Diffusion Limit Research Articles

The formation of carbon─heteroatom bonds is a key strategy that enables the modular construction of molecules in synthetic chemistry, but activating inert carbonyl compounds to forge C─X bonds remains a longstanding synthetic challenge. Herein, we report a universal visible light-driven photocatalytic system that enables efficient C─X (X=SS, S, Se) bond formation under mild, redox-neutral conditions. Guided by Marcus electron transfer theory, we employed a computational redox-pair screening strategy to identify triplet-state pathways with optimal electronic coupling matrix element (Hif) and thermodynamic alignment. High-level multireference calculations confirmed an ultrafast single-electron transfer mechanism with ultrafast kinetics approaching the diffusion limit. To translate this mechanistic insight into a functional platform, we designed a dual-functionalization strategy for α-diketones, wherein one carbonyl acts as a conventional synthon while the other forms a light-responsive dihydroquinazolinone (DHQZ) radical precursor. This system exhibits broad substrate scope, excellent functional group tolerance, and compatibility with late-stage functionalization of bioactive scaffolds. Overall, this study establishes a general and mechanistically predictive photocatalytic strategy that transforms Marcus theory from a conceptual foundation into a design principle for efficient, light-driven C─heteroatom bond construction.

Abstract The formation of carbon─heteroatom bonds is a key strategy that enables the modular construction of molecules in synthetic chemistry, but activating inert carbonyl compounds to forge C─X bonds remains a longstanding synthetic challenge. Herein, we report a universal visible light‐driven photocatalytic system that enables efficient C─X (X = SS, S, Se) bond formation under mild, redox–neutral conditions. Guided by Marcus electron transfer theory, we employed a computational redox‐pair screening strategy to identify triplet‐state pathways with optimal electronic coupling matrix element (H if ) and thermodynamic alignment. High‐level multireference calculations confirmed an ultrafast single‐electron transfer mechanism with ultrafast kinetics approaching the diffusion limit. To translate this mechanistic insight into a functional platform, we designed a dual‐functionalization strategy for α‐diketones, wherein one carbonyl acts as a conventional synthon while the other forms a light‐responsive dihydroquinazolinone (DHQZ) radical precursor. This system exhibits broad substrate scope, excellent functional group tolerance, and compatibility with late‐stage functionalization of bioactive scaffolds. Overall, this study establishes a general and mechanistically predictive photocatalytic strategy that transforms Marcus theory from a conceptual foundation into a design principle for efficient, light‐driven C─heteroatom bond construction.

Edible polymeric composite hydrogel films offer a promising solution for cultured meat production. These films are made by incorporating natural polysaccharides, synthetic biocompatible polymers, and antioxidants within the scaffolds. This approach can help combat global climate change and meet the increasing demand for sustainable food sources. The utilization of edible polysaccharides in the fabrication of hydrogels is a cost-effective and sustainable approach, which serves as effective scaffolding in the cultivation of meat. The polymeric composite hydrogel films, designated as “CSCP” (curcumin–starch–carrageenan–PVA) with varying concentrations of polymers, consist of curcumin (an antioxidant and coloring agent), starch (potato), kappa (κ)-carrageenan, and poly(vinyl alcohol) (PVA), with PVA being classified as generally recognized as safe (GRAS) for use in food applications. These edible polymeric composite hydrogel films were prepared with glycerol, serving as a plasticizer, and succinic acid, a crosslinker, through solvent casting and thermal treatment methods. Analytical techniques, including field-emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and tensile strength testing, were employed to evaluate the morphology, crystalline nature, composition, and mechanical properties of the fabricated CSCP scaffolds. The incorporation of glycerol and succinic acid facilitates the plasticizing and cross-linking of the polymeric materials via hydroxyl and carboxyl group interactions during film formation. Increasing the potato starch content in the CSCP-2 composite hydrogel film reduced its mechanical strength. This is because the starch disrupted the polymer’s crystalline regions. The resulting amorphous structure improved the film’s flexibility and elasticity. Nevertheless, the increased potato starch content adversely affects interfacial adhesion, reducing tensile strength. The swelling ratio of the CSCP-2 composite hydrogel film slightly decreases with higher potato starch content, which limits hydrogen bonding interactions with water. Notably, the CSCP composite hydrogel films support adhesion and proliferation of bovine muscle satellite cells (MuSCs) with good cytocompatibility for up to 21 days. However, a slight decrease in metabolic activity on CSCP-2 films was observed. This was likely due to nutrient depletion and limited oxygen diffusion caused by cell multilayering. Overall, the starch-based edible CSCP composite hydrogel films exhibit significant potential as scaffolds for culturing bovine muscle satellite cells (myosatellite cells), paving the way for large-scale production of three-dimensional (3D) cultured meat.

