It is important to understand the molecular-level properties of aqueous organic mixtures that can affect the environment as well as a variety of chemical systems. Mixtures of acetonitrile and water solutions have been shown to have different properties at the surface and in the bulk at different bulk acetonitrile concentrations. According to surface sensitive studies and molecular dynamic simulations, at 0.07 mole fraction, hydrogen bonding is lost at the interface with increasing acetonitrile concentration, leading to a reorientation of the acetonitrile at the surface. In addition, water and acetonitrile clusters have been shown to coexist and interact by dipole interactions between 0.2 and 0.8 mole fraction of acetonitrile. The reorientation of another nitrile at the surface, propionitrile, by hydrogen bonding has also been observed, but for this molecule, there is a lack of bulk studies of water-nitrile solutions.

In our studies, liquid-jet X-ray photoelectron spectroscopy was used to determine the nature of aqueous solutions of these two nitriles. The C1s, N1s and O1s regions suggest that clustering of the nitrile and water is apparent at the surface as well as the bulk. A full range of nitrile concentrations was studied. In addition, we made comparisons between experiments in which the liquid jet is in contact with a few torr of vapor and experiments in which the jet is exposed to high vacuum. The surface and bulk properties, as determined by XPS, are the same under these two experimental conditions. Our results also allow us to compare the differences between solubility of the two nitrile aqueous solutions and their hydrogen bonding properties at the surface and in the bulk.

The air-liquid interface of aerosols is an important site for heterogeneous chemistry in the atmosphere, associated, for instance, with the formation of reaction products relevant for ozone depletion. Concentrated (5-14 M) super-cooled aqueous solutions of sulfuric acid are known as sulfate aerosols and are one of the most abundant types of atmospheric aerosols. Fully understanding the dissociation of sulfuric acid, on the molecular level, is important because heterogeneous chemistry occurring on the surface of sulfate aerosols depends on the availability, speciation, location, and solvation structure of the species in solution. Aqueous solutions of sulfuric acid and the subsequent acid dissociation are useful models for sulfate aerosols. As a strong acid, the bulk of an aqueous solution of sulfuric acid will have H₃O⁺, HSO₄^- and SO₄^2-, and at high concentrations when the water concentration is very low, un-dissociated H₂SO₄ may be present. The bulk species composition is a function of the initial solution concentration, as well as temperature, and this composition as been well characterized by a variety of methods, such as sum frequency generation and Raman spectroscopy. Here, the chemistry of sulfuric acid aqueous solutions is explored by photoelectron spectroscopy on a liquid micro-jet. Experiments were performed at Beamline U41-PGM at the BESSY II synchrotron facility. A series of sulfuric acid aqueous solutions is measured at a low temperature of 6˚C. Deconvolution of the photoelectron spectra yields electronic information on the ionization species of sulfuric acid.

The adsorption of water molecule on a reduced rutile TiO₂(110)-(1×1) surface has been investigated using scanning tunneling microscopy (STM) and density functional theory (DFT) calculations. STM results indicate that water monomer adsorbs on top of Ti(5f) atom on the Ti row. The DFT calculations show that the most stable configuration of adsorbed water on TiO₂(110) has the binding energy of 23.6 kcal/mol. In this configuration, the oxygen atom is positioned on top of a Ti(5f) atom with one of the O-H bonds pointing toward a bridging oxygen via H-bonding and the other pointing along the Ti row direction. The water monomer can be dissociated by the electron injection from the STM tip into an oxygen adatom on Ti row. As the coverage increases, water molecules start to form one-dimensional chains via H-bonding along the Ti row direction. Thermal annealing after the adsorption of water at low temperature on TiO₂(110) is also found to be effective in the formation of the one-dimensional water chain. The effects of other coadsorbates such as CO₂ and O₂ in the formation of water chain will also be discussed.

Marangoni experiments with a large diameter, 50 mm, were carried out under microgravity condition in Japanese Experiment Module to make clear critical Marangoni number dependence in liquid bridge configuration such as liquid bridge aspect ratios(length/diameter of liquid bridge). The experiments with the different aspect ratios (length/diameter of liquid bridge) were changed from 0.25 to 1.2 which determined each critical Marangoni numbers. The critical Marangoni numbers decreased up to around 0.4, and after that the number increased monotonically up to 1.2. The most smallest number is observed at critical Mac(20000) at 0.4 and the maximum is Mac (50000) at 1.2. The large liquid bridge was vibrated by crew activity, so that all experiments were done during crew sleeping. This behavior can be qualitatively explained by considering thermal boundary layers which form at both heating and cooling desks of the liquid bridge. The experimental data were good agreement with the numerical results.