ACS Publications最新文献

We present the first quantum computing simulation of wavepacket dynamics in an HO₂-water cluster. These systems are of great interest in atmospheric chemistry and, due to anharmonicity, can display multidimensional quantum nuclear effects arising from delocalized hydrogen bond networks. Here, we utilize the Quantum Shannon Decomposition (QSD) method to represent a quantum propagator for the nuclear degrees of freedom of the HO₂ radical interacting with one and two water molecules, in the presence of an electronic potential energy surface, and in terms of the R_y, R_z, and CNOT quantum gates. The resultant time evolution of the quantum wavepacket, constructed by using the Qiskit quantum simulation tool, with a Python driver, yields a vibrational spectrum that is in very good agreement with the classically obtained result. The numerical demonstration here is restricted to one- and two-nuclear dimensions and hence is a proof of principle, but future implementations will include novel tensor network strategies to reduce quantum circuit depth and expand to higher dimensions.

Dynamic excimer formation in solution-phase π-conjugated systems presents a promising route toward tunable photophysical properties, yet precise control over these transient species remains limited. Herein, a series of bisphenalenyl derivatives is shown to exhibit excimer emission that is modulated through strategic tailoring of side chains (ethylphenyl, n-butylphenyl, and n-hexyl). Two phenyl-substituted derivatives exhibit reversible, concentration-dependent excimer emission consistent with excited-state dimerization. In contrast, an aliphatically substituted bisphenalenyl moiety displays exclusively monomeric emission. Steady-state and time-resolved spectroscopy, time-dependent density functional theory, and diffusion-ordered NMR spectroscopy are employed to confirm that excimer formation arises due to excited-state encounters, with no evidence of ground-state aggregation in acetonitrile. However, diffusion-ordered NMR spectroscopy data reveal dimer formation in tetrachloroethane. Notably, the introduction of substoichiometric molar ratios of HBF₄ induces excimer emission at even lower concentrations of the bisphenalenyl moiety, demonstrating a route to stimulus-responsive control. These results provide a structure-environment framework for modulating dynamic excimer formation in charged π-systems and inform the rational design of responsive fluorescent materials.

Developing new technology in membrane desalination is crucial for addressing the global water crisis. Reverse osmosis (RO) membranes exhibit numerous advantages, such as high efficiency, cost-effectiveness, environmental sustainability, etc. In this work, we observe an abnormal RO phenomenon for the first time in dipalmitoylphosphatidylcholine (DPPC) bilayers under the stimuli of terahertz (THz) waves. Our RO model contains two DPPC bilayers that divide the saline and aqueous solutions. Surprisingly, under specific field strength and frequency, we observe considerable net water flow from the saline solution chamber, crossing the bilayers, to the aqueous solution chamber, which suggests a new RO phenomenon in a highly controllable fashion. The mechanism for this abnormal RO process is that in THz waves, some ions can strip off their hydration shells and directly adsorb onto the lipid heads, resulting in local aggregation of head groups. This creates large gaps between some lipids and loose membrane structures in the saline solution region, breaking the structural symmetry in bilayers that facilitates the RO permeation. The reduced potential of mean force (PMF) barriers, ion hydration number, ion density behavior, and membrane structure strongly support our explanation of the RO mechanism. Our findings shed light on a complete new mechanism of RO for biological membranes, and breaking the membrane structural symmetry provides a potential new pathway for the design of RO membranes.

