Formation of thin luminescent Eu3+-LB films by in situ coordination with 2,3,5,6-tetra(2′-pyridyl)pyrazine and 1-octadecanol in pure and mixed Langmuir monolayers

International Nuclear Information System (INIS)

Fugisawa, Fernanda P.; Ramos, Ana P.; Sousa Filho, Paulo C. de; Serra, Osvaldo A.; Zaniquelli, Maria E.D.

2012-01-01

The in situ complexation between 2,3,5,6-tetra(2-pyridyl)pyrazine (tppz) molecules and europium ions at the air–liquid interface by means of mixed 1-octadecanol Langmuir films is reported. These films were transferred to solid supports by means of the Langmuir–Blodgett (LB) technique. The EDS maps attested the homogeneity of the LB films as well as the presence of the europium ions. The mixed alcohol/tppz LB film contained a larger amount of europium ions as compared to the pure octadecanol LB film. This work reports the production of a thin luminescent Eu 3+ film containing europium ions using only alcohol molecules as ligands—an unexpected result, since it is well known that there is an occurrence of non-radiative deactivation of excited europium by hydroxyl groups. Europium ion multiple binding sites were detected from lifetime decay measurements of these films in the presence of tppz molecules. - Highlights: ► In situ complexation of Eu (III) ions with 1-octadecanol and tppz. ► Formation of thin luminescent Eu(III)-LB films. ► EDS and luminescence studies attest to the presence of Eu(III) in the films. ► Eu(III) coordinates with both tppz and alcohol molecules at air/liquid interface. ► Relatively strong luminescence is observed in LB-films containing only Eu(III) and O–H oscillators.

Two-dimensional ferroelectrics

Energy Technology Data Exchange (ETDEWEB)

Blinov, L M; Fridkin, Vladimir M; Palto, Sergei P [A.V. Shubnikov Institute of Crystallography, Russian Academy of Sciences, Moscow, Russian Federaion (Russian Federation); Bune, A V; Dowben, P A; Ducharme, Stephen [Department of Physics and Astronomy, Behlen Laboratory of Physics, Center for Materials Research and Analysis, University of Nebraska-Linkoln, Linkoln, NE (United States)

2000-03-31

The investigation of the finite-size effect in ferroelectric crystals and films has been limited by the experimental conditions. The smallest demonstrated ferroelectric crystals had a diameter of {approx}200 A and the thinnest ferroelectric films were {approx}200 A thick, macroscopic sizes on an atomic scale. Langmuir-Blodgett deposition of films one monolayer at a time has produced high quality ferroelectric films as thin as 10 A, made from polyvinylidene fluoride and its copolymers. These ultrathin films permitted the ultimate investigation of finite-size effects on the atomic thickness scale. Langmuir-Blodgett films also revealed the fundamental two-dimensional character of ferroelectricity in these materials by demonstrating that there is no so-called critical thickness; films as thin as two monolayers (1 nm) are ferroelectric, with a transition temperature near that of the bulk material. The films exhibit all the main properties of ferroelectricity with a first-order ferroelectric-paraelectric phase transition: polarization hysteresis (switching); the jump in spontaneous polarization at the phase transition temperature; thermal hysteresis in the polarization; the increase in the transition temperature with applied field; double hysteresis above the phase transition temperature; and the existence of the ferroelectric critical point. The films also exhibit a new phase transition associated with the two-dimensional layers. (reviews of topical problems)

Formation of thin luminescent Eu{sup 3+}-LB films by in situ coordination with 2,3,5,6-tetra(2 Prime -pyridyl)pyrazine and 1-octadecanol in pure and mixed Langmuir monolayers

Energy Technology Data Exchange (ETDEWEB)

Fugisawa, Fernanda P. [Departamento de Quimica, Faculdade de Filosofia, Ciencias e Letras de Ribeirao Preto, Universidade de Sao Paulo, 14040-901 Ribeirao Preto, SP (Brazil); Ramos, Ana P., E-mail: anapr@ffclrp.usp.br [Departamento de Quimica, Faculdade de Filosofia, Ciencias e Letras de Ribeirao Preto, Universidade de Sao Paulo, 14040-901 Ribeirao Preto, SP (Brazil); Sousa Filho, Paulo C. de; Serra, Osvaldo A.; Zaniquelli, Maria E.D. [Departamento de Quimica, Faculdade de Filosofia, Ciencias e Letras de Ribeirao Preto, Universidade de Sao Paulo, 14040-901 Ribeirao Preto, SP (Brazil)

2012-05-15

The in situ complexation between 2,3,5,6-tetra(2-pyridyl)pyrazine (tppz) molecules and europium ions at the air-liquid interface by means of mixed 1-octadecanol Langmuir films is reported. These films were transferred to solid supports by means of the Langmuir-Blodgett (LB) technique. The EDS maps attested the homogeneity of the LB films as well as the presence of the europium ions. The mixed alcohol/tppz LB film contained a larger amount of europium ions as compared to the pure octadecanol LB film. This work reports the production of a thin luminescent Eu{sup 3+} film containing europium ions using only alcohol molecules as ligands-an unexpected result, since it is well known that there is an occurrence of non-radiative deactivation of excited europium by hydroxyl groups. Europium ion multiple binding sites were detected from lifetime decay measurements of these films in the presence of tppz molecules. - Highlights: Black-Right-Pointing-Pointer In situ complexation of Eu (III) ions with 1-octadecanol and tppz. Black-Right-Pointing-Pointer Formation of thin luminescent Eu(III)-LB films. Black-Right-Pointing-Pointer EDS and luminescence studies attest to the presence of Eu(III) in the films. Black-Right-Pointing-Pointer Eu(III) coordinates with both tppz and alcohol molecules at air/liquid interface. Black-Right-Pointing-Pointer Relatively strong luminescence is observed in LB-films containing only Eu(III) and O-H oscillators.

Transition from two-dimensional to three-dimensional melting in Langmuir-Blodgett films

International Nuclear Information System (INIS)

Mukhopadhyay, M.K.; Sanyal, M.K.; Datta, A.; Mukherjee, M.; Geue, Th.; Grenzer, J.; Pietsch, U.

2004-01-01

Results of energy-dispersive x-ray reflectivity and grazing incidence diffraction studies of Langmuir-Blodgett films exhibited evolution of conventional three-dimensional melting from continuous melting, characteristic of two-dimensional systems, as a function of deposited monolayers. Continuous expansion followed by a sharp phase transition of the in-plane lattice was observed before the melting point and found to be independent of number of deposited layers. Evolution of conventional melting with an increase in the number of monolayers could be quantified by measuring stiffness against tilting of the vertical stack of molecules, which are kept together by an internal field. The internal field as defined in this model reduces as the in-plane lattice expands and the sample temperature approaches melting point. The sharpness of the melting transition, which has been approximated by a Langevin function, increases with the number of deposited monolayers

Two-dimensional models for the optical response of thin films

Science.gov (United States)

Li, Yilei; Heinz, Tony F.

2018-04-01

In this work, we present a systematic study of 2D optical models for the response of thin layers of material under excitation by normally incident light. The treatment, within the framework of classical optics, analyzes a thin film supported by a semi-infinite substrate, with both the thin layer and the substrate assumed to exhibit local, isotropic linear response. Starting from the conventional three-dimensional (3D) slab model of the system, we derive a two-dimensional (2D) sheet model for the thin film in which the optical response is described by a sheet optical conductivity. We develop criteria for the applicability of this 2D sheet model for a layer with an optical thickness far smaller than the wavelength of the light. We examine in detail atomically thin semi-metallic and semiconductor van-der-Waals layers and ultrathin metal films as representative examples. Excellent agreement of the 2D sheet model with the 3D slab model is demonstrated over a broad spectral range from the radio frequency limit to the near ultraviolet. A linearized version of system response for the 2D model is also presented for the case where the influence of the optically thin layer is sufficiently weak. Analytical expressions for the applicability and accuracy of the different optical models are derived, and the appropriateness of the linearized treatment for the materials is considered. We discuss the advantages, as well as limitations, of these models for the purpose of deducing the optical response function of the thin layer from experiment. We generalize the theory to take into account in-plane anisotropy, layered thin film structures, and more general substrates. Implications of the 2D model for the transmission of light by the thin film and for the implementation of half- and totally absorbing layers are discussed.

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

Energy Technology Data Exchange (ETDEWEB)

Ishida, Takuya; Tachikiri, Yuki; Sako, Takayuki [Department of Materials Physics and Chemistry, Graduate School of Engineering, Kyushu University, 744 Moto-oka, Nishi-ku, Fukuoka 819-0395 (Japan); Takahashi, Yukina, E-mail: yukina@mail.cstm.kyushu-u.ac.jp [Department of Applied Chemistry, Faculty of Engineering, Kyushu University, 744 Moto-oka, Nishi-ku, Fukuoka 819-0395 (Japan); Yamada, Sunao, E-mail: yamada@mail.cstm.kyushu-u.ac.jp [Department of Applied Chemistry, Faculty of Engineering, Kyushu University, 744 Moto-oka, Nishi-ku, Fukuoka 819-0395 (Japan); Center for Future Chemistry, Kyushu University, 744 Moto-oka, Nishi-ku, Fukuoka 819-0395 (Japan)

2017-05-15

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

Anisotropic strain in YBa2Cu3O7-δ films analysed by deconvolution of two-dimensional intensity data

International Nuclear Information System (INIS)

Broetz, J.; Fuess, H.

2001-01-01

The influence of the instrumental resolution on two-dimensional reflection profiles of epitaxic YBa 2 Cu 3 O 7-δ films on SrTiO 3 (001) has been studied in order to investigate the strain in the superconducting films. The X-ray diffraction intensity data were obtained by two-dimensional scans in reciprocal space (q-scan). Since the reflection broadening caused by the apparatus differs for each position in reciprocal space, a highly crystalline substrate was used as a standard. Thus it was possible to measure a standard very close to the YBa 2 Cu 3 O 7-δ reflections in reciprocal space. The two-dimensional deconvolution of reflections by a new computer program revealed an anisotropic strain of the two twinning systems of the film. (orig.)

Formation of hemoglobin (Hb)-octadecylamine (ODA) Langmuir-Blodgett (LB) film by spreading Hb solution directly onto subphase covered with a layer of ODA and its electrochemical property

International Nuclear Information System (INIS)

Yin Fan; Shin, Hoon-Kyu; Kwon, Young-Soo

2006-01-01

The formation of hemoglobin (Hb)-octadecylamine (ODA) Langmuir-Blotgett (LB) film by spreading Hb solution directly onto subphase covered with a layer of ODA and its electrochemical properties were studied in this paper. This method ensured better electrode activity because almost no protein was adsorbed onto electrode surface before depositing Hb-ODA monolayer onto electrode surface. The optimum equilibrium time of Hb interacted with ODA layer, the optimum protein amount spread onto subphase's interface and the optimum ionic strength and pH of subphase were obtained from the experimental results. The compressibility analyses of Hb-ODA films showed that the surface pressure of this film from liquid-expanded to liquid-condensed state ranged between 16 and 40 mN/m. Direct electron transfer of Hb immobilized on gold electrode by LB technique was observed by cyclic voltammetry. Results showed that Hb molecules still kept their electrochemical activity. The electrode with Hb-ODA LB film displayed the fastest electron transfer rate when the film transferred under the surface pressure of 35 mN/m

Formation of hemoglobin (Hb)-octadecylamine (ODA) Langmuir-Blodgett (LB) film by spreading Hb solution directly onto subphase covered with a layer of ODA and its electrochemical property

Energy Technology Data Exchange (ETDEWEB)

Yin Fan [Department of Electrical Engineering, Dong-A University, Busan 604-714 (Korea, Republic of); Department of Chemistry, Changshu Institute of Technology, Changshu, 215500 (China); Shin, Hoon-Kyu [Department of Electrical Engineering, Dong-A University, Busan 604-714 (Korea, Republic of); Kwon, Young-Soo [Department of Electrical Engineering, Dong-A University, Busan 604-714 (Korea, Republic of)]. E-mail: yskwon@daunet.donga.ac.kr

2006-03-21

The formation of hemoglobin (Hb)-octadecylamine (ODA) Langmuir-Blotgett (LB) film by spreading Hb solution directly onto subphase covered with a layer of ODA and its electrochemical properties were studied in this paper. This method ensured better electrode activity because almost no protein was adsorbed onto electrode surface before depositing Hb-ODA monolayer onto electrode surface. The optimum equilibrium time of Hb interacted with ODA layer, the optimum protein amount spread onto subphase's interface and the optimum ionic strength and pH of subphase were obtained from the experimental results. The compressibility analyses of Hb-ODA films showed that the surface pressure of this film from liquid-expanded to liquid-condensed state ranged between 16 and 40 mN/m. Direct electron transfer of Hb immobilized on gold electrode by LB technique was observed by cyclic voltammetry. Results showed that Hb molecules still kept their electrochemical activity. The electrode with Hb-ODA LB film displayed the fastest electron transfer rate when the film transferred under the surface pressure of 35 mN/m.

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

Science.gov (United States)

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

2015-08-01

Introduction of hydrogen-bonding interaction into π-conjugated systems is a promising strategy, since the highly selective and directional hydrogen-bonding can increase the binding strength, provide enhanced stability to the assemblies, and position the π-conjugated molecules in a desired arrangement. The helical packing of the rigid melamine cores seems to play a dominating role in the subsequent formation of the peripheral helical PDA backbone. The polymerized Langmuir-Blodgett (LB) films exhibited reversible colorimetric and chiroptical changes during repeated heating-cooling cycles, which should be ascribed to the strong hydrogen-bonding interaction between the carboxylic acid and the melamine core. Further, the closely helical packing of the melamine cores could be destroyed upon exposure to HCl or NH(3) gas, whereas the peripheral helical polyaniline and polydiacetylene (PDA) backbone exhibited excellent stability. Although similar absorption changes could be observed for the films upon exposure to HCl or NH(3) gas, their distinct circular dichroism (CD) responses enabled us to distinguish the above two stimuli. © 2015 Wiley Periodicals, Inc.

Two-dimensional Dirac fermions in thin films of C d3A s2

Science.gov (United States)

Galletti, Luca; Schumann, Timo; Shoron, Omor F.; Goyal, Manik; Kealhofer, David A.; Kim, Honggyu; Stemmer, Susanne

2018-03-01

Two-dimensional states in confined thin films of the three-dimensional Dirac semimetal C d3A s2 are probed by transport and capacitance measurements under applied magnetic and electric fields. The results establish the two-dimensional Dirac electronic spectrum of these states. We observe signatures of p -type conduction in the two-dimensional states as the Fermi level is tuned across their charge neutrality point and the presence of a zero-energy Landau level, all of which indicate topologically nontrivial states. The resistance at the charge neutrality point is approximately h /e2 and increases rapidly under the application of a magnetic field. The results open many possibilities for gate-tunable topological devices and for the exploration of novel physics in the zero-energy Landau level.

Soap film flows: Statistics of two-dimensional turbulence

International Nuclear Information System (INIS)

Vorobieff, P.; Rivera, M.; Ecke, R.E.

1999-01-01

Soap film flows provide a very convenient laboratory model for studies of two-dimensional (2-D) hydrodynamics including turbulence. For a gravity-driven soap film channel with a grid of equally spaced cylinders inserted in the flow, we have measured the simultaneous velocity and thickness fields in the irregular flow downstream from the cylinders. The velocity field is determined by a modified digital particle image velocimetry method and the thickness from the light scattered by the particles in the film. From these measurements, we compute the decay of mean energy, enstrophy, and thickness fluctuations with downstream distance, and the structure functions of velocity, vorticity, thickness fluctuation, and vorticity flux. From these quantities we determine the microscale Reynolds number of the flow R λ ∼100 and the integral and dissipation scales of 2D turbulence. We also obtain quantitative measures of the degree to which our flow can be considered incompressible and isotropic as a function of downstream distance. We find coarsening of characteristic spatial scales, qualitative correspondence of the decay of energy and enstrophy with the Batchelor model, scaling of energy in k space consistent with the k -3 spectrum of the Kraichnan endash Batchelor enstrophy-scaling picture, and power-law scalings of the structure functions of velocity, vorticity, vorticity flux, and thickness. These results are compared with models of 2-D turbulence and with numerical simulations. copyright 1999 American Institute of Physics

Quasi-two-dimensional superconductivity in wurtzite-structured InN films

International Nuclear Information System (INIS)

Ling, D.C.; Cheng, J.H.; Lo, Y.Y.; Du, C.H.; Chiu, A.P.; Chang, P.H.; Chang, C.A.

2007-01-01

C-axis oriented InN films with wurtzite structure were grown on sapphire(0001) substrate by MOCVD method. Superconductivity with transition onset temperature T c,onset around 3.5 K has been characterized by magnetotransport measurements in fields up to 9 Tesla for films with carrier concentration in the range of 1 x 10 19 cm -3 to 7 x 10 20 cm -3 . Among them, the film with a nitridation buffer layer has the highest zero-resistance temperature T c0 of 2 K. The normal-state magnetoresistance follows Kohler's rule ΔR/R∝(H/R) 2 , indicating that there is a single species of charge carrier with single scattering time at all points on the Fermi surface. The extrapolated value of zero-temperature upper critical field H c2 ab (0) and H c2 c (0) is estimated to be 5900 G and 2800 G, respectively, giving rise to the anisotropy parameter γ about 2.1. The angular dependence of the upper critical field is in good agreement with the behavior predicted by Lawrence-Doniach model in the two-dimensional (2D) limit strongly suggesting that the InN film is a quasi-2D superconductor. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

Two-dimensional flexible nanoelectronics

Science.gov (United States)

Akinwande, Deji; Petrone, Nicholas; Hone, James

2014-12-01

2014/2015 represents the tenth anniversary of modern graphene research. Over this decade, graphene has proven to be attractive for thin-film transistors owing to its remarkable electronic, optical, mechanical and thermal properties. Even its major drawback--zero bandgap--has resulted in something positive: a resurgence of interest in two-dimensional semiconductors, such as dichalcogenides and buckled nanomaterials with sizeable bandgaps. With the discovery of hexagonal boron nitride as an ideal dielectric, the materials are now in place to advance integrated flexible nanoelectronics, which uniquely take advantage of the unmatched portfolio of properties of two-dimensional crystals, beyond the capability of conventional thin films for ubiquitous flexible systems.

A soap film shock tube to study two-dimensional compressible flows

Energy Technology Data Exchange (ETDEWEB)

Wen, C.Y.; Chen, Y.M.; Chang-Jian, S.K. [Dept. of Mechanical Engineering, Da-Yeh University Chang-Hwa (Taiwan)

2001-07-01

A new experimental approach to the study of the two-dimensional compressible flow phenomena is presented. In this technique, a variety of compressible flows were generated by bursting plane vertical soap films. An aureole and a ''shock wave'' preceding the rim of the expanding hole were clearly observed using traditional high-speed flash photography and a fast line-scan charge coupled device (CCD) camera. The moving shock wave images obtained from the line-scan CCD camera were similar to the x-t diagrams in gas dynamics. The moving shock waves cause thickness jumps and induce supersonic flows. Photographs of the supersonic flows over a cylinder and a wedge are presented. The results suggest clearly the feasibility of the ''soap film shock tube''. (orig.)

The theory of critical phenomena in two-dimensional systems

International Nuclear Information System (INIS)

Olvera de la C, M.

1981-01-01

An exposition of the theory of critical phenomena in two-dimensional physical systems is presented. The first six chapters deal with the mean field theory of critical phenomena, scale invariance of the thermodynamic functions, Kadanoff's spin block construction, Wilson's renormalization group treatment of critical phenomena in configuration space, and the two-dimensional Ising model on a triangular lattice. The second part of this work is made of four chapters devoted to the application of the ideas expounded in the first part to the discussion of critical phenomena in superfluid films, two-dimensional crystals and the two-dimensional XY model of magnetic systems. Chapters seven to ten are devoted to the following subjects: analysis of long range order in one, two, and three-dimensional physical systems. Topological defects in the XY model, in superfluid films and in two-dimensional crystals. The Thouless-Kosterlitz iterated mean field theory of the dipole gas. The renormalization group treatment of the XY model, superfluid films and two-dimensional crystal. (author)

Antibacterial activity of novel peptide derived from Cry1Ab16 toxin and development of LbL films for foodborne pathogens control

International Nuclear Information System (INIS)

Plácido, Alexandra; Bragança, Idalina; Marani, Mariela; Rodrigues de Araujo, Alyne; Vasconcelos, Andreanne Gomes; Batziou, Krystallenia; Domingues, Valentina F.

2017-01-01

Escherichia coli is one of the most common etiological agents of diarrhea in developing countries. The appearance of resistant E. coli prevents treatment of these infections. Biotechnological products incorporating antimicrobial peptides are currently being considered in applications to prevent intestinal infections by these bacteria. The aim of this study was to evaluate the antibacterial activity of the peptide PcL342-354C, which is derived from the toxin Cry1Ab16 from Bacillus thuringiensis, against E. coli strains. We also report the preparation, characterization and evaluation of the antibacterial activity of LbL films containing PcL342-354C. The results showed that the PcL342-354C peptide inhibited the growth of different strains of E. coli with minimal inhibitory concentration ranging from 15.62–31.25 μg/mL and minimal bactericidal concentration was 250 μg/mL, indicating a potential antibacterial activity. The morphology of an ITO/Cashew gum/PcL342-354C film was analysed using atomic force microscopy which showed an increase of roughness due to the increase in the number of layers. The LbL films showed significant antibacterial activity against E. coli NCTC 9001 in both conditions tested (10 and 20 bilayers). Our results indicate that the peptide exhibits an antibacterial potential that can be tapped to develop biomaterials with antibacterial activity for use against foodborne pathogens. - Highlights: • The PcL342–354C peptide inhibited the growth of E. coli. • The peptide can be simply incorporated into edible films combined with cashew gum. • LbL films incorporating the peptide have antibacterial activity against E. coli. • The PcL342–354C exhibits an antibacterial potential that can be tapped to develop biomaterials.

Antibacterial activity of novel peptide derived from Cry1Ab16 toxin and development of LbL films for foodborne pathogens control

Energy Technology Data Exchange (ETDEWEB)

Plácido, Alexandra, E-mail: alexandra.placido@gmail.com [REQUIMTE/LAQV, Instituto Superior de Engenharia do Porto, ISEP, Instituto Politécnico do Porto, Porto (Portugal); Bragança, Idalina, E-mail: linab_20@hotmail.com [REQUIMTE/LAQV, Instituto Superior de Engenharia do Porto, ISEP, Instituto Politécnico do Porto, Porto (Portugal); Marani, Mariela, E-mail: mmarani@cenpat-conicet.gob.ar [IPEEC-CONICET, Consejo Nacional de Investigaciones Científicas y Técnicas, Puerto Madryn, Chubut (Argentina); Rodrigues de Araujo, Alyne, E-mail: alyne_biomed@hotmail.com [Núcleo de Pesquisa em Biodiversidade e Biotecnologia, BIOTEC, Campus Ministro Reis Velloso, CMRV, Universidade Federal do Piauí, UFPI, Parnaíba, PI (Brazil); Vasconcelos, Andreanne Gomes, E-mail: andreannegv@gmail.com [Núcleo de Pesquisa em Biodiversidade e Biotecnologia, BIOTEC, Campus Ministro Reis Velloso, CMRV, Universidade Federal do Piauí, UFPI, Parnaíba, PI (Brazil); Batziou, Krystallenia, E-mail: batkrysta@gmail.com [REQUIMTE/UCIBIO, Departamento de Química e Bioquímica, Faculdade de Ciências da Universidade do Porto, Porto (Portugal); Domingues, Valentina F., E-mail: vfd@isep.ipp.pt [REQUIMTE/LAQV, Instituto Superior de Engenharia do Porto, ISEP, Instituto Politécnico do Porto, Porto (Portugal); and others

2017-06-01

Escherichia coli is one of the most common etiological agents of diarrhea in developing countries. The appearance of resistant E. coli prevents treatment of these infections. Biotechnological products incorporating antimicrobial peptides are currently being considered in applications to prevent intestinal infections by these bacteria. The aim of this study was to evaluate the antibacterial activity of the peptide PcL342-354C, which is derived from the toxin Cry1Ab16 from Bacillus thuringiensis, against E. coli strains. We also report the preparation, characterization and evaluation of the antibacterial activity of LbL films containing PcL342-354C. The results showed that the PcL342-354C peptide inhibited the growth of different strains of E. coli with minimal inhibitory concentration ranging from 15.62–31.25 μg/mL and minimal bactericidal concentration was 250 μg/mL, indicating a potential antibacterial activity. The morphology of an ITO/Cashew gum/PcL342-354C film was analysed using atomic force microscopy which showed an increase of roughness due to the increase in the number of layers. The LbL films showed significant antibacterial activity against E. coli NCTC 9001 in both conditions tested (10 and 20 bilayers). Our results indicate that the peptide exhibits an antibacterial potential that can be tapped to develop biomaterials with antibacterial activity for use against foodborne pathogens. - Highlights: • The PcL342–354C peptide inhibited the growth of E. coli. • The peptide can be simply incorporated into edible films combined with cashew gum. • LbL films incorporating the peptide have antibacterial activity against E. coli. • The PcL342–354C exhibits an antibacterial potential that can be tapped to develop biomaterials.

The interaction between the gas sensing and surface morphology properties of LB thin films of porphyrins in terms of the adsorption kinetics

International Nuclear Information System (INIS)

Capan, İ.; Erdoğan, M.; Stanciu, G.A.; Stanciu, S.G.; Hristu, R.; Göktepe, M.

2012-01-01

In this work we investigate the adsorption characteristics due to exposure to benzene, toluene and chloroform vapor of 2,3,7,8,12,13,17,18-Octaethyl-21H,23H-porphine metal free thin films fabricated by using the Langmuir–Blodgett (LB) thin film technique and its derivatives containing iron chloride, cobalt and magnesium. By using the surface pressure–surface area (Π–A) isotherm graphs the optimum conditions for the thin film deposition and mean molecular area values of each porphyrin have been determined. Quartz Crystal Microbalance (QCM) system was employed to investigate the gas sensing performances of thin films during the exposure to Volatile Organic Compounds (VOCs). The surface properties have been investigated by using Atomic Force Microscopy (AFM) and analyzed together with the QCM results to understand the adsorption kinetics of the gas sensing mechanism. The rate constants, k a for each thin film interacting with the saturated concentration of vapors have been calculated. The gas sensing interaction has been considered in terms of rate constants in each case. The highest value for k a has been observed for benzene exposure. -- Highlights: ► We model an adsorption behavior for gas sensing porphyrin LB thin films. ► Adsorption coefficients are consistent with the gas experiments. ► The higher rate constant values point out the faster response.

The generation of two-dimensional vortices by transverse oscillation of a soap film

International Nuclear Information System (INIS)

Afenchenko, V.O.; Ezersky, A.B.; Kiyashko, S.V.; Rabinovich, M.I.; Weidman, P.D.

1998-01-01

An experimental investigation of the dynamics of horizontal soap films stretched over circular or square boundaries undergoing periodic transverse oscillations at frequencies in the range 20 - 200 Hz is reported. Concomitant with modes of transverse flexural oscillations, it was observed that two-dimensional vortices in the plane of the film are excited. The vortices may be either (i) large, scaling with the size of the cavity or (ii) small, localized at a wavelength or half-wavelength of the membrane modes. In the experiments a stable generation of one, two, hor-ellipsis, ten pairs of counter-rotating vortices were observed in finite regions of amplitude-frequency parameter space. The circulation strength of vortices in a given vortex pattern increases with increasing external forcing and with decreasing soap film thickness. A theoretical model based on the wave-boundary interaction of excited Marangoni waves reveals a vorticity generation mechanism active in vibrating soap films. This model shows that vorticity is generated throughout the entire liquid volume by viscous diffusion, and qualitatively reproduces many steady vortex patterns observed in the experiment. However, the model cannot explain the existence of the sometimes intense vortices observed far from the film boundary that do not appear to be generated by diffusive processes. copyright 1998 American Institute of Physics

Two-dimensional mapping of underdosed areas using radiochromic film for patients undergoing total skin electron beam radiotherapy

International Nuclear Information System (INIS)

Gamble, Lisa M.; Farrell, Thomas J.; Jones, Glenn W.; Hayward, Joseph E.

2005-01-01

Purpose: To demonstrate the viability of radiochromic film as an in vivo, two-dimensional dosimeter for the measurement of underdosed areas in patients undergoing total skin electron beam (TSEB) radiotherapy. The results were compared with thermoluminescent dosimeter measurements. Methods and Materials: Dosimetry results are reported for an inframammary fold of 2 patients treated using a modified version of the Stanford six-position (i.e., six-field and dual-beam) TSEB technique. The results are presented as contour plots of film optical density and percentage of dose. A linear dose profile measured from film was compared with the thermoluminescent dosimeter measurements. Results: The results showed that the percentage doses as measured by film are in good agreement with those measured by the thermoluminescent dosimeters. The isodose contour plots provided by film can be used as a two-dimensional dose map for a patient when determining the size of the supplemental patch fields. Conclusion: Radiochromic film is a viable dosimetry tool that the radiation oncologist can use to understand the surface dose heterogeneity better across complex concave regions of skin to help establish more appropriate margins to patch underdosed areas. Film could be used for patients undergoing TSEB for disorders such as mycosis fungoides or undergoing TSEB or regional skin electron beam for widespread skin metastases from breast cancer and other malignancies

Multiple surface plasmon polaritons modes on thin silver film controlled by a two-dimensional lattice of silver nanodimers

Energy Technology Data Exchange (ETDEWEB)

Chang, Ying; Jiang, Yongyuan, E-mail: jiangyy@hit.edu.cn [Harbin Institute of Technology, Department of Physics (China)

2015-01-15

We study the optical resonant spectrum of a two-dimensional periodic array of silver nanodimers on a thin silver film using multiple scattering formalism. The excited multiple plasmonic modes on two interfaces of the silver film reveal that the dispersion relationships of surface plasmon polaritons on metallic film are modified by doubly periodic lattice due to the fact that wave vectors matching conditions are satisfied. Moreover, we demonstrate that the plasmonic modes are directly controlled by the thickness of silver film, as well as the gap between nanodimer array and silver film. These effects provide novel high-efficient and steady way for excitation in future plasmonic nanodevices.

Supramolecular 1-D polymerization of DNA origami through a dynamic process at the 2-dimensionally confined air-water interface.

Science.gov (United States)

Yonamine, Yusuke; Cervantes-Salguero, Keitel; Minami, Kosuke; Kawamata, Ibuki; Nakanishi, Waka; Hill, Jonathan P; Murata, Satoshi; Ariga, Katsuhiko

2016-05-14

In this study, a Langmuir-Blodgett (LB) system has been utilized for the regulation of polymerization of a DNA origami structure at the air-water interface as a two-dimensionally confined medium, which enables dynamic condensation of DNA origami units through variation of the film area at the macroscopic level (ca. 10-100 cm(2)). DNA origami sheets were conjugated with a cationic lipid (dioctadecyldimethylammonium bromide, 2C18N(+)) by electrostatic interaction and the corresponding LB-film was prepared. By applying dynamic pressure variation through compression-expansion processes, the lipid-modified DNA origami sheets underwent anisotropic polymerization forming a one-dimensionally assembled belt-shaped structure of a high aspect ratio although the thickness of the polymerized DNA origami was maintained at the unimolecular level. This approach opens up a new field of mechanical induction of the self-assembly of DNA origami structures.

Synthesis of Sub-10 nm Two-Dimensional Covalent Organic Thin Film with Sharp Molecular Sieving Nanofiltration

KAUST Repository

Gadwal, Ikhlas; Sheng, Guan; Thankamony, Roshni Lilly; Liu, Yang; Li, Huifang; Lai, Zhiping

2018-01-01

We demonstrated here a novel and facile synthesis of two-dimensional (2D) covalent organic thin film with pore size around 1.5 nm using a planar, amphiphilic and substituted heptacyclic truxene based triamine and a simple dialdehyde as building

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

Directory of Open Access Journals (Sweden)

Henrry M. Osorio

2015-05-01

Full Text Available Monolayer Langmuir–Blodgett (LB films of 1,4-bis(pyridin-4-ylethynylbenzene (1 together with the “STM touch-to-contact” method have been used to study the nature of metal–monolayer–metal junctions in which the pyridyl group provides the contact at both molecule–surface interfaces. Surface pressure vs area per molecule isotherms and Brewster angle microscopy images indicate that 1 forms true monolayers at the air–water interface. LB films of 1 were fabricated by deposition of the Langmuir films onto solid supports resulting in monolayers with surface coverage of 0.98 × 10−9 mol·cm−2. The morphology of the LB films that incorporate compound 1 was studied using atomic force microscopy (AFM. AFM images indicate the formation of homogeneous, monomolecular films at a surface pressure of transference of 16 mN·m−1. The UV–vis spectra of the Langmuir and LB films reveal that 1 forms two dimensional J-aggregates. Scanning tunneling microscopy (STM, in particular the “STM touch-to-contact” method, was used to determine the electrical properties of LB films of 1. From these STM studies symmetrical I–V curves were obtained. A junction conductance of 5.17 × 10−5 G0 results from the analysis of the pseudolinear (ohmic region of the I–V curves. This value is higher than that of the conductance values of LB films of phenylene-ethynylene derivatives contacted by amines, thiols, carboxylate, trimethylsilylethynyl or acetylide groups. In addition, the single molecule I–V curve of 1 determined using the I(s method is in good agreement with the I–V curve obtained for the LB film, and both curves fit well with the Simmons model. Together, these results not only indicate that the mechanism of transport through these metal–molecule–metal junctions is non-resonant tunneling, but that lateral interactions between molecules within the LB film do not strongly influence the molecule conductance. The results presented here

The infrared transmission through gold films on ordered two-dimensional non-close-packed colloidal crystals

International Nuclear Information System (INIS)

Ju Jing; Zhou Yuqin; Dong Gangqiang

2014-01-01

We studied the infrared transmission properties of gold films on ordered two-dimensional non-close-packed polystyrene (PS) colloidal crystal. The gold films consist of gold half-shells on the PS spheres and gold film with 2D arrays of holes on the glass substrate. An extraordinary optical transmission phenomenon could be found in such a structure. Simulations with the finite-difference time-domain method were also employed to get the transmission spectra and electric field distribution. The transmission response of the samples can be adjusted by controlling the thickness of the gold films. Angle-resolved measurements were performed using polarized light to obtain more information about the surface plasmon polariton resonances of the gold films. As the angle changes, the transmission spectra change a lot. The transmission spectra of p-polarized light have quite different properties compared to those of s-polarized light. (semiconductor physics)

Note: Automatic layer-by-layer spraying system for functional thin film coatings

Science.gov (United States)

Seo, Seongmin; Lee, Sangmin; Park, Yong Tae

2016-03-01

In this study, we have constructed an automatic spray machine for producing polyelectrolyte multilayer films containing various functional materials on wide substrates via the layer-by-layer (LbL) assembly technique. The proposed machine exhibits advantages in terms of automation, process speed, and versatility. Furthermore, it has several features that allow a fully automated spraying operation, such as various two-dimensional spraying paths, control of the flow rate and operating speed, air-assist fan-shaped twin-fluid nozzles, and an optical display. The robot uniformly sprays aqueous mixtures containing complementary (e.g., oppositely charged, capable of hydrogen bonding, or capable of covalent bonding) species onto a large-area substrate. Between each deposition of opposite species, samples are spray-rinsed with deionized water and blow-dried with air. The spraying, rinsing, and drying areas and times are adjustable by a computer program. Twenty-bilayer flame-retardant thin films were prepared in order to compare the performance of the spray-assisted LbL assembly with a sample produced by conventional dipping. The spray-coated film exhibited a reduction of afterglow time in vertical flame tests, indicating that the spray-LbL technique is a simple method to produce functional thin film coatings.

Influence of magnetic disorders on quantum anomalous Hall effect in magnetic topological insulator films beyond the two-dimensional limit

Science.gov (United States)

Xing, Yanxia; Xu, Fuming; Cheung, King Tai; Sun, Qing-feng; Wang, Jian; Yao, Yugui

2018-04-01

Quantum anomalous Hall effect (QAHE) has been experimentally realized in magnetic topological insulator (MTI) thin films fabricated on magnetically doped {({{Bi}},{{Sb}})}2{{{Te}}}3. In an MTI thin film with the magnetic easy axis along the normal direction (z-direction), orientations of magnetic dopants are randomly distributed around the magnetic easy axis, acting as magnetic disorders. With the aid of the non-equilibrium Green's function and Landauer–Büttiker formalism, we numerically study the influence of magnetic disorders on QAHE in an MTI thin film modeled by a three-dimensional tight-binding Hamiltonian. It is found that, due to the existence of gapless side surface states, QAHE is protected even in the presence of magnetic disorders as long as the z-component of magnetic moment of all magnetic dopants are positive. More importantly, such magnetic disorders also suppress the dissipation of the chiral edge states and enhance the quality of QAHE in MTI films. In addition, the effect of magnetic disorders depends very much on the film thickness, and the optimal influence is achieved at certain thickness. These findings are new features for QAHE in three-dimensional systems, not present in two-dimensional systems.

Synergistic interaction between gold nanoparticles and nickel phthalocyanine in layer-by-layer (LbL) films: evidence of constitutional dynamic chemistry (CDC).

Science.gov (United States)

Alencar, Wagner S; Crespilho, Frank N; Martins, Marccus V A; Zucolotto, Valtencir; Oliveira, Osvaldo N; Silva, Welter C

2009-07-07

The concept of constitutional dynamic chemistry (CDC) based on the control of non-covalent interactions in supramolecular structures is promising for having a large impact on nanoscience and nanotechnology if adequate nanoscale manipulation methods are used. In this study, we demonstrate that the layer-by-layer (LbL) technique may be used to produce electroactive electrodes with ITO coated by tetrasulfonated nickel phthalocyanine (NiTsPc) alternated with poly(allylamine hydrochloride) (PAH) incorporating gold nanoparticles (AuNP), in which synergy has been achieved in the interaction between the nanoparticles and NiTsPc. The catalytic activity toward hydrogen peroxide (H(2)O(2)) in multilayer films was investigated using cyclic voltammetry, where oxidation of H(2)O(2) led to increased currents in the PAH-AuNP/NiTsPc films for the electrochemical processes associated with the phthalocyanine ring and nickel at 0.52 and 0.81 V vs. SCE, respectively, while for PAH/NiTsPc films (without AuNP) only the first redox process was affected. In control experiments we found out that the catalytic activity was not solely due to the presence of AuNP, but rather to the nanoparticles inducing NiTsPc supramolecular structures that favored access to their redox sites, thus yielding strong charge transfer. The combined effects of NiTsPc and AuNP, which could only be observed in nanostructured LbL films, point to another avenue to pursue within the CDC paradigm.

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

International Nuclear Information System (INIS)

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

2013-01-01

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

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

Energy Technology Data Exchange (ETDEWEB)

Fernández, Raquel; Mondragon, Iñaki [‘Materials - Technologies’ Group, Department of Chemical and Environmental Engineering, Polytechnic School, Universidad País Vasco/Euskal Herriko Unibertsitatea, Pza Europa 1, 20018 Donostia-San Sebastián (Spain); Sanfelice, Rafaela C.; Pavinatto, Felippe J.; Oliveira, Osvaldo N. [Instituto de Física de São Carlos, Universidade de São Paulo, Av. Trabalhador São Carlense, 400, Centro, CEP 13560-970, São Carlos (Brazil); Oyanguren, Patricia [Institute of Materials Science and Technology (INTEMA), University of Mar del Plata and National Research Council (CONICET), J. B. Justo 4302, 7600 Mar del Plata (Argentina); Galante, María J., E-mail: galant@fi.mdp.edu.ar [Institute of Materials Science and Technology (INTEMA), University of Mar del Plata and National Research Council (CONICET), J. B. Justo 4302, 7600 Mar del Plata (Argentina)

2013-04-01

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

Photopatterning of heterostructured polymer Langmuir-Blodgett films

International Nuclear Information System (INIS)

Li Tiesheng; Mitsuishi, Masaya; Miyashita, Tokuji

2008-01-01

Heterostructured polymer Langmuir-Blodgett (LB) film prepared by using poly(N-dodecylacrylamide-co-t-butyl 4-vinylphenyl carbonate) (p(DDA-tBVPC53)) and poly(N-neopentyl methacrylamide-co-9-anthrylmethyl methacrylate) (p(nPMA-AMMA10)) polymer LB films which can act as photogenerator layers were investigated. Patterns with a resolution of 0.75 μm were obtained on heterostructured polymer LB films composed of 4 layers of p(nPMA-AMMA10) LB film (top layers) and 40 layers of p(DDA-tBVPC53) LB film (under layers) on a silicon wafer by deep UV irradiation followed by development with 1% tetramethylammonium hydroxide aqueous solution. The sensitivity of the heterostructured polymer LB films was improved without loss of the resolution compared with p(DDA-tBVPC53) LB film. The etch resistance of the heterostructured polymer LB films was sufficiently good to allow patterning of a copper film suitable for photomask fabrication

Third sound in one and two dimensional modulated structures

International Nuclear Information System (INIS)

Komuro, T.; Kawashima, H., Shirahama, K.; Kono, K.

1996-01-01

An experimental technique is developed to study acoustic transmission in one and two dimensional modulated structures by employing third sound of a superfluid helium film. In particular, the Penrose lattice, which is a two dimensional quasiperiodic structure, is studied. In two dimensions, the scattering of third sound is weaker than in one dimension. Nevertheless, the authors find that the transmission spectrum in the Penrose lattice, which is a two dimensional prototype of the quasicrystal, is observable if the helium film thickness is chosen around 5 atomic layers. The transmission spectra in the Penrose lattice are explained in terms of dynamical theory of diffraction

Two-dimensional photonic crystal bandedge laser with hybrid perovskite thin film for optical gain

Energy Technology Data Exchange (ETDEWEB)

Cha, Hyungrae [Department of Biophysics and Chemical Biology, Seoul National University, Seoul 08826 (Korea, Republic of); Inter-University Semiconductor Research Center, Seoul National University, Seoul 08826 (Korea, Republic of); Bae, Seunghwan [Department of Materials Science and Engineering, Seoul National University, Seoul 08826 (Korea, Republic of); Lee, Myungjae [Inter-University Semiconductor Research Center, Seoul National University, Seoul 08826 (Korea, Republic of); Department of Physics and Astronomy, Seoul National University, Seoul 08826 (Korea, Republic of); Jeon, Heonsu, E-mail: hsjeon@snu.ac.kr [Department of Biophysics and Chemical Biology, Seoul National University, Seoul 08826 (Korea, Republic of); Inter-University Semiconductor Research Center, Seoul National University, Seoul 08826 (Korea, Republic of); Department of Physics and Astronomy, Seoul National University, Seoul 08826 (Korea, Republic of)

2016-05-02

We report optically pumped room temperature single mode laser that contains a thin film of hybrid perovskite, an emerging photonic material, as gain medium. Two-dimensional square lattice photonic crystal (PhC) backbone structure enables single mode laser operation via a photonic bandedge mode, while a thin film of methyl-ammonium lead iodide (CH{sub 3}NH{sub 3}PbI{sub 3}) spin-coated atop provides optical gain for lasing. Two kinds of bandedge modes, Γ and M, are employed, and both devices laser in single mode at similar laser thresholds of ∼200 μJ/cm{sup 2} in pulse energy density. Polarization dependence measurements reveal a clear difference between the two kinds of bandedge lasers: isotropic for the Γ-point laser and highly anisotropic for the M-point laser. These observations are consistent with expected modal properties, confirming that the lasing actions indeed originate from the corresponding PhC bandedge modes.

Phase transitions in two-dimensional systems

International Nuclear Information System (INIS)

Salinas, S.R.A.

1983-01-01

Some experiences are related using synchrotron radiation beams, to characterize solid-liquid (fusion) and commensurate solid-uncommensurate solid transitions in two-dimensional systems. Some ideas involved in the modern theories of two-dimensional fusion are shortly exposed. The systems treated consist of noble gases (Kr,Ar,Xe) adsorbed in the basal plane of graphite and thin films formed by some liquid crystal shells. (L.C.) [pt

Two-dimensional dissipation in third sound resonance

International Nuclear Information System (INIS)

Buck, A.L.; Mochel, J.M.; Illinois Univ., Urbana

1981-01-01

The first determination of non-linear superflow dissipation in a truly two-dimensional helium film is reported. Superfluid velocities were measured using third sound resonance on a closed superfluid film. The predicted power law dissipation function, with exponent of approximately eight, is observed at three temperatures in a film of 0.58 mobile superfluid layers. (orig.)

Two-dimensional x-ray diffraction

CERN Document Server

He, Bob B

2009-01-01

Written by one of the pioneers of 2D X-Ray Diffraction, this useful guide covers the fundamentals, experimental methods and applications of two-dimensional x-ray diffraction, including geometry convention, x-ray source and optics, two-dimensional detectors, diffraction data interpretation, and configurations for various applications, such as phase identification, texture, stress, microstructure analysis, crystallinity, thin film analysis and combinatorial screening. Experimental examples in materials research, pharmaceuticals, and forensics are also given. This presents a key resource to resea

Characteristics of angular cross correlations studied by light scattering from two-dimensional microsphere films

Science.gov (United States)

Schroer, M. A.; Gutt, C.; Grübel, G.

2014-07-01

Recently the analysis of scattering patterns by angular cross-correlation analysis (CCA) was introduced to reveal the orientational order in disordered samples with special focus to future applications on x-ray free-electron laser facilities. We apply this CCA approach to ultra-small-angle light-scattering data obtained from two-dimensional monolayers of microspheres. The films were studied in addition by optical microscopy. This combined approach allows to calculate the cross-correlations of the scattering patterns, characterized by the orientational correlation function Ψl(q), as well as to obtain the real-space structure of the monolayers. We show that CCA is sensitive to the orientational order of monolayers formed by the microspheres which are not directly visible from the scattering patterns. By mixing microspheres of different radii the sizes of ordered monolayer domains is reduced. For these samples it is shown that Ψl(q) quantitatively describes the degree of hexagonal order of the two-dimensional films. The experimental CCA results are compared with calculations based on the microscopy images. Both techniques show qualitatively similar features. Differences can be attributed to the wave-front distortion of the laser beam in the experiment. This effect is discussed by investigating the effect of different wave fronts on the cross-correlation analysis results. The so-determined characteristics of the cross-correlation analysis will be also relevant for future x-ray-based studies.

Self-assembled three-dimensional and compressible interdigitated thin-film supercapacitors and batteries

Science.gov (United States)

Nyström, Gustav; Marais, Andrew; Karabulut, Erdem; Wågberg, Lars; Cui, Yi; Hamedi, Mahiar M.

2015-01-01

Traditional thin-film energy-storage devices consist of stacked layers of active films on two-dimensional substrates and do not exploit the third dimension. Fully three-dimensional thin-film devices would allow energy storage in bulk materials with arbitrary form factors and with mechanical properties unique to bulk materials such as compressibility. Here we show three-dimensional energy-storage devices based on layer-by-layer self-assembly of interdigitated thin films on the surface of an open-cell aerogel substrate. We demonstrate a reversibly compressible three-dimensional supercapacitor with carbon nanotube electrodes and a three-dimensional hybrid battery with a copper hexacyanoferrate ion intercalating cathode and a carbon nanotube anode. The three-dimensional supercapacitor shows stable operation over 400 cycles with a capacitance of 25 F g−1 and is fully functional even at compressions up to 75%. Our results demonstrate that layer-by-layer self-assembly inside aerogels is a rapid, precise and scalable route for building high-surface-area 3D thin-film devices. PMID:26021485

Explanation of the photocurrent quantum efficiency (Φ) enhancements through the CAN's model equation for the p-CuI sensitized methylviolet-C18 LB films in the photoelectrochemical cells (PECs) and Cu/n-Cu2O/M-C18/p-CuI solid-state photovoltaic cells

International Nuclear Information System (INIS)

Fernando, C A N; Liyanaarachchi, U S; AARajapaksha, R D

2013-01-01

Photocurrent enhancements in a dye sensitized photoelectrochemical cell (PEC) with a Cu/p-CuI/M-C 18 photoelectrode and a dye sensitized solid state photovoltaic cell (DSSC) with Cu/n-Cu 2 O/M-C 18 /p-CuI are studied by controlling the formation of dye aggregates of M-C 18 Langmuir–Blodgett (LB) films on the p-CuI layer. LB films of M-C 18 are deposited under biasing conditions during the LB deposition process on Cu/p-CuI, Cu/n-Cu 2 O/p-CuI and conductive glass plates with the three-electrode configuration setup coupling to the LB trough. LB films prepared under positive biasing conditions enhance the photocurrent quantum efficiencies for both PECs and DSSCs controlling and minimizing the formation of dye aggregates. The electrolyte used for LB deposition and photocurrent measurements is (10 −2 M) Fe 2+ + Fe 3+ (10 −2 M) and (10 −2 M) NaH 2 PO 4 –Na 2 HPO 4 , pH = 6 buffer solution. Maximum photocurrent quantum efficiencies (φmax%) obtained are ≈22% for PEC and ≈20% for DSSCs, where the M-C 18 LB film deposition applied potentials +0.3 V versus Ag/AgCl. The mechanism of the photocurrent enhancement is discussed through the CAN's model equation, φ = AD 0 –BD 0 2 , where A = k 1 k 2 /F, B = I k 1 2 k 2 [2k 6 /F 3 + k 2 k 4 /k 3 2 X 2 F 2 ], F = k 2 + k 5 Y + k 7 + k 1 I [1 + k 2 /k 3 X], presented from our previous study [1]. Experimental evidence for the formation of the aggregates of M-C 18 LB films for the negative applied potentials and suppression of the aggregates with positive applied potentials are presented from absorption spectra, AFM pictures and fluorescence measurements of the samples. Conversion efficiency obtained is ≈2.5%, V oc ≈750 mV and I sc ≈ 5.8 mA cm −2 for DSSC fabricated with +0.3 V versus Ag/AgCl applied deposition potential of M-C 18 LB films. (paper)

Explanation of the photocurrent quantum efficiency (Φ) enhancements through the CAN's model equation for the p-CuI sensitized methylviolet-C18 LB films in the photoelectrochemical cells (PECs) and Cu/n-Cu2O/M-C18/p-CuI solid-state photovoltaic cells

Science.gov (United States)

Fernando, C. A. N.; Liyanaarachchi, U. S.; AARajapaksha, R. D.

2013-04-01

Photocurrent enhancements in a dye sensitized photoelectrochemical cell (PEC) with a Cu/p-CuI/M-C18 photoelectrode and a dye sensitized solid state photovoltaic cell (DSSC) with Cu/n-Cu2O/M-C18/p-CuI are studied by controlling the formation of dye aggregates of M-C18 Langmuir-Blodgett (LB) films on the p-CuI layer. LB films of M-C18 are deposited under biasing conditions during the LB deposition process on Cu/p-CuI, Cu/n-Cu2O/p-CuI and conductive glass plates with the three-electrode configuration setup coupling to the LB trough. LB films prepared under positive biasing conditions enhance the photocurrent quantum efficiencies for both PECs and DSSCs controlling and minimizing the formation of dye aggregates. The electrolyte used for LB deposition and photocurrent measurements is (10-2 M) Fe2+ + Fe3+ (10-2 M) and (10-2 M) NaH2PO4-Na2HPO4, pH = 6 buffer solution. Maximum photocurrent quantum efficiencies (Фmax%) obtained are ≈22% for PEC and ≈20% for DSSCs, where the M-C18 LB film deposition applied potentials +0.3 V versus Ag/AgCl. The mechanism of the photocurrent enhancement is discussed through the CAN's model equation, Ф = AD0-BD02, where A = k1k2/F, B = I k12 k2[2k6/F3 + k2k4/k32 X2F2], F = k2 + k5Y + k7 + k1 I [1 + k2/k3 X], presented from our previous study [1]. Experimental evidence for the formation of the aggregates of M-C18 LB films for the negative applied potentials and suppression of the aggregates with positive applied potentials are presented from absorption spectra, AFM pictures and fluorescence measurements of the samples. Conversion efficiency obtained is ≈2.5%, Voc ≈750 mV and Isc ≈ 5.8 mA cm-2 for DSSC fabricated with +0.3 V versus Ag/AgCl applied deposition potential of M-C18 LB films.

Sugar-Responsive Layer-by-Layer Film Composed of Phenylboronic Acid-Appended Insulin and Poly(vinyl alcohol).

Science.gov (United States)

Takei, Chihiro; Ohno, Yui; Seki, Tomohiro; Miki, Ryotaro; Seki, Toshinobu; Egawa, Yuya

2018-01-01

Previous studies have shown that reversible chemical bond formation between phenylboronic acid (PBA) and 1,3-diol can be utilized as the driving force for the preparation of layer-by-layer (LbL) films. The LbL films composed of a PBA-appended polymer and poly(vinyl alcohol) (PVA) disintegrated in the presence of sugar. This type of LbL films has been recognized as a promising approach for sugar-responsive drug release systems, but an issue preventing the practical application of LbL films is combining them with insulin. In this report, we have proposed a solution for this issue by using PBA-appended insulin as a component of the LbL film. We prepared two kinds of PBA-appended insulin derivatives and confirmed that they retained their hypoglycemic activity. The LbL films composed of PBA-appended insulin and PVA were successfully prepared through reversible chemical bond formation between the boronic acid moiety and the 1,3-diol of PVA. The LbL film disintegrated upon treatment with sugars. Based on the results presented herein, we discuss the suitability of the PBA moiety with respect to hypoglycemic activity, binding ability, and selectivity for D-glucose.

Phase and Texture of Solution-Processed Copper Phthalocyanine Thin Films Investigated by Two-Dimensional Grazing Incidence X-Ray Diffraction

Directory of Open Access Journals (Sweden)

Lulu Deng

2011-07-01

Full Text Available The phase and texture of a newly developed solution-processed copper phthalocyanine (CuPc thin film have been investigated by two-dimensional grazing incidence X-ray diffraction. The results show that it has β phase crystalline structure, with crystallinity greater than 80%. The average size of the crystallites is found to be about 24 nm. There are two different arrangements of crystallites, with one dominating the diffraction pattern. Both of them have preferred orientation along the thin film normal. Based on the similarities to the vacuum deposited CuPc thin films, the new solution processing method is verified to offer a good alternative to vacuum process, for the fabrication of low cost small molecule based organic photovoltaics.

Imprinting of metal receptors into multilayer polyelectrolyte films: fabrication and applications in marine antifouling† †Electronic supplementary information (ESI) available: FTIR, NMR spectra of synthesized polymers, XPS spectra and AFM images of non-cross linked and cross linked LBLA and LBLB films, UV-Visible absorption spectra of copper complexation with PAH-His, QCM data of LBLA and LBLB films and stability of the films are provided in the electronic supplementary information. See DOI: 10.1039/c4sc02367f Click here for additional data file.

Science.gov (United States)

Puniredd, Sreenivasa Reddy; Go, Dewi Pitrasari; Zhu, Xiaoying; Guo, Shifeng; Ming Teo, Serena Lay; Chen Lee, Serina Siew

2015-01-01

Polymeric films constructed using the layer-by-layer (LbL) fabrication process were employed as a platform for metal ion immobilization and applied as a marine antifouling coating. The novel Cu2+ ion imprinting process described is based on the use of metal ion templates and LbL multilayer covalent cross-linking. Custom synthesized, peptide mimicking polycations composed of histidine grafted poly(allylamine) (PAH) to bind metal ions, and methyl ester containing polyanions for convenient cross-linking were used in the fabrication process. Two methods of LbL film formation have been investigated using alternate polyelectrolyte deposition namely non-imprinted LbLA, and imprinted LbLB. Both LbL films were cross linked at mild temperature to yield covalent bridging of the layers for improved stability in a sea water environment. A comparative study of the non-imprinted LbLA films and imprinted LbLB films for Cu2+ ion binding capacity, leaching rate and stability of the films was performed. The results reveal that the imprinted films possess enhanced affinity to retain metal ions due to the preorganization of imidazole bearing histidine receptors. As a result the binding capacity of the films for Cu2+ could be improved by seven fold. Antifouling properties of the resulting materials in a marine environment have been demonstrated against the settlement of barnacle larvae, indicating that controlled release of Cu ions was achieved. PMID:28966763

Second harmonic generation in anisotropic Langmuir-Blodgett films of N-docosyl-4-nitroaniline

DEFF Research Database (Denmark)

Geisler, T.; Rosenkilde, S.; Ramanujam, P.S.

1992-01-01

Langmuir-Blodgett (LB) films of N-docosyl-4-nitroaniline have been made and their nonlinear optical properties studied by second harmonic generation (SHG) measurements. A significant enhancement of the intensity of the second harmonic of the 1.064-mu-m YAG was observed when a two layer Y-type film...... structure. Both of these observations are not common for Y-type LB films and the usual assumption of C(infinity nu) symmetry is therefore not valid. The results make us suggest that these LB films possess C(s) and C2-nu symmetry for mono- and multilayers, respectively. Theoretical expressions...

Two dimensional Raman mapping with respect to carbon bonds of radiochromic films: An approach to micro-dosimetry

International Nuclear Information System (INIS)

Heo, Taemin; Park, Hyeonsuk; Ye, Sung-Joon

2015-01-01

Raman spectroscopy usually provides fingerprints of chemical component species and molecular motion. Raman peak intensity can be quantified as dose changes. Using that Raman peak intensity is proportional to the electric field intensity of incidence beam and the concentration of compounds, the dose trend would have the linearity with the concentration change of radio-active compounds. Raman spectroscopy has been applied to be utilized as a dosimetry in our group in the previous study. Then, laser effect and film homogeneity issues were required to be overcome. Two dimensional scan method was adapted to reduce measurement uncertainty since Raman cross-section is very sensitive to atomic bonds concentration and a large number of point measurements would guarantee reliable data group. The concentration in carbon double and triple bonds of radiochromic films would change by polymerization process. Thus, two dimensional analysis based on Raman mapping provides more reliable data in light of polymerization quantity due to radiation ionization than optical scanning. Its high spatial resolution (fifty micrometers) and low dose sensitivity (10 cGy) were demonstrated as a potential dosimeter. Raman analysis is expected as more precise analysis for micro-dosimetry in the future

Structure of the Buried Metal-Molecule Interface in Organic Thin Film Devices

DEFF Research Database (Denmark)

Hansen, Christian Rein; Sørensen, Thomas Just; Glyvradal, Magni

2009-01-01

By use of specular X-ray reflectivity (XR) the structure of a metal-covered organic thin film device is measured with angstrom resolution. The model system is a Langmuir-Blodgett (LB) film, sandwiched between a silicon substrate and a top electrode consisting of 25 Å titanium and 100 Å aluminum....... By comparison of XR data for the five-layer Pb2+ arachidate LB film before and after vapor deposition of the Ti/Al top electrode, a detailed account of the structural damage to the organic film at the buried metal-molecule interface is obtained. We find that the organized structure of the two topmost LB layers...

