Peiji Wu

The preparation, characterization of amorphous Cu–TCNQ film with a low degree of charge-transfer (DCT) and its electric switching properties

Abstract Two sorts of Cu–TCNQ films were prepared and characterized. One kind of film is amorphous, exhibiting novel electrical switching effects. The device configuration is a sandwich structure, typically, Al/amorphous Cu–TCNQ thin film/Cu. Films are grown on a Cu substrate by immersion in saturated malononitrile solutions of TCNQ (7,7,8,8-tetracyanoquinodimethane) at 50∼80 °C. The degree of charge transfer (DCT) in this film is estimated at 0.41 according to the position of the IR absorption line of the CN vibration. The current–voltage ( I – V ) characteristics reveal an abrupt decrease of the impedance from 2.4 KΩ to 6Ω (for a typical sample) at a field strength about 4×10 3 V cm −1 for a 1 μm thick film. The low impedance memory state can be erased by the application of large current in either direction. Moreover, the device switches to the low impedance state again when the field strength across the film is decreased below 2×10 4 V cm −1 . The device is stable over a long period of time and has a life time of roughly 50 switching cycles. A possible switching mechanism is proposed.

SYNTHESIS, ELECTRICAL PROPERTIES OF NI(DMIT)2 - COMPLEXES AND X-RAY CRYSTAL STRUCTURE OF EDA NI(DMIT)2 (DMIT=1,3-DITHIOL-2-THIONE-4,5-DITHIOLATE)

Abstract The complexes [MDC][Ni(dmit)2] (1) (MDC = dimethylamino-dithiolmethyl carbonium), [MDA][Ni(dmit)2] (2) (MDA = 2-dimethylamino-1,3-dithiolanylium), [PDA][Ni(dmit)2] (3) (PDA = 2-cyclopentaamino-1,3-dithiolanylium) and [EDA][Ni(dmit)2] (4) (EDA = 2-diethylamino-1,3-dithiolanylium) have been prepared. All these complexes behave as semiconductors. However, the conductivities increased by 103−105 times when they were doped with iodine. A single X-ray crystal structure analysis of complex 4 reveals that there are short S···S contacts between cation and anion complexes. The triclinic system, space group P 1 , has cell dimensions a = 10.113(3), b = 13.612(4), c = 9.151(3) A , α = 69.57(3), β = 77.22(3), γ = 82.54(3)° and Z = 2 . Full-matrix least-squares refinement, based on 2801 reflections converged at R = 0.062.

Formation of disk-like aggregates of cadmium sulfide nanocrystals at the oil–water interface

Abstract In the present study, we report the synthesis of CdS nanoparticles using a liquid–liquid interface reaction technique. CdS nano-particles and disk-like aggregates of CdS nano-particles were obtained at the oil/water interface. The disk-like aggregates of CdS nano-particles were characterized by transmission electron microscopy and electron diffraction. Energy-dispersive spectroscopy was employed to confirm the components of the disk-like aggregates of CdS nano-particles.

The new semiconducting magnetic charge transfer salt (BEDT-TTF)4·H2O·Fe(C2O4)3·C6H5NO2: crystal structure and physical properties

Abstract The structure, resistivity and ESR of a new molecular charge transfer salt β-(BEDT-TTF)4·H2O·Fe(C2O4)3·C6H5NO2 (BEDT-TTF = bis(ethylenedithio)tetrathiofulvalene) are studied. The structure of the salt consists of successive layers of BEDT-TTF which are packed according to β-type and layers of approximately hexagonal geometry containing alternating H2O and Fe(C2O4)33−, with C6H5NO2 lying within the hexagonal cavity. Its main crystallographic parameters are found to be: M = 1999.6(1), a = 10.31(8), b = 20.14(8), c = 35.34(4) A , β = 92.21(9)°; V = 7342.0(5) A 3 , space group C2 c ; Z = 4 . The conductivity of this salt at room temperature is 10 S cm−1 and it shows semiconducting behaviour from 20 to 300 K. The ESR linewidth is found to be 38.1 (300 K), which is substantially wider than a typical linewidth for BEDT-TTF based radical cation salts of the β-type, indicating a two-dimensional character. The comparison of crystal structure and properties of the title compound with other salts of this family (BEDT-TTF)4·A·Fe(C2O4)3·C6H5NO2, where A = H2O, K+, NH4+, is also carried out.

Synthesis, structure and physical properties of ET2Br·3H2O

Abstract Electrochemical oxidation of BEDT-TTF (bis(ethylenedithio)tetrathiofulvalene) in the solution chloroform/carbon disulfide (3:1) in the presence of TBABr as a supporting electrolyte at low current results in the formation of (BEDT-TTF) 2 Br·3H 2 O complex. The complexs composition has been determined by X-ray analysis and its main crystallographic parameters are found to be: M =903.2(1); a =32.784(6) A, b =6.729(2) A, c =14.991(4) A, α = s = γ =90°, V =3307.3(12) A 3 ; Z =4; space group P cca . The conductivity of this complex at room temperature is 5.1 Ω −1 cm −1 . It shows weak metallic behavior above 230 k and below this temperature it becomes semiconducting. The ESR line width is found to be 40.10 G at room temperature.

