| 3711. |
- Zhang, Teng, 1988-, et al.
(författare)
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Electronic structure modifications induced by increased molecular complexity : from triphenylamine to m-MTDATA
- 2019
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : ROYAL SOC CHEMISTRY. - 1463-9076 .- 1463-9084. ; 21:32, s. 17959-17970
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Tidskriftsartikel (refereegranskat)abstract
- The starburst pi-conjugated molecule 4,4 ',4 ''-tris(N-3-methylphenyl-N-phenyl-amino)triphenylamine (C57H48N4, m-MTDATA), based on triphenylamine (TPA) building blocks, is widely used in optoelectronic devices due to its good electron-donor characteristics. The electronic structure of m-MTDATA was investigated for the first time in the gas phase by means of PhotoElectron Spectroscopy (PES) and Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy. The combination of Density Functional Theory (DFT) calculations with the experimental spectra provides a comprehensive description of the molecular electronic structure. Moreover, by comparing the results with previous TPA measurements, we could shed light on how the electronic structure evolves when the molecular size is increased. We found that the C 1s photoelectron spectra of m-MTDATA and TPA are similar, due to the balance of the counter-acting effects of the electronegativity of the N atoms and the delocalization of the amine lone-pair electrons. In contrast, the increased number of N atoms (i.e. N lone pairs) in m-MTDATA determines a three-peak feature in the outermost valence binding energy region with strong contributions by the N 2p(z) orbitals. We also obtained a decrease of the HOMO-LUMO gap for m-MTDATA, which points to improved electron donating properties of m-MTDATA with respect to TPA.
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| 3712. |
- Zhang, Wennan, et al.
(författare)
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A PRELIMINARY TEST ON AN INDUSTRIAL BIOMASS CFB GASIFIER
- 2002
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Ingår i: 12th European Biomass Conference. - 889004425X ; , s. 745-748
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Konferensbidrag (övrigt vetenskapligt)abstract
- A test was carried out on an 6 MW industrial biomass atmospheric CFB gasifier in a power plant. The gas composition, NH3 and tar contents in the product gas at different temperatures were measured and analyzed. Ash (char in the present case) analysis was also made to make mass balance of chemical element in solid and gas phases during gasification based on Si balance analysis. The measurement results show that a gas productivity of 2 Nm3/kg (daf biomass) with gas LHV of 5MJ/Nm3 can be achieved at 750℃.The conversion of fuel-bound nitrogen (FBN) to NH3 ranges from 6 wt% to 70 wt% depending on temperature. Tar content in the product gas ranges from 2.5 to 16.7 g/m3. Small fractions of H, O, N, Cl and S contents in fuel remain in the ash while most of mineral metal element remains in the ash.
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| 3713. |
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| 3714. |
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| 3715. |
- Zhang, Wenhua, et al.
(författare)
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Electronic structure of aromatic amino acids studied by soft x-ray spectroscopy
- 2009
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 131:3, s. 035103-
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Tidskriftsartikel (refereegranskat)abstract
- The electronic structure of phenylalanine, tyrosine, tryptophan, and 3-methylindole in the gas phase was investigated by x-ray photoemission spectroscopy (XPS) and near edge x-ray absorption fine structure (NEXAFS) spectroscopy at the C, N, and O K-edges. The XPS spectra have been calculated for the four principal conformers of each amino acid, and the spectra weighted by the Boltzmann population ratios calculated from published free energies. Instead of the single peaks expected from the stoichiometry of the compounds, the N 1s core level spectra of phenylalanine and tryptophan show features indicating that more than one conformer is present. The calculations reproduce the experimental features. The C and O 1s spectra do not show evident effects due to conformational isomerism. The calculations predict that such effects are small for carbon, and for oxygen it appears that only broadening occurs. The carbon K-edge NEXAFS spectra of these aromatic amino acids are similar to the published data of the corresponding molecules in the solid state, but show more structure due to the higher resolution in the present study. The N K-edge spectra of tryptophan and 3-methylindole differ from phenylalanine and tyrosine, as the first two both contain a nitrogen atom located in a pyrrole ring. The nitrogen K-edge NEXAFS spectra of aromatic amino acids do not show any measurable effects due to conformational isomerism, in contrast to the photoemission results. Calculations support this result and show that variations of the vertical excitation energies of different conformers are small, and cannot be resolved in the present experiment. The O NEXAFS spectra of these three aromatic compounds are very similar to other, simpler amino acids, which have been studied previously.
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| 3716. |
- Zhang, Wennan, et al.
(författare)
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Further test on the Sanya 6MW biomass CFB gasifier
- 2004
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Ingår i: 2nd World Conference and Exhibition on Biomass for Energy, Industry and Climate Protection. Rome, Italy, 10 - 14 May 2004.
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Konferensbidrag (övrigt vetenskapligt)abstract
- Following a preliminary test on the 6 MW Sanya biomass CFB gasifier (reported in the last conference at Amsterdam), a further test has been carried out focusing on the use of in-bed dolomite in order to reduce the tar content in the product gas. The gas composition and tar contents in the product gas at different temperatures were measured and analyzed. The results show that there is no big difference between two cases with and without dolomite at low temperature of 700C. However, at high temperature of 900C, the tar content was reduced significantly by the addition of in-bed dolomite. Temperature has a strong effect on the efficiency of dolomite catalyst
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| 3717. |
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| 3718. |
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| 3719. |
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| 3720. |
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