Electrospinning fabrication and oxygen sensing properties of Cu(I) complex-polystyrene composite microfibrous membranes

In this paper, a phosphorescent Cu(I) complex of [Cu(POP)(ECI-Phen)]BF₄, where POP=bis[2-(diphenylphosphino)phenyl]ether, and ECI-Phen=1-ethyl-2-(N-ethyl-carbazole-yl-4-)imidazo[4,5-f]1,10-phenanthroline, is incorporated into a polystyrene matrix of polystyrene (PS) to form microfibers membranes. The possibility of using the resulted composite microfibrous membranes as an optical oxygen sensor is explored. Good linearity and short response time are obtained with a sensitivity of 9.8. These results suggest that phosphorescent [Cu(POP)(ECI-Phen)]BF₄ is a promising candidate for oxygen-sensors and PS is an excellent matrix for oxygen sensing material because it owns a large surface-area-to-volume ratio and can supply a homogeneous matrix for probe molecules. Further analysis suggests that the molecular structure of diamine ligand in Cu(I) complexes is critical for sensitivity due to the characteristic electronic structure of excited state Cu(I) complexes.     

The effect of length of single‐walled carbon nanotubes (SWNTs) on electrical properties of conducting polymer–SWNT composites

DC conductivity of conjugated polymer‐single‐walled carbon nanotube (SWNT) composite films has been measured for different SWNT concentrations. The composite was prepared by dispersing SWNTs in the poly (3‐octylthiophene), P3OT matrix already dissolved in xylene. The conductivity of the composite films showed a rapid increase as the SWNT concentration increases beyond a certain value. This behavior is explained in terms of percolating paths provided by the SWNTs in the volume of polymer matrix. To investigate the effect of length of nanotubes on the percolation conductivity, different SWNT samples were employed with similar diameter but varying tube lengths. It was found that the conductivity of the composite films is strongly dominated by the length of the nanotubes. Lower percolation limit and high conductivity value of composite films is observed for longer nanotubes. Furthermore, the conductivity is observed to be dependent on the size of the host polymer molecule also. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 89–95, 2010     

Ferroelectricity and structure of BaTiO3 grown on YBa 2Cu3O_{7 - \delta } thin films

We have investigated the crystal structure and the ferroelectric properties of BaTiO₃ thin films with YBa₂Cu₃O as the bottom and Au as the top electrode. Epitaxial heterostructures of YBa₂Cu₃O and BaTiO₃ were prepared by dc and rf sputtering, respectively. The crystal structure of the films was characterised by X-ray diffraction. The ferroelectric behaviour of the BaTiO₃ films was confirmed by hysteresis loop measurements using a Sawyer Tower circuit. We obtain a coercive field of 30 kV/cm and a remanent polarisation of 1.25 μC/cm². At sub-switching fields the capacitance of the films obeys a relation analogous to the Rayleigh law. This behaviour indicates an interaction of domain walls with randomly distributed pinning centres. At a field of 5 MV/m we calculate a 3% contribution of the irreversible domain wall motion to the total dielectric constant. Received 24 June 1999 and Received in final form 27 August 1999     

A comparative study of thermal properties of similar Zn-free and Zn-doped thin films

Zn-doped sprayed thin films have been grown on binary In₂S₃ substrates under the mean temperature (T_d = 320 °C). Further studies Amlouk et al. [M. Amlouk, M.A. Ben Said, N. Kamoun, S. Belgacem, N. Brunet, D. Barjon, Japan Journal of Applied Physics 38 (1999) 26-30]; Lazzez et al. [S. Lazzez, K. Boubaker, M. Amlouk, Indirect measurement of Zn-doped In₂S₃ NANO films SPECIFIC heat capacity, International Journal of Nanoscience 7 (2008) 1–5.]; Lazzez et al. [S. Lazzez, K. Boubaker, T. Ben Nasrallah, M. Mnari, R. Chtourou, M. Amlouk, S. Belgacem, Structural and optoelectronic properties of InZnS sprayed layers, Acta Physica Polonica A 114 (2008) 869–880.] investigated the band gap shift, the structural and morphological changes induced by this doping. In this study, a quantitative comparative evaluation of the thermal properties of the as-grown layers is carried out. The obtained results, parallel to further information, plea for the superior thermal efficiency of the recently proposed Zn-doped ternary compounds.     

