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Fujita M, Toyotama A, Okuzono T, Niinomi H, Yamanaka J. Formation of two-dimensional diamond-like colloidal crystals using layer-by-layer electrostatic self-assembly. Soft Matter 2024; 20:985-992. [PMID: 38197135 DOI: 10.1039/d3sm01278f] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2024]
Abstract
We report here that a two-dimensional (2D) diamond-like structure of micron-sized colloidal particles can be obtained by layer-by-layer self-assembly. Positively and negatively charged silica particles, 1 μm in diameter, were used in the experiments. On a positively charged, flat glass substrate, the first layer of negatively charged particles was prepared to form a non-close-packed 2D crystal. Then the second and third layers were fabricated using electrostatic adsorption. The positions of adsorbed particles were controllable by tuning the zeta-potential of the particles and the salt concentration of the medium. The FDTD calculations show that the 2D diamond structures of particles with higher refractive index (titania) have an absorption band in the wavelength range corresponding to the photonic band gap of the 3D bulk crystal. We expect these findings to be useful for the fabrication of novel photonic materials.
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Affiliation(s)
- Minori Fujita
- Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe, Mizuho, Nagoya 467-8603, Japan.
| | - Akiko Toyotama
- Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe, Mizuho, Nagoya 467-8603, Japan.
| | - Tohru Okuzono
- Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe, Mizuho, Nagoya 467-8603, Japan.
| | - Hiromasa Niinomi
- Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba, Sendai 980-8577, Japan
| | - Junpei Yamanaka
- Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe, Mizuho, Nagoya 467-8603, Japan.
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Miki H, Ishigami T, Yamanaka J, Okuzono T, Toyotama A, Mata J, Komazawa H, Takeda Y, Minami M, Fujita M, Doi M, Higuchi T, Takase H, Adachi S, Sakashita T, Shimaoka T, Nagai M, Watanabe Y, Fukuyama S. Clustering of charged colloidal particles in the microgravity environment of space. NPJ Microgravity 2023; 9:33. [PMID: 37120425 PMCID: PMC10148850 DOI: 10.1038/s41526-023-00280-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2022] [Accepted: 04/12/2023] [Indexed: 05/01/2023] Open
Abstract
We conducted a charge-charge clustering experiment of positively and negatively charged colloidal particles in aqueous media under a microgravity environment at the International Space Station. A special setup was used to mix the colloid particles in microgravity and then these structures were immobilized in gel cured using ultraviolet (UV) light. The samples returned to the ground were observed by optical microscopy. The space sample of polystyrene particles with a specific gravity ρ (=1.05) close to the medium had an average association number of ~50% larger than the ground control and better structural symmetry. The effect of electrostatic interactions on the clustering was also confirmed for titania particles (ρ ~ 3), whose association structures were only possible in the microgravity environment without any sedimentation they generally suffer on the ground. This study suggests that even slight sedimentation and convection on the ground significantly affect the structure formation of colloids. Knowledge from this study will help us to develop a model which will be used to design photonic materials and better drugs.
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Affiliation(s)
- Hiroyuki Miki
- Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe, Mizuho, Nagoya, Japan
| | - Teruyoshi Ishigami
- Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe, Mizuho, Nagoya, Japan
| | - Junpei Yamanaka
- Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe, Mizuho, Nagoya, Japan.