The presence and persistence of microplastics (MPs) in the marine environment pose increasing threats to marine organisms and ecosystem health. Environmental monitoring of MPs facilitates assessment of their potential impacts on ecosystems and biota. Although numerous studies have confirmed the widespread presence of MPs pollution in the marine environment, there are still significant differences in the sampling methods and sample quantities used for MPs monitoring. To address these issues, this study investigated the influence of different sampling methods and quantities on the survey results of MPs in the marine environment. The impact of different sample mass on the detection of MPs abundance in sandy and muddy beach sediments of the supratidal, intertidal, and subtidal zones was examined. And the effects of different seawater MPs collection methods (trawl sampling, water collector sampling, and pump sampling) and quantities on MPs abundance detection in seawater were also explored. Results show that the most suitable sample mass for detecting MPs in beach sediments is at least 30 g. Additionally, comprehensive sampling and monitoring of the supratidal, intertidal, and subtidal zones should be conducted to ensure accurate assessment of MPs abundance. Seawater samples were collected via trawl, water collector sampling, and pump sampling to evaluate effects of methods, sample quantities, filter aperture, and sampling depth on the monitoring abundance of MPs. Results show that the optimal sampling parameters are trawl durations at least 10 min and water collector sampling volumes at least 10 L. In the water collector sampling method, the total abundances of MPs after filtration through 48 and 330 μm filters are at the same order of magnitude, indicating that the filtration pore size has no significant effect on the total abundance of MPs. However, the size ranges of retained MPs differ significantly between the two pore sizes. Furthermore, while no significant difference is observed in MPs abundance among different water layers in Leizhou Bay, variations are found in polymer composition and MPs size distribution. This research is helpful in improving the accurate monitoring of MPs in the marine environment.

Liquid-liquid interfacial tension (LL-IFT) and the associated nanoscale interfacial structure are key to an extraction-based separation process. Here, we apply the perturbed-chain statistical associating fluid theory (PC-SAFT)-based classical density functional theory (cDFT) to predict the LL-IFT, interfacial density, and hydrogen-bonding profiles of methanol-n-alkane (n-hexane, n-heptane, and n-octane) mixtures under atmospheric pressure. Each mixture is modeled by using a single temperature-independent binary interaction parameter. To determine the optimal modeling strategy, we systematically assess six combinations derived from four published PC-SAFT parameter sets for methanol and three nonlocal association functionals (i.e., aFMT, aWDA, and iSAFT). The first three parameter sets incorporated the vapor pressure, saturated liquid density, and vapor-liquid interfacial tension (VL-IFT) into the fitting process, with VL-IFT calculated by aFMT, aWDA, and iSAFT for sets 1, 2, and 3, respectively. Parameter set 4 was optimized exclusively to the bulk phase equilibrium data. Notably, despite their superior accuracy in predicting binary VL-IFT, parameter sets 1-3 do not outperform set 4 in predicting binary LL-IFT. Furthermore, both iSAFT and aWDA show good agreement with experimental LL-IFT data, whereas aFMT consistently overestimates the values across all systems and temperatures, irrespective of the methanol parameters used. Although the optimal combination varies by system, the overall performance of the current cDFT framework demonstrates remarkable precision in reproducing LL-IFT. From a structural perspective, monotonic density and hydrogen-bonding profiles with intersection points have been identified: two for density profiles (one per component) and one for hydrogen-bonding profiles.

Cluster-cluster heterostructures (CCheteros) are emerging as promising catalysts for alkaline hydrogen evolution reaction (HER), benefiting from coupled interfaces and functional complementarity. Among various design parameters, cluster size can be experimentally controlled and plays a pivotal role in the structure-activity relationship. However, the impacts of cluster sizes on interfacial electronic structures remain underexplored. Herein, in this paper, 20 Ru-CrO_x CCheteros obtained by systematically varying the sizes of Ru and CrO_x clusters are analyzed via first-principles simulations to derive size-dependent interfacial electronic properties based on the experimentally validated Ru-CrO_x CChetero, an effective HER catalyst in alkaline media. The results reveal that the interfacial electronic properties arise from nonlinear and cooperative effects of both cluster sizes. Compared to CCheteros with small Ru clusters (<15 Ru atoms), those with larger Ru clusters exhibit saturated electronic structure features, such as formation energy, binding energy, work function, and d-band center, indicating diminished tunability. Thus, maintaining a limited Ru cluster size is essential for electronic modulation. Enlarging Ru clusters increases the dipole magnitude and aligns it more closely with the interface normal, whereas increasing CrO_x cluster size tends to orient the dipole away from the interface normal. Furthermore, the d-band centers may be pinned when the Ru cluster in CCheteros is too large (>30 Ru atoms) and leading to a nontunable surface adsorption capacity. In contrast, with smaller Ru clusters, increasing CrO_x size downshifts the d-band center, suggesting the reduction of the adsorption capability. As a result, tuning cluster sizes may be an experimentally feasible way in designing high-performance CCheteros for surface science.

