Janus particle-based microprobes: Determination of object orientation

Cui, Jingqin; Long, Deng; Shapturenka, Pavel; Kretzschmar, Ilona; Chen, Xin Yi; Wang, Taihong

doi:10.1016/j.colsurfa.2016.11.017

Cited by 8 publications

(9 citation statements)

References 34 publications

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“…In order to characterize the orientation and rotational behavior of the passive Pt-SiO 2 particles, a previously published imaging analysis technique is applied (Figure ). A representative optical image is shown in Figure A.…”

Section: Results and Discussionmentioning

confidence: 99%

“…51 The equivalent of this assumption is to average the two-dimensional (2D) diffusion coefficients for water (D 2D,water = 0.081 μm 2 /s) and decalin (D 2D,decalin = 0.027 μm 2 /s) yielding D 2D,avg = 0.054 μm 2 /s, which is close to the observed D trapped = 0.050 ± 0.007 μm 2 /s. In order to characterize the orientation and rotational behavior of the passive Pt-SiO 2 particles, a previously published imaging analysis technique 49 is applied (Figure 3). A representative optical image is shown in Figure 3A.…”

Section: ■ Results and Discussionmentioning

confidence: 99%

“…The orientation of both passive and active Pt-SiO 2 Janus particles is tracked through the platinum cap (Pt-cap), which acts as a mask so that a Janus particle appears in different configurations with distinguishable bright and dark regions different from the background, i.e., moon-shaped configurations. In the analysis based on a previously published technique, 49 the image sequences from the Pt-SiO 2 Janus particle videos are first converted to grayscale frames. Two weighted centers of a Janus particle in each frame, namely, both the centroid of its circular diffraction ring and the centroid of its bright SiO 2 hemisphere, are identified with a different Matlab particle tracking script.…”

Section: ■ Experimental Detailsmentioning

confidence: 99%

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Pt-SiO₂ Janus Particles and the Water/Oil Interface: A Competition between Motility and Thermodynamics

et al. 2020

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Various aspects of the behavior of Janus particles near liquid/liquid interfaces have been studied through different experimental and theoretical realizations, but the effect of motility on the behavior of Janus particles near liquid/liquid interfaces has not been investigated, yet. Here, we demonstrate the ability to engineer the behavior of highly interfacial active Janus particles near a water/oil interface by introducing motility to the system. Passive, i.e., nonmotile, platinum-capped 8 μm silica (Pt-SiO 2 ) Janus particles exhibit a strong tendency to attach to water/oil interfaces with the Pt-cap facing the oil and the SiO 2 side facing the water phase. In contrast, we show that active, i.e., motile, 8 μm Pt-SiO 2 Janus particles approach the interface, orient in a sideways fashion with the Janus boundary perpendicular to the interface, and then swim in the vicinity of the interface similar to observations reported near solid/liquid interfaces. Active Pt-SiO 2 Janus particles near the water/oil interface show motility as a result of adding H 2 O 2 to the particle solution. The decomposition of H 2 O 2 into O 2 and H 2 O creates a nonuniform gradient of O 2 around the particle that hydrodynamically interacts with the water/decalin boundary. The interaction enables rotation of the particle within the swimming plane that is parallel to the interface but restricts rotation in and out of the swimming plane, thereby preventing adsorption to the liquid/liquid interface.

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Section: Results and Discussionmentioning

confidence: 99%

Section: ■ Results and Discussionmentioning

confidence: 99%

Section: ■ Experimental Detailsmentioning

confidence: 99%

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Pt-SiO₂ Janus Particles and the Water/Oil Interface: A Competition between Motility and Thermodynamics

et al. 2020

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“…Tracking translational and rotational displacement of Janus particles at the various boundary, physiochemical, and rheological conditions could help with predicting the dynamics of these particles [33][34][35][36]. Various studies have focused on the rotation of isotropic [37,38] and anisotropic colloids [39,40]. There has been some work on the translational and rotational dynamics of Janus particles near a boundary [41,42] and also on the effect of mass-anisotropic coating on the dynamics of active particles away from a boundary [43,44].…”

