Electrical characterization of copper phthalocyanine thin-film transistors with fluoride gate insulator

Different fluoride materials are used as gate dielectrics to fabricate copper phthalocyanine (CuPc) thin film. transistors (OTFTs). The fabricated devices exhibit good electrical characteristics and the mobility is found to be dependent on the gate voltage from 10(-3) to 10(-1) cm(2) V(-1)s(-1). The observed noticeable electron injection at the drain electrode is of great significance in achieving ambipolar OTFTs. The same method for formation of organic semiconductors and gate dielectric films greatly simplifies the fabrication process. This provides a convenient way to produce high-performance OTFTs on a large scale and should be useful for integration in organic displays.

Electrical characteristics of copper phthalocyanine thin-film transistors with polyamide-6/polytetrafluoroethylene gate insulator

Polyamide- 6(PA 6)/polytetrafluoroethylene is studied as a potential gate dielectric for flexible organic thin film transistors. The same method used for the formation of organic semiconductor and gate dielectric films greatly simplifies the fabrication process of devices. The fabricated transistors show good electrical characteristics. Ambipolar behaviour is observed even when the device is operated in air.

Polyaniline for corrosion prevention of mild steel coupled with copper

Polyaniline emeraldine base/epoxy resin (EB/ER) coating was investigated for corrosion protection of mild steel coupled with copper in 3.5% NaCl solution. EB/ER coating with 5-10 wt% EB had long-term corrosion resistance on both uncoupled steel and copper due to the passivation effect of EB on the metal surfaces. During the 150 immersion days, the impedance at 0.1 Hz for the coating increased in the first 1-40 days and subsequently remained constant above 10(9) Omega cm(2), whereas that for pure ER coating fell below 10(6) Omega cm(2) after only 30 or 40 days. Immersion tests on coated steel-copper galvanic couple showed that EB/ER coating offered 100 times more protection than ER coating against steel dissolution and coating delamination on copper, which was mainly attributed to the passive metal oxide films formed by EB blocking both the anodic and cathodic reactions. Salt spray tests showed that 100 mu m EB/ER coating protected steel-copper couple for at least 2000 h.

PH-Dependent syntheses and structures of two Copper(II)/Phenanthroline/p-Sulfonatocalix[4]arene supramolecular compounds with 1D water-filled channels

Two copper-organic framework supramolecular assemblies of p-sulfonatocalix[4]arene and 1,10-phenanthroline Cu-2[C12H8N2][C28H20S4O16][H2O](23.5) (1) and Cu-3[C12H8N2](3)[C28H19S4O16]Cl[H2O](17.6) (2) were obtained by pH-dependent synthesis at room temperature. Both structures show ID water-filled channels (rectangular shape in I and triangular in 2) with the solvent-accessible volume occupying 30.8% (1) and 24.2% (2) of the unit-cell volume, respectively. The calixarene molecules in both structures assume analogous cone shapes of C-2 nu symmetry instead of the conventional C-4 nu symmetry. Their connecting to different amounts of copper/phenanthroline cations leads to the formation of different structures.

The first polyoxometalate polymer constructed by assembly of the heptamolybdic anion and copper coordination groups

The first example of one-dimensional organic-inorganic polymetallic coordination polymer based on heptamolybdate anions, formulated (NH4)[Cu(en)(2)][Na(en)Cu(en)(2)(H2O)(Mo7O24)].4H(2)O (en = ethylenediamine) (1) has been hydrothermally synthesized and characterized by element analysis, IR, EPR, CV and single crystal X-ray diffraction. The structure of 1 is fabricated by self-assembly of integrated heptamolybdic anions without collapse of primary structure and copper-ethylenediamine(en) coordination groups into one-dimensional zigzag-shaped chains.

Hydrothermal synthesis and crystal structure of a sulfur-bridged binuclear copper(II) coordination polymer generated by a spontaneous reduction

A simultaneous reduction SO42- to S2- by 2,5-pyridinedicarboxylate under hydrothermal conditions produced a new binuclear copper(II) coordination polymer [CuS(4,4'-bipy)](n) (4,4-bipy = 4,4'-bipyridine) (1). Single crystal X-ray analysis revealed that compound I consisted of sulfur-bridged binuclear copper(II) units with Cu-Cu bonding which were combined with 4,4-bipy to generate a three-dimensional network constructed from mutual interpenetration of two-dimensional (6,3) nets. Crystal data for 1:C10H8CuN2S, tetragonal 14(1)/acd, a = 14.0686(5) Angstrom, b = 14.0686(5) Angstrom, c = 38.759(2) Angstrom, Z = 32. Other characterizations by elemental analysis, IR, EPR and TGA analysis were also described in this paper.

Study on the instability of organic field-effect transistors based on fluorinated copper phthalocyanine

The effects of positive and negative gate-bias stress on organic field-effect transistors (OFET) based on tantalum (Ta)/tantalum pentoxide (Ta2O5)/fluorinated copper phthalocyanine (F16CuPc) structure are investigated as a function of stress time and stress temperature. It is shown that gate-bias stress induces a parallel threshold voltage shift (DeltaV(T)) of OFETs without changes of field-effect mobility mu(EF) and sub-threshold slope (DeltaS). The DeltaV(T) is observed to be logarithmically dependent on time at high gate-bias appropriate to OFET operation. More importantly, the shift is directional, namely, be large shift under positive stress and almost do not move under negative stress. The threshold voltage shift is temperature dependent with activation energy of 0.51 eV We concluded that threshold voltage shift of the OFET with F16CuPc as active layer is due to charge trapping in the insulator in which trapped carriers have redistribution.

