Nanoconfinement Effect Research Articles

Thermochemical Properties of Synthesized Urea from Recovered Ammonia and Carbon Dioxide in Well-Ordered Nanospaces of Hollow Silica Spheres.

The present work investigated the thermochemical properties of urea synthesized in well-ordered nanospaces of porous hollow silica spheres' shells from recovered ammonia and carbon dioxide in aqueous solution. Thermochemical behaviors of the urea synthesized in well-ordered nanospaces of the hollow spheres' shells prepared with 1-dodeclyamine were analyzed from the results of thermogravimetric analysis (TGA) and differential thermal analysis (DTA), and endothermic peaks assigned as the phase transition and decomposition were observed at ca. 440 and 514 K, respectively, which were higher than those of pristine urea (405 and 408 K, respectively), probably because of the nanoconfinement effect. The decomposition behavior was also confirmed by the result of diffuse reflectance infrared Fourier transform (DRIFT) spectra of the samples treated at various temperatures up to 573 K, and the decomposition of urea synthesized in the well-ordered nanospaces of the hollow spheres' shells started at 468 K and completed up to 533 K.

Fluid phase behavior in multi-scale shale reservoirs with nano-confinement effect

Shale reservoirs are featured by widely distributed micro-scale fractures and nano-scale pores. The phase behavior of reservoir fluids in these complex environments remains uncertain. Hence, an efficient model is developed to investigate the fluid phase behavior in multi-scale shale reservoirs based on a pore-size-dependent equation of state. The porous space is discretized into specific sizes of nanopores and fractures regions. Phase equilibrium calculations for pure components, binary mixtures and multi-component shale oils show that adsorption and critical properties shifts display opposite effects on a fluid distribution, and the shifts in the critical properties are the main reason for more lighter components present in nanopores. The nano-confinement effect enhances the ability of CO2 to enter nanopores. An innovative multi-scale model of partial equilibrium is developed to explore changes in fluid properties during pressure depletion. The results reveal that gas appears in the fracture region, while the confined fluids within nanopores are always kept in the oil phase. Lighter components within nanopores are rapidly released as pressure drops. However, the content of heavier components within nanopores gradually decreases if the pressure stabilizes for a while, meaning that a slow pressure drop is more conducive to the recovery of shale oil from nanopores.

The tuning of crystallization behavior of ferroelectric poly(vinylidene fluoride‐co‐trifluoroethylene)

AbstractPoly (vinylidene fluoride‐co‐trifluoroethylene) [P(VDF‐TrFE)] has three crystal forms, including paraelectric α, ferroelectric β, and γ phases. In previous studies, the properties and performances of P(VDF‐TrFE) have been the focus of research. However, the formation mechanism and regulation mode of various crystal forms remain unclear. Therefore, it is an important topic for further research to elucidate, summarize, and prospect the polymorphism of P(VDF‐TrFE) and regulate the crystal forms. This review systematically summarizes the crystalline structure and phase transition between ferroelectric and paraelectric phase of P(VDF‐TrFE) crystals; discusses the influence of annealing, blending and electric field on the crystallinity, selection of polymorphic crystals, and phase transition behavior between them; reviews the effects of annealing, melt‐recrystallization, substrate and nanoconfinement on the crystal orientation. Finally, the effects of the crystal structure of P(VDF‐TrFE) on its properties are briefly summarized.