Section: Introductionmentioning

confidence: 99%

Influence of cap weight on the motion of a Janus particle very near a wall

2020

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The dynamics of anisotropic nano-to microscale 'colloidal' particles in confined environments, either near neighboring particles or boundaries, is relevant to a wide range of applications. We utilized Brownian dynamics simulations to predict the translational and rotational fluctuations of a Janus sphere with a cap of non-matching density. The presence of the cap significantly impacted the rotational dynamics of the particle as a consequence of gravitational torque at experimentally relevant conditions. Gravitational torque dominated stochastic torque for a particle > 1 m in diameter and with a 20 nm thick gold cap. Janus particles at these conditions sampled mostly cap-down or 'quenched' orientations. Although the results summarized herein showed that particles of smaller diameter (< 1 m) with a thin gold coating (< 5 nm) behave similar to an isotropic particle, small increases in either particle diameter or coating thickness drastically quenched the polar rotation of the particle. Histogram landscapes of the separation distance from the boundary and orientation observations of particles with larger diameters or thicker gold coatings were mostly populated with quenched configurations. Finally, the histogram landscapes were inverted to obtain the potential energy landscapes, providing a path for experimental data to be interpreted. 3 I. INTRODUCTION. Colloidal particles dispersed in a liquid interact via surface forces that play a critical role in dictating the properties and performance of complex fluid. Over the past decade, the dynamics and interactions of anisotropic colloidal particles have gained attention [1] because of potential applications in various fields such as optical displays [2], magnetorheological system [3], controlling interfacial microstructure [4], self-assembly [5,6], microfluidic devices [7], tuning interparticle interactions [8,9], and biomaterials or drug delivery [10].Supporting these efforts have been a variety of new techniques for the synthesis of anisotropic colloidal particles [5,[10][11][12][13][14][15][16][17][18][19][20][21]. Newly developed fabrication techniques provided the ability to tune the shape and the surface properties of these materials. Janus particles are one class of anisotropic colloid, typically with some property difference in the hemispherical domain. Each hemispherical domain of a Janus particle may have its own surface chemistry, shape, or other properties [22].Predicting the dynamics of anisotropic colloids is important for applications in real systems, for example during processing when complex fluids are often not at equilibrium [23,24].Various parameters influence the dynamics of anisotropic colloids [25][26][27][28]. Particle confinement will strongly impact the hydrodynamic interactions between the colloid and boundary, thereby strongly influencing particle mobility. Brownian motion and conservative (i.e. path independent) forces, such as electrostatic double layer repulsion and gravity, will also impact the dynamics of a confined spherical Janus part...

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“…In recent years, much research has been carried out on the fabrication and applications of Janus materials for their intriguing properties. − There are several methods to fabricate Janus materials, such as surface protection, − self-assembly, − phase separation, , microfluid, − and so on. − Among them, the surface protection method is the most simple and suitable for fabrication on a large scale. The application fields of Janus materials are covered from solid surfactants, − interfacial compatilizers, − probes, − sensors, catalysts − to self-driven motors, − and so on. − However, for their interface affinity property, one of the most important applications of Janus materials is to serve as solid surfactants to emulsify immiscible liquids. Theoretical studies have shown that Janus materials offered advantages over those homogeneous counterparts as solid surfactants .…”

Section: Introductionmentioning

confidence: 99%

Magnetic-Responsive Janus Nanosheets with Catalytic Properties

Xue

Meng

Song

2019

ACS Appl. Mater. Interfaces

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In this article, we describe a method to fabricate magnetic-responsive Janus nanosheets with catalytic properties via the surface protection method. Fe3O4 nanoparticles and PW12O40 3–-based ionic liquid are located on the two opposite sides of the Janus nanosheets, respectively. The Janus nanosheets are characterized by Fourier transform infrared, scanning electron microscopy, transmission electron microscopy, atomic force microscopy, and ζ-potential analyses. They are used as recyclable catalysts to the esterification reaction of methanol and oleic acid for their magnetic-responsive and catalytic properties. The esterification ratio is up to 80% and there is nearly no change when Fe3O4 nanoparticles/PW12O40 3–-based ionic liquid composite nanosheets were recycled four times.

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Janus particle-based microprobes: Determination of object orientation

Cited by 8 publications

References 34 publications

Pt-SiO₂ Janus Particles and the Water/Oil Interface: A Competition between Motility and Thermodynamics

Pt-SiO₂ Janus Particles and the Water/Oil Interface: A Competition between Motility and Thermodynamics

Influence of cap weight on the motion of a Janus particle very near a wall

Magnetic-Responsive Janus Nanosheets with Catalytic Properties

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Janus particle-based microprobes: Determination of object orientation

Cited by 8 publications

References 34 publications

Pt-SiO2 Janus Particles and the Water/Oil Interface: A Competition between Motility and Thermodynamics

Pt-SiO2 Janus Particles and the Water/Oil Interface: A Competition between Motility and Thermodynamics

Influence of cap weight on the motion of a Janus particle very near a wall

Magnetic-Responsive Janus Nanosheets with Catalytic Properties

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Product

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Pt-SiO₂ Janus Particles and the Water/Oil Interface: A Competition between Motility and Thermodynamics

Pt-SiO₂ Janus Particles and the Water/Oil Interface: A Competition between Motility and Thermodynamics