1
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Feigl E, Jedlovszky P, Sega M. Percolation transition and bimodal density distribution in hydrogen fluoride. J Chem Phys 2024; 160:204503. [PMID: 38785286 DOI: 10.1063/5.0207202] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2024] [Accepted: 05/06/2024] [Indexed: 05/25/2024] Open
Abstract
Hydrogen-bond networks in associating fluids can be extremely robust and characterize the topological properties of the liquid phase, as in the case of water, over its whole domain of stability and beyond. Here, we report on molecular dynamics simulations of hydrogen fluoride (HF), one of the strongest hydrogen-bonding molecules. HF has more limited connectivity than water but can still create long, dynamic chains, setting it apart from most other small molecular liquids. Our simulation results provide robust evidence of a second-order percolation transition of HF's hydrogen bond network occurring below the critical point. This behavior is remarkable as it underlines the presence of two different cohesive mechanisms in liquid HF, one at low temperatures characterized by a spanning network of long, entangled hydrogen-bonded polymers, as opposed to short oligomers bound by the dispersion interaction above the percolation threshold. This second-order phase transition underlines the presence of marked structural heterogeneity in the fluid, which we found in the form of two liquid populations with distinct local densities.
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Affiliation(s)
- Elija Feigl
- Faculty of Physics, University of Vienna, Boltzmanngasse 5, Wien A-1090, Austria
| | - Pál Jedlovszky
- Department of Chemistry, Eszterházy Károly Catholic University, Leányka utca 12, H-3300 Eger, Hungary
| | - Marcello Sega
- Department of Chemical Engineering, University College London, WC1E 7JE London, United Kingdom
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2
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Messina R, Kemgang E. The relevance of curvature-induced quadrupolar interactions in dipolar chain aggregation. J Chem Phys 2023; 159:174903. [PMID: 37916594 DOI: 10.1063/5.0164168] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2023] [Accepted: 10/14/2023] [Indexed: 11/03/2023] Open
Abstract
The aggregation of dipolar chains driven by thermal fluctuations in an external strong (electric or magnetic) field is investigated theoretically. We discover a new simple electrostatic mechanism that rationalizes the counter-intuitive lateral coalescence of dipolar chains. There, we first demonstrate that two bent dipolar chains can either attract or repel each other depending if they possess similar or opposite curvatures, respectively. Upon bending, dipolar chains become the siege of polarization-induced local charges that in turn lead to quadrupolar couplings. This striking feature is then exploited to understand our conducted Monte Carlo simulations at finite temperature where thermal fluctuations cause local curvatures in the formed dipolar chains. The related quadrupolar attractive mode with correlated chain-curvatures is clearly identified in the simulation snapshots. Our findings shed new light on a longstanding problem in soft matter and related areas.
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Affiliation(s)
- René Messina
- Laboratoire de Physique et Chimie Théoriques, LPCT-UMR CNRS 7019, Université de Lorraine, 1 Boulevard Arago, 57070 Metz, France
| | - Ebenezer Kemgang
- Laboratoire de Physique et Chimie Théoriques, LPCT-UMR CNRS 7019, Université de Lorraine, 1 Boulevard Arago, 57070 Metz, France
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3
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Biersack M, Lakkis A, Richter R, Bilous O, Sánchez PA, Kantorovich SS. Controlling the coarsening dynamics of ferrogranular networks by means of a vertical magnetic field. Phys Rev E 2023; 108:054905. [PMID: 38115481 DOI: 10.1103/physreve.108.054905] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2023] [Accepted: 10/16/2023] [Indexed: 12/21/2023]
Abstract
We are exploring in experiments the aggregation process in a shaken granular mixture of glass and magnetized steel beads, filled in a horizontal vessel, after the shaking amplitude is suddenly decreased. Then the magnetized beads form a transient network that coarsens in time into compact clusters, resembling a viscoelastic phase separation [Tanaka, J. Phys.: Condens. Matter 12, R207 (2000)0953-898410.1088/0953-8984/12/15/201], where attached beads represent the slow phase. Here we investigate how a homogeneous magnetic field oriented in vertical direction impedes the emergence and growth of the networks. With increasing field amplitude this phase is replaced by a fluctuating arrangement of repelling, isolated steel beads. The experimental results are compared with those of computer simulations. Coarse-grained molecular dynamics confirms the impact of an applied magnetic field on the structural transitions and allows us to investigate long-time regimes and magnetic response not yet accessible in the experiment. It turns out that an applied magnetic field has different impacts, depending on it strength. It can be used either to slow down the dynamics of the structural transitions without changing the type of the resulting phases and only affecting the amount and sizes of clusters, or to fully impede the formation of network-like and compact aggregates of steel beads.
