Broadband short-range surface plasmon structures for absorption enhancement in organic photovoltaics

We theoretically demonstrate a polarization-independent nanopatterned ultra-thin metallic structure supporting short-range surface plasmon polariton (SRSPP) modes to improve the performance of organic solar cells. The physical mechanism and the mode distribution of the SRSPP excited in the cell device were analyzed, and reveal that the SRSPP-assisted broadband absorption enhancement peak could be tuned by tailoring the parameters of the nanopatterned metallic structure. Three-dimensional finite-difference time domain calculations show that this plasmonic structure can enhance the optical absorption of polymer-based photovoltaics by 39% to 112%, depending on the nature of the active layer (corresponding to an enhancement in short-circuit current density by 47% to 130%). These results are promising for the design of organic photovoltaics with enhanced performance.

Solution-processable highly efficient yellow- and red-emitting phosphorescent organic light emitting devices from a small molecule bipolar host and iridium complexes

A bipolar transport compound, 2,5-bis(4-(9-(2-ethylhexyl)-9H-carbazol-3-yl) phenyl)-1,3,4-oxadiazole (CzOXD), incorporating both electron-and hole-transport functionalities, was synthesized and fully characterized by H-1 NMR, C-13 NMR, elemental analysis and mass spectrometry. Its thermal, electrochemical, electronic absorption and photoluminescent properties were studied

Enhanced resonance light scattering based on biocatalytic growth of gold nanoparticles for biosensors design

The biocatalytic growth of gold nanoparticles (Au-NPs) has been employed in the design of new optical biosensors based on the enhanced resonance light scattering (RLS) signals. Both absorption spectroscopy and transmission electron microscopy (TEM) analysis revealed Au-NP seeds could be effectively enlarged upon the reaction with H2O2, an important metabolite that could be generated by many biocatalytic reactions.

Injection, Transport, Absorption and Phosphorescence Properties of a Series of Blue-Emitting Ir(III) Emitters in OLEDs: a DFT and Time-Dependent DFT Study

Quantum-chemistry methods were explored to investigate the electronic structures, injection and transport properties, absorption and phosphorescence mechanism of a series of blue-emitting Ir(III) complexes {[(F-2-ppy)(2)Ir(pta -X/pyN4)], where F-2-ppy = (2,4-difluoro)phenylpyridine; pta = pyridine-1,2,4-triazole; X = phenyl(1); p-tolyl (2); 2,6-difluororophenyl (3); -CF3 (4), and pyN4 = pyridine-1,2,4-tetrazolate (5)}, which are used as emitters in organic light-emitting diodes (OLEDs). The mobility of hole and electron were studied computationally based on the Marcus theory. Calculations of Ionization potentials (IPs) and electron affinities (EAs) were used to evaluate the injection abilities of holes and electrons into these complexes.

A novel technique for NACE coupled with simultaneous electrochemiluminescence and electrochemical detection for fast analysis of tertiary amines

A simultaneous electrochemiluminescence (ECL) and electrochemical (EC) detection scheme for NACE was presented for fast analysis of tertiary amines. Both ECL and EC signals were generated at the same Pt electrode. Triethylamine (TEA), tripropylamine (TPrA), chlorpromazine, promethazine, and dioxopromethazine (DPZ) were selected to validate NACE-ECL/EC dual detection strategy. The linear ranges for TEA and TPrA were 0.01-500 and 0.01-10 mu M with the detection limits of 8.0 and 5.0 nM (S/N=3), respectively. The RSDs (n = 6) of the migration time and the ECL intensity for 1 mu M TEA and 0.5 mu M TPrA were 0.1 and 2.8%, and 0.2 and 1.8% with theoretical plate numbers of 180 000 and 700 000 per meter, respectively. These two analytes could be separated within 92 s and the Pt electrode did not need reactivation during the experiments.

Combining chemical reduction with an electrochemical technique for the simultaneous detection of Cr(VI), Pb(II) and Cd(II)

This work herein reports the approach for the simultaneous determination of heavy metal ions including cadmium (Cd(II)), lead (Pb(II)), and chromium (Cr(VI)) using a bismuth film electrode (BFE) by anodic stripping voltammertry (ASV). The BFE used was plated in situ. Due to the reduction of Cr(VI) with H2O2 in the acid medium, on one hand, the Cr(III) was produced and Cr(VI) was indirectly detected by monitoring the content of Cr(III) using square-wave ASV. On the other hand, Pb(II) was also released from the complex between Pb(II) and Cr(VI). Furthermore, the coexistence of the Cd(II) was also simultaneously detected with Pb(II) and Cr(VI) in this system as a result of the formation of an alloy with Bi. The detection limits of this method were 1.39 ppb for Cd(II), 2.47 ppb for Pb(II) and 5.27 ppb for Cr(VI) with a preconcentration time of 120 s under optimal conditions (S/N = 3), respectively. Furthermore, the sensitivity of this method can be improved by controlling the deposition time or by using a cation-exchange polymer (such as Nafion) modified electrode.

