Author: Melissa C. Kido Dianne SoulePublisher:
ISBN:
Category : Surface chemistry
Languages : en
Pages : 312
Book Description
Nonlinear Vibrational Spectroscopic Studies of the Absorption and Orientation of Environmentally Important Molecules at the Vapor/water Interface
Author: Melissa C. Kido Dianne SoulePublisher:
ISBN:
Category : Surface chemistry
Languages : en
Pages : 312
Book Description
Nonlinear Vibrational Spectroscopic Studies of Molecular Interaction and Charging Behavior at Solid/liquid Interfaces
Author: Luning ZhangVibrational Spectroscopy of Water Interfaces
Author: Quan DuVibrational Spectroscopy of Water Interfaces
Author: Publisher:
ISBN:
Category :
Languages : en
Pages : 133
Book Description
The second order nonlinear optical processes of second harmonic generation and sum frequency generation are powerful and versatile tools for studying all kinds of surfaces. They possess unusual surface sensitivity due to the symmetry properties of the second order nonlinear susceptibility. The technique of infrared-visible sum frequency generation (SFG) is particularly attractive because it offers a viable way to do vibrational spectroscopy on any surfaces accessible to light with submonolayer sensitivity. In this thesis, the author applies SFG to study a number of important water interfaces. At the air/water interface, hydrophobic solid/water and liquid/water interfaces, it was found that approximately 25% of surface water molecules have one of their hydrogen pointing away from the liquid water. The large number of unsatisfied hydrogen bonds contributes significantly to the large interfacial energy of the hydrophobic surfaces. At the hydrophilic fused quartz/water interface and a fatty acid monolayer covered water surface, the structure and orientation of surface water molecules are controlled by the hydrogen bonding of water molecules with the surface OH groups and the electrostatic interaction with the surface field from the ionization of surface groups. A change of pH value in the bulk water can significantly change the relative importance of the two interactions and cause a drastic change in orientation of the surface water molecules. SFG has also been applied to study the tribological response of some model lubricant films. Monolayers of Langmuir-Blodgett films were found to disorder orientationaly under mildly high pressure and recover promptly upon removal of the applied pressure.
Structures and Dynamics of Interfacial Water
Author: Fujie TangPublisher: Springer
ISBN: 9811389659
Category : Science
Languages : en
Pages : 93
Book Description
This book focuses on the study of the interfacial water using molecular dynamics simulation and experimental sum frequency generation spectroscopy. It proposes a new definition of the free O-H groups at water-air interface and presents research on the structure and dynamics of these groups. Furthermore, it discusses the exponential decay nature of the orientation distribution of the free O-H groups of interfacial water and ascribes the origin of the down pointing free O-H groups to the presence of capillary waves on the surface. It also describes how, based on this new definition, a maximum surface H-bond density of around 200 K at ice surface was found, as the maximum results from two competing effects. Lastly, the book discusses the absorption of water molecules at the water–TiO2 interface. Providing insights into the combination of molecular dynamics simulation and experimental sum frequency generation spectroscopy, it is a valuable resource for researchers in the field.
Ultrafast Dynamics of Phospholipid-Water Interfaces
Author: René CostardPublisher: Springer
ISBN: 3319220667
Category : Science
Languages : en
Pages : 112
Book Description
This thesis presents a highly innovative study of the ultrafast structural and vibrational dynamics of hydrated phospholipids, the basic constituents of cell membranes. As a novel approach to the water-phospholipid interface, the author studies phosphate vibrations using the most advanced methods of nonlinear vibrational spectroscopy, including femtosecond two-dimensional infrared spectroscopy. He shows for the first time that the structure of interfacial water undergoes very limited fluctuations on a 300 fs time scale and that the lifetimes of hydrogen bonds with the phospholipid are typically longer than 10 ps. Such properties originate from the steric hindrance of water fluctuations at the interface and the orienting action of strong electric fields from the phospholipid head group dipoles. In an extensive series of additional experiments, the vibrational lifetimes of the different vibrations and the processes of energy dissipation are elucidated in detail.
