Packing Of Nanoparticles Research Articles

Biomineralization of Electrospun Bacteria-Encapsulated Fibers: A Relevant Step toward Living Ceramic Fibers.

Living ceramic materials are proposed as high-performance engineered living materials due to their expected properties, including improved mechanical stability and performance, which could impact a wide range of applications across various fields. Particularly, living ceramic fibers are anticipated to exhibit even superior mechanical and structural properties, considering their fibril nature. This work presents the foundation for developing the family of living ceramic fibers. Ureolytic bacteria, Sporosarcina pasteurii, are encapsulated within electrospun alginate fibers, which are further subjected to biomineralization. A live-dead assay reveals that the encapsulated bacteria survive the electrospinning process. Successful biomineralization of the fibers results in the precipitation of near-spherical calcium carbonate nanoparticles at the fiber sites. The cell density within the fibers exhibits a significant impact on the packing of calcium carbonate nanoparticles. While further extensive research is required to fully realize the potential of living ceramic fibers, the findings of this study represent a significant step toward their development.

The effect of charge screening for cationic surfactants on the rigidity of interfacial nanoparticle assemblies

HypothesisFunctionalizing colloidal particles with oppositely charged surfactants is crucial for stabilizing emulsions, foams, all-liquid structures, and bijels. However, surfactants can reduce the attachment energy, the driving force for colloidal self-assembly at interfaces. An open question remains on how the inherent interfacial activity of cationic surfactants influences the interfacial rigidity of particle-laden interfaces. We hypothesize that charge screening among cationic surfactants regulates the rigidity of oil/water interfaces by reducing the attachment energy of nanoparticles. ExperimentsWe investigate the interfacial rigidity of cetyltrimethylammonium bromide (CTAB) functionalized silica nanoparticles (Ludox® TMA) by analyzing the shape deformation of 1,4-butanediol diacrylate (BDA) droplets under varying salt and alcohol concentrations. The nanoparticle packing density is assessed using scanning electron microscopy. Attachment energy is characterized through interfacial tension measurements, three-phase contact angle analysis, and CTAB adsorption studies. We also examine the effects of interfacial rigidities on the structure of bijel films formed via roll-to-roll solvent transfer-induced phase separation (R2R-STrIPS) using confocal laser scanning microscopy. FindingsIncreasing salt and alcohol concentrations decrease the interfacial rigidity of CTAB-functionalized nanoparticle films by reducing the interfacial tension. The contact angle has a minor influence on the rigidity. These results indicate that CTAB charge screening weakens the nanoparticle attachment energy to the interface. Controlling the rigidity enables the mass production of bijel sheets with consistent flatness, which is crucial for their potential applications in catalysis, energy storage, tissue engineering, and filtration membranes.

Probing Molecular Packing of Lipid Nanoparticles from 31P Solution and Solid-State NMR.

Lipid nanoparticles (LNPs) are intricate multicomponent systems widely recognized for their efficient delivery of oligonucleotide cargo to host cells. Gaining insights into the molecular properties of LNPs is crucial for their effective design and characterization. However, analysis of their internal structure at the molecular level presents a significant challenge. This study introduces 31P nuclear magnetic resonance (NMR) methods to acquire structural and dynamic information about the phospholipid envelope of LNPs. Specifically, we demonstrate that the 31P chemical shift anisotropy (CSA) parameters serve as a sensitive indicator of the molecular assembly of distearoylphosphatidylcholine (DSPC) lipids within the particles. An analytical protocol for measuring 31P CSA is developed, which can be implemented using either solution NMR or solid-state NMR, offering wide accessibility and adaptability. The capability of this method is demonstrated using both model DSPC liposomes and real-world pharmaceutical LNP formulations. Furthermore, our method can be employed to investigate the impact of formulation processes and composition on the assembly of specifically LNP particles or, more generally, phospholipid-based delivery systems. This makes it an indispensable tool for evaluating critical pharmaceutical properties such as structural homogeneity, batch-to-batch reproducibility, and the stability of the particles.

Increase in the effective viscosity of polyethylene under extreme nanoconfinement.