Sr3Al2O5Cl2:Ce3+,Eu2+: A potential tunable yellow-to-white-emitting phosphor for ultraviolet light emitting diodes

The Sr3Al2O5Cl2:Ce3+,Eu2+ phosphors were prepared by solid state reaction. The obtained phosphors exhibit a strong absorption in the UV-visible region and have two intense emission bands at 444 and 609 nm. The energy transfer from the Ce3+ to Eu2+ ions was observed, and the critical distance has been estimated to be about 24.5 A by spectral overlap method. Furthermore, the developed phosphors can generate lights from yellow-to-white region under the excitation of UV radiation by appropriately tuning the activator content, indicating that they have potential applications as an UV-convertible phosphor for white light emitting diodes.

High-pressure sintering the novel light (W0.25Al0.75)C hard material without binder phase

A novel hard material of (W0.25Al75)C has been successfully prepared by the high-pressure sintering process without the addition of any binder phase. The high-pressure is a suitable and powerful technique for sintering the binderless hard material, the relative density of the hard material can reach 99.6% under high-pressure sintering. The density of the novel light hard material is only 6.2371 g cm(-3), which is much lighter than the normal hard material. The hardness of the light hard material can reach 18.89 GPa even the aluminum content get the astonished 75%.

New carbazole-based copolymers as amorphous hole-transporting materials for multilayer light-emitting diodes

New carbazole-based copolymers, which contain various concentrations of 9-alkyl-3, 6-carbazole fragments in the main chain connected via alkylene spacers, have been synthesized by Ni(0)-catalyzed Yamamoto-type aryl-aryl coupling reactions. Full characterization of the copolymer structure by NMR spectroscopy and elemental analysis is presented. These compounds represent amorphous materials of high thermal stability with glass transition temperatures of 151-162 degrees C and thermal decomposition starting at temperatures > 390 degrees C. UV-Vis absorption and photoluminescence emission of the copolymers confirmed that the effectively conjugated segment in the 3,6-linked carbazole-type copolymers is limited to dyads (dimeric units). However, copolymers with varying concentrations of the oligocarbazole chromophores demonstrate different charge injection and transport properties in multilayer light-emitting diodes with the copolymers as the hole transport and Alq(3) as the electroluminescent/electron transport layer. The device based on a copolymer composed of oligocarbazole blocks with an average length of around four carbazoles exhibited the best overall performance with a turn-on voltage of 3.5 V, a maximal photometric efficiency of 4.1 cd center dot A(-1) and maximum brightness of about 4 200 cd center dot m(-2).

Highly efficient iridium(III) complexes with diphenylquinoline ligands for organic light-emitting diodes: Synthesis and effect of fluorinated substitutes on electrochemistry, photophysics and electroluminescence

A series of novel cyclometalated iridium(III) complexes bearing 2,4-diphenylquinoline ligands with fluorinated substituent were prepared and characterized by elemental analysis, NMR and mass spectroscopy. The cyclic voltammetry, absorption, emission and electroluminescent properties of these complexes were systematically investigated. Electrochemical studies showed that the oxidation of the fluorinated complexes occurred at more positive potentials (in the range 0.57-0.69 V) than the unfluorinated complex 1 (0.42 V). In view of the energy level, the lowering of the LUMO by fluorination is significantly less than that of the HOMO. The weak and low energies absorption bands in the range of 300-600 nm are well resolved, likely associated with MLCT and (3)pi-pi* transitions. These complexes show strong orange red emission both in the solution and solid state. The emission maxima of the fluorinated complexes showed blue shift by 9, 24 and 15 nm for 2, 3 and 4, respectively, with respect to the unfluorinated analogous 1. Multilayered organic light-emitting diodes (OLEDs) were fabricated by using the complexes as dopant materials. Significantly higher performance and lower turn-on voltage were achieved using the fluorinated complexes as the emitter than that using the unfluorinated counterpart 1 under the same doping level.

Novel PPV-based light-emitting polymers containing siloxane moiety

Two PPV-based copolymers consisting siloxane linkage have been synthesized by melt condensation of bisphenol and dianilinodimethylsilane. The rigid PPV segments act as chromosphere and allow fine turning of band gap for blue-light emission, while the flexible siloxane units lead to the effective interruption of conjugation and the enhancement of solubility. The UV-vis absorption, photoluminescent and eletroluminescent properties have been studied.

