Nanofibrous Covalent Organic Frameworks as the Cathode, Separator, and Anode for Batteries with High Energy Density and Ultrafast-Charging Performance.

To meet the demand for longer driving ranges and shorter charging times of power equipment in electric vehicles, engineering fast-charging batteries with exceptional capacity and extended lifespan is highly desired. In this work, we have developed a stable ultrafast-charging and high-energy-density all-nanofibrous covalent organic framework (COF) battery (ANCB) by designing a series of imine-based nanofibrous COFs for the cathode, separator, and anode by Schiff-base reactions. Hierarchical porous structures enabled by nanofibrous COFs were constructed for enhanced kinetics. Rational chemical structures have been designed for the cathode, separator, and anode materials, respectively. A nanofibrous COF (AA-COF) with bipolarization active sites and a wider layer spacing has been designed using a triphenylamine group for the cathode to achieve high voltage limits with fast mass transport. For the anode, a nanofibrous COF (TT-COF) with abundant polar groups, active sites, and homogenized Li+ flux based on imine, triazine, and benzene has been synthesized to ensure stable fast-charging performance. As for the separator, a COF-based electrospun polyacrylonitrile (PAN) composite nanofibrous separator (BB-COF/PAN) with hierarchical pores and high-temperature stability has been prepared to take up more electrolyte, promote mass transport, and enable as high-temperature operation as possible. The as-assembled ANCB delivers a high energy density of 517 Wh kg-1, a high power density of 9771 W kg-1 with only 56 s of ultrafast-charging time, and high-temperature operational potential, accompanied by a 0.56% capacity fading rate per cycle at 5 A g-1 and 100 °C. This ANCB features an ultralong lifespan and distinguished ultrafast-charging performance, making it a promising candidate for powering equipment in electric vehicles.

Magnetically Enhanced Oxygen Evolution Reaction in Mild Alkaline Electrolytes by Building Catalysts on Magnetic Frame.

Under large current densities, the excessive hydroxide ion (OH) consumption hampers alkaline water splitting involving the oxygen evolution reaction (OER). High OH concentration (≈30 wt.%) is often used to enhance the catalytic activity of OER, but it also leads to higher corrosion in practical systems. To achieve higher catalytic activity in low OH concentration, catalysts on magnetic frame (CMF) are built to utilize the local magnetic convection induced from the host frame's magnetic field distributions. This way, a higher reaction rate can be achieved in relatively lower OH concentrations. A CMF model system with catalytically active CoFeOx nanograins grown on the magnetic Ni foam is demonstrated. The OER current of CoFeOx@NF receives ≈90% enhancement under 400 mT (900 mA cm-2 at 1.65 V) compared to that in zero field, and exhibits remarkable durability over 120 h. As a demonstration, the water-splitting performance sees a maximum 45% magnetic enhancement under 400 mT in 1 m KOH (700 mA cm-2 at 2.4 V), equivalent to the concentration enhancement of the same electrode in a more corrosive 2 m KOH electrolyte. Therefore, the catalyst-on-magnetic-frame strategy can make efficient use of the catalysts and achieve higher catalytic activity in low OH concentration by harvesting local magnetic convection.

Spatially Confined Alloying of Pt Accelerates Mass Transport for Fuel Cell Oxygen Reduction.

Pt-based alloy with high mass activity and durability is highly desired for proton exchange membrane fuel cells, yet a great challenge remains due to the high mass transport resistance near catalysts with lowering Pt loading. Herein, an extensible approach employing atomic layer deposition to accurately introduce a gas-phase metal precursor into platinum nanoparticles (NPs) pre-filled mesoporous channels is reported, achieved by controlling both the deposition site and quantity. Following the spatially confined alloying treatment, the prepared PtSn alloy catalyst within mesopores demonstrates a small size and homogeneous distribution (2.10 ± 0.53 nm). The membrane electrode assembly with mesoporous carbon-supported PtSn alloy catalyst achieves a high initial mass activity of 0.85 A mg Pt - 1 ${\mathrm{mg}}_{\mathrm{Pt}}^{-1}$ at 0.9 V, which is attributed to the smallest local oxygen transport resistance (3.68 S m-1) ever reported. The mass activity of the catalyst only decreases by 11% after 30000 cycles of accelerated durability test, representing superior full-cell durability among the reported Pt-based alloy catalysts. The enhanced activity and durability are attributed to the decreased adsorption energy of oxygen intermediates on Pt surface and the strong electronic interaction between Pt and Sn inhibiting Pt dissolution.