Understanding polymer transport in nanopores is crucial for optimizing heterogeneously catalyzed processes in polymer upcycling and fabricating high-performance nanocomposite films and membranes. Although confined polymer dynamics have been extensively studied, the behavior of polyethylene (PE)-the most widely used commodity polymer-in pores smaller than 20nm remains largely unexplored. We investigate the effects of extreme nanoconfinement on PE transport using capillary rise infiltration in silica nanoparticle packings with average pore radii ranging from ∼1 to ∼9nm. Using in situ ellipsometry and the Lucas-Washburn model, we discover a previously unknown inverse relationship between effective viscosity (ηeff) and average pore radius (Rpore). Additonally, we determine that PE transport under these extreme conditions is primarily governed by physical confinement, rather than pore surface chemistry. We refine an existing theory to provide a generalized formalism to describe the polymer transport dynamics over a wide range of pore radii (from 1nm and larger). Our results offer valuable insights for optimizing catalyst supports in polymer upcycling and improving infiltration processes for nanocomposite fabrication.

Mixed Nanosphere Assemblies at a Liquid-Liquid Interface.

The in-plane packing of gold (Au), polystyrene (PS), and silica (SiO2) spherical nanoparticle (NP) mixtures at a water-oil interface is investigated in situ by UV-vis reflection spectroscopy. All NPs are functionalized with carboxylic acid such that they strongly interact with amine-functionalized ligands dissolved in an immiscible oil phase at the fluid interface. This interaction markedly increases the binding energy of these nanoparticle surfactants (NPSs). The separation distance between the Au NPSs and Au surface coverage are measured by the maximum plasmonic wavelength (λmax) and integrated intensities as the assemblies saturate for different concentrations of non-plasmonic (PS/SiO2) NPs. As the PS/SiO2 content increases, the time to reach intimate Au NP contact also increases, resulting from their hindered mobility. λmax changes within the first few minutes of adsorption due to weak attractive inter-NP forces. Additionally, a sharper peak in the reflection spectrum at NP saturation reveals tighter Au NP packing for assemblies with intermediate non-plasmonic NP content. Grazing incidence small angle X-ray scattering (GISAXS) and scanning electron microscopy (SEM) measurements confirm a decrease in Au NP domain size for mixtures with larger non-plasmonic NP content. The results demonstrate a simple means to probe interfacial phase separation behavior using in situ spectroscopy as interfacial structures densify into jammed, phase-separated NP films.

Evidence of Size Stratification in Colloidal Glass Microgranules Realized by Rapid Evaporative Assembly.

Evaporation is a ubiquitous phenomenon. Rapid evaporation of the continuous phase from micrometric colloidal droplets can be used to realize nanostructured microgranules, constituting the assembled nanoparticles. One of the important aspects of such nonequilibrium assembly is the nature of the packing of nanoparticles in the microgranules. The present work demonstrates the evidence of size stratification of the nanoparticles in such far-from-equilibrium configurations. Small-angle X-ray scattering, in combination with particle packing simulation, reveals the "large on top"-type stratification in such assembled microgranules, where the larger particles get concentrated at the outer shell of the granules while the smaller particles reside in the core region. It also reveals the presence of local clusters in such a rapid evaporative assembly in aerosolized colloidal droplets.

Revealing the Impact of Polystyrene Functionalization of Au Octahedral Nanocrystals of Different Sizes on the Formation and Structure of Mesocrystals

AbstractThe self‐assembly of anisotropic nanocrystals (stabilized by organic capping molecules) with pre‐selected composition, size, and shape allows for the creation of nanostructured materials with unique structures and features. For such a material, the shape and packing of the individual nanoparticles play an important role. This work presents a synthesis procedure for ω‐thiol‐terminated polystyrene (PS‐SH) functionalized gold nanooctahedra of variable size (edge length 37, 46, 58, and 72 nm). The impact of polymer chain length (Mw: 11k, 22k, 43k, and 66k g⋅mol−1) on the growth of colloidal crystals (e. g. mesocrystals) and their resulting crystal structure is investigated. Small‐angle X‐ray scattering (SAXS) and scanning transmission electron microscopy (STEM) methods provide a detailed structural examination of the self‐assembled faceted mesocrystals based on octahedral gold nanoparticles of different size and surface functionalization. Three‐dimensional angular X‐ray cross‐correlation analysis (AXCCA) enables high‐precision determination of the superlattice structure and relative orientation of nanoparticles in mesocrystals. This approach allows us to perform non‐destructive characterization of mesocrystalline materials and reveals their structure with resolution down to the nanometer scale.

