhydride (PTCDA) monolayer film adsorbed on Ag(111). Although this system exhibits twelve differently oriented molecules, the angular resolved photoemission data still allow a meaningful analysis of the different local density of states and reveal different electronic structures for symmetrically inequivalent molecules. We also discuss the precision of the orbital tomography technique in terms of counting statistics and linear regression fitting algorithm. Our results demonstrate that orbital tomography is not limited to low-symmetry surfaces, a finding which makes a broad field of complex adsorbate systems accessible to this powerful technique.

  18. A rapid microwave-assisted synthesis of a sodium-cadmium metal-organic framework having improved performance as a CO2 adsorbent for CCS.

    PubMed

    Palomino Cabello, Carlos; Arean, Carlos Otero; Parra, José B; Ania, Conchi O; Rumori, P; Turnes Palomino, G

    2015-06-01

    We report on a facile and rapid microwave-assisted method for preparing a sodium-cadmium metal-organic framework (having coordinatively unsaturated sodium ions) that considerably shortens the conventional synthesis time from 5 days to 1 hour. The obtained (Na,Cd)-MOF showed an excellent volumetric CO2 adsorption capacity (5.2 mmol cm(-3) at 298 K and 1 bar) and better CO2 adsorption properties than those shown by the same metal-organic framework when synthesized following a more conventional procedure. Moreover, the newly prepared material was found to display high selectivity for adsorption of carbon dioxide over nitrogen, and good regenerability and stability during repeated CO2 adsorption-desorption cycles, which are the required properties for any adsorbent intended for carbon dioxide capture and sequestration (CSS) from the post-combustion flue gas of fossil fuelled power stations. PMID:25939594

  19. Thin Film Solar Cells: Organic, Inorganic and Hybrid

    NASA Technical Reports Server (NTRS)

    Dankovich, John

    2004-01-01

    Thin film solar cells are an important developing resource for hundreds of applications including space travel. In addition to being more cost effective than traditional single crystal silicon cells, thin film multi-crystaline cells are plastic and light weight. The plasticity of the cells allows for whole solar panels to be rolled out from reams. Organic layers are being investigated in order to increase the efficiency of the cells to create an organic / inorganic hybrid cell. The main focus of the group is a thin film inorganic cell made with the absorber CuInS2. So far the group has been successful in creating the layer from a single-source precursor. They also use a unique method of film deposition called chemical vapor deposition for this. The general makeup of the cell is a molybdenum back contact with the CuInS2 layer, then CdS, ZnO and aluminum top contacts. While working cells have been produced, the efficiency so far has been low. Along with quantum dot fabrication the side project of this that is currently being studied is adding a polymer layer to increase efficiency. The polymer that we are using is P3OT (Poly(3-octylthiopene-2,5-diyll), retroregular). Before (and if) it is added to the cell, it must be understood in itself. To do this simple diodes are being constructed to begin to look at its behavior. The P3OT is spin coated onto indium tin oxide and silver or aluminum contacts are added. This method is being studied in order to find the optimal thickness of the layer as well as other important considerations that may later affect the composition of the finished solar cell. Because the sun is the most abundant renewable, energy source that we have, it is important to learn how to harness that energy and begin to move away from our other depleted non-renewable energy sources. While traditional silicon cells currently create electricity at relatively high efficiencies, they have drawbacks such as weight and rigidness that make them unattractive

  20. Controlled Growth of Ultrathin Film of Organic Semiconductors by Balancing the Competitive Processes in Dip-Coating for Organic Transistors.

    PubMed

    Wu, Kunjie; Li, Hongwei; Li, Liqiang; Zhang, Suna; Chen, Xiaosong; Xu, Zeyang; Zhang, Xi; Hu, Wenping; Chi, Lifeng; Gao, Xike; Meng, Yancheng

    2016-06-28

    Ultrathin film with thickness below 15 nm of organic semiconductors provides excellent platform for some fundamental research and practical applications in the field of organic electronics. However, it is quite challenging to develop a general principle for the growth of uniform and continuous ultrathin film over large area. Dip-coating is a useful technique to prepare diverse structures of organic semiconductors, but the assembly of organic semiconductors in dip-coating is quite complicated, and there are no reports about the core rules for the growth of ultrathin film via dip-coating until now. In this work, we develop a general strategy for the growth of ultrathin film of organic semiconductor via dip-coating, which provides a relatively facile model to analyze the growth behavior. The balance between the three direct factors (nucleation rate, assembly rate, and recession rate) is the key to determine the growth of ultrathin film. Under the direction of this rule, ultrathin films of four organic semiconductors are obtained. The field-effect transistors constructed on the ultrathin film show good field-effect property. This work provides a general principle and systematic guideline to prepare ultrathin film of organic semiconductors via dip-coating, which would be highly meaningful for organic electronics as well as for the assembly of other materials via solution processes. PMID:27267545

  1. High performance small-molecule organic thin film transistors

    NASA Astrophysics Data System (ADS)

    Kuo, Chung-Chen

    The roadmap of developing microelectronics has a new branch: organic electronics. Organic electronics, which utilizes the electrical properties of organic materials in the active or passive layers, is an emerging technology that has received much attention. In conjunction with today's demands for new materials and devices, many technologies have emerged for developing organic electronics and consolidating applications and markets. An organic thin-film transistor is the essential device in this paradigm in addition to organic photodiodes and organic light emitting diodes. This thesis presents advances made in design and fabrication of organic thin-film transistors (OTFTs) using small-molecule organic semiconductors (pentacene, anthradithiophene, and their derivatives) as the active layer with record device performance. In this work OTFT test structures fabricated on oxidized silicon substrates were utilized to provide a convenient substrate, gate contact, and gate insulator for the processing and characterization of vapor-deposited organic materials and their transistors. By developing a gate dielectric treatment using silane coupling agents the performance and yield of pentacene OTFTs was improved and a field-effect mobility of larger than 2 cm2/V-s was achieved. Such device performance is comparable to a-Si:H TFTs and have the potential for electronic applications. In addition, the first direct photolithographic process for top contacts to pentacene OTFTs on oxidized silicon with an acceptable performance (a field-effect mobility of 0.3 cm2/V-s, an on/off current ratio of 10 7, and a subthreshold slope of 1 V/decade) was developed. The multiple layer photoresist process demonstrated the feasibility of creating source and drain metallic electrodes on vapor-deposited pentacene thin films with a resolution less than 10 mum. Subsequently, solution-processed OTFTs were then investigated and high performance transistors, with field-effect mobilities > 1 cm2/V-s and an

  2. Quantitation of persistent organic pollutants adsorbed on plastic debris from the Northern Pacific Gyre's "eastern garbage patch".

    PubMed

    Rios, Lorena M; Jones, Patrick R; Moore, Charles; Narayan, Urja V

    2010-12-01

    Floating marine plastic debris was found to function as solid-phase extraction media, adsorbing and concentrating pollutants out of the water column. Plastic debris was collected in the North Pacific Gyre, extracted, and analyzed for 36 individual PCB congeners, 17 organochlorine pesticides, and 16 EPA priority PAHs. Over 50% contained PCBs, 40% contained pesticides, and nearly 80% contained PAHs. The PAHs included 2, 3 and 4 ring congeners. The PCBs were primarily CB-11, 28, 44, 52, 66, and 101. The pesticides detected were primarily p,p-DDTs and its metabolite, o,p-DDD, as well as BHC (a,b,g and d). The concentrations of pollutants found ranged from a few ppb to thousands of ppb. The types of PCBs and PAHs found were similar to those found in marine sediments. However, these plastic particles were mostly polyethylene which is resistant to degradation and although functioning similarly to sediments in accumulating pollutants, these had remained on or near the ocean surface. Particles collected included intact plastic items as well as many pieces less than 5 mm in size. PMID:21042605

  3. Mutagenicity of organic pollutants adsorbed on suspended particulate matter in the center of Wrocław (Poland)

    NASA Astrophysics Data System (ADS)

    Bełcik, Maciej; Trusz-Zdybek, Agnieszka; Galas, Ewa; Piekarska, Katarzyna

    2014-10-01

    Mutagenicity of pollutants adsorbed on suspended dust of the PM10 fraction, collected in winter and summer season alike over the Wrocław city centre (Poland) was studied using the standard Salmonella assay (plate-incorporation) and the Kado modified assay (microsuspension method). The dust was collected using Staplex high volume air sampler. Further on it was extracted with dichloromethane in a Soxhlet apparatus. PAH content in extracts was determined by the high performance liquid chromatography technique using fluorescence detection, whereas the nitro-PAH content- by the gas chromatography using mass detection. Two Salmonella typhimurium strains, TA98 and YG1041, were used in the assays. The assays were conducted with and without a metabolic activation. Investigated air pollution extracts differed against each other with regard to a total content as well as to a percentage of individual compounds, depending on the sampling season. Both the total PAH content and the nitro-PAH content in the tested samples, and their spectrum as well, were found the highest in winter season. Higher mutagenic effect was noted for the dust extract from samples collected in wintertime than from those collected in summer. Pollutants directly affecting the genetic material and those showing such indirect action were present in the examined samples. The YG1041 strain turned out to be the most sensitive, which was the sign that large amounts of nitro-aromatic compounds were present in the tested samples. Obtained results proved that the Kado modified Salmonella assay would be useful for the atmospheric air pollution monitoring in urban agglomerations. Mutagenic effect in assays conducted according to the Kado procedure was obtained by using in the assays lower concentrations of tested extracts, compared to the classical assay.

  4. A novel photoelectrochromic device with dual application based on poly(3,4-alkylenedioxythiophene) thin film and an organic dye

    NASA Astrophysics Data System (ADS)

    Hsu, Chih-Yu; Lee, Kun-Mu; Huang, Jen-Hsien; Justin Thomas, K. R.; Lin, Jiann T.; Ho, Kuo-Chuan

    A novel photoelectrochromic device (PECD) with dual application was studied using an electrochromic polymer thin film, poly(3,3-diethyl-3,4-dihydro-2 H-thieno-[3,4- b][1,4]dioxepine) (PProDot-Et 2), and an organic photosensitive dye, FL dye1, which was adsorbed on a TiO 2 electrode. In the presence of the redox couple, the electron transfer reaction at the electrolyte/PProDot-Et 2 conducting polymer interface was found to determine the electrochromism of the PECD. The rate constants of the electron transfer (k 0) for different redox couples at the PProDot-Et 2 film were obtained by using electrochemical impedance spectroscopy (EIS) and were correlated with the coloration depth of the thin film. Since I -/I 3 - and Br -/Br 3 - couples possess the highest and the lowest k 0 value, respectively, the PECD was investigated using these two redox couples under constant light illumination of 50 mW cm -2. The I -/I 3 - couple provided a higher short circuit current density (J SC) when acting as a dye-sensitized solar cell (DSSC), thus the switching response upon coloration (ca. 3 s) was much faster than that of the PECD using the Br -/Br 3 - couple (ca. 2 min). On the contrary, the PECD using Br -/Br 3 - exhibited a larger transmittance attenuation of ca. 33.7%, in comparison to that using I -/I 3 - (ca. 14.1%).

  5. Light amplification device using organic electroluminescent diode coupled with photoresponsive organic pigment film

    NASA Astrophysics Data System (ADS)

    Katsume, Tadashi; Hiramoto, Masahiro; Yokoyama, Masaaki

    1995-05-01

    An all-organic light amplification device was successfully constructed using the organic electroluminescent diode coupled with photoresponsive perylene pigment film. Light amplification gain, such as the quantum efficiency of photon conversion, reached as large as 25-folds. Optical switching behavior caused by the feedback of output light to the photoresponsive perylene layer was noted. Because the spatial pattern of light was verified to be conserved precisely, the current device had the potential to evolve into the light amplification device, optical switching device, and optical memory device for two-dimensional parallel image processing.

  6. Adsorbed Water Illustration

    NASA Technical Reports Server (NTRS)

    2008-01-01

    The Thermal and Electrical Conductivity Probe on NASA's Phoenix Mars Lander detected small and variable amounts of water in the Martian soil.

    In this schematic illustration, water molecules are represented in red and white; soil minerals are represented in green and blue. The water, neither liquid, vapor, nor solid, adheres in very thin films of molecules to the surfaces of soil minerals. The left half illustrates an interpretation of less water being adsorbed onto the soil-particle surface during a period when the tilt, or obliquity, of Mars' rotation axis is small, as it is in the present. The right half illustrates a thicker film of water during a time when the obliquity is greater, as it is during cycles on time scales of hundreds of thousands of years. As the humidity of the atmosphere increases, more water accumulates on mineral surfaces. Thicker films behave increasingly like liquid water.

    The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver.

  7. Organic and inorganic-organic thin film structures by molecular layer deposition: A review.

    PubMed

    Sundberg, Pia; Karppinen, Maarit

    2014-01-01

    The possibility to deposit purely organic and hybrid inorganic-organic materials in a way parallel to the state-of-the-art gas-phase deposition method of inorganic thin films, i.e., atomic layer deposition (ALD), is currently experiencing a strongly growing interest. Like ALD in case of the inorganics, the emerging molecular layer deposition (MLD) technique for organic constituents can be employed to fabricate high-quality thin films and coatings with thickness and composition control on the molecular scale, even on complex three-dimensional structures. Moreover, by combining the two techniques, ALD and MLD, fundamentally new types of inorganic-organic hybrid materials can be produced. In this review article, we first describe the basic concepts regarding the MLD and ALD/MLD processes, followed by a comprehensive review of the various precursors and precursor pairs so far employed in these processes. Finally, we discuss the first proof-of-concept experiments in which the newly developed MLD and ALD/MLD processes are exploited to fabricate novel multilayer and nanostructure architectures by combining different inorganic, organic and hybrid material layers into on-demand designed mixtures, superlattices and nanolaminates, and employing new innovative nanotemplates or post-deposition treatments to, e.g., selectively decompose parts of the structure. Such layer-engineered and/or nanostructured hybrid materials with exciting combinations of functional properties hold great promise for high-end technological applications. PMID:25161845

  8. Organic and inorganic–organic thin film structures by molecular layer deposition: A review

    PubMed Central

    Sundberg, Pia

    2014-01-01

    Summary The possibility to deposit purely organic and hybrid inorganic–organic materials in a way parallel to the state-of-the-art gas-phase deposition method of inorganic thin films, i.e., atomic layer deposition (ALD), is currently experiencing a strongly growing interest. Like ALD in case of the inorganics, the emerging molecular layer deposition (MLD) technique for organic constituents can be employed to fabricate high-quality thin films and coatings with thickness and composition control on the molecular scale, even on complex three-dimensional structures. Moreover, by combining the two techniques, ALD and MLD, fundamentally new types of inorganic–organic hybrid materials can be produced. In this review article, we first describe the basic concepts regarding the MLD and ALD/MLD processes, followed by a comprehensive review of the various precursors and precursor pairs so far employed in these processes. Finally, we discuss the first proof-of-concept experiments in which the newly developed MLD and ALD/MLD processes are exploited to fabricate novel multilayer and nanostructure architectures by combining different inorganic, organic and hybrid material layers into on-demand designed mixtures, superlattices and nanolaminates, and employing new innovative nanotemplates or post-deposition treatments to, e.g., selectively decompose parts of the structure. Such layer-engineered and/or nanostructured hybrid materials with exciting combinations of functional properties hold great promise for high-end technological applications. PMID:25161845

  9. Method for measurement of the density of thin films of small organic molecules

    SciTech Connect

    Xiang Haifeng; Xu Zongxiang; Roy, V. A. L.; Che Chiming; Lai, P. T.

    2007-03-15

    An accurate and sensitive method is reported to measure the thin-film density of vacuum-deposited, small-molecular organic semiconductor materials. A spectrophotometer and surface profiler had been used to determine the mass and thickness of organic thin film, respectively. The calculated density of tris-(8-hydroxyquinolato) aluminum (Alq{sub 3}) thin film was 1.31{+-}0.01 g/cm{sup 3}. Vacuum pressures and thin-film growth rates are found to have less impact on the thin-film density of organic material. However, the thin-film density of organic material strongly depends on its chemical structure and molecular weight. Specifically, the chemical structure determines the density of organic material that affects the molecular volume and intermolecular stacking.

  10. Influence of organic acids on kinetic release of chromium in soil contaminated with leather factory waste in the presence of some adsorbents.

    PubMed

    Taghipour, Marzieh; Jalali, Mohsen

    2016-07-01

    In this study, batch experiments were conducted to investigate the effects of nanoparticles (NPs) (MgO, ZnO, TiO2) and clay minerals (bentonite, zeolite) on the release of chromium (Cr) from leather factory waste (LFW) and LFW treated soil using organic acids. Chromium release from all treatments was studied in the presence of citric acid, oxalic acid and CaCl2 solutions. The results showed that, in all treatments, organic acids released more Cr than inorganic salt (CaCl2). The release of Cr by citric acid was higher than that by oxalic acid. In LFW treated soil and LFW, the release of Cr from the all treatments with NPs was less than that from the clay mineral treatments. On the other hand, in the presence of organic acids, Cr release by NPs and clay minerals decreased. Two kinetic models including pseudo-first- and pseudo-second-order model were tested to describe the time dependent Cr release data. Among the kinetic models used, the pseudo-second-order model generally gave the best fits to experimental data. Before and after release experiments, Cr in LFW, treated LFW, control soil and LFW treated soils were fractionated. In all treatments, the greatest amounts of Cr were found in the residual fraction (RES). The organic acids were effective in reducing the exchangeable (EXC), bound to organic matter (OM) and bound to carbonate (CAR) fractions of Cr in all treatments, whereas, after release of Cr from treated soils, Cr remained mainly in the RES fraction. The application of NPs and clay minerals in soil led to a significant transformation of Cr from mobile fractions to the RES fraction. Therefore, organic ligands played a dominant role in mobility and bioavailability of Cr and the removal of Cr by adsorbents. PMID:27139119

  11. QSAR models for removal rates of organic pollutants adsorbed by in situ formed manganese dioxide under acid condition.

    PubMed

    Su, Pingru; Zhu, Huicen; Shen, Zhemin

    2016-02-01

    Manganese dioxide formed in oxidation process by potassium permanganate exhibits promising adsorptive capacity which can be utilized to remove organic pollutants in wastewater. However, the structure variances of organic molecules lead to wide difference of adsorption efficiency. Therefore, it is of great significance to find a general relationship between removal rate of organic compounds and their quantum parameters. This study focused on building up quantitative structure activity relationship (QSAR) models based on experimental removal rate (r(exp)) of 25 organic compounds and 17 quantum parameters of each organic compounds computed by Gaussian 09 and Material Studio 6.1. The recommended model is rpre = -0.502-7.742 f(+)x + 0.107 E HOMO + 0.959 q(H(+)) + 1.388 BOx. Both internal and external validations of the recommended model are satisfied, suggesting optimum stability and predictive ability. The definition of applicability domain and the Y-randomization test indicate all the prediction is reliable and no possibility of chance correlation. The recommended model contains four variables, which are closely related to adsorption mechanism. f(+)x reveals the degree of affinity for nucleophilic attack. E HOMO represents the difficulty of electron loss. q(H(+)) reflect the distribution of partial charge between carbon and hydrogen atom. BO x shows the stability of a molecule. PMID:26490942

  12. Molecular assembly and organic film growth on complex intermetallic surfaces

    NASA Astrophysics Data System (ADS)

    Al-Mahboob, Abdullah; Sharma, Hem Raj; Sadowski, Jerzy T.; Ledieu, Julian; Fournée, Vincent; McGrath, Ronan

    We extensively studied the role of molecular symmetry and symmetry/structures of wide ranges of substrate-surfaces from non-periodic to periodic to quasi-crystalline in nucleation, growth and phase transition in films made of organic molecular materials. Recently, most interest in quasicrystals is due to the generalization of aperiodic ordering to several classes of systems. Compared to periodic materials, these provide a closer approximation to an isotropic first Brillouin zone, which is of great importance to the design of new functional materials. Here, we present results obtained from our ongoing study of interface mediated molecular assembly extended on complex intermetallic surfaces with specific examples of C60 and Zn-phthalocyanine on quasicrystalline and approximant surfaces. We employed in-situ real-time low-energy electron microscopy (LEEM) for investigation of the processes in assembly and film growth and post-growth STM study and DFT calculations to understand structural details and growth mechanism. Research were carried out in part at the Center for Functional Nanomaterials, Brookhaven National Lab, USA; partly at Institut Jean Lamour, Université de Lorraine, France; and partly at the Surface Science Research Centre, University of Liverpool, UK.

  13. Simultaneous removal of multiple pesticides from water: effect of organically modified clays as coagulant aid and adsorbent in coagulation-flocculation process.

    PubMed

    Shabeer, T P Ahammed; Saha, Ajoy; Gajbhiye, V T; Gupta, Suman; Manjaiah, K M; Varghese, Eldho

    2014-01-01

    Contamination of drinking water sources with agrochemical residues became a major concern in the twenty-first century. Coagulation-flocculation is the most widely used water-treatment process, but the efficiency to remove pesticides and other organic pollutants are limited compared to adsorption process. Thus, simultaneous action of adsorption on normal bentonite or organo-modified montmorillonite clays [modified with octadecylamine (ODA-M) and octadecylamine + amino-propyltriethoxysilane (ODAAPS-M)] followed by coagulation-flocculation by alum and poly aluminium chloride has been evaluated for removal of 10 different pesticides, namely atrazine, lindane, metribuzin, aldrin, chlorpyriphos, pendimethalin, alpha-endosulphan, beta-endosulphan, p,p'-DDT, cypermethrin and two of its metabolites, endosulphan sulphate and p,p'-DDE, from water. The coagulation without integration of adsorption was less effective (removal % varies from 12 to 49) than the adsorption-coagulation integrated system (removal % varies from 71 to 100). Further, coagulation integrated with adsorption was more effective when organically modified montmorillonite was used as adsorbent compared to normal bentonite. The removal efficiency of organic clay depends upon the concentration of pesticides, doses of clay minerals, and efficiency was more for ODAAPS-M as compared to ODA-M. The combination of ODAAPS-M-clay with coagulants was also used efficiently for the removal of pesticides from natural and fortified natural water collected and the results exhibit the usefulness of this remediation technique for application in water decontamination and in treatment of industrial and agricultural waste waters. PMID:25145219

  14. Organic Thin Film Devices for Displays and Lighting

    NASA Astrophysics Data System (ADS)

    Weiss, Oliver J.; Krause, Ralf; Paetzold, Ralph

    Organic materials can be used for fabrication of, e.g., electronic circuits, solar cells, light sensors, memory cells and light emitting diodes. Especially organic light emitting diodes (OLEDs) are increasingly attractive because of their huge market potential. The feasibility of efficient OLEDs was first shown in 1987 [3]. Only about ten years later the first product, a display for car radios, entered the market. Today monochrome and full colour OLED-displays can be found in many applications replacing established flat panel display technologies like TFT-LCDs. This substitution is a consequence of the outstanding attributes of OLED technology: Organic light emitting displays are self-emissive, thin, video capable and in addition they show a wide temperature operation range and allow a viewing angle of nearly 180 degree in conjunction with a low power consumption. As performance has steadily increased over the last years, today OLEDs are also under investigation as next generation light source. In contrast to inorganic LEDs, they can be built as flat 2-dimensional light sources that are lightweight, colour tunable, and potentially cheap. This will open up new degrees of freedom in design leading also to completely new applications. In this contribution we will have a brief view on the history of organic electroluminescent materials before we introduce the basic principles of OLEDs with a focus on the physical processes leading to light generation in thin organic films. Along with an overview of different concepts and technologies used to build OLEDs, the current status of OLED development will be illustrated. The last part focuses on the challenges that have to be overcome to enable a sustainable success in the display and lighting markets.

  15. Inorganic-organic composite nanoengineered films using self-assembled monolayers for directed zeolite film growth

    SciTech Connect

    Dye, R.C.; Hermes, R.E.; Martinez, M.G.; Peachey, N.M.

    1997-10-01

    This is the final report of a one-year, Laboratory Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). Zeolites, or molecular sieves, are aluminosilicate cage structures that are typically grown from a heterogeneous mixture of organic template molecules, inorganic salts of alumina and silica, and water. These zeolites are used in industry for catalytic cracking of hydrocarbons (gasoline manufacture from oil), and contaminant removal from chemical production processes. Within one year, we developed a viable method for the deposition of a quaternary ammonium salt amphiphile onto silicon wafer substrates. Using a biomimetic growth process, we were also able to demonstrate the first thin-film formation of a zeolite structure from such an organic template. Additionally, we synthesized the precursor to another amphiphile which was to be for further studies.

  16. Organically Modified Nanoclay-Reinforced Rigid Polyurethane Films

    NASA Astrophysics Data System (ADS)

    Park, Yong Tae; Qian, Yuqiang; Lindsay, Chris; Stein, Andreas; Macosko, Christopher

    2012-02-01

    The nanodispersion of vermiculite in polyurethanes was investigated to produce organoclay-reinforced rigid gas barrier films. Reducing gas transport can improve the insulation performance of closed cell polyurethane foam. In a previous study, the dispersion of vermiculite in polyurethanes without organic modification was not sufficient due to the non-uniform dispersion morphology. When vermiculite was modified by cation exchange with long-chain quaternary ammonium cations, the dispersion in methylene diphenyl diisocyanate (MDI) was significantly improved. Dispersion was improved by combining high intensity dispersive mixing with efficient distributive mixing. Polymerization conditions were also optimized in order to provide a high state of nanodispersion in the polyurethane nanocomposite. The dispersions were characterized using rheological, microscopic and scattering/diffraction techniques. The final nanocomposites showed enhancement of mechanical properties and reduction in permeability to carbon dioxide at low clay concentration (around 2 wt percent).

  17. REUSABLE ADSORBENTS FOR DILUTE SOLUTIONS SEPARATION. 5: PHOTODEGRADATION OF ORGANIC COMPOUNDS ON SURFACTANT-MODIFIED TITANIA. (R828598C753)

    EPA Science Inventory

    A semiconductor titania (TiO2) surface was modified by surfactant adsorption to make it more hydrophobic and to increase the adsorption of hydrophobic organic compounds (HOCs) and their photodegradation rates under UV irradiation. Photocatalytic experiments using Ti...

  18. Optical properties of organic films, multilayers and plasmonic metal-organic waveguides fabricated by organic molecular beam deposition

    NASA Astrophysics Data System (ADS)

    Wickremasinghe, Niranjala D.

    In this thesis, the optical properties of tris (8-hydroxyquinoline) aluminum (Alq3) and 3,5,9,10-perylentetracarboxylic dianhydride (PTCDA) organic films, PTCDA/ Alq3 multilayers and plasmonic Alq3 -metal waveguides are investigated. The organic films and heterostructures used for this work were fabricated by organic molecular beam deposition (OMBD). We investigated the quenching of the light emission in Alq3 films grown on a Si substrate as a function of cw laser excitation intensity at varying temperatures from 15 to 300 K. The saturation of the singlet-singlet annihilation coefficient was measured with spectrally-integrated (SI) photoluminescence (PL) using a photodiode. The bimolecular quenching coefficient was further studied with time-resolved (TR) PL as a function of 100 fs pulse fluences. The PL quenching is attributed to the annihilation of trapped excitons at Alq3 nanocrystal grain boundaries. The saturation is explained by the limited density of available trapping states at the grain boundaries. Our interpretation is supported by structural investigations of ultrathin Alq3 films with atomic force microscopy (AFM), scanning electron microscopy (SEM) and by comparing the experimental data with calculations using a coupled rate equation model. The wavelength dispersion of the refractive indices of PTCDA and Alq 3 layers and of PTCDA/Alq3 multilayer waveguides grown on Pyrex substrates was investigated. The m-line technique, an evanescent prism coupling technique, was used to determine the layers' thickness and the in-plane (TE modes) and normal (TM modes) refractive indices. The potential for controlling the refractive index dispersion and anisotropy by tailored organic multilayer waveguides is discussed.

  19. Organic crystalline films for optical applications and related methods of fabrication

    NASA Technical Reports Server (NTRS)

    Leyderman, Alexander (Inventor); Cui, Yunlong (Inventor)

    2003-01-01

    The present invention provides organic single crystal films of less than 20 .mu.m, and devices and methods of making such films. The crystal films are useful in electro-optical applications and can be provided as part of an electro-optical device which provides strength, durability, and relative ease of manipulation of the mono-crystalline films during and after crystal growth.

  20. Reduction of ferrihydrite with adsorbed and coprecipitated organic matter: microbial reduction by Geobacter bremensis vs. abiotic reduction by Na-dithionite

    NASA Astrophysics Data System (ADS)

    Eusterhues, K.; Hädrich, A.; Neidhardt, J.; Küsel, K.; Keller, T. F.; Jandt, K. D.; Totsche, K. U.

    2014-04-01

    Ferrihydrite (Fh) is a widespread poorly crystalline Fe oxide which becomes easily coated by natural organic matter (OM) in the environment. This mineral-bound OM entirely changes the mineral surface properties and therefore the reactivity of the original mineral. Here, we investigated the reactivity of 2-line Fh, Fh with adsorbed OM and Fh coprecipitated with OM towards microbial and abiotic reduction of Fe(III). As a surrogate for dissolved soil OM we used a water extract of a Podzol forest floor. Fh-OM associations with different OM-loadings were reduced either by Geobacter bremensis or abiotically by Na-dithionite. Both types of experiments showed decreasing initial Fe reduction rates and decreasing degrees of reduction with increasing amounts of mineral-bound OM. At similar OM-loadings, coprecipitated Fhs were more reactive than Fhs with adsorbed OM. The difference can be explained by the smaller crystal size and poor crystallinity of such coprecipitates. At small OM loadings this led to even faster Fe reduction rates than found for pure Fh. The amount of mineral-bound OM also affected the formation of secondary minerals: goethite was only found after reduction of OM-free Fh and siderite was only detected when Fhs with relatively low amounts of mineral-bound OM were reduced. We conclude that direct contact of G. bremensis to the Fe oxide mineral surface was inhibited when blocked by OM. Consequently, mineral-bound OM shall be taken into account besides Fe(II) accumulation as a further widespread mechanism to slow down reductive dissolution.

  1. Organic and inorganic contaminants removal from water with biochar, a renewable, low cost and sustainable adsorbent--a critical review.

    PubMed

    Mohan, Dinesh; Sarswat, Ankur; Ok, Yong Sik; Pittman, Charles U

    2014-05-01

    Biochar is used for soil conditioning, remediation, carbon sequestration and water remediation. Biochar application to water and wastewater has never been reviewed previously. This review focuses on recent applications of biochars, produced from biomass pyrolysis (slow and fast), in water and wastewater treatment. Slow and fast pyrolysis biochar production is briefly discussed. The literature on sorption of organic and inorganic contaminants by biochars is surveyed and reviewed. Adsorption capacities for organic and inorganic contaminants by different biochars under different operating conditions are summarized and, where possible, compared. Mechanisms responsible for contaminant remediation are briefly discussed. Finally, a few recommendations for further research have been made in the area of biochar development for application to water filtration. PMID:24636918

  2. Organic Single-Crystal Semiconductor Films on a Millimeter Domain Scale.

    PubMed

    Kwon, Sooncheol; Kim, Jehan; Kim, Geunjin; Yu, Kilho; Jo, Yong-Ryun; Kim, Bong-Joong; Kim, Junghwan; Kang, Hongkyu; Park, Byoungwook; Lee, Kwanghee

    2015-11-18

    Nucleation and growth processes can be effectively controlled in organic semiconductor films through a new concept of template-mediated molecular crystal seeds during the phase transition; the effective control of these processes ensures millimeter-scale crystal domains, as well as the performance of the resulting organic films with intrinsic hole mobility of 18 cm(2) V(-1) s(-1). PMID:26425962

  3. Organic thin film devices with stabilized threshold voltage and mobility, and method for preparing the devices

    DOEpatents

    Nastasi, Michael Anthony; Wang, Yongqiang; Fraboni, Beatrice; Cosseddu, Piero; Bonfiglio, Annalisa

    2013-06-11

    Organic thin film devices that included an organic thin film subjected to a selected dose of a selected energy of ions exhibited a stabilized mobility (.mu.) and threshold voltage (VT), a decrease in contact resistance R.sub.C, and an extended operational lifetime that did not degrade after 2000 hours of operation in the air.

  4. Low resistance thin film organic solar cell electrodes

    SciTech Connect

    Forrest, Stephen; Xue, Jiangeng

    2008-01-01

    A method which lower the series resistance of photosensitive devices includes providing a transparent film of a first electrically conductive material arranged on a transparent substrate; depositing and patterning a mask over the first electrically conductive material, such that openings in the mask have sloping sides which narrow approaching the substrate; depositing a second electrically conductive material directly onto the first electrically conductive material exposed in the openings of the mask, at least partially filling the openings; stripping the mask, leaving behind reentrant structures of the second electrically conductive material which were formed by the deposits in the openings of the mask; after stripping the mask, depositing a first organic material onto the first electrically conductive material in between the reentrant structures; and directionally depositing a third electrically conductive material over the first organic material deposited in between the reentrant structures, edges of the reentrant structures aligning deposition so that the third electrically conductive material does not directly contact the first electrically conductive material, and does not directly contact the second electrically conductive material.

  5. Clean graphene electrodes on organic thin-film devices via orthogonal fluorinated chemistry.

    PubMed

    Beck, Jonathan H; Barton, Robert A; Cox, Marshall P; Alexandrou, Konstantinos; Petrone, Nicholas; Olivieri, Giorgia; Yang, Shyuan; Hone, James; Kymissis, Ioannis

    2015-04-01

    Graphene is a promising flexible, highly transparent, and elementally abundant electrode for organic electronics. Typical methods utilized to transfer large-area films of graphene synthesized by chemical vapor deposition on metal catalysts are not compatible with organic thin-films, limiting the integration of graphene into organic optoelectronic devices. This article describes a graphene transfer process onto chemically sensitive organic semiconductor thin-films. The process incorporates an elastomeric stamp with a fluorinated polymer release layer that can be removed, post-transfer, via a fluorinated solvent; neither fluorinated material adversely affects the organic semiconductor materials. We used Raman spectroscopy, atomic force microscopy, and scanning electron microscopy to show that chemical vapor deposition graphene can be successfully transferred without inducing defects in the graphene film. To demonstrate our transfer method's compatibility with organic semiconductors, we fabricate three classes of organic thin-film devices: graphene field effect transistors without additional cleaning processes, transparent organic light-emitting diodes, and transparent small-molecule organic photovoltaic devices. These experiments demonstrate the potential of hybrid graphene/organic devices in which graphene is deposited directly onto underlying organic thin-film structures. PMID:25774924

  6. Fabrication of Isolated Metal-Organic Polyhedra in Confined Cavities: Adsorbents/Catalysts with Unusual Dispersity and Activity.

    PubMed

    Kang, Ying-Hu; Liu, Xiao-Dan; Yan, Ni; Jiang, Yao; Liu, Xiao-Qin; Sun, Lin-Bing; Li, Jian-Rong

    2016-05-18

    Metal-organic polyhedra (MOPs) have attracted great attention due to their intriguing structure. However, the applications of MOPs are severely hindered by two shortcomings, namely low dispersity and poor stability. Here we report the introduction of four MOPs (constructed from dicopper and carboxylates) to cavity-structured mesoporous silica SBA-16 via a double-solvent strategy to overcome both shortcomings simultaneously. By judicious design, the dimension of MOPs is just between the size of cavities and entrances of SBA-16, MOP molecules are thus confined in the cavities. This leads to the formation of isolated MOPs with unusual dispersion, making the active sites highly accessible. Hence, the adsorption capacity on carbon dioxide and propene as well as catalytic performance on ring opening are much superior to bulk MOPs. More importantly, the structure and catalytic activity of MOPs in confined cavities are well preserved after exposure to humid atmosphere, whereas those of bulk MOPs are degraded seriously. PMID:27049737

  7. Conductance Thin Film Model of Flexible Organic Thin Film Device using COMSOL Multiphysics

    NASA Astrophysics Data System (ADS)

    Carradero-Santiago, Carolyn; Vedrine-Pauléus, Josee

    We developed a virtual model to analyze the electrical conductivity of multilayered thin films placed above a graphene conducting and flexible polyethylene terephthalate (PET) substrate. The organic layers of poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) as a hole conducting layer, poly(3-hexylthiophene-2,5-diyl) (P3HT), as a p-type, phenyl-C61-butyric acid methyl ester (PCBM) and as n-type, with aluminum as a top conductor. COMSOL Multiphysics was the software we used to develop the virtual model to analyze potential variations and conductivity through the thin-film layers. COMSOL Multiphysics software allows simulation and modeling of physical phenomena represented by differential equations such as heat transfer, fluid flow, electromagnetism, and structural mechanics. In this work, using the AC/DC, electric currents module we defined the geometry of the model and properties for each of the six layers: PET/graphene/PEDOT:PSS/P3HT/PCBM/aluminum. We analyzed the model with varying thicknesses of graphene and active layers (P3HT/PCBM). This simulation allowed us to analyze the electrical conductivity, and visualize the model with varying voltage potential, or bias across the plates, useful for applications in solar cell devices.

  8. EMERGING TECHNOLOGY SUMMARY: DEMONSTRATION OF AMBERSORB 563 ADSORBENT TECHNOLOGY

    EPA Science Inventory

    A field pilot study was conducted to demonstrate the technical feasibility and cost-effectiveness of Ambersorb® 5631 carbonaceous adsorbent for remediating groundwater contaminated with volatile organic compounds (VOCs). The Ambersorb adsorbent technology demonstration consist...

  9. Influence of surface chemistry on the structural organization of monomolecular protein layers adsorbed to functionalized aqueous interfaces.

    PubMed Central

    Lösche, M; Piepenstock, M; Diederich, A; Grünewald, T; Kjaer, K; Vaknin, D

    1993-01-01

    The molecular organization of streptavidin (SA) bound to aqueous surface monolayers of biotin-functionalized lipids and binary lipid mixtures has been investigated with neutron reflectivity and electron and fluorescence microscopy. The substitution of deuterons (2H) for protons (1H), both in subphase water molecules and in the alkyl chains of the lipid surface monolayer, was utilized to determine the interface structure on the molecular length scale. In all cases studied, the protein forms monomolecular layers underneath the interface with thickness values of approximately 40 A. A systematic dependence of the structural properties of such self-assembled SA monolayers on the surface chemistry was observed: the lateral protein density depends on the length of the spacer connecting the biotin moiety and its hydrophobic anchor. The hydration of the lipid head groups in the protein-bound state depends on the dipole moment density at the interface. Images FIGURE 1 FIGURE 2 FIGURE 3 FIGURE 5 FIGURE 11 FIGURE 12 FIGURE A1 PMID:8298041

  10. Combined optical and acoustical method for determination of thickness and porosity of transparent organic layers below the ultra-thin film limit

    NASA Astrophysics Data System (ADS)

    Rodenhausen, K. B.; Kasputis, T.; Pannier, A. K.; Gerasimov, J. Y.; Lai, R. Y.; Solinsky, M.; Tiwald, T. E.; Wang, H.; Sarkar, A.; Hofmann, T.; Ianno, N.; Schubert, M.

    2011-10-01

    Analysis techniques are needed to determine the quantity and structure of materials composing an organic layer that is below an ultra-thin film limit and in a liquid environment. Neither optical nor acoustical techniques can independently distinguish between thickness and porosity of ultra-thin films due to parameter correlation. A combined optical and acoustical approach yields sufficient information to determine both thickness and porosity. We describe application of the combinatorial approach to measure single or multiple organic layers when the total layer thickness is small compared to the wavelength of the probing light. The instrumental setup allows for simultaneous in situ spectroscopic ellipsometry and quartz crystal microbalance dynamic measurements, and it is combined with a multiple-inlet fluid control system for different liquid solutions to be introduced during experiments. A virtual separation approach is implemented into our analysis scheme, differentiated by whether or not the organic adsorbate and liquid ambient densities are equal. The analysis scheme requires that the film be assumed transparent and rigid (non-viscoelastic). We present and discuss applications of our approach to studies of organic surfactant adsorption, self-assembled monolayer chemisorption, and multiple-layer target DNA sensor preparation and performance testing.

  11. Combined optical and acoustical method for determination of thickness and porosity of transparent organic layers below the ultra-thin film limit.

    PubMed

    Rodenhausen, K B; Kasputis, T; Pannier, A K; Gerasimov, J Y; Lai, R Y; Solinsky, M; Tiwald, T E; Wang, H; Sarkar, A; Hofmann, T; Ianno, N; Schubert, M

    2011-10-01

    Analysis techniques are needed to determine the quantity and structure of materials composing an organic layer that is below an ultra-thin film limit and in a liquid environment. Neither optical nor acoustical techniques can independently distinguish between thickness and porosity of ultra-thin films due to parameter correlation. A combined optical and acoustical approach yields sufficient information to determine both thickness and porosity. We describe application of the combinatorial approach to measure single or multiple organic layers when the total layer thickness is small compared to the wavelength of the probing light. The instrumental setup allows for simultaneous in situ spectroscopic ellipsometry and quartz crystal microbalance dynamic measurements, and it is combined with a multiple-inlet fluid control system for different liquid solutions to be introduced during experiments. A virtual separation approach is implemented into our analysis scheme, differentiated by whether or not the organic adsorbate and liquid ambient densities are equal. The analysis scheme requires that the film be assumed transparent and rigid (non-viscoelastic). We present and discuss applications of our approach to studies of organic surfactant adsorption, self-assembled monolayer chemisorption, and multiple-layer target DNA sensor preparation and performance testing. PMID:22047284

  12. A Multi-technique Characterization of Adsorbed Protein Films: Orientation and Structure by ToF-SIMS, NEXAFS, SFG, and XPS

    NASA Astrophysics Data System (ADS)

    Baio, Joseph E.

    immobilization schemes. This protein contained both a hexahistidine tag and a cysteine residue, introduced at opposite ends of the HuLys Fv, for immobilization onto nitrilotriacetic acid (NTA) and maleimide oligo- (ethylene glycol) (MEG)-terminated substrates. The thiol group on the cysteine residue selectively binds to the MEG groups, while the his-tag selectively binds to the Ni-loaded NTA groups. XPS was used to monitor protein coverage on both surfaces by following the change in the nitrogen atomic %. The ToF-SIMS data provided a clear differentiation between the two samples due to the intensity differences of secondary ions originating from asymmetrically located amino acids in HuLys Fv. Indicating that the HuLys Fv fragment when adsorbed into the NTA and MEG substrates will be induced into two different orientations. On the NTA substrate the protein's binding site is accessible, while on the MEG substrate the binding site is oriented towards the surface. By taking advantage of the electron pathway through the heme group in cytochrome c (CytoC) electrochemists have built sensors based upon CytoC immobilized onto functionalized metal electrodes. When immobilized onto a charged surface, CytoC, with its distribution of lysine and glutamate residues around its surface, should orient and form a well-ordered protein film. Here a detailed examination of CytoC orientation when electrostatically immobilized onto both amine (NH 3+) and carboxyl (COO-) functionalized gold is presented. Again, protein coverage, on both surfaces, was monitored by the change in the atomic % N, as determined by XPS. ToF-SIMS data demonstrated a clear separation between the two samples based on the intensity differences of secondary ions stemming from amino acids located asymmetrically within CytoC, indicating opposite orientations of the protein on the two different surfaces. Spectral features within the in situ sum frequency generation vibrational spectra, acquired for the protein interacting with

  13. Heterogeneous Reactions of Surface-Adsorbed Catechol: A Comparison of Tropospheric Aerosol Surrogates

    NASA Astrophysics Data System (ADS)

    Hinrichs, R. Z.; Woodill, L. A.