Evidence for nanoscale two-dimensional Co clusters in CoPt{sub 3} films with perpendicular magnetic anisotropy

Energy Technology Data Exchange (ETDEWEB)

Cross, J O [Department of Physics, University of Washington, Seattle, WA 98195 (United States); Newville, M [Consortium for Advanced Radiation Sources, University of Chicago, Chicago, IL 60637 (United States); Maranville, B B; Hellman, F [Department of Physics, University of California at San Diego, La Jolla, CA 92093 (United States); Bordel, C [Department of Physics, University of California at Berkeley, CA 94720 (United States); Harris, V G, E-mail: cbordel@berkeley.ed [Department of Electrical and Computer Engineering, Northeastern University, Boston, MA 02115 (United States)

2010-04-14

The length scale of the local chemical anisotropy responsible for the growth-temperature-induced perpendicular magnetic anisotropy of face-centered cubic CoPt{sub 3} alloy films was investigated using polarized extended x-ray absorption fine structure (EXAFS). These x-ray measurements were performed on a series of four (111) CoPt{sub 3} films epitaxially grown on (0001) sapphire substrates. The EXAFS data show a preference for Co-Co pairs parallel to the film plane when the film exhibits magnetic anisotropy, and random chemical order otherwise. Furthermore, atomic pair correlation anisotropy was evidenced only in the EXAFS signal from the next neighbors to the absorbing Co atoms and from multiple scattering paths focused through the next neighbors. This suggests that the Co clusters are no more than a few atoms in extent in the plane and one monolayer in extent out of the plane. Our EXAFS results confirm the correlation between perpendicular magnetic anisotropy and two-dimensional Co segregation in CoPt{sub 3} alloy films, and establish a length scale on the order of 10 A for the Co clusters.

Preliminary Characterization of Genipin-Cross-Linked Silk Sericin/Poly(vinyl alcohol Films as Two-Dimensional Wound Dressings for the Healing of Superficial Wounds

Directory of Open Access Journals (Sweden)

Tippawan Siritientong

2013-01-01

Full Text Available The genipin-cross-linked silk sericin/poly(vinyl alcohol (PVA films were developed aiming to be applied as two-dimensional wound dressings for the treatment of superficial wounds. The effects of genipin cross-linking concentration on the physical and biological properties of the films were investigated. The genipin-cross-linked silk sericin/PVA films showed the increased surface density, tensile strength, and percentage of elongation, but decreased percentage of light transmission, water vapor transmission rate, and water swelling, compared to the non-cross-linked films. This explained that the cross-linking bonds between genipin and silk sericin would reduce the mobility of molecular chains within the films, resulting in the more rigid molecular structure. Silk sericin was released from the genipin-cross-linked films in a sustained manner. In addition, either L929 mouse fibroblast or HaCat keratinocyte cells showed high percentage of viability when cultured on the silk sericin/PVA films cross-linked with 0.075 and 0.1% w/v genipin. The in vivo safety test performed according to ISO 10993-6 confirmed that the genipin-cross-linked silk sericin/PVA films were safe for the medical usages. The efficacy of the films for the treatment of superficial skin wounds will be further investigated in vivo and clinically. The genipin-cross-linked silk sericin/PVA films would be promising choices of two-dimensional wound dressings for the treatment of superficial wounds.

Growth and time dependent alignment of KCl crystals in Hemoglobin LB monolayer

International Nuclear Information System (INIS)

Mahato, Mrityunjoy; Pal, Prabir; Tah, Bidisha; Kamilya, Tapanendu; Talapatra, G.B.

2012-01-01

Nature and organism often use the biomineralization technique to build up various highly regular structures such as bone, teeth, kidney stone etc., and recently this becomes the strategy to design and synthesis of novel biocomposite materials. We report here the controlled crystallization of KCl in Langmuir and Langmuir Blodgett (LB) monolayer of Hemoglobin (Hb) at ambient condition. The nucleation and growth of KCl crystals in Hb monolayer has temporal and KCl concentration dependency. The growth of KCl crystals in LB film of Hb has distinct behavior in the alignment of crystals from linear to fractal like structures depending on growth time. The crystallographic identity of the biomineralized KCl crystal is confirmed from HR-TEM, XRD, and from powder diffraction simulation. Our results substantiated that the template of Langmuir monolayer of proteins plays a crucial role in biomineralization as well as in designing and synthesizing of novel biocomposite materials. Highlights: ► Biomineralization of KCl crystal has been studied in Hemoglobin LB film. ► KCl crystal growth is time and concentration of KCl dependent. ► The alignment of KCl crystal growth is fractal nature with time. ► The unfolding of Hb and evaporation factor has some role in crystallization and fractal growth.

Low-Dimensional Nanomaterials as Active Layer Components in Thin-Film Photovoltaics

Science.gov (United States)

Shastry, Tejas Attreya

Thin-film photovoltaics offer the promise of cost-effective and scalable solar energy conversion, particularly for applications of semi-transparent solar cells where the poor absorption of commercially-available silicon is inadequate. Applications ranging from roof coatings that capture solar energy to semi-transparent windows that harvest the immense amount of incident sunlight on buildings could be realized with efficient and stable thin-film solar cells. However, the lifetime and efficiency of thin-film solar cells continue to trail their inorganic silicon counterparts. Low-dimensional nanomaterials, such as carbon nanotubes and two-dimensional metal dichalcogenides, have recently been explored as materials in thin-film solar cells due to their exceptional optoelectronic properties, solution-processability, and chemical inertness. Thus far, issues with the processing of these materials has held back their implementation in efficient photovoltaics. This dissertation reports processing advances that enable demonstrations of low-dimensional nanomaterials in thin-film solar cells. These low-dimensional photovoltaics show enhanced photovoltaic efficiency and environmental stability in comparison to previous devices, with a focus on semiconducting single-walled carbon nanotubes as an active layer component. The introduction summarizes recent advances in the processing of carbon nanotubes and their implementation through the thin-film photovoltaic architecture, as well as the use of two-dimensional metal dichalcogenides in photovoltaic applications and potential future directions for all-nanomaterial solar cells. The following chapter reports a study of the interaction between carbon nanotubes and surfactants that enables them to be sorted by electronic type via density gradient ultracentrifugation. These insights are utilized to construct of a broad distribution of carbon nanotubes that absorb throughout the solar spectrum. This polychiral distribution is then shown

Structural disorder in two-dimensional random magnets: Very thin films of rare earths and transition metals

Science.gov (United States)

Ruiz, J. M.; Zhang, X. X.; Iglesias, O.; García, A.; Tejada, J.

1993-05-01

The low-temperature isothermal magnetization curves, M(H), of SmCo4 and Fe3Tb thin films are studied according to the two-dimensional correlated spin-glass model of Chudnovsky. We have calculated the magnetization law in approach to saturation and shown that the M(H) data fit well the theory at high and low fields. In our fit procedure we have used three different correlation functions. The Gaussian decay correlation function fits well the experimental data for both samples.

Third-order nonlinearities and structural features in Langmuir-Blodgett films of 1-benzyl-9-hydrofullerene-60

International Nuclear Information System (INIS)

Shihong Ma; Liying Liu; Xingze Lu

1995-01-01

Third-order nonlinear susceptibilities χ xxxx (3) (-3ω; ω, ω, ω) have been deduced by measuring third-harmonic generation in Langmuir-Blodgett (LB) films of 1-benzyl-9-hydrofullerene-60 (C 60 -Be). The structural features of the condensed layer at the air-water interface and LB films of the C 60 -Be were investigated by small angle x-ray diffraction (SAXD) and optical measurements. The third-order nonlinear susceptibilities (χ (3) ) were obtained by measuring the THG intensities in LB films of C 60 -Be and comparing with that of CS 2 used as the reference. The value of χ xxxx (3) (2.1 x 10 -11 esu) was deduced at a 65 nm thick films. The χ (3) is attributed to a three-photon near resonance at the energy level of 29410 cm -1 . A new-type of two-chain amphiphilic molecule 1,10-bistearyl-4,6,13, 15-tetra-18-nitrogencrown-6 (NC) was used as insert material to construct mixed C 60 -Be/NC LB films. Our π-A, UV-visible absorption and SAXD measurements showed that the structural improvement in the mixed C 60 -Be/NC LB films was realized by insertion of the C 60 -Be molecules between the two hydrophobic chains of the NC molecules

Interaction of Ions with Two-Dimensional Transition Metal Carbide (MXene) Films

Science.gov (United States)

Ren, Chang

Nowadays, society is relying more on nanotechnology for solving critical issues, such as the increasing demand for clean energy and freshwater. Among nanotechnologies, two-dimensional (2D) materials with unique properties are investigated with elevated expectations. In 2011, a new family of 2D materials MXenes were discovered, which became an important addition to the 2D word. The general formula of MXene is Mn+1XnTx, where M stands for transition metal atom, X is C and/or N, n = 1, 2 or 3, and Tx represents surface groups. Nanosheets of MXene obtained by delamination can form flexible films. Additionally, ions can intercalate MXene layers, suggesting potential applications in energy storage and water purification. The Ti3C2Tx MXene films of various thicknesses, which have orderly stacked 2D structure, high density and flexibility, and metallic electrical conductivity of 2400 to 5690 S/cm were fabricated by vacuum-assisted filtration. Ti3C2Tx surface was negatively charged and hydrophilic. Additionally, Ti3C 2Tx films showed sufficient mechanical strength for handling, and the tensile strength of a Ti3C2Tx film was comparable to GO membranes. Metal cations intercalated between the MXene layers, and led to intercalation capacitance. Binder-free Ti3C 2Tx films showed volumetric capacitance of 350 to over 1000 F/cm3 in aqueous electrochemical capacitors (ECs), depending on the electrolyte, and the size of Ti3C2Tx nanosheets. Smaller flakes were obtained by increasing time of ultrasonic treatment. They had a lower electrical conductivity, but a higher capacitance. By introducing polymer nanofillers, such as poly(vinyl alcohol) (PVA) between MXene nanosheets, composite films were prepared and showed controllable electrical conductivity, increased interlayer spacing, improved mechanical strength and capacitive performance. By introducing carbon nanomaterials between MXene layers or creating mesopores on MXene, the films were made more accessible to intercalation and

Formation and control of excimer of a coumarin derivative in Langmuir–Blodgett films

Energy Technology Data Exchange (ETDEWEB)

Chakraborty, Santanu; Bhattacharjee, D.; Hussain, Syed Arshad, E-mail: sa_h153@hotmail.com

2014-01-15

In this communication we report the formation and control of excimer of a coumerin derivative 7-Hydroxy-N-Octadecyl Coumarin-3-Carboxamide (7HNO3C) assembled onto Langmuir–Blodgett (LB) films. Surface pressure–area per molecule isotherm revealed that 7HNO3C formed stable Langmuir monolayer at the air–water interface. Spectroscoipic characterizations confirmed the formation of excimer of 7HNO3C in the LB film prepared at 20 mN/m surface pressure. The excimer band remains present even when 7HNO3C molecules are diluted with a long chain fatty acid stearic acid in LB films. The excimer formation of 7HNO3C can be controlled by incorporating clay particle laponite in the LB film. The excimer band is totally absent in the hybrid 7HNO3C–laponite LB films. In-situ fluorescence imaging microscopy and atomic force microscopy confirmed the incorporation of clay laponite onto LB films. -- Highlights: • Formation of Langmuir monolayer and Langmuir–Blodgett (LB) film of a coumarin derivative. • Presence of excimeric species in the LB film lifted at 20 mN/m surface pressure is confirmed from the spectroscopic studies. • Control of excimer formation by incorporating clay particle laponite on to the LB film. • In-situ fluorescence imaging microscopy and atomic force microscopy confirmed the incorporation of clay laponite onto LB films.

Preparation of large-area molecular junctions with metallic conducting Langmuir–Blodgett films

Energy Technology Data Exchange (ETDEWEB)

Mochizuki, Kengo [Division of Marine Technology, Tokyo University of Marine Science and Technology, 2-1-6 Etchujima Koto-ku, Tokyo 135-8533 (Japan); Ohnuki, Hitoshi, E-mail: ohnuki@kaiyodai.ac.jp [Division of Marine Technology, Tokyo University of Marine Science and Technology, 2-1-6 Etchujima Koto-ku, Tokyo 135-8533 (Japan); Shimizu, Daisuke [Division of Marine Technology, Tokyo University of Marine Science and Technology, 2-1-6 Etchujima Koto-ku, Tokyo 135-8533 (Japan); Imakubo, Tatsuro [Department of Materials and Technology, Nagaoka University of Technology, 1603-1 Kamitomioka, Nagaoka, Niigata 940-2188 (Japan); Tsuya, Daiju [National Institute for Materials Science,1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Izumi, Mitsuru [Division of Marine Technology, Tokyo University of Marine Science and Technology, 2-1-6 Etchujima Koto-ku, Tokyo 135-8533 (Japan)

2014-03-03

Metallic conducting Langmuir–Blodgett (LB) films were used as soft electrodes to fabricate molecular junctions with self-assembled monolayers (SAMs) of alkanethiols (CH{sub 3}(CH{sub 2}){sub n−1}SH) on an Au surface. Alkanethiols can form highly ordered, stable dielectric SAMs on metal surfaces over large areas. However, it is difficult to establish electrical contacts on such SAMs, which has limited their application. In this work, we used metallic conducting LB films composed of bis(ethylenedioxy)tetrathiafulvalene and stearic acid as a soft electrode onto alkanethiol SAMs (C{sub n}-SAM, n = 12, 14, 16, 18) to prepare Au/SAM/metal junctions of relatively large size (∼ 15.6 × 10{sup 3} μm{sup 2}). The current density–voltage (J–V) characteristics across the junctions exhibited rectifying behavior with a ratio R of ∼ 5 (R = |J(V)|/|J(− V)| at ± 1 V). The lower transfer rate corresponding to the electron transport from Au to the LB films exhibited nonlinear J–V characteristics, while the higher transfer rate of electrons from the LB film to Au showed linear J–V characteristics. Kelvin probe force microscopy revealed that the work function of the metallic LB films was smaller than that of Au. The observed rectification behavior is probably caused by different electron transport mechanisms between the two current directions. - Highlights: • Metallic Langmuir–Blodgett (LB) films were used as soft electrodes. • Molecular junctions of metal–alkanethiol–LB films were fabricated. • The current–voltage curve across the junctions exhibited rectifying behavior. • This is the first observation for alkanethiol monolayer junctions. • The work function difference between the electrodes induces the rectification.

Block copolymer assisted self-assembly of nanoparticles into Langmuir–Blodgett films: Effect of polymer concentration

International Nuclear Information System (INIS)

Martín-García, Beatriz; Velázquez, M. Mercedes

2013-01-01

We propose to use the self-assembly ability of a block copolymer to obtain CdSe quantum dots (QDs) structures of different morphology. The methodology proposed consist in transferring mixed Langmuir monolayers of QDs and the polymer poly (styrene-co-maleic anhydride) partial 2 buthoxy ethyl ester cumene terminated, PS-MA-BEE onto mica by the Langmuir–Blodgett (LB) methodology. The morphology of the LB films was analyzed by AFM and TEM measurements. Our results show that it is possible to modulate the self-assembly process by modifying the composition of the mixed Langmuir monolayer precursor of the LB film. The different morphologies are interpreted according to two different dewetting mechanisms, growth of holes and spinodal-like dewetting. The growth of holes dewetting process is driven by gravitatory effects and was observed for LB films obtained by transferring Langmuir monolayer of the smallest elasticity values in which the polymer is in brush conformation. The spinodal dewetting mechanism prevailed when the Langmuir monolayer presents the highest elasticity values. - Graphical abstract: Display Omitted - Highlights: • Effect of the surface composition on the LB films architecture. • QDs/polymer LB films morphology interpreted in terms of dewetting mechanism. • The dewetting mechanism depends on the Langmuir monolayer state

Block copolymer assisted self-assembly of nanoparticles into Langmuir–Blodgett films: Effect of polymer concentration

Energy Technology Data Exchange (ETDEWEB)

Martín-García, Beatriz; Velázquez, M. Mercedes, E-mail: mvsal@usal.es

2013-08-15

We propose to use the self-assembly ability of a block copolymer to obtain CdSe quantum dots (QDs) structures of different morphology. The methodology proposed consist in transferring mixed Langmuir monolayers of QDs and the polymer poly (styrene-co-maleic anhydride) partial 2 buthoxy ethyl ester cumene terminated, PS-MA-BEE onto mica by the Langmuir–Blodgett (LB) methodology. The morphology of the LB films was analyzed by AFM and TEM measurements. Our results show that it is possible to modulate the self-assembly process by modifying the composition of the mixed Langmuir monolayer precursor of the LB film. The different morphologies are interpreted according to two different dewetting mechanisms, growth of holes and spinodal-like dewetting. The growth of holes dewetting process is driven by gravitatory effects and was observed for LB films obtained by transferring Langmuir monolayer of the smallest elasticity values in which the polymer is in brush conformation. The spinodal dewetting mechanism prevailed when the Langmuir monolayer presents the highest elasticity values. - Graphical abstract: Display Omitted - Highlights: • Effect of the surface composition on the LB films architecture. • QDs/polymer LB films morphology interpreted in terms of dewetting mechanism. • The dewetting mechanism depends on the Langmuir monolayer state.

Voltammetric Response of Alizarin Red S-Confined Film-Coated Electrodes to Diol and Polyol Compounds: Use of Phenylboronic Acid-Modified Poly(ethyleneimine) as Film Component.

Science.gov (United States)

Takahashi, Shigehiro; Suzuki, Iwao; Ojima, Takuto; Minaki, Daichi; Anzai, Jun-Ichi

2018-01-22

Alizarin red S (ARS) was confined in layer-by-layer (LbL) films composed of phenylboronic acid-modified poly(ethyleneimine) (PBA-PEI) and carboxymethylcellulose (CMC) to study the voltammetric response to diol and polyol compounds. The LbL film-coated gold (Au) electrode and quartz slide were immersed in an ARS solution to uptake ARS into the film. UV-visible absorption spectra of ARS-confined LbL film suggested that ARS formed boronate ester (ARS-PBS) in the film. The cyclic voltammetry of the ARS-confined LbL film-coated electrodes exhibited oxidation peaks at -0.50 and -0.62 V, which were ascribed to the oxidation reactions of ARS-PBS and free ARS, respectively, in the LbL film. The peak current at -0.62 V increased upon the addition of diol or polyol compounds such as L-dopa, glucose, and sorbitol into the solution, depending on the concentration, whereas the peak current at -0.50 V decreased. The results suggest a possible use of ARS-confined PBA-PEI/CMC LbL film-coated Au electrodes for the construction of voltammetric sensors for diol and polyol compounds.

Ultrathin protective films of two-dimensional polymers on passivated iron against corrosion in 0.1M NaCl

International Nuclear Information System (INIS)

Aramaki, Kunitsugu; Shimura, Tadashi

2005-01-01

Prevention of iron corrosion in an aerated 0.1M NaCl solution was investigated by polarization and mass-loss measurements of a passivated iron electrode covered with ultrathin and ordered films of two-dimensional polymers. The films were prepared on the passivated electrode by modification of a 16-hydroxyhexadecanoate ion HO(CH 2 ) 15 CO 2 - self-assembled monolayer with 1,2-bis(triethoxysilyl)ethane (C 2 H 5 O) 3 Si(CH 2 ) 2 Si(OC 2 H 5 ) 3 and alkyltriethoxysilane C n H 2n+1 Si(OC 2 H 5 ) 3 (n=8 or 18). Because crevice corrosion occurred at the initial stage of immersion in the solution preferentially, the edge of electrode covered with the polymer film was coated with epoxy resin. The open-circuit potentials of the covered electrodes in the solution were maintained high, more than -0.2V/SCE for several hours, indicating that no breakdown of the passive film occurred on the surface. The protective efficiencies of the films were extremely high, more than 99.9% unless the passive film was broken down. The efficiencies after immersion for 24h almost agreed with those obtained by mass-loss measurements. X-ray photoelectron spectroscopy and electron-probe microanalysis of the passivated surface covered with the polymer film after immersion in the solution for 4h revealed that pit initiation on the passive film was suppressed by coverage with the polymer film completely

Synthesis and organisation of poly-substituted porphyrins in thin films for the elaboration of a highly conjugated 2D polymer

International Nuclear Information System (INIS)

Da Cruz, Fernande

1997-01-01

This research thesis addresses the production and characterization of organic thin layers for the elaboration of a wholly conjugated bi-dimensional polymer. The author first reports the synthesis of molecules belonging to the substituted porphyrin family substituted by reactive functions (acetylenic and thiophene functions). He reports how these molecules are organised under the form of a plane paving by using the Langmuir-Blodgett (LB) technique and self-assembly. It has been possible to obtain steady and organised LB films from one the synthesized porphyrins. A new method of organisation based on self-assembly has been developed, and allowed polymerizable organised porphyrin single layers to be obtained. This opens a promising way to the production of the bi-dimensional polymer. Thin films have been characterized by UV-visible spectrophotometry, IR spectrometry, X-ray diffraction, and linear dichroism [fr

Selective enhancement of Selényi rings induced by the cross-correlation between the interfaces of a two-dimensional randomly rough dielectric film

Science.gov (United States)

Banon, J.-P.; Hetland, Ø. S.; Simonsen, I.

2018-02-01

By the use of both perturbative and non-perturbative solutions of the reduced Rayleigh equation, we present a detailed study of the scattering of light from two-dimensional weakly rough dielectric films. It is shown that for several rough film configurations, Selényi interference rings exist in the diffusely scattered light. For film systems supported by dielectric substrates where only one of the two interfaces of the film is weakly rough and the other planar, Selényi interference rings are observed at angular positions that can be determined from simple phase arguments. For such single-rough-interface films, we find and explain by a single scattering model that the contrast in the interference patterns is better when the top interface of the film (the interface facing the incident light) is rough than when the bottom interface is rough. When both film interfaces are rough, Selényi interference rings exist but a potential cross-correlation of the two rough interfaces of the film can be used to selectively enhance some of the interference rings while others are attenuated and might even disappear. This feature may in principle be used in determining the correlation properties of interfaces of films that otherwise would be difficult to access.

The type specimen (LB1) of Homo floresiensis did not have Laron syndrome.

Science.gov (United States)

Falk, Dean; Hildebolt, Charles; Smith, Kirk; Jungers, William; Larson, Susan; Morwood, Michael; Sutikna, Thomas; Jatmiko; Saptomo, E Wahyu; Prior, Fred

2009-09-01

The type specimen (LB1) of Homo floresiensis has been hypothesized to be a pathological human afflicted with Laron Syndrome (LS), a type of primary growth hormone insensitivity (Hershkovitz et al.: Am J Phys Anthropol 134 [2007] 198-208). Comparing measurements, photographs and three-dimensional, computed-tomography reconstructions of LB1 with data and diagnoses from the literature on LS, we critically evaluate numerous skull and postcranial traits that Hershkovitz et al. identified as being shared by LB1 and patients with LS. The statements regarding most of these traits are new to the clinical literature and lack quantitative support. LB1 and patients with LS differ markedly in the size and shape of the cranium; thickness and pneumatization of cranial bones; morphology of the face, mandible, teeth, and chin; form of the shoulder, wrist, and pelvis; and general body proportions including relative foot size. Claims that patients with LS are similar to LB1 in displaying protracted scapulae, short clavicles, low degrees of humeral torsion, flaring ilia, and curved tibiae are not supported by data or corroborating images. Some points of similarity (e.g., femoral neck-shaft angle, femoral bicondylar angle, and estimated stature) can be found in other hominins, and cannot be considered diagnostic. From our review and analysis, we conclude that LB1 did not suffer from LS. Copyright 2009 Wiley-Liss, Inc.

Nanostructured hybrid films containing nanophosphor: Fabrication and electronic spectral properties

Energy Technology Data Exchange (ETDEWEB)

Camacho, S.A. [Instituto de Biociencias, Letras e Ciencias Exatas, UNESP - Univ Estadual Paulista, Rua Cristovao Colombo, 2265, 15054-000 Sao Jose do Rio Preto, SP (Brazil); Aoki, P.H.B.; Constantino, C.J.L. [Faculdade de Ciencias e Tecnologia, UNESP - Univ Estadual Paulista, Rua Roberto Simonsen, 305, 19060-900 Presidente Prudente, SP (Brazil); Aroca, R.F. [Materials and Surface Science Group, University of Windsor, Windsor, Ont., Canada N9B3P4 (Canada); Pires, A.M., E-mail: anapires@fct.unesp.br [Faculdade de Ciencias e Tecnologia, UNESP - Univ Estadual Paulista, Rua Roberto Simonsen, 305, 19060-900 Presidente Prudente, SP (Brazil)

2012-11-15

Highlights: Black-Right-Pointing-Pointer Hybrid film containing the cationic polyelectrolyte PAH and Y{sub 2}O{sub 3}: Er, Yb nanophosphor. Black-Right-Pointing-Pointer LbL film growth was monitored by absorbance x concentration in UV-Vis absorption. Black-Right-Pointing-Pointer FTIR indicated existence of secondary interactions between PAH - nanophosphor layers. Black-Right-Pointing-Pointer The morphology and the spatial distribution of the LbL film were analyzed by Raman. Black-Right-Pointing-Pointer We observed intense electronic emission lines from doping ions in the micro-Raman. - Abstract: The intensive research of the optical properties of rare-earth ions is due to the high quantum efficiency of their emission, very narrow bands, and excellent fluorescence monochromaticity. The photoluminescence data presented here show that the nanophosphor remains a green emitter in Layer-by-Layer (LbL) films leading to potential application in optical devices or biological labeling. The LbL technique, an established method for thin film fabrication with molecular architecture control, is used in the manufacture of a hybrid film containing the cationic polyelectrolyte poly (allylamine hydrochloride) (PAH) and Y{sub 2}O{sub 3}: Er, Yb nanophosphor. The spectroscopic properties of this luminescent nanomaterial are extracted from the spectral data of the powder, cast film and LbL films. The growth of the LbL film was monitored by absorbance versus concentration plots in ultraviolet-visible (UV-Vis) absorption spectroscopy. The presence of both PAH and nanophosphor in the LbL film was confirmed by Fourier transform infrared (FTIR) absorption spectroscopy. The FTIR data also ruled out the existence of chemical interactions between the PAH and nanophosphor layers, which means that secondary interactions (like Van der Waals forces) might be the driving forces for LbL film growth. The morphology and the spatial distribution of the LbL film components along the film surface were

Two-dimensional turning of thermal flux from normal to lateral propagation in thin metal film irradiated by femtosecond laser pulse

Science.gov (United States)

Shepelev, V. V.; Inogamov, N. A.

2018-01-01

There are various geometrical variants of laser illumination and target design. Important direction of investigations is connected with tightly focused action (spot size may be less than micron) onto a thin metal film: thickness of a film is just few skin-layer depths. Duration of a pulse is τ L ˜ 0.1 ps. In these conditions energy absorbed in a skin layer first propagates normally to a surface: gradient ∂Te /∂x dominates, here and below x and y are normal and lateral directions. This process in 1-2 ps homogenizes electron temperature T e along thickness of a film. We consider conditions when a film or is supported by weakly conducting substrate, or is free standing. Therefore all absorbed energy is confined inside the film. At the next stage the internal energy begin to flow along the lateral direction—thus direction of energy expansion is changed from x to y because of the heat non-penetrating boundary condition imposed on the rear-side of the film. At the short two-temperature stage of lateral expansion the thermal conductivity κ is high. After that electron and ion temperatures equilibrates and later on the heat propagates with usual value of κ. Lateral expansion cools down the hot spot on long time scales and finally the molten spot recrystallizes. Two-dimensional approach allows us to consider all these stages from propagation in x direction (normal to a film) to propagation in y direction (along a film).

The composite phthalocyanine-based Langmuir-Blodgett films: structural peculiarities and NO-sensitive properties

Energy Technology Data Exchange (ETDEWEB)

Emelianov, I.L.; Khatko, V.V. [Nat. Acad. of Sci., Minsk (Belarus). Phys. Tech. Inst.

1999-10-08

Surface pressure versus area per molecule isotherms of the Langmuir monolayers of copper tetra-tert-butyl phthalocyanine (abbreviated as CuTTBPc), arachidic acid (abbreviated as AA), and their mixtures were measured depending upon the film component ratio and ionic content of the subphase. Substantial deviations of the mixed monolayer behaviour from an ideal one, which is characteristic of fully immiscible compounds forming separate surface domains on the liquid subphase, were observed if the molar fraction of AA in mixed monolayers exceeded 50%. This abnormality in the monolayer behaviour correlated with the drastic changes in the kinetics responses to NO gas of the sensors based on the mixed Langmuir-Blodgett (LB) films. The comparison and analysis of the results obtained suggest that the gas-sensitive properties of the two-component LB films are determined by two features of their structure, namely, hole-like defects existing in the AA matrix and interlayer cavities. The corresponding structure model of the mixed films is proposed. The results obtained may be useful for understanding the gas-sensitive mechanism of the composite phthalocyanine-based LB films. (orig.)

Characterization of Langmuir and Langmuir–Blodgett films of an octasubstituted zinc phthalocyanine

International Nuclear Information System (INIS)

Torrent-Burgués, J.; Cea, P.; Giner, I.; Guaus, E.

2014-01-01

In this work we report the fabrication of Langmuir and Langmuir–Blodgett (LB) films of a substituted ZnPc (octakis(oxyoctyl)phthalocyanine of zinc), and their characterization by means of several techniques. These characterization techniques include surface pressure (π-A) and surface potential (ΔV-A) isotherms as well as UV–vis Reflection spectroscopy and Brewster Angle Microscopy (BAM) for the films at the air–water interface together with UV–vis absorption and IR spectroscopies and Atomic Force Microscopy (AFM) for the LB films. The π-A and ΔV-A isotherms and BAM images indicate a phase transition at a surface pressure of ca. 9 mN/m and a multilayer formation at surface pressures around 19–20 mN/m; at a surface pressure around 27 mN/m a disordered collapse of the film occurs. In addition, AFM images of LB films at π = 10 mN/m and π = 20 mN/m show a monomolecular and a multilayered film, respectively. The comparison of the UV–vis spectrum of ZnPc in solution, the reflection spectra of the Langmuir films and UV–vis spectra of LB films reveals a significant reduction in the Q band intensity for the films, indicative of an organization of ZnPc in the Langmuir and LB films versus the random distribution in solution. The UV–vis Reflection spectra are also consistent with multilayer formation at surface pressures around 19–20 mN/m. The relative intensities of the IR spectrum bands change from the KBr pellet to the LB film which is also attributable to orientation effects in the film. Cyclic voltammetric experiments of LB films incorporating the ZnPc derivative show peaks that can be correlated with redox processes occurring in the phthalocyanine ring. A small but significant influence of the surface pressure and the number of deposited layers in the electrochemical behaviour is observed. The electrochemical response of cast films exhibits some differences with respect to that of LB films which have been attributed to their different molecular

Characterization of Langmuir and Langmuir–Blodgett films of an octasubstituted zinc phthalocyanine

Energy Technology Data Exchange (ETDEWEB)

Torrent-Burgués, J. [Department of Chemical Engineering, Universitat Politècnica de Catalunya (UPC), C/Colom 1, 08222 Terrassa, Barcelona (Spain); Institut de Bioenginyeria de Catalunya (IBEC), 08028 Barcelona (Spain); Cea, P. [Departamento de Química Orgánica y Química Física, Facultad de Ciencias, Universidad de Zaragoza, 50009 Zaragoza (Spain); Instituto de Nanociencia de Aragón (INA) y Laboratorio de Microscopias Avanzadas (LMA), Edificio i+d, Campus Rio Ebro, Universidad de Zaragoza, C/Mariano Esquillor, s/n, 50017 Zaragoza (Spain); Giner, I. [Departamento de Química Orgánica y Química Física, Facultad de Ciencias, Universidad de Zaragoza, 50009 Zaragoza (Spain); Guaus, E. [Department of Chemical Engineering, Universitat Politècnica de Catalunya (UPC), C/Colom 1, 08222 Terrassa, Barcelona (Spain)

2014-04-01

In this work we report the fabrication of Langmuir and Langmuir–Blodgett (LB) films of a substituted ZnPc (octakis(oxyoctyl)phthalocyanine of zinc), and their characterization by means of several techniques. These characterization techniques include surface pressure (π-A) and surface potential (ΔV-A) isotherms as well as UV–vis Reflection spectroscopy and Brewster Angle Microscopy (BAM) for the films at the air–water interface together with UV–vis absorption and IR spectroscopies and Atomic Force Microscopy (AFM) for the LB films. The π-A and ΔV-A isotherms and BAM images indicate a phase transition at a surface pressure of ca. 9 mN/m and a multilayer formation at surface pressures around 19–20 mN/m; at a surface pressure around 27 mN/m a disordered collapse of the film occurs. In addition, AFM images of LB films at π = 10 mN/m and π = 20 mN/m show a monomolecular and a multilayered film, respectively. The comparison of the UV–vis spectrum of ZnPc in solution, the reflection spectra of the Langmuir films and UV–vis spectra of LB films reveals a significant reduction in the Q band intensity for the films, indicative of an organization of ZnPc in the Langmuir and LB films versus the random distribution in solution. The UV–vis Reflection spectra are also consistent with multilayer formation at surface pressures around 19–20 mN/m. The relative intensities of the IR spectrum bands change from the KBr pellet to the LB film which is also attributable to orientation effects in the film. Cyclic voltammetric experiments of LB films incorporating the ZnPc derivative show peaks that can be correlated with redox processes occurring in the phthalocyanine ring. A small but significant influence of the surface pressure and the number of deposited layers in the electrochemical behaviour is observed. The electrochemical response of cast films exhibits some differences with respect to that of LB films which have been attributed to their different molecular

Influence of the Fin on Two-Dimensional Characteristics of Dispersed Flow With Wall Liquid Film in the Vicinity of Obstacle

International Nuclear Information System (INIS)

Stosic, Zoran V.; Stevanovic, Vladimir D.; Serizawa, Akimi

2002-01-01

Spacers have positive effects on the heat transfer enhancement and critical heat flux (CHF) increase downstream of their location in the boiling channel. These effects are further increased by the inclusion of the fin on the spacer rear edge. Numerical simulation of a separation in a high void gas phase and dispersed droplets flow around a spacer, with a liquid film flowing on the wall, is performed. Mechanisms leading to the CHF increase due to the two-phase flow separation and liquid film thickening downstream the spacer are demonstrated. Numerical simulations of gas phase, entrained droplets and wall liquid film flows were performed with the three-fluid model and with the application of the high order numerical scheme for the liquid film surface interface tracking. Predicted is a separation of gas and entrained droplets streams around the spacer without and with a fin inclined 30 and 60 degrees to the wall, as well as a change of wall liquid film thickness in the vicinity of spacer. Results of liquid film dynamic behaviour are compared with the recently obtained experimental results. Multi-dimensional characteristics of surface waves on the liquid film were measured with newly developed ultrasonic transmission technique in a 3 3 rod bundle test section with air-water flow under atmospheric conditions. Obtained numerical results are in good agreement with experimental observations. The presented investigation gives insight into the complex mechanisms of separated two-phase flow with wall liquid film around the spacer and support thermal-hydraulic design and optimisation of flow obstacles in various thermal equipment. (authors)

Quantum transport in new two-dimensional heterostructures: Thin films of topological insulators, phosphorene

Science.gov (United States)

Majidi, Leyla; Zare, Moslem; Asgari, Reza

2018-06-01

The unusual features of the charge and spin transport characteristics are investigated in new two-dimensional heterostructures. Intraband specular Andreev reflection is realized in a topological insulator thin film normal/superconducting junction in the presence of a gate electric field. Perfect specular electron-hole conversion is shown for different excitation energy values in a wide experimentally available range of the electric field and also for all angles of incidence when the excitation energy has a particular value. It is further demonstrated that the transmission probabilities of the incoming electrons from different spin subbands to the monolayer phosphorene ferromagnetic/normal/ferromagnetic (F/N/F) hybrid structure have different behavior with the angle of incidence and perfect transmission occurs at defined angles of incidence to the proposed structure with different length of the N region, and different alignments of magnetization vectors. Moreover, the sign change of the spin-current density is demonstrated by tuning the chemical potential and exchange field of the F region.

Surface Reconstruction-Induced Coincidence Lattice Formation Between Two-Dimensionally Bonded Materials and a Three-Dimensionally Bonded Substrate

NARCIS (Netherlands)

Boschker, Jos E.; Momand, Jamo; Bragaglia, Valeria; Wang, Ruining; Perumal, Karthick; Giussani, Alessandro; Kooi, Bart J.; Riechert, Henning; Calarco, Raffaella

Sb2Te3 films are used for studying the epitaxial registry between two-dimensionally bonded (2D) materials and three-dimensional bonded (3D) substrates. In contrast to the growth of 3D materials, it is found that the formation of coincidence lattices between Sb2Te3 and Si(111) depends on the geometry

Continuous Reduced Graphene Oxide Film Prepared by Stitching of Nanosheets at the Interface of Two Immiscible Solutions

International Nuclear Information System (INIS)

Sohn, Young Ku; Kim, Seog K.; Min, Bong Ki

2011-01-01

RGO sheets dispersed in water are prepared by chemical reduction of GO using ascorbic acid. By mixing and sonication of submicron-size RGO sheets in two immiscible liquids (e. g., chloroform and water) for the first time we have prepared a continuous large-area RGO film at the interface. In other words, we have shown that aggregated RGO sheets could be fully stretched at the interface to form a continuous film. The RGO film has been characterized by SEM, TEM, UV-vis absorption, XPS and Raman. The film exhibits high flexibility, transparency, and very long-term stability without forming aggregations. Without requiring vapor deposition, a special instrument, or a filtration followed by a removing the filter paper one could easily achieve a continuous RGO-film in any laboratories. Our solution-based method is much simpler and cost-effective, and very good for large scale mass production. This finding could boost real applications of graphene in laboratory and industry, and provide a new methodology for the fabrication of large-area continuous graphene films. Graphene, an atom-thick two-dimensional (2D) honeycomb lattice sheet of sp 2 -bonded carbon atoms, has recently been emerged as a new promising material in various fields. Because of its gigantic charge carrier mobility it could be applied to field-effect transistors as a substitute of silicon. Due to its transparency and high electrical conductivity, it could be used as a substitute of ITO electrode in solar cells and light-emitting diodes. Other superior properties include large surface area, flexibility, strength, stiffness, and thermal conductivity. These provides wide applications of graphene including supercapa-citor, battery, sensor, storage and drug delivery. For real applications, large-scale of graphene sheets or films needs to be prepared. Large-area (orders of centimeters) graphene films have recently been fabricated using a chemical vapor deposition (CVD) method on various metal substrates. This

Microscopic and spectroscopic properties of Langmuir–Blodgett films composed of flavins and their aggregation structures

International Nuclear Information System (INIS)

Lim, Jong Kuk; Jo, Jihee; Jang, Dasol; Jang, Hyeong Ju

2015-01-01

Isoalloxazine derivatives (flavins) are commonly found in natural systems that are involved in an electron transfer process, such as photosynthetic or metabolic systems, and are also frequently used as electron donors in organic-based electronic devices. As an example, molecular photodiodes composed of 7,8-dimethyl-10-dodecyl isoalloxazine (DDI) have been fabricated by the Langmuir–Blodgett (LB) technique, and such devices showed characteristic properties of photodiodes. The efficiency of molecular photodiodes is dependent on the assembled structure of the LB films, which is related to the morphology of the LB films. For that reason, Lim has investigated the morphology of LB films, and found that rod-shaped domains are formed when a DDI monolayer is transferred to a solid substrate above a specific surface pressure (Thin Solid Films, 531 (2013) 499). In that paper, rod-shaped domains were revealed to be collapsed triple layers, i.e., double layers collapsed on the monolayer; however, the detailed aggregation structure of the constituent molecules (DDI) has not been studied. Herein, we investigate the microscopic and spectroscopic properties of LB films composed of DDI. We apply the extended dipole model to explain spectral changes in the absorption spectra and propose an aggregation structure for DDI in the LB films. - Highlights: • Aggregation structure of DDI in LB films was experimentally investigated. • Theoretical estimation is in good agreement with experimental result. • Molecular aggregation structure for DDI in LB films was proposed. • Molecular configuration in LB films is changed from side-by-side to face-to-face.

Layer-by-layer films for biomedical applications

CERN Document Server

Picart, Catherine; Voegel, Jean-Claude

2015-01-01

The layer-by-layer (LbL) deposition technique is a versatile approach for preparing nanoscale multimaterial films: the fabrication of multicomposite films by the LbL procedure allows the combination of literally hundreds of different materials with nanometer thickness in a single device to obtain novel or superior performance. In the last 15 years the LbL technique has seen considerable developments and has now reached a point where it is beginning to find applications in bioengineering and biomedical engineering. The book gives a thorough overview of applications of the LbL technique in the c

Damping kinetics of annihilation slowed fluorescence of aromatic molecules in Langmuir films

International Nuclear Information System (INIS)

Ibraev, N.Kh.; Latonin, V.A.; Satybaldina, D.Zh.

1996-01-01

The paper is devoted to study of decay mechanism of phosphors molecules triplet states in the Langmuir-Blogett (L-B) films. The L-B-films have being prepared on the base of anthracene, pyrene, 3,4-benzopyrene and 1,2-benzanthracene molecules. Spectral and kinetic investigations were carried out in photons counting regime. Long-lived luminescence was observed under excitation of the LB-film by nitrogen laser radiation (λ=337 nm) .Spectrum of the long-lived luminescence coincides with spectrum of fast fluorescence of same film. Received spectral data indicate on similarity of LB-films structure of aromatic molecules and its crystals. It was defined, that deactivation of triplet states of aromatic molecules in LB-films has being carried out mainly in the result of annihilation of triplet excitation. 14 refs., 2 tabs., 5 figs

Model of two-dimensional electron gas formation at ferroelectric interfaces

Energy Technology Data Exchange (ETDEWEB)

Aguado-Puente, P.; Bristowe, N. C.; Yin, B.; Shirasawa, R.; Ghosez, Philippe; Littlewood, P. B.; Artacho, Emilio

2015-07-01

The formation of a two-dimensional electron gas at oxide interfaces as a consequence of polar discontinuities has generated an enormous amount of activity due to the variety of interesting effects it gives rise to. Here, we study under what circumstances similar processes can also take place underneath ferroelectric thin films. We use a simple Landau model to demonstrate that in the absence of extrinsic screening mechanisms, a monodomain phase can be stabilized in ferroelectric films by means of an electronic reconstruction. Unlike in the LaAlO3/SrTiO3 heterostructure, the emergence with thickness of the free charge at the interface is discontinuous. This prediction is confirmed by performing first-principles simulations of free-standing slabs of PbTiO3. The model is also used to predict the response of the system to an applied electric field, demonstrating that the two-dimensional electron gas can be switched on and off discontinuously and in a nonvolatile fashion. Furthermore, the reversal of the polarization can be used to switch between a two-dimensional electron gas and a two-dimensional hole gas, which should, in principle, have very different transport properties. We discuss the possible formation of polarization domains and how such configuration competes with the spontaneous accumulation of free charge at the interfaces.

Study of magnetic materials in Langmuir-Blodgett films

International Nuclear Information System (INIS)

Coronel, Philippe

1990-01-01

As one of the key issue in molecular electronics is the fabrication of organised systems with specific properties born by molecules, one of these properties being the possibility of information storage, this research thesis reports an exploratory study based on the development of a magnetic complex in a two-dimensional organisation in order to obtain a molecular magnetic memory. For this purpose, the chosen property for the complex was the molecular bi-stability which is a characteristic of magnetic materials which display a spin transition phenomenon. Two types of complex families have been studied: [(Phenanthroline)_2Fe'' (NCS)_2] and [Fe''' (8-quinolyl-salicyl-aldimine)_2](X''). The fabrication of a two-dimensional organised system is performed by using the Langmuir-Blodgett technique. With this technique, three synthesis ways are considered: an in-situ synthesis, a semi-amphiphilic way, and an amphiphilic way. Within this research, the author tried to see whether the existence of 3D (powder) spin transition phenomenon was transposable in 2D (case of a LB film) [fr

Molecular recognition applied to gas detection: the contribution of Langmuir-Blodgett films

International Nuclear Information System (INIS)

Clemendot, Sylvain

1992-01-01

In the first part of this research thesis, the author presents the Langmuir-Blodgett technique and outlines how it can face the challenge of molecular electronics. Then, he proposes an overview of the state-of-the-art of chemical sensors based on LB films, and an assessment of the state of the art of conductive LB films based on TCNQ (tetracyanoquinodimethane) and on tetrathiafulvalene for which the author proposes a modelling. He describes how phosphine sensors with varying conductivity based on TCNQ-based conductive LB films have been developed and reports the study of electric performance of these sensors. He describes and compares mechanisms of interaction of phosphine with conductive LB films for films based on TCNQ and those based on tetrathiafulvalene [fr

Complete protection of a passive film on iron from breakdown in a borate buffer containing 0.1M of Cl- by coverage with an ultrathin film of two-dimensional polymer

International Nuclear Information System (INIS)

Aramaki, Kunitsugu; Shimura, Tadashi

2006-01-01

An ultrathin film of two-dimensional polymer was prepared on a passivated iron electrode by modification of a 16-hydroxyhexadecanoate ion HO(CH 2 ) 15 CO 2 - self-assembled monolayer with 1,2-bis(triethoxysilyl)ethane (C 2 H 5 O) 3 Si(CH 2 ) 2 Si(OC 2 H 5 ) 3 and octadecyltriethoxysilane C 18 H 37 Si(OC 2 H 5 ) 3 . This film prevented passive film breakdown examined by potentiodynamic anodic polarization of the coated electrode in the borate buffer solution containing 0.1M of Cl - . Neither current spikes nor the pitting potential was observed in the passive and transpassive regions of polarization curve. The anodic current density was decreased in these regions markedly, implying hindrance to permeation of Cl - and water through the film. Structure of the film was clarified by X-ray photoelectron and FTIR reflection spectroscopies and contact angle measurement with a drop of water. Electron-probe microanalysis of the passivated surface coated with the film after anodic polarization scanning up to the transpassive region revealed that the polymer film prevents pit initiation by an attack on the passive film with Cl -

Electrochemical properties of carbon nanotubes-hydrogenase conjugates Langmuir-Blodgett films

International Nuclear Information System (INIS)

Liu, Ai-Rong; Wakayama, Tatsuki; Nakamura, Chikashi; Miyake, Jun; Zorin, Nikolay A.; Qian, Dong-Jin

2007-01-01

We report the preparation of Langmuir-Blodgett (LB) films composed of oxidized carbon nanotubes (CNTs) and hydrogenase (H 2 ase) conjugates and their electrochemical properties. Both single-walled (SWNTs) and multi-walled CNTs (MWNTs) were used to form mixed monolayers with H 2 ase on the Tris-HCl subphase surfaces. By using the LB method, the CNTs-H 2 ase monolayers were transferred onto CaF 2 and indium tin oxide (ITO) electrode surfaces. The LB film modified electrodes showed a couple of waves centered at around -500 mV (versus Ag/AgCl), which corresponding to the redox reaction of [4Fe-4S] 2+/1+ clusters in the H 2 ase. The current intensity was enhanced after co-assembly with CNTs. Because of the different diameters of CNTs, this current intensity was proportional to the scan rate (υ) for the electrodes modified with the LB films of pure H 2 ase and SWNTs-H 2 ase, but to the root of scan rate (υ 1/2 ) for those modified with the MWNTs-H 2 ase LB film. The products of diffusion coefficient and concentration (D 1/2 C) increased in the order of pure H 2 ase, SWNTs-H 2 ase, and MWNTs-H 2 ase LB films

Hydrokinetic simulations of nanoscopic precursor films in rough channels

International Nuclear Information System (INIS)

Chibbaro, S; Biferale, L; Binder, K; Milchev, A; Dimitrov, D; Diotallevi, F; Succi, S

2009-01-01

We report on simulations of capillary filling of highly wetting fluids in nanochannels with and without obstacles. We use atomistic (molecular dynamics) and hydrokinetic (lattice Boltzmann; LB) approaches which indicate clear evidence of the formation of thin precursor films, moving ahead of the main capillary front. The dynamics of the precursor films is found to obey a square-root law like that obeyed by the main capillary front, z 2 (t)∝t, although with a larger prefactor, which we find to take the same value for the different geometries (2D–3D) under inspection. The two methods show a quantitative agreement which indicates that the formation and propagation of thin precursors can be handled at a mesoscopic/hydrokinetic level. This can be considered as a validation of the LB method and opens the possibility of using hydrokinetic methods to explore space–time scales and complex geometries of direct experimental relevance. Then, the LB approach is used to study the fluid behaviour in a nanochannel when the precursor film encounters a square obstacle. A complete parametric analysis is performed which suggests that thin-film precursors may have an important influence on the efficiency of nanochannel-coating strategies

Comparing Short- and Long-Term Learning Effects between Stereoscopic and Two-Dimensional Film at a Planetarium

Science.gov (United States)

Price, C. Aaron; Lee, Hee-Sun; Subbarao, Mark; Kasal, Evan; Aguileara, Julieta

2015-01-01

Science centers such as museums and planetariums have used stereoscopic ("three-dimensional") films to draw interest from and educate their visitors for decades. Despite the fact that most adults who are finished with their formal education get their science knowledge from such free-choice learning settings very little is known about the…

Direct Reconstruction of Two-Dimensional Currents in Thin Films from Magnetic-Field Measurements

Science.gov (United States)

Meltzer, Alexander Y.; Levin, Eitan; Zeldov, Eli

2017-12-01

An accurate determination of microscopic transport and magnetization currents is of central importance for the study of the electric properties of low-dimensional materials and interfaces, of superconducting thin films, and of electronic devices. Current distribution is usually derived from the measurement of the perpendicular component of the magnetic field above the surface of the sample, followed by numerical inversion of the Biot-Savart law. The inversion is commonly obtained by deriving the current stream function g , which is then differentiated in order to obtain the current distribution. However, this two-step procedure requires filtering at each step and, as a result, oversmooths the solution. To avoid this oversmoothing, we develop a direct procedure for inversion of the magnetic field that avoids use of the stream function. This approach provides enhanced accuracy of current reconstruction over a wide range of noise levels. We further introduce a reflection procedure that allows for the reconstruction of currents that cross the boundaries of the measurement window. The effectiveness of our approach is demonstrated by several numerical examples.

Two-dimensional superconducting state of monolayer Pb films grown on GaAs(110) in a strong parallel magnetic field.

Science.gov (United States)

Sekihara, Takayuki; Masutomi, Ryuichi; Okamoto, Tohru

2013-08-02

Two-dimensional (2D) superconductivity was studied by magnetotransport measurements on single-atomic-layer Pb films on a cleaved GaAs(110) surface. The superconducting transition temperature shows only a weak dependence on the parallel magnetic field up to 14T, which is higher than the Pauli paramagnetic limit. Furthermore, the perpendicular-magnetic-field dependence of the sheet resistance is almost independent of the presence of the parallel field component. These results are explained in terms of an inhomogeneous superconducting state predicted for 2D metals with a large Rashba spin splitting.

Phase transition of LB films of mixed diblock copolymer at the air/water interface

Science.gov (United States)

Seo, Y. S.; Kim, K. S.; Samuilov, V.; Rafailovich, M. H.; Sokolov, J.; Lammertink, Rob G. H.; Vancso, G. J.

2000-03-01

We have studied the morphology of Langmuir blodgett films at the air/water interface of mixed diblock copolymer films. Solutions of poly(styrene-b-ferrocenyldimethylsilane) and PS-b-P2VP mixed in a ratio of 20/80 in chloroform were spread at the air/water interface. The morphology of the films was studied with AFM as a function of the surface pressure and the diblock copolymer molecular weight. The results show that the two diblock copolymers can be induced to mix at the air/water interface with increasing surface pressure. A reversible transition from spherical to cylindrical morphologies is induced in the mixture which can not be observed in films formed of the two components separately. The effective surface phase diagram as a function of block copolymer composition and pressure will be presented.

Spray layer-by-layer films based on phospholipid vesicles aiming sensing application via e-tongue system

International Nuclear Information System (INIS)

Aoki, P.H.B.; Volpati, D.; Cabrera, F.C.; Trombini, V.L.; Riul, A.; Constantino, C.J.L.

2012-01-01

The Layer-by-Layer (LbL) technique via spraying (spray-LbL) has been applied as new and alternative methodology to fabricate ultrathin films due to its versatility in relation to the conventional dipping-LbL method, mainly in terms of faster layer deposition and larger coated area. In this work, the possibility of immobilizing vesicles of dipalmitoyl phosphatidyl glycerol (DPPG) phospholipid onto alternating layers of the polyelectrolyte poly(allylamine hydrochloride) (PAH) using the spray-LbL method was investigated, being the results compared to the conventional dipping-LbL method. The growth of (PAH/DPPG) n spray-LbL films was systematically monitored by quartz crystal microbalance (QCM) and ultraviolet–visible (UV–vis) absorption spectroscopy, revealing a linear increase of the absorbance vs deposited layers. In relation to a possible electrostatic interaction between the groups PO 4 − (DPPG) and NH 3 + (PAH), it was observed through Fourier transform infrared (FTIR) absorption spectroscopy that the spectrum recorded for the spray-LbL film is basically a simple superposition of the FTIR spectra from PAH and DPPG casting films. The latter indicates a weak interaction between both materials, differently of the trend observed for (PAH/DPPG) n grown via dipping-LbL method. Atomic force microscopy (AFM) images of spray-LbL films showed evidences that the DPPG vesicles present in the aqueous dispersion are not destroyed when submitted to pressure conditions during the spray deposition. However, comparing to dipping-LbL, the DPPG vesicles do not cover completely the PAH layer for the spray-LbL film, which was further confirmed by surface-enhanced Raman scattering (SERS) measurements. Moreover, the AFM analysis showed that the spray-LbL deposition led to thicker PAH/DPPG bilayers in average than via dipping-LbL for the same concentrations of PAH solution and DPPG dispersion, which is consistent with QCM and UV–vis absorption results. PAH/DPPG films deposited by

Cloning strategies for heterologous expression of the bacteriocin enterocin A by Lactobacillus sakei Lb790, Lb. plantarum NC8 and Lb. casei CECT475.

Science.gov (United States)

Jiménez, Juan J; Diep, Dzung B; Borrero, Juan; Gútiez, Loreto; Arbulu, Sara; Nes, Ingolf F; Herranz, Carmen; Cintas, Luis M; Hernández, Pablo E

2015-10-15

Bacteriocins produced by lactic acid bacteria (LAB) attract considerable interest as natural and nontoxic food preservatives and as therapeutics whereas the bacteriocin-producing LAB are considered potential probiotics for food, human and veterinary applications, and in the animal production field. Within LAB the lactobacilli are increasingly used as starter cultures for food preservation and as probiotics. The lactobacilli are also natural inhabitants of the gastrointestinal (GI) tract and attractive vectors for delivery of therapeutic peptides and proteins, and for production of bioactive peptides. Research efforts for production of bacteriocins in heterologous hosts should be performed if the use of bacteriocins and the LAB bacteriocin-producers is ever to meet the high expectations deposited in these antimicrobial peptides. The recombinant production and functional expression of bacteriocins by lactobacilli would have an additive effect on their probiotic functionality. The heterologous production of the bacteriocin enterocin A (EntA) was evaluated in different Lactobacillus spp. after fusion of the versatile Sec-dependent signal peptide (SP usp45 ) to mature EntA plus the EntA immunity gene (entA + entiA) (fragment UAI), and their cloning into plasmid vectors that permitted their inducible (pSIP409 and pSIP411) or constitutive (pMG36c) production. The amount, antimicrobial activity (AA) and specific antimicrobial activity (SAA) of the EntA produced by Lactobacillus sakei Lb790, Lb. plantarum NC8 and Lb. casei CECT475 transformed with the recombinant plasmids pSIP409UAI, pSIP411UAI and pMGUAI varied depending of the expression vector and the host strain. The Lb. casei CECT475 recombinant strains produced the largest amounts of EntA, with the highest AA and SAA. Supernatants from Lb. casei CECT (pSIP411UAI) showed a 4.9-fold higher production of EntA with a 22.8-fold higher AA and 4.7-fold higher SAA than those from Enterococcus faecium T136, the natural

Craniometric ratios of microcephaly and LB1, Homo floresiensis, using MRI and endocasts

Science.gov (United States)

Vannucci, Robert C.; Barron, Todd F.; Holloway, Ralph L.

2011-01-01

The designation of Homo floresiensis as a new species derived from an ancient population is controversial, because the type specimen, LB1, might represent a pathological microcephalic modern Homo sapiens. Accordingly, two specific craniometric ratios (relative frontal breadth and cerebellar protrusion) were ascertained in 21 microcephalic infants and children by using MRI. Data on 118 age-equivalent control (normocephalic) subjects were collected for comparative purposes. In addition, the same craniometric ratios were determined on the endocasts of 10 microcephalic individuals, 79 normal controls (anatomically modern humans), and 17 Homo erectus specimens. These ratios were then compared with those of two LB1 endocasts. The findings showed that the calculated cerebral/cerebellar ratios of the LB1 endocast [Falk D, et al. (2007) Proc Natl Acad Sci USA 104:2513–2518] fall outside the range of living normocephalic individuals. The ratios derived from two LB1 endocasts also fall largely outside the range of modern normal human and H. erectus endocasts and within the range of microcephalic endocasts. The findings support but do not prove the contention that LB1 represents a pathological microcephalic Homo sapiens rather than a new species, (i.e., H. floresiensis). PMID:21825126

A Review on the Low-Dimensional and Hybridized Nanostructured Diamond Films

Directory of Open Access Journals (Sweden)

Hongdong Li

2015-01-01

Full Text Available In the last decade, besides the breakthrough of high-rate growth of chemical vapor deposited single-crystal diamonds, numerous nanostructured diamond films have been rapidly developed in the research fields of the diamond-based sciences and industrial applications. The low-dimensional diamonds of two-dimensional atomic-thick nanofilms and nanostructural diamond on the surface of bulk diamond films have been theoretically and experimentally investigated. In addition, the diamond-related hybrid nanostructures of n-type oxide/p-type diamond and n-type nitride/p-type diamond, having high performance physical and chemical properties, are proposed for further applications. In this review, we first briefly introduce the three categories of diamond nanostructures and then outline the current advances in these topics, including their design, fabrication, characterization, and properties. Finally, we address the remaining challenges in the research field and the future activities.

Development of Functional Thin Polymer Films Using a Layer-by-Layer Deposition Technique.

Science.gov (United States)

Yoshida, Kentaro

2017-01-01

Functional thin films containing insulin were prepared using layer-by-layer (LbL) deposition of insulin and negatively- or positively-charged polymers on the surface of solid substrates. LbL films composed of insulin and negatively-charged polymers such as poly(acrylic acid) (PAA), poly(vinylsulfate) (PVS), and dextran sulfate (DS) were prepared through electrostatic affinity between the materials. The insulin/PAA, insulin/PVS, and insulin/DS films were stable in acidic solutions, whereas they decomposed under physiological conditions as a result of a change in the net electric charge of insulin from positive to negative. Interestingly, the insulin-containing LbL films were stable even in the presence of a digestive-enzyme (pepcin) at pH 1.4 (stomach pH). In contrast, LbL films consisting of insulin and positively-charged polymers such as poly(allylamine hydrochloride) (PAH) decomposed in acidic solutions due to the positive charges of insulin generated in acidic media. The insulin-containing LbL films can be prepared not only on the surface of flat substrates, such as quartz slides, but also on the surface of microparticles, such as poly(lactic acid) (PLA) microbeads. Thus, insulin-containing LbL film-coated PLA microbeads can be handled as a powder. In addition, insulin-containing microcapsules were prepared by coating LbL films on the surface of insulin-doped calcium carbonate (CaCO 3 ) microparticles, followed by dissolution of the CaCO 3 core. The release of insulin from the microcapsules was accelerated at pH 7.4, whereas it was suppressed in acidic solutions. These results suggest the potential use of insulin-containing microcapsules in the development of oral formulations of insulin.

