A comprehensive methodology to study double emulsion stability.

Hypothesis: The stability of emulsions requires the fast formation of viscoelastic interfaces between water and oil phases. In double emulsions, two surfactant types (hydrophilic and lipophilic) are present and two interfacial films are involved. Understanding cooperative adsorption of these surfactants and its implication on properties of water/oil/water interfacial films will enable replacing the empirical methodologies used in designing double emulsion systems with a knowledge-based approach.

Dos and don'ts tutorial for sample alignment in sum frequency generation spectroscopy.

This Tutorial aims to provide a concise yet practical guideline for different scenarios that one may face in a sum frequency generation (SFG) spectroscopy laboratory, especially when it comes to sample alignment. The effort is made to reconstruct the real and often challenging sample alignment conditions for a broad range of liquid or solid samples interfacing solid, liquid, or gas phases, with a pedagogical approach. Both newcomer operators of an SFG setup without a strong experience in nonlinear spectroscopy and the more experienced SFG users can utilize the approaches that are provided in this Tutorial for an easier and more reliable sample alignment in their SFG laboratories.

Effect of Surfactants on the Molecular Structure of the Buried Oil/Water Interface.

The oil/water interface, for instance in emulsions, is often stabilized by surfactants. Hence, the co-existence of oil, water, and surfactant molecules at the buried oil/water interface determines macroscopic properties such as surface tension or emulsion stability. Utilizing an inherently surface sensitive spectroscopic method, sum frequency generation (SFG) spectroscopy, we show that adsorption of an anionic surfactant to the buried oil/water interface increases the magnitude of the interfacial electric field.

Water Orientation at the Calcite-Water Interface.

Mineral-water interfaces play an important role in many natural as well as technological fields. Fundamental properties of these interfaces are governed by the presence of the interfacial water and its specific structure at the surface. Calcite is particularly interesting as a dominant rock-forming mineral in the earth's crust.

Effect of pH and urea on the proteins secondary structure at the water/air interface and in solution.

Hypothesis: The secondary structure of proteins affects their functionality and performance in physiological environments or industrial applications. Change of the solution pH or the presence of protein denaturants are the main chemical means that can alter the secondary structure of proteins or lead to protein denaturation. Since proteins in the bulk solution and those residing at the solution/air interface experience different local environments, their response to chemical denaturation can be different.

The nature of self-assembled octadecylphosphonic acid (ODPA) layers on copper substrates.

Hypothesis: The self-assembly of amphiphilic molecules onto solid substrates can result both in the formation of monolayers and multilayers. However, on oxidized and non-oxidized copper (Cu), only monolayer formation was reported for phosphonic acids possessing one phosphate head group. Here, the adsorption of octadecylphosphonic acid (ODPA) on Cu substrates through a self-assembly process was investigated with the initial hypothesis of monolayer formation.

Effect of Substrate Grain Size on Structural and Corrosion Properties of Electrodeposited Nickel Layer Protected with Self-Assembled Film of Stearic Acid.

In the present study, the impact of copper substrate grain size on the structure of the succeeding electrodeposited nickel film and its consequent corrosion resistance in 3.5% NaCl medium were evaluated before and after functionalization with stearic acid. Nickel layers were electrodeposited on two different copper sheets with average grain size of 12 and 25 µm, followed by deposition of stearic acid film through self-assembly.

Structure and Dynamics of Interfacial Peptides and Proteins from Vibrational Sum-Frequency Generation Spectroscopy.

Proteins at interfaces play important roles in cell biology, immunology, bioengineering, and biomimetic material design. Many biological processes are based on interfacial protein action, ranging from cellular communication to immune responses and the protein-driven mineralization of bone. Despite the importance of interfacial proteins, comparatively little is known about their structure.

How water flips at charged titanium dioxide: an SFG-study on the water-TiO interface.

Photocatalytic splitting of water into hydrogen and oxygen by utilizing sunlight and a photocatalyst is a promising way of generating clean energy. Here, we report a molecular-level study on heavy water (D2O) interacting with TiO2 as a model photocatalyst. We employed the surface specific technique Sum-Frequency-Generation (SFG) spectroscopy to determine the nature of the hydrogen bonding environment and the orientation of interfacial water molecules using their OD-stretch vibrations as reporters.

Isoelectric Points of Proteins at the Air/Liquid Interface and in Solution.

Electrostatic interactions play essential roles in determining the function, colloidal stability, and adsorption of proteins on different surfaces and interfaces. Therefore, a molecular-level understanding of the charge state of the proteins under different conditions is required to explain their macroscopic properties. In this study, we have employed an inherently surface-sensitive spectroscopic tool, sum frequency generation spectroscopy, to determine the charge state of a wide range of proteins as a function of pH at the air/liquid interface via measurement of the degree of orientation of water molecules.

Insights into Galvanic Corrosion Behavior of Ti-Cu Dissimilar Joint: Effect of Microstructure and Volta Potential.

The effect of microstructure on corrosion behavior of a solid-state explosion welded Ti-Cu bimetal is investigated by means of alternating current-direct current (AC-DC) electrochemical measurements, optical microscopy, scanning electron microscopy, and scanning Kelvin probe force microscopy (SKPFM). The results indicate that the titanium regions in the welding interface, local melted zone (LMZ), and LMZ-Cu interface are potential sites for initiation of corrosion attacks. SKPFM mapping clearly shows that before exposure of the sample to a 3.

Monolayer study by VSFS: in situ response to compression and shear in a contact.

Self-assembled octadecyltrichlorosilane ((OTS), CH3(CH2)17SiCl3) layers on hydroxyl-terminated silicon oxide (SiO2) were prepared. The monolayers were characterized with atomic force microscopy (AFM) and contact angle measurements; their conformation was studied before, during, and after contact with a polymer (either PDMS or PTFE) surface using the vibrational sum frequency spectroscopy (VSFS) technique. During contact, the effect of pressure was studied for both polymer surfaces, but in the case of PTFE, the effect of shear rate on the contact was simultaneously studied.

Combined in situ quartz crystal microbalance with dissipation monitoring, indirect nanoplasmonic sensing, and vibrational sum frequency spectroscopic monitoring of alkanethiol-protected copper corrosion.

In this study, we have applied three techniques to simultaneously and in situ study the initial stage of corrosion of copper protected by a self-assembled monolayer of octadecanethiol (ODT). We combined quartz crystal microbalance with dissipation monitoring (QCM-D), indirect nanoplasmonic sensing (INPS), and vibrational sum frequency spectroscopy (VSFS) and obtained complementary information about mass uptake and optical and spectroscopic changes taking place during the initial corrosion phase. All three techniques are very sensitive to the formation of a corrosion film (thickness in the range 0-0.