Ligand-Insertion Strategy for Constructing 2D Conjugated Metal-Organic Framework with Large Pore Size for Electrochemical Analytics.

Two-dimensional conjugated metal-organic frameworks (2D c-MOFs) have shown great promise in various electrochemical applications due to their intrinsic electrical conductivity. A large pore aperture is a favorable feature of this type of material because it facilitates the mass transport of chemical species and electrolytes. In this work, we propose a ligand insertion strategy in which a linear ligand is inserted into the linkage between multitopic ligands, extending the metal ion into a linear unit of -M-ligand-M-, for the construction of 2D c-MOFs with large pore apertures, utilizing only small ligands. As a proof-of-concept trial of this strategy, a 2D c-MOF with mesopores of 3.2 nm was synthesized using commercially available ligands hexahydrotriphenylene and 2,5-dihydroxybenzoquinone. The facilitation of the diffusion of redox species by the large pore size of this MOF was demonstrated through a series of probes. With this feature, it showed superior performance in the electrochemical analysis of a variety of biological species.

Enhancement of Mass Transport in Catalyst Layers of HT-PEMFC with Tetrafluorophenyl Phosphonic Acid Binder.

The design and development of new and efficient catalyst binder materials are important for improving cell performance in high-temperature proton-exchange membrane fuel cells (HT-PEMFCs). In this study, a series of tetrafluorophenyl phosphonic acid-based binder materials (PF-y-P, y = 1, 0.83, and 0.67) with rigid structures and controllable degrees of phosphonation were prepared and used in HT-PEMFCs using the ultra-strong acid-catalyzed Friedel-Crafts reaction and the combined Michaelis-Arbuzov reaction. The samples exhibited high stability, low water uptake, superior proton conductivity, and cell performance. In addition, the oxygen mass transport properties of the PF-1-P binder were investigated using high-temperature microelectrode electrochemical testing techniques. Compared with the phosphoric acid-doped polybenzimidazole (PBI) binder, the O2 solubility of PF-1-P binder material increased by 30% (5.36 × 10-6 mol cm-3) and the PF-1-P binder material exhibited better cell stability in HT-PEMFCs. After 10.5 h of discharge at a constant current of 0.12 A cm-2, the MEA voltage decreased by 7.1% and 20.8% in case of the PF-1-P and PBI binders, respectively.

Fluorine-Doped Carbon Support Enables Superfast Oxygen Reduction Kinetics by Breaking the Scaling Relationship.

It is well-established that Pt-based catalysts suffer from the unfavorable linear scaling relationship (LSR) between *OOH and *OH (ΔG(*OOH)=ΔG(*OH)+3.2±0.2 eV) for the oxygen reduction reaction (ORR), resulting in a great challenge to significantly reduced ORR overpotentials. Herein, we propose a universal and feasible strategy of fluorine-doped carbon supports, which optimize interfacial microenvironment of Pt-based catalysts and thus significantly enhance their reactive kinetics. The introduction of C-F bonds not only weakens the *OH binding energy, but also stabilizes the *OOH intermediate, resulting in a break of LSR. Furthermore, fluorine-doped carbon constructs a local super-hydrophobic interface that facilitates the diffusion of H2O and the mass transfer of O2. Electrochemical tests show that the F-doped carbon-supported Pt catalysts exhibit over 2-fold higher mass activities than those without F modification. More importantly, those catalysts also demonstrate excellent stability in both rotating disk electrode (RDE) and membrane electrode assembly (MEA) tests. This study not only validates the feasibility of tuning the electrocatalytic microenvironment to improve mass transport and to break the scaling relationship, but also provides a universal catalyst design paradigm for other gas-involving electrocatalytic reactions.

