Rod-like Particles Research Articles

Heterogeneous catalyst synthesis from Ribbon vittata shells and its characterization for biodiesel production from Blighia sapida seed oil

The global campaign to achieve net zero emissions have necessitated the switch from fossil fuels to biofuels. Owing to the limited resources and high overall production costs, the use of biobased materials has been considered as an economic approach to produce low carbon emitting biofuels. The utilization of heterogeneous catalyst synthesized from Ribbon vittata shells for biodiesel production from Blighia sapida seed oil is discussed in this paper. The crushed shells of Ribbon vittata was placed in a crucible and calcined in a furnace for 4 hr at a temperature of 900 °C to develop the heterogeneous catalyst. The calcined Ribbon vittata shells were characterized using scanning electron microscopy (SEM) and the energy-dispersive electroscope (EDS) to reveal the microstructure and elemental composition. Oil was extracted from Blighia sapida seeds using n-hexane solvent in a chemical extraction process. The biodiesel was produced from the extracted oil using the developed heterogeneous catalyst under selected optimal reaction conditions of 65 °C, 120 min, 2 wt.% catalyst content, and methanol to oil ratio of 9:1. Selected fuel properties of the produced biodiesel were determined using American Standards for Testing and Materials (ASTM) standards. The calcined Ribbon vittata shells showed regular rod-like porous particles, indicating its suitability as a catalyst material. The EDS analysis revealed Ca, O, and C to be the significant elements in the developed heterogeneous catalyst. An average biodiesel of 95.60% was obtained from the transesterification reaction. All the determined fuel properties were found to be within the ASTM D6751 limits for biodiesel. The utilization of calcined Ribbon vittata shells as a heterogeneous catalyst for transesterification of Blighia sapida oil is an economic approach to lower the cost of biodiesel and promote its adoption.

Spontaneous symmetry-breaking of the active cluster drives the directed movement and self-sustained oscillation of symmetric rod-like passive particles.

Active particles without detailed balance can rectify their random motions to drive the directed movement or rotation of asymmetric passive obstacles. However, whether they can drive the directed movement of symmetric passive obstacles is still unclear. Here, we show that a rod-like passive particle which is fixed to move along the x-axis in an active bath can keep long-lived directed movement at nearly constant speed due to the spontaneous symmetry breaking of the neighboring active particle cluster. If the passive particle is further confined by a harmonic potential, it may undergo self-sustained periodic oscillation for an appropriate length of the passive particle and self-propelled velocity of active particles. The restoring force from the harmonic potential will trigger the velocity jump-off and thus lead to self-sustained periodic oscillation. Remarkably, the relationship between the velocity of the passive particle and the external force shows that the effective viscosity of the active bath may become negative in some regime. Finally, we develop a minimum 1D theoretical model to further probe the mechanism underlying the directed movement and self-sustained oscillation of the passive particle. Our findings reveal the effect of the moving boundary on the active bath and demonstrate a novel method to extract practical mechanical work from the active bath to propel microdevices.

Effect of the particle aspect ratio on the aggregate structures of ferromagnetic rod-like particles in a simple shear flow

Effect of the particle aspect ratio on the aggregate structures of ferromagnetic rod-like particles in a simple shear flow

Oriented attachment kinetics for rod-like particles at a flat surface: Buffon's needle at the nanoscale.

The adsorption of large rod-like molecules or crystallites on a flat crystal face, similar to Buffon's needle, requires the rods to "land," with their binding sites in precise orientational alignment with matching sites on the surface. An example is provided by long, helical antifreeze proteins (AFPs), which bind at specific facets and orientations on the ice surface. The alignment constraint for adsorption, in combination with the loss in orientational freedom as the molecule diffuses toward the surface, results in an entropic barrier that hinders the adsorption. Prior kinetic models do not factor in the complete geometry of the molecule, nor explicitly enforce orientational constraints for adsorption. Here, we develop a diffusion-controlled adsorption theory for AFP molecules binding at specific orientations to flat ice surfaces. We formulate the diffusion equation with relevant boundary conditions and present analytical solutions to the attachment rate constant. The resulting rate constant is a function of the length and aspect ratio of the AFP, the distance threshold associated with binding, and solvent conditions such as temperature and viscosity. These results and methods of calculation may also be useful for predicting the kinetics of crystal growth through oriented attachment.