The New Semiconducting Magnetic Charge Transfer Salt (BEDT-TTF)4 • H2O • Fe(C2O4)3 • C6H5NO2: Crystal Structure and Physical Properties

Abstract The structure, resistivity and ESR of a new molecular charge transfer salt β-(salt (BEDT-TTF)4 • H2O • Fe(C2O4)3 • C6H5NO2 (BEDT-TTF = bis (ethylenedithio)tetrathiofulvalene) are studied. The structure of the salt consists of successive layers of BEDT-TTF which are packed according to β-type and layers of approximately hexagonal geometry containing alternating H2O and Fe(C2O4)3 3−, with C6H5NO2 lying within the hexagonal cavity. Its main crystallographic parameters are found to be: M = 1999.6(1), a = 10.31(8), b = 20.14(8), c = 35.34(4) A, β = 92.21(9)° V = 7342.0(5) A3, space group C2/c; Z = 4. The conductivity of this salt at room temperature is l0 Scm−1 and shows semiconducting behaviour from 20 to 300K. The ESR line width is found to be 38.1 (300 K), which is substantially wider than a typical line width for BEDT-TTF based radical cation salts of the β-type, indicating a two-dimensional character. The comparison of crystal structure and properties of the title compound with other salts of thi...

Nonlinear optical polyimide with high thermal stability prepared by simultaneous poling and polymerization

The highTg polyimide embedded with a novel imidazol-typed chromophore 2-[5-(4-nitrostilbenyl)thienyl]-4,5-di(4-aminophenyl)imidazole (NSTDAPI) was prepared using the “simultaneous poling and polymerization” technique. The glass transition temperature (Tg) is 304° C and the initial decomposition temperature (Td) is 330° C. Thein-situ second harmonic generation (in-situ SHG) measurement was performed to study its poling behavior and the stability of the poling-induced orientation. The nonlinear optical (NLO) coefficientd33 of poled polyimide film is 32.2 pm/V at 1064 nm fundamental wavelength. The SHG signal of the poled polymer film was quite stable below 200°C, and then began to decay rapidly above 220° C. The half-decay temperature of dipole orientation for the film is 250° C.

Preparation, crystal structure and electrical conductivity of [EDA][Ni(dmit)2]3 (dmit=1,3-dithiole-2-thione-4,5-dithiolate)

Abstract The synthesis, conductivity behavior and crystal structure of the ion radical salt [EDA][Ni(dmit)2]3 (EDA=2-diethylamino-1,3-dithiolanylium; dmit=1,3-dithiole-2-thione-4,5-dithiolate) are described. The crystal possesses the triclinic system. The structure consists of thick layers of stacked Ni(dmit)2 entities separated by EDA cations. Short S⋯S interstack distances are observed such that two-dimensional networks of closely spaced Ni(dmit)2 are formed and reflected in low anisotropy in conductivities measured in the ab plane (σa:σb: σc=1:2:10−4). The room-temperature four-probe conductivity measured along the longest axis (b axis) is about 0.2 S cm−1. Temperature dependence shows a thermally activated conductivity with activation energy of 0.11 eV.

New bisdithiolene metal complex of the 2-thioxo-1,3-dithiole-4,5-dithiolato(dmit) ligand. Preparation, structure and physical properties

Abstract The complex HMEDA[Ni(dmit) 2 ] 2 I (HMEDA=Hexamethylethylenediammonium) has been prepared. A single X-ray crystal structure analysis reveals that there are short S⋯S contacts between Ni(dmit) 2 dimmers. The monoclinic system, space group p 2/ n , has cell dimensions: a =11.710(3) A, b =22.559(5) A, c =7.374(2) A, β =93.000(3) 0 , V =1945.3(8) A 3 , z =4. Full-matrix least-squares refinement, based on 2989 reflections converged at R =0.0686. The conductivity of this salt at room temperature is 0.1 S cm −1 and it shows semiconducting behavior from 20 to 300 K.

PREPARATION AND ELECTROCHEMICAL PROPERTIES OF A NEW ORGANIC DONOR BIS-(HYDROXYMETHYLETHYLENEDITHIO)-TETRATHIAFULV ALENE

Abstract Preparation and characterization of a new organic donor molecule bis(hydroxymethylethylenedithio)-tetrathiafulvalene is reported. Cyclic voltammogram (Figure 1) of the donor molecule shows two reversible redox processes in n-Bu4NBF4/DMF system at half-wave potentials of 0.64 and 0.81 V vs SCE, respectively, which are higher than those of the well-known organic donor molecule bis(ethylenedithio)-tetrathiafulvalene with the corresponding values of 0.60 and 0.73 V, respectively. In addition, the π-donor ability of some related donor molecules of the same series is compared and the effects of solvents on the half-wave potentials of the donors are studied.