Construction of smartphone-adapted signal visualization platform for dual-mode detection of H2S based on integrated metal-organic framework nanoprobes

Hydrogen sulfide (H2S) is a toxic contaminant and has great influence on many physiological processes. Due to various pathophysiological roles and environmental pollution problems, it is necessary to construct and develop simple and portable monitoring sensors for the precise detection of H2S. Herein, we developed a smartphone-adapted dual-mode detection platform by integrating the colorimetric and photothermal imaging analysis into a metal-organic framework-based chip (ZIF-8/Cu). Due to the nanoconfinement effect of ZIF-8, small-sized plasmonic CuS could be in-situ formed during the detection procedure of H2S and endowed the chips with excellent photothermal properties. By constructing a smartphone-adapted photothermal imager, the metal-organic framework-based chip could achieve a portable photothermal imaging analysis of H2S. Moreover, as the formed CuS was a good peroxidase-like nanozyme, the chips could also be used to trigger the enzymic catalytic reaction toward the chromogenic reaction of 3,3′,5,5′-tetramethylbenzidine (TMB)-H2O2, thus providing another colorimetric sensing mode by using a smartphone App. In this smartphone-adapted visualization platform, the portable chemosensors could simultaneously achieve double detection modes at one electrode, which provided a new pathway for the accurate detection of H2S and circumvented the false-positive or negative errors during the detection process. Besides, by using the finite difference time domain (FDTD) simulation method, the in-depth mechanism, including the plasmonic effect and spatial electromagnetic field distribution, was explored to provide a possible reason for the excellent sensing performance of the dual-mode visualization platform. This work provides a new insight into the construction of the accurate, portable and smart sensing platform in the visual screening of H2S.

Nanoconfinement boosts affinity of hydrated zirconium oxides to arsenate: Surface complexation modeling study

Nanoscale hydrated zirconium oxide (HZO) holds great potential in groundwater purification due to its ability to form inner-sphere coordination with arsenate. Despite being frequently used, especially as encapsulations in host materials for practical application in water treatment, the adsorption mechanisms of solutes on HZO are not appropriately explored, in particular for arsenate adsorption. In this study, we investigated the Zr–As coordination configuration and identified the most credible Zr–As configuration using surface complexation modeling (SCM), XPS and FT-IR analysis. The corresponding intrinsic coordination constants (Kintr) values was calculated by SCM, and the nanoconfinement effects were distinguished by comparing bare HZO with the HZO nanoparticles (NPs) encapsulated inside the strongly basic anion exchanger D201. Potentiometric titration suggests that the surface Zirconium hydroxyl groups (≡ZrOH) mainly exist in protonated form (≡ZrOH2+). Batch adsorption experiments demonstrate that the D201 hosts could adsorb As(V) through ion exchange by the quaternary ammonium groups under the low ionic strength (≤0.01 M NaNO3) and at pH > 6. The nanocomposite (HZO@D201) exhibits a higher adsorption capacity in a wide range of pH (3-10) and ionic strength (0.001–0.1 M NaNO3) than bare HZO. SCM simulations reveal that the coordination configuration of diprotonated monodentate mononuclear (MM-H2) dominates at pH 3–6, while deprotonated bidentate binuclear (BB–H0) dominates at pH > 7. For each configuration, the intrinsic coordination constants (Kintr) of HZO@D201 (10−0.66 and 10−16.10, respectively) are significantly higher than those of bare HZO (10−12.24 and 10−44.42, respectively), indicating a superior chemical bonding affinity caused by nanoconfinement. The obtained Kintr values are used to predict arsenate adsorption isotherms in pH 3 and 9, and the results align with the SCM simulation outcomes. This study may offer a feasible method for investigating the nanoconfinement effect of emerging nanocomposite adsorbents from a thermodynamic perspective, and provide reference coordination equilibrium constants of HZO for research and practical application.

Selective and asymmetric ion transport in covalent organic framework-based two-dimensional nanofluidic devices

ABSTRACT Two-dimensional (2D) covalent organic framework (COF) membranes featuring well-aligned and programmable vertical nanochannels have emerged as a promising candidate for advanced nanofluidic devices and showcased vast potential in the fields of smart-gating, ion-separation, and energy-harvesting. However, the transverse interlayer nanochannels with a height of sub-nanometer-scale in 2D-COF membranes have scarcely been studied in comparison. Here, we report the ion transport characteristics in 2D interlayer nanochannels of protonated COF membranes. The distinct surface-charge-governed ionic conductance in domination of electrolyte concentration below 10−3 M as well as the exceptional anion/cation (Cl−/K+) selectivity is revealed due to the pronounced charge and nano-confinement effects. Additionally, evident ion current rectification is witnessed when incorporating asymmetric geometry into the system, which is attributed to the dynamic process of ion enrichment and dissipation within the protonated nanochannels. This work offers immense prospects for 2D-COF membranes in the fields of biomimetic nanofluidic devices and cutting-edge electronic devices.