Discovery of Oriented Gaseous Water Molecules in the Vapor-Liquid Interface of Water
Author: Publisher:
ISBN:
Category :
Languages : en
Pages : 0
Book Description
We present the first experimental measurements of the orientation and hydrogen bonding character of interfacial water molecules in their gaseous state in coexistence with the bulk liquid water. These interfacial vapor state molecules are distinct from the surface free OH and the interfacial liquid state water molecules and show a preferred orientation with their hydrogen atoms directed towards the liquid surface. The goal to develop a molecular level picture of water orientation and bonding at this vapor-liquid boundary where liquid phase water molecules coexist with vapor phase molecules has fascinated scientists for decades. Whereas most theoretical and experimental studies in recent years are converging on a consistent description of interfacial water on the liquid side of the interface, there is considerable disparity in the theoretical description of water molecules on the vapor side. A primary factor in this lack of consensus is the paucity of available data that unequivocally measures the properties of these interfacial vapor state molecules. As with theoretical efforts in this area, the low density of these vapor state interfacial water molecules is experimentally problematic. In this paper we present the first vibrational spectroscopic measurements of interfacial water vapor species in coexistence with their liquid phase. These detected vapor state molecules have a preferred orientation relative to the surface plane and have minimal hydrogen bonding to adjacent water molecules as manifested in the energy and linewidth of the spectral OH stretching modes examined. These molecules are distinctly different than the water molecules with a dangling bond into the vapor phase, or water in the liquid portion of the interface where hydrogen bonding between water molecules is strong.
Interfacial Water Organization and Ion Distributions Investigated with Vibrational Sum Frequency Spectroscopy
Author: Wei HuaPublisher:
ISBN:
Category :
Languages : en
Pages : 219
Book Description
Abstract: Here, interface-specific nonlinear optical spectroscopies, conventional vibrational sum frequency generation (VSFG) and heterodyne-detected vibrational sum frequency generation (HD-VSFG), are employed to probe interfacial water molecules at the molecular level. HD-VSFG spectroscopy allows for direct interrogation of the average orientation of the transition dipole moment of interfacial water molecules that is intrinsically contained in the sign of the second-order nonlinear susceptibility, X(2). The water organization and ion distributions at air/aqueous interfaces of inorganic salt solutions are inferred from Im X(2) spectra obtained by HD-VSFG spectroscopy.
Vibrational Spectroscopy of Molecules at Liquid/Liquid Interfaces
Author: Publisher:
ISBN:
Category :
Languages : en
Pages : 27
Book Description
Measurement of the nonlinear vibrational spectrum of molecules at a liquid/liquid interface has recently been achieved by the use of total internal reflection sum frequency vibrational spectroscopy (TIR SFVS). This report describes this nonlinear optical technique and gives examples of the type of information which has been obtained about interfacial water and surfactants adsorbed at this interface. The surfactants examined include simple alkyl cationic and anionic surfactants commonly used in cleaning products, and phosphatidylcholines which comprise the major component of cell membranes. Studies of interfacial water involve comparative studies at air/water and oil/water interfaces, and the effect of adsorbed surfactant on the water structure and orientation at these two interfaces.
Ultrafast Dynamics of Phospholipid-Water Interfaces
Author: René CostardPublisher:
ISBN: 9783319220673
Category :
Languages : en
Pages :
Book Description
This thesis presents a highly innovative study of the ultrafast structural and vibrational dynamics of hydrated phospholipids, the basic constituents of cell membranes. As a novel approach to the water-phospholipid interface, the author studies phosphate vibrations using the most advanced methods of nonlinear vibrational spectroscopy, including femtosecond two-dimensional infrared spectroscopy. He shows for the first time that the structure of interfacial water undergoes very limited fluctuations on a 300 fs time scale and that the lifetimes of hydrogen bonds with the phospholipid are typically longer than 10 ps. Such properties originate from the steric hindrance of water fluctuations at the interface and the orienting action of strong electric fields from the phospholipid head group dipoles. In an extensive series of additional experiments, the vibrational lifetimes of the different vibrations and the processes of energy dissipation are elucidated in detail.