Immobilization and direct electrochemistry of copper-containing enzymes on active carbon

Two typical and important copper-containing enzymes, laccase (Lac) and tyrosinase (Tyr), have been immobilized on the surface of active carbon with simple adsorption method. The cyclic voltammetric results indicated that the active carbon could promote the direct electron transfer of both Lac and Tyr and a pair of well-defined and nearly symmetric redox peaks appeared on the cyclic voltammograms of Lac or Tyr with the formal potential, E-0', independent on the scan rate. The further experimental results showed that the immobilized copper-containing oxidase displayed an excellent electrocatalytic activity to the electrochemical reduction of O-2. The immobilization method presented here has several advantages, such as simplicity, easy to operation and keeping good activity of enzyme etc., and could be further used to study the direct electrochemistry of other redox proteins and enzymes and fabricate the catalysts for biofuel cell.

Interfacial electronic structure of copper phthalocyanine and copper hexadecafluorophthalocyanine studied by photoemission

Electronic structures of the heterojunction between copper phthalocyanine (CuPc) and copper hexadecafluorophthalocyanine (F16CuPc) were studied with ultraviolet photoemission spectroscopy. Band bending and an interface dipole were observed at the interface due to the formation of an electron accumulation layer and a depletion layer in F16CuPc and CuPc, respectively. Such an energy level alignment leads to interesting ambipolar characteristics for application of the CuPc/F16CuPc junction in organic field-effect transistors.

Copper phthalocyanine based hybrid p-type permeable-base transistor in vertical architecture

We demonstrate the production of copper phthalocyanine (CuPc) based p-type hybrid permeable-base transistors, which operate at low voltages having high common-base current gains. These transistors are prepared by evaporating a thin metal layer (Ag or Al) that acts as base on top of a Si substrate that acts as collector. In the sequence CuPc and Au are thermally sublimated to produce the emitter, constituting a quite simple device production procedure with the additional advantage of allowing higher integration due to its vertical architecture.

Structure and catalytic properties of magnesia-supported copper salts of molybdovanadophosphoric acid

The structure and stability of magnesia-supported copper salts of molybdovanadophosphoric acid (Cu2PMo11VO40) were characterized by different techniques. The catalyst was prepared in ethanol by impregnation because this solvent does not hurt texture of the water-sensitive MgO and Cu2PMo11VO40. The Keggin-type structure compound may be degraded partially to form oligomerized polyoxometalate when supported on MgO. However, the oligomers can rebuild as the Keggin structure again after thermal treatment in air or during the reaction. Meanwhile, the V atoms migrate out of the Keggin structure to form a lacunary structure, as observed by Fourier transform IR spectroscopy. Moreover, the presence of Cu2+ as a countercation showed an affirmative influence on the migration of V atoms, and the active sites derived from the lacunary species generated after release of V from the Keggin anion. The electron paramagnetic resonance data imply that V5+ autoreduces to V4+ in the fresh catalyst, and during the catalytic reaction a large number of V4+ ions are produced, which enhance the formation of O2- vacancies around the metal atoms. These oxygen vacancies may also improve the reoxidation function of the catalyst. This behavior is correlated to higher catalytic properties of this catalyst. The oxidative dehydrogenation of hexanol to hexanal was studied over this catalyst.

Copper hexacyanoferrate multilayer films on glassy carbon electrode modified with 4-aminobenzoic acid in aqueous solution

4-Aminobenzoic acid (4-ABA) was covalently grafted on a glassy carbon electrode (GCE) by amine cation radical formation during the electrooxidation process in 0.1 M KCl aqueous Solution. X-ray photoelectron spectroscopy (XPS) measurement proves the presence of 4-carboxylphenylamine on the GCE. Electron transfer processes of Fe(CN)(6)(3-) in solutions of various pHs at the modified electrode are studied by both cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). Changing the solution pH would result in the variation of the terminal group's charge state, based on which the surface pK(a) values were estimated. The copper hexacyanoferrate (CuHCF) multilayer films were formed on 4-ABA/GCE prepared in aqueous solution, and which exhibit good electrochemical behavior with high stability.

Effect of valence of copper in La2-xThxCuO4 on NO decomposition reaction

NO decomposition reaction was investigated over La2-xThxCuO4, in which the valence of copper was controlled by Th substitution and was characterized by XPS measurement. A close correlation between the valence of copper and the activity was observed. The activity increased with the decrease of the average oxidation number of copper, and increased with the increase of Cu+ content, suggesting that the transition metal with low valence (Cu+) is active for the reaction in the present cases.

An investigation on air stability of copper phthalocyanine-based organic thin-film transistors and device encapsulation

The device performances of copper phthalocyanine (CuPc)-based organic thin-film transistors (OTFTs) in main components of air were studied. We found that the device stored in O-2 humidified by water exhibited the changes of electric characteristics including positive-shifted threshold voltage and lower I-on/I-off but unchanged mobility, which was similar to the device exposed to room air. These changes are attributed to O-2 doping to copper phthalocyanine thin film assisted by water. Furthermore, a cross-linked polyvinyl alcohol film was used as encapsulation layer to prevent the permeation of O-2 and water, which resulted in excellent stability even when devices were placed in air for over a year. Therefore, current studies will push the development of OTFTs for practical applications.

Copper phthalocyanine organic thin-film transistors with calcium fluoride gate insulator

We report the fabrication of organic thin-film transistors (OTFTs) with copper phthalocyanine (CuPc) as the semiconductor and calcium fluoride (CaF2) as the gate dielectric on the glass substrate. The fabricated transistors show a gate voltage dependent carrier field effect mobility that ranges from 0.001 to 0.5 cm(2) V-1 s(-1). In the devices, the CaF2 dielectric is formed by thermal evaporation; thus OTFTs with a top-gate structure can be fabricated. This provides a convenient way to produce high-performance OTFTs on a large scale and should be useful for the integration of organic displays.