Close-packed Research Articles

Квантовая проводимость в одиночных и связанных квантово-размерных частицах узкозонных полупроводников

An organo-modified ordered layered structure with three-dimensional close packing based on colloidal quantum-sized particles (QP) of InSb, PbS, CdSe semiconductors and Langmuir-Blodgett films has been fabricated and studied. According to the current-voltage characteristics (CVC) of single-electron transport in the model of a nanocell with a linear chain QP across the layers, the processes limiting conductivity were established: emission-injection tunneling from a probe into a nanoparticle, motion in a nanoparticle determined by the establishment of an electronic wave process in it, and tunneling through a nanogap between nanoparticles. Quasi-periodic oscillations of the current and resonant peaks of quantum conductivity are observed on the I–V characteristics, which were estimated in the quantum wire model. For an even number of layers (QP, 2, or 4), the I–V characteristics were used to determine the attenuation of size quantization and the decrease in current due to the weak interaction of nanoparticles. With an odd number (3 or 5), the nanochain acts as a single quantum thread with manifestations on the CVC similar to the cases of one QP. In this case, the motion of an electron can be considered as a one-electron charge wave.

A double rigidity transition rules the fate of drying colloidal drops.

The evaporation of drops of colloidal suspensions plays an important role in numerous contexts, such as the production of powdered dairies, the synthesis of functional supraparticles, and virus and bacteria survival in aerosols or drops on surfaces. The presence of colloidal particles in the evaporating drop eventually leads to the formation of a dense shell that may undergo a shape instability. Previous works propose that, for drops evaporating very fast, the instability occurs when the particles form a rigid porous solid, constituted of permanently aggregated particles at random close packing. To date, however, no measurements could directly test this scenario and assess whether it also applies to drops drying at lower evaporation rates, severely limiting our understanding of this phenomenon and the possibility of harnessing it in applications. Here, we combine macroscopic imaging and space- and time-resolved measurements of the microscopic dynamics of colloidal nanoparticles in drying drops sitting on a hydrophobic surface, measuring the evolution of the thickness of the shell and the spatial distribution and mobility of the nanoparticles. We find that, above a threshold evaporation rate, the drop undergoes successively two distinct shape instabilities, invagination and cracking. While permanent aggregation of nanoparticles accompanies the second instability, as hypothesized in previous works on fast-evaporating drops, we show that the first one results from a reversible glass transition of the shell, unreported so far. We rationalize our findings and discuss their implications in the framework of a unified state diagram for the drying of colloidal drops sitting on a hydrophobic surface.

Close packings of identical proteins in small spherical capsids and similar proteinaceous shells.

Understanding the principles governing protein arrangement in viral capsids and structurally similar protein shells can enable the development of new antiviral strategies and the design of artificial protein cages for various applications. We study these principles within the context of the close packing problem, by analyzing dozens of small spherical shells assembled from a single type of protein. First, we use icosahedral spherical close packings containing 60T identical disks, where T ≤ 4, to rationalize the protein arrangement in twenty real icosahedral shells both satisfying and violating the paradigmatic Caspar-Klug model. We uncover a striking correspondence between the protein mass centers in the considered shells and the centers of disks in the close packings. To generalize the packing model, we consider proteins with a weak shape anisotropy and propose an interaction energy, minimization of which allows us to obtain spherical dense packings of slightly anisotropic structural units. In the case of strong anisotropy, we model the proteins as sequences of overlapping discs of different sizes, with minimum energy configuration not only resulting in packings, accurately reproducing locations and orientations of individual proteins, but also revealing that icosahedral packings that display the handedness of real capsids are energetically more favorable. Finally, by introducing effective disc charges, we rationalize the formation of inter-protein bonds in protein shells.

