Shape Of Colloids Research Articles

Ionic liquid-based Ionogel: A novel strategy to improve dermal delivery and in vivo efficacy of etodolac in rheumatoid arthritis management

The systemic delivery of Etodolac (ETO) often triggers side effects e.g., myocardial problems, bleeding, etc. thus impeding its clinical usage. Also, ETO exhibits unfavourable physicochemical properties, compelling the need for chronic dosing which could aggravate the condition. The transdermal route not only avoids the systemic toxicity but also enables site-specific action. Yet, the efficacy of this route is constrained due to skin barriers. In the present work, a choline geranate ionic liquid based transdermal gel (CAGE Ionogel) was prepared to improve permeation of ETO. The solubility of ETO increased by ∼19,600-fold in CAGE IL than water. TEM revealed the colloidal shape of ETO-CAGE IL. Moreover, ETO-CAGE Ionogel displayed sustained release for up to 48 h. The ex vivo permeation study revealed a higher flux (∼1.3-fold) than ETO gel. Cytotoxicity assay showed reduced IC50 (∼2.17) relative to ETO in RAW 264.7 cells. In vivo studies in CIA-induced model revealed a decrease in clinical signs of RA. X-ray imaging displayed reduced bone erosion and swelling. The toxicity study showcased no changes in biomarker level suggesting the safety of formulation. Skin compatibility study showed low TEWL implying suitability for topical delivery. The findings affirm the efficacy of transdermal ETO therapy in alleviating RA manifestations.

Microbially controlled colloidal shaping of advanced ceramics

Advanced ceramics find applications in aerospace, energy harvesting and medical technologies. Despite their unique properties, the controlled manufacturing of ceramics with complex geometries is a recurring challenge in the field. Here, a novel manufacturing platform is reported for the colloidal shaping of advanced ceramics using the metabolism of living microorganisms. In this method, bacteria are employed to change the pH of colloidal suspensions in situ, thus enabling casting and time-delayed coagulation of ceramic wet parts in complex-shaped molds. Two distinct bacteria, S. pasteurii and E. coli, are used to investigate the coagulation kinetics of the fabrication process using alumina and zirconia as representative examples of ceramic particles with distinct surface chemistries. The experimental results reveal that the metabolism of bacteria provide an effective mechanism to generate strong ceramic parts with controllable coagulation speed combined with the cost-effective recovery of the microorganisms. These unique features illustrate the potential of engineered living materials for the manufacturing of advanced ceramics.

Exploring Colloidal Phase Transitions of Imogolite Nanotubes by Evaporation Induced Self‐Assembly in Levitation

AbstractEvaporation‐induced self‐assembly (EISA) is a versatile method for generating organized superstructures from colloidal particles, offering diverse design possibilities through the manipulation of colloid size, shape, substrate nature, and environmental conditions. While some work highlighted the potential of EISA to investigate phase transitions of inorganic liquid crystals, the influence of sample environment to determine their phase diagrams is often overlooked. In this work, the self‐assembly of lyotropic liquid crystals is compared by EISA on substrates, and by acoustic levitation (absence of substrate). The focus is on imogolite nanotubes, a model colloidal system of 1D charged objects, due to their tunable morphology and rich liquid‐crystalline phase behavior. It demonstrates the feasibility to obtain phase transitions in levitating droplets and on soft hydrophobic substrates, whereas self‐assembly is limited on rigid hydrophilic supports. Moreover, the aspect ratio of the nanotubes proves to be a pivotal factor, influencing both transitions and the resulting materials shape and surface. Besides material shaping, acoustic levitation emerges as a promising method for studying phase transitions by EISA, toward the rapid establishment of phase diagrams from diluted to highly concentrated states using a limited volume of sample.

A facile bio–inspired route of synthesizing Solanum sisymbriifolium fruit extract mediated silver nanoparticles: Pharmaceutical and environmental aspects