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Affiliation(s)
| | - Ali Lakkis
- Experimentalphysik V, Universität Bayreuth, 95440 Bayreuth, Germany
| | - Reinhard Richter
- Experimentalphysik V, Universität Bayreuth, 95440 Bayreuth, Germany
| | - Oksana Bilous
- University of Vienna, Faculty of Physics, Kolingasse 14-16, 1090 Vienna, Austria
| | - Pedro A Sánchez
- University of Vienna, Faculty of Physics, Kolingasse 14-16, 1090 Vienna, Austria
| | - Sofia S Kantorovich
- University of Vienna, Faculty of Physics, Kolingasse 14-16, 1090 Vienna, Austria
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4
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Rosenberg M, Kantorovich S. The influence of anisotropy on the microstructure and magnetic properties of dipolar nanoplatelet suspensions. Phys Chem Chem Phys 2023; 25:2781-2792. [PMID: 36129024 DOI: 10.1039/d2cp03360g] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
In recent years, there has been an increasing interest in magnetic nanoparticles with non-spherical shapes. This is largely due to their broad span of tuneable properties, which allow for tailoring of the colloidal properties by altering the magnetic anisometry or shape anisotropy of the nanoparticle. Although extensive research has gone into novel synthesis methods, the theoretical and analytical treatment of magnetic colloidal suspensions still predominantly focuses on spherical particles. This paper explores the microstructure and initial static magnetic susceptibility of systems of anisometric dipolar magnetic nanoplatelets in order to understand the applicability of dipolar sphere-based theories and models for such systems. We find that the microstructure as characterized by the particle distribution and magnetic clustering of platelets diverges significantly from that of spheres both quantitatively and qualitatively. We find lower initial static magnetic susceptibilities in nanoplatelet systems than in comparable suspensions of dipolar spheres. At lower values of the magnetic coupling constant, this can be accounted for by applying corrections to the volume fraction. However, this approach is less accurate for systems with stronger magnetic interactions. By providing predictions of and explanations for the observed effects, we aim to facilitate the use of magnetic nanoplatelet suspensions in the broad range of applications.
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Affiliation(s)
- Margaret Rosenberg
- Faculty of Physics, University of Vienna, Bolzmanngasse 5, Vienna 1090, Austria.
| | - Sofia Kantorovich
- Faculty of Physics, University of Vienna, Bolzmanngasse 5, Vienna 1090, Austria. .,Research Platform MMM Mathematics-Magnetism-Materials, Vienna, Austria
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5
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Hierarchical Porous Magnetite Structures: From Nanoparticle Assembly to Monolithic Aerogels. J Colloid Interface Sci 2022; 615:206-214. [DOI: 10.1016/j.jcis.2022.01.154] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2021] [Revised: 01/11/2022] [Accepted: 01/24/2022] [Indexed: 11/19/2022]
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6
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Facile synthesis of zein-based emulsion gels with adjustable texture, rheology and stability by adding β-carotene in different phases. Food Hydrocoll 2022. [DOI: 10.1016/j.foodhyd.2021.107178] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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7
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Liao GJ, Klapp SHL. Emergent vortices and phase separation in systems of chiral active particles with dipolar interactions. SOFT MATTER 2021; 17:6833-6847. [PMID: 34223596 DOI: 10.1039/d1sm00545f] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
Using Brownian dynamics (BD) simulations we investigate the self-organization of a monolayer of chiral active particles with dipolar interactions. Each particle is driven by both, translational and rotational self-propulsion, and carries a permanent point dipole moment at its center. The direction of the translational propulsion for each particle is chosen to be parallel to its dipole moment. Simulations are performed at high dipolar coupling strength and a density below that related to motility-induced phase separation in simple active Brownian particles. Despite this restriction, we observe a wealth of phenomena including formation of two types of vortices, phase separation, and flocking transitions. To understand the appearance and disappearance of vortices in the many-particle system, we further investigate the dynamics of simple ring structures under the impact of self-propulsion.
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Affiliation(s)
- Guo-Jun Liao
- Institut für Theoretische Physik, Technische Universität Berlin, Hardenbergstr. 36, D-10623 Berlin, Germany.
| | - Sabine H L Klapp
- Institut für Theoretische Physik, Technische Universität Berlin, Hardenbergstr. 36, D-10623 Berlin, Germany.
