NADP(H)-dependent biocatalysis without adding NADP(H).

Isocitrate dehydrogenase 1 (IDH1) naturally copurifies and crystallizes in a resting state with a molecule of its exchangeable cofactor, NADP+/NADPH, bound in each monomer of the homodimer. We report electrochemical studies with IDH1 that exploit this property to reveal the massive advantage of nanoconfinement to increase the efficiency of multistep enzyme-catalyzed cascade reactions. When coloaded with ferredoxin NADP+ reductase in a nanoporous conducting indium tin oxide film, IDH1 carries out the complete electrochemical oxidation of 6 mM isocitrate (in 4mL) to 2-oxoglutarate (2OG), using only the NADP(H) that copurified with IDH1 and was carried into the electrode pores as cargo-the system remains active for days. The entrapped cofactor, now quantifiable by cyclic voltammetry, undergoes ~160,000 turnovers during the process. The results from a variety of electrocatalysis experiments imply that the local concentrations of the two nanoconfined enzymes lie around the millimolar range. The combination of crowding and entrapment results in a 102 to 103-fold increase in the efficiency of NADP(H) redox cycling. The ability of the method to drive cascade catalysis in either direction (oxidation or reduction) and remove and replace substrates was exploited to study redox-state dependent differences in cofactor binding between wild-type IDH1 and the cancer-linked R132H variant that catalyzes the "gain of function" reduction of 2OG to 2-hydroxyglutarate instead of isocitrate oxidation. The combined results demonstrate the power of nanoconfinement for facilitating multistep enzyme catalysis (in this case energized and verified electrochemically) and reveal insights into the dynamic role of nicotinamide cofactors as redox (hydride) carriers.

Interlayer Charge Transfer Induced Electrical Behavior Transition in 1D AgI@sSWCNT van der Waals Heterostructures.

The emergence of one-dimensional van der Waals heterostructures (1D vdWHs) opens up potential fields with unique properties, but precise synthesis remains a challenge. The utilization of mixed conductive types of carbon nanotubes as templates has imposed restrictions on the investigation of the electrical behavior and interlayer interaction of 1D vdWHs. In this study, we efficiently encapsulated silver iodide in high-purity semiconducting single-walled carbon nanotubes (sSWCNTs), forming 1D AgI@sSWCNT vdWHs. We characterized the semiconductor-metal transition and increased the carrier concentration of individual AgI@sSWCNTs via sensitive dielectric force microscopy and confirmed the results through electrical device tests. The electrical behavior transition was attributed to an interlayer charge transfer, as demonstrated by Kelvin probe force microscopy. Furthermore, we showed that this method of synthesizing 1D heterostructures can be extended to other metal halides. This work opens the door for the further exploration of the electrical properties of 1D vdWHs.

Nanoconfinement Enables Photoelectrochemical Selective Oxidation of Glycerol via the Microscale Fluid Effect.

The glycerol oxidation reaction (GOR) run with photoelectrochemical cells (PECs) is one of the most promising ways to upgrade biomass because it is thermodynamically favorable, while irreversible overoxidation leads to unsatisfactory product selectivities. Herein, a tunable one-dimensional nanoconfined environment was introduced into the GOR process, which accelerated mass transfer of glycerol via the microscale fluid effect and changed the main oxidation product from formic acid (FA) to glyceraldehyde (GLD), which led to retention of the heavier multicarbon products. The rate of glycerol diffusion in the nanochannels increased by a factor of 4.92 with decreasing inner diameters. The main product from the PEC-selective oxidation of glycerol changed from the C1 product FA to the C3 product GLD with a great selectivity of 60.7%. This work provides a favorable approach for inhibiting further oxidation of multicarbon products and illustrates the importance of microenvironmental regulation in biomass oxidation.

Reorientation of Hydrogen Bonds Renders Unusual Enhancement in Thermal Transport of Water in Nanoconfined Environments.