Синтез токопроводящих серебряных чернил с низкой температурой спекания для применения в струйной печати

Transparent silver ink based on silver amino complex for inkjet printing has been developed. 1,2-diaminopropane, which acts as a solvent and complexing agent, significantly lowered the decomposition temperature of the silver salt and ensured the chemical stability of the resulting ink at room temperature. The annealed films were characterized by close packing and low electrical resistance values (8.5 μOhm·cm at an annealing temperature of 150°C). The ink provides productive inkjet printing while maintaining stable operation of the print head nozzles.

A rod- and tessellation-based comparative analysis of polymorphic and structurally-invariant molecular crystals: application to sulfathiazole and 2-benzyl-5-benzylidenecyclopentanones.

A rationalization of the alternative crystal structures adopted by a given molecular compound or by a set of substitutionally related molecular compounds is provided by reference to the five known polymorphs of sulfathiazole and 16 substituted 2-benzyl-5-benzylidene cyclopentanones (BBCPs), respectively. Two-dimensional (2D) packing fractions (ϕ2D) take space-group symmetry into account, with a clear demarcation of closed-packed zones (CPZ) and molecular junction zones (JZ) in all Z' = 1 structures. Representation of the molecules as two linked rods allows a concise treatment of conformation and rapid visualization of crystal packing. Combined with calculations of intermolecular potential energies, the rod method provides insight into the stabilization mechanisms of alternative polymorphs. In sulfathiazole, the primary factor is to obtain satisfactory hydrogen bonding, with close packing a secondary consideration. In BBCP derivatives, by comparison, close packing is the primary mechanism of stabilization. Whereas the 2D structures arising in CPZ can be analysed as tessellations of molecular-based cells, a method based on 2D Dirichlet cells is required for the JZ. These are calculated from the centroids of the molecular envelopes in high-symmetry planes. It is shown that these centroid coordinates, when combined with space-group symmetry and unit cell coordinates, provide a concise parameterization of all structures containing JZ. It is anticipated that this parameterization may be exploited to predict such crystal structures from powder diffraction data.

Моделирование распространения электромагнитных волн в магнитно-неоднородных средах

This paper discusses the FDTD-algorithm for modeling electromagnetic
 wave propagation in randomly inhomogeneous
 magnetic media. We present the modeling results of square
 wave signals propagation in time-independent nanocomposite
 films with magnetic inhomogeneities of two types: with a
 random distribution of inhomogeneities throughout the film
 thickness and the “close packing” in the center.

Boost Up the Mechanical and Electrical Property of CNT Fibers by Governing Lyotropic Liquid Crystalline Mesophases with Aramid Polymers for Robust Lightweight Wiring Applications

Monofilament type of polyaromatic amide (PA) and carbon nanotube (CNT) composite fibers is presented. A concept of a lyotropic liquid crystal (LLC) constructed via a spontaneous self-assembly is introduced to mitigate the extremely low compatibility between PA and CNT. These approaches provide an effective co-processing route of PA and CNT simultaneously to fabricate the uniform, continuous, and reliable composite fibers through a wet-spinning. Interestingly, the addition of a small amount PA into the dope solution of CNT governs the LLC mesophase not only in a spinneret stage but also in a coagulant region. Thus, the developed PA/CNT composite fibers have the high uniaxial orientational order and the close interfacial packing compared to the pure CNT fibers. The PA/CNT composite fibers achieve the outstanding tensile strength, electrical conductivity, and electrochemical response, while maintaining a lightweight. They also exhibit the chemical, mechanical, and thermal robustness. All of these advantages can make flexible, sewable, and washable PA/CNT composite fibers ideal nanocomposite materials for use in next-generation information and energy transporting system by replacing conventional metal electrical conductors.Graphical The lyotropic liquid crystal self-assembly governed by doping the aramid polymers shows the ability to construct mechanically strong and continuous carbon nanotube-based composite fibers that can be used in the lightweight and robust electrical wiring for extreme environmental applications.

