Enhanced efficiency of light-emitting polymers through intra-molecular energy transfer

To enhance the photoluminescence and electroluminescence efficiency, light-emitting polymers with energy transferring chromophores including N,N,N'N'-phenylene-diamine, naphthalene-imide, oxadiazole, meta-phenylene vinylene are designed and synthesized.

Improved efficiency of PPV due to bulky tetraphenylmethane pendants

A PPV derivative containing bulky tetraphenylmethane side chains was synthesised. Its optical properties were examined. Compared to its parent PPV polymer, its UV-Vis absorption and PL showed less red-shift from solution to film, its PL showed much less concentration quenching effect and higher efficiency, its EL device showed 9-fold enhanced efficiency. These improvements were attributed to weakened inter-chain interaction caused by the tetraphenylmethane group.

Exploring the ester-exchange reactions of diester-diterpenoid alkaloids in the aconite decoction process by electrospray ionization tandem mass spectrometry

The chemical components in the decoctions of Chinese herbal medicines are not always the same as those in the crude herbs because of the insolubility or instability of some compounds. In this work electrospray ionization tandem mass spectrometry was used to explore the ester-exchange reactions for aconitine-type diester-diterpenoid alkaloids occurring during the process of decocting aconite root. The aconitines were screened in a diverse range of samples, including crude aconite, decoction of crude aconite, residues from decoction of crude aconite, prepared aconite, decoction of prepared aconite, decoction of prepared aconite with added palmitic acid, and decoction of a mixture of mesaconitine and hypaconitine standards with liquorice root. It was found that diester-diterpenoid aconitines were converted into lipo-alkaloids as well as monoester alkaloids by the decoction of aconite.

Characterization of aconitine-type alkaloids in the flowers of Aconitum kusnezoffii by electrospray ionization tandem mass spectrometry

The fragmentation mechanism of aconitine-type alkaloids in the flowers of Aconitum kusnezoffii (FAK) was investigated using electrospray ionization tandem mass spectrometry (ESI-MSn) firstly. The analysis of the collision-induced dissociation (CID) spectra of three purified aconitine standards and six previously reported aconitines indicated that the fragmentation of the protonated aconitines at low-energy CID follows a similar pathway. The elimination of a C-8-substituent such as an acetic acid or a fatty acid is the dominant fragmentation mode in MS2. Successive losses of CH3COOH, CH3OH, H2O, BzOH, and CO are the main fragmentation pathways of aconitine-type alkaloids in MS3 spectra. Based on these features, a rapid method for the direct detection and characterization of alkaloids from an ethanolic extract of FAK is described. All the known aconitum alkaloids are detected and a series of lipo-aconitines has been found for the first time in this plant.

Structure identification of five unknown dilipo-alkaloids extracted from processed tuber of Aconitum carmiechaeli by electrospray ionization tandem mass spectrometry

The alkaloids in processed aconite tuber of Aconitum Carmiechaeli were studied, and five novel alkaloids in extract from processed aconite tuber were found. The first step involved the use of electrospray ionization mass spectrometry (ESI-MS), and then multi-stage tandem mass spectrometry (MSn) was used to provide structural information. Based on their MSn spectra, the structures of the five novel compounds were elucidated to be C3,C8-difatty acid esters of mesaconitine, aconitine and 10-hydroxyaconitine.

Studies on the non-covalent complexes between oleanolic acid and cyclodextrins using electrospray ionization tandem mass spectrometry

Non-covalent inclusion complexes formed between an anti-inflammatory drug, oleanolic acid (OA), and alpha-, beta- and gamma-cyclodextrins (CDs) were investigated by means of solubility studies and electrospray ionization tandem mass spectrometry (ESI-MSn). The order of calculated association constants (K-1:1) of complexes between OA and different CDs in solution is in good agreement with the order of their relative peak intensities and the relative CID energies of the complexes under the same ESI-MSn conditions. These results indicate a direct correlation between the behaviors of solution- and gas-phase complexes. ESI-MS can thus be used to evaluate solution-phase non-covalent complexes successfully. The experimental results show that the most stable 1:1 inclusion complexes between three CDs and OA can be formed, but 2:1 CD-OA complexes can be formed with beta- and gamma-CDs. Multi-component complexes of alpha-CD-OA-beta-CD (1:1:1), alpha-CD-OA-gamma-CD (1:1:1) and beta-CD-OA-gamma-CD (1:1:1) were found in equimolar CD mixtures with excess OA. The formation of 2:1 and multi-component 1:1:1 non-covalent CD-OA complexes indicates that beta- and gamma-CD are able to form sandwich-type inclusion non-covalent complexes with OA. The above results can be partly supported by the relative sizes of OA and CD cavities by molecular modeling calculations.

Measurement of the single-color three-photon resonant ionization spectrum of atomic uranium under the "equivalent wavelength effect laser" interaction

Using Nd: YAG laser (532 nm) pumped mixed-dye laser. we obtained the output of this dye enhanced at the wavelength interval equivalent to that given by the copper vapor laser pumped dye laser. This measure favored is with the measurement of single-color three-photon resonant ionization spectrum of atomic uranium in the range of 562-586 nm,which is otherwise not efficiently covered by Nd: YAG laser pumped dye laser with any single dye. Thus 140 U I energy levels were obtained and the peaks of interest 575.814 nm and 575.836 rim were well resolved and their relative intensity determined.