Solution-Based Processing and Applications of Two-Dimensional Heterostructures

Science.gov (United States)

Hersam, Mark

Two-dimensional materials have emerged as promising candidates for next-generation electronics and optoelectronics, but advances in scalable nanomanufacturing are required to exploit this potential in real-world technology. This talk will explore methods for improving the uniformity of solution-processed two-dimensional materials with an eye toward realizing dispersions and inks that can be deposited into large-area thin-films. In particular, density gradient ultracentrifugation allows the solution-based isolation of graphene, boron nitride, montmorillonite, and transition metal dichalcogenides (e.g., MoS2, WS2, ReS2, MoSe2, WSe2) with homogeneous thickness down to the atomically thin limit. Similarly, two-dimensional black phosphorus is isolated in organic solvents or deoxygenated aqueous surfactant solutions with the resulting phosphorene nanosheets showing field-effect transistor mobilities and on/off ratios that are comparable to micromechanically exfoliated flakes. By adding cellulosic polymer stabilizers to these dispersions, the rheological properties can be tuned by orders of magnitude, thereby enabling two-dimensional material inks that are compatible with a range of additive manufacturing methods including inkjet, gravure, screen, and 3D printing. The resulting solution-processed two-dimensional heterostructures show promise in several device applications including photodiodes, anti-ambipolar transistors, gate-tunable memristors, and heterojunction photovoltaics.

Radicals as EPR probes of magnetization of gadolinium stearate Langmuir-Blodgett film

DEFF Research Database (Denmark)

Koksharov, Y.A.; Bykov, I.V.; Malakho, A.P.

2002-01-01

In the present work we have applied the method of the EPR spin probes which allows performing simultaneously EPR and magnetization measurements to the investigation of magnetism of the Cid stearate Langmuir-Blodgett (LB) films. For this purpose we have prepared and studied by the EPR technique...... the Gd and Y stearate LB films. Placing the small BDPA crystal on the film surface we have found that for the Gd LB sample the effective g-value of the radical's resonance depends on the film orientation in respect to the external magnetic field direction. The relative shift of the EPR signal...

Distance-dependent energy transfer between indole and anthracene moieties in Langmuir Blodgett films

Science.gov (United States)

Saha, D. C.; Bhattacharjee, D.; Misra, T. N.

1998-09-01

1,2-Diphenyl indole (DPI) and 9,10-diphenyl anthracene (DPA) are non-amphiphilic molecules but form excellent LB films when mixed with stearic acid (SA). Spectroscopic investigations of these films indicate formation of aggregates of DPI and DPA in the mixed LB films. DPA has been used as the quencher of the fluorescence of the DPI donor. Distance-dependent energy transfer between donor and acceptor monolayers in the LB film, where they can be precisely separated by inert spacers of stearic acid layers of varied thickness, is shown to satisfy Khun's quadratic equation. This suggests that the donor excitations are delocalized. The large critical transfer distance estimated from the experimental results has been attributed to the formation of aggregates of the molecules in a LB monolayer.

Stability of J-aggregated species in an indocarbocyanine dye in Langmuir–Blodgett Films

Energy Technology Data Exchange (ETDEWEB)

Debnath, Pintu [Thin film and Nanoscience Laboratory, Department of Physics, Tripura University, Suryamaninagar 799022, Tripura (India); Chakraborty, Santanu [Department of Physics, NIT Agartala, Jiraniya 799046, Tripura (India); Deb, Subrata [Department of Physics, Women' s College, Agartala 799001, Tripura (India); Nath, Jayasree [Department of Chemistry, Tripura University, Suryamaninagar 799022, Tripura (India); Dey, Bapi; Bhattacharjee, D. [Thin film and Nanoscience Laboratory, Department of Physics, Tripura University, Suryamaninagar 799022, Tripura (India); Hussain, Syed Arshad, E-mail: sa_h153@hotmail.com [Thin film and Nanoscience Laboratory, Department of Physics, Tripura University, Suryamaninagar 799022, Tripura (India)

2016-11-15

Here, the stability behaviour of J-aggregate of an indocarbocyanine dye 1,1′-Dioctadecyl-3,3,3′,3′-Tetramethylindocarbocynine perchlorate (DiI) in fatty acid mixed (X{sub DiI}=0.4) Langmuir–Blodgett (LB) films under different condition was reported. Surface pressure–area per molecule (π–A) isotherm measurement suggest that the molecular interaction between the constituent molecules changes with subphase temperature. UV–vis absorption and fluorescence spectroscopy and Atomic Force Microscopy (AFM) were used to study the stability behaviour. It has been observed that prominent J-aggregate of DiI occurred in the mixed films at subphase temperature 15 °C. With the passage of time as well as post heat treatment DiI J-aggregate decayed to excimer in both mono- and multilayer LB films. Total transition from J-aggregate to excimer occurred in monolayer films, whereas, the transition was partial in multilayer films. The stability of DiI J-aggregate in monolayer films was increased by two ways – (i) depositing the DiI-SA mixed LB films at higher surface pressure, (ii) exposing the films at 50 °C for 5 min. It has been observed that after heat treatment the DiI J-aggregate remained almost stable even after 200 days. AFM investigations gave the compelling visual evidences of the same.

Nonequilibrium dephasing in two-dimensional indium oxide films

International Nuclear Information System (INIS)

Ovadyahu, Z.

2001-01-01

We report on results of resistance R and magnetoresistance in diffusive indium oxide films measured down to T=0.28K. Analyzing the data using weak-localization theory shows that the phase-coherent time τ v ar-phi increases without bound as T->0. However, this result is obtained only when the voltage applied to the sample V is sufficiently small. When V is not small, τ v ar-phi may appear to 'saturate' while R continues to increase as T->0. Possible reasons for this intriguing behavior are discussed. It is argued that in out-of-equilibrium situations R(T) and τ v ar-phi(T) need not behave similarly. We suggest a heuristic picture, involving two-level systems, which might be consistent with our observations

Border-crossing model for the diffusive coarsening of two-dimensional and quasi-two-dimensional wet foams

Science.gov (United States)

Schimming, C. D.; Durian, D. J.

2017-09-01

For dry foams, the transport of gas from small high-pressure bubbles to large low-pressure bubbles is dominated by diffusion across the thin soap films separating neighboring bubbles. For wetter foams, the film areas become smaller as the Plateau borders and vertices inflate with liquid. So-called "border-blocking" models can explain some features of wet-foam coarsening based on the presumption that the inflated borders totally block the gas flux; however, this approximation dramatically fails in the wet or unjamming limit where the bubbles become close-packed spheres and coarsening proceeds even though there are no films. Here, we account for the ever-present border-crossing flux by a new length scale defined by the average gradient of gas concentration inside the borders. We compute that it is proportional to the geometric average of film and border thicknesses, and we verify this scaling by numerical solution of the diffusion equation. We similarly consider transport across inflated vertices and surface Plateau borders in quasi-two-dimensional foams. And we show how the d A /d t =K0(n -6 ) von Neumann law is modified by the appearance of terms that depend on bubble size and shape as well as the concentration gradient length scales. Finally, we use the modified von Neumann law to compute the growth rate of the average bubble area, which is not constant.

Photon management in two-dimensional disordered media.

Science.gov (United States)

Vynck, Kevin; Burresi, Matteo; Riboli, Francesco; Wiersma, Diederik S

2012-12-01

Elaborating reliable and versatile strategies for efficient light coupling between free space and thin films is of crucial importance for new technologies in energy efficiency. Nanostructured materials have opened unprecedented opportunities for light management, notably in thin-film solar cells. Efficient coherent light trapping has been accomplished through the careful design of plasmonic nanoparticles and gratings, resonant dielectric particles and photonic crystals. Alternative approaches have used randomly textured surfaces as strong light diffusers to benefit from their broadband and wide-angle properties. Here, we propose a new strategy for photon management in thin films that combines both advantages of an efficient trapping due to coherent optical effects and broadband/wide-angle properties due to disorder. Our approach consists of the excitation of electromagnetic modes formed by multiple light scattering and wave interference in two-dimensional random media. We show, by numerical calculations, that the spectral and angular responses of thin films containing disordered photonic patterns are intimately related to the in-plane light transport process and can be tuned through structural correlations. Our findings, which are applicable to all waves, are particularly suited for improving the absorption efficiency of thin-film solar cells and can provide a new approach for high-extraction-efficiency light-emitting diodes.

Two-dimensional wetting: the role of atomic steps on the nucleation of thin water films on BaF2(111) at ambient conditions.

Science.gov (United States)

Cardellach, M; Verdaguer, A; Santiso, J; Fraxedas, J

2010-06-21

The interaction of water with freshly cleaved BaF(2)(111) surfaces at ambient conditions (room temperature and under controlled humidity) has been studied using scanning force microscopy in different operation modes. The images strongly suggest a high surface diffusion of water molecules on the surface indicated by the accumulation of water at step edges forming two-dimensional bilayered structures. Steps running along the 110 crystallographic directions show a high degree of hydrophilicity, as evidenced by small step-film contact angles, while steps running along other directions exhibiting a higher degree of kinks surprisingly behave in a quite opposite way. Our results prove that morphological defects such as steps can be crucial in improving two-dimensional monolayer wetting and stabilization of multilayer grown on surfaces that show good lattice mismatch with hexagonal ice.

Electron-phonon heat exchange in quasi-two-dimensional nanolayers

Science.gov (United States)

Anghel, Dragos-Victor; Cojocaru, Sergiu

2017-12-01

We study the heat power P transferred between electrons and phonons in thin metallic films deposited on free-standing dielectric membranes. The temperature range is typically below 1 K, such that the wavelengths of the excited phonon modes in the system is large enough so that the picture of a quasi-two-dimensional phonon gas is applicable. Moreover, due to the quantization of the components of the electron wavevectors perpendicular to the metal film's surface, the electrons spectrum forms also quasi two-dimensional sub-bands, as in a quantum well (QW). We describe in detail the contribution to the electron-phonon energy exchange of different electron scattering channels, as well as of different types of phonon modes. We find that heat flux oscillates strongly with thickness of the film d while having a much smoother variation with temperature (Te for the electrons temperature and Tph for the phonons temperature), so that one obtains a ridge-like landscape in the two coordinates, (d, Te) or (d, Tph), with crests and valleys aligned roughly parallel to the temperature axis. For the valley regions we find P ∝ Te3.5 - Tph3.5. From valley to crest, P increases by more than one order of magnitude and on the crests P cannot be represented by a simple power law. The strong dependence of P on d is indicative of the formation of the QW state and can be useful in controlling the heat transfer between electrons and crystal lattice in nano-electronic devices. Nevertheless, due to the small value of the Fermi wavelength in metals, the surface imperfections of the metallic films can reduce the magnitude of the oscillations of P vs. d, so this effect might be easier to observe experimentally in doped semiconductors.

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

Energy Technology Data Exchange (ETDEWEB)

Ozmen, Mustafa, E-mail: musozmen@gmail.com [Department of Chemistry, University of Selcuk, 42075 Konya (Turkey); Ozbek, Zikriye, E-mail: zikriye@comu.edu.tr [Department of Bioengineering, University of Canakkale Onsekiz Mart, 17100 Canakkale (Turkey); Bayrakci, Mevlut [Department of Bioengineering, University of Karamanoglu Mehmetbey, 70200 Karaman (Turkey); Ertul, Seref; Ersoz, Mustafa [Department of Chemistry, University of Selcuk, 42075 Konya (Turkey); Capan, Rifat [Department of Physics, University of Balikesir, 10145 Balikesir (Turkey)

2015-12-30

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

Thickness dependence of the quantum Hall effect in films of the three-dimensional Dirac semimetal Cd3As2

Directory of Open Access Journals (Sweden)

Manik Goyal

2018-02-01

Full Text Available Low-temperature magnetotransport studies are reported for (112Cd3As2 films grown on (111CdTe by molecular beam epitaxy as a function of the Cd3As2 film thickness. All films show Shubnikov-de Haas oscillations. An even-integer quantum Hall effect is observed for films thinner than 70 nm. For the thinnest films, the bulk is gapped and transport at low temperatures occurs only via the gapless, two-dimensional states. The lowest Landau level is reached at ∼10 T, and the longitudinal resistance nearly vanishes at the plateaus in the Hall resistance. The results are discussed in the context of the current theoretical understanding of topological surface states in three-dimensional Dirac semimetals.

Layer-by-layer assembled polyaniline nanofiber/multiwall carbon nanotube thin film electrodes for high-power and high-energy storage applications.

Science.gov (United States)

Hyder, Md Nasim; Lee, Seung Woo; Cebeci, Fevzi Ç; Schmidt, Daniel J; Shao-Horn, Yang; Hammond, Paula T

2011-11-22

Thin film electrodes of polyaniline (PANi) nanofibers and functionalized multiwall carbon nanotubes (MWNTs) are created by layer-by-layer (LbL) assembly for microbatteries or -electrochemical capacitors. Highly stable cationic PANi nanofibers, synthesized from the rapid aqueous phase polymerization of aniline, are assembled with carboxylic acid functionalized MWNT into LbL films. The pH-dependent surface charge of PANi nanofibers and MWNTs allows the system to behave like weak polyelectrolytes with controllable LbL film thickness and morphology by varying the number of bilayers. The LbL-PANi/MWNT films consist of a nanoscale interpenetrating network structure with well developed nanopores that yield excellent electrochemical performance for energy storage applications. These LbL-PANi/MWNT films in lithium cell can store high volumetric capacitance (~238 ± 32 F/cm(3)) and high volumetric capacity (~210 mAh/cm(3)). In addition, rate-dependent galvanostatic tests show LbL-PANi/MWNT films can deliver both high power and high energy density (~220 Wh/L(electrode) at ~100 kW/L(electrode)) and could be promising positive electrode materials for thin film microbatteries or electrochemical capacitors. © 2011 American Chemical Society

Multiphase flow in geometrically simple fracture intersections

Science.gov (United States)

Basagaoglu, H.; Meakin, P.; Green, C.T.; Mathew, M.; ,

2006-01-01

A two-dimensional lattice Boltzmann (LB) model with fluid-fluid and solid-fluid interaction potentials was used to study gravity-driven flow in geometrically simple fracture intersections. Simulated scenarios included fluid dripping from a fracture aperture, two-phase flow through intersecting fractures and thin-film flow on smooth and undulating solid surfaces. Qualitative comparisons with recently published experimental findings indicate that for these scenarios the LB model captured the underlying physics reasonably well.

Quasi-One-Dimensional Intermittent Flux Behavior in Superconducting Films

Directory of Open Access Journals (Sweden)

A. J. Qviller

2012-01-01

Full Text Available Intermittent filamentary dynamics of the vortex matter in superconductors is found in films of YBa_{2}Cu_{3}O_{7-δ} deposited on tilted substrates. Deposition of this material on such substrates creates parallel channels of easy flux penetration when a magnetic field is applied perpendicular to the film. As the applied field is gradually increased, magneto-optical imaging reveals that flux penetrates via numerous quasi-one-dimensional jumps. The distribution of flux avalanche sizes follows a power law, and data collapse is obtained by finite-size scaling, with the depth of the flux front used as crossover length. The intermittent behavior shows no threshold value in the applied field, in contrast to conventional flux jumping. The results strongly suggest that the quasi-one-dimensional flux jumps are of a different nature than the thermomagnetic dendritic (branching avalanches that are commonly found in superconducting films.

Self-assembled graphene/azo polyelectrolyte multilayer film and its application in electrochemical energy storage device.

Science.gov (United States)

Wang, Dongrui; Wang, Xiaogong

2011-03-01

Graphene/azo polyelectrolyte multilayer films were fabricated through electrostatic layer-by-layer (LbL) self-assembly, and their performance as electrochemical capacitor electrode was investigated. Cationic azo polyelectrolyte (QP4VP-co-PCN) was synthesized through radical polymerization, postpolymerization azo coupling reaction, and quaternization. Negatively charged graphene nanosheets were prepared by a chemically modified method. The LbL films were obtained by alternately dipping a piece of the pretreated substrates in the QP4VP-co-PCN and nanosheet solutions. The processes were repeated until the films with required numbers of bilayers were obtained. The self-assembly and multilayer surface morphology were characterized by UV-vis spectroscopy, AFM, SEM, and TEM. The performance of the LbL films as electrochemical capacitor electrode was estimated using cyclic voltammetry. Results show that the graphene nanosheets are densely packed in the multilayers and form random graphene network. The azo polyelectrolyte cohesively interacts with the nanosheets in the multilayer structure, which prevents agglomeration of graphene nanosheets. The sheet resistance of the LbL films decreases with the increase of the layer numbers and reaches the stationary value of 1.0 × 10(6) Ω/square for the film with 15 bilayers. At a scanning rate of 50 mV/s, the LbL film with 9 bilayers shows a gravimetric specific capacitance of 49 F/g in 1.0 M Na(2)SO(4) solution. The LbL films developed in this work could be a promising type of the electrode materials for electric energy storage devices.

LB 3459, an O-type subdwarf eclipsing binary system

International Nuclear Information System (INIS)

Kilkenny, D.; Penfold, J.E.; Hilditch, R.W.

1979-01-01

Four-colour photometry of the short-period eclipsing binary system LB 3459 confirms features seen in earlier less-detailed data. An analysis of all the observational data suggests the system to be an O-type subdwarf plus a hot white dwarf rather than two sdO stars. A value of 0.03 is obtained for the linear limb-darkening coefficient of the primary and estimates of the absolute magnitudes of the two components give a distance of 70 +- 25 pc for the system. The primary and secondary may have radii as small as 0.04 solar radius and 0.02 solar radius respectively, indicating a component separation of only 0.25 solar radius. Several unsolved problems connected with the nature and evolution of the LB 3459 system are noted. (author)

Three-dimensional microporous polypyrrole/polysulfone composite film electrode for supercapacitance performance

International Nuclear Information System (INIS)

Feng, Xiaojuan; Shi, Yanlong; Jin, Shuping

2015-01-01

The three-dimensional microporous polypyrrole/polysulfone (PPY/PSF) composite film was fabricated via a simple polymerization method. The morphology structure and chemical composition of the composite film were characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR), respectively. The electrochemical properties of the composite film electrode were evaluated by cyclic voltammetry, galvanostatic charging-discharging and electrochemical impedance spectroscopy. The material exhibits excellent capacitance performance including high capacitance of 500 F g"−"1 at 0.3 A g"−"1 current density, good cycle stability in 800 continuous cycles (only 4.5% decay after 800 cycles at 0.3 A g"−"1), and low inter resistance. The good property of the PPY/PSF electrode should be attributed to its structural features, including two-layer microporous structure which facilitates the penetration of electrolytes into the inner surface, high surface area which provides more active sites. These results show that the composite film is a promising candidate for high energy electrochemical capacitors.

Three-dimensional microporous polypyrrole/polysulfone composite film electrode for supercapacitance performance

Energy Technology Data Exchange (ETDEWEB)

Feng, Xiaojuan, E-mail: cherry-820@163.com; Shi, Yanlong; Jin, Shuping

2015-10-30

The three-dimensional microporous polypyrrole/polysulfone (PPY/PSF) composite film was fabricated via a simple polymerization method. The morphology structure and chemical composition of the composite film were characterized by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR), respectively. The electrochemical properties of the composite film electrode were evaluated by cyclic voltammetry, galvanostatic charging-discharging and electrochemical impedance spectroscopy. The material exhibits excellent capacitance performance including high capacitance of 500 F g{sup −1} at 0.3 A g{sup −1} current density, good cycle stability in 800 continuous cycles (only 4.5% decay after 800 cycles at 0.3 A g{sup −1}), and low inter resistance. The good property of the PPY/PSF electrode should be attributed to its structural features, including two-layer microporous structure which facilitates the penetration of electrolytes into the inner surface, high surface area which provides more active sites. These results show that the composite film is a promising candidate for high energy electrochemical capacitors.

Plans for the Study of the Spin Properties of the $\\Lb$ Baryon Using the Decay Channel $\\Lb \\ra \\jpsi(\\mumu) \\Lambda(p\\pi^{-})$

CERN Document Server

The ATLAS Collaboration

2009-01-01

This note summarizes the results of a study of the feasibility of measuring certain spin properties of $\\Lb$ baryon in the ATLAS experiment. We present an assessment of approaches for extracting the inclusive $\\Lb$ polarization and the parity violating $\\alpha_{\\Lb}$ parameter for the decay $\\Lb \\ra \\jpsi(\\mumu)\\Lambda(p\\pi^{-})$ from the reconstructed four final state charged particles. As a key test, we generated Monte Carlo samples of $\\Lb$ events of fixed polarization in the ATLAS detector and evaluated our ability to precisely extract the input polarization from the reconstructed events. The physics motivation for the planned measurements in ATLAS include the search for an explanation of the anomalous spin effects in hyperon inclusive production observed at lower energies, tests of various decay models based on HQET, tests of CP in an area not yet directly explored, and the development of $\\Lb$ polarimetry as a possible tool for spin analysis in future SUSY and other studies.

One- and two-dimensional fluids properties of smectic, lamellar and columnar liquid crystals

CERN Document Server

Jakli, Antal

2006-01-01

Smectic and lamellar liquid crystals are three-dimensional layered structures in which each layer behaves as a two-dimensional fluid. Because of their reduced dimensionality they have unique physical properties and challenging theoretical descriptions, and are the subject of much current research. One- and Two-Dimensional Fluids: Properties of Smectic, Lamellar and Columnar Liquid Crystals offers a comprehensive review of these phases and their applications. The book details the basic structures and properties of one- and two-dimensional fluids and the nature of phase transitions. The later chapters consider the optical, magnetic, and electrical properties of special structures, including uniformly and non-uniformly aligned anisotropic films, lyotropic lamellar systems, helical and chiral structures, and organic anisotropic materials. Topics also include typical and defective features, magnetic susceptibility, and electrical conductivity. The book concludes with a review of current and potential applications ...

Structural studies of Langmuir-Blodgett films containing rare-earth metal cations

DEFF Research Database (Denmark)

Khomutov, G.B.; Antipina, M.N.; Bykov, I.V.

2002-01-01

Comparative structural study of gadolinium stearate Langmuir-Blodgett (LB) films formed by monolayer deposition from either aqueous gadolinium acetate or gadolinium chloride solutions have been carried out. Structure of the films was characterized by X-ray diffraction, Fourier transform infrared...... spectroscopy, high-energy electron diffraction, atomic force microscopy and scanning electron microscopy. It was found that when subphase pH had a value at which all monolayer stearic acid molecules were ionized and bound with Gd3+ cations (pH > 5), the LB films deposited from gadolinium acetate and gadolinium....... The data obtained indicate that the control of multivalent metal cations complexes formation in the subphase and at the monolayer surface can be an instrument for optimization, the conditions to form metal-containing LB film with regulated structure and properties....

Wake structure and thrust generation of a flapping foil in two-dimensional flow

DEFF Research Database (Denmark)

Andersen, Anders Peter; Bohr, Tomas; Schnipper, Teis

2017-01-01

We present a combined numerical (particle vortex method) and experimental (soap film tunnel) study of a symmetric foil undergoing prescribed oscillations in a two-dimensional free stream. We explore pure pitching and pure heaving, and contrast these two generic types of kinematics. We compare...... measurements and simulations when the foil is forced with pitching oscillations, and we find a close correspondence between flow visualisations using thickness variations in the soap film and the numerically determined vortex structures. Numerically, we determine wake maps spanned by oscillation frequency...

Stable Graphene-Two-Dimensional Multiphase Perovskite Heterostructure Phototransistors with High Gain.

Science.gov (United States)

Shao, Yuchuan; Liu, Ye; Chen, Xiaolong; Chen, Chen; Sarpkaya, Ibrahim; Chen, Zhaolai; Fang, Yanjun; Kong, Jaemin; Watanabe, Kenji; Taniguchi, Takashi; Taylor, André; Huang, Jinsong; Xia, Fengnian

2017-12-13

Recently, two-dimensional (2D) organic-inorganic perovskites emerged as an alternative material for their three-dimensional (3D) counterparts in photovoltaic applications with improved moisture resistance. Here, we report a stable, high-gain phototransistor consisting of a monolayer graphene on hexagonal boron nitride (hBN) covered by a 2D multiphase perovskite heterostructure, which was realized using a newly developed two-step ligand exchange method. In this phototransistor, the multiple phases with varying bandgap in 2D perovskite thin films are aligned for the efficient electron-hole pair separation, leading to a high responsivity of ∼10 5 A W -1 at 532 nm. Moreover, the designed phase alignment method aggregates more hydrophobic butylammonium cations close to the upper surface of the 2D perovskite thin film, preventing the permeation of moisture and enhancing the device stability dramatically. In addition, faster photoresponse and smaller 1/f noise observed in the 2D perovskite phototransistors indicate a smaller density of deep hole traps in the 2D perovskite thin film compared with their 3D counterparts. These desirable properties not only improve the performance of the phototransistor, but also provide a new direction for the future enhancement of the efficiency of 2D perovskite photovoltaics.

Fabrication of hydrogenase-cationic electrolyte biohybrids at interfaces and their electrochemical properties in Langmuir-Blodgett films

International Nuclear Information System (INIS)

Liu An; Zorin, Nikolay A.; Nakamura, Chikashi; Miyake, Jun; Qian Dongjin

2010-01-01

Hydrogenase (H 2 ase)-cationic electrolyte biohybrids were assembled at the air-water interface via intermolecular electrostatic interaction. The H 2 ase used was purified from the phototropic bacterium of Thiocapsa roseopersicina. Two kinds of cationic electrolyte compounds (CECs) were used, the difference of which was whether they contained viologen substituent or not. Surface pressure-area isotherms indicated that these CECs were co-existed with the H 2 ase in the monolayers, which were then transferred to substrate surfaces to form H 2 ase-CECs hybrid films by the Langmuir-Blodgett (LB) method. Uniform film was formed when polyelectrolyte was used as the subphase. Cyclic voltammograms (CVs) of the LB films showed a couple of redox waves in the potential range of -0.4 to -0.65 V vs. Ag/AgCl, which was ascribed to one electron process of either [4Fe-4S] clusters of H 2 ase or viologens of the CECs. A direct electron transfer between the H 2 ase and electrode surface was achieved in the LB films. Stronger current intensity was recorded when the CV measurements were done in H 2 saturated electrolyte solution than that in Ar. It was confirmed that the H 2 ase biocatalytic activity remained in the LB films. Thus, we suggest that the present H 2 ase-CECs biohybrids could act as potential materials for the studies of interconversion reaction of H 2 and protons.

PEDOT:PSS self-assembled films to methanol crossover reduction in Nafion{sup ®} membranes

Energy Technology Data Exchange (ETDEWEB)

Almeida, Tiago P. [Universidade Federal de São Carlos, Sorocaba, SP (Brazil); Miyazaki, Celina M. [Universidade Estadual Paulista, POSMAT, SP (Brazil); Paganin, Valdecir A. [Universidade de São Paulo, IQSC, São Carlos, SP (Brazil); Ferreira, Marystela [Universidade Federal de São Carlos, Sorocaba, SP (Brazil); Saeki, Margarida J. [Universidade Estadual Paulista, Instituto de Biociências, Botucatu, SP (Brazil); Perez, Joelma [Universidade de São Paulo, IQSC, São Carlos, SP (Brazil); Riul, Antonio, E-mail: riul@ifi.unicamp.br [Universidade Estadual de Campinas, IFGW, Campinas (Brazil)

2014-12-30

Highlights: • PAH/PEDOT:PSS LbL films were regularly multilayered onto Nafion. • The LbL modified membranes were succesfully applied to reduce methanol crossover in Nafion. • PAH/PEDO:PSS films also decreased the proton conduction, reducing in 15% the DMFC performance. - Abstract: Alternative energy sources are on a global demand, with fuel cells as promising devices from mobile to stationary applications. Nafion{sup ®} is at the heart of many of these appliances, being mostly used due to its high proton conduction and good chemical stability at ambient temperature in proton exchange membranes (PEM). Therefore, methanol permeation throughout Nafion{sup ®} films reduces drastically the performance of direct methanol fuel cells (DMFC). We present here the deposition of layer-by-layer (LbL) nanostructured thin films of poly(allylamine hydrochloride) (PAH) and poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate) (PEDOT:PSS) onto commercial Nafion{sup ®} 212 membranes. It was observed a good adherence of the LbL films onto Nafion{sup ®} 212, with UV–vis results displaying a linear characteristic growth, indicative that the same amount of material was deposited at each deposition step during the layer-by-layer assembly. In addition, the LbL films also act as a good barrier to avoid methanol crossover, with an observed reduction in the methanol permeation from 5.5 × 10{sup −6} cm{sup 2} s{sup −1} to 3.2 × 10{sup −6} cm{sup 2} s{sup −1}, respectively to pristine Nafion{sup ®} 212 and a 5-bilayer PAH/PEDOT:PSS LbL film deposited on Nafion{sup ®}212. The measured power density in a DMFC set-up was not significantly changed (∼12 mW cm{sup −2}) due to the LbL films, since the PAH/PEDOT:PSS nanostructure is impeding water and ion transport, consequently affecting the proton conduction throughout the membrane.

Thermodynamic and structural study of two-dimensional phase transitions within films of molecules physi-sorbed on graphite; the role of orientational order in wetting and roughening phenomena

International Nuclear Information System (INIS)

Angerand, Francois

1987-01-01

Two-dimensional phase transitions within films physi-sorbed upon the basal face of graphite have been investigated using two experimental methods: volumetric measurements of adsorption isotherms and neutron diffraction. Our main objective was to study the role played by orientational order in these films, its influence on their thermodynamic and structural properties, and its significance in wetting and roughening phenomena, which are indirectly accessible from adsorption studies. A comparative study of the adsorption isotherms of two molecules having comparable dipole moments, NH 3 and C 2 H 3 F, discloses very dissimilar behaviours, due to the fact that hydrogen bonding is involved in the interaction between NH 3 , but not C 2 H 3 F, molecules. The impossibility of such a bond for the interaction of the adsorbate with the substrate results in a poor cohesion energy of the NH 3 ad-film in comparison with those of its bulk condensed phases. The situation is opposite for the film of C 2 H 3 F which behaves almost as a rare gas film. From multilayer adsorption isotherms of CO it is shown that graphite (0001) is perfectly wet by the plastic (orientationally disordered) crystal phase, β-CO, whereas it is incompletely wet by the low-temperature crystal phase α-CO, in which the molecules are orientationally ordered. The critical temperatures of two-dimensional condensation have been measured for the successive ad-layers, up to the fifth. They seem to converge towards a value of 65 K, which we consider as representing the temperature of the roughening transition of the (0001) face of β-CO. A neutron diffraction study of the monolayers of N 2 O and C(CD 3 ) 4 adsorbed on graphite has been carried out. For N 2 O our results suggest a structure more involved than conjectured. For C(CD 3 ) 4 we have evidence for a triple point at 178 K. The crystal monolayer has a compact hexagonal structure. (author) [fr

Layer-by-layer composite film of nickel phthalocyanine and montmorillonite clay for synergistic effect on electrochemical detection of dopamine

Science.gov (United States)

de Lucena, Nathalia C.; Miyazaki, Celina M.; Shimizu, Flávio M.; Constantino, Carlos J. L.; Ferreira, Marystela

2018-04-01

Dopamine (DA) abnormal levels are related to diseases which makes important the development of fast, reliable, low-cost and sensitive devices for diagnosis and pharmaceutical controls. Nanostructured film composite of sodium montmorillonite clay (Na+MMT) and nickel phthalocyanine (NiTsPc) was self-assembled by layer-by-layer (LbL) technique and applied as electrochemical sensor for DA in the presence of common natural interferents as ascorbic acid (AA) and uric acid (UA). Three different LbL architecture films were investigated: LbL films of clay (PEI/Na+MMT) and phthalocyanine (PEI/NiTsPc) in a bilayer structure with a conventional polyelectrolyte (PEI) and a composite film formed by both materials to verify the synergistic effect in the LbL film in a quadri-layer assembly (PEI/Na+MMT/PEI/NiTsPc). Structural characterization indicated molecular level interactions between the layers forming the LbL films. The ITO/(PEI/Na+MMT/PEI/NiTsPc)10 electrode exhibited a LOD of 1.0 μmol L-1 and linear range 5-150 μmol L-1.

LB1 and LB6 Homo floresiensis are not modern human (Homo sapiens) cretins.

Science.gov (United States)

Brown, Peter

2012-02-01

Excavations in the late Pleistocene deposits at Liang Bua cave, Flores, have uncovered the skeletal remains of several small-bodied and small-brained hominins in association with stone artefacts and the bones of Stegodon. Due to their combination of plesiomorphic, unique and derived traits, they were ascribed to a new species, Homo floresiensis, which, along with Stegodon, appears to have become extinct ∼17 ka (thousand years ago). However, recently it has been argued that several characteristics of H. floresiensis were consistent with dwarfism and evidence of delayed development in modern human (Homo sapiens) myxoedematous endemic (ME) cretins. This research compares the skeletal and dental morphology in H. floresiensis with the clinical and osteological indicators of cretinism, and the traits that have been argued to be associated with ME cretinism in LB1 and LB6. Contrary to published claims, morphological and statistical comparisons did not identify the distinctive skeletal and dental indicators of cretinism in LB1 or LB6 H. floresiensis. Brain mass, skeletal proportions, epiphyseal union, orofacial morphology, dental development, size of the pituitary fossa and development of the paranasal sinuses, vault bone thickness and dimensions of the hands and feet all distinguish H. floresiensis from modern humans with ME cretinism. The research team responsible for the diagnosis of ME cretinism had not examined the original H. floresiensis skeletal materials, and perhaps, as a result, their research confused taphonomic damage with evidence of disease, and thus contained critical errors of fact and interpretation. Behavioural scenarios attempting to explain the presence of cretinous H. sapiens in the Liang Bua Pleistocene deposits, but not unaffected H. sapiens, are both unnecessary and not supported by the available archaeological and geochronological evidence from Flores. Crown Copyright © 2011. Published by Elsevier Ltd. All rights reserved.

Two-dimensional errors

International Nuclear Information System (INIS)

Anon.

1991-01-01

This chapter addresses the extension of previous work in one-dimensional (linear) error theory to two-dimensional error analysis. The topics of the chapter include the definition of two-dimensional error, the probability ellipse, the probability circle, elliptical (circular) error evaluation, the application to position accuracy, and the use of control systems (points) in measurements

Vertical drying of a suspension of sticks: Monte Carlo simulation for continuous two-dimensional problem

Science.gov (United States)

Lebovka, Nikolai I.; Tarasevich, Yuri Yu.; Vygornitskii, Nikolai V.

2018-02-01

The vertical drying of a two-dimensional colloidal film containing zero-thickness sticks (lines) was studied by means of kinetic Monte Carlo (MC) simulations. The continuous two-dimensional problem for both the positions and orientations was considered. The initial state before drying was produced using a model of random sequential adsorption with isotropic orientations of the sticks. During the evaporation, an upper interface falls with a linear velocity in the vertical direction, and the sticks undergo translational and rotational Brownian motions. The MC simulations were run at different initial number concentrations (the numbers of sticks per unit area), pi, and solvent evaporation rates, u . For completely dried films, the spatial distributions of the sticks, the order parameters, and the electrical conductivities of the films in both the horizontal, x , and vertical, y , directions were examined. Significant evaporation-driven self-assembly and stratification of the sticks in the vertical direction was observed. The extent of stratification increased with increasing values of u . The anisotropy of the electrical conductivity of the film can be finely regulated by changes in the values of pi and u .

Electronic Tongue Based on Nanostructured Hybrid Films of Gold Nanoparticles and Phthalocyanines for Milk Analysis

Directory of Open Access Journals (Sweden)

Luiza A. Mercante

2015-01-01

Full Text Available The use of gold nanoparticles combined with other organic and inorganic materials for designing nanostructured films has demonstrated their versatility for various applications, including optoelectronic devices and chemical sensors. In this study, we reported the synthesis and characterization of gold nanoparticles stabilized with poly(allylamine hydrochloride (Au@PAH NPs, as well as the capability of this material to form multilayer Layer-by-Layer (LbL nanostructured films with metal tetrasulfonated phthalocyanines (MTsPc. Film growth was monitored by UV-Vis absorption spectroscopy, atomic force microscopy (AFM, and Fourier transform infrared spectroscopy (FTIR. Once LbL films have been applied as active layers in chemical sensors, Au@PAH/MTsPc and PAH/MTsPc LbL films were used in an electronic tongue system for milk analysis regarding fat content. The capacitance data were treated using Principal Component Analysis (PCA, revealing the role played by the gold nanoparticles on the LbL films electrical properties, enabling this kind of system to be used for analyzing complex matrices such as milk without any prior pretreatment.

A theoretical model for the pyroelectric response in Langmuir-Blodgett films

International Nuclear Information System (INIS)

Capan, R.; Basaran, I.; Richardson, T.H.; Lacey, D.

2002-01-01

Understanding the structure of pyroelectric materials is important to elucidate the nature of the temperature-dependent microscopic and macroscopic electric polarisation. Pyroelectric materials must have a non-centrosymmetric structure. Previously, researchers [C.A. Jones, PhD thesis, University of Durham, (1987); J. Mater. Chem. 1 (1991) 819; Langmuir 11 (1995) 4623] have reported the pyroelectric effect of non-centrosymmetric ultrathin LB films prepared using the alternate layer Langmuir-Blodgett (LB) deposition technique. They have proposed three main mechanisms to explain the origin of the pyroelectric activity, namely, tilting, proton transfer, and ionic processes. Linear and cyclic polysiloxane materials with aliphatic and aromatic side groups have been studied in this work. These materials have been alternately deposited with eicosylamine to form the active pyroelectric material in metal-LB film-metal (MIM) devices, whose pyroelectric coefficients have been measured using a quasi-static measurement technique [W.H. Majid, Abd., PhD thesis, Univ. of Sheffield (1994); Mater. Sci. Eng., C, Biomim. Mater., Sens. Syst. 3 (1995) 197; Thin Solid Films 327-329 (1998) 369]. The relation between pyroelectric mechanism(s) and microscopic and macroscopic pyroelectric response for polysiloxane/eicosylamine alternate layer LB films will be explained in this work. Results indicate that the physical mechanism by which the pyroelectric activity arises in the LB films is critically dependent upon their structural quality, the ions within the multilayer arrangement and the molecular dipole moments of the molecules

Water-Triggered Dimensional Swelling of Cellulose Nanofibril Films: Instant Observation Using Optical Microscope

International Nuclear Information System (INIS)

Qing, Y.; Wu, Y.; Li, X.; Qing, Y.; Cai, Z.

2013-01-01

To understand the swelling behavior of cellulose nano fibril (CNF) films, the dimensional variation of untreated and phenol formaldehyde modified CNF (CNF/PF) films soaked in distilled water was examined in situ with microscopic image recording combined with pixel calculation. Results showed that a dramatic thickness increase exhibited in both CNF and CNF/PF films, despite being at different swelling levels. Compared to thickness swelling, however, the width expansion for these films is negligible. Such significant difference in dimensional swelling for CNF and PF modified films is mainly caused by nano fibril deposition and their meso structure. However, addition of PF modifier has a positive effect on the constraint of water absorption and thickness swelling, which is strongly dependent on PF loadings

Burkholderia xenovorans LB400 harbors a multi-replicon, 9.73-Mbp genome shaped for versatility.

Science.gov (United States)

Chain, Patrick S G; Denef, Vincent J; Konstantinidis, Konstantinos T; Vergez, Lisa M; Agulló, Loreine; Reyes, Valeria Latorre; Hauser, Loren; Córdova, Macarena; Gómez, Luis; González, Myriam; Land, Miriam; Lao, Victoria; Larimer, Frank; LiPuma, John J; Mahenthiralingam, Eshwar; Malfatti, Stephanie A; Marx, Christopher J; Parnell, J Jacob; Ramette, Alban; Richardson, Paul; Seeger, Michael; Smith, Daryl; Spilker, Theodore; Sul, Woo Jun; Tsoi, Tamara V; Ulrich, Luke E; Zhulin, Igor B; Tiedje, James M

2006-10-17

Burkholderia xenovorans LB400 (LB400), a well studied, effective polychlorinated biphenyl-degrader, has one of the two largest known bacterial genomes and is the first nonpathogenic Burkholderia isolate sequenced. From an evolutionary perspective, we find significant differences in functional specialization between the three replicons of LB400, as well as a more relaxed selective pressure for genes located on the two smaller vs. the largest replicon. High genomic plasticity, diversity, and specialization within the Burkholderia genus are exemplified by the conservation of only 44% of the genes between LB400 and Burkholderia cepacia complex strain 383. Even among four B. xenovorans strains, genome size varies from 7.4 to 9.73 Mbp. The latter is largely explained by our findings that >20% of the LB400 sequence was recently acquired by means of lateral gene transfer. Although a range of genetic factors associated with in vivo survival and intercellular interactions are present, these genetic factors are likely related to niche breadth rather than determinants of pathogenicity. The presence of at least eleven "central aromatic" and twenty "peripheral aromatic" pathways in LB400, among the highest in any sequenced bacterial genome, supports this hypothesis. Finally, in addition to the experimentally observed redundancy in benzoate degradation and formaldehyde oxidation pathways, the fact that 17.6% of proteins have a better LB400 paralog than an ortholog in a different genome highlights the importance of gene duplication and repeated acquirement, which, coupled with their divergence, raises questions regarding the role of paralogs and potential functional redundancies in large-genome microbes.

Burkholderia xernovorans LB400 harbors a multi-replicon, 9.73-Mbp genome shaped for versatility

Energy Technology Data Exchange (ETDEWEB)

Chain, Patrick S. G. [Lawrence Livermore National Laboratory (LLNL); Denef, Vincent [University of California, Berkeley; Konstantinidis, Konstantinos T [Michigan State University, East Lansing; Vergez, Lisa [Lawrence Livermore National Laboratory (LLNL); Agullo, Loreine [Universidad Tecnica Federico Santa Maria, Casilla 110-V; Reyes, Valeria Latorre [Universidad Tecnica Federico Santa Maria, Casilla 110-V; Hauser, Loren John [ORNL; Cordova, Macarena [Universidad Tecnica Federico Santa Maria, Casilla 110-V; Gomez, Luis [Universidad Tecnica Federico Santa Maria, Casilla 110-V; Gonzalez, Myriam [Universidad Tecnica Federico Santa Maria, Casilla 110-V; Land, Miriam L [ORNL; Lao, Victoria [Lawrence Livermore National Laboratory (LLNL); Larimer, Frank W [ORNL; LiPuma, John J [University of Michigan; Mahenthiralingam, Eshwar [Cardiff University, Wales; Malfatti, Stephanie [Lawrence Livermore National Laboratory (LLNL); Marx, Christopher J [Harvard University; Parnell, J Jacob [Michigan State University, East Lansing; Ramette, Alban [Michigan State University, East Lansing; Richardson, P M [U.S. Department of Energy, Joint Genome Institute; Seeger, Michael [Universidad Tecnica Federico Santa Maria, Casilla 110-V; Smith, Daryl [University of British Columbia, Vancouver; Spilker, Theodore [University of Michigan; Sul, Woo Jun [Michigan State University, East Lansing; Tsoi, Tamara V [Michigan State University, East Lansing; Zhulin, Igor B [University of Tennessee, Knoxville (UTK) & Oak Ridge National Laboratory (ORNL); Tiedje, James M. [Michigan State University, East Lansing

2006-01-01

Burkholderia xenovorans LB400 (LB400), a well studied, effective polychlorinated biphenyl-degrader, has one of the two largest known bacterial genomes and is the first nonpathogenic Burkholderia isolate sequenced. From an evolutionary perspective, we find significant differences in functional specialization between the three replicons of LB400, as well as a more relaxed selective pressure for genes located on the two smaller vs. the largest replicon. High genomic plasticity, diversity, and specialization within the Burkholderia genus are exemplified by the conservation of only 44% of the genes between LB400 and Burkholderia cepacia complex strain 383. Even among four B. xenovorans strains, genome size varies from 7.4 to 9.73 Mbp. The latter is largely explained by our findings that >20% of the LB400 sequence was recently acquired by means of lateral gene transfer. Although a range of genetic factors associated with in vivo survival and intercellular interactions are present, these genetic factors are likely related to niche breadth rather than determinants of pathogenicity. The presence of at least eleven 'central aromatic' and twenty 'peripheral aromatic' pathways in LB400, among the highest in any sequenced bacterial genome, supports this hypothesis. Finally, in addition to the experimentally observed redundancy in benzoate degradation and formaldehyde oxidation pathways, the fact that 17.6% of proteins have a better LB400 paralog than an ortholog in a different genome highlights the importance of gene duplication and repeated acquirement, which, coupled with their divergence, raises questions regarding the role of paralogs and potential functional redundancies in large-genome microbes.

Supramolecular nano-architectures and two-dimensional/three-dimensional aggregation of a bolaamphiphilic diacid at the air/water interface

International Nuclear Information System (INIS)

Jiao Tifeng; Liu Minghua

2005-01-01

The spreading behavior and nano-architectures of a bolaamphiphilic diacid, 1, 13-tridecandicarboxylic acid (TDA) on water surface and the subphase containing Eu(III) ion were investigated. It was found that although TDA itself could not spread on water surface, it could form an ultrathin film on the aqueous subphase containing Eu(III) ion. In addition, interesting nano-architectures were observed for the transferred film on mica surface. It was found that the formation and change of the nano-architectures were depended on the surface pressure and concentration of Eu(III) ion in the subphase. A rectangular slide morphology was observed for the film spread on an aqueous subphase containing lower concentration of Eu(III), while a walnut-like nano-architectures were observed for the film spread on a higher concentration of Eu(III) ion. Flower structure was observed at a higher surface pressure. The nano-architecture can be further regulated through mixing TDA with octadecylamine (OA) in which linear fiber nanostructure was obtained. It was revealed that while the nano-architectures were formed mainly through a three dimensional aggregation in the case of TDA/Eu(III) films, a two-dimensional aggregation occurred when TDA was mixed with OA. A series of methods such as atomic force microscope, field emission scanning electron microscopy, Fourier transform infrared spectroscopy and X-ray diffraction were used to characterize the supramolecular structures. A possible mechanism for the formation of these nano-architectures was discussed

A microprocessor based on a two-dimensional semiconductor

Science.gov (United States)

Wachter, Stefan; Polyushkin, Dmitry K.; Bethge, Ole; Mueller, Thomas

2017-04-01

The advent of microcomputers in the 1970s has dramatically changed our society. Since then, microprocessors have been made almost exclusively from silicon, but the ever-increasing demand for higher integration density and speed, lower power consumption and better integrability with everyday goods has prompted the search for alternatives. Germanium and III-V compound semiconductors are being considered promising candidates for future high-performance processor generations and chips based on thin-film plastic technology or carbon nanotubes could allow for embedding electronic intelligence into arbitrary objects for the Internet-of-Things. Here, we present a 1-bit implementation of a microprocessor using a two-dimensional semiconductor--molybdenum disulfide. The device can execute user-defined programs stored in an external memory, perform logical operations and communicate with its periphery. Our 1-bit design is readily scalable to multi-bit data. The device consists of 115 transistors and constitutes the most complex circuitry so far made from a two-dimensional material.

ONE-DIMENSIONAL AND TWO-DIMENSIONAL LEADERSHIP STYLES

Directory of Open Access Journals (Sweden)

Nikola Stefanović

2007-06-01

Full Text Available In order to motivate their group members to perform certain tasks, leaders use different leadership styles. These styles are based on leaders' backgrounds, knowledge, values, experiences, and expectations. The one-dimensional styles, used by many world leaders, are autocratic and democratic styles. These styles lie on the two opposite sides of the leadership spectrum. In order to precisely define the leadership styles on the spectrum between the autocratic leadership style and the democratic leadership style, leadership theory researchers use two dimensional matrices. The two-dimensional matrices define leadership styles on the basis of different parameters. By using these parameters, one can identify two-dimensional styles.

Topotactic transformations of superstructures: from thin films to two-dimensional networks to nested two-dimensional networks.

Science.gov (United States)

Guo, Chuan Fei; Cao, Sihai; Zhang, Jianming; Tang, Haoying; Guo, Shengming; Tian, Ye; Liu, Qian

2011-06-01

Design and synthesis of super-nanostructures is one of the key and prominent topics in nanotechnology. Here we propose a novel methodology for synthesizing complex hierarchical superstructures using sacrificial templates composed of ordered two-dimensional (2D) nanostructures through lattice-directed topotactic transformations. The fabricated superstructures are nested 2D orthogonal Bi(2)S(3) networks composed of nanorods. Further investigation indicates that the lattice matching between the product and sacrificial template is the dominant mechanism for the formation of the superstructures, which agrees well with the simulation results based on an anisotropic nucleation and growth analysis. Our approach may provide a promising way toward a lattice-directed nonlithographic nanofabrication technique for making functional porous nanoarchitectures and electronic devices. © 2011 American Chemical Society

New depositing method of Langmuir-Blodgett film of fatty acid soap as a radioactive source

Energy Technology Data Exchange (ETDEWEB)

Iwahashi, Makio; Watanabe, Norifumi; Seimiya, Tsutomu; Naito, Fujio

1985-02-01

A stable radioactive source in vacuo was obtained by a new depositing method of Langmuir-Blodgett (L/B) film. In spite of the slight consumption of the substrate solution (only 2-2.5 ml) for preparing a 15 mm x 25 mm sized L/B film containing four molecular layers of /sup 109/Cd-eicosanoate, the deposition of the film was complete. (author).

Interfacial engineering of two-dimensional nano-structured materials by atomic layer deposition

Energy Technology Data Exchange (ETDEWEB)

Zhuiykov, Serge, E-mail: serge.zhuiykov@ugent.be [Ghent University Global Campus, Department of Applied Analytical & Physical Chemistry, Faculty of Bioscience Engineering, 119 Songdomunhwa-ro, Yeonsu-Gu, Incheon 406-840 (Korea, Republic of); Kawaguchi, Toshikazu [Global Station for Food, Land and Water Resources, Global Institution for Collaborative Research and Education, Hokkaido University, N10W5 Kita-ku, Sapporo, Hokkaido 060-0810 (Japan); Graduate School of Environmental Science, Hokkaido University, N10W5 Kita-ku, Sapporo, Hokkaido 060-0810 (Japan); Hai, Zhenyin; Karbalaei Akbari, Mohammad; Heynderickx, Philippe M. [Ghent University Global Campus, Department of Applied Analytical & Physical Chemistry, Faculty of Bioscience Engineering, 119 Songdomunhwa-ro, Yeonsu-Gu, Incheon 406-840 (Korea, Republic of)

2017-01-15

Highlights: • Advantages of atomic layer deposition technology (ALD) for two-dimensional nano-crystals. • Conformation of ALD technique and chemistry of precursors. • ALD of semiconductor oxide thin films. • Ultra-thin (∼1.47 nm thick) ALD-developed tungsten oxide nano-crystals on large area. - Abstract: Atomic Layer Deposition (ALD) is an enabling technology which provides coating and material features with significant advantages compared to other existing techniques for depositing precise nanometer-thin two-dimensional (2D) nanostructures. It is a cyclic process which relies on sequential self-terminating reactions between gas phase precursor molecules and a solid surface. ALD is especially advantageous when the film quality or thickness is critical, offering ultra-high aspect ratios. ALD provides digital thickness control to the atomic level by depositing film one atomic layer at a time, as well as pinhole-free films even over a very large and complex areas. Digital control extends to sandwiches, hetero-structures, nano-laminates, metal oxides, graded index layers and doping, and it is perfect for conformal coating and challenging 2D electrodes for various functional devices. The technique’s capabilities are presented on the example of ALD-developed ultra-thin 2D tungsten oxide (WO{sub 3}) over the large area of standard 4” Si substrates. The discussed advantages of ALD enable and endorse the employment of this technique for the development of hetero-nanostructure 2D semiconductors with unique properties.

Effect of the nanofilm thickness on the properties of the two-dimensional electron gas at the interface between two dielectrics

Energy Technology Data Exchange (ETDEWEB)

Gadiev, R. M., E-mail: gadiev.radik@gmail.com; Lachinov, A. N. [M. Akmullah Baskir State Pedagogical University (Russian Federation); Karamov, D. D. [Russian Academy of Sciences, Ufa Scientific Center (Russian Federation); Kiselev, D. A. [National University of Science and Technology MISiS (Russian Federation); Kornilov, V. M. [M. Akmullah Baskir State Pedagogical University (Russian Federation)

2016-07-15

The mechanism of formation of the two-dimensional conductivity along the interface between two polymer dielectrics is experimentally studied. The idea of “polar catastrophe,” which was successfully used earlier to explain the electronic properties of the interface between two perovskites LaAlO{sub 3}/SrTiO{sub 3}, is chosen as a base hypothesis. Piezoelectric response microscopy is used to reveal the presence of spontaneous polarization on the surface of a polymer film, and the remanent polarization is found to decrease with increasing film thickness. As in the case of perovskites, the polymer film thickness is found to strongly affect the electrical conductivity along the interface. Substantial differences between these phenomena are detected. The change in the electrical conductivity is shown to be caused by a significant increase in the charge carrier mobility when the film thickness decreases below a certain critical value. The relation between the change in the carrier mobility and the change in the spontaneous surface polarization of the polymer film when its thickness decreases is discussed.

Structure and frictional properties of Langmuir-Blodgett films of Cu nanoparticles modified by dialkyldithiophosphate

International Nuclear Information System (INIS)

Xu Jun; Dai Shuxi; Cheng Gang; Jiang Xiaohong; Tao Xiaojun; Zhang Pingyu; Du Zuliang

2006-01-01

Langmuir-Blodgett (LB) films of dialkyldithiophosphate (DDP) modified Cu nanoparticles were prepared. The structure, microfrictional behaviors and adhesion of the LB films were investigated by transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and atomic/friction force microscopy (AFM/FFM). Our results showed that the modified Cu nanoparticles have a typical core-shell structure and fine film-forming ability. The images of AFM/FFM showed that LB films of modified Cu nanoparticles were composed of many nanoparticles arranged closely and orderly and the nanoparticles had favorable behaviors of lower friction. The friction loop of the films indicated that the friction force was affected prominently by the surface slope of the Cu nanoparticles and the microfrictional behaviors showed obvious 'ratchet effect'. The adhesion experiment showed that the modified Cu nanoparticle had a very small adhesive force

Quasi-one-dimensional intermittent flux behavior in superconducting films

OpenAIRE

Qviller, A. J.; Yurchenko, V. V.; Galperin, Y. M.; Vestgården, J. I.; Mozhaev, Peter; Hansen, Jørn Bindslev; Johansen, T. H.

2012-01-01

Intermittent filamentary dynamics of the vortex matter in superconductors is found in films of YBa_{2}Cu_{3}O_{7-δ} deposited on tilted substrates. Deposition of this material on such substrates creates parallel channels of easy flux penetration when a magnetic field is applied perpendicular to the film. As the applied field is gradually increased, magneto-optical imaging reveals that flux penetrates via numerous quasi-one-dimensional jumps. The distribution of flux avalanche sizes follows a ...

Two-dimensional NMR spectrometry

International Nuclear Information System (INIS)

Farrar, T.C.

1987-01-01

This article is the second in a two-part series. In part one (ANALYTICAL CHEMISTRY, May 15) the authors discussed one-dimensional nuclear magnetic resonance (NMR) spectra and some relatively advanced nuclear spin gymnastics experiments that provide a capability for selective sensitivity enhancements. In this article and overview and some applications of two-dimensional NMR experiments are presented. These powerful experiments are important complements to the one-dimensional experiments. As in the more sophisticated one-dimensional experiments, the two-dimensional experiments involve three distinct time periods: a preparation period, t 0 ; an evolution period, t 1 ; and a detection period, t 2

Improving the Sound Pressure Level of Two-Dimensional Audio Actuators by Coating Single-Walled Carbon Nanotubes on Piezoelectric Films.

Science.gov (United States)

Um, Keehong

2015-10-01

As devices for amplifying or transforming electronic signals into audible signals through electromechanical operations, acoustic actuators in the form of loudspeakers are usually solid structures in three dimensional space. Recently there has been increasing demand for mobile electronic devices, such as mobile phones, to become smaller, thinner, and lighter. In contrast to a three dimensional audio system with magnets, we have invented a new type of flexible two dimensional device by utilizing the reverse piezoelectric effect in certain piezoelectric materials. Crystalline piezoelectric materials show electromechanical interaction between the mechanical state and the electrically-charged state. The piezoelectric effect is a reversible process in that materials exhibiting the direct piezoelectric effect (the internal generation of electrical charge resulting from an applied mechanical force) also exhibit the reverse piezoelectric effect (the internal generation of a mechanical strain resulting from an applied electrical field). We have adopted the plasma surface treatment in order to put coating materials on the surface of piezoelectric film. We compared two kinds of coating material, indium tin oxide and single-walled carbon nanotube, and found that single-walled carbon nanotube shows better performance. The results showed improvement of output power in a wider range of operating frequency; for the surface resistance of 0.5 kΩ/square, the single-walled CNT shows the range of operating frequency to be 0.75-17.5 kHz, but ITO shows 2.5-13.4 kHz. For the surface resistance of 1 kΩ/square, single-walled CNT shows the range of operating frequency to be 0.81-17 kHz, but ITO shows it cannot generate audible sound.

Incorporation in Langmuir-Blodgett films of an amphiphilic derivative of fullerene C{sub 60} and oligo-para-phenylenevinylene

Energy Technology Data Exchange (ETDEWEB)

Alvarez-Venicio, V. [Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico (UNAM), Circuito Exterior, CU, C.P. 04510, D.F. (Mexico); Gutierrez-Nava, M. [CIATEQ, A.C., Centro de Tecnologia Avanzada, Circuito de la Industria Poniente Lote: 11, Mza. 3, No. 11, Colonia Parque Industrial Ex Hacienda Dona Rosa, Lerma C.P. 52004, Estado de Mexico (Mexico); Amelines-Sarria, O. [Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico (UNAM), Circuito Exterior, CU, C.P. 04510, D.F. (Mexico); Alvarez-Zauco, E. [Facultad de Ciencias, UNAM, Circuito Exterior, C.U., C.P. 04510, D.F. (Mexico); Basiuk, V.A. [Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico (UNAM), Circuito Exterior, CU, C.P. 04510, D.F. (Mexico); Carreon-Castro, M.P., E-mail: pilar@nucleares.unam.mx [Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico (UNAM), Circuito Exterior, CU, C.P. 04510, D.F. (Mexico)

2012-12-30

Langmuir (L) and Langmuir-Blodgett (LB) films of fullerene C{sub 60}-oligo-para-phenylenevinylene (OPV) derivative with six C{sub 12}H{sub 25} aliphatic chains were characterized. For the Langmuir films, isotherms of surface pressure versus molecular area, compression/expansion cycles (hysteresis curves) and Brewster angle microscopic images were obtained. We performed molecular mechanics and density functional theory calculations to determine the molecular and electronic structure of our compound at a water-air interface. We found agreement between experimental and theoretical values for the molecular surface area. LB films of up to ten layers were obtained on glass substrates, and were characterized by ultraviolet-visible spectroscopy. We observed that the absorbance at a wavelength of 326 nm grows almost linearly as a function of the number of layers. Films on glass-indium tin oxide were characterized by atomic force microscopy. We also observed a uniform deposition over the whole area of the scanned substrate. We demonstrated that the fullerene C{sub 60}-OPV derivative is able to form both L and LB films preventing fullerene aggregation with its aliphatic chains. We suggest that, due to its electron-acceptor properties, the C{sub 60}-OPV derivative could be used for organic-photovoltaic and organic-electronic applications. - Highlights: Black-Right-Pointing-Pointer We performed isotherm and hysteresis studies of fullerene derivative compound. Black-Right-Pointing-Pointer We found that the theoretical and experimental molecular areas agree. Black-Right-Pointing-Pointer We deposited Langmuir-Blodgett (LB) films on glass-indium tin oxide. Black-Right-Pointing-Pointer LB films were characterized using UV-visible spectroscopy. Black-Right-Pointing-Pointer We observed the morphology of the LB films through atomic force microscopy.