    2009-12-01

    Surface-adsorbed organics can alter the chemistry of tropospheric solid-air interfaces, such as aerosol and ground level surfaces, thereby impacting photochemical cycles and altering aerosol properties. The nature of the surface can also influence the chemistry of the surface-adsorbed organic. We employed diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) to monitor the adsorption of gaseous catechol on several tropospheric aerosol surrogates and to investigate the subsequent reactivity of adsorbed-catechol with nitrogen dioxide and, in separate preliminary experiments, ozone. Graphite, kaolinite, and sodium halide (NaF, NaCl, NaBr) powders served as carbonaceous, mineral and sea salt aerosol surrogates, respectively. Broad OH stretching bands for adsorbed catechol shifted to lower wavenumber with peak frequencies following the trend NaBr > NaCl > NaF ≈ kaolinite, consistent with the increasing basicity of the halide anions and basic Brønsted sites on kaolinite. The dark heterogeneous reaction of NO2 with NaCl-adsorbed catechol at relative humidity (RH) <2% promoted nitration forming 4-nitrocatechol and oxidation forming 1,2-benzoquinone and the ring cleavage product muconic acid, with product yields of 88%, 8%, and 4%, respectively. 4-Nitrocatechol was the dominant product for catechol adsorbed on NaF and kaolinite, while NaBr-adsorbed catechol produced less 4-nitrocatechol and more 1,2-benzoquinone and muconic acid. For all three sodium halides, the reactions of NO2 with adsorbed catechol were orders of magnitude faster than between NO2 and each NaX substrate. 4-Nitrocatechol rates and product yields were consistent with the relative ability of each substrate to enhance the deprotonated nature of adsorbed-catechol. Increasing the relative humidity caused the rate of each product channel to decrease and also altered the product branching ratios. Most notably, 1,2-benzoquinone formation decreased significantly even at 13% RH. The dramatic

  14. Doped thin films of two organic molecules for light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Giovanella, Umberto; Botta, Chiara; Pasini, Mariacecilia; Porzio, William; Destri, Silvia

    2003-11-01

    The photoluminescence and electroluminescence of doped organic materials are reported for thin films prepared by ultrahigh-vacuum coevaporation and by spin coating from solution of two emitting molecules. For both films, efficient energy transfer from the donor to the acceptor molecules is observed without relevant dopant segregation for molar concentrations up to 10%. In spin-coated films the energy transfer from the matrix to the dopant is due to purely resonant energy transfer processes while the cosublimated films show the presence of additional thermally activated hopping processes. Light-emitting diodes fabricated with coevaporated films yield electroluminescence with higher efficiency and stability.

  15. Electroless plating of honeycomb and pincushion polymer films prepared by self-organization.

    PubMed

    Yabu, Hiroshi; Hirai, Yuji; Shimomura, Masatsugu

    2006-11-01

    This report describes the fabrication and electroless plating of regular porous and pincushion-like polymer structures prepared by self-organization. Honeycomb-patterned films were prepared by simple casting of polymer solution under applied humid air and pincushion structures by peeling off the top layer of the former films. Silver-deposited honeycomb-patterned films and pincushion films were obtained by simple electroless plating of the respective original structures. XPS revealed Ag deposition on the honeycomb-patterned film. After thermal decomposition or solvent elution of the template polymer, unique metal mesoscopic structures were obtained. PMID:17073508

  16. Adsorption mechanism of ester phosphate on baryum titanate in organic medium. Preliminary results on the structure of the adsorbed layer

    NASA Astrophysics Data System (ADS)

    Le Bars, N.; Tinet, D.; Faugère, A. M.; van Damme, H.; Levitz, P.

    1991-05-01

    The purpose of this work is to evidence the adsorption mechanism and the structure of commercial phosphate ester surfactant stabilized BaTiO3 in organic suspension, and to relate these characteristics to rheological behaviour. Binders and plasticizers are omitted to reduce the number of system components. Firstly adsorption isotherm were determined by inductively coupled argon plasma technique and interpretated based on transmission electron microscopy and ^{31}P nuclear magnetic resonance studies. Preliminary rheological measurements were then performed and related to suspension structure. Structure of the adsorption layer is critically discussed. L'objectif de cette étude est la compréhension du mécanisme d'adsorption d'agents dispersants phosphatés dans des suspensions organiques de BaTiO3, ainsi que la caractérisation de la structure, et du comportement rhéologique de ces suspensions. Liants et plastifiants ne sont pas utilisés, afin de réduire le nombre de composants dans le système. Dans un premier temps, l'isotherme d'adsorption est établie par dosage en émission plasma, puis interprétée sur la base de résultats de Microscopie Eloctronique à Transmission, et de spectroscopie par Résonance Magnétique Nucléaire du ^{31}P. Des mesures rhéologiques préliminaires sont effectuées pour caractériser la structure des suspensions.

  17. Fabrication and Performance of Organic Thin Film Solar Cells Using the Brush Painting Method

    NASA Astrophysics Data System (ADS)

    Ishihara, Hirohumi; Kojima, Kenzo; Mizutani, Teruyoshi; Ochiai, Shizuyasu

    As organic solar thin films fabricated by an active layer of organic materials are economical, lightweight, and flexible, as well as facilitating processing, organic solar cells have attracted considerable attention within the past few decades as a clean energy source. With this in mind, there have been global investigations and studies of the power conversion efficiency (PCE) within organic solar cells. In organic thin-film solar cells, the effect of the performance is not only dependent on an adopted active material but also the molecular orientation on the electrode. Using the mixed solution of Poly (3-hexylthiophene) and PCBM, both dissolved by solvent, an organic thin film is fabricated using the paint method (The conceptual diagram of the paint method is shown in Fig. 1) The form of the thin film was evaluated, an organic thin-film solar cell using the paint method for the active layer was made, and its performance was evaluated and examined. Using the mixed solution of Poly(3-hexylthiophene) and PCBM, both dissolved by solvent, an organic thin film is fabricated using the paint method (The conceptual diagram of the paint method is shown in Fig. 1) The morphology of the thin film was evaluated using an AFM image, UV/vis spectra, and so forth. Based on these data, an organic thin-film solar cell that used the paint method for the active layer was fabricated, and the performance was evaluated and examined. For the organic thin film solar cell fabricated using the brush painting method, the open-circuit voltage (Voc) is 0.41 V, the short circuit current density (Jsc) is 2.07 mA/cm2, and the fill factor is 0.34. The efficiency η of PCE becomes 0.29%.

  18. Effect of the adsorbate (Bromacil) equilibrium concentration in water on its adsorption on powdered activated carbon. Part 3: Competition with natural organic matter.

    PubMed

    Al Mardini, Fadi; Legube, Bernard

    2010-10-15

    This study (part 3) was carried out to investigate the effect of the natural organic matter (NOM) concentration on Bromacil (pesticide) adsorption on powdered activated carbon (PAC) in the same experimental conditions as in our previous studies (parts 1 and 2). Our previous findings showed that Bromacil adsorption in buffered pure water (pH 7.8) occurred at two types of site. In the presence of NOM (three kinds), we noted a significant reduction in Bromacil adsorption capacities due to the competitive effects exerted by NOM. Highly reactive sites (or pores) in PAC appeared to be blocked by NOM adsorption, as demonstrated by the application of a pseudo-single solute isotherm and of the simplified ideal adsorbed solution theory (IAST), regardless of the initial Bromacil and NOM concentrations. The competing effect of low-molecular weight NOM was found to be greater than the competing effect of high-molecular weight NOM. The pseudo-second order surface-reaction model fitted Bromacil adsorption particularly well, even in the presence of NOM. However, the adsorption-kinetic constant values were found to be independent of the aqueous equilibrium concentration of the target compound, contrary to that observed in pure water. The kinetic data thus confirmed that high reactivity PAC sites were blocked by NOM adsorption. A practical approach concluded this work. PMID:20619963

  19. A novel dispersive solid-phase extraction method using metal-organic framework MIL-101 as the adsorbent for the analysis of benzophenones in toner.

    PubMed

    Li, Ning; Zhu, Quanfei; Yang, Yang; Huang, Jianlin; Dang, Xueping; Chen, Huaixia

    2015-01-01

    Metal-organic frameworks (MOFs) have been paid widespread attention in the field of adsorption and separation materials due to its porosity, large specific surface area, unsaturated metal-ligand sites and structural diversity. In this study, the green powder MIL-101 was synthesized and used for the extraction of benzophenone, 2,4-dihydroxybenzophenone and 2-hydroxy-4-methoxy-benzophenone from toner samples for the first time. The synthesized MIL-101 was characterized by X-ray diffraction, scanning electron microscopy, thermogravimetry and nitrogen adsorption porosimetry. The MIL-101 was applied as the dispersive solid phase extraction (DSPE) adsorbent for the extraction and preconcentration of benzophenone, 2,4-dihydroxybenzophenone and 2-hydroxy-4-methoxy-benzophenone from toner samples. The extraction conditions were investigated. Under the optimized conditions, a DSPE-HPLC method for the determination of benzophenone, 2,4-dihydroxybenzophenone and 2-hydroxy-4-methoxy-benzophenone was developed. The method yielded a linear calibration curve in the concentration ranges from 4.0 to 3500 μg L(-1) for the three analytes in toner samples with regression coefficients (r(2)) of 0.9992, 0.9999 and 0.9990, respectively. Limits of detection were 1.2, 1.2 and 0.9 μg L(-1), respectively. Both the intra-day and inter-day precisions (RSDs) were <10%. PMID:25476369

  20. Magnetic metal-organic nanotubes: An adsorbent for magnetic solid-phase extraction of polychlorinated biphenyls from environmental and biological samples.

    PubMed

    Li, Qiu-Lin; Wang, Lei-Lei; Wang, Xia; Wang, Ming-Lin; Zhao, Ru-Song

    2016-06-01

    A new type of three-dimensional, echinus-like magnetic Fe3O4 @ cobalt(Ⅱ)-based metal-organic nanotube (Fe3O4 @ Co-MONT) yolk-shell microspheres, have been designed and synthesized for the first time. Fe3O4 @ Co-MONTs yolk-shell microspheres were characterized by scanning electron micrographs, transmission electron microscopy, Fourier transform infrared spectra, X-ray diffraction, and vibrating sample magnetometry. The feasibility of the new material for use as an absorbent was investigated for magnetic solid phase-extraction (MSPE) of polychlorinated biphenyls (PCBs) from environmental water samples and biological samples. The Plackett-Burman design and Box-Behnken design were used to determine and optimize the extraction parameters influencing the extraction efficiency through response surface methodology. Under the optimized conditions, the developed method showed good linearity within the range of 5-1000ngL(-1), low limits of detection (0.31-0.49ngL(-1)), and good reproducibility (RSD<10%). The proposed method was successfully applied for the analysis of PCBs in real environmental water samples. These results demonstrated that Fe3O4 @ Co-MONTs is a promising adsorbent material for the MSPE of PCBs at trace levels from environmental water samples and biological samples. PMID:27156750

  1. Magnetic porous carbon derived from a Zn/Co bimetallic metal-organic framework as an adsorbent for the extraction of chlorophenols from water and honey tea samples.

    PubMed

    Li, Menghua; Wang, Junmin; Jiao, Caina; Wang, Chun; Wu, Qiuhua; Wang, Zhi

    2016-05-01

    A novel magnetic porous carbon derived from a bimetallic metal-organic framework, Zn/Co-MPC, was prepared by introducing cobalt into ZIF-8. Magnetic porous carbon that possesses magnetic properties and a large specific surface area was firstly fabricated by the direct carbonization of Zn/Co-ZIF-8. The prepared magnetic porous carbon material was characterized by scanning electron microscopy, transmission electron microscopy, powder X-ray diffraction, N2 adsorption, and vibrating sample magnetometry. The prepared magnetic porous carbon was used as a magnetic solid-phase extraction adsorbent for the enrichment of chlorophenols from water and honey tea samples before high-performance liquid chromatography analysis. Several experimental parameters that could influence the extraction efficiency were investigated and optimized. Under the optimum conditions, good linearities (r > 0.9957) for all calibration curves were obtained with low limits of detection, which are in the range of 0.1-0.2 ng mL(-1) for all the analytes. The results showed that the prepared magnetic porous carbon had an excellent adsorption capability toward the target analytes. PMID:26991637

  2. Simulation study of twisted crystal growth in organic thin films

    NASA Astrophysics Data System (ADS)

    Fang, Alta; Haataja, Mikko

    2015-10-01

    Many polymer and organic small-molecule thin films crystallize with microstructures that twist or curve in a regular manner as crystal growth proceeds. Here we present a phase-field model that energetically favors twisting of the three-dimensional crystalline orientation about and along particular axes, allowing morphologies such as banded spherulites, curved dendrites, and "s"- or "c"-shaped needle crystals to be simulated. When twisting about the fast-growing crystalline axis is energetically favored and spherulitic growth conditions are imposed, crystallization occurs in the form of banded spherulites composed of radially oriented twisted crystalline fibers. Due to the lack of symmetry, twisting along the normal growth direction leads to heterochiral banded spherulites with opposite twist handedness in each half of the spherulite. When twisting is instead favored about the axis perpendicular to the plane of the substrate and along the normal growth direction under diffusion-limited single-crystalline growth conditions, crystallization occurs in the form of curved dendrites with uniformly rotating branches. We show that the rate at which the branches curve affects not only the morphology but also the overall kinetics of crystallization, as the total crystallized area at a given time is maximized for a finite turning rate.

  3. Simulation study of twisted crystal growth in organic thin films.

    PubMed

    Fang, Alta; Haataja, Mikko

    2015-10-01

    Many polymer and organic small-molecule thin films crystallize with microstructures that twist or curve in a regular manner as crystal growth proceeds. Here we present a phase-field model that energetically favors twisting of the three-dimensional crystalline orientation about and along particular axes, allowing morphologies such as banded spherulites, curved dendrites, and "s"- or "c"-shaped needle crystals to be simulated. When twisting about the fast-growing crystalline axis is energetically favored and spherulitic growth conditions are imposed, crystallization occurs in the form of banded spherulites composed of radially oriented twisted crystalline fibers. Due to the lack of symmetry, twisting along the normal growth direction leads to heterochiral banded spherulites with opposite twist handedness in each half of the spherulite. When twisting is instead favored about the axis perpendicular to the plane of the substrate and along the normal growth direction under diffusion-limited single-crystalline growth conditions, crystallization occurs in the form of curved dendrites with uniformly rotating branches. We show that the rate at which the branches curve affects not only the morphology but also the overall kinetics of crystallization, as the total crystallized area at a given time is maximized for a finite turning rate. PMID:26565254

  4. Hysteresis in pentacene-based organic thin-film transistors

    NASA Astrophysics Data System (ADS)

    Gu, Gong; Kane, Michael G.

    2006-08-01

    Memory effects are commonly seen in organic thin-film transistor (OTFT) characteristics. In the absence of memory effects associated with the gate dielectric, the hysteresis in p-channel pentacene-based OTFTs, as measured in air and under illumination, was found to be dominated by trapped electrons, rather than trapped holes, in the semiconductor. The responsible acceptor type traps have very long lifetime. The immobile, previously stored negative charge requires extra holes to balance it, resulting in early establishment of the channel and extra drain current. This model is unique in that it discusses the majority carrier population influenced by trapped charge opposite in sign to the majority carriers in a simple electrostatic manner, to explain history dependence. The model was supported by drain current transient decay data. This memory effect is ambient and illumination sensitive. We studied the presence or absence of this effect under various ambient and illumination conditions, and found the responsible acceptor type traps mostly extrinsic and their formation reversible. Efforts were taken in the quantitative analysis to exclude the bias stress effect from the memory effect due to the charged acceptors.

  5. Perylene Diimide Based ``Nanofabric'' Thin Films for Organic Photovoltaic Cells

    NASA Astrophysics Data System (ADS)

    Carter, Austin; Park, June Hyoung; Min, Yong; Epstein, Arthur

    2011-03-01

    We report progress in using a perylene diimide (PDI) nanofabric as an effective electron accepting nanostructure for organic photovoltaics (OPV). A key challenge in OPV continues to be the recovery of electrons after charge separation due to the relatively poor mobility of C60 and related materials. A series of PDI compounds and complexes have been synthesized and used to fabricate nanofibers and thin films using solution and vacuum deposition techniques. Overlaping PDI-based nanofibers form a fast electron-transporting ``nanofabric'' that has been characterized (AFM, PL, UV-vis, etc.) and can be blended with electron donating materials. A solution-processible OPV configuration containing a nanofabric heterojunction (FHJ) of poly(3-hexylthiophene) and the PDI nanofabric was investigated. We observed a significant improvement in power-conversion efficiency due in part to expansion of the interfacial area and the presence of high mobility electron pathways to the LiF/Al electrode. This work is supported by the Wright Center for Photovoltaic Innovation and Commercialization, the Institute for Materials Research and the Center for Affordable Nanoengineering of Polymeric Biomedical Devices.

  6. Adsorption of Polyethylene from Solution onto Starch Film Surfaces

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Since starch adsorbs onto polyethylene (PE) surfaces from cooled solutions of jet cooked starch, this study was carried out to determine whether adsorption of PE onto hydrophilic starch film surfaces would also take place if starch films were placed in hot solutions of PE in organic solvents, and th...

  7. 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.

  8. Chemical and biological sensing with organic thin-film transistors

    NASA Astrophysics Data System (ADS)

    Mabeck, Jeffrey Todd

    Organic thin-film transistors (OTFTs) offer a great deal of promise for applications in chemical and biological sensing where there is a demand for small, portable, and inexpensive sensors. OTFTs have many advantages over other types of sensors, including low-cost fabrication, straightforward miniaturization, simple instrumentation, and inherent signal amplification. This dissertation examines two distinct types of OTFTs: organic field-effect transistors (OFETs) based on pentacene, and organic electrochemical transistors (OECTs) based on poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS). The bulk of the previous work on sensing with OFETs has focused on gas sensing, and this dissertation contributes to this body of work by briefly treating the large, reversible response of pentacene OFETs to humidity. However, there are many applications where the analyte of interest must be detected in an aqueous environment rather than a gaseous environment, and very little work has been done in this area for OFETs. Therefore, the integration of pentacene OFETs with microfluidics is treated in detail. Using poly(dimethylsiloxane) (PDMS) microfluidic channels to confine aqueous solutions over the active region of pentacene transistors, it is demonstrated that the current-voltage characteristics remain stable under aqueous flow with a decrease in mobility of ˜30% compared to its value when dry. The operation of PEDOT:PSS transistors is also treated in detail. It is demonstrated that their transistor behavior cannot be attributed solely to a field effect and that ion motion is key to the switching mechanism. It is also demonstrated that simple glucose sensors based on PEDOT:PSS OECTs are sensitive to low glucose concentrations below 1 mM, therefore showing promise for potential application in the field of noninvasive glucose monitoring for diabetic patients using saliva rather than blood samples. Furthermore, a novel microfluidic gating technique has been

  9. High flux thin film nanocomposite membranes based on metal-organic frameworks for organic solvent nanofiltration.

    PubMed

    Sorribas, Sara; Gorgojo, Patricia; Téllez, Carlos; Coronas, Joaquín; Livingston, Andrew G

    2013-10-01

    Thin-film nanocomposite membranes containing a range of 50-150 nm metal-organic framework (MOF) nanoparticles [ZIF-8, MIL-53(Al), NH2-MIL-53(Al) and MIL-101(Cr)] in a polyamide (PA) thin film layer were synthesized via in situ interfacial polymerization on top of cross-linked polyimide porous supports. MOF nanoparticles were homogeneously dispersed in the organic phase containing trimesoyl chloride prior to the interfacial reaction, and their subsequent presence in the PA layer formed was inferred by a combination of contact angle measurements, FT-IR spectroscopy, SEM, EDX, XPS, and TEM. Membrane performance in organic solvent nanofiltration was evaluated on the basis of methanol (MeOH) and tetrahydrofuran (THF) permeances and rejection of styrene oligomers (PS). The effect of different post-treatments and MOF loadings on the membrane performance was also investigated. MeOH and THF permeance increased when MOFs were embedded into the PA layer, whereas the rejection remained higher than 90% (molecular weight cutoff of less than 232 and 295 g·mol(-1) for MeOH and THF, respectively) in all membranes. Moreover, permeance enhancement increased with increasing pore size and porosity of the MOF used as filler. The incorporation of nanosized MIL-101(Cr), with the largest pore size of 3.4 nm, led to an exceptional increase in permeance, from 1.5 to 3.9 and from 1.7 to 11.1 L·m(-2)·h(-1)·bar(-1) for MeOH/PS and THF/PS, respectively. PMID:24044635

  10. Protection of MoO{sub 3} high work function by organic thin film

    SciTech Connect

    Wang, Chenggong; Irfan, Irfan; Gao, Yongli

    2014-11-03

    The effects of air exposure are investigated for molybdenum trioxide (MoO{sub 3}) covered with organic thin films using ultraviolet photoemission spectroscopy. It is found that the severe drop of the work function of MoO{sub 3} by air exposure is substantially reduced by the organic thin films. Both CuPc and C{sub 60} are used for the investigations. The results indicate that the MoO{sub 3} surface can be passivated by approximately two monolayers of organic thin films against exposure to air.

  11. Fluorescence dynamics of microsphere-adsorbed sunscreens

    NASA Astrophysics Data System (ADS)

    Krishnan, R.

    2005-03-01

    Sunscreens are generally oily substances which are prepared in organic solvents, emulsions or dispersions with micro- or nanoparticles. These molecules adsorb to and integrate into skin cells. In order to understand the photophysical properties of the sunscreen, we compare steady-state and time-resolved fluorescence in organic solvent of varying dielectric constant ɛ and adsorbed to polystyrene microspheres and dispersed in water. Steady-state fluorescence is highest and average fluorescence lifetime longest in toluene, the solvent of lowest ɛ. However, there is no uniform dependence on ɛ. Sunscreens PABA and padimate-O show complex emission spectra. Microsphere-adsorbed sunscreens exhibit highly non-exponential decay, illustrative of multiple environments of the adsorbed molecule. The heterogeneous fluorescence dynamics likely characterizes sunscreen adsorbed to cells.

  12. New method for fast morphological characterization of organic polycrystalline films by polarized optical microscopy

    NASA Astrophysics Data System (ADS)

    He, Xiao-Chuan; Yang, Jian-Bing; Yan, Dong-Hang; Weng, Yu-Xiang

    2015-07-01

    A new method to visualize the large-scale crystal grain morphology of organic polycrystalline films is proposed. First, optical anisotropic transmittance images of polycrystalline zinc phthalocyanine (ZnPc) films vacuum deposited by weak epitaxial growth (WEG) method were acquired with polarized optical microscopy (POM). Then morphology properties including crystal grain size, distribution, relative orientation, and crystallinity were derived from these images by fitting with a transition dipole model. At last, atomic force microscopy (AFM) imaging was carried out to confirm the fitting and serve as absolute references. This method can be readily generalized to other organic polycrystalline films, thus providing an efficient way to access the large-scale morphologic properties of organic polycrystalline films, which may prove to be useful in industry as a film quality monitoring method. Project supported by the National Natural Science Foundation of China (Grant No. 20933010) and the National Basic Research Program of China (Grant No. 2013CB834800).

  13. Emission Characteristics of Organic Light-Emitting Diodes and Organic Thin-Films with Planar and Corrugated Structures

    PubMed Central

    Wei, Mao-Kuo; Lin, Chii-Wann; Yang, Chih-Chung; Kiang, Yean-Woei; Lee, Jiun-Haw; Lin, Hoang-Yan

    2010-01-01

    In this paper, we review the emission characteristics from organic light-emitting diodes (OLEDs) and organic molecular thin films with planar and corrugated structures. In a planar thin film structure, light emission from OLEDs was strongly influenced by the interference effect. With suitable design of microcavity structure and layer thicknesses adjustment, optical characteristics can be engineered to achieve high optical intensity, suitable emission wavelength, and broad viewing angles. To increase the extraction efficiency from OLEDs and organic thin-films, corrugated structure with micro- and nano-scale were applied. Microstructures can effectively redirects the waveguiding light in the substrate outside the device. For nanostructures, it is also possible to couple out the organic and plasmonic modes, not only the substrate mode. PMID:20480033

  14. Using Organic Light-Emitting Electrochemical Thin-Film Devices to Teach Materials Science

    ERIC Educational Resources Information Center

    Sevian, Hannah; Muller, Sean; Rudmann, Hartmut; Rubner, Michael F.

    2004-01-01

    Materials science can be taught by applying organic light-emitting electrochemical thin-film devices and in this method students were allowed to make a light-emitting device by spin coating a thin film containing ruthenium (II) complex ions onto a glass slide. Through this laboratory method students are provided with the opportunity to learn about…

  15. Highly Crystalline Films of Organic Small Molecules with Alkyl Chains Fabricated by Weak Epitaxy Growth.

    PubMed

    Zhu, Yangjie; Chen, Weiping; Wang, Tong; Wang, Haibo; Wang, Yue; Yan, Donghang

    2016-05-12

    Because side-chain engineering of organic conjugated molecules has been widely utilized to tune organic solid-state optoelectronic properties, the achievement of their high-quality films is important for realizing high-performance devices. Here, highly crystalline films of an organic molecule with short alkyl chains, 5,8,15,18-tetrabutyl-5,8,15,18-tetrahydroindolo[3,2-a]indole[30,20:5,6]quinacridone (C4-IDQA), are fabricated by weak epitaxy growth, and highly oriented, large-area, and continuous films are obtained. Because of the soft matter properties, the C4-IDQA molecules can adjust themselves to realize commensurate epitaxy growth on the inducing layers and exhibited good lattice matching in the thin film phase. The crystalline phase is also observed in thicker C4-IDQA films. The growth behavior of C4-IDQA on the inducing layer is further investigated, including the strong dependence of film morphologies on substrate temperatures and deposition rates due to the poor diffusion ability of C4-IDQA molecules. Moreover, highly crystalline films and high electron field-effect mobility are also obtained for the small molecule N,N'-dioctyl-3,4:9,10-perylene tetracarboxylic diimide (C8-PTCDI), which demonstrate that the weak epitaxy growth method could be an effective way to fabricate highly crystalline films of organic small molecules with flexible side chains. PMID:27116036

  16. PERVAPORATION USING ADSORBENT-FILLED MEMBRANES

    EPA Science Inventory

    Membranes containing selective fillers, such as zeolites and activated carbon, can improve the separation by pervaporation. Applications of adsorbent-filled membranes in pervaporation have been demonstrated by a number of studies. These applications include removal of organic co...

  17. Integration of metal-organic frameworks into an electrochemical dielectric thin film for electronic applications

    PubMed Central

    Li, Wei-Jin; Liu, Juan; Sun, Zhi-Hua; Liu, Tian-Fu; Lü, Jian; Gao, Shui-Ying; He, Chao; Cao, Rong; Luo, Jun-Hua

    2016-01-01

    The integration of porous metal-organic frameworks onto the surface of materials, for use as functional devices, is currently emerging as a promising approach for gas sensing and flexible displays. However, research focused on potential applications in electronic devices is in its infancy. Here we present a facile strategy by which interpenetrated, crystalline metal-organic framework films are deposited onto conductive metal-plate anodes via in situ temperature-controlled electrochemical assembly. The nanostructure of the surface as well as the thickness and uniformity of the film are well controlled. More importantly, the resulting films exhibit enhanced dielectric properties compared to traditional inorganic or organic gate dielectrics. This study demonstrates the successful implementation of the rational design of metal-organic framework thin films on conductive supports with high-performance dielectric properties. PMID:27282348

  18. Integration of metal-organic frameworks into an electrochemical dielectric thin film for electronic applications

    NASA Astrophysics Data System (ADS)

    Li, Wei-Jin; Liu, Juan; Sun, Zhi-Hua; Liu, Tian-Fu; Lü, Jian; Gao, Shui-Ying; He, Chao; Cao, Rong; Luo, Jun-Hua

    2016-06-01

    The integration of porous metal-organic frameworks onto the surface of materials, for use as functional devices, is currently emerging as a promising approach for gas sensing and flexible displays. However, research focused on potential applications in electronic devices is in its infancy. Here we present a facile strategy by which interpenetrated, crystalline metal-organic framework films are deposited onto conductive metal-plate anodes via in situ temperature-controlled electrochemical assembly. The nanostructure of the surface as well as the thickness and uniformity of the film are well controlled. More importantly, the resulting films exhibit enhanced dielectric properties compared to traditional inorganic or organic gate dielectrics. This study demonstrates the successful implementation of the rational design of metal-organic framework thin films on conductive supports with high-performance dielectric properties.

  19. Vibrational studies of molecular organization in evaporated phthalocyanine thin solid films

    SciTech Connect

    Aroca, R.; Thedchanamoorthy, A.

    1995-01-01

    This report presents results on the study of the molecular organization, utilizing transmission and reflection absorption FTIR spectroscopy, of thin films of phthalocyanine complexes and metal free phthalocyanine. The spatial anisotropy was probed.

  20. Contribution of selected perfluoroalkyl and polyfluoroalkyl substances to the adsorbable organically bound fluorine in German rivers and in a highly contaminated groundwater.

    PubMed

    Willach, Sarah; Brauch, Heinz-Jürgen; Lange, Frank T

    2016-02-01

    Due to the lack of analytical standards the application of surrogate parameters for organofluorine detection in the aquatic environment is a complementary approach to single compound target analysis of perfluoroalkyl and polyfluoroalkyl chemicals (PFASs). The recently developed method adsorbable organically bound fluorine (AOF) is based on adsorption of organofluorine chemicals to activated carbon followed by combustion ion chromatography. This AOF method was further simplified to enable measurement of larger series of environmental samples. The limit of quantification (LOQ) was 0.77 μg/L F. The modified protocol was applied to 22 samples from German rivers, a municipal wastewater treatment plant (WWTP) effluent, and four groundwater samples from a fire-fighting training site. The WWTP effluent (AOF = 1.98 μg/L F) and only three river water samples (AOF between 0.88 μg/L F and 1.47 μg/L F) exceeded the LOQ. The AOF levels in a PFASs plume at a heavily contaminated site were in the range of 162 ± 3 μg/L F to 782 ± 43 μg/L F. In addition to AOF 17 PFASs were analyzed by high performance liquid chromatography-tandem mass spectrometry. 32-51% of AOF in the contaminated groundwater samples were explained by individual PFASs wheras in the surface waters more than 95% remained unknown. Organofluorine of two fluorinated pesticides, one pesticide metabolite and three fluorinated pharmaceuticals was recovered as AOF by >50% from all four tested water matrices. It is suggested that in the diffusely contaminated water bodies such fluorinated chemicals and not monitored PFASs contribute significantly to AOF. PMID:26692511

  1. 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.

  2. Solvent-induced changes in PEDOT:PSS films for organic electrochemical transistors

    SciTech Connect

    Zhang, Shiming; Kumar, Prajwal; Nouas, Amel Sarah; Fontaine, Laurie; Tang, Hao; Cicoira, Fabio

    2015-01-01

    Organic electrochemical transistors based on the conducting polymer poly(3,4-ethylenedioxythiophene) doped with poly(styrenesulfonate) (PEDOT:PSS) are of interest for several bioelectronic applications. In this letter, we investigate the changes induced by immersion of PEDOT:PSS films, processed by spin coating from different mixtures, in water and other solvents of different polarities. We found that the film thickness decreases upon immersion in polar solvents, while the electrical conductivity remains unchanged. The decrease in film thickness is minimized via the addition of a cross-linking agent to the mixture used for the spin coating of the films.

  3. Investigation of thin films of organic-based magnets grown by physical vapor deposition

    SciTech Connect

    Kao, C. Y.; Lu, Y.; Li, B.; Yoo, J.-W.; Epstein, A. J.

    2014-10-06

    Thin films of organic-based magnet, V[TCNE]{sub x} (TCNE: tetracyanoethylene), were deposited by physical vapor deposition (PVD) based reactive evaporation. The growth conditions were studied in detail. A saturated composition of V[TCNE]{sub ∼1.9} was determined by optimizing the growth condition. Two sets of films with different V to TCNE ratios were characterized. Both films were magnetic ordered up to 400 K and held coercive field of 60 Oe at room temperature. With the presence of excess vanadium within the film, the increase of defects created by PVD results in significant change in electronic property.

  4. Adhesive flexible barrier film, method of forming same, and organic electronic device including same

    DOEpatents

    Blizzard, John Donald; Weidner, William Kenneth

    2013-02-05

    An adhesive flexible barrier film comprises a substrate and a barrier layer disposed on the substrate. The barrier layer is formed from a barrier composition comprising an organosilicon compound. The adhesive flexible barrier film also comprises an adhesive layer disposed on the barrier layer and formed from an adhesive composition. A method of forming the adhesive flexible barrier film comprises the steps of disposing the barrier composition on the substrate to form the barrier layer, disposing the adhesive composition on the barrier layer to form the adhesive layer, and curing the barrier layer and the adhesive layer. The adhesive flexible barrier film may be utilized in organic electronic devices.

  5. Organic ferroelectric gate field-effect transistor memory using high-mobility rubrene thin film

    NASA Astrophysics Data System (ADS)

    Kanashima, Takeshi; Katsura, Yuu; Okuyama, Masanori

    2014-01-01

    An organic ferroelectric gate field-effect transistor (FET) memory has been fabricated using an organic semiconductor of rubrene thin film with a high mobility and a gate insulating layer of poly(vinylidene fluoride-tetrafluoroethylene) [P(VDF-TeFE)] thin film. A rubrene thin-film sheet was grown by physical vapor transport (PVT), and placed onto a spin-coated P(VDF-TeFE) thin-film layer, and Au source and drain electrodes were formed on this rubrene thin film. A hysteresis loop of the drain current-gate voltage (ID-VG) characteristic has been clearly observed in the ferroelectric gate FET, and is caused by the ferroelectricity. The maximum drain current is 1.5 × 10-6 A, which is about two orders of magnitude larger than that of the P(VDF-TeFE) gate FET using a pentacene thin film. Moreover, the mobility of this organic ferroelectric gate FET using rubrene thin film is 0.71 cm2 V-1 s-1, which is 35 times larger than that of the FET with pentacene thin film.

  6. Intramolecular and Intermolecular Interactions in Hybrid Organic-Inorganic Alucone Films Grown by Molecular Layer Deposition.

    PubMed

    Park, Yi-Seul; Kim, Hyein; Cho, Boram; Lee, Chaeyun; Choi, Sung-Eun; Sung, Myung Mo; Lee, Jin Seok

    2016-07-13

    Investigation of molecular interactions in polymeric films is crucial for understanding and engineering multiscale physical phenomena correlated to device function and performance, but this often involves a compromise between theoretical and experimental data, because of poor film uniformity. Here, we report the intramolecular and intermolecular interactions inside the ultrathin and conformal hybrid organic-inorganic alucone films grown by molecular layer deposition, based on sequential and self-limiting surface reactions. Varying the carbon chain length of organic precursors, which affects their molecular flexibility, caused intramolecular interactions such as double reactions by bending of the molecular backbone, resulting in formation of hole vacancies in the films. Furthermore, intermolecular interactions in alucone polymeric films are dependent on the thermal kinetics of molecules, leading to binding failures and cross-linking at low and high growth temperatures, respectively. We illustrate these key interactions and identify molecular geometries and potential energies by density functional theory calculations. PMID:27314844

  7. Hybrid Transparent Conductive Films of Multilayer Graphene and Metal Grid for Organic Photovoltaics

    NASA Astrophysics Data System (ADS)

    Kim, Sung Man; Walker, Bright; Seo, Jung Hwa; Kang, Seong Jun

    2013-12-01

    Organic solar cells (OSCs) were fabricated on hybrid transparent conductive films consisting of multilayer graphene (MLG) and metal grids. MLG was transferred onto Ag grids to form hybrid transparent conductive films. The optical transmittance was found to be 87% at a wavelength of 550 nm, while the sheet resistance was measured to be 28 +/-7.9 Ω/square. The device characteristics of OSCs prepared on the hybrid films include an open circuit voltage of 0.58 V, a short circuit current of 8.05 mA/cm2, a fill factor of 51%, and a power conversion efficiency (PCE) of 2.38%. The PCE shows 11% improvement compared with that of OSCs fabricated using MLG films without Ag grids. This improvement can be attributed to the reduced sheet resistance of the hybrid film. These results indicate that hybrid films comprising MLG deposited on Ag grids constitute a promising transparent electrode for improving performance in OSCs.

  8. Metal-organic chemical vapor deposition of aluminum oxide thin films via pyrolysis of dimethylaluminum isopropoxide

    SciTech Connect

    Schmidt, Benjamin W.; Sweet, William J. III; Rogers, Bridget R.; Bierschenk, Eric J.; Gren, Cameron K.; Hanusa, Timothy P.

    2010-03-15

    Metal-organic chemical vapor deposited aluminum oxide films were produced via pyrolysis of dimethylaluminum isopropoxide in a high vacuum reaction chamber in the 417-659 deg. C temperature range. Deposited films contained aluminum, oxygen, and carbon, and the carbon-to-aluminum ratio increased with increased deposition temperature. Aluminum-carbon bonding was observed in films deposited at 659 deg. C by x-ray photoelectron spectroscopy, but not in films deposited at 417 deg. C. The apparent activation energy in the surface reaction controlled regime was 91 kJ/mol. The O/Al and C/Al ratios in the deposited films were greater and less than, respectively, the ratios predicted by the stoichiometry of the precursor. Flux analysis of the deposition process suggested that the observed film stoichiometries could be explained by the participation of oxygen-containing background gases present in the reactor at its base pressure.

  9. Room temperature synthesis of covalent-organic framework films through vapor-assisted conversion.

    PubMed

    Medina, Dana D; Rotter, Julian M; Hu, Yinghong; Dogru, Mirjam; Werner, Veronika; Auras, Florian; Markiewicz, John T; Knochel, Paul; Bein, Thomas

    2015-01-28

    We describe the facile synthesis of several two-dimensional covalent-organic frameworks (2D COFs) as films by vapor-assisted conversion at room temperature. High-quality films of benzodithiophene-containing BDT-COF and COF-5 with tunable thickness were synthesized under different conditions on various substrates. BDT-COF films of several micrometer thickness exhibit mesoporosity as well as textural porosity, whereas thinner BDT-COF films materialize as a cohesive dense layer. In addition, we studied the formation of COF-5 films with different solvent mixture compositions serving as vapor source. Room temperature vapor-assisted conversion is an excellent method to form COF films of fragile precursors and on sensitive substrates. PMID:25539131

  10. Room Temperature Synthesis of Covalent–Organic Framework Films through Vapor-Assisted Conversion

    PubMed Central

    2014-01-01

    We describe the facile synthesis of several two-dimensional covalent–organic frameworks (2D COFs) as films by vapor-assisted conversion at room temperature. High-quality films of benzodithiophene-containing BDT-COF and COF-5 with tunable thickness were synthesized under different conditions on various substrates. BDT-COF films of several micrometer thickness exhibit mesoporosity as well as textural porosity, whereas thinner BDT-COF films materialize as a cohesive dense layer. In addition, we studied the formation of COF-5 films with different solvent mixture compositions serving as vapor source. Room temperature vapor-assisted conversion is an excellent method to form COF films of fragile precursors and on sensitive substrates. PMID:25539131

  11. The origin of inverse absorption bands observed in the far-infrared RAIRS spectra of SnCl 4 and SnBr 4 adsorbed on thin-film SnO 2 surfaces

    NASA Astrophysics Data System (ADS)

    Awaluddin, A.; Pilling, M. J.; Wincott, P. L.; LeVent, S.; Surman, M.; Pemble, M. E.; Gardner, P.

    2002-04-01

    The adsorption of SnCl 4 and SnBr 4 on polycrystalline SnO 2 has been studied using synchrotron radiation based far-infrared reflection absorption infrared spectroscopy FIR-RAIRS. In order to exploit the sensitivity advantages of the buried metal layer method, the SnO 2 is in the form of a thin film deposited on a tungsten foil substrate. Adsorption of SnCl 4 and SnBr 4 on an oxygen sputtered surface at 120 K results in spectra characteristic of condensed multilayers. In addition, both spectra exhibit an inverse absorption band centred at 355 cm -1. Modified 4-layer, wavelength-dependent, Greenler calculations show that this inverse absorption band is induced by the presence of the adsorbate but is characteristic of the SnO 2 layer. The lack of any frequency shift upon changing the adsorbate from SnCl 4 to SnBr 4 rules out the possibility that the inverse absorption band is due to a dipole-forbidden parallel mode of the molecule excited via the interaction with free electron oscillations in the metal, resulting from the radiation induced oscillating electric field just below the surface.

  12. Detection of volatile organic compounds using optical fibre long period grating modified with metal organic framework thin films

    NASA Astrophysics Data System (ADS)

    Hromadka, Jiri; Tokay, Begum; Korposh, Sergiy; James, Stephen; Tatam, Ralph P.

    2015-09-01

    An optical fibre long period grating (LPG) modified with a thin film of ZIF-8, a zeolitic immidazol framework (ZIF) material, a subgroup of the metal organic framework (MOF) family, was employed for the detection of organic vapours. ZIF-8 film was deposited onto the surface of the LPG using an in-situ crystallization technique. The sensing mechanism is based on the measurement of the refractive index (RI) change induced by the penetration of the chemical molecules into the ZIF-8 pores. An LPG modified with 5 growth cycles of ZIF-8 responded to exposure to methanol and ethanol vapours.

  13. 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

  14. 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

  15. On the dielectric and optical properties of surface-anchored metal-organic frameworks: A study on epitaxially grown thin films

    NASA Astrophysics Data System (ADS)

    Redel, Engelbert; Wang, Zhengbang; Walheim, Stefan; Liu, Jinxuan; Gliemann, Hartmut; Wöll, Christof

    2013-08-01

    We determine the optical constants of two highly porous, crystalline metal-organic frameworks (MOFs). Since it is problematic to determine the optical constants for the standard powder modification of these porous solids, we instead use surface-anchored metal-organic frameworks (SURMOFs). These MOF thin films are grown using liquid phase epitaxy (LPE) on modified silicon substrates. The produced SURMOF thin films exhibit good optical properties; these porous coatings are smooth as well as crack-free, they do not scatter visible light, and they have a homogenous interference color over the entire sample. Therefore, spectroscopic ellipsometry (SE) can be used in a straightforward fashion to determine the corresponding SURMOF optical properties. After careful removal of the solvent molecules used in the fabrication process as well as the residual water adsorbed in the voids of this highly porous solid, we determine an optical constant of n = 1.39 at a wavelength of 750 nm for HKUST-1 (stands for Hong Kong University of Science and Technology-1; and was first discovered there) or [Cu3(BTC)2]. After exposing these SURMOF thin films to moisture/EtOH atmosphere, the refractive index (n) increases to n = 1.55-1.6. This dependence of the optical properties on water/EtOH adsorption demonstrates the potential of such SURMOF materials for optical sensing.

