Counterion Distribution in the Stern Layer on Charged Surfaces.

Counterion adsorption at the solid-liquid interface affects numerous applications. However, the counterion adsorption density in the Stern layer has remained poorly evaluated. Here we report the direct determination of surface charge density at the shear plane between the Stern layer and the diffuse layer. By the Grahame equation extension and streaming current measurements for different solid surfaces in different aqueous electrolytes, we are able to obtain the counterion adsorption density in the Stern layer, which is mainly related to the surface charge density but is less affected by the bulk ion concentration. The charge inversion concentration is further found to be sensitive to the ion type and ion valence rather than to the charged surface, which is attributed to the ionic competitive adsorption and ion-ion correlations. Our findings offer a framework for understanding ion distribution in many physical and chemical processes where the Stern layer is ubiquitous.

Three-Dimensional Reconstruction and Visualization of Underwater Bridge Piers Using Sonar Imaging.

The quality of underwater bridge piers significantly impacts bridge safety and long-term usability. To address limitations in conventional inspection methods, this paper presents a sonar-based technique for the three-dimensional (3D) reconstruction and visualization of underwater bridge piers. Advanced MS1000 scanning sonar is employed to detect and image bridge piers. Automated image preprocessing, including filtering, denoising, binarization, filling, and morphological operations, introduces an enhanced wavelet denoising method to accurately extract the foundation contour coordinates of bridge piers from sonar images. Using these coordinates, along with undamaged pier dimensions and sonar distances, a model-driven approach for a 3D pier reconstruction algorithm is developed. This algorithm leverages multiple sonar data points to reconstruct damaged piers through multiplication. The Visualization Toolkit (VTK) and surface contour methodology are utilized for 3D visualization, enabling interactive manipulation for enhanced observation and analysis. Experimental results indicate a relative error of 13.56% for the hole volume and 10.65% for the spalling volume, demonstrating accurate replication of bridge pier defect volumes by the reconstructed models. Experimental validation confirms the method's accuracy and effectiveness in reconstructing underwater bridge piers in three dimensions, providing robust support for safety assessments and contributing significantly to bridge stability and long-term safety assurance.

Phosphonium Iodide Featuring Blue Thermally Activated Delayed Fluorescence for Highly Efficient X-Ray Scintillator.

Organic scintillators are praised for their abundant element reserves, facile preparation procedures, and rich structures. However, the weak X-ray attenuation ability and low exciton utilization efficiency result in unsatisfactory scintillation performance. Herein, a new family of highly efficient organic phosphonium halide salts with thermally activated delayed fluorescence (TADF) are designed by innovatively adopting quaternary phosphonium as the electron acceptor, while dimethylamine group and halide anions (I-) serve as the electron donor. The prepared butyl(2-[2-(dimethylamino)phenyl]phenyl)diphenylphosphonium iodide (C4-I) exhibits bright blue emission and an ultra-high photoluminescence quantum yield (PLQY) of 100 %. Efficient charge transfer is realized through the unique n-π and anion-π stacking in solid-state C4-I. Photophysical studies of C4-I suggest that the incorporation of I accounts for high intersystem crossing rate (kISC) and reverse intersystem crossing rate (kRISC), suppressing the intrinsic prompt fluorescence and enabling near-pure TADF emission at room temperature. Benefitting from the large Stokes shift, high PLQY, efficient exciton utilization, and remarkable X-ray attenuation ability endowed by I, C4-I delivers an outstanding light yield of 80721 photons/MeV and a low limit of detection (LoD) of 22.79 nGy ⋅ s-1. This work would provide a rational design concept and open up an appealing road for developing efficient organic scintillators with tunable emission, strong X-ray attenuation ability, and excellent scintillator performance.

Lipase and pH-responsive diblock copolymers featuring fluorocarbon and carboxyl betaine for methicillin-resistant staphylococcus aureus infections.

The emergence of multidrug-resistant bacteria along with their resilient biofilms necessitates the development of creative antimicrobial remedies. We designed versatile fluorinated polymer micelles with surface-charge-switchable properties, demonstrating enhanced efficacy against Methicillin-Resistant Staphylococcus Aureus (MRSA) in planktonic and biofilm states. Polymethacrylate diblock copolymers with pendant fluorocarbon chains and carboxyl betaine groups were prepared using reversible addition-fragmentation chain transfer polymerization. Amphiphilic fluorinated copolymers self-assembled into micelles, encapsulating ciprofloxacin in their cores (CIP@FCBMs) for antibacterial and antibiofilm applications. As a control, fluorine-free copolymer micelles loaded with ciprofloxacin (CIP@BCBMs) were prepared. Although both CIP@FCBMs and CIP@BCBMs exhibited pH-responsive surface charges and lipase-triggered drug release, CIP@FCBMs exhibited powerful antimicrobial and antibiofilm activities in vitro and in vivo, attributed to superior serum stability, higher drug loading, enhanced fluorination-facilitated cellular uptake, and lipase-triggered drug release. Collectively, reversing surface charge, on-demand antibiotic release, and fluorination-mediated nanoparticles hold promise for treating bacterial infections and biofilms.