In this work, we provided an in-depth understanding of the low-temperature oxidation of o-xylene by focusing on its peroxy radical chemistry. High-precision theoretical calculations were performed to investigate the kinetics of reactions involving o-methylbenzylperoxy radical (RO₂•) and o-hydroperoxymethyl-benzyl radical (•QOOH), including their formation by the reaction of o-xylyl radical with O₂, as well as the consumption to form the cyclic oxide and 2-methylbenzaldehyde. These peroxy radicals are characterized by both aromatic and aliphatic properties, and the C₀² diagnostic calculations revealed the non-negligible multireference characters in these reaction systems, prompting us to calculate their reaction kinetics based on highly accurate PESs obtained by CASPT2 and WMS methods. The multistructural variational transition state theory incorporating the multistructural torsional anharmonicity based on a coupled torsional potential and the small-curvature tunneling approximation was employed to obtain the high-pressure-limit (HPL) rate constants of elementary reaction steps. The tunneling results show that both hydrogen and heavy-atom tunneling play a crucial role in the low-temperature chemical oxidation of o-xylene. In particular, at a room temperature of 298.15 K, hydrogen tunneling increases the rate constant of related reactions by about 3 orders of magnitude, and heavy-atom tunneling doubles it; even at a combustion temperature of 600 K, they can also enhance the reactions by 3-5 times and 17%, respectively. This observation highlights the subtle but decisive role of hydrogen and heavy-atom tunneling in driving the low-temperature reactivity of o-xylene. Lastly, we investigated the pressure dependence of three dissociation pathways of the •QOOH radical using the SS-QRRK method. The calculated branching fractions under varying temperatures and pressures provide a theoretical basis for optimizing combustion processes and controlling product distributions.

Cathepsin B (CTSB) plays a key role in several processes that promote breast cancer progression, making its activity detection crucial for cancer analysis. In this study, we developed a surface-enhanced Raman scattering (SERS) and fluorescence seesaw nanosensor for probing CTSB activity in breast cancer cells. The nanosensor, termed Au-pep-TAMRA, was fabricated by conjugating carboxytetramethylrhodamine (TAMRA)-labeled peptide substrates (pep-TAMRA) to gold nanoparticles (Au NPs). The peptide substrates served dual functions: (1) as recognition units specifically cleavable by CTSB and (2) as linkers bridging the plasmonic Au NPs and TAMRA signal molecules. Upon CTSB-mediated proteolytic cleavage, the altered distance between Au NPs and TAMRA generated inversely correlated signal changes in the SERS (reduction) and fluorescence (recovery) channels. This dual-mode nanosensor exhibited an expanded detection range of 5-200 ng/mL (compared to the single-mode detection) while achieving a low limit of detection of 1.16 ng/mL. Cell experiment validated the nanosensor's capacity to precisely determine CTSB activity in MDA-MB-231 cell lysates. The SERS-fluorescence switchable nanosensor demonstrates potential for advancing accurate diagnosis and personalized therapeutic strategies for breast cancer in clinical settings.

Anharmonic effects can significantly influence thermodynamic properties at high temperatures and, consequently, the predictive performance of combustion mechanisms. While anharmonicity associated with low-frequency internal rotations is often considered, contributions from other vibrational modes are frequently neglected. This study fully investigates the impact of anharmonic corrections on the thermodynamic properties of 24 species within a methane combustion mechanism. Torsional anharmonicity is treated using both hindered- and free-rotor models, and their applicability is discussed in the context of high-temperature combustion conditions. The anharmonic effects from other vibrational modes were estimated by three schemes: the uncoupled rigid-rotor anharmonic oscillator (uncoupled RRAO), the coupled rigid-rotor anharmonic oscillator (coupled RRAO), and the nonrigid-rotor anharmonic oscillator (NRRAO). The results for H₂O reveal that the NRRAO reduces the relative deviation of C_p (2000 K) from 3.41% in the RRHO to 0.56%. For CH₄, this reduction is from 7.67 to 2.90%. By combining corrections from both torsional and nontorsional anharmonic effects, thermodynamic properties of methane combustion-related species were calculated, and ignition delay time simulations and theoretical adiabatic flame temperature calculations were conducted by incorporating the revised thermodynamic parameters into the methane combustion mechanism. The simulated results indicate that including the anharmonic effect in thermodynamic calculations significantly improves the performance of reaction mechanisms.