Two-dimensional inverse opal hydrogel for pH sensing.

Science.gov (United States)

Xue, Fei; Meng, Zihui; Qi, Fenglian; Xue, Min; Wang, Fengyan; Chen, Wei; Yan, Zequn

2014-12-07

A novel hydrogel film with a highly ordered macropore monolayer on its surface was prepared by templated photo-polymerization of hydrogel monomers on a two-dimensional (2D) polystyrene colloidal array. The 2D inverse opal hydrogel has prominent advantages over traditional three-dimensional (3D) inverse opal hydrogels. First, the formation of the 2D array template through a self-assembly method is considerably faster and simpler. Second, the stable ordering structure of the 2D array template makes it easier to introduce the polymerization solution into the template. Third, a simple measurement, a Debye diffraction ring, is utilized to characterize the neighboring pore spacing of the 2D inverse opal hydrogel. Acrylic acid was copolymerized into the hydrogel; thus, the hydrogel responded to pH through volume change, which resulted from the formation of the Donnan potential. The 2D inverse opal hydrogel showed that the neighboring pore spacing increased by about 150 nm and diffracted color red-shifted from blue to red as the pH increased from pH 2 to 7. In addition, the pH response kinetics and ionic strength effect of this 2D mesoporous polymer film were also investigated.

Langmuir-Blodgett films prepared from pre-formed cholestanic liquid-crystalline polymers

Energy Technology Data Exchange (ETDEWEB)

Tundo, P.; Hodge, P.; Valli, L.; Davis, F. (Venice Univ. (Italy). Dip. di Scienze Ambientali Lecce Univ. (Italy). Dip. di Scienza dei Materiali Manchester Univ. (United Kingdom). Dep. of Chemistry)

1992-01-01

A series of alternating copolymers of maleic anhydride and a-olefins functionalized through different alkyl chains with cholestanic groups were synthetised and derivatives prepared by reactions of the anhydride residues with methanol, water, dimethylamine and morpholine, respectively. The same starting functionalized a-olefins were used to prepare other suitable compounds in order to correlate the features of the liquid-crystalline behaviour of the mesogenic cholestanic group with the stability of the forthcoming polymeric or not polymeric Langmuir-Blodgett (LB) films. For some copolymers surface pressure against area per molecule isotherms are reported. In some multilayer (LB) films, the spacings between the layers were determined by the detection of BRAGG peaks by X-ray diffraction. The (LB) films of these polymers are closed packed, owing to either the polymeric skeleton or liquid-crystalline interaction.

Liquid structure and freezing of the two-dimensional classical electron fluid

International Nuclear Information System (INIS)

Ballone, P.; Pastore, G.; Rovere, M.; Tosi, M.P.

1984-11-01

Accurate theoretical results are reported for the pair correlation function of the classical two-dimensional electron liquid with r -1 interactions at strong coupling. The approach involves an evaluation of the bridge diagram corrections to the hypernetted-chain approximation, the role of low dimensionality being evident, relative to the case of the three-dimensional classical plasma, in an enhanced sensitivity to long range correlations. The liquid structure results are utilized in a density-wave theory of first-order freezing into the triangular lattice, the calculated coupling strength at freezing being in reasonable agreement with computer simulation results and with data on electron films on a liquid-He surface. The stability of the triangular electron lattice against deformation into a body-centered rectangular lattice is also discussed. (author)

Contribution of the cashew gum (Anacardium occidentale L.) for development of layer-by-layer films with potential application in nanobiomedical devices

Energy Technology Data Exchange (ETDEWEB)

Araujo, I.M.S. [Departamento de Quimica, Centro de Ciencias da Natureza, CCN, Universidade Federal do Piaui, UFPI, Teresina, PI, 64049-550 (Brazil); Nucleo de Pesquisa em Biodiversidade e Biotecnologia, BIOTEC, Campus Parnaiba, CMRV, Universidade Federal do Piaui, UFPI, Parnaiba, PI, 64202-020 (Brazil); Zampa, M.F. [Nucleo de Pesquisa em Biodiversidade e Biotecnologia, BIOTEC, Campus Parnaiba, CMRV, Universidade Federal do Piaui, UFPI, Parnaiba, PI, 64202-020 (Brazil); Campus Parnaiba, Instituto Federal de Educacao Ciencia e Tecnologia do Piaui, IFPI, Parnaiba, PI, 64210-260 (Brazil); Moura, J.B.; Santos, J.R. dos [Departamento de Quimica, Centro de Ciencias da Natureza, CCN, Universidade Federal do Piaui, UFPI, Teresina, PI, 64049-550 (Brazil); Eaton, P. [REQUIMTE, Faculdade de Ciencias da Universidade do Porto, Rua do Campo Alegre, Porto, 4169-007 (Portugal); Zucolotto, V. [Grupo de Biofisica Molecular Sergio Mascarenhas, Instituto de Fisica de Sao Carlos, IFSC, USP, Sao Carlos, SP, 13566-590 (Brazil); and others

2012-08-01

The search for bioactive molecules to be employed as recognition elements in biosensors has stimulated researchers to pore over the rich Brazilian biodiversity. In this sense, we introduce the use of natural cashew gum (Anacardium occidentale L.) as an active biomaterial to be used in the form of layer-by-layer films, in conjunction with phthalocyanines, which were tested as electrochemical sensors for dopamine detection. We investigated the effects of chemical composition of cashew gum from two different regions of Brazil (Piaui and Ceara states) on the physico-chemical characteristics of these nanostructures. The morphology of the nanostructures containing cashew gum was studied by atomic force microscopy which indicates that smooth films punctuated by globular features were formed that showed low roughness values. The results indicate that, independent of the origin, cashew gum stands out as an excellent film forming material with potential application in nanobiomedical devices as electrochemical sensors. Highlights: Black-Right-Pointing-Pointer This study focused on the use of cashew gum for the formation of LbL films. Black-Right-Pointing-Pointer LbL films containing cashew gums were investigated by AFM and cyclic voltammetry. Black-Right-Pointing-Pointer Cashew gum contributed to obtain stable films with well-defined redox processes. Black-Right-Pointing-Pointer Cashew gum films detected dopamine in low concentrations. Black-Right-Pointing-Pointer These LbL films presented potential application in nanobiomedical devices.

Contribution of the cashew gum (Anacardium occidentale L.) for development of layer-by-layer films with potential application in nanobiomedical devices

International Nuclear Information System (INIS)

Araújo, I.M.S.; Zampa, M.F.; Moura, J.B.; Santos, J.R. dos; Eaton, P.; Zucolotto, V.

2012-01-01

The search for bioactive molecules to be employed as recognition elements in biosensors has stimulated researchers to pore over the rich Brazilian biodiversity. In this sense, we introduce the use of natural cashew gum (Anacardium occidentale L.) as an active biomaterial to be used in the form of layer-by-layer films, in conjunction with phthalocyanines, which were tested as electrochemical sensors for dopamine detection. We investigated the effects of chemical composition of cashew gum from two different regions of Brazil (Piauí and Ceará states) on the physico-chemical characteristics of these nanostructures. The morphology of the nanostructures containing cashew gum was studied by atomic force microscopy which indicates that smooth films punctuated by globular features were formed that showed low roughness values. The results indicate that, independent of the origin, cashew gum stands out as an excellent film forming material with potential application in nanobiomedical devices as electrochemical sensors. Highlights: ► This study focused on the use of cashew gum for the formation of LbL films. ► LbL films containing cashew gums were investigated by AFM and cyclic voltammetry. ► Cashew gum contributed to obtain stable films with well-defined redox processes. ► Cashew gum films detected dopamine in low concentrations. ► These LbL films presented potential application in nanobiomedical devices.

Plasma-treated Langmuir-Blodgett reduced graphene oxide thin film for applications in biophotovoltaics

Science.gov (United States)

Ibrahim, Siti Aisyah; Jaafar, Muhammad Musoddiq; Ng, Fong-Lee; Phang, Siew-Moi; Kumar, G. Ghana; Majid, Wan Haliza Abd; Periasamy, Vengadesh

2018-01-01

The surface optimization and structural characteristics of Langmuir-Blodgett (LB) reduced graphene oxide thin (rGO) film treated by argon plasma treatment were studied. In this work, six times deposition of rGO was deposited on a clean glass substrate using the LB method. Plasma technique involving a variation of plasma power, i.e., 20, 60, 100 and 140 W was exposed to the LB-rGO thin films under argon ambience. The plasma treatment generally improves the wettability or hydrophilicity of the film surface compared to without treatment. Maximum wettability was observed at a plasma power of 20 W, while also increasing the adhesion of the rGO film with the glass substrate. The multilayer films fabricated were characterized by means of spectroscopic, structural and electrical studies. The treatment of rGO with argon plasma was found to have improved its biocompatibility, and thus its performance as an electrode for biophotovoltaic devices has been shown to be enhanced considerably.

Three-dimensional thin film for lithium-ion batteries and supercapacitors.

Science.gov (United States)

Yang, Yang; Peng, Zhiwei; Wang, Gunuk; Ruan, Gedeng; Fan, Xiujun; Li, Lei; Fei, Huilong; Hauge, Robert H; Tour, James M

2014-07-22

Three-dimensional heterogeneously nanostructured thin-film electrodes were fabricated by using Ta2O5 nanotubes as a framework to support carbon-onion-coated Fe2O3 nanoparticles along the surface of the nanotubes. Carbon onion layers function as microelectrodes to separate the two different metal oxides and form a nanoscale 3-D sandwich structure. In this way, space-charge layers were formed at the phase boundaries, and it provides additional energy storage by charge separation. These 3-D nanostructured thin films deliver both excellent Li-ion battery properties (stabilized at 800 mAh cm(–3)) and supercapacitor (up to 18.2 mF cm(–2)) performance owing to the synergistic effects of the heterogeneous structure. Thus, Li-ion batteries and supercapacitors are successfully assembled into the same electrode, which is promising for next generation hybrid energy storage and delivery devices.

Conductivity of Langmuir-Blodgett films of a disk-shaped liquid-crystalline molecule-DNA complex studied by current-sensing atomic force microscopy

Science.gov (United States)

Nayak, Alpana; Suresh, K. A.

2008-08-01

We have studied the electrical conductivity in monolayer films of an ionic disk-shaped liquid-crystal molecule, pyridinium tethered with hexaalkoxytriphenylene (PyTp), and its complex with DNA by current-sensing atomic force microscopy (CS-AFM). The pure PyTp and PyTp-DNA complex monolayer films were first formed at the air-water interface and then transferred onto conducting substrates by the Langmuir-Blodgett (LB) technique to study the nanoscale electron transport through these films. The conductive tip of CS-AFM, the LB film, and the metal substrate form a nanoscopic metal-LB film-metal (M-LB-M) junction. We have measured the current-voltage (I-V) characteristics for the M-LB-M junction using CS-AFM and have analyzed the data quantitatively. We find that the I-V curves fit well to the Fowler-Nordheim (FN) model, suggesting electron tunneling to be a possible mechanism for electron transport in our system. Further, analysis of the I-V curves based on the FN model yields the barrier heights of PyTp-DNA complex and pure PyTp films. Electron transport studies of films of ionic disk-shaped liquid-crystal molecules and their complex with DNA are important from the point of view of their applications in organic electronics.

Diamond-like carbon films deposited on three-dimensional shape substrate model by liquid electrochemical technique

International Nuclear Information System (INIS)

He, Y.Y.; Zhang, G.F.; Zhao, Y.; Liu, D.D.; Cong, Y.; Buck, V.

2015-01-01

Diamond-like carbon (DLC) films were deposited on three-dimensional (3D) shape substrate model by electrolysis of 2-propanol solution at low temperature (60 °C). This 3D shape model was composed of a horizontally aligned stainless steel wafer and vertically aligned stainless steel rods. Morphology and microstructure of the films were analyzed by scanning electron microscopy (SEM), atomic force microscopy (AFM) and Raman spectroscopy, respectively. The results suggested there were only differences in film uniformity and thickness for two kinds of samples. The hydrogenated amorphous carbon films deposited on horizontally aligned substrate were smooth and homogeneous. And the film thickness of DLC films gained on the vertical substrates decreased along vertical direction. It is believed that bubble formation could enhance nucleation on the wetted capillary area. This experiment shows that deposition of DLC films by liquid phase deposition on 3D shape conductive substrates is possible. - Highlights: • DLC film is expected to be deposited on complex surface/shape substrate. • DLC film is deposited on 3D shape substrate by liquid electrochemical method. • Horizontal substrate is covered by smooth and homogeneous DLC films. • Film thickness decreases along vertical direction due to boiling effect

Diamond-like carbon films deposited on three-dimensional shape substrate model by liquid electrochemical technique

Energy Technology Data Exchange (ETDEWEB)

He, Y.Y. [Institute of Nano-photonics, School of Physics and Materials Engineering, Dalian Nationalities University, 116600 Dalian (China); Zhang, G.F. [School of Materials Science and Engineering, Dalian University of Technology, 116024, Dalian China (China); Zhao, Y.; Liu, D.D. [Institute of Nano-photonics, School of Physics and Materials Engineering, Dalian Nationalities University, 116600 Dalian (China); Cong, Y., E-mail: congyan@ciomp.ac.cn [Institute of Nano-photonics, School of Physics and Materials Engineering, Dalian Nationalities University, 116600 Dalian (China); Buck, V. [Thin Film Technology Group, Faculty of Physics, University Duisburg-Essen and CeNIDE, 47057 Duisburg (Germany)

2015-09-01

Diamond-like carbon (DLC) films were deposited on three-dimensional (3D) shape substrate model by electrolysis of 2-propanol solution at low temperature (60 °C). This 3D shape model was composed of a horizontally aligned stainless steel wafer and vertically aligned stainless steel rods. Morphology and microstructure of the films were analyzed by scanning electron microscopy (SEM), atomic force microscopy (AFM) and Raman spectroscopy, respectively. The results suggested there were only differences in film uniformity and thickness for two kinds of samples. The hydrogenated amorphous carbon films deposited on horizontally aligned substrate were smooth and homogeneous. And the film thickness of DLC films gained on the vertical substrates decreased along vertical direction. It is believed that bubble formation could enhance nucleation on the wetted capillary area. This experiment shows that deposition of DLC films by liquid phase deposition on 3D shape conductive substrates is possible. - Highlights: • DLC film is expected to be deposited on complex surface/shape substrate. • DLC film is deposited on 3D shape substrate by liquid electrochemical method. • Horizontal substrate is covered by smooth and homogeneous DLC films. • Film thickness decreases along vertical direction due to boiling effect.

Evolutionary selection growth of two-dimensional materials on polycrystalline substrates

Science.gov (United States)

Vlassiouk, Ivan V.; Stehle, Yijing; Pudasaini, Pushpa Raj; Unocic, Raymond R.; Rack, Philip D.; Baddorf, Arthur P.; Ivanov, Ilia N.; Lavrik, Nickolay V.; List, Frederick; Gupta, Nitant; Bets, Ksenia V.; Yakobson, Boris I.; Smirnov, Sergei N.

2018-03-01

There is a demand for the manufacture of two-dimensional (2D) materials with high-quality single crystals of large size. Usually, epitaxial growth is considered the method of choice1 in preparing single-crystalline thin films, but it requires single-crystal substrates for deposition. Here we present a different approach and report the synthesis of single-crystal-like monolayer graphene films on polycrystalline substrates. The technological realization of the proposed method resembles the Czochralski process and is based on the evolutionary selection2 approach, which is now realized in 2D geometry. The method relies on `self-selection' of the fastest-growing domain orientation, which eventually overwhelms the slower-growing domains and yields a single-crystal continuous 2D film. Here we have used it to synthesize foot-long graphene films at rates up to 2.5 cm h-1 that possess the quality of a single crystal. We anticipate that the proposed approach could be readily adopted for the synthesis of other 2D materials and heterostructures.

Large area synthesis, characterization, and anisotropic etching of two dimensional tungsten disulfide films

International Nuclear Information System (INIS)

Mutlu, Zafer; Ozkan, Mihrimah; Ozkan, Cengiz S.

2016-01-01

Emergent properties of tungsten disulfide at the quantum confinement limit hold promise for electronic and optoelectronic applications. Here we report on the large area synthesis of atomically thin tungsten disulfide films with strong photoluminescence properties via sulfurization of the pre-deposited tungsten films. Detailed characterization of the pre-deposited tungsten films and tungsten disulfide films are performed using microscopy and spectroscopy methods. By directly heating tungsten disulfide films in air, we have shown that the films tend to be etched into a series of triangular shaped pits with the same orientations, revealing the anisotropic etching behavior of tungsten disulfide edges. Moreover, the dimensions of the triangular pits increase with the number of layers, suggesting a thickness dependent behavior of etching in tungsten disulfide films. This method offers a promising new avenue for engineering the edge structures of tungsten disulfide films. - Highlights: • Large-scale synthesis of WS_2 films is achieved via sulfurization of W films. • Annealing of W films leads to a substantial improvement in the quality of WS_2 films. • WS_2 films show laser power dependent photoluminescence characteristics. • WS_2 films are etched with well-oriented triangular pits upon annealing in air. • Anisotropic oxidative etching is greatly affected by the thickness of WS_2 films.

Superconductor-Metal-Insulator transition in two dimensional Ta thin Films

Science.gov (United States)

Park, Sun-Gyu; Kim, Eunseong

2013-03-01

Superconductor-insulator transition has been induced by tuning film thickness or magnetic field. Recent electrical transport measurements of MoGe, Bi, Ta thin films revealed an interesting intermediate metallic phase which intervened superconducting and insulating phases at certain range of magnetic field. Especially, Ta thin films show the characteristic IV behavior at each phase and the disorder tuned intermediate metallic phase [Y. Li, C. L. Vicente, and J. Yoon, Physical Review B 81, 020505 (2010)]. This unexpected metallic phase can be interpreted as a consequence of vortex motion or contribution of fermionic quasiparticles. In this presentation, we report the scaling behavior during the transitions in Ta thin film as well as the transport measurements in various phases. Critical exponents v and z are obtained in samples with wide ranges of disorder. These results reveal new universality class appears when disorder exceeds a critical value. Dynamical exponent z of Superconducting sample is found to be 1, which is consistent with theoretical prediction of unity. z in a metallic sample is suddenly increased to be approximately 2.5. This critical exponent is much larger than the value found in other system and theoretical prediction. We gratefully acknowledge the financial support by the National Research Foundation of Korea through the Creative Research Initiatives.

Zero- and two-dimensional hybrid carbon phosphors for high colorimetric purity white light-emission.

Science.gov (United States)

Ding, Yamei; Chang, Qing; Xiu, Fei; Chen, Yingying; Liu, Zhengdong; Ban, Chaoyi; Cheng, Shuai; Liu, Juqing; Huang, Wei

2018-03-01

Carbon nanomaterials are promising phosphors for white light emission. A facile single-step synthesis method has been developed to prepare zero- and two-dimensional hybrid carbon phosphors for the first time. Zero-dimensional carbon dots (C-dots) emit bright blue luminescence under 365 nm UV light and two-dimensional nanoplates improve the dispersity and film forming ability of C-dots. As a proof-of-concept application, the as-prepared hybrid carbon phosphors emit bright white luminescence in the solid state, and the phosphor-coated blue LEDs exhibit high colorimetric purity white light-emission with a color coordinate of (0.3308, 0.3312), potentially enabling the successful application of white emitting phosphors in the LED field.

Langmuir-Blodgett film based on MEH-PPV for cholesterol biosensor

International Nuclear Information System (INIS)

Matharu, Zimple; Arya, Sunil K.; Singh, S.P.; Gupta, Vinay; Malhotra, B.D.

2009-01-01

Cholesterol oxidase (ChOx) has been immobilized onto conducting poly[2-methoxy,5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV)/stearic acid (SA) Langmuir-Blodgett film transferred onto octadecanethiol (ODT) modified gold plate. The ChOx/MEH-PPV/SA LB film bioelectrode exhibits has been characterized by FT-IR, contact angle, and atomic force microscopy. The response of the ChOx/MEH-PPV/SA LB film bioelectrode carried out using differential pulse voltammetry (DPV) studies reveal linearity from 1.29 to 12.91 mM of cholesterol concentration and response time as 30 s. This ChOx/MEH-PPV/SA bioelectrode exhibits values of correlation coefficient as 0.9939, standard deviation as 0.0029 μA and limit of detection as 1.66 mM. UV-visible spectrophotometer studies reveal that 5.2 x 10 -3 U of ChOx are actively working per cm 2 area of ChOx/MEH-PPV/SA LB film bioelectrode and this bioelectrode is thermally stable upto 55 deg. C with reusability of about 60 times

Langmuir-Blodgett film based on MEH-PPV for cholesterol biosensor

Energy Technology Data Exchange (ETDEWEB)

Matharu, Zimple [Biomolecular Electronics and Conducting Polymer Research Group, National Physical Laboratory, Dr. K.S. Krishnan Marg, New Delhi 110012 (India); Department of Physics and Astrophysics, University of Delhi, Delhi 110007 (India); Arya, Sunil K.; Singh, S.P. [Biomolecular Electronics and Conducting Polymer Research Group, National Physical Laboratory, Dr. K.S. Krishnan Marg, New Delhi 110012 (India); Gupta, Vinay [Department of Physics and Astrophysics, University of Delhi, Delhi 110007 (India); Malhotra, B.D. [Biomolecular Electronics and Conducting Polymer Research Group, National Physical Laboratory, Dr. K.S. Krishnan Marg, New Delhi 110012 (India)], E-mail: bansi.malhotra@gmail.com

2009-02-23

Cholesterol oxidase (ChOx) has been immobilized onto conducting poly[2-methoxy,5-(2'-ethyl-hexyloxy)-1,4-phenylene vinylene] (MEH-PPV)/stearic acid (SA) Langmuir-Blodgett film transferred onto octadecanethiol (ODT) modified gold plate. The ChOx/MEH-PPV/SA LB film bioelectrode exhibits has been characterized by FT-IR, contact angle, and atomic force microscopy. The response of the ChOx/MEH-PPV/SA LB film bioelectrode carried out using differential pulse voltammetry (DPV) studies reveal linearity from 1.29 to 12.91 mM of cholesterol concentration and response time as 30 s. This ChOx/MEH-PPV/SA bioelectrode exhibits values of correlation coefficient as 0.9939, standard deviation as 0.0029 {mu}A and limit of detection as 1.66 mM. UV-visible spectrophotometer studies reveal that 5.2 x 10{sup -3} U of ChOx are actively working per cm{sup 2} area of ChOx/MEH-PPV/SA LB film bioelectrode and this bioelectrode is thermally stable upto 55 deg. C with reusability of about 60 times.

Quantum Dots in Two-Dimensional Perovskite Matrices for Efficient Near-Infrared Light Emission

KAUST Repository

Yang, Zhenyu

2017-03-13

Quantum-dot-in-perovskite solids are excellent candidates for infrared light-emitting applications. The first generation of dot-in-perovskite light-emitting diodes (LEDs) has shown bright infrared electroluminescence with tunable emission wavelength; however, their performance has been limited by degradation of the active layer at practical operating voltages. This arises from the instability of the three-dimensional (3D) organolead halide perovskite matrix. Herein we report the first dot-in-perovskite solids that employ two-dimensional (2D) perovskites as the matrix. 2D perovskite passivation is achieved via an in situ alkylammonium/alkylamine substitution carried out during the quantum dot (QD) ligand exchange process. This single-step film preparation process enables deposition of the QD/perovskite active layers with thicknesses of 40 nm, over seven times thinner than the first-generation dot-in-perovskite thin films that relied on a multistep synthesis. The dot-in-perovskite film roughness improved from 31 nm for the first-generation films to 3 nm for films as a result of this new approach. The best devices exhibit external quantum efficiency peaks exceeding 2% and radiances of ∼1 W sr–1 m–2, with an improved breakdown voltage up to 7.5 V. Compared to first-generation dot-in-perovskites, this new process reduces materials consumptions 10-fold and represents a promising step toward manufacturable devices.

Quantum Dots in Two-Dimensional Perovskite Matrices for Efficient Near-Infrared Light Emission

KAUST Repository

Yang, Zhenyu; Voznyy, Oleksandr; Walters, Grant; Fan, James Z.; Liu, Min; Kinge, Sachin; Hoogland, Sjoerd; Sargent, Edward H.

2017-01-01

Quantum-dot-in-perovskite solids are excellent candidates for infrared light-emitting applications. The first generation of dot-in-perovskite light-emitting diodes (LEDs) has shown bright infrared electroluminescence with tunable emission wavelength; however, their performance has been limited by degradation of the active layer at practical operating voltages. This arises from the instability of the three-dimensional (3D) organolead halide perovskite matrix. Herein we report the first dot-in-perovskite solids that employ two-dimensional (2D) perovskites as the matrix. 2D perovskite passivation is achieved via an in situ alkylammonium/alkylamine substitution carried out during the quantum dot (QD) ligand exchange process. This single-step film preparation process enables deposition of the QD/perovskite active layers with thicknesses of 40 nm, over seven times thinner than the first-generation dot-in-perovskite thin films that relied on a multistep synthesis. The dot-in-perovskite film roughness improved from 31 nm for the first-generation films to 3 nm for films as a result of this new approach. The best devices exhibit external quantum efficiency peaks exceeding 2% and radiances of ∼1 W sr–1 m–2, with an improved breakdown voltage up to 7.5 V. Compared to first-generation dot-in-perovskites, this new process reduces materials consumptions 10-fold and represents a promising step toward manufacturable devices.

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

International Nuclear Information System (INIS)

Xu Jianhua; Yang Yajie; Yu Junsheng; Jiang Yadong

2009-01-01

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

Composite polyaniline/calixarene Langmuir - Blodgett films for gas sensing

Science.gov (United States)

Lavrik, N. V.; DeRossi, D.; Kazantseva, Z. I.; Nabok, A. V.; Nesterenko, B. A.; Piletsky, S. A.; Kalchenko, V. I.; Shivaniuk, A. N.; Markovskiy, L. N.

1996-12-01

Mixtures of the polyaniline (emeraldine base) and phosphorylated calix[4]resorcinolarene derivative (CA) are proposed to prepare LB films for conductometric gas sensors. They are quite stable at the air - water interface and give LB films of high quality. The average thickness of the mixed monolayers is found to be 1.6 nm. The as-deposited films are insulating. Doping with HCl increases the conductivity up to between 0957-4484/7/4/002/img12 and 0957-4484/7/4/002/img13 which depends on the component ratio. The films containing more than 20 wt% of CA are doped reversibly in part. Thus, the films which are highly sensitive to either 0957-4484/7/4/002/img14 or HCl films are prepared by choosing the component ratio. Detection of 0957-4484/7/4/002/img14 and HCl in the ppm range is demonstrated.

Two-dimensional wavelet transform feature extraction for porous silicon chemical sensors.

Science.gov (United States)

Murguía, José S; Vergara, Alexander; Vargas-Olmos, Cecilia; Wong, Travis J; Fonollosa, Jordi; Huerta, Ramón

2013-06-27

Designing reliable, fast responding, highly sensitive, and low-power consuming chemo-sensory systems has long been a major goal in chemo-sensing. This goal, however, presents a difficult challenge because having a set of chemo-sensory detectors exhibiting all these aforementioned ideal conditions are still largely un-realizable to-date. This paper presents a unique perspective on capturing more in-depth insights into the physicochemical interactions of two distinct, selectively chemically modified porous silicon (pSi) film-based optical gas sensors by implementing an innovative, based on signal processing methodology, namely the two-dimensional discrete wavelet transform. Specifically, the method consists of using the two-dimensional discrete wavelet transform as a feature extraction method to capture the non-stationary behavior from the bi-dimensional pSi rugate sensor response. Utilizing a comprehensive set of measurements collected from each of the aforementioned optically based chemical sensors, we evaluate the significance of our approach on a complex, six-dimensional chemical analyte discrimination/quantification task problem. Due to the bi-dimensional aspects naturally governing the optical sensor response to chemical analytes, our findings provide evidence that the proposed feature extractor strategy may be a valuable tool to deepen our understanding of the performance of optically based chemical sensors as well as an important step toward attaining their implementation in more realistic chemo-sensing applications. Copyright © 2013 Elsevier B.V. All rights reserved.

Self-organized dendritic patterns in the polymer Langmuir-Blodgett film

Energy Technology Data Exchange (ETDEWEB)

Matsui, Jun, E-mail: jun_m@tagen.tohoku.ac.j [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1, Katahira, Aoba-ku Sendai, 980-8577 (Japan); Precursory Research for Embryonic Science and Technology (PRESTO), Japan Science and Technology Agency, 4-1-8, Honcho, Kawaguchi 332-0012 (Japan); Suzuki, Toshio; Mikayama, Takeshi [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1, Katahira, Aoba-ku Sendai, 980-8577 (Japan); Aoki, Atsushi [Materials Science and Engineering, Graduate School of Engineering, Nagoya Institute of Technology Gokiso, Shouwa-ku, Nagoya 466-8555 (Japan); Miyashita, Tokuji [Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1, Katahira, Aoba-ku Sendai, 980-8577 (Japan)

2011-01-03

We report the formation of a self-organized dendritic pattern of nanometer thickness in polymer Langmuir-Blodgett (LB) films. Poly(N-dodecylacrylamide) (pDDA)/chloroform solution was spread on a water surface to form a stable polymer monolayer. A pDDA monolayer was deposited onto a hydrophilic silicon substrate by upward deposition from a water subphase, and a second layer was then deposited by downward deposition. The substrate with the two layers was withdrawn from a clean water surface at a high speed to form the dendritic pattern, which was imaged by atomic force microscopy. The height of the pattern, 3.5 nm, corresponds to the height of a bilayer pDDA LB film, suggesting that the pattern forms when the deposited outermost layer overturns by meniscus oscillation. A similar dendritic structure of narrower width and lower height was fabricated on a hydrophobic silicon substrate.

Boron nitride as two dimensional dielectric: Reliability and dielectric breakdown

Energy Technology Data Exchange (ETDEWEB)

Ji, Yanfeng; Pan, Chengbin; Hui, Fei; Shi, Yuanyuan; Lanza, Mario, E-mail: mlanza@suda.edu.cn [Institute of Functional Nano and Soft Materials, Collaborative Innovation Center of Suzhou Nano Science and Technology, Soochow University, 199 Ren-Ai Road, Suzhou 215123 (China); Zhang, Meiyun; Long, Shibing [Key Laboratory of Microelectronics Devices & Integrated Technology, Institute of Microelectronics, Chinese Academy of Sciences, Beijing 100029 (China); Lian, Xiaojuan; Miao, Feng [National Laboratory of Solid State Microstructures, School of Physics, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093 (China); Larcher, Luca [DISMI, Università di Modena e Reggio Emilia, 42122 Reggio Emilia (Italy); Wu, Ernest [IBM Research Division, Essex Junction, Vermont 05452 (United States)

2016-01-04

Boron Nitride (BN) is a two dimensional insulator with excellent chemical, thermal, mechanical, and optical properties, which make it especially attractive for logic device applications. Nevertheless, its insulating properties and reliability as a dielectric material have never been analyzed in-depth. Here, we present the first thorough characterization of BN as dielectric film using nanoscale and device level experiments complementing with theoretical study. Our results reveal that BN is extremely stable against voltage stress, and it does not show the reliability problems related to conventional dielectrics like HfO{sub 2}, such as charge trapping and detrapping, stress induced leakage current, and untimely dielectric breakdown. Moreover, we observe a unique layer-by-layer dielectric breakdown, both at the nanoscale and device level. These findings may be of interest for many materials scientists and could open a new pathway towards two dimensional logic device applications.

Micromechanical exfoliation of two-dimensional materials by a polymeric stamp

International Nuclear Information System (INIS)

Costa, M C Ferraz da; Ribeiro, H B; Kessler, F; Souza, E A T de; Fechine, G J M

2016-01-01

In this work, an alternative technique to the traditional micromechanical exfoliation of two-dimensional materials is proposed, consisting of isolated flakes of graphite and molybdenum disulphide onto polymeric surfaces films. The set made up of polymer and flakes is fabricated by using a hot-press machine called polymeric stamp. The polymeric stamp was used to allocate flakes and also to allow the exfoliation process to take place just in one face of isolated flake. Optical microscopy, Raman spectroscopy and photoluminescence spectroscopy results showed that multilayers, bilayers and single layers of graphene and MoS 2 were obtained by using a polymeric stamp as tool for micromechanical exfoliation. These crystals were more easily found because the exfoliation process concentrates them in well-defined locations. The results prove the effectiveness of the method by embedding two-dimensional materials into polymers to fabricate fewer layers crystals in a fast, economic and clean way. (paper)

Micromechanical exfoliation of two-dimensional materials by a polymeric stamp

Science.gov (United States)

Ferraz da Costa, M. C.; Ribeiro, H. B.; Kessler, F.; de Souza, E. A. T.; Fechine, G. J. M.

2016-02-01

In this work, an alternative technique to the traditional micromechanical exfoliation of two-dimensional materials is proposed, consisting of isolated flakes of graphite and molybdenum disulphide onto polymeric surfaces films. The set made up of polymer and flakes is fabricated by using a hot-press machine called polymeric stamp. The polymeric stamp was used to allocate flakes and also to allow the exfoliation process to take place just in one face of isolated flake. Optical microscopy, Raman spectroscopy and photoluminescence spectroscopy results showed that multilayers, bilayers and single layers of graphene and MoS2 were obtained by using a polymeric stamp as tool for micromechanical exfoliation. These crystals were more easily found because the exfoliation process concentrates them in well-defined locations. The results prove the effectiveness of the method by embedding two-dimensional materials into polymers to fabricate fewer layers crystals in a fast, economic and clean way.

Carbon-based layer-by-layer nanostructures: from films to hollow capsules

Science.gov (United States)

Hong, Jinkee; Han, Jung Yeon; Yoon, Hyunsik; Joo, Piljae; Lee, Taemin; Seo, Eunyong; Char, Kookheon; Kim, Byeong-Su

2011-11-01

Over the past years, the layer-by-layer (LbL) assembly has been widely developed as one of the most powerful techniques to prepare multifunctional films with desired functions, structures and morphologies because of its versatility in the process steps in both material and substrate choices. Among various functional nanoscale objects, carbon-based nanomaterials, such as carbon nanotubes and graphene sheets, are promising candidates for emerging science and technology with their unique physical, chemical, and mechanical properties. In particular, carbon-based functional multilayer coatings based on the LbL assembly are currently being actively pursued as conducting electrodes, batteries, solar cells, supercapacitors, fuel cells and sensor applications. In this article, we give an overview on the use of carbon materials in nanostructured films and capsules prepared by the LbL assembly with the aim of unraveling the unique features and their applications of carbon multilayers prepared by the LbL assembly.

Three-dimensional growth simulation: A study of substrate oriented films

International Nuclear Information System (INIS)

Besnard, A; Martin, N; Carpentier, L

2010-01-01

Monte Carlo simulations are developed to simulate the growth of three-dimensional columnar microstructure in thin films. We are studying in particular oriented microstructure like those produced with the Glancing Angle Deposition technique (GLAD). Some geometrical characteristics of the particles flux, the organization of defect sites on the substrate surface and the atomic surface diffusion are mainly investigated in order to predict the growth processes and the resulting features of the films. This study reports on simulations of thin film growth exhibiting an oblique and zigzag columnar microstructure. Column angle evolution and density are investigated versus incidence angle α or period number n and compared with experimental measurements.

Numerical analysis for conductance probes, for the measurement of liquid film thickness in two-phase flow

International Nuclear Information System (INIS)

No, Hee Cheon; Mayinger, F.

1995-01-01

A three-dimensional numerical tool is developed to calculate the potential distribution, electric field, and conductance for any types of conductance probes immersed in the wavy liquid film with various shapes of its free surface. The tool is validated against various analytical solutions. It is applied to find out the characteristics of the wire-wire probe, the flush-wire probe and the flush-flush probe in terms of resolution, linearity, and sensitivity. The wire-wire probe shows high resolution and excellent linearity for various film thickness, but comparably low sensitivity for low film thickness fixed. The flush-wire probe shows good linearity and high sensitivity for varying film thickness, but resolution degrading with an increase in film thickness. In order to check the applicability of the three types of probes in the real situation, the Korteweg-de Vries(KdV) two-dimensional solitary wave is simulated. The wire-wire probe is strongly affected by the installation direction of the two wires; when the wires are installed perpendicularly to the flow direction, the wire-wire probe shows large distortion of the solitary wave. In order to measure the transverse profile of waves, the wire-wire probes and the flush-wire probes are required to be separately installed 2mm and 2mm, respectively

A Three-Dimensional Coupled Internal/External Simulation of a Film-Cooled Turbine Vane

Science.gov (United States)

Heidmann, James D.; Rigby, David L.; Ameri, Ali A.

1999-01-01

A three-dimensional Navier-Stokes simulation has been performed for a realistic film-cooled turbine vane using the LeRC-HT code. The simulation includes the flow regions inside the coolant plena and film cooling holes in addition to the external flow. The vane is the subject of an upcoming NASA Glenn Research Center experiment and has both circular cross-section and shaped film cooling holes. This complex geometry is modeled using a multi-block grid which accurately discretizes the actual vane geometry including shaped holes. The simulation matches operating conditions for the planned experiment and assumes periodicity in the spanwise direction on the scale of one pitch of the film cooling hole pattern. Two computations were performed for different isothermal wall temperatures, allowing independent determination of heat transfer coefficients and film effectiveness values. The results indicate separate localized regions of high heat transfer coefficient values, while the shaped holes provide a reduction in heat flux through both parameters. Hole exit data indicate rather simple skewed profiles for the round holes, but complex profiles for the shaped holes with mass fluxes skewed strongly toward their leading edges.

Langmuir–Blodgett films based on poly(p-phenylene vinylene) and protein-stabilised palladium nanoparticles: Implications in luminescent and conducting properties

Energy Technology Data Exchange (ETDEWEB)

Goto, Thiago E.; Sakai, Andrei [Institute of Environmental, Chemical and Pharmaceutical Sciences, Federal University of São Paulo, Diadema, SP 09972-270 (Brazil); Iost, Rodrigo M. [Institute of Chemistry of de São Carlos, University of São Paulo, São Carlos, SP 13560-970 (Brazil); Silva, Welter C. [Center of Nature Sciences, Federal University of Piauí, Teresina, PI 64049-550 (Brazil); Crespilho, Frank N. [Institute of Chemistry of de São Carlos, University of São Paulo, São Carlos, SP 13560-970 (Brazil); Péres, Laura O. [Institute of Environmental, Chemical and Pharmaceutical Sciences, Federal University of São Paulo, Diadema, SP 09972-270 (Brazil); Caseli, Luciano, E-mail: lcaseli@unifesp.br [Institute of Environmental, Chemical and Pharmaceutical Sciences, Federal University of São Paulo, Diadema, SP 09972-270 (Brazil)

2013-07-01

In this paper, poly(p-phenylene vinylene) block copolymers (PPV) were immobilised in stearic acid (HSt) Langmuir–Blodgett (LB) films, and their conducting and luminescent properties were enhanced by the incorporation of palladium nanoparticles stabilised by glucose oxidase (GOx-PdNPs). The nanobiocomposite, based on HSt, PPV, and GOx-PdNPs, was transferred from the air-water interface onto solid supports using the LB technique. The films were characterised by surface pressure–area isotherms, polarisation modulation infrared reflection–absorption spectroscopy, fluorescence spectroscopy, and conductivity measurements. The results indicated that the incorporation of GOx-PdNPs in PPV-HSt LB films enhances the luminescence and conducting properties of the PPV. Based on the higher conductivity and emission obtained with the hybrid LB films and the ability to tune the molecular-level interactions between the film components by changing the experimental conditions, thus allowing for further optimisation, one may envisage applications for these films in optical and electronic devices, such as organic light-emitting diodes. - Highlights: • Palladium nanoparticles were introduced in conducting polymer-fatty acid monolayers. • Hybrid films were characterised with tensiometry and infrared spectroscopy. • Films were transferred to solid supports with the Langmuir–Blodgett technique. • Nanoparticles enhanced luminescence and conducting properties.

A metrological study of autoradiographs from two-dimensional gel electrophoresis.

Science.gov (United States)

Valiron, O; Lefkovits, I; Garderet, P; Steinberg, C

1984-12-01

Samples prepared from a single batch of labeled cells were subjected to two-dimensional gel electrophoresis and autoradiography. Three factors were varied: total quantity of protein, quantity of labeled protein, and exposure time. The mean background absorbance of the film remained identical (about 0.5 A) for all the treated series, whatever the exposure time and whether or not there were unlabeled proteins in the sample. Hence any spot with a peak A of the same order of magnitude can be seen. The standard deviation was about 0.05 A. Thus, the measurement precision is 2.5% of full scale for digitalization over 0 to 2 A. We derived experimental calibration curves, which are neither linear nor logarithmic because of the film response and which can be used on randomly chosen spots.

Phase-field-based lattice Boltzmann modeling of large-density-ratio two-phase flows

Science.gov (United States)

Liang, Hong; Xu, Jiangrong; Chen, Jiangxing; Wang, Huili; Chai, Zhenhua; Shi, Baochang

2018-03-01

In this paper, we present a simple and accurate lattice Boltzmann (LB) model for immiscible two-phase flows, which is able to deal with large density contrasts. This model utilizes two LB equations, one of which is used to solve the conservative Allen-Cahn equation, and the other is adopted to solve the incompressible Navier-Stokes equations. A forcing distribution function is elaborately designed in the LB equation for the Navier-Stokes equations, which make it much simpler than the existing LB models. In addition, the proposed model can achieve superior numerical accuracy compared with previous Allen-Cahn type of LB models. Several benchmark two-phase problems, including static droplet, layered Poiseuille flow, and spinodal decomposition are simulated to validate the present LB model. It is found that the present model can achieve relatively small spurious velocity in the LB community, and the obtained numerical results also show good agreement with the analytical solutions or some available results. Lastly, we use the present model to investigate the droplet impact on a thin liquid film with a large density ratio of 1000 and the Reynolds number ranging from 20 to 500. The fascinating phenomena of droplet splashing is successfully reproduced by the present model and the numerically predicted spreading radius exhibits to obey the power law reported in the literature.

High performance top-gated ferroelectric field effect transistors based on two-dimensional ZnO nanosheets

Science.gov (United States)

Tian, Hongzheng; Wang, Xudong; Zhu, Yuankun; Liao, Lei; Wang, Xianying; Wang, Jianlu; Hu, Weida

2017-01-01

High quality ultrathin two-dimensional zinc oxide (ZnO) nanosheets (NSs) are synthesized, and the ZnO NS ferroelectric field effect transistors (FeFETs) are demonstrated based on the P(VDF-TrFE) polymer film used as the top gate insulating layer. The ZnO NSs exhibit a maximum field effect mobility of 588.9 cm2/Vs and a large transconductance of 2.5 μS due to their high crystalline quality and ultrathin two-dimensional structure. The polarization property of the P(VDF-TrFE) film is studied, and a remnant polarization of >100 μC/cm2 is achieved with a P(VDF-TrFE) thickness of 300 nm. Because of the ultrahigh remnant polarization field generated in the P(VDF-TrFE) film, the FeFETs show a large memory window of 16.9 V and a high source-drain on/off current ratio of more than 107 at zero gate voltage and a source-drain bias of 0.1 V. Furthermore, a retention time of >3000 s of the polarization state is obtained, inspiring a promising candidate for applications in data storage with non-volatile features.

Resistive transition in two-dimensional array of proximity-coupled superconducting weak links

International Nuclear Information System (INIS)

Gao Peng; Yu Zheng; Wei Wang; Yao Xi-xian

1988-01-01

The Kosterlitz Thouless transition in two-dimensional arrays of proximity-coupled superconducting weak links has been studied in this paper. The samples were prepared by application of the vacuum-evaporation/photoengraving/chemical-etching technique. The experimental results of measurements on some samples of array film showed the existence of the K-T transition in these samples and were consistent with the theory of Lobb, Abraham, and Tinkham

Annealing assisted structural and surface morphological changes in Langmuir–Blodgett films of nickel octabutoxy phthalocyanine

Energy Technology Data Exchange (ETDEWEB)

Shilpa Harish, T.; Viswanath, P., E-mail: viswanath@cnsms.res.in

2016-01-01

We report our studies on thin films of metallo-phthalocyanine (MPc), Nickel(II)1,4,8,11,15,18,22,25-octabutoxy-29H,31H-phthalocyanine (NiPc(OBu){sub 8}) transferred in a well defined thermodynamic state over a self assembled monolayer (octadecyl trichlorosilane)/SiO{sub 2}/Si substrate using the Langmuir–Blodgett (LB) method. The films are characterized using differential scanning calorimetry (DSC), grazing incidence X-ray diffraction (GIXD) and atomic force microscopy (AFM) techniques. DSC studies on powdered samples in the bulk indicate enantiotropic solid–solid phase transition. GIXD studies on the as-deposited LB film show a Bragg peak indicating crystallinity of the thin film. Annealing (373 K) results in reduction of lattice spacing (1.21 Å) signifying changes in molecular packing within the unit cell. At this stage, an additional Bragg peak is observed which grows at the expense of the former one and they coexist between 373 K and 423 K. A discontinuity in lattice spacing from 20.73 to 15.12 Å with annealing indicates clearly a structural change of the underlying crystalline lattice. Correspondingly, the surface morphology images obtained using AFM show, with annealing, a transformation from spherical granular morphology to elongated, flat crystallites suggesting asymmetric growth process. Statistical parameters of the grain extracted from the AFM images show that the size, fractal dimension and circularity are affected by annealing. Based on these studies, we infer the structural and surface morphological changes of the meta-stable phase (Form I) to the stable phase (Form II) in annealed LB films of phthalocyanine. - Highlights: • Langmuir–Blodgett (LB) films of phthalocyanine subjected to thermal annealing. • Structural transformation and coexistence of polymorphs in LB films • Surface morphology changes from nanoscale grains to elongated crystallites. • Reduction of fractal dimension and circularity index reveals asymmetric growth.

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

Energy Technology Data Exchange (ETDEWEB)

Greene, J. E. [University of Illinois, Urbana, Illinois 61801 (United States); Linköping University, 581 83 Linköping (Sweden); National Taiwan University of Science and Technology, Taipei 10607, Taiwan (China)

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

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

International Nuclear Information System (INIS)

Greene, J. E.

2015-01-01

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 SiO 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

LB3D : A parallel implementation of the Lattice-Boltzmann method for simulation of interacting amphiphilic fluids

NARCIS (Netherlands)

Schmieschek, S.; Shamardin, L.; Frijters, S.; Krüger, T.; Schiller, U.D.; Harting, J.; Coveney, P.V.

2017-01-01

We introduce the lattice-Boltzmann code LB3D, version 7.1. Building on a parallel program and supporting tools which have enabled research utilising high performance computing resources for nearly two decades, LB3D version 7 provides a subset of the research code functionality as an open source

Plasmon-exciton polaritons in two-dimensional semiconductor/metal interfaces

Science.gov (United States)

Gonçalves, P. A. D.; Bertelsen, L. P.; Xiao, Sanshui; Mortensen, N. Asger

2018-01-01

The realization and control of polaritons is of paramount importance in the prospect of novel photonic devices. Here, we investigate the emergence of plasmon-exciton polaritons in hybrid structures consisting of a two-dimensional transition-metal dichalcogenide (TMDC) deposited onto a metal substrate or coating a metallic thin film. We determine the polaritonic spectrum and show that, in the former case, the addition of a top dielectric layer and, in the latter case, the thickness of the metal film can be used to tune and promote plasmon-exciton interactions well within the strong-coupling regime. Our results demonstrate that Rabi splittings exceeding 100 meV can readily be achieved in planar dielectric/TMDC/metal structures under ambient conditions. We thus believe that this Rapid Communication provides a simple and intuitive picture to tailor strong coupling in plexcitonics with potential applications for engineering compact photonic devices with tunable optical properties.

Two-dimensional grating guided-mode resonance tunable filter.

Science.gov (United States)

Kuo, Wen-Kai; Hsu, Che-Jung

2017-11-27

A two-dimensional (2D) grating guided-mode resonance (GMR) tunable filter is experimentally demonstrated using a low-cost two-step nanoimprinting technology with a one-dimensional (1D) grating polydimethylsiloxane mold. For the first nanoimprinting, we precisely control the UV LED irradiation dosage and demold the device when the UV glue is partially cured and the 1D grating mold is then rotated by three different angles, 30°, 60°, and 90°, for the second nanoimprinting to obtain 2D grating structures with different crossing angles. A high-refractive-index film ZnO is then coated on the surface of the grating structure to form the GMR filter devices. The simulation and experimental results demonstrate that the passband central wavelength of the filter can be tuned by rotating the device to change azimuth angle of the incident light. We compare these three 2D GMR filters with differential crossing angles and find that the filter device with a crossing angle of 60° exhibits the best performance. The tunable range of its central wavelength is 668-742 nm when the azimuth angle varies from 30° to 90°.

Molecular view of the interaction between iota-carrageenan and a phospholipid film and its role in enzyme immobilization.

Science.gov (United States)

Nobre, Thatyane M; de Sousa e Silva, Heurison; Furriel, Rosa P M; Leone, Francisco A; Miranda, Paulo B; Zaniquelli, Maria Elisabete D

2009-05-28

Proteins incorporated into phospholipid Langmuir-Blodgett (LB) films are a good model system for biomembranes and enzyme immobilization studies. The specific fluidity of biomembranes, an important requisite for enzymatic activity, is naturally controlled by varying phospholipid compositions. In a model system, instead, LB film fluidity may be varied by covering the top layer with different substances able to interact simultaneously with the phospholipid and the protein to be immobilized. In this study, we immobilized a carbohydrate rich Neurospora crassa alkaline phosphatase (NCAP) in monolayers of the sodium salt of dihexadecylphosphoric acid (DHP), a synthetic phospholipid that provides very condensed Langmuir films. The binding of NCAP to DHP Langmuir-Blodgett (LB) films was mediated by the anionic polysaccharide iota-carrageenan (iota-car). Combining results from surface isotherms and the quartz crystal microbalance technique, we concluded that the polysaccharide was essential to promote the interaction between DHP and NCAP and also to increase the fluidity of the film. An estimate of DHP:iota-car ratio within the film also revealed that the polysaccharide binds to DHP LB film in an extended conformation. Furthermore, the investigation of the polysaccharide conformation at molecular level, using sum-frequency vibrational spectroscopy (SFG), indicated a preferential conformation of the carrageenan molecules with the sulfate groups oriented toward the phospholipid monolayer, and both the hydroxyl and ether groups interacting preferentially with the protein. These results demonstrate how interfacial electric fields can reorient and induce conformational changes in macromolecules, which may significantly affect intermolecular interactions at interfaces. This detailed knowledge of the interaction mechanism between the enzyme and the LB film is relevant to design strategies for enzyme immobilization when orientation and fluidity properties of the film provided by the

Recent Advances in Gas Barrier Thin Films via Layer-by-Layer Assembly of Polymers and Platelets.

Science.gov (United States)

Priolo, Morgan A; Holder, Kevin M; Guin, Tyler; Grunlan, Jaime C

2015-05-01

Layer-by-layer (LbL) assembly has emerged as the leading non-vacuum technology for the fabrication of transparent, super gas barrier films. The super gas barrier performance of LbL deposited films has been demonstrated in numerous studies, with a variety of polyelectrolytes, to rival that of metal and metal oxide-based barrier films. This Feature Article is a mini-review of LbL-based multilayer thin films with a 'nanobrick wall' microstructure comprising polymeric mortar and nano-platelet bricks that impart high gas barrier to otherwise permeable polymer substrates. These transparent, water-based thin films exhibit oxygen transmission rates below 5 × 10(-3) cm(3) m(-2) day(-1) atm(-1) and lower permeability than any other barrier material reported. In an effort to put this technology in the proper context, incumbent technologies such as metallized plastics, metal oxides, and flake-filled polymers are briefly reviewed. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Book of specifications (StLB) and solar technology in data processing

Energy Technology Data Exchange (ETDEWEB)

Jaehnig, W; Schiemann, W

1982-06-01

The book of specifications (StLB) is to create a common language for a system of integrated data processing in building construction to be used by all those participating in the process of construction. The StLB comprises e.g. special sectors from the field of framework construction and extension as well as of technical extension. Special performance sectors concerning solar energy are not yet included in the StLB. It can be expected that relevant texts for solar technology shall be included along with other editorial work. At present, analogous texts from various performance sectors can be transferred to solar technology. Different user programmes are available for the data-related utilization of the StLlB. The article illustrates the fields of application of the StLB and its data-related utilization procedure including text input as well as the various devices which are suitable for the individual processes of the StLB.

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

Science.gov (United States)

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

2009-03-03

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

Noncontact Cohesive Swimming of Bacteria in Two-Dimensional Liquid Films.

Science.gov (United States)

Li, Ye; Zhai, He; Sanchez, Sandra; Kearns, Daniel B; Wu, Yilin

2017-07-07

Bacterial swimming in confined two-dimensional environments is ubiquitous in nature and in clinical settings. Characterizing individual interactions between swimming bacteria in 2D confinement will help to understand diverse microbial processes, such as bacterial swarming and biofilm formation. Here we report a novel motion pattern displayed by flagellated bacteria in 2D confinement: When two nearby cells align their moving directions, they tend to engage in cohesive swimming without direct cell body contact, as a result of hydrodynamic interaction but not flagellar intertwining. We further found that cells in cohesive swimming move with higher directional persistence, which can increase the effective diffusivity of cells by ∼3 times as predicted by computational modeling. As a conserved behavior for peritrichously flagellated bacteria, cohesive swimming in 2D confinement may be key to collective motion and self-organization in bacterial swarms; it may also promote bacterial dispersal in unsaturated soils and in interstitial space during infections.

Evaluation of two-dimensional bolus effect of immobilization/support devices on skin doses: A radiochromic EBT film dosimetry study in phantom

International Nuclear Information System (INIS)

Chiu-Tsao, Sou-Tung; Chan, Maria F.

2010-01-01

Purpose: In this study, the authors have quantified the two-dimensional (2D) perspective of skin dose increase using EBT film dosimetry in phantom in the presence of patient immobilization devices during conventional and IMRT treatments. Methods: For 6 MV conventional photon field, the authors evaluated and quantified the 2D bolus effect on skin doses for six different common patient immobilization/support devices, including carbon fiber grid with Mylar sheet, Orfit carbon fiber base plate, balsa wood board, Styrofoam, perforated AquaPlast sheet, and alpha-cradle. For 6 and 15 MV IMRT fields, a stack of two film layers positioned above a solid phantom was exposed at the air interface or in the presence of a patient alpha-cradle. All the films were scanned and the pixel values were converted to doses based on an established calibration curve. The authors determined the 2D skin dose distributions, isodose curves, and cross-sectional profiles at the surface layers with or without the immobilization/support device. The authors also generated and compared the dose area histograms (DAHs) and dose area products from the 2D skin dose distributions. Results: In contrast with 20% relative dose [(RD) dose relative to d max on central axis] at 0.0153 cm in the film layer for 6 MV 10x10 cm 2 open field, the average RDs at the same depth in the film layer were 71%, 69%, 55%, and 57% for Orfit, balsa wood, Styrofoam, and alpha-cradle, respectively. At the same depth, the RDs were 54% under a strut and 26% between neighboring struts of a carbon fiber grid with Mylar sheet, and between 34% and 56% for stretched perforated AquaPlast sheet. In the presence of the alpha-cradle for the 6 MV (15 MV) IMRT fields, the hot spot doses at the effective measurement depths of 0.0153 and 0.0459 cm were 140% and 150% (83% and 89%), respectively, of the isocenter dose. The enhancement factor was defined as the ratio of a given DAH parameter (minimum dose received in a given area) with and without

Formation of three-dimensional nano-porous silver films and application toward electrochemical detection of hydrogen peroxide

Energy Technology Data Exchange (ETDEWEB)

Fan, Junpeng [Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials, Ministry of Education, Shandong University, Jinan 250061 (China); Bian, Xiufang, E-mail: xfbian@sdu.edu.cn [Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials, Ministry of Education, Shandong University, Jinan 250061 (China); Niu, Yuchao [Department of Materials Science and Engineering, Shandong Jianzhu University, Fengming Road, Lingang Development Zone, Jinan 250101 (China); Bai, Yanwen; Xiao, Xinxin; Yang, Chuncheng; Yang, Jianfei; Yang, Jinyue [Key Laboratory for Liquid-Solid Structural Evolution and Processing of Materials, Ministry of Education, Shandong University, Jinan 250061 (China)

2013-11-15

By using the chemically dealloying method, three-dimensional nano-porous silver films (3-D NPSFs) are fabricated into a novel sensor for detecting hydrogen peroxide. The precursor films are prepared by high vacuum magnetron co-sputtering. High-resolution transmission electron microscope (HRTEM) and scanning electron microscope (SEM) are taken to investigate the structure and the micro morphology of the precursor films and nano-porous films. We find that the precursor films are composed of glassy matrix and nanocrystallines. After dealloying, the films exhibit a combination of homogenously distributed pores and silver filaments, and exhibit an open, three dimensional bicontinuous interpenetrating ligament–channel structure. Thickness and morphology of the films can be easily controlled by the sputtering time and alloy composition of the precursor films, respectively. In addition, NPSFs show a good linear responding for the concentration of hydrogen peroxide in phosphate buffered solutions, which indicates NPSFs could be a promising electrochemical material for hydrogen peroxide detection.

Characterizing microbial communities and processes in a modern stromatolite (Shark Bay) using lipid biomarkers and two-dimensional distributions of porewater solutes

DEFF Research Database (Denmark)

Pagès, Anais; Grice, Kliti; Vacher, Michael

2014-01-01

Summary: Modern microbial mats are highly complex and dynamic ecosystems. Diffusive equilibration in thin films (DET) and diffusive gradients in thin films (DGT) samplers were deployed in a modern smooth microbial mat from Shark Bay in order to observe, for the first time, two-dimensional distrib......Summary: Modern microbial mats are highly complex and dynamic ecosystems. Diffusive equilibration in thin films (DET) and diffusive gradients in thin films (DGT) samplers were deployed in a modern smooth microbial mat from Shark Bay in order to observe, for the first time, two...