Influence of core-twisted structure on singlet fission in perylenediimide film

To reveal the relationship between molecular packing and singlet fission (SF) property is necessary for developing efficient SF materials, yet it remains unclear. Herein, we investigated SF in two perylenediimide (PDI) films (PDI-C4 and ClPDI-C4) with different molecular arrangements. Crystal structure analysis reveals that PDI-C4 with no substituent at the bay position has a planar structure and shows a close intermolecular packing with a sufficient π-π overlap. Compared to PDI-C4, ClPDI-C4, with four chlorine groups at the bay position, exhibits a twisted core structure that prevents a close intermolecular packing and shows a small π-π overlap. This leads to a smaller intermolecular interaction in ClPDI-C4 film with respect to PDI-C4 as revealed by their steady-state absorption spectra. Transient absorption spectra demonstrate that ClPDI-C4 shows a relatively slower SF rate compared to PDI-C4, but with a longer triplet lifetime. This may be caused by the looser molecular packing and the more endothermic SF in ClPDI-C4 film. This indicates that the introduction of substituents onto the bay position of PDI may be a good choice to tune the PDI packing for achieving long-lived triplets.

GPU-based discrete element model of realistic non-convex aggregates: Mesoscopic insights into ITZ volume fraction and diffusivity of concrete

Aggregates with realistic non-convex morphologies and their surrounding interfacial transition zones (ITZs) significantly affect the diffusivity of concrete. Herein, we initially propose a mathematical-controllable parameterized method to devise three-dimensional (3D) non-convex aggregates. Then, we develop a GPU-based discrete element modelling (DEM) to generate random close packing of polydisperse non-convex aggregates. Next, we establish three-phase concrete mesostructures containing non-convex aggregates and ITZs and obtain the ITZ volume fraction by a Monte Carlo random point sampling method. Finally, we develop a dual-probability-Brownian motion (DP-BM) scheme to obtain the effective diffusivity of concrete. Moreover, the effects of volume fraction, size polydispersity and shape of aggregates as well as ITZ thickness on the ITZ volume fraction and concrete diffusivity are researched to probe rigorous component-structure-property relations for concrete. This work provides a comprehensive numerical framework for mesostructure characterization and diffusivity evaluation for concrete, which can be a valuable tool for durability assessment of concrete.

Overcoming double Poisson limitation for co-encapsulation in droplets through hydrodynamic close packing of cells

Overcoming double Poisson limitation for co-encapsulation in droplets through hydrodynamic close packing of cells

Physical and Oxidative Water-in-Oil Emulsion Stability by the Addition of Liposomes from Shrimp Waste Oil with Antioxidant and Anti-Inflammatory Properties.

Liposomes made of partially purified phospholipids (PL) from Argentine red shrimp waste oil were loaded with two antioxidant lipid co-extracts (hexane-soluble, Hx and acetone-soluble, Ac) to provide a higher content of omega-3 fatty acids. The physical properties of the liposomes were characterized by Transmission Electron Microscopy (TEM), Dynamic Light Scattering (DLS) and Differential Scanning Calorimetry (DSC). The antioxidant and anti-inflammatory activity of the lipid extracts and liposomal suspensions were evaluated in terms of Superoxide and ABTS radical scavenging capacities and TNF-α inhibition. Uni-lamellar spherical liposomes (z-average ≈ 145 nm) with strong negative ζ potential (≈ -67 mV) were obtained in all cases. The high content of neutral lipids in the Hx extract caused structural changes in the bilayer membrane and decreased entrapment efficiency regarding astaxanthin and EPA + DHA contents. The liposomes loaded with the Hx/Ac extracts showed higher antioxidant and anti-inflammatory activity compared with empty liposomes. The liposomal dispersions improved the physical and oxidative stability of water-in-oil emulsions as compared with the PL extract, inducing pronounced close packing of water droplets. The liposomes decreased hydroperoxide formation in freshly made emulsions and prevented thio-barbituric acid-reactive substances (TBARS) accumulation during chilled storage. Liposomes from shrimp waste could be valuable nanocarriers and stabilizers in functional food emulsions.

