Browsing by Subject "Hydration"

Now showing 1 - 5 of 5

Open Access
A hybrid Au/Ru catalyst for sequential alkyne hydration/asymmetric transfer hydrogenation reactions
(Royal Society of Chemistry, 2024-05-05) Öztürk, Bengi Özgün; Durmuş Ağlamaz, Burcu; Aşkun, Mina; Tunalı, Zeynep; Özer, Halenur; Sağdıç, Kutay; İnci, Fatih
The utilization of organic/inorganic core/shell support materials by compartmentalizing of Au(i)/Ru(ii) catalysts has led to the formation of chiral alcohol derivatives from alkynes via sequential alkyne hydration and asymmetric transfer hydrogenation reactions. A Ru(ii) complex was supported on chiral ligand end-capped amphiphilic ROMP polymers. The micellar Ru(ii) catalyst was coated with a mesoporous silica shell to produce a secondary compartment where an IPrAuCl complex was confined in mesopores of silica gel through post-pore size reduction. A variety of alkynes were converted to chiral alcohol derivatives in quantitative yields with high enantioselectivity in a MeOH/H2O mixture using sequential alkyne hydration/asymmetric transfer hydrogenation reactions. A hybrid catalytic system was developed for sequential alkyne hydration/asymmetric transfer hydrogenation reactions through the confinement of an amphiphilic polymer supported ruthenium and gold catalysts within core/shell silica gel.
Open Access
A complementary electrochromic device with highly improved performance based on brick-like hydrated tungsten trioxide film
(American Scientific Publishers, 2012) Jiao, Z.; Wang, J.; Ke, L.; Sun, X. W.; Demir, Hilmi Volkan
Uniform and well adhesive nanostructured hydrated tungsten trioxide (3WO 3•H 2O) films were grown on fluorine doped tin oxide (FTO) substrate via a facile and template-free crystal-seed-assisted hydrothermal method by addition of ammonium sulfate ((NH 4) 2SO 4) and hydrogen peroxide (H 2O 2). X-ray diffraction (XRD) studies indicated that the films are of orthorhombic structure. Scanning electron microscopy (SEM) and high resolution transmission electron microscopy (HRTEM) analysis showed that the film was composed of brick-like nanostructures with a preferred growing direction along (002). The influence of seed layer, (NH 4) 2SO 4 and H 2O 2 on the products were also studied. The film showed good cyclic stability, comparable switching speed and coloration efficiency (30.1 cm 2 C -1). A complementary electrochromic device based on the film and Prussian blue depicted highly improved color contrast, coloration/bleaching response (1.8 and 3.7 s respectively) and coloration efficiency (164.6 cm 2 C -1).
Open Access
Insight on tricalcium silicate hydration and dissolution mechanism from molecular simulations
(American Chemical Society, 2015) Manzano, H.; Durgun, Engin; Arbeloa, I. L.; Grossman, J. C.
Hydration of mineral surfaces, a critical process for many technological applications, encompasses multiple coupled chemical reactions and topological changes, challenging both experimental characterization and computational modeling. In this work, we used reactive force field simulations to understand the surface properties, hydration, and dissolution of a model mineral, tricalcium silicate. We show that the computed static quantities, i.e., surface energies and water adsorption energies, do not provide useful insight into predict mineral hydration because they do not account for major structural changes at the interface when dynamic effects are included. Upon hydration, hydrogen atoms from dissociated water molecules penetrate into the crystal, forming a disordered calcium silicate hydrate layer that is similar for most of the surfaces despite wide-ranging static properties. Furthermore, the dynamic picture of hydration reveals the hidden role of surface topology, which can lead to unexpected water tessellation that stabilizes the surface against dissolution.
Open Access
Lipid melting transitions involve structural redistribution of interfacial water
(American Chemical Society, 2021-11-03) Schönfeldová, T.; Piller, P.; Kovacik, F.; Pabst, G.; Okur, Halil İbrahim; Roke, S.
Morphological and gel-to-liquid phase transitions of lipid membranes are generally considered to primarily depend on the structural motifs in the hydrophobic core of the bilayer. Structural changes in the aqueous headgroup phase are typically not considered, primarily because they are difficult to quantify. Here, we investigate structural changes of the hydration shells around large unilamellar vesicles (LUVs) in aqueous solution, using differential scanning calorimetry (DSC), and temperature-dependent ζ-potential and high-throughput angle-resolved second harmonic scattering measurements (AR-SHS). Varying the lipid composition from 1,2-dimyristoyl-sn-glycero-3-phosphocholine(DMPC) to 1,2-dimyristoyl-sn-glycero-3-phosphate (DMPA), to 1,2-dimyristoyl-sn-glycero-3-phospho-l-serine (DMPS), we observe surprisingly distinct behavior for the different systems that depend on the chemical composition of the hydrated headgroups. These differences involve changes in hydration following temperature-induced counterion redistribution, or changes in hydration following headgroup reorientation and Stern layer compression.
Open Access
Uptake of Ba2+ ions by natural bentonite and CaCO3: a radiotracer, EDXRF and PXRD study
(Akademiai Kiado Rt., 2002) Shahwan, T.; Atesin, A. C.; Erten, H. N.; Zararsiz, A.
Ba2+ uptake by natural bentonite, CaCO3 in addition to a number of bentonite-CaCO3 mixtures with variable compositions as a function of pH and Ba2+ concentration was studied. Radiotracer method, EDXRF, and PXRD were used. The results of radiotracer experiments showed that the uptake of Ba2+ by CaCO3 was larger than its uptake by natural bentonite samples, particularly at low initial concentrations of Ba2+ and higher pH values. This finding was supported by the EDXRF results, According to the sorption data, the apparent ΔG° values of sorption were in the range -9±1 to -13±3 kJ/mol. The PXRD studies revealed the formation of BaCO3 upon sorption of Ba2+ on pure CaCO3 and on some of the bentonite-CaCO3 mixtures.