Biogeochemical stratification governs microbial hydrocarbon degradation potential in a petrochemical contaminated site.

Self-replicating DNA circuit for high-fidelity in situ imaging of T4 polynucleotide kinase activity in living cells.

Development of relevant human induced pluripotent stem cell-derived cardiac organoids is essential to recapitulate myocardium physiology and functionality for the assessment of drug-induced toxicity evaluations. However, the optimal conditions for culturing self-aggregating multicellular cardiac organoids are not well-elucidated, particularly the impact of noncardiomyocytes. In this study, we generated cardiac organoids at varying seeding densities to formulate organoids that meet or exceed the biological diffusion limit. We assessed their morphology, gene expression profiles, beating functionality, viability, and mitochondrial activity over time. Our results show that organoid sizes stabilize by 7 days of culture, regardless of seeding density. However, organoids seeded with 20,000 cells retained a more optimal cardiac signature that promotes cardiac maturity and minimizes fibrotic tendencies, especially when cultured for longer than 7 days. While all organoid populations maintained their beating functionalities, those seeded with 80,000 cells exhibited greater cell shedding and increased apoptosis at long-term culture. In contrast, minimal apoptosis was observed in organoids seeded with 20,000 cells after 7 days. Mitochondrial staining further revealed that organoids seeded with 20,000 cells consistently demonstrated higher metabolic activity. Taken together, organoids seeded with 20,000 cells and cultured for 7 days yielded the healthiest morphology, transcriptional signature, and viability while maintaining robust beating kinetics. Importantly, the organoid model identified in this study demonstrated a selectivity index (SI) that is over an order of magnitude larger than that of two-dimensional cultures, showing improved sensitivity to clinically relevant doxorubicin-induced cardiotoxicity, enabling more accurate dose-response evaluations that better reflect therapeutic conditions.

Garnet-type Li7La3Zr2O12 (LLZO) is a solid electrolyte candidate for ASSLBs, owing to its wide electrochemical window and intrinsic safety. Yet phase-pure LLZO remains difficult because secondary phases form, and the transition towards the tetragonal phase, aliovalent doping, mitigates these issues. Still, the phase formation pathway is not fully understood. Here, we present comparative in situ and ex situ studies of Nb- and Ta-doped LLZO (LLZNO and LLZTO) that were synthesized by a solid-state reaction. In situ/ex situ XRD reveals that the lithium precursor dictates the reaction path: differing decomposition temperatures of the lithium precursor define reaction windows that control cubic-phase purity and particle morphology. In air, limited Li diffusion favors oxycarbonates and pyrochlore, necessitating 950–1050 °C to achieve phase-pure cubic LLZO. Under N2, faster Li availability and diffusion enable uniform nucleation and a route to cubic LLZO without detectable secondary phases. These findings demonstrate the coupled effects of temperature, precursor, dopant, and atmosphere, guiding process optimization and scalable production.

Traditional electrolyte systems are struggle to meet practical needs for high performance of sodium-ion batteries (SIBs) due to their limited functionality. The design of electrolytes today relies largely on expensive trial-and-error methodologies and intricate solvent-structure engineering, in which various additives and solvents are arbitrarily used without any reasonable selection rules. Motivated by this, we herein establish a descriptor-guided framework centered on solvent oxidative stability and Na+-solvent coordination chemistry to identify intrinsically flame-proof, ester-based electrolytes that overcome conventional diffusion limits. By screening a number of fluorinated phosphate and cyclic carbonate candidates, the electrolytes with the comprehensive properties, including the electrolyte desolvation processes, oxidation resistance, and flame retardancy, were successfully designed and synthesized, thereby realizing intrinsic flameproofing with fast-charging capability. Impressively, our optimized electrolytes sustain over 98% capacity retention for 350 cycles at 1.0 C with a Coulombic efficiency of nearly 100% when deployed in Na3V2(PO4)3 (NVP) cells, whereas benchmark carbonate systems fail within a few tens of cycles. By linking the explicit performance descriptors of solvent electronic structure and ion-solvent coordination, this work delivers a rational pathway to flame-proof and high-rate SIB electrolytes, breaking the long-standing diffusion limit and brute-force screening.

