Mukta Tripathy

Bio: Mukta Tripathy is an academic researcher from University of Illinois at Urbana–Champaign. The author has contributed to research in topics: Volume fraction & Janus. The author has an hindex of 6, co-authored 9 publications receiving 732 citations.

Janus Particle Synthesis and Assembly

Abstract: Janus particles, colloid-sized particles with two regions of different surface chemical composition, possess energetic interactions that depend not only on their separation but also on their orientation. Research on Janus and colloidal particles that are chemically patchy in even more complicated fashion has opened a new chapter in the colloid research field. This article highlights recent progress in both experiment and theory regarding synthesis and self-assembly of Janus particles, and tentatively outlines some areas of future opportunity.

The influence of shape on the glassy dynamics of hard nonspherical particle fluids. I. Dynamic crossover and elasticity.

Abstract: We extend and apply the center-of-mass version of the microscopic naive mode coupling theory to study the ideal kinetic glass transition of dense fluids and suspensions composed of broad families of one-, two-, and three- dimensional hard nonspherical particles. A kinetic arrest diagram is constructed which indicates a dynamical crossover or onset of activated barrier hopping controlled transport. We find (quasi-) one-dimensional rods and rings form ideal glasses at the lowest volume fractions which decrease strongly with aspect ratio. Two-dimensional disks form ideal glasses at intermediate volume fractions which decrease slowly with the number of particles comprising the planar objects. Compact three-dimensional cluster particles exhibit a subtle nonmonotonic variation of the onset volume fraction that depends on their detailed shape, surface corrugation, and intraparticle interstitial volume. A strong correlation between the ideal kinetic arrest volume fraction and dimensionless compressibility (amplit...

The influence of shape on the glassy dynamics of hard nonspherical particle fluids. II. Barriers, relaxation, fragility, kinetic vitrification, and universality.

Abstract: We extend and apply the nonlinear Langevin equation theory of activated barrier hopping dynamics in glassy fluids and colloidal suspensions to study broad families of one-, two-, and three-dimensional hard nonspherical particles. Beyond the ideal kinetic arrest volume fraction, entropic barriers emerge with heights (alpha relaxation times, inverse diffusion constants) that increase nonlinearly (nonexponentially) with volume fraction and in a manner that becomes stronger with particle dimensionality. Partial collapse of the volume fraction dependence of barrier heights and reduced relaxation times of different particle shapes within a fixed dimensionality class are achieved based on a difference volume fraction variable that quantifies the distance from the ideal mode coupling theory dynamic crossover. However, the barrier, alpha relaxation time, and self-diffusion constant results of all shapes are remarkably well collapsed onto a single universal master curve based on a theoretically motivated coupling c...

Activated dynamics in dense fluids of attractive nonspherical particles. I. Kinetic crossover, dynamic free energies, and the physical nature of glasses and gels

Abstract: We apply the center-of-mass versions of na\"{\i}ve mode coupling theory and nonlinear Langevin equation theory to study how short-range attractive interactions modify the onset of localization, activated single-particle dynamics, and the physical nature of the transiently arrested state of a variety of dense nonspherical particle fluids (and the spherical analog) as a function of volume fraction and attraction strength. The form of the dynamic crossover boundary depends on particle shape, but the reentrant glass-fluid-gel phenomenon and the repulsive glass-to-attractive glass crossover always occur. Diverse functional forms of the dynamic free energy are found for all shapes including glasslike, gel-like, a glass-gel form defined by the coexistence of two localization minima and two activation barriers, and a ``mixed'' attractive glass characterized by a single, very short localization length but an activation barrier located at a large displacement as in repulsive-force caged glasses. For the latter state, particle trajectories are expected to be of a two-step activated form and can be accessed at high attraction strength by increasing volume fraction, or by increasing attraction strength at fixed high enough volume fraction. A new classification scheme for slow dynamics of fluids of dense attractive particles is proposed based on specification of both the nature of the localized state and the particle displacements required to restore ergodicity via activated barrier hopping. The proposed physical picture appears to be in qualitative agreement with recent computer simulations and colloid experiments.

Theoretical study of the structure and assembly of Janus rods.

Abstract: Microscopic integral equation theory is applied to investigate the real and Fourier space structure and phase behavior of compositionally symmetric AB Janus rods that interact via hard core excluded volume interactions and competing repulsive and attractive tail potentials. If the spatial range of the latter are short and equal, chemical asymmetry results in attraction-driven assembly into a cylindrical micellar structure of spatial periodicity between one and two rods lengths. The apparent microphase spinodal ordering temperature increases with attraction range and rod length, and the microdomain coherence length strongly grows upon cooling. However, as the tail repulsion range increases significantly, the micellar morphology is destroyed and a new repulsion-driven ordering emerges at high volume fractions characterized by a much smaller spatial periodicity. We also find a tight correlation between the local attraction-induced clustering (quantified by the excess number of nearest neighbors) and the micr...

Directed Self-Assembly of Nanoparticles

Abstract: Within the field of nanotechnology, nanoparticles are one of the most prominent and promising candidates for technological applications. Self-assembly of nanoparticles has been identified as an important process where the building blocks spontaneously organize into ordered structures by thermodynamic and other constraints. However, in order to successfully exploit nanoparticle self-assembly in technological applications and to ensure efficient scale-up, a high level of direction and control is required. The present review critically investigates to what extent self-assembly can be directed, enhanced, or controlled by either changing the energy or entropy landscapes, using templates or applying external fields.

Fabrication, properties and applications of Janus particles

Abstract: Although the concept of Janus particles was raised in the early 1990s, the related research has not attracted considerable interest until recently due to the special properties and applications of these colloidal particles as well as the advances in new fabrications. Janus particles can be divided into three categories: polymeric, inorganic, and polymeric–inorganic, and each kind of Janus particles can be spherical, dumbbell-like, half raspberry-like, cylindrical, disk-like, or any of a variety of other shapes. Different Janus particles may share common preparation principles or require specific fabrication processes, and may have different assembly behaviours and properties. This critical review discusses the main fabrication methods of the three kinds of Janus particles, and then highlights the important properties and applications of these Janus particles developed in recent years, and finally proposes some perspectives on the future of Janus particle research and development.

Anisotropic particles with patchy, multicompartment and Janus architectures: preparation and application.

Abstract: Anisotropic particles, such as patchy, multicompartment and Janus particles, have attracted significant attention in recent years due to their novel morphologies and diverse potential applications. The non-centrosymmetric features of these particles make them a unique class of nano- or micro-colloidal materials. Patchy particles usually have different compositional patches in the corona, whereas multicompartment particles have a multi-phasic anisotropic architecture in the core domain. In contrast, Janus particles, named after the double-faced Roman god, have a strictly biphasic geometry of distinct compositions and properties in the core and/or corona. The term Janus particles, multicompartment particles and patchy particles frequently appears in the literature, however, they are sometimes misused due to their structural similarity. Therefore, in this critical review we classify the key features of these different anisotropic colloidal particles and compare structural properties as well as discuss their preparation and application. This review brings together and highlights the significant advances in the last 2 to 3 years in the fabrication and application of these novel patchy, multicompartment and Janus particles (98 references).