Splay-bend nematic phases of bent colloidal silica rods induced by polydispersity

Liquid crystal (LC) phases are in between solids and liquids with properties of both. Nematic LCs composed of rod-like molecules or particles exhibit long-range orientational order, yielding characteristic birefringence, but they lack positional order, allowing them to flow like a liquid. This combination of properties as well as their sensitivity to external fields make nematic LCs fundamental for optical applications e.g. liquid crystal displays (LCDs). When rod-like particles become bent, spontaneous bend deformations arise in the LC, leading to geometric frustration which can be resolved by complementary twist or splay deformations forming intriguing twist-bend (NTB) and splay-bend (NSB) nematic phases. Here, we show experimentally that the elusive NSB phases can be stabilized in systems of polydisperse micron-sized bent silica rods. Our results open avenues for the realization of NTB and NSB phases of colloidal and molecular LCs.

The behavior and heat generation effect of a magnetic rod-like particle suspension in an alternating and a rotating magnetic field

We have investigated the behavior of magnetic rod-like particles and their relationship with the heat generation effect for both alternating and rotating magnetic fields, by means of Brownian dynamics simulations. As a common feature for both type of magnetic field variations, in the case of significantly strong particle-particle interaction strengths, densely-packed clusters are formed, which do not contribute to the heat generation. For the case of the alternating magnetic field, in the intermediate frequency range, linear thick chain-like clusters are formed and the constituent rod-like particles themselves tend to rotate to follow the change in the field. In contrast, for the case of the rotating field, linear clusters rotate as a whole body to respond to the magnetic field rotation. In both type of magnetic field variations, the magnetic interactions between the constituent particles in a cluster tend to function to suppress the relaxational motion of the rod-like particles, which, as a result, leads to increase in the heat generation effect in certain situations. In a relatively large frequency region, the rotating applied magnetic field gives rise to a larger heat generation effect, whereas in contrast, in the lower frequency region the alternating magnetic field yields the larger heating effect. Highlights The behavior of magnetic rod-like magnetic particles has been elucidated in the case of an alternating and a rotating magnetic field. The magnetic interactions between the constituent particles in a cluster tend to suppress the relaxation motion of the rod-like particles. The frequency and strength of a time-dependent magnetic field have complex influences on the heating effect. In a relatively large frequency region, the rotating applied magnetic field gives rise to a larger heat generation effect. In a relatively lower frequency region, the alternating magnetic field is superior to the rotating field.

Fabrication of in-situ rod-like TiC particles dispersed Ti matrix composite using graphite power sheet

Titanium matrix composites (TMCs) with TiC reinforcements were fabricated by an in-situ method that evolves pure titanium foils (thick: 100 μm) and graphite powder sheets by spark plasma sintering. 20 μm thick graphite powder sheets with PVA (polyvinyl alcohol) were fabricated as carbon resources. The effects of different sintering temperatures and heating time on microstructural features, interface, and properties of the composites were investigated. The structural and microstructural analyses were performed by EPMA, FE-SEM, and EDS. The XRD patterns taken from the cross-section of the prepared composites revealed the composites are composed of TiCx and hexagonal close-packed (HCP) α-Ti. Homogeneous rod-like TiCx particles reinforced TMCs were evaluated by tensile property. The tensile properties of the rod-like TiCx-reinforced TMC show that the tensile strength (UTS) is 479 Mpa, which is 81.4% higher than pure titanium. The formation mechanism and enhancement mechanism of rod-like TiCx particles are also discussed.

Influence of sulfur source on properties of CuSbS2 particles

CuSbS2 is a direct p-type semiconductor with a two-dimensional layered structure of orthorhombic system, excellent electrical performance, and a band gap of 1.1–1.5 eV, which has a light absorption coefficient of more than 104cm−1 in the visible light range. CuSbS2 particles were synthesized by microwave irradiation method, and the effects of different sulfur sources on the phase structure, morphology and electrochemical performance of CuSbS2 particles were studied. The results showed that the sample prepared by thiourea as sulfur source was CuSbS2 phase, and the morphology was composed of flower-like microspheres and rod-like particles. However, nanorod-like CuSbS2 particles were obtained using L-cysteine or 3-thiopropionic acid as sulfur sources, and the phase of samples contained CuSbS2 and Sb2S3 phase. Electrochemical tests showed that L-cysteine based CuSbS2 particles had the largest photocurrent response, a photocurrent density of 1.03 μA cm−2 and impedance of 14.66 Ω.

