| 1. |
- Ge, Linke, et al.
(författare)
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Aqueous multivariate phototransformation kinetics of dissociated tetracycline : implications for the photochemical fate in surface waters
- 2018
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Ingår i: Environmental Science and Pollution Research. - : Springer Science and Business Media LLC. - 0944-1344 .- 1614-7499. ; 25:16, s. 15726-15732
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Tidskriftsartikel (refereegranskat)abstract
- Antibiotics are ubiquitous pollutants in aquatic systems and can exist as different dissociated species depending on the water pH. New knowledge of their multivariate photochemical behavior (i.e., the photobehavior of different ionized forms) is needed to improve our understanding on the fate and possible remediation of these pharmaceuticals in surface and waste waters. In this study, the photochemical degradation of aqueous tetracycline (TC) and its dissociated forms (TCH20, TCH-, and TC2-) was investigated. Simulated sunlight experiments and matrix calculations indicated that the three dissociated species had dissimilar photolytic kinetics and photo-oxidation reactivities. TC2- photo-degraded the fastest due to apparent photolysis with a kinetic constant of 0.938 +/- 0.021 min(-1), followed by TCH- (0.020 +/- 0.005 min(-1)) and TCH20 (0.012 +/- 0.001 min(-1)), whereas Tar was found to be the most highly reactive toward center dot OH (105.78 +/- 3.40 M(-1 )s(-1)), and TC2- reacted the fastest with O-1(2) (344.96 +/- 45.07 M-1 s(-1)). Water with relatively high pH (e.g., similar to 8-9) favors the dissociated forms of TCH- and TC2- which are most susceptible to photochemical loss processes compared to neutral TC. The calculated corresponding environmental half-lives (t(1/2,E) ) in sunlit surface waters ranged from 0.05 h for pH = 9 in midsummer to 3.68 h for pH = 6 in midwinter at 45 degrees N latitude. The moms was dominated by apparent photolysis (especially in summer, 62-91%), followed by O-1(2) and center dot OH oxidation. Adjusting the pH to slightly alkaline conditions prior to UV or solar UV light treatment may be an effective way of enhancing the photochemical removal of TC from contaminated water.
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| 2. |
- Zhu, Yong, et al.
(författare)
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Stabilization of a molecular water oxidation catalyst on a dye−sensitized photoanode by a pyridyl anchor
- 2020
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Ingår i: Nature Communications. - : Springer Nature. - 2041-1723. ; 11:1
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Tidskriftsartikel (refereegranskat)abstract
- Understanding and controlling the properties of water-splitting assemblies in dye-sensitized photoelectrosynthesis cells is a key to the exploitation of their properties. We demonstrate here that, following surface loading of a [Ru(bpy)3]2+ (bpy = 2,2′-bipyridine) chromophore on nanoparticle electrodes, addition of the molecular catalysts, Ru(bda)(L)2 (bda = 2,2′-bipyridine-6,6′-dicarboxylate) with phosphonate or pyridyl sites for water oxidation, gives surfaces with a 5:1 chromophore to catalyst ratio. Addition of the surface-bound phosphonate derivatives with L = 4-pyridyl phosphonic acid or diethyl 3-(pyridin-4-yloxy)decyl-phosphonic acid, leads to well-defined surfaces but, following oxidation to Ru(III), they undergo facile, on-surface dimerization to give surface-bound, oxo-bridged dimers. The dimers have a diminished reactivity toward water oxidation compared to related monomers in solution. By contrast, immobilization of the Ru-bda catalyst on TiO2 with the 4,4′-dipyridyl anchoring ligand can maintain the monomeric structure of catalyst and gives relatively stable photoanodes with photocurrents that reach to 1.7 mA cm−2 with an optimized, applied bias photon-to-current efficiency of 1.5%.
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| 3. |
- Zhu, Yong, et al.
(författare)
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Water oxidation by a noble metal-free photoanode modified with an organic dye and a molecular cobalt catalyst
- 2022
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Ingår i: Journal of Materials Chemistry A. - : Royal Society of Chemistry (RSC). - 2050-7488 .- 2050-7496. ; 10:16, s. 9121-9128
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Tidskriftsartikel (refereegranskat)abstract
- A low-cost and easy-to-construct dye-sensitized photoanode for water oxidation was prepared by co-loading a new triphenylamine donor-acceptor organic chromophore (D1) and a Co4O4 cobalt cubane-based water oxidation catalyst (CoF) on TiO2 thin films. As the first example of a molecular catalyst-based, noble metal-free, dye-sensitized photoanode, the electrode, TiO2|D1,CoF, produces a higher photocurrent than other noble metal-free, dye-sensitized photoanodes with a relatively high faradaic efficiency for O2 production. The success of the dyad system lies in retarded interfacial charge recombination and extended light absorption both of which take advantage of the pyridine anchor-functionalized chromophore. In addition, the CoF catalyst, decorated with hydrophobic aliphatic chains, serves as a protective layer for stabilizing the organic dyes on electrode surfaces. Transient absorption measurement suggests the accumulation of oxidative equivalents on CoF by electron transfer on the TiO2 surface. The results and design principles presented here demonstrate the use of molecular engineering as a powerful tool for the exploration of low-cost solar water-splitting devices.
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