Direct measurement and modeling of viscoelastic-viscoplastic properties of freely standing thin polystyrene films.

The demand for applications, such as coatings, separation filters, and electronic packaging, has greatly driven the research of polymer films. At nanometer scale, mechanical properties of thin polymer films can significantly deviate from bulk. Despite outstanding progresses, there still lack deep discussions on nonlinear viscoelastic-viscoplastic response and their interactions under nanoconfinement. In this work, by conducting measurements via the bubble inflation method and modelling using Schapery and Perzyna equations, we demonstrate nonlinear viscoelastic-viscoplastic properties of freely standing thin polystyrene (PS) films. The results show the unchanged glassy compliance and the rubbery stiffening phenomenon for thin PS films, where the lower rubbery plateau in rubbery stiffening may originate from the induced molecular orientation by plastic deformation. With decreasing film thickness, viscosity and yield stress in viscoplasticity increase in an exponential and a linear trend, respectively, indicating the significant role of nanoconfinement effect on viscoplastic properties. These findings may reveal that there are many properties from linear viscoelasticity to nonlinear viscoelasticity-viscoplasticity that need to be explored and unveiled for sufficient understanding of the nanoconfinement effect on altering mechanical behavior of polymers.

Effect of processing on thermal properties of pentaglycerine-based solid-solid phase change materials

Plastic crystals hold great potential for compact and cost-effective thermal energy storage (TES) systems due to their solid-solid transitions, high latent heat, and tunable transition temperatures. However, the impact of processing on their thermal properties remains underexplored. Pentaglycerine (PG)-based composites, suitable for TES applications at 80 °C, doped with two sizes of expanded graphite (EG) are investigated in this work. Effects of pressing and casting and common processing methods are evaluated. A comprehensive analysis of key thermal properties characterizing phase change materials was conducted. Specifically, the research focuses on the evaluation of thermal conductivity in both radial and axial directions, performing a thorough study of latent heats and subcooling using differential scanning calorimetry, conducting in situ characterization through solid-state nuclear magnetic resonance, and assessing solid-solid transition kinetics. This study highlights the significant influence of processing on the thermal properties of organic plastic crystals. Adequate processing enhances the effectiveness of EG in addressing the low thermal conductivity of plastic crystals and preventing latent heat drops associated with nanoconfinement effects. Additionally, notable reductions in subcooling can be achieved in PG-based composites simply through this processing, by reducing grain size and consequently lowering the activation energies in the plastic-to-crystal transitions.

Facile synthesis of porous TiO2/SnO2 nanocomposite as lithium ion battery anode with enhanced cycling stability via nanoconfinement effect

SnO2 is a potential anode material with high theoretical capacity for lithium-ion batteries (LIBs), however, its applications have been limited by the severe volume expansion during charging-discharging process. In this work, an inverse opal TiO2/SnO2 composite with an interconnect network nanostructure was designed to confine SnO2 nanoparticles in the porous TiO2. Due to this nanoconfinement structure, the volume expansion in the process was effectively alleviated, therefore the safety performance and cycling stability of the battery were effectively improved. At the same time, with a large number of microporous structures in the framework, the appearance of pseudocapacitance improves the rate performance and reversible capacity. In terms of electrochemical kinetics, its framework provides the connected path for charge migration, effectively reducing the charge transfer impedance, meanwhile, quantities of micropores in its skeleton could provide a smoother channel for lithium ions, thus greatly improving the diffusion rate of LIBs. The design of this nanostructure provides a new idea for the research of SnO2-based anode with effectively enhanced electrochemical performance, which is promising anode for practical application.