Ultralow-Friction at Cryogenic Temperature Induced by Hydrogen Correlated Quantum Effect.

Temperature is one of the governing factors affecting friction of solids. Undesired high friction state has been generally reported at cryogenic temperatures due to the prohibition of thermally activated processes, following conventional Arrhenius equation. This has brought huge difficulties to lubrication at extremely low temperatures in industry. Here, the study uncovers a hydrogen-correlated sub-Arrhenius friction behavior in hydrogenated amorphous carbon (a-C:H) film at cryogenic temperatures, and a stable ultralow-friction over a wide temperature range (103-348 K) is achieved. This is attributed to hydrogen-transfer-induced mild structural ordering transformation, confirmed by machine-learning-based molecular dynamics simulations. The anomalous sub-Arrhenius temperature dependence of structural ordering transformation rate is well-described by a quantum mechanical tunneling (QMT) modified Arrhenius model, which is correlated with quantum delocalization of hydrogen in tribochemical reactions. This work reveals a hydrogen-correlated friction mechanism overcoming the Arrhenius temperature dependence and provides a new pathway for achieving ultralow friction under cryogenic conditions.

Overview of mechanisms of Fe-based catalysts for the selective catalytic reduction of NOx with NH3 at low temperature.

With the increasingly stringent control of NOx emissions, NH3-SCR, one of the most effective de-NOx technologies for removing NOx, has been widely employed to eliminate NOx from automobile exhaust and industrial production. Researchers have favored iron-based catalysts for their low cost, high activity, and excellent de-NOx performance. This paper takes a new perspective to review the research progress of iron-based catalysts. The influence of the chemical form of single iron-based catalysts on their performance was investigated. In the section on composite iron-based catalysts, detailed reviews were conducted on the effects of synergistic interactions between iron and other elements on catalytic performance. Regarding loaded iron-based catalysts, the catalytic performance of iron-based catalysts on different carriers was systematically examined. In the section on iron-based catalysts with novel structures, the effects of the morphology and crystallinity of nanomaterials on catalytic performance were analyzed. Additionally, the reaction mechanism and poisoning mechanism of iron-based catalysts were elucidated. In conclusion, the paper delved into the prospects and future directions of iron-based catalysts, aiming to provide ideas for the development of iron-based catalysts with better application prospects. The comprehensive review underscores the significance of iron-based catalysts in the realm of de-NOx technologies, shedding light on their diverse forms and applications. The hope is that this paper will serve as a valuable resource, guiding future endeavors in the development of advanced iron-based catalysts.

Direct Visualization of Dark Interlayer Exciton Transport in Moiré Superlattices.

Moiré superlattices have emerged as an unprecedented manipulation tool for engineering correlated quantum phenomena in van der Waals heterostructures. With moiré potentials as a naturally configurable solid-state that sustains high exciton density, interlayer excitons in transition metal dichalcogenide heterostructures are expected to achieve high-temperature exciton condensation. However, the exciton degeneracy state is usually optically inactive due to the finite momentum of interlayer excitons. Experimental observation of dark interlayer excitons in moiré potentials remains challenging. Here we directly visualize the dark interlayer exciton transport in WS2/h-BN/WSe2 heterostructures using femtosecond transient absorption microscopy. We observe a transition from classical free exciton gas to quantum degeneracy by imaging temperature-dependent exciton transport. Below a critical degeneracy temperature, exciton diffusion rates exhibit an accelerating downward trend, which can be explained well by a nonlinear quantum diffusion model. These results open the door to quantum information processing and high-precision metrology in moiré superlattices.

Enhanced Catalytic Soot Oxidation over Co-Based Metal Oxides: Effects of Transition Metal Doping.

A series of Co-M (M = Fe, Cr, and Mn) catalysts were synthesized by the sol-gel method for soot oxidation in a loose contact mode. The Co-Fe catalyst exhibited the best catalytic activity among the tested samples, with the characteristic temperatures (T10, T50, and T90) of 470 °C, 557 °C, and 602 °C, respectively, which were 57 °C, 51 °C, and 51 °C lower than those of the CoOx catalyst. Catalyst characterizations of N2 adsorption-desorption, X-ray diffraction (XRD), X-ray photo-electron spectrometry (XPS), and the temperature programmed desorption of O2 (O2-TPD) were performed to gain insights into the relationships between the activity of catalytic soot oxidation and the catalyst properties. The content of Co2+ (68.6%) increased due to the interactions between Co and Fe, while the redox properties and the relative concentration of surface oxygen adsorption (51.7%) were all improved, which could significantly boost the activity of catalytic soot oxidation. The effects of NO and contact mode on soot oxidation were investigated over the Co-Fe catalyst. The addition of 1000 ppm of NO led to significant reductions in T10, T50, and T90 by 92 °C, 106 °C, and 104 °C, respectively, compared to the case without the NO addition. In the tight contact mode, the soot oxidation was accelerated over the Co-Fe catalyst, resulting in 46 °C, 50 °C, and 50 °C reductions in T10, T50, and T90 compared to the loose contact mode. The comparison between real soot and model Printex-U showed that the T50 value of real soot (455 °C) was 102 °C lower than the model Printex-U soot.