The Journal of Physical Chemistry Letters最新文献

Isotope-selective photodissociation is a promising route to laser-based separation, yet its efficiency remains constrained by fixed molecular cross sections. Here, we introduce an active optical-switching strategy that utilizes a nonresonant ultraviolet control pulse to generate and tailor isotopologue-specific Fano resonances. By coupling high-lying vibrational levels of the electronic ground state to a dissociative continuum, this pulse dynamically modulates photodissociation cross sections without direct electronic excitation. Using full quantum wave packet simulations of HF and DF isotopologues, we demonstrate that the photofragment yield ratio can be reversibly switched by orders of magnitude through tuning of the probe frequency across a light-induced resonance. This approach enables selective suppression or enhancement of dissociation for a target isotopologue with high spectral precision. Our work establishes a versatile and efficient mechanism for isotope-selective photochemistry and opens a pathway toward coherent optical control of molecular photodissociation.

Artificial arrays of tin phthalocyanine molecules have been studied on Pb(100) using scanning tunneling microscopy (STM). The molecules adopt two azimuthal orientations with distinct spin states, which results in a checkerboard pattern in STM images. Upon converting the central molecule by current injection from its pristine state with the Sn ion above the molecular plane to a conformation with Sn between the macrocycle and the substrate, the orientations of all molecules are swapped. This cooperative rotation is modeled by combining the potential energies of the intermolecular and the molecule–substrate interactions.

In this study, we use low-energy electron diffraction, X-ray photoelectron spectroscopy, temperature-programmed desorption, and density functional theory calculations to unveil that low-energy electron irradiation (140.8 eV) induces local reconstruction of the irradiated area on the anatase TiO₂(001)-(1 × 4) surface to the (1 × 1) domain, accompanied by the formation of Ti³⁺ species in the subsurface region and subsurface oxygen vacancies/surface hydroxyl groups, whereas the unirradiated regions retain the (1 × 4) periodicity. The low-energy electrons locally stimulate desorption of oxygen from the anatase TiO₂(001)-(1 × 4) surface probably via interatomic Auger processes, creating surface oxygen vacancies with associated Ti³⁺ species that consequently trigger the local (1 × 4) → (1 × 1) surface reconstruction. Such a local surface reconstruction process is facilitated by surface hydroxyl groups. The created surface oxygen vacancies and Ti³⁺ species tend to migrate into the bulk, leading to a recovery of the (1 × 4) surface structure. The anatase TiO₂(001)-(1 × 1) domain provides reactive Ti_5c surface sites with a much larger density than the reactive Ti_4c surface sites on the corresponding anatase TiO₂(001)-(1 × 4) surface. These results demonstrate the sensitivity of TiO₂ surface structures to the surface reduction, which commonly occurs for TiO₂-involved (photo/electro)catalysts.

Offshore oil spills and oily wastewater cause severe water pollution. Membrane separation offers a promising solution for efficient oil–water separation; however, conventional membranes often exhibit poor fouling resistance and face a trade-off between flux and separation efficiency due to mismatched pore sizes. To overcome these challenges, we developed a hydrolyzed polyacrylonitrile by tetraethyl orthosilicate modification (HPANT) nanofibrous membrane based on the synergistic mechanism of selective wettability and pore-size exclusion. And it achieves superhydrophilicity and underwater superoleophobicity, with the pore size regulated to ∼20 nm. This design achieves excellent fouling resistance and separation efficiencies of 98.29% for immiscible mixtures and 97.80% for surfactant-stabilized emulsions, with high fluxes of 6,941.5 L·L·m^–2·h^–1·bar^–1 and 8,379.6 L·m^–2·h^–1·bar^–1, respectively. Multiscale simulations (DFT, MD, FEM) further clarify the dual mechanism: the stable hydration layer resisting oil adhesion and tailored nanopores providing a physical barrier. This strategy provides guidance for the development of oil–water separation membranes.

Metastable materials are attractive candidates for new catalysts, electrodes, and unconventional superconductors. Their unusual properties are rooted in nonstandard bonding, oxidation states, or coordination. However, potential applications of metastable materials are understudied, as it is difficult to obtain them via standard high-temperature solid-state synthesis methods, which result in the most thermodynamically stable products. Here, we computationally model a photochemical reaction that transforms synthetically available semiconducting crystals with a general formula K₂X₂ (X = S, Se, Te) into metastable materials with hypervalently bonded chains. The proposed reactions are an extension of well-documented ultrafast light-induced phase transitions, indicating the plausibility of these transformations under similar conditions.

Nuclear quantum effects of protons on electronic excitations in hydrogen-bonded organic materials remains underexplored. In theoretical studies, modeling excitons in these extended systems is particularly difficult, because they tend to have a large exciton binding energy and sometimes exhibit charge transfer character. We demonstrate how first-principles Green’s function theory combined with the nuclear-electronic orbital method enables us to examine the nature of excitons in a prototypical organic solid of eumelanin, for which extensive hydrogen bonds have been proposed to facilitate the formation of delocalized excitons. We investigate how the quantization of protons impacts electronic excitations. We discuss the extent to which the resulting proton quantum effects can be described as being derived from the structure and how they induce molecular-level anisotropy for the excitons in the organic solid.