零价金属降解多氯联苯(PCBs)

多氯联苯(polychlorinated biphenyls,简称PCBs)是一类对环境有不利影响的有毒有机物,它在环境中广泛而大量分布。许多科学家都在致力于有效处理PCBs污染介质(包括水、油、沉积物和土壤)的修复技术的研究。本文综述了国内外在零价金属还原脱氯降解PCBs领域的研究状况。在高温等特殊条件下或有钯、铂、镍和铜等催化剂存在的条件下,零价金属能有效促进PCBs还原脱氯。讨论了零价铁还原脱氯的3个可能的途径:金属直接反应,将零价铁表面的电子转移到有机氯化物使之脱氯;铁腐蚀的直接产物Fe2+具有还原能力,它可使得一部分氯代烃脱氯;铁反应产生的氢气可使有机氯化物还原。评述了零价金属还原脱氯PCBs具有有效、廉价和易得的特点。展望了零价金属还原脱氯降解PCBs研究领域的发展前景。

污染土壤中多环芳烃的共代谢降解过程

The biodegradation of most PAHs with high molecular weight is carried out by means of cometabolism. The development of the theory about cometabolic degradation is reviewed in this paper, and the achievements on the cometabolic degradations of PAHs are also summarized. It is demonstrated that glucose, biphenyl, organic acids and mineral oil could be used as cometabolic substrate to enhance the degradation rate of PAHs, and there are complex interactions in the microbiological degradation process among different PAHs. Some low molecular PAHs could serve as cometabolic substrate, which could also be used to enhance the transformation rate of high molecular weight recalcitrant PAHs. To achieve the cometabolic degradation of the PAHs in the soils, the following problems must be solved: the screening out of efficient degradative strains, the selection of the appropriate cometabolic substrate, the addition of surfactant if necessary and the optimization of operational parameters with the contaminated soils. These problems are the important parts of the project for the cometabolic degradation of PAHs in the soils.

Synthesis and structure of new low dimensional polymeric haloplumbate(II) complexes [Pb4Br12(C40H40N8)] and [Pb4Cl12(C40H40N8)]center dot H2O

New low dimensional polymeric haloplumbate(II) complexes of the dication of (4,4'-bis(imidazolyl-ylmethyl)biphenyl) were synthesised and their crystal structures determined. Complex 1, [Pb4Br12(C40H40N8)], has cis-edge-shared, octahedral, lead bromide double chains. In compound 2 [Pb4Cl12(C40H40N8)]center dot H2O, the inorganic chains are corner-shared, square pyramidal chains of lead chloride. In both compounds the organic ammoniums form regular layers that alternate with the inorganic chains.

High gain in hybrid transistors with BAlq(3)/Alq(3) isotype heterostructure emitter

We report the fabrication of permeable metal-base transistors based on bis(2-methyl-8-quinolinolato-N1,O8)-(1,1'-biphenyl-4-olato) aluminum (BAlq(3))/tri(8-hydroxyquinoline) aluminum (Alq(3)) isotype heterostructure as emitter layer. In this transistor, n-Si was used as the collector, LiF/Al as the emitter electrode, and Au/Al bilayer metal as the base. We show that the leakage current is greatly reduced in Al/n-Si/Au/Al/BAlq(3)/Alq(3)/LiF/Al devices with respect to Al/n-Si/Au/Al/Alq(3)/LiF/Al devices due to the utilization of BAlq(3)/Alq(3) isotype heterostructure emitter, leading to high common-base and common-emitter current gains at low driving voltages.

Hybrid permeable metal-base transistor with large common-emitter current gain and low operational voltage

We demonstrate the suitability of N,N'-diphenyl-N,N'-bis(1-naphthylphenyl)-1,1'-biphenyl-4,4'-diamine (NPB), an organic semiconductor widely used in organic light-emitting diodes (OLEDs), for high-gain, low operational voltage nanostructured vertical-architecture transistors, which operate as permeable-base transistors. By introducing vanadium oxide (V2O5) between the injecting metal and NPB layer at the transistor emitter, we reduced the emitter operational voltage.

Mechanisms of efficiency enhancement in the doped electroluminescent devices based on a europium complex

In this study, we investigated the dependence of electroluminescence (EL) efficiency on carrier distribution in the light-emitting layer (EML) of the device based on Eu(TTA)(3)phen (TTA = thenoyltrifluoroacetone, phen = 1, 10-phenanthroline) doped 4,4'-N,N'-dicarbazole- biphenyl (CBP) system. We found that EL efficiency increases monotonously with increasing hole injection even when holes are the majority carriers. This phenomenon was attributed to the accumulation of holes in EML, which improves the balance of holes and electrons on Eu(TTA)(3)phen molecules, thus enhancing the EL efficiency.