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

Energy Technology Data Exchange (ETDEWEB)

Choudhary, Keerti; Manjuladevi, V.; Gupta, R. K., E-mail: raj@pilani.bits-pilani.ac.in [Department of physics, Birla Institute of Technology & Science, Pilani-333031, Rajasthan (India)

2016-05-06

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

Three-Dimensional Microstructural Properties of Nanofibrillated Cellulose Films

Directory of Open Access Journals (Sweden)

Arttu Miettinen

2014-04-01

Full Text Available Nanofibrillated cellulose (NFC films have potential as oxygen barriers for, e.g., food packaging applications, but their use is limited by their hygroscopic characteristics. The three-dimensional microstructure of NFC films made of Pinus radiata (Radiata Pine kraft pulp fibres has been assessed in this study, considering the structural development as a function of relative humidity (RH. The surface roughness, micro-porosity, thickness and their correlations were analyzed using X-ray microtomography (X–μCT and computerized image analysis. The results are compared to those from scanning electron microscopy and laser profilometry. Based on a series of films having varying amounts of 2,2,6,6-tetramethylpiperidinyl-1-oxyl (TEMPO-mediated oxidated nanofibrils, it was demonstrated that X–μCT is suitable for assessing the surface and bulk 3D microstructure of the cellulose films. Additionally, one of the series was assessed at varying humidity levels, using the non-destructive capabilities of X–μCT and a newly developed humidity chamber for in-situ characterization. The oxygen transmission rate (OTR of the films (20 g=m2 was below 3:7mLm-2 day-1 at humidity levels below 60% RH. However, the OTR increased considerably to 12:4mLm-2 day-1 when the humidity level increased to 80% RH. The increase in OTR was attributed to a change of the film porosity, which was reflected as an increase in local thickness. Hence, the characterization techniques applied in this study shed more light on the structures of NFC films and how they are affected by varying humidity levels. It was demonstrated that in increasing relative humidity the films swelled and the oxygen barrier properties decreased.

Photophysical behavior of layer-by-layer electrostatic self-assembled film of azo dye Chromotrope-2R and a polycation

Energy Technology Data Exchange (ETDEWEB)

Hansda, Chaitali [Department of Physics, Jadavpur University, Jadavpur, Kolkata 700032 (India); Department of Physics, The University of Burdwan, Golapbag, Burdwan 713104 (India); Dutta, Bipan [Department of Physics, Sammilani Mahavidyalaya, Baghajatin Station, E.M. Bypass, Kolkata 700075 (India); Chakraborty, Utsav; Singha, Tanmoy [Department of Physics, Jadavpur University, Jadavpur, Kolkata 700032 (India); Hussain, Syed Arshad; Bhattacharjee, Debajyoti [Department of Physics, Tripura University, Suryamaninagar 799022, Tripura West (India); Paul, Sharmistha [West Bengal State Council of Science and Technology, Vigyan Chetana Bhavan, Sector-I, Salt Lake, Kolkata 700064 (India); Paul, Pabitra Kumar, E-mail: pabitra_tu@yahoo.co.in [Department of Physics, Jadavpur University, Jadavpur, Kolkata 700032 (India)

2016-10-15

This communication reports the fabrication of layer-by-layer electrostatic self-assembled films of an azo dye Chromotrope-2R (CH2R) and a Polycation poly(allylamine hydrochloride) (PAH) onto solid substrate. UV–vis absorption and steady state fluorescence emission spectroscopy successfully confirm the incorporation of dye molecules onto the PAH coated quartz substrate. The adsorption behavior of CH2R onto PAH backbone in LbL films highly depends upon the variation of the microenvironment namely pH of the dye solution from which the film was fabricated. PAH layer onto quartz substrate was able to swell sufficiently in the dye solution at very high pH. The Density functional theory was also utilized here to explain the origin of various spectral transitions from the ground electronic states for both in neutral and anionic form of CH2R. In LbL films the more closure association of dye molecules causes their aggregations which are reflected in their absorption and steady state fluorescence emission spectra when compared to those of pure dye solution. Atomic force microscopic images of LbL films assembled from CH2R aqueous solution at different pH clearly reveal the change in the surface morphology of the films and different degree of association of dye molecules in LbL films deposited at various pH of CH2R.

Photophysical behavior of layer-by-layer electrostatic self-assembled film of azo dye Chromotrope-2R and a polycation

International Nuclear Information System (INIS)

Hansda, Chaitali; Dutta, Bipan; Chakraborty, Utsav; Singha, Tanmoy; Hussain, Syed Arshad; Bhattacharjee, Debajyoti; Paul, Sharmistha; Paul, Pabitra Kumar

2016-01-01

This communication reports the fabrication of layer-by-layer electrostatic self-assembled films of an azo dye Chromotrope-2R (CH2R) and a Polycation poly(allylamine hydrochloride) (PAH) onto solid substrate. UV–vis absorption and steady state fluorescence emission spectroscopy successfully confirm the incorporation of dye molecules onto the PAH coated quartz substrate. The adsorption behavior of CH2R onto PAH backbone in LbL films highly depends upon the variation of the microenvironment namely pH of the dye solution from which the film was fabricated. PAH layer onto quartz substrate was able to swell sufficiently in the dye solution at very high pH. The Density functional theory was also utilized here to explain the origin of various spectral transitions from the ground electronic states for both in neutral and anionic form of CH2R. In LbL films the more closure association of dye molecules causes their aggregations which are reflected in their absorption and steady state fluorescence emission spectra when compared to those of pure dye solution. Atomic force microscopic images of LbL films assembled from CH2R aqueous solution at different pH clearly reveal the change in the surface morphology of the films and different degree of association of dye molecules in LbL films deposited at various pH of CH2R.

Magnetization of correlated electron systems. MnSi thin films, CrB2 single crystals and two-dimensional electron systems in MgZnO/ZnO

International Nuclear Information System (INIS)

Brasse, Matthias

2014-01-01

Torque magnetometry at low temperature is performed to investigate the magnetic properties of MnSi thin films, of a CrB 2 single crystal and of a two-dimensional electron system (2DESs) formed at the interface of MgZnO/ZnO. The magnetic anisotropy and phase diagram of MnSi as well as information on the electronic structure of CrB 2 are obtained. The MgZnO/ZnO 2DESs exhibits the de Haas-van Alphen effect and non-equilibrium currents which are analyzed in order to determine ground state properties and excited states, respectively.

Enhanced resolution of DNA restriction fragments: A procedure by two-dimensional electrophoresis and double-labeling

International Nuclear Information System (INIS)

Yi, M.; Au, L.C.; Ichikawa, N.; Ts'o, P.O.

1990-01-01

A probe-free method was developed to detect DNA rearrangement in bacteria based on the electrophoretic separation of twice-digested restriction fragments of genomic DNA into a two-dimensional (2-D) pattern. The first restriction enzyme digestion was done in solution, followed by electrophoresis of the restriction fragments in one dimension. A second restriction enzyme digestion was carried out in situ in the gel, followed by electrophoresis in a second dimension perpendicular to the first electrophoresis. The 2-D pattern provides for the resolution of 300-400 spots, which are defined and indexed by an x,y coordinate system with size markers. This approach has greatly increased the resolution power over conventional one-dimensional (1-D) electrophoresis. To study DNA rearrangement, a 2-D pattern from a test strain was compared with the 2-D pattern from a reference strain. After the first digestion, genomic DNA fragments from the test strain were labeled with 35S, while those from the reference strain were labeled with 32P. This was done to utilize the difference in the energy emission of 35S and 32P isotopes for autoradiography when two x-ray films were exposed simultaneously on top of the gel after the 2-D electrophoresis. The irradiation from the decay of 35S exposed only the lower film, whereas the irradiation from the decay of 32P exposed both the lower and upper films. Different DNA fragments existed in the test DNA compared with the reference DNA can be identified unambiguously by the differential two 2-D patterns produced on two films upon exposure to the 35S and 32P fragments in the same gel. An appropriate photographic procedure further simplified the process, allowing only the difference in DNA fragments between these two patterns to be shown in the map

Sprayed films of europium complexes toward light conversion devices

Energy Technology Data Exchange (ETDEWEB)

Camacho, Sabrina A.; Aoki, Pedro H.B.; Constantino, Carlos J.L.; Pires, Ana Maria, E-mail: anapires@fct.unesp.br

2014-09-15

Rare-earth complexes have become subject of intensive research due to the high quantum efficiency of their emission, very narrow bands, and excellent fluorescence monochromaticity. The chemical design and characterization of Eu complexes based on β-diketone ligands hexafluoroacetylacetate (hfac) and dibenzoylmetanate (dbm) is reported here. K[Eu(dbm){sub 4}] and K[Eu(hfac){sub 4}] complexes were immobilized as thin films by using the spray technique, a promising methodology for practical applications. The latter provides not only a faster layer deposition but also larger coated areas compared to conventional methods, such as layer-by-layer (LbL) and Langmuir–Blodgett (LB). The growth of the sprayed films was monitored through microbalance (QCM) and ultraviolet–visible (UV–Vis) absorption spectroscopy, which reveal a higher mass and absorbance per deposited layer of K[Eu(dbm){sub 4}] film. Micro-Raman images display a more homogeneous spatial distribution of the K[Eu(dbm){sub 4}] complex throughout the film, when compared to K[Eu(hfac){sub 4}] film. At nanometer scale, atomic force microscopy (AFM) images indicate that the roughness of the K[Eu(hfac){sub 4}] film is approximately one order of magnitude higher than that for the K[Eu(dbm){sub 4}] film, which pattern is kept at micrometer scale according to micro-Raman measurements. The photoluminescence data show that the complexes remain as pure red emitters upon spray immobilization. Besides, the quantum efficiency for the sprayed films are found equivalent to the values achieved for the powders, highlighting the potential of the films for application in light conversion devices. - Highlights: • Rare earth complexes thin films based on β-diketone ligands. • Spraying procedures to fabricate layer-by-layer (LbL) luminescent thin films. • Chemical design of Eu complexes based on hfac and dbm β-diketones ligands immobilized as sprayed films. • Pure red emitters upon spray immobilization. • Sprayed

Peptoid nanosheets as soluble, two-dimensional templates for calcium carbonate mineralization.

Science.gov (United States)

Jun, Joo Myung V; Altoe, M Virginia P; Aloni, Shaul; Zuckermann, Ronald N

2015-06-25

Nacre-mimetic materials are of great interest, but difficult to synthesize, because they require the ordering of organic and inorganic materials on several length scales. Here we introduce peptoid nanosheets as a versatile two-dimensional platform to develop nacre mimetic materials. Free-floating zwitterionic nanosheets were mineralized with thin films of amorphous calcium carbonate (of 2-20 nm thickness) on their surface to produce planar nacre synthons. These can serve as tunable building blocks to produce layered brick and mortar nanoarchitectures.

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

Science.gov (United States)

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

2012-05-01

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

Resistance scaling function for two-dimensional superconductors and Monte Carlo vortex-fluctuation simulations

International Nuclear Information System (INIS)

Minnhagen, P.; Weber, H.

1985-01-01

A Monte Carlo simulation of the Ginsburg-Landau Coulomb-gas model for vortex fluctuations is described and compared to the measured resistance scaling function for two-dimensional superconductors. This constitutes a new, more direct way of confirming the vortex-fluctuation explanation for the resistive tail of high-sheet-resistance superconducting films. The Monte Carlo data obtained indicate a striking accordance between theory and experiments

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

Science.gov (United States)

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

2016-03-01

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

Correlates of the MMPI LB Scale in a College Population.

Science.gov (United States)

Klein, Steven; Cross, Herbert J.

1984-01-01

Administered the Low Back Pain Scale (LB) of the Minnesota Multiphasic Personality Inventory and other measures to 123 college freshmen. Subjects with a psychosomatic disorder scored higher on LB. Females who reported problems with their mothers were more likely to have a psychosomatic disorder, suggesting different etiology between males and…

Reversible and nonvolatile ferroelectric control of two-dimensional electronic transport properties of ZrCuSiAs-type copper oxyselenide thin films with a layered structure

Science.gov (United States)

Zhao, Xu-Wen; Gao, Guan-Yin; Yan, Jian-Min; Chen, Lei; Xu, Meng; Zhao, Wei-Yao; Xu, Zhi-Xue; Guo, Lei; Liu, Yu-Kuai; Li, Xiao-Guang; Wang, Yu; Zheng, Ren-Kui

2018-05-01

Copper-based ZrCuSiAs-type compounds of LnCuChO (Ln =Bi and lanthanides, Ch =S , Se, Te) with a layered crystal structure continuously attract worldwide attention in recent years. Although their high-temperature (T ≥ 300 K) electrical properties have been intensively studied, their low-temperature electronic transport properties are little known. In this paper, we report the integration of ZrCuSiAs-type copper oxyselenide thin films of B i0.94P b0.06CuSeO (BPCSO) with perovskite-type ferroelectric Pb (M g1 /3N b2 /3 ) O3-PbTi O3 (PMN-PT) single crystals in the form of ferroelectric field effect devices that allow us to control the electronic properties (e.g., carrier density, magnetoconductance, dephasing length, etc.) of BPCSO films in a reversible and nonvolatile manner by polarization switching at room temperature. Combining ferroelectric gating and magnetotransport measurements with the Hikami-Larkin-Nagaoka theory, we demonstrate two-dimensional (2D) electronic transport characteristics and weak antilocalization effect as well as strong carrier-density-mediated competition between weak antilocalization and weak localization in BPCSO films. Our results show that ferroelectric gating using PMN-PT provides an effective and convenient approach to probe the carrier-density-related 2D electronic transport properties of ZrCuSiAs-type copper oxyselenide thin films.

Equivalence of two-dimensional gravities

International Nuclear Information System (INIS)

Mohammedi, N.

1990-01-01

The authors find the relationship between the Jackiw-Teitelboim model of two-dimensional gravity and the SL(2,R) induced gravity. These are shown to be related to a two-dimensional gauge theory obtained by dimensionally reducing the Chern-Simons action of the 2 + 1 dimensional gravity. The authors present an explicit solution to the equations of motion of the auxiliary field of the Jackiw-Teitelboim model in the light-cone gauge. A renormalization of the cosmological constant is also given

Circular patterns of calcium oxalate monohydrate induced by defective Langmuir-Blodgett film on quartz substrates

Energy Technology Data Exchange (ETDEWEB)

He Jieyu [Institute of Biomineralization and Lithiasis Research, Jinan University, Guangzhou 510632 (China); Institute of Biomineralization and Lithiasis Research, Jinan University, Guangzhou 510632 (China); Ouyang Jianming [Institute of Biomineralization and Lithiasis Research, Jinan University, Guangzhou 510632 (China); Institute of Biomineralization and Lithiasis Research, Jinan University, Guangzhou 510632 (China)], E-mail: toyjm@jnu.edu.cn

2009-01-01

The defective Langmuir-Blodgett (LB) film of dipalmitoylphosphatidylcholine (DPPC) on quartz injured by potassium oxalate (K{sub 2}C{sub 2}O{sub 4}) was used as a model system to induce growth of calcium oxalate crystals. Atomic force microscopy (AFM) indicated that circular defective domains with a diameter of 1-200 {mu}m existed in the LB film. Scanning electron microscopy (SEM) showed circular patterns of aggregated calcium oxalate monohydrate (COM) crystallites were induced by these defective domains. It was ascribed to that the interaction between the negatively-charged oxalate ions and the phosphatidyl groups in DPPC headgroups makes the phospholipid molecules rearranged and exist in an out-of-order state in the LB film, especially at the boundaries of liquid-condensed (LC)/liquid-expanded (LE) phases, which provide much more nucleating sites for COM crystals.

Structural studies on Langmuir-Blodgett ultra-thin films on tin (IV) stearate using X-ray diffraction technique

International Nuclear Information System (INIS)

Mohamad Deraman; Muhamad Mat Salleh; Mohd Ali Sulaiman; Mohd Ali Sufi

1991-01-01

X-ray diffraction measurements were carried out on Langmuir-Blodgett (LB) ultra-thin films of tin (IV) stearate for different numbers of layers. The structural information such as interplanar spacing, unit cells spacing, molecular length and orientation of molecular chains were obtained from the diffraction data. This information is discussed and compared with that previously published for LB ultra-thin films of manganese stearate and cadmium stearate

Two-dimensional metamaterial optics

International Nuclear Information System (INIS)

Smolyaninov, I I

2010-01-01

While three-dimensional photonic metamaterials are difficult to fabricate, many new concepts and ideas in the metamaterial optics can be realized in two spatial dimensions using planar optics of surface plasmon polaritons. In this paper we review recent progress in this direction. Two-dimensional photonic crystals, hyperbolic metamaterials, and plasmonic focusing devices are demonstrated and used in novel microscopy and waveguiding schemes

Electronic Transport in Two-Dimensional Materials

Science.gov (United States)

Sangwan, Vinod K.; Hersam, Mark C.

2018-04-01

Two-dimensional (2D) materials have captured the attention of the scientific community due to the wide range of unique properties at nanometer-scale thicknesses. While significant exploratory research in 2D materials has been achieved, the understanding of 2D electronic transport and carrier dynamics remains in a nascent stage. Furthermore, because prior review articles have provided general overviews of 2D materials or specifically focused on charge transport in graphene, here we instead highlight charge transport mechanisms in post-graphene 2D materials, with particular emphasis on transition metal dichalcogenides and black phosphorus. For these systems, we delineate the intricacies of electronic transport, including band structure control with thickness and external fields, valley polarization, scattering mechanisms, electrical contacts, and doping. In addition, electronic interactions between 2D materials are considered in the form of van der Waals heterojunctions and composite films. This review concludes with a perspective on the most promising future directions in this fast-evolving field.

Two-dimensional phase separated structures of block copolymers on solids

Science.gov (United States)

Sen, Mani; Jiang, Naisheng; Endoh, Maya; Koga, Tadanori; Ribbe, Alexander

The fundamental, yet unsolved question in block copolymer (BCP) thin films is the self-organization process of BCPs at the solid-polymer melt interface. We here focus on the self-organization processes of cylinder-forming polystyrene-block-poly (4-vinylpyridine) diblock copolymer and lamellar-forming poly (styrene-block-butadiene-block-styrene) triblock copolymer on Si substrates as model systems. In order to reveal the buried interfacial structures, the following experimental protocols were utilized: the BCP monolayer films were annealed under vacuum at T>Tg of the blocks (to equilibrate the melts); vitrification of the annealed BCP films via rapid quench to room temperature; subsequent intensive solvent leaching (to remove unadsorbed chains) with chloroform, a non-selective good solvent for the blocks. The strongly bound BCP layers were then 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 blocks lie flat on the substrate, forming the two-dimensional, randomly phase-separated structure irrespective of their microdomain structures and interfacial energetics. Acknowledgement of financial support from NSF Grant (CMMI -1332499).

A spectroscopic study of water-soluble pyronin B and pyronin Y in Langmuir-Blodgett films mixed with stearic acid

International Nuclear Information System (INIS)

Meral, Kadem; Erbil, H. Yıldırım; Onganer, Yavuz

2011-01-01

Mono and multilayer of water-soluble pyronin B (PyB) and pyronin Y (PyY) mixed with stearic acid (SA) have been incorporated in Langmuir-Blodgett (LB) films. The surface pressure-area (π-A) isotherm studies pointed out that pure PyB and PyY are incapable of forming stable films at air-water interface and collapsed readily at low surface pressures. However, mixture of PyB or PyY with SA easily formed stable films at the air-water interface and they were easily transferred onto solid substrates. The average area per molecule of mixed films of PyB and PyY at the air-water interface was observed to decrease with increasing concentrations of PyB and PyY. The spectroscopic characteristics of PyB and PyY in chloroform, in SA containing chloroform and in LB films have also been investigated by using absorption and steady-state and time-resolved fluorescence spectroscopy techniques. The morphology of the LB film surfaces has been characterized by using atomic force microscopy (AFM).

A spectroscopic study of water-soluble pyronin B and pyronin Y in Langmuir-Blodgett films mixed with stearic acid

Energy Technology Data Exchange (ETDEWEB)

Meral, Kadem [Department of Chemistry, Faculty of Sciences, Atatuerk University, 25240 Erzurum (Turkey); Erbil, H. Y Latin-Small-Letter-Dotless-I ld Latin-Small-Letter-Dotless-I r Latin-Small-Letter-Dotless-I m [Department of Chemical Engineering, Gebze Institute of Technology, Cay Latin-Small-Letter-Dotless-I rova, Gebze 41400, Kocaeli (Turkey); Onganer, Yavuz, E-mail: yonganer@atauni.edu.tr [Department of Chemistry, Faculty of Sciences, Atatuerk University, 25240 Erzurum (Turkey)

2011-12-01

Mono and multilayer of water-soluble pyronin B (PyB) and pyronin Y (PyY) mixed with stearic acid (SA) have been incorporated in Langmuir-Blodgett (LB) films. The surface pressure-area ({pi}-A) isotherm studies pointed out that pure PyB and PyY are incapable of forming stable films at air-water interface and collapsed readily at low surface pressures. However, mixture of PyB or PyY with SA easily formed stable films at the air-water interface and they were easily transferred onto solid substrates. The average area per molecule of mixed films of PyB and PyY at the air-water interface was observed to decrease with increasing concentrations of PyB and PyY. The spectroscopic characteristics of PyB and PyY in chloroform, in SA containing chloroform and in LB films have also been investigated by using absorption and steady-state and time-resolved fluorescence spectroscopy techniques. The morphology of the LB film surfaces has been characterized by using atomic force microscopy (AFM).

Function and application of ultra thin films

Energy Technology Data Exchange (ETDEWEB)

Sasabe, Hiroyuki

1988-02-01

A film 10-100mm thick which is strong dynamically to some extent and has possibility to manifest fuctions of high degree different from the nature extrapolated from the normal thin film is called an ultra thin film. As an example of its concrete application, there is an electro-luminescence element which is made by laminating 5 layers of LB films of poly-L-phenylalanine on a n-GaP and has vapor-deposited gold electrodes. When voltage of 5V is imposed to it, light emission of 565nm can be observed and the emission efficiency of 2% is obtained. Besides, it has an excellent stability through the lapse of time. There is also a junction element and the ion concentration injected into macromolecule films of this element has a Gaussian distribution from the surface towards the direction of depth. Accordingly, the most active domain in terms of semiconductor as the result of doping is the location in the neighborhood of the peak. Furthermore, a photo memory is also proposed. It is applied to the artificial hemoglobine which is made of LB films, suggesting the feasibility of creating the artificial protein capable of functioning in the conditions in which the natural protein is unable to function. (5 figs, 1 tab, 7 refs)

Structure and Sensor Properties of Thin Ordered Solid Films

Directory of Open Access Journals (Sweden)

Jadwiga Sołoducho

2009-09-01

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

Intrinsic colossal magnetoresistance effect in thin-film Pr0.5Sr0.5MnO3 through dimensionality switching.

Science.gov (United States)

Uozu, Y; Wakabayashi, Y; Ogimoto, Y; Takubo, N; Tamaru, H; Nagaosa, N; Miyano, K

2006-07-21

A homogeneous colossal magnetoresistance (CMR) effect at low temperatures has been found in a thin-film perovskite manganite Pr0.5Sr0.5MnO3. The transition is driven not by the spin alignment as in usual CMR in bulk samples but by the localization-delocalization transition switched by the change in the effective dimensionality. Two-dimensional (x2-y2)-orbital ordering enhanced by the substrate strain is essential for the stabilization of the insulating localized state, which is on the verge of the first-order transition to the three-dimensional metallic ferromangetic state.

Best-estimated multi-dimensional calculation during LB LOCA for APR1400

International Nuclear Information System (INIS)

Oh, D. Y.; Bang, Y. S.; Cheong, A. J.; Woong, S.; Korea, W.

2010-01-01

Best-estimated (BE) calculation with uncertainty quantification for the emergency core cooling system (ECCS) performance analysis during Loss of Coolant Accident (LOCA) is more broadly used in nuclear industries and regulations. In Korea, demand on regulatory audit calculation is continuously increasing to support the safety review for life extension, power up-rating and advanced nuclear reactor design. The thermal-hydraulic system code, MARS (Multi-dimensional Analysis of Reactor Safety), with multi-dimensional capability is used for audit calculation. It achieves to describe the complicated phenomena in reactor coolant system by very effectively consolidating the one dimensional RELAP5/MOD3 with the multidimensional COBRA-TF codes. The advanced power reactors (APR1400) to be evaluated has four separated hydraulic trains of the high pressure injection system (HPSI) with direct vessel injection (DVI) which is different from the existing commercial PWRs. Also, the therma-hydraulic behavior of DVI plant would be considerably different from that of a cold-leg safety injection since the low pressure safety injection system are eliminated and the high pressure safety flow are injected into the specific elevation of reactor vessel downcomer. The ECCS bypass induced by the downcomer boiling due to hot wall heating of reactor vessel during reflooding phase is one of the important phenomena which should be considered in DVI plants. Therefore, in this study, BE calculation with one-dimensional (1-D) and multi-dimensional (multi-D) MARS models during LBLOCA are performed for APR1400 plant. In the multi-D evaluation, the reactor vessel is modeled by multi-D components and the specific treatment of flow path inside reactor vessel, e.g., upper guide structure, is essential. The concept of hot zone is adopted to simulate the limiting thermal-hydraulic conditions surrounding hot rod, which is similar to hot channel in 1-D. Also, alternative treatment of the hot rods in multi-D is

ATR-IR spectroscopy for the detection of induced-phase transition in Langmuir-Blodgett monolayer film

International Nuclear Information System (INIS)

Widayati, Suci

1996-01-01

The rate at which a solid substrate is transferred through the Air/Water interface in the Langmuir-Blodgett process of preparing monomolecular films influences the final structure of the transferred film. This phenomenon has been observed from the attenuated total reflectance infra-red (ATR-IR) spectra of fatty acid monolayer transferred onto germanium substrate. This transfer-induced effect is most evidence when the monolayer is transferred from an expanded region of the surface-pressure-molecular area isotherm, but has limited influence on the hydrocarbon chain conformation of film molecules transferred in the condensed phases at high surface pressure. Such a conformational ordering may due to a kinetically limited phase transition taking place in the meniscus formed between the solid substrate and aqueous sub phase. In addition, these results suggest that the structure of the amphiphilic molecules may modulate the extent and nature of the dipping-speed-induced structural changes taking place in the monomolecular L-B film. In order to use monomolecular L-B films to accurately characterize the structure, orientation and phase properties of monolayers at the Air/Water interface, the L-B transfer must be performed at transfer speeds that minimize this structural phase transition

Comprehensive evaluation of the Berthold LB1200 survey meter

International Nuclear Information System (INIS)

Davis, M.W.

1986-05-01

The performance of two Berthod LB1200 survey meters was evaluated under the influence of a range of beta and photon radiation energies and environmental conditions likely to be encountered in the field. The survey meters responded satisfactorily to the range of beta particle and photon radiation energies emitted by most radioisotopes commonly used in Canada. The survey meters performed acceptably under most of the environmental conditions tested here with the exception of radiofrequency interference and electrostatic charge

Two-dimensional simulations of the superconducting proximity in superconductor-semiconductor junctions

Science.gov (United States)

Chua, Victor; Vissers, Michael; Law, Stephanie A.; Vishveshwara, Smitha; Eckstein, James N.

2015-03-01

We simulate the consequences of the superconducting proximity effect on the DC current response of a semiconductor-superconductor proximity device within the quasiclassical formalism in the diffusively disordered limit. The device is modeled on in-situ fabricated NS junctions of superconducting Nb films on metallic doped InAs films, with electrical terminals placed in an N-S-N T-junction configuration. Due to the non-collinear configuration of this three terminal device, a theoretical model based on coupled two dimensional spectral and distributional Usadel equations was constructed and numerically solved using Finite-Elements methods. In the regime of high junction conductance, our numerical results demonstrate strong temperature and spatial dependencies of the proximity induced modifications to spectral and transport properties. Such characteristics deviate strongly from usual tunnel junction behavior and aspects of this have been observed in prior experiments[arXiv:1402.6055].

Studies on applications of functional organic-thin-films for lithography on semiconductor device production

International Nuclear Information System (INIS)

Ogawa, Kazufumi

1988-12-01

This report describes some experimental results of studies in an attempt to contribute to the development of ultra-fine lithography which is used for the manufacture of semiconductor devices with design rule below 0.5 μm, and contains (1) manufacture of the exposure apparatus, (2) establishment of the resist process technology, and (3) preparation of the resist materials. The author designed and manufactured the KrF excimer laser stepper which is supposed to be most promising for practical uses. In the resist processing technology, the water-soluble contrast enhanced lithography (CEL) process was developed and this process has advantages is that high pattern contrast and large focus depth latitude were easily obtained. Finally, for resist materials, use of Langmuir-Blodgett (LB) films was investigated since the LB technique provides the method to prepare extremely thin organic films which are uniform in molecular level, and the reaction mechanism of the LB films of unsaturated compounds under irradiation with high energy beams was elucidated. (author)

X-ray specular reflection and fluorescence study of nano-films

International Nuclear Information System (INIS)

Zheludeva, S.; Novikova, N.

2001-01-01

The techniques that combine the advantages of high-resolution structure sensitive x-ray methods with spectroscopic selectivity of data obtained are shown to be extremely promising for characterization of organic and inorganic nano films and nano structures. Fluorescence yield angular dependences exited by complicated evanescent wave / x-ray standing wave pattern at total reflection and glancing incidence can be used to detect structure position of different ions in organic systems and alien interfacial layers in inorganic multilayers;, to get information about interdiffusion at the interfaces of Langmuir- Blodgett (L-B) films and artificial inorganic - x-ray mirrors; to study ion permeation through L-B nano structures - models of biomembrans; to obtain nano - film thickness and density; to get precisely the parameters of small d-space multilayer mirrors, ets

Use of a two-dimensional ionization chamber array for proton therapy beam quality assurance

International Nuclear Information System (INIS)

Arjomandy, Bijan; Sahoo, Narayan; Ding Xiaoning; Gillin, Michael

2008-01-01

Two-dimensional ion chamber arrays are primarily used for conventional and intensity modulated radiotherapy quality assurance. There is no commercial device of such type available on the market that is offered for proton therapy quality assurance. We have investigated suitability of the MatriXX, a commercial two-dimensional ion chamber array detector for proton therapy QA. This device is designed to be used for photon and electron therapy QA. The device is equipped with 32x32 parallel plate ion chambers, each with 4.5 mm diam and 7.62 mm center-to-center separation. A 250 MeV proton beam was used to calibrate the dose measured by this device. The water equivalent thickness of the buildup material was determined to be 3.9 mm using a 160 MeV proton beam. Proton beams of different energies were used to measure the reproducibility of dose output and to evaluate the consistency in the beam flatness and symmetry measured by MatriXX. The output measurement results were compared with the clinical commissioning beam data that were obtained using a 0.6 cc Farmer chamber. The agreement was consistently found to be within 1%. The profiles were compared with film dosimetry and also with ion chamber data in water with an excellent agreement. The device is found to be well suited for quality assurance of proton therapy beams. It provides fast two-dimensional dose distribution information in real time with the accuracy comparable to that of ion chamber measurements and film dosimetry

Tank Applied Testing of Load-Bearing Multilayer Insulation (LB-MLI)

Science.gov (United States)

Johnson, Wesley L.; Valenzuela, Juan G.; Feller, Jerr; Plachta, Dave

2014-01-01

The development of long duration orbital cryogenic storage systems will require the reduction of heat loads into the storage tank. In the case of liquid hydrogen, complete elimination of the heat load at 20 K is currently impractical due to the limitations in lift available on flight cryocoolers. In order to reduce the heat load, without having to remove heat at 20 K, the concept of Reduced Boil-Off uses cooled shields within the insulation system at approximately 90 K. The development of Load-Bearing Multilayer Insulation (LB-MLI) allowed the 90 K shield with tubing and cryocooler attachments to be suspended within the MLI and still be structurally stable. Coupon testing both thermally and structurally were performed to verify that the LB-MLI should work at the tank applied level. Then tank applied thermal and structural (acoustic) testing was performed to demonstrate the functionality of the LB-MLI as a structural insulation system. The LB-MLI showed no degradation of thermal performance due to the acoustic testing and showed excellent thermal performance when integrated with a 90 K class cryocooler on a liquid hydrogen tank.

Transparent nanocellulosic multilayer thin films on polylactic acid with tunable gas barrier properties.

Science.gov (United States)

Aulin, Christian; Karabulut, Erdem; Tran, Amy; Wågberg, Lars; Lindström, Tom

2013-08-14

The layer-by-layer (LbL) deposition method was used for the build-up of alternating layers of nanofibrillated cellulose (NFC) or carboxymethyl cellulose (CMC) with a branched, cationic polyelectrolyte, polyethyleneimine (PEI) on flexible poly (lactic acid) (PLA) substrates. With this procedure, optically transparent nanocellulosic films with tunable gas barrier properties were formed. 50 layer pairs of PEI/NFC and PEI/CMC deposited on PLA have oxygen permeabilities of 0.34 and 0.71 cm(3)·μm/m(2)·day·kPa at 23 °C and 50% relative humidity, respectively, which is in the same range as polyvinyl alcohol and ethylene vinyl alcohol. The oxygen permeability of these multilayer nanocomposites outperforms those of pure NFC films prepared by solvent-casting. The nanocellulosic LbL assemblies on PLA substrates was in detailed characterized using a quartz crystal microbalance with dissipation (QCM-D). Atomic force microscopy (AFM) reveals large structural differences between the PEI/NFC and the PEI/CMC assemblies, with the PEI/NFC assembly showing a highly entangled network of nanofibrils, whereas the PEI/CMC surfaces lacked structural features. Scanning electron microscopy images showed a nearly perfect uniformity of the nanocellulosic coatings on PLA, and light transmittance results revealed remarkable transparency of the LbL-coated PLA films. The present work demonstrates the first ever LbL films based on high aspect ratio, water-dispersible nanofibrillated cellulose, and water-soluble carboxymethyl cellulose polymers that can be used as multifunctional films and coatings with tailorable properties, such as gas barriers and transparency. Owing to its flexibility, transparency and high-performance gas barrier properties, these thin film assemblies are promising candidates for several large-scale applications, including flexible electronics and renewable packaging.

Electrodeposition of flake-like Cu_2O on vertically aligned two-dimensional TiO_2 nanosheet array films for enhanced photoelectrochemical properties

International Nuclear Information System (INIS)

Yang, Lei; Zhang, Miao; Zhu, Kerong; Lv, Jianguo; He, Gang; Sun, Zhaoqi

2017-01-01

Highlights: • Flake-like Cu_2O/TNS with exposed {001} facets constructed p-n heterostructure. • The TNS arrays were used as starting substrates for Cu_2O growth. • The Cu_2O/TNS prepared at −0.4 V exhibits the best photoelectrochemical property. - Abstract: A novel Cu_2O/TNS composite structure of single crystal TiO_2 nanosheet (TNS) arrays decorated with flake-like Cu_2O were synthesized by a facile hydrothermal reaction followed by the electrodeposition process. The effects of deposition potential on the microstructure, morphology, and optical property of the thin films were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and UV–vis spectrophotometer. When the deposition potential is higher than −0.4 V, peaks corresponding to Cu appear, meanwhile, flake-like Cu_2O become agglomerating, and transform into dense Cu_2O particles. Additionally, photoelectrochemical experiments indicate that the films deposited at −0.4 V show the lowest resistivity and highest exciton separation efficiency. This enhanced photoelectrochemical properties can be explained by synergistic effect of p-type flake-like Cu_2O and n-type TiO_2 heterojunctions combined with two-dimensional TiO_2 nanosheet with exposed highly reactive {001} facets.

Polyaniline Langmuir-Blodgett film modified glassy carbon electrode as a voltammetric sensor for determination of Ag+ ions

International Nuclear Information System (INIS)

Liu Qiongyan; Wang Fei; Qiao Yonghui; Zhang Shusheng; Ye Baoxian

2010-01-01

A highly sensitive electrochemical sensor made of a glassy carbon electrode (GCE) coated with a Langmuir-Blodgett film (LB) containing polyaniline (PAn) doped with p-toluenesulfonic acid (PTSA) (LB/PAn-PTSA/GCE) has been used for the detection of trace concentrations of Ag + . UV-vis absorption spectra indicated that the PAn was doped by PTSA. The surface morphology of the PAn LB film was characterized by atomic force microscopy (AFM). The electrochemical properties of this LB/PAn-PTSA/GCE were studied using electrochemical impedance spectroscopy (EIS) and cyclic voltammetry. The LB/PAn-PTSA/GCE was used as a voltammetric sensor for determination of trace Ag + at pH 5.0 using linear scanning stripping voltammetry. Under the optimal experimental conditions, the stripping current was proportional to the Ag + concentration over the range from 6.0 x 10 -10 mol L -1 to 1.0 x 10 -6 mol L -1 , with a detection limit of 4.0 x 10 -10 mol L -1 . The high sensitivity, selectivity, and stability of this LB/PAn-PTSA/GCE also demonstrated its practical utility for simple, rapid and economical determination of Ag + in water samples.

Dipolar local field in homogeneously magnetized quasi-two-dimensional crystals

International Nuclear Information System (INIS)

Leon, H; Estevez-Rams, E

2009-01-01

A formalism to calculate the dipolar local field in homogeneously magnetized quasi-two-dimensional (Q2D) crystals is comprehensively presented. Two fundamental tests for this formalism are accomplished: the transition from the Q2D quantities to the corresponding 3D ones; and the recovering of the macroscopic quantities of the 3D continuum theory. The additive separation between lattice and shape contributions to the local field allows an unambiguous interpretation of the respective effects. Calculated demagnetization tensors for square and circular lateral geometries of dipole layers show that for a single crystal layer an extremely thin film, but still with a finite thickness, is a better physical representation than a strictly 2D plane. Distinct close-packed structures are simulated and calculations of the local field at the nodes of the stacked 2D lattices allow one to establish the number of significantly coupled dipole layers, depending on the ratio between the interlayer distance and the 2D lattice constant. The conclusions drawn are of interest for the study of the dipolar interaction in magnetic ultrathin films and other nanostructured materials, where magnetic nanoparticles are embedded in non-magnetic matrices.

Two-dimensional silica opens new perspectives

Science.gov (United States)

Büchner, Christin; Heyde, Markus

2017-12-01

In recent years, silica films have emerged as a novel class of two-dimensional (2D) materials. Several groups succeeded in epitaxial growth of ultrathin SiO2 layers using different growth methods and various substrates. The structures consist of tetrahedral [SiO4] building blocks in two mirror symmetrical planes, connected via oxygen bridges. This arrangement is called a silica bilayer as it is the thinnest 2D arrangement with the stoichiometry SiO2 known today. With all bonds saturated within the nano-sheet, the interaction with the substrate is based on van der Waals forces. Complex ring networks are observed, including hexagonal honeycomb lattices, point defects and domain boundaries, as well as amorphous domains. The network structures are highly tuneable through variation of the substrate, deposition parameters, cooling procedure, introducing dopants or intercalating small species. The amorphous networks and structural defects were resolved with atomic resolution microscopy and modeled with density functional theory and molecular dynamics. Such data contribute to our understanding of the formation and characteristic motifs of glassy systems. Growth studies and doping with other chemical elements reveal ways to tune ring sizes and defects as well as chemical reactivities. The pristine films have been utilized as molecular sieves and for confining molecules in nanocatalysis. Post growth hydroxylation can be used to tweak the reactivity as well. The electronic properties of silica bilayers are favourable for using silica as insulators in 2D material stacks. Due to the fully saturated atomic structure, the bilayer interacts weakly with the substrate and can be described as quasi-freestanding. Recently, a mm-scale film transfer under structure retention has been demonstrated. The chemical and mechanical stability of silica bilayers is very promising for technological applications in 2D heterostacks. Due to the impact of this bilayer system for glass science

Approaches for Achieving Superlubricity in Two-Dimensional Materials.

Science.gov (United States)

Berman, Diana; Erdemir, Ali; Sumant, Anirudha V

2018-03-27

Controlling friction and reducing wear of moving mechanical systems is important in many applications, from nanoscale electromechanical systems to large-scale car engines and wind turbines. Accordingly, multiple efforts are dedicated to design materials and surfaces for efficient friction and wear manipulation. Recent advances in two-dimensional (2D) materials, such as graphene, hexagonal boron nitride, molybdenum disulfide, and other 2D materials opened an era for conformal, atomically thin solid lubricants. However, the process of effectively incorporating 2D films requires a fundamental understanding of the atomistic origins of friction. In this review, we outline basic mechanisms for frictional energy dissipation during sliding of two surfaces against each other, and the procedures for manipulating friction and wear by introducing 2D materials at the tribological interface. Finally, we highlight recent progress in implementing 2D materials for friction reduction to near-zero values-superlubricity-across scales from nano- up to macroscale contacts.

On the two-dimensional Saigo-Maeda fractional calculus asociated with two-dimensional Aleph TRANSFORM

Directory of Open Access Journals (Sweden)

Dinesh Kumar

2013-11-01

Full Text Available This paper deals with the study of two-dimensional Saigo-Maeda operators of Weyl type associated with Aleph function defined in this paper. Two theorems on these defined operators are established. Some interesting results associated with the H-functions and generalized Mittag-Leffler functions are deduced from the derived results. One dimensional analog of the derived results is also obtained.

Imprinting of metal receptors into multilayer polyelectrolyte films: fabrication and applications in marine antifouling

NARCIS (Netherlands)

Puniredd, S.R.; Janczewski, D.; Go, D.P.; Zhu, X.; Guo, S.; Teo, S.L-M.; Lee, S.S.C.; Vancso, Gyula J.

2015-01-01

Polymeric films constructed using the layer-by-layer (LbL) fabrication process were employed as a platform for metal ion immobilization and applied as a marine antifouling coating. The novel Cu2+ ion imprinting process described is based on the use of metal ion templates and LbL multilayer covalent

Electroforming free resistive switching memory in two-dimensional VOx nanosheets

KAUST Repository

Hota, Mrinal Kanti

2015-10-21

We report two-dimensional VOx nanosheets containing multi-oxidation states (V5+, V4+, and V3+), prepared by a hydrothermal process for potential applications in resistive switching devices. The experimental results demonstrate a highly reproducible, electroforming-free, low SET bias bipolar resistive switching memory performance with endurance for more than 100 cycles maintaining OFF/ON ratio of ∼60 times. These devices show better memory performance as compared to previously reported VOx thin film based devices. The memory mechanism in VOx is proposed to be originated from the migration of oxygen vacancies/ions, an influence of the bottom electrode and existence of multi-oxidation states.

Hydrothermally formed three-dimensional nanoporous Ni(OH)2 thin-film supercapacitors.

Science.gov (United States)

Yang, Yang; Li, Lei; Ruan, Gedeng; Fei, Huilong; Xiang, Changsheng; Fan, Xiujun; Tour, James M

2014-09-23

A three-dimensional nanoporous Ni(OH)2 thin-film was hydrothermally converted from an anodically formed porous layer of nickel fluoride/oxide. The nanoporous Ni(OH)2 thin-films can be used as additive-free electrodes for energy storage. The nanoporous layer delivers a high capacitance of 1765 F g(-1) under three electrode testing. After assembly with porous activated carbon in asymmetric supercapacitor configurations, the devices deliver superior supercapacitive performances with capacitance of 192 F g(-1), energy density of 68 Wh kg(-1), and power density of 44 kW kg(-1). The wide working potential window (up to 1.6 V in 6 M aq KOH) and stable cyclability (∼90% capacitance retention over 10,000 cycles) make the thin-film ideal for practical supercapacitor devices.

Two-dimensional nuclear magnetic resonance spectroscopy

International Nuclear Information System (INIS)

Bax, A.; Lerner, L.

1986-01-01

Great spectral simplification can be obtained by spreading the conventional one-dimensional nuclear magnetic resonance (NMR) spectrum in two independent frequency dimensions. This so-called two-dimensional NMR spectroscopy removes spectral overlap, facilitates spectral assignment, and provides a wealth of additional information. For example, conformational information related to interproton distances is available from resonance intensities in certain types of two-dimensional experiments. Another method generates 1 H NMR spectra of a preselected fragment of the molecule, suppressing resonances from other regions and greatly simplifying spectral appearance. Two-dimensional NMR spectroscopy can also be applied to the study of 13 C and 15 N, not only providing valuable connectivity information but also improving sensitivity of 13 C and 15 N detection by up to two orders of magnitude. 45 references, 10 figures

Orientation of One-Dimensional Silicon Polymer Films Studied by X-Ray Absorption Spectroscopy

Directory of Open Access Journals (Sweden)

Md. Abdul Mannan

2012-01-01

Full Text Available Molecular orientations for thin films of one-dimensional silicon polymers grown by vacuum evaporation have been assigned by near-edge X-ray absorption fine structure (NEXAFS using linearly polarized synchrotron radiation. The polymer investigated was polydimethylsilane (PDMS which is the simplest stable silicon polymer, and one of the candidate materials for one-dimensional molecular wire. For PDMS films deposited on highly oriented pyrolytic graphite (HOPG, four resonance peaks have been identified in the Si K-edge NEXAFS spectra. Among these peaks, the intensities of the two peaks lower-energy at 1842.0 eV and 1843.2 eV were found to be strongly polarization dependent. The peaks are assigned to the resonance excitations from the Si 1s to σ∗ pyz and σ∗ px orbitals localized at the Si–C and Si–Si bonds, respectively. Quantitative evaluation of the polarization dependence of the NEXAFS spectra revealed that the molecules are self-assembled on HOPG surface, and the backbones of the PDMS are oriented nearly parallel to the surface. The observed orientation is opposite to the previously observed results for PDMS on the other surfaces such as oxide (indium tin oxide and metal (polycrystalline copper. The flat-lying feature of PDMS observed only on HOPG surface is attributed to the interaction between CH bonds in PDMS and π orbitals in HOPG surface.

Characteristics of a commercially available film digitizer and their significance for film dosimetry

International Nuclear Information System (INIS)

Mersseman, B.; De Wagter, C.

1998-01-01

Dosimetric detectors used in high-energy photon radiation dosimetry mainly perform a zero- or one-dimensional measurement. These low-dimensional methods are not always adequate in the context of conformal radiotherapy. Therefore, two-dimensional film dosimetry has attracted attention. We studied a 12-bit CCD-based film digitizer (Vidar VXR-12) with regard to accurate film dosimetry. We investigated the stability, linearity, noise, effects of aberrant light scatter and built-in conversion tables. A digitizing resolution of 75 dpi and a digitizing speed of 20 ms/line result in an optimal signal-to-noise ratio. At optical densities above 2.0, the reading accuracy of the digitizer is limited by noise. The results of various experiments prove both the capabilities and limitations of the digitizer studied. We also propose a method to acquire and process film data using such a digitizer. (author)

On some classes of two-dimensional local models in discrete two-dimensional monatomic FPU lattice with cubic and quartic potential

International Nuclear Information System (INIS)

Quan, Xu; Qiang, Tian

2009-01-01

This paper discusses the two-dimensional discrete monatomic Fermi–Pasta–Ulam lattice, by using the method of multiple-scale and the quasi-discreteness approach. By taking into account the interaction between the atoms in the lattice and their nearest neighbours, it obtains some classes of two-dimensional local models as follows: two-dimensional bright and dark discrete soliton trains, two-dimensional bright and dark line discrete breathers, and two-dimensional bright and dark discrete breather. (condensed matter: structure, thermal and mechanical properties)

Layer-by-Layer Assembly of Fluorine-Free Polyelectrolyte-Surfactant Complexes for the Fabrication of Self-Healing Superhydrophobic Films.

Science.gov (United States)

Wu, Mengchun; An, Ni; Li, Yang; Sun, Junqi

2016-11-29

Fluorine-free self-healing superhydrophobic films are of significance for practical applications because of their extended service life and cost-effective and eco-friendly preparation process. In this study, we report the fabrication of fluorine-free self-healing superhydrophobic films by layer-by-layer (LbL) assembly of poly(sodium 4-styrenesulfonate) (PSS)-1-octadecylamine (ODA) complexes (PSS-ODA) and poly(allylamine hydrochloride) (PAH)-sodium dodecyl sulfonate (SDS) (PAH-SDS) complexes. The wettability of the LbL-assembled PSS-ODA/PAH-SDS films depends on the film structure and can be tailored by changing the NaCl concentration in aqueous dispersions of PSS-ODA complexes and the number of film deposition cycles. The freshly prepared PSS-ODA/PAH-SDS film with micro- and nanoscaled hierarchical structures is hydrophilic and gradually changes to superhydrophobic in air because the polyelectrolyte-complexed ODA and SDS surfactants tend to migrate to the film surface to cover the film with hydrophobic alkyl chains to lower its surface energy. The large amount of ODA and SDS surfactants loaded in the superhydrophobic PSS-ODA/PAH-SDS films and the autonomic migration of these surfactants to the film surface endow the resultant superhydrophobic films with an excellent self-healing ability to restore the damaged superhydrophobicity. The self-healing superhydrophobic PSS-ODA/PAH-SDS films are mechanically robust and can be deposited on various flat and nonflat substrates. The LbL assembly of oppositely charged polyelectrolyte-surfactant complexes provides a new way for the fabrication of fluorine-free self-healing superhydrophobic films with satisfactory mechanical stability, enhanced reliability, and extended service life.

Two-dimensional models

International Nuclear Information System (INIS)

Schroer, Bert; Freie Universitaet, Berlin

2005-02-01

It is not possible to compactly review the overwhelming literature on two-dimensional models in a meaningful way without a specific viewpoint; I have therefore tacitly added to the above title the words 'as theoretical laboratories for general quantum field theory'. I dedicate this contribution to the memory of J. A. Swieca with whom I have shared the passion of exploring 2-dimensional models for almost one decade. A shortened version of this article is intended as a contribution to the project 'Encyclopedia of mathematical physics' and comments, suggestions and critical remarks are welcome. (author)

Solution-Processed Dielectrics Based on Thickness-Sorted Two-Dimensional Hexagonal Boron Nitride Nanosheets

Energy Technology Data Exchange (ETDEWEB)

Zhu, Jian; Kang, Joohoon; Kang, Junmo; Jariwala, Deep; Wood, Joshua D.; Seo, Jung-Woo T.; Chen, Kan-Sheng; Marks, Tobin J.; Hersam, Mark C.

2015-10-14

Gate dielectrics directly affect the mobility, hysteresis, power consumption, and other critical device metrics in high-performance nanoelectronics. With atomically flat and dangling bond-free surfaces, hexagonal boron nitride (h-BN) has emerged as an ideal dielectric for graphene and related two-dimensional semiconductors. While high-quality, atomically thin h-BN has been realized via micromechanical cleavage and chemical vapor deposition, existing liquid exfoliation methods lack sufficient control over h-BN thickness and large-area film quality, thus limiting its use in solution-processed electronics. Here, we employ isopycnic density gradient ultracentrifugation for the preparation of monodisperse, thickness-sorted h-BN inks, which are subsequently layer-by-layer assembled into ultrathin dielectrics with low leakage currents of 3 × 10–9 A/cm2 at 2 MV/cm and high capacitances of 245 nF/cm2. The resulting solution-processed h-BN dielectric films enable the fabrication of graphene field-effect transistors with negligible hysteresis and high mobilities up to 7100 cm2 V–1 s–1 at room temperature. These h-BN inks can also be used as coatings on conventional dielectrics to minimize the effects of underlying traps, resulting in improvements in overall device performance. Overall, this approach for producing and assembling h-BN dielectric inks holds significant promise for translating the superlative performance of two-dimensional heterostructure devices to large-area, solution-processed nanoelectronics.

Two-dimensional Si(x)Ge(1-x) films with variable composition made via multilayer colloidal template-guided ionic liquid electrodeposition.

Science.gov (United States)

Xin, Wuhong; Zhao, Jiupeng; Ge, Dengteng; Ding, Yanbo; Li, Yao; Endres, Frank

2013-02-21

The binary alloy system Si(x)Ge(1-x) provides a continuous series of materials with gradually varying properties. In this paper, we report on a fundamental basis a method to make large-area macroporous Si(x)Ge(1-x) films with variable Ge content by electrodeposition in an ionic liquid, with SiCl(4) and GeCl(4) as precursors. The chemical composition of the products can be modified by changing the molar ratio of the precursors. Periodical macroporous Si(x)Ge(1-x) was made by a multilayer polystyrene (PS) template assembled as face-centered cubic lattice. Two-dimensional (2-D) Si(x)Ge(1-x) bowl-like and fishing-net structures can be obtained by applying different deposition temperatures. The results highlight the potential applications, including photonic bandgap and battery materials, as well as ultra-thin gratings, due to the effect of modification of light and improved tunability of composition, although Si(x)Ge(1-x) made by our method is sensitive to oxidation by air.

Conductive Langmuir-Blodgett films. Doping with iodine or self-doping?

International Nuclear Information System (INIS)

Bourgoin, Jean-Philippe

1991-01-01

In this research thesis dealing with molecular architecture, the author reports the testing of two strategies aiming at reducing the importance of defects in conductive Langmuir-Blodgett films, and at enabling the production of conductive mono-molecular layer. According to the first strategy, conductive films are obtained after doping based on the use of iodine vapours of an insulating precursor film of molecules derived from BEDT-TTF. The so-produced films display a high conductivity and can be used as sensitive elements in gas sensors, but remain macroscopically insulating, probably because molecular reorganisation, as shown by a study based on different techniques (IR and UV linear dichroism, Raman spectroscopy, X ray diffraction), generates too many defects. The second strategy, self-doping, is based on a mixing of two derivatives of the same electro-active nucleus (the TCNQ, tetracyanoquinodimethane), an amphiphilic one and a semi-amphiphilic one. This strategy opens new perspectives in molecular engineering as it is a general way to produce conductive LB films from TCNQ [fr

Two-dimensional multifractal cross-correlation analysis

International Nuclear Information System (INIS)

Xi, Caiping; Zhang, Shuning; Xiong, Gang; Zhao, Huichang; Yang, Yonghong

2017-01-01

Highlights: • We study the mathematical models of 2D-MFXPF, 2D-MFXDFA and 2D-MFXDMA. • Present the definition of the two-dimensional N 2 -partitioned multiplicative cascading process. • Do the comparative analysis of 2D-MC by 2D-MFXPF, 2D-MFXDFA and 2D-MFXDMA. • Provide a reference on the choice and parameter settings of these methods in practice. - Abstract: There are a number of situations in which several signals are simultaneously recorded in complex systems, which exhibit long-term power-law cross-correlations. This paper presents two-dimensional multifractal cross-correlation analysis based on the partition function (2D-MFXPF), two-dimensional multifractal cross-correlation analysis based on the detrended fluctuation analysis (2D-MFXDFA) and two-dimensional multifractal cross-correlation analysis based on the detrended moving average analysis (2D-MFXDMA). We apply these methods to pairs of two-dimensional multiplicative cascades (2D-MC) to do a comparative study. Then, we apply the two-dimensional multifractal cross-correlation analysis based on the detrended fluctuation analysis (2D-MFXDFA) to real images and unveil intriguing multifractality in the cross correlations of the material structures. At last, we give the main conclusions and provide a valuable reference on how to choose the multifractal algorithms in the potential applications in the field of SAR image classification and detection.

Calixarene Langmuir-Blodgett Thin Films For Volatile Organic Compounds

International Nuclear Information System (INIS)

Capan, R.

2010-01-01

Volatile Organic Compounds (VOC's) such as benzene, toluene, chloroform are chemicals that evaporate easily at room temperature and create many health effects on young children, elderly and a person with heightened sensitivity to chemicals. Concentrations of many VOC's are consistently higher indoors (up to ten times higher) than outdoors because many household products (for example paints, varnishes, many cleaning, disinfecting, cosmetic, degreasing, hobby products etc.) contains VOC's. Some effects of VOC's for human beings can be followed as the eye, nose, and throat irritations; headaches, loss of coordination, nausea; damage to liver, kidneys, and central nervous system. These are big incentives for the development of portable, user-friendly VOC's sensors and for the investigation of the sensing properties of new materials to be prepared as a thin film sensing element. Langmuir-Blodgett (LB) ultra-thin film technique allows us to produce monolayer or multilayer organic thin films that can be used as chemical sensing elements.In this work, materials known as the calix[n]arene are investigated for the production of sensing material against several VOC's such as the chloroform, benzene, ethylbenzene and toluene by using LB thin film techniques. UV-visible, Quartz Crystal Microbalance (QCM) system and Surface Plasmon Resonance (SPR) measurement techniques are used to check the quality of the deposition process onto a solid substrate. Surface morphology and sensing properties of the final sensing layers are then studied by Atomic Force Microscopy (AFM) and SPR techniques. Our results indicated that selected calixarene materials are sensitive enough and quite suitable to fabricate a highly ordered, reproducible and uniform LB film that can be used as a very thin sensing layer against VOC's.

Phase transition of two-dimensional 3He from a dilute to a dense phase

International Nuclear Information System (INIS)

Bhattacharyya, B.K.; Gasparini, F.M.

1985-01-01

We have measured the heat capacity of 3 He in films of 4 He as thin as 10 A formed on a Nuclepore filter substrate. At low temperatures, where the 3 He is in the lowest state as far as motion perpendicular to the film surface, we find that the 3 He undergoes a transition from a dilute phase to a dense phase. We have observed this transition for films of 4 He of 12.3- and 10-A thickness and for coverages of 3 He below about 0.2 atomic layers. For thicker 4 He films, and higher 3 He coverages, the 3 He remains homogeneously spread out over the surface of the 4 He. The striking characteristic of the transition is the sudden onset of linear temperature dependence with a slope which is proportional to the amount of 3 He in the calorimeter. This is consistent with the formation of islands of a dense two-dimensional phase which grows in extent proportionately to the amount of 3 He. Two puzzling aspects of our results are the lack of a significant heat-capacity jump at the transition and, based on a linear extrapolation of the data to zero temperature, a substantial amount of missing entropy

Two-dimensional beam profiles and one-dimensional projections

Science.gov (United States)

Findlay, D. J. S.; Jones, B.; Adams, D. J.

2018-05-01

One-dimensional projections of improved two-dimensional representations of transverse profiles of particle beams are proposed for fitting to data from harp-type monitors measuring beam profiles on particle accelerators. Composite distributions, with tails smoothly matched on to a central (inverted) parabola, are shown to give noticeably better fits than single gaussian and single parabolic distributions to data from harp-type beam profile monitors all along the proton beam transport lines to the two target stations on the ISIS Spallation Neutron Source. Some implications for inferring beam current densities on the beam axis are noted.