Liquid confined in a nanochannel or nanotube has exhibited a superfast transport phenomenon, providing an ideal heat and mass transfer platform to meet the increasingly stringent challenge of thermal management in developing high-power-density nanoelectronics and nanochips. However, understanding the thermal transport of confined liquid is currently lacking and is speculated to be fundamentally different from that of bulk counterparts due to the unprecedented thermodynamics of liquid in nanoconfined environments. Here, we report that the thermal conductivity of water confined in a silica nanotube is nearly 2-fold as that of bulk status. Further molecular dynamics simulations reveal that this unusual enhancement originates from the densification and reorientation of local hydrogen bonds close to the nanotubes. Thermal-confinement scaling law is established and quantitatively supported by comprehensive simulations with remarkable agreement. Our findings lay a theoretical foundation for designing nanofluidics-enabled cooling strategies and devices.

The Interplay of Solvation and Polarization Effects on Ion Pairing in Nanoconfined Electrolytes.

The nature of ion-ion interactions in electrolytes confined to nanoscale pores has important implications for energy storage and separation technologies. However, the physical effects dictating the structure of nanoconfined electrolytes remain debated. Here we employ machine-learning-based molecular dynamics simulations to investigate ion-ion interactions with density functional theory level accuracy in a prototypical confined electrolyte, aqueous NaCl within graphene slit pores. We find that the free energy of ion pairing in highly confined electrolytes deviates substantially from that in bulk solutions, observing a decrease in contact ion pairing but an increase in solvent-separated ion pairing. These changes arise from an interplay of ion solvation effects and graphene's electronic structure. Notably, the behavior observed from our first-principles-level simulations is not reproduced even qualitatively with the classical force fields conventionally used to model these systems. The insight provided in this work opens new avenues for predicting and controlling the structure of nanoconfined electrolytes.

Nanoencapsulated MgBu2@ZIF-67 to Construct High Loading Mg-Co@C Nanocomposites: Breaking Through the Barrier of Room Temperature Onset Dehydrogenation.

The synergies of nanoconfinement and catalysis is an effective strategy to improve the kinetic and thermodynamic properties of Mg-based materials. However, obtaining Mg-based materials with high loading, anti-aggregation, and containing nanocatalysts to achieve dehydrogenation at room temperature remains a huge challenge. Herein, a novel and universal preparation strategy for Mg-Co@C nanocomposites with 9.5 nm Mg nanoparticles and 9.4 nm Co nanocatalysts embedded in carbon scaffold is reported. The 9.3 nm MgBu2 nanosheets precipitated by solvent displacement are encapsulated in ZIF-67 to prepare MgBu2@ZIF-67 precursors, then removing excess MgBu2 on the precursor surface and pyrolysis to obtain Mg-Co@C. It is worth noting that the Mg loading rate of Mg-Co@C is as high as rare 69.7%. Excitingly, the Mg-Co@C begins to dehydrogenate at room temperature with saturate capacity of 5.1 wt.%. Meanwhile, its dehydrogenation activation energy (Ea(des) = 68.8 kJ mol-1) and enthalpy (ΔH(des) = 61.6 kJ mol-1) significantly decrease compared to bulk Mg. First principles calculations indicate that the hydrogen adsorption energy on the Mg2CoH5 surface is only -0.681 eV. This work provides a universally applicable novel method for the preparation of nanoscale Mg-based materials with various nanocatalysts added, and provides new ideas for Mg-based materials to achieve room temperature hydrogen storage.

Intervention-Free Graphitization of Carbon Microspheres from a Non-Graphitizing Polymer at Low Temperature: Nanopores as Dynamic Nanoreactors.