  16. O K-edge x-ray magnetic circular dichroism of atomic O adsorbed on an ultrathin Co/Cu(100) film: Comparison with molecular CO on Co/Cu(100)

    NASA Astrophysics Data System (ADS)

    Amemiya, Kenta; Yokoyama, Toshihiko; Yonamoto, Yoshiki; Matsumura, Daiju; Ohta, Toshiaki

    2001-10-01

    We observed O K-edge x-ray magnetic circular dichroism (XMCD) of atomic O adsorbed on a fcc Co thin film grown epitaxially on Cu(100). The XMCD of c(2×2)O showed a negative sign at the O1s-->2p transition. The negative sign indicates parallel alignment of the O orbital moment with the substrate magnetization. This finding is in contrast to the CO/Co/Cu(100) case where a positive XMCD was observed at the O1s-->CO2π* transition. A possible explanation for this discrepancy is proposed referring to recent theoretical prediction [Pick et al., Phys. Rev. B 59, 4195 (1999)].

  17. Initial stages of organic film growth characterized by thermal desorption spectroscopy

    NASA Astrophysics Data System (ADS)

    Winkler, Adolf

    2016-01-01

    In the wake of the increasing importance of organic electronics, a more in-depth understanding of the early stages of organic film growth is indispensable. In this review a survey of several rod-like and plate-like organic molecules (p-quaterphenyl, p-sexiphenyl, hexaazatriphenylene-hexacarbonitrile (HATCN), rubicene, indigo) deposited on various application relevant substrates (gold, silver, mica, silicon dioxide) is given. The focus is particularly put on the application of thermal desorption spectroscopy to shed light on the kinetics and energetics of the molecule-substrate interaction. While each adsorption system reveals a manifold of features that are specific for the individual system, one can draw some general statements on the early stages of organic film formation from the available datasets. Among the important issues in this context is the formation of wetting layers and the dewetting as a function of the substrate surface conditions, organic film thickness and temperature.

  18. Initial stages of organic film growth characterized by thermal desorption spectroscopy

    PubMed Central

    Winkler, Adolf

    2015-01-01

    In the wake of the increasing importance of organic electronics, a more in-depth understanding of the early stages of organic film growth is indispensable. In this review a survey of several rod-like and plate-like organic molecules (p-quaterphenyl, p-sexiphenyl, hexaazatriphenylene-hexacarbonitrile (HATCN), rubicene, indigo) deposited on various application relevant substrates (gold, silver, mica, silicon dioxide) is given. The focus is particularly put on the application of thermal desorption spectroscopy to shed light on the kinetics and energetics of the molecule-substrate interaction. While each adsorption system reveals a manifold of features that are specific for the individual system, one can draw some general statements on the early stages of organic film formation from the available datasets. Among the important issues in this context is the formation of wetting layers and the dewetting as a function of the substrate surface conditions, organic film thickness and temperature. PMID:26778860

  19. Fabrication of organic-inorganic perovskite thin films for planar solar cells via pulsed laser deposition

    NASA Astrophysics Data System (ADS)

    Liang, Yangang; Yao, Yangyi; Zhang, Xiaohang; Hsu, Wei-Lun; Gong, Yunhui; Shin, Jongmoon; Wachsman, Eric D.; Dagenais, Mario; Takeuchi, Ichiro

    2016-01-01

    We report on fabrication of organic-inorganic perovskite thin films using a hybrid method consisting of pulsed laser deposition (PLD) of lead iodide and spin-coating of methylammonium iodide. Smooth and highly crystalline CH3NH3PbI3 thin films have been fabricated on silicon and glass coated substrates with fluorine doped tin oxide using this PLD-based hybrid method. Planar perovskite solar cells with an inverted structure have been successfully fabricated using the perovskite films. Because of its versatility, the PLD-based hybrid fabrication method not only provides an easy and precise control of the thickness of the perovskite thin films, but also offers a straightforward platform for studying the potential feasibility in using other metal halides and organic salts for formation of the organic-inorganic perovskite structure.

  20. Permeability of acetic acid through organic films at the air-aqueous interface.

    PubMed

    Gilman, Jessica B; Vaida, Veronica

    2006-06-22

    Recent field studies of collected aerosol particles, both marine and continental, show that the outermost layers contain long-chain (C >or= 18) organics. The presence of these long-chain organics could impede the transport of gases and other volatile species across the interface. This could effect the particle's composition, lifetime, and heterogeneous chemistry. In this study, the uptake rate of acetic acid vapor across a clean interface and through films of long-chain organics into an aqueous subphase solution containing an acid-base indicator (bromocresol green) was measured under ambient conditions using visible absorption spectroscopy. Acetic acid is a volatile organic compound (VOC) and is an atmospherically relevant organic acid. The uptake of acetic acid through single-component organic films of 1-octadecanol (C(18)H(38)O), 1-triacontanol (C(30)H(62)O), cis-9-octadecen-1-ol (C(18)H(36)O), and nonacosane (C(29)H(60)) in addition to two mixed films containing equimolar 1-triacontanol/nonacosane and equimolar 1-triacontanol/cis-9-octadecen-1-ol was determined. These species represent long-chain organic compounds that reside at the air-aqueous interface of atmospheric aerosols. The cis-9-octadecen-1-ol film had little effect on the net uptake rate of acetic acid vapor into solution; however, the uptake rate was reduced by almost one-half by an interfacial film of 1-triacontanol. The measured uptake rates were used to calculate the permeability of acetic acid through the various films which ranged from 1.5 x 10(-3) cm s(-1) for 1-triacontanol, the least permeable film, to 2.5 x 10(-2) cm s(-1) for cis-9-octadecen-1-ol, the most permeable film. Both mixed films had permeabilities that were between that of the single-component films comprising the mixture. This shows that the permeability of a mixed film may not be solely determined by the most permeable species in the mixture. The permeabilities of all the films studied here are discussed in relation to their

  1. The structure of deuterated benzene films adsorbed on the graphite (0001) basal plane: what happens below and above the monolayer coverage?

    PubMed

    Bahn, Emanuel; Hedgeland, Holly; Jardine, Andrew P; Henry, Paul F; Hansen, Thomas C; Fouquet, Peter

    2014-10-28

    An exact description of the interactions in aromatic carbon systems is a key condition for the design of carbon based nanomaterials. In this paper we investigate the binding and adsorbate structure of the simplest prototype system in this class - the single aromatic ring molecule benzene on graphite. We have collected neutron diffraction data of the ordered phase of deuterated benzene, C6D6, adsorbed on the graphite (0001) basal plane surface. We examined relative coverages from 0.15 up to 1.3 monolayers (ML) in a temperature range of 80 to 250 K. The results confirm the flat lying commensurate (√7 × √7)R19.1° monolayer with lattice constants a = b = 6.5 Å at coverages of less than 1 ML. For this structure we observe a progressive melting well below the desorption temperature. At higher coverages we do neither observe an ordered second layer nor a densification of the structure by upright tilting of first layer molecules, as generally assumed up to now. Instead, we see the formation of clusters with a bulk crystalline structure for coverages only weakly exceeding 1 ML. PMID:25209023

  2. Interfacial properties of mixed films of long-chain organics at the air-water interface

    NASA Astrophysics Data System (ADS)

    Gilman, Jessica B.; Tervahattu, Heikki; Vaida, Veronica

    Organic molecules residing at the air-water interface of atmospheric aerosols will have a critical and direct effect on the aerosols' chemical, physical, and optical properties. It is important to study the interfacial properties of such compounds in order to accurately assess these effects. In this study, the compositions of two organic binary films at the air-water interface were monitored as a function of exposure time to the ambient atmosphere. One film was composed of tetracosanoic acid (lignoceric acid, CH 3(CH 2) 22COOH) and nonacosane (C 29H 60), and the second film was composed of octadecanoic acid (stearic acid, CH 3(CH 2) 16COOH) and octadecane (C 18H 38). These films were used as simplified proxies for the organic coating on atmospheric aerosols. The effect of lengthening the hydrocarbon chain on the interfacial longevity of the compounds in the mixed organic film at the air-aqueous interface was determined. The results show that octadecane in a mixed film desorbs from the interface after 72 h while octadecanoic acid remains. For nonacosane, further lengthening of the carbon chain greatly increased its interfacial longevity so that it was comparable with the fatty acids, which remained stable at the interface for at least 144 h. These results are used to explain the preponderance of long-chain fatty acids on the surfaces of collected aerosols and give insight into the degree to which the presence of other long-chain organics may affect the aerosol's chemical and physical properties.

  3. A new 68Ge/68Ga generator system using an organic polymer containing N-methylglucamine groups as adsorbent for 68Ge.

    PubMed

    Nakayama, M; Haratake, M; Ono, M; Koiso, T; Harada, K; Nakayama, H; Yahara, S; Ohmomo, Y; Arano, Y

    2003-01-01

    A macroporous styrene-divinylbenzene copolymer containing N-methylglucamine groups was selected for a new 68Ge/68Ga generator system. This resin packed into a column effectively adsorbed the parent nuclide 68Ge. The daughter 68Ga was eluted from the resin with a solution of a low-affinity gallium chelating ligand such as citric or phosphoric acid. The 68Ge leakage was less than 0.0004% of the 68Ge adsorbed on the resin. By simple mixing of transferrin and desferoxamine conjugated HSA and IgG with the eluate from the column, 68Ga-labeling was completed in high yield. PMID:12485657

  4. Determination of the optical properties of organic thin films by spectroscopic ellipsometry

    NASA Astrophysics Data System (ADS)

    Sward, Mark L.

    1990-12-01

    This theses demonstrated the feasibility of determining the optical properties of organic and polymer thin films through the use of Spectroscopic Ellipsometry (SE). Tan Psi and cos Delta data from 300 to 800 nanometers (NM) were taken with a Rudolph Research s2000 spectroscopic ellipsometer four samples: indium tin oxide (ITO) coated glass; five layer poly-benzyl-L glutamate (PBLG) organic film on ITO coated glass; eight layer PBLG film on ITO coated glass; and a thiophene polymer film on a microscope slide. The data sets were fit to a choice of four computer models based on a paper written by Dwight Berreman in 1972. The four were written in MATLAB to take advantage of its matrix manipulative capabilities. The models were: a single layer isotropic film on an isotropic substrate; a single layer anisotropic film on an isotropic substrate; two isotropic films on an isotropic substrate; and two anisotropic films on an isotropic substrate. Using only tan Psi data over a restricted wavelength region, all four data sets were fit to variances of 0.01 or less.

  5. Influence of organic films on the evaporation and condensation of water in aerosol

    PubMed Central

    Davies, James F.; Miles, Rachael E. H.; Haddrell, Allen E.; Reid, Jonathan P.

    2013-01-01

    Uncertainties in quantifying the kinetics of evaporation and condensation of water from atmospheric aerosol are a significant contributor to the uncertainty in predicting cloud droplet number and the indirect effect of aerosols on climate. The influence of aerosol particle surface composition, particularly the impact of surface active organic films, on the condensation and evaporation coefficients remains ambiguous. Here, we report measurements of the influence of organic films on the evaporation and condensation of water from aerosol particles. Significant reductions in the evaporation coefficient are shown to result when condensed films are formed by monolayers of long-chain alcohols [CnH(2n+1)OH], with the value decreasing from 2.4 × 10−3 to 1.7 × 10−5 as n increases from 12 to 17. Temperature-dependent measurements confirm that a condensed film of long-range order must be formed to suppress the evaporation coefficient below 0.05. The condensation of water on a droplet coated in a condensed film is shown to be fast, with strong coherence of the long-chain alcohol molecules leading to islanding as the water droplet grows, opening up broad areas of uncoated surface on which water can condense rapidly. We conclude that multicomponent composition of organic films on the surface of atmospheric aerosol particles is likely to preclude the formation of condensed films and that the kinetics of water condensation during the activation of aerosol to form cloud droplets is likely to remain rapid. PMID:23674675

  6. 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.

  7. VERUCLAY – a new type of photo-adsorbent active in the visible light range: modification of montmorillonite surface with organic surfactant

    EPA Science Inventory

    Montmorillonite K10 was treated with VeruSOL-3, a biodegradable and food-grade surfactant mixture of coconut oil, castor oil and citrus extracts, to manufacture a benign catalytic adsorbent that is active in the visible light. Veruclay was characterized by SEM, XRD, TGA, UVDRS, a...

  8. Nucleation and strain-stabilization during organic semiconductor thin film deposition.

    PubMed

    Li, Yang; Wan, Jing; Smilgies, Detlef-M; Bouffard, Nicole; Sun, Richard; Headrick, Randall L

    2016-01-01

    The nucleation mechanisms during solution deposition of organic semiconductor thin films determine the grain morphology and may influence the crystalline packing in some cases. Here, in-situ optical spectromicroscopy in reflection mode is used to study the growth mechanisms and thermal stability of 6,13-bis(trisopropylsilylethynyl)-pentacene thin films. The results show that the films form in a supersaturated state before transforming to a solid film. Molecular aggregates corresponding to subcritical nuclei in the crystallization process are inferred from optical spectroscopy measurements of the supersaturated region. Strain-free solid films exhibit a temperature-dependent blue shift of optical absorption peaks due to a continuous thermally driven change of the crystalline packing. As crystalline films are cooled to ambient temperature they become strained although cracking of thicker films is observed, which allows the strain to partially relax. Below a critical thickness, cracking is not observed and grazing incidence X-ray diffraction measurements confirm that the thinnest films are constrained to the lattice constants corresponding to the temperature at which they were deposited. Optical spectroscopy results show that the transition temperature between Form I (room temperature phase) and Form II (high temperature phase) depends on the film thickness, and that Form I can also be strain-stabilized up to 135 °C. PMID:27600905

  9. Nucleation and strain-stabilization during organic semiconductor thin film deposition

    PubMed Central

    Li, Yang; Wan, Jing; Smilgies, Detlef-M.; Bouffard, Nicole; Sun, Richard; Headrick, Randall L.

    2016-01-01

    The nucleation mechanisms during solution deposition of organic semiconductor thin films determine the grain morphology and may influence the crystalline packing in some cases. Here, in-situ optical spectromicroscopy in reflection mode is used to study the growth mechanisms and thermal stability of 6,13-bis(trisopropylsilylethynyl)-pentacene thin films. The results show that the films form in a supersaturated state before transforming to a solid film. Molecular aggregates corresponding to subcritical nuclei in the crystallization process are inferred from optical spectroscopy measurements of the supersaturated region. Strain-free solid films exhibit a temperature-dependent blue shift of optical absorption peaks due to a continuous thermally driven change of the crystalline packing. As crystalline films are cooled to ambient temperature they become strained although cracking of thicker films is observed, which allows the strain to partially relax. Below a critical thickness, cracking is not observed and grazing incidence X-ray diffraction measurements confirm that the thinnest films are constrained to the lattice constants corresponding to the temperature at which they were deposited. Optical spectroscopy results show that the transition temperature between Form I (room temperature phase) and Form II (high temperature phase) depends on the film thickness, and that Form I can also be strain-stabilized up to 135 °C. PMID:27600905

  10. Comparison of physicomechanical properties of films prepared from organic solutions and aqueous dispersion of Eudragit RL

    PubMed Central

    Sadeghi, F.; shahabi, M.; Afrasiabi, H.

    2011-01-01

    Background and the purpose of the study Mechanical properties of films prepared from aqueous dispersion and organic solutions of Eudragit RL were assessed and the effects of plasticizer type, concentration and curing were examined. Methods Films were prepared from aqueous dispersion and solutions of Eudragit RL (isopropy alcohol-water 9:1) containing 0, 10 or 20% (based on polymer weight) of PEG 400 or Triethyl Citrate (TEC) as plasticizer using casting method. Samples of films were stored in oven at 60°C for 24 hrs (Cured). The stress-strain curve was obtained for each film using material testing machine and tensile strength, elastic modulus, %elongation and work of failure were calculated. Results and major conclusion The films with no plasticizer showed different mechanical properties depending on the vehicle used. Addition of 10% or 20% of plasticizer decreased the tensile strength and elastic modulus and increased %elongation and work of failure for all films. The effect of PEG 400 on mechanical properties of Eudragit RL films was more pronounced. The differences in mechanical properties of the films due to vehicle decreased with addition of plasticizer and increase in its concentration. Curing process weakened the mechanical properties of the films with no plasticizer and for films with 10% plasticizer no considerable difference in mechanical properties was observed before and after curing. For those with 20% plasticizer only films prepared from aqueous dispersion showed remarkable difference in mechanical properties before and after curing. Results of this study suggest that the mechanical properties of the Eudragit RL films were affected by the vehicle, type of plasticizer and its concentration in the coating liquid. PMID:22615646

  11. Near edge X-ray absorption fine structure spectroscopy as a tool to probe electronic and structural properties of thin organic films and liquids.

    PubMed

    Hähner, Georg

    2006-12-01

    Synchrotron-based spectroscopic techniques have contributed significantly to a better understanding of the properties of materials on the macroscopic and microscopic scale over the last decades. They can be applied to samples from a diversity of fields, including Biology, Life Sciences, Chemistry and Materials. One of these techniques is Near Edge X-Ray Absorption Fine Structure (NEXAFS) spectroscopy, revealing electronic structure and information on the orientation of adsorbed molecules. The present article describes the basics of the technique and the progress it has made over the last three decades, and summarizes some of its more recent developments and applications. This tutorial review article should be accessible for novices to the field from Physics, Chemistry, Biology, Materials, and the Life Sciences, interested in thin organic films and liquid systems. PMID:17225886

  12. Optical and morphological characteristics of organic thin films for optoelectronic devices

    NASA Astrophysics Data System (ADS)

    Zhong, Zhiyou; Sun, Fenglou

    2007-12-01

    Organic semiconductor thin films of tri-(8-hydroxyquinoline)-aluminum (Alq), 9,10-di-(2-naphthyl)-anthracene (ADN), and N,N'bis(naphthalen-1-yl)-N,N'bis(phenyl)-benzidine (NPB) for optoelectronic devices were deposited onto glass substrates by vacuum sublimation technique. The surface morphology and roughness of the thin film were characterized by means of atomic force microscopy (AFM). Experimental results indicate that all thin films present similar granular topography but different surface roughness. In addition, the optical transmittance spectra of thin films were measured by a double beam spectrophotometer and their corresponding optical properties were investigated. The complex refractive index and the optical band gap of thin films were obtained, respectively. Meanwhile, the dispersion behavior of the refractive index was studied in terms of Wemple-DiDomenico single oscillator model, and the oscillator parameters were achieved.

  13. Influence of underneath pentacene thickness on performance of p-n heterojunction organic thin film transistors

    NASA Astrophysics Data System (ADS)

    Zhou, Jianlin; Jiang, Yuyu; Wang, Zhen; Hu, Shengdong; Gan, Ping; Shen, Xiaoqing

    2016-02-01

    Organic thin film transistors (OTFTs) with heterojunction semiconducting layers composed of p-type pentacene and n-type fluorinated copper phthalocyanine (F16CuPc) have been fabricated. The influence of pentacene film thickness on performance of transistors is carefully investigated. It has been found that, with the increase of pentacene film thickness, the electron mobility increases at first and then decreases intensely. But the shift of VT is opposite comparing with electron mobility. The performance improvement can be attributed to the increase of free electron carriers by band bending at the pentacene/F16CuPc interface, and better F16CuPc film quality grown upon pentacene. Comparing with island growth-mode, layer-by-layer growth-mode of pentacene facilitates the growth of the upper F16CuPc film.

  14. Formation of thin films of organic-inorganic perovskites for high-efficiency solar cells.

    PubMed

    Stranks, Samuel D; Nayak, Pabitra K; Zhang, Wei; Stergiopoulos, Thomas; Snaith, Henry J

    2015-03-01

    Organic-inorganic perovskites are currently one of the hottest topics in photovoltaic (PV) research, with power conversion efficiencies (PCEs) of cells on a laboratory scale already competing with those of established thin-film PV technologies. Most enhancements have been achieved by improving the quality of the perovskite films, suggesting that the optimization of film formation and crystallization is of paramount importance for further advances. Here, we review the various techniques for film formation and the role of the solvents and precursors in the processes. We address the role chloride ions play in film formation of mixed-halide perovskites, which is an outstanding question in the field. We highlight the material properties that are essential for high-efficiency operation of solar cells, and identify how further improved morphologies might be achieved. PMID:25663077

  15. Flexible barrier film, method of forming same, and organic electronic device including same

    DOEpatents

    Blizzard, John; Tonge, James Steven; Weidner, William Kenneth

    2013-03-26

    A flexible barrier film has a thickness of from greater than zero to less than 5,000 nanometers and a water vapor transmission rate of no more than 1.times.10.sup.-2 g/m.sup.2/day at 22.degree. C. and 47% relative humidity. The flexible barrier film is formed from a composition, which comprises a multi-functional acrylate. The composition further comprises the reaction product of an alkoxy-functional organometallic compound and an alkoxy-functional organosilicon compound. A method of forming the flexible barrier film includes the steps of disposing the composition on a substrate and curing the composition to form the flexible barrier film. The flexible barrier film may be utilized in organic electronic devices.

  16. Simulation of heterojunction organic thin film devices and exciton diffusion analysis in stacked-hetero device

    NASA Astrophysics Data System (ADS)

    Kamohara, Itaru; Townsend, Mark; Cottle, Bob

    2005-01-01

    A two-dimensional device simulation methodology for organic heterojunction thin film devices has been developed. Multilayer organic light emitting diodes, organic thin film heterojunction field effect transistors, and stacked heterojunction organic complementary devices were simulated. Heterojunction organic layer devices have been analyzed using a two-dimensional simulator with heterointerface models and organic material specific models. The stacked heterojunction organic double carrier device exhibits both horizontal and vertical carrier flow in the organic thin film. This unique dual-directional carrier flow shows efficient electron-hole recombination resulting in exciton generation in the organic heterojunction layers. Furthermore, the enhanced behavior of the generated excitons has been analyzed using a self-consistent exciton diffusion model. The vertical (thickness) diffusion of the excitons and the lateral (along heterointerface) diffusion (accompanied by exciton hopping) were simulated. The exciton diffusion model is applicable to electroluminescent characteristics in organic devices. This feature is one of the essential differences between the present model for high-injected polymer devices and conventional drift-diffusion transport in nonpolymer semiconductor devices.

  17. Fine structures of organic photovoltaic thin films probed by frequency-shift electrostatic force microscopy

    NASA Astrophysics Data System (ADS)

    Araki, Kento; Ie, Yutaka; Aso, Yoshio; Matsumoto, Takuya

    2016-07-01

    The localized charge and electrostatic properties of organic photovoltaic thin films are predominating factors for controlling energy conversion efficiency. The surface potential and electrostatic structures of organic photovoltaic thin films were investigated by frequency shift mode Kelvin force microscopy (KFM) and electrostatic force microscopy (EFM). The KFM images of a poly[2-methoxy-5-(3‧,7‧-dimethyloctyloxy)-1,4-phenylene vinylene]/phenyl-C61-butyric-acid-methyl ester (PCBM) blend thin film reveals that the PCBM domains precipitate as the topmost layer on the thin films. We find fine structures that were not observed in the topography and KFM images. The bias dependence of the EFM images suggests that the EFM contrast reflects the field-induced polarization, indicating the presence of charge trapping sites.

  18. Rapid and efficient redox processes within 2D covalent organic framework thin films.

    PubMed

    DeBlase, Catherine R; Hernández-Burgos, Kenneth; Silberstein, Katharine E; Rodríguez-Calero, Gabriel G; Bisbey, Ryan P; Abruña, Héctor D; Dichtel, William R

    2015-03-24

    Two-dimensional covalent organic frameworks (2D COFs) are ideally suited for organizing redox-active subunits into periodic, permanently porous polymer networks of interest for pseudocapacitive energy storage. Here we describe a method for synthesizing crystalline, oriented thin films of a redox-active 2D COF on Au working electrodes. The thickness of the COF film was controlled by varying the initial monomer concentration. A large percentage (80-99%) of the anthraquinone groups are electrochemically accessible in films thinner than 200 nm, an order of magnitude improvement over the same COF prepared as a randomly oriented microcrystalline powder. As a result, electrodes functionalized with oriented COF films exhibit a 400% increase in capacitance scaled to electrode area as compared to those functionalized with the randomly oriented COF powder. These results demonstrate the promise of redox-active COFs for electrical energy storage and highlight the importance of controlling morphology for optimal performance. PMID:25672785

  19. Tetracene films for light-emitting transistors: chemical and physical effects of the organic dielectric substrates

    NASA Astrophysics Data System (ADS)

    Santato, Clara; Cicoira, Fabio; Bertolazzi, Simone

    2010-03-01

    Tetracene vacuum-sublimed films have been used to demonstrate the first Organic Light Emitting Field Effect Transistor (OLEFET), in 2003. Because of their planar configuration, OLEFET are excellent systems to study fundamental processes such as charge injection, transport, and light emission in organic semiconductor films. OLEFET are intensively investigated for applications in active matrix full-color displays and, ultimately, lasers. Since the first Tetracene-OLEFET, a number of excellent studies have been reported on vacuum-sublimed as well as solution-processed films of organic semiconductors incorporated into OLEFET. Investigating the role played by the surface substrate chemistry and establishing sound structure-property relationships in organic semiconductor films incorporated into OLEFET structures are the keys to understand and improve the optoelectronic characteristics of OLEFET. Here we present our results on the morphological, structural, light-emission, and charge transport properties in field-effect transistor configuration of vacuum-sublimed tetracene films deposited on chemically and physically different organic dielectric substrates (HMDS- and OTS-treated SiO2, polystyrene, parylene, PMMA).

  20. Material properties and applications of blended organic thin films with nanoscale domains deposited by RIR-MAPLE

    NASA Astrophysics Data System (ADS)

    Stiff-Roberts, Adrienne D.; McCormick, Ryan D.; Ge, Wangyao

    2015-03-01

    Resonant-infrared, matrix-assisted pulsed laser evaporation (RIR-MAPLE) has been used to deposit blended, organic thin-films with nanoscale domain sizes of constituent polymers, small molecules, or colloidal nanoparticles. In the emulsion-based RIR-MAPLE process, the target contains a nonpolar, organic solvent phase and a polar, water phase. The emulsion properties have a direct impact on the nanoscale morphology of single-component organic thin films, while the morphology of blended, organic thin films also depends on the RIR-MAPLE deposition mode. In addition to these fundamental aspects, applications of blended organic films (organic solar cells, anti-reflection coatings, and multi-functional surfaces) deposited by emulsion-based RIR-MAPLE are presented. Importantly, domain sizes in the blended films are critical to thin-film functionality.

  1. Organization of nanoparticles on hard substrates using block copolymer films as templates.

    PubMed

    Minelli, Caterina; Geissbuehler, Isabelle; Hinderling, Christian; Heinzelmann, Harry; Vogel, Horst; Pugin, Raphael; Liley, Martha

    2006-06-01

    We present a technique for the organization of pre-synthesized nanoparticles on hard substrates, using block copolymer films as sacrificial templates. A thin block copolymer film is dip-coated on the substrate of interest and the sample is exposed to a solution containing nanoparticles. Spontaneous preferential adsorption of the nanoparticles on one phase of the block copolymer film results in their lateral organization. An oxygen plasma etch is used to remove the polymer film; the nanoparticles end up organized on the substrate. We demonstrate that this is a general approach for the patterning of inorganic nanoparticles on hard substrates, showing the organization of metal and semiconductor nanoparticles having different chemistries at the particle/solvent and solvent/polymer interfaces. The nanoparticle patterns that we present have typical periodicities in the nanometer scale. In some cases, microcontact printing is used to create a double length scale of organization, on the micrometer and on the nanometer level. The characteristic periodicity of the template is studied with respect to the nanoparticle size in order to optimize the organization. Finally, we describe how to extend this technique for the production of continuous gold nanowires on hard substrates. We expect that the flexibility of this approach and the degree of control that can be obtained over nanoparticle organization should make it a powerful tool for nanoscale fabrication. PMID:17025059

  2. Corrosion protection by sonoelectrodeposited organic films on zinc coated steel.

    PubMed

    Et Taouil, Abdeslam; Mahmoud, Mahmoud Mourad; Lallemand, Fabrice; Lallemand, Séverine; Gigandet, Marie-Pierre; Hihn, Jean-Yves

    2012-11-01

    A variety of coatings based on electrosynthesized polypyrrole were deposited on zinc coated steel in presence or absence of ultrasound, and studied in terms of corrosion protection. Cr III and Cr VI commercial passivation were used as references. Depth profiling showed a homogeneous deposit for Cr III, while SEM imaging revealed good surface homogeneity for Cr VI layers. These chromium-based passivations ensured good protection against corrosion. Polypyrrole (PPy) was also electrochemically deposited on zinc coated steel with and without high frequency ultrasound irradiation in aqueous sodium tartrate-molybdate solution. Such PPy coatings act as a physical barrier against corrosive species. PPy electrosynthesized in silent conditions exhibits similar properties to Cr VI passivation with respect to corrosion protection. Ultrasound leads to more compact and more homogeneous surface structures for PPy, as well as to more homogeneous distribution of doping molybdate anions within the film. Far better corrosion protection is exhibited for such sonicated films. PMID:22516111

  3. Exciton diffusion lengths of organic semiconductor thin films measured by spectrally resolved photoluminescence quenching

    NASA Astrophysics Data System (ADS)

    Lunt, Richard R.; Giebink, Noel C.; Belak, Anna A.; Benziger, Jay B.; Forrest, Stephen R.

    2009-03-01

    We demonstrate spectrally resolved photoluminescence quenching as a means to determine the exciton diffusion length of several archetype organic semiconductors used in thin film devices. We show that aggregation and crystal orientation influence the anisotropy of the diffusion length for vacuum-deposited polycrystalline films. The measurement of the singlet diffusion lengths is found to be in agreement with diffusion by Förster transfer, whereas triplet diffusion occurs primarily via Dexter transfer.

  4. A Naphthalenediimide-Based Metal-Organic Framework and Thin Film Exhibiting Photochromic and Electrochromic Properties.

    PubMed

    Xie, Yi-Xin; Zhao, Wen-Na; Li, Guo-Chang; Liu, Peng-Fei; Han, Lei

    2016-01-19

    A multifunctional metal-organic framework, NBU-3, has been explored as a 2D three-connected network based on a naphthalenediimide-based ligand. The NBU-3 crystals display photochromic properties, and NBU-3 thin films on FTO substrates exhibit electrochromic properties. NBU-3 is the first example of MOF materials containing both photochromic and electrochromic properties, which can be desirable for thin film devices. PMID:26713454

  5. Kinetics of Dewetting of Ultra-Thin Films of Organic Glasses

    NASA Astrophysics Data System (ADS)

    Fakhraai, Zahra; Zhang, Yue; Riggleman, Robert

    Physical vapor deposition (PVD) is widely used in manufacturing ultra-thin layers of amorphous organic solids. It is generally assumed that the properties of these ultra-thin films are the same as bulk dynamics. In this work, we demonstrate that these films exhibit a sharp transition from glassy solid to liquid-like behavior with thickness below 30 nm. This liquid-like behavior persists even at temperatures well below the glass transition temperature, Tg, where bulk properties suggest that the film should be vitrified. The enhanced dynamics in these films can produce large scale morphological features during PVD and lead to dewetting instability in films held at temperatures as low as Tg-35 K. We measure an effective viscosity of organic glass films by monitoring the dewetting kinetics. These measurements combined with cooling rate-dependent Tg measurements show that the apparent activation barrier for rearrangement decreases sharply in films thinner than 30 nm. These observations suggest long-range facilitation of dynamics induced by the free surface. These observations can help understand correlated dynamics in glassy systems and elucidate the processes that lead to the formation of exceptionally stable glasses.

  6. Ionization sensitization of doping in co-deposited organic semiconductor films

    SciTech Connect

    Shinmura, Yusuke Yamashina, Yohei; Kaji, Toshihiko; Hiramoto, Masahiro

    2014-11-03

    Sensitization of the dopant ionization in co-deposited films of organic semiconductors was found. The ionization rate of cesium carbonate (Cs{sub 2}CO{sub 3}), which acts as a donor dopant in single films of metal-free phthalocyanine (H{sub 2}Pc) and fullerene (C{sub 60}), was increased from 10% to 97% in a H{sub 2}Pc:C{sub 60} co-deposited film. A charge separation superlattice model that includes electron transfer from the conduction band of H{sub 2}Pc to that of C{sub 60}, which increases the rate of dopant ionization, is proposed.

  7. Nanostructuring on zinc phthalocyanine thin films for single-junction organic solar cells

    NASA Astrophysics Data System (ADS)

    Chaudhary, Dhirendra K.; Kumar, Lokendra

    2016-05-01

    Vertically aligned and random oriented crystalline molecular nanorods of organic semiconducting Zinc Phthalocyanine (ZnPc) have been grown on ITO coated glass substrate using solvent volatilization method. Interesting changes in surface morphology were observed under different solvent treatment. Vertically aligned nanorods of ZnPc thin film were observed in the films treated with acetone, where as the random oriented nanorods were observed in the films treated with chloroform. The X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM) have been used for characterization of nanostructures. The optical properties of the nanorods have been investigated by UV-Vis. absorption spectroscopy.

  8. Ionization sensitization of doping in co-deposited organic semiconductor films

    NASA Astrophysics Data System (ADS)

    Shinmura, Yusuke; Yamashina, Yohei; Kaji, Toshihiko; Hiramoto, Masahiro

    2014-11-01

    Sensitization of the dopant ionization in co-deposited films of organic semiconductors was found. The ionization rate of cesium carbonate (Cs2CO3), which acts as a donor dopant in single films of metal-free phthalocyanine (H2Pc) and fullerene (C60), was increased from 10% to 97% in a H2Pc:C60 co-deposited film. A charge separation superlattice model that includes electron transfer from the conduction band of H2Pc to that of C60, which increases the rate of dopant ionization, is proposed.

  9. Film Properties and Polycrystallization of Organic Dyes on ITOs with Surface Treatment for Organic Light-Emitting Diodes

    NASA Astrophysics Data System (ADS)

    Iwama, Yuki; Mori, Tatsuo; Mizutani, Teruyoshi

    ITO(Indium-Tin-Oxide) has been now widely used as the transparent anode for organic light-emitting devices(OLEDs). We used various methods of ITO surface treatment and examined the effects of them by measuring contact angle and calculating surface energy. We also prepared OLEDs with ITO treated by each method, and estimated their characteristics. The surface of ITO treated by UV-O3 or O2-plasma was more hydrophilic than that treated by only organic rinse or no treatment, and consequently the characteristic of the OLED was improved. We suppose these treatments affect the hole injection from ITO into organic layer, due to ionization potential or surface cleanness. We also investigated time degradation of NPD films on the ITO substrates. The films deposited with high deposition rate porycrystallized faster.

  10. Wrinkling of YBa2Cu3O7-x film prepared by trifluoroacetate metal organic deposition

    NASA Astrophysics Data System (ADS)

    Jin, L. H.; Li, C. S.; Yu, Z. M.; Feng, J. Q.; Zhang, S. N.; Sulpice, A.; Wang, Y.; Zhang, P. X.

    2015-11-01

    YBa2Cu3O7-x (YBCO) films with wrinkles have been fabricated on LaAlO3(1 0 0) substrates by trifluoroacetate metal organic deposition (TFA-MOD). The decomposition behavior of YBCO-TFA gel and the formation mechanism of wrinkles were analyzed by thermal analysis, Fourier transform infrared spectroscopy, and atomic force microscopy. The effects of wrinkles on the texture, microstructure and critical current density of the final crystallized film were also investigated by X-ray diffraction and scanning electron microscopy. The heating rate in the decomposition process was a crucial parameter to control the wavelength and wave amplitude of wrinkles on the surface of YBCO precursor film. Furthermore, the wrinkles of precursor films were transformed into the ridges of crystallized films during the crystallization process. Large ridges resulted in the degradation of texture of YBCO crystallized films. The decrease of critical current density (Jc) of YBCO crystallized films could be ascribed to the formation of ridges, the segregated phases and the degradation of texture. It suggested that the smooth morphology of YBCO precursor films would be beneficial to the enhancement of Jc value.

  11. Solution-Processed Organic Thin-Film Transistor Array for Active-Matrix Organic Light-Emitting Diode

    NASA Astrophysics Data System (ADS)

    Harada, Chihiro; Hata, Takuya; Chuman, Takashi; Ishizuka, Shinichi; Yoshizawa, Atsushi

    2013-05-01

    We developed a 3-in. organic thin-film transistor (OTFT) array with an ink-jetted organic semiconductor. All layers except electrodes were fabricated by solution processes. The OTFT performed well without hysteresis, and the field-effect mobility in the saturation region was 0.45 cm2 V-1 s-1, the threshold voltage was 3.3 V, and the on/off current ratio was more than 106. We demonstrated a 3-in. active-matrix organic light-emitting diode (AMOLED) display driven by the OTFT array. The display could provide clear moving images. The peak luminance of the display was 170 cd/m2.

  12. Interference effects in the sum frequency generation spectra of thin organic films. II: Applications to different thin-film systems

    NASA Astrophysics Data System (ADS)

    Tong, Yujin; Zhao, Yanbao; Li, Na; Ma, Yunsheng; Osawa, Masatoshi; Davies, Paul B.; Ye, Shen

    2010-07-01

    In this paper, the results of the modeling calculations carried out for predicting the interference effects expected in the sum frequency generation (SFG) spectra of a specific thin-layer system, described in the accompanying paper, are tested by comparing them with the experimental spectra obtained for a real thin-layer film comprising an organic monolayer/variable thickness dielectric layer/gold substrate. In this system, two contributions to the SFG spectra arise, a resonant contribution from the organic film and a nonresonant contribution from the gold substrate. The modeling calculations are in excellent agreement with the experimental spectra over a wide range of thicknesses and for different polarization combinations. The introduction of another resonant monolayer adjacent to the gold substrate and with the molecules having a reverse orientation has a significant affect on the spectral shapes which is predicted. If a dielectric substrate such as CaF2 is used instead of a gold substrate, only the spectral intensities vary with the film thickness but not the spectral shapes. The counterpropagating beam geometry will change both the thickness dependent spectral shapes and the intensity of different vibrational modes in comparison with a copropagating geometry. The influences of these experimental factors, i.e., the molecular orientational structure in the thin film, the nature of the substrate, and the selected incident beam geometry, on the experimental SFG spectra are quantitatively predicted by the calculations. The thickness effects on the signals from a SFG active monolayer contained in a thin liquid-layer cell of the type frequently used for in situ electrochemical measurements is also discussed. The modeling calculation is also valid for application to other thin-film systems comprising more than two resonant SFG active interfaces by appropriate choice of optical geometries and relevant optical properties.

  13. Organic Gate Silicon Field Effect Transistors with Poly Methylmethacrylate Films for Science Education

    NASA Astrophysics Data System (ADS)

    Hirose, Fumihiko; Miyagi, Tatsuro; Narita, Yuzuru

    We have developed an easy fabrication method of Si field effect transistors (FETs) with poly (methyl methacrylate) (PMMA) gate films for science education. In this process, we can easily fabricate the silicon FETs only by means of metal deposition and thermal diffusion without any lithography processes. The organic isolation films of PMMA can be deposited by casting or painting at room temperature in air. The metal-organic-semiconductor FETs with PMMA exhibited almost the same drain current — gate voltage characteristics as those of conventional Si metal-oxide-semiconductor FETs, which are suitable for the education material of semiconductor engineering. The organic gate Si FETs can be used not only for education but also as thin film transistors for active matrix displays.

  14. Single crystal films and waveguides of organic materials: Preparation and nonlinear optical properties

    NASA Astrophysics Data System (ADS)

    Thakur, Mrinal

    1994-03-01

    The objective of this program is to establish a generic method for the growth of thin single crystal films of important organic nonlinear optical materials and measurement of their nonlinear optical properties. Through the last year's effort we have successfully prepared single crystal films of three organic materials which are: (1) (N-(4-Nitrophenyl)-L-prolinol) abbreviated as NPP, (2) 2-cyclooctylamino- 5-nitropyridine, abbreviated as COANP, and (3) 4'-N, N-dimethylamino- 4-N-methylstilbazolium toluene-p-sulfonate, abbreviated as DAST. These materials have very large second order susceptibilities. Both NPP and COANP have an amphiphillic molecular structure, while DAST is an organic molecular salt. The single crystal films were prepared by a method called the shear method, with appropriate choice of the growth conditions. The shear method involves crystal growth at an interface and was originally applied to the growth of polydiacetylene films. Our results show that using the principles involved in the shear method, if the growth conditions are properly optimized for each compound, then molecules other than diacetylene are possible to organize as single crystal films. The only major condition that needs to be satisfied for this method to be applicable is that the molecule must be of an elongated shape with polar chemical groups at one or both ends.

  15. Fabrication and performance of organic thin film solar cells using a painting method

    NASA Astrophysics Data System (ADS)

    Ochiai, S.; Ishihara, H.; Mizutani, T.; Kojima, K.

    2010-05-01

    As organic thin film solar cells fabricated by the active layer of organic materials are economical, lightweight, and flexible, as well as generating no CO2, and being easy to fabricate, they have attracted significant attention as green energy sources from a past decade to date. Therefore, their power conversion efficiency (PCE) has been investigated and studied worldwide. In organic thinfilm solar cells, the effect of the performance depends not only on the adopted active material but also relates to the molecular orientation on the electrode. Using a mixed solution of Poly(3-hexylthiophene) and PCBM, both of which were dissolved in a solvent, the organic thin films were fabricated using the paint and spray methods, while the morphology of the thin film was evaluated by an AFM image, UV/vis spectra, and so forth. Based on these data, an organic thin-film solar cell using both solution methods for the active layer was fabricated, and the performance evaluated and examined. For organic thin film solar cells fabricated using a spin-coating method, the open-circuit voltage (Voc) is 0.41V, the short circuit current density (Jsc) is 2.07mA/cm2, and the fill factor is 0.34, while the efficiency η of PCE become 0.29%. In the spray method, the short circuit current (Isc) is 2.5 mA/cm2, the open circuit voltage (Voc) is 0.45 V, the fill factor (FF) is 0.28, and the power conversion factor (PCE) 0.35%. The area of organic solar cells fabricated by spin coating and spray methods is 1 cm2 respectively. The organic solar cells are not thermally treated, and hence have high respective power conversion efficiencies.

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

    PubMed

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

    2005-06-30

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

  17. How long may a breath sample be stored for at  -80 °C? A study of the stability of volatile organic compounds trapped onto a mixed Tenax:Carbograph trap adsorbent bed from exhaled breath.