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

Science.gov (United States)

Casford, Michael T L; Davies, Paul B

2009-08-01

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

Preparation of three-dimensionally ordered macroporous polycysteine film and application in sensitive detection of 4-chlorophenol

International Nuclear Information System (INIS)

Zhang, Shenghui; Shi, Zhen; Wang, Jinshou; Cheng, Qin; Wu, Kangbing

2014-01-01

Highlights: • Polycysteine film with three-dimensionally ordered porous structures was prepared. • 3-DOM polycysteine film exhibited large active area and signal enhancement effects. • 3-DOM polycysteine film increased oxidation signal of 4-chlorophenol by 5-fold. - Abstract: Polystyrene microspheres with diameter of 350 nm were prepared, and then used to arrange on the surface of glassy carbon electrode (GCE) as structure-directing template. By successive cyclic sweeps between −1.0 V and 2.0 V in pH 7 phosphate buffer containing 10 mM cysteine, polycysteine film was electrodeposited on polystyrene microspheres-arranged GCE. After removing polystyrene template, a three-dimensionally ordered macroporous (3-DOM) polycysteine film was achieved, as confirmed by scanning electron microscopy measurements. Electrochemical responses of K 3 [Fe(CN) 6 ] probe indicated that 3-DOM polycysteine film-modified GCE exhibited larger active area, compared with GCE, polycysteine film-modified GCE and electrochemically oxidized GCE. The application of 3-DOM polycysteine film in electrochemical detection of 4-chlorophenol was studied. Due to ordered porous structures, the 3-DOM polycysteine film-modified GCE displayed signal enhancement effects, and enhanced the oxidation peak currents of 4-chlorophenol. As a result, a sensitive electrochemical method was developed for the detection of 4-chlorophenol, and the detection limit was 1.67 × 10 −8 M. This new method was used to detect 4-chlorophenol in water samples, and the value of recovery was over the range from 99.6% to 107%

FPGA Implementation of one-dimensional and two-dimensional cellular automata

International Nuclear Information System (INIS)

D'Antone, I.

1999-01-01

This report describes the hardware implementation of one-dimensional and two-dimensional cellular automata (CAs). After a general introduction to the cellular automata, we consider a one-dimensional CA used to implement pseudo-random techniques in built-in self test for VLSI. Due to the increase in digital ASIC complexity, testing is becoming one of the major costs in the VLSI production. The high electronics complexity, used in particle physics experiments, demands higher reliability than in the past time. General criterions are given to evaluate the feasibility of the circuit used for testing and some quantitative parameters are underlined to optimize the architecture of the cellular automaton. Furthermore, we propose a two-dimensional CA that performs a peak finding algorithm in a matrix of cells mapping a sub-region of a calorimeter. As in a two-dimensional filtering process, the peaks of the energy clusters are found in one evolution step. This CA belongs to Wolfram class II cellular automata. Some quantitative parameters are given to optimize the architecture of the cellular automaton implemented in a commercial field programmable gate array (FPGA)

Two-dimensional distribution of carbon nanotubes in copper flake powders

Energy Technology Data Exchange (ETDEWEB)

Tan Zhanqiu; Li Zhiqiang; Fan Genlian; Li Wenhuan; Liu Qinglei; Zhang Wang; Zhang Di, E-mail: lizhq@sjtu.edu.cn, E-mail: zhangdi@sjtu.edu.cn [State Key Laboratory of Metal Matrix Composites, Shanghai Jiao Tong University, Shanghai 200240 (China)

2011-06-03

We report an approach of flake powder metallurgy to the uniform, two-dimensional (2D) distribution of carbon nanotubes (CNTs) in Cu flake powders. It consists of the preparation of Cu flakes by ball milling in an imidazoline derivative (IMD) aqueous solution, surface modification of Cu flakes with polyvinyl alcohol (PVA) hydrosol and adsorption of CNTs from a CNT aqueous suspension. During ball milling, a hydrophobic monolayer of IMD is adsorbed on the surface of the Cu flakes, on top of which a hydrophilic PVA film is adsorbed subsequently. This PVA film could further interact with the carboxyl-group functionalized CNTs and act to lock the CNTs onto the surfaces of the Cu flakes. The CNT volume fraction is controlled easily by adjusting the concentration/volume of CNT aqueous suspension and Cu flake thickness. The as-prepared CNT/Cu composite flakes will serve as suitable building blocks for the self-assembly of CNT/Cu laminated composites that enable the full potential of 2D distributed CNTs to achieve high thermal conductivity.

Two-dimensional distribution of carbon nanotubes in copper flake powders

International Nuclear Information System (INIS)

Tan Zhanqiu; Li Zhiqiang; Fan Genlian; Li Wenhuan; Liu Qinglei; Zhang Wang; Zhang Di

2011-01-01

We report an approach of flake powder metallurgy to the uniform, two-dimensional (2D) distribution of carbon nanotubes (CNTs) in Cu flake powders. It consists of the preparation of Cu flakes by ball milling in an imidazoline derivative (IMD) aqueous solution, surface modification of Cu flakes with polyvinyl alcohol (PVA) hydrosol and adsorption of CNTs from a CNT aqueous suspension. During ball milling, a hydrophobic monolayer of IMD is adsorbed on the surface of the Cu flakes, on top of which a hydrophilic PVA film is adsorbed subsequently. This PVA film could further interact with the carboxyl-group functionalized CNTs and act to lock the CNTs onto the surfaces of the Cu flakes. The CNT volume fraction is controlled easily by adjusting the concentration/volume of CNT aqueous suspension and Cu flake thickness. The as-prepared CNT/Cu composite flakes will serve as suitable building blocks for the self-assembly of CNT/Cu laminated composites that enable the full potential of 2D distributed CNTs to achieve high thermal conductivity.

Two-dimensional distribution of carbon nanotubes in copper flake powders.

Science.gov (United States)

Tan, Zhanqiu; Li, Zhiqiang; Fan, Genlian; Li, Wenhuan; Liu, Qinglei; Zhang, Wang; Zhang, Di

2011-06-03

We report an approach of flake powder metallurgy to the uniform, two-dimensional (2D) distribution of carbon nanotubes (CNTs) in Cu flake powders. It consists of the preparation of Cu flakes by ball milling in an imidazoline derivative (IMD) aqueous solution, surface modification of Cu flakes with polyvinyl alcohol (PVA) hydrosol and adsorption of CNTs from a CNT aqueous suspension. During ball milling, a hydrophobic monolayer of IMD is adsorbed on the surface of the Cu flakes, on top of which a hydrophilic PVA film is adsorbed subsequently. This PVA film could further interact with the carboxyl-group functionalized CNTs and act to lock the CNTs onto the surfaces of the Cu flakes. The CNT volume fraction is controlled easily by adjusting the concentration/volume of CNT aqueous suspension and Cu flake thickness. The as-prepared CNT/Cu composite flakes will serve as suitable building blocks for the self-assembly of CNT/Cu laminated composites that enable the full potential of 2D distributed CNTs to achieve high thermal conductivity.

Lie algebra contractions on two-dimensional hyperboloid

International Nuclear Information System (INIS)

Pogosyan, G. S.; Yakhno, A.

2010-01-01

The Inoenue-Wigner contraction from the SO(2, 1) group to the Euclidean E(2) and E(1, 1) group is used to relate the separation of variables in Laplace-Beltrami (Helmholtz) equations for the four corresponding two-dimensional homogeneous spaces: two-dimensional hyperboloids and two-dimensional Euclidean and pseudo-Euclidean spaces. We show how the nine systems of coordinates on the two-dimensional hyperboloids contracted to the four systems of coordinates on E 2 and eight on E 1,1 . The text was submitted by the authors in English.

Quasi-two-dimensional holography

International Nuclear Information System (INIS)

Kutzner, J.; Erhard, A.; Wuestenberg, H.; Zimpfer, J.

1980-01-01

The acoustical holography with numerical reconstruction by area scanning is memory- and time-intensive. With the experiences by the linear holography we tried to derive a scanning for the evaluating of the two-dimensional flaw-sizes. In most practical cases it is sufficient to determine the exact depth extension of a flaw, whereas the accuracy of the length extension is less critical. For this reason the applicability of the so-called quasi-two-dimensional holography is appropriate. The used sound field given by special probes is divergent in the inclined plane and light focussed in the perpendicular plane using cylindrical lenses. (orig.) [de

Topology optimization of two-dimensional waveguides

DEFF Research Database (Denmark)

Jensen, Jakob Søndergaard; Sigmund, Ole

2003-01-01

In this work we use the method of topology optimization to design two-dimensional waveguides with low transmission loss.......In this work we use the method of topology optimization to design two-dimensional waveguides with low transmission loss....

Traditional Semiconductors in the Two-Dimensional Limit.

Science.gov (United States)

Lucking, Michael C; Xie, Weiyu; Choe, Duk-Hyun; West, Damien; Lu, Toh-Ming; Zhang, S B

2018-02-23

Interest in two-dimensional materials has exploded in recent years. Not only are they studied due to their novel electronic properties, such as the emergent Dirac fermion in graphene, but also as a new paradigm in which stacking layers of distinct two-dimensional materials may enable different functionality or devices. Here, through first-principles theory, we reveal a large new class of two-dimensional materials which are derived from traditional III-V, II-VI, and I-VII semiconductors. It is found that in the ultrathin limit the great majority of traditional binary semiconductors studied (a series of 28 semiconductors) are not only kinetically stable in a two-dimensional double layer honeycomb structure, but more energetically stable than the truncated wurtzite or zinc-blende structures associated with three dimensional bulk. These findings both greatly increase the landscape of two-dimensional materials and also demonstrate that in the double layer honeycomb form, even ordinary semiconductors, such as GaAs, can exhibit exotic topological properties.

Extensibility effect of poly(3-hexylthiophene) on the glucose sensing performance of mixed poly(3-hexylthiophene)/octadecylamine/glucose oxidase Langmuir-Blodgett films.

Science.gov (United States)

Wang, Ke-Hsuan; Hsu, Wen-Ping; Chen, Liang-Huei; Lin, Wei-Don; Lee, Yuh-Lang

2017-07-01

Poly(3-hexylthiophene) (P3HT) is utilized as a material to enhance the glucose sensing performance of glucose oxidase (GOx) Langmuir-Blodgett (LB) films. To enhance the extensibility and homogeneity of the P3HT in the LB films, octadecylamine (ODA) is introduced. The characteristics of the mixed P3HT/ODA Langmuir monolayers are investigated first and then, utilized as template layers to adsorb GOx from the subphase, preparing P3HT/ODA/GOx Langmuir-Blodgett films for glucose sensing. The results show that P3HT molecules tend to aggregate at the air/liquid interface and, furthermore, the P3HT monolayer has a weak ability to adsorb GOx from the subphase. By using mixed P3HT/ODA monolayer, the presence of ODA not only inhibits the aggregation of P3HT, but also increases the adsorption ability of the monolayer to GOx. The extensibility of P3HT and the homogeneity of the P3HT/ODA monolayers are closely related to the concentration of P3HT/ODA stock solutions. On the glucose sensing experiments, the performance of the P3HT/ODA/GOx LB film is greatly improved due to the presence of P3HT and, furthermore, the sensibility increases with increasing extensibility of P3HT molecules. The best sensitivity achieved for the P3HT/ODA/GOx film is 5.4μAmM -1 cm -2 which is over two times the value obtained by the ODA/GOx film (2.3μAmM -1 cm -2 ). Copyright © 2017 Elsevier B.V. All rights reserved.

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

International Nuclear Information System (INIS)

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

2015-01-01

Highlights: • For the first time functionalized NPs immobilized in LB films have been used as voltammetric sensors. • Films showed excellent electrocatalytic properties toward phenols and acids found in wines. • Improved performance is due to combination of electrocatalytic NPs with the high surface/volume of LB films. • The potential applications in the wine industry have been evidenced. - Abstract: A chemically modified electrode consisting of Langmuir–Blodgett (LB) films of n-dodecanethiol functionalized gold nanoparticles (S DOD AuNP-LB), was investigated as a voltammetric sensor of organic and phenolic acids of interest in the wine industry. The nanostructured films demonstrated interfacial properties being able to detect the main organic acids present in grapes and wines (tartaric, malic, lactic and citric). Compared to a bare ITO electrode, the modified electrodes exhibited a shift of the reduction potential in the less positive direction and a marked enhancement in the current response. Moreover, the increased electrocatalytic properties made it possible to distinguish between the different dissociable protons of polyprotic acids. The S DOD AuNP-LB sensor was also able to provide enhanced responses toward aqueous solutions of phenolic acids commonly found in wines (caffeic and gallic acids). The presence of nanoparticles increased drastically the sensitivity toward organic acids and phenolic compounds. Limits of detection as low as 10 −6 mol L −1 were achieved. Efficient catalytic activity was also observed in mixtures of phenolic acid/tartaric in the range of pHs typically found in wines. In such mixtures, the electrode was able to provide simultaneous information about the acid and the phenol concentrations with a complete absence of interferences. The excellent sensing properties shown by these sensors could be attributed to the electrocatalytic properties of the nanoparticles combined with the high surface to volume ratio and homogeneity

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

Energy Technology Data Exchange (ETDEWEB)

Medina-Plaza, C. [Department of Inorganic Chemistry, Engineers School, Universidad de Valladolid (Spain); García-Cabezón, C. [Department of Materials Science, Engineers School, Universidad de Valladolid (Spain); García-Hernández, C.; Bramorski, C. [Department of Inorganic Chemistry, Engineers School, Universidad de Valladolid (Spain); Blanco-Val, Y.; Martín-Pedrosa, F. [Department of Materials Science, Engineers School, Universidad de Valladolid (Spain); Kawai, T. [Department of Industrial Chemistry, Tokyo University of Science (Japan); Saja, J.A. de [Department of Condensed Matter Physics, Universidad de Valladolid (Spain); Rodríguez-Méndez, M.L., E-mail: mluz@eii.uva.es [Department of Inorganic Chemistry, Engineers School, Universidad de Valladolid (Spain)

2015-01-01

Highlights: • For the first time functionalized NPs immobilized in LB films have been used as voltammetric sensors. • Films showed excellent electrocatalytic properties toward phenols and acids found in wines. • Improved performance is due to combination of electrocatalytic NPs with the high surface/volume of LB films. • The potential applications in the wine industry have been evidenced. - Abstract: A chemically modified electrode consisting of Langmuir–Blodgett (LB) films of n-dodecanethiol functionalized gold nanoparticles (S{sub DOD}AuNP-LB), was investigated as a voltammetric sensor of organic and phenolic acids of interest in the wine industry. The nanostructured films demonstrated interfacial properties being able to detect the main organic acids present in grapes and wines (tartaric, malic, lactic and citric). Compared to a bare ITO electrode, the modified electrodes exhibited a shift of the reduction potential in the less positive direction and a marked enhancement in the current response. Moreover, the increased electrocatalytic properties made it possible to distinguish between the different dissociable protons of polyprotic acids. The S{sub DOD}AuNP-LB sensor was also able to provide enhanced responses toward aqueous solutions of phenolic acids commonly found in wines (caffeic and gallic acids). The presence of nanoparticles increased drastically the sensitivity toward organic acids and phenolic compounds. Limits of detection as low as 10{sup −6} mol L{sup −1} were achieved. Efficient catalytic activity was also observed in mixtures of phenolic acid/tartaric in the range of pHs typically found in wines. In such mixtures, the electrode was able to provide simultaneous information about the acid and the phenol concentrations with a complete absence of interferences. The excellent sensing properties shown by these sensors could be attributed to the electrocatalytic properties of the nanoparticles combined with the high surface to volume ratio

Universal Distribution of Centers and Saddles in Two-Dimensional Turbulence

International Nuclear Information System (INIS)

Rivera, Michael; Wu, Xiao-Lun; Yeung, Chuck

2001-01-01

The statistical properties of the local topology of two-dimensional turbulence are investigated using an electromagnetically forced soap film. The local topology of the incompressible 2D flow is characterized by the Jacobian determinant Λ(x,y)=1/4 (ω 2 -σ 2 ) , where ω(x,y) is the local vorticity and σ(x,y) is the local strain rate. For turbulent flows driven by different external force configurations, P(Λ) is found to be a universal function when rescaled using the turbulent intensity. A simple model that agrees with the measured functional form of P(Λ) is constructed using the assumption that the stream function, ψ(x,y) , is a Gaussian random field

Sufficient Controllability Condition for Affine Systems with Two-Dimensional Control and Two-Dimensional Zero Dynamics

Directory of Open Access Journals (Sweden)

D. A. Fetisov

2015-01-01

Full Text Available The controllability conditions are well known if we speak about linear stationary systems: a linear stationary system is controllable if and only if the dimension of the state vector is equal to the rank of the controllability matrix. The concept of the controllability matrix is extended to affine systems, but relations between affine systems controllability and properties of this matrix are more complicated. Various controllability conditions are set for affine systems, but they deal as usual either with systems of some special form or with controllability in some small neighborhood of the concerned point. An affine system is known to be controllable if the system is equivalent to a system of a canonical form, which is defined and regular in the whole space of states. In this case, the system is said to be feedback linearizable in the space of states. However there are examples, which illustrate that a system can be controllable even if it is not feedback linearizable in any open subset in the space of states. In this article we deal with such systems.Affine systems with two-dimensional control are considered. The system in question is assumed to be equivalent to a system of a quasicanonical form with two-dimensional zero dynamics which is defined and regular in the whole space of states. Therefore the controllability of the original system is equivalent to the controllability of the received system of a quasicanonical form. In this article the sufficient condition for an available solution of the terminal problem is proven for systems of a quasicanonical form with two-dimensional control and two-dimensional zero dynamics. The condition is valid in the case of an arbitrary time interval and arbitrary initial and finite states of the system. Therefore the controllability condition is set for systems of a quasicanonical form with two-dimensional control and two-dimensional zero dynamics. An example is given which illustrates how the proved

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

Energy Technology Data Exchange (ETDEWEB)

Wang, S. [Institute of Near-Field Optics and Nano Technology, School of Physics and Optoelectronic Technology, Dalian University of Technology, Street No. 2 Linggong Road, Dalian 116024 (China); Li, Y.L.; Zhao, H.L.; Liang, H. [Institute of Photo-Biophysics, School of Physics and Electronic, Henan University, Jinming, Kaifeng 475004, Henan (China); Liu, B., E-mail: boliu@henu.edu.cn [Institute of Photo-Biophysics, School of Physics and Electronic, Henan University, Jinming, Kaifeng 475004, Henan (China); Pan, S., E-mail: span@dlut.edu.cn [Institute of Near-Field Optics and Nano Technology, School of Physics and Optoelectronic Technology, Dalian University of Technology, Street No. 2 Linggong Road, Dalian 116024 (China)

2012-11-15

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

QDs Supported on Langmuir-Blodgett Films of Polymers and Gemini Surfactant

Directory of Open Access Journals (Sweden)

T. Alejo

2013-01-01

Full Text Available Different LB films of poly(octadecene-co-maleic anhydride, PMAO, poly(styrene-co-maleic anhydride partial 2 butoxy ethyl ester cumene terminated, PS-MA-BEE, and Gemini surfactant ethyl-bis(dimethyl octadecylammonium bromide, 18-2-18, have been used to study the effect of the substrate coating on the surface self-assembly of CdSe quantum dots (QDs. Results show that all the “coating molecules” avoid the 3D aggregation of QDs observed when these nanoparticles are directly deposited on mica. Different morphologies were observed depending on the molecules used as coatings, and this was related to the surface properties, such as wetting ability, and the morphology of the coating LB films.

Analogy between soap film and gas dynamics. II. Experiments on one-dimensional motion of shock waves in soap films

Energy Technology Data Exchange (ETDEWEB)

Wen, C.Y.; Chang-Jian, S.K.; Chuang, M.C. [Department of Mechanical Engineering, Da-Yeh University, Chang-Hwa (Taiwan)

2003-02-01

This paper presents an experimental investigation of one-dimensional moving shock waves in vertical soap films. The shock waves were generated by bursting the films with a perforating spark. Images of propagating shock waves and small disturbances were recorded using a fast line scan CCD camera. An aureole and a shock wave preceding the rim of the expanding hole were clearly observed. These images are similar to the x-t diagrams in gas dynamics and give the velocities of shock and sound waves. The moving shock waves cause jumps in thickness. The variations of the induced Mach number, M{sub 2} and the ratio of film thickness across the shock wave, {delta}{sub 2}/{delta}{sub 1}, are plotted versus the shock Mach number, M{sub s}. Both results suggest that soap films are analogous to compressible gases with a specific heat ratio of {gamma}{approx_equal}1.0. (orig.)

Metal-insulator transition induced in CaVO3 thin films

International Nuclear Information System (INIS)

Gu Man; Laverock, Jude; Chen, Bo; Smith, Kevin E.; Wolf, Stuart A.; Lu Jiwei

2013-01-01

Stoichiometric CaVO 3 (CVO) thin films of various thicknesses were grown on single crystal SrTiO 3 (STO) (001) substrates using a pulsed electron-beam deposition technique. The CVO films were capped with a 2.5 nm STO layer. We observed a temperature driven metal-insulator transition (MIT) in CVO films with thicknesses below 4 nm that was not observed in either thick CVO films or STO films. The emergence of this MIT can be attributed to the reduction in effective bandwidth due to a crossover from a three-dimensional metal to a two-dimensional insulator. The insulating phase was only induced with a drive current below 0.1 μA. X-ray absorption measurements indicated different electronic structures for thick and very thin films of CVO. Compared with the thick film (∼60 nm), thin films of CVO (2–4 nm) were more two-dimensional with the V charge state closer to V 4+ .

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

International Nuclear Information System (INIS)

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

2016-01-01

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

Thin films on the basis of magnetic nanoparticles

Directory of Open Access Journals (Sweden)

G. Alimbekova

2012-09-01

Full Text Available The present work is to study the adsorption of magnetic nanoparticles in the structure of nanohybrid films by layer-by-layer (LbL method. Obtained by UV-VIS absorption spectra of 5% magnetic nanoparticles and the aqueous solution polyvinyl alcohol consisting of 5 and 10 nanohybrid layers. Analysis of the optical absorption spectra shows the homogeneity and mechanical stability of the nanohybrid films.

Universality of modular symmetries in two-dimensional magnetotransport

Science.gov (United States)

Olsen, K. S.; Limseth, H. S.; Lütken, C. A.

2018-01-01

We analyze experimental quantum Hall data from a wide range of different materials, including semiconducting heterojunctions, thin films, surface layers, graphene, mercury telluride, bismuth antimonide, and black phosphorus. The fact that these materials have little in common, except that charge transport is effectively two-dimensional, shows how robust and universal the quantum Hall phenomenon is. The scaling and fixed point data we analyzed appear to show that magnetotransport in two dimensions is governed by a small number of universality classes that are classified by modular symmetries, which are infinite discrete symmetries not previously seen in nature. The Hall plateaux are (infrared) stable fixed points of the scaling-flow, and quantum critical points (where the wave function is delocalized) are unstable fixed points of scaling. Modular symmetries are so rigid that they in some cases fix the global geometry of the scaling flow, and therefore predict the exact location of quantum critical points, as well as the shape of flow lines anywhere in the phase diagram. We show that most available experimental quantum Hall scaling data are in good agreement with these predictions.

Incorporation of nano-clay saponite layers in the organo-clay hybrid films using anionic amphiphile stearic acid by Langmuir–Blodgett technique

Energy Technology Data Exchange (ETDEWEB)

Hussain, Syed Arshad, E-mail: sa_h153@hotmail.com [Department of Physics, Tripura University, Suryamaninagar-799022 (India); Chakraborty, S.; Bhattacharjee, D. [Department of Physics, Tripura University, Suryamaninagar-799022 (India); Schoonheydt, R.A. [Centres for Surface Chemistry and Catalysis, K.U. Leuven, Kasteelpark Arenberg 23, 3001 Leuven (Belgium)

2013-06-01

In general cationic amphiphiles are used to prepare organo-clay hybrid film in Langmuir–Blodgett (LB) technique. In this present communication we demonstrated a unique technique to prepare the organo–clay hybrid films using an anionic amphiphile. The T–O–T type clay saponite was incorporated onto a floating stearic acid monolayer via a divalent cation Mg{sup 2+}. Salt MgCl{sub 2} was mixed along with the clay dispersion in the LB trough and amphiphile solution was spread onto the subphase in order to make the organo-clay hybrid films. It was observed that salt (MgCl{sub 2}) concentration on the subphase affects the organization of nano-dimensional clay platelet (saponite) in organo-clay hybrid films at air–water interface as well as in LB films. Noticeable changes in area per molecule and shape of the isotherms were observed and measured at subphases with different salt concentrations. Infrared reflection absorption spectroscopy studies reveal that only an in-plane (996 cm{sup −1}) vibration of ν (Si-O) band occurred when the salt concentration was 10 mM. However, both in-plane (996 cm{sup −1}) and out-of-plane (1063 cm{sup −1}) vibrations of the ν (Si-O) band of saponite occurred when the subphase salt concentration was 100 mM. Also the out-of-plane vibration of ν (OH) of saponite was prominent at higher salt concentration. This is because at lower salt concentration clay sheets remain flat on the surface whereas; at higher MgCl{sub 2} concentration they aggregated and form stacks of saponite layers. Also they may be slightly tilted with a very small tilt angle at higher salt concentration making a favorable condition for both in-plane and out-of-plane vibrations of ν (Si-O) in the hybrid films. Observed decrease in starting area per molecule in the pressure area isotherm measured at higher salt concentration also supports the tilting of clay layers at air–clay dispersion interface. Attentuated total reflectance Fourier transform infrared

Fluorescence studies on native and bound to trifluraline soy bean Lb "a" in the enhanced N 2 fixation

Science.gov (United States)

Kolev, Kolyo; Dolashka-Angelova, Pavlina

2001-10-01

The differences in the tryptophan (Trp) fluorescence of native (control) Lb "a" and experimental substance isolated from nodules of the 'Williams' soy beans variety treated with trifluraline at a concentration of 2.1×10 -10 M have been studied. A positively charged environment has been proved for the tryptophans of the native Lb "a" and a negative one for the tryptophans of the experimental Lb "a". The difference in the tryptophan emission spectra at λex=280 and 300 nm may be assigned to conformational alterations occurring in the experimental Lb "a". This is also confirmed by the greater energy transfer from tyrosine to tryptophan in the experimental Lb "a"—30% compared to the 10% in the native Lb "a". The value of the constant of acrylamide quenching ( Ksv=2.77 M -1) shows that the tryptophans are buried more deeply in the experimental Lb "a" than in the native Lb "a" ( Ksv=4 M -1). They are substantially lower than Ksv of the standard compound N-Ac-Trp-NH 2 (16.30 M -1). The activation energy ( Ea) of the thermal quenching of tryptophan fluorescence is higher for the experimental Lb "a" (37 kJ mol -1) as compared to the standard compound N-Ac-Trp-NH 2 (24 kJ mol -1) and the native Lb "a" (32 kJ mol -1). The dissociation constant of the complex of trifluraline with Lb "a" (6.32×10 -11 M) has been determined as well as the stoichiometric ratio trifluraline/Lb "a" (1:1). The estimated nitrogenase activity (μM/gfrw h) and the total Lb (mg/gfrw) for trifluraline are higher as compared to those for the control.

Approximate solutions for the two-dimensional integral transport equation. Solution of complex two-dimensional transport problems

International Nuclear Information System (INIS)

Sanchez, Richard.

1980-11-01

This work is divided into two parts: the first part deals with the solution of complex two-dimensional transport problems, the second one (note CEA-N-2166) treats the critically mixed methods of resolution. A set of approximate solutions for the isotropic two-dimensional neutron transport problem has been developed using the interface current formalism. The method has been applied to regular lattices of rectangular cells containing a fuel pin, cladding, and water, or homogenized structural material. The cells are divided into zones that are homogeneous. A zone-wise flux expansion is used to formulate a direct collision probability problem within a cell. The coupling of the cells is effected by making extra assumptions on the currents entering and leaving the interfaces. Two codes have been written: CALLIOPE uses a cylindrical cell model and one or three terms for the flux expansion, and NAUSICAA uses a two-dimensional flux representation and does a truly two-dimensional calculation inside each cell. In both codes, one or three terms can be used to make a space-independent expansion of the angular fluxes entering and leaving each side of the cell. The accuracies and computing times achieved with the different approximations are illustrated by numerical studies on two benchmark problems and by calculations performed in the APOLLO multigroup code [fr

On the effect of ammonia and wet atmospheres on the conducting properties of different lutetium bisphthalocyanine thin films

International Nuclear Information System (INIS)

Parra, Vicente; Bouvet, Marcel; Brunet, Jerome; Rodriguez-Mendez, Maria Luz; Saja, Jose Antonio de

2008-01-01

In this article, we present new experimental data regarding the influence of ammonia (NH 3 ) and water (from wet atmospheres) in the conducting properties of lutetium bisphthalocyanine (LuPc 2 )-based films in two very different structural features, namely Langmuir-Blodgett (LB) and vacuum evaporated (VE) films, deposited onto interdigitated electrodes. We pay particular attention to the effect of the mass flow rate ratios of the active gases, which certainly influence the mechanism of conduction of the chemiresistors. The particular trends observed are discussed on the basis of two main contributions: the electronic effects and the competition between gases in the adsorption process

Two-dimensional topological field theories coupled to four-dimensional BF theory

International Nuclear Information System (INIS)

Montesinos, Merced; Perez, Alejandro

2008-01-01

Four-dimensional BF theory admits a natural coupling to extended sources supported on two-dimensional surfaces or string world sheets. Solutions of the theory are in one to one correspondence with solutions of Einstein equations with distributional matter (cosmic strings). We study new (topological field) theories that can be constructed by adding extra degrees of freedom to the two-dimensional world sheet. We show how two-dimensional Yang-Mills degrees of freedom can be added on the world sheet, producing in this way, an interactive (topological) theory of Yang-Mills fields with BF fields in four dimensions. We also show how a world sheet tetrad can be naturally added. As in the previous case the set of solutions of these theories are contained in the set of solutions of Einstein's equations if one allows distributional matter supported on two-dimensional surfaces. These theories are argued to be exactly quantizable. In the context of quantum gravity, one important motivation to study these models is to explore the possibility of constructing a background-independent quantum field theory where local degrees of freedom at low energies arise from global topological (world sheet) degrees of freedom at the fundamental level

Metal-insulator transition induced in CaVO{sub 3} thin films

Energy Technology Data Exchange (ETDEWEB)

Gu Man [Department of Physics, University of Virginia, 382 McCormick Rd., Charlottesville, Virginia 22904 (United States); Laverock, Jude; Chen, Bo; Smith, Kevin E. [Department of Physics, Boston University, 590 Commonwealth Avenue, Boston, Massachusetts 02215 (United States); Wolf, Stuart A. [Department of Physics, University of Virginia, 382 McCormick Rd., Charlottesville, Virginia 22904 (United States); Department of Materials Science and Engineering, University of Virginia, 395 McCormick Rd., Charlottesville, Virginia 22904 (United States); Lu Jiwei [Department of Materials Science and Engineering, University of Virginia, 395 McCormick Rd., Charlottesville, Virginia 22904 (United States)

2013-04-07

Stoichiometric CaVO{sub 3} (CVO) thin films of various thicknesses were grown on single crystal SrTiO{sub 3} (STO) (001) substrates using a pulsed electron-beam deposition technique. The CVO films were capped with a 2.5 nm STO layer. We observed a temperature driven metal-insulator transition (MIT) in CVO films with thicknesses below 4 nm that was not observed in either thick CVO films or STO films. The emergence of this MIT can be attributed to the reduction in effective bandwidth due to a crossover from a three-dimensional metal to a two-dimensional insulator. The insulating phase was only induced with a drive current below 0.1 {mu}A. X-ray absorption measurements indicated different electronic structures for thick and very thin films of CVO. Compared with the thick film ({approx}60 nm), thin films of CVO (2-4 nm) were more two-dimensional with the V charge state closer to V{sup 4+}.

Single-walled carbon nanotubes: a nano-specific enhancer of cellular growth in LB culture

International Nuclear Information System (INIS)

Zhao Jinming; Yang Xiafeng; Zhao Yun; Huang Qing; Li Jiang; Lu Min

2012-01-01

We conducted a study to characterize the antimicrobial properties of SWNTs to B.subtilis in a saline solution or in a LB culture. Dimensions and the antibacterial ability of SWNTs in a saline solution were different from those in a LB culture. Transmission and scanning electron microscopes were used to characterize the SWNTs structure with and without LB culture. The antibacterial ability of SWNTs was affected by the environment of bacterial growth. The antibacterial mechanism of SWNTs was studied,too. (authors)

Beginning Introductory Physics with Two-Dimensional Motion

Science.gov (United States)

Huggins, Elisha

2009-01-01

During the session on "Introductory College Physics Textbooks" at the 2007 Summer Meeting of the AAPT, there was a brief discussion about whether introductory physics should begin with one-dimensional motion or two-dimensional motion. Here we present the case that by starting with two-dimensional motion, we are able to introduce a considerable…

Two-dimensional thermofield bosonization

International Nuclear Information System (INIS)

Amaral, R.L.P.G.; Belvedere, L.V.; Rothe, K.D.

2005-01-01

The main objective of this paper was to obtain an operator realization for the bosonization of fermions in 1 + 1 dimensions, at finite, non-zero temperature T. This is achieved in the framework of the real-time formalism of Thermofield Dynamics. Formally, the results parallel those of the T = 0 case. The well-known two-dimensional Fermion-Boson correspondences at zero temperature are shown to hold also at finite temperature. To emphasize the usefulness of the operator realization for handling a large class of two-dimensional quantum field-theoretic problems, we contrast this global approach with the cumbersome calculation of the fermion-current two-point function in the imaginary-time formalism and real-time formalisms. The calculations also illustrate the very different ways in which the transmutation from Fermi-Dirac to Bose-Einstein statistics is realized

MgB2 thick films on three-dimensional structures fabricated by HPCVD

Science.gov (United States)

Guo, Zhengshan; Cai, Xingwei; Liao, Xuebin; Chen, Yiling; Yang, Can; Niu, Ruirui; Luo, Wenhao; Huang, Zigeng; Feng, Qingrong; Gan, Zizhao

2018-06-01

Magnetic shielding has been a key factor in the measurement of ultra-weak magnetic fields, especially for shielding from low frequency electromagnetic noise. With the recent development of superconducting quantum interference devices, superconducting magnetic shielding has become an important area of research. MgB2 has shown great potential in magnetic shielding for its remarkable superconducting properties, the feasibility of its use in this capacity having been demonstrated by MgB2 bulk samples. However, the potential for application of such bulk samples is limited. In this work, we have investigated the possibility of the fabrication of MgB2 films on three-dimensional (3D) structures using a hybrid physical‑chemical vapor deposition system. MgB2 films 10 μm thick have been fabricated on the outer surface of a polycrystalline Al2O3 cylinder. The deposited film showed a transition temperature (TC) of 39 K and J C of 5.1 × 105 A · cm‑2, which are comparable to those of planar MgB2 films. This work shows the feasibility of depositing MgB2 films onto a 3D structure, and sheds light on the potential use of MgB2 films in superconducting magnetic shielding.

Piezoelectricity in Two-Dimensional Materials

KAUST Repository

Wu, Tao

2015-02-25

Powering up 2D materials: Recent experimental studies confirmed the existence of piezoelectricity - the conversion of mechanical stress into electricity - in two-dimensional single-layer MoS2 nanosheets. The results represent a milestone towards embedding low-dimensional materials into future disruptive technologies. © 2015 Wiley-VCH Verlag GmbH & Co. KGaA.

A Procedure to Address the Fuel Rod Failures during LB-LOCA Transient in Atucha-2 NPP

Directory of Open Access Journals (Sweden)

Martina Adorni

2011-01-01

Full Text Available Depending on the specific event scenario and on the purpose of the analysis, the availability of calculation methods that are not implemented in the standard system thermal hydraulic codes might be required. This may imply the use of a dedicated fuel rod thermomechanical computer code. This paper provides an outline of the methodology for the analysis of the 2A LB-LOCA accident in Atucha-2 NPP and describes the procedure adopted for the use of the fuel rod thermomechanical code. The methodology implies the application of best estimate thermalhydraulics, neutron physics, and fuel pin performance computer codes, with the objective to verify the compliance with the specific acceptance criteria. The fuel pin performance code is applied with the main objective to evaluate the extent of cladding failures during the transient. The procedure consists of a deterministic calculation by the fuel performance code of each individual fuel rod during its lifetime and in the subsequent LB-LOCA transient calculations. The boundary and initial conditions are provided by core physics and three-dimensional neutron kinetic coupled thermal-hydraulic system codes calculations. The procedure is completed by the sensitivity calculations and the application of the probabilistic method, which are outside the scope of the current paper.

Probing Carrier Transport and Structure-Property Relationship of Highly Ordered Organic Semiconductors at the Two-Dimensional Limit.

Science.gov (United States)

Zhang, Yuhan; Qiao, Jingsi; Gao, Si; Hu, Fengrui; He, Daowei; Wu, Bing; Yang, Ziyi; Xu, Bingchen; Li, Yun; Shi, Yi; Ji, Wei; Wang, Peng; Wang, Xiaoyong; Xiao, Min; Xu, Hangxun; Xu, Jian-Bin; Wang, Xinran

2016-01-08

One of the basic assumptions in organic field-effect transistors, the most fundamental device unit in organic electronics, is that charge transport occurs two dimensionally in the first few molecular layers near the dielectric interface. Although the mobility of bulk organic semiconductors has increased dramatically, direct probing of intrinsic charge transport in the two-dimensional limit has not been possible due to excessive disorders and traps in ultrathin organic thin films. Here, highly ordered single-crystalline mono- to tetralayer pentacene crystals are realized by van der Waals (vdW) epitaxy on hexagonal BN. We find that the charge transport is dominated by hopping in the first conductive layer, but transforms to bandlike in subsequent layers. Such an abrupt phase transition is attributed to strong modulation of the molecular packing by interfacial vdW interactions, as corroborated by quantitative structural characterization and density functional theory calculations. The structural modulation becomes negligible beyond the second conductive layer, leading to a mobility saturation thickness of only ∼3  nm. Highly ordered organic ultrathin films provide a platform for new physics and device structures (such as heterostructures and quantum wells) that are not possible in conventional bulk crystals.

Large scale solvothermal synthesis and a strategy to obtain stable Langmuir–Blodgett film of CoFe2O4 nanoparticles

International Nuclear Information System (INIS)

Thampi, Arya; Babu, Keerthi; Verma, Seema

2013-01-01

Highlights: • Large scale, monodisperse CoFe 2 O 4 nanoparticles by solvothermal route. • LB technique to obtain stable film of CoFe 2 O 4 nanoparticles over a large area. • Hydrophobicity of substrate was enhanced utilizing LB films of cadmium arachidate. • P–A isotherm and AFM cross sectional height profile analysis confirms stability. • Large scale organization of nanoparticles for surface pressure higher than 15 mN/m. -- Abstract: Nearly monodisperse oleic acid coated cobalt ferrite nanoparticles were synthesized in large scale by a simple solvothermal method utilizing N-methyl 2-Pyrrolidone (NMP) as a high boiling solvent. The magnetic oxide was further investigated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM) and vibrating sample magnetometer (VSM). Langmuir–Blodgett (LB) technique is discussed to obtain a 2D assembly of oleic acid coated CoFe 2 O 4 nanoparticles over a large area. We describe a method to obtain stable, condensed three layers of cadmium arachidate on a piranha treated glass substrate. The hydrophobic surface thus obtained was subsequently used for forming a stable monolayer of oleic acid stabilized cobalt ferrite nanoparticles at the air–water interface. The stability of the LB films at the air–water interface was studied by pressure–area isotherm curves and atomic force microscopy (AFM) cross sectional height profile analysis. 2D organization of the magnetic nanoparticles at different surface pressures was studied by TEM. Preparation of large area LB films of CoFe 2 O 4 nanoparticles is reported for a surface pressure more than 15 mN/m

Two-dimensional confinement of heavy fermions

International Nuclear Information System (INIS)

Shishido, Hiroaki; Shibauchi, Takasada; Matsuda, Yuji; Terashima, Takahito

2010-01-01

Metallic systems with the strongest electron correlations are realized in certain rare-earth and actinide compounds whose physics are dominated by f-electrons. These materials are known as heavy fermions, so called because the effective mass of the conduction electrons is enhanced via correlation effects up to as much as several hundreds times the free electron mass. To date the electronic structure of all heavy-fermion compounds is essentially three-dimensional. Here we report on the first realization of a two-dimensional heavy-fermion system, where the dimensionality is adjusted in a controllable fashion by fabricating heterostructures using molecular beam epitaxy. The two-dimensional heavy fermion system displays striking deviations from the standard Fermi liquid low-temperature electronic properties. (author)

Two-dimensional topological photonics

Science.gov (United States)

Khanikaev, Alexander B.; Shvets, Gennady

2017-12-01

Originating from the studies of two-dimensional condensed-matter states, the concept of topological order has recently been expanded to other fields of physics and engineering, particularly optics and photonics. Topological photonic structures have already overturned some of the traditional views on wave propagation and manipulation. The application of topological concepts to guided wave propagation has enabled novel photonic devices, such as reflection-free sharply bent waveguides, robust delay lines, spin-polarized switches and non-reciprocal devices. Discrete degrees of freedom, widely used in condensed-matter physics, such as spin and valley, are now entering the realm of photonics. In this Review, we summarize the latest advances in this highly dynamic field, with special emphasis on the experimental work on two-dimensional photonic topological structures.

Structures of two-dimensional three-body systems

International Nuclear Information System (INIS)

Ruan, W.Y.; Liu, Y.Y.; Bao, C.G.

1996-01-01

Features of the structure of L = 0 states of a two-dimensional three-body model system have been investigated. Three types of permutation symmetry of the spatial part, namely symmetric, antisymmetric, and mixed, have been considered. A comparison has been made between the two-dimensional system and the corresponding three-dimensional one. The effect of symmetry on microscopic structures is emphasized. (author)

Dimensional scaling of perovskite ferroelectric thin films

Science.gov (United States)

Keech, Ryan R.

Dimensional size reduction has been the cornerstone of the exponential improvement in silicon based logic devices for decades. However, fundamental limits in the device physics were reached ˜2003, halting further reductions in clock speed without significant penalties in power consumption. This has motivated the research into next generation transistors and switching devices to reinstate the scaling laws for clock speed. This dissertation aims to support the scaling of devices that are based on ferroelectricity and piezoelectricity and to provide a roadmap for the corresponding materials performance. First, a scalable growth process to obtain highly {001}-oriented lead magnesium niobate - lead titanate (PMN-PT) thin films was developed, motivated by the high piezoelectric responses observed in bulk single crystals. It was found that deposition of a 2-3 nm thick PbO buffer layer on {111} Pt thin film bottom electrodes, prior to chemical solution deposition of PMN-PT reduces the driving force for Pb diffusion from the PMN-PT to the bottom electrode, and facilitates nucleation of {001}-oriented perovskite grains. Energy dispersive spectroscopy demonstrated that up to 10% of the Pb from a PMN-PT precursor solution may diffuse into the bottom electrode. PMN-PT grains with a mixed {101}/{111} orientation in a matrix of Pb-deficient pyrochlore phase were then promoted near the interface. When this is prevented, phase pure films with {001} orientation with Lotgering factors of 0.98-1.0, can be achieved. The resulting films of only 300 nm in thickness exhibit longitudinal effective d33,f coefficients of ˜90 pm/V and strain values of ˜1% prior to breakdown. 300 nm thick epitaxial and polycrystalline lead magnesium niobate - lead titanate (70PMN-30PT) blanket thin films were studied for the relative contributions to property thickness dependence from interfacial and grain boundary low permittivity layers. Epitaxial PMN-PT films were grown on SrRuO 3 /(001)SrTiO3, while

X-ray imaging device for one-dimensional and two-dimensional radioscopy

International Nuclear Information System (INIS)

1978-01-01

The X-ray imaging device for the selectable one-dimensional or two-dimensional pictures of objects illuminated by X-rays, comprising an X-ray source, an X-ray screen, and an opto-electrical picture development device placed behind the screen, is characterized by an anamorphotic optical system, which is positioned with a one-dimensional illumination between the X-ray screen and the opto-electrical device and that a two-dimensional illumination will be developed, and that in view of the lens system which forms part of the opto-electrical device, there is placed an X-ray screen in a specified beam direction so that a magnified image may be formed by equalisation of the distance between the X-ray screen and the lens system. (G.C.)

Hamiltonian formalism of two-dimensional Vlasov kinetic equation.

Science.gov (United States)

Pavlov, Maxim V

2014-12-08

In this paper, the two-dimensional Benney system describing long wave propagation of a finite depth fluid motion and the multi-dimensional Russo-Smereka kinetic equation describing a bubbly flow are considered. The Hamiltonian approach established by J. Gibbons for the one-dimensional Vlasov kinetic equation is extended to a multi-dimensional case. A local Hamiltonian structure associated with the hydrodynamic lattice of moments derived by D. J. Benney is constructed. A relationship between this hydrodynamic lattice of moments and the two-dimensional Vlasov kinetic equation is found. In the two-dimensional case, a Hamiltonian hydrodynamic lattice for the Russo-Smereka kinetic model is constructed. Simple hydrodynamic reductions are presented.

Novel target design algorithm for two-dimensional optical storage (TwoDOS)

NARCIS (Netherlands)

Huang, Li; Chong, T.C.; Vijaya Kumar, B.V.K.; Kobori, H.

2004-01-01

In this paper we introduce the Hankel transform based channel model of Two-Dimensional Optical Storage (TwoDOS) system. Based on this model, the two-dimensional (2D) minimum mean-square error (MMSE) equalizer has been derived and applied to some simple but common cases. The performance of the 2D

Post-assembly transformations of porphyrin-containing metal-organic framework (MOF) films fabricated via automated layer-by-layer coordination

KAUST Repository

So, Monica; Beyzavi, M. Hassan; Sawhney, Rohan; Shekhah, Osama; Eddaoudi, Mohamed; Al-Juaid, Salih Salem; Hupp, Joseph T.; Farha, Omar K.

2015-01-01

Herein, we demonstrate the robustness of layer-by-layer (LbL)-assembled, pillared-paddlewheel-type MOF films toward conversion to new or modified MOFs via solvent-assisted linker exchange (SALE) and post-assembly linker metalation. Further, we show that LbL synthesis can afford MOFs that have proven inaccessible through other de novo strategies.

A stability investigation of two-dimensional surface waves on evaporating, isothermal or condensing liquid films - Part I, Thermal non-equilibrium effects on wave velocity

International Nuclear Information System (INIS)

Chunxi, L.; Xuemin, Y.

2004-01-01

The temporal stability equation of the two-dimensional traveling waves of evaporating or condensing liquid films falling down on an inclined wall is established based on the Prandtl boundary layer theory and complete boundary conditions. The model indicates that the wave velocity is related to the effects of evaporating, isothermal and condensing states, thermo-capillarity, Reynolds number, fluid property and inclined angle, and the effects of above factors are distinctly different under different Reynolds numbers. The theoretical studies show that evaporation process induces the wave velocity to increase slightly compared with the isothermal case, and condensation process induces the wave velocity to decrease slightly. Furthermore, the wave velocity decreases because of the effects of thermo-capillarity under evaporation and increases because of the effects of thermo-capillarity under condensation. The effects of thermal non-equilibrium conditions have relatively obvious effects under lower Reynolds numbers and little effects under higher Reynolds numbers

Two-Dimensional Materials for Sensing: Graphene and Beyond

Directory of Open Access Journals (Sweden)

Seba Sara Varghese

2015-09-01

Full Text Available Two-dimensional materials have attracted great scientific attention due to their unusual and fascinating properties for use in electronics, spintronics, photovoltaics, medicine, composites, etc. Graphene, transition metal dichalcogenides such as MoS2, phosphorene, etc., which belong to the family of two-dimensional materials, have shown great promise for gas sensing applications due to their high surface-to-volume ratio, low noise and sensitivity of electronic properties to the changes in the surroundings. Two-dimensional nanostructured semiconducting metal oxide based gas sensors have also been recognized as successful gas detection devices. This review aims to provide the latest advancements in the field of gas sensors based on various two-dimensional materials with the main focus on sensor performance metrics such as sensitivity, specificity, detection limit, response time, and reversibility. Both experimental and theoretical studies on the gas sensing properties of graphene and other two-dimensional materials beyond graphene are also discussed. The article concludes with the current challenges and future prospects for two-dimensional materials in gas sensor applications.

Electrodeposition of flake-like Cu{sub 2}O on vertically aligned two-dimensional TiO{sub 2} nanosheet array films for enhanced photoelectrochemical properties

Energy Technology Data Exchange (ETDEWEB)

Yang, Lei [School of Physics & Material Science, Anhui University, Hefei 230601 (China); Co-operative Innovation Research Center for Weak Signal-Detecting Materials and Devices Integration, Anhui University, Hefei 230601 (China); Institute of Applied Physics AOA, Hefei 230031 (China); Zhang, Miao; Zhu, Kerong [School of Physics & Material Science, Anhui University, Hefei 230601 (China); Lv, Jianguo [School of Electronic & Information Engineering, Hefei Normal University, Hefei 230601 (China); He, Gang [School of Physics & Material Science, Anhui University, Hefei 230601 (China); Sun, Zhaoqi, E-mail: szq@ahu.edu.cn [School of Physics & Material Science, Anhui University, Hefei 230601 (China)

2017-01-01

Highlights: • Flake-like Cu{sub 2}O/TNS with exposed {001} facets constructed p-n heterostructure. • The TNS arrays were used as starting substrates for Cu{sub 2}O growth. • The Cu{sub 2}O/TNS prepared at −0.4 V exhibits the best photoelectrochemical property. - Abstract: A novel Cu{sub 2}O/TNS composite structure of single crystal TiO{sub 2} nanosheet (TNS) arrays decorated with flake-like Cu{sub 2}O were synthesized by a facile hydrothermal reaction followed by the electrodeposition process. The effects of deposition potential on the microstructure, morphology, and optical property of the thin films were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM) and UV–vis spectrophotometer. When the deposition potential is higher than −0.4 V, peaks corresponding to Cu appear, meanwhile, flake-like Cu{sub 2}O become agglomerating, and transform into dense Cu{sub 2}O particles. Additionally, photoelectrochemical experiments indicate that the films deposited at −0.4 V show the lowest resistivity and highest exciton separation efficiency. This enhanced photoelectrochemical properties can be explained by synergistic effect of p-type flake-like Cu{sub 2}O and n-type TiO{sub 2} heterojunctions combined with two-dimensional TiO{sub 2} nanosheet with exposed highly reactive {001} facets.

Thermodynamic and structural study of two-dimensional phase transitions and orientational order in films of linear molecules with a large quadrupole moment, physi-sorbed on lamellar substrates

International Nuclear Information System (INIS)

Terlain, Anne

1984-01-01

The 2D (two-dimensional) phase transitions and orientational order in N 2 O, CO 2 , C 2 N 2 and C 2 D 2 films physi-sorbed on the (0001) face of graphite or lamellar halides, were studied experimentally by adsorption isotherm measurements and neutron diffraction. The thermodynamic functions derived from sets of isotherms suggest that crystal monolayers of N 2 O, CO 2 , and C 2 N 2 adsorbed on graphite are orientationally ordered and that the quadrupolar interaction stabilizes the 2D crystal with respect to the 2D liquid. This stabilization leads to an increase in the 2D triple point temperature, T 2t as compared with the 2D critical temperature T 2c . For C 2 N 2 this stabilization is so pronounced that T 2t becomes virtually higher than T 2c , and the phase diagram qualitatively different, having no gas-liquid coexistence domain. From a neutron diffraction experiment we have determined the crystal structure of the C 2 N 2 monolayer. It supports our interpretation of the monolayer phase diagram. In N 2 O, CO 2 , C 2 N 2 films adsorbed on graphite the molecules lie flat on the surface and their orientational order hence differs from that in the bulk crystals resulting in a loss of adsorbate-adsorbate interaction energy. Beyond a given film thickness this loss will not be compensated by the adsorbate-substrate interaction and the film will stop growing. For most of the films studied a partial wetting transition is observed at which the film thickness increases discontinuously with temperature. Although C 2 N 2 and C 2 D 2 monolayers on graphite have comparable adsorption energies, only C 2 D 2 is adsorbed on lamellar halides. This adsorption is possible only because the monolayer has a large entropy due to orientational disorder. For C 2 N 2 , which has a higher moment of inertia, such an orientational disorder cannot exist. (author) [fr

Two-dimensional calculus

CERN Document Server

Osserman, Robert

2011-01-01

The basic component of several-variable calculus, two-dimensional calculus is vital to mastery of the broader field. This extensive treatment of the subject offers the advantage of a thorough integration of linear algebra and materials, which aids readers in the development of geometric intuition. An introductory chapter presents background information on vectors in the plane, plane curves, and functions of two variables. Subsequent chapters address differentiation, transformations, and integration. Each chapter concludes with problem sets, and answers to selected exercises appear at the end o

Stress relaxation in quasi-two-dimensional self-assembled nanoparticle monolayers

Science.gov (United States)

Boucheron, Leandra S.; Stanley, Jacob T.; Dai, Yeling; You, Siheng Sean; Parzyck, Christopher T.; Narayanan, Suresh; Sandy, Alec R.; Jiang, Zhang; Meron, Mati; Lin, Binhua; Shpyrko, Oleg G.

2018-05-01

We experimentally probed the stress relaxation of a monolayer of iron oxide nanoparticles at the water-air interface. Upon drop-casting onto a water surface, the nanoparticles self-assembled into islands of two-dimensional hexagonally close packed crystalline domains surrounded by large voids. When compressed laterally, the voids gradually disappeared as the surface pressure increased. After the compression was stopped, the surface pressure (as measured by a Wilhelmy plate) evolved as a function of the film aging time with three distinct timescales. These aging dynamics were intrinsic to the stressed state built up during the non-equilibrium compression of the film. Utilizing x-ray photon correlation spectroscopy, we measured the characteristic relaxation time (τ ) of in-plane nanoparticle motion as a function of the aging time through both second-order and two-time autocorrelation analysis. Compressed and stretched exponential fitting of the intermediate scattering function yielded exponents (β ) indicating different relaxation mechanisms of the films under different compression stresses. For a monolayer compressed to a lower surface pressure (between 20 mN/m and 30 mN/m), the relaxation time (τ ) decreased continuously as a function of the aging time, as did the fitted exponent, which transitioned from being compressed (>1 ) to stretched (stress release through crystalline domain reorganization. However, for a monolayer compressed to a higher surface pressure (around 40 mN/m), the relaxation time increased continuously and the compressed exponent varied very little from a value of 1.6, suggesting that the system may have been highly stressed and jammed. Despite the interesting stress relaxation signatures seen in these samples, the structural ordering of the monolayer remained the same over the sample lifetime, as revealed by grazing incidence x-ray diffraction.

Direct calculation of unambiguous electron-density distributions of Langmuir-Blodgett films normal to the membrane plane

International Nuclear Information System (INIS)

Frieling, M. von; Bradaczek, H.

1990-01-01

In regard to X-ray diffraction, Langmuir-Blodgett (LB) films consisting of lipid bilayers represent a 'one-dimensional crystal' with a very small number of unit cells in the direction of stacking. Such bounded systems yield X-ray diffraction diagrams which, in certain respects, contain more information than those of the conventional effectively infinite single crystals. This additional information consists of the profiles of the broadened reflections and their dislocation from the reciprocal-lattice points. These profiles are specific for each different structure and hence enable the direct calculation of unambiguous electron-density distributions from a single set of intensity data. At first, the Q function (the generalized Patterson function), i.e. the distance statistics of the structure sought after is calculated from the intensity data. Thereafter, the unambiguous convolution square root of the Q function must be determined, which is identical to the unknown electron-density distribution. For this purpose two mathematically completely different methods were established and compared. They were applied to diffraction patterns of Langmuir-Blodgett films of simple synthetic lipids with characteristic molecular subunits and showed identical results within the experimental resolution. This verifies the structures and the methods to calculate them. Furthermore, all features of the simple structures were compatible with the expectations. All one-dimensional electron-density distributions showed the common features of lipid bilayers. The characteristic molecular subunits can be recognized and reveal some interesting details. In general, they yield information about orientation, conformation and localization of molecular subunits and membrane components. (orig.)

Monoamine oxidase B layer-by-layer film fabrication and characterization toward dopamine detection.

Science.gov (United States)

Miyazaki, Celina Massumi; Pereira, Tamyris Paschoal; Mascagni, Daniela Branco Tavares; de Moraes, Marli Leite; Ferreira, Marystela

2016-01-01

In this work nanostructured film composites of the monoamine oxidase B (MAO-B) enzyme, free or encapsulated in liposomes, were fabricated by the layer-by-layer (LbL) self-assembly technique, employing polyethylene imine (PEI) as polycation. Initially, the MAO-B enzyme was incorporated into liposomes in order to preserve its enzymatic structure ensuring their activity and catalytic stability. The LbL film growth was monitored by surface plasmon resonance (SPR) by gold resonance angle shift analysis after each bilayer deposition. Subsequently, the films were applied as amperometric biosensors for dopamine detection using Prussian Blue (PB) as the electron mediator. The biosensor fabricated by MAO-B incorporated into liposomes composed of DPPG:POPG in the ratio (1:4) (w/w) showed the best performance with a sensitivity of 0.86 (μA cm(-2))/(mmol L(-1)) and a detection limit of 0.33 mmol L(-1).

Observation of Internal Photoinduced Electron and Hole Separation in Hybrid Two-Dimentional Perovskite Films.

Science.gov (United States)

Liu, Junxue; Leng, Jing; Wu, Kaifeng; Zhang, Jun; Jin, Shengye

2017-02-01

Two-dimensional (2D) organolead halide perovskites are promising for various optoelectronic applications. Here we report a unique spontaneous charge (electron/hole) separation property in multilayered (BA) 2 (MA) n-1 Pb n I 3n+1 (BA = CH 3 (CH 2 ) 3 NH 3 + , MA = CH 3 NH 3 + ) 2D perovskite films by studying the charge carrier dynamics using ultrafast transient absorption and photoluminescence spectroscopy. Surprisingly, the 2D perovskite films, although nominally prepared as "n = 4", are found to be mixture of multiple perovskite phases, with n = 2, 3, 4 and ≈ ∞, that naturally align in the order of n along the direction perpendicular to the substrate. Driven by the band alignment between 2D perovskites phases, we observe consecutive photoinduced electron transfer from small-n to large-n phases and hole transfer in the opposite direction on hundreds of picoseconds inside the 2D film of ∼358 nm thickness. This internal charge transfer efficiently separates electrons and holes to the upper and bottom surfaces of the films, which is a unique property beneficial for applications in photovoltaics and other optoelectronics devices.