Graphitizability of organic precursors is the topic of numerous investigations due to the wide applications of graphitic materials in the industry and emerging technologies of supercapacitors, batteries, etc. Most polymers, such as polydivinyl benzene (PDVB) are classified as non-graphitizings that do not convert to Graphite even after heating to 3000℃. Here, for the first time, the development of graphitic structure in the hierarchal porous sulfonated-PDVB microspheres without employing specific equipment or additives like metal catalysts, organic ingredients, or graphite particles, at 1100°C is reported. The abnormal additive-free graphitic structure formation is confirmed by Raman spectroscopy (ID/IG = 0.87), high-resolution transmission electron microscopy (HRTEM), and selected area diffraction patterns (SAED), as well as x-ray diffraction patterns (XRD), while preservation of aromatic compounds from the carbonization is detected by Fourier transform infrared (FTIR) analysis. Polymer evolution from room temperature to 1100°C is also studied by FTIR, Raman spectroscopy, and XRD techniques. Based on the obtained results, it is suggested that the hierarchal and complicated ink-bottle pore network with a high surface area besides super micropores in the sulfonated-PDVB microspheres has served as nano-sized reaction media. These pores, hereafter referred as "dynamic nanoreactors", are expected to have confined the in-situ produced thermal decomposition products containing broken bond benzene rings, while changing dimensionally and structurally during the designed carbonization regime. This confinement has led to the benzene rings fusion at 250°C, a remarkable extension of them at 450°C, their growth to graphene sheets at 900°C and finally, the stacking of curved graphene layers at 1100°C. The results of this research put stress on the capability of nanopores as nanoreactors to facilitate reactions of decomposition products at low temperatures and ambient pressures to form stacked layers of graphene; A transformation that normally requires catalysts and very high pressures for only specific polyaromatic hydrocarbons.

Ion Transport Behavior in van der Waals Gaps of 2D Materials.

2D materials, with advantages of atomic thickness and novel physical/chemical characteristics, have emerged as the vital building blocks for advanced lamellar membranes which possess promising potential in energy storage, ion separation, and catalysis. When 2D materials are stacked together, the van der Waals (vdW) force generated between adjacent layered nanosheets induces the construction of an ordered lamellar membrane. By regulating the interlayer spacing down to the nanometer or even sub-nanometer scale, rapid and selective ion transport can be achieved through such vdW gaps. The further improvement and application of qualified 2D materials-based lamellar membranes (2DLMs) can be fulfilled by the rational design of nanochannels and the intelligent micro-environment regulation under different stimuli. Focusing on the newly emerging advances of 2DLMs, in this review, the common top-down and bottom-up synthesis approaches of 2D nanosheets and the design strategy of functional 2DLMs are briefly introduced. Two essential ion transport mechanisms within vdW gaps are also involved. Subsequently, the responsive 2DLMs based on different types of external stimuli and their unique applications in nanofluid transport, membrane-based filters, and energy storage are presented. Based on the above analysis, the existing challenges and future developing prospects of 2DLMs are further proposed.

Adsorption at Nanoconfined Solid-Water Interfaces.

Reactions at solid-water interfaces play a foundational role in water treatment systems, catalysis, and chemical separations, and in predicting chemical fate and transport in the environment. Over the last century, experimental measurements and computational models have made tremendous progress in capturing reactions at solid surfaces. The interfacial reactivity of a solid surface, however, can change dramatically and unexpectedly when it is confined to the nanoscale. Nanoconfinement can arise in different geometries such as pores/cages (3D confinement), channels (2D confinement), and slits (1D confinement). Therefore, measurements on unconfined surfaces, and molecular models parameterized based on these measurements, fail to capture chemical behaviors under nanoconfinement. This review evaluates recent experimental and theoretical advances, with a focus on adsorption at solid-water interfaces. We review how nanoconfinement alters the physico-chemical properties of water, and how the structure and dynamics of nanoconfined water dictate energetics, pathways, and products of adsorption in nanopores. Finally, the implications of these findings and future research directions are discussed.

Nanoconfinement of microvilli alters gene expression and boosts T cell activation.

