| 1. |
- Svensson, S, et al.
(författare)
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New end station for the study of gases, liquids, and solid films at the MAX laboratory
- 1996
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Ingår i: REVIEW OF SCIENTIFIC INSTRUMENTS. - : AMER INST PHYSICS. ; 67:6, s. 2149-2156
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Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- A new end station equipped with a very high-resolution SES-200 electron energy analyzer has been constructed for the study of gases and soft molecular materials. The analyzer is rotatable around the direction of the photon beam, allowing angular-dependent
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| 2. |
- Svärd, C., et al.
(författare)
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Fasting affects the surface and diving metabolic rates of Steller sea lions Eumetopias jubatus
- 2009
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Ingår i: Aquatic Biology. - Oldenorf/Luhe : Inter-Research. - 1864-7782 .- 1864-7790. ; 8:1, s. 71-82
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Tidskriftsartikel (refereegranskat)abstract
- Changes in metabolic rates were measured in 3 captive female Steller sea lions Eumetopias jubatus that experienced fasts during summer and winter. We measured metabolic rates (via O2 consumption) before (MRs, surface) and after (DMR, dive + surface interval) the sea lions dove to 10–50 m depths. Measurements were obtained prior to and immediately after 9 to 10 d fasts, and during a 14 d recovery period. The sea lions lost significantly more body mass (Mb) during the winter fast (10.6%), compared with the summer (9.5%). Mass-corrected dive metabolic rate (cDMR = DMR × Mb–0.714) was not affected by dive depth or duration, but increased significantly following the winter fasts (13.5 ± 8.1%), but did not change during summer (–1.1 ± 3.2%). However, mass-corrected surface metabolic rate (cMRs) decreased significantly after both the summer (–16.4 ± 4.7%) and winter (–8.0 ± 9.0%) fasts. Consequently, the ratio between cDMR and cMRs was significantly higher in winter, suggestive of an increased thermal challenge and convective heat loss while diving. Increased cMRs following the fast indicated that digestion began during foraging and was not deferred, implying that access to ingested energy was of higher priority than optimizing diving ability. cDMR was elevated throughout the recovery period, independent of season, resulting in a 12% increase in foraging cost in winter and a 3% increase in summer. Our data suggest that Steller sea lions are more sensitive to changes in body condition due to food shortages in the winter compared with the summer.
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| 3. |
- Bröms, P., et al.
(författare)
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Optical absorption studies of sodium doped poly(cyanoterephthalylidene)
- 1994
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Ingår i: Synthetic metals. - : Elsevier. - 0379-6779 .- 1879-3290. ; 67:1-3, s. 93-96
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Tidskriftsartikel (refereegranskat)abstract
- The effects of doping poly(cyanoterephthalylidene) with sodium in ultrahighvacuum been studied by optical absorption spectroscopy. Upon doping, new optical transitions are observed within the bandgap; the characteristics of these transitions are consistent with the formation of bipolarons. The optical absorption results are confirmed by direct measurements of the doping-induced gap states using ultraviolet photoelectron spectroscopy.
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| 4. |
- Greczynski, G., et al.
(författare)
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Electronic structure of poly(9,9-dioctylfluorene) in the pristine and reduced state
- 2002
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Ingår i: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 116:4, s. 1700-1706
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Tidskriftsartikel (refereegranskat)abstract
- The electronic structure of a polymer of interest in polymer-based light emitting devices, poly(9,9-dioctyl-fluorene), was studied using a combined experimental-theoretical approach. Results were compared with those of equivalent studies of the electronic structure of two related conjugated polymers: poly(p-phenylene) and a latter-type poly (p-phenylene) (LPPP). Finally, it was shown that electrons added to the polymer system lead to the formation of polarons at low doping levels, and bipolarons at high doping levels. The energies of the polaron and bipolaron states were measured directly, and agree with the theoretical modeling of the added electrons.
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| 5. |
- Ji, Fuxiang, 1991-, et al.
(författare)
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Remarkable Thermochromism in the Double Perovskite Cs2NaFeCl6
- 2024
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Ingår i: Advanced Optical Materials. - : John Wiley & Sons. - 2162-7568 .- 2195-1071. ; 12:8
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Tidskriftsartikel (refereegranskat)abstract
- Lead-free halide double perovskites (HDPs) have emerged as a new generation of thermochromic materials. However, further materials development and mechanistic understanding are required. Here, a highly stable HDP Cs2NaFeCl6 single crystal is synthesized, and its remarkable and fully reversible thermochromism with a wide color variation from light-yellow to black over a temperature range of 10 to 423 K is investigated. First-principles, density functional theory (DFT)-based calculations indicate that the thermochromism in Cs2NaFeCl6 is an effect of electron-phonon coupling. The temperature sensitivity of the bandgap in Cs2NaFeCl6 is up to 2.52 meVK(-1) based on the Varshni equation, which is significantly higher than that of lead halide perovskites and many conventional group-IV, III-V semiconductors. Meanwhile, this material shows excellent environmental, thermal, and thermochromic cycle stability. This work provides valuable insights into HDPs' thermochromism and sheds new light on developing efficient thermochromic materials.