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8
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Donaldson JG, Schall P, Rossi L. Magnetic Coupling in Colloidal Clusters for Hierarchical Self-Assembly. ACS NANO 2021; 15:4989-4999. [PMID: 33650847 PMCID: PMC8155334 DOI: 10.1021/acsnano.0c09952] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
Manipulating the way in which colloidal particles self-organize is a central challenge in the design of functional soft materials. Meeting this challenge requires the use of building blocks that interact with one another in a highly specific manner. Their fabrication, however, is limited by the complexity of the available synthesis procedures. Here, we demonstrate that, starting from experimentally available magnetic colloids, we can create a variety of complex building blocks suitable for hierarchical self-organization through a simple scalable process. Using computer simulations, we compress spherical and cubic magnetic colloids in spherical confinement, and investigate their suitability to form small clusters with reproducible structural and magnetic properties. We find that, while the structure of these clusters is highly reproducible, their magnetic character depends on the particle shape. Only spherical particles have the rotational degrees of freedom to produce consistent magnetic configurations, whereas cubic particles frustrate the minimization of the cluster energy, resulting in various magnetic configurations. To highlight their potential for self-assembly, we demonstrate that already clusters of three magnetic particles form highly nontrivial Archimedean lattices, namely, staggered kagome, bounce, and honeycomb, when focusing on different aspects of the same monolayer structure. The work presented here offers a conceptually different way to design materials by utilizing preassembled magnetic building blocks that can readily self-organize into complex structures.
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Affiliation(s)
- Joe G. Donaldson
- Department
of Chemical Engineering, Delft University
of Technology, 2629 HZ Delft, The Netherlands
| | - Peter Schall
- Institute
of Physics, University of Amsterdam, 1098 XH Amsterdam, The Netherlands
| | - Laura Rossi
- Department
of Chemical Engineering, Delft University
of Technology, 2629 HZ Delft, The Netherlands
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9
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Dobroserdova AB, Kantorovich SS. Self-diffusion in bidisperse systems of magnetic nanoparticles. Phys Rev E 2021; 103:012612. [PMID: 33601641 DOI: 10.1103/physreve.103.012612] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2020] [Accepted: 12/09/2020] [Indexed: 12/11/2022]
Abstract
In the present paper, we study the self-diffusion of aggregating magnetic particles in bidisperse ferrofluids. We employ density functional theory (DFT) and coarse-grained molecular dynamics (MD) simulations to investigate the impact of granulometric composition of the system on the cluster self-diffusion. We find that the presence of small particles leads to the overall increase of the self-diffusion rate of clusters due the change in cluster size and composition.
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Affiliation(s)
- Alla B Dobroserdova
- Ural Mathematical Centre, Ural Federal University, Named after the First President of Russia B. N. Yeltsin, Ekaterinburg 620002, Russia
| | - Sofia S Kantorovich
- University of Vienna, Faculty of Physics, Kolingasse 14-16, 1090, Vienna, Austria, and Ural Federal University Named after the First President of Russia B. N. Yeltsin, Ekaterinburg 620002, Russia; and Research Platform MMM, University of Vienna, Oskar-Morgenstern-Platz 1, 1090, Vienna, Austria
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10
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Veloso SR, Andrade RG, Castanheira EM. Review on the advancements of magnetic gels: towards multifunctional magnetic liposome-hydrogel composites for biomedical applications. Adv Colloid Interface Sci 2021; 288:102351. [PMID: 33387893 DOI: 10.1016/j.cis.2020.102351] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2020] [Revised: 12/18/2020] [Accepted: 12/19/2020] [Indexed: 12/11/2022]
Abstract
Magnetic gels have been gaining great attention in nanomedicine, as they combine features of hydrogels and magnetic nanoparticles into a single system. The incorporation of liposomes in magnetic gels further leads to a more robust multifunctional system enabling more functions and spatiotemporal control required for biomedical applications, which includes on-demand drug release. In this review, magnetic gels components are initially introduced, as well as an overview of advancements on the development, tuneability, manipulation and application of these materials. After a discussion of the advantages of combining hydrogels with liposomes, the properties, fabrication strategies and applications of magnetic liposome-hydrogel composites (magnetic lipogels or magnetolipogels) are reviewed. Overall, the progress of magnetic gels towards smart multifunctional materials are emphasized, considering the contributions for future developments.