T cells sense and respond to their local environment at the nanoscale by forming small actin-rich protrusions, called microvilli, which play critical roles in signaling and antigen recognition, particularly at the interface with the antigen presenting cells. However, the mechanism by which microvilli contribute to cell signaling and activation is largely unknown. Here, we present a tunable engineered system that promotes microvilli formation and T cell signaling via physical stimuli. We discovered that nanoporous surfaces favored microvilli formation and markedly altered gene expression in T cells and promoted their activation. Mechanistically, confinement of microvilli inside of nanopores leads to size-dependent sorting of membrane-anchored proteins, specifically segregating CD45 phosphatases and T cell receptors (TCR) from the tip of the protrusions when microvilli are confined in 200-nm pores but not in 400-nm pores. Consequently, formation of TCR nanoclustered hotspots within 200-nm pores allows sustained and augmented signaling that prompts T cell activation even in the absence of TCR agonists. The synergistic combination of mechanical and biochemical signals on porous surfaces presents a straightforward strategy to investigate the role of microvilli in T cell signaling as well as to boost T cell activation and expansion for application in the growing field of adoptive immunotherapy.

Nature of dynamic gradients, glass formation, and collective effects in ultrathin freestanding films.

Molecular, polymeric, colloidal, and other classes of liquids can exhibit very large, spatially heterogeneous alterations of their dynamics and glass transition temperature when confined to nanoscale domains. Considerable progress has been made in understanding the related problem of near-interface relaxation and diffusion in thick films. However, the origin of "nanoconfinement effects" on the glassy dynamics of thin films, where gradients from different interfaces interact and genuine collective finite size effects may emerge, remains a longstanding open question. Here, we combine molecular dynamics simulations, probing 5 decades of relaxation, and the Elastically Cooperative Nonlinear Langevin Equation (ECNLE) theory, addressing 14 decades in timescale, to establish a microscopic and mechanistic understanding of the key features of altered dynamics in freestanding films spanning the full range from ultrathin to thick films. Simulations and theory are in qualitative and near-quantitative agreement without use of any adjustable parameters. For films of intermediate thickness, the dynamical behavior is well predicted to leading order using a simple linear superposition of thick-film exponential barrier gradients, including a remarkable suppression and flattening of various dynamical gradients in thin films. However, in sufficiently thin films the superposition approximation breaks down due to the emergence of genuine finite size confinement effects. ECNLE theory extended to treat thin films captures the phenomenology found in simulation, without invocation of any critical-like phenomena, on the basis of interface-nucleated gradients of local caging constraints, combined with interfacial and finite size-induced alterations of the collective elastic component of the structural relaxation process.

Gradient Nanoconfinement Facilitates Binding of Transcriptional Factor NF-κB to Histone- and Protamine-DNA Complexes.

Mechanically induced chromosome reorganization plays important roles in transcriptional regulation. However, the interplay between chromosome reorganization and transcription activities is complicated, such that it is difficult to decipher the regulatory effects of intranuclear geometrical cues. Here, we simplify the system by introducing DNA, packaging proteins (i.e., histone and protamine), and transcription factor NF-κB into a well-defined fluidic chip with changing spatical confinement ranging from 100 to 500 nm. It is uncovered that strong nanoconfinement suppresses higher-order folding of histone- and protamine-DNA complexes, the fracture of which exposes buried DNA segments and causes increased quantities of NF-κB binding to the DNA chain. Overall, these results reveal a pathway of how intranuclear geometrical cues alter the open/closed state of a DNA-protein complex and therefore affect transcription activities: i.e., NF-κB binding.

Production of Noble-Metal Nanohelices Based on Nonlinear Dynamics in Electrodeposition of Binary Copper Alloys.

