ACS Physical Chemistry Au最新文献

Two donor-acceptor diethylaminoquinolin-2-(1H)-ones featuring carbonyl or nitroisoxazole groups as acceptors were synthesized (DQCh and DQI), and their emissive spectral behavior was recorded in a wide range of solvent polarities. The carbonyl-containing compound nitroisoxazole derivative (DQI) represents a newly reported synthesis in this work. Interestingly, the two fluorophores exhibited distinct solvatochromic emission behaviors, with DQCh showing a significant bathochromic shift with the increase in solvent polarity, while DQI exhibited an unusual inversion in its emission energy at intermediate solvent polarities, transitioning from a bathochromic to a hypsochromic behavior. With multiparametric analysis this unique solvatochromic emission behavior was linked to the different sensibilities of the excited states of DQCh and DQI to hydrogen bonding from the solvent. These findings position quinolin-2-(1H)-ones as a promising scaffold for designing polarity-sensitive emissive dyes, offering new insights into the fundamental understanding and rational design of solvatochromic materials.

Photoredox catalysis often relies on excited-state quenching data to rationalize performance, yet such metrics can obscure the impact of solvent cage escape on overall efficiency. We report a systematic study of the effect of electrostatic interactions on the excited-state quenching, cage escape, and back-electron transfer processes in a benchmark system comprising methyl viologen (MV²⁺) and differently carboxylated ruthenium polypyridyl complexes with net charges from 2+ to 4-. Increasing electrostatic attraction between photosensitizer and MV²⁺ enhances the quenching rate constant (k _q ) up to the diffusion limit but simultaneously suppresses cage escape quantum yields, resulting in an inverse correlation between k _q and photochemical MV^•+ production. Transient absorption spectroscopy confirms that cage escape, rather than quenching or back-electron transfer, governs the quantum yield of product formation. Protonation of carboxylate groups to yield uniformly 2+ complexes equalizes quenching rates and substantially increases cage escape efficiency for the originally anionic species. These results establish electrostatic control of charge separation as a decisive factor in photoredox catalysis and challenge the practice of predicting yields solely from quenching experiments. Consideration of both the initial and post-electron-transfer charges of the photocatalyst/quencher pair emerges as a general design principle for maximizing cage escape and, consequently, photoredox reaction efficiency.

The development of high-performance electrodes for supercapacitors and batteries remains hindered by an incomplete atomic-scale understanding of how material structure and polarization govern electric double-layer formation. In this work, we employ ab initio molecular dynamics (AIMD) simulations to probe the interface between a neutral phosphorene electrode and the ionic liquid EMIM-BF₄, elucidating the mechanisms of charge redistribution and ionic ordering. Key findings include a detailed quantification of phosphorene's structural flexibility, interplanar P-P distances averaging 0.224 and 0.231 nm with angular fluctuations up to 10°, and the characterization of a weak yet functionally significant electrode-electrolyte interaction energy of -138.2 kJ mol^-1 nm^-2 that drives pronounced interfacial ionic layering. Electron density and Hartree potential profiles reveal alternating regions of charge accumulation and depletion extending ∼2.5 nm from the surface, with local electric fields reaching 10⁸ V/m. Under zero bias, no appreciable charge transfer is observed, yet substantial local polarization effects underscore the critical role of the ionic liquid in modulating interfacial electrostatics.

High-precision dynamic simulations of hypersonic flows are crucial for high-temperature aerodynamics, particularly in addressing nonequilibrium effects in turbulent flows. The quasi-classical trajectory (QCT) method, based on microscopic molecular collisions, is a key approach to tackle this challenge. By generating state-to-state (StS) integral cross sections (ICSs), QCT simulations enable detailed modeling of high-temperature thermochemical nonequilibrium flows. However, existing dynamic programs do not have an automated workflow that converts trajectory data into reaction rate coefficients. This work introduces WDK-VENUS, a modular QCT workflow for dynamics and kinetics of atom-diatom (A + BC) collisions built upon the VENUS program. The VENUS program is amended to enable handling high rovibrational states. An automated and efficient b _max test module is introduced. Additionally, an external Python code is provided with four modules: sampling, Gaussian process regression (GPR), model validation, and equilibrium/nonequilibrium rate coefficient calculation. The main function of this workflow is to use GPR machine learning methods to fit models, export large amounts of high-precision ICSs, and calculate equilibrium/nonequilibrium rate coefficients with less human intervention. The modular design of WDK-VENUS simplifies QCT calculations, supports batch processing, and integrates Python analysis tools. This workflow is expected to facilitate broader applications in interdisciplinary fields.

Efficient wastewater treatment requires nanofiltration membranes with both high water flux and strong dye rejection. Although graphene oxide (GO) membranes offer excellent molecular sieving capability, their narrow interlayer spacing severely restricts water transport. MXene quantum dots (MQDs), possessing abundant surface terminations, high hydrophilicity, and structural tunability, offer an effective strategy to tailor interlayer channels and enhance transport. Here, a GO/Ti₃C₂ QDs composite membrane is fabricated, where the QDs are uniformly intercalated between GO lamellae, preventing restacking, enlarging the interlayer spacing, and imparting favorable physicochemical characteristics. The GO/Ti₃C₂ QDs membrane displayed excellent hydrophilicity and outstanding water purification performance. Compared with pristine GO membranes, the GO/Ti₃C₂ QDs composite (mass ratio of 1:2) exhibited a 121% increase in water flux, reaching 64 L·m^-2·h^-1·bar^-1, while maintaining high dye rejection. These GO/Ti₃C₂ QDs membranes demonstrate high permeability, efficient dye removal, and promising potential for practical water purification applications.