Determination of molecular weight and molecular sizes of polymers by high temperature gel permeation chromatography with a static and dynamic laser light scattering detector

Flow-mode static and dynamic laser light scattering (SLS/DLS) studies of polymers, including polystyrene, polyethylene, polypropylene and poly(dimethylsiloxane) (PDMS), in 1,2,4-trichlorobenzene (TCB) at 150 degreesC were performed on a high temperature gel permeation chromatography (GPC) coupled with a SLS/DLS detector. Both absolute molecular weight (M) and molecular sizes (radius of gyration, R-g and hydrodynamic radius, R-h) of polymers eluting from the GPC columns were obtained simultaneously. The conformation of different polymers in TCB at 150 degreesC were discussed according to the scaling relationships between R-g, R-h and M and the rho-ratio (p = R-g/R-h). Flow-mode DLS results of PDMS were verified by batch-mode DLS study of the same sample. The presented technique was proved to be a convenient and quick method to study the shape and conformation of polymers in solution at high temperature. However, the flow-mode DLS was only applicable for high molecular weight polymers with a higher refractive index increment such as PDMS.

Liquid crystalline and light emitting polyacetylenes: Synthesis and properties of biphenyl-containing poly(1-alkynes) with different functional bridges and spacer lengths

Biphenyl- (Biph-) containing 1-alkynes (3 and 4) and their polymers (1 and 2) with varying bridge groups and spacer lengths were synthesized and the effects of the structural variation on their properties, especially their mesomorphism and photoluminescence behaviors, were studied. The acetylene monomers 3(3) [HCdropC(CH2)(3)O-Biph-OCO(CH2)(10)CH3] and 4(m) [HCdropC(CH2)(m)OCO-Biph-OCO(CH2)(10)-CH3, m = 3, 4] were prepared by sequential etherization and esterification reactions of 1-alkynes. While 3(3) exhibits enantiotropic crystal E and SmB mesophases, its structural cousin 4(3) displays only a monotropic SmB phase. Enantiotropic SmA and SmB mesophases are, however, developed when the spacer length is increased to 4. Polymerizations of the monomers are effected by Mo-, W-, Rh-, and Fe-based catalysts, with the WCl6-Ph4Sn catalyst giving the best results (isolation yield up to 85% and M-w up to 59000). The polymers were characterized by IR, UV, NMR, TGA, DSC, POM, XRD, and PL analyses. Compared to 1(3), 2(3) shows a red-shifted absorption, a higher T-i, and a better packed interdigitated bilayer SmA(d) structure, while the mesophase of 2(4) involves monolayer-packing arrangements of the mesogens. Upon photoexcitation, 1(3) emits almost no light but 2(m) gives a strong ultraviolet emission (lambda(max) similar to 350 nm), whose intensity increases with the spacer length.

A DYNAMIC LASER LIGHT-SCATTERING STUDY OF CHITOSAN IN AQUEOUS-SOLUTION

The solution behavior of four chitosans (91% deacetylated chitin) with different molecular weights in 0.2M CH3COOH/0.1M CH3COONa aqueous solution was investigated at 25 degrees C by dynamic laser light scattering (LLS). The Laplace inversion of the precisely measured intensity-intensity time correlation function leads us to an estimate of the line-width distribution G(Gamma), which could be further reduced to a translational diffusion coefficient distribution G(D). By using a combination of static and dynamic LLS results, i.e. Mw and G(D), we were able to establish a calibration of D = k(D)M(-alpha D) with k(D) = (3.14 +/- 0.20) X 10(-4) and alpha(D) = 0.655 +/- 0.015. By using this calibration, we successfully converted G(D) into a molecular weight distribution f(w)(M). The larger alpha(D) value confirms that the chitosan chain is slightly extended in aqueous solution even in the presence of salts. This is mainly due to its backbone and polyelectrolytes nature. As a very sensitive technique, our dynamic LLS results also revealed that even in dilute solution chitosan still forms a small amount of larger sized aggregates that have ben overlooked in previous studies. The calibration obtained in this study will provide another way to characterize the molecular weight distribution of chitosan in aqueous solution at room temperature. (C) 1995 John Wiley & Sons, Inc.

Isolation of the main light-harvesting chlorophyll a/b-protein complex from thylakoid membranes of marine alga, Bryopsis corticulans by a direct method

The main chlorophyll a/b light-harvesting complex (LHC 11) has been isolated directly from thylakoid membranes of marine green alga (Bryopsis corticulans Setch.) by two consecutive runs of anion exchange and gel-filtration chromatography. LHC 11 proteins in the membrane extracts treated with 3% n-Octyl-b-D-glucopyranoside (OG) obtained specific binding ability on Q Sepharose column, and thus were isolated from the thylakoid membranes in a highly selective fraction. The monomeric, trimeric and oligomeric subcomplexes of LHC 11 have been obtained by fractionation of the LHC 11 mixes with sucrose density gradient ultracentrifugation. The SDS-PAGE analysis of peptide composition and absorption spectrum showed that LHC 11 monomers, trimers and oligomers prepared through this work were intact and in high purity. Our report is the first to show that it is possible to purify LHC If directly from thylakoid membranes without extensively biochemical purification.