Electric-field-induced rupture of polymer-stabilized oil films

Water-in-oil emulsions stabilized by polymeric surfactants are robust, but the reasons for their stability are poorly understood. We studied oil films stabilized by a comb–graft copolymer having a poly(siloxane) backbone and poly(ethylene oxide)/poly (propylene oxide) and C₁₆ grafts (Abil EM-90) with a total number-average molecular weight of 62,000. Electric fields imposed in the aqueous phases on either side of the oil films were used to induce rapid rupture, and the response of the film was monitored using optical interference and electrical conductance measurements. Film thickness values ranged between 30 and 50 nm and rupture at field strength values between 2 × 10⁷ and 5 × 10⁷ V/m. Unexpectedly, in some cases, stable pores were formed and the films became electrically conductive. Often the pores persisted for more than 20 min after the voltage had been removed. Since the current was independent of film area, very few pores are involved in conduction. This behavior is similar to that found in lipid films; however, the persistence time is greater for polymer-stabilized films. Because the films are thick, it is possible that pores are formed by multimolecular self-assembly as with pore-forming proteins. Polymer purification also influenced film stability. Received: 4 February 1999 Accepted: 21 May 1999     

Textured PLCT Thin Films Prepared on Pt/Ti/SiO2/Si Substrate by Metal-Organic Decomposition

Textured calcium modified (Pb,La)TiO₃ (PLCT) films were deposited on Pt/Ti/SiO₂/Si substrates by using a metal-organic decomposition (MOD) process. The PLCT films exhibit good ferroelectric properties, a very low leakage current and a sharp PLCT/Pt interface. The (100) texture of the PLCT film is growth-controlled; the (100) oriented grains grow preferentially so as to minimize the surface energy. Particularly, the (100) preferred orientation is easy to form in the PLCT film with a layered structure for which the substrate almost does not affect the nucleation and growth of the film.     

Covalently attached self‐assembly of ultrathin films from hydroxy‐containing porphyrin and diazoresin

Ultrathin films from 5,10,15,20‐tetrakis(4‐hydroxyphenyl) porphyrin (HPP) and diazoresin (DR) via a H bonding interaction were fabricated with the self‐assembly technique. Under UV irradiation, the H bonds between the layers will convert to covalent bonds following the decomposition of the diazonium group of DR. The stability of the film against the polar solvent and electrolyte aqueous solution increases a lot because of the formation of the covalent crosslinking structure. Thus, the photoelectric conversion property of DR/HPP film can be measured directly with a normal photoelectric chemical cell with potassium chloride as the electrolyte. The maximum of the anodic photocurrent was measured as 1.7 μ Å for an eight bilayer DR/HPP film deposited on an indium–tin oxide glass electrode. The action spectrum of the photocurrent generation indicated that the HPP contained in the film is responsible for the generation of the observed photocurrent. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3103–3108, 2003     

Dynamics of thin polymer films: Recent insights from incoherent neutron scattering

Incoherent neutron scattering is presented as a powerful tool for interpreting changes in molecular dynamics as a function of film thickness for a range of polymers. Motions on approximately nanosecond and faster timescales are quantified in terms of a mean-square atomic displacement (〈u²〉) from the Debye–Waller factor. Thin-film confinement generally leads to a reduction of 〈u²〉 in comparison with the bulk material, and this effect becomes especially pronounced when the film thickness approaches the unperturbed dimensions of the macromolecule. Generally, there is a suppression (never an enhancement) of 〈u²〉 at temperatures T above the bulk calorimetric glass-transition temperature (T_g). Below T_g, the reduction in the magnitude of 〈u²〉 depends on the polymer and the length scales being probed. Polymers with extensive segmental or local mobility in the glass are particularly susceptible to reductions of 〈u²〉 with confinement, especially at the Q vectors probing these longer length scales, whereas materials lacking these sub-T_g motions are relatively insensitive. Moreover, a reduced 〈u²〉 value correlates with reduced mobility at long time and spatial scales, as measured by diffusion in these thin polymer films. Finally, this reduced thin-film mobility is not reliably predicted by thermodynamic assessments of an apparent T_g, as measured by discontinuities or kinks in the T dependence of the thermal expansion, specific volume, index of refraction, specific heat, and so forth. These measurements illustrate that 〈u²〉 is a powerful and predictive tool for understanding dynamic changes in thin polymer films. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3218–3234, 2004     

Kinetics of dark excitons and excitonic trions in InGaAs single quantum well

Magnetooptical studies performed on a wide InGaAs/GaAs single quantum well indicate that optically non-active (dark) excitons with total angular momentum play the role of a reservoir for the creation of free multiparticle excitonic complexes. After analyzing the magnetic field evolution of the circularly polarized components of the low energy structure appearing in the main excitonic luminescence line we assign this feature to the excitonic trion formation. The binding energy of the excitonic trions was estimated to be of the order of 1 meV. Received: 29 October 1997 / Received in final form: 20 February 1998 / Accepted: 21 February 1998