Expanding the Enzymatic Polymerization Landscape by Lipid Mesophase Soft Nanoconfinement.

Soft nanoconfinement can increase chemical reactivity in nature and has therefore led to considerable interest in transferring this universal feature to artificial biological systems. However, little is known about the underlying principles of soft nanoconfinement responsible for the enhancement of biochemical reactions. Herein we demonstrate how enzymatic polymerization can be expanded, optimized, and engineered when carried out under soft nanoconfinement mediated by lipidic mesophases. By systematically varying the water content in the mesophase and thus the diameter of the confined water nanochannels, we show higher efficiency, turnover rate, and degrees of polymerization as compared to the bulk aqueous solution, all controlled by soft nanoconfinement effects. Furthermore, we exploit the unique properties of unfreezing soft nanoconfined water to perform the first enzymatic polymerization at -20 °C in pure aqueous media. These results underpin lipidic mesophases as a versatile host system for chemical reactions and promote them as an original and unexplored platform for enzymatic polymerization.

Expanding the Enzymatic Polymerization Landscape by Lipid Mesophase Soft Nanoconfinement

AbstractSoft nanoconfinement can increase chemical reactivity in nature and has therefore led to considerable interest in transferring this universal feature to artificial biological systems. However, little is known about the underlying principles of soft nanoconfinement responsible for the enhancement of biochemical reactions. Herein we demonstrate how enzymatic polymerization can be expanded, optimized, and engineered when carried out under soft nanoconfinement mediated by lipidic mesophases. By systematically varying the water content in the mesophase and thus the diameter of the confined water nanochannels, we show higher efficiency, turnover rate, and degrees of polymerization as compared to the bulk aqueous solution, all controlled by soft nanoconfinement effects. Furthermore, we exploit the unique properties of unfreezing soft nanoconfined water to perform the first enzymatic polymerization at −20 °C in pure aqueous media. These results underpin lipidic mesophases as a versatile host system for chemical reactions and promote them as an original and unexplored platform for enzymatic polymerization.

In Vitro Detection of S100B and Severity Evaluation of Traumatic Brain Injury Based on Biomimetic Peptide-Modified Nanochannels.

The diagnosis and evaluation of traumatic brain injury (TBI) are crucial steps toward the treatment and prognosis of patients. A common question remains as to whether it is possible to introduce an ideal device for signal detection and evaluation that can directly connect digital signals with TBI, thereby enabling prompt response of the evaluation signal and sensitive and specific functioning of the detection process. Herein, a method is presented utilizing polymetric porous membranes with TRTK-12 peptide-modified nanochannels for the detection of S100B (a TBI biomarker) and assessment of TBI severity. The method leverages the specific bonding force between TRTK-12 peptide and S100B protein, along with the nanoconfinement effect of nanochannels, to achieve high sensitivity (LOD: 0.002ngmL-1) and specificity (∆I/I0: 44.7%), utilizing ionic current change as an indicator. The proposed method, which is both sensitive and specific, offers a simple yet responsive approach for real-time evaluation of TBI severity. This innovative technique provides valuable scientific insights into the advancement of future diagnostic and therapeutic integration devices.

