| 43061. |
- Wang, Ying, et al.
(författare)
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Mechanistic studies on proton transfer in a [FeFe] hydrogenase mimic complex
- 2013
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Ingår i: Dalton Transactions. - : Royal Society of Chemistry (RSC). - 1477-9226 .- 1477-9234. ; 42:21, s. 7816-7822
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Tidskriftsartikel (refereegranskat)abstract
- Four different pathways for deprotonation of [(mu-pdt){Fe(CO)(3)}{Fe(CO)(kappa(2)-Me2PCH2N(Me)CH2PMe2)}] (pdt = propane-1,3-dithiolate) [1H(mu)](1+) were examined, including (1) the "Direct" deprotonation; (2) the "Indirect" deprotonation via the pendant amine N; (3) the "Indirect" deprotonation via the distal metal Fe; and (4) the "Indirect" deprotonation via the dithiolate S. Only deprotonation of the "Indirect" pathway via the pendant amine N is feasible at room temperature. The most favorable migration destination for the bridging hydride in [1H(mu)](1+) is the pendant amine N (activation energy barrier 16.1 kcal mol(-1)). Migrations to the other two possible sites including the distal metal Fe (34.6 kcal mol(-1)) and the S in the dithiolate group (41.5 kcal mol(-1)) were hindered by high proton shuttling barriers. Once the migration barriers of those three "Indirect" pathways are overcome, the following deprotonations from all three positions including the distal atom Fe, the dithiolate S and the pendant amine N, are all feasible. The results also demonstrate a large difference for deprotonation of the hydride from the terminal and bridging sites. The low energy of the virtual orbital associated with the antibonding M-H interaction of [1H(Fe)](1+) implies the high activity for the interaction with aniline.
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| 43062. |
- Wang, Y., et al.
(författare)
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Model for phase coexistence in phase transitions
- 2004
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Ingår i: International Journal of Quantum Chemistry. - : Wiley. - 0020-7608 .- 1097-461X. ; 97:6, s. 961-965
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Tidskriftsartikel (refereegranskat)abstract
- We propose a general model for describing the phenomena of phase coexistence in relation to pressure induced phase transformations by means of the T-P distribution in statistical thermodynamics. Using the well-known B1-B2 transition in NaCl as a prototype, we demonstrate how phase coexistence gives rise to the changes in the bulk modulus and the equation-of-state across the transition.
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| 43063. |
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| 43064. |
- Wang, Yan, et al.
(författare)
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Molecular mechanisms for the adhesion of chitin and chitosan to montmorillonite clay
- 2015
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Ingår i: RSC Advances. - : RSC Publishing. - 2046-2069. ; 5:67, s. 54580-54588
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Tidskriftsartikel (refereegranskat)abstract
- Molecular dynamics simulations have been performed to investigate molecular adhesion of chitin and chitosan oligomers to montmorillonite (Mnt) clay at different degrees of acetylation (DA, 0%, 20%, 40%, 60%, 80% and 100%) and different degree of protonation (DPr, 0%, 50%, 100% mimicking pH > 6.5, pH = 6.5, pH < 4, respectively) under fully hydrated conditions. Although the Mnt surface is negatively charged and a variation in DA also implies going from a positively charged oligomer at DA = 0% to a neutral oligomer at DA = 100%, the simulations show unexpectedly small variation of the total molecular adhesion as a function of DA. From our analysis we propose that this quantitatively similar adhesion arises from two different mechanisms. At low DA, the oligomer is rich in positively charged amino groups interacting strongly with the negatively charged surface by direct electrostatic interaction. On the other hand, at high DA, electrically neutral acetyl groups are strongly correlated with the Na+ counter ions, which are in all cases stuck at the surface and the counter ions seem to act as 'glue' between the acetyl groups and the Mnt. However, when protonation was decreased, adhesion was affected and significantly lowered at neutral conditions (DPr = 0%). The reason is concluded to be differences in charge distributions of the respective functional groups. A further investigation on the intramolecular hydrogen bonds formed in CHT or CHS shows that the adsorbed conformation of the polymer is also highly affected by DA. This work provides fundamental insights into adhesion mechanisms and is of potential importance for the development of polymer-clay based composite materials.
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| 43065. |
- Wang, Ying, et al.
(författare)
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Nano-analysis Reveals High Fraction of Serotonin Release during Exocytosis from a Gut Epithelium Model Cell
- 2021
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Ingår i: Angewandte Chemie-International Edition. - : Wiley. - 1433-7851 .- 1521-3773.
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Tidskriftsartikel (refereegranskat)abstract
- Electrochemical methods were used to explore the exocytotic nature of serotonin (5-HT) release in human carcinoid BON cells, an in vitro human enterochromaffin cell model, to understand the mechanisms operating the release of gut-derived 5-HT in the intestinal mucosal epithelium. We show that the fractional vesicular 5-HT release in BON cells is 80 % compared to previous work in pancreatic beta cells (34 %). The fractional release increased from 80 % in control BON cells to 87 % with 5-HT preincubation and nearly 100 % with the combination of 5-HT and the 5-HT4 autoreceptor agonist, cisapride. Thus, partial release is the primary mechanism of exocytosis in BON cells, resulting in a variable amount of the vesicular content being released. Factors that control secretion of 5-HT from enterochromaffin cells or BON cells are important as partial release provides a mechanism for development of effective therapeutic strategies to treat gastrointestinal diseases.
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| 43066. |
- Wang, Ying, et al.