Dual Porosity-Enhanced Antireflection Coatings with Continuous Gradient.

The incorporation of porous structures into films and coatings can transform their properties for applications in optics, separation, electronics, and energy generation and storage. Packing nanoparticles (NPs) is a versatile approach for fabricating nanoporous films with a tunable structure and properties. The mechanical fragility of NP packing-based films and coatings, however, significantly impedes their widespread utilization. Although infiltrating a polymer into the interstices of these NP packings has been shown to enhance their mechanical durability, this method completely eliminates the porosity of the structures, compromising their properties and functionality. This study presents a new approach to fabricate highly loaded porous nanocomposite films with a gradient in the refractive index by infiltrating subsaturating amounts of poly(methyl methacrylate) (PMMA) into disordered packings of hollow silica NPs. We demonstrate that dual porosity is a critical feature that enhances their antireflection (AR) and mechanical properties. The hollow cores of NPs prevent a substantial increase in the refractive index of the resulting films. Moreover, the interparticle voids allow for mechanical reinforcement to occur when the NP packings are infiltrated with PMMA, making them even more suitable for AR coatings. The refractive index and gradient across the nanocomposites can be tailored by adjusting the amount of PMMA infiltrated into the NP packing, the shape of hollow NPs, and the annealing time. The nanocomposite coatings with a continuous gradient in refractive index exhibit excellent AR properties and enhanced mechanical durability. Combined with the unique structural tunability afforded by the dual porosity, this approach provides a scalable and effective way to create robust and graded nanoporous structures for various applications.

Partially miscible droplet microfluidics to enhance interfacial adsorption of hydrophilic nanoparticles for colloidosome synthesis

Colloidosomes are spherical shells composed of closed-packed nanoparticles, which can be prepared through the self-assembly of nanoparticles at the interphase of two immiscible liquids. However, the method leads to colloidosomes of various sizes and limited synthesis due to charge repulsion and nanoparticle wettability. Herein, a microfluidic droplet device and partially miscible liquids are integrated for colloidosome synthesis. Dissolving liquids within droplets enables hydrophilic nanoparticles to close packing at the liquid interface to form colloidosomes. Moreover, the microfluidic droplet system achieved colloidosomes within a narrow and specific range of sizes. The close-packing of nanoparticles is proved by modifying colloidosomes into probes in signal-enhanced lateral flow assays (LFAs). Due to the plasmon resonance effect, the testing lines are black, demonstrating the close packing of nanoparticles and their signal enhancement property compared to traditional LFAs. Accordingly, this approach is a potential bacterial detection platform with a detection time of 10 min, higher sensitivity, and specificity. Moreover, since colloidosomes are hollow spheres, they are capable of drug cargo with an encapsulation rate of 99.76 %. With this proposed partially miscible fluid-based droplet microfluidic system, colloidosomes can be fabricated with versatile properties, extending their application to advanced material fabrication, drug encapsulation, and biosensing.

Interfacial assembling of flexible silica membranes with high chlorine resistance for dye separation

Inorganic membranes have gained extensive attention due to their more uniform pore size, higher flux, and better chemical stability over traditional polymeric membranes. However, the development of inorganic membranes still faces substantial obstacles in the form of a difficult preparation procedure and the high cost of a large-scale synthesis. Herein, a facile interfacial assembly strategy is designed to prepare flexible silica membranes by the close and strong packing of ultra-small nanoparticles via crosslinking with trimesoyl chloride. Profiting from the extremely small size and tight packing of silica nanoparticles, the permeance of flexible silica membrane with a uniform pore size of 3.4 nm exceeds 210 L m−2 h−1 MPa−1, which is nearly 11 times higher than the polyamide membrane simultaneously ensuring the rejection effect. Meanwhile, the flexible silica membrane has no performance deterioration after exposure to 50000 ppm h of chlorine (NaOCl), indicating its excellent chlorine resistance. The facile interfacial assembly strategy applied for the synthesis of the membrane is highly reproducible and scalable (high-performance silica membrane with 100 cm2 has been obtained), which has overall flexibility after the curvature of 100 m−1, paving the way for the development of future applications.