Molecular Simulation of H2 Loss by Dissolution in Caprock Water-Saturated Nanopores under the Nanoconfinement Effect for Underground Hydrogen Storage

Molecular Simulation of H₂ Loss by Dissolution in Caprock Water-Saturated Nanopores under the Nanoconfinement Effect for Underground Hydrogen Storage

New insights into Co3O4-carbon nanotube membrane for enhanced water purification: Regulated peroxymonosulfate activation mechanism via nanoconfinement

Co-based peroxymonosulfate (PMS) activation system with fascinating catalytic performance has become a promising technology for water purification, but it always suffers from insufficient mass transfer, less exposed active sites and toxic metal leaching. In this work, a carbon nanotube membrane confining Co3O4 inside (Co3O4-in-CNT) was prepared and was coupled with PMS activation (catalytic membrane process) for sulfamethoxazole (SMX) removal. Compared with counterpart with surface-loaded Co3O4 (Co3O4-out-CNT), the Co3O4-in-CNT catalytic membrane process exhibited enhanced SMX removal (99.5% vs. 89.1%) within residence time of 2.89 s, reduced Co leaching (20 vs. 147 μg L−1) and more interestingly, the nonradical-to-radical mechanism transformation (from 1O2 and electron transfer to SO4•− and •OH). These phenomena were ascribed to the nanoconfinement effect in CNT, which enhanced mass transfer (2.80 × 10−4 vs. 5.98 × 10−5 m s−1), accelerated Co3+/Co2+ cycling (73.4% vs. 65.0%) and showed higher adsorption energy for PMS (cleavage of O–O bond). Finally, based on the generated abundant reactive oxygen species (ROS), the seven degradation pathways of SMX were formed in system.

Multiphase Chemistry under Nanoconfinement: An Electrochemical Perspective.

Most relevant systems of interest to modern chemists rarely consist of a single phase. Real-world problems that require a rigorous understanding of chemical reactivity in multiple phases include the development of wearable and implantable biosensors, efficient fuel cells, single cell metabolic characterization techniques, and solar energy conversion devices. Within all of these systems, confinement effects at the nanoscale influence the chemical reaction coordinate. Thus, a fundamental understanding of the nanoconfinement effects of chemistry in multiphase environments is paramount. Electrochemistry is inherently a multiphase measurement tool reporting on a charged species traversing a phase boundary. Over the past 50 years, electrochemistry has witnessed astounding growth. Subpicoampere current measurements are routine, as is the study of single molecules and nanoparticles. This Perspective focuses on three nanoelectrochemical techniques to study multiphase chemistry under nanoconfinement: stochastic collision electrochemistry, single nanodroplet electrochemistry, and nanopore electrochemistry.

Investigating the Phase Transition Kinetics of 1-Octadecanol/Sorbitol Derivative/Expanded Graphite Composite Phase Change Material with Isoconversional and Multivariate Non-Linear Regression Methods.

Organic composite phase change materials (PCMs) have been extensively studied, and it is important to investigate the effect of added components on the phase change process of the organic matrix. Herein, the phase transition process of the composite PCM with 1-octadecanol (OD) as the matrix adsorbed by a network framework composed of 1,3:2,4-di-(3,4-dimethyl) benzylidene sorbitol (DMDBS) and expanded graphite (EG) was measured using differential scanning calorimetry (DSC) at several linear heating rates. Using isoconversional and multivariate non-linear regression methods, a two-step consecutive reaction model for the composite PCM was established, while the apparent activation energies and pre-exponential factors were determined. The reaction mechanism of the first step was altered compared to pure OD, while the activation energies significantly decreased at the initial stage of the phase transition process and increased at the later stage. Combined with microscopic morphology analysis, the main reasons were the size and nanoconfinement effect. The predictions of the composite PCM under various conditions suggested that the composite PCM had a wider available temperature range compared to pure OD. This research provided a new idea for the in-depth study of the phase transition process of organic composite PCMs, which was helpful for the evaluation of organic composite PCMs.