    PubMed

    Kang, S; Paul Thomas, C L

    2016-06-01

    Thermal desorption is used extensively in exhaled breath volatile organic compound (VOC) analysis, and it is often necessary to store the adsorbent tube samples before analysis. The possible introduction of storage artefacts is an important potential confounding factor in the development of standard methodologies for breath sampling and analysis. The stability of VOCs trapped from breath samples onto a dual bed Tenax(®) TA:Carbograph adsorbent tube and stored  -80°C was studied over 12.5 month. 25 samples were collected from a single male participant over 3 h and then stored at  -80 °C. Randomly selected adsorbent tubes were subsequent analysed by thermal desorption-gas chromatography-mass spectrometry at 5 times points throughout the 12.5 month of the study. Toluene-d8, decane-d22 and hexadecane-d34 internal standards were used to manage the instrument variability throughout the duration of the study. A breath-matrix consisting of 161 endogenous and 423 exogenous VOC was created. Iterative orthogonal partial least squared discriminant analysis (OPLS-DA) and principal components analysis (PCA) indicated that it was not possible to detect storage artefacts at 1.5 month storage. By 6 month storage artefacts were discernible with significant changes observed for 27% of the recovered VOC. Endogenous VOC were observed to be more susceptible to storage. A paired two-tailed t-test on the endogenous compounds indicated that the maximum storage duration under these conditions was 1.5 month with 94% of the VOCs stable. This study indicates that a prudent approach is best adopted for the storage of adsorbent samples; storage times should be minimised, and storage time examined as a possible discriminatory factor in multivariate analysis. PMID:27272219

  18. Atomic/molecular layer deposition: a direct gas-phase route to crystalline metal-organic framework thin films.

    PubMed

    Ahvenniemi, E; Karppinen, M

    2016-01-21

    Atomic/molecular layer deposition offers us an elegant way of fabricating crystalline copper(ii)terephthalate metal-organic framework (MOF) thin films on various substrate surfaces. The films are grown from two gaseous precursors with a digital atomic/molecular level control for the film thickness under relatively mild conditions in a simple and fast one-step process. PMID:26612265

  19. Molecular Adsorber Coating

    NASA Technical Reports Server (NTRS)

    Straka, Sharon; Peters, Wanda; Hasegawa, Mark; Hedgeland, Randy; Petro, John; Novo-Gradac, Kevin; Wong, Alfred; Triolo, Jack; Miller, Cory

    2011-01-01

    A document discusses a zeolite-based sprayable molecular adsorber coating that has been developed to alleviate the size and weight issues of current ceramic puck-based technology, while providing a configuration that more projects can use to protect against degradation from outgassed materials within a spacecraft, particularly contamination-sensitive instruments. This coating system demonstrates five times the adsorption capacity of previously developed adsorber coating slurries. The molecular adsorber formulation was developed and refined, and a procedure for spray application was developed. Samples were spray-coated and tested for capacity, thermal optical/radiative properties, coating adhesion, and thermal cycling. Work performed during this study indicates that the molecular adsorber formulation can be applied to aluminum, stainless steel, or other metal substrates that can accept silicate-based coatings. The coating can also function as a thermal- control coating. This adsorber will dramatically reduce the mass and volume restrictions, and is less expensive than the currently used molecular adsorber puck design.

  20. Formation of High-Capacity Protein-Adsorbing Membranes Through Simple Adsorption of Poly(acrylic acid)-Containing Films at low pH

    PubMed Central

    Bhattacharjee, Somnath; Dong, Jinlan; Ma, Yiding; Hovde, Stacy; Geiger, James H; Baker, Gregory L.; Bruening, Merlin L.

    2012-01-01

    Layer-by-layer polyelectrolyte adsorption is a simple, convenient method for introducing ion-exchange sites in porous membranes. This study demonstrates that adsorption of poly(acrylic acid) (PAA)-containing films at pH 3 rather than pH 5 increases the protein-binding capacity of such polyelectrolyte-modified membranes 3- to 6-fold. The low adsorption pH generates a high density of –COOH groups that function as either ion-exchange sites or points for covalent immobilization of metal-ion complexes that selectively bind tagged proteins. When functionalized with nitrilotriacetate (NTA)-Ni2+ complexes, membranes containing PAA/polyethyleneimine (PEI)/PAA films bind 93 mg of histidine6-tagged (His-tagged) ubiquitin per cm3 of membrane. Additionally these membranes isolate His-tagged COP9 signalosome complex subunit 8 from cell extracts and show >90% recovery of His-tagged ubiquitin. Although modification with polyelectrolyte films occurs by simply passing polyelectrolyte solutions through the membrane for as little as 5 min, with low-pH deposition the protein binding capacities of such membranes are as high as for membranes modified with polymer brushes and 2–3 fold higher than for commercially available IMAC resins. Moreover, the buffer permeabilities of polyelectrolyte-modified membranes that bind His-tagged protein are ~30% of the corresponding permeabilities of unmodified membranes, so protein capture can occur rapidly with low pressure drops. Even at a solution linear velocity of 570 cm/h, membranes modified with PAA/PEI/PAA exhibit a lysozyme dynamic binding capacity (capacity at 10% breakthrough) of ~ 40 mg/cm3. Preliminary studies suggest that these membranes are stable under depyrogenation conditions (1 M NaOH). PMID:22468687

  1. In-situ spectro-microscopy on organic films: Mn-Phthalocyanine on Ag(100)

    NASA Astrophysics Data System (ADS)

    Al-Mahboob, Abdullah; Sadowski, Jerzy T.; Vescovo, Elio

    2013-03-01

    Metal phthalocyanines are attracting significant attention, owing to their potential for applications in chemical sensors, solar cells and organic magnets. As the electronic properties of molecular films are determined by their crystallinity and molecular packing, the optimization of film quality is important for improving the performance of organic devices. Here, we present the results of in situ low-energy electron microscopy / photoemission electron microscopy (LEEM/PEEM) studies of incorporation-limited growth of manganese-phthalocyanine (MnPc) on Ag(100) surfaces. MnPc thin films were grown on both, bulk Ag(100) surface and thin Ag(100)/Fe(100) films, where substrate spin-polarized electronic states can be modified through tuning the thickness of the Ag film. We also discuss the electronic structure and magnetic ordering in MnPc thin films, investigated by angle- and spin-resolved photoemission spectroscopy. Research carried out at the Center for Functional Nanomaterials and National Synchrotron Light Source, Brookhaven National Laboratory, which are supported by the U.S. Dept. of Energy, Office of Basic Energy Sciences, under Contract No. DE-AC02-98CH10886.

  2. X-Ray and Optical Studies of Thin Organic Films

    NASA Astrophysics Data System (ADS)

    Foster, William Joseph, Jr.

    1995-01-01

    In order to quantitatively understand the fundamental statistical physics of Langmuir monolayers (LMs) it is essential that their properties be measured under equilibrium conditions. In order to address this issue, the phase diagrams of relaxed films of doeicosanoic acid and methyl eicosanoate were mapped out over the temperature range of 5.5^circ to 26 ^circC. In contrast to the prevailing technique in which isotherms are taken at a constant rate of compression, isotherms in this study were taken through a series of incremental compressions, separated by variable waiting periods that allowed the monolayer to relax to a steady state. X-ray diffraction, Brewster angle microscopy, and surface pressure measurements at each area were interpreted to characterize the structure of the phases of a relaxed LM of methyl eicosanoate. Below 12^circ C and 2.25 dynes/cm the I(L_2^ {''}) phase, an orthorhombic structure with tilt toward nearest neighbor was observed. Between 12^circ and 22^ circC and below 8 dynes/cm the F(L _2^') phase, with tilt toward next nearest neighbor and an orthorhombic structure was seen. Above 22^circC the Ov phase, with tilt toward nearest neighbor and a hexagonal structure was seen. At higher pressures, the U ^'(CS)/U(S)/R(LS) sequence of phases, typical of most saturated alkane systems, was detected. In order to better understand issues of equilibrium and relaxation for LMs of the fatty acids and to compare our results to previous "fast" measurements, a detailed study of relaxed films of doeicosanoic acid was conducted. Both relaxation isotherms and isochores were performed simultaneously with x-ray diffraction measurements. It was found that, despite uncertainty in the macroscopic trough area per molecule due to collapse of the film, a physically useful phase diagram could be constructed in terms of the microscopic area per molecule, derived from diffraction measurements. In addition, by using a two-dimensional analog of the Clausius -Clapeyron

  3. SORPTION PROPERTIES OF MODEL COMPOUNDS ON C18 ADSORBENTS

    EPA Science Inventory

    The bonded silica adsorbent Bondapak-C18 was evaluated for removing organic matter from secondary sewage effluents and from solutions of pure organic compounds. The adsorbent is hydrophobic and its behavior with water samples may be erratic unless first wet with a solvent. Howeve...

  4. Nanomechanical investigation of thin-film electroceramic/metal-organic framework multilayers

    NASA Astrophysics Data System (ADS)

    Best, James P.; Michler, Johann; Liu, Jianxi; Wang, Zhengbang; Tsotsalas, Manuel; Maeder, Xavier; Röse, Silvana; Oberst, Vanessa; Liu, Jinxuan; Walheim, Stefan; Gliemann, Hartmut; Weidler, Peter G.; Redel, Engelbert; Wöll, Christof

    2015-09-01

    Thin-film multilayer stacks of mechanically hard magnetron sputtered indium tin oxide (ITO) and mechanically soft highly porous surface anchored metal-organic framework (SURMOF) HKUST-1 were studied using nanoindentation. Crystalline, continuous, and monolithic surface anchored MOF thin films were fabricated using a liquid-phase epitaxial growth method. Control over respective fabrication processes allowed for tuning of the thickness of the thin film systems with a high degree of precision. It was found that the mechanical indentation of such thin films is significantly affected by the substrate properties; however, elastic parameters were able to be decoupled for constituent thin-film materials (EITO ≈ 96.7 GPa, EHKUST-1 ≈ 22.0 GPa). For indentation of multilayer stacks, it was found that as the layer thicknesses were increased, while holding the relative thickness of ITO and HKUST-1 constant, the resistance to deformation was significantly altered. Such an observation is likely due to small, albeit significant, changes in film texture, interfacial roughness, size effects, and controlling deformation mechanism as a result of increasing material deposition during processing. Such effects may have consequences regarding the rational mechanical design and utilization of MOF-based hybrid thin-film devices.

  5. Nanomechanical investigation of thin-film electroceramic/metal-organic framework multilayers

    SciTech Connect

    Best, James P. E-mail: engelbert.redel@kit.edu Michler, Johann; Maeder, Xavier; Liu, Jianxi; Wang, Zhengbang; Tsotsalas, Manuel; Liu, Jinxuan; Gliemann, Hartmut; Weidler, Peter G.; Redel, Engelbert E-mail: engelbert.redel@kit.edu Wöll, Christof E-mail: engelbert.redel@kit.edu; Röse, Silvana; Oberst, Vanessa; Walheim, Stefan

    2015-09-07

    Thin-film multilayer stacks of mechanically hard magnetron sputtered indium tin oxide (ITO) and mechanically soft highly porous surface anchored metal-organic framework (SURMOF) HKUST-1 were studied using nanoindentation. Crystalline, continuous, and monolithic surface anchored MOF thin films were fabricated using a liquid-phase epitaxial growth method. Control over respective fabrication processes allowed for tuning of the thickness of the thin film systems with a high degree of precision. It was found that the mechanical indentation of such thin films is significantly affected by the substrate properties; however, elastic parameters were able to be decoupled for constituent thin-film materials (E{sub ITO} ≈ 96.7 GPa, E{sub HKUST−1} ≈ 22.0 GPa). For indentation of multilayer stacks, it was found that as the layer thicknesses were increased, while holding the relative thickness of ITO and HKUST-1 constant, the resistance to deformation was significantly altered. Such an observation is likely due to small, albeit significant, changes in film texture, interfacial roughness, size effects, and controlling deformation mechanism as a result of increasing material deposition during processing. Such effects may have consequences regarding the rational mechanical design and utilization of MOF-based hybrid thin-film devices.

  6. Self-organization of thin polymer films guided by electrostatic charges on the substrate.

    PubMed

    Zhao, Dan; Martinez, Aaron D; Xi, Xiaolei; Ma, Xinlei; Wu, Ning; Cao, Tingbing

    2011-08-22

    The self-organization of thin polymer films into functional patterns is important both scientifically and technologically. Electric fields have been exploited as an efficient and powerful means to induce the destabilization and self-organization of soft materials. Previous attention, however, has mainly focused on externally applied electric fields. It is shown herein that the internal electric field is strong enough to guide the self-organization of thin polymer films as well. Patterns of electrostatic charges with micrometer resolution are first introduced on a dielectric substrate. A thin polymer film is then spin-coated onto the topographically flat substrate. Upon thermal annealing, the thin polymer film destabilizes due to a lateral gradient of electrostatic stress and flows away from the electroneutral regime to the charged area, resembling the patterns of charges on the substrate. Theoretical and numerical modeling based on the electrohydrodynamic instability shows excellent agreement with experimental observations both qualitatively and quantitatively. It is also demonstrated that the interplay between charge-driven instability with spinodal dewetting and Rayleigh instabilities can generate finer and hierarchical polymeric patterns that are completely different from the charge patterns preintroduced on the substrate. This study provides direct evidence that the internal electric field caused by charges on the substrate is strong enough to destabilize thin polymeric films and generate patterns. This study also demonstrates new strategies for bottom-up fabrication of structured functional materials. PMID:21638784

  7. Remarkable Lattice Shrinkage in Highly Oriented Crystalline Three-Dimensional Metal-Organic Framework Thin Films.

    PubMed

    Haraguchi, Tomoyuki; Otsubo, Kazuya; Sakata, Osami; Fujiwara, Akihiko; Kitagawa, Hiroshi

    2015-12-21

    Highly oriented crystalline thin films of metal-organic frameworks (MOFs) have promising practical applications, such as in gas separation, catalysis, and sensing. We report on the successful fabrication of highly oriented crystalline thin films of three-dimensional porous MOFs, Fe(pz)[M(CN)4] (M = Ni, Pd; pz = pyrazine). Synchrotron X-ray diffraction studies reveal not only the highly oriented crystalline nature but also the remarkable shrunken structure of the thin films (∼3-7% volume shrinkage) compared with bulk samples. Furthermore, because of lattice shrinkage, these films exhibit large lattice expansions upon guest adsorption, in marked contrast to the almost unchanged lattice in the bulk samples. PMID:26641131

  8. Influence of inserting a thin fullerene layer on pentacene organic thin-film transistor

    NASA Astrophysics Data System (ADS)

    Li, Yu-Chang; Lin, Yu-Ju; Wei, Chia-Yu; Chou, Dei-Wei; Tsao, Chun-Ho; Wang, Yeong-Her

    2012-03-01

    The performance of organic thin-film transistors (TFTs) with a pentacene/fullerene(C60)/pentacene (PCP) sandwich structure is presented. Using a 3.5 nm-thick C60 layer inserted between the pentacene films, the obtained hole mobility is improved by more than six times. By applying atomic force microscopy, x-ray diffraction, Raman spectrum, and transmission line method analysis, one can reasonably infer that the smoother surface of the pentacene film covered with thin C60 layer delays the phase transformation of the upper pentacene film, resulting in stronger intermolecular coupling and the reduction of channel resistance of the PCP TFTs from 3.03 to 1.72 MΩ, and, therefore, improving the device performance.

  9. Ordered nanocolumn-array organic semiconductor thin films with controllable molecular orientation

    NASA Astrophysics Data System (ADS)

    Yang, Bingchu; Duan, Haichao; Zhou, Conghua; Gao, Yongli; Yang, Junliang

    2013-12-01

    Ordered nanocolumn-array phthalocynine semiconductor thin films with controllable molecular orientation were fabricated by combining molecular template growth (MTG) and glancing angle deposition (GLAD) techniques. The pre-deposited planar perylene-3,4,9,10-tetracarboxylic-3,4,9,10-dianhydride (PTCDA) molecular template layer induces phthalocynine molecules arrange with a lying-down molecular orientation, in which the π-π stacking is vertical to the substrate improving the charge transport along the vertical direction; While the GLAD technique supports the formation of nanocolumn-array thin films, supplying a much larger exposed surface area than the conventional compact thin films. The ordered nanocolumn-array thin films with controllable molecular orientation fabricated by combining MTG and GLAD techniques show the potentials to fabricate ordered bulk heterojunction for improving the performance in organic photovoltaics.

  10. Growth and alignment of thin film organic single crystals from dewetting patterns.

    PubMed

    Tisserant, Jean-Nicolas; Wicht, Gaëtan; Göbel, Ole F; Bocek, Eva; Bona, Gian-Luca; Geiger, Thomas; Hany, Roland; Mezzenga, Raffaele; Partel, Stefan; Schmid, Peter; Schweizer, Wolfhard Bernd; Heier, Jakob

    2013-06-25

    Studying and understanding the conditions under which organic semiconductors can be engineered to form aligned single crystals in thin films is of primary importance owing to their unique orientation-dependent optoelectronic properties. Efforts to reach this goal by self-assembly from solution-processed films have been rewarded only with limited success. In this article we present a new method to grow single crystalline thin films via solvent annealing. We identify solvate crystal growth in combination with a specific film dewetting morphology as key to successful fabrication of single crystals. Furthermore, these 2D single crystals can align on chemically patterned substrates to minimize their interfacial energy. We explore in situ the conditions for crystal formation and alignment. PMID:23706086

  11. Tunable electrical conductivity in oriented thin films of tetrathiafulvalene-based covalent organic framework

    SciTech Connect

    Cai, SL; Zhang, YB; Pun, AB; He, B; Yang, JH; Toma, FM; Sharp, ID; Yaghi, OM; Fan, J; Zheng, SR; Zhang, WG; Liu, Y

    2014-09-16

    Despite the high charge-carrier mobility in covalent organic frameworks (COFs), the low intrinsic conductivity and poor solution processability still impose a great challenge for their applications in flexible electronics. We report the growth of oriented thin films of a tetrathiafulvalene-based COF (TTF-COF) and its tunable doping. The porous structure of the crystalline TTF-COF thin film allows the diffusion of dopants such as I-2 and tetracyanoquinodimethane (TCNQ) for redox reactions, while the closely packed 2D grid sheets facilitate the cross-layer delocalization of thus-formed TTF radical cations to generate more conductive mixed-valence TTF species, as is verified by UV-vis-NIR and electron paramagnetic resonance spectra. Conductivity as high as 0.28 S m(-1) is observed for the doped COF thin films, which is three orders of magnitude higher than that of the pristine film and is among the highest for COF materials.

  12. Layer-by-layer deposited organic/inorganic hybrid multilayer films containing noncentrosymmetrically orientated azobenzene chromophores.

    PubMed

    Kang, En-Hua; Bu, Tianjia; Jin, Pengcheng; Sun, Junqi; Yang, Yanqiang; Shen, Jiacong

    2007-07-01

    Organic/inorganic hybrid multilayer films with noncentrosymmetrically orientated azobenzene chromophores were fabricated by the sequential deposition of ZrO2 layers by a surface sol-gel process and subsequent layer-by-layer (LbL) adsorption of the nonlinear optical (NLO)-active azobenzene-containing polyanion PAC-azoBNS and poly(diallyldimethylammonium chloride) (PDDA). Noncentrosymmetric orientation of the NLO-active azobenzene chromophores was achieved because of the strong repulsion between the negatively charged ZrO(2) and the sulfonate groups of the azobenzene chromophore in PAC-azoBNS. Regular deposition of ZrO(2)/PAC-azoBNS/PDDA multilayer films was verified by UV-vis absorption spectroscopy and quartz crystal microbalance measurements. Both UV-vis absorption spectroscopy and transmission second harmonic generation (SHG) measurements confirmed the noncentrosymmetric orientation of the azobenzene chromophores in the as-prepared ZrO2/PAC-azoBNS/PDDA multilayer films. The square root of the SHG signal (I(2omega)(1/2)) increases with the increase of the azobenzene graft ratio in PAC-azoBNS as the number of deposition cycles of the ZrO(2)/PAC-azoBNS/PDDA films remains the same, while the second-order susceptibility chi(zzz)(2) of the film decreases with the increase of the azobenzene graft ratio. Furthermore, the present method was successfully extended to realize the noncentrosymmetric orientation of azobenzene chromophores in multilayer films when small organic azobenzene compounds with carboxylic acid and/or hydroxyl groups at one end and sulfonate groups at the other end were used. The present method was characterized by its simplicity and flexibility in film preparation, and it is anticipated to be a facile way to fabricate second-order nonlinear optical film materials. PMID:17555337

  13. Film-coupled nanoparticles by atomic layer deposition: Comparison with organic spacing layers

    SciTech Connect

    Ciracì, Cristian Mock, Jack J.; McGuire, Felicia; Liu, Xiaojun; Smith, David R.; Chen, Xiaoshu; Oh, Sang-Hyun

    2014-01-13

    Film-coupled nanoparticle systems have proven a reliable platform for exploring the field enhancement associated with sub-nanometer sized gaps between plasmonic nanostructures. In this Letter, we present a side-by-side comparison of the spectral properties of film-coupled plasmon-resonant, gold nanoparticles, with dielectric spacer layers fabricated either using atomic layer deposition or using organic layers (polyelectrolytes or self-assembled monolayers of molecules). In either case, large area, uniform spacer layers with sub-nanometer thicknesses can be accurately deposited, allowing extreme coupling regimes to be probed. The observed spectral shifts of the nanoparticles as a function of spacer layer thickness are similar for the organic and inorganic films and are consistent with numerical calculations taking into account the nonlocal response of the metal.

  14. Hard X-rays for processing hybrid organic-inorganic thick films.

    PubMed

    Jiang, Yu; Carboni, Davide; Pinna, Alessandra; Marmiroli, Benedetta; Malfatti, Luca; Innocenzi, Plinio

    2016-01-01

    Hard X-rays, deriving from a synchrotron light source, have been used as an effective tool for processing hybrid organic-inorganic films and thick coatings up to several micrometres. These coatings could be directly modified, in terms of composition and properties, by controlled exposure to X-rays. The physico-chemical properties of the coatings, such as hardness, refractive index and fluorescence, can be properly tuned using the interaction of hard X-rays with the sol-gel hybrid films. The changes in the microstructure have been correlated especially with the modification of the optical and the mechanical properties. A relationship between the degradation rate of the organic groups and the rise of fluorescence from the hybrid material has been observed; nanoindentation analysis of the coatings as a function of the X-ray doses has shown a not linear dependence between thickness and film hardness. PMID:26698073

  15. V2O5 thin film deposition for application in organic solar cells

    NASA Astrophysics Data System (ADS)

    Arbab, Elhadi A. A.; Mola, Genene Tessema

    2016-04-01

    Vanadium pentoxide V2O5 films were fabricated by way of electrochemical deposition technique for application as hole transport buffer layer in organic solar cell. A thin and uniform V2O5 films were successfully deposited on indium tin oxide-coated glass substrate. The characterization of surface morphology and optical properties of the deposition suggest that the films are suitable for photovoltaic application. Organic solar cell fabricated using V2O5 as hole transport buffer layer showed better devices performance and environmental stability than those devices fabricated with PEDOT:PSS. In an ambient device preparation condition, the power conversion efficiency increases by nearly 80 % compared with PEDOT:PSS-based devices. The devices lifetime using V2O5 buffer layer has improved by a factor of 10 over those devices with PEDOT:PSS.

  16. Strongly Dichroic Organic Films via Controlled Assembly of Modular Aromatic Charge-Transfer Liquid Crystals.

    PubMed

    Bé, Ariana Gray; Tran, Cheryl; Sechrist, Riley; Reczek, Joseph J

    2015-10-01

    The formation of highly anisotropic organic thin films based on the designed self-assembly of mixed-stack liquid crystals is reported. A series of alkoxyanthracene donors is combined in a modular fashion with a naphthalenediimide acceptor to generate new charge-transfer columnar liquid crystals. Materials characterization and molecular modeling provides insight into structure-function relationships in these organic materials that lead to the striking bulk dichroic properties of certain molecular assemblies. PMID:26375256

  17. Organic films on atmospheric aerosol particles, fog droplets, cloud droplets, raindrops, and snowflakes

    NASA Astrophysics Data System (ADS)

    Gill, P. S.; Graedel, T. E.; Weschler, C. J.

    1983-05-01

    If surface-active organic molecules are present as surface films, the transfer of gases into the atmospheric water system could be impeded, evaporation could be slowed, and the aqueous chemical reactions could be influenced. The results of new measurements of the surface tension of aqueous solutions of common atmospheric organic compounds (beta-pinene, n-hexanol, eugenol, and anethole) are reported, and it is shown that the compounds produce films with properties similar to those of the better known surfactants. It is concluded that organic films are probably common on atmospheric aerosol particles and that they may occur under certain circumstances on fog droplets, cloud droplets, and snowflakes. If they are present, they will increase the lifetimes of aerosol particles, fog droplets, and cloud droplets, both by inhibiting water vapor evaporation and by reducing the efficiency with which these atmospheric components are scavenged. It is thought likely that the transport of gaseous molecules into and out of the aqueous solution will be impeded by factors of several hundred or more when organic films are present.

  18. Fully Solution-Processed Flexible Organic Thin Film Transistor Arrays with High Mobility and Exceptional Uniformity

    PubMed Central

    Fukuda, Kenjiro; Takeda, Yasunori; Mizukami, Makoto; Kumaki, Daisuke; Tokito, Shizuo

    2014-01-01

    Printing fully solution-processed organic electronic devices may potentially revolutionize production of flexible electronics for various applications. However, difficulties in forming thin, flat, uniform films through printing techniques have been responsible for poor device performance and low yields. Here, we report on fully solution-processed organic thin-film transistor (TFT) arrays with greatly improved performance and yields, achieved by layering solution-processable materials such as silver nanoparticle inks, organic semiconductors, and insulating polymers on thin plastic films. A treatment layer improves carrier injection between the source/drain electrodes and the semiconducting layer and dramatically reduces contact resistance. Furthermore, an organic semiconductor with large-crystal grains results in TFT devices with shorter channel lengths and higher field-effect mobilities. We obtained mobilities of over 1.2 cm2 V−1 s−1 in TFT devices with channel lengths shorter than 20 μm. By combining these fabrication techniques, we built highly uniform organic TFT arrays with average mobility levels as high as 0.80 cm2 V−1 s−1 and ideal threshold voltages of 0 V. These results represent major progress in the fabrication of fully solution-processed organic TFT device arrays. PMID:24492785

  19. Fully Solution-Processed Flexible Organic Thin Film Transistor Arrays with High Mobility and Exceptional Uniformity

    NASA Astrophysics Data System (ADS)

    Fukuda, Kenjiro; Takeda, Yasunori; Mizukami, Makoto; Kumaki, Daisuke; Tokito, Shizuo

    2014-02-01

    Printing fully solution-processed organic electronic devices may potentially revolutionize production of flexible electronics for various applications. However, difficulties in forming thin, flat, uniform films through printing techniques have been responsible for poor device performance and low yields. Here, we report on fully solution-processed organic thin-film transistor (TFT) arrays with greatly improved performance and yields, achieved by layering solution-processable materials such as silver nanoparticle inks, organic semiconductors, and insulating polymers on thin plastic films. A treatment layer improves carrier injection between the source/drain electrodes and the semiconducting layer and dramatically reduces contact resistance. Furthermore, an organic semiconductor with large-crystal grains results in TFT devices with shorter channel lengths and higher field-effect mobilities. We obtained mobilities of over 1.2 cm2 V-1 s-1 in TFT devices with channel lengths shorter than 20 μm. By combining these fabrication techniques, we built highly uniform organic TFT arrays with average mobility levels as high as 0.80 cm2 V-1 s-1 and ideal threshold voltages of 0 V. These results represent major progress in the fabrication of fully solution-processed organic TFT device arrays.

  20. Intricacies of Polymer Dewetting: Nanoscaled Architectures for the Tailored Control of Polystyrene Thin Film Stability

    NASA Astrophysics Data System (ADS)

    Cheung, Justin; Sen, Mani; Chen, Zhizhao; Jiang, Naisheng; Endoh, Maya; Koga, Tadanori; Satija, Sushil

    Recently, structural properties of polymer thin films have garnered attention for their relevance in the fields of organic photovoltaics and biosensors. The dewetting of polymer films poses an obstacle in the face of widespread implementation. For this study, we show that adsorbed polymer chains on a substrate surface play crucial roles in film stability. Polystyrene (PS) thin films (20 nm in thickness) with different molecular weights (Mw) on silicon (Si) substrates were used as a model. The PS films were annealed at high temperatures for several days, and Mw dependence on film stability was evidenced. At the same time, the annealed PS films were leached with a good solvent and the residue films (i.e., irreversibly adsorbed layers) were characterized by x-ray reflectivity (XR). We reveal strong correlation between film stability and two different interfacial structures of the adsorbed polymer chains: their opposing wettability against chemically identical free polymer chains results in a wetting-dewetting transition at the adsorbed polymer-free polymer interface. This is a unique aspect of polymer thin film stability and may be generalizable to other polymer systems regardless of the magnitude of solid-polymer attractive interactions. We acknowledge the financial support of NSF Grant (CMMI-1332499).

  1. Self-organized behavior in thin-film recording media

    NASA Astrophysics Data System (ADS)

    Zhu, Jian-Gang; Bertram, H. Neal

    1991-04-01

    Magnetization domain structures in thin metallic films utilized as recording media are modeled by a cellular automation on a two-dimensional triangular lattice. This alternative approach permits significantly large arrays (≳ 106 grains) to be investigated as compared to an exact calculation (≊ 5 × 103 grains). Thus a study of the statistical distribution of the domain sizes and their power spectra can be made. Magnetostatic interactions and intergranular exchange coupling are included in a simple manner so that collective behavior is incorporated. It is found that away from the saturation remanent state, the distribution of the size of the avalanches (or the number of sites reversed in a single reversal sequence) follows a power-law behavior: D(S) = AS-α where S is the avalanche size and α varies in the vicinity of 1 depending on the interaction strength. The reversal field keeps the system marginally stable. It is found that the reproduce noise power varies as the derivative of the M-H loop.

  2. Endohedral Fullerenes in Organic Thin Film Photovoltaic Devices

    NASA Astrophysics Data System (ADS)

    Ross, Russel; Vankeuren, Edward; Drees, Martin; Cardona, Claudia; Holloway, Brian; Guldi, Dirk

    2008-03-01

    Cost factors in inorganic solar cells have opened up a new path to less expensive manufacturing techniques using bulk heterojunction polymer/fullerene based solar cells. Using empty cage fullerene derivatives as the acceptor material, state-of-the-art organic photovoltaics currently display ˜5% overall conversion efficiency. One of the main factors limiting the efficiency in organic solar cells is the low open circuit voltage. The open circuit voltage is governed by the molecular orbitals of the donor and acceptor material; therefore better matching of the orbitals will lead to improved voltages. We present a novel acceptor material based on TRIMETASPHERE^ carbon nanomaterials (TMS). TMS are endohedral metallofullerenes that consist of a trimetal nitride cluster enclosed in a C80 cage. First-generation TMS derivatives have been synthesized; electrochemical and photophysical studies show behavior consistent with C60 but with improved molecular orbitals. The electrochemical data suggests a maximum voltage increase of up to 280 mV over C60-PCBM-based devices. Organic solar cell devices are currently under construction and performance results will also be presented.

  3. Mid-infrared resonant ablation for selective patterning of thin organic films

    NASA Astrophysics Data System (ADS)

    Naithani, Sanjeev; Duterte, Charles; Levichkova, Marieta; Grisard, Arnaud; Schaubroeck, David; Lallier, Eric; Hernandez, Yves; Walzer, Karsten; Van Steenberge, Geert

    2014-05-01

    The fast growing market of organic electronics, including organic photovoltaics (OPV), stimulates the development of versatile technologies for structuring thin-film materials. Ultraviolet lasers have proven their full potential for patterning single organic layers, but in a multilayer organic device the obtained layer selectivity is limited as all organic layers show high UV absorption. In this paper, we introduce mid-infrared (IR) resonant ablation as an alternative approach, in which a short pulse mid-infrared laser can be wavelength tuned to one of the molecular vibrational transitions of the organic material to be ablated. As a result, the technique is selective in respect of processing a diversity of organics, which usually have different infrared absorption bands. Mid-IR resonant ablation is demonstrated for a variety of organic thin films, employing both nanosecond (15 ns) and picosecond (250 ps) laser pulses tunable between 3 and 4 microns. The nanosecond experimental set-up is based on a commercial laser at 1064 nm pumping a singly resonant Optical Parametric Oscillator (OPO) built around a Periodically-Poled Lithium Niobate (PPLN) crystal with several Quasi-Phase Matching (QPM) periods, delivering more than 0.3 W of mid-IR power, corresponding to 15 μJ pulses. The picosecond laser set-up is based on Optical Parametric Amplification (OPA) in a similar crystal, allowing for a comparison between both pulse length regimes. The wavelength of the mid-infrared laser can be tuned to one of the molecular vibrational transitions of the organic material to be ablated. For that reason, the IR absorption spectra of the organic materials used in a typical OPV device were characterized in the wavelength region that can be reached by the laser setups. Focus was on OPV substrate materials, transparent conductive materials, hole transport materials, and absorber materials. The process has been successfully demonstrated for selective thin film patterning, and the

  4. Using Resonant Soft X-rays to Reveal Internal Organic Thin Film Structure

    NASA Astrophysics Data System (ADS)

    Gann, Eliot

    This dissertation details the establishment and expansion of resonant soft X-ray scattering techniques to reveal the internal structure of organic thin films. These films are increasingly important in numerous electronic systems, including organic thin film transistors, organic photovoltaics, and organic light emitting diodes. These devices use the electrical properties of polymers to respectively turn on and off conduction, turn light into electricity, and create light. The performance of each of these systems depends critically on their physical structure but unfortunately, traditional techniques fail to adequately characterize that structure. This dissertation will explore the use of soft X-ray scattering to reveal the mesoscale structure or organic electronic devices. This begins with an overview of the field to make the case for soft X-rays being an appropriate and novel tool. Next, to explain how to collect accurate soft X-ray scattering, the development of a new and unique soft X-ray scattering facility will be presented. Having the tools, the next step is to develop scattering theories and models for understanding and correctly analyzing scattering from these complicated devices. This includes development and comparison of analysis techniques and theory to simulate scattering. This simulation system is then used in the development of a theory to understand the novel phenomenon of anisotropic X-ray scattering from isotropic organic samples. Finally, I will describe the development and first use of a method able to simultaneously measure size scales and chemical structure with depth sensitivity in thin films: Grazing Resonant Soft X-ray Scattering. This work provides valuable understanding and tools to the field of materials characterization, opening up new opportunities for principled design of organic electronics.

  5. Sol-gel-derived silica films with tailored microstructures for applications requiring organic dyes

    SciTech Connect

    Logan, M.N.; Prabakar, S.; Brinker, C.J. |

    1994-09-01

    A three-step sol-gel process was developed to prepare organic dye-doped thin films with tailored porosity for applications in chemical sensing and optoelectronics. Varying the acid- and base-catalyzed hydrolysis steps of sols prepared from tetraethoxysilane with identical final H{sub 2}O/Si ratios, dilution factors and pH resulted in considerably different distributions of the silicate polymers in the sol (determined by {sup 29}Si NMR) and considerably different structures for the polymer clusters (determined by SAXS). During film formation these kinetic effects cause differences in the packing and collapse of the silicate network, leading to thin films with different refractive indices and volume fraction porosities. Under conditions where small pore-plugging species were avoided, the porosities of as-deposited films could be varied by aging the sol prior to film deposition. This strategy, which relies on the growth and aggregation of fractal polymeric clusters, is compatible with the low temperature and near neutral pH requirements of organic dyes.

  6. [Differential Reflectance Spectroscopy for In-Situ Monitoring of Organic Thin Films Growth in Vacuum Environment].

    PubMed

    Yao, Yao; Hu, Chun-guang; Xu, Zhen-yuan; Zhang, Lei; Fu, Xing; Hu, Xiao-tang

    2015-05-01

    For realizing the real-time monitoring of organic thin film preparation process in vacuum environment, the present paper proposes a high precision measurement approach based on differential reflectance spectroscopy (DRS). An optical system was constructed with off the shelf optical components, such as off-axis parabolic mirror, optical flat and optical fiber. A differential algorithm was employed to analyze the spectral signals. Based on the homebuilt setup, instability induced by variation of temperature was investigated. It was concluded that with the good control of temperature and air flow, the measurement repeatability of this system is better than 2 per thousand for a long-term period. Furthermore, an initial stage of organic thin film growth of pentacene molecules on the surface of Au was studied. As compared with the data of film thickness gauge and atomic force microscope, DR spectra accurately recorded the fine optical evolution with sub-monolayer resolution, which is related to the growth of the thin film. As a result, the DR optical system exhibits characteristics of broad spectrum (range from 300 to 820 nm), high stability (repeatability better than 2X 10(-3)), and high precision (sub-monolayer resolution) after efforts were done to decrease the influences on the spectral quality produced by misalignments of the optical components, the defects of the optics, and the disturbances of the environmental conditions. It is indicated that the proposed DR method is suitable for real-time online monitoring of thin film growth with high precision. PMID:26415453

  7. Thermal expansion of self-organized and shear-oriented cellulose nanocrystal films.

    PubMed

    Diaz, Jairo A; Wu, Xiawa; Martini, Ashlie; Youngblood, Jeffrey P; Moon, Robert J

    2013-08-12

    The coefficient of thermal expansion (CTE) of cellulose nanocrystal (CNC) films was characterized using novel experimental techniques complemented by molecular simulations. The characteristic birefringence exhibited by CNC films was utilized to calculate the in-plane CTE of self-organized and shear-oriented self-standing CNC films from room temperature to 100 °C using polarized light image correlation. CNC alignment was estimated via Hermans order parameter (S) from 2D X-ray diffraction measurements. We found that films with no preferential CNC orientation through the thickness (S: ∼ 0.0) exhibited an isotropic CTE (∼25 ppm/K). In contrast, films with aligned CNC orientations (S: ∼0.4 to 0.8) had an anisotropic CTE response: For the highest CNC alignment (S: 0.8), the CTE parallel to CNC alignment was ∼9 ppm/K, while that perpendicular to CNC alignment was ∼158 ppm/K. CNC film thermal expansion was proposed to be due primarily to single crystal expansion and CNC-CNC interfacial motion. The relative contributions of inter- and intracrystal responses to heating were explored using molecular dynamics simulations. PMID:23841850

  8. Optical performance of mesostructured composite silica film loaded with organic dye.

    PubMed

    Guli, Mina; Chen, Shijian; Zhang, Dingke; Li, Xiaotian; Yao, Jianxi; Chen, Lei; Xiao, Li

    2014-01-10

    A mesoporous composite silica film loaded with organic dye has been successfully synthesized by a solgel reaction process and a simple postgrafting method at room temperature. The composite film was characterized by x-ray diffraction, transmission electron microscopy, UV-Vis, photoluminescence (PL) spectra, and laser performance, and the results confirmed the existence of dyes in the channels of the silica film. A blue-shift and fluorescence property in the PL spectrum was observed from the composite film compared with that of dye molecules in C₂H₅OH solution. The spectrum narrowing phenomena has been observed when the composite film is pumped at λp=355  nm by a Nd:YAG pulsed laser. A narrower, higher peak was observed in emission spectra from the mesostructured composite silica film compared with the PL spectrum of dye in C₂H₅OH solution. There is a substantial reduction in the full width at half-maximum of the emitting light, which results in peaks with linewidths of 26 nm or more. This collapse of the emission spectrum is one of the signatures of the presence of amplified spontaneous emission. PMID:24514063

  9. Lithography-Free Broadband Ultrathin-Film Absorbers with Gap-Plasmon Resonance for Organic Photovoltaics.

    PubMed

    Choi, Minjung; Kang, Gumin; Shin, Dongheok; Barange, Nilesh; Lee, Chang-Won; Ko, Doo-Hyun; Kim, Kyoungsik

    2016-05-25

    Strategies to confine electromagnetic field within ultrathin film emerge as essential technologies for applications from thin-film solar cells to imaging and sensing devices. We demonstrate a lithography-free, low-cost, large-scale method to realize broadband ultrathi-film metal-dielectric-metal (MDM) absorbers, by exploiting gap-plasmon resonances for strongly confined electromagnetic field. A two-steps method, first organizing Au nanoparticles via thermal dewetting and then transferring the nanoparticles to a spacer-reflector substrate, is used to achieve broader absorption bandwidth by manipulating geometric shapes of the top metallic layer into hemiellipsoids. A fast-deposited nominal Au film, instead of a conventional slow one, is employed in the Ostwald ripening process to attain hemiellipsoidal nanoparticles. A polymer supported transferring step allows a wider range of dewetting temperature to manipulate the nanoparticles' shape. By incorporating circularity with ImageJ software, the geometries of hemiellipsoidal nanoparticles are quantitatively characterized. Controlling the top geometry of MDM structure from hemisphere to hemiellipsoid increases the average absorption at 500-900 nm from 23.1% to 43.5% in the ultrathin film and full width at half-maximum of 132-324 nm, which is consistently explained by finite-difference time-domain simulation. The structural advantages of our scheme are easily applicable to thin-film photovoltaic devices because metal electrodes can act as metal reflectors and semiconductor layers as dielectric spacers. PMID:27160410

  10. Synthesis and assembly of gold nanoparticles in organized molecular films of gemini amphiphiles.

    PubMed

    Zhong, Ling; Jiao, Tifeng; Liu, Minghua

    2008-10-21

    Generation and assembly of gold nanostructures were investigated in the organized molecular films of a series of gemini amphiphiles. The chloroauric acid, dissolved in the aqueous subphase, was incorporated into the monolayers of the gemini amphiphiles containing ethyleneamine spacers through an interfacial assembly. The in situ formed complex monolayers were transferred onto solid substrates, and gold nanoparticles were generated in the film by a chemical or photochemical reduction. Discrete gold nanoparticles with an absorption maximum at 550 nm were generated in the films by photoirradiation, while different gold nanostructures were obtained by chemical reduction. Depending on the chemical reductant, various shape and assembly of gold nanostructures were obtained. When reduced by hydroquinone, a tree-branched assembly of the nanoparticles was obtained and the film showed a broad band centered at around 900 nm. When NaBH 4 was applied, crooked nanowires or assembly of nanoparticles were obtained, depending on concentration, and the film showed absorption at 569 or 600 nm. Furthermore, by combining the photochemical and chemical reduction methods, i.e., the chloroaurate ion-incorporated film was initially irradiated with UV light and then subjected to chemical reduction, the optical absorption of the formed gold nanostructures can be regulated. PMID:18823092

  11. Understanding surface core-level shifts using the Auger parameter: A study of Pd atoms adsorbed on ultrathin SiO2 films

    NASA Astrophysics Data System (ADS)

    Kaden, William E.; Büchner, Christin; Lichtenstein, Leonid; Stuckenholz, Stefanie; Ringleb, Franziska; Heyde, Markus; Sterrer, Martin; Freund, Hans-Joachim; Giordano, Livia; Pacchioni, Gianfranco; Nelin, Connie J.; Bagus, Paul S.

    2014-03-01

    Auger parameter (Δα) measurements have been employed to determine the extent to which initial- and final-state effects govern surface core-level shifts in x-ray photoelectron spectroscopy (XPS) measurements of Pd atoms confined between a bilayer SiO2 film and its Ru(0001) support. For atoms bound in this manner, we note negative binding energy shifts (ΔBEs) of ˜0.3 eV, relative to the Pd 3d peak position in the bulk, and attribute these shifts to large variations in the initial-state orbital energies of the supported atoms (˜1.1 eV towards EF), coupled with decreased final-state relaxation contributions (˜0.8 eV). Theoretical calculations reveal that, despite small partial positive charges and decreased final-state screening, the decreased 4d-5sp hybridization of the undercoordinated Pd atoms results in large enough upward 3d orbital-energy shifts to yield the net-negative ΔBE noted by XPS.

  12. Regenerative adsorbent heat pump

    NASA Technical Reports Server (NTRS)

    Jones, Jack A. (Inventor)

    1991-01-01

    A regenerative adsorbent heat pump process and system is provided which can regenerate a high percentage of the sensible heat of the system and at least a portion of the heat of adsorption. A series of at least four compressors containing an adsorbent is provided. A large amount of heat is transferred from compressor to compressor so that heat is regenerated. The process and system are useful for air conditioning rooms, providing room heat in the winter or for hot water heating throughout the year, and, in general, for pumping heat from a lower temperature to a higher temperature.