(författare)
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Nucleophilic Attack by OH2 or OH- : A Detailed Investigation on pH Dependent Performance of a Ru Catalyst
- 2019
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Ingår i: Organometallics. - : AMER CHEMICAL SOC. - 0276-7333 .- 1520-6041. ; 38:6, s. 1264-1268
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Tidskriftsartikel (refereegranskat)abstract
- The considerable rate enhancements along with the increase in pH values may be due to the direct involvement of hydroxide anion in attacking electrophilic [Ru-V(tda)(py)(2)O](+) (1; tda = [2,2':6',2 ''-terpyridine]-6,6 ''-dicarboxylate, py = pyridine). The enhanced reaction rate is well in agreement with the descending activation barriers in our calculation. The addition of four extra water molecules in the geometry optimization plays a key role in stabilizing hydroxide anion as well as building a reasonable hydrogen-bonding network, and three of these molecules are required to stabilize the OH as an anion instead of a radical.
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| 43067. |
- Wang, Yudi, et al.
(författare)
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Optimization of the Performance of Dye-Sensitized Solar Cells Based on Pt-Like TiC Counter Electrodes
- 2012
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Ingår i: European Journal of Inorganic Chemistry. - : Wiley. - 1434-1948 .- 1099-1948 .- 1099-0682. ; :22, s. 3557-3561
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Tidskriftsartikel (refereegranskat)abstract
- Titanium carbide (TiC) has been used as a counter electrode (CE) catalyst in place of Pt for triiodide reduction in dye-sensitized solar cells (DSCs). Its catalytic activity can be comparable to that of Pt. The effect of the thickness of the TiC layer on the performance of the DSCs was investigated by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), and Tafel polarization measurements. We found that as the film thickness increased, the fill factor and short-circuit current density increased, which led to improved power-conversion efficiency. When the TiC film was thicker than 20 mu m, however, no significant continuous improvement in the catalytic activity was observed. A high power-conversion efficiency of 6.46?% was obtained for the DSC by using a TiC CE at the optimized film thickness, a value similar to that obtained with a Pt CE.
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| 43068. |
- Wang, Ying, et al.
(författare)
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Pendant amine bases speed up proton transfers to metals by splitting the barriers
- 2012
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Ingår i: Chemical Communications. - : Royal Society of Chemistry (RSC). - 1359-7345 .- 1364-548X. ; 48:37, s. 4450-4452
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Tidskriftsartikel (refereegranskat)abstract
- By using density functional theory on [FeFe]-hydrogenase mimics we deconvolute the function of pendant amine bases in proton transfer to and from the metal center. By dividing the high free energy barrier into one high enthalpy-low entropy barrier and one with a low enthalpy-high entropy, a lower free energy barrier is reached.
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| 43069. |
- Wang, Yong, et al.
(författare)
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Photocatalytic water oxidation via combination of BiVO4-RGO and molecular cobalt catalysts
- 2016
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Ingår i: Chemical Communications. - : Royal Society of Chemistry. - 1359-7345 .- 1364-548X. ; 52:14, s. 3050-3053
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Tidskriftsartikel (refereegranskat)abstract
- A BiVO4-reduced graphene oxide (RGO) composite in conjugation with the cubic molecular complex Co4O4(O2CMe)(4)(py)(4) (py = pyridine) has been found to be highly efficient towards visible light-driven water oxidation. A 4-fold enhancement in the average oxygen evolution rate and 100% yield based on the consumption of the sacrificial electron acceptor were obtained upon the addition of molecular cocatalysts to BiVO4-RGO in pure water.
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| 43070. |
- Wang, Yueqiang, et al.
(författare)
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Porphyrins bearing long alkoxyl chains and carbazole for dye-sensitized solar cells : tuning cell performance through an ethynylene bridge
- 2013
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Ingår i: RSC Advances. - : Royal Society of Chemistry (RSC). - 2046-2069. ; 3:34, s. 14780-14790
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Tidskriftsartikel (refereegranskat)abstract
- Two novel porphyrin dyes (Q1 and Q2) bearing alkoxyl chains with a carbazole moiety as the electron donor have been synthesized and utilized as sensitizers for dye-sensitized solar cells (DSSCs). Compared with Q2, the molecule of Q1 has an additional ethynylene bridge between the carbazole moiety and the porphyrin framework. Photophysical and electrochemical properties of the two dyes were investigated by UV-vis, fluorescence spectroscopy and cyclic voltammetry. DFT calculations indicated that Q2 has a more twisted non-planar conformation associated with a smaller p conjugation size because of the absence of ethynylene bridge, which resulted in its better solubility and larger amount of adsorption on TiO2. Compared with Q1, Q2 showed better photovoltaic performance, with a short-circuit photocurrent density (J(sc)) of 11.3 mA cm(-2), an open-circuit photovoltage (V-oc) of 0.68 V, and a fill factor (ff) of 0.71, corresponding to an overall conversion efficiency of 5.51% under standard global AM 1.5 solar light conditions. The additional ethynylene bridge in Q1 extends the absorption bands to a longer wavelength region with the absorption threshold of 743 nm on the TiO2 film compared with that of 681 nm for Q2, but the cell efficiency is decreased to 2.22%, which may be ascribed to the worse solubility and stronger aggregation tendency resulting from the better molecule planarity. These results indicate that the extension of the absorption bands to a longer wavelength region by the introduction of an additional ethynylene bridge may result in worse solubility and more severe aggregation, and thus decrease the cell efficiency. For the design of efficient DSSC sensitizers, these contradictory effects must be fully considered and well balanced.
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