Colloidal Rod-Like Particles with Temperature-Driven Tunable Interactions.

Temperature-sensitive rod-like colloidal particles were synthesized by grafting a temperature-responsive polymer, poly(2-(dimethylamino)ethyl methacrylate) (PDMA), on the surface of high aspect ratio silica rods by surface-initiated atom transfer radical polymerization. The stability of the grafted polymer on the surface of the particles in aqueous solutions was found to deteriorate with time, leading to a gradual decrease of the polymer content of the hybrid colloids, which was attributed to the mechanically activated hydrolysis of the labile bonds at the polymer-silica interface. The polymer degrafting was significantly suppressed by first growing a hydrophobic poly(methyl methacrylate) block onto the particle surface to act as a barrier layer for the penetration of water molecules at the polymer-particle interface, followed by chain-extension with the hydrophilic PDMA chains. Dynamic light scattering, microscopy, and rheological measurements revealed that the PDMA block conferred a temperature-responsive behavior to the rod-like particles, which formed aggregates at temperatures above the lower critical solution temperature (LCST) of the polymer. However, in contrast to their spherical counterparts, the polymer-grafted rod-like particles did not exhibit complete thermo-reversibility upon lowering the solution temperature below the LCST of PDMA, which was reflected by different values of the diffusion coefficient for the heating and cooling cycles, indicating an irreversible rod particle aggregation upon increasing the temperature.

Drop shape stability vs shape shifting: Role of surfactant adsorption layer

Emulsion droplets, composed of long linear molecules (e.g. n-alkanes) and stabilized by long chain surfactants, can spontaneously change their shape upon cooling and morph from spheres into regular polyhedra, polygonal platelets, rods and thin fibers. Until now, these dynamic shape changes have been studied upon continuous temperature decrease. Therefore, it had remained unclear whether the observed shapes were stable or they appeared as intermediate states during the transformation of the initial sphere into some final shape(s). In the current study, we performed dedicated experiments at fixed temperature to distinguish between the stable, metastable and unstable shapes and to define the factors which affect the kinetics of the observed transitions. The results showed that the stable shapes are equilateral triangular platelets (in all surfactant solutions) and the rod-like particles, when stabilized by surfactants with narrow compositional variations. The distorted octahedrons (seen as hexagonal platelets in transmitted light) were metastable and preserved their shape for many minutes. The other shapes, e.g. the flat hexagonal and tetragonal platelets, were unstable and continued to transform until they reached one of the stable states or alternatively – until they formed spheroidal droplets extruding thin fibers from their bodies. These experimental results are in general agreement with the theoretical model developed by Haas et al. (Phys. Rev. Lett. 2017, Phys. Rev. Res. 2019). The rate of shape transformations increased with the level of subcooling and/or with the decrease of drop size.

Facile Fabrication of Starch-Based Microrods by Shear-Assisted Antisolvent-Induced Nanoprecipitation and Solidification.

Rod-like particles have attracted increasing attention because of their unique shape-dependent properties, which enable their superior performance compared to their isotropic counterparts. Thus, rod-like particles have potential applications in many fields, especially in biomedicine. However, the fabrication of uniform rod-like particles is challenging because of the principle of interfacial energy minimization. Herein, we present a facile, rapid, and cost-effective strategy for preparing starch-based microrods with tunable aspect ratios via shear-assisted antisolvent-induced nanoprecipitation and solidification. The preformed spherical particles swollen by the mixed solvent were elongated by the shear force and solidified in rod-like shape by antisolvent induction. The resulting starch-based microrods can encapsulate hydrophobic active substances and be modified with functional groups, indicating their potential applications as drug carriers and biologically active materials. The formation mechanism of the starch-based microrods discovered in this study provides a new perspective on the fabrication of rod-like polymer particles.