Efficient removal of Cr(VI) from aqueous solutions using chitosan/Na‐alginate bio‐based nanocomposite hydrogel

AbstractThis research article aimed to assist the works conducted to save water resources, which are rapidly depleted as a result of climate change by eliminating toxic chromium ions Cr(VI) from simulated solution. In this regard, chitosan/Na‐alginate/polyacrylic acid (CS/Na‐Alg/PAAc) and Ni/chitosan/Na‐alginate/polyacrylic acid (Ni@CS/Na‐Alg/PAAc) were created as eco‐friendly hydrogel composites via gamma radiation. The hydrogel matrix served as a basin for the in‐situ formation of Ni nanoparticles. The prepared composites were characterized by the FTIR and XRD analyses. The surface morphology of the nanocomposite was also verified via the SEM. It exhibited a dense packing of the Ni nanoparticles representing about 2.5% of the atomic percentage depicted by the EDX analysis. The swelling performance was investigated versus different pH values and the maximum swelling percent was attained as a non‐Fickian character at pH = 13 and 5 for CS/Na‐Alg/PAAc and Ni@CS/Na‐Alg/PAAc, respectively. Furthermore, the surface topographies of CS/Na‐Alg/PAAc and Ni@CS/Na‐Alg/PAAc loaded with Cr(VI) were examined by AFM at different pH values. The maximum Cr(VI) removal was top achieved at pH 8 (58.06 and 74.5 mg/g for CS/Na‐Alg/PAAc and Ni@CS/Na‐Alg/PAAc, respectively) and best fit with the Freundlich isotherm model with calculated RL values indicated a favorable adsorption.

Increases in Miscibility of a Binary Polymer Blend Confined within a Nanoparticle Packing

Despite various physical and chemical strategies that have been explored, compatibilization of polymer blends has proved elusive. Confinement of polymers has shown to induce substantial and at times unexpected changes in glass-transition temperature, dynamics, and morphology of these materials. Although confinement of blends to thin films have shown to influence phase separation structure and chain mobility, the impact of confinement on the miscibility of polymer mixtures is much less understood. Here, we present a computational study using field-theoretic simulations to understand the thermodynamics of polymer blends that are confined in the interstices of nanoparticle packings where both polymers have neutral interactions with the nanoparticle surfaces. We calculate their binodal phase envelopes and show that two polymers that would undergo macroscopic phase separation become miscible when they are subjected to extreme nanoconfinement. The strength of the repulsion required to induce phase separation increases significantly as confinement increases. We find that this enhanced miscibility is driven by both an increase in entropic penalty upon phase separation and a decrease in enthalpic repulsion with increasing confinement. We relate the change in enthalpy to a reduction in the number of polymer–polymer contacts near nanoparticle surfaces and the change in entropy to a reduction in conformational freedom due to the formation of a polymer–polymer interface near nanoparticle surfaces. Confinement-induced mixing of polymers in nanoparticle packings could enable precise tuning of mechanical and transport properties of nanocomposite films and membranes.

Dual-responsive colloidosome-like microgels as the building blocks for phase inversion of Pickering emulsions.

The intelligent regulation of microgel-stabilized Pickering emulsions with multi-responsiveness is presently constrained to the processes of emulsification and destabilization. However, the expansion of multi-control over Pickering emulsions to involve phase inversion and the investigation of the accompanying processes and mechanisms present a great challenge. In this study, a microgel with dual responsiveness to both pH and temperature was synthesized using an emulsion template. The resulting microgel exhibited a robust colloidosome-like structure, distinguished by the presence of monolayer-adsorbed silica nanoparticles. The regulation of the packing of surface-covered silica nanoparticles was easily achieved through the swelling of the microgel matrix. Furthermore, the wettability of the microgel can be adjusted between hydrophilic and hydrophobic intervals, allowing for the effective and dual-responsive phase inversion of Pickering emulsions. Moreover, it has been observed that colloidosome-like microgels can lead to unique interfacial structures during the emulsification process, thereby elucidating the fundamental mechanism governing emulsion phase inversion.