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11
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Kim H, Sau M, Furst EM. An Expanded State Diagram for the Directed Self-Assembly of Colloidal Suspensions in Toggled Fields. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2020; 36:9926-9934. [PMID: 32697093 DOI: 10.1021/acs.langmuir.0c01616] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
The suspension structure and assembly kinetics of micrometer-diameter paramagnetic spheres in toggled magnetic fields are investigated at a constant field strength H = 1750A·m-1 while toggling the field on and off over the frequency range 0.3<f<5 Hz and duty ratio values (the fraction of time the field is on over one toggle period) 0.05 ≤ ξ ≤ 0.8. Five microstructures form after sufficient time in the toggled field, fluid, columnar, percolated, ellipsoidal-shaped, and perpendicular, and their kinetic pathways are identified. For ellipsoidal-shaped microstructures, diffusion-driven particle aggregation at early times gives way to a fluid-like breakup. For columnar and percolated structures, this coarsening arrests before breakup. As the toggling duty cycle decreases, the range of frequencies for each structure narrows, giving way to an unstructured fluid; below ξ<0.1, only the fluid state is observed. The existence of fluid, columnar, percolated, and ellipsoidal-shaped microstructures agrees well with those predicted by the theoretical and computational work of Sherman et al. (Sherman, Z. M.; Rosenthal, H.; Swan, J. W. Langmuir 2018, 34, 1029-1041). Microstructures that connect perpendicularly to the magnetic field are identified for 0.1 ≤ ξ ≤ 0.3 and 1.6<f<3.7 Hz. Perpendicular microstructures also exhibit emergent dynamics with continuous rotation, breakup, and coalescence events.
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Affiliation(s)
- Hojin Kim
- Department of Chemical and Biomolecular Engineering, Allan P. Colburn Laboratory, University of Delaware, Newark, Delaware 19716, United States
| | - Moujhuri Sau
- Department of Chemical and Biomolecular Engineering, Allan P. Colburn Laboratory, University of Delaware, Newark, Delaware 19716, United States
| | - Eric M Furst
- Department of Chemical and Biomolecular Engineering, Allan P. Colburn Laboratory, University of Delaware, Newark, Delaware 19716, United States
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12
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Liao GJ, Hall CK, Klapp SHL. Dynamical self-assembly of dipolar active Brownian particles in two dimensions. SOFT MATTER 2020; 16:2208-2223. [PMID: 32090218 DOI: 10.1039/c9sm01539f] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Based on Brownian Dynamics (BD) simulations, we study the dynamical self-assembly of active Brownian particles with dipole-dipole interactions, stemming from a permanent point dipole at the particle center. The propulsion direction of each particle is chosen to be parallel to its dipole moment. We explore a wide range of motilities and dipolar coupling strengths and characterize the corresponding behavior based on several order parameters. At low densities and low motilities, the most important structural phenomenon is the aggregation of the dipolar particles into chains. Upon increasing the particle motility, these chain-like structures break, and the system transforms into a weakly correlated isotropic fluid. At high densities, we observe that the motility-induced phase separation is strongly suppressed by the dipolar coupling. Once the dipolar coupling dominates the thermal energy, the phase separation disappears, and the system rather displays a flocking state, where particles form giant clusters and move collective along one direction. We provide arguments for the emergence of the flocking behavior, which is absent in the passive dipolar system.
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Affiliation(s)
- Guo-Jun Liao
- Institut für Theoretische Physik, Technische Universität Berlin, Hardenbergstr. 36, D-10623 Berlin, Germany.
| | - Carol K Hall
- Department of Chemical & Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695, USA
| | - Sabine H L Klapp
- Institut für Theoretische Physik, Technische Universität Berlin, Hardenbergstr. 36, D-10623 Berlin, Germany.
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13
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Brito ME, Carignano MA, Marconi VI. Self-assembly of Pseudo-Dipolar Nanoparticles at Low Densities and Strong Coupling. Sci Rep 2020; 10:3971. [PMID: 32132549 PMCID: PMC7055284 DOI: 10.1038/s41598-020-60417-4] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2019] [Accepted: 02/07/2020] [Indexed: 12/05/2022] Open
Abstract
Nanocolloids having directional interactions are highly relevant for designing new self-assembled materials easy to control. In this article we report stochastic dynamics simulations of finite-size pseudo-dipolar colloids immersed in an implicit dielectric solvent using a realistic continuous description of the quasi-hard Coulombic interaction. We investigate structural and dynamical properties near the low-temperature and highly-diluted limits. This system self-assembles in a rich variety of string-like configurations, depicting three clearly distinguishable regimes with decreasing temperature: fluid, composed by isolated colloids; string-fluid, a gas of short string-like clusters; and string-gel, a percolated network. By structural characterization using radial distribution functions and cluster properties, we calculate the state diagram, verifying the presence of string-fluid regime. Regarding the string-gel regime, we show that the antiparallel alignment of the network chains arises as a novel self-assembly mechanism when the characteristic interaction energy exceeds the thermal energy in two orders of magnitude, ud/kBT ≈ 100. This is associated to relevant structural modifications in the network connectivity and porosity. Furthermore, our results give insights about the dynamically-arrested nature of the string-gel regime, where we show that the slow relaxation takes place in minuscule energy steps that reflect local rearrangements of the network.
