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Synthetic Metals (v.158, #13)

Editorial Board (pp. iii).

Characteristics and performance of functionalized MWNT blended cellulose electro-active paper actuator by Sungryul Yun; Jaehwan Kim (pp. 521-526).
Functionalized multi-walled carbon nanotubes (F-MWNTs) were blended with cellulose solution to fabricate F-MWNTs/cellulose electro-active paper (EAPap) actuators. Cellulose was dissolved in LiCl/ N, N-dimethylacetamide (DMAc) solution by solvent exchange process and blended with F-MWNTs to make F-MWNTs/cellulose EAPap actuators. Their characteristics were investigated by taking X-ray diffractometer (XRD), SEM, Young's modulus measurement and water retention measurement. Actuator performance of F-MWNT/cellulose EAPap was evaluated in terms of bending displacement, resonance frequency, output force and electrical power consumption. A large bending displacement of 4.5mm and improved output force of the actuator were obtained. The actuation principle of cellulose EAPap was more likely based on ion migration effect, especially in humid condition. More explanation about the characteristics, actuation principle and performance of actuator is introduced.

Keywords: Electro-active paper; Cellulose; Functionalized multi-walled carbon nanotubes (F-MWNTs); Bending actuator; Ion migration effect

Effect on response time and diffraction efficiency of co-usage azo dye and carbon nanoparticle in nematic liquid crystal by Oğuz Köysal; S. Eren San (pp. 527-531).
In this work, the formation of the photo-induced grating and nonlinear optical properties such as diffraction efficiency ( η), refractive index modulation (Δ n), nonlinear index coefficient ( n2) of nematic liquid crystal (E7) doped by azo dye(Methyl Red) and C60 have been investigated by diffraction grating measurements. Diffraction efficiencies of 441nm pump and 632nm probe beams were measured in two-wave mixing experiment. Maximum diffraction efficiency was found 26% doped with both 1% MR and 0.5% C60, while cells without C60 had maximum diffraction efficiency of 19% under 30mW laser illumination. Rise time was found to increase with Methyl Red concentration. The nonlinear index coefficient, n2, was calculated to be 11×10−3cm2/W and highly depend on MR concentration.

Keywords: Liquid crystals; Rise time; Nonlinear index coefficient; Diffraction efficiency

Preparation and ionophoric properties of coronene fluoroionophores containing azacrown and calix[4]azacrown ethers by In-Ho Lee; Young-Min Jeon; Myoung-Seon Gong (pp. 532-538).
Novel coronene fluoroionophores, N, N′-dipropyl-5,11-bis[4-(1-aza-18-crown-6)phenyl]cornene-2,3,8,9-tetracarboxy diimide (4), and N, N′-dipropyl-5,11-bis[4-(calix[4]azacrown-5-crown-5)phenyl]coronene-2,3,8,9-tetracarboxy diimide (6), were prepared by reacting N, N′-dipropyl-5,11-bis( p-chlorophenyl)coronene-2,3,8,9-tetracarboxy diimide (3) with 1-aza-18-crown-6 or calix[4] azacrown-5-crown-5. Alternating copolymers,5 and7, with a similar repeating unit were prepared by reacting 7,16-diaza-18-crown-6 or calix[4]bisazacrown-5 with compound3. The fluoroionophoric characteristics were investigated by binding alkali, alkali earth metal and various metal ions. The model and polymeric fluoroionophores exhibited significant decreasing fluorescence effects with K+, Ag+ and Ba2+, which were attributed to photoinduced charge transfer (PCT).

Keywords: Calix[4]azacrown; Azacrown; Coronene; PCT; Fluoroionophore

Energy level alignment in N, N′-bis(1-naphthyl)- N, N′-diphenyl-1,1′-biphenyl-4,4′-diamine (NPB)/hexadecafluoro copper phthalocyanine (F16CuPc)/Au and NPB/CuPc/Au heterojunction by Sang Wan Cho; Yeonjin Yi; Myungkeun Noh; Mann-Ho Cho; Kyung-Hwa Yoo; Kwangho Jeong; Chung-Nam Whang (pp. 539-543).
The interfacial electronic structures of N, N′-bis(1-naphthyl)- N, N′-diphenyl-1,1′-biphenyl-4,4′-diamine (NPB)/hexadecafluoro copper phthalocyanine (F16CuPc)/Au and NPB/copper phthalocyanine (CuPc)/Au were investigated by in situ X-ray and ultraviolet photoelectron spectroscopy to study the hole-injection barrier depending on the ionization energy of hole-injection layer materials. Although the measured ionization energy of F16CuPc (6.30eV) was much higher than that of CuPc (5.15eV), the difference in the barrier heights of the two different films was relatively marginal (0.27eV) due to the formation of interface dipole caused by the charge redistribution. We confirmed that the interface dipole of the buffer layer (CuPc and F16CuPc) pushed down the core levels as well as the valence levels of the top organic layer (NPB) in the NPB/F16CuPc/Au and NPB/CuPc/Au heterojunction.