  13. High-efficiency THz modulator based on phthalocyanine-compound organic films

    SciTech Connect

    He, Ting; Zhang, Bo E-mail: sjl-phy@cnu.edu.cn; Shen, Jingling E-mail: sjl-phy@cnu.edu.cn; Zang, Mengdi; Chen, Tianji; Hu, Yufeng; Hou, Yanbing

    2015-02-02

    We report a high efficiency, broadband terahertz (THz) modulator following a study of phthalocyanine-compound organic films irradiated with an external excitation laser. Both transmission and reflection modulations of each organic/silicon bilayers were measured using THz time-domain and continuous-wave systems. For very low intensities, the experimental results show that AlClPc/Si can achieve a high modulation factor for transmission and reflection, indicating that AlClPc/Si has a superior modulation efficiency compared with the other films (CuPc and SnCl{sub 2}Pc). In contrast, the strong attenuation of the transmitted and reflected THz waves revealed that a nonlinear absorption process takes place at the organic/silicon interface.

  14. High-efficiency THz modulator based on phthalocyanine-compound organic films

    NASA Astrophysics Data System (ADS)

    He, Ting; Zhang, Bo; Shen, Jingling; Zang, Mengdi; Chen, Tianji; Hu, Yufeng; Hou, Yanbing

    2015-02-01

    We report a high efficiency, broadband terahertz (THz) modulator following a study of phthalocyanine-compound organic films irradiated with an external excitation laser. Both transmission and reflection modulations of each organic/silicon bilayers were measured using THz time-domain and continuous-wave systems. For very low intensities, the experimental results show that AlClPc/Si can achieve a high modulation factor for transmission and reflection, indicating that AlClPc/Si has a superior modulation efficiency compared with the other films (CuPc and SnCl2Pc). In contrast, the strong attenuation of the transmitted and reflected THz waves revealed that a nonlinear absorption process takes place at the organic/silicon interface.

  15. Mixed Polarization Vibrational Sum Frequency Generation Spectra of Organic Semiconducting Thin Films

    NASA Astrophysics Data System (ADS)

    Kearns, Patrick; Sohrabpour, Zahara; Massari, Aaron M.

    2014-06-01

    The buried interface of an organic semiconductor at the dielectric has a large on influence on the function of organic field effect transistors (OFETs). The use of vibrational sum frequency generation (VSFG) to obtain structural and orientational information on the buried interfaces of organic thin films has historically been complicated by the signals from other interfaces in the system. A thin film of N,N'-Dioctyl-3,4,9,10-perylenedicarboximide (PTCDI-C8) was deposited on a SiO2 dielectric to simulate the interfaces found in OFETs. We will show how probing the sample with a varying mixture of linear polarizations in the experimental setup can deconvolute contributions to the overall signal from multiple interfaces.

  16. Modifying the thermal conductivity of small molecule organic semiconductor thin films with metal nanoparticles

    PubMed Central

    Wang, Xinyu; Parrish, Kevin D.; Malen, Jonathan A.; Chan, Paddy K. L.

    2015-01-01

    Thermal properties of organic semiconductors play a significant role in the performance and lifetime of organic electronic devices, especially for scaled-up large area applications. Here we employ silver nanoparticles (Ag NPs) to modify the thermal conductivity of the small molecule organic semiconductor, dinaphtho[2,3-b:2’,3’-f]thieno[3,2-b]thiophene (DNTT). The differential 3-ω method was used to measure the thermal conductivity of Ag-DNTT hybrid thin films. We find that the thermal conductivity of pure DNTT thin films do not vary with the deposition temperature over a range spanning 24 °C to 80 °C. The thermal conductivity of the Ag-DNTT hybrid thin film initially decreases and then increases when the Ag volume fraction increases from 0% to 32%. By applying the effective medium approximation to fit the experimental results of thermal conductivity, the extracted thermal boundary resistance of the Ag-DNTT interface is 1.14 ± 0.98 × 10−7 m2-K/W. Finite element simulations of thermal conductivity for realistic film morphologies show good agreement with experimental results and effective medium approximations. PMID:26531766

  17. Research on the electronic and optical properties of polymer and other organic molecular thin films

    SciTech Connect

    1997-02-01

    The main goal of the work is to find materials and methods of optimization of organic layered electroluminescent cells and to study such properties of polymers and other organic materials that can be used in various opto-electronic devices. The summary of results obtained during the first year of work is presented. They are: (1) the possibility to produce electroluminescent cells using a vacuum deposition photoresist technology for commercial photoresists has been demonstrated; (2) the idea to replace the polyaryl polymers by other polymers with weaker hole conductivity for optimization of electroluminescent cells with ITO-Al electrodes has been suggested. The goal is to obtain amorphous processable thin films of radiative recombination layers in electroluminescent devices; (3) procedures of preparation of high-quality vacuum-deposited poly (p-phenylene) (PPP) films on various substrates have been developed; (4) it was found for the first time that the fluorescence intensity of PPP films depends on the degree of polymerization; (5) the role of interfaces between organic compounds, on one side, and metals or semiconductors, on the other side, has been studied and quenching of the fluorescence caused by semiconductor layer in thin sandwiches has been observed; (6) studies of the dynamics of photoexcitations revealed the exciton self-trapping in quasi-one-dimensional aggregates; and (7) conditions for preparation of highly crystalline fullerene C{sub 60} films by vacuum deposition have been found. Composites of C{sub 60} with conjugated polymers have been prepared.

  18. pn-homojunction organic solar cells formed in phase-separated co-deposited films

    NASA Astrophysics Data System (ADS)

    Kubo, Masayuki; Kaji, Toshihiko; Hiramoto, Masahiro

    2013-12-01

    Simultaneous control of the doping and phase-separation in organic co-deposited films consisting of metal-free phthalocyanine and fullerene was performed. The doping was used to form pn-homojunctions in the phase-separated co-deposited films. The diffusion length of the minority carriers reached 0.3 μm allowing the fabrication of very thick cells up to 0.5 μm thick. It was shown that suppression of the interfacial recombination processes is crucial for obtaining cells with high performance.

  19. Electric dipolar interaction assisted growth of single crystalline organic thin films

    SciTech Connect

    Jin-ming, Cai; Yu-Yang, Zhang; Hao, Hu; Li-Hong, Bao; Li-Da, Pan; Wei, Tang; Guo, Li; Shi-Xuan, Du; Jian, Shen; Hong-Jun, Gao

    2010-01-01

    We report on a forest-like-to-desert-like pattern evolution in the growth of an organic thin film observed by using an atomic force microscope. We use a modified diffusion limited aggregation model to simulate the growth process and are able to reproduce the experimental patterns. The energy of electric dipole interaction is calculated and determined to be the driving force for the pattern formation and evolution. Based on these results, single crystalline films are obtained by enhancing the electric dipole interaction while limiting effects of other growth parameters.

  20. Nanoscale aluminum concaves for light-trapping in organic thin-films

    NASA Astrophysics Data System (ADS)

    Goszczak, Arkadiusz Jarosław; Adam, Jost; Cielecki, Paweł Piotr; Fiutowski, Jacek; Rubahn, Horst-Günter; Madsen, Morten

    2016-07-01

    Anodic aluminum oxide (AAO) templates, fabricated from oxalic acid and phosphoric acid, lead to non-periodic nanoscale concave structures in their underlying aluminum layer, which are investigated for their field-enhancement properties by applying a thin-film polymer coating based laser ablation technique. Local ablation spots, corresponding to field enhancement on the ridge edges of the aluminum concave nanostructures, are observed in surface-covering polymer films, and confirmed with FDTD studies. The field enhancement leads to improved light absorption in the applied polymer layers, which may be used as an efficient method for enhancing the power conversion efficiency of organic solar cells.

  1. Three approaches to economical photovoltaics: Conformal copper sulfide , organic luminescent films, and lead selenide nanocrystal superlattices

    NASA Astrophysics Data System (ADS)

    Carbone, Ian A.

    Three routes to more efficient photovoltaics using conformal Cu2S, organic luminescent films, and nanocrystalline PbSe films are outlined below. Properties of these materials are investigated experimentally and numerically in separate studies. In the first study, chemical vapor deposition (CVD) processes were used to fabricate Cu2S using hydrogen sulfide and the metal-organic precursor, KI5. The alternating exposure of mesoporous TiO2 and planar ZnO to the two precursors resulted in films that penetrated porous structures and deposited at a constant rate of 0.08nm/cycle over the temperature range 150C-400°C. Sheet resistance and optical absorption measurements suggest the presence of a metallic copper-poor phase of less than 100nm thick forming at the Cu2S/substrate boundary. In a separate study, organic films doped with luminescent dyes were placed above CdTe/CdS solar cells to convert high energy photons to lower energies, better matched to the CdTe/CdS quantum efficiency peak. Efficiency improvements of up to 8.5% were obtained after optimizing dye concentration, dye chemistry, and the host material. Long-term stability tests show that the organic films are stable for at least 5000 hours under 1 sun illumination provided that the dye is encapsulated in an oxygen and water free environment. Finally, a Monte Carlo model was developed to simulate electron and hole transport in nanocrystalline PbSe films. Transport is carried out as a series of thermally activated tunneling events between neighboring sites on a cubic lattice. Each site, representing an individual nanocrystal, is assigned a size-dependent electronic structure, and the effects of crystal size, charging, inter-crystal coupling, and energetic disorder on electron and hole mobilities/conductivities are investigated. Results of simulated field effect measurements confirm that electron mobilities and conductivities increase by an order of magnitude when the average nanocrystal diameter is increased in the

  2. An asymmetric oligomer based on thienoacene for solution processed crystal organic thin-film transistors.

    PubMed

    Tian, Hongkun; Han, Yang; Bao, Cheng; Yan, Donghang; Geng, Yanhou; Wang, Fosong

    2012-04-11

    A novel thienoacene-based conjugated oligomer, i.e.BTTT-T-C12, was designed and synthesized. Its highly asymmetric structural feature enables the preparation of two-dimensional single-crystalline thin films in millimetre size and ~100 nm thick by a solution processing method directly on the Si/SiO(2) substrate. Single crystal organic thin film transistors exhibit a mobility of 0.70 cm(2) V(-1) s(-1) and an on/off ratio of 5.7 × 10(4). PMID:22389169

  3. Mechanical properties of metal-organic frameworks: An indentation study on epitaxial thin films

    NASA Astrophysics Data System (ADS)

    Bundschuh, S.; Kraft, O.; Arslan, H. K.; Gliemann, H.; Weidler, P. G.; Wöll, C.

    2012-09-01

    We have determined the hardness and Young's modulus of a highly porous metal-organic framework (MOF) using a standard nanoindentation technique. Despite the very low density of these films, 1.22 g cm-3, Young's modulus reaches values of almost 10 GPa for HKUST-1, demonstrating that this porous coordination polymer is substantially stiffer than normal polymers. This progress in characterizing mechanical properties of MOFs has been made possible by the use of high quality, oriented thin films grown using liquid phase epitaxy on modified Au substrates.

  4. Structure dependence of lasing action in organic polymer films on DFB gratings for dinitrotoluene vapor detection.

    PubMed

    Liu, Qiufeng; Qiu, Keqiang; He, Shengnan; Liu, Honglin; Liu, Zhengkun; Hong, Yilin; Fu, Shaojun

    2016-06-20

    Structure effects of distributed feedback (DFB) gratings on lasing action have been investigated for detecting explosive vapors. For the first time, we have established the optimized profiles of the DFB grating, and given the theoretical path to design its structure for amplified spontaneous emission (ASE) of organic polymer films based on Bragg conditions. A poly(p-phenylene ethynylene) (PPE) film can realize detection of dinitrotoluene (DNT) vapors in 2 min with a reduced excitation threshold of 26 mJ cm(-2) by using a simple and common 405 nm laser. PMID:27277339

  5. Trapping light with micro lenses in thin film organic photovoltaic cells.

    PubMed

    Tvingstedt, Kristofer; Dal Zilio, Simone; Inganäs, Olle; Tormen, Massimo

    2008-12-22

    We demonstrate a novel light trapping configuration based on an array of micro lenses in conjunction with a self aligned array of micro apertures located in a highly reflecting mirror. When locating the light trapping element, that displays strong directional asymmetric transmission, in front of thin film organic photovoltaic cells, an increase in cell absorption is obtained. By recycling reflected photons that otherwise would be lost, thinner films with more beneficial electrical properties can effectively be deployed. The light trapping element enhances the absorption rate of the solar cell and increases the photocurrent by as much as 25%. PMID:19104592

  6. In situ spectroelectrochemical and theoretical study on the oxidation of a 4H-imidazole-ruthenium dye adsorbed on nanocrystalline TiO2 thin film electrodes.

    PubMed

    Zhang, Ying; Kupfer, Stephan; Zedler, Linda; Schindler, Julian; Bocklitz, Thomas; Guthmuller, Julien; Rau, Sven; Dietzek, Benjamin

    2015-11-28

    Terpyridine 4H-imidazole-ruthenium(II) complexes are considered promising candidates for use as sensitizers in dye sensitized solar cells (DSSCs) by displaying broad absorption in the visible range, where the dominant absorption features are due to metal-to-ligand charge transfer (MLCT) transitions. The ruthenium(III) intermediates resulting from photoinduced MLCT transitions are essential intermediates in the photoredox-cycle of the DSSC. However, their photophysics is much less studied compared to the ruthenium(II) parent systems. To this end, the structural alterations accompanying one-electron oxidation of the RuIm dye series (including a non-carboxylic RuIm precursor, and, carboxylic RuImCOO in solution and anchored to a nanocrystalline TiO2 film) are investigated via in situ experimental and theoretical UV-Vis absorption and resonance Raman (RR) spectroelectrochemistry. The excellent agreement between the experimental and the TDDFT spectra derived in this work allows for an in-depth assignment of UV-Vis and RR spectral features of the dyes. A concordant pronounced wavelength dependence with respect to the charge transfer character has been observed for the model system RuIm, and both RuImCOO in solution and attached on the TiO2 surface. Excitation at long wavelengths leads to the population of ligand-to-metal charge transfer states, i.e. photoreduction of the central ruthenium(III) ion, while high-energy excitation features an intra-ligand charge transfer state localized on the 4H-imidazole moiety. Therefore, these 4H-imidazole ruthenium complexes investigated here are potential multi-photoelectron donors. One electron is donated from MLCT states, and additionally, the 4H-imidazole ligand reveals electron-donating character with a significant contribution to the excited states of the ruthenium(III) complexes upon blue-light irradiation. PMID:26478575

  7. Al2O3/TiO2 nanolaminate thin film encapsulation for organic thin film transistors via plasma-enhanced atomic layer deposition.

    PubMed

    Kim, Lae Ho; Kim, Kyunghun; Park, Seonuk; Jeong, Yong Jin; Kim, Haekyoung; Chung, Dae Sung; Kim, Se Hyun; Park, Chan Eon

    2014-05-14

    Organic electronic devices require a passivation layer that protects the active layers from moisture and oxygen because most organic materials are very sensitive to such gases. Passivation films for the encapsulation of organic electronic devices need excellent stability and mechanical properties. Although Al2O3 films obtained with plasma enhanced atomic layer deposition (PEALD) have been tested as passivation layers because of their excellent gas barrier properties, amorphous Al2O3 films are significantly corroded by water. In this study, we examined the deformation of PEALD Al2O3 films when immersed in water and attempted to fabricate a corrosion-resistant passivation film by using a PEALD-based Al2O3/TiO2 nanolamination (NL) technique. Our Al2O3/TiO2 NL films were found to exhibit excellent water anticorrosion and low gas permeation and require only low-temperature processing (<100 °C). Organic thin film transistors with excellent air-stability (52 days under high humidity (a relative humidity of 90% and a temperature of 38 °C)) were fabricated. PMID:24712401

  8. Use of surface and thin film analysis techniques to study metal-organic and metal-polymer interaction

    SciTech Connect

    Tompkins, H.G.

    1984-01-01

    Very thin organic or polymer films can be analyzed using several analytic techniques. The thickness of the films discussed ranges from monolayers to several thousand angstroms thick. The techniques described are x-ray photoelectron spectroscopy, infrared spectroscopy, ellipsometry, and the quartz crystal oscillator microbalance. The latter technique is applied to a fluoropolymer deposited on a silver surface. The parameters which control film thickness and uniformity are discussed along with how one measures these parameters. The second example discussed is the application of nitrogen containing organic molecules to copper and iron surfaces. The chemical bonding is discussed along with the orientation of the molecules in the resulting film and the analytical techniques used.

  9. Solution-grown small-molecule organic semiconductor with enhanced crystal alignment and areal coverage for organic thin film transistors

    DOE PAGESBeta

    Bi, Sheng; He, Zhengran; Chen, Jihua; Li, Dawen

    2015-07-24

    Drop casting of small-molecule organic semiconductors typically forms crystals with random orientation and poor areal coverage, which leads to significant performance variations of organic thin-film transistors (OTFTs). In this study, we utilize the controlled evaporative self-assembly (CESA) method combined with binary solvent system to control the crystal growth. A small-molecule organic semiconductor,2,5-Di-(2-ethylhexyl)-3,6-bis(5"-n-hexyl-2,2',5',2"]terthiophen-5-yl)-pyrrolo[3,4-c]pyrrole-1,4-dione (SMDPPEH), is used as an example to demonstrate the effectiveness of our approach. By optimizing the double solvent ratios, well-aligned SMDPPEH crystals with significantly improved areal coverage were achieved. As a result, the SMDPPEH based OTFTs exhibit a mobility of 1.6 × 10-2 cm2/V s, which is themore » highest mobility from SMDPPEH ever reported.« less

  10. Solution-grown small-molecule organic semiconductor with enhanced crystal alignment and areal coverage for organic thin film transistors

    SciTech Connect

    Bi, Sheng; He, Zhengran; Chen, Jihua; Li, Dawen

    2015-07-24

    Drop casting of small-molecule organic semiconductors typically forms crystals with random orientation and poor areal coverage, which leads to significant performance variations of organic thin-film transistors (OTFTs). In this study, we utilize the controlled evaporative self-assembly (CESA) method combined with binary solvent system to control the crystal growth. A small-molecule organic semiconductor,2,5-Di-(2-ethylhexyl)-3,6-bis(5"-n-hexyl-2,2',5',2"]terthiophen-5-yl)-pyrrolo[3,4-c]pyrrole-1,4-dione (SMDPPEH), is used as an example to demonstrate the effectiveness of our approach. By optimizing the double solvent ratios, well-aligned SMDPPEH crystals with significantly improved areal coverage were achieved. As a result, the SMDPPEH based OTFTs exhibit a mobility of 1.6 × 10-2 cm2/V s, which is the highest mobility from SMDPPEH ever reported.

  11. Recent progress on thin-film encapsulation technologies for organic electronic devices

    NASA Astrophysics Data System (ADS)

    Yu, Duan; Yang, Yong-Qiang; Chen, Zheng; Tao, Ye; Liu, Yun-Fei

    2016-03-01

    Among the advanced electronic devices, flexible organic electronic devices with rapid development are the most promising technologies to customers and industries. Organic thin films accommodate low-cost fabrication and can exploit diverse molecules in inexpensive plastic light emitting diodes, plastic solar cells, and even plastic lasers. These properties may ultimately enable organic materials for practical applications in industry. However, the stability of organic electronic devices still remains a big challenge, because of the difficulty in fabricating commercial products with flexibility. These organic materials can be protected using substrates and barriers such as glass and metal; however, this results in a rigid device and does not satisfy the applications demanding flexible devices. Plastic substrates and transparent flexible encapsulation barriers are other possible alternatives; however, these offer little protection to oxygen and water, thus rapidly degrading the devices. Thin-film encapsulation (TFE) technology is most effective in preventing water vapor and oxygen permeation into the flexible devices. Because of these (and other) reasons, there has been an intense interest in developing transparent barrier materials with much lower permeabilities, and their market is expected to reach over 550 million by 2025. In this study, the degradation mechanism of organic electronic devices is reviewed. To increase the stability of devices in air, several TFE technologies were applied to provide efficient barrier performance. In this review, the degradation mechanism of organic electronic devices, permeation rate measurement, traditional encapsulation technologies, and TFE technologies are presented.

  12. Polarization-resolved spectroscopy imaging of grain boundaries and optical excitations in crystalline organic thin films

    PubMed Central

    Pan, Z.; Rawat, N.; Cour, I.; Manning, L.; Headrick, R. L.; Furis, M.

    2015-01-01

    Exploration of optical properties of organic crystalline semiconductors thin films is challenging due to submicron grain sizes and the presence of numerous structural defects, disorder and grain boundaries. Here we report on the results of combined linear dichroism (LD)/ polarization-resolved photoluminescence (PL) scanning microscopy experiments that simultaneously probe the excitonic radiative recombination and the molecular ordering in solution-processed metal-free phthalocyanine crystalline thin films with macroscopic grain sizes. LD/PL images reveal the relative orientation of the singlet exciton transition dipoles at the grain boundaries and the presence of a localized electronic state that acts like a barrier for exciton diffusion across the grain boundary. We also show how this energy barrier can be entirely eliminated through the optimization of deposition parameters that results in films with large grain sizes and small-angle boundaries. These studies open an avenue for exploring the influence of long-range order on exciton diffusion and carrier transport. PMID:26365682

  13. Polarization-dependent differential reflectance spectroscopy for real-time monitoring of organic thin film growth.

    PubMed

    Navarro-Quezada, A; Aiglinger, M; Ghanbari, E; Wagner, Th; Zeppenfeld, P

    2015-11-01

    By monitoring the reflectance of a sample surface during deposition of a thin organic film, one can obtain information with submonolayer resolution in real-time. A special kind of optical spectroscopy is Differential Reflectance Spectroscopy (DRS), which compares the reflectance before and during deposition of a thin film or any other change of the surface optical properties. In this work, we present an extended DRS setup that allows monitoring simultaneously both linear polarization states (s and p) of the reflected light. We implement polarization-dependent DRS to monitor the growth of perflouropentacene thin films on a Ag(110) single crystal. The setup allows us to deduce the optical anisotropy of the sample and, in particular, the preferred orientation of the molecules on the surface. PMID:26628122

  14. High-sensitivity organic phototransistors prepared by floating film transfer method

    NASA Astrophysics Data System (ADS)

    Bhargava, Kshitij; Singh, Vipul

    2016-09-01

    In this report, the performance characteristics of organic phototransistors (OPTs) prepared by the floating film transfer method (FTM) and spin coating (SC) technique are compared. The FTM OPT shows a 2-order-higher photosensitivity under an electrically induced off-state as compared with the SC OPT. Furthermore, the FTM OPT shows improved gate voltage tunabilities of photosensitivity and responsivity as compared with the SC OPT. These observed results are explained on the basis of the improved thin film morphology of the active poly(3-hexylthiophene-2,5-diyl) (P3HT) layer in the FTM OPT, pointing towards the significance of thin film processing conditions in obtaining high-sensitivity OPTs.

  15. Removal of organic films from solid surfaces using aqueous solutions of nonionic surfactants. 1: Experiments

    SciTech Connect

    Beaudoin, S.P.; Grant, C.S.; Carbonell, R.G.

    1995-10-01

    An important step in the production of printed wiring assemblies (PWAs) is the postsolder removal of flux residues from the surface. Traditionally, this has been accomplished using CFC-113-based solutions, but the Montreal Protocol and the Clean Air Acts have forced the development of alternative cleaners. This is a study of the mechanisms by which aqueous solutions of a nonionic surfactant (pentaethylene glycol mono-n-dodecyl either (C{sub 12}E{sub 5})) remove films of flux residues (abietic acid in isopropyl alcohol) from PWA surfaces. Cleaning rates were studied in a rotating disk apparatus to control hydrodynamic conditions. The cleaning process followed a three-step mechanism. In the first stage, surfactant liquefies the organic by partitioning into the film. In the second and third stages, shear stresses at the PWA surface remove aggregates of the surfactant-laden liquefied AA from the bulk AA film and the PWA substrate, respectively.

  16. Adsorbent and adsorbent bed for materials capture and separation processes

    SciTech Connect

    Liu, Wei

    2011-01-25

    A method device and material for performing adsorption wherein a fluid mixture is passed through a channel in a structured adsorbent bed having a solid adsorbent comprised of adsorbent particles having a general diameter less than 100 um, loaded in a porous support matrix defining at least one straight flow channel. The adsorbent bed is configured to allow passage of a fluid through said channel and diffusion of a target material into said adsorbent under a pressure gradient driving force. The targeted molecular species in the fluid mixture diffuses across the porous support retaining layer, contacts the adsorbent, and adsorbs on the adsorbent, while the remaining species in the fluid mixture flows out of the channel.

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

    PubMed

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

    2014-12-10

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

  18. [Effects of white organic light-emitting devices using color conversion films on electroluminescence spectra].

    PubMed

    Hou, Qing-Chuan; Wu, Xiao-Ming; Hua, Yu-Lin; Qi, Qing-Jin; Li, Lan; Yin, Shou-Gen

    2010-06-01

    The authors report a novel white organic light-emitting device (WOLED), which uses a strategy of exciting organic/ inorganic color conversion film with a blue organic light-emitting diode (OLED). The luminescent layer of the blue OLED was prepared by use of CBP host blended with a blue highly fluorescent dye N-BDAVBi. The organic/inorganic color conversion film was prepared by dispersing a mixture of red pigment VQ-D25 and YAG : Ce3+ phosphor in PMMA. The authors have achieved a novel WOLED with the high color stability by optimizing the thickness and fluorescent pigment concentration of the color conversion film. When the driving voltage varied between 6 and 14 V, the color coordinates (CIE) varied slightly from (0.354, 0.304) to (0.357, 0.312) and the maximum current efficiency is about 5.8 cd x A(-1) (4.35 mA x cm(-2)), the maximum brightness is 16 800 cd x m(-2) at the operating voltage of 14 V. PMID:20707129

  19. High performance organic thin film transistors with solution processed TTF-TCNQ charge transfer salt as electrodes.

    PubMed

    Mukherjee, Biswanath; Mukherjee, Moumita

    2011-09-01

    Fabrication of high-performance organic thin film transistors (OTFTs) with solution processed organic charge transfer complex (TTF-TCNQ) film as bottom contact source-drain electrodes is reported. A novel capillary based method was used to deposit the source-drain electrodes from solution and to create the channel between the electrodes. Both p- and n-type OTFTs have been fabricated with solution deposited organic charge transfer film as contact electrodes. Comparison of the device performances between OTFTs with TTF-TCNQ as source-drain electrodes and those with Au electrodes (both top and bottom contact) indicate that better results have been obtained in organic complex film contacted OTFT. The high mobility, low threshold voltage, and efficient carrier injection in both types of OTFTs implies the potential use of the TTF-TCNQ based complex material as low-cost contact electrodes. The lower work function of the TTF-TCNQ electrode and better contact of the complex film with the organic thin film owing to the organic-organic interface results in efficient charge transfer into the semiconductor yielding high device performance. The present method having organic metal as contact materials promises great potential for the fabrication of all-organics and plastic electronics devices with high throughput and low-cost processing. PMID:21812432

  20. Improvement of the outcoupling efficiency of an organic light-emitting device by attaching microstructured films

    NASA Astrophysics Data System (ADS)

    Lin, Hoang-Yan; Lee, Jiun-Haw; Wei, Mao-Kuo; Dai, Ching-Liang; Wu, Chia-Fang; Ho, Yu-Hsuan; Lin, Hung-Yi; Wu, Tung-Chuan

    2007-07-01

    In this paper, we present and analyse the optical characteristics, such as spectral shift, CIE coordinates, viewing angle dependence, luminous current efficiency and luminous power efficiency, of an organic light-emitting device (OLED) with a commercial diffuser film or a brightness-enhancement film (BEF) attached. Compared to a planar green OLED, the luminous current efficiencies of the OLED with an attached diffuser film or BEF increase by 29% and 23%, respectively. The overall luminous power efficiencies are enhanced by 28% and 7%. Compared to the planar green device, we observe blue shifts at different viewing angles when microstructured films are attached, which is the evidence that the waveguiding modes are being extracted. In our planar OLED, the peak wavelength blue shifts and the full width at the half maximum (FWHM) decrease with increasing viewing angles due to the microcavity effect. When the diffuser is attached, the spectral peak has a constant blue shift (6 nm) compared to that of the planar OLED. On the other hand, in the BEF case, the spectral shift depends on the viewing angle (2-12 nm blue shifts from 0 to 80°). This is due to the different operating principles (scattering and redirected light) of the diffuser and BEF. Since the transmittance spectra of both the diffuser film and the BEF are flat over the visible range, it is suitable for lighting applications by using white OLED. When attaching the films on a commercial white OLED, the luminous current efficiencies of the OLED with an attached diffuser film or BEF increase by 34% and 31%, respectively. The overall luminous power efficiencies are enhanced by 42% and 8%.

  1. PEDOT as a Flexible Organic Electrode for a Thin Film Acoustic Energy Harvester.

    PubMed

    Kim, Younghoon; Na, Jongbeom; Park, Chihyun; Shin, Haijin; Kim, Eunkyoung

    2015-08-01

    An efficient thin film acoustic energy harvester was explored using flexible poly(3,4-ethylene dioxythiophene) (PEDOT) films as electrodes in an all-organic triboelectric generator (AO-TEG). A thin film AO-TEG structured as PEDOT/Kapton//PET/PEDOT was prepared by the solution casting polymerization(SCP) on the dielectric polymer films. As-prepared AO-TEG showed high flexibility and durability due to the strong adhesion between the electrodes and the dielectric polymer. The short-circuit current density (Jsc), open-circuit voltage (Voc), and maximum power density (Pw) reached 50 mA/m(2), 700 V, and 12.9 W/m(2) respectively. The output current density decreased with the increase in the electrode resistance (Re), but the energy loss in the organic electrodes was negligible. The AO-TEG could light up 180 LEDs instantaneously upon touching of the AO-TEG with a palm (∼120 N). With the flexible structure, the AO-TEG was worn as clothes and generated electricity to light LEDs upon regular human movement. Furthermore, the AO-TEG was applicable as a thin film acoustic energy harvester, which used music to generate electricity enough for powering of 5 LEDs. An AO-TEG with a PEDOT electrode (Re = 200 Ω) showed instantaneous peak-to-peak voltage generation of 11 V under a sound pressure level (SPL) of 90-100 dB. The harvested acoustic energy through the AO-TEG was 350 μJ from the 4 min playing of the same single song. This is the first demonstration of a flexible triboelectric generator (TEG) using an organic electrode for harvesting acoustic energy from ambient environment. PMID:26153798

  2. Synthesis of metal-organic framework films by pore diffusion method

    NASA Astrophysics Data System (ADS)

    Murayama, Naohiro; Nishimura, Yuki; Kajiro, Hiroshi; Kishida, Satoru; Kinoshita, Kentaro; Tottori Univ Team; Nippon Steel; Sumitomo Metal Co. Collaboration; Tottori Integrated Frontier Resaerch Center (Tifrec) Collaboration; Tottori University Electronic Display Resaerch Center (Tedrec) Collaboration

    Metal-organic frameworks (MOFs) presents high controllability in designing the nano-scale pore, and this enable molecular storages, catalysts, gas sensors, gas separation membranes, and electronic devices for next-generation. Therefore, a simple method for film synthesis of MOFs compared with conventional methods [1] is strongly required. In this paper, we provide pore diffusion method, in which a substrate containing constituent metals of MOF is inserted in solution that includes only linker molecules of MOF. As a result, 2D growth of MOF was effectively enhanced, and the formation of flat and dense MOF films was attained. The growth time, t, dependence of film thickness, d, can be expressed by the relation of d = Aln(t + 1) + B, where A and B are constants. It means that ionized coppers diffuse through the pores of MOFs and the synthesis reaction proceeds at the MOF/solvent interface. We demonstrated the fabrication of a HKUST-1/Cu-TPA hetero structure by synthesizing a Cu-TPA film continuously after the growth of a HKUST-1 film on the CuOx substrate.

  3. Topological insulator Bi2Te3 films synthesized by metal organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Cao, Helin; Venkatasubramanian, Rama; Liu, Chang; Pierce, Jonathan; Yang, Haoran; Zahid Hasan, M.; Wu, Yue; Chen, Yong P.

    2012-10-01

    Topological insulator (TI) materials such as Bi2Te3 and Bi2Se3 have attracted strong recent interests. Large scale, high quality TI thin films are important for developing TI-based device applications. In this work, structural and electronic properties of Bi2Te3 thin films deposited by metal organic chemical vapor deposition (MOCVD) on GaAs (001) substrates were characterized via x-ray diffraction (XRD), Raman spectroscopy, angle-resolved photoemission spectroscopy (ARPES), and electronic transport measurements. The characteristic topological surface states with a single Dirac cone have been clearly revealed in the electronic band structure measured by ARPES, confirming the TI nature of the MOCVD Bi2Te3 films. Resistivity and Hall effect measurements have demonstrated relatively high bulk carrier mobility of ˜350 cm2/Vs at 300 K and ˜7400 cm2/Vs at 15 K. We have also measured the Seebeck coefficient of the films. Our demonstration of high quality topological insulator films grown by a simple and scalable method is of interests for both fundamental research and practical applications of thermoelectric and TI materials.

  4. Air-stable solution-processed n-channel organic thin film transistors with polymerenhanced morphology

    DOE PAGESBeta

    He, Zhengran; Shaik, Shoieb; Bi, Sheng; Chen, Jihua; Li, Dawen

    2015-05-04

    N,N0-1H,1H-perfluorobutyl dicyanoperylenecarboxydiimide (PDIF-CN2) is an n-type semiconductor exhibiting high electron mobility and excellent air stability. However, the reported electron mobility based on spin-coated PDIF-CN2 film is much lower than the value of PDIF-CN2 single crystals made from vapor phase deposition, indicating significant room for mobility enhancement. In this study, various insulating polymers, including poly(vinyl alcohol), poly(methyl methacrylate) (PMMA), and poly(alpha-methylstyrene) (PaMS), are pre-coated on silicon substrate aiming to enhance the morphology of the PDIF-CN2 thin film, thereby improving the charge transport and air stability. Atomic force microscopy images reveal that with the pre-deposition of PaMS or PMMA polymers, the morphologymore » of the PDIF-CN2 polycrystalline films is optimized in semiconducting crystal connectivity, domain size, and surface roughness, which leads to significant improvement of organic thin-film transistor (OTFT) performance. Particularly, an electron mobility of up to 0.55 cm2/V s has been achieved from OTFTs based on the PDIF-CN2 film with the pre-deposition of PaMS polymer.« less

  5. Air-stable solution-processed n-channel organic thin film transistors with polymerenhanced morphology

    SciTech Connect

    He, Zhengran; Shaik, Shoieb; Bi, Sheng; Chen, Jihua; Li, Dawen

    2015-05-04

    N,N0-1H,1H-perfluorobutyl dicyanoperylenecarboxydiimide (PDIF-CN2) is an n-type semiconductor exhibiting high electron mobility and excellent air stability. However, the reported electron mobility based on spin-coated PDIF-CN2 film is much lower than the value of PDIF-CN2 single crystals made from vapor phase deposition, indicating significant room for mobility enhancement. In this study, various insulating polymers, including poly(vinyl alcohol), poly(methyl methacrylate) (PMMA), and poly(alpha-methylstyrene) (PaMS), are pre-coated on silicon substrate aiming to enhance the morphology of the PDIF-CN2 thin film, thereby improving the charge transport and air stability. Atomic force microscopy images reveal that with the pre-deposition of PaMS or PMMA polymers, the morphology of the PDIF-CN2 polycrystalline films is optimized in semiconducting crystal connectivity, domain size, and surface roughness, which leads to significant improvement of organic thin-film transistor (OTFT) performance. Particularly, an electron mobility of up to 0.55 cm2/V s has been achieved from OTFTs based on the PDIF-CN2 film with the pre-deposition of PaMS polymer.

  6. Nucleation And Growth Of Ba-Reduced Metal Organic Deposited YBCO Films

    SciTech Connect

    Talantsev, E. F.; Xia, J. A.; Strickland, N. M.; Hoffmann, C.; Morgan, S.; Long, N. J.; Rupich, M. W.; Li, X.; Sathyamurthy, S.

    2009-07-23

    In this study, YBCO films were fabricated on RABiTS metal substrates by metal-organic deposition of trifluoroacetates. Precursor solutions were made with different Ba concentrations (Ba/Y = 1.50, 1.70, 1.85, 2.0) with the aim of optimizing the critical current density (J{sub c}). Our results confirmed that YBCO films with Ba/Y = 1.70(J{sub c} = 3.6 MA/cm{sup 2} at T 77 K) have significantly higher J{sub c} than stoichiometric (Ba/Y = 2.0) YBCO (J{sub c} 2.4 MA/cm{sup 2}). Application of low-angle polishing techniques and X-ray diffraction (XRD) studies for quenched (partially reacted) films has shown that YBCO films with Ba/Y = 1.70 nucleate more rapidly than other films, but that the crystal growth rate is increased when the Ba-concentration is increased. These results provide new insights into the physical mechanisms required to achieve high J{sub c} in YBCO.

  7. Organic self-assembled layer-by-layer thin films for second-order nonlinear optics

    NASA Astrophysics Data System (ADS)

    Guzy, Matthew T.

    Layer-by-layer deposition techniques were used to fabricate films with second order nonlinear optical (NLO) properties. These materials are key to the development of electro-optic modulators used in fiber optic communication systems. Performance benefits and lower manufacturing costs are driving the development of organic NLO materials as replacements for inorganic crystalline materials such as lithium niobate. The layer-by-layer deposition technique in which polyelectrolytes are deposited on a surface by electrostatic effects is called the Ionically Self-Assembled Monolayer or ISAM method. The role of the optically inactive polycation's structure on deposition and chromophore orientation was studied by fabricating films with several different polycations. While the specific interactions responsible for chromophore orientation in ISAM films remains unclear, hydrogen bonding and electrostatic effects are ruled out as the sole sources of orientation. The highest values of chi(2) were observed under pH conditions that resulted in flat and thin layers. The relationship between pH and the optical homogeneity of the film was also explored. Deposition of polymers under pH conditions in which the polymer chains were aggregated in solution results in films that are not suitable for use in devices. In this work, a new layer-by-layer deposition technique was developed. Coined hybrid deposition, it relies on covalent bonds and electrostatic interactions for film fabrication. Optically inactive polyamines were used as sources of positive charges and as binding sites with optically active low molecular weight chromophores functionalized with a reactive triazine ring and negative charged sulfonate groups. Polar ordering of the chromophores was obtained when the deposition was done under conditions in which covalent bonding was the preferred attachment mechanism for the chromophore molecules. pH conditions in which electrostatic attachment dominated resulted in poorer orientation

  8. Thin-film encapsulation of the air-sensitive organic-based ferrimagnet vanadium tetracyanoethylene

    SciTech Connect

    Froning, I. H.; Harberts, M.; Yu, H.; Johnston-Halperin, E.; Lu, Y.; Epstein, A. J.

    2015-03-23

    The organic-based ferrimagnet vanadium tetracyanoethylene (V[TCNE]{sub x∼2}) has demonstrated potential for use in both microwave electronics and spintronics due to the combination of high temperature magnetic ordering (T{sub C} > 600 K), extremely sharp ferromagnetic resonance (peak to peak linewidth of 1 G), and low-temperature conformal deposition via chemical vapor deposition (deposition temperature of 50 °C). However, air-sensitivity leads to the complete degradation of the films within 2 h under ambient conditions, with noticeable degradation occurring within 30 min. Here, we demonstrate encapsulation of V[TCNE]{sub x∼2} thin films using a UV-cured epoxy that increases film lifetime to over 710 h (30 days) as measured by the remanent magnetization. The saturation magnetization and Curie temperature decay more slowly than the remanence, and the coercivity is unchanged after 340 h (14 days) of air exposure. Fourier transform infrared spectroscopy indicates that the epoxy does not react with the film, and magnetometry measurements show that the presence of the epoxy does not degrade the magnetic properties. This encapsulation strategy directly enables a host of experimental protocols and investigations not previously feasible for air-sensitive samples and lays the foundation for the development of practical applications for this promising organic-based magnetic material.

  9. Dielectric properties of crystalline organic molecular films in the limit of zero overlap

    NASA Astrophysics Data System (ADS)

    D'Avino, Gabriele; Vanzo, Davide; Soos, Zoltán G.

    2016-01-01

    We present the calculation of the static dielectric susceptibility tensor and dipole field sums in thin molecular films in the well-defined limit of zero intermolecular overlap. Microelectrostatic and charge redistribution approaches are applied to study the evolution of dielectric properties from one to a few molecular layers in films of different conjugated molecules with organic electronics applications. Because of the conditional convergence of dipolar interactions, dipole fields depend on the shape of the sample and different values are found in the middle layer of a thick film and in the bulk. The shape dependence is eliminated when depolarization is taken into account, and the dielectric tensor of molecular films converges to the bulk limit within a few molecular layers. We quantify the magnitude of surface effects and interpret general trends among different systems in terms of molecular properties, such as shape, polarizability anisotropy, and supramolecular organization. A connection between atomistic models for molecular dielectrics and simpler theories for polarizable atomic lattices is also provided.

  10. Graphene-based electrodes for enhanced organic thin film transistors based on pentacene.

    PubMed

    Basu, Sarbani; Lee, Mu Chen; Wang, Yeong-Her

    2014-08-21

    This paper presents 6,13-bis(triisopropylsilylethynyl)pentacene (TIPS-pentacene) and pentacene-based organic thin film transistors (OTFTs) with monolayer graphene source-drain (S-D) electrodes. The electrodes are patterned using conventional photolithographic techniques combined with reactive ion etching. The monolayer graphene film grown by chemical vapor deposition on Cu foil was transferred on a Si dioxide surface using a polymer-supported transfer method to fabricate bottom-gate, bottom-contact OTFTs. The pentacene OTFTs with graphene S-D contacts exhibited superior performance with a mobility of 0.1 cm(2) V(-1) s(-1) and an on-off ratio of 10(5) compared with OTFTs with Au-based S-D contacts, which had a mobility of 0.01 cm(2) V(-1) s(-1) and an on-off ratio of 10(3). The crystallinity, grain size, and microscopic defects (or the number of layers of graphene films) of the TIPS-pentacene/pentacene films were analyzed by X-ray diffraction spectroscopy, atomic force microscopy, and Raman spectroscopy, respectively. The feasibility of using graphene as an S-D electrode in OTFTs provides an alternative material with high carrier injection efficiency, chemical stability, and excellent interface properties with organic semiconductors, thus exhibiting improved device performance of C-based electronic OTFTs at a reduced cost. PMID:25000388

  11. Rigidity-patterned polyelectrolyte films to control myoblast cell adhesion and spatial organization

    PubMed Central

    Monge, Claire; Saha, Naresh; Boudou, Thomas; Pózos-Vásquez, Cuauhtemoc; Dulong, Virginie; Glinel, Karine; Picart, Catherine

    2014-01-01

    In vivo, cells are sensitive to the stiffness of their micro-environment and especially to the spatial organization of the stiffness. In vitro studies of this phenomenon can help to better understand the mechanisms of the cell response to spatial variations of the matrix stiffness. In this work, we design polelyelectrolyte multilayer films made of poly(L-lysine) and a photo-reactive hyaluronan derivative. These films can be photo-crosslinked through a photomask to create spatial patterns of rigidity. Quartz substrates incorporating a chromium mask are prepared to expose selectively the film to UV light (in a physiological buffer), without any direct contact between the photomask and the soft film. We show that these micropatterns are chemically homogeneous and flat, without any preferential adsorption of adhesive proteins. Three groups of pattern geometries differing by their shape (circles or lines), size (form 2 to 100 μm) or interspacing distance between the motifs are used to study the adhesion and spatial organization of myoblast cells. On large circular micropatterns, the cells form large assemblies that are confined to the stiffest parts. Conversely, when the size of the rigidity patterns is subcellular, the cells respond by forming protrusions. Finally, on linear micropatterns of rigidity, myoblasts align and their nuclei drastically elongate in specific conditions. These results pave the way for the study of the different steps of myoblast fusion in response to matrix rigidity in well-defined geometrical conditions. PMID:25100929

  12. Novel Organic Membrane-based Thin-film Microsensors for the Determination of Heavy Metal Cations

    PubMed Central

    Arida, Hassan A.; Kloock, Joachim P.; Schöning, Michael J.