Cellulose nanocrystal-based enhancement of ultrasound microbubbles for increased tolerance of mechanical index values

Enhancements in the echo intensity and mechanical index (MI) tolerance of ideal ultrasound contrast agents (UCAs) are urgently needed to realize precise clinical ultrasound (US). Solid cellulose nanocrystals (CNCs) have the advantages of imparting strong sound wave propagation and echo intensity when irradiated by US. This study aimed to fabricate improved UCAs via CNC-modified SonoVue ultrasound microbubbles (MBs), characterize the resulting SonoVue@CNC MBs, and evaluate the performance of the SonoVue@CNC MBs in US imaging in vitro and in vivo. SonoVue@CNC MBs were successfully prepared by incorporating CNCs into SonoVue MBs via self-assembly. The SonoVue@CNC MBs were spherical in shape with mean particle sizes of (5.50 ± 1.60) μm. The CNCs were mainly distributed on the polymeric shells of the SonoVue@CNC MBs. When the MI was 0.4, the echo intensity of the SonoVue@CNC MBs was 1.5-fold greater than that of the SonoVue MBs in vitro. The CNC concentration regulated the quality of SonoVue@CNC-promoted contrast-enhanced ultrasound (CEUS) images. Enhanced US images of both the livers and kidneys of Sprague–Dawley (SD) rats showed that the CNC-loaded UCA led to a higher echo intensity than SonoVue. In CCK-8 assays using MCF-10A cells, both SonoVue@CNC MBs and CNCs exhibited weak toxicities against MCF-10A cells. Ultimately, the spherical SonoVue@CNC MBs with a uniform particle size displayed an enhanced safety profile and improved the imaging quality of US in vivo and in vitro. Next, drugs and targeting moieties will be loaded onto the SonoVue@CNC MBs via the CNCs to develop UCA-based selective ultrasonic theranostic methods.Graphical abstractAs shown in the graphical abstract, the white bubble in the left-middle position symbolized SonoVue microbubble (MB), the green rod-like particle signified CNC nanorod. The big white bubble decorated with green rod-like nanorod next to the mouse was SonoVue@CNC MB which was successfully prepared by incorporating CNCs into SonoVue MB via self-assembly. The purple square frame on the upper left displayed CNC, SonoVue MB, SonoVue@CNC MB and their relative diagrammatic drawings. Picture (I) displayed the transmission electron microscopy results for CNCs (a) and SonoVue@CNC MBs (b, c and d) of morphological study. Picture (II) displayed the in vitro ultrasound (US) imaging of SonoVue (a) MB and SonoVue@CNC (b, c and d) MBs with different CNCs concentrations. Picture (III and IV) displayed the in vivo US imaging of SonoVue (a) and SonoVue@CNC (b, c and d) MBs with different CNCs concentrations for SD mouse liver and kidney, respectively.

The electrodynamics of rod-like microparticles based on optically induced dielectrophoresis.

Due to its characteristics of noncontact, non-damage, high flux, and easy-to-achieve flexible manipulation, optically induced dielectrophoresis (ODEP) technology has been employed to manipulate microspherical biological particles, including separation, enrichment, capture, arrangement, and fusion. However, in nature, biomolecules are morphologically diverse, and some of them are rodlike. In order to illustrate the electrodynamics of rodlike particles under the action of ODEP, a transient multi-physical field coupling model of ODEP chip under the hypothesis of electrical double layer thin layer was established in this paper. The arbitrary Lagrangian-Eulerian method is used to track single-rod particle in the strong coupled flow field and electric field simultaneously. The influence of several key factors, including the applied alternating current (AC) electric voltage, the width of optical bright area, and the initial position of particle, on the trajectory of particle center was analyzed in positive dielectrophoresis (DEP) action and negative DEP action, respectively. Especially, the planar motion process of rodlike particles was discussed together. The research results reveal the electrodynamics behavior of rodlike particles based on the action of ODEP, which may provide theoretical support for the further design of rodlike biological cells manipulation chip based on AC ODEP technology in the future.