| | - Tohru Okuzono
- Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe, Mizuho, Nagoya, Japan
| | - Akiko Toyotama
- Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe, Mizuho, Nagoya, Japan
| | - Jitendra Mata
- Australian Centre for Neutron Scattering (ACNS), Australian Nuclear Science and Technology Organisation (ANSTO), Lucas Heights, NSW, 2234, Australia
| | - Honoka Komazawa
- Faculty of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe, Mizuho, Nagoya, Japan
| | - Yushi Takeda
- Faculty of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe, Mizuho, Nagoya, Japan
| | - Madoka Minami
- Faculty of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe, Mizuho, Nagoya, Japan
| | - Minori Fujita
- Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe, Mizuho, Nagoya, Japan
| | - Maho Doi
- Faculty of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe, Mizuho, Nagoya, Japan
| | - Tsunehiko Higuchi
- Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe, Mizuho, Nagoya, Japan
| | - Hiroshi Takase
- Core Laboratory, Graduate School of Medical Sciences, Nagoya City University, 1 Kawasumi, Mizuho, Nagoya, Japan
| | - Satoshi Adachi
- Japan Aerospace Exploration Agency (JAXA), 2-1-1 Sengen, Tsukuba, Japan
| | - Tetsuya Sakashita
- Japan Aerospace Exploration Agency (JAXA), 2-1-1 Sengen, Tsukuba, Japan
| | - Taro Shimaoka
- Japan Space Forum (JSF), 3-2-1 Kandasurugadai, Chiyoda, Tokyo, Japan
| | - Masae Nagai
- Japan Space Forum (JSF), 3-2-1 Kandasurugadai, Chiyoda, Tokyo, Japan
| | - Yuki Watanabe
- Advanced Engineering Services (AES) Co., Ltd., 1-6-1 Takezono, Tsukuba, Japan
| | - Seijiro Fukuyama
- Advanced Engineering Services (AES) Co., Ltd., 1-6-1 Takezono, Tsukuba, Japan
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Ilie F, Minea IL, Cotici CD, Hristache AF. The Effects of Friction and Temperature in the Chemical-Mechanical Planarization Process. Materials (Basel) 2023; 16:2550. [PMID: 37048844 PMCID: PMC10095230 DOI: 10.3390/ma16072550] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/28/2022] [Revised: 03/03/2023] [Accepted: 03/21/2023] [Indexed: 06/19/2023]
Abstract
Chemical-mechanical planarization (CMP) represents the preferred technology in which both chemical and mechanical interactions are combined to achieve global planarization/polishing of wafer surfaces (wafer patterns from metal with a selective layer, in this paper). CMP is a complex process of material removal process by friction, which interferes with numerous mechanical and chemical parameters. Compared with chemical parameters, mechanical parameters have a greater influence on the material removal rate (MRR). The mechanical parameters manifest by friction force (Ff) and heat generated by friction in the CMP process. The Ff can be estimated by its monitoring in the CMP process, and process temperature is obtained with help of an infrared rays (IR) sensor. Both the Ff and the MRR increase by introducing colloidal silica (SiO2) as an abrasive into the selective layer CMP slurry. The calculated wafer non-uniformity (WNU) was correlated with the friction coefficient (COF). The control of Ff and of the slurry stability is important to maintain a good quality of planarization with optimal results, because Ff participates in mechanical abrasion, and large Ff may generate defects on the wafer surface. Additionally, the temperature generated by the Ff increases as the SiO2 concentration increases. The MRR of the selective layer into the CMP slurry showed a non-linear (Prestonian) behavior, useful not only to improve the planarization level but to improve its non-uniformity due to the various pressure distributions. The evaluation of the Ff allowed the calculation of the friction energy (Ef) to highlight the chemical contribution in selective-layer CMP, from which it derived an empirical model for the material removal amount (MRA) and validated by the CMP results. With the addition of abrasive nanoparticles into the CMP slurry, their concentration increased and the MRA of the selective layer improved; Ff and MRR can be increased due to the number of chemisorbed active abrasive nanoparticles by the selective layer. Therefore, a single abrasive was considered to better understand the effect of SiO2 concentration as an abrasive and of the MRR features depending on abrasive nanoparticle concentration. This paper highlights the correlation between friction and temperature of the SiO2 slurry with CMP results, useful to examine the temperature distribution. All the MRRs depending on Ef after planarization with various SiO2 concentrations had a non-linear characteristic. The obtained results can help in developing a CMP process more effectively.