The present research work focused on biological synthesis of silver nanoparticles using Solanum sisymbriifolium aqueous fruit extract (AgNPs@SsFE) and determining their pharmaceutical and environmental aspects for the first time. The phytochemicals extracted from S. sisymbriifolium fruit extract (SsFE) contributed in reducing the average particle size of green synthesized AgNPs@SsFE to 23.17 nm and served as capping agents. Further, when AgNPs@SsFE were characterized using PSA, ZP, FE–SEM, Elemental mapping, EDX, HR–TEM, SAED, FTIR and XRD, exhibited the high colloidal stability, spherical shape and crystalline nature of the nanoparticles. Moreover, the synthesized AgNPs@SsFE exhibited enhanced antioxidant activity in comparison to SsFE when assayed via DPPH, FRAP, •NO and H2O2 scavenging methods. The Agar well–diffusion analysis unveiled AgNPs@SsFE to possess greater antibacterial activity against highly pathogenic gram–negative strains than gram–positive strains. Besides, the synthesized AgNPs@SsFE established itself to be a strong photocatalyst by degrading the methylene blue cationic dye under Solar and UV irradiations. These features of synthesized AgNPs@SsFE are found promising to convince the efficacy of SsFE in synthesizing the nanoparticles which can be useful in modern medicine and clinical applications.

Nanoparticle Superlattices with Nonequilibrium Crystal Shapes.

Nanoparticle assembly is a material synthesis strategy that enables precise control of nanoscale structural features. Concepts from traditional crystal growth research have been tremendously useful in predicting and programming the unit cell symmetries of these assemblies, as their thermodynamically favored structures are often identical to atomic crystal analogues. However, these analogies have not yielded similar levels of influence in programming crystallite shapes, which are a consequence of both the thermodynamics and kinetics of crystal growth. Here, we demonstrate kinetic control of the colloidal crystal shape using nanoparticle building blocks that rapidly assemble over a broad range of concentrations, thereby producing well-defined crystal habits with symmetrically oriented dendritic protrusions and providing insight into the crystals' morphological evolution. Counterintuitively, these nonequilibrium crystal shapes actually become more common for colloidal crystals synthesized closer to equilibrium growth conditions. This deviation from typical crystal growth processes observed in atomic or molecular crystals is shown to be a function of the drastically different time scales of atomic and colloidal mass transport. Moreover, the particles are spherical with isotropic ligand grafts, and these kinetic crystal habits are achieved without the need for specifically shaped particle building blocks or external templating or shape-directing agents. Thus, this work provides generalizable design principles to expand the morphological diversity of nanoparticle superlattice crystal habits beyond the anhedral or equilibrium polyhedral shapes synthesized to date. Finally, we use this insight to synthesize crystallite shapes that have never before been observed, demonstrating the ability to both predict and program kinetically controlled superlattice morphologies.

Synthesis and Assembly of Photoresponsive Colloidal Tubes.

Inspired by the sophisticated multicomponent and multistage assembly of proteins and their mixtures in living cells, this study rationally designs and fabricates photoresponsive colloidal tubes that can self-assemble and hybrid-assemble when mixed with colloidal spheres and rods. Time-resolved observation and computer simulation reveal that the assembly is driven by phoretic attraction originating from osmotic pressures. These pressures are induced by the chemical concentration gradients generated by the photochemical reaction caused by colloidal tubes in a H2O2 solution under ultraviolet (UV) irradiation. The assembled structure is dictated by the size and shape of the constituent colloids as well as the intensity of the UV irradiation. Additionally, the resulting assembly can undergo self-propelled motion originating from the broken symmetry of the surrounding concentration gradients. This motion can be steered by a magnetic field and used for microscale cargo delivery. The study demonstrates a facile synthesis method for colloidal tubes and highlights their unique potential for controlled, hierarchical self-assembly and hybrid-assembly.

Rheology of moderated dilute suspensions of star colloids: The shape factor

Star colloids are rigid particles with long and slender arms connected to a central core. We show numerically that the colloid shapes control the rheology of their suspensions. In particular, colloids with curved arms and hooks can entangle with neighbor particles and form large clusters that can sustain high stresses. When a large cluster permeates the whole system, the viscosity increases many fold. Contrary to the case of spherical colloids, we observe that these effects are very strong even at moderate volumes fraction over a wide range of Péclet numbers.

Self-Assembled Ring-Based Complex Colloidal Particles by Lock-And-Key Interaction and Their Self-Assembly into Unusual Colloidal Crystals.