Abstract Electrocatalytic conversions offer a promising route for sustainable chemical production using renewable energy. Gas diffusion layers (GDLs) enable selective product formation at high current densities but suffer from electrolyte flooding, and polytetrafluoroethylene (PTFE)‐based GDLs typically require metal conductive layers, which constrain catalyst development. A recently developed GDL configuration, electropolymerized poly(3,4‐ethylenedioxythiophene) (PEDOT)‐coated PTFE, demonstrates notable flooding resistance, but suffers from gas diffusion limitations at elevated currents due to limited gas diffusion through the PEDOT layer. Here, different dopants in PEDOT are exploited to modify the physical properties and enhance gas transport. ClO 4 − ‐doped PEDOT exhibits superior performance due to optimized physical structure, leading to increased gas permeance and faradaic efficiency (FE) for CO production during electrocatalytic CO 2 reduction. Further optimization of coverage and thickness achieved by adjusting charge density led to an optimal configuration at 33 mC cm −2 . This GDL supports various metal electrocatalysts and demonstrates FE CO of > 90% for over 150 h at −200 mA cm − 2 using a commercial silver electrocatalyst. This work highlights the importance of GDL engineering in enhancing performance and durability for long‐term electrocatalytic processes.

Internal wall insulation is crucial for reducing CO₂ emissions in historic buildings where external interventions are undesirable. Despite its importance, adoption remains limited. The InRenova project aims to understand and remove the barriers to this limited diffusion. An online survey targeting key stakeholders explored participants' experiences with internal insulation, challenges, materials and techniques used, and design tools. The survey revealed substantial barriers, including concerns about moisture-related damages, technical complexities in the practical implementation, and a lack of validated examples. It revealed also that although dynamic hygrothermal simulations are perceived as essential for designing effective solutions, their application remains limited. Finally, participants showed little knowledge of existing guidelines, highlighting the need for better dissemination of scientific results targeting designers

The thin films of nanoporous materials, including zeolites, metal-organic frameworks (MOFs), and mesoporous materials, are promising for applications in electrodes, separations, catalysis, and sensing. While microporous materials offer high surface areas that expose numerous active sites, their limited diffusion pathways for reactants and products constrain performance. Hierarchically structured mesoporous-microporous materials offer an ideal solution by combining extensive surface areas with enhanced diffusion; however, the complexity of creating and integrating dual pore systems has hindered progress in this area, and reports on these materials remain scarce. Here, evaporation-induced methods (spin-coating and spray-coating) are introduced for the rapid synthesis of continuous mesoporous amorphous MOF thin films on solid substrates, achieved through the cooperative self-assembly of block copolymer micelles and MOF precursors (metal ions and organic linkers). The resulting mesoporous amorphous MOF films exhibit uniform pore distribution with low surface roughness. Furthermore, these films exhibit great potential for application on various substrates, benefiting from the versatility of this synthesis approach.

Organic solar cells (OSCs) have garnered significant interest for their lightweight, flexible, and low-cost properties; however, their commercial viability remains constrained by suboptimal light absorption, limited exciton diffusion lengths, and poor long-term stability. Au TiO2 provides the highest fill factor (FF), indicating superior charge extraction due to effective interfacial alignment, while TiN ZnO extends absorption into the near-infrared and offers the best thermal stability, retaining 92% of its original PCE after 1000 h of accelerated aging. Field simulation analyses reveal that shell thickness directly modulates near-field localization and recombination dynamics, with optimal suppression achieved at 15–18 nm.