Dose evaluation of three-dimensional small animal phantom with film dosimetry

International Nuclear Information System (INIS)

Han, Su Chul; Park, Seung Woo

2017-01-01

The weight of small animal dosimetry has been continuously increased in pre-clinical studies using radiation in small animals. In this study, three-dimensional(3D) small animal phantom was fabricated using 3D printer which has been continuously used and studied in the various fields. The absorbed dose of 3D animal phantom was evaluated by film dosimetry. Previously, the response of film was obtained from the materials used for production of 3D small animal phantom and compared with the bolus used as the tissue equivalent material in the radiotherapy. When irradiated with gamma rays from 0.5 Gy to 6 Gy, it was confirmed that there was a small difference of less than 1% except 0.5 Gy dose. And when small animal phantom was irradiated with 5 Gy, the difference between the irradiated dose and calculated dose from film was within 2%. Based on this study, it would be possible to increase the reliability of dose in pre-clinical studies using irradiation in small animals by evaluating dose of 3D small animal phantom

Dose evaluation of three-dimensional small animal phantom with film dosimetry

Energy Technology Data Exchange (ETDEWEB)

Han, Su Chul [Div. of Medical Radiation Equipment, Korea Institute of Radiological and Medical Sciences, Seoul (Korea, Republic of); Park, Seung Woo [Radilogcial and Medico-Oncological Sciences, University of Sciences and Technology, Daejeon (Korea, Republic of)

2017-03-15

The weight of small animal dosimetry has been continuously increased in pre-clinical studies using radiation in small animals. In this study, three-dimensional(3D) small animal phantom was fabricated using 3D printer which has been continuously used and studied in the various fields. The absorbed dose of 3D animal phantom was evaluated by film dosimetry. Previously, the response of film was obtained from the materials used for production of 3D small animal phantom and compared with the bolus used as the tissue equivalent material in the radiotherapy. When irradiated with gamma rays from 0.5 Gy to 6 Gy, it was confirmed that there was a small difference of less than 1% except 0.5 Gy dose. And when small animal phantom was irradiated with 5 Gy, the difference between the irradiated dose and calculated dose from film was within 2%. Based on this study, it would be possible to increase the reliability of dose in pre-clinical studies using irradiation in small animals by evaluating dose of 3D small animal phantom.

Two-dimensional versus three-dimensional treatment planning of tangential breast irradiation

International Nuclear Information System (INIS)

Damen, E.M.F.; Bruinvis, I.A.D.; Mijnheer, B.J.

1995-01-01

Purpose: Full three-dimensional (3-D) treatment planning requires 3-D patient contours and density information, derived either from CT scanning or from other 3-D contouring methods. These contouring techniques are time consuming, and are often not available or cannot be used. Two-dimensional (2-D) treatment planning can be performed using only a few patient contours, made with much simpler techniques, in combination with simulator images for estimating the lung position. In order to investigate the need for full 3-D planning, we compared the performance of both a 2-D and a 3-D planning system in calculating absolute dose values and relative dose distributions in tangential breast irradiation. Methods: Two breast-shaped phantoms were used in this study. The first phantom consists of a polyethylene mould, filled with water and cork to mimic the lung. An ionization chamber can be inserted in the phantom at fixed positions. The second phantom is made of 25 transverse slices of polystyrene and cork, made with a computerized milling machine from CT information. In this phantom, films can be inserted in three sagittal planes. Both phantoms have been irradiated with two tangential 8 MV photon beams. The measured dose distribution has been compared with the dose distribution predicted by the two planning systems. Results: In the central plane, the 3-D planning system predicts the absolute dose with an accuracy of 0.5 - 4%. The dose at the isocentre of the beams agrees within 0.5% with the measured dose. The 2-D system predicts the dose with an accuracy of 0.9 - 3%. The dose calculated at the isocentre is 2.6% higher than the measured dose, because missing lateral scatter is not taken into account in this planning system. In off-axis planes, the calculated absolute dose agrees with the measured dose within 4% for the 2-D system and within 6% for the 3-D system. However, the relative dose distribution is predicted better by the 3-D planning system. Conclusions: This study

Development of polyelectrolyte multilayer thin film composite membrane for water desalination application

KAUST Repository

Fadhillah, F.; Zaidi, S.M.J.; Khan, Z.; Khaled, M.M.; Rahman, F.; Hammond, P.T.

2013-01-01

Thin film composite membranes were fabricated via spin assisted layer by layer (SA-LbL) assembly by depositing alternate layers of poly(allyl amine hydrochloride) (PAH) and poly(acrylic acid) (PAA) on a polysulfone (PSF) ultrafiltration membrane as support. The suitability of these membranes for potential water purification applications was explored by testing the stability of the deposited thin films and their permeation characteristic using cross-flow permeation cell. Permeation test conducted at a pressure of 40bar, temperature of 25°C, pH of 6 and feed water concentration of 2000ppm NaCl demonstrated that the PAH/PAA multilayer film deposited on polysulfone support remained stable and intact under long-term test conditions. The 120 bilayers of PAH/PAA membrane tested at the above condition showed flux of 15L/m2.h and salt rejection of 65%. The membrane performance evaluation also revealed that SA-LbL PAH/PAA membrane follows the characteristics of the solution diffusion membrane. © 2013 Elsevier B.V.

Development of polyelectrolyte multilayer thin film composite membrane for water desalination application

KAUST Repository

Fadhillah, F.

2013-06-01

Thin film composite membranes were fabricated via spin assisted layer by layer (SA-LbL) assembly by depositing alternate layers of poly(allyl amine hydrochloride) (PAH) and poly(acrylic acid) (PAA) on a polysulfone (PSF) ultrafiltration membrane as support. The suitability of these membranes for potential water purification applications was explored by testing the stability of the deposited thin films and their permeation characteristic using cross-flow permeation cell. Permeation test conducted at a pressure of 40bar, temperature of 25°C, pH of 6 and feed water concentration of 2000ppm NaCl demonstrated that the PAH/PAA multilayer film deposited on polysulfone support remained stable and intact under long-term test conditions. The 120 bilayers of PAH/PAA membrane tested at the above condition showed flux of 15L/m2.h and salt rejection of 65%. The membrane performance evaluation also revealed that SA-LbL PAH/PAA membrane follows the characteristics of the solution diffusion membrane. © 2013 Elsevier B.V.

On the effect of ammonia and wet atmospheres on the conducting properties of different lutetium bisphthalocyanine thin films

Energy Technology Data Exchange (ETDEWEB)

Parra, Vicente [Ecole Superieure de Physique et Chimie Industrielles (ESPCI) and Laboratoire de Chimie Inorganique et Materiaux Moleculaires-CNRS UMR 7071, Universite Pierre et Marie Curie (Paris 6) (France); Bouvet, Marcel [Ecole Superieure de Physique et Chimie Industrielles (ESPCI) and Laboratoire de Chimie Inorganique et Materiaux Moleculaires-CNRS UMR 7071, Universite Pierre et Marie Curie (Paris 6) (France)], E-mail: marcel.bouvet@espci.fr; Brunet, Jerome [Universite Blaise Pascal, LASMEA-CNRS UMR 6602, Clermont-Ferrand (France); Rodriguez-Mendez, Maria Luz [Dept. Quimica Fisica y Quimica Inorganica, Escuela Tecnica Superior de Ingenieros Industriales (E.T.S.I.I), Universidad de Valladolid (Spain); Saja, Jose Antonio de [Dept. Fisica de la Materia Condensada, Facultad de Ciencias, Universidad de Valladolid (Spain)

2008-10-31

In this article, we present new experimental data regarding the influence of ammonia (NH{sub 3}) and water (from wet atmospheres) in the conducting properties of lutetium bisphthalocyanine (LuPc{sub 2})-based films in two very different structural features, namely Langmuir-Blodgett (LB) and vacuum evaporated (VE) films, deposited onto interdigitated electrodes. We pay particular attention to the effect of the mass flow rate ratios of the active gases, which certainly influence the mechanism of conduction of the chemiresistors. The particular trends observed are discussed on the basis of two main contributions: the electronic effects and the competition between gases in the adsorption process.

Large scale solvothermal synthesis and a strategy to obtain stable Langmuir–Blodgett film of CoFe{sub 2}O{sub 4} nanoparticles

Energy Technology Data Exchange (ETDEWEB)

Thampi, Arya; Babu, Keerthi; Verma, Seema, E-mail: sa.verma@iiserpune.ac.in

2013-07-05

Highlights: • Large scale, monodisperse CoFe{sub 2}O{sub 4} nanoparticles by solvothermal route. • LB technique to obtain stable film of CoFe{sub 2}O{sub 4} nanoparticles over a large area. • Hydrophobicity of substrate was enhanced utilizing LB films of cadmium arachidate. • P–A isotherm and AFM cross sectional height profile analysis confirms stability. • Large scale organization of nanoparticles for surface pressure higher than 15 mN/m. -- Abstract: Nearly monodisperse oleic acid coated cobalt ferrite nanoparticles were synthesized in large scale by a simple solvothermal method utilizing N-methyl 2-Pyrrolidone (NMP) as a high boiling solvent. The magnetic oxide was further investigated by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), transmission electron microscopy (TEM), high resolution transmission electron microscopy (HRTEM) and vibrating sample magnetometer (VSM). Langmuir–Blodgett (LB) technique is discussed to obtain a 2D assembly of oleic acid coated CoFe{sub 2}O{sub 4} nanoparticles over a large area. We describe a method to obtain stable, condensed three layers of cadmium arachidate on a piranha treated glass substrate. The hydrophobic surface thus obtained was subsequently used for forming a stable monolayer of oleic acid stabilized cobalt ferrite nanoparticles at the air–water interface. The stability of the LB films at the air–water interface was studied by pressure–area isotherm curves and atomic force microscopy (AFM) cross sectional height profile analysis. 2D organization of the magnetic nanoparticles at different surface pressures was studied by TEM. Preparation of large area LB films of CoFe{sub 2}O{sub 4} nanoparticles is reported for a surface pressure more than 15 mN/m.

Characterization and obtainment of thin films based on N,N,N-trimethyl chitosan and heparin through the technical layer-by-layer; Caracterizacao e obtencao de filmes finos de N,N,N-trimetil quitosana e heparina atraves da tecnica layer-by-layer

Energy Technology Data Exchange (ETDEWEB)

NONE

2011-07-01

Thin films of Heparin (HP) and N,N,N-trimethyl chitosan (TMC) with a high degree of quaternization (DQ) were obtained at pH 7.4 through the layer-by-layer (LbL) technique. Polystyrene (PS) was oxidized with aqueous solution of sodium persulfate and subsequently employed as substrate. The characterization of TMC and the respective determination of DQ were performed through {sup 1}H NMR spectroscopy. The thin films de TMC/HP were characterized by FTIR-ATR and AFM. Both techniques confirmed the adsorption of TMC and HP in surface of the PS. The increasing of the bilayers provides a decrease of the projections and/or roughness, further of minimizing the depressions at the surface of the films. Studies of thin films the base of TMC/HP prepared from the LbL technique has not been reported in the literature. It is expected that the thin films of TMC/HP present anti-adhesive and antimicrobial properties. (author)

Selective growth of two-dimensional phosphorene on catalyst surface.

Science.gov (United States)

Qiu, L; Dong, J C; Ding, F

2018-02-01

Although the study of black phosphorene (BP) and its isomers has attracted enormous attention, the method of synthesizing high-quality samples in a large area is still pending. Here we explore the potential of using the chemical vapor deposition method to synthesize large-area two-dimensional (2D) phosphorene films on metal surfaces. Our ab initio calculations show that BP can be synthesized by using tin (Sn) as a catalyst, while one of its isomers, blue phosphorene (BLP), is very possible to be synthesized by using most other metals, such as Ag and Au. Besides, our study also suggests that the large binding energy between the 2D phosphorene and the active metal substrate may prohibit the exfoliation of the 2D phosphorene for real applications and, therefore, tin, silver and gold are predicted to be the most suitable catalysts for the synthesis of BP and BLP.

Nanostructured Thin Films Obtained from Fischer Aminocarbene Complexes

Directory of Open Access Journals (Sweden)

Rosa E. Lazo-Jiménez

2016-03-01

Full Text Available The synthesis of four amphiphilic organometallic complexes with the general formula RC = M(CO5NH(CH215CH3, where R is a ferrocenyl 2(a-b or a phenyl 4(a-b group as a donor moiety and a Fischer carbene of chromium (0 or tungsten (0 as an acceptor group, are reported. These four push-pull systems formed Langmuir (L monolayers at the air-water interface, which were characterized by isotherms of surface pressure versus molecular area and compression/expansion cycles (hysteresis curves; Brewster angle microscopic images were also obtained. By using the Langmuir–Blodgett (LB method, molecular monolayers were transferred onto glass substrates forming Z-type multilayers. LB films were characterized through ultraviolet-visible spectroscopy, atomic force microscopy and X-ray diffraction techniques. Results indicated that films obtained from 2b complex [(Ferrocenyl(hexadecylaminemethylidene] pentacarbonyl tungsten (0 are the most stable and homogeneous; due to their properties, these materials may be incorporated into organic electronic devices.

Nanostructured Thin Films Obtained from Fischer Aminocarbene Complexes

Science.gov (United States)

Lazo-Jiménez, Rosa E.; Ortega-Alfaro, M. Carmen; López-Cortés, José G.; Alvarez-Toledano, Cecilio; Chávez-Carvayar, José Á.; Ignés-Mullol, Jordi; González-Torres, Maykel; Carreón-Castro, Pilar

2016-01-01

The synthesis of four amphiphilic organometallic complexes with the general formula RC = M(CO)5NH(CH2)15CH3, where R is a ferrocenyl 2(a-b) or a phenyl 4(a-b) group as a donor moiety and a Fischer carbene of chromium (0) or tungsten (0) as an acceptor group, are reported. These four push-pull systems formed Langmuir (L) monolayers at the air-water interface, which were characterized by isotherms of surface pressure versus molecular area and compression/expansion cycles (hysteresis curves); Brewster angle microscopic images were also obtained. By using the Langmuir–Blodgett (LB) method, molecular monolayers were transferred onto glass substrates forming Z-type multilayers. LB films were characterized through ultraviolet-visible spectroscopy, atomic force microscopy and X-ray diffraction techniques. Results indicated that films obtained from 2b complex [(Ferrocenyl)(hexadecylamine)methylidene] pentacarbonyl tungsten (0) are the most stable and homogeneous; due to their properties, these materials may be incorporated into organic electronic devices. PMID:28773289

A general analytical equation for phase diagrams of an N-layer ferroelectric thin film with two surface layers

Energy Technology Data Exchange (ETDEWEB)

Lu, Z X; Teng, B H; Rong, Y H; Lu, X H; Yang, X [School of Physical Electronics, University of Electronic Science and Technology of China, Chengdu 610054 (China)], E-mail: phytbh@163.com

2010-03-15

Within the framework of effective-field theory with correlations, the phase diagrams of an N-layer ferroelectric thin film with two surface layers are studied by the differential operator technique based on the spin-1/2 transverse Ising model. A general analytical equation for the phase diagram of a ferroelectric thin film with arbitrary layer number as well as exchange interactions and transverse fields is derived, and then the effects of exchange interactions and transverse fields on phase diagrams are discussed for an arbitrary layer number N. Meanwhile, the crossover features, from the ferroelectric-dominant phase diagram (FPD) to the paraelectric-dominant phase diagram (PPD), for various parameters of an N-layer ferroelectric thin film with two surface layers are investigated. As a result, an N-independent common intersection point equation is obtained, and the three-dimensional curved surfaces for the crossover values are constructed. In comparison with the usual mean-field approximation, the differential operator technique with correlations reduces to some extent the ferroelectric features of a ferroelectric thin film.

Triply responsive films in bioelectrocatalysis with a binary architecture: combined layer-by-layer assembly and hydrogel polymerization.

Science.gov (United States)

Yao, Huiqin; Hu, Naifei

2011-05-26

In this work, triply responsive films with a specific binary architecture combining layer-by-layer assembly (LbL) and hydrogel polymerization were successfully prepared. First, concanavalin A (Con A) and dextran (Dex) were assembled into {Con A/Dex}(5) LbL layers on electrode surface by the lectin-sugar biospecific interaction between them. The poly(N,N-diethylacrylamide) (PDEA) hydrogels with entrapped horseradish peroxidase (HRP) were then synthesized by polymerization on the surface of LbL inner layers, forming {Con A/Dex}(5)-(PDEA-HRP) films. The films demonstrated reversible pH-, thermo-, and salt-responsive on-off behavior toward electroactive probe Fe(CN)(6)(3-) in its cyclic voltammetric responses. This multiple stimuli-responsive films could be further used to realize triply switchable electrochemical reduction of H(2)O(2) catalyzed by HRP immobilized in the films and mediated by Fe(CN)(6)(3-) in solution. The responsive mechanism of the films was explored and discussed. The pH-sensitive property of the system was attributed to the electrostatic interaction between the {Con A/Dex}(5) inner layers and the probe at different pH, and the thermo- and salt-responsive behaviors should be ascribed to the structure change of PDEA hydrogels for the PDEA-HRP outermost layers under different conditions. The concept of binary architecture was also used to fabricate {Con A/Dex}(5)-(PDEA-GOD) films on electrodes, where GOD = glucose oxidase, which was applied to realize the triply switchable bioelectrocatalysis of glucose by GOD in the films with ferrocenedicarboxylic acid as the mediator in solution. This film system with the unique binary architecture may establish a foundation for fabricating a novel type of multicontrollable biosensors based on bioelectrocatalysis with immobilized enzymes.

Discriminating plants using the DNA barcode rbcLb: an appraisal based on a large data set.

Science.gov (United States)

Dong, Wenpan; Cheng, Tao; Li, Changhao; Xu, Chao; Long, Ping; Chen, Chumming; Zhou, Shiliang

2014-03-01

The ideal DNA barcode for plants remains to be discovered, and the candidate barcode rbcL has been met with considerable skepticism since its proposal. In fact, the variability within this gene has never been fully explored across all plant groups from algae to flowering plants, and its performance as a barcode has not been adequately tested. By analysing all of the rbcL sequences currently available in GenBank, we attempted to determine how well a region of rbcL performs as a barcode in species discrimination. We found that the rbcLb region was more variable than the frequently used rbcLa region. Both universal and plant group-specific primers were designed to amplify rbcLb, and the performance of rbcLa and rbcLb was tested in several ways. Using blast, both regions successfully identified all families and nearly all genera; however, the successful species identification rates varied significantly among plant groups, ranging from 24.58% to 85.50% for rbcLa and from 36.67% to 90.89% for rbcLb. Successful species discrimination ranged from 5.19% to 96.33% for rbcLa and from 22.09% to 98.43% for rbcLb in species-rich families, and from 0 to 88.73% for rbcLa and from 2.04% to 100% for rbcLb in species-rich genera. Both regions performed better for lower plants than for higher plants, although rbcLb performed significantly better than rbcLa overall, particularly for angiosperms. Considering the applicability across plants, easy and unambiguous alignment, high primer universality, high sequence quality and high species discrimination power for lower plants, we suggest rbcLb as a universal plant barcode. © 2013 John Wiley & Sons Ltd.

Polymer/surfactant assisted self-assembly of nanoparticles into Langmuir–Blodgett films

International Nuclear Information System (INIS)

Alejo, T.; Merchán, M.D.; Velázquez, M.M.; Pérez-Hernández, J.A.

2013-01-01

We studied the ability of poly(octadecene-co-maleic anhydride) (PMAO) and a Gemini surfactant [C 18 H 37 (CH 3 ) 2 N + Br − –(CH 2 ) 2 –N + Br − (CH 3 ) 2 C 18 H 37 ] (18-2-18) to assist in the self-assembly process of CdSe quantum dots (QDs) at the air–water interface. Results show that, while QD agglomeration is generally inhibited by the addition of these components to the Langmuir monolayer of QDs, structure of the film transferred onto mica by the Langmuir–Blodgett method is strongly affected by the dewetting process. Nucleation-and-growth of holes and spinodal-like dewetting were respectively observed in the presence of either PMAO or 18-2-18. When PMAO/18-2-18 mixtures were used, both mechanisms were allowed; nevertheless, even in films prepared with mixtures of low polymer contents, characteristic morphology from the polymer dewetting route prevailed. Highlights: ► Effect of the composition on the LB films of QDs/polymer. ► Effect of the composition on the LB films of QDs/Gemini surfactant. ► Dewetting mechanisms

What do cranial bones of LB1 tell us about Homo floresiensis?

Science.gov (United States)

Balzeau, Antoine; Charlier, Philippe

2016-04-01

Cranial vault thickness (CVT) of Liang Bua 1, the specimen that is proposed to be the holotype of Homo floresiensis, has not yet been described in detail and compared with samples of fossil hominins, anatomically modern humans or microcephalic skulls. In addition, a complete description from a forensic and pathological point of view has not yet been carried out. It is important to evaluate scientifically if features related to CVT bring new information concerning the possible pathological status of LB1, and if it helps to recognize affinities with any hominin species and particularly if the specimen could belong to the species Homo sapiens. Medical examination of the skull based on a micro-CT examination clearly brings to light the presence of a sincipital T (a non-metrical variant of normal anatomy), a scar from an old frontal trauma without any evident functional consequence, and a severe bilateral hyperostosis frontalis interna that may have modified the anterior morphology of the endocranium of LB1. We also show that LB1 displays characteristics, related to the distribution of bone thickness and arrangements of cranial structures, that are plesiomorphic traits for hominins, at least for Homo erectus s.l. relative to Homo neanderthalensis and H. sapiens. All the microcephalic skulls analyzed here share the derived condition of anatomically modern H. sapiens. Cranial vault thickness does not help to clarify the definition of the species H. floresiensis but it also does not support an attribution of LB1 to H. sapiens. We conclude that there is no support for the attribution of LB1 to H. sapiens as there is no evidence of systemic pathology and because it does not have any of the apomorphic traits of our species. Copyright © 2016 Elsevier Ltd. All rights reserved.

Evolutionary model of the subdwarf binary system LB3459

International Nuclear Information System (INIS)

Paczynski, B.; Dearborn, D.S.

1980-01-01

An evolutionary model is proposed for the eclipsing binary system LB 3459 (=CPD-60 0 389 = HDE 269696). The two stars are hot subdwarfs with degenerate helium cores, hydrogen burning shell sources and low mass hydrogen rich envelopes. The system probably evolved through two common envelope phases. After the first such phase it might look like the semi-detached binary AS Eri. Soon after the second common envelope phase the system might look like UU Sge, an eclipsing binary nucleus of a planetary nebula. The present mass of the optical (spectroscopic) primary is probably close to 0.24 solar mass, and the predicted radial velocity amplitude of the primary is about 150 km/s. The optical secondary should be hotter and bolometrically brighter, with a mass of 0.32 solar mass. The primary eclipse is an occultation. (author)

Three dimensional analysis of self-structuring organic thin films using time-of-flight secondary ion mass spectrometry

Energy Technology Data Exchange (ETDEWEB)

Mayerhofer, Karl E.; Heier, Jakob; Maniglio, Ylenia; Keller, Beat Andreas, E-mail: beat.keller@empa.ch

2011-07-01

Selective sub-micrometer structuring of phase-separating organic semiconductor materials has recently got into focus for providing the opportunity of further improvements in optoelectronic device applications. Here we present a 3D-time-of-flight secondary ion mass spectrometry (3D-TOF-SIMS) depth profiling investigation on spin-coated blends consisting of [6,6]-phenyl-C{sub 61}-butyric acid methyl ester (PCBM) and a cationic cyanine dye (1,1'-diethyl-3,3,3',3'-tetramethylcarbocyanine iodide). TOF-SIMS provides the required lateral and depth resolution to resolve material and molecular inhomogeneities and phase separation in the blend. The data are illustrating the three-dimensional arrangement of the substances involved and confirm results of earlier studies using atomic force microscopy, UV-vis spectroscopy and x-ray photoelectron spectroscopy, and which have shown well distinguishable morphological features. The formation of this domain structure has been found to be dependent on the absolute as well as the individual film thickness, in accordance with models based on thin liquid two-layer films. Honey-comb like primary structures with micrometer dimension were found in samples containing small amounts of dye molecules in the deposition solution. In this case a thin dye deposit on PCBM was detected, which is well separated from the dye layer at the substrate. For this type of sample, we discuss an extended model of film formation based on partial depletion of dye molecules during film solidification, resulting in two individual dye layers.

Two- and three-dimensional CT analysis of ankle fractures

International Nuclear Information System (INIS)

Magid, D.; Fishman, E.K.; Ney, D.R.; Kuhlman, J.E.

1988-01-01

CT with coronal and sagittal reformatting (two-dimensional CT) and animated volumetric image rendering (three-dimensional CT) was used to assess ankle fractures. Partial volume limits transaxial CT in assessments of horizontally oriented structures. Two-dimensional CT, being orthogonal to the plafond, superior mortise, talar dome, and tibial epiphysis, often provides the most clinically useful images. Two-dimensional CT is most useful in characterizing potentially confusing fractures, such as Tillaux (anterior tubercle), triplane, osteochondral talar dome, or nondisplaced talar neck fractures, and it is the best study to confirm intraarticular fragments. Two-and three-dimensional CT best indicate the percentage of articular surface involvement and best demonstrate postoperative results or complications (hardware migration, residual step-off, delayed union, DJD, AVN, etc). Animated three-dimensional images are the preferred means of integrating the two-dimensional findings for surgical planning, as these images more closely simulate the clinical problem

On two-dimensionalization of three-dimensional turbulence in shell models

DEFF Research Database (Denmark)

Chakraborty, Sagar; Jensen, Mogens Høgh; Sarkar, A.

2010-01-01

Applying a modified version of the Gledzer-Ohkitani-Yamada (GOY) shell model, the signatures of so-called two-dimensionalization effect of three-dimensional incompressible, homogeneous, isotropic fully developed unforced turbulence have been studied and reproduced. Within the framework of shell m......-similar PDFs for longitudinal velocity differences are also presented for the rotating 3D turbulence case....

Two-dimensional turbulent convection

Science.gov (United States)

Mazzino, Andrea

2017-11-01

We present an overview of the most relevant, and sometimes contrasting, theoretical approaches to Rayleigh-Taylor and mean-gradient-forced Rayleigh-Bénard two-dimensional turbulence together with numerical and experimental evidences for their support. The main aim of this overview is to emphasize that, despite the different character of these two systems, especially in relation to their steadiness/unsteadiness, turbulent fluctuations are well described by the same scaling relationships originated from the Bolgiano balance. The latter states that inertial terms and buoyancy terms balance at small scales giving rise to an inverse kinetic energy cascade. The main difference with respect to the inverse energy cascade in hydrodynamic turbulence [R. H. Kraichnan, "Inertial ranges in two-dimensional turbulence," Phys. Fluids 10, 1417 (1967)] is that the rate of cascade of kinetic energy here is not constant along the inertial range of scales. Thanks to the absence of physical boundaries, the two systems here investigated turned out to be a natural physical realization of the Kraichnan scaling regime hitherto associated with the elusive "ultimate state of thermal convection" [R. H. Kraichnan, "Turbulent thermal convection at arbitrary Prandtl number," Phys. Fluids 5, 1374-1389 (1962)].

Quasi-one-dimensional electron transport over the surface of a liquid-helium film

International Nuclear Information System (INIS)

Sokolov, Sviatoslav; Studart, Nelson

2003-01-01

Quasi-one-dimensional mobility of surface electrons over a liquid-helium suspended film is studied for a conducting channel. The electron mobility is calculated taking into account the electron scattering by helium atoms in the vapor phase, ripplons, and surface defects of the film substrate both in one-electron regime and in the so-called complete-control limit where the influence of inter-electron collisions on the electron distribution function is taken into account. It is shown that the mobility for low temperatures is dominated by the surface-defect scattering and its temperature dependence is essentially different from that of the electron-ripplon scattering

Multi-perspective views of students’ difficulties with one-dimensional vector and two-dimensional vector

Science.gov (United States)

Fauzi, Ahmad; Ratna Kawuri, Kunthi; Pratiwi, Retno

2017-01-01

Researchers of students’ conceptual change usually collects data from written tests and interviews. Moreover, reports of conceptual change often simply refer to changes in concepts, such as on a test, without any identification of the learning processes that have taken place. Research has shown that students have difficulties with vectors in university introductory physics courses and high school physics courses. In this study, we intended to explore students’ understanding of one-dimensional and two-dimensional vector in multi perspective views. In this research, we explore students’ understanding through test perspective and interviews perspective. Our research study adopted the mixed-methodology design. The participants of this research were sixty students of third semester of physics education department. The data of this research were collected by testand interviews. In this study, we divided the students’ understanding of one-dimensional vector and two-dimensional vector in two categories, namely vector skills of the addition of one-dimensionaland two-dimensional vector and the relation between vector skills and conceptual understanding. From the investigation, only 44% of students provided correct answer for vector skills of the addition of one-dimensional and two-dimensional vector and only 27% students provided correct answer for the relation between vector skills and conceptual understanding.

Optimizing separations in online comprehensive two-dimensional liquid chromatography.

Science.gov (United States)

Pirok, Bob W J; Gargano, Andrea F G; Schoenmakers, Peter J

2018-01-01

Online comprehensive two-dimensional liquid chromatography has become an attractive option for the analysis of complex nonvolatile samples found in various fields (e.g. environmental studies, food, life, and polymer sciences). Two-dimensional liquid chromatography complements the highly popular hyphenated systems that combine liquid chromatography with mass spectrometry. Two-dimensional liquid chromatography is also applied to the analysis of samples that are not compatible with mass spectrometry (e.g. high-molecular-weight polymers), providing important information on the distribution of the sample components along chemical dimensions (molecular weight, charge, lipophilicity, stereochemistry, etc.). Also, in comparison with conventional one-dimensional liquid chromatography, two-dimensional liquid chromatography provides a greater separation power (peak capacity). Because of the additional selectivity and higher peak capacity, the combination of two-dimensional liquid chromatography with mass spectrometry allows for simpler mixtures of compounds to be introduced in the ion source at any given time, improving quantitative analysis by reducing matrix effects. In this review, we summarize the rationale and principles of two-dimensional liquid chromatography experiments, describe advantages and disadvantages of combining different selectivities and discuss strategies to improve the quality of two-dimensional liquid chromatography separations. © 2017 The Authors. Journal of Separation Science published by WILEY-VCH Verlag GmbH & Co. KGaA.

Two-dimensional liquid chromatography

DEFF Research Database (Denmark)

Græsbøll, Rune

-dimensional separation space. Optimization of gradients in online RP×RP is more difficult than in normal HPLC as a result of the increased number of parameters and their influence on each other. Modeling the coverage of the compounds across the two-dimensional chromatogram as a result of a change in gradients could...... be used for optimization purposes, and reduce the time spend on optimization. In this thesis (chapter 6), and manuscript B, a measure of the coverage of the compounds in the twodimensional separation space is defined. It is then shown that this measure can be modeled for changes in the gradient in both...

The response of quartz crystals coated with thin fatty acid film to organic gases

CERN Document Server

Jin, C N; Kim, K H; Kwon, Y S

1999-01-01

We tried to apply a quartz crystal as a sensor by using the resonant frequency and the resistance properties of quartz crystals. Four kinds of fatty acids that have the same head groups were coated on the surfaces of the quartz crystals, and the shift of the resonant frequency and the resistance were observed based on the lengths of the tail groups. Myristic acid (C sub 1 sub 4), palmitic acid (C sub 1 sub 6), stearic acid (C sub 1 sub 8), and arachidic acid (C sub 2 sub 0) were deposited on the surfaces of quartz crystals by using the Langmuir-Blodgett (LB) method. As a result, the resonant frequency change was more sensitive to high molecular-weight fatty acids than to low molecular-weight ones. We also observed the effect of temperature on stearic acid LB films, and the response properties of quartz crystals coated with stearic-acid LB films to organic gases were investigated. As a result, the sensitivity of quartz crystals to organic gases was higher for higher molecular-weight gas, and we found that quar...

Elasticity, biodegradability and cell adhesive properties of chitosan/hyaluronan multilayer films

Energy Technology Data Exchange (ETDEWEB)

Schneider, Aurore; Richert, Ludovic; Francius, Gregory; Voegel, Jean-Claude; Picart, Catherine [Present address: Universite de Montpellier II, CNRS-UMR 5539, cc107, Place Eugene Bataillon, 34 095 Montpellier Cedex 5 (France)

2007-03-01

In the bioengineering field, a recent and promising approach to modifying biomaterial surfaces is the layer-by-layer (LbL) technique used to build thin polyelectrolyte multilayer films. In this work, we focused on polyelectrolyte multilayer films made of two polysaccharides, chitosan (CHI) and hyaluronan (HA), and on the control of their physico-chemical and cell adhesive properties by chemical cross-linking. CHI/HA films were cross-linked using a water soluble carbodiimide and observed by confocal laser scanning microscopy (CLSM) with a fluorescently labeled CHI. Film thicknesses were similar for native and cross-linked films. The film nanometer roughness was measured by atomic force microscopy and was found to be higher for cross-linked films. Cross-linking the films also leads to a drastic change in film stiffness. The elastic modulus of the films (Young's modulus) as measured by AFM nano-indentation was about tenfold increased for cross-linked films as compared to native ones. From a biological point of view, cross-liked films are more resistant to enzymatic degradation by hyaluronidase. Furthermore, the increase in film stiffness has a favorable effect on the adhesion and spreading of chondrosarcoma cells. Thus, the CHI/HA cross-linked films could be used for various applications due to their adhesive properties and to their mechanical properties (including stability in enzymatic media)

Two-dimensional simulation of sintering process

International Nuclear Information System (INIS)

Vasconcelos, Vanderley de; Pinto, Lucio Carlos Martins; Vasconcelos, Wander L.

1996-01-01

The results of two-dimensional simulations are directly applied to systems in which one of the dimensions is much smaller than the others, and to sections of three dimensional models. Moreover, these simulations are the first step of the analysis of more complex three-dimensional systems. In this work, two basic features of the sintering process are studied: the types of particle size distributions related to the powder production processes and the evolution of geometric parameters of the resultant microstructures during the solid-state sintering. Random packing of equal spheres is considered in the sintering simulation. The packing algorithm does not take into account the interactive forces between the particles. The used sintering algorithm causes the densification of the particle set. (author)

PVA-based nanographene film by electrospinning

Directory of Open Access Journals (Sweden)

Pang Jing

2013-01-01

Full Text Available Two-dimensional polyvinyl alcohol based graphene films with the thickness of less than 20 nm were fabricated directly by using polyvinyl alcohol/graphite solution or polyvinyl alcohol/ash solution by electrospinning. It was found that ash particles are good candidate for substitution of graphite particles to fabricate nanographene films. The relationship between the thickness and width of the film is elucidated, and the periodic morphology of the film is explained.

Imprinting of metal receptors into multilayer polyelectrolyte films: fabrication and applications in marine antifouling

OpenAIRE

Puniredd, S.R.; Janczewski, D.; Go, D.P.; Zhu, X.; Guo, S.; Teo, S.L-M.; Lee, S.S.C.; Vancso, Gyula J.

2015-01-01

Polymeric films constructed using the layer-by-layer (LbL) fabrication process were employed as a platform for metal ion immobilization and applied as a marine antifouling coating. The novel Cu2+ ion imprinting process described is based on the use of metal ion templates and LbL multilayer covalent cross-linking. Custom synthesized, peptide mimicking polycations composed of histidine grafted poly(allylamine) (PAH) to bind metal ions, and methyl ester containing polyanions for convenient cross...

Chaotic dynamics in two-dimensional noninvertible maps

CERN Document Server

Mira, Christian; Cathala, Jean-Claude; Gardini, Laura

1996-01-01

This book is essentially devoted to complex properties (Phase plane structure and bifurcations) of two-dimensional noninvertible maps, i.e. maps having either a non-unique inverse, or no real inverse, according to the plane point. They constitute models of sets of discrete dynamical systems encountered in Engineering (Control, Signal Processing, Electronics), Physics, Economics, Life Sciences. Compared to the studies made in the one-dimensional case, the two-dimensional situation remained a long time in an underdeveloped state. It is only since these last years that the interest for this resea

Determination of degree of ionization of poly(allylamine hydrochloride) (PAH) and poly[1-[4-(3-carboxy-4 hydroxyphenylazo)benzene sulfonamido]-1,2-ethanediyl, sodium salt] (PAZO) in layer-by-layer films using vacuum photoabsorption spectroscopy.

Science.gov (United States)

Ferreira, Q; Gomes, P J; Ribeiro, P A; Jones, N C; Hoffmann, S V; Mason, N J; Oliveira, O N; Raposo, M

2013-01-08

Electrostatic and hydrophobic interactions govern most of the properties of supramolecular systems, which is the reason determining the degree of ionization of macromolecules has become crucial for many applications. In this paper, we show that high-resolution ultraviolet spectroscopy (VUV) can be used to determine the degree of ionization and its effect on the electronic excitation energies of layer-by-layer (LbL) films of poly(allylamine hydrochloride) (PAH) and poly[1-[4-(3-carboxy-4 hydroxyphenylazo)benzene sulfonamido]-1,2-ethanediyl, sodium salt] (PAZO). A full assignment of the VUV peaks of these polyelectrolytes in solution and in cast or LbL films could be made, with their pH dependence allowing us to determine the pK(a) using the Henderson-Hasselbach equation. The pK(a) for PAZO increased from ca. 6 in solution to ca. 7.3 in LbL films owing to the charge transfer from PAH. Significantly, even using solutions at a fixed pH for PAH, the amount adsorbed on the LbL films still varied with the pH of the PAZO solutions due to these molecular-level interactions. Therefore, the procedure based on a comparison of VUV spectra from solutions and films obtained under distinct conditions is useful to determine the degree of dissociation of macromolecules, in addition to permitting interrogation of interface effects in multilayer films.

Application of a method for comparing one-dimensional and two-dimensional models of a ground-water flow system

International Nuclear Information System (INIS)

Naymik, T.G.

1978-01-01

To evaluate the inability of a one-dimensional ground-water model to interact continuously with surrounding hydraulic head gradients, simulations using one-dimensional and two-dimensional ground-water flow models were compared. This approach used two types of models: flow-conserving one-and-two dimensional models, and one-dimensional and two-dimensional models designed to yield two-dimensional solutions. The hydraulic conductivities of controlling features were varied and model comparison was based on the travel times of marker particles. The solutions within each of the two model types compare reasonably well, but a three-dimensional solution is required to quantify the comparison

Three dimensional strained semiconductors

Science.gov (United States)

Voss, Lars; Conway, Adam; Nikolic, Rebecca J.; Leao, Cedric Rocha; Shao, Qinghui

2016-11-08

In one embodiment, an apparatus includes a three dimensional structure comprising a semiconductor material, and at least one thin film in contact with at least one exterior surface of the three dimensional structure for inducing a strain in the structure, the thin film being characterized as providing at least one of: an induced strain of at least 0.05%, and an induced strain in at least 5% of a volume of the three dimensional structure. In another embodiment, a method includes forming a three dimensional structure comprising a semiconductor material, and depositing at least one thin film on at least one surface of the three dimensional structure for inducing a strain in the structure, the thin film being characterized as providing at least one of: an induced strain of at least 0.05%, and an induced strain in at least 5% of a volume of the structure.

Supramolecular architectures in layer-by-layer films of single-walled carbon nanotubes, chitosan and cobalt (II) phthalocyanine

International Nuclear Information System (INIS)

Sousa Luz, Roberto A. de; Martins, Marccus Victor A.; Magalhaes, Janildo L.; Siqueira, Jose R.; Zucolotto, Valtencir; Oliveira, Osvaldo N.; Crespilho, Frank N.; Cantanhede da Silva, Welter

2011-01-01

Highlights: → Platforms were assembled from cobalt phthalocyanine, chitosan and carbon nanotubes. → Supramolecular organization of multilayer films was investigated. → Increase of the supramolecular charge transfer after carbon nanotube incorporation. → Functional modulation based on constitutional dynamic chemistry was achieved. - Abstract: The building of supramolecular structures in nanostructured films has been exploited for a number of applications, with the film properties being controlled at the molecular level. In this study, we report on the layer-by-layer (LbL) films combining cobalt (II) tetrasulfonated phthalocyanine (CoTsPc), chitosan (Chit) and single-walled carbon nanotubes (SWCNTs) in two architectures, {Chit/CoTsPc} n and {Chit-SWCNTs/CoTsPc} n (n = 1-10). The physicochemical properties of the films were evaluated and the multilayer formation was monitored with microgravimetry measurements using a quartz microbalance crystal and an electrochemical technique. According to atomic force microscopy (AFM) results, the incorporation of SWCNTs caused the films to be thicker, with a thickness ca. 3 fold that of a 2-bilayer LbL film with no SWCNTs. Cyclic voltammetry revealed a quasi-reversible, one electron process with E 1/2 at -0.65 V (vs SCE) and an irreversible oxidation process at 0.80 V in a physiological medium for both systems, which can be attributed to [CoTsPc(I)] 5- /[CoTsPc(II)] 4- and CoTsPc(II) to CoTsPc(III), respectively. The {Chit-SWCNTs/CoTsPc} 5 multilayer film exhibited an increased faradaic current, probably associated with the supramolecular charge transfer interaction between cobalt phthalocyanine and SWCNTs. The results demonstrate that an intimate contact at the supramolecular level between functional SWCNTs immobilized into biocompatible chitosan polymer and CoTsPc improves the electron flow from CoTsPc redox sites to the electrode surface.

Two-dimensional analytic weighting functions for limb scattering

Science.gov (United States)

Zawada, D. J.; Bourassa, A. E.; Degenstein, D. A.

2017-10-01

Through the inversion of limb scatter measurements it is possible to obtain vertical profiles of trace species in the atmosphere. Many of these inversion methods require what is often referred to as weighting functions, or derivatives of the radiance with respect to concentrations of trace species in the atmosphere. Several radiative transfer models have implemented analytic methods to calculate weighting functions, alleviating the computational burden of traditional numerical perturbation methods. Here we describe the implementation of analytic two-dimensional weighting functions, where derivatives are calculated relative to atmospheric constituents in a two-dimensional grid of altitude and angle along the line of sight direction, in the SASKTRAN-HR radiative transfer model. Two-dimensional weighting functions are required for two-dimensional inversions of limb scatter measurements. Examples are presented where the analytic two-dimensional weighting functions are calculated with an underlying one-dimensional atmosphere. It is shown that the analytic weighting functions are more accurate than ones calculated with a single scatter approximation, and are orders of magnitude faster than a typical perturbation method. Evidence is presented that weighting functions for stratospheric aerosols calculated under a single scatter approximation may not be suitable for use in retrieval algorithms under solar backscatter conditions.

Diffraction of a plane wave on two-dimensional conductive structures and a surface wave

Science.gov (United States)

Davidovich, Mikhael V.

2018-04-01

We consider the structures type of two-dimensional electron gas in the form of a thin conductive, in particular, graphene films described by tensor conductivity, which are isolated or located on the dielectric layers. The dispersion equation for hybrid modes, as well as scattering parameters. We show that free wave (eigenwaves) problem follow from the problem of diffraction when linking the amplitude of the current of the linear equations are unsolvable, i.e., the determinant of this system is zero. As a particular case the dispersion equation follow from the conditions of matching (with zero reflection coefficient).

Langmuir-Blodgett films of polyaniline for low density lipoprotein detection

Energy Technology Data Exchange (ETDEWEB)

Matharu, Zimple [Department of Science and Technology Centre on Biomolecular Electronics, Biomedical Instrumentation Section, National Physical Laboratory (CSIR), Dr. K. S. Krishnan Marg, New Delhi-110012 (India); Department of Physics and Astrophysics, University of Delhi, Delhi-110007 (India); Sumana, G. [Department of Science and Technology Centre on Biomolecular Electronics, Biomedical Instrumentation Section, National Physical Laboratory (CSIR), Dr. K. S. Krishnan Marg, New Delhi-110012 (India); Gupta, Vinay [Department of Physics and Astrophysics, University of Delhi, Delhi-110007 (India); Malhotra, B.D., E-mail: bansi.malhotra@gmail.co [Department of Science and Technology Centre on Biomolecular Electronics, Biomedical Instrumentation Section, National Physical Laboratory (CSIR), Dr. K. S. Krishnan Marg, New Delhi-110012 (India)

2010-11-30

Langmuir-Blodgett (LB) films of polyaniline (PANI) were utilized for the fabrication of impedimetric immunosensor for detection of human plasma low density lipoprotein (LDL) by immobilizing anti-apolipoprotein B (AAB) via EDC-NHS coupling. The modified electrodes were characterized by electrochemical impedance spectroscopy (EIS) and scanning electron microscopy. AAB/PANI-SA LB immunoelectrodes studied by EIS spectroscopy revealed detection of LDL in the wide range of 0.018 {mu}M (6 mg/dl) to 0.39 {mu}M (130 mg/dl), covering the physiological range in blood, with a sensitivity of 11.25 k{Omega} {mu}M{sup -1}.

Langmuir-Blodgett films of polyaniline for low density lipoprotein detection

International Nuclear Information System (INIS)

Matharu, Zimple; Sumana, G.; Gupta, Vinay; Malhotra, B.D.

2010-01-01

Langmuir-Blodgett (LB) films of polyaniline (PANI) were utilized for the fabrication of impedimetric immunosensor for detection of human plasma low density lipoprotein (LDL) by immobilizing anti-apolipoprotein B (AAB) via EDC-NHS coupling. The modified electrodes were characterized by electrochemical impedance spectroscopy (EIS) and scanning electron microscopy. AAB/PANI-SA LB immunoelectrodes studied by EIS spectroscopy revealed detection of LDL in the wide range of 0.018 μM (6 mg/dl) to 0.39 μM (130 mg/dl), covering the physiological range in blood, with a sensitivity of 11.25 kΩ μM -1 .

Right ventricular volume determination by two-dimensional echocardiography and radiography in model hearts using a subtraction method

International Nuclear Information System (INIS)

Krebs, W.; Erbel, R.; Schweizer, P.; Richter, H.A.; Massberg, I.; Meyer, J.; Effert, S.; Henn, G.

1982-01-01

The irregularity and complexity of the right ventricle is the reason why no accurate method for right ventricular volume determination exists. A new method for right ventricular volume determination particularly for two-dimensional echocardiography was developed - it is called subtraction method - and was compared with the pyramid and Simpson's methods. The partial volume of the left ventricle and septum was subtracted from total volume of right and left ventricle including interventricular septum. Thus right ventricular volume resulted. Total and partial volume were computer-assisted calculated by use of biplane methods, preferably Simpson's rule. The method was proved with thinwall silicon-rubber model hearts of the left and right ventricle. Two orthogonal planes in the long-axis were filmed by radiography or scanned in a water bath by two-dimensional echocardiography equivalent to RAO and LAO-projections of cineangiocardiograms or to four- and two-chamber views of apical two-dimensional echocardiograms. For calculation of the major axes of the elliptical sections, summed up by Simpson's rule, they were derived from the LAO-projection and the four-chamber view, respectively, the minor axis approximated from the RAO-projection and the two-chamber view. For comparison of direct-measured volume and two-dimensional echocardiographically determined volume, regression equation was given by y = 1.01 x - 3.2, correlation-coefficient, r = 0.977, and standard error of estimate (SEE) +-10.5 ml. For radiography, regression equation was y = 0.909 x + 13.3, r = 0.983, SEE = +-8.0 ml. For pyramid method and Simpson's rule, higher standard errors and lower correlation coefficients were found. Between radiography and two-dimensional echocardiography a mean difference of 4.3 +- 13.2 ml, using subtraction method, and -10.2 +- 22.9 ml, using pyramid method, as well as -0.6 +- 18.5 ml, using Simpson's rule, were calculated for right ventricular volume measurements. (orig./APR) [de

Depth-enhanced three-dimensional-two-dimensional convertible display based on modified integral imaging.

Science.gov (United States)

Park, Jae-Hyeung; Kim, Hak-Rin; Kim, Yunhee; Kim, Joohwan; Hong, Jisoo; Lee, Sin-Doo; Lee, Byoungho

2004-12-01

A depth-enhanced three-dimensional-two-dimensional convertible display that uses a polymer-dispersed liquid crystal based on the principle of integral imaging is proposed. In the proposed method, a lens array is located behind a transmission-type display panel to form an array of point-light sources, and a polymer-dispersed liquid crystal is electrically controlled to pass or to scatter light coming from these point-light sources. Therefore, three-dimensional-two-dimensional conversion is accomplished electrically without any mechanical movement. Moreover, the nonimaging structure of the proposed method increases the expressible depth range considerably. We explain the method of operation and present experimental results.

Reducing Water Vapor Permeability of Poly(lactic acid Film and Bottle through Layer-by-Layer Deposition of Green-Processed Cellulose Nanocrystals and Chitosan

Directory of Open Access Journals (Sweden)

Katalin Halász

2015-01-01

Full Text Available Layer-by-layer electrostatic self-assembly technique was applied to improve the barrier properties of poly(lactic acid (PLA films and bottles. The LbL process was carried out by the alternate adsorption of chitosan (CH (polycation and cellulose nanocrystals (CNC produced via ultrasonic treatment. Four bilayers (on each side of chitosan and cellulose nanocrystals caused 29 and 26% improvement in barrier properties in case of films and bottles, respectively. According to the results the LbL process with CH and CNC offered a transparent “green” barrier coating on PLA substrates.

Characterization of nonlinear effects in a two-dimensional dielectric elastomer actuator

International Nuclear Information System (INIS)

Jhong, Y; Mikolas, D; Fu, C; Yeh, T; Fang, W; Shaw, D; Chen, J

2010-01-01

Dielectric elastomer actuators (DEAs) possess great potential for the realization of lightweight and inexpensive multiple-degrees-of-freedom (multi-DOF) biomimetic robotics. In this study, a two-dimensional DEA was built and tested in order to characterize the issues associated with the use in multi-DOF actuation. The actuator is a single circular DEA film with four, electrically isolated quadrant electrode areas. The actuator was driven in a quasi-circular manner by applying sine and cosine signals to orthogonal pairs of electrodes, and the resultant motion was recorded using image processing techniques. The effects of nonlinear voltage–strain behavior, creep and stress relaxation on the motion were all pronounced and clearly differentiated. A simple six-parameter empirical model was used and showed excellent agreement with the measured data

Water-Induced Dimensionality Reduction in Metal-Halide Perovskites

KAUST Repository

Turedi, Bekir; Lee, Kwangjae; Dursun, Ibrahim; Alamer, Badriah Jaber; Wu, Zhennan; Alarousu, Erkki; Mohammed, Omar F.; Cho, Namchul; Bakr, Osman

2018-01-01

. Here we employ water to directly transform films of the three-dimensional (3D) perovskite CsPbBr3 to stable two-dimensional (2D) perovskite-related CsPb2Br5. A sequential dissolution-recrystallization process governs this water induced transformation

Building a road map for tailoring multilayer polyelectrolyte films

International Nuclear Information System (INIS)

Ankner, John Francis; Bardoel, Agatha A.; Sukishvili, Svetlana

2012-01-01

Researchers are moving a step closer to a definite road map for building layer-by-layer (LbL) assembled polyelectrolyte films, with the assistance of the Liquids Reflectometer at Oak Ridge National Laboratory's Spallation Neutron Source, in Oak Ridge, Tennessee. Scientists using the liquids reflectometer have successfully taken snapshots in close to real time of these multilayered structures for different applications when they modify the structure and function parameters. Polyelecrolytes are polymers that carry charge in aqueous solutions. They contain chemical groups that dissociate in water, making such polymers charged. Most polyelectrolytes are water soluble. They are important components in foods, soaps, shampoos, and cosmetics products. They show promise for such environmental work as oil recovery and water treatment. Polyelectrolytes are compelling because researchers can chemically modify how they interact with water for multiple applications. When two types of polyelectrolytes of opposite charge are assembled at a surface in a sequential way using the LbL assembly technique, 'the result is the forming of surface films, useful for coatings, biomedical implants and devices, controlling adhesion of biological molecules, and controlling delivery of therapeutic molecules from surfaces,' said Svetlana Sukhishvili of the Stevens Institute of Technology in New Jersey, the lead chemist on the collaboration. 'Medical doctors often prefer to deliver multiple therapeutic compounds from the coatings in a time-resolved manner,' Sukhishvili said. 'To assist them, material scientists need to learn how to build coatings in which polymer layering will not be compromised when exposed to normal physiological conditions.' 'Being able to control these properties, understanding how what you do to the materials affects their properties, this allows you to apply them to situations where interacting with an environment is very helpful, whether in a biological context or any other

Functional inks and printing of two-dimensional materials.

Science.gov (United States)

Hu, Guohua; Kang, Joohoon; Ng, Leonard W T; Zhu, Xiaoxi; Howe, Richard C T; Jones, Christopher G; Hersam, Mark C; Hasan, Tawfique

2018-05-08

Graphene and related two-dimensional materials provide an ideal platform for next generation disruptive technologies and applications. Exploiting these solution-processed two-dimensional materials in printing can accelerate this development by allowing additive patterning on both rigid and conformable substrates for flexible device design and large-scale, high-speed, cost-effective manufacturing. In this review, we summarise the current progress on ink formulation of two-dimensional materials and the printable applications enabled by them. We also present our perspectives on their research and technological future prospects.

K-FIX: a computer program for transient, two-dimensional, two-fluid flow. THREED: an extension of the K-FIX code for three-dimensional calculations

International Nuclear Information System (INIS)

Rivard, W.C.; Torrey, M.D.

1978-10-01

The transient, two-dimensional, two-fluid code K-FIX has been extended to perform three-dimensional calculations. This capability is achieved by adding five modification sets of FORTRAN statements to the basic two-dimensional code. The modifications are listed and described, and a complete listing of the three-dimensional code is provided. Results of an example problem are provided for verification

An introduction to ultrathin organic films from Langmuir-Blodgett to self-assembly

CERN Document Server

Ulman, Abraham

1991-01-01

The development of oriented organic monomolecular layers by the Langmuir-Blodgett (LB) and self-assembly (SA) techniques has led researchers toward their goal of assembling individual molecules into highly ordered architectures. Thus the continually growing contribution of LB and SA systems to the chemistry and physics of thin organic films is widely recognized. Equally well-known is the difficulty in keeping up to date with the burgeoning multidisciplinary research in this area. Dr. Ulman provides a massive survey of the available literature. The book begins with a section on analytical tools

Large-sized and highly radioactive 3H and 109Cd Langmuir-Blodgett films

International Nuclear Information System (INIS)

Shibata, S.; Kawakami, H.; Kato, S.

1994-02-01

A device for the deposition of a radioactive Langmuir-Blodgett (LB) film was developed with the use of: (1) a modified horizontal lifting method, (2) an extremely shallow trough, and (3) a surface pressure-generating system without piston oil. It made a precious radioactive subphase solution repeatedly usable while keeping its radioactivity concentration as high as possible. Any large-size thin films can be prepared by just changing the trough size. Two monomolecular-layers of Y-type films of cadmium [ 3 H] icosanoate and 109 Cd icosanoate were built up as 3 H and 109 Cd β-sources for electron spectroscopy with intensities of 1.5 GBq (40 mCi) and 7.4 MBq (200 μCi), respectively, and a size of 65x200 mm 2 . Excellent uniformity of the distribution of deposited radioactivity was confirmed by autoradiography and photometry. (author)

Cu-based metal-organic framework thin films: A morphological and photovoltaic study

Science.gov (United States)

Khajavian, Ruhollah; Ghani, Kamal

2018-06-01

This work explores the layer-by-layer (LbL) fabrication of [Cu2(bdc)2(bpy)]n thin films by using pyridine and acetic acid as capping agents onto mesoporous titania surface. While in the presence of acetic acid highly-ordered crystals with nanoplate morphology are formed, modulation with pyridine gives rise to formation of leaf-like crystals. In addition, processing sequence also matters when modulator is added. According to our results, modulators should be added to metal solution rather than linker/pillar during LbL assembly. These films were subsequently shown to generate photocurrent in a sandwich-type Grätzel solar cell device in response to simulated 1 sun illumination. The results also demonstrated that the device consisted of well-aligned nanoplates exhibits higher power conversion efficiency than the similar cell with disordered leaf-like crystals after iodine loading.

Development and characterization of multilayer films of polyaniline, titanium dioxide and CTAB for potential antimicrobial applications

International Nuclear Information System (INIS)

Farias, Emanuel Airton O.; Dionisio, Natália A.; Quelemes, Patrick V.; Leal, Sergio Henrique; Matos, José Milton E.; Filho, Edson C. Silva; Bechtold, Ivan H.; Leite, José Roberto S.A.; Eiras, Carla

2014-01-01

Composites prepared from polyaniline (PANI) and the ceramic technology of titanium dioxide (TiO 2 ) have been proposed, however, the interaction of these materials with greater control of molecular arrangement becomes attractive in order to achieve properties not previously described or yet the optimization of those already reported. Therefore, in this study, thin hybrid films made of polyaniline (PANI), a conductive polymer, and the technological ceramic, titanium dioxide (TiO 2 ), were prepared by the layer-by-layer (LbL) self-assembly technique. The films were characterized by cyclic voltammetry (CV), UV–VIS spectroscopy and atomic force microscopy (AFM). Aiming to improve the dispersion of the ceramic in the polymer matrix, the commercial surfactant, cetyl trimethylammonium bromide (CTAB), was used in the formation of the films. The best condition of deposition was found showing synergic interactions between the conjugated materials. The antibacterial activity of the PANI(TiO 2 )/CTAB films was studied and the obtained results suggest their use as antimicrobial coatings. - Highlights: • Nanocomposite films of PANI and TiO2 prepared by the LbL technique • Ceramic dispersion in PANI improved with CTAB for antimicrobial applications. • Optimized film deposition for synergic interactions of the conjugated materials • Antibacterial activity of the films suggests their use as antimicrobial coatings

Two-dimensional critical phenomena

International Nuclear Information System (INIS)

Saleur, H.

1987-09-01

Two dimensional critical systems are studied using transformation to free fields and conformal invariance methods. The relations between the two approaches are also studied. The analytical results obtained generally depend on universality hypotheses or on renormalization group trajectories which are not established rigorously, so numerical verifications, mainly using the transfer matrix approach, are presented. The exact determination of critical exponents; the partition functions of critical models on toruses; and results as the critical point is approached are discussed [fr

Monoamine oxidase B layer-by-layer film fabrication and characterization toward dopamine detection

International Nuclear Information System (INIS)

Miyazaki, Celina Massumi; Pereira, Tamyris Paschoal; Mascagni, Daniela Branco Tavares; Leite de Moraes, Marli; Ferreira, Marystela

2016-01-01

In this work nanostructured film composites of the monoamine oxidase B (MAO-B) enzyme, free or encapsulated in liposomes, were fabricated by the layer-by-layer (LbL) self-assembly technique, employing polyethylene imine (PEI) as polycation. Initially, the MAO-B enzyme was incorporated into liposomes in order to preserve its enzymatic structure ensuring their activity and catalytic stability. The LbL film growth was monitored by surface plasmon resonance (SPR) by gold resonance angle shift analysis after each bilayer deposition. Subsequently, the films were applied as amperometric biosensors for dopamine detection using Prussian Blue (PB) as the electron mediator. The biosensor fabricated by MAO-B incorporated into liposomes composed of DPPG:POPG in the ratio (1:4) (w/w) showed the best performance with a sensitivity of 0.86 (μA cm −2 )/(mmol L −1 ) and a detection limit of 0.33 mmol L −1 . - Highlights: • Monoamine oxidase B incorporation in liposomes was proposed to preserve the enzyme. • Layer-by-layer films composed of MAO-B (free and in liposomes) were fabricated. • Amperometric response using ITO/Prussian Blue covered with the MAO-B films was studied. • Sensitivity, limit of detection and apparent Michaelis–Menten constant were compared.

