Sheng-Gao Liu

The gas sensitivity of a metal-insulator-semiconductor field-effect-transistor based on Langmuir–Blodgett films of a new asymmetrically substituted phthalocyanine

Abstract Langmuir–Blodgett (LB) films of an amino-tri- tert -butyl-phthalocyanine (AmBuPc) were fabricated as the semiconductor thin layer for a metal-insulator-semiconductor field-effect-transistor (MISFET). The gas sensitivity of the low-conducting LB films MISFET was measured in a NO 2 atmosphere at different concentration. The results showed that the gas concentration and the drain-source current of the AmBuPc gas sensor satisfy Langmuir adsorption isotherm.

The application of Langmuir-Blodgett films of a new asymmetrically substituted phthalocyanine, amino-tri-tert-butyl-phthalocyanine, in diodes and in all organic field-effect-transistors

Abstract Amino-tri- tert -butyl-phthalocyanine (AmBuPc) was used as the semiconductor thin layers in model Schottky diode and all organic field-effect transistor (OFET). The diode cell showed a rectifying effect with a rectification ratio of 60 at ±3.2 V. The ideality factors were 1.38 in the low voltage region and 3.09 in the high voltage region, respectively. The results of OFET proved that AmBuPc Langmuir–Blodgett (LB) films could be used as the semiconducting layer of OFET, and the OFET could function as a p-channel accumulation device. From the OFET electrical characteristics, the channel carrier mobility is calculated to be about 5.2×10 −6 cm 2 V −1 s −1 , which is higher than that of vacuum-deposited film OFET (7.8×10 −7 cm 2 V −1 s −1 ) utilizing the same polymer. This phenomenon can be explained as the highly ordered structure of AmBuPc molecules in the LB films. This suggests that a wide conduction channel is able to form in this all organic device, which provides a new method to simplify the fabrication process of OFET and improve their properties.

THE GAS SENSITIVITY OF LANGMUIR-BLODGETT FILMS OF A NEW ASYMMETRICALLY SUBSTITUTED PHTHALOCYANINE

Abstract Langmuir–Blodgett (LB) films of amino-tri- tert -butyl-phthalocyanine (AmBuPc) were fabricated. The gas sensitivities of the low-conducting LB films were measured in different concentrations of NO 2 atmosphere. The results showed that a good linear relationship exists between the logarithm of the resistance of AmBuPc gas sensor and the concentration of NO 2 , which could be explained in terms of the gas diffusion theory in the LB films. XPS results proved that the attack centers of NO 2 are the two pyrrole N-linked free H atoms of the Pc macro-ring. Temperature had significant influences to the recovery and cyclic properties of sensor and the conductivity of gas sensor. The values of activation energy are 0.14 and 0.43 eV, respectively, at temperatures lower and higher than 60°C in NO 2 .

Crystal structure, spectral and electrochemical properties of [TBA]2[Ni(i-MNT)2] , [TBA] [Ni(i-MNT)2] , [TBA]2[Ni(i-MNS)2] and related bis( 1,2-dithiolene) metal complexes

Abstract The synthesis, crystal structure and physical properties of bis(1,1-dithiolene) or bis (1,1-diselenolene) metal complexes of [TBA]2[Ni(i-MNT)2], [TBA][Ni(i-MNT)2] and [TBA]2[Ni(i-MNS)2] (i-MNT = 2,2-dicyanoethylene-1,1-dithiolate,i-MNS = 2, 2-dicyanoethylene-1, 1-diselenolate) were studied and compared to one another or to the related bis (1,2-dithiolene) metal complexes of 5,6-dihydro-1,4-dithiin-2,3-dithiolate, 1,3-dithiole-2-thione-4,5-dithiolate and 1,3-dithiole-2-one-4,5-dithiolate ligands. The structures of the complexes contain equidistant anionic stacks well separated by the counter cation sheets. The planarity and short C-S or C-Se distances in the structures indicate extensive delocalization of the π-system in the compounds. The relative low conductivities for the complexes are due to the low polarizability, large intra-and inter-stack S ··· S distances, and the relative high on-site electron-electron repulsion energy in the compounds.