Creating hierarchical crystalline materials using simple colloids or nanoparticles is very challenging, as it is usually impossible to achieve hierarchical structures without nonhierarchical colloidal interactions. Here, we present a hierarchical self-assembly (SA) route that employs colloidal rings and anisotropic colloidal particles to form complex colloids and uses them as building blocks to form unusual colloidal columnar liquid crystals or crystals. This route is realized by designing hierarchical SA driving forces that is controlled by the colloidal shape and shape-dependent depletion attraction. Depletion-induced lock-and-key interaction is the first driving force, which ensures a high efficiency (>90%) to load colloidal particles of other shapes such as spheres, spherocylinders, and oblate ellipsoids into rings, providing high-quality building blocks. Their SA into ordered superstructures has to require a second driving force such as higher volume fraction and/or stronger depletion attraction. As a result, unusual hierarchical colloidal (liquid) crystals, which have previously been difficult to fabricate by simple binary assembly, can be achieved. This work presents a significant advancement in the field of hierarchical SA, demonstrating a promising strategy for constructing many unprecedented crystalline materials by the SA route.

Depletion-induced crystallization of anisotropic triblock colloids.

The intricate interplay between colloidal particle shape and precisely engineered interaction potentials has paved the way for the discovery of unprecedented crystal structures in both two and three dimensions. Here, we make use of anisotropic triblock colloidal particles composed of two distinct materials. The resulting surface charge heterogeneity can be exploited to generate regioselective depletion interactions and directional bonding. Using extensive molecular dynamics simulations and a dimensionality reduction analysis approach, we map out state diagrams for the self-assembly of such colloids as a function of their aspect ratio and for varying depletant features in a quasi two-dimensional set-up. We observe the formation of a wide variety of crystal structures such as a herringbone, brick-wall, tilted brick-wall, and (tilted) ladder-like structures. More specifically, we determine the optimal parameters to enhance crystallization, and investigate the nucleation process. Additionally, we explore the potential of using crystalline monolayers as templates for deposition, thereby creating complex three-dimensional structures that hold promise for future applications.

One-Pot Synthesis and Characterization of CuCrS2/ZnS Core/Shell Quantum Dots as New Blue-Emitting Sources.

In this paper, we introduce a new blue-emitting material, CuCrS2/ZnS QDs (CCS QDs). To obtain bright and stable photoluminescent probes, we prepared a core/shell structure; the synthesis was conducted in a one-pot system, using 1-dodecanethiol as a sulfur source and co-ligand. The CCS QDs exhibited a semi-spherical colloidal nanocrystalline shape with an average diameter of 9.0 nm and ZnS shell thickness of 1.6 nm. A maximum photoluminescence emission peak (PL max) was observed at 465 nm with an excitation wavelength of 400 nm and PLQY was 5% at an initial [Cr3+]/[Cu+] molar ratio of one in the core synthesis. With an off-stoichiometric modification for band gap engineering, the CCS QDs exhibited slightly blue-shifted PL emission spectra and PLQY was 10% with an increase in initial molar ratio of 2.0 (462 nm PL max). However, when the initial molar ratio exceeded two, the CCS QDs exhibited a lower photoluminescence quantum yield of 4.5% with 461 nm of PL max at the initial molar ratio of four due to the formation of non-emissive Cr2S3 nanoflakes.

Light-Activated Colloidal Micromotors with Synthetically Tunable Shapes and Shape-Directed Propulsion.

Controlling the propulsion modes of colloidal micromotors, from translational to spinning and helical motion, expands the versatility of their potential applications in microrobotics and micromachinery. Engineering colloidal shapes with designed asymmetry can regulate their propulsion behaviors, yet current methods rely on complicated and costly fabrication processes such as lithography. Herein, we present a solution-based synthesis of light-activated colloidal motors adopting straight and various tunable bent geometries, which feature controlled asymmetry and allow shape-directed propulsions. The keys for our strategy are the synthesis of bent silica rods with a tailored bending position and degree, together with the site-specific installation of a photoactive engine. Upon light illumination, the resulting particles propel autonomously, whereby their shape information is translated to various propulsion modes including linear locomotion, steering, and spinning. This low-cost, scalable method for fabricating micromotors with a high degree of control of shapes could promote study in microscale actuation, in active assembly, and eventually for fabrication of colloidal functional materials.

Entropically engineered formation of fivefold and icosahedral twinned clusters of colloidal shapes

Fivefold and icosahedral symmetries induced by multiply twinned crystal structures have been studied extensively for their role in influencing the shape of synthetic nanoparticles, and solution chemistry or geometric confinement are widely considered to be essential. Here we report the purely entropy-driven formation of fivefold and icosahedral twinned clusters of particles in molecular simulation without geometric confinement or chemistry. Hard truncated tetrahedra self-assemble into cubic or hexagonal diamond colloidal crystals depending on the amount of edge and vertex truncation. By engineering particle shape to achieve a negligible entropy difference between the two diamond phases, we show that the formation of the multiply twinned clusters is easily induced. The twinned clusters are entropically stabilized within a dense fluid by a strong fluid-crystal interfacial tension arising from strong entropic bonding. Our findings provide a strategy for engineering twinning behavior in colloidal systems with and without explicit bonding elements between particles.