Facile Preparation of Macro-Microporous Thorium Oxide via a Colloidal Sol-Gel Route toward Safe MOX Fuel Fabrication.

The identification of new colloidal sol-gel routes for the preparation of actinide oxides, which have a homogeneous and accessible porosity that can easily be impregnated by any concentrated actinide solution, opens new perspectives for the preparation of homogeneous nuclear fuel for minor actinide transmutation. This homogeneity allows us to avoid "hot spot" formation due to the local accumulation of more fissile elements. Here, we report the preparation of macro-microporous ThO2 materials by a colloidal sol-gel route. Using a thorium salt with 6-aminocaproic acid as a complexing agent at a controlled pH, we were able to pilot the condensation of thorium hydroxo species forming colloids of tuned nanometric size and thus the sol stability. After a freeze-drying process to concentrate colloids and a thermal treatment allowing complexing agent removal and macroporosity formation by a brutal gas release during combustion, a loose packing of ThO2 nanoparticles with an ordered distribution of interparticular porosity and a fraction of nanometric crystallites, whose size depends on the initial colloidal size, were obtained. The sols, pastes, and final materials were characterized by small- and wide-angle X-ray scattering to determine the colloidal size and the final structure of the materials, which was also confirmed by transmission electron microscopy. The most promising material was finally successfully impregnated by a simulating minor actinide solution and thermally treated to prepare a mixed actinide oxide material. This safe technology, relying on the colloidal sol-gel process and the formulation of complex fluids forming tunable precursors, opens new perspectives for the reuse of nuclear waste solutions as new fuel.

Supercrystal engineering of atomically precise gold nanoparticles promoted by surface dynamics.

The controllable packing of functional nanoparticles (NPs) into crystalline lattices is of interest in the development of NP-based materials. Here we demonstrate that the size, morphology and symmetry of such supercrystals can be tailored by adjusting the surface dynamics of their constituent NPs. In the presence of excess tetraethylammonium cations, atomically precise [Au25(SR)18]- NPs (where SR is a thiolate ligand) can be crystallized into micrometre-sized hexagonal rod-like supercrystals, rather than as face-centred-cubic superlattices otherwise. Experimental characterization supported by theoretical modelling shows that the rod-like crystals consist of polymeric chains in which Au25 NPs are held together by a linear SR-[Au(I)-SR]4 interparticle linker. This linker is formed by conjugation of two dynamically detached SR-[Au(I)-SR]2 protecting motifs from adjacent Au25 particles, and is stabilized by a combination of CH⋯π and ion-pairing interactions between tetraethylammonium cations and SR ligands. The symmetry, morphology and size of the resulting supercrystals can be systematically tuned by changing the concentration and type of the tetraalkylammonium cations.

Infrared Plasmonic Metamaterials Based on Transparent Nanoparticle Films of In2O3:Sn for Solar-Thermal Shielding Applications.

Three-dimensional nanoparticle (NP) assemblies show interesting optical responses that differ from naturally occurring materials, such as metals, oxides, and semiconductors. In this study, we investigate the optical response of thin films comprising Sn:In2O3 NPs (ITO NP films) based on the correlation between complex permittivity and infrared (IR) reflectance for solar-thermal shielding applications. IR ellipsometry measurements are conducted to clarify the presence of Lorentz resonances in plasmonic metamaterials. The Lorentz resonances are correlated to the electric field strength at interparticle gaps by varying the Sn dopant concentration, as confirmed using finite-difference time-domain (FDTD) simulations. High solar-thermal shielding performance was obtained owing to selective near-IR reflection based on strong Lorentz resonances as the ITO NP films were electrically polarizable but magnetically inactive. Thermal shielding efficiency was demonstrated via a comparison of the air temperature change in a simulated box used as a model house. Additionally, we demonstrate the significance of NP packing density on the enhancement of the near-IR reflectance. The role of interparticle spacing for high near-IR reflectance was revealed by comparing effective medium approximation analyses and FDTD simulations. This relationship was also demonstrated by the reduction of solar-thermal shielding performance when using aggregated ITO NPs. Our work confirmed that the control of complex permittivity in plasmonic metamaterials must be considered in the structural design of transparent and reflective materials for solar-thermal shielding applications.