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Affiliation(s)
- Filip Ilie
- Department of Machine Elements and Tribology, Polytechnic University of Bucharest, Spl. Independentei 313, 060042 Bucharest, Romania
| | - Ileana-Liliana Minea
- Department of Biotechnical Systems, Polytechnic University of Bucharest, Spl. Independentei 313, 060042 Bucharest, Romania
| | - Constantin Daniel Cotici
- Department of Biotechnical Systems, Polytechnic University of Bucharest, Spl. Independentei 313, 060042 Bucharest, Romania
| | - Andrei-Florin Hristache
- Department of Biotechnical Systems, Polytechnic University of Bucharest, Spl. Independentei 313, 060042 Bucharest, Romania
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Alsharif NB, Muráth S, Katana B, Szilagyi I. Composite materials based on heteroaggregated particles: Fundamentals and applications. Adv Colloid Interface Sci 2021; 294:102456. [PMID: 34107320 DOI: 10.1016/j.cis.2021.102456] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2021] [Revised: 05/27/2021] [Accepted: 05/27/2021] [Indexed: 01/08/2023]
Abstract
Homoaggregation of dispersed particles, i.e., aggregation of particles of the same shape, charge, size, and composition, is a well-studied field and various theoretical and experimental approaches exist to understand the major phenomena involved in such processes. Besides, heteroaggregation of particles, i.e., aggregation of particles of different shape, charge, size, or composition, has attracted widespread interest due to its relevance in various biomedical, industrial, and environmental systems. For instance, heteroaggregation of plastic contaminant particles with naturally occurring solid materials in waters (e.g., clays, silica and organic polymers) plays an important role in the decontamination technologies. Moreover, nanofabrication processes involving heteroaggregation of particles to prepare novel composite materials are widely implemented in fundamental science and in more applied disciplines. In such procedures, stable particle dispersions are mixed and the desired structure forms owing to the presence of interparticle forces of various origins, which can be tuned by performing appropriate surface functionalization as well as altering the experimental conditions. These composites are widely used in different fields from sensing through catalysis to biomedical delivery. The present review summarizes the recent progresses in the field including new findings regarding the basic principles in particle heteroaggregation, preparation strategies of heteroaggregated structures of different morphology, and the application of the obtained hybrid composites. Such information will be very helpful to those involved in the design of novel composites consisting of different nano or colloidal particles.
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Abstract
The preparation of colloidal molecules (CMs), that is, clusters of colloids with a defined aggregation number and configuration, is of continued and significant interest in colloid chemistry and materials science and numerous interactions have been utilized to drive their (self-)assembly. However, only very few reports are available on the assembly of CMs based on host-guest chemistry. In this paper, we investigate the assembly of like-charged silica particles into well-defined, core-satellite ABn-type CMs in water, mediated by host-guest interactions and geometric constraints. Exploiting the inherent dynamics of noncovalent attraction and making use of a soft polymer shell to enhance multivalent host-guest interactions, we successfully synthesized AB3, AB4, and AB6 CMs by selecting the appropriate size ratio of satellite to core particles.
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Affiliation(s)
- Dustin W Kurka
- Organic Chemistry Institute and Center for Soft Nanoscience, Westfälische Wilhelms-Universität Münster, Corrensstraße 40, 48149 Münster, Germany
| | - Maximilian Niehues
- Organic Chemistry Institute and Center for Soft Nanoscience, Westfälische Wilhelms-Universität Münster, Corrensstraße 40, 48149 Münster, Germany
| | - Bart Jan Ravoo
- Organic Chemistry Institute and Center for Soft Nanoscience, Westfälische Wilhelms-Universität Münster, Corrensstraße 40, 48149 Münster, Germany
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Cao H, An B, Wang Y, Zhou K, Lu N. Investigation of Surfactant AOT Mediated Charging of PS Particles Dispersed in Aqueous Solutions. Coatings 2019; 9:471. [DOI: 10.3390/coatings9080471] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Nano/submicron particles can be activated by surfactants and aggregate at the air-water interface to generate and stabilize foams. Such systems have been applied extensively in the food, medicine, and cosmetic industries. Studying particle charging behavior in a particle/surfactant/water system is a fundamental way to understand the activation of the particle surface. This paper presents an investigation of the charging behavior of polystyrene (PS) particles dispersed in aqueous solutions of the surfactant sodium di-2-ethylhexylsulfosuccinate (AOT). The results showed that zeta potential of PS was related to the AOT concentration with two different concentration regions. Below the critical micelle concentration (CMC), the charging of PS particles was effected by AOT ions; while above the CMC, it came from both AOT ions and AOT micelles. This behavior was different from that observed for PS in aqueous salt solutions. Additionally, the particle concentration and size were found to affect the zeta potential differently in the two AOT concentration regions. By analyzing these results, the charging mechanism of the PS/AOT/water system was revealed to be preferential adsorption. In summary, the study disclosed the internal connection between the PS charging in aqueous AOT solution and the activation of PS particles, as well as their influence to foam formation and stability.