    2006-01-01

    A first step towards the fabrication and electrochemical evaluation of thin-film microsensors based on organic PVC membranes for the determination of Hg(II), Cd(II), Pb(II) and Cu(II) ions in solutions has been realised. The membrane-coating mixture used in the preparation of this new type of microsensors is incorporating PVC as supporting matrix, o-nitrophenyloctylether (o-NPOE) as solvent mediator and a recently synthesized Hg[dimethylglyoxime(phene)]2+ and Bis-(4-hydroxyacetophenone)-ethylenediamine as electroactive materials for Hg(II) and Cd(II), respectively. A set of three commercialised ionophores for Cd(II), Pb(II) and Cu(II) has been also used for comparison. Thin-film microsensors based on these membranes showed a Nernstian response of slope (26-30 mV/dec.) for the respective tested cations. The potentiometric response characteristics (linear range, pH range, detection limit and response time) are comparable with those obtained by conventional membranes as well as coated wire electrodes prepared from the same membrane. The realisation of the new organic membrane-based thin-film microsensors overcomes the problem of an insufficient selectivity of solid-state-based thin-film sensors.

  13. Organic film and contaminant removal from surfaces in the manufacture of integrated circuits

    NASA Astrophysics Data System (ADS)

    Chavez, Kristi Lynn (Albrecht)

    This work focuses on the development of novel approaches to organic film removal, surface cleaning, and conditioning that ensures compatibility of this critical fabrication step with vacuum sequences in integrated circuit (IC) manufacturing. The general approach investigated for organic film and contaminant removal is the use of a fluid under elevated temperature and pressure conditions. A fluid in the vicinity of its boiling point remains a liquid by increasing the pressure; a reduction in pressure, however, results in liquid evaporation, permitting subsequent transfer of substrates into a vacuum chamber. An additional advantage of this approach is the elimination of a drying step. Addition of carbon dioxide to water at 165°C and 850 psi enhances water interaction with organic materials, and thus provides a means to remove ion-implanted photoresist films up to an implant density of 1016 atoms/cm2. Resist removal was also demonstrated with this approach by use of acetic acid, although reasonable removal rates were obtained at much lower temperature and pressure conditions. Therefore, in order to slow the removal rates and thereby allow more detailed investigations of organic film removal by acetic acid, 35°C and atmospheric conditions were used. If an adhesion-promoting layer was applied to the silicon surface prior to the polymer application, a thin polymeric residue remained on the silicon surface. Potential etching or roughening of the underlying surface was also studied. In the case of acetic acid, the native copper oxide inherent to air-exposed copper films was removed by acetic acid, leaving an oxide-free copper surface without attack of the underlying metallic copper. As applied to a semiconductor manufacturing line, these approaches are capable of removing organic films from surfaces, yielding carbon concentrations comparable to those of an RCA-cleaned surface. Also, since a nitrogen dry is effective after the removal methods investigated, the need for a

  14. Effects of postannealing process on the properties of RuO2 films and their performance as electrodes in organic thin film transistors or solar cells.

    PubMed

    Yun, Dong-Jin; Ra, Hye-min; Jo, Sae Byeok; Maeng, Wanjoo; Lee, Seung-hyup; Park, Sunghoon; Jang, Ji-Wook; Cho, Kilwon; Rhee, Shi-Woo

    2012-09-26

    RuO(2) films were deposited on SiO(2) (300 nm)/N++Si substrates using radio frequency magnetron sputtering at room temperature. As-deposited RuO(2) films were annealed at different temperatures (100, 300, and 500 °C) and ambients (Ar, O(2) and vacuum), and the resulting effects on the electrical and physical properties of RuO(2) films were characterized. The effect of annealing atmosphere was negligible, however the temperature highly influenced the resistivity and crystallinity of RuO(2) films. RuO(2) films annealed at high temperature exhibited lower resistivity and higher crystallinity than as-deposited RuO(2). To investigate the possibility to use RuO(2) film as alternative electrodes in flexible devices, as-deposited and annealed RuO(2) films were applied as the source/drain (S/D) electrodes in organic thin film transistor (OTFT), catalytic electrodes in dye sensitized solar cell (DSSC) and as the hole-injection buffer layer (HIL) in organic photovoltaic (OPV). Except for OTFTs (μ ≈ 0.45 cm(2)/(V s) and on/off ratio ≈ 5× 10(5)) with RuO(2) S/D electrodes, the DSSC and OPV (3.5% and 2.56%) incorporating annealed RuO(2) electrodes showed higher performance than those with as-deposited RuO(2) electrodes (3.0% and 1.61%, respectively). PMID:22909412

  15. Highly Non-Linear Optical (NLO) organic crystals and films. Electrooptical organic materials

    NASA Technical Reports Server (NTRS)

    Mcmanus, Samuel P.; Rosenberger, Franz; Matthews, John

    1987-01-01

    Devices employing nonlinear optics (NLO) hold great promise for important applications in integrated optics, optical information processing and telecommunications. Properly designed organics possess outstanding optical and electrooptical properties which will substantially advance many technologies including electrooptical switching, optical amplification for communications, and parallel processing for hybrid optical computers. A brief comparison of organic and inorganic materials is given.

  16. Growth of thin films of organic nonlinear optical materials by vapor growth processes - An overview and examination of shortfalls

    NASA Technical Reports Server (NTRS)

    Frazier, D. O.; Penn, B. G.; Witherow, W. K.; Paley, M. S.

    1991-01-01

    Research on the growth of second- and third-order nonlinear optical (NLO) organic thin film by vapor deposition is reviewed. Particular attention is given to the experimental methods for growing thin films of p-chlorophenylurea, diacetylenes, and phthalocyanines; characteristics of the resulting films; and approaches for advancing thin film technology. It is concluded that the growth of NLO thin films by vapor processes is a promising method for the fabrication of planar waveguides for nonlinear optical devices. Two innovative approaches are proposed including a method of controlling the input beam frequency to maximize nonlinear effects in thin films and single crystals, and the alternate approach to the molecular design of organic NLO materials by increasing the transition dipole moment between ground and excited states of the molecule.

  17. High mobility high efficiency organic films based on pure organic materials

    DOEpatents

    Salzman, Rhonda F.; Forrest, Stephen R.

    2009-01-27

    A method of purifying small molecule organic material, performed as a series of operations beginning with a first sample of the organic small molecule material. The first step is to purify the organic small molecule material by thermal gradient sublimation. The second step is to test the purity of at least one sample from the purified organic small molecule material by spectroscopy. The third step is to repeat the first through third steps on the purified small molecule material if the spectroscopic testing reveals any peaks exceeding a threshold percentage of a magnitude of a characteristic peak of a target organic small molecule. The steps are performed at least twice. The threshold percentage is at most 10%. Preferably the threshold percentage is 5% and more preferably 2%. The threshold percentage may be selected based on the spectra of past samples that achieved target performance characteristics in finished devices.

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

    NASA Astrophysics Data System (ADS)

    Sekkat, Zouheir; Knoll, Wolfgang

    1997-01-01

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

  19. High index of refraction films for dielectric mirrors prepared by metal-organic chemical vapor deposition

    SciTech Connect

    Brusasco, R.M.

    1989-01-01

    A wide variety of metal oxides with high index of refraction can be prepared by Metal-Organic Chemical Vapor Deposition. We present some recent optical and laser damage results on oxide films prepared by MOCVD which could be used in a multilayer structure for highly reflecting (HR) dielectric mirror applications. The method of preparation affects both optical properties and laser damage threshold. 10 refs., 8 figs., 4 tabs.

  20. Ultraselective Gas Separation by Nanoporous Metal-Organic Frameworks Embedded in Gas-Barrier Nanocellulose Films.

    PubMed

    Matsumoto, Makoto; Kitaoka, Takuya

    2016-03-01

    Metal-organic frameworks (MOFs) are synthesized at carboxy groups on crystalline TEMPO-oxidized cellulose nanofibers (TOCNs). MOF-TOCN films coated on a paper filter have a hierarchical structure from the nano- to macroscale, and demonstrate a high CO2 /CH4 selectivity, over 120 for CO2 at a high gas flux, by the combination of the nanoporous MOFs and the gas-barrier TOCNs, which have strong affinity with each other. PMID:26669724

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

    PubMed

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

    2007-12-28

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

  2. Defect-Controlled Preparation of UiO-66 Metal-Organic Framework Thin Films with Molecular Sieving Capability.

    PubMed

    Zhang, Caiqin; Zhao, Yajing; Li, Yali; Zhang, Xuetong; Chi, Lifeng; Lu, Guang

    2016-01-01

    Metal-organic framework (MOF) UiO-66 thin films are solvothermally grown on conducting substrates. The as-synthesized MOF thin films are subsequently dried by a supercritical process or treated with polydimethylsiloxane (PDMS). The obtained UiO-66 thin films show excellent molecular sieving capability as confirmed by the electrochemical studies for redox-active species with different sizes. PMID:26548455

  3. Investigations Into the Interactions of a MALDI Matrix with Organic Thin Films Using C60+ SIMS Depth Profiling

    PubMed Central

    Lerach, Jordan O.; Keskin, Selda; Winograd, Nicholas

    2015-01-01

    Molecular depth profiling of multilayer organic films is now an established protocol for cluster secondary ion mass spectrometry (SIMS). This unique capability is exploited here to study the ionization mechanism associated with matrix-enhanced SIMS and possibly matrix assisted laser desorption/ionization (MALDI). Successful depth profiling experiments were performed on model bi-layer systems using 2,5-dihydroxybenzoic acid (DHB) as the matrix with dipalmitoylphosphatidylcholine (DPPC) or phenylalanine (PHE). The interaction between the matrix and organic analyte is monitored at the interface of the films. Tri-layer films with D2O as a thin-film sandwiched between the matrix and organic layers are also investigated to determine what role, if any, water plays during ionization. The results show successful depth profiles when taken at 90K. Mixing is observed at the interfaces of the films due to primary ion bombardment, but this mixing does not recreate the conditions necessary for ionization enhancement. PMID:26494930

  4. Continuum studies of microstructure formation in metallic and organic thin films

    NASA Astrophysics Data System (ADS)

    Muralidharan, Srevatsan

    In this dissertation, microstructure formation processes in binary metallic ultra-thin films and organic polycrystalline thin films are studied through a combination of theoretical model development, analysis, and numerical simulations. In binary metallic films, to investigate compositional patterning and misfit dislocation formation, a quantitative approach based on the so called phase-field crystal method is developed. Both through analysis and simulations of the model, a number of generic and limiting cases of surface alloy epitaxial systems are investigated to examine the effects of lattice mismatch, adlayer-substrate interaction potential, and line tension on equilibrium compositional domain size. A procedure is developed to quantitatively relate the parameters of the model to a specific system [CoAg/Ru(0001)], and it is demonstrated that simulations capture experimentally observed morphologies. Then, the model is employed to investigate the effects of misfit strain fields in the substrate on both heterogeneous nucleation behavior and anisotropic growth of islands at submonolayer coverages and compositional patterning at complete monolayer coverage via simulations. In particular, in the case of binary systems at complete monolayer coverage, strain-stabilized compositional domains emerge at low line tension values for both substrates. Interestingly, the compositional domains on the QC substrate inherit their symmetries at sufficiently low line tension values, while at larger line tension values, the domain structure begins to resemble the classical spinodal microstructure. These studies will enable physically-based design of nanoscale features for a broad range of applications, such as catalysis. In organic polycrystalline films, our focus is on determining the effects of additives and substrate templating on nucleation and grain growth behavior of solution processed triethylsilylethynyl anthradithiophene films. Through a mean-field approach, it is demonstrated

  5. The formation of organic (propolis films)/inorganic (layered crystals) interfaces for optoelectronic applications

    NASA Astrophysics Data System (ADS)

    Drapak, S. I.; Bakhtinov, A. P.; Gavrylyuk, S. V.; Kovalyuk, Z. D.; Lytvyn, O. S.

    2008-10-01

    Propolis (honeybee glue) organic films were prepared from an alcoholic solution on the surfaces of inorganic layered semiconductors (indium, gallium and bismuth selenides). Atomic force microscopy (AFM) and X-ray diffraction (XRD) are used to characterize structural properties of an organic/inorganic interfaces. It is shown that nanodimensional linear defects and nanodimensional cavities of various shapes are formed on the van der Waals (VDW) surfaces of layered crystals as a result of chemical interaction between the components of propolis (flavonoids, aminoacids and phenolic acids) and the VDW surfaces as well as deformation interaction between the VDW surfaces and propolis films during their polymerization. The nanocavities are formed as a result of the rupture of strong covalent bonds in the upper layers of layered crystals and have the shape of hexagons or triangles in the (0001) plane. The shape, lateral size and distribution of nanodimensional defects on the VDW surfaces depends on the type of crystals, the magnitude and distribution of surface stresses. We have obtained self-organized nanofold structures of propolis/InSe interface. It is established that such heterostructures have photosensitivity in the infrared range hν<1.2 eV (the values of energy gap are 1.2 eV for InSe and 3.07 eV for propolis films at room temperature).

  6. Characteristics of Sputtered ZnO Thin Films for an Inverted Organic Solar Cell.

    PubMed

    Park, Yong Seob; Park, Chul Min; Lee, Jaehyeong

    2016-05-01

    Several research groups have claimed high energy conversion efficiency in organic solar cells. However, it still has low efficiency and is unstable, because organic materials are easily oxidized by atmospheric humidity and UV light. In this work, ZnO thin film as the blocking layer attributed to the interference of the injection of the hole from the P3HT and no charge carrier recombination. We obtained the maximum power conversion efficiency of 1.9% under AM 1.5 G spectral illumination of 100 MWcm(-2), when we used a ZnO film of 60 nm and the optimized P3HT:PCBM, and Au as the back electrode to solve the reaction problem of Al electrode and to control the work function between the HOMO level of P3HT and the energy level of the metal electrode. Power conversion efficiency of inverted organic solar cell (IOSC) is significantly dependent on the thickness of the ZnO thin film deposited by unbalanced magnetron sputtering method. Also, the stability of IOSC is measured under ambient conditions. PMID:27483875

  7. Properties of whey protein-based films containing organic acids and nisin to control Listeria monocytogenes.

    PubMed

    Pintado, Cristina M B S; Ferreira, Maria A S S; Sousa, Isabel

    2009-09-01

    Whey protein isolate and glycerol were mixed to form a matrix to incorporate antimicrobial agents and produce edible films with antimicrobial activity against Listeria monocytogenes strains isolated from cheeses. Various organic acids were used to decrease pH down to approximately 3. In a preliminary assay without nisin, the effect of each organic acid was evaluated with respect to the rheological properties of the film solutions and the inhibitory and mechanical properties of the films. Lactic, malic, and citric acids (3%, wt/vol), which were used in a subsequent study of their combined inhibitory effect with nisin (50 IU/ml), had significantly higher antilisterial activity (P < 0.05) compared with the control (2 N HCl, 3% [wt/vol], with nisin). The largest mean zone of inhibition was 4.00 +/- 0.92 mm for malic acid with nisin. Under small-amplitude oscillatory stress, the protein-glycerol-acid film solutions exhibited a predominantly viscous behavior or a weak gel behavior, with the storage modulus (G') slightly higher than the loss modulus (G"). The malic acid-based solution was the only one whose viscosity was not influenced by the addition of nisin. The addition of nisin resulted in a nonsignificant (P > 0.05) increase in the percentage of elongation at break. Results from tensile and puncture stress were variable, but in general no significant differences were found after the incorporation of nisin. The overall results support the use of malic acid with nisin to produce effective antimicrobial films to control L. monocytogenes growth. PMID:19777891

  8. The interaction of organic adsorbate vibrations with substrate lattice waves in methyl-Si(111)-(1 × 1)

    SciTech Connect

    Brown, Ryan D.; Hund, Zachary M.; Sibener, S. J.; Campi, Davide; Bernasconi, M.; O’Leary, Leslie E.; Lewis, Nathan S.; Benedek, G.

    2014-07-14

    A combined helium atom scattering and density functional perturbation theory study has been performed to elucidate the surface phonon dispersion relations for both the CH{sub 3}-Si(111)-(1 × 1) and CD{sub 3}-Si(111)-(1 × 1) surfaces. The combination of experimental and theoretical methods has allowed characterization of the interactions between the low energy vibrations of the adsorbate and the lattice waves of the underlying substrate, as well as characterization of the interactions between neighboring methyl groups, across the entire wavevector resolved vibrational energy spectrum of each system. The Rayleigh wave was found to hybridize with the surface rocking libration near the surface Brillouin zone edge at both the M{sup ¯}-point and K{sup ¯}-point. The calculations indicated that the range of possible energies for the potential barrier to the methyl rotation about the Si-C axis is sufficient to prevent the free rotation of the methyl groups at a room temperature interface. The density functional perturbation theory calculations revealed several other surface phonons that experienced mode-splitting arising from the mutual interaction of adjacent methyl groups. The theory identified a Lucas pair that exists just below the silicon optical bands. For both the CH{sub 3}- and CD{sub 3}-terminated Si(111) surfaces, the deformations of the methyl groups were examined and compared to previous experimental and theoretical work on the nature of the surface vibrations. The calculations indicated a splitting of the asymmetric deformation of the methyl group near the zone edges due to steric interactions of adjacent methyl groups. The observed shifts in vibrational energies of the -CD{sub 3} groups were consistent with the expected effect of isotopic substitution in this system.

  9. Nondestructive inspection of organic films on sandblasted metals using diffuse reflectance infrared spectroscopy

    SciTech Connect

    Powell, G.L.; Cox, R.L.; Barber, T.E.; Neu, J.T.

    1996-07-08

    Diffuse reflectance infrared spectroscopy is a very useful tool for the determination of surface contamination and characterization of films in manufacturing applications. Spectral data from the surfaces of a host of practical materials may be obtained with sufficient insensitivity to characterize relatively thick films, such as paint, and the potential exists to detect very thin films, such as trace oil contamination on metals. The SOC 400 Surface Inspection Machine/InfraRed (SIMIR) has been developed as a nondestructive inspection tool to exploit this potential in practical situations. This SIMIR is a complete and ruggidized Fourier transform infrared spectrometer with a very efficient and robust barrel ellipse diffuse reflectance optical collection system and operating software system. The SIMIR weighs less than 8 Kg, occupies less than 14 L volume, and may be manipulated into any orientation during operation. The surface to be inspected is placed at the focal point of the SIMIR by manipulating the SIMIR or the surface. The SIMIR may or may not contact the surface being inspected. For flat or convex items, there are no size limits to items being inspected. For concave surfaces, the SIMIR geometry limits the surface to those having a radius of curvature greater than 0.2 m. For highly reflective metal surfaces, the SIMIR has a noise level approaching 1 {times} 10{sup {minus}4} absorbance units, which is sufficient for detecting nanometer thick organic film residues on metals. The use of this nondestructive inspection tool is demonstrated by the spatial mapping of organic stains on sand blasted metals in which organic stains such as silicone oils, mineral oils, and triglycerides are identified both qualitatively and quantitatively over the surface of the metal specimen.

  10. INFLUENCE OF FILM STRUCTURE AND LIGHT ON CHARGE TRAPPING AND DISSIPATION DYNAMICS IN SPUN-CAST ORGANIC THIN-FILM TRANSISTORS MEASURED BY SCANNING KELVIN PROBE MICROSCOPY

    SciTech Connect

    Teague, L.; Moth, M.; Anthony, J.

    2012-05-03

    Herein, time-dependent scanning Kelvin probe microscopy of solution processed organic thin film transistors (OTFTs) reveals a correlation between film microstructure and OTFT device performance with the location of trapped charge within the device channel. The accumulation of the observed trapped charge is concurrent with the decrease in I{sub SD} during operation (V{sub G}=-40 V, V{sub SD}= -10 V). We discuss the charge trapping and dissipation dynamics as they relate to the film structure and show that application of light quickly dissipates the observed trapped charge.

  11. Enhanced Performance Consistency in Nanoparticle/TIPS Pentacene-Based Organic Thin Film Transistors

    SciTech Connect

    He, Zhengran; Xiao, Kai; Durant, William Mark; Anthony, John E.; Kilbey, II, S Michael; Chen, Jihua; Li, Dawen

    2011-01-01

    In this study, inorganic silica nanoparticles are used to manipulate the morphology of 6,13-bis(triisopropylsilylethynyl)-pentacene (TIPS pentacene) thin films and the performance of solution-processed organic thin-film transistors (OTFTs). This approach is taken to control crystal anisotropy, which is the origin of poor consistency in TIPS pentacene based OTFT devices. Thin film active layers are produced by drop-casting mixtures of SiO{sub 2} nanoparticles and TIPS pentacene. The resultant drop-cast films yield improved morphological uniformity at {approx}10% SiO{sub 2} loading, which also leads to a 3-fold increase in average mobility and nearly 4 times reduction in the ratio of measured mobility standard deviation ({mu}{sub Stdev}) to average mobility ({mu}{sub Avg}). Grazing-incidence X-ray diffraction, scanning and transmission electron microscopy as well as polarized optical microscopy are used to investigate the nanoparticle-mediated TIPS pentacene crystallization. The experimental results suggest that the SiO{sub 2} nanoparticles mostly aggregate at TIPS pentacene grain boundaries, and 10% nanoparticle concentration effectively reduces the undesirable crystal misorientation without considerably compromising TIPS pentacene crystallinity.

  12. Uncovering location-specific ultrafast exciton dynamics in organic semiconducting thin films

    NASA Astrophysics Data System (ADS)

    Ginsberg, Naomi

    2014-03-01

    In solid state semiconducting molecular materials used in electro-optical applications, relatively long exciton diffusion lengths hold the promise to boost device performance by relaxing proximity constraints on the locations for light absorption and interfacial charge separation. The architecture of such materials determines their optical and electronic properties as a result of spacing- and orientation-dependent Coulomb couplings between adjacent molecules. Exciton character and dynamics are generally inferred from bulk optical measurements, which can present a severe limitation on our understanding of these films because their constituent molecules are neither perfectly ordered nor perfectly disordered. Nevertheless, such microstructure can have profound impacts on transport properties. The ultrafast spectroscopy of single domains of polycrystalline films of TIPS-pentacene, a small-molecule organic semiconductor of interest in electronic and photovoltaic applications, is investigated using transient absorption microscopy. Individual domains are distinguished by their different polarization-dependent linear and nonlinear optical responses. As compared to bulk measurements, we show that the nonlinear response within a given domain can be tied more concretely to specific physical processes that transfer exciton populations between specified electronic states. By use of this approach and a simple kinetic model, the signatures of singlet fission as well as vibrational relaxation of the initially excited singlet state are identified. As such, observing exciton dynamics within and comparing exciton dynamics between different TIPS-pentacene domains reveal the relationship between photophysics and film morphology and the potential to resolve unique signatures at interfaces between different regions of the film.

  13. Charge Transfer-Induced Molecular Hole Doping into Thin Film of Metal-Organic Frameworks.

    PubMed

    Lee, Deok Yeon; Kim, Eun-Kyung; Shrestha, Nabeen K; Boukhvalov, Danil W; Lee, Joong Kee; Han, Sung-Hwan

    2015-08-26

    Despite the highly porous nature with significantly large surface area, metal-organic frameworks (MOFs) can be hardly used in electronic and optoelectronic devices due to their extremely poor electrical conductivity. Therefore, the study of MOF thin films that require electron transport or conductivity in combination with the everlasting porosity is highly desirable. In the present work, thin films of Co3(NDC)3DMF4 MOFs with improved electronic conductivity are synthesized using layer-by-layer and doctor blade coating techniques followed by iodine doping. The as-prepared and doped films are characterized using FE-SEM, EDX, UV/visible spectroscopy, XPS, current-voltage measurement, photoluminescence spectroscopy, cyclic voltammetry, and incident photon to current efficiency measurements. In addition, the electronic and semiconductor properties of the MOF films are characterized using Hall Effect measurement, which reveals that, in contrast to the insulator behavior of the as-prepared MOFs, the iodine doped MOFs behave as a p-type semiconductor. This is caused by charge transfer-induced hole doping into the frameworks. The observed charge transfer-induced hole doping phenomenon is also confirmed by calculating the densities of states of the as-prepared and iodine doped MOFs based on density functional theory. Photoluminescence spectroscopy demonstrates an efficient interfacial charge transfer between TiO2 and iodine doped MOFs, which can be applied to harvest solar radiations. PMID:26226050

  14. Air-Flow Navigated Crystal Growth for TIPS Pentacene-Based Organic Thin-Film Transistors

    SciTech Connect

    He, Zhengran; Chen, Jihua; Sun, Zhenzhong; Szulczewski, Greg; Li, Dawen

    2012-01-01

    6,13-bis(triisopropylsilylethynyl)pentacene (TIPS pentacene) is a promising active channel material of organic thin-film transistors (OTFTs) due to its solubility, stability, and high mobility. However, the growth of TIPS pentacene crystals is intrinsically anisotropic and thus leads to significant variation in the performance of OTFTs. In this paper, air flow is utilized to effectively reduce the TIPS pentacene crystal anisotropy and enhance performance consistency in OTFTs, and the resulted films are examined with optical microscopy, grazing-incidence X-ray diffraction, and thin-film transistor measurements. Under air-flow navigation (AFN), TIPS pentacene drop-cast from toluene solution has been observed to form thin films with improved crystal orientation and increased areal coverage on substrates, which subsequently lead to a four-fold increase of average hole mobility and one order of magnitude enhancement in performance consistency defined by the ratio of average mobility to the standard deviation of the field-effect mobilities.

  15. Molecular-Orientation-Induced Rapid Roughening and Morphology Transition in Organic Semiconductor Thin-Film Growth

    PubMed Central

    Yang, Junliang; Yim, Sanggyu; Jones, Tim S.

    2015-01-01

    We study the roughening process and morphology transition of organic semiconductor thin film induced by molecular orientation in the model of molecular semiconductor copper hexadecafluorophthalocyanine (F16CuPc) using both experiment and simulation. The growth behaviour of F16CuPc thin film with the thickness, D, on SiO2 substrate takes on two processes divided by a critical thickness: (1) D ≤ 40 nm, F16CuPc thin films are composed of uniform caterpillar-like crystals. The kinetic roughening is confirmed during this growth, which is successfully analyzed by Kardar-Parisi-Zhang (KPZ) model with scaling exponents α = 0.71 ± 0.12, β = 0.36 ± 0.03, and 1/z = 0.39 ± 0.12; (2) D > 40 nm, nanobelt crystals are formed gradually on the caterpillar-like crystal surface and the film growth shows anomalous growth behaviour. These new growth behaviours with two processes result from the gradual change of molecular orientation and the formation of grain boundaries, which conversely induce new molecular orientation, rapid roughening process, and the formation of nanobelt crystals. PMID:25801646

  16. Novel adhesive properties of poly(ethylene-oxide) adsorbed nanolayers

    NASA Astrophysics Data System (ADS)

    Zeng, Wenduo

    Solid-polymer interfaces play crucial roles in the multidisciplinary field of nanotechnology and are the confluence of physics, chemistry, biology, and engineering. There is now growing evidence that polymer chains irreversibly adsorb even onto weakly attractive solid surfaces, forming a nanometer-thick adsorbed polymer layer ("adsorbed polymer nanolayers"). It has also been reported that the adsorbed layers greatly impact on local structures and properties of supported polymer thin films. In this thesis, I aim to clarify adhesive and tribological properties of adsorbed poly(ethylene-oxide) (PEO) nanolayers onto silicon (Si) substrates, which remain unsolved so far. The adsorbed nanolayers were prepared by the established protocol: one has to equilibrate the melt or dense solution against a solid surface; the unadsorbed chains can be then removed by a good solvent, while the adsorbed chains are assumed to maintain the same conformation due to the irreversible freezing through many physical solid-segment contacts. I firstly characterized the formation process and the surface/film structures of the adsorbed nanolayers by using X-ray reflectivity, grazing incidence X-ray diffraction, and atomic force microscopy. Secondly, to compare the surface energy of the adsorbed layers with the bulk, static contact angle measurements with two liquids (water and glycerol) were carried out using a optical contact angle meter equipped with a video camera. Thirdly, I designed and constructed a custom-built adhesion-testing device to quantify the adhesive property. The experimental results provide new insight into the microscopic structure - macroscopic property relationship at the solid-polymer interface.

  17. A monolithic and flexible fluoropolymer film microreactor for organic synthesis applications.

    PubMed

    Kim, Jin-Oh; Kim, Heejin; Ko, Dong-Hyeon; Min, Kyoung-Ik; Im, Do Jin; Park, Soo-Young; Kim, Dong-Pyo

    2014-11-01

    A photocurable and viscous fluoropolymer with chemical stability is a highly desirable material for fabrication of microchemical devices. Lack of a reliable fabrication method, however, limits actual applications for organic reactions. Herein, we report fabrication of a monolithic and flexible fluoropolymer film microreactor and its use as a new microfluidic platform. The fabrication involves facile soft lithography techniques that enable partial curing of thin laminates, which can be readily bonded by conformal contact without any external forces. We demonstrate fabrication of various functional channels (~300 μm thick) such as those embedded with either a herringbone micromixer pattern or a droplet generator. Organic reactions under strongly acidic and basic conditions can be carried out in this film microreactor even at elevated temperature with excellent reproducibility. In particular, the transparent film microreactor with good deformability could be wrapped around a light-emitting lamp for close contact with the light source for efficient photochemical reactions with visible light, which demonstrates easy integration with optical components for functional miniaturized systems. PMID:25220762

  18. Natural Transformation of Azotobacter vinelandii by Adsorbed Chromosomal DNA: Role of Adsorbed DNA Conformation

    NASA Astrophysics Data System (ADS)

    Lv, N.; Zilles, J.; Nguyen, H.

    2008-12-01

    Recent increases in antibiotic resistance among pathogenic microorganisms and the accompanying public health concerns result both from the widespread use of antibiotics and from the transfer of antibiotic resistance genes among microorganisms. To understand the transfer of antibiotic resistance genes and identify efficient measures to minimize these transfers, an interdisciplinary approach was used to identify physical and chemical factors that control the fate and biological availability of extracellular DNA. Quartz crystal microbalance with dissipation (QCM-D) was used to study extracellular DNA adsorption and the conformation of the adsorbed DNA on silica and natural organic matter (NOM) surfaces. Solution chemistry was varied systematically to investigate the role of adsorbed DNA conformation on transformation. Gene transfer was assessed under the same conditions using natural transformation of chromosomal DNA into the soil bacteria Azotobacter vinelandii. DNA adsorbed to both silica and NOM surfaces has a more compact and rigid conformation in the presence of Ca2+ compared to Na+. Extracellular DNA adsorbed on silica and NOM surfaces transformed A. vinelandii. The transformation efficiency of adsorbed DNA was up to 4 orders of magnitude lower than that of dissolved DNA. Preliminary results suggest that the presence of Ca2+ in groundwater (e.g. hardness) reduces the availability of adsorbed DNA for transformation.

  19. Organic solar cells based on liquid crystalline and polycrystalline thin films

    NASA Astrophysics Data System (ADS)

    Yoo, Seunghyup

    This dissertation describes the study of organic thin-film solar cells in pursuit of affordable, renewable, and environmentally-friendly energy sources. Particular emphasis is given to the molecular ordering found in liquid crystalline or polycrystalline films as a way to leverage the efficiencies of these types of cells. Maximum efficiencies estimated based on excitonic character of organic solar cells show power conversion efficiencies larger than 10% are possible in principle. However, their performance is often limited due to small exciton diffusion lengths and poor transport properties which may be attributed to the amorphous nature of most organic semiconductors. Discotic liquid crystal (DLC) copper phthalocyanine was investigated as an easily processible building block for solar cells in which ordered molecular arrangements are enabled by a self-organization in its mesophases. An increase in photocurrent and a reduction in series resistance have been observed in a cell which underwent an annealing process. X-ray diffraction (XRD) and atomic force microscopy (AFM) measurements suggest that structural and morphological changes induced after the annealing process are related to these improvements. In an alternative approach, p-type pentacene thin films prepared by physical vapor deposition were incorporated into heterojunction solar cells with C60 as n-type layers. Power conversion efficiencies of 2.7% under broadband illumination (350--900 nm) with a peak external quantum efficiency of 58% have been achieved with the broad spectral coverage across the visible spectrum. Analysis using an exciton diffusion model shows this efficient carrier generation is mainly due to the large exciton diffusion length of pentacene films. Joint XRD and AFM studies reveal that the highly crystalline nature of pentacene films can account for the observed large exciton diffusion length. In addition, the electrical characteristics are studied as a function of light intensity using

  20. [Melting in adsorbed films]. Progress report 1992

    SciTech Connect

    Simon, M.I.

    1992-12-31

    Over the past several years we have been developing a new approach to cloning large fragments of mammalian DNA in E. coli. which will permit detailed analysis of complex genomes. In January 1992 we began construction of an arrayed total human genomic library prepared in our BAC vector. Our goal is to create a 4-5X library which will be accessible for screening both by colony hybridization and by PCR. Our efforts in 1992 have been focused on expanding this library, characterizing specific clones isolated from the library, and demonstrating the use of BACs and Fosmids in creating physical maps. As a Model for the use of BACs in physical mapping, we have begun mapping human chromosome 22. In addition to their stability and ease of handling, BACs and Fosniids offer the advantage of permitting isolation of relatively large amounts of pure DNA which should greatly facilitate contig construction. We have created a 7X chromosome 22-specific Fosmid library consisting of clones obtained from DNA from a hybrid cell line.

  1. Organic soluble and uniform film forming oligoethylene glycol substituted BODIPY small molecules with improved hole mobility.

    PubMed

    Singh, Saumya; Venugopalan, Vijay; Krishnamoorthy, Kothandam

    2014-07-14

    Judiciously chosen side chains of conjugated molecules have a positive impact on charge transport properties when used as the active material in organic electronic devices. Amongst the side chains, oligoethylene glycols (OEGs) have been relatively unexplored due to their hydrophilic nature. OEGs also affect the smooth film formation of conjugated molecules, which preclude device fabrication. However, X-ray diffraction studies have shown that OEGs facilitate intermolecular contact, which is a desirable property for the fabrication of organic electronic devices. Thus the challenge is to design and synthesize organic solvent soluble and uniform film forming conjugated molecules with OEG side chains. We have designed and synthesized conjugated small molecules (CSMs) comprising BODIPY as acceptor and triphenylamine as donor with an OEG side chain. This molecule forms smooth films when processed from organic solvents. In order to understand the impact of the OEG side chain, we have also synthesized alkyl chain analogs. All the molecules exhibit exactly the same HOMO and LUMO energy levels, but the packing in the solid state is different. CSM with methyl side chains exhibit an inter planar distance of 4.15 Å. Contrary to this, the OEG side chain containing CSM showed an inter planar spacing of 4.30 Å, which is 0.2 Å less than the alkyl side chain comprising CSMs. Please note that the length of the hydrophobic and hydrophilic side chains is the same. Interestingly, the OEG side chain comprising CSM showed two orders of higher hole carrier mobilities compared to all the other derivatives. The same molecule also showed an extremely low threshold voltage of -0.27 V indicating the OEG side chains' favourable interaction between substrate as well as between molecules. PMID:24874914

  2. Layer-Resolved Evolution of Organic Thin Films Monitored by Photoelectron Emission Microscopy and Optical Reflectance Spectroscopy

    PubMed Central

    2015-01-01

    Photoelectron emission microscopy (PEEM) and differential (optical) reflectance spectroscopy (DRS) have proven independently to be versatile analytical tools for monitoring the evolution of organic thin films during growth. In this paper, we present the first experiment in which both techniques have been applied simultaneously and synchronously. We illustrate how the combined PEEM and DRS results can be correlated to obtain an extended perspective on the electronic and optical properties of a molecular film dependent on the film thickness and morphology. As an example, we studied the deposition of the organic molecule α-sexithiophene on Ag(111) in the thickness range from submonolayers up to several monolayers. PMID:26523159

  3. SUPERCRITICAL FLUID EXTRACTION OF PARTICULATE AND ADSORBENT MATERIALS

    EPA Science Inventory

    The report is a summary of work performed by PNL on the extraction of semivolatile organic materials (SVOCs), for example, polynuclear aromatic compounds, from various adsorbents and environmental matrices, using supercritical fluids (SCFs) as extractants. The results of the work...

  4. Fabrication of Vanadium Oxide Thin Films on Fused Quartz Substrates by Metal-Organic Decomposition for Bolometer Detectors

    NASA Astrophysics Data System (ADS)

    Son, Le Ngoc; Tachiki, Takashi; Uchida, Takashi

    2012-08-01

    Axis-oriented V2O5 thin films were prepared on fused quartz substrates by metal-organic decomposition (MOD). Then these films were reduced to VOx thin films by heat treatment at a temperature of 530 °C and a pressure of 1.2 Pa in O2. The obtained VOx thin films exhibited an abrupt phase transition with a resistivity change of up to 4 orders of magnitude. These VOx films had a high temperature coefficient of resistance (TCR) of up to 4.8%/K at 300 K and these values were over two times higher than those of the films fabricated on SiO2/Si substrates.

  5. Ultra-thin crystalline films of CdSe and CuSe formed at the organic-aqueous interface.

    PubMed

    Kalyanikutty, K P; Gautam, Ujjal K; Rao, C N R

    2007-06-01

    Two-dimensional nanostructures in the form of ultra-thin crystalline films of CdSe and CuSe have been prepared at the organic-aqueous interface by reacting toluene solutions of metal cupferronates with an aqueous solution of N,N-dimethyl selenourea. The films have been examined using electron microscopy and optical spectroscopy. At lower concentrations of the reacting species, the CdSe films formed at the toluene-water interface at approximately 30 degrees C consisted mostly of nanocrystals. With increase in concentration as well as temperature, the interface reaction yielded thicker films which are mostly single-crystalline. We have studied the time-dependent growth of the CdSe film at the interface using UV-visible absorption spectroscopy. Ultra-thin films of CuSe formed at the toluene-water interface are generally single-crystalline. PMID:17654965

  6. Nanopore reactive adsorbents for the high-efficiency removal of waste species

    DOEpatents

    Yang, Arthur Jing-Min; Zhang, Yuehua

    2005-01-04

    A nanoporous reactive adsorbent incorporates a relatively small number of relatively larger reactant, e.g., metal, enzyme, etc., particles (10) forming a discontinuous or continuous phase interspersed among and surrounded by a continuous phase of smaller adsorbent particles (12) and connected interstitial pores (14) therebetween. The reactive adsorbent can effectively remove inorganic or organic impurities in a liquid by causing the liquid to flow through the adsorbent. For example, silver ions may be adsorbed by the adsorbent particles (12) and reduced to metallic silver by reducing metal, such as ions, as the reactant particles (10). The column can be regenerated by backwashing with the liquid effluent containing, for example, acetic acid.

  7. Ordering of pentacene in organic thin film transistors induced by irradiation of infrared light

    SciTech Connect

    Wang, C. H.; Chen, S. W.; Hwang, J.

    2009-09-07

    The device performances of pentacene-based organic thin film transistors (OTFTs) were greatly improved by irradiation of infrared light. The field effect mobility and maximum drain current increase from 0.20{+-}0.01 to 0.57{+-}0.02 cm{sup 2}/V s and 1.14x10{sup -5} to 4.91x10{sup -5} A, respectively. The (001) peak of the pentacene 'thin film' phase increases in intensity by 4.5 times after infrared irradiation at 50 W for 2 h. Two types of crystal orientations, i.e., 'crystal I' (2{theta}=5.91 deg.) and 'crystal II' (2{theta}=5.84 deg.), coexist in the pentacene. The improvement of the characteristics of OTFTs is attributed to crystallization and crystal reorientation induced by infrared light.

  8. Solution-processed hybrid organic-inorganic complementary thin-film transistor inverter

    NASA Astrophysics Data System (ADS)

    Cheong, Heajeong; Kuribara, Kazunori; Ogura, Shintaro; Fukuda, Nobuko; Yoshida, Manabu; Ushijima, Hirobumi; Uemura, Sei

    2016-04-01

    We investigated hybrid organic-inorganic complementary inverters with a solution-processed indium-gallium-zinc-oxide (IGZO) n-channel thin-film transistor (TFT) and p-channel TFTs using the high-uniformity polymer poly[2,5-bis(alkyl)pyrrolo[3,4-c]pyrrolo-1,4(2H,5H)-dione-alt-5,5-di(thiophene-2-yl)-2,2-(E)-2-(2-(thiophen-2-yl)vinyl)thiophene] (PDVT-10). The IGZO TFT was fabricated at 150 °C for 1 min. It showed a high field-effect mobility of 0.9 cm2·V-1·s-1 and a high on/off current ratio of 107. A hybrid complementary inverter was fabricated by combining IGZO with a PDVT-10 thin-film transistor and its operation was confirmed.

  9. Extremely bendable thin-film encapsulation of organic light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Seo, Seung-Woo; Chae, Heeyeop; Joon Seo, Sang; Kyoon Chung, Ho; Min Cho, Sung

    2013-04-01

    We report on an extremely bendable moisture barrier for the thin-film encapsulation of organic light-emitting diodes (OLEDs). Hybrid barriers with various dyads of alternating aluminum oxide (Al2O3) and plasma-polymerized layers, which are utilizable for the thin-film encapsulation of flexible OLEDs, were prepared by atomic layer deposition and plasma chemical vapor deposition, respectively. When the total thickness of Al2O3 was fixed at 20 nm, an ultimate 200-dyad multilayer barrier showed change of less than 20% in water vapor transmission rate from its initial value of the order of 10-4 g/m2/day, even after 10 000 times of bending with a bending radius of 5 mm.

  10. High efficiency THz-wave modulators based on conjugated polymer-based organic films

    NASA Astrophysics Data System (ADS)

    He, Ting; Zhang, Bo; Wang, Guo-cui; Zang, Meng-di; Hou, Yan-bing; Shen, Jing-ling

    2016-02-01

    A study of the modulation mechanisms of conjugated polymer-based organic films and high-efficiency, broadband and all-optically controlled terahertz modulators based on these films is presented in this paper. Under very low-level external laser excitation, modulation efficiency of more than 99% is achieved using MEH-PPV/Si, PFO/Si and F8BT/Si bilayers. By analyzing the changes in the photo-excited carrier density and photoconductivity with changes in the external laser intensity, we introduce a nonlinear photo-induced absorption process to explain the strong attenuation mechanism for the transmitted terahertz waves. Finally, a simple THz communication test is carried out to demonstrate the potential future applications of the high-efficiency all-optically controlled terahertz modulator.