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Affiliation(s)
- Mariano E Brito
- Institute of Complex Systems (ICS-3), Forschungszentrum Jülich, D-52425, Jülich, Germany.,Facultad de Matemática, Astronomía, Física y Computación, Universidad Nacional de Córdoba, X5000HUA, Córdoba, Argentina
| | - Marcelo A Carignano
- Qatar Environment and Energy Research Institute, Hamad Bin Khalifa University, P.O. Box 34110, Doha, Qatar
| | - Verónica I Marconi
- Facultad de Matemática, Astronomía, Física y Computación, Universidad Nacional de Córdoba, X5000HUA, Córdoba, Argentina. .,IFEG-CONICET, X5000HUA, Córdoba, Argentina.
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14
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Steinbach G, Schreiber M, Nissen D, Albrecht M, Novak E, Sánchez PA, Kantorovich SS, Gemming S, Erbe A. Field-responsive colloidal assemblies defined by magnetic anisotropy. Phys Rev E 2019; 100:012608. [PMID: 31499847 DOI: 10.1103/physreve.100.012608] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2019] [Indexed: 11/07/2022]
Abstract
Particle dispersions provide a promising tool for the engineering of functional materials that exploit self-assembly of complex structures. Dispersion made from magnetic colloidal particles is a great choice; they are biocompatible and remotely controllable among many other advantages. However, their dominating dipolar interaction typically limits structural complexity to linear arrangements. This paper shows how a magnetostatic equilibrium state with noncollinear arrangement of the magnetic moments, as reported for ferromagnetic Janus particles, enables the controlled self-organization of diverse structures in two dimensions via constant and low-frequency external magnetic fields. Branched clusters of staggered chains, compact clusters, linear chains, and dispersed single particles can be formed and interconverted reversibly in a controlled way. The structural diversity is a consequence of both the inhomogeneity and the spatial extension of the magnetization distribution inside the particles. We draw this conclusion from calculations based on a model of spheres with multiple shifted dipoles. The results demonstrate that fundamentally new possibilities for responsive magnetic materials can arise from interactions between particles with a spatially extended, anisotropic magnetization distribution.
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Affiliation(s)
- Gabi Steinbach
- Institute of Physics, Technische Universität Chemnitz, 09107 Chemnitz, Germany.,Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstrasse 400, 01328 Dresden, Germany
| | - Michael Schreiber
- Institute of Physics, Technische Universität Chemnitz, 09107 Chemnitz, Germany
| | - Dennis Nissen
- Institute of Physics, University of Augsburg, 86159 Augsburg, Germany
| | - Manfred Albrecht
- Institute of Physics, University of Augsburg, 86159 Augsburg, Germany
| | - Ekaterina Novak
- Ural Federal University, Lenin av. 51, Ekaterinburg, 620000, Russia
| | - Pedro A Sánchez
- Ural Federal University, Lenin av. 51, Ekaterinburg, 620000, Russia
| | - Sofia S Kantorovich
- Ural Federal University, Lenin av. 51, Ekaterinburg, 620000, Russia.,Computational Physics, Universität Wien, Sensengasse 8, Vienna, 1090, Austria
| | - Sibylle Gemming
- Institute of Physics, Technische Universität Chemnitz, 09107 Chemnitz, Germany.,Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstrasse 400, 01328 Dresden, Germany
| | - Artur Erbe
- Helmholtz-Zentrum Dresden-Rossendorf, Bautzner Landstrasse 400, 01328 Dresden, Germany
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15
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Novak E, Pyanzina E, Rozhkov D, Ronti M, Cerdà J, Sintes T, Sánchez P, Kantorovich S. Suspensions of supracolloidal magnetic polymers: Self-assembly properties from computer simulations. J Mol Liq 2018. [DOI: 10.1016/j.molliq.2018.08.145] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
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16
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Ronti M, Rovigatti L, Tavares JM, Ivanov AO, Kantorovich SS, Sciortino F. Free energy calculations for rings and chains formed by dipolar hard spheres. SOFT MATTER 2017; 13:7870-7878. [PMID: 29019510 DOI: 10.1039/c7sm01692a] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We employ a method based on Monte Carlo grand-canonical simulations to precisely calculate partition functions of non-interacting chains and rings formed by dipolar hard spheres (DHS) at low temperature. The extended low temperature region offered by such cluster calculations, compared to what had been previously achieved with standard simulations, opens up the possibility of exploring a part of the DHS phase diagram which was inaccessible before. The reported results offer the unique opportunity of verifying well-established theoretical models based on the ideal gas of cluster approximation in order to clarify their range of validity. They also provide the basis for future studies in which cluster-cluster interactions will be included.
