The Hydrated Electron as a Pseudo-Atom in Cavity-Bound Water Clusters

2007 ◽  
Vol 3 (3) ◽  
pp. 1054-1063 ◽  
Author(s):  
Alexis Taylor ◽  
Chérif F. Matta ◽  
Russell J. Boyd
Keyword(s):  
Water Clusters ◽  
Bound Water ◽  
Hydrated Electron ◽  
Pseudo Atom

scholarly journals Water inside β-cyclodextrin cavity: amount, stability and mechanism of binding

2019 ◽  
Vol 15 ◽  
pp. 1592-1600 ◽  
Author(s):  
Stiliyana Pereva ◽  
Valya Nikolova ◽  
Silvia Angelova ◽  
Tony Spassov ◽  
Todor Dudev
Keyword(s):  
Inclusion Complexes ◽  
Water Clusters ◽  
Bound Water ◽  
Thermodynamic Characteristics ◽  
Water Molecules ◽  
Native State ◽  
Hydrophobic Substances ◽  
Cyclodextrin Cavity ◽  
Stabilizing Factors ◽  
Native Host

Cyclodextrins (CDs) are native host systems with inherent ability to form inclusion complexes with various molecular entities, mostly hydrophobic substances. Host cyclodextrins are accommodative to water molecules as well and contain water in the native state. For β-cyclodextrin (β-CD), there is no consensus regarding the number of bound water molecules and the location of their coordination. A number of intriguing questions remain: (1) Which localities of the host’s macrocycle are the strongest attractors for the guest water molecules? (2) What are the stabilizing factors for the water clusters in the interior of β-CD and what type of interactions between water molecules and cavity walls or between the water molecules themselves are dominating the energetics of the β-CD hydration? (3) What is the maximum number of water molecules inside the cavity of β-CD? (4) How do the thermodynamic characteristics of β-CD hydration compare with those of its smaller α-cyclodextrin (α-CD) counterpart? In this study, we address these questions by employing a combination of experimental (DSC/TG) and theoretical (DFT) approaches.

scholarly journals Methane adsorption onto silicas with various degree of hydrophobicity

Surface ◽  
2021 ◽  
Vol 13(28) ◽  
pp. 94-126
Author(s):  
V. V. Turov ◽  
◽  
V. M. Gun'ko ◽  
T. V. Krupska ◽  
◽  
...  
Keyword(s):  
Water Clusters ◽  
Chemical Shifts ◽  
Physical Adsorption ◽  
Bound Water ◽  
Adsorbed Water ◽  
Methane Adsorption ◽  
Methane Hydrates ◽  
Degree Of Hydration ◽  
Surface Condensation ◽  
Wide Range

The methane adsorption onto a hydrated surface of hydrophobic silica AM1 alone and impregnated by arginine, and silica gel Si-100 has been studied using low-temperature 1H NMR spectroscopy. It has been shown that the methane adsorption onto the AM1 surface depends on the degree of hydration and pretreatment type. The maximum adsorption (up to 80 mg/g) is observed for a sample hydrated after complete drying. It has been established that the adsorption is determined by a number of clusters of bound water of small radii. Based on a shape of the temperature dependence of the adsorption, it has been assumed that not only physical adsorption occurs, but also the quasi-solid methane hydrates are formed. It has been established that the amount of methane adsorbed onto a surface of a composite system AM1/arginine under isobaric conditions increases by tens of times (from 0.5 to 80 mg/g) in the presence of pre-adsorbed water pre-adsorbed at the surface. Probable mechanisms of the methane adsorption are physical adsorption on a surface, condensation in narrow voids between silica nanoparticles and nano-scaled (1-10 nm) water clusters, and the formation of solid (clathrate) methane hydrates. Water, adsorbed at a surface in a wide range of hydration, forms various clusters. This water is mainly strongly associated and characterized by chemical shifts in the range dH = 4-6 ppm. The hydrate structures with methane/water are quite stable and can exist even in the chloroform medium. However, in this case, a part of water transforms into a weakly associated state and it is observed at dH = 1.5-2 ppm.

Can a Dipole-Bound Electron Form a Pseudo-Atom? An Atoms-In-Molecules Study of the Hydrated Electron

2011 ◽  
Vol 115 (45) ◽  
pp. 13201-13209 ◽  
Author(s):  
Qadir K. Timerghazin ◽  
Inessa Rizvi ◽  
Gilles H. Peslherbe
Keyword(s):  
Hydrated Electron ◽  
Atoms In Molecules ◽  
Bound Electron ◽  
Pseudo Atom

scholarly journals Structured free-water clusters near lubricating surfaces are essential in water-based lubrication

2016 ◽  
Vol 13 (123) ◽  
pp. 20160554 ◽  
Author(s):  
Jiapeng Hou ◽  
Deepak H. Veeregowda ◽  
Joop de Vries ◽  
Henny C. Van der Mei ◽  
Henk J. Busscher
Keyword(s):  
Photoelectron Spectroscopy ◽  
Water Clusters ◽  
Crystal Surface ◽  
Bound Water ◽  
Free Water ◽  
Crystal Surfaces ◽  
Absorption Bands ◽  
Water Contact ◽  
Water Binding ◽  
Water Based

Water-based lubrication provides cheap and environmentally friendly lubrication and, although hydrophilic surfaces are preferred in water-based lubrication, often lubricating surfaces do not retain water molecules during shear. We show here that hydrophilic (42° water contact angle) quartz surfaces facilitate water-based lubrication to the same extent as more hydrophobic Si crystal surfaces (61°), while lubrication by hydrophilic Ge crystal surfaces (44°) is best. Thus surface hydrophilicity is not sufficient for water-based lubrication. Surface-thermodynamic analyses demonstrated that all surfaces, regardless of their water-based lubrication, were predominantly electron donating, implying water binding with their hydrogen groups. X-ray photoelectron spectroscopy showed that Ge crystal surfaces providing optimal lubrication consisted of a mixture of –O and =O functionalities, while Si crystal and quartz surfaces solely possessed –O functionalities. Comparison of infrared absorption bands of the crystals in water indicated fewer bound-water layers on hydrophilic Ge than on hydrophobic Si crystal surfaces, while absorption bands for free water on the Ge crystal surface indicated a much more pronounced presence of structured, free-water clusters near the Ge crystal than near Si crystal surfaces. Accordingly, we conclude that the presence of structured, free-water clusters is essential for water-based lubrication. The prevalence of structured water clusters can be regulated by adjusting the ratio between surface electron-donating and electron-accepting groups and between –O and =O functionalities.

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