  11. Charge Transport in Thin Organic Semiconducting Films: Seebeck and Field Effect Studies

    NASA Astrophysics Data System (ADS)

    Böhm, W.; Fritz, T.; Leo, K.

    1997-03-01

    We have investigated the charge transport properties of vapor-deposited thin organic films, using the Seebeck effect for determining conduction type and Fermi energy and the field effect to measure mobility and total charge carrier density. We show that the combination of both techniques gives a complete picture of the electrical properties of the films. Wir untersuchen den Ladungsträgertransport in aufgedampften dünnen organischen Schichten, wobei der Seebeck-Effekt zur Bestimmung des Leitfähigkeitstyps und der Lage des Ferminiveaus und der Feldeffekt zur Bestimmung der Leitfähigkeit und der gesamten Ladungsträgerdichte benutzt wird. Es wird gezeigt, daß durch die Kombination beider Methoden ein geschlossenes Bild der elektrischen Eigenschaften erhalten wird.

  12. Measurement of desorbed products during organic polymer thin film etching by plasma beam irradiation

    SciTech Connect

    Kurihara, Kazuaki; Karahashi, Kazuhiro; Egami, Akihiro; Nakamura, Moritaka

    2006-11-15

    The authors investigated the etching characteristics of three kinds of methacrylate polymer films, which have the same main chain but with different side chains, using a plasma beam irradiation apparatus. The polymers are polytbutylmethacrylate, polybenzylmethacrylate, and polycyclohexylmethacrylate. The major desorbed products during nitrogen plasma beam etching were found to be HCN and C{sub 2}N{sub 2} for all methacrylate polymer films. The desorbed products originating from the polymer structure, namely, the main chain and the side chain, were hardly observed. The energy distributions of desorbed products were mainly composed of Maxwell-Boltzmann distribution with a small component of collision cascade distribution for all three polymers and were slightly dependent on the ion energy. It is concluded that chemical sputtering, which can be defined as the production of weakly bound species by ion bombardment, followed by thermal desorption, is the significant ion induced mechanism of organic polymer etching.

  13. Numerical modeling of time-resolved photocurrent in organic semiconductor films

    NASA Astrophysics Data System (ADS)

    Johnson, Brian; Paudel, Keshab; Kendrick, Mark J.; Ostroverkhova, Oksana

    2013-10-01

    We performed numerical simulations of transient photocurrents in organic thin films, in conjunction with experiments. This enabled us to quantify the contribution of multiple charge generation pathways to charge carrier photogeneration, as well as extract parameters that characterize charge transport, in functionalized anthradithiophene (ADT-TES-F) films prepared using two different deposition methods: drop casting on an untreated substrate and spin casting on a pentauorobenzenethiol (PFBT)-treated substrate. These deposition methods yielded polycrystalline lms with considerably larger grain sizes in the case of the spin cast lm. In both drop cast and spin cast films, simulations revealed two competing charge photogeneration pathways: fast charge generation on a picosecond (ps) or sub-ps time scale with efficiencies below 10%, and slow charge generation, on the time scale of tens of nanoseconds, with efficiencies of 11-12% in drop cast and 50-60% in spin cast films, depending on the applied electric field. The total charge photogeneration efficiency in the spin cast sample was 59-67% compared to 14-20% in the drop cast sample, whereas the remaining 33-41% and 80-86%, respectively, of the absorbed photon density did not contribute to charge carrier generation on these time scales. The spin cast film also exhibited higher hole mobilities, lower trap densities, shallower traps, and lower charge carrier recombination, as compared to the drop cast lm. As a result, the spin cast lm exhibited higher photocurrents despite a considerably lower lm thickness (and thus reduced optical absorption and cross section of the current flow).

  14. Singlet-based photon upconversion in multichromophore organic thin films (Presentation Recording)

    NASA Astrophysics Data System (ADS)

    Weingarten, Daniel H.; LaCount, Michael; Rumbles, Garry; van de Lagemaat, Jao; Lusk, Mark T.; Shaheen, Sean E.

    2015-10-01

    Solid-state energy upconversion has many potential applications, from nonlinear photonics and biophotonics to expanding the spectrum available for solar energy harvest. In organic molecular systems, upconversion is frequently done in solution to mitigate aggregation-induced photoluminescence quenching or to facilitate the diffusion of triplet donors in Triplet-Triplet Annihilation (TTA) systems. Here we demonstrate an organic thin film upconversion system utilizing two-photon absorption (TPA) properties to improve upconversion efficiency. In blend films of Stilbene-420 and Rhodamine 6G we observe a tenfold increase in up-converted fluorescence compared to the fluorescence yield of TPA in pristine stilbene films. While TPA normally has quadratic dependence on excitation intensity, these blend films exhibit sub-quadratic intensity dependence, indicating a combination of linear and quadratic upconversion processes and dramatically improving upconversion efficiency at lower excitation intensities. This improvement in intensity dependence allows for relatively efficient upconversion upon excitation by a nanosecond laser pulse, in contrast to the more expensive femtosecond lasers generally required for excitation in TPA microscopy and similar systems. Time-resolved photoluminescence decay measurements reveal that all excited states involved in this upconversion process are singlets, which indicates the potential for reduced energy losses when compared to TTA upconversion systems and their inherent intersystem-crossing energy losses. We observe emission from both the Rhodamine 6G donor molecules and Stilbene-420 acceptor molecules, indicating the presence of prompt fluorescence from the donor as well as upconversion to the acceptor, and FRET losses from acceptor back to donor. By fitting to a kinetic model we extract rates for these competing processes.

  15. Investigation of the spin-lattice relaxation of 13CO and 13CO2 adsorbed in the metal-organic frameworks Cu3(btc)2 and Cu3-xZnx(btc)2

    NASA Astrophysics Data System (ADS)

    Gul-E-Noor, Farhana; Michel, Dieter; Krautscheid, Harald; Haase, Jürgen; Bertmer, Marko

    2013-07-01

    The 13C nuclear spin-lattice relaxation time of 13CO and 13CO2 molecules adsorbed in the metal-organic frameworks (MOFs) Cu2.97Zn0.03(btc)2 and Cu3(btc)2 is investigated over a wide range of temperatures at resonance frequencies of 75.468 and 188.62 MHz. In all cases a mono-exponential relaxation is observed, and the 13C spin-lattice relaxation times (T1) reveal minima within the temperature range of the measurements and both frequencies. This allows us to carry out a more detailed analysis of the 13C spin relaxation data and to consider the influence due to the spectral functions of the thermal motion. In a model-free discussion of the temperature dependence of the ratios T1 (T)/T1,min we observe a motional mechanism that can be described by a single correlation time. In relation to the discussion of the relaxation mechanisms this can be understood in terms of dominating translational motion with mean jump distance being larger than the minimum distances between neighboring adsorption sites in the MOFs. A more detailed discussion of the jump-like motion observed here might be carried out on the basis of self-diffusion coefficients. From the present spin relaxation measurements activation energies for the local motion of the adsorbed molecules in the MOFs can be estimated to be 3.3 kJ/mol and 2.2 kJ/mol, for CO and CO2 molecules, respectively. Finally, our findings are compared with our recent results derived from the 13C line shape analysis.

  16. Post-annealed gallium and aluminum co-doped zinc oxide films applied in organic photovoltaic devices

    PubMed Central

    2014-01-01

    Gallium and aluminum co-doped zinc oxide (GAZO) films were produced by magnetron sputtering. The GAZO films were post-annealed in either vacuum or hydrogen microwave plasma. Vacuum- and hydrogen microwave plasma-annealed GAZO films show different surface morphologies and lattice structures. The surface roughness and the spacing between adjacent (002) planes decrease; grain growth occurs for the GAZO films after vacuum annealing. The surface roughness increases and nanocrystals are grown for the GAZO films after hydrogen microwave plasma annealing. Both vacuum and hydrogen microwave plasma annealing can improve the electrical and optical properties of GAZO films. Hydrogen microwave plasma annealing improves more than vacuum annealing does for GAZO films. An electrical resistivity of 4.7 × 10−4 Ω-cm and average optical transmittance in the visible range from 400 to 800 nm of 95% can be obtained for the GAZO films after hydrogen microwave plasma annealing. Hybrid organic photovoltaic (OPV) devices were fabricated on the as-deposited, vacuum-annealed, and hydrogen microwave plasma-annealed GAZO-coated glass substrates. The active layer consisted of blended poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61 butyric acid methyl ester (PCBM) in the OPV devices. The power conversion efficiency of the OPV devices is 1.22% for the hydrogen microwave plasma-annealed GAZO films, which is nearly two times higher compared with that for the as-deposited GAZO films. PMID:25352768

  17. Post-annealed gallium and aluminum co-doped zinc oxide films applied in organic photovoltaic devices.

    PubMed

    Chang, Shang-Chou

    2014-01-01

    Gallium and aluminum co-doped zinc oxide (GAZO) films were produced by magnetron sputtering. The GAZO films were post-annealed in either vacuum or hydrogen microwave plasma. Vacuum- and hydrogen microwave plasma-annealed GAZO films show different surface morphologies and lattice structures. The surface roughness and the spacing between adjacent (002) planes decrease; grain growth occurs for the GAZO films after vacuum annealing. The surface roughness increases and nanocrystals are grown for the GAZO films after hydrogen microwave plasma annealing. Both vacuum and hydrogen microwave plasma annealing can improve the electrical and optical properties of GAZO films. Hydrogen microwave plasma annealing improves more than vacuum annealing does for GAZO films. An electrical resistivity of 4.7 × 10(-4) Ω-cm and average optical transmittance in the visible range from 400 to 800 nm of 95% can be obtained for the GAZO films after hydrogen microwave plasma annealing. Hybrid organic photovoltaic (OPV) devices were fabricated on the as-deposited, vacuum-annealed, and hydrogen microwave plasma-annealed GAZO-coated glass substrates. The active layer consisted of blended poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61 butyric acid methyl ester (PCBM) in the OPV devices. The power conversion efficiency of the OPV devices is 1.22% for the hydrogen microwave plasma-annealed GAZO films, which is nearly two times higher compared with that for the as-deposited GAZO films. PMID:25352768

  18. Post-annealed gallium and aluminum co-doped zinc oxide films applied in organic photovoltaic devices

    NASA Astrophysics Data System (ADS)

    Chang, Shang-Chou

    2014-10-01

    Gallium and aluminum co-doped zinc oxide (GAZO) films were produced by magnetron sputtering. The GAZO films were post-annealed in either vacuum or hydrogen microwave plasma. Vacuum- and hydrogen microwave plasma-annealed GAZO films show different surface morphologies and lattice structures. The surface roughness and the spacing between adjacent (002) planes decrease; grain growth occurs for the GAZO films after vacuum annealing. The surface roughness increases and nanocrystals are grown for the GAZO films after hydrogen microwave plasma annealing. Both vacuum and hydrogen microwave plasma annealing can improve the electrical and optical properties of GAZO films. Hydrogen microwave plasma annealing improves more than vacuum annealing does for GAZO films. An electrical resistivity of 4.7 × 10-4 Ω-cm and average optical transmittance in the visible range from 400 to 800 nm of 95% can be obtained for the GAZO films after hydrogen microwave plasma annealing. Hybrid organic photovoltaic (OPV) devices were fabricated on the as-deposited, vacuum-annealed, and hydrogen microwave plasma-annealed GAZO-coated glass substrates. The active layer consisted of blended poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61 butyric acid methyl ester (PCBM) in the OPV devices. The power conversion efficiency of the OPV devices is 1.22% for the hydrogen microwave plasma-annealed GAZO films, which is nearly two times higher compared with that for the as-deposited GAZO films.

  19. Zeolite thin film-coated spherical end-face fiber sensors for detection of trace organic vapors

    NASA Astrophysics Data System (ADS)

    Ning, Xiangping; Zhao, Chun Liu; Yang, Jingyi; Chan, Chi Chiu

    2016-04-01

    A novel zeolite thin film-coated spherical end face fiber sensor for detection of trace organic vapors was experimentally demonstrated. The spherical end-face was fabricated by electrical arc discharge on the end face of a standard single-mode fiber. The proposed sensor comprise of the fiber's spherical end-face covered with a layer of zeolite thin film. The zeolite film and spherical end face constituted an arc-shaped inline Fabry-Perot (F-P) cavity, which improves the interference performance. The trace chemical vapor concentration was measured by monitoring the shift of F-P interference wavelength which induced by the organic vapor molecular adsorption of the zeolite film. The proposed trace organic vapors sensor performed with the enhanced sensitivity 0.91 nm/ppm with the range from 0 to 70 ppm.

  20. Processing of functional polymers and organic thin films by the matrix-assisted pulsed laser evaporation (MAPLE) technique

    NASA Astrophysics Data System (ADS)

    Piqué, A.; Wu, P.; Ringeisen, B. R.; Bubb, D. M.; Melinger, J. S.; McGill, R. A.; Chrisey, D. B.

    2002-01-01

    The matrix-assisted pulsed laser evaporation (MAPLE) technique has been successfully used to deposit highly uniform thin films of various functional materials such as non-linear optical (NLO) organic materials, conductive polymers, luminescent organic molecules and several types of proteinaceous compounds. MAPLE is a laser evaporation technique for growing thin films of organic and polymeric materials which involves directing a pulsed laser beam (λ=193 nm; fluence=0.01-0.5 J cm -2) onto a frozen target (-40 to -160 °C) consisting of a solute polymeric or organic compound dissolved in a solvent matrix. Using MAPLE, thin films of N-(4-nitrophenyl)-( L)-prolinol or NPP, an NLO material; polypyrrole, a conductive polymer; and tris-(8-hydroxyquinoline) aluminum or Alq3, a luminescent organic compound, have been separately deposited with minor (in the case of Alq3) or no degradation (for the NPP and polypyrrole) to their optical and electrical properties. The MAPLE process has also been used to deposit discrete thin film micro-arrays of biotinylated bovine serum albumin (BSA). The deposited BSA films, after washing with a blocking protein and fluorescently tagged streptavidin, fluoresce when exposed to UV. This fluorescence indicates that the biochemical specificity of the transferred biotinylated protein is unaffected by the MAPLE process. These results demonstrate that the MAPLE technique can be used for growing thin films of functional polymer and active biomaterials.

  1. Nanostructured thin films for organic photovoltaic cells and organic light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Zheng, Ying

    2009-12-01

    Achieving efficient organic optoelectronic devices, such as organic photovoltaic (OPV) cells and organic light-emitting diodes (OLEDs), relies on the understanding of the formation of various organic nanostructures as well as the fundamental of physical processes in device operation. The research presented in this thesis systematically investigates the controlled growth of organic nanostructure through different approaches and their relationship to OPV cell performance. Moreover, new materials and device structure are explored to achieve efficient OLEDs, which also provide further insight of the physical processes governing the performance of these devices. We first investigated the phase separation process in a molecular mixed donor-acceptor (D -- A) bulk heterojunction (BHJ) composed of pentacene and C60 suing a combination of experimental and computational approaches. Both experiment characterization and the MD simulation reveals that strong aggregation of pentacene exists in the pentacene:C60 mixtures due to the strong pi -- pi interaction among pentacene molecules. By controlling the processing conditions to suppress the pentacene aggregation to nanoscale leads to higher device efficiency as the more photogenerated excitons are able to reach the D -- A interface and contribute to the photocurrent. To circumvent the limits on phase separated D -- A mixed heterojunction, an interdigitated D -- A BHJ is synthesized through the oblique angle deposition (OAD) of copper phthalocyanine (CuPc). The morphology of CuPc nanorod arrays grown under the OAD process can be controlled by careful selection of the processing conditions, and we have achieved a high density, vertically aligned, polycrystalline CuPc nanorod array with nanorod size as small as 20-30 nm. Successful infiltration of [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) into the optimized CuPc nanorod arrays has resulted in doubling of the power conversion efficiency of the OPV cell over planar

  2. Organic and organic-inorganic hybrid polymer thin films deposited by PECVD using TEOS and cyclohexene for ULSI interlayer-dielectric application

    NASA Astrophysics Data System (ADS)

    Seo, Hyeon Jin; Nam, Sang-Hun; Kim, Sungsoo; Boo, Jin-Hyo

    2015-11-01

    Organic and organic-inorganic hybrid polymer thin films were deposited on Si(1 0 0) substrates at various ratios of TEOS (tetraethoxysilane) to cyclohexene by the plasma enhanced chemical vapor deposition (PECVD) method. The as-grown polymerized thin films were first analyzed by FT-IR and XPS. The results of FT-IR showed that the hybrid polymer thin films were polymerized with each fragmented precursor. The XPS results showed the chemical species and binding energies of each species. The Si 2p core-level spectra from the hybrid polymer thin film showed the status of the Si oxidation number. Impedance analysis was utilized for the measurement of the capacitance values and I-V curves, and an ultra low-k value and leakage current density of 1.75 and 10-9 A/cm2 at 1 MV/cm were obtained, respectively.

  3. α,ω-dihexyl-sexithiophene thin films for solution-gated organic field-effect transistors

    NASA Astrophysics Data System (ADS)

    Schamoni, Hannah; Noever, Simon; Nickel, Bert; Stutzmann, Martin; Garrido, Jose A.

    2016-02-01

    While organic semiconductors are being widely investigated for chemical and biochemical sensing applications, major drawbacks such as the poor device stability and low charge carrier mobility in aqueous electrolytes have not yet been solved to complete satisfaction. In this work, solution-gated organic field-effect transistors (SGOFETs) based on the molecule α,ω-dihexyl-sexithiophene (DH6T) are presented as promising platforms for in-electrolyte sensing. Thin films of DH6T were investigated with regard to the influence of the substrate temperature during deposition on the grain size and structural order. The performance of SGOFETs can be improved by choosing suitable growth parameters that lead to a two-dimensional film morphology and a high degree of structural order. Furthermore, the capability of the SGOFETs to detect changes in the pH or ionic strength of the gate electrolyte is demonstrated and simulated. Finally, excellent transistor stability is confirmed by continuously operating the device over a period of several days, which is a consequence of the low threshold voltage of DH6T-based SGOFETs. Altogether, our results demonstrate the feasibility of high performance and highly stable organic semiconductor devices for chemical or biochemical applications.

  4. Effect of fractal silver electrodes on charge collection and light distribution in semiconducting organic polymer films

    SciTech Connect

    Chamousis, RL; Chang, LL; Watterson, WJ; Montgomery, RD; Taylor, RP; Moule, AJ; Shaheen, SE; Ilan, B; van de Lagemaat, J; Osterloh, FE

    2014-08-21

    Living organisms use fractal structures to optimize material and energy transport across regions of differing size scales. Here we test the effect of fractal silver electrodes on light distribution and charge collection in organic semiconducting polymer films made of P3HT and PCBM. The semiconducting polymers were deposited onto electrochemically grown fractal silver structures (5000 nm x 500 nm; fractal dimension of 1.71) with PEDOT:PSS as hole-selective interlayer. The fractal silver electrodes appear black due to increased horizontal light scattering, which is shown to improve light absorption in the polymer. According to surface photovoltage spectroscopy, fractal silver electrodes outperform the flat electrodes when the BHJ film thickness is large (>400 nm, 0.4 V photovoltage). Photocurrents of up to 200 microamperes cm(-2) are generated from the bulk heterojunction (BHJ) photoelectrodes under 435 nm LED (10-20 mW cm(-2)) illumination in acetonitrile solution containing 0.005 M ferrocenium hexafluorophosphate as the electron acceptor. The low IPCE values (0.3-0.7%) are due to slow electron transfer to ferrocenium ion and due to shunting along the large metal-polymer interface. Overall, this work provides an initial assessment of the potential of fractal electrodes for organic photovoltaic cells.

  5. Effect of fractal silver electrodes on charge collection and light distribution in semiconducting organic polymer films

    SciTech Connect

    Chamousis, RL; Chang, LL; Watterson, WJ; Montgomery, RD; Taylor, RP; Moule, AJ; Shaheen, SE; Ilan, B; van de Lagemaat, J; Osterloh, FE

    2014-10-21

    Living organisms use fractal structures to optimize material and energy transport across regions of differing size scales. Here we test the effect of fractal silver electrodes on light distribution and charge collection in organic semiconducting polymer films made of P3HT and PCBM. The semiconducting polymers were deposited onto electrochemically grown fractal silver structures (5000 nm x 500 nm; fractal dimension of 1.71) with PEDOT:PSS as hole-selective interlayer. The fractal silver electrodes appear black due to increased horizontal light scattering, which is shown to improve light absorption in the polymer. According to surface photovoltage spectroscopy, fractal silver electrodes outperform the flat electrodes when the BHJ film thickness is large (>400 nm, 0.4 V photovoltage). Photocurrents of up to 200 microamperes cm(-2) are generated from the bulk heterojunction (BHJ) photoelectrodes under 435 nm LED (10-20 mW cm(-2)) illumination in acetonitrile solution containing 0.005 M ferrocenium hexafluorophosphate as the electron acceptor. The low IPCE values (0.3-0.7%) are due to slow electron transfer to ferrocenium ion and due to shunting along the large metal-polymer interface. Overall, this work provides an initial assessment of the potential of fractal electrodes for organic photovoltaic cells.

  6. Synchrotron-radiation XPS analysis of ultra-thin silane films: Specifying the organic silicon

    NASA Astrophysics Data System (ADS)

    Dietrich, Paul M.; Glamsch, Stephan; Ehlert, Christopher; Lippitz, Andreas; Kulak, Nora; Unger, Wolfgang E. S.

    2016-02-01

    The analysis of chemical and elemental in-depth variations in ultra-thin organic layers with thicknesses below 5 nm is very challenging. Energy- and angle-resolved XPS (ER/AR-XPS) opens up the possibility for non-destructive chemical ultra-shallow depth profiling of the outermost surface layer of ultra-thin organic films due to its exceptional surface sensitivity. For common organic materials a reliable chemical in-depth analysis with a lower limit of the XPS information depth z95 of about 1 nm can be performed. As a proof-of-principle example with relevance for industrial applications the ER/AR-XPS analysis of different organic monolayers made of amino- or benzamidosilane molecules on silicon oxide surfaces is presented. It is demonstrated how to use the Si 2p core-level region to non-destructively depth-profile the organic (silane monolayer) - inorganic (SiO2/Si) interface and how to quantify Si species, ranging from elemental silicon over native silicon oxide to the silane itself. The main advantage of the applied ER/AR-XPS method is the improved specification of organic from inorganic silicon components in Si 2p core-level spectra with exceptional low uncertainties compared to conventional laboratory XPS.

  7. From adsorption to condensation: the role of adsorbed molecular clusters.

    PubMed

    Yaghoubian, Sima; Zandavi, Seyed Hadi; Ward, C A

    2016-08-01

    The adsorption of heptane vapour on a smooth silicon substrate with a lower temperature than the vapour is examined analytically and experimentally. An expression for the amount adsorbed under steady state conditions is derived from the molecular cluster model of the adsorbate that is similar to the one used to derive the equilibrium Zeta adsorption isotherm. The amount adsorbed in each of a series of steady experiments is measured using a UV-vis interferometer, and gives strong support to the amount predicted to be adsorbed. The cluster distribution is used to predict the subcooling temperature required for the adsorbed vapour to make a disorder-order phase transition to become an adsorbed liquid, and the subcooling temperature is found to be 2.7 ± 0.4 K. The continuum approach for predicting the thickness of the adsorbed liquid film originally developed by Nusselt is compared with that measured and is found to over-predict the thickness by three-orders of magnitude. PMID:27426944

  8. Self-organized broadband light trapping in thin film amorphous silicon solar cells.

    PubMed

    Martella, C; Chiappe, D; Delli Veneri, P; Mercaldo, L V; Usatii, I; Buatier de Mongeot, F

    2013-06-01

    Nanostructured glass substrates endowed with high aspect ratio one-dimensional corrugations are prepared by defocused ion beam erosion through a self-organized gold (Au) stencil mask. The shielding action of the stencil mask is amplified by co-deposition of gold atoms during ion bombardment. The resulting glass nanostructures enable broadband anti-reflection functionality and at the same time ensure a high efficiency for diffuse light scattering (Haze). It is demonstrated that the patterned glass substrates exhibit a better photon harvesting than the flat glass substrate in p-i-n type thin film a-Si:H solar cells. PMID:23633473

  9. Scanning gate study of organic thin-film field-effect transistor

    NASA Astrophysics Data System (ADS)

    Aoki, N.; Sudou, K.; Matsusaki, K.; Okamoto, K.; Ochiai, Y.

    2008-03-01

    Scanning gate microscopy (SGM) has been applied for a study of organic thin-film field effect transistor (OFET). In contrast to one-dimensional nano-material such a carbon nanonube or nano-structure such a quantum point contact, visualization a transport characteristic of OFET channel is basically rather difficult since the channel width is much larger than the size of the SGM tip. Nevertheless, Schottky barriers are successfully visualized at the boundary between the metal electrodes and the OFET channel at ambient atmosphere.

  10. Detection of saliva-range glucose concentrations using organic thin-film transistors

    NASA Astrophysics Data System (ADS)

    Elkington, D.; Belcher, W. J.; Dastoor, P. C.; Zhou, X. J.

    2014-07-01

    We describe the development of a glucose sensor through direct incorporation of an enzyme (glucose oxidase) into the gate of an organic thin film transistor (OTFT). We show that glucose diffusion is the key determinant of the device response time and present a mechanism of glucose sensing in these devices that involves protonic doping of the transistor channel via enzymatic oxidation of glucose. The integrated OTFT sensor is sensitive across 4 decades of glucose concentration; a range that encompasses both the blood and salivary glucose concentration levels. As such, this work acts as a proof-of-concept for low-cost printed biosensors for salivary glucose.

  11. [Photoexcitation mechanism of photoconductive device by organic/inorganic thin-film heteropairing].

    PubMed

    Jin, Hui; Teng, Feng; Liu, Jun-Feng; Meng, Xian-Guo; Xu, Zheng; Hou, Yan-Bing; Xu, Xu-Rong

    2004-08-01

    Photoconductive devices with organic (polyvinylcarbazole-PVK)/inorganic (zinc-sulfide--ZnS) thin-film heteropairing were fabricated. In external field, the excitation profile of the steady-state photoconductivity and the primary photoexcitation process of hybrid devices were presented and discussed. Comparison of photoconductivity of the devices and absorption spectra of PVK and ZnS implied that both layers absorption contributes to the photocurrent, but the effective part is at the interface of PVK and ZnS. The dependence of maximum photocurrent on the applied voltage and the dark and illuminated current spectra indicates the ultrafast charge transfer at the interface. PMID:15766107

  12. Efficient organic light-emitting diodes using polycrystalline silicon thin films as semitransparent anode

    NASA Astrophysics Data System (ADS)

    Zhu, X. L.; Sun, J. X.; Peng, H. J.; Meng, Z. G.; Wong, M.; Kwok, H. S.

    2005-08-01

    Polycrystalline silicon (p-Si) is a good material for the construction of thin-film transistors (TFT). It is used for fabricating active-matrix organic light-emitting diode (AMOLED) displays. In this letter, we propose and demonstrate the application of boron-doped p-Si as a semi-transparent anode in making different color OLEDs. Without removing the ultrathin native oxide on the p-Si surface and employing p-doped hole transport layer to enhance holes injection, these OLEDs show comparable or even better performance to conventional OLEDs which use ITO as anodes. The present technique has the advantage of less masking steps in making AMOLED.

  13. All solution processed organic thin film transistor-backplane with printing technology for electrophoretic display

    USGS Publications Warehouse

    Lee, Myung W.; Song, C.K.

    2012-01-01

    In this study, solution processes were developed for backplane using an organic thin film transistor (OTFT) as a driving device for an electrophoretic display (EPD) panel. The processes covered not only the key device of OTFTs but also interlayer and pixel electrodes. The various materials and printing processes were adopted to achieve the requirements of devices and functioning layers. The performance of OTFT of the backplane was sufficient to drive EPD sheet by producing a mobility of 0.12 cm2/v x sec and on/off current ratio of 10(5).

  14. Detection of saliva-range glucose concentrations using organic thin-film transistors

    SciTech Connect

    Elkington, D.; Belcher, W. J.; Dastoor, P. C.; Zhou, X. J.

    2014-07-28

    We describe the development of a glucose sensor through direct incorporation of an enzyme (glucose oxidase) into the gate of an organic thin film transistor (OTFT). We show that glucose diffusion is the key determinant of the device response time and present a mechanism of glucose sensing in these devices that involves protonic doping of the transistor channel via enzymatic oxidation of glucose. The integrated OTFT sensor is sensitive across 4 decades of glucose concentration; a range that encompasses both the blood and salivary glucose concentration levels. As such, this work acts as a proof-of-concept for low-cost printed biosensors for salivary glucose.

  15. Ambipolar organic thin-film transistor-based nano-floating-gate nonvolatile memory

    SciTech Connect

    Han, Jinhua; Wang, Wei Ying, Jun; Xie, Wenfa

    2014-01-06

    An ambipolar organic thin-film transistor-based nano-floating-gate nonvolatile memory was demonstrated, with discrete distributed gold nanoparticles, tetratetracontane (TTC), pentacene as the floating-gate layer, tunneling layer, and active layer, respectively. The electron traps at the TTC/pentacene interface were significantly suppressed, which resulted in an ambipolar operation in present memory. As both electrons and holes were supplied in the channel and trapped in the floating-gate by programming/erasing operations, respectively, i.e., one type of charge carriers was used to overwrite the other, trapped, one, a large memory window, extending on both sides of the initial threshold voltage, was realized.

  16. Mercury adsorption properties of sulfur-impregnated adsorbents

    USGS Publications Warehouse

    Hsi, N.-C.; Rood, M.J.; Rostam-Abadi, M.; Chen, S.; Chang, R.

    2002-01-01

    Carbonaceous and noncarbonaceous adsorbents were impregnated with elemental sulfur to evaluate the chemical and physical properties of the adsorbents and their equilibrium mercury adsorption capacities. Simulated coal combustion flue gas conditions were used to determine the equilibrium adsorption capacities for Hg0 and HgCl2 gases to better understand how to remove mercury from gas streams generated by coal-fired utility power plants. Sulfur was deposited onto the adsorbents by monolayer surface deposition or volume pore filling. Sulfur impregnation increased the total sulfur content and decreased the total and micropore surface areas and pore volumes for all of the adsorbents tested. Adsorbents with sufficient amounts of active adsorption sites and sufficient microporous structure had mercury adsorption capacities up to 4,509 ??g Hg/g adsorbent. Elemental sulfur, organic sulfur, and sulfate were formed on the adsorbents during sulfur impregnation. Correlations were established with R2>0.92 between the equilibrium Hg0/HgCl2 adsorption capacities and the mass concentrations of elemental and organic sulfur. This result indicates that elemental and organic sulfur are important active adsorption sites for Hg0 and HgCl2.

  17. Microchip electrophoresis with background electrolyte containing polyacrylic acid and high content organic solvent in cyclic olefin copolymer microchips for easily adsorbed dyes.

    PubMed

    Wei, Xuan; Sun, Ping; Yang, Shenghong; Zhao, Lei; Wu, Jing; Li, Fengyun; Pu, Qiaosheng

    2016-07-29

    Plastic microchips can significantly reduce the fabrication cost but the adsorption of some analytes limits their application. In this work, background electrolyte containing ionic polymer and high content of organic solvent was adopted to eliminate the analyte adsorption and achieve highly efficient separation in microchip electrophoresis. Two dyes, rhodamine 6G (Rh6G) and rhodamine B (RhB) were used as the model analytes. By using methanol as the organic solvent and polyacrylic acid (PAA) as a multifunctional additive, successful separation of the two dyes within 75μm id. microchannels was realized. The role of PAA is multiple, including viscosity regulator, selectivity modifier and active additive for counteracting analyte adsorption on the microchannel surface. The number of theoretical plate of 7.0×10(5)/m was attained within an effective separation distance of 2cm using background electrolyte consisting 80% methanol, 0.36% PAA and 30mmol/L phosphate at pH 5.0. Under optimized conditions, relative standard deviations of Rh6G and RhB detection (n=5) were no more than 1.5% for migration time and 2.0% for peak area, respectively. The limit of detection (S/N=3) was 0.1nmol/L for Rh6G. The proposed technique was applied in the determination of both Rh6G and RhB in chilli powder and lipstick samples with satisfactory recoveries of 81.3-103.7%. PMID:27371017

  18. Element-Doped Polyacrylic Acid Thin Films as SIMS Standards for Organic Materials

    NASA Astrophysics Data System (ADS)

    Davisson, M.; Phinney, D. L.; Weber, P. K.

    2009-12-01

    To constrain relative sensitive factors for SIMS elemental analysis of organic materials, calibration standards are being developed by coordinating ppm quantities of Group I, Group II, and transition metals with polyacrylic acid resin and depositing them as thin films. Each element is prepared as an aqueous acetate, oxalate, or nitrate solution to avoid unwanted elements that compromise thin film uniformity or produce interfering masses. These are subsequently mixed proportionally with reagent grade resins (Mw ~2000 and ~50,000), and dried passively on an Al bullet or spin-coated for thin layering (~100nm). Initial results using an O- primary beam on a Cameca NanoSIMS demonstrate excellent lateral homogeneity for Na, K, Fe, Co, and Cd at nanometer scale and consistent ratios to 12C (stdev <10%) over multiple 10um raster areas, whereas Mg, Ca, Sr, and Cu show variable ratios to 12C over sputter depth (stdev >10%). Depth profiling over the entire film thickness using a Cameca 3f show high reproducibility of element trends at 250um raster areas. Additional measurements will incorporate multi-element suites of biologically-relevant species (e.g. Na, K, Ca, P) to facilitate quantitative analysis of sensitivity factors with compositional changes.

  19. Transient phases during crystallization of solution-processed organic thin films

    NASA Astrophysics Data System (ADS)

    Wan, Jing; Li, Yang; Ulbrandt, Jeffery; Smilgies, Detlef-M.; Hollin, Jonathan; Whalley, Adam; Headrick, Randall

    We report an in-situ study of 2,7-dioctyl[1]benzothieno[3,2-b][1]benzothiophene (C8-BTBT) organic semiconductor thin film deposition from solution via hollow pen writing, which exhibits multiple transient phases during crystallization. Under high writing speed (25 mm/s) the films have an isotropic morphology, although the mobilities range up to 3.0 cm2/V.s. To understand the crystallization in this highly non-equilibrium regime, we employ in-situ microbeam grazing incidence wide-angle X-ray scattering combined with optical video microscopy at different deposition temperatures. A sequence of crystallization was observed in which a layered liquid-crystalline (LC) phase of C8-BTBT precedes inter-layer ordering. For films deposited above 80ºC, a transition from LC phase to a transient crystalline state that we denote as Cr1 occurs after a temperature-dependent incubation time, which is consistent with classical nucleation theory. After an additional ~ 0.5s, Cr1 transforms to the final stable structure Cr2. Based on these results, we demonstrate a method to produce large crystalline grain size and high carrier mobility during high-speed processing by controlling the nucleation rate during the transformation from the LC phase. Nsf DMR-1307017, NSF DMR-1332208.

  20. Reliable thermal processing of organic perovskite films deposited on ZnO

    NASA Astrophysics Data System (ADS)

    Zakhidov, Alex; Manspeaker, Chris; Lyashenko, Dmitry; Alex Zakhidov Team

    Zinc oxide (ZnO) is a promising semiconducting material to serve as an electron transport layer (ETL) for solar cell devices based on organo-halide lead perovskites. ZnO ETL for perovskite photovoltaics has a combination of attractive electronic and optical properties: i) the electron affinity of ZnO is well aligned with valence band edge of the CH3NH3PbI3, ii) electron mobility of ZnO is >1 cm2/(Vs), which is a few orders of magnitude higher than that of TiO2 (another popular choice of ETL for perovskite photovoltaic devices), and iii) ZnO has a large of band gap of 3.3 eV, which ensures optical transparency and large barrier for the hole injection. Moreover, ZnO nanostructures can be printed on flexible substrates at room temperatures in cost effective manner. However, it was recently found that organic perovskites deposited on ZnO are unstable and readily decompose at >90°C. In this work, we further investigate the mechanism of decomposition of CH3NH3PbI3 film deposited on ZnO and reveal the role of the solvent in the film during the annealing process. We also develop a restricted volume solvent annealing (RVSA) process for post annealing of the perovskite film on ZnO without decomposition. We demonstrate that RVSA enables reliable perovskite solar cell fabrication.

  1. Apple, carrot, and hibiscus edible films containing plant antimicrobials inactivate Salmonella Newport in packaged organic leafy greens

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The increased demand for organic leafy green may raise the risk of foodborne illness outbreaks due to consumption of contaminated produce. Edible films incorporated with natural antimicrobials have the potential to be used as ingredients into organic bagged salads to control contamination from path...

  2. Cellular porous anodic alumina grown in neutral organic electrolyte. 1. Structure, composition, and properties of the films

    SciTech Connect

    Liu, Y.; Alwitt, R.S.; Shimizu, K.

    2000-04-01

    Anodic alumina films with cellular porous structure grow in neutral organic electrolytes with low water content and containing ethylene glycol and a large dicarboxylic acid. An Al carboxylate precipitates in the pore and is extruded from the coating. The porous structure develops even though the current efficiency for film formation is near 95%. The coating matrix contains substantial organic material, 15 wt % by thermal analysis. It is an oxide/organic composite with higher field strength and lower dielectric constant than pure anodic alumina.

  3. Ultra-thin ceramic films for low-temperature embedding of decoupling capacitors into organic printed wiring boards

    NASA Astrophysics Data System (ADS)

    Balaraman, Devarajan

    As microprocessors move towards higher frequencies, lower operating voltages and higher power consumption, supplying noise-free power to the ICs becomes increasingly challenging. Decoupling capacitors with low inductance interconnections are critical to meet the power supply impedance targets. A variety of capacitors are used today to provide decoupling at different frequencies. Surface-mount multi-layer ceramic capacitors currently used at package level provide decoupling only till about 100 MHz because of the component and lead inductances. Embedding thin film capacitors into the package can expand the operating range of package level capacitors to low GHz frequencies. Thin films with capacitance of several microfarads and organic-compatible processes are required for embedding decoupling capacitors at package level. The organic-compatible high-permittivity materials available today do not provide adequate capacitance for the application on hand. While ferroelectric thin films can provide the required capacitance, processing temperatures over 300° C are required to achieve crystalline films with high permittivity. Hence, there is a need to develop novel materials and processes to integrate decoupling capacitors into currently prevalent organic packages. To this end, hydrothermal synthesis and sol-gel synthesis of BaTiO3 films were explored in this study. BaTiO3 films were synthesized by low temperature hydrothermal conversion of metallic titanium. Hydrothermal process parameters such as bath molarity and temperature were optimized to obtain thin films with grain sizes close to 100 nm, at temperatures less than 100° C. Novel post-hydrothermal treatments were developed to improve the dielectric properties of the films. Sol-gel process requires sintering at >700° C to obtain crystalline BaTiO3 films. However, the films can be synthesized on free-standing copper foils and subsequently integrated into organic packages using lamination. Prevention of foil oxidation

  4. I. Fundamental Practicum: Temperature Measurements of Falling Droplets, July, 1989. II. Industrial Practicum: Interaction and Effect of Adsorbed Organics on Reference Clays and Reservoir Rock, April, 1988. III. Apprenticeship Practicum: Studies of Group XIII Metal Inclusion Complexes, March, 1987

    NASA Astrophysics Data System (ADS)

    Wells, Mark Richard

    The temperature of 225 μm decane droplets falling through a hot, quiescent, oxygen -free environment were measured using laser-induced exciplex fluorescence thermometry. The temperature of the droplets was found to increase approximately 0.42^ circC/^circC increase in the environment temperature as the environment temperature was increased to 250^circ C. Less than 10% evaporation of the droplets was observed at the highest environment temperatures. This represents one of the first successful applications of a remote-sensing technique for the temperature determination of droplets in a dynamic system. Industrial practicum. The industrial practicum report, entitled "Interaction and Effect of Adsorbed Organics on Reference Clays and Reservoir Rock," is a discussion of the measurement of the effect adsorbed organic material, especially from crude petroleum, has on the surface area, cation exchange capacity, and zeta potential of reference clay material and reservoir rock. In addition, the energetics of adsorption of a petroleum extract onto several reference clays and reservoir rock were measured using both flow and batch microcalorimetry. These results are very important in evaluating and understanding the wettability of reservoir rock and its impact on the recovery of crude oil from a petroleum reservoir. Apprenticeship practicum. "Studies of Group XIII Metal Inclusion Complexes" investigates the structure and dynamics of liquid inclusion complexes having the general formula (R_4N) (Al_2 Me_6I) cdot (C_6H_6) _{rm x}. ^1H and ^{13}C spin-lattice relaxation times, nuclear Overhauser enhancements, and molecular correlation times were measured as well as diffusion coefficients of the various species in solution. The dynamics of transfer between "guest" and free solvent molecules were measured using a variety of techniques. The inherent structure of liquid inclusion complexes as an ordered medium for homogeneous catalysis was studied using hydrogenation catalyzed by

  5. Transparent conductive PVP/AgNWs films for flexible organic light emitting diodes by spraying method

    NASA Astrophysics Data System (ADS)

    Hu, Jun-tao; Mei, Wen-juan; Ye, Kang-li; Wei, Qing-qing; Hu, Sheng

    2016-05-01

    In this study, a simple spraying method is used to prepare the transparent conductive films (TCFs) based on Ag nanowires (AgNWs). Polyvinylpyrrolidone (PVP) is introduced to modify the interface of substrate. The transmittance and bending performance are improved by optimizing the number of spraying times and the solution concentration and controlling the annealing time. The spraying times of 20, the concentration of 2 mg/mL and the annealing time of 10 min are chosen to fabricate the PVP/AgNWs films. The transmittance of PVP/AgNWs films is 53.4%—67.9% at 380—780 nm, and the sheet resistance is 30 Ω/□ which is equivalent to that of commercial indium tin oxide (ITO). During cyclic bending tests to 500 cycles with bending radius of 5 mm, the changes of resistivity are negligible. The performance of PVP/AgNW transparent electrodes has little change after being exposed to the normal environment for 1 000 h. The adhesion to polymeric substrate and the ability to endure bending stress in AgNWs network films are both significantly improved by introducing PVP. Spraying method makes AgNWs form a stratified structure on large-area polymer substrates, and the vacuum annealing method is used to weld the AgNWs together at junctions and substrates, which can improve the electrical conductivity. The experimental results indicate that PVP/AgNW transparent electrodes can be used as transparent conductive electrodes in flexible organic light emitting diodes (OLEDs).