Nonlinear Optical Properties of Zinc Oxide Nanoparticle Colloids Prepared by Pulsed Laser Ablation in Distilled Water

The nonlinear optical properties of zinc oxide nanoparticles (ZnONPs) in distilled water were measured using a femtosecond laser and the Z-scan technique. The ZnONPs colloids were created by the ablation of zinc bulk in distilled water with a 532 nm Nd: YAG laser. Transmission electron microscopy, an ultraviolet-visible spectrophotometer, and atomic absorption spectrophotometry were used to determine the size, shape, absorption spectra, and concentration of the ZnONPs colloids. The nonlinear absorption coefficient and nonlinear refractive index were measured at different excitation wavelengths and intensities. The nonlinear absorption coefficient of the ZnONPs colloids was found to be positive, caused by reverse saturable absorption, whereas the nonlinear refractive index was found to be negative due to self-defocusing in the ZnONPs. Both laser parameters, such as excitation wavelength and input intensity, and nanoparticle features, such as concentration and size, were found to influence the nonlinear optical properties of the ZnONPs.

The importance of being a cube: Active cubes in a microchannel

• The shape anisotropy of cubes matter for their interaction with active hydrodynamic flow fields. • Active colloidal cubes move parallel to planar boundaries and tubes. • The body internal orientation of the active force determines the trajectory of active cubic colloids. Cubic shaped micrometer and nanometer sized colloids have become a popular research subject in experimental and theoretical soft matter physics. However, they are underrepresented in the field of active matter where the most investigated colloidal shapes are spheres or rods, for which hydrodynamic interactions vary from cube ones due to distinct body shape anisotropies. In this article, we are building on this knowledge by performing simulations to elucidate how active cubes in microchannels interact hydrodynamically with planar and curved boundaries through the flow field generated by an active force. We find that cubes tend to not show the same oscillatory behaviour previously found for other particle shapes, but move along a straight line near the channel centre for a range of initial conditions and parameters that can be accounted for in simulations. This effect arises through the cubes unique shape anisotropy interacting with the flow field and demonstrates that a cube constitutes an interesting hydrodynamic shape that deserves more attention in colloidal active matter research, in order to fully utilise its potential as an enrichment to commonly used particle shapes.

Rheology of a Nanopolymer Synthesized through Directional Assembly of DNA Nanochambers, for Magnetic Applications.

We present a numerical study of the effects of monomer shape and magnetic nature of colloids on the behavior of a single magnetic filament subjected to the simultaneous action of shear flow and a stationary external magnetic field perpendicular to the flow. We find that based on the magnetic nature of monomers, magnetic filaments exhibit a completely different phenomenology. Applying an external magnetic field strongly inhibits tumbling only for filaments with ferromagnetic monomers. Filament orientation with respect to the flow direction is in this case independent of monomer shape. In contrast, reorientational dynamics in filaments with superparamagnetic monomers are not inhibited by applied magnetic fields, but enhanced. We find that the filaments with spherical, superparamagnetic monomers, depending on the flow and external magnetic field strength, assume semipersistent, collapsed, coiled conformations, and their characteristic time of tumbling is a function of field strength. However, external magnetic fields do not affect the characteristic time of tumbling for filaments with cubic, superparamagnetic monomers, but increase how often tumbling occurs.

Superconducting HfO2-added solution-derived YBa2Cu3O7 nanocomposite films: the effect of colloidal nanocrystal shape and crystallinity on pinning mechanism

Two different types of monoclinic HfO2 nanocrystals were employed in this work to study the effect of nanocrystal shape and crystallinity on the structural defects in the YBa2Cu3O7−δ (YBCO) matrix as it leads to an enhancement of pinning performances of solution-derived YBCO nanocomposite films. In this work the nanorod-like HfO2 nanocrystals obtained from surfactant-controlled synthesis led to short intergrowths surrounding the particles, while spherical HfO2 nanocrystals from the solvent-controlled synthesis led to the formation of long stacking faults in the YBCO matrix. It means that the small difference in crystallinity, lattice parameters, nanocrystal structures, core diameter of preformed nanocrystals in colloidal solutions have a strong influence on the formation of the structural defects around the particles in the YBCO matrix, leading to different pinning performances.