Spatiotemporal analysis of structured Langmuir films formed from stabilised CdSe/CdS/ZnS quantum dots

Langmuir-Blodgett Films (LBFs) were studied using X-ray Diffraction (XRD), Raman Scattering (RS), Fourier-Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM), Energy-Dispersive X-ray Spectroscopy (EDX), Transmission Electron Microscopy (TEM), High Resolution TEM (HRTEM), Electronic Data Processing (EDP), Atomic Force Microscopy (AFM), and ab-initio simulations. Unlike in the classical form of compression isotherms π(t), the transition to the time dependence Δπ(t) = π(t2) - π(t1) made it possible to reveal the “liquid–solid phase” transition starting from 500 s to 650 s, and nanofilm collapse after 1400 s as illustrated by Brewster images. According to AFM, HRTEM images, and XRD data, it is established that the formation of an LBF from CdSe/CdS/ZnS quantum dots is accompanied by a structural transition from sphalerite to dominant wurtzite close packing, which is in qualitative agreement with the results from combinatorial geometry and ab-initio calculations. The dominance of the wurtzite crystal structure was established by X-ray diffraction, HRTEM and RS methods.

Ultra-high Tg and ultra-low CTE polyimide films based on tunable interchain crosslinking

A novel interchain crosslinking system was designed to improve the thermal performance of PI films. A diamine containing Cl atom (Cl-DAXBA) was prepared and polycondensed with pyromellitic dianhydride and 3,3′,4,4′-biphenyl tetracarboxylic dianhydride, respectively. Two series of PI films (PM and BP) were prepared under different curing temperatures in the range of 320–380 °C. The crosslinking of free radicals produced by Cl-DAXBA decomposition occurred between the molecular chains, and the crosslinking degree increased with raising the curing temperature. The network structure formed by crosslinking effectively inhibited the movement of molecular chains and promoted their close packing. The glass transition temperature (Tg) of PM films increased from 378 °C to >450 °C, and the coefficient of thermal expansion (CTE) decreased from 66.3 ppm·K−1 to 4.9 ppm·K−1. The Tg of BP films increased from 349 °C to >450 °C, and the CTE decreased from 50.4 ppm·K−1 to 17.7 ppm·K−1. Definitely, the tunable interchain crosslinking provides an effective strategy to improve both Tg and CTE simultaneously.

Charge Transport Capabilities of Dibenzo[n]phenacenes (n = 5–7): Influence of Trap States and Molecular Packing

A high carrier transport capability with strong π–π interactions is expected to result from the extension of π conjugation in small molecules. This is an important factor to create promising molecules, leading to the development of high-performance and new applications in organic electronic devices. We systematically demonstrate the charge transport capability and trap density of states in dibenzo[n]phenacenes (DBnPs) (n = 5–7) with a hybrid π structure between the phenacene and acene cores. A DB6P field-effect transistor (FET) achieves a relatively high-field-effect mobility beyond 2 cm2 V–1 s–1, which indicates excellent FET performance in comparison with DB5P and DB7P. The calculated charge-transfer integrals based on the crystal structure and the distribution of the trap density of states confirm the superior transport capability and FET properties in DB6P. We demonstrate that molecules with C2h symmetry result in high crystallinity and close packing in crystals, leading to high-performance FETs.