Insight into different roles of chitin nanocrystals and cellulose nanocrystals towards stabilizing Pickering emulsions

Rod-like polysaccharide particles such as chitin nanocrystals (ChNCs) and cellulose nanocrystals (CNCs) have been widely used for the preparation of Pickering emulsion. Both are believed playing good role of particle emulsifiers. However, these two kinds of nanocrystals have completely different surface properties: electronegative CNC is more hydrophilic and has higher surface charge level as compared to electropositive ChNC. To reveal their difference as emulsifiers in Pickering emulsions is therefore of interest. In this work, ChNCs and CNCs with the same structural parameters (aspect ratio = 28) were used to prepare olive oil- in -water emulsions for a comparative study. The two kinds of nanocrystals show the same mechanical state in emulsions, behaving like rigid rods, instead flexible fibers because they have 10 4 level of effective stiffness. Therefore, their roles of emulsifying oil/water system are dominated by their surface properties: ChNCs reveal higher emulsifying capacity relative to CNCs due to better ChNC-oil affinity, and can even emulsify the oil/water (7/3 w/w) system with high oil fractions. However, ChNC-stabilized emulsions are not that stable to centrifugation as compared to CNC-stabilized emulsions at low oil fractions due to the formation of the cluster structure resulted from less coating of droplets. Thus, the former reveals higher strain sensitivity and stronger thixotropy than the latter in shear flow. The correlation between viscoelasticity and morphology/phase behavior of the two kinds of Pickering systems was assessed, then. This work provides valuable information on formulating preparation of Pickering emulsions by using different types of rod-like polysaccharide nanocrystals. • CNCs and ChNCs have different roles towards emulsifying oil- in -water system. • ChNC has better emulsifying capacity and can emulsify high-oil-fraction system. • CNC-stabilized emulsions are stabler as compared to the ChNC-stabilized ones. • The morphology of emulsions can be well tuned by using different nanocrystals.

Collective diffusion in a two-dimensional liquid composed of Janus particles

The collective diffusion of anisotropic particles in liquids plays a crucial role in many processes, such as self-assembly. The patchy particle, which is usually nearly spherical in shape, is an important anisotropic particle with different properties from other anisotropic particles like the ellipsoid liquid crystal particles. In the present study, molecular dynamics simulations are performed to study the collective diffusion of a two-dimensional anisotropic liquid system composed of Janus particles. The static structures and diffusion behaviours of anisotropic and isotropic Lennard-Jones liquids are compared. The long-time diffusion behaviour of an anisotropic liquid of nearly spherical Janus particles is found to be similar to that of an isotropic liquid because the orientation of the particles disappears over long-term averaging. The anisotropic properties of the Janus particles are mainly reflected in the spatial correlation of particle orientations and mid-time diffusion behaviour. The difference between nearly spherical anisotropic particles and rod-like particles is also discussed in this paper.

Hyperbolic Systems of Moment Equations Describing Sedimentation in Suspensions of Rod-Like Particles

Hyperbolic Systems of Moment Equations Describing Sedimentation in Suspensions of Rod-Like Particles

Copper Oxide Coupled Titanium Dioxide (CuO/TiO<sub>2</sub>) Nanocomposite Photocatalyst for Degradation of Methyl Orange Dye

Titanium dioxide (TiO2) was utilized in photocatalysis applications due to their non- toxic, cheap and high photocatalytic activity. However, its photocatalytic reaction is limited by low surface area as well as the rapid recombination of photogenerated electron-hole pairs and only has ability to absorb a small fraction (<5%) of indoor light. In this study, copper oxide coupled titanium dioxide (CuO/TiO2) nanocomposite photocatalyst was synthesized using hydrothermal method. The synthesised photocatalyst was characterized by using Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction analysis (XRD), Scanning electron microscopy(SEM), Brunauer, Emmett, teller (BET) and UV- Visible Spectroscopy. Spectra obtained from FTIR have proved that there are existence of O-H stretching, O-H vibration and metal-O bond that correlates to the functional groups of the samples. As affirmed by XRD analysis, highly crystalline rutile TiO2 phase was obtained for pure TiO2 samples. Rutile TiO2 phase is remained and additional peaks belong to copper oxide was observed for CuO/TiO2 nanocomposite photocatalyst sample. This finding suggesting that copper oxide was successfully loaded onto TiO2. Morphological study from SEM shows the presence of short rod-like particles of copper oxide and agglomerated TiO2 bulk particles. BET surface area for CuO, TiO2 and CuO/TiO2 nanocomposite photocatalysts were 20.50 m2/g, 15.26 m2/g and 17.13 m2/g, respectively. The photocatalytic degradation of methyl orange (MO) was found to be 85.0% using CuO/TiO2 nanocomposite photocatalyst, which is better than pure TiO2 and pure CuO after 3 hours reaction.