Rapid molecular weight determination of recombinant hirudin by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

The molecular weight of recombinant hirudin ( rHV-2) was determined rapidly by matrix-assisted laser desorption/ionization time of fight mass spectrometry (MALDI-TOF-MS). The effects of the three types of matrixes were compared and discussed, alpha-cynao-4-hydroxycinnamic acid was proved to be the best matrix. It showed that MALDI-TOF-MS was superior to the traditional method of molecular weight determination of the biological macromolecules. The mass spectrum data proved that the primary structure of rHV-2 was correct and there was no amino acid deletion, mutation and modification in its expression, refolding and purification.

Improved efficiency by a graded emissive region in organic light-emitting diodes

Electrical and optical properties of organic light-emitting diodes (OLEDs) with a stepwise graded bipolar transport emissive layer for a better control of charge transport and recombination are presented. The graded bipolar transport layer was formed by co-evaporating a hole-transporting material N,N-'-diphenyl-N,N-'-bis(1,1(')-biphenyl)-4,4(')-diamine (NPB) and an electron-transporting/emissive material tris-(8-hydroxyquinoline) aluminum (Alq(3)) in steps, where each step has a different concentration ratio of NPB to Alq(3). Compared to a conventional heterojunction OLED, electroluminescence efficiency was enhanced by a factor of more than 1.5, whereas the turn-on voltage remained unchanged in the graded structure.

Improvement of luminescence efficiency by electrical annealing in single-layer organic light-emitting diodes based on a conjugated dendrimer

In this paper, we study the effects of electrical annealing at different voltages on the performance of organic light-emitting diodes. The light-emitting diodes studied here are single-layer devices based on a conjugated dendrimer doped with 2-(4-biphenylyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole as the emissive layer. We find that these devices can be annealed electrically by applying a voltage. This process reduces the turn-on voltage and enhances the brightness and efficiency. We obtained an external electroluminescence quantum efficiency of 0.07% photon/electron and a brightness of 2900 cd m(-2) after 12.4 V electrical annealing, which are about 6 times and 9 times higher than un-annealing devices, respectively. The improved luminance and efficiency are attributed to the presence of a space charge field near the electrodes caused by charging of traps.

Electrospray ionization tandem mass spectrometric study of the aconitines in the roots of aconite

Fragmentation pathways of aconitine-type alkaloids were investigated by electrospray ionization/ion trap multistage tandem mass spectrometry. Low-energy collision-induced dissociation of protonated aconitines follows a dominant first step, the elimination of the C-8-substituent as acetic acid or fatty acid in MS2 spectra. Successive losses of 1-4 CH3OH molecules, 1-3 H2O, CO, benzoic acid, and CH3 or C2H5 (N-substituents) are all fragmentation pathways observed in MS3 and MS4 spectra. By applying knowledge of these fragmentation pathways to the aconitines in the ethanolic extract of aconite roots, all the known aconitines were detected and also 23 unknown aconitine-type alkaloids, in which the lipo-alkaloids containing residues of 15C, 17C and 19C saturated or unsaturated fatty acids were characterized. These odd-carbon-number fatty acid substituents have not been reported previously.

A study of resonance electron capture ionization on a quadrupole tandem mass spectrometer

Procedures that allow the realization of resonance electron capture (REC) mode on a commercial triple-quadrupole mass spectrometer, after some simple modifications, are described, REC mass spectrometry (MS) and tandem mass spectrometry (MS/MS) experiments were performed and spectra for some compounds were recorded. In particular, the charge-remote fragmentation (CRF) spectra of [M - H](-) ions of docosanoic and docosenoic acids under low-energy collisionally activated dissociation (CAD) conditions were obtained, and showed that there were no significant differences for [M - H](-) ions produced at different resonances (i,e. for [M - H](-) ions with different structures). This observation was explained on the basis of results obtained from deuterium-labeled fatty acids, which showed that different CRF ions (but with the same m/z value in the absence of labels) could be produced by different mechanisms, and all of them were obviously realized under CAD conditions that made spectra practically indistinguishable. The other example, which compared the REC-MS/MS spectrum of [M - H](-) ions and EI-MS/MS spectrum of M+. ions of daidzein, demonstrated the potential of the REC-MS/MS technique for more complex structure elucidation. Copyright (C) 2000 John Wiley & Sons, Ltd.

Matrix effects in inductively coupled plasma mass spectrometry by use of organic solvents

Matrix effects arising from ethanol, propanol, glycerol, acetic acid, ethylenediamine and triethanolamine in inductively coupled plasma mass spectrometry have been studied. Addition of ethanol, propanol, glycerol, acetic acid, ethylenediamine and triethanolamine into solution has an enhancement effect on the signal intensity of analyte with ionization potential between 9 and 11 eV. The ethylenediamine and triethanolamine have higher enhancement effect on the signal intensity of Hg than that of ethanol, propanol, glycerol and acetic acid. Addition of ethylenediamine and triethanolamine into solution has a suppression effect on the signal intensity of Ph and Sr. The mechanism of the enhancement or suppression was investigated. The signal enhancement of Hg in the presence of ethylenediamine and triethanolamine is not caused by improved degree of ionization of Hg and nebulization efficiency. The suppression effects of Ph and Sr in the presence of ethylenediamine and triethanolamine are due to decrease of atomization efficiency of these elements. A method for the determination of Hg in the biological standard samples Ly ICP-MS was developed.

Analysis of monodispersed polyaniline oligomers by matrix-assisted laser desorption ionization mass spectrometry

Monodispersed polyaniline oligomers was studied by matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF-MS), It is found that MALDI-TOF-MS is not only a direct, accurate and rapid tool for the analysis of monodispersed polyaniline oligomers, but also a useful technique for the design of synthetic route.