MOF-derived 2D Co@C nanosheet membrane with enhanced catalytic activity: Mechanism and stability insights

Two-dimensional (2D) metal-organic frameworks (MOFs) membranes have recently gained attention as novel material membranes for advanced oxidation processes (AOPs). Nonetheless, the susceptibility of 2D MOFs to reactive oxygen species (ROS) limits 2D MOF membranes’ effectiveness in AOPs. In this study, we introduce a novel approach, fabricating a 2D Co-MOF-derived nanosheet membrane (referred to as Co@C NS), assembled from pyrolyzed and exfoliated Co-MOF nanosheets, for the activation of peroxymonosulfate (PMS) in the removal of bisphenol A (BPA). Crucially, the synthesis process involves the pyrolysis of a carbon layer, serving as a protective barrier. This barrier effectively prevents the release of Co ions, ensuring the long-term structural and catalytic stability of the Co@C NS membrane. Notably, the membrane exhibits remarkable capabilities in discriminating between natural organic matter (NOM) and BPA through size exclusion, significantly mitigating the impact of NOM competition for ROS. Additionally, our study demonstrates an exceptional removal efficiency, achieving 100% BPA removal at an ultrahigh permeance of 1100 L m−2 h−1 bar−1, corresponding to an exceedingly short retention time of 0.14 s. Our mechanistic investigation reveals the involvement of singlet oxygen and sulfate radicals in the removal of BPA within the nanochannels, facilitated by the nanoconfinement effect. This study introduces valuable strategies for the development of 2D MOF-derived nanosheet membranes characterized by high catalytic activity and excellent stability, underlining their practical potential in AOP applications.

Selectivity of Electrochemical Reactions Based on Adsorption at Nanoporous Electrodes.

Enhancing selectivity is a pivotal area of research when electrodes are utilized as catalysts or sensors. Nanoporous electrodes are representative electrode materials for diverse applications, such as catalysts and sensors. Selectivity arising from nanoporous structures has been applied to systems involving nonfaradaic reactions such as capacitive deionization, electrochemical supercapacitors, and conductometry. Since selectivity in faradaic reactions has primarily been explored based on reactivity and molecular charge and size, we propose that the surface adsorption of reactant molecules can be considered as another crucial factor in achieving selectivity. Our observations reveal that the nonadsorptive reaction of 2-propanol and 2-butanol experienced a more pronounced enhancement compared to the adsorptive reaction of 1-propanol and 1-butanol at nanoporous Pt electrodes, owing to the nanoconfinement effect. Even within the same molecule with a mixture of adsorptive and nonadsorptive reactions, the degree of influence of the nanostructure depends on the adsorptive capacity of the reaction, which affects the overall selectivity. Moreover, the size effect of the reactants in the nanoporous electrode is also dependent on the degree of adsorption. These findings provide valuable insights into the effective utilization of nanoporous materials as catalysts or sensors.

Anomalous water molecular gating from atomic-scale graphene capillaries for precise and ultrafast molecular sieving

The pressing crisis of clean water shortage requires membranes to possess effective ion sieving as well as fast water flux. However, effective ion sieving demands reduction of pore size, which inevitably hinders water flux in hydrophilic membranes, posing a major challenge for efficient water/ion separation. Herein, we introduce anomalous water molecular gating based on nanofiltration membranes full of graphene capillaries at 6 Å, which were fabricated from spontaneous π-π restacking of island-on-nanosheet graphitic microstructures. We found that the membrane can provide effective ion sieving by suppressing osmosis-driven ion diffusion to negligible levels (~10–4 mol m–2 h–1); unexpectedly, ultrafast bulk flow of water (45.4 L m–2 h–1) was still functional with ease, as gated on/off by adjusting hydrostatic pressures within only 10–2 bar. We attribute this seemingly incompatible observation to graphene nanoconfinement effect, where crystal-like water confined within the capillaries hinders diffusion under osmosis but facilitates high-speed, diffusion-free water transport in the way analogous to Newton’s cradle-like Grotthus conduction. This strategy establishes a type of liquid-solid-liquid, phase-changing molecular transport for precise and ultrafast molecular sieving.

Sheng Zhu.

"In five years, I hope to be an experienced researcher studying the nanoconfinement effect in material synthesis, structure modulation, and emerging properties… My motto is: 'Diligence redeems stupidity.' " Find out more about Sheng Zhu in his Introducing… Profile.