Spatiotemporal pattern formation is dynamic self-organization widely observed in nature and drives various functions. Among these functions, chirality plays a central role. The relationship between dynamic self-organization and chirality has been an open question; therefore, the production of chiral nanomaterials by dynamic self-organization has not been achieved. Here, we show that the confinement of a two-dimensional spatiotemporal micropattern via the electrodeposition of a binary Cu alloy into a nanopore induces mirror symmetry breaking to produce a helical nanostructure of the noble-metal component although it is still not yet possible to control the handedness at this stage. This result suggests that spatiotemporal symmetry breaking functions as a mirror symmetry breaking if cylindrical pores are given as the boundary condition. This study can be a model system of how spatiotemporal symmetry breaking plays a role in mirror symmetry breaking, and it proposes a new approach to producing helical nanomaterials through dynamic self-organization.

Flexible Glass-Based Hybrid Nanofluidic Device to Enable the Active Regulation of Single-Molecule Flows.

Single-molecule studies offer deep insights into the essence of chemistry, biology, and materials science. Despite significant advances in single-molecule experiments, the precise regulation of the flow of single small molecules remains a formidable challenge. Herein, we present a flexible glass-based hybrid nanofluidic device that can precisely block, open, and direct the flow of single small molecules in nanochannels. Additionally, this approach allows for real-time tracking of regulated single small molecules in nanofluidic conditions. Therefore, the dynamic behaviors of single small molecules confined in different nanofluidic conditions with varied spatial restrictions are clarified. Our device and approach provide a nanofluidic platform and mechanism that enable single-molecule studies and applications in actively regulated fluidic conditions, thus opening avenues for understanding the original behavior of individual molecules in their natural forms and the development of single-molecule regulated chemical and biological processes in the future.

Unravelling Ultrafast Li Ion Transport in Functionalized Metal-Organic Framework-Based Battery Electrolytes.

Nonaqueous fluidic transport and ion solvation properties under nanoscale confinement are poorly understood, especially in ion conduction for energy storage and conversion systems. Herein, metal-organic frameworks (MOFs) and aprotic electrolytes are studied as a robust platform for molecular-level insights into electrolyte behaviors in confined spaces. By employing computer simulations, along with spectroscopic and electrochemical measurements, we demonstrate several phenomena that deviate from the bulk, including modulated solvent molecular configurations, aggregated solvation structures, and tunable transport mechanisms from quasi-solid to quasi-liquid in functionalized MOFs. Technologically, taking advantage of confinement effects may prove useful for addressing stability concerns associated with volatile organic electrolytes while simultaneously endowing ultrafast transport of solvates, resulting in improved battery performance, even at extreme temperatures. The molecular-level insights presented here further our understanding of structure-property relationships of complex fluids at the nanoscale, information that can be exploited for the predictive design of more efficient electrochemical systems.

Nanoscale Confinement Effects on Ionic Conductivity of Solid Polymer Electrolytes: The Interplay between Diffusion and Dissociation.

Solid polymer electrolytes (SPEs) are attractive for next-generation lithium metal batteries but still suffer from low ionic conductivity. Nanostructured materials offer design concepts for SPEs with better performance. Using molecular dynamics simulation, we examine SPEs under nanoscale confinement, which has been demonstrated to accelerate the transport of neutral molecules such as water. Our results show that while ion diffusion indeed accelerates by more than 2 orders of magnitude as the channel diameter decreases from 15 to 2 nm, the ionic conductivity does not increase significantly in parallel. Instead, the ionic conductivity shows a nonmonotonic variation, with an optimal value above, but on the same order as, its bulk counterparts. This trend is due to enhanced ion association with decreasing channel size, which reduces the number of effective charge carriers. This effect competes with accelerated ion diffusion, leading to the nonmonotonicity in ion conductivity.

Orientational Ordering in Nano-confined Polar Liquids.

Water and other polar liquids exhibit nanoscale structuring near charged interfaces. When a polar liquid is confined between two charged surfaces, the interfacial solvent layers begin to overlap, resulting in solvation forces. Here, we perform molecular dynamics simulations of polar liquids with different dielectric constants and molecular shapes and sizes confined between charged surfaces, demonstrating strong orientational ordering in the nanoconfined liquids. To rationalize the observed structures, we apply a coarse-grained continuum theory that captures the orientational ordering and solvation forces of those liquids. Our findings reveal the subtle behavior of different nanoconfined polar liquids and establish a simple law for the decay length of the interfacial orientations of the solvents, which depends on their molecular size and polarity. These insights shed light on the nature of solvation forces, which are important in colloid and membrane science, scanning probe microscopy, and nano-electrochemistry.

