pH-dependent reactivity of water at MgO(100) and MgO(111) surfaces.

Facet-dependent surface charging of metal oxides in water dominates the ion transport behavior across the interface, in turn impacting many natural and industrial processes such as adsorption, the formation and stabilization of nanoparticle suspensions, corrosion, and heterogeneous catalysis. Here we investigated the pH-dependent surface chemistry of two low-index MgO single crystal surfaces, namely MgO(100) and MgO(111), using vibrational sum frequency generation (vSFG) spectroscopy. This allowed us to evaluate facet-dependent pH effects on the hydration and hydroxylation at the solid/aqueous interface and point-of-zero charge (PZC) values.

Vibrational sum frequency generation (VSFG) spectroscopy of water adsorption on surfaces of yttria-stabilized cubic zirconia (YSZ).

Yttria-stabilized zirconia (YSZ) is found in a wide range of applications, from solid-oxide fuel cells to medical devices and implants. A molecular-level understanding of the hydration of YSZ surfaces is essential for optimizing its performance and durability in these applications. Nevertheless, only a limited amount of literature is available about the surface hydration of YSZ single crystals.

Facet-dependent dispersion and aggregation of aqueous hematite nanoparticles.

Nanoparticle aggregates in solution controls surface reactivity and function. Complete dispersion often requires additive sorbents to impart a net repulsive interaction between particles. Facet engineering of nanocrystals offers an alternative approach to produce monodisperse suspensions simply based on facet-specific interaction with solvent molecules.

Polymer-solvent interaction and conformational changes at a molecular level: Implication to solvent-assisted deformation and aggregation at the polymer surface.

Hypothesis: We hypothesize that varying the chemical structure of the monomeric unit in a polymer will affect the surface structure and interfacial molecular group orientations of the polymer film leveraging its response to solvents of different chemical affinities.

Experiments: Poly (2-methoxy ethyl methacrylate) and poly (2-tertbutoxy ethyl methacrylate) thin films exposed to either deuterated water (DO) or deuterated chloroform (CDCl) were studied by sum frequency generation (SFG) spectroscopy, contact angle goniometry, and atomic force microscopy (AFM) at the polymer-solvent interface, supported with molecular simulation studies.

Findings: SFG spectral analysis of the polymer thin films corroborated molecular re-organization at the surface when exposed to different chemical environments.

Evident phase separation and surface segregation of hydrophobic moieties at the copolymer surface using atomic force microscopy and SFG spectroscopy.

Hypothesis: Copolymers are developed to enhance the overall physical and chemical properties of polymers. The surface nature of a copolymer is relevant to creating efficient materials to improve adhesion and biocompatibility. We hypothesize that the improved adhesion, as a surface property, is due to phase separation, surface segregation, and the overall molecular organization of different polymer components at the copolymer surface.

Organothiol Monolayer Formation Directly on Muscovite Mica.

Organothiol monolayers on metal substrates (Au, Ag, Cu) and their use in a wide variety of applications have been extensively studied. Here, the growth of layers of organothiols directly onto muscovite mica is demonstrated using a simple procedure. Atomic force microscopy, surface X-ray diffraction, and vibrational sum-frequency generation IR spectroscopy studies revealed that organothiols with various functional endgroups could be self-assembled into (water) stable and adaptable ultra-flat organothiol monolayers over homogenous areas as large as 1 cm .

Orientational Analysis of Monolayers at Low Surface Concentrations Due to an Increased Signal-to-Noise Ratio (S/N) Using Broadband Sum Frequency Generation Vibrational Spectroscopy.

Sum frequency generation (SFG) * Equal contributors. spectroscopy was used to deduce the orientation of the terminal methyl (CH) group of self-assembled monolayers (SAMs) at the air-solid and air-liquid interfaces at surface concentrations as low as 1% protonated molecules in the presence of 99% deuterated molecules. The SFG spectra of octadecanethiol (ODT) and deuterated octadecanethiol (d ODT) SAMs on gold were used for analysis at the air-solid interface.

Sum frequency generation vibrational spectroscopy of methacrylate-based functional monomers at the hydrophilic solid-liquid interface.

2-Substituted ethyl methacrylate monomers were characterized using sum frequency generation vibrational spectroscopy (SFGVS) to study the effect of substituent groups in the organization of the monomers at the monomer-hydrophilic quartz interface. The SFG spectra of the methacrylate-based functional monomers collected at the hydrophilic quartz interface were found to be different from those collected at the air-monomer interface. The various spectral profiles indicated different conformations of the molecular groups at the solid-liquid interface.