High-resolution mapping of three-dimensional structures in biological tissues is essential for understanding various biological processes. However, the optical heterogeneity of these tissues, marked by varying optical properties, causes light scattering and absorption, complicating imaging. Current tissue clearing methods can take between 48 h and 32 days, and the limited diffusion depth of fluorescent probes restricts whole-tissue imaging. This study introduces an innovative Sonication-Assisted Tissue Clearing and Immunofluorescent Staining method (SoniC/S), which combines low-frequency ultrasound with a commercial chemical clearing kit and iDISCO staining techniques. When tested on the soft tissue of mouse muscle, the dense collagenous tissue of rat tendon, and the heme-rich tissue of mouse spleen, SoniC/S achieved complete clearing in just 36 h and uniform labeling in 15 h. Overall, SoniC/S provides a rapid and effective approach for tissue clearing and deep immunostaining, facilitating high-resolution volumetric imaging in biological research.Supplementary InformationThe online version contains supplementary material available at 10.1038/s41598-025-18928-5.

Abstract The growth of the solid electrolyte interphase (SEI) on the anode is the main cause for electrochemical degradation of lithium-ion batteries. While the growth rate of the SEI layer is influenced by reaction kinetics and solvent diffusion limits, these two effects have been traditionally combined using the sum of reciprocals. Here, a physics-based methodology is proposed considering a two-stage process, with a piecewise kinetic-diffusion (PKD) control mechanism of the SEI formation in the electrochemical degradation model. The kinetic and diffusion limits are separately determined by calculating the molar fluxes of Li+ and ethylene carbonate (EC) solvent as two reactant species for SEI, which are compared at the reaction interphase to identify the limiting mechanism. The simulation results are validated with both calendar and cycle life data, under different SOCs, temperatures, and charging profiles. The PKD method more accurately captures the temperature and SOC dependency of capacity and voltage fade, as compared to the empirical and simplified sum-of-reciprocal assumptions. The switch point (SP) between kinetic and diffusion limited process is identified as an optimizable parameter and its impact on battery life is studied. The analysis shows that the SEI-related electrochemical degradation is suppressed when the SP occurs late in the cycle.

With the global expansion of hydrogen infrastructure, the safe and efficient transportation of hydrogen is becoming more important. In this study, several technical factors, including material degradation, pressure variations, and monitoring effectiveness, that influence hydrogen transportation using pipelines are examined using system dynamics. The results show that hydrogen embrittlement, which is the result of microstructural trapping and limited diffusion in certain steels, can have a profound effect on pipeline integrity. Material incompatibility and pressure fluctuations deepen fatigue damage and leakage risk. Moreover, pipeline monitoring inefficiency, combined with hydrogen’s high flammability and diffusivity, can raise serious safety issues. An 80% decrease in monitoring efficiency will result in a 52% reduction in the total hydrogen provided to the end users. On the other hand, technical risks such as pressure fluctuations and material weakening from hydrogen embrittlement also affect overall system performance. It is essential to understand that real-time detection using hydrogen monitoring is particularly important and will lower the risk of leakage. It is crucial to know where hydrogen is lost and how it impacts transport efficiency. The model offers practical insights for developing stronger and more reliable hydrogen transport systems, thereby supporting the transition to a low-carbon energy future.

This study investigates the electrochemical contribution of silicon carbide (SiC) in SiC/carbon black (CB) composites for the use in lithium‐ion battery anodes. High‐purity, nitrogen‐doped 3C‐SiC is synthesized via an environmentally friendly sol–gel method, producing silicon dioxide (SiO2)‐free microsized crystals. Due to the low interparticle conductivity, conductive carbon additives are therefore necessary to enable lithiation. However, the electrochemical activity of these conductive carbon additives is often overlooked, with the measured capacity typically attributed solely to SiC. Here, the contributions of SiC and CB to the overall electrode capacity are clearly differentiated. The findings support the hypothesis that charge storage involves both CB and SiC, whereas CB still remains the main contributor. For a typical SiC electrode with 20% CB, a reversible capacity of 72 mAh g−1 is achieved at 1C in the 10th cycle, with SiC contributing 47% to the total capacity. Kinetic analysis reveals that lithium (Li) storage in SiC/CB is predominantly surface‐controlled, with SiC contributing partially through Li+ diffusion. This provides direct evidence that SiC actively participates in lithium storage, with lithiation occurring primarily through a surface‐controlled process within the first few SiC layers, complemented by limited bulk diffusion. This explains the relatively low capacity of SiC compared to the theoretical capacity.