  6. Structural measurements of polymer-fullerene blend films for organic photovoltaics

    NASA Astrophysics Data System (ADS)

    Delongchamp, Dean

    2011-03-01

    Organic photovoltaic (OPV) technology has the potential to greatly lower the cost of solar cell fabrication by enabling ink-based deposition of active layers. In bulk heterojunction (BHJ) OPV devices, the power conversion efficiency critically depends on the distribution of the polymer absorber and the fullerene electron acceptor (e.g., the blend morphology). I will describe measurement methods to probe the structure of OPV devices, with a focus on the morphology of the BHJ layer. For example, the vertical distribution of absorber and electron acceptor in BHJ films follows segregation behavior similar to that of miscible polymer blends. The top (air) interface becomes rich in the polymer absorber, whereas the bottom interface composition depends on the substrate surface energy. Thin film transistors fabricated from BHJs can therefore exhibit ambipolar or hole-only transport depending on the dielectric, because of different interfacial segregation. We extend these results to practical photovoltaic devices by comparing BHJs cast upon hole transport layers that have similar work functions but different surface energies. This study includes the application of variable angle spectroscopic ellipsometry (VASE) to BHJ films, and emphasizes the importance of absorber anisotropy and vertical heterogeneity in the optical model. Additional results will describe the nanometer-scale structure in the BHJ interior. The application of solid-state nuclear magnetic resonance (SS-NMR) can reveal details about the segregation of absorber and acceptor in a BHJ film. Nanoscale BHJ morphology information can also be collected using tomographic transmission electron microscopy (TEM). Together these measurements allow us to reveal a detailed picture of BHJ morphology, explain how the morphology originates from materials and processing choices, and relate the morphology to device performance and stability.

  7. Modification of carbon nanotube transparent conducting films for electrodes in organic light-emitting diodes

    NASA Astrophysics Data System (ADS)

    Gao, Jing; Mu, Xue; Li, Xiao-Yun; Wang, Wen-Yi; Meng, Yan; Xu, Xiao-Bing; Chen, Li-Ting; Cui, Li-Jun; Wu, Xiaoming; Geng, Hong-Zhang

    2013-11-01

    Single-walled carbon nanotube (SWCNT) transparent conducting films (TCFs) were fabricated for the electrodes of organic light-emitting diodes (OLEDs); three types of film were studied. The as-prepared SWCNT TCFs displayed a relatively low sheet resistance of 82.6 Ω/sq at 80.7 T% with a relatively large surface roughness of 30 nm. The TCFs were top-coated with poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) to obtain PEDOT:PSS-coated TCFs. The PEDOT:PSS cover improved the conductivity and decreased the surface roughness to 12 nm at the cost of film transmittance. The SWCNT TCFs mixed with PEDOT:PSS (PM-TCFs) exhibited a high conductivity (70.6 Ω/sq at 81 T%) and a low surface roughness (3 nm) and were thus selected as the best TCFs for OLEDs. Blue flexible OLEDs with 4,4‧-bis(2,2‧-diphenylvinyl)-1,1‧-biphenyl (Dpvbi) as the emitting layer were fabricated on TCFs with the same structures to evaluate the performances of the different types of SWCNT films for use in OLEDs. Of these three types of OLEDs, the PM-TCF devices exhibited the optimal performance with a maximum luminance of 2587 cd m-2 and a current efficiency of 5.44 cd A-1. This result was explored using field-emission scanning electron microscopy and atomic force microscopy to further study the mechanisms that are involved in applying SWCNT TCFs to OLEDs.

  8. Burnout of the organic vehicle in an electrically conductive thick-film paste

    NASA Astrophysics Data System (ADS)

    Liu, Zongrong; Chung, D. D. L.

    2004-11-01

    The burnout of the organic vehicle in a silver-particle, glass-free, electrically conductive, thick-film paste during firing in air was studied. For a vehicle consisting of ethyl cellulose dissolved in ether, burnout primarily involves the thermal decomposition of ethyl cellulose. The presence of ether with dissolved ethyl cellulose facilitates the burnout of ethyl cellulose. Excessive ethyl cellulose hinders the burnout. A high heating rate results in more residue after burnout. By interrupting the heating at 160°C for 15 min, the residue after subsequent burnout is diminished probably because of reduced temporal overlap of the processes of organic burnout and silver particle necking. By interrupting the heating at either 300°C or 385°C for 30 min, the temperature required for complete burnout is reduced. The addition of silver particles facilitates drying at room temperature and burnout upon heating.

  9. Molecular doping for control of gate bias stress in organic thin film transistors

    SciTech Connect

    Hein, Moritz P. Lüssem, Björn; Jankowski, Jens; Tietze, Max L.; Riede, Moritz K.; Zakhidov, Alexander A.; Leo, Karl; Fraunhofer COMEDD, Maria-Reiche-Str. 2, 01109 Dresden

    2014-01-06

    The key active devices of future organic electronic circuits are organic thin film transistors (OTFTs). Reliability of OTFTs remains one of the most challenging obstacles to be overcome for broad commercial applications. In particular, bias stress was identified as the key instability under operation for numerous OTFT devices and interfaces. Despite a multitude of experimental observations, a comprehensive mechanism describing this behavior is still missing. Furthermore, controlled methods to overcome these instabilities are so far lacking. Here, we present the approach to control and significantly alleviate the bias stress effect by using molecular doping at low concentrations. For pentacene and silicon oxide as gate oxide, we are able to reduce the time constant of degradation by three orders of magnitude. The effect of molecular doping on the bias stress behavior is explained in terms of the shift of Fermi Level and, thus, exponentially reduced proton generation at the pentacene/oxide interface.

  10. Electrical mobility in organic thin-film transistors determined by noise spectroscopy

    NASA Astrophysics Data System (ADS)

    Bonavolontà, C.; Albonetti, C.; Barra, M.; Valentino, M.

    2011-11-01

    Organic field-effect transistors (OFET) based on both n-type (perylene derivative) and p-type (α-sexithiophene and pentacene) organic thin films are characterized using low-frequency noise spectroscopy to estimate the charge carrier mobility. The power spectral density shows that the exposure of OFET to air affects the thermal noise fluctuations and that the thermal noise RMS value depends on gate voltage. The power spectral density noise proves that the carrier mobility is gate-voltage dependent. Unlike the I-V measurements, the noise spectroscopy analysis demonstrates the dependence of the mobility on the carrier polarity. We discuss the charge mobility and transport mechanism of a pentacene device with and without electrodes functionalized by an octanethiol chain. The results show that in the functionalized device the carrier mobility is improved and does not depend on the high gate voltage.

  11. Electronic properties of organic thin film transistors with nanoscale tapered electrodes

    NASA Astrophysics Data System (ADS)

    Park, Jeongwon

    2008-10-01

    Organic thin-film transistors (OTFTs) have received increasing attention because of their potential applications in displays, optoelectronics, logic circuits, and sensors. Ultrathin OTFTs are of technical interest as a possible route toward reduced bias stress in standard OTFTs and enhanced sensitivity in chemical field-effect transistors (ChemFETs). ChemFETs are OTFTs whose output characteristics are sensitive to the presence of analytes via changes in the channel mobility and/or threshold voltage induced by analyte chemisorption onto the channel materials. The fundamental understanding of charge transport properties of organic thin-films is critical for the applications. OTFT has been demonstrated by many groups; however, there has been much less progress towards more reliable contact structure between organic materials and electrodes. This thesis investigates the electrical properties of metal phthalocyanine thin-film devices. In chapter 1, the basic electrical properties in OTFTs are reviewed. In chapter 2, we have investigated the microfabrication process of OTFTs to control the contact morphology and the charge transport properties of phthalocyanine thin-film devices. In chapter 3, the channel thickness dependence of the mobility was investigated in bottom-contact copper phthalocyanine (CuPc) OTFTs. The current-voltage characteristics of bottom contact CuPc OTFTs with low contact resistance fabricated by the bilayer photoresist lift-off process were analyzed to determine the mobility, threshold voltage and contact resistance. The independence of measured electronic properties from channel thickness is due to the contact resistance being negligible for all channel thicknesses. For practical applications, the aging and recovery process in CuPc OTFTs were investigated in chapter 4. An origin of the aging process on CuPc OTFTs has been investigated based on the responses of thick 1000ML CuPc OTFTs under a controlled atmosphere. The recovery process under 30

  12. Implementation of radiochromic film dosimetry protocol for volumetric dose assessments to various organs during diagnostic CT procedures

    SciTech Connect

    Brady, Samuel; Yoshizumi, Terry; Toncheva, Greta; Frush, Donald; and others

    2010-09-15

    Purpose: The authors present a means to measure high-resolution, two-dimensional organ dose distributions in an anthropomorphic phantom of heterogeneous tissue composition using XRQA radiochromic film. Dose distributions are presented for the lungs, liver, and kidneys to demonstrate the organ volume dosimetry technique. XRQA film response accuracy was validated using thermoluminescent dosimeters (TLDs). Methods: XRQA film and TLDs were first exposed at the center of two CTDI head phantoms placed end-to-end, allowing for a simple cylindrical phantom of uniform scatter material for verification of film response accuracy and sensitivity in a computed tomography (CT) exposure geometry; the TLD and film dosimeters were exposed separately. In a similar manner, TLDs and films were placed between cross-sectional slabs of a 5 yr old anthropomorphic phantom's thorax and abdomen regions. The anthropomorphic phantom was used to emulate real pediatric patient geometry and scatter conditions. The phantom consisted of five different tissue types manufactured to attenuate the x-ray beam within 1%-3% of normal tissues at CT beam energies. Software was written to individually calibrate TLD and film dosimeter responses for different tissue attenuation factors, to spatially register dosimeters, and to extract dose responses from film for TLD comparison. TLDs were compared to film regions of interest extracted at spatial locations corresponding to the TLD locations. Results: For the CTDI phantom exposure, the film and TLDs measured an average difference in dose response of 45%(SD{+-}2%). Similar comparisons within the anthropomorphic phantom also indicated a consistent difference, tracking along the low and high dose regions, for the lung (28%) (SD{+-}8%) and liver and kidneys (15%) (SD{+-}4%). The difference between the measured film and TLD dose values was due to the lower response sensitivity of the film that arose when the film was oriented with its large surface area parallel to

  13. Application of ZnO films to glass substrates by the dipping-pyrolysis method using organic acid salt

    NASA Astrophysics Data System (ADS)

    Kondow, Takeshi; Ninomiya, Kanae

    1992-12-01

    Transparent ZnO films having more than 1 micrometers in thickness were prepared by one dipping-pyrolysis process. The starting solution, produced by dissolving zinc 2- ethylhexanoate, dehydrated caster oil fatty acid and dimethyl silicone oil as a leveling agent into an organic solvent, was coated on the plate glass and cured at 200 degree(s)C and heated up to 500 degree(s)C. The thick ZnO films covered with SiO2 films are very useful for UV cut-offs at about 380 nm and for high transparency in the visible region. The ZnO films with the durable films have a possible application to automobile windows and the like. Characterizations are also reported by scanning electron microscopy (SEM), X-ray diffraction (XRD), secondary ion mass spectrometry (SIMS), optical spectroscopy and Taber abrasion test.

  14. Stopping power of fluorides and semiconductor organic films for low-velocity protons

    SciTech Connect

    Serkovic Loli, L. N.; Sanchez, E. A.; Grizzi, O.; Arista, N. R.

    2010-02-15

    A combined experimental and theoretical study of the energy loss of protons in fluorides and organic films is presented. The measurements were performed in fresh AlF{sub 3}, LiF, and N,N{sup '}-bis(1-ethylpropyl)-perylene-3,4,9,10-tetracarboxdiimide (EP-PTCDI) evaporated in situ on self-supported C or Ag foils, covering the very low energy range from 25 keV down to 0.7 keV. The transmission method is used in combination with time-of-flight (TOF) spectrometry. In the case of fluorides with large band gap energies (AlF{sub 3} and LiF), the experimental stopping power increases almost linearly with the mean projectile velocity showing a velocity threshold at about 0.1 a.u. These features are well reproduced by a model based on quantum scattering theory that takes into account the velocity distribution and the excitation of the active 2p electrons in the F{sup -} anions, and the properties of the electronic bands of the insulators. In the case of the semiconductor organic film with a lower gap, the experimental stopping power increases linearly with the mean projectile velocity without presenting a clear threshold. This trend is also reproduced by the proposed model.

  15. Laser-induced self-organization in silicon-germanium thin films

    SciTech Connect

    Weizman, M.; Nickel, N. H.; Sieber, I.; Yan, B.

    2008-05-01

    We report on the formation of self-organized structures in thin films of silicon-germanium (Si{sub 1-x}Ge{sub x}) with 0.3films to laser irradiation. Amorphous SiGe samples that are exposed to a single laser pulse exhibit a ripple structure that changes to a hillock structure when the samples are irradiated with additional laser pulses. The topographic structure is coupled to a periodic compositional variation of the SiGe alloy. The periodicity length of the structure after a single laser pulse is in the range of 0.3-1.1 {mu}m, depending on Ge content, layer thickness, and laser fluence, and rapidly grows with increasing number of laser pulses. In situ conductivity measurements during solidification support the theoretical instability analysis that we have done, based on the Mullins-Sekerka theory, to elucidate the nature of this phenomenon. Moreover, as theoretically predicted, the self-organization phenomenon can be turned off by increasing the solidification velocity.

  16. Self-organization of highly ordered honeycomb buckling patterns in crystalline thin films

    NASA Astrophysics Data System (ADS)

    Choi, Yun Jeong; Naoi, Yoshiki; Tomita, Takuro

    2015-10-01

    Highly ordered honeycomb buckling patterns were self-organized by a simple annealing process. The patterns were formed by thin, layered crystalline films of Al4C3 and carbon synthesized on a sapphire c-plane substrate by chemical vapor deposition. While annealing at 1000 °C, the thin bilayer film wrinkled and began to develop a two-dimensionally periodic pattern. Two patterns, with periodicities of 34 and 20 µm, were observed by two-dimensional fast Fourier transform (2D-FFT) analysis. Both patterns showed clear and sharp peaks at six orientations, corresponding to the vertices of a regular hexagon, similarly to the crystallinity of sapphire. Additionally, a shift of the Raman peak to a lower frequency was observed after annealing. These results reveal that the self-organization of a periodic buckling pattern is possible without complicated conventional lithography through the use of crystalline materials. Thus, the highly periodic hexagonal patterns obtained with thin crystal materials have a high symmetry, as characterized from 2D-FFT, and can be applied as an optical grating.

  17. The Integration and Applications of Organic Thin Film Transistors and Ferroelectric Polymers

    NASA Astrophysics Data System (ADS)

    Hsu, Yu-Jen

    Organic thin film transistors and ferroelectric polymer (polyvinylidene difluoride) sheet material are integrated to form various sensors for stress/strain, acoustic wave, and Infrared (heat) sensing applications. Different from silicon-based transistors, organic thin film transistors can be fabricated and processed in room-temperature and integrated with a variety of substrates. On the other hand, polyvinylidene difluoride (PVDF) exhibits ferroelectric properties that are highly useful for sensor applications. The wide frequency bandwidth (0.001 Hz to 10 GHz), vast dynamic range (100n to 10M psi), and high elastic compliance (up to 3 percent) make PVDF a more suitable candidate over ceramic piezoelectric materials for thin and flexible sensor applications. However, the low Curie temperature may have impeded its integration with silicon technology. Organic thin film transistors, however, do not have the limitation of processing temperature, hence can serve as transimpedance amplifiers to convert the charge signal generated by PVDF into current signal that are more measurable and less affected by any downstream parasitics. Piezoelectric sensors are useful for a range of applications, but passive arrays suffer from crosstalk and signal attenuation which have complicated the development of array-based PVDF sensors. We have used organic field effect transistors, which are compatible with the low Curie temperature of a flexible piezoelectric polymer,PVDF, to monolithically fabricate transimpedance amplifiers directly on the sensor surface and convert the piezoelectric charge signal into a current signal which can be detected even in the presence of parasitic capacitances. The device couples the voltage generated by the PVDF film under strain into the gate of the organic thin film transistors (OFET) using an arrangement that allows the full piezoelectric voltage to couple to the channel, while also increasing the charge retention time. A bipolar detector is created by

  18. Highly Ordered Organic Molecular Thin Films on Silicon Studied by STM and LEED

    NASA Astrophysics Data System (ADS)

    Wagner, Sean; Zhang, Pengpeng

    2014-03-01

    Achieving growth of long-range ordered organic molecular thin films on inorganic substrates continues to be a significant challenge for organic electronics applications. Here, we report the growth of highly ordered zinc phthalocyanine (ZnPc) thin films both in-plane and out-of-plane on the deactivated Si(111) surface by scanning tunneling microscopy (STM) and low energy electron diffraction (LEED). By adjusting the substrate temperature during deposition, the anisotropic step-flow growth mode can be accessed causing a reduction in the substrate symmetry which allows for the long-range in-plane ordering as well as the decrease of grain boundary density. Additionally, the ZnPc molecules are able to maintain a highly ordered configuration in multi-layers despite a gradual decrease in the molecule-substrate interaction, which is attributed to the strong interlayer π- π interaction. We appreciate the fruitful discussion with Prof. Richard Lunt. This research is funded by the DOE Office of Science Early Career Research Program (Grant number DE-SC0006400) through the Office of Basic Energy Sciences.

  19. Bi2O3 nanoparticles encapsulated in surface mounted metal-organic framework thin films

    NASA Astrophysics Data System (ADS)

    Guo, Wei; Chen, Zhi; Yang, Chengwu; Neumann, Tobias; Kübel, Christian; Wenzel, Wolfgang; Welle, Alexander; Pfleging, Wilhelm; Shekhah, Osama; Wöll, Christof; Redel, Engelbert

    2016-03-01

    We describe a novel procedure to fabricate a recyclable hybrid-photocatalyst based on Bi2O3@HKUST-1 MOF porous thin films. Bi2O3 nanoparticles (NPs) were synthesized within HKUST-1 (or Cu3(BTC)2) surface-mounted metal-organic frame-works (SURMOFs) and characterized using X-ray diffraction (XRD), a quartz crystal microbalance (QCM) and transmission electron microscopy (TEM). The Bi2O3 semiconductor NPs (diameter 1-3 nm)/SURMOF heterostructures exhibit superior photo-efficiencies compared to NPs synthesized using conventional routes, as demonstrated via the photodegradation of the nuclear fast red (NFR) dye.We describe a novel procedure to fabricate a recyclable hybrid-photocatalyst based on Bi2O3@HKUST-1 MOF porous thin films. Bi2O3 nanoparticles (NPs) were synthesized within HKUST-1 (or Cu3(BTC)2) surface-mounted metal-organic frame-works (SURMOFs) and characterized using X-ray diffraction (XRD), a quartz crystal microbalance (QCM) and transmission electron microscopy (TEM). The Bi2O3 semiconductor NPs (diameter 1-3 nm)/SURMOF heterostructures exhibit superior photo-efficiencies compared to NPs synthesized using conventional routes, as demonstrated via the photodegradation of the nuclear fast red (NFR) dye. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr00532b

  20. The influence of sediment particle size on the properties of adsorbed dissolved organic matter in the Yangtze Estuary and its interactions with As/Sb.

    PubMed

    Wang, Ying; Zhang, Manman; Zhang, Di; Shen, Zhenyao

    2016-04-15

    The characteristics of dissolved organic matter (DOM) extracted from sediments with four particle sizes (<25, 63-25, 200-63 and >200μm) in the Yangtze Estuary were compared. The differences in their binding capacities for individual fluorescent components with As/Sb were studied using fluorescence-quenching titrations combined with excitation-emission matrix (EEM) spectra. The results indicated that the particle size influenced the quality and quantity of extracted DOM. With increasing particle size, the extracted DOM content, value of UV280 and acidic functional group content of the DOM decreased. Three protein-like components (C2, C3 and C4) and one humic-like component (C1) were identified using the parallel factor analysis (PARAFAC) model. Wherein, protein-like material dominated in DOM on different particle-size fractions and possessed a stronger complex capacity with As/Sb. A significant positive correlation between the complexation capacity of extracted DOM from samples, as well as with the acidic functional group content, was observed. PMID:26965093

  1. Systematic Investigation of Nanoscale Adsorbate Effects at Organic Light-Emitting diode Interfaces. Interfacial Structure-Charge Injection-Luminance Relationships

    SciTech Connect

    Huang,Q.; Li, J.; Evmenenko, G.; Dutta, P.; Marks, T.

    2006-01-01

    Molecule-scale structure effects at indium tin oxide (ITO) anode-hole transport layer (HTL) interfaces in organic light-emitting diode (OLED) heterostructures are systematically probed via a self-assembly approach. A series of ITO anode-linked silyltriarylamine precursors differing in aryl group and linker density are synthesized for this purpose and used to probe the relationship between nanoscale interfacial chemical structure and charge-injection/electroluminescence properties. These precursors form conformal and largely pinhole-free self-assembled monolayers (SAMs) on the ITO anode surface with angstrom-level thickness control. Deposition of a HTL on top of the SAMs places the probe molecules precisely at the anode-HTL interface. OLEDs containing ITO/SAM/HTL configurations have dramatically varied hole-injection magnitudes and OLED responses. These can be correlated with the probe molecular structures and electrochemically derived heterogeneous electron-transfer rates for such triarylamine fragments. The large observed interfacial molecular structure effects offer an approach to tuning OLED hole-injection flux over 1-2 orders of magnitude, resulting in up to 3-fold variations in OLED brightness at identical bias and up to a 2 V driving voltage reduction at identical brightness. Very bright and efficient ({approx}70 000 cd/m{sup 2}, {approx}2.5% forward external quantum efficiency, {approx}11 lm/W power efficiency) Alq (tris(8-hydroxyquinolinato)aluminum(III))-based OLEDs can thereby be fabricated.

  2. A novel structure of directly patterned isolating layer for organic thin-film transistor-driven organic light emitting diodes

    NASA Astrophysics Data System (ADS)

    Wang, Yi-Kai; Lin, Tsung-Hsien; Yan, Jing-Yi; Lee, Tzu-Wei; Shen, Yu-Yuan; Yeh, Shu-Tang; Tseng, Mei-Rurng; Wu, Po-Sheng; Lin, Kuo-Tong; Chen, Chia-Hsun; Ho, Jia-Chong

    2007-09-01

    Mono-chrome phosphorescence Organic light emitting diodes (OLEDs) operated by organic thin-film transistors (OTFTs) with a 32×32 array are fabricated with a novel method, and the results reveal a fabulous demonstration. The later isolation, which segregated source/drain electrodes and an OLED cathode, was designed in our OTFT-OLED pixel. In the OTFT-OLED process; we used the polymer isolating layer which was deposited by spin coating and patterned by traditional photo-lithography before the organic semiconductor and OLED deposition. However, the residue polymer affect of OTFT electric properties which have poor mobility (5×10-4 cm2/V-s), a lower on/off ratio (~103), and a positive threshold voltage (4.5 V), and devices, have poor uniformity. Using UV-Ozone treatment could enhance OTFT mobility (2×10-2 cm2/V-s) and permit higher devices uniformity, but the threshold voltage would still have a positive 5.1 V. This threshold voltage was not a good operation mode for display application because this operation voltage was not fit for our driving systems. In order to overcome this problem, a new structure of OTFT-OLED pixel was designed and combined with a new-material isolating layer process. This new process could fabricate an OTFT-OLED array successfully and have a nice uniformity. After the isolating layer process, OTFT devices have a higher mobility (0.1×10-2 cm2/V-s), a higher on-off ratio (~107) a lower threshold voltage (-9.7 V), and a higher devices uniformity.

  3. One-step growth of lanthanoid metal-organic framework (MOF) films under solvothermal conditions for temperature sensing.

    PubMed

    Liu, Xue; Fu, Wentian; Bouwman, Elisabeth

    2016-05-25

    A one-step direct solvothermal synthesis of an Ln metal-organic framework (MOF) film is reported. The LnHL (Ln = Tb and Gd) films that were deposited on a Gd2O3 subtrate are continuous and smooth. The Gd0.9Tb0.1HL film can be used as a ratiometric thermometer, showing good linear behaviour in the temperature range of 110-250 K with a sensitivity up to 0.8% K(-1). PMID:27147478

  4. Block copolymer adsorbed layers on solids

    NASA Astrophysics Data System (ADS)

    Sen, Mani; Jiang, Naisheng; Gowd, Bhoje; Endoh, Maya; Koga, Tadanori

    Block copolymer thin films offer a simple and effective route to fabricate highly ordered periodic microdomain structures. The fundamental, yet unsolved question is whether these highly oriented microdomain structures persist even near an impenetrable solid wall. We here report the adsorbed structures of polystyrene-block-poly (4-vinylpyridine) (PS-block-P4VP, Mw = 41,000, PS (weight fraction =0.81) formed on planar silicon substrates. Perpendicularly aligned cylindrical microdomains were created by solvent vapor annealing (Gowd et al., Soft Matter, 2014, 10, 7753), and the adsorbed layer was derived by solvent leaching with chloroform, a good solvent for the polymers and thereafter characterized by using atomic force microscopy, scanning electron microscopy, grazing incidence small angle x-ray scattering, and x-ray reflectivity. The results showed that both PS and P4VP chains lie flat on the substrate, forming a microphase-separated structure (MSS) without long-range order. Moreover, a spin-coated PS-block-P4VP thin film annealed under vacuum at 190 °C showed similar MSS on the substrate, indicating the generality of the interfacial polymer structure. Details will be discussed in the presentation. NSF Grant No. CMMI-1332499.

  5. Towards cost-effective, solution processed, encapsulant films for organic electronic devices -- controlling flow instabilities during film formation

    NASA Astrophysics Data System (ADS)

    Granstrom, Jimmy; Roy, Anshuman; Rowell, Griffin; Moon, Ji Sun; Jerkunica, Evan; Heeger, Alan

    2010-03-01

    We present a general method for making thin and smooth films of a water-repelling perfluorinated polymer. These films function as encapsulation barrier layers against water and oxygen permeation. Based on a phenomenological analysis, we find that disturbances in flow due to the Rayleigh-Benard-Marangoni instability during drying of spin-cast perfluorinated polymer films cause high surface roughness and the formation of ``pinholes.'' Atomic Force Microscopy measurements show that this instability can increase the surface roughness by an order of magnitude. Casting films from solutions with higher polymer concentration and from solvents with higher viscosity suppress the instability and significantly reduce the roughness. Suppression of the instability results in improved barrier properties as indicated by the calcium thin film optical transmission test.

  6. Confocal and near-field spectroscopic investigation of P3HT:PCBM organic blend film upon thermal annealing

    NASA Astrophysics Data System (ADS)

    Wang, Xiao; Zhang, Dai; Braun, Kai; Egelhaaf, Hans-Joachim; Meixner, Alfred J.

    2009-08-01

    The poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61 butyric acid methyl ester (PCBM) organic films are widely employed as electronic donor and acceptor in the field of organic film solar cell because of their high photovoltaic conversion efficiency. A home-built parabolic mirror assisted confocal and apertureless near-field optical microscope was used to investigate the degradation behavior of the film and to distinguish the donor and acceptor domains both topographically and optically. Under ambient condition, the degradation rates are decreased in the sequence of pristine P3HT, blend P3HT:PCBM film and pristine PCBM. N2 protection dramatically slows down the film degradation rate. Using confocal spectroscopic mapping, we are able to distinguish the local distributions of P3HT and PCBM. Micrometer PCBM aggregates were observed due to the thermal annealing process. Our experimental methods show the possibility to investigate morphology and the photochemistry properties of the organic solar cell films with high spatial resolution.

  7. In situ intercalation dynamics in inorganic-organic layered perovskite thin films.

    PubMed

    Ahmad, Shahab; Kanaujia, Pawan K; Niu, Wendy; Baumberg, Jeremy J; Vijaya Prakash, G

    2014-07-01

    The properties of layered inorganic semiconductors can be manipulated by the insertion of foreign molecular species via a process known as intercalation. In the present study, we investigate the phenomenon of organic moiety (R-NH3I) intercalation in layered metal-halide (PbI2)-based inorganic semiconductors, leading to the formation of inorganic-organic (IO) perovskites [(R-NH3)2PbI4]. During this intercalation strong resonant exciton optical transitions are created, enabling study of the dynamics of this process. Simultaneous in situ photoluminescence (PL) and transmission measurements are used to track the structural and exciton evolution. On the basis of the experimental observations, a model is proposed which explains the process of IO perovskite formation during intercalation of the organic moiety through the inorganic semiconductor layers. The interplay between precursor film thickness and organic solution concentration/solvent highlights the role of van der Waals interactions between the layers, as well as the need for maintaining stoichiometry during intercalation. Nucleation and growth occurring during intercalation matches a Johnson-Mehl-Avrami-Kolmogorov model, with results fitting both ideal and nonideal cases. PMID:24905435

  8. Detection of organic vapors by graphene films functionalized with metallic nanoparticles

    NASA Astrophysics Data System (ADS)

    Gautam, Madhav; Jayatissa, Ahalapitiya H.

    2012-12-01

    Graphene synthesized by chemical vapor deposition has been used to study the sensing behavior of graphene for different organic vapors in ppm level. All the measurements were carried out at a room temperature with dry air as the background gas. Synthesis of graphene was carried out on a copper foil using methane gas as a precursor. The Raman spectroscopy was used to monitor the quality of graphene films transferred to SiO2/Si substrates, revealing the sensing channel to be mostly monolayer, bilayer, or tri-layer graphene. Graphene surface was functionalized with gold and platinum nanoparticles to enhance the gas sensing behavior. The adsorption/desorption behavior of organic vapors in dry air was analyzed based on the change in the conductivity with the different exposure times in different concentrations. Among the vapors tested, the sensitivity was in the order: acetic acid > ethanol > acetone from all surfaces (bare graphene, graphene decorated with gold and platinum nanoparticles). The devices were successfully tested for four key characteristics (response, recovery, repeatability, and reliability) of any practical gas sensors. The dynamic response behavior of the devices was also analyzed and fitted with the first order exponential function relating to the Langmuir approach. Based on the fit, the average response rate was obtained between 0.22% and 1.04% per ppm for different organic vapors with different surfaces. Average response rate of around 0.5% per ppm for organic vapors demonstrates a high sensitivity of the device at the room temperature under the ambient conditions.

  9. In Situ Intercalation Dynamics in Inorganic–Organic Layered Perovskite Thin Films

    PubMed Central

    2014-01-01

    The properties of layered inorganic semiconductors can be manipulated by the insertion of foreign molecular species via a process known as intercalation. In the present study, we investigate the phenomenon of organic moiety (R-NH3I) intercalation in layered metal-halide (PbI2)-based inorganic semiconductors, leading to the formation of inorganic–organic (IO) perovskites [(R-NH3)2PbI4]. During this intercalation strong resonant exciton optical transitions are created, enabling study of the dynamics of this process. Simultaneous in situ photoluminescence (PL) and transmission measurements are used to track the structural and exciton evolution. On the basis of the experimental observations, a model is proposed which explains the process of IO perovskite formation during intercalation of the organic moiety through the inorganic semiconductor layers. The interplay between precursor film thickness and organic solution concentration/solvent highlights the role of van der Waals interactions between the layers, as well as the need for maintaining stoichiometry during intercalation. Nucleation and growth occurring during intercalation matches a Johnson–Mehl–Avrami–Kolmogorov model, with results fitting both ideal and nonideal cases. PMID:24905435

  10. Electrochemical fabrication of copper-containing metal-organic framework films as amperometric detectors for bromate determination.

    PubMed

    Shi, Erbin; Zou, Xiaoqin; Liu, Jia; Lin, Huiming; Zhang, Feng; Shi, Shaoxuan; Liu, Fenghua; Zhu, Guangshan; Qu, Fengyu

    2016-05-01

    A facile electrochemical plating strategy has been employed to prepare the electroactive metal-organic framework film (NENU-3) onto a copper electrode in the acid electrolyte containing 1,3,5-benzenetricarboxylic acid (H3BTC) and phosphotungstic acid (PTA). The as-made NENU-3 films have been characterized using powder X-ray diffraction (PXRD), scanning electron microscopy (SEM), Fourier transform infrared (FT-IR) spectroscopy and thermogravimetric analyses (TGA). These analyses indicate that NENU-3 films have high phase purity and high stability. Further, different electrochemical techniques are utilized for measuring the electrochemical behaviors of the NENU-3 film electrodes. Accordingly, the kinetic parameters of a NENU-3 film electrode towards the electrocatalytic reduction of bromate are obtained, including the electron transfer coefficient (α), the catalytic rate constant (ks), and the diffusion coefficient (D). The film electrodes present excellent electrocatalytic ability for the bromate reduction, and can be used successfully for the amperometric detection of bromate. Under the optimized conditions, the proposed sensor exhibits a wide linear range (0.05-72.74 mM) and a lower detection limit (12 μM) measured by chronoamperometry (CA). Moreover, the films possess high electrochemical stability and strong anti-interference capability in the bromate detection process. It has been demonstrated that the electrochemical plating method reported here offers a reliable and efficient way to fabricate MOF films on conductive substrates for bromate detection. PMID:27054956

  11. Nanoscale engineering of thin film morphology for efficient organic photovoltaic cells

    NASA Astrophysics Data System (ADS)

    Pandey, Richa

    Organic photovoltaic cells (OPVs) have received significant industrial and academic interest in the last decade as a promising source of inexpensive renewable energy. However, further improvements in device performance and improved lifetimes are required for the commercialization of OPVs. This work is primarily focused on developing a novel device architecture to improve device performance and characterizing structure-property-performance relationships for OPVs. The excitonic nature of organic semiconductors necessitates the use of an electron donor-acceptor (D-A) heterojunction for efficient exciton dissociation and the generation of photocurrent. In many organic semiconductors, the optical absorption length is much larger than the exciton diffusion length. This trade-off between absorption and exciton diffusion is often overcome by increasing the area of the dissociating D-A interface using engineered film morphologies. This thesis presents an approach to maximize cell efficiency using a continuously graded D-A heterojunction. The graded heterojunction allows for an increase in the D-A interface area for an enhanced exciton diffusion efficiency, while also preserving the charge collection efficiency, leading to a significant improvement in device performance relative to that of optimized planar and uniformly mixed OPVs. In addition, this work correlates the optimized D-A composition gradient to the underlying film morphology and charge transport properties of uniform D-A mixtures. Subsequently, a new characterization technique to calculate the charge collection efficiency of OPVs is discussed. This technique is used to demonstrate the enhanced charge collection efficiency in graded heterojunctions relative to uniformly mixed heterojunctions. Afterwards, the properties of a new material and its potential as an electron donor material in OPVs are examined. Finally, an overview of the results and the ideas for future work are presented.

  12. Modification of surface energy, dry etching, and organic film removal using atmospheric-pressure pulsed-corona plasma

    SciTech Connect

    Yamamoto, Toshiaki; Newsome, J.R.; Ensor, D.S.

    1995-05-01

    A laboratory-scale atmospheric-pressure plasma reactor, using a nanosecond pulsed corona, was constructed to demonstrate potential applications ranging from modification of surface energy to removal of surface organic films. For surface modification studies, three different substrates were selected to evaluate the surface energies: bare aluminum, polyurethane, and silicon coated with photoresist. The critical surface energy for all materials studied significantly increased after the plasma treatment. The effects of gas composition and plasma treatment time were also investigated. Photoresist, ethylene glycol, and Micro surfactant were used as test organic films. The etching rate of a photoresist coating on silicon was 9 nm/min. Organic film removal using atmospheric pressure plasma technology was shown to be feasible.

  13. Sub-micron phase coexistence in small-molecule organic thin films revealed by infrared nano-imaging

    NASA Astrophysics Data System (ADS)

    Westermeier, Christian; Cernescu, Adrian; Amarie, Sergiu; Liewald, Clemens; Keilmann, Fritz; Nickel, Bert

    2014-06-01

    Controlling the domain size and degree of crystallization in organic films is highly important for electronic applications such as organic photovoltaics, but suitable nanoscale mapping is very difficult. Here we apply infrared-spectroscopic nano-imaging to directly determine the local crystallinity of organic thin films with 20-nm resolution. We find that state-of-the-art pentacene films (grown on SiO2 at elevated temperature) are structurally not homogeneous but exhibit two interpenetrating phases at sub-micrometre scale, documented by a shifted vibrational resonance. We observe bulk-phase nucleation of distinct ellipsoidal shape within the dominant pentacene thin-film phase and also further growth during storage. A faint topographical contrast as well as X-ray analysis corroborates our interpretation. As bulk-phase nucleation obstructs carrier percolation paths within the thin-film phase, hitherto uncontrolled structural inhomogeneity might have caused conflicting reports about pentacene carrier mobility. Infrared-spectroscopic nano-imaging of nanoscale polymorphism should have many applications ranging from organic nanocomposites to geologic minerals.

  14. Sub-micron phase coexistence in small-molecule organic thin films revealed by infrared nano-imaging

    PubMed Central

    Westermeier, Christian; Cernescu, Adrian; Amarie, Sergiu; Liewald, Clemens; Keilmann, Fritz; Nickel, Bert

    2014-01-01

    Controlling the domain size and degree of crystallization in organic films is highly important for electronic applications such as organic photovoltaics, but suitable nanoscale mapping is very difficult. Here we apply infrared-spectroscopic nano-imaging to directly determine the local crystallinity of organic thin films with 20-nm resolution. We find that state-of-the-art pentacene films (grown on SiO2 at elevated temperature) are structurally not homogeneous but exhibit two interpenetrating phases at sub-micrometre scale, documented by a shifted vibrational resonance. We observe bulk-phase nucleation of distinct ellipsoidal shape within the dominant pentacene thin-film phase and also further growth during storage. A faint topographical contrast as well as X-ray analysis corroborates our interpretation. As bulk-phase nucleation obstructs carrier percolation paths within the thin-film phase, hitherto uncontrolled structural inhomogeneity might have caused conflicting reports about pentacene carrier mobility. Infrared-spectroscopic nano-imaging of nanoscale polymorphism should have many applications ranging from organic nanocomposites to geologic minerals. PMID:24916130

  15. Nanoporous Zeolite Thin Film-Based Fiber Intrinsic Fabry-Perot Interferometric Sensor for Detection of Dissolved Organics in Water

    PubMed Central

    Liu, Ning; Hui, Juan; Sun, Cunqiang; Dong, Junhang; Zhang, Luzheng; Xiao, Hai

    2006-01-01

    A fiber optic intrinsic Fabry-Perot interferometric (IFPI) chemical sensor was developed by fine-polishing a thin layer of polycrystalline nanoporous MFI zeolite synthesized on the cleaved endface of a single mode fiber. The sensor operated by monitoring the optical thickness changes of the zeolite thin film caused by the adsorption of organic molecules into the zeolite channels. The optical thickness of the zeolite thin film was measured by white light interferometry. Using methanol, 2-propanol, and toluene as the model chemicals, it was demonstrated that the zeolite IPFI sensor could detect dissolved organics in water with high sensitivity.

  16. RAPID COMMUNICATION: YBCO thin films prepared by fluorine-reduced metal organic deposition using trifluoroacetates

    NASA Astrophysics Data System (ADS)

    Cui, X. M.; Tao, B. W.; Tian, Z.; Xiong, J.; Liu, X. Z.; Li, Y. R.

    2006-04-01

    Solution deposition is a promising method for YBCO coated conductor fabrication. We developed a new fluorine-reduced 'metal-organic deposition using trifluoroacetates' (TFA-MOD) method with copper acetate as one of the starting materials. Using the fluorine-reduced TFA-MOD method, we were able to get high performance YBCO films with good out-of-plane and in-plane orientations within a shortened calcining time, which was reduced by at least 4 h in comparison with that for the normal TFA-MOD process. Good superconducting properties, with Jc of 2 MA cm-2 at 77 K and Tc of 88.3 K (ΔTc = 0.9 K), have been obtained for 350 nm epitaxial YBCO thin films on LaAlO3 single-crystal substrates. Owing to the low price of copper acetate and the shorter calcining time, fluorine-reduced TFA-MOD is a very effective and cost-cutting process.

  17. Influence of organic semiconductor-metal interfaces on the photoresponse of functionalized anthradithiophene thin films

    NASA Astrophysics Data System (ADS)

    Day, J.; Platt, A. D.; Subramanian, S.; Anthony, J. E.; Ostroverkhova, O.

    2009-05-01

    We report on the contribution of effects at the organic semiconductor-metal interfaces to dark current and to transient and continuous wave (cw) photocurrent in high-performance functionalized anthradithiophene (ADT) films deposited from solution on glass substrates with gold (Au) and aluminum (Al) electrodes. In all samples, fast sub-30 ps charge carrier photogeneration was observed under photoexcitation with 100 fs, 400 nm laser pulses. Amplitudes of the transient photocurrent measured in samples with Au and Al electrodes were similar within a factor of 2-4, depending on the sample and on the applied voltage. Compared to transient photocurrents, dark currents, and cw photocurrents exhibited pronounced differences between ADT films on Au and Al electrodes, with considerably higher currents in samples with Au electrodes. Measurements of photoresponse under uniform illumination were complemented by scanning photocurrent microscopy performed on the same samples. Photocurrent profiles were obtained by scanning the gap between coplanar electrodes with a tightly focused beam, either pulsed or cw, and measuring photocurrent, either transient or steady-state at every point. While samples with Au and Al electrodes exhibited similar distributions of the transient photocurrent amplitudes in the gap, those of the cw photocurrents exhibited dramatic differences, in agreement with results obtained under uniform illumination.

  18. Inverted organic light-emitting diodes using different transparent conductive oxide films as a cathode

    NASA Astrophysics Data System (ADS)

    Takada, Makoto; Kobayashi, Takashi; Nagase, Takashi; Naito, Hiroyoshi

    2016-03-01

    We report on poly(dioctylfluorene-alt-benzothiadiazole) (F8BT) based inverted organic light-emitting diodes (iOLEDs) using commercially available transparent conductive oxide (TCO) films as a cathode, indium tin oxide (ITO), Ga doped ZnO (GZO), and Al doped ZnO (AZO). The ITO, GZO, and AZO glasses work as an electron-injecting layer (EIL) and cathode. The device configuration that we prepared is ITO, GZO, or AZO/F8BT/MoO3/Au. The device characteristics of these iOLEDs are almost comparable to those of conventional iOLEDs with ZnO films prepared by spray pyrolysis as an EIL, indicating that the electron injection properties of ITO, GZO, or AZO as a cathode are similar to those of ZnO layer in conventional iOLEDs. These results demonstrate the low-cost fabrication of iOLEDs utilizing commercially available TCO glasses as a cathode without deposition of ZnO layers on ITO glass.

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

    PubMed

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

    2015-02-01

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

  20. Light-induced processes on atoms and clusters confined in nanoporous silica and organic films

    NASA Astrophysics Data System (ADS)

    Moi, L.; Burchianti, A.; Bogi, A.; Marinelli, C.; Maibohm, C.; Mariotti, E.

    2007-03-01

    The study of light induced processes on atoms and nanoparticles confined in organic films or in dielectric structures is motivated both by fundamental interest and applications in optics and photonics. Depending on the light intensity and frequency and the kind of confinement, different processes can be activated. Among them photodesorption processes have a key role. Non thermal light induced atomic desorption has been observed from siloxane and paraffin films previously exposed to alkali vapors. This effect has been extensively investigated and used both to develop photo-atom sources and to load magneto-optical traps. Recently we observed huge photodesorption of alkali atoms embedded in nanoporous silica. In this case the atomic photodesorption causes, by properly tuning the light frequency, either formation or evaporation of clusters inside the silica matrix. Green-blue light desorbs isolated adatoms from the glass surface eventually producing clusters, whereas red-near infrared (NIR) light causes cluster evaporation due to direct excitation of surface plasmon oscillations. Green-blue light induces cluster formation taking advantage of the dense atomic vapor, which diffuses through the glass nano-cavities. Both processes are reversible and even visible to the naked eye. By alternatively illuminating the porous glass sample with blue-green and red-NIR light we demonstrate that the glass remembers the illumination sequences behaving as an effective rereadable and rewritable optical medium.