(Invited, Digital Presentation) Understanding the Self-Assembly of Polymer-Grafted Nanocrystals

Combination of inorganic nanocrystals (NCs) and polymeric materials is promising for the design of novel functional materials due to their complementary properties. For the preparation of such hybrid nanomaterials with tailored functionalities, it is important to precisely control their nanostructures since material properties of NCs strongly depend not only on the morphology of each NC building block, but also their assembled packing symmetries. In this talk, I will present precise control of polystyrene-grafted Au NC (Au@PS) superlattice symmetry, which shows non-conventional assembly behavior compared to short alkyl chain-coated NCs. Au@PS NCs were synthesized by ligand exchange using thiol-terminated PS with various molecular weights (M n). The Au@PS particles were self-assembled through liquid-air interface self-assembly process. Transmission electron microscopy images and grazing incidence small-angle X-ray scattering data indicated long-range ordered Au@PS superlattices. In particular, symmetry transitions from hexagonal close packing (hcp) to body centered cubic (bcc) symmetry were found as M n of PS increases or diameter of NCs decreases. We tried to understand the structural transitions by proposing “effective softness” model, which considers concentrated polymer brushes around NC surface as part of “hard core.” Finally, I will show how these polymer-grafted NCs can be self-assembled with block copolymers for the development of colloidal hybrid particles with stimuli-responsive photoluminescence behavior, which have great potential for the applications in smart material systems.

Pectin degree of esterification influences rheology and digestibility of whey protein isolate-pectin stabilized bilayer oil-in-water nanoemulsions

Gelation in nanoemulsions happens at a lower oil volume fraction ( φ ) compared to conventional emulsions due to the increasing contribution of interfacial shell-layer thickness. In this study, the shell-layer thickness was increased by depositing a second layer of pectin on whey protein isolate (WPI)-stabilized nanodroplets. Pectin with two different degrees of esterification (DE), 33% and 73%, was used to investigate the effect of interfacial charge on the repulsive shell layer thickness. Excess WPI was removed from the primary 20 wt% canola oil-in-water nanoemulsion stabilized with 4 wt% WPI (pH 7) by ultracentrifugation before pectin addition. At pH 7, the added pectin remained in the continuous phase and led to almost two orders of magnitude increase in emulsion viscosity, but they were flowable. Changing to pH 3 led to electrostatic complexation of pectin with WPI either mostly in the aqueous phase for the emulsions with excess proteins (WTEP) or at the oil droplet surface for the emulsions without excess proteins (WOEP). The addition of pectin transformed the liquid primary emulsions into viscoelastic gels at only 20 wt% oil due to extensive droplet aggregation for the emulsion WTEP. For the emulsion WOEP, gelation was manifested by the close packing of repulsive droplets. The higher pectin charge (DE33) increased the gel strength of bilayer emulsions compared to the lower pectin charge (DE73) due to the charge cloud-induced enhanced interfacial repulsive barrier. The deposition of pectin also reduced lipid digestibility from 37.2% for the monolayer emulsions to 24.0% and 16.1% for DE73 and DE33-coated bilayer emulsions, respectively. Such findings can be used to better understand and modify the rheological and digestion properties of repulsive emulsion gels for application in reduced fat foods. • WPI-pectin bilayer nanoemulsion was created using layer-by-layer electrostatic deposition. • Excess whey protein in the continuous phase led to attractive gelation in nanoemulsion. • Removal of excess protein led to repulsive gelation in bilayer nanoemulsion. • Higher pectin charge was more effective in enhancing repulsive gelation in bilayer nanoemulsions. • Lipid digestibility was reduced with pectin bilayer and increasing pectin charge.

Turbulence-dependent reversible liquid-gel transition of micellar casein-stabilised emulsions

