Correction: Perylene-derivative singlet exciton fission in water solution.

[This corrects the article DOI: 10.1039/D4SC04732J.].

Chemistry at Oxide/Water Interfaces: The Role of Interfacial Water.

Oxide-water interfaces host many chemical reactions in nature and industry. There, reaction free energies markedly differ from those of the bulk. While we can experimentally and theoretically measure these changes, we are often unable to address the fundamental question: what catalyzes these reactions? Recent studies suggest that surface and electrostatic contributions are an insufficient answer.

Perylene-derivative singlet exciton fission in water solution.

We provide direct evidence of singlet fission occurring with water-soluble compounds. We show that perylene-3,4,9,10-tetracarboxylate forms dynamic dimers in aqueous solution, with lifetimes long enough to allow intermolecular processes such as singlet fission. As these are transient dimers rather than stable aggregates, they retain a significant degree of disorder.

A simplified method for theoretical sum frequency generation spectroscopy calculation and interpretation: The "pop model".

Existing methods to compute theoretical spectra are restricted to the use of time-correlation functions evaluated from accurate atomistic molecular dynamics simulations, often at the ab initio level. The molecular interpretation of the computed spectra requires additional steps to deconvolve the spectroscopic contributions from local water and surface structural populations at the interface. The lack of a standard procedure to do this often hampers rationalization.

A molecular understanding of citrate adsorption on calcium oxalate polyhydrates.

Calcium oxalate precipitation is a common pathological calcification in the human body, whereby crystallite morphology is influenced by the chelating properties of biological ions such as citrate. It has been suggested that citrate could steer oxalate formation towards its dihydrated form and away from the monohydrated form, which was identified as a major cause for disease. To assess the influence of the citrate ion on the resulting calcium oxalate, surface energies were calculated at the dispersion-corrected density functional level of theory for both monohydrated and dihydrated calcium oxalate.

On the Trail of Molecular Hydrophilicity and Hydrophobicity at Aqueous Interfaces.

Uncovering microscopic hydrophilicity and hydrophobicity at heterogeneous aqueous interfaces is essential as it dictates physico/chemical properties such as wetting, the electrical double layer, and reactivity. Several molecular and spectroscopic descriptors were proposed, but a major limitation is the lack of connections between them. Here, we combine density functional theory-based MD simulations (DFT-MD) and SFG spectroscopy to explore how interfacial water responds in contact with self-assembled monolayers (SAM) of tunable hydrophilicity.

Molecular Fingerprints of Hydrophobicity at Aqueous Interfaces from Theory and Vibrational Spectroscopies.

Hydrophobicity/hydrophilicity of aqueous interfaces at the molecular level results from a subtle balance in the water-water and water-surface interactions. This is characterized here via density functional theory-molecular dynamics (DFT-MD) coupled with vibrational sum frequency generation (SFG) and THz-IR absorption spectroscopies. We show that water at the interface with a series of weakly interacting materials is organized into a two-dimensional hydrogen-bonded network (2D-HB-network), which is also found above some macroscopically hydrophilic silica and alumina surfaces.

Ions Tune Interfacial Water Structure and Modulate Hydrophobic Interactions at Silica Surfaces.

The structure and ultrafast dynamics of the electric double layer (EDL) are central to chemical reactivity and physical properties at solid/aqueous interfaces. While the Gouy-Chapman-Stern model is widely used to describe EDLs, it is solely based on the macroscopic electrostatic attraction of electrolytes for the charged surfaces. Structure and dynamics in the Stern layer are, however, more complex because of competing effects due to the localized surface charge distribution, surface-solvent-ion correlations, and the interfacial hydrogen bonding environment.

Molecular hydrophobicity at a macroscopically hydrophilic surface.

Interfaces between water and silicates are ubiquitous and relevant for, among others, geochemistry, atmospheric chemistry, and chromatography. The molecular-level details of water organization at silica surfaces are important for a fundamental understanding of this interface. While silica is hydrophilic, weakly hydrogen-bonded OH groups have been identified at the surface of silica, characterized by a high O-H stretch vibrational frequency.

Influence of argon and D tagging on the hydrogen bond network in Cs(HO); kinetic trapping below 40 K.

The influence of enthalpic and entropic effects as well as of kinetic trapping processes on the structure of Ar/D2-tagged Cs+(H2O)3 clusters is studied by temperature-dependent infrared photodissociation spectroscopy combined with harmonic vibrational spectra calculations and anharmonic free energy profiles from finite temperature metadynamics molecular dynamics simulations. Each tag favors a different hydrogen bond network of water molecules, with Ar-tagging (vs. D2-tagging) of Cs+(H2O)3 leading to the lower energy conformation.