Monoamine oxidase B layer-by-layer film fabrication and characterization toward dopamine detection

Energy Technology Data Exchange (ETDEWEB)

Miyazaki, Celina Massumi; Pereira, Tamyris Paschoal [Universidade Federal de São Carlos, UFSCar, CCTS, Sorocaba, São Paulo (Brazil); Mascagni, Daniela Branco Tavares [Universidade Estadual de São Paulo — UNESP, Sorocaba, São Paulo (Brazil); Leite de Moraes, Marli [Universidade Federal de São Paulo, Unifesp, São José dos Campos, São Paulo (Brazil); Ferreira, Marystela, E-mail: marystela@ufscar.br [Universidade Federal de São Carlos, UFSCar, CCTS, Sorocaba, São Paulo (Brazil)

2016-01-01

In this work nanostructured film composites of the monoamine oxidase B (MAO-B) enzyme, free or encapsulated in liposomes, were fabricated by the layer-by-layer (LbL) self-assembly technique, employing polyethylene imine (PEI) as polycation. Initially, the MAO-B enzyme was incorporated into liposomes in order to preserve its enzymatic structure ensuring their activity and catalytic stability. The LbL film growth was monitored by surface plasmon resonance (SPR) by gold resonance angle shift analysis after each bilayer deposition. Subsequently, the films were applied as amperometric biosensors for dopamine detection using Prussian Blue (PB) as the electron mediator. The biosensor fabricated by MAO-B incorporated into liposomes composed of DPPG:POPG in the ratio (1:4) (w/w) showed the best performance with a sensitivity of 0.86 (μA cm{sup −2})/(mmol L{sup −1}) and a detection limit of 0.33 mmol L{sup −1}. - Highlights: • Monoamine oxidase B incorporation in liposomes was proposed to preserve the enzyme. • Layer-by-layer films composed of MAO-B (free and in liposomes) were fabricated. • Amperometric response using ITO/Prussian Blue covered with the MAO-B films was studied. • Sensitivity, limit of detection and apparent Michaelis–Menten constant were compared.

Characterization and obtainment of thin films based on N,N,N-trimethyl chitosan and heparin through the technical layer-by-layer

International Nuclear Information System (INIS)

Martins, Alessandro F.; Follmann, Heveline D.M.; Rubira, Adley F.; Muniz, Edvani C.

2011-01-01

Thin films of Heparin (HP) and N,N,N-trimethyl chitosan (TMC) with a high degree of quaternization (DQ) were obtained at pH 7.4 through the layer-by-layer (LbL) technique. Polystyrene (PS) was oxidized with aqueous solution of sodium persulfate and subsequently employed as substrate. The characterization of TMC and the respective determination of DQ were performed through 1 H NMR spectroscopy. The thin films de TMC/HP were characterized by FTIR-ATR and AFM. Both techniques confirmed the adsorption of TMC and HP in surface of the PS. The increasing of the bilayers provides a decrease of the projections and/or roughness, further of minimizing the depressions at the surface of the films. Studies of thin films the base of TMC/HP prepared from the LbL technique has not been reported in the literature. It is expected that the thin films of TMC/HP present anti-adhesive and antimicrobial properties. (author)

NiCo2O4 nanosheets in-situ grown on three dimensional porous Ni film current collectors as integrated electrodes for high-performance supercapacitors

Science.gov (United States)

Wang, Tao; Guo, Ying; Zhao, Bo; Yu, Shuhui; Yang, Hai-Peng; Lu, Daniel; Fu, Xian-Zhu; Sun, Rong; Wong, Ching-Ping

2015-07-01

Three dimensional interconnected hierarchical porous Ni films are easily fabricated as effective current collectors through hydrogen bubble template electrochemical deposition. The binder-free integrated electrodes of spinel NiCo2O4 nanosheets directly coated the three dimensional porous Ni films are facilely obtained through successively electrochemical co-deposition of Ni/Co alloy layer then followed by subsequent annealing at 350 °C in air. Compared with NiCo2O4 nanosheets on smooth Ni foil or porous NiO/Ni film electrodes, the porous NiCo2O4/Ni integrated film electrodes for supercapacitors demonstrate remarkably higher area specific capacitance. The porous NiCo2O4/Ni film electrodes also exhibit excellent rate capability and cycling stability. The super electrochemical capacitive performances are attributed to the unique integrated architecture of NiCo2O4 nanosheets in-situ grown on three dimensional continuous hierarchical porous Ni collector collectors, which could provide large electrode-electrolyte interface area, high active sites, low contact resistance between current collector and active materials, fast electron conduction and ion/electrolyte diffusion.

Two-dimensional inverse planning and delivery with a preclinical image guided microirradiator

International Nuclear Information System (INIS)

Stewart, James M. P.; Lindsay, Patricia E.; Jaffray, David A.

2013-01-01

Purpose: Recent advances in preclinical radiotherapy systems have provided the foundation for scaling many of the elements of clinical radiation therapy practice to the dimensions and energy demanded in small animal studies. Such systems support the technical capabilities to accurately deliver highly complex dose distributions, but methods to optimize and deliver such distributions remain in their infancy. This study developed an optimization method based on empirically measured two-dimensional dose kernel measurements to deliver arbitrary planar dose distributions on a recently developed small animal radiotherapy platform.Methods: A two-dimensional dose kernel was measured with repeated radiochromic film measurements for the circular 1 mm diameter fixed collimator of the small animal radiotherapy system at 1 cm depth in a solid water phantom. This kernel was utilized in a sequential quadratic programming optimization framework to determine optimal beam positions and weights to deliver an arbitrary desired dose distribution. The positions and weights were then translated to a set of stage motions to automatically deliver the optimized dose distribution. End-to-end efficacy of the framework was quantified through five repeated deliveries of two dosimetric challenges: (1) a 5 mm radius bullseye distribution, and (2) a “sock” distribution contained within a 9 × 13 mm bounding box incorporating rectangular, semicircular, and exponentially decaying geometric constructs and a rectangular linear dose gradient region. These two challenges were designed to gauge targeting, geometric, and dosimetric fidelity.Results: Optimization of the bullseye and sock distributions required 2.1 and 5.9 min and utilized 50 and 77 individual beams for delivery, respectively. Automated delivery of the resulting optimized distributions, validated using radiochromic film measurements, revealed an average targeting accuracy of 0.32 mm, and a dosimetric delivery error along four line

Carbon decorative coatings by dip-, spin-, and spray-assisted layer-by-layer assembly deposition.

Science.gov (United States)

Hong, Jinkee; Kang, Sang Wook

2011-09-01

We performed a comparative surface analysis of all-carbon nano-objects (multiwall carbon nanotubes (MWNT) or graphene oxide (GO) sheets) based multilayer coatings prepared using three widely used nanofilm fabrication methods: dip-, spin-, and spray-assisted layer-by-layer (LbL) deposition. The resultant films showed a marked difference in their growth mechanisms and surface morphologies. Various carbon decorative coatings were synthesized with different surface roughness values, despite identical preparation conditions. In particular, smooth to highly rough all-carbon surfaces, as determined by atomic force microscopy (AFM) and scanning electron microscopy (SEM), were readily obtained by manipulating the LbL deposition methods. As was confirmed by the AFM and SEM analyses, this finding indicated the fundamental morphological evolution of one-dimensional nano-objects (MWNT) and two-dimensional nano-objects (GO) by control of the surface roughness through the deposition method. Therefore, an analysis of the three LbL-assembly methods presented herein may offer useful information about the industrial use of carbon decorative coatings and provide an insight into ways to control the structures of multilayer coatings by tuning the morphologies of carbon nano-objects.

Polymer/surfactant assisted self-assembly of nanoparticles into Langmuir–Blodgett films

Energy Technology Data Exchange (ETDEWEB)

Alejo, T.; Merchán, M.D. [Departamento de Química Física, Facultad de Ciencias Químicas, Universidad de Salamanca, Plaza de los Caídos s/n, E-37008 Salamanca (Spain); Velázquez, M.M., E-mail: mvsal@usal.es [Departamento de Química Física, Facultad de Ciencias Químicas, Universidad de Salamanca, Plaza de los Caídos s/n, E-37008 Salamanca (Spain); Pérez-Hernández, J.A. [Centro de Láseres Pulsados Ultraintensos (CLPU), E-37008 Salamanca (Spain)

2013-02-15

We studied the ability of poly(octadecene-co-maleic anhydride) (PMAO) and a Gemini surfactant [C{sub 18}H{sub 37} (CH{sub 3}){sub 2}N{sup +}Br{sup −}–(CH{sub 2}){sub 2}–N{sup +}Br{sup −}(CH{sub 3}){sub 2} C{sub 18}H{sub 37}] (18-2-18) to assist in the self-assembly process of CdSe quantum dots (QDs) at the air–water interface. Results show that, while QD agglomeration is generally inhibited by the addition of these components to the Langmuir monolayer of QDs, structure of the film transferred onto mica by the Langmuir–Blodgett method is strongly affected by the dewetting process. Nucleation-and-growth of holes and spinodal-like dewetting were respectively observed in the presence of either PMAO or 18-2-18. When PMAO/18-2-18 mixtures were used, both mechanisms were allowed; nevertheless, even in films prepared with mixtures of low polymer contents, characteristic morphology from the polymer dewetting route prevailed. Highlights: ► Effect of the composition on the LB films of QDs/polymer. ► Effect of the composition on the LB films of QDs/Gemini surfactant. ► Dewetting mechanisms.

Growth of large-size-two-dimensional crystalline pentacene grains for high performance organic thin film transistors

Directory of Open Access Journals (Sweden)

Chuan Du

2012-06-01

Full Text Available New approach is presented for growth of pentacene crystalline thin film with large grain size. Modification of dielectric surfaces using a monolayer of small molecule results in the formation of pentacene thin films with well ordered large crystalline domain structures. This suggests that pentacene molecules may have significantly large diffusion constant on the modified surface. An average hole mobility about 1.52 cm2/Vs of pentacene based organic thin film transistors (OTFTs is achieved with good reproducibility.

Constructing anisotropic single-Dirac-cones in Bi(1-x)Sb(x) thin films.

Science.gov (United States)

Tang, Shuang; Dresselhaus, Mildred S

2012-04-11

The electronic band structures of Bi(1-x)Sb(x) thin films can be varied as a function of temperature, pressure, stoichiometry, film thickness, and growth orientation. We here show how different anisotropic single-Dirac-cones can be constructed in a Bi(1-x)Sb(x) thin film for different applications or research purposes. For predicting anisotropic single-Dirac-cones, we have developed an iterative-two-dimensional-two-band model to get a consistent inverse-effective-mass-tensor and band gap, which can be used in a general two-dimensional system that has a nonparabolic dispersion relation as in the Bi(1-x)Sb(x) thin film system. © 2012 American Chemical Society

Two-dimensional capillary origami

Energy Technology Data Exchange (ETDEWEB)

Brubaker, N.D., E-mail: nbrubaker@math.arizona.edu; Lega, J., E-mail: lega@math.arizona.edu

2016-01-08

We describe a global approach to the problem of capillary origami that captures all unfolded equilibrium configurations in the two-dimensional setting where the drop is not required to fully wet the flexible plate. We provide bifurcation diagrams showing the level of encapsulation of each equilibrium configuration as a function of the volume of liquid that it contains, as well as plots representing the energy of each equilibrium branch. These diagrams indicate at what volume level the liquid drop ceases to be attached to the endpoints of the plate, which depends on the value of the contact angle. As in the case of pinned contact points, three different parameter regimes are identified, one of which predicts instantaneous encapsulation for small initial volumes of liquid. - Highlights: • Full solution set of the two-dimensional capillary origami problem. • Fluid does not necessarily wet the entire plate. • Global energy approach provides exact differential equations satisfied by minimizers. • Bifurcation diagrams highlight three different regimes. • Conditions for spontaneous encapsulation are identified.

Two-dimensional capillary origami

International Nuclear Information System (INIS)

Brubaker, N.D.; Lega, J.

2016-01-01

We describe a global approach to the problem of capillary origami that captures all unfolded equilibrium configurations in the two-dimensional setting where the drop is not required to fully wet the flexible plate. We provide bifurcation diagrams showing the level of encapsulation of each equilibrium configuration as a function of the volume of liquid that it contains, as well as plots representing the energy of each equilibrium branch. These diagrams indicate at what volume level the liquid drop ceases to be attached to the endpoints of the plate, which depends on the value of the contact angle. As in the case of pinned contact points, three different parameter regimes are identified, one of which predicts instantaneous encapsulation for small initial volumes of liquid. - Highlights: • Full solution set of the two-dimensional capillary origami problem. • Fluid does not necessarily wet the entire plate. • Global energy approach provides exact differential equations satisfied by minimizers. • Bifurcation diagrams highlight three different regimes. • Conditions for spontaneous encapsulation are identified.

Two-dimensional black holes and non-commutative spaces

International Nuclear Information System (INIS)

Sadeghi, J.

2008-01-01

We study the effects of non-commutative spaces on two-dimensional black hole. The event horizon of two-dimensional black hole is obtained in non-commutative space up to second order of perturbative calculations. A lower limit for the non-commutativity parameter is also obtained. The observer in that limit in contrast to commutative case see two horizon

Two dimensional MoS{sub 2}/graphene p-n heterojunction diode: Fabrication and electronic characteristics

Energy Technology Data Exchange (ETDEWEB)

Su, Wei-Jhih [Graduate Institute of Electro-Optical Engineering, National Taiwan University of Science and Technology, 43, Section 4, Keelung Road, Taipei 10607, Taiwan (China); Chang, Hsuan-Chen [Department of Electronic and Computer Engineering, National Taiwan University of Science and Technology, 43, Section 4, Keelung Road, Taipei 10607, Taiwan (China); Shih, Yi-Ting [Graduate Institute of Electro-Optical Engineering, National Taiwan University of Science and Technology, 43, Section 4, Keelung Road, Taipei 10607, Taiwan (China); Wang, Yi-Ping [Department of Electronic and Computer Engineering, National Taiwan University of Science and Technology, 43, Section 4, Keelung Road, Taipei 10607, Taiwan (China); Hsu, Hung-Pin [Department of Electronic Engineering, Ming Chi University of Technology, 84 Gungjuan Road, New Taipei City 24301, Taiwan (China); Huang, Ying-Sheng [Graduate Institute of Electro-Optical Engineering, National Taiwan University of Science and Technology, 43, Section 4, Keelung Road, Taipei 10607, Taiwan (China); Department of Electronic and Computer Engineering, National Taiwan University of Science and Technology, 43, Section 4, Keelung Road, Taipei 10607, Taiwan (China); Lee, Kuei-Yi, E-mail: kylee@mail.ntust.edu.tw [Graduate Institute of Electro-Optical Engineering, National Taiwan University of Science and Technology, 43, Section 4, Keelung Road, Taipei 10607, Taiwan (China); Department of Electronic and Computer Engineering, National Taiwan University of Science and Technology, 43, Section 4, Keelung Road, Taipei 10607, Taiwan (China)

2016-06-25

Molybdenum disulfide (MoS{sub 2}) films are currently the most potential semiconductor materials of the two-dimensional nano-material heterojunction. Few-layer MoS{sub 2} is an n-type semiconductor that has good mechanical strength, high carrier mobility, and has similar thickness as graphene. Graphene is presently the thinnest two-dimensional material with good thermal conductivity and high carrier mobility. The graphene Fermi level can be precisely controlled using the oxygen adsorption. Therefore, graphene can be tuned from zero-gap to p-type semiconductor material using the amount of adsorbed oxygen. In this study we combine few-layer MoS{sub 2} and graphene to produce a heterojunction and exhaustively study the interface properties for heterojunction diode application. According to the results, the MoS{sub 2} band-gap increases with decreasing thickness. The I–V characteristics of the MoS{sub 2}/Graphene p-n junction diodes can be precisely tuned by adjusting different thicknesses of the MoS{sub 2} films. By applying our fabricating method, MoS{sub 2}/Graphene heterojunction diode can be easily constructed and have potential to different applications. - Highlights: • We controlled the layer thickness of MoS{sub 2} by different exfoliation times. • We presented Raman scattering of MoS{sub 2} and define their layers number. • The few-layer MoS{sub 2}/graphene pn junction diode was synthesized. • We measured the device current and voltage characteristics. • The built-in potential barrier could be adjusted by controlling MoS{sub 2} thicknesses.

Assembly of 1D nanofibers into a 2D bi-layered composite nanofibrous film with different functionalities at the two layers via layer-by-layer electrospinning.

Science.gov (United States)

Wang, Zijiao; Ma, Qianli; Dong, Xiangting; Li, Dan; Xi, Xue; Yu, Wensheng; Wang, Jinxian; Liu, Guixia

2016-12-21

A two-dimensional (2D) bi-layered composite nanofibrous film assembled by one-dimensional (1D) nanofibers with trifunctionality of electrical conduction, magnetism and photoluminescence has been successfully fabricated by layer-by-layer electrospinning. The composite film consists of a polyaniline (PANI)/Fe 3 O 4 nanoparticle (NP)/polyacrylonitrile (PAN) tuned electrical-magnetic bifunctional layer on one side and a Tb(TTA) 3 (TPPO) 2 /polyvinylpyrrolidone (PVP) photoluminescent layer on the other side, and the two layers are tightly combined face-to-face together into the novel bi-layered composite film of trifunctionality. The brand-new film has totally different characteristics at the double layers. The electrical conductivity and magnetism of the electrical-magnetic bifunctional layer can be, respectively, tunable via modulating the PANI and Fe 3 O 4 NP contents, and the highest electrical conductivity can reach up to the order of 10 -2 S cm -1 , and predominant intense green emission at 545 nm is obviously observed in the photoluminescent layer under the excitation of 357 nm single-wavelength ultraviolet light. More importantly, the luminescence intensity of the photoluminescent layer remains almost unaffected by the electrical-magnetic bifunctional layer because the photoluminescent materials have been successfully isolated from dark-colored PANI and Fe 3 O 4 NPs. By comparing with the counterpart single-layered composite nanofibrous film, it is found that the bi-layered composite nanofibrous film has better performance. The novel bi-layered composite nanofibrous film with trifunctionality has potential in the fields of nanodevices, molecular electronics and biomedicine. Furthermore, the design conception and fabrication technique for the bi-layered multifunctional film provide a new and facile strategy towards other films of multifunctionality.

A three-dimensional computer graphic imaging for neurosurgery

International Nuclear Information System (INIS)

Uchino, Masafumi; Onagi, Atsuo; Seiki, Yoshikatsu

1987-01-01

Information offered by conventional diagnostic tools for medical use, including X-ray films, CT, MRI, RI images and PET, are usually two-dimensional. However, the human body and pathological lesions are really extended in 3 dimensions. Interpreters have to reconstruct an imaginative, 3-dimensional configuration of lesions from 2-dimensional information on many films, according to their knowledge and experience. All this sometimes wastes a lot of time and gives rise to inconclusive discussion among interpreters. The advent and rapid progress of new computer graphic techniques, however, makes it possible to draw an apparent 3-dimensional image of a lesion on the basis of a 2-dimensional display; this is named a pseudo-3-dimensional image. After the region of interest of the CT-sliced image has been extracted by means of a semi-automatic contour extraction algorithm, multi-slice CT images are constructed by the voxel method. A 3-dimensional image is then generated by the use of the Z-buffer. Subsequently, transparent, semi-transparent, and color display are provided. This new method of display was used for CT-scan films of various intracerebral pathological lesions, including tumors, hematomas, and congenital anomalies: The benefits, prospects, and technical limits of this imaging technique for clinical use were discussed. (author)

Two-dimensional Navier-Stokes turbulence in bounded domains

NARCIS (Netherlands)

Clercx, H.J.H.; van Heijst, G.J.F.

In this review we will discuss recent experimental and numerical results of quasi-two-dimensional decaying and forced Navier–Stokes turbulence in bounded domains. We will give a concise overview of developments in two-dimensional turbulence research, with emphasis on the progress made during the

Two-dimensional Navier-Stokes turbulence in bounded domains

NARCIS (Netherlands)

Clercx, H.J.H.; Heijst, van G.J.F.

2009-01-01

In this review we will discuss recent experimental and numerical results of quasi-two-dimensional decaying and forced Navier–Stokes turbulence in bounded domains. We will give a concise overview of developments in two-dimensional turbulence research, with emphasis on the progress made during the

Creating Two-Dimensional Electron Gas in Nonpolar/Nonpolar Oxide Interface via Polarization Discontinuity: First-Principles Analysis of CaZrO3/SrTiO3 Heterostructure.

Science.gov (United States)

Nazir, Safdar; Cheng, Jianli; Yang, Kesong

2016-01-13

We studied strain-induced polarization and resulting conductivity in the nonpolar/nonpolar CaZrO3/SrTiO3 (CZO/STO) heterostructure (HS) system by means of first-principles electronic structure calculations. By modeling four types of CZO/STO HS-based slab systems, i.e., TiO2/CaO and SrO/ZrO2 interface models with CaO and ZrO2 surface terminations in each model separately, we found that the lattice-mismatch-induced compressive strain leads to a strong polarization in the CZO film and that as the CZO film thickness increases there exists an insulator-to-metal transition. The polarization direction and critical thickness of the CZO film for forming interfacial metallic states depend on the surface termination of CZO film in both types of interface models. In the TiO2/CaO and SrO/ZrO2 interface models with CaO surface termination, the strong polarization drives the charge transfer from the CZO film to the first few TiO2 layers in the STO substrate, leading to the formation of two-dimensional electron gas (2DEG) at the interface. In the HS models with ZrO2 surface termination, two polarization domains with opposite directions are in the CZO film, which results in the charge transfer from the middle CZO layer to the interface and surface, respectively, leading to the coexistence of the 2DEG on the interface and the two-dimensional hole gas (2DHG) at the middle CZO layer. These findings open a new avenue to achieve 2DEG (2DHG) in perovskite-based HS systems via polarization discontinuity.

Piezoelectricity in Two-Dimensional Materials

KAUST Repository

Wu, Tao; Zhang, Hua

2015-01-01

Powering up 2D materials: Recent experimental studies confirmed the existence of piezoelectricity - the conversion of mechanical stress into electricity - in two-dimensional single-layer MoS2 nanosheets. The results represent a milestone towards

Development of a Novel Biosensor Using Cationic Antimicrobial Peptide and Nickel Phthalocyanine Ultrathin Films for Electrochemical Detection of Dopamine

Directory of Open Access Journals (Sweden)

Maysa F. Zampa

2012-01-01

Full Text Available The antimicrobial peptide dermaseptin 01 (DS 01, from the skin secretion of Phyllomedusa hypochondrialis frogs, was immobilized in nanostructured layered films in conjunction with nickel tetrasulfonated phthalocyanines (NiTsPc, widely used in electronic devices, using layer-by-layer technique. The films were used as a biosensor to detect the presence of dopamine (DA, a neurotransmitter associated with diseases such as Alzheimer's and Parkinson's, with detection limits in the order of 10−6 mol L−1. The use of DS 01 in LbL film generated selectivity in the detection of DA despite the presence of ascorbic acid found in biological fluids. This work is the first to report that the antimicrobial peptide and NiTsPc LbL film exhibits electroanalytical activity to DA oxidation. The selectivity in the detection of DA is a fundamental aspect for the development of electrochemical sensors with potential applications in the biomedical and pharmaceutical industries.

Carbon Nanotubes and Algal Polysaccharides To Enhance the Enzymatic Properties of Urease in Lipid Langmuir-Blodgett Films.

Science.gov (United States)

Rodrigues, Raul T; Morais, Paulo V; Nordi, Cristina S F; Schöning, Michael J; Siqueira, José R; Caseli, Luciano

2018-03-06

Algal polysaccharides (extracellular polysaccharides) and carbon nanotubes (CNTs) were adsorbed on dioctadecyldimethylammonium bromide Langmuir monolayers to serve as a matrix for the incorporation of urease. The physicochemical properties of the supramolecular system as a monolayer at the air-water interface were investigated by surface pressure-area isotherms, surface potential-area isotherms, interfacial shear rheology, vibrational spectroscopy, and Brewster angle microscopy. The floating monolayers were transferred to hydrophilic solid supports, quartz, mica, or capacitive electrolyte-insulator-semiconductor (EIS) devices, through the Langmuir-Blodgett (LB) technique, forming mixed films, which were investigated by quartz crystal microbalance, fluorescence spectroscopy, and field emission gun scanning electron microscopy. The enzyme activity was studied with UV-vis spectroscopy, and the feasibility of the thin film as a urea sensor was essayed in an EIS sensor device. The presence of CNT in the enzyme-lipid LB film not only tuned the catalytic activity of urease but also helped to conserve its enzyme activity. Viability as a urease sensor was demonstrated with capacitance-voltage and constant capacitance measurements, exhibiting regular and distinctive output signals over all concentrations used in this work. These results are related to the synergism between the compounds on the active layer, leading to a surface morphology that allowed fast analyte diffusion owing to an adequate molecular accommodation, which also preserved the urease activity. This work demonstrates the feasibility of employing LB films composed of lipids, CNT, algal polysaccharides, and enzymes as EIS devices for biosensing applications.

Layer-by-Layer Nanoassembly of Copper Indium Gallium Selenium Nanoparticle Films for Solar Cell Applications

Directory of Open Access Journals (Sweden)

A. Hemati

2012-01-01

Full Text Available Thin films of CIGS nanoparticles interdigited with polymers have been fabricated through a cost-effective nonvacuum film deposition process called layer-by-layer (LbL nanoassembly. CIGS nanoparticles synthesized by heating copper chloride, indium chloride, gallium chloride, and selenium in oleylamine were dispersed in water, and desired surface charges were obtained through pH regulation and by coating the particles with polystyrene sulfonate (PSS. Raising the pH of the nanoparticle dispersion reduced the zeta-potential from +61 mV at pH 7 to −51 mV at pH 10.5. Coating the CIGS nanoparticles with PSS (CIGS-PSS produced a stable dispersion in water with −56.9 mV zeta-potential. Thin films of oppositely charged CIGS nanoparticles (CIGS/CIGS, CIGS nanoparticles and PSS (CIGS/PSS, and PSS-coated CIGS nanoparticles and polyethylenimine (CIGS-PSS/PEI were constructed through the LbL nanoassembly. Film thickness and resistivity of each bilayer of the films were measured, and photoelectric properties of the films were studied for solar cell applications. Solar cell devices fabricated with a 219 nm CIGS film, when illuminated by 50 W light-source, produced 0.7 V open circuit voltage and 0.3 mA/cm2 short circuit current density.

Giant enhancement of Kerr rotation in two-dimensional Bismuth iron garnet/Ag photonic crystals

International Nuclear Information System (INIS)

Liang Hong; Zhang Qiang; Liu Huan; Fu Shu-Fang; Zhou Sheng; Wang Xuan-Zhang

2015-01-01

Kerr effects of two-dimensional (2D) Bismuth iron garnet (BIG)/Ag photonic crystals (PCs) combined magnetic and plasmonic functionalities is investigated with the effective medium theory. An analytical expression of Kerr rotation angles is derived, in which the effects of the surface pasmons polaritons (SPP) on magneto–optical (MO) activities are reflected. The largest enhancement of Kerr rotation up to now is demonstrated, which is improved three orders of magnitude compared with that of BIG film. When λ < 750 nm all of the reflection are over 10% for the arbitrary filling ratio f 1 , in addition, the enhancement of Kerr rotation angles are at least one order of magnitude. (paper)

Solution of the two-dimensional spectral factorization problem

Science.gov (United States)

Lawton, W. M.

1985-01-01

An approximation theorem is proven which solves a classic problem in two-dimensional (2-D) filter theory. The theorem shows that any continuous two-dimensional spectrum can be uniformly approximated by the squared modulus of a recursively stable finite trigonometric polynomial supported on a nonsymmetric half-plane.

Development of Two-Dimensional NMR

Indian Academy of Sciences (India)

Home; Journals; Resonance – Journal of Science Education; Volume 20; Issue 11. Development of Two-Dimensional NMR: Strucure Determination of Biomolecules in Solution. Anil Kumar. General Article Volume 20 Issue 11 November 2015 pp 995-1002 ...

ONE-DIMENSIONAL AND TWO-DIMENSIONAL LEADERSHIP STYLES

OpenAIRE

Nikola Stefanović

2007-01-01

In order to motivate their group members to perform certain tasks, leaders use different leadership styles. These styles are based on leaders' backgrounds, knowledge, values, experiences, and expectations. The one-dimensional styles, used by many world leaders, are autocratic and democratic styles. These styles lie on the two opposite sides of the leadership spectrum. In order to precisely define the leadership styles on the spectrum between the autocratic leadership style and the democratic ...

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

Science.gov (United States)

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

2017-09-01

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

Infrared magneto-spectroscopy of two-dimensional and three-dimensional massless fermions: A comparison

Energy Technology Data Exchange (ETDEWEB)

Orlita, M., E-mail: milan.orlita@lncmi.cnrs.fr [Laboratoire National des Champs Magnétiques Intenses, CNRS-UJF-UPS-INSA, 38042 Grenoble (France); Faculty of Mathematics and Physics, Charles University, Ke Karlovu 5, 121 16 Prague 2 (Czech Republic); Faugeras, C.; Barra, A.-L.; Martinez, G.; Potemski, M. [Laboratoire National des Champs Magnétiques Intenses, CNRS-UJF-UPS-INSA, 38042 Grenoble (France); Basko, D. M. [LPMMC UMR 5493, Université Grenoble 1/CNRS, B.P. 166, 38042 Grenoble (France); Zholudev, M. S. [Laboratoire Charles Coulomb (L2C), UMR CNRS 5221, GIS-TERALAB, Université Montpellier II, 34095 Montpellier (France); Institute for Physics of Microstructures, RAS, Nizhny Novgorod GSP-105 603950 (Russian Federation); Teppe, F.; Knap, W. [Laboratoire Charles Coulomb (L2C), UMR CNRS 5221, GIS-TERALAB, Université Montpellier II, 34095 Montpellier (France); Gavrilenko, V. I. [Institute for Physics of Microstructures, RAS, Nizhny Novgorod GSP-105 603950 (Russian Federation); Mikhailov, N. N.; Dvoretskii, S. A. [A.V. Rzhanov Institute of Semiconductor Physics, Siberian Branch, Russian Academy of Sciences, Novosibirsk 630090 (Russian Federation); Neugebauer, P. [Institut für Physikalische Chemie, Universität Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart (Germany); Berger, C. [School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States); Institut Néel/CNRS-UJF BP 166, F-38042 Grenoble Cedex 9 (France); Heer, W. A. de [School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States)

2015-03-21

Here, we report on a magneto-optical study of two distinct systems hosting massless fermions—two-dimensional graphene and three-dimensional HgCdTe tuned to the zero band gap condition at the point of the semiconductor-to-semimetal topological transition. Both materials exhibit, in the quantum regime, a fairly rich magneto-optical response, which is composed from a series of intra- and interband inter-Landau level resonances with for massless fermions typical √(B) dependence. The impact of the system's dimensionality and of the strength of the spin-orbit interaction on the optical response is also discussed.

One-dimensional versus two-dimensional electronic states in vicinal surfaces

International Nuclear Information System (INIS)

Ortega, J E; Ruiz-Oses, M; Cordon, J; Mugarza, A; Kuntze, J; Schiller, F

2005-01-01

Vicinal surfaces with periodic arrays of steps are among the simplest lateral nanostructures. In particular, noble metal surfaces vicinal to the (1 1 1) plane are excellent test systems to explore the basic electronic properties in one-dimensional superlattices by means of angular photoemission. These surfaces are characterized by strong emissions from free-electron-like surface states that scatter at step edges. Thereby, the two-dimensional surface state displays superlattice band folding and, depending on the step lattice constant d, it splits into one-dimensional quantum well levels. Here we use high-resolution, angle-resolved photoemission to analyse surface states in a variety of samples, in trying to illustrate the changes in surface state bands as a function of d

Densis. Densimetric representation of two-dimensional matrices

International Nuclear Information System (INIS)

Los Arcos Merino, J.M.

1978-01-01

Densis is a Fortran V program which allows off-line control of a Calcomp digital plotter, to represent a two-dimensional matrix of numerical elements in the form of a variable shading intensity map in two colours. Each matrix element is associated to a square of a grid which is traced over by lines whose number is a function of the element value according to a selected scale. Program features, subroutine structure and running instructions, are described. Some typical results, for gamma-gamma coincidence experimental data and a sampled two-dimensional function, are indicated. (author)

Resonance fluorescence based two- and three-dimensional atom localization

Science.gov (United States)

Wahab, Abdul; Rahmatullah; Qamar, Sajid

2016-06-01

Two- and three-dimensional atom localization in a two-level atom-field system via resonance fluorescence is suggested. For the two-dimensional localization, the atom interacts with two orthogonal standing-wave fields, whereas for the three-dimensional atom localization, the atom interacts with three orthogonal standing-wave fields. The effect of the detuning and phase shifts associated with the corresponding standing-wave fields is investigated. A precision enhancement in position measurement of the single atom can be noticed via the control of the detuning and phase shifts.

Toward two-dimensional search engines

International Nuclear Information System (INIS)

Ermann, L; Shepelyansky, D L; Chepelianskii, A D

2012-01-01

We study the statistical properties of various directed networks using ranking of their nodes based on the dominant vectors of the Google matrix known as PageRank and CheiRank. On average PageRank orders nodes proportionally to a number of ingoing links, while CheiRank orders nodes proportionally to a number of outgoing links. In this way, the ranking of nodes becomes two dimensional which paves the way for the development of two-dimensional search engines of a new type. Statistical properties of information flow on the PageRank–CheiRank plane are analyzed for networks of British, French and Italian universities, Wikipedia, Linux Kernel, gene regulation and other networks. A special emphasis is done for British universities networks using the large database publicly available in the UK. Methods of spam links control are also analyzed. (paper)

Subjective figure reversal in two- and three-dimensional perceptual space.

Science.gov (United States)

Radilová, J; Radil-Weiss, T

1984-08-01

A permanently illuminated pattern of Mach's truncated pyramid can be perceived according to the experimental instruction given, either as a three-dimensional reversible figure with spontaneously changing convex and concave interpretation (in one experiment), or as a two-dimensional reversible figure-ground pattern (in another experiment). The reversal rate was about twice as slow, without the subjects being aware of it, if it was perceived as a three-dimensional figure compared to the situation when it was perceived as two-dimensional. It may be hypothetized that in the three-dimensional case, the process of perception requires more sequential steps than in the two-dimensional one.

Two multi-dimensional uncertainty relations

International Nuclear Information System (INIS)

Skala, L; Kapsa, V

2008-01-01

Two multi-dimensional uncertainty relations, one related to the probability density and the other one related to the probability density current, are derived and discussed. Both relations are stronger than the usual uncertainty relations for the coordinates and momentum

Mechanical exfoliation of two-dimensional materials

Science.gov (United States)

Gao, Enlai; Lin, Shao-Zhen; Qin, Zhao; Buehler, Markus J.; Feng, Xi-Qiao; Xu, Zhiping

2018-06-01

Two-dimensional materials such as graphene and transition metal dichalcogenides have been identified and drawn much attention over the last few years for their unique structural and electronic properties. However, their rise begins only after these materials are successfully isolated from their layered assemblies or adhesive substrates into individual monolayers. Mechanical exfoliation and transfer are the most successful techniques to obtain high-quality single- or few-layer nanocrystals from their native multi-layer structures or their substrate for growth, which involves interfacial peeling and intralayer tearing processes that are controlled by material properties, geometry and the kinetics of exfoliation. This procedure is rationalized in this work through theoretical analysis and atomistic simulations. We propose a criterion to assess the feasibility for the exfoliation of two-dimensional sheets from an adhesive substrate without fracturing itself, and explore the effects of material and interface properties, as well as the geometrical, kinetic factors on the peeling behaviors and the torn morphology. This multi-scale approach elucidates the microscopic mechanism of the mechanical processes, offering predictive models and tools for the design of experimental procedures to obtain single- or few-layer two-dimensional materials and structures.

Stable high efficiency two-dimensional perovskite solar cells via cesium doping

KAUST Repository

Zhang, Xu

2017-08-15

Two-dimensional (2D) organic-inorganic perovskites have recently emerged as one of the most important thin-film solar cell materials owing to their excellent environmental stability. The remaining major pitfall is their relatively poor photovoltaic performance in contrast to 3D perovskites. In this work we demonstrate cesium cation (Cs) doped 2D (BA)(MA)PbI perovskite solar cells giving a power conversion efficiency (PCE) as high as 13.7%, the highest among the reported 2D devices, with excellent humidity resistance. The enhanced efficiency from 12.3% (without Cs) to 13.7% (with 5% Cs) is attributed to perfectly controlled crystal orientation, an increased grain size of the 2D planes, superior surface quality, reduced trap-state density, enhanced charge-carrier mobility and charge-transfer kinetics. Surprisingly, it is found that the Cs doping yields superior stability for the 2D perovskite solar cells when subjected to a high humidity environment without encapsulation. The device doped using 5% Cs degrades only ca. 10% after 1400 hours of exposure in 30% relative humidity (RH), and exhibits significantly improved stability under heating and high moisture environments. Our results provide an important step toward air-stable and fully printable low dimensional perovskites as a next-generation renewable energy source.

Bi-substituted iron garnet films for one-dimensional magneto-photonic crystals: Synthesis and properties

International Nuclear Information System (INIS)

Shaposhnikov, A.N.; Karavainikov, A.V.; Prokopov, A.R.; Berzhansky, V.N.; Salyuk, O.Y.

2012-01-01

Graphical abstract: Faraday hysteresis loops for Bi 1.0 Y 0.5 Gd 1.5 Fe 4.2 Al 0.8 O 12 film on glass-ceramic substrate (a), Bi 2.8 Y 0.2 Fe 5 O 12 film on gallium–gadolinium garnet (b) and for glass-ceramic/SiO 2 /Bi 1.0 Y 0.5 Gd 1.5 Fe 4.2 Al 0.8 O 12 /Bi 2.8 Y 0.2 Fe 5 O 12 structure (c). Highlights: ► Bismuth-substituted iron garnet films as magneto-optical layers in magneto-photonic crystals. ► It is impossible to crystallize the films with high Bi content on amorphous substrates. ► The crystallization of the films can be achieved by their deposition on buffer layer with low bismuth content. -- Abstract: The crystallization processes in Bi 2.8 Y 0.2 Fe 5 O 12 , Bi 2.5 Gd 0.5 Fe 3.8 Al 1.2 O 12 , Bi 1.5 Gd 1.5 Fe 4.5 Al 0.5 O 12 and Bi 1.0 Y 0.5 Gd 1.5 Fe 4.2 Al 0.8 O 12 garnet films deposited by reactive ion beam sputtering on (1 1 1) gadolinium–gallium garnet substrates, optical glass-ceramic and SiO 2 films have been studied. Films were annealed at low pressure in oxygen atmosphere and in the air. The possibility of preparation of crystalline garnet films with high concentration of bismuth on the SiO 2 films using a buffer layer with low concentration of Bi has been shown. This allows to produce one-dimensional magneto-photonic crystals with high effective Faraday rotation (several tens of°/μm for the visible optical spectrum).

Stepwise Reduction of Immobilized Mono layer Graphene Oxides

DEFF Research Database (Denmark)

Petersen, Søren; He, Yudong; Lang, Jiang

2013-01-01

to the pronounced aggregation that accompanies deoxygenation of GO in solution. Surface immobilization of monolayered graphene oxide (mGO) in Langmuir-Blodgett (LB) films was investigated as a method to circumvent this problem. Two types of LB films with different density of mGO flakes were prepared, i.e., diluted...

Two-dimensional MoS2-graphene hybrid nanosheets for high gravimetric and volumetric lithium storage

Science.gov (United States)

Deng, Yakai; Ding, Lixin; Liu, Qixing; Zhan, Liang; Wang, Yanli; Yang, Shubin

2018-04-01

Two-dimensional (2D) MoS2-graphene (MoS2-G) hybrid is fabricated simultaneously and scalablely with an efficient electrochemical exfoliation approach from the combined bulk MoS2-graphite wafer. The as-prepared 2D MoS2-G hybrid is tightly covered with each other with lateral sizes of 600 nm to few micrometers and can be directly assembled to flexible films for lithium storage. When used as anode material for lithium ion battery, the resultant MoS2-G hybrid film exhibits both high gravimetric (750 mA h g-1 at 50 mA g-1) and volumetric capacities (1200 mA h cm-3 at 0.1 mA cm-2). Such excellent electrochemical performance should attributed to the unique 2D structure and good conductive graphene network, which not only facilitates the diffusion of lithium ions, but also improves the fast transfer of electrons, satisfying the kinetics requirements for rapid lithium storage.

Luminescence of two-dimensional ordered array of the ZnO quantum nanodots, obtained by means of the synthetic opal

International Nuclear Information System (INIS)

Gruzintsev, A.N.; Volkov, V.T.; Emelchenko, G.A.; Karpov, I.A.; Maslov, W.M.; Michailov, G.M.; Yakimov, E.E.

2004-01-01

The luminescence properties of ZnO films of different thickness obtained on a synthetic opal were investigated. Several narrow peaks in the exciton emission region related to the size quantum effect of the electron wave functions were detected. Two-dimensional ordered array of ZnO quantum dots formed inside the opal pores on the second sphere layer were found by the atomic force microscopy (AFM) and angle dependence of the luminescence spectra

Development and characterization of multilayer films of polyaniline, titanium dioxide and CTAB for potential antimicrobial applications

Energy Technology Data Exchange (ETDEWEB)

Farias, Emanuel Airton O.; Dionisio, Natália A.; Quelemes, Patrick V. [Núcleo de Pesquisa em Biodiversidade e Biotecnologia, BIOTEC, CMRV, UFPI, Parnaíba, PI 64202-020 (Brazil); Leal, Sergio Henrique [CCNH, UFABC, Santo André, SP 09210-170 (Brazil); Matos, José Milton E.; Filho, Edson C. Silva [Laboratório Interdisciplinar de Materiais Avançados, LIMAv, CCN, UFPI, Teresina, PI 64049-550 (Brazil); Bechtold, Ivan H. [Departamento de Física — UFSC, Florianópolis, SC 88040-900 (Brazil); Leite, José Roberto S.A. [Núcleo de Pesquisa em Biodiversidade e Biotecnologia, BIOTEC, CMRV, UFPI, Parnaíba, PI 64202-020 (Brazil); Eiras, Carla, E-mail: carla.eiras.ufpi@gmail.com [Núcleo de Pesquisa em Biodiversidade e Biotecnologia, BIOTEC, CMRV, UFPI, Parnaíba, PI 64202-020 (Brazil); Laboratório Interdisciplinar de Materiais Avançados, LIMAv, CCN, UFPI, Teresina, PI 64049-550 (Brazil)

2014-02-01

Composites prepared from polyaniline (PANI) and the ceramic technology of titanium dioxide (TiO{sub 2}) have been proposed, however, the interaction of these materials with greater control of molecular arrangement becomes attractive in order to achieve properties not previously described or yet the optimization of those already reported. Therefore, in this study, thin hybrid films made of polyaniline (PANI), a conductive polymer, and the technological ceramic, titanium dioxide (TiO{sub 2}), were prepared by the layer-by-layer (LbL) self-assembly technique. The films were characterized by cyclic voltammetry (CV), UV–VIS spectroscopy and atomic force microscopy (AFM). Aiming to improve the dispersion of the ceramic in the polymer matrix, the commercial surfactant, cetyl trimethylammonium bromide (CTAB), was used in the formation of the films. The best condition of deposition was found showing synergic interactions between the conjugated materials. The antibacterial activity of the PANI(TiO{sub 2})/CTAB films was studied and the obtained results suggest their use as antimicrobial coatings. - Highlights: • Nanocomposite films of PANI and TiO2 prepared by the LbL technique • Ceramic dispersion in PANI improved with CTAB for antimicrobial applications. • Optimized film deposition for synergic interactions of the conjugated materials • Antibacterial activity of the films suggests their use as antimicrobial coatings.

Asymptotics for Two-dimensional Atoms

DEFF Research Database (Denmark)

Nam, Phan Thanh; Portmann, Fabian; Solovej, Jan Philip

2012-01-01

We prove that the ground state energy of an atom confined to two dimensions with an infinitely heavy nucleus of charge $Z>0$ and $N$ quantum electrons of charge -1 is $E(N,Z)=-{1/2}Z^2\\ln Z+(E^{\\TF}(\\lambda)+{1/2}c^{\\rm H})Z^2+o(Z^2)$ when $Z\\to \\infty$ and $N/Z\\to \\lambda$, where $E^{\\TF}(\\lambd......We prove that the ground state energy of an atom confined to two dimensions with an infinitely heavy nucleus of charge $Z>0$ and $N$ quantum electrons of charge -1 is $E(N,Z)=-{1/2}Z^2\\ln Z+(E^{\\TF}(\\lambda)+{1/2}c^{\\rm H})Z^2+o(Z^2)$ when $Z\\to \\infty$ and $N/Z\\to \\lambda$, where $E......^{\\TF}(\\lambda)$ is given by a Thomas-Fermi type variational problem and $c^{\\rm H}\\approx -2.2339$ is an explicit constant. We also show that the radius of a two-dimensional neutral atom is unbounded when $Z\\to \\infty$, which is contrary to the expected behavior of three-dimensional atoms....

Effects of SiNx on two-dimensional electron gas and current collapse of AlGaN/GaN high electron mobility transistors

International Nuclear Information System (INIS)

Fan, Ren; Zhi-Biao, Hao; Lei, Wang; Lai, Wang; Hong-Tao, Li; Yi, Luo

2010-01-01

SiN x is commonly used as a passivation material for AlGaN/GaN high electron mobility transistors (HEMTs). In this paper, the effects of SiN x passivation film on both two-dimensional electron gas characteristics and current collapse of AlGaN/GaN HEMTs are investigated. The SiN x films are deposited by high- and low-frequency plasma-enhanced chemical vapour deposition, and they display different strains on the AlGaN/GaN heterostructure, which can explain the experiment results. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

Spin dynamics in a two-dimensional quantum gas

DEFF Research Database (Denmark)

Pedersen, Poul Lindholm; Gajdacz, Miroslav; Deuretzbacher, Frank

2014-01-01

We have investigated spin dynamics in a two-dimensional quantum gas. Through spin-changing collisions, two clouds with opposite spin orientations are spontaneously created in a Bose-Einstein condensate. After ballistic expansion, both clouds acquire ring-shaped density distributions with superimp......We have investigated spin dynamics in a two-dimensional quantum gas. Through spin-changing collisions, two clouds with opposite spin orientations are spontaneously created in a Bose-Einstein condensate. After ballistic expansion, both clouds acquire ring-shaped density distributions...

Two-Dimensional Layered Oxide Structures Tailored by Self-Assembled Layer Stacking via Interfacial Strain.

Science.gov (United States)

Zhang, Wenrui; Li, Mingtao; Chen, Aiping; Li, Leigang; Zhu, Yuanyuan; Xia, Zhenhai; Lu, Ping; Boullay, Philippe; Wu, Lijun; Zhu, Yimei; MacManus-Driscoll, Judith L; Jia, Quanxi; Zhou, Honghui; Narayan, Jagdish; Zhang, Xinghang; Wang, Haiyan

2016-07-06

Study of layered complex oxides emerge as one of leading topics in fundamental materials science because of the strong interplay among intrinsic charge, spin, orbital, and lattice. As a fundamental basis of heteroepitaxial thin film growth, interfacial strain can be used to design materials that exhibit new phenomena beyond their conventional forms. Here, we report a strain-driven self-assembly of bismuth-based supercell (SC) with a two-dimensional (2D) layered structure. With combined experimental analysis and first-principles calculations, we investigated the full SC structure and elucidated the fundamental growth mechanism achieved by the strain-enabled self-assembled atomic layer stacking. The unique SC structure exhibits room-temperature ferroelectricity, enhanced magnetic responses, and a distinct optical bandgap from the conventional double perovskite structure. This study reveals the important role of interfacial strain modulation and atomic rearrangement in self-assembling a layered singe-phase multiferroic thin film, which opens up a promising avenue in the search for and design of novel 2D layered complex oxides with enormous promise.

Procedures for two-dimensional electrophoresis of proteins

Energy Technology Data Exchange (ETDEWEB)

Tollaksen, S.L.; Giometti, C.S.

1996-10-01

High-resolution two-dimensional gel electrophoresis (2DE) of proteins, using isoelectric focusing in the first dimension and sodium dodecyl sulfate/polyacrylamide gel electrophoresis (SDS-PAGE) in the second, was first described in 1975. In the 20 years since those publications, numerous modifications of the original method have evolved. The ISO-DALT system of 2DE is a high-throughput approach that has stood the test of time. The problem of casting many isoelectric focusing gels and SDS-PAGE slab gels (up to 20) in a reproducible manner has been solved by the use of the techniques and equipment described in this manual. The ISO-DALT system of two-dimensional gel electrophoresis originated in the late 1970s and has been modified many times to improve its high-resolution, high-throughput capabilities. This report provides the detailed procedures used with the current ISO-DALT system to prepare, run, stain, and photograph two-dimensional gels for protein analysis.

Quantum oscillations in quasi-two-dimensional conductors

CERN Document Server

Galbova, O

2002-01-01

The electronic absorption of sound waves in quasi-two-dimensional conductors in strong magnetic fields, is investigated theoretically. A longitudinal acoustic wave, propagating along the normal n-> to the layer of quasi-two-dimensional conductor (k-> = left brace 0,0,k right brace; u-> = left brace 0,0,u right brace) in magnetic field (B-> = left brace 0, 0, B right brace), is considered. The quasiclassical approach for this geometry is of no interest, due to the absence of interaction between electromagnetic and acoustic waves. The problem is of interest in strong magnetic field when quantization of the charge carriers energy levels takes place. The quantum oscillations in the sound absorption coefficient, as a function of the magnetic field, are theoretically observed. The experimental study of the quantum oscillations in quasi-two-dimensional conductors makes it possible to solve the inverse problem of determining from experimental data the extrema closed sections of the Fermi surface by a plane p sub z = ...

Two-dimensional membranes in motion

NARCIS (Netherlands)

Davidovikj, D.

2018-01-01

This thesis revolves around nanomechanical membranes made of suspended two - dimensional materials. Chapters 1-3 give an introduction to the field of 2D-based nanomechanical devices together with an overview of the underlying physics and the measurementtools used in subsequent chapters. The research

Electrostatic Spray Deposition-Based Manganese Oxide Films-From Pseudocapacitive Charge Storage Materials to Three-Dimensional Microelectrode Integrands.

Science.gov (United States)

Agrawal, Richa; Adelowo, Ebenezer; Baboukani, Amin Rabiei; Villegas, Michael Franc; Henriques, Alexandra; Wang, Chunlei

2017-07-26

In this study, porous manganese oxide (MnO x ) thin films were synthesized via electrostatic spray deposition (ESD) and evaluated as pseudocapacitive electrode materials in neutral aqueous media. Very interestingly, the gravimetric specific capacitance of the ESD-based electrodes underwent a marked enhancement upon electrochemical cycling, from 72 F∙g -1 to 225 F∙g -1 , with a concomitant improvement in kinetics and conductivity. The change in capacitance and resistivity is attributed to a partial electrochemical phase transformation from the spinel-type hausmannite Mn₃O₄ to the conducting layered birnessite MnO₂. Furthermore, the films were able to retain 88.4% of the maximal capacitance after 1000 cycles. Upon verifying the viability of the manganese oxide films for pseudocapacitive applications, the thin films were integrated onto carbon micro-pillars created via carbon microelectromechanical systems (C-MEMS) for examining their application as potential microelectrode candidates. In a symmetric two-electrode cell setup, the MnO x /C-MEMS microelectrodes were able to deliver specific capacitances as high as 0.055 F∙cm -2 and stack capacitances as high as 7.4 F·cm -3 , with maximal stack energy and power densities of 0.51 mWh·cm -3 and 28.3 mW·cm -3 , respectively. The excellent areal capacitance of the MnO x -MEs is attributed to the pseudocapacitive MnO x as well as the three-dimensional architectural framework provided by the carbon micro-pillars.

Two-Dimensional Titanium Carbide (MXene) as Surface-Enhanced Raman Scattering Substrate

Energy Technology Data Exchange (ETDEWEB)

Sarycheva, Asia [Drexel Univ., Philadelphia, PA (United States); Makaryan, Taron [Drexel Univ., Philadelphia, PA (United States); Maleski, Kathleen [Drexel Univ., Philadelphia, PA (United States); Satheeshkumar, Elumalai [National Cheng Kung Univ., Tainan (Taiwan); National Institute of Technology-Trichy, Tamil Nadu (India); Melikyan, Armen [Russian-Armenian (Slavonic) State Univ., Yerevan (Armenia); Minassian, Hayk [A. Alikhanian National Science Lab., Yerevan (Armenia); Yoshimura, Masahiro [National Cheng Kung Univ., Tainan (Taiwan); Gogotsi, Yury G. [Drexel Univ., Philadelphia, PA (United States)

2017-08-22

Here, noble metal (gold or silver) nanoparticles or patterned films are typically used as substrates for surface-enhanced Raman spectroscopy (SERS). Two-dimensional (2D) carbides and nitrides (MXenes) exhibit unique electronic and optical properties, including metallic conductivity and plasmon resonance in the visible or near-infrared range, making them promising candidates for a wide variety of applications. Herein, we show that 2D titanium carbide, Ti₃C₂T_x, enhances Raman signal from organic dyes on a substrate and in solution. As a proof of concept, MXene SERS substrates were manufactured by spray-coating and used to detect several common dyes, with calculated enhancement factors reaching ~10⁶. Titanium carbide MXene demonstrates SERS effect in aqueous colloidal solutions, suggesting the potential for biomedical or environmental applications, where MXene can selectively enhance positively charged molecules.

Soap Films as 1D waveguides

Directory of Open Access Journals (Sweden)

Emile Olivier

2014-01-01

Full Text Available Laser light is injected in a free standing horizontal draining soap film through the glass frame sustaining the film. Two propagation regimes are clearly identified depending on the film thickness. At the beginning of the drainage, the soap film behaves as a multimode-one dimensional optofiuidic waveguide. In particular, we observe that the injected light creates a bottleneck in the film and part of the injected light is refracted leading to whiskers. At the end of the drainage where the film thickness is below 1μm, there is a strong selection among the various possible optical modes in the film, and part of the light is defiected. This leads to a self selection of the mode propagation inside the film.

Optimization of charge-carrier generation in amorphous-silicon thin-film tandem solar cell backed by two-dimensional metallic surface-relief grating

Science.gov (United States)

Civiletti, Benjamin J.; Anderson, Tom H.; Ahmad, Faiz; Monk, Peter B.; Lakhtakia, Akhlesh

2017-08-01

The rigorous coupled-wave approach was implemented in a three-dimensional setting to calculate the chargecarrier-generation rate in a thin-film solar cell with multiple amorphous-silicon p-i-n junctions. The solar cell comprised a front antireflection window; three electrically isolated p-i-n junctions in tandem; and a periodically corrugated silver back-reflector with hillock-shaped corrugations arranged on a hexagonal lattice. The differential evolution algorithm (DEA) was used to maximize the charge-carrier-generation rate over a set of selected optical and electrical parameters. This optimization exercise minimized the bandgap of the topmost i-layer but all other parameters turned out to be uninfluential. More importantly, the exercise led to a configuration that would very likely render the solar cell inefficient. Therefore, another optimization exercise was conducted to maximize power density. The resulting configuration was optimal over all parameters.

Incorrectness of conventional one-dimensional parallel thermal resistance circuit model for two-dimensional circular composite pipes

International Nuclear Information System (INIS)

Wong, K.-L.; Hsien, T.-L.; Chen, W.-L.; Yu, S.-J.

2008-01-01

This study is to prove that two-dimensional steady state heat transfer problems of composite circular pipes cannot be appropriately solved by the conventional one-dimensional parallel thermal resistance circuits (PTRC) model because its interface temperatures are not unique. Thus, the PTRC model is definitely different from its conventional recognized analogy, parallel electrical resistance circuits (PERC) model, which has unique node electric voltages. Two typical composite circular pipe examples are solved by CFD software, and the numerical results are compared with those obtained by the PTRC model. This shows that the PTRC model generates large error. Thus, this conventional model, introduced in most heat transfer text books, cannot be applied to two-dimensional composite circular pipes. On the contrary, an alternative one-dimensional separately series thermal resistance circuit (SSTRC) model is proposed and applied to a two-dimensional composite circular pipe with isothermal boundaries, and acceptable results are returned

Adsorption and enzyme activity of asparaginase at lipid Langmuir and Langmuir-Blodgett films

International Nuclear Information System (INIS)

Rocha Junior, Carlos da; Caseli, Luciano

2017-01-01

In this present work, the surface activity of the enzyme asparaginase was investigated at the air-water interface, presenting surface activity in high ionic strengths. Asparaginase was incorporated in Langmuir monolayers of the phospholipid dipalmitoylphosphatidylcholine (DPPC), forming a mixed film, which was characterized with surface pressure-area isotherms, surface potential-area isotherms, polarization-modulated infrared reflection-absorption spectroscopy (PM-IRRAS), and Brewster angle microscopy (BAM). The adsorption of the enzyme at the air-water interface condensed the lipid monolayer and increased the film compressibility at high surface pressures. Amide bands in the PM-IRRAS spectra were identified, with the C−N and C =O dipole moments lying parallel to monolayer plane, revealing the structuring of the enzyme into α-helices and β-sheets. The floating monolayers were transferred to solid supports as Langmuir-Blodgett (LB) films and characterized with fluorescence spectroscopy and atomic force microscopy. Catalytic activities of the films were measured and compared to the homogenous medium. The enzyme accommodated in the LB films preserved more than 78% of the enzyme activity after 30 days, in contrast for the homogeneous medium, which preserved less than 13%. The method presented in this work not only allows for an enhanced catalytic activity, but also can help explain why certain film architectures exhibit better performance. - Highlights: • Biomembranes are mimicked with Langmuir monolayers. • Asparaginase is incorporated into the lipid monolayer. • Enzyme adsorption is confirmed with tensiometry and infrared spectroscopy. • Langmuir-Blodgett films of the enzyme present enzyme activity.

Adsorption and enzyme activity of asparaginase at lipid Langmuir and Langmuir-Blodgett films

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Rocha Junior, Carlos da; Caseli, Luciano, E-mail: lcaseli@unifesp.br

2017-04-01

In this present work, the surface activity of the enzyme asparaginase was investigated at the air-water interface, presenting surface activity in high ionic strengths. Asparaginase was incorporated in Langmuir monolayers of the phospholipid dipalmitoylphosphatidylcholine (DPPC), forming a mixed film, which was characterized with surface pressure-area isotherms, surface potential-area isotherms, polarization-modulated infrared reflection-absorption spectroscopy (PM-IRRAS), and Brewster angle microscopy (BAM). The adsorption of the enzyme at the air-water interface condensed the lipid monolayer and increased the film compressibility at high surface pressures. Amide bands in the PM-IRRAS spectra were identified, with the C−N and C =O dipole moments lying parallel to monolayer plane, revealing the structuring of the enzyme into α-helices and β-sheets. The floating monolayers were transferred to solid supports as Langmuir-Blodgett (LB) films and characterized with fluorescence spectroscopy and atomic force microscopy. Catalytic activities of the films were measured and compared to the homogenous medium. The enzyme accommodated in the LB films preserved more than 78% of the enzyme activity after 30 days, in contrast for the homogeneous medium, which preserved less than 13%. The method presented in this work not only allows for an enhanced catalytic activity, but also can help explain why certain film architectures exhibit better performance. - Highlights: • Biomembranes are mimicked with Langmuir monolayers. • Asparaginase is incorporated into the lipid monolayer. • Enzyme adsorption is confirmed with tensiometry and infrared spectroscopy. • Langmuir-Blodgett films of the enzyme present enzyme activity.