Ion-Specific Nanoconfinement Effect in Multilayered Graphene Membranes: A Combined Nuclear Magnetic Resonance and Computational Study.

Ion adsorption within nanopores is involved in numerous applications. However, a comprehensive understanding of the fundamental relationship between in-pore ion concentration and pore size, particularly in the sub-2 nm range, is scarce. This study investigates the ion-species-dependent concentration in multilayered graphene membranes (MGMs) with tunable nanoslit sizes (0.5-1.6 nm) using nuclear magnetic resonance and computational simulations. For Na+-based electrolytes in MGMs, the concentration of anions in graphene nanoslits increases in correlation with their chaotropic properties. As the nanoslit size decreases, the concentration of chaotropic ion (BF4-) increases, whereas the concentration of kosmotropic ions (Cit3-, PO43-) and other ions (Ac-, F-) decreases or changes slightly. Notably, anions remain more concentrated than counter Na+ ions, leading to electroneutrality breakdown and unipolar anion packing in MGMs. A continuum modeling approach, integrating molecular dynamic simulation with the Poisson-Boltzmann model, elucidates these observations by considering water-mediated ion-graphene non-electrostatic interactions and charge screening from graphene walls.

Dynamic Response of Ion Transport in Nanoconfined Electrolytes.

Ion transport in nanoconfined electrolytes exhibits nonlinear effects caused by large driving forces and pronounced boundary effects. An improved understanding of these impacts is urgently needed to guide the design of key components of the electrochemical energy systems. Herein, we employ a nonlinear Poisson-Nernst-Planck theory to describe ion transport in nanoconfined electrolytes coupled with two sets of boundary conditions to mimic different cell configurations in experiments. A peculiar nonmonotonic charging behavior is discovered when the electrolyte is placed between a blocking electrode and an electrolyte reservoir, while normal monotonic behaviors are seen when the electrolyte is placed between two blocking electrodes. We reveal that impedance shapes depend on the definition of surface charge and the electrode potential. Particularly, an additional arc can emerge in the intermediate-frequency range at potentials away from the potential of zero charge. The obtained insights are instrumental to experimental characterization of ion transport in nanoconfined electrolytes.

Structural and Vibrational Properties of Carboxylates Intercalated into Layered Double Hydroxides: A Joint Computational and Experimental Study.

Layered double hydroxides (LDHs) are fascinating clay-like materials that display versatile properties, making them an extremely fertile playground for diverse applications, ranging from bio-compatible materials to the pharmaceutical industry to catalysis and photocatalysis. When intercalating organic and bio-organic species between the inorganic layers, such materials are named hybrid LDHs. The structure-property relation in these systems is particularly relevant, since most of the properties of the materials may be fine-tuned if a comprehensive understanding of the microscopic structure in the interlamellar space is achieved, especially with respect to the reorganization under water uptake (swelling). In this work, we combined experiments and simulations to rationalize the behavior of LDHs intercalating three carboxylates, the general structure of which can be given as [Mg4Al2(OH)12]A2-·XH2O (with A2- = succinate, aspartate, or glutamate and X representing increasing water content). Following this strategy, we were able to provide an interpretation of the different shapes observed for the experimental water adsorption isotherms and for the evolution of the infrared carboxylate band of the anions. Apart from small differences, due to the different reorganization of the conformational space under confinement, the behavior of the two amino acids is very similar. However, such behavior is quite different in the case of succinate. We were able to describe the different response of the anions, which has a significant impact on the isotherm and on the size of the interlamellar region, in terms of a different interaction mechanism with the inorganic layer.