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| 6. |
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| 7. |
- Wong, K.Y., et al.
(författare)
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Electronic state of nitrogen containing polypyridine at the interfaces with model sulfonic acid containing polymer and molecule
- 2003
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Konferensbidrag (refereegranskat)abstract
- We present results of an X-ray photoelectron spectroscopy (XPS) study of the interfaces between polypyridine (PPy) and model sulfonic acid containing polymer and molecule. We show that the N 1s level splits reflecting protonation of a substantial fraction of the PPy N sites. Density functional theory (DFT) is employed to compare excitation energies, bond angles, highest occupied molecular orbital (HOMO), lowest unoccupied molecular orbital (LUMO), and density of states of oligomers of pyridine and protonated pyridine. These results are in accord with the proposed origin of the red shift of the emitted light under forward bias in color-variable alternating-current light emitting (SCALE) devices.
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| 8. |
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| 9. |
- Bhatt, Pramod, et al.
(författare)
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Electronic structure of thin film iron-tetracyanoethylene : Fe(TCNE)x
- 2009
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Ingår i: Applied Physics A. - : Springer Science and Business Media LLC. - 0947-8396 .- 1432-0630. ; 95:1, s. 131-138
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Tidskriftsartikel (refereegranskat)abstract
- Thin film iron-tetracyanoethylene Fe(TCNE) x , x∼2, as determined by photoelectron spectroscopy, was grown in situ under ultra-high vacuum conditions using a recently developed physical vapor deposition-based technique for fabrication of oxygen- and precursor-free organic-based molecular magnets. Photoelectron spectroscopy results show no spurious trace elements in the films, and the iron is of Fe2+ valency. The highest occupied molecular orbital of Fe(TCNE) x is located at ∼1.7 eV vs. Fermi level and is derived mainly from the TCNE− singly occupied molecular orbital according to photoelectron spectroscopy and resonant photoelectron spectroscopy results. The Fe(3d)-derived states appear at higher binding energy, ∼4.5 eV, which is in contrast to V(TCNE)2 where the highest occupied molecular orbital is mainly derived from V(3d) states. Fitting ligand field multiplet and charge transfer multiplet calculations to the Fe L-edge near edge X-ray absorption fine structure spectrum yields a high-spin Fe2+ (3d6) configuration with a crystal field parameter 10Dq∼0.6 eV for the Fe(TCNE) x system. We propose that the significantly weaker Fe-TCNE ligand interaction as compared to the room temperature magnet V(TCNE)2 (10Dq∼2.3 eV) is a strongly contributing factor to the substantially lower magnetic ordering temperature (T C ) seen for Fe(TCNE) x -type magnets.
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| 10. |
- Chen, Yongzhen, et al.
(författare)
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In Situ Spectroscopic and Electrical Investigations of Ladder-type Conjugated Polymers Doped with Alkali Metals
- 2022
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Ingår i: Macromolecules. - : American Chemical Society (ACS). - 0024-9297 .- 1520-5835. ; 55:16, s. 7294-7302
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Tidskriftsartikel (refereegranskat)abstract
- Ladder-type conjugated polymers exhibit a remarkable performance in (opto)electronic devices. Their double-stranded planar structure promotes an extended pi-conjugation compared to inter-ring-twisted analogues, providing an excellent basis for exploring the effects of charge localization on polaron formation. Here, we investigated alkali-metal n -doping of the ladder-type conjugated polymer (polybenzimidazobenzophe-nanthroline) (BBL) through detailed in situ spectroscopic and electrical characterizations. Photoelectron spectroscopy and ultraviolet-visible-near-infrared (UV-vis-NIR) spectroscopy indicate polaron formation upon potassium (K) doping, which agrees well with theoretical predictions. The semiladder BBB displays a similar evolution in the valence band with the appearance of two new features below the Fermi level upon K-doping. Compared to BBL, distinct differences appear in the UV-vis-NIR spectra due to more localized polaronic states in BBB. The high conductivity (2 S cm(-1)) and low activation energy (44 meV) measured for K-doped BBL suggest disorder-free polaron transport. An even higher conductivity (37 S cm(-1)) is obtained by changing the dopant from K to lithium (Li). We attribute the enhanced conductivity to a decreased perturbation of the polymer nanostructure induced by the smaller Li ions. These results highlight the importance of polymer chain planarity and dopant size for the polaronic state in conjugated polymers.
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