Keywords: PACS; 72.80.Le; 73.20.−r; 73.20.At; 85.30.TvNPB; CuPc; F; 16; CuPc; Photoemission; Interface dipole; Band diagram

Polyaniline nanofibers synthesized by rapid mixing polymerization by Junfeng Qiang; Zhuhuan Yu; Hongcai Wu; Daqin Yun (pp. 544-547).
Polyaniline (PANI) nanofibers were chemically synthesized by a rapid mixing polymerization with aniline concentration of 0.5M. The time needed for the formation of PANI in the reaction medium decreased with increase of the molar ratio of ammonium peroxydisulphate (APS)/aniline and temperature. Morphological study showed at the end of polymerization, only the ones prepared with low molar ratio of APS/aniline (e.g. 0.25 and 0.50) and temperature (e.g. 0 and 20°C) are nanofibers with diameters of ∼50nm, though the initially formed products are all nanofibers, while with increasing of molar ratio of APS/aniline to 1 and temperature to 20°C or higher, agglomerates of PANI nanofibers with diameters of ∼100nm and larger sized irregular particles were formed. The yield of PANI nanofibers was in the range of 13.4–42.3%, which is favorable for mass production of PANI nanofibers. Conductivity measurement, UV–vis and FTIR spectra were performed to characterize the products. The conductivity of the PANI nanofibers increased with molar ratio of APS/aniline at low temperature, while decreased at higher temperature, which might be resulted from the degradation of PANI molecules in the presence of more APS molecules at higher temperature.

Keywords: Polyaniline; Nanofiber; Morphology; Yield; Conductivity

Toward the saturated red phosphorescence for OLED: New iridium complexes of 2,3-bis(4-fluorophenyl)quinoxaline derivatives by Yunkyoung Ha; Ji-Hyun Seo; Young Kwan Kim (pp. 548-552).
For development of an optimized red dopant in the organic light emitting devices (OLEDs), new iridium complexes containing 2,3-dpqx derivatives as a ligand were prepared. The ligands were prepared according to Friedlander reaction. The complexes, Ir(2,3-dpqx-F2)2(acac) (2,3-dpqx-F2=2,3-bis(4-fluorophenyl)-quinoxaline; acac=acetylacetonate) and Ir(6-Me-2,3-dpqx-F2)2(acac) (6-Me-2,3-dpqx-F2=2,3-bis(4-fluorophenyl)-6-methylquinoxaline) were synthesized from the two-step reactions of IrCl3· xH2O with the corresponding ligand and characterized by1H NMR, mass spectrometry and elemental analysis. Ir(2,3-dpqx-F2)2(acac) and Ir(6-Me-2,3-dpqx-F2)2(acac) exhibited the luminescence peaks at 632 and 630nm, respectively. Their UV-spectra showed the strong3MLCT transition due to the strong coupling between the 5d orbital of the iridium center and the highest occupied molecular orbitals (HOMOs) of the ligands. The organic light emitting devices employing these compounds as the dopant were prepared and their electroluminescence was investigated. Both of the complexes exhibited the phosphorescence close to the saturated red emission at the CIE coordinate of x=0.68, y=0.31.

Keywords: Fluorinated 2,3-diphenylquinoxaline ligand; Iridium complex; Red; Phosphorescence; OLED

Comparison of electrical characteristics for p-type and n-type organic thin film transistors using copper phthalocyanine by Kihyun Kim; Tae Ho Kwak; Mi Yeon Cho; Jin Woo Lee; Jinsoo Joo (pp. 553-555).
The p-type and n-type organic thin film transistors (OTFTs) were fabricated in the same experimental conditions by using hexadecahydro copper phthalocyanine (H16CuPc) and hexadecafluoro copper phthalocynine (F16CuPc) molecules, respectively. The mobilities of H16CuPc and F16CuPc-based OTFT devices in saturation region were measured to be ∼1.22×10−3cm2/Vs and ∼1.04×10−3cm2/Vs, respectively. The temperature dependence of the mobility and activation energy ( Ea) for both OTFTs were measured in saturation and linear regions of the drain-source current. We found that the Ea of the F16CuPc-based OTFTs was lower than that of H16CuPc-based ones. The gate voltage ( Vg) dependence of the field-effect mobility measured in linear region for the F16CuPc-based OTFTs was more stable, i.e., weaker variation of the field-effect mobility with increasing Vg, than that of the H16CuPc-based ones. The high electron affinity of the hexadecafluorine (F16) in CuPc contributed to the effective electron accumulation in the active channel.

Keywords: Organic thin film transistor; n-Type; p-Type; Copper phthalocyanine; Mobility

Inkjet printed electrochemical organic electronics by Richard Mannerbro; Martin Ranlöf; Nathaniel Robinson; Robert Forchheimer (pp. 556-560).
A conventional desktop inkjet printer has been used as a combined deposition and patterning tool of electrochemical organic transistors on rough flexible carriers. The functionality of these devices rely upon redox reactions occurring at the interface between a conjugated polymer film and an electrolyte. Both the electrolyte and the conjugated polymer suspension (an aqueous dispersion of poly(3,4-ethylenedioxythiophene):poly(styrene sulphonic acid)) were additively patterned with the inkjet printer, making the electrochemical device all-inkjet printed. Basic implementations of the transistor in simple electrochemical logical circuitry have been produced. The printing technique can be anticipated to be used for the production of small series of devices based on the electrochemical technology discussed.

Keywords: Electrochemical transistor; Inkjet printing; Organic electronics; PEDOT:PSS

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