An equilibrium criterion for plastic debris fate in wave-driven transport.

The nearshore zone turns out to be the area with the higher concentration of plastic debris and, for this reason, it is important to know the processes that affect the transport and the fate of this type of litter. This study focuses on investigating the dynamics of various plastic types under several hydrodynamic conditions primarily induced by waves. 2D tests were carried out at the Hydraulic Laboratory of the University of Messina reproducing the main phenomena that occurred during the wave propagation on a planar beach. More than 200 different conditions were tested changing the wave characteristics, the water depth, the plastic debris characteristics (density and shape), and the roughness of the fixed bottom. In general, it can be observed that the reduction in particle displacement occurs due to: i) a decrease in wave steepness; ii) an increase in depth; iii) an increase in particle size; iv) an increase in plastic density. However, the experimental investigation shows that some plastic characteristics and bed roughness, even when hydraulically smooth, can alter these results. The experimental data analysis identified a criterion for predicting the short-term fate of plastic debris under wave action. This criterion to determine equilibrium conditions, based on an empirical relationship, takes into account the wave characteristics, the bed roughness and slope, and the weight of the debris.

[Evolution Characteristics of PM2.5 and O3 and Their Synergistic Effects on Atmospheric Compound Pollution in Tangshan].

The concentrations of atmospheric pollutants PM2.5, O3, SO2, NO2, and CO together with the meteorological factors of temperature （T）, relative humidity （RH）, wind speed, and other relevant data in Tangshan from 2015 to 2021 were collected to study the variation characteristics of PM2.5 and O3 at different periods in Tangshan City in the past seven years and their influencing factors, to discuss the contributions of air mass transport to PM2.5 and O3 pollution, and to reveal the synergistic influence mechanism of PM2.5 and O3 on atmospheric compound pollution by using correlation analysis and backward trajectory cluster analysis techniques. The results showed that PM2.5 concentrations in Tangshan decreased year by year from 2015 to 2021, whereas O3 concentration showed a unimodal trend, with the peak appearing in 2017. Both PM2.5 and O3 concentrations showed obvious seasonal variation trends； PM2.5 was characterized by the highest concentration in winter and the lowest concentration in summer, whereas O3 was characterized by the highest concentration in summer and the lowest concentration in winter. In addition, the diurnal variation in PM2.5 showed a bimodal distribution, with the peak occurring during the morning and evening on weekdays, and O3 showed a unimodal distribution, with the peak value appearing during the period with strong ultraviolet radiation in the afternoon. PM2.5 had a significant positive correlation with SO2, NO2, and CO, whereas O3 had a significant positive correlation with radiation and temperature. Under the different pollution conditions, PM2.5 and O3 were affected by air mass transports from different directions. Being impacted by various factors, the synergistic effect of PM2.5 and O3 on atmospheric compound pollution showed an obvious negative effect in winter, whereas there was an obvious positive effect in spring, summer, and autumn. Under the backgrounds of different pollutions, when the concentration of PM2.5 exceeded 150 µg·m-3, the synergistic effect of PM2.5 and O3 showed an obvious negative effect.

A Model for Reversible Electroporation to Deliver Drugs into Diseased Tissues.

Drug delivery through electroporation could be highly beneficial for the treatment of different types of diseased tissues within the human body. In this work, a mathematical model of reversible tissue electroporation is presented for injecting drug into the diseased cells. The model emphasizes the tissue boundary where the drug is injected as a point source. In addition, the effect of drug loss at tissue boundaries through extracellular space is studied elaborately. Multiple pulses are applied to deliver a sufficient amount of drug into the targeted cells. The set of differential equations that model the physical circumstances are solved numerically. This model obtains a mass transfer coefficient (MTC), in terms of pore fraction coefficient and drug permeability that controls the drug transport from extracellular to intracellular space. The drug penetration throughout the tissue is captured for the application of different pulses. The boundary effects on drug concentration are highlighted in this study. The advocated model is able to perform homogeneous drug transport into the cells so that the affected tissue is treated completely. This model can be applied to optimize clinical experiments by avoiding the lengthy and costly in vivo and in vitro experiments.