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Affiliation(s)
- Michela Ronti
- University of Vienna, Sensengasse 8, 1090 Vienna, Austria.
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17
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18
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19
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Donaldson JG, Linse P, Kantorovich SS. How cube-like must magnetic nanoparticles be to modify their self-assembly? NANOSCALE 2017; 9:6448-6462. [PMID: 28466944 DOI: 10.1039/c7nr01245d] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/15/2023]
Abstract
Systems whose magnetic response can be finely tuned using control parameters, such as temperature and external magnetic field strength, are extremely desirable, functional materials. Magnetic nanoparticles, in particular suspensions thereof, offer opportunities for this controllability to be realised. Cube-like particles are particularly mono-disperse examples that, together with their favourable packing behaviour, make them of significant interest for study. Using a combination of analytical calculations and molecular dynamics we have studied the self-assembly of permanently magnetised dipolar superballs. The superball shape parameter was varied in order to interpolate the region between the already well-studied sphere system and that of the recently investigated cube. Our findings show that as a superball particle becomes more cubic the chain to ring transition, observed in the ground state of spherical particles, occurs at an increasingly larger cluster size. This effect is mitigated, however, by the appearance of a competing configuration; asymmetric rings, a conformation that we show superballs can readily adopt.
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Affiliation(s)
- Joe G Donaldson
- Faculty of Physics, Boltzmanngasse 5, University of Vienna, Vienna, Austria.
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20
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Rutkowski DM, Velev OD, Klapp SHL, Hall CK. Simulation study on the structural properties of colloidal particles with offset dipoles. SOFT MATTER 2017; 13:3134-3146. [PMID: 28397900 DOI: 10.1039/c7sm00226b] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
A major research theme in materials science is determining how the self-assembly of new generations of colloidal particles of complex shape and surface charge is guided by their interparticle interactions. In this paper, we describe results from quasi-2D Monte Carlo simulations of systems of colloidal particles with offset transversely-oriented extended dipole-like charge distributions interacting via an intermediate-ranged Yukawa potential. The systems are cooled slowly through an annealing procedure during which the temperature is lowered in discrete steps, allowing the system to equilibrate. We perform ground state calculations for two, three and four particles at several shifts of the dipole vector from the particle center. We create state diagrams in the plane spanned by the temperature and the area fraction outlining the boundaries between fluid, string-fluid and percolated states at various values of the shift. Remarkably we find that the effective cooling rate in our simulations has an impact on the structures formed, with chains being more prevalent if the system is cooled quickly and cyclic structures more prevalent if the system is cooled slowly. As the dipole is further shifted from the center, there is an increased tendency to assemble into small cyclic structures at intermediate temperatures. These systems further self-assemble into open lattice-like arrangements at very low temperatures. The novel structures identified might be useful for photonic applications, new types of porous media for filtration and catalysis, and gel matrices with unusual properties.
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Affiliation(s)
- David M Rutkowski
- Department of Chemical & Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina 27695-7905, USA.
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21
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Zhang CY, Jian XL, Lu W. Ring formation in the quasi-two-dimensional system of the patchy magnetic spheres. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2016; 28:145101. [PMID: 26965459 DOI: 10.1088/0953-8984/28/14/145101] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
Fabricating new functional materials has always been at the center of colloidal science, and how to form circular rings is a meaningful challenge due to their special electronic, magnetic and optical properties. Magnetic colloidal spheres can self-assemble into rings, but these rings have an uncontrollable length and shape and also have to coexist with chains and defected clusters. To make the most of magnetic spheres being able to self-assemble into rings, a patch is added to the surface of the sphere to form a chiral link between particles. The structural transition in the system of patchy magnetic spheres is studied using the Monte Carlo simulation. When the patch angle is in the interval 60° to 75°, rings become the dominant structure if the strength of patchy interaction exceeds a particular threshold and the shape of these rings is close to the circle. With an increase in the patch angle, the threshold of patchy interaction decreases and the average length of the circular ring increases approximately from 5 to 8.5.