The effect of morphology of ZnO particle on properties of asphalt binder and mixture

To study the effects of the morphology of ZnO particles on the properties of asphalt binder and asphalt mixture, the micro ZnO particles with different morphologies (agglomerate, sphere, rod and flower), whose average size were 2 µm, were made by the homogeneous precipitation and hydrothermal methods. A series of tests, including the softening point, bending beam rheometer (BBR), dynamic shear rheological (DSR), Marshall test, rutting test and so on, were used for evaluating the properties of asphalt binder and asphalt mixture. The analysis of variance (ANOVA) and the maximum relative difference (MRD) were introduced to study the effects of the morphology of ZnO particles on the properties of asphalt binder and asphalt mixture. Finally, the optimal morphology of the ZnO particle was recommended. The results show that the morphology of the ZnO particle has a significant effect on the rutting factor, has an effect on the viscosity in the situation of the dosages of SBS are 0% and 4%, has no effect on the low temperature ability of asphalt binder. In terms of asphalt mixture, the morphology of the ZnO particle has a noticeable effect on the high temperature stability, has an effect on the low temperature ability, has almost no effect on the water stability of asphalt mixture. Furthermore, the rod-like ZnO particles are more conducive to promote the properties of asphalt binder and asphalt mixture. As a result, the rod-like ZnO particle is recommended.

Effect of anisotropy on the formation of active particle films.

Active colloids belong to a class of nonequilibrium systems where energy uptake, conversion, and dissipation occur at the level of individual colloidal particles, which can lead to particles' self-propelled motion and surprising collective behavior. Examples include coexistence of vapor- and liquid-like steady states for active particles with repulsive interactions only, phenomena known as motility-induced phase transitions. Similarly to motile unicellular organisms, active colloids tend to accumulate at confining surfaces forming dense adsorbed films. In this work, we study the structure and dynamics of aggregates of self-propelled particles near confining solid surfaces, focusing on the effects of the particle anisotropic interactions. We performed Langevin dynamics simulations of two complementary models for active particles: ellipsoidal particles interacting through the Gay-Berne potential and rodlike particles composed of several repulsive Lennard-Jones beads. We observe a nonmonotonic behavior of the structure of clusters formed along the confining surface as a function of the particle aspect ratio, with a film spreading when particles are near-spherical, compact clusters with hedgehog-like particle orientation for more elongated active particles, and a complex dynamical behavior for an intermediate aspect ratio. The stabilization time of cluster formation along the confining surface also displays a nonmonotonic dependence on the aspect ratio, with a local minimum at intermediate values. Additionally, we demonstrate that the hedgehog-like aggregates formed by Gay-Berne ellipsoids exhibit higher structural stability as compared to the ones formed by purely repulsive active rods, which are stable due to the particle activity only.

Microrheology of isotropic and liquid-crystalline phases of hard rods by dynamic Monte Carlo simulations

Particle tracking in soft materials allows one to characterise the material’s local viscoelastic response, a technique referred to as microrheology (MR). In particular, MR can be especially powerful to ponder the impact of structural ordering on the tracer’s transport mechanism and thus disclose intriguing elements that cannot be observed in isotropic fluids. In this work, we perform Dynamic Monte Carlo simulations of isotropic and liquid–crystalline phases of rod-like particles and employ MR to characterise their linear viscoelastic response. By incorporating tracers of different diameters, we can assess the combined effect of size and ordering across the relevant time and length scales of the systems’ relaxation. While the dynamics of small tracers is dramatically determined by the background ordering, sufficiently large tracers have a reduced perception of the medium nanostructure and this difference directly influences the observed MR. Our results agree very well with the picture of a microviscosity increasing with the relevant system length scales, but also suggest the crucial relevance of long-ranged order as a key element governing the system’s viscoelastic response.