Porous Transport Layers with Laser Micropatterning for Enhanced Mass Transport in PEM Water Electrolyzers.

Efficient electrochemical energy conversion technologies, such as fuel cells and water electrolyzers, require high current densities to lower the capital cost for large-scale commercialization but are often limited by mass transport. In this study, we demonstrated exceptional electrochemical performances in proton electrolyte membrane water electrolyzers (PEMWEs) creating micropatterned pore channels in the porous transport layer (MPC PTL) using a picosecond laser. This approach yielded an impressive performance of 1.82 V @ 2 A·cm-2, which is better than commercial PTL of 1.90 V @ 2 A cm-2. The significant performance enhancement is attributed to the micropatterned porous channel structure, facilitating the efficient expulsion of oxygen bubbles and input of reactant water. This work provides valuable insights for the design of PTL responsible for biphasic transport in electrochemical energy conversion technologies.

Spatiotemporal Nitric Oxide Modulation via Electrochemical Platform to Profile Tumor Cell Response.

Nitric oxide (NO) is a gaseous molecule intricately implicated in oncologic processes, encompassing the modulation of angiogenesis and instigating apoptosis. Investigation of the antitumor effects of NO is currently underway, necessitating a detailed understanding of its cellular-level reactions. Regulating the behavior of radical NO species has been a significant challenge, primarily due to its instability in aqueous environments by rapid O2-induced degradation. In this study, we devised an electrochemical platform to investigate the cellular responses to reactive gaseous molecules. Our designed platform precisely controlled the NO flux and diffusion rates of NO to tumor cells. COMSOL Multiphysics calculations based on diffusion and reaction kinetics were conducted to simulate the behavior of electrochemically generated NO. We discerned that the effective radius, NO flux, and electrolysis duration are pivotal factors governing cellular response by NO.

Design of novel triply periodic minimal surface (TPMS) bone scaffold with multi-functional pores: lower stress shielding and higher mass transport capacity.

Background: The bone repair requires the bone scaffolds to meet various mechanical and biological requirements, which makes the design of bone scaffolds a challenging problem. Novel triply periodic minimal surface (TPMS)-based bone scaffolds were designed in this study to improve the mechanical and biological performances simultaneously. Methods: The novel bone scaffolds were designed by adding optimization-guided multi-functional pores to the original scaffolds, and finite element (FE) method was used to evaluate the performances of the novel scaffolds. In addition, the novel scaffolds were fabricated by additive manufacturing (AM) and mechanical experiments were performed to evaluate the performances. Results: The FE results demonstrated the improvement in performance: the elastic modulus reduced from 5.01 GPa (original scaffold) to 2.30 GPa (novel designed scaffold), resulting in lower stress shielding; the permeability increased from 8.58 × 10-9 m2 (original scaffold) to 5.14 × 10-8 m2 (novel designed scaffold), resulting in higher mass transport capacity. Conclusion: In summary, the novel TPMS scaffolds with multi-functional pores simultaneously improve the mechanical and biological performances, making them ideal candidates for bone repair. Furthermore, the novel scaffolds expanded the design domain of TPMS-based bone scaffolds, providing a promising new method for the design of high-performance bone scaffolds.

Capillarity in Interfacial Liquids and Marbles: Mechanisms, Properties, and Applications.

The mechanics of capillary force in biological systems have critical roles in the formation of the intra- and inter-cellular structures, which may mediate the organization, morphogenesis, and homeostasis of biomolecular condensates. Current techniques may not allow direct and precise measurements of the capillary forces at the intra- and inter-cellular scales. By preserving liquid droplets at the liquid-liquid interface, we have discovered and studied ideal models, i.e., interfacial liquids and marbles, for understanding general capillary mechanics that existed in liquid-in-liquid systems, e.g., biomolecular condensates. The unexpectedly long coalescence time of the interfacial liquids revealed that the Stokes equation does not hold as the radius of the liquid bridge approaches zero, evidencing the existence of a third inertially limited viscous regime. Moreover, liquid transport from a liquid droplet to a liquid reservoir can be prohibited by coating the droplet surface with hydrophobic or amphiphilic particles, forming interfacial liquid marbles. Unique characteristics, including high stability, transparency, gas permeability, and self-assembly, are observed for the interfacial liquid marbles. Phase transition and separation induced by the formation of nanostructured materials can be directly observed within the interfacial liquid marbles without the need for surfactants and agitation, making them useful tools to research the interfacial mechanics.