Magnesium-Based 3D Metal-Organic Framework Exhibiting Hydrogen-Sorption Hysteresis

A new magnesium metal-organic framework (MOF) based on an asymmetrical ligand, biphenyl-3,4',5-tricarboxylate (H3PT) has been synthesized and structurally characterized. MOF Mg-3(BPT)(2)(H2O)(4) (1) consists of 10 hexagonal nanotube-like channels and exhibits pronounced hydrogen-sorption hysteresis at medium pressure.

Synthesis and properties of novel sulfonated poly(phenylquinoxaline)s as proton exchange membranes

Two series of sulfonated poly(phenylquinoxaline)s (SPPQ-x and SPPQ(O)-x, x refers to molar percentage of sulfonated tetraamine monomer) were first synthesized from a sulfonated tetraamine (4,4'-bis(3,4-diaminophenoxy)biphenyl-3.3'-disulfonic acid) and two aromatic bisbenzils (4-phenylglyoxalylbenzil and p,p'-oxydibenzil) in a mild condition. The structures of SPPQ-x and SPPQ(0)-x were characterized by IR and H-1 NMR spectra. The properties of these polymer films, such as water uptake, water swelling ratio, proton conductivity, thermal properties, methanol permeability, hydrolytic and oxidative stability were also investigated. The resulting polymers generally showed good solubility in DMAc and DMSO. Flexible and tough membranes with high mechanical strength were prepared. They show very high thermal, thermooxidative, hydrolytic stabilities and low methanol permeability. SPPQ-100 with the IEC value (2.41 mmol/g) displays the conductivity of 0.1 S/cm and a swelling ratio of 7.3% at 100 degrees C.

Synthesis and properties of water stable poly[bis(benzimidazobenzisoquinolinone)] ionomers for proton exchange membranes fuel cells

A novel sulfonated tetraamine, di(triethylammonium)-4,4'-bis(3,4-diaminophenoxy)biphenyl-3,3'-disulfonate (BAPBDS), was successfully synthesized by nucleophilic aromatic substitution of 4,4'-dihydroxybiphenyl with 5-chloro-2-nitroaniline, followed by sulfonation and reduction. A high-temperature polycondensation of sulfonated tetraamine, non-sulfonated tetraamine (4,4 -bis(3,4-aminophenoxy)biphenyl) and 1,4,5,8-naphthalenetetracarboxylic dianhydride (a) or 4,4'-binaphthyl-1,1',8,8'-tetracarboxylic dianydride (b) gave the poly[bis(benzimidazobenzisoquinolinones)] ionomers SPBIBI-a(x) or SPBIBI-b(x), where x refers to the molar percentage of the sulfonated tetraamine monomer. Flexible and tough membranes of high mechanical strength were obtained by solution casting and the electrolyte properties of the polymers were intensively investigated. The ionomer membranes displayed excellent dimensional and hydrolytic stabilities.

Ambipolar permeable metal-base transistor based on NPB/C-60 heterojunction

In this paper, we report the fabrication of permeable metal-base organic transistors based on N,N'-diphenyl-N,N'-bis(1-naphthylphenyl)-1,1'-biphenyl-4,4'-diamine (NPB)/C-60 heterojunction as both emitter and collector. By applying different polarities of voltage bias to the collector and the base, and input current to the emitter, the ambipolar behavior can be observed. The device demonstrates excellent common-base characteristics both in P-type and N-type modes with common-base current gains of 0.998 and 0.999, respectively.

Achieving highly efficient white organic light-emitting diodes with reduced efficiency roll-off

A highly efficient and colour-stable three-wavelength white organic light-emitting diode with the structure of indium tin oxide (ITO)/MoO3/N,N'-diphenyl-N,N'-bis (1-naphthylphenyl)-1,1'-biphenyl-4,4'-diamine (NPB)/4,4'-N,N'-dicarbazole-biphenyl (CBP): bis(2,4-diphenylquinolyl-N,C-2') iridium( acetylacetonate) (PPQ)(2)Ir(acac)/NPB/p-bis(p-N,N-diphenyl-aminostyryl)benzene (DSA-Ph):2-methyl-9,10-di(2-naphthyl) anthracene (MADN)/tris (8-hydroxyquinoline) aluminum (AlQ): 10-(2-Benzothiazolyl)-2,3,6,7-tetrahydro-1,1,7,7-tetramethyl-1H,5H,11H-(1)-benzopyropyrano(6,7-8-i,j)quinolizin-11-one (C545T)/AlQ/LiF/Al is fabricated and characterized. A current efficiency of 12.3 cdA(-1) at an illumination-relevant brightness of 1000 cd m(-2) is obtained, which rolls off slightly to 10.3 cdA(-1) at a rather high brightness of 10 000 cd m(-2). We attribute this great reduction in the efficiency roll-off to the wise management of singlet and triplet excitons between emissive layers as well as the superior charge injection and diffusion balance in the device.