A comprehensive vibrational analysis of squaraine dyes, a relevant class of molecules for dye-sensitized solar cell devices, is presented here. Exploiting density functional theory (DFT) in conjunction with second-order vibrational perturbation theory (VPT2), fundamental, overtone, and combination vibrational bands are computed and analyzed, comparing them directly to experimental infrared and Raman spectra. Our results unequivocally demonstrate that VPT2 calculations are mandatory for accurately interpreting the experiments, particularly in the 1100-1650 cm^-1 region, where anharmonic effects such as frequency shifts, intensity redistribution, and mode couplings are most prominent. Only going beyond harmonic treatment, we were able to undoubtedly identify peculiar vibrational features among symmetric N,N-disubstituted squaraines and highlight the critical role of low-frequency modes and intramolecular hydrogen-bonding dynamics. These findings provide a refined framework for interpreting coherent vibrational phenomena in squaraine-based molecular systems, offering a transferable computational approach for the spectroscopic characterization of functional chromophores in energy and photonic applications.

Combining thermally activated delayed fluorescence (TADF) with aggregation-induced enhanced emission (AIEE) provides an effective strategy to improve solid-state emission in organic materials. Here, we design four fluorenyl-benzothiadiazole (FL-BTD) derivatives bearing additional donor groups, aryloxy (-OAr), aryl (-Ar), iminodibenzyl (-IDB), and phenoxazine (-PXZ), to investigate how molecular structure influences their photophysical properties. FL-BTD-OAr and FL-BTD-IDB display AIEE, with quantum yields that are significantly higher in the solid state (0.70 and 0.30, respectively) than in solution. FL-BTD-IDB also exhibits delayed emission (t _d = 1.03 μs) and enhanced luminescence under vacuum compared to an O₂ atmosphere, consistent with TADF. Organic light-emitting diodes (OLEDs) fabricated with these materials show green emission (FL-BTD-Ar and FL-BTD-OAr) or orange emission (FL-BTD-IDB). Device performance trends closely follow the solid-state photophysics. FL-BTD-Ar, subject to partial aggregation quenching, delivers the weakest performance, whereas FL-BTD-OAr benefits from AIEE, resulting in improved brightness and efficiency. The best-performing device is based on FL-BTD-IDB, which combines AIEE and TADF to achieve high brightness (15,000 cd m^-2) and higher external quantum efficiency (EQE) compared to the analogs.

²¹¹At is a radionuclide of great interest in nuclear medicine for cancer therapy, provided it is firmly bound to an appropriate targeting agent. In recent years, original ²¹¹At-labeled compounds have shown promising in vivo stability, without the underlying logic being identified. Herein, molecular modeling (two-component relativistic density functional theory) is used to assess the hypothesis that the degradation mechanism(s), leading to the release of free ²¹¹At, is related to the ability of labeled compounds to form halogen-bond interactions involving astatine. We highlight inhibition phenomena at play for a variety of compounds, in line with observations of enhanced stability, paving the way for a potentially applicable strategy to access robust radiopharmaceuticals.

The development of antibacterial coatings is very important for reducing pathogenic microorganisms on frequently touched surfaces. This study explores the formation of copper-based antibacterial coatings on 304 stainless steel using laser powder bed fusion (L-PBF) and integrates molecular dynamics (MD) simulations to analyze the melting and coalescence processes at the nanoscale. Experimental results showed heterogeneous copper distribution in the melting pool, with Cu-rich regions reaching up to 69 at. %. SEM-EDS analysis confirmed localized phase separation due to rapid solidification and Marangoni convection. MD simulations of Cu-304SS nanoparticles demonstrated significant copper surface segregation at 1600 K, validating experimental observations. The antibacterial efficacy of the coatings was assessed against Escherichia coli and Acinetobacter baumannii. Results showed complete bacterial inactivation within 1 h of exposure. These findings provide insights into optimizing L-PBF parameters for creating durable and efficient self-disinfecting surfaces.

A comprehensive study of quaternary Ni-Cu-Fe-Co nanoparticles with sizes ranging from 2,000 to 10,000 atoms (≈10-30 nm) was carried out by combining solution combustion synthesis, X-ray diffraction (XRD), transmission electron microscopy (TEM-HAADF-EDS), and atomistic modeling (molecular dynamics and Monte Carlo simulations). Experimental XRD patterns confirmed the predominance of the face-centered cubic (fcc) structure with broadened reflections, indicative of nanocrystalline domains and partial coexistence of hexagonal close-packed (hcp) phases. TEM-EDS analysis showed well-defined crystallites and pronounced surface segregation of Cu (≈25-30%) enrichment relative to bulk composition and partial Co enrichment, in contrast to Ni and Fe, which concentrated in the particle cores. Molecular dynamics simulations showed that the melting temperature (T _m) increases with particle size, from 1371-1379 (2000 atoms) to 1479-1488 K (10,000 atoms), corresponding to an 8.5% rise. Conversely, crystallization temperatures (Tc) decrease with faster cooling, e.g., from 1159 at 0.25 to 1086 at 0.75 K/ps, reflecting kinetic effects on solidification. The potential energy stabilized from -3.98 (2000 atoms) to -4.06 eV/atom (10,000 atoms), while surface energy decreased from 2320-2361 to 2231-2283 mJ/m², in agreement with experimental evidence of Cu segregation. These combined experimental and computational insights reveal that Ni-Cu-Fe-Co nanoparticles inherently form hierarchical, labyrinth-like structures with Cu-rich shells and Ni/Fe-dominated cores.