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Affiliation(s)
- Cheng-yu Zhang
- College of Engineering, Nanjing Agricultural University, Nanjing 210031, People's Republic of China
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Sánchez PA, Pyanzina ES, Novak EV, Cerdà JJ, Sintes T, Kantorovich SS. Supramolecular Magnetic Brushes: The Impact of Dipolar Interactions on the Equilibrium Structure. Macromolecules 2015; 48:7658-7669. [PMID: 26538768 PMCID: PMC4625168 DOI: 10.1021/acs.macromol.5b01086] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2015] [Revised: 09/08/2015] [Indexed: 11/30/2022]
Abstract
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The
equilibrium structure of supramolecular magnetic filament brushes
is analyzed at two different scales. First, we study the density and
height distributions for brushes with various grafting densities and
chain lengths. We use Langevin dynamics simulations with a bead–spring
model that takes into account the cross-links between the surface
of the ferromagnetic particles, whose magnetization is characterized
by a point dipole. Magnetic filament brushes are shown to be more
compact near the substrate than nonmagnetic ones, with a bimodal height
distribution for large grafting densities. This latter feature makes
them also different from brushes with electric dipoles. Next, in order
to explain the observed behavior at the filament scale, we introduce
a graph theory analysis to elucidate for the first time the structure
of the brush at the scale of individual beads. It turns out that,
in contrast to nonmagnetic brushes, in which the internal structure
is determined by random density fluctuations, magnetic forces introduce
a certain order in the system. Because of their highly directional
nature, magnetic dipolar interactions prevent some of the random connections
to be formed. On the other hand, they favor a higher connectivity
of the chains’ free and grafted ends. We show that this complex
dipolar brush microstructure has a strong impact on the magnetic response
of the brush, as any weak applied field has to compete with the dipole–dipole
interactions within the crowded environment.
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Affiliation(s)
| | - Elena S Pyanzina
- Ural Federal University , Lenin av. 51, 620000, Ekaterinburg, Russia
| | - Ekaterina V Novak
- Ural Federal University , Lenin av. 51, 620000, Ekaterinburg, Russia
| | - Joan J Cerdà
- Instituto de Física Interdisciplinar y Sistemas Complejos, IFISC (CSIC-UIB) , E-07122 Palma de Mallorca, Spain
| | - Tomas Sintes
- Instituto de Física Interdisciplinar y Sistemas Complejos, IFISC (CSIC-UIB) , E-07122 Palma de Mallorca, Spain
| | - Sofia S Kantorovich
- University of Vienna , Sensengasse 8, 1090, Vienna, Austria ; Ural Federal University , Lenin av. 51, 620000, Ekaterinburg, Russia
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Pshenichnikov AF, Kuznetsov AA. Self-organization of magnetic moments in dipolar chains with restricted degrees of freedom. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2015; 92:042303. [PMID: 26565236 DOI: 10.1103/physreve.92.042303] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2015] [Indexed: 06/05/2023]
Abstract
Equilibrium behavior of a single chain of dipolar spheres is investigated by the method of molecular dynamics in a wide range of the dipolar coupling constant λ. Two cases are considered: rodlike and flexible chains. In the first case, particle centers are immovably fixed on one axis, but their magnetic moments retain absolute orientational freedom. It has been found that at λ≳1.5 particle moments are chiefly aligned parallel to the chain axis, but the total moment of the chain continuously changes its sign with some mean frequency, which exponentially decreases with the growth of λ. Such behavior of the rodlike chain is analogous to the Néel relaxation of a superparamagnetic particle with a finite energy of magnetic anisotropy. In the flexible chain particles are able to move in the three-dimensional space, but the distance between centers of the first-nearest neighbors never exceeds a given limiting value r(max). If r(max)≃d (d is the particle diameter) then the most probable shape of the chain of five or more particles at λ≳6 is that of a ring. The behavior of chains with r(max)≥2d is qualitatively different: At λ≃4 long chains collapse into dense quasispherical globules and at λ≳8 these globules take toroidal configuration with a spontaneous azimuthal ordering of magnetic dipoles. With the increase of r(max) to larger values (r(max)>10d) globules expand and break down to form separate rings.
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Affiliation(s)
- Alexander F Pshenichnikov
- Laboratory of Dynamics of Dispersed Systems, Institute of Continuous Media Mechanics UB RAS, Korolyov Street 1, Perm 614013, Russia
| | - Andrey A Kuznetsov
- Laboratory of Dynamics of Dispersed Systems, Institute of Continuous Media Mechanics UB RAS, Korolyov Street 1, Perm 614013, Russia
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Kaiser A, Popowa K, Löwen H. Active dipole clusters: From helical motion to fission. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2015; 92:012301. [PMID: 26274156 DOI: 10.1103/physreve.92.012301] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/11/2015] [Indexed: 06/04/2023]
Abstract
The structure of a finite particle cluster is typically determined by total energy minimization. Here we consider the case where a cluster of soft-sphere dipoles becomes active, i.e., when the individual particles exhibit an additional self-propulsion along their dipole moments. We numerically solve the overdamped equations of motion for soft-sphere dipoles in a solvent. Starting from an initial metastable dipolar cluster, the self-propulsion generates a complex cluster dynamics. The final cluster state has in general a structure widely different to the initial one, the details depend on the model parameters and on the protocol of how the self-propulsion is turned on. The center of mass of the cluster moves on a helical path, the details of which are governed by the initial cluster magnetization. An instantaneous switch to a high self-propulsion leads to fission of the cluster. However, fission does not occur if the self-propulsion is increased slowly to high strengths. Our predictions can be verified through experiments with self-phoretic colloidal Janus particles and for macroscopic self-propelled dipoles in a highly viscous solvent.