Vertical structure permeable-base hybrid transistors based on multilayered metal base for stable electrical characteristics

In this work we present a permeable base transistor consisting of a 60 nm thick N,N'diphenyl-N,N'-bis(1-naphthylphenyl)-1,1'-biphenyl-4,4'-diamine layer or a 40 nm thick 2,6-diphenyl-indenofluorene layer as the emitter, a CalAl/Ca multilayer as the metal base, and p-Si as collector. In the base, the Ca layers are 5 nm thick and the Al layer was varied between 10 and 40 nm. the best results obtained with a 20 nm thick layer. The devices present common-base current gain with both organic layer and silicon acting as emitter, but there is only observable common-emitter current gain when the organic semiconductor acts as emitter. The obtained common-emitter current gain, similar to 2, is independent on collector-emitter voltage, base current and organic emitter in a reasonable wide interval. Air exposure or annealing of the base is necessary to achieve these characteristics, indicating that an oxide layer is beneficial to proper device operation.

Nonconjugated Carbazoles: A Series of Novel Host Materials for Highly Efficient Blue Electrophosphorescent OLEDs

A series of carbazole derivatives was synthesized and their electrical and photophysical properties were investigated. It is shown that the triplet energy levels of these hosts are higher than that of the most popular blue phosphorescent material iridium(III) bis[(4,6-difluorophenyl)pyridinato-N,C-2'] picolinate (FIrpic) and the most extensively used phosphorescent host material 4,4'-N,N'-dicarbazole-biphenyl (CBP). These new host materials also showed good thermal stability and high glass transition temperatures (T-g) ranging from 78 to 115 degrees C as the linkage group between the carbazoles was altered. Photophysical measurements indicate that the energy transfer between these new hosts and FIrpic is more efficient than that between CBP and FIrpic. Devices incorporating these novel carbazole derivatives as the host material doped with FIrpic were fabricated with the configurations of ITO/NPB (40 nm)/host:FIrpic (30 nm)/BCP (15 nm)/AlQ (30 nm)/LiF (1 nm)/Al (150 nm). High efficiencies (up to 13.4 cd/A) have been obtained when 1,4-bis (4-(9H-carbazol-9-yl)phenyl)cyclohexane (CBPCH) and bis(4-(9H-carbazol-9-yl)phenyl) ether (CBPE) were used as the host, respectively.

A new class of high T-g and organosoluble polynaphthalimides

A new class of soluble six-membered ring polynaphthalimides (PNIs) was synthesized from asymmetrical fluorinated naphthalenesubstituted monomers. All the resulting PNIs were easily soluble in many organic solvents, such as N-methyl-2-pyrrolidinone (NMP), N,N-dimethylacetamide (DMAc), dimethyl sulfoxide (DMSO). and chloroform. They also showed good thermal stability with glass transition temperature of 340-386 degrees C, 10% weight loss temperature in excess of 529 degrees C. Polyimide 3c could be solution-cast into tough and flexible film. The film had a tensile strength, elongation at break, and Young's modulus of about 117.6 Wa, 23.6%, and 1.77 GPa, respectively. The gas permeation property of the film of 3c was investigated with oxygen permeability coefficient (PO2 = 3.99) and permeability selectivity coefficient of oxygen to nitrogen (P-O2/P-N2 = 5.27). Therefore, these materials are expected to be a good alternative to PIs based on five-membered rings with applications in gas separation membranes.

Conversion process of the dominant electroluminescence mechanism in a molecularly doped organic light-emitting device with only electron trapping

In this work, the detailed conversion process of the dominant electroluminescence (EL) mechanism in a device with Eu(TTA)(3)phen (TTA=thenoyltrifluoroacetone, phen=1,10-phenanthroline) doped CBP (4,4(')-N,N-'-dicarbazole-biphenyl) film as the emitting layer was investigated by analyzing the evolution of carrier distribution on dye and host molecules with increasing voltage. Firstly, it was confirmed that only electrons can be trapped in Eu(TTA)(3)phen doped CBP. As a result, holes and electrons would be situated on CBP and Eu(TTA)(3)phen molecules, respectively, and thus creates an unbalanced carrier distribution on both dye and host molecules. With the help of EL and photoluminescence spectra, the distribution of holes and electrons on both Eu(TTA)(3)phen and CBP molecules was demonstrated to change gradually with increasing voltage. Therefore, the dominant EL mechanism in this device changes gradually from carrier trapping at relatively low voltage to Forster energy transfer at relatively high voltage.