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- Ivanova, Ekaterina V., et al.
(författare)
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Enantio selectivity of resolved Delta and Lambda orthoruthenated 2-phenylpyridine complexes Ru(o-C6H4-2-py)(LL)(2) PF6 (LL = bpy and phen) toward glucose oxidase
- 2006
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Ingår i: Journal of Molecular Catalysis B. - : Elsevier BV. - 1381-1177 .- 1873-3158. ; 41:04-mar, s. 110-116
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Tidskriftsartikel (refereegranskat)abstract
- Cyclometalated 2-phenylpyridine complexes [Ru-II(o-C6H4-2-py)(LL)(2)]PF6, LL=2,2'-bipyridine (1) and 1,10-phenanthroline (2) were resolved into A and A enantiomers using column chromatography on SP Sephadex C-25 in the presence of (+)-2,3-dibenzoyl-D-tartrate. The absolute configuration of enantiomers was established using circular dichroism spectroscopy. The rate constants k(et) for the electron transfer from reduced glucose oxidase (GO from Aspergillus niger) and PQQ-dependent glucose dehydrogenase (GDH) at the generated Ru-III species were measured by cyclic voltammetry and UV-vis spectroscopy. The electron transfer shows enantioselectivity. In the case of GO, the bell-shaped pH profile for the ratio k(Lambda)/k(Delta) has a maximum at pH 7 (k(Lambda)/k(Delta) equals 3.4 and 3.9 for 1 and 2, respectively), but its inversion is observed at pH around 5 and 9. The k(Lambda)/k(Delta) ratio equals 2.0 for 2 and GDH at pH 7. The results of theoretical modeling of biological electron transfer for GO using functional docking Monte-Carlo simulations are presented and analyzed together with the experimental observations.
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| 2. |
- Shi, Juanzi, et al.
(författare)
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Photoluminescence Polarization of MAPbBr3 Perovskite Nanostructures. Can the Dielectric Contrast Effect Explain It?
- 2022
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Ingår i: ACS Photonics. - : American Chemical Society (ACS). - 2330-4022. ; 9:12, s. 3888-3898
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Tidskriftsartikel (refereegranskat)abstract
- The dielectric contrast effect is usually evoked to explain anisotropy of optical properties of elongated nanoobjects, for example, semiconductor nanowires. We applied two-dimensional polarization imaging microscopy to measure the polarization of photoluminescence (PL) excitation and PL intensity of nanoaggregates of in-situ formed MAPbBr3perovskite nanoparticles in a stretched polymeric matrix. Scanning electron microscopy images of these objects were also acquired to characterize their sizes and shapes. We find that individual perovskite aggregates with sizes of 100-300 nm often possess a PL excitation polarization degree as high as 0.5-0.9, which is up to three times higher than the polarization degree of absorption predicted by the dielectric contrast effect. Small aggregates of nanoparticles possess an emission polarization degree substantially higher than that of excitation. Computer simulations of many possible scenarios show that the dielectric contrast alone cannot quantitatively explain the polarization properties of the studied objects. We propose energy transfer to localized emitting sites and the dependence of PL yield on excitation power density as possible factors strongly influencing the polarization properties of PL emission and PL excitation, respectively.
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