Mass Transport Limitations in Plasmonic Photocatalysis.

The interpretation of mechanisms governing hot carrier reactivity on metallic nanostructures is critical, yet elusive, for advancing plasmonic photocatalysis. In this work, we explored the influence of the diffusion of molecules on the hot carrier extraction rate at the solid-liquid interface, which is of fundamental interest for increasing the efficiency of photodevices. Through a spatially defined scanning photoelectrochemical microscopy investigation, we identified a diffusion-controlled regime hindering the plasmon-driven photochemical activity of metallic nanostructures. Using low-power monochromatic illumination (<2 W cm-2), we unveiled the hidden influence of mass transport on the quantum efficiency of plasmonic photocatalysts. The availability of molecules at the solid-liquid interface directly limits the extraction of hot holes, according to their nature and energy, at the reactive spots in Au nanoislands on an ultrathin TiO2 substrate. An intriguing question arises: does the mass transport enhancement caused by thermal effects unlock the reactivity of nonthermal carriers under steady state?

3D Printed Drug Delivery Systems in Action-Magnetic Resonance Imaging and Relaxometry for Monitoring Mass Transport Phenomena.

The hypothesis of the study was that (1) 3D printed drug delivery systems (DDS) could be characterized in situ during drug release using NMR/MRI techniques in terms of mass transport phenomena description (interfacial phenomena), particularly for systems dealing with two mobile phases (e.g., water and low molecular weight liquid polymer); (2) consequently, it could be possible to deduce how these interfacial mass transport phenomena influence functional properties of 3D printed DDS. Matrix drug delivery systems, prepared using masked stereolithography (MSLA), containing poly(ethylene glycol) diacrylate (PEGDA) and low molecular weight polyethylene glycol (PEG) with ropinirole hydrochloride (RH) were studied as example formulations. The PEGDA to PEG (mobile phase) concentration ratio influenced drug release. It was reflected in spatiotemporal changes in parametric T2 relaxation time (T2) and amplitude (A) images obtained using magnetic resonance imaging (MRI) and T1-T2 relaxation time correlations obtained using low-field time-domain nuclear magnetic resonance (LF TD NMR) relaxometry during incubation in water. For most of the tested formulations, two signal components related to PEG and water were assessed in the hydrated matrices by MRI relaxometry (parametric T2/A images). The PEG component faded out due to outward PEG diffusion and was gradually replaced by the water component. Both components spatially and temporally changed their parameters, reflecting evolving water-polymer interactions. The study shows that dynamic phenomena related to bidirectional mass transport can be quantified in situ using NMR and MRI techniques to gain insight into drug release mechanisms from 3D printed DDS systems.

Studying surfactant mass transport through dynamic interfacial tension measurements: A review of the models, experiments, and the contribution of microfluidics.

Surfactant mass transport towards an interface plays a critical role during formation of emulsions, foams and in industrial processes where two immiscible phases coexist. The understanding of these mechanisms as experimentally observed by dynamic interfacial tension measurements, is crucial. In this review, theoretical models describing both equilibrated systems and surfactant kinetics are covered. Experimental results from the literature are analysed based on the nature of surfactants and the tensiometry methods used. The innovative microfluidic techniques that have become available to study both diffusion and adsorption mechanisms during surfactant mass transport are discussed and compared with classical methods. This review focuses on surfactant transport during formation of droplets or bubbles; stabilisation of dispersed systems is not discussed here.

Decorating the Node of a Zirconium-Based Metal-Organic Framework to Tune Adsorption Behavior and Surface Permeation.