Self-assembly of colloidal superballs under spherical confinement of a drying droplet

Understanding the relationship between colloidal building block shape and self-assembled material structure is important for the development of novel materials by self-assembly. In this regard, colloidal superballs are unique building blocks because their shape can smoothly transition between spherical and cubic. Assembly of colloidal superballs under spherical confinement results in macroscopic clusters with ordered internal structure. By utilizing Small Angle X-Ray Scattering (SAXS), we probe the internal structure of colloidal superball dispersion droplets during confinement. We observe and identify four distinct drying regimes that arise during compression via evaporating droplets, and we track the development of the assembled macrostructure. As the superballs assemble, we found that they arrange into the predicted paracrystalline, rhombohedral C1-lattice that varies by the constituent superballs’ shape. This provides insights in the behavior between confinement and particle shape that can be applied in the development of new functional materials.

Mass fractal dimension from 2D microscopy images via an aggregation model with variable compactness.

Microscopy-image analysis provides precious information on size and structure of colloidal aggregates and agglomerates. The structure of colloids is often characterized using the mass fractal dimension , which is different from the two-dimensional (2D) fractal dimension that can be computed from microscopy images. In this work, we propose to use a recent morphological aggregation model to find a relationship between 2D image fractal dimension and 3D mass fractal dimension of aggregates and agglomerates. Our case study is represented by scanning transmission electron microscopy images of boehmite colloidal suspensions. The behaviour of the computed at different acid and base concentration shows a fair agreement with the results of small angle x-ray scattering and with the literature, enabling to use the versus relationship to study the impact of the composition of the colloidal suspension on the density of colloidal aggregates andagglomerates.

Shape Matters in Magnetic-Field-Assisted Assembly of Prolate Colloids.

An anisotropic colloidal shape in combination with an externally tunable interaction potential results in a plethora of self-assembled structures with potential applications toward the fabrication of smart materials. Here we present our investigation on the influence of an external magnetic field on the self-assembly of hematite-silica core–shell prolate colloids for two aspect ratios ρ = 2.9 and 3.69. Our study shows a rather counterintuitive but interesting phenomenon, where prolate colloids self-assemble into oblate liquid crystalline (LC) phases. With increasing concentration, particles with smaller ρ reveal a sequence of LC phases involving para-nematic, nematic, smectic, and oriented glass phases. The occurrence of a smectic phase for colloidal ellipsoids has been neither predicted nor reported before. Quantitative shape analysis of the particles together with extensive computer simulations indicate that in addition to ρ, a subtle deviation from the ideal ellipsoidal shape dictates the formation of this unusual sequence of field-induced structures. Particles with ρ = 2.9 exhibit a hybrid shape containing features from both spherocylinders and ellipsoids, which make their self-assembly behavior richer than that observed for either of the “pure” shapes. The shape of the particles with higher ρ matches closely with the ideal ellipsoids, as a result their phase behavior follows the one expected for a “pure” ellipsoidal shape. Using anisotropic building blocks and external fields, our study demonstrates the ramifications of the subtle changes in the particle shape on the field-directed self-assembled structures with externally tunable properties.

Using femtosecond laser pulses to investigate the nonlinear optical properties of silver nanoparticles colloids in distilled water synthesized by laser ablation

The nonlinear optical properties of silver nanoparticles (AgNPs) colloids in distilled water, when irradiated with 100 fs laser pulses, were investigated experimentally using the Z-scan technique. At a constant wavelength of 760 nm and different excitation powers, the nonlinear absorption coefficient and nonlinear refractive index were measured. The AgNPs colloids are synthesized by laser ablation of silver bulk in distilled water using a 532 nm Nd: YAG laser with different ablation energies fluence of 9, 15.5, and 26 ⨯104 (J/cm2) over a 30min ablation time. The nanoparticle size, shape, and absorption spectra of nanoparticle colloids were determined using transmission electron microscopy and an ultraviolet–visible spectrophotometer. Spherical AgNPs are formed with an average diameter ranging from 7.5 to 12 nm. As the laser ablation energy fluence increases, the average size of the AgNPs decreases while the bandgap energy increases. As the excitation laser power and AgNPs size increase, the nonlinear absorption coefficient and nonlinear refractive index decrease. The optical limiting performance of AgNPs improves with increasing laser ablation energy fluence, with the best performance at 26⨯104 (J/cm2).