Background/Objectives: Understanding the interactions between nanoparticles and mucosal tissues is crucial for the development of advanced drug delivery systems, as the diffusion behavior of nanoparticles through mucus is strongly influenced by their size and surface properties, and the viscoelastic nature of the hydrogel matrix. In this study, we investigated the impact of nanoparticle size, surface charge, and hydrogel crosslinking density on nanoparticle diffusion in a mucus model in vitro. Method: Citrate-stabilized and PEGylated 30 and 100 nm gold nanoparticles were used as a model of nanoparticle and their diffusion through mucus-mimicking mucin-based hydrogels of two different crosslinking densities was assessed. Results: Citrate-stabilized 30 nm nanoparticles demonstrated greater diffusion in hydrogels mimicking native mucus compared to more densely crosslinked ones, reaching approximately 50.3 ± 0.2% diffusion within the first 5 min of the assay. This size-dependent effect was not observed for the 100 nm citrate-stabilized nanoparticles, which showed limited diffusion in both hydrogel types. To confer different surface charge, gold nanoparticles were functionalized by the conjugation of poly(ethylene glycol) (PEG) derivatives of identical molecular weight with different terminal moieties (neutral, and positively and negatively charged) to modulate the surface charge and assess their interaction with the negatively charged mucin matrix. PEGylated particles exhibited significantly greater mobility than their citrate-stabilized counterparts, regardless of size or hydrogel density owing to the muco-penetration effect of PEG. Among PEGylated particles, the neutral and negatively charged 30 nm variants demonstrated higher diffusion than the positively charged ones due to weaker interactions with the negatively charged mucin hydrogel. For the 100 nm particles, the neutral PEGylated nanoparticles exhibited greater diffusion than their positively charged counterparts. Conclusions: Overall findings could provide valuable insights into the more rational design of nanoparticle-based drug delivery systems targeting mucosal tissues.

Eco-friendly and flexible carbon electrode materials are crucial for advancing next-generation clean energy technologies owing to their abundance, chemical stability, thermal resilience, and excellent processability. Nevertheless, conventional carbon electrodes often suffer from low ionic conductivity, limited ion diffusion, and reduced power density. In this study, we report the synthesis of mesoporous activated carbon derived from the sepals of Kigelia africana flowers (KASP), activated with potassium hydroxide (KOH) at different temperatures (KASP-600, KASP-700, KASP-800, and KASP-900). Among these, KASP-800 shows outstanding electrochemical performance, delivering a specific capacitance of 372.2 F g−1 nearly double that of commercial activated carbon (169.5 F g−1). When assembled into a flexible symmetric supercapacitor, the KASP-800 electrode achieves a specific capacitance of 84.12 F g−1, an energy density of 6.38 Wh kg−1, and a power density of 14.48 kW kg−1, operating efficiently within a wide potential window of 1.6 V. Furthermore, the KASP-800-based device exhibits excellent cycling stability, retaining 97% Coulombic efficiency after 9350 charge–discharge cycles. These findings highlight the potential of KASP-derived mesoporous carbons as sustainable, high-performance electrodes for next-generation clean energy storage systems.

Mass transport in and around porous objects immersed in fluid flow is prevalent in a wide range of industrial and biomedical applications. These include medical devices, drug delivery, membrane-based processes, and pathophysiology of various disease scenarios, such as thrombosis. Numerical modeling using techniques, such as finite element method, is an important avenue for quantitative analysis of such transport processes. However, the presence of large discontinuities in concentrations, driven by discontinuous diffusivity and porosity, can lead to spurious numerical oscillations in finite element solutions. Here, we adopt a numerically consistent jump-stabilized finite element formulation, coupled with immersed non-conforming discretizations of the porous domain, to mitigate such spurious oscillatory behavior. We demonstrate that the resulting stabilized numerical method is robust in the pure advection (hyperbolic) and the pure diffusion (parabolic) limits of the transport equation. The stabilization contribution includes a tunable diffusion contribution to the system, ensuring that the solution does not become over-diffused. Subsequently, we present a series of illustrative simulation case studies, to show that the resulting stabilized algorithm can model transport processes in two- and three-dimensional settings, involving high spatial heterogeneity in porosity and highly arbitrary porous domain geometries that can vary non-trivially in space and time.

Advances in auricular drug delivery for the management of different otitic conditions.