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Affiliation(s)
- Andreas Kaiser
- Institut für Theoretische Physik II: Weiche Materie, Heinrich-Heine-Universität Düsseldorf, Universitätsstraße 1, 40225 Düsseldorf, Germany
| | - Katarina Popowa
- Institut für Theoretische Physik II: Weiche Materie, Heinrich-Heine-Universität Düsseldorf, Universitätsstraße 1, 40225 Düsseldorf, Germany
| | - Hartmut Löwen
- Institut für Theoretische Physik II: Weiche Materie, Heinrich-Heine-Universität Düsseldorf, Universitätsstraße 1, 40225 Düsseldorf, Germany
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Novak EV, Pyanzina ES, Kantorovich SS. Behaviour of magnetic Janus-like colloids. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2015; 27:234102. [PMID: 26010700 DOI: 10.1088/0953-8984/27/23/234102] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We present a theoretical study of Janus-like magnetic particles at low temperature. To describe the basic features of the Janus-type magnetic colloids, we put forward a simple model of a spherical particle with a dipole moment shifted outwards from the centre and oriented perpendicular to the particle radius. Using direct calculations and molecular dynamics computer simulations, we investigate the ground states of small clusters and the behaviour of bigger systems at low temperature. In both cases the important parameter is the dipolar shift, which leads to different ground states and, as a consequence, to a different microscopic behaviour in the situation when the thermal fluctuations are finite. We show that the head-to-tail orientation of dipoles provides a two-particle energy minima only if the dipoles are not shifted from the particle centres. This is one of the key differences from the system of shifted dipolar particles (sd-particles), in which the dipole was shifted outwards radially, studied earlier (Kantorovich et al 2011 Soft Matter 7 5217-27). For sd-particles the dipole could be shifted out of the centre for almost 40% before the head-to-tail orientation was losing its energetic advantage. This peculiarity manifests itself in the topology of the small clusters in the ground state and in the response of the Janus-like particle systems to an external magnetic field at finite temperatures.
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Sánchez PA, Cerdà JJ, Sintes TM, Ivanov AO, Kantorovich SS. The effect of links on the interparticle dipolar correlations in supramolecular magnetic filaments. SOFT MATTER 2015; 11:2963-72. [PMID: 25727452 DOI: 10.1039/c5sm00172b] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
We present a combined computational and analytical study of supramolecular magnetic filaments, i.e., permanently linked chains of ferromagnetic nanocolloids. We put forward two different models for the interparticle connectivity within the chain. In the first model, the magnetic dipoles of the particles are free to rotate independently from the permanent links. The second model penalises the misalignment of the dipoles by coupling their orientations to the chain backbone. We show that the effect of the long-range magnetic dipolar interactions on the zero field net magnetic moment of the chain becomes less significant in the second case. However, the overall magnetic response in the model of freely rotating dipoles is much weaker.
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Affiliation(s)
- Pedro A Sánchez
- Faculty of Physics, University of Vienna, Boltzmanngasse 5, 1090 Vienna, Austria.
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27
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Chung S, Malherbe J, Amokrane S. Effect of an external field on the structure and the phase transitions of a confined mixture of neutral and dipolar hard spheres. Mol Phys 2015. [DOI: 10.1080/00268976.2015.1014003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
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28
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Kantorovich SS, Ivanov AO, Rovigatti L, Tavares JM, Sciortino F. Temperature-induced structural transitions in self-assembling magnetic nanocolloids. Phys Chem Chem Phys 2015; 17:16601-8. [DOI: 10.1039/c5cp01558h] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
With the help of a unique combination of density functional theory and computer simulations, we discover two possible scenarios, depending on concentration, for the hierarchical self-assembly of magnetic nanoparticles on cooling.
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Affiliation(s)
| | | | | | - Jose M. Tavares
- Centro de Física Teórica e Computacional da Universidade de Lisboa
- Faculdade de Ciências
- Campo Grande
- 1749-016 Lisboa
- Portugal
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