Gel-like emulsions formed with colloidal particles have attracted great attention in various research fields, with studies on food applications surging in an effort to discover new food-grade particle stabilisers that can replace chemical emulsifiers and stabilisers. Turbulence-induced emulsion gels (TIEGs) have recently been reported as a novel means of producing stable gel-like food emulsions. Here we investigate the ability to alternate between liquid and gel-like textures for emulsions stabilised by bovine casein micelles. We describe a reversible emulsion textural transition between free-flowing liquids and semi-solid gels, controlled solely by the application of rotor-stator mixing and high-intensity low-frequency ultrasound (HILF-US), respectively. Rheological and microstructural analyses of the emulsions were performed over five treatment cycles, revealing the importance of the droplet close packing at the submicron level, unique to HILF-US. The amino acid content of the casein was not altered by sonochemical effects. However, the overall secondary structure of the casein protein changed during TIEG formation due to resulting interfacial associations. In-vitro digestion results showed that the initial emulsion texture did not alter protein digestibility. However, TIEG emulsions had smaller droplets that were more stable during digestion. The outcomes aim to deepen the understanding of turbulent-induced emulsion gel formation and advance knowledge on emulsion textural manipulation for food applications.

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.

Enhancing the Backbone Coplanarity of n-Type Copolymers for Higher Electron Mobility and Stability in Organic Electrochemical Transistors.

Electron-transporting (n-type) conjugated polymers have recently been applied in numerous electrochemical applications, where both ion and electron transport are required. Despite continuous efforts to improve their performance and stability, n-type conjugated polymers with mixed conduction still lag behind their hole-transporting (p-type) counterparts, limiting the functions of electrochemical devices. In this work, we investigate the effect of enhanced backbone coplanarity on the electrochemical activity and mixed ionic-electronic conduction properties of n-type polymers during operation in aqueous media. Through substitution of the widely employed electron-deficient naphthalene diimide (NDI) unit for the core-extended naphthodithiophene diimide (NDTI) units, the resulting polymer shows a more planar backbone with closer packing, leading to an increase in the electron mobility in organic electrochemical transistors (OECTs) by more than two orders of magnitude. The NDTI-based polymer shows a deep-lying lowest unoccupied molecular orbital level, enabling operation of the OECT closer to 0 V vs Ag/AgCl, where fewer parasitic reactions with molecular oxygen occur. Enhancing the backbone coplanarity also leads to a lower affinity toward water uptake during cycling, resulting in improved stability during continuous electrochemical charging and ON–OFF switching relative to the NDI derivative. Furthermore, the NDTI-based polymer also demonstrates near-perfect shelf-life stability over a month-long test, exhibiting a negligible decrease in both the maximum on-current and transconductance. Our results highlight the importance of polymer backbone design for developing stable, high-performing n-type materials with mixed ionic-electronic conduction in aqueous media.

Microstructure-Sensitive Uncertainty Quantification for Crystal Plasticity Finite Element Constitutive Models Using Stochastic Collocation Methods

Uncertainty quantification (UQ) plays a major role in verification and validation for computational engineering models and simulations, and establishes trust in the predictive capability of computational models. In the materials science and engineering context, where the process-structure-property-performance linkage is well known to be the only road mapping from manufacturing to engineering performance, numerous integrated computational materials engineering (ICME) models have been developed across a wide spectrum of length-scales and time-scales to relieve the burden of resource-intensive experiments. Within the structure-property linkage, crystal plasticity finite element method (CPFEM) models have been widely used since they are one of a few ICME toolboxes that allows numerical predictions, providing the bridge from microstructure to materials properties and performances. Several constitutive models have been proposed in the last few decades to capture the mechanics and plasticity behavior of materials. While some UQ studies have been performed, the robustness and uncertainty of these constitutive models have not been rigorously established. In this work, we apply a stochastic collocation (SC) method, which is mathematically rigorous and has been widely used in the field of UQ, to quantify the uncertainty of three most commonly used constitutive models in CPFEM, namely phenomenological models (with and without twinning), and dislocation-density-based constitutive models, for three different types of crystal structures, namely face-centered cubic (fcc) copper (Cu), body-centered cubic (bcc) tungsten (W), and hexagonal close packing (hcp) magnesium (Mg). Our numerical results not only quantify the uncertainty of these constitutive models in stress-strain curve, but also analyze the global sensitivity of the underlying constitutive parameters with respect to the initial yield behavior, which may be helpful for robust constitutive model calibration works in the future.