Highly Selective Photocatalytic Conversion of Glucose on Holo-Symmetrically Spherical Three-Dimensionally Ordered Macroporous Heterojunction Photonic Crystal

Highly Selective Photocatalytic Conversion of Glucose on Holo-Symmetrically Spherical Three-Dimensionally Ordered Macroporous Heterojunction Photonic Crystal

Interfacial Friction Controls the Motion of Confined Polymers in the Pores of Nanoparticle Packings

Interfacial Friction Controls the Motion of Confined Polymers in the Pores of Nanoparticle Packings

Three-dimensional charge transfer pathway in close-packed nickel hexacyanoferrate−on−MXene nano-stacking for high-performance capacitive deionization

Prussian blue analogues (PBAs), as a kind of metal–organic framework–like materials, has attracted great attention in capacitive deionization (CDI) field due to excellent redox activity, but its desalination performance, especially its desalination rate, is greatly limited due to its poor electrical conductivity. Hybridization of PBAs with MXene can potentially solve this problem, but still remains intrinsic limitation, such as poor vertical charge transfer between nano-sheets. Herein, we engineered a three-dimensional (3D) charge transfer pathway in nickel hexacyanoferrate (NiHCF)/MXene through in situ close packing of NiHCF nanoparticles on MXene nano-stacking by electrostatic attraction. Compared to charge transfer mode in two-dimensional (2D) nano-sheets, 3D MXene nano-stacking can not only have excellent conductivity like MXene to provide horizonal charge transfer pathway alongside nano-sheets, but also possess unique vertical charge transfer pathway between nano-sheets. As a result, the NiHCF/MXene exhibits a superior desalination performance with a high desalination capacity of 30 mg g−1, ultrahigh desalination rate of 9.5 mg g−1 min−1 and good cycling stability over 30 cycles. This work demonstrates an effective way to address the poor CDI performance of nickel hexacyanoferrate nanoparticles by employing 3D MXene nano-stacking as charge transfer support, and is of significance to be applied for other nanoparticle materials.

Conflicting Effects of Extreme Nanoconfinement on the Translational and Segmental Motion of Entangled Polymers

Physically confining polymers into nanoscale pores induces significant changes in their dynamics. Although different results on the effect of confinement on the dynamics of polymers have been reported, changes in the segmental mobility of polymers typically are correlated with changes in their chain mobility due to increased monomeric relaxation times. In this study, we show that translational and segmental dynamics of polymers confined in disordered packings of nanoparticles can exhibit completely opposite behavior. We monitor the capillary rise dynamics of entangled polystyrene (PS) in disordered packings of silica nanoparticles (NPs) of 7 and 27 nm diameter. The effective viscosity of PS in 27 nm $SiO_2$ NP packings, inferred based on the Lucas-Washburn equation, is significantly smaller than the bulk viscosity, and the extent of reduction in the translational motion due to confinement increases with the molecular weight of PS, reaching 4 orders of magnitude reduction for PS with a molecular weight of 4M g/mol. The glass transition temperature of entangled PS in the packings of 27 nm $SiO_2$ NPs, however, increases by 45 K, indicating significant slowdown of segmental motion. Interestingly, confinement of the polymers into packings made of 7 nm $SiO_2$ NPs results in molecular weight-independent effective viscosity. The segmental dynamics of PS in 7 nm $SiO_2$ NP packings are slowed down even further as evidenced by 65 K increase in glass transition temperature. These seemingly disparate effects are explained by the microscopic reptation-like transport controlling the translational motion and the physical confinement affecting the segmental dynamics under extreme nanoconfinement.