Characterisation and electrical property of molten-grown CuTCNQ film material

Metallic copper foil directly reacted with molten TCNQ (7,7,8,8,-tetracyano-p-quinodimethane) under nitrogen atmosphere resulted in a CuTCNQ semiconducting film with electrical switching and memory properties. The material was characterized by Raman and UV-Vis spectral analyses as well as current-voltage characteristic measurement. The degree of charge transfer from copper to TCNQ and the electrical memory switching property are discussed. The spectral analyses, degree of charge transfer and electrical property are compared with those of both metathetically synthesised pure CuTCNQ powder and a solution-grown film material.

Reddish orange light-emitting diodes made with N, N'-bis(1-naphthyl)-3,4,9,10-perylenbis(dicarboximide)

Abstract The electroluminescence (EL) of N,N ′-bis(1-naphthyl)-3,4,9,10-perylenbis(dicarboximide) (BPD) is reported. BPD is an electron acceptor. Red emission from multilayered light-emitting diodes (LEDs) using BPD as light-emitting layer with a maximum brightness of 26 cd/m 2 was observed. The metal materials of the cathode have an effect on both the turn-on voltage and the peaks and shapes of the EL spectra of the devices. This implies that some kind of interaction exists between BPD and the cathode. In LEDs with both hole transport layer and electron transport layer, it was found that the peaks and shapes of the EL spectra of BPD change greatly with the applied bias. When the forward biased voltage is low, the EL emission colour is scarlet. As the voltage increases, the emission colour gradually blue-shifts to reddish orange. Fine structure of the EL spectrum was observed.

Preparation and spectral properties of new molecular conductors based on anion salt

Abstract Preparation, IR, UV—Vis and X-ray photoelectron spectroscopy (XPS) of three molecular conductors derived from metal complexes of DMID ligand [TBA]0.6[Ni(DMID)2], [TBA]0.44][Ni(DMID)2] and TTF[TBA]0.35[Ni(DMID)2]2 are reported (DMID = 1,3-dithiolene-2-one-4,5-dithiolate, TBA = tetrabutylammonium, TTF = tetrathiafulvalene). Electronic spectra show that the characteristic π-electronic delocalization absorption band over the ligand through π—d interactions in the complexes red-shifts with the increase of oxidization degree. In addition, XPS shows that there is a characteristic ‘satellite’ peak centered at around 168.7 eV, higher by about 4.7–5.4 eV than the main peak, in the S(2p) core-level region spectra of these partially oxidized or charge transfer conductive bisdithiolene metal complexes and, furthermore, the relative intensity of the ‘satellite’ peak increases with the oxidization degree of the complexes.

The response mechanism of aminotri-tert-butylphthalocyanine thin films to nitrogen dioxide

Asymmetrical phthalocyanines are seldom applied to gas sensor field because of its difficulties in synthesis, but asymmetrical phthalocyanines possess donor or acceptor substituents in its peripheral ring, thus have many advantages over symmetrical phthalocyanines. Aminotri-tert-butylphthalocyanine (AmBuPc) is a new asymmetrical phthalocyanines, which possesses three tertbutyl groups and one amino group that both are electron-donating substituents; this paper reports its vacuum evaporated thin films gas sensitivity in 4.1×10−5 kg/m3 nitrogen dioxide environment. The gas sensor appears good gas sensitivity to nitrogen dioxide and a linear relationship between log (resistance) and log (NO2 concentration) was observed. A possible interaction mechanism between NO2 and AmBuPc was reported using UV–Vis, IR, SEM and XPS.

The first two novel phthalocyanine-based dyads

Abstract Tri- tert -butylphthalocyanine and 1, 8-naphthaimide or 3, 4, 9, 10-perylenebis-(dicar☐imide) have been covalently linked in close proximity via a C-N bond. Through-bond electronic interaction between the two chromophores is demonstrated by electronic spectroscopy.

An Organic Field-Effect-Transistor Based on Langmuir-Blodgett Films of a New Asymmetrically Substituted Phthalocyanine, 1,8-Naphthaimide-Tri-Tert-Butylphthalocyanine

Abstract The Langmuir-Blodgett films of 1,8-naphthaimide-tri-tert-butylphthalocyanine were prepared, which can be used as the semiconductor thin layers of organic field-effect transistor (FET), functioned as a p-channel accumulation device with carriers mobility about 2.05 × 10−5cm2V−1s−1