Surface barriers are commonly observed in nanoporous materials. Although researchers have explored methods to repair defects or create flawless crystals to mitigate surface barriers, these approaches may not always be practical or readily achievable in targeted metal-organic frameworks (MOFs). In our study, we propose an alternative approach focusing on the introduction of diverse ligands onto a MOF-808 node to finely adjust its adsorption and mass transport characteristics. Significantly, our findings indicate that while adsorption curves can be inferred based on the MOF's chemical composition and the probing molecule, surface permeabilities exhibit variations dependent on the specific probe utilized and the incorporated ligand. Our investigation, considering van der Waals forces exclusively between the adsorbate (e.g., n-hexane, propane, and benzene) and the adsorbent, revealed that augmenting these interactions can indeed improve surface permeation to a certain extent. Conversely, strong adsorption resulting from hydrogen bonding interactions, particularly with water in modified MOFs, led to compromised permeation within the MOF crystals. These outcomes provide valuable insights for the porous materials community and offer guidance in the development of adsorbents with enhanced affinity and superior mass transport properties for gases and vapors.

Measuring Mass Transfer of n-Hexane and 2-Chloroethyl Ethyl Sulfide in Sorbent/Polymer Fiber Composites Using a Volumetric Adsorption Apparatus.

The integration of metal-organic frameworks (MOFs) into composite systems serves as an effective strategy to increase the processability of these materials. Notably, MOF/fiber composites have shown much promise as protective equipment for the capture and remediation of chemical warfare agents. However, the practical application of these composites requires an understanding of their mass transport properties, as both mass transfer resistance at the surface and diffusion within the materials can impact the efficacy of these materials. In this work, we synthesized composite fibers of MOF-808 and amidoxime-functionalized polymers of intrinsic microporosity (PIM-1-AX) and measured the adsorption and mass transport behavior of n-hexane and 2-chloroethyl ethyl sulfide (CEES), a sulfur mustard simulant. We developed a new Fickian diffusion model for cylindrical shapes to fit the dynamic adsorption data obtained from a commercial volumetric adsorption apparatus and found that mass transport behavior in composite fibers closely resembled that in the pure PIM fibers, regardless of MOF loading. Moreover, we found that n-hexane adsorption mirrors that of CEES, indicating that it could be used as a structural mimic for future adsorption studies of the sulfur mustard simulant. These preliminary insights and the new model introduced in this work lay the groundwork for the design of next-generation composite materials for practical applications.

Enhancing the Efficiency of Conventional Surface Immunoassays Within Standard Labware Using Microscale Flows.

In this chapter, we present the design and fabrication of a device and implementation of a protocol to realize increased efficiency of immunoassays within microtiter plates. The device, WellProbe, is a 3D-structured probe that can be used to deliver precise flows at the bottom of standard well plates to establish concentric areas of shear stress intensities using hydrodynamically confined flows. The protocols involve both operation and data analysis.

Solubility vs Dissolution in Physiological Bicarbonate Buffer.

BACKGROUND: Phosphate buffer is often used as a replacement for the physiological bicarbonate buffer in pharmaceutical dissolution testing, although there are some discrepancies in their properties making it complicated to extrapolate dissolution results in phosphate to the in vivo situation. This study aims to characterize these discrepancies regarding solubility and dissolution behavior of ionizable compounds. METHODS: The dissolution of an ibuprofen powder with a known particle size distribution was simulated in silico and verified experimentally in vitro at two different doses and in two different buffers (5 mM pH 6.8 bicarbonate and phosphate). RESULTS: The results showed that there is a solubility vs. dissolution mismatch in the two buffers. This was accurately predicted by the in-house simulations based on the reversible non-equilibrium (RNE) and the Mooney models. CONCLUSIONS: The results can be explained by the existence of a relatively large gap between the initial surface pH of the drug and the bulk pH at saturation in bicarbonate but not in phosphate, which is caused by not all the interfacial reactions reaching equilibrium in bicarbonate prior to bulk saturation. This means that slurry pH measurements, while providing surface pH estimates for buffers like phosphate, are poor indicators of surface pH in the intestinal bicarbonate buffer. In addition, it showcases the importance of accounting for the H2CO3-CO2 interconversion kinetics to achieve good predictions of intestinal drug dissolution.