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Abstract
Recent experimental results using in particular small-angle scattering to characterize the self-assembly of mainly hard spherical nanoparticles into higher ordered structures ranging from fractal aggregates to ordered assemblies are reviewed. The crucial control of interparticle interactions is discussed, from chemical surface-modification, or the action of additives like depletion agents, to the generation of directional patches and the use of external fields. It is shown how the properties of interparticle interactions have been used to allow inducing and possibly controlling aggregation, opening the road to the generation of colloidal molecules or potentially metamaterials. In the last part, studies of the microstructure of polymer nanocomposites as an application of volume-spanning and stress-carrying aggregates are discussed.
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Affiliation(s)
- Anne-Caroline Genix
- Laboratoire Charles Coulomb (L2C), Université de Montpellier, CNRS, F-34095 Montpellier, France.
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Musino D, Genix AC, Chaussée T, Guy L, Meissner N, Kozak R, Bizien T, Oberdisse J. Aggregate Formation of Surface-Modified Nanoparticles in Solvents and Polymer Nanocomposites. Langmuir 2018; 34:3010-3020. [PMID: 29443532 DOI: 10.1021/acs.langmuir.7b03932] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
A new method based on the combination of small-angle scattering, reverse Monte Carlo simulations, and an aggregate recognition algorithm is proposed to characterize the structure of nanoparticle suspensions in solvents and polymer nanocomposites, allowing detailed studies of the impact of different nanoparticle surface modifications. Experimental small-angle scattering is reproduced using simulated annealing of configurations of polydisperse particles in a simulation box compatible with the lowest experimental q-vector. Then, properties of interest like aggregation states are extracted from these configurations and averaged. This approach has been applied to silane surface-modified silica nanoparticles with different grafting groups, in solvents and after casting into polymer matrices. It is shown that the chemistry of the silane function, in particular mono- or trifunctionality possibly related to patch formation, affects the dispersion state in a given medium, in spite of an unchanged alkyl-chain length. Our approach may be applied to study any dispersion or aggregation state of nanoparticles. Concerning nanocomposites, the method has potential impact on the design of new formulations allowing controlled tuning of nanoparticle dispersion.
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Affiliation(s)
- Dafne Musino
- Laboratoire Charles Coulomb (L2C) , Université de Montpellier, CNRS , F-34095 Montpellier , France
| | - Anne-Caroline Genix
- Laboratoire Charles Coulomb (L2C) , Université de Montpellier, CNRS , F-34095 Montpellier , France
| | - Thomas Chaussée
- Solvay Silica , 15 rue Pierre Pays BP52 , 69660 Collonges au Mont d'Or , France
| | - Laurent Guy
- Solvay Silica , 15 rue Pierre Pays BP52 , 69660 Collonges au Mont d'Or , France
| | | | - Radoslaw Kozak
- Synthos Spółka Akcyjna , Chemików 1 , 32600 Oświęcim , Poland
| | - Thomas Bizien
- SOLEIL Synchrotron , L'Orme des Merisiers , Gif-Sur-Yvette , 91192 Saint-Aubin France
| | - Julian Oberdisse
- Laboratoire Charles Coulomb (L2C) , Université de Montpellier, CNRS , F-34095 Montpellier , France
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Affiliation(s)
- Naoko Sato
- Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe, Mizuho, Nagoya, Aichi 467-8603
| | - Junpei Yamanaka
- Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe, Mizuho, Nagoya, Aichi 467-8603
| | - Akiko Toyotama
- Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe, Mizuho, Nagoya, Aichi 467-8603
| | - Tohru Okuzono
- Graduate School of Pharmaceutical Sciences, Nagoya City University, 3-1 Tanabe, Mizuho, Nagoya, Aichi 467-8603
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Singh G, Bremmell K, Griesser HJ, Kingshott P. Colloid-probe AFM studies of the surface functionality and adsorbed proteins on binary colloidal crystal layers. RSC Adv 2017. [DOI: 10.1039/c6ra28491d] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
We demonstrate the applicability of colloid-probe AFM to detect different surface chemistries on binary colloidal crystal layers of different chemical and protein patterns.
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Affiliation(s)
- Gurvinder Singh
- Interdisciplinary Nanoscience Centre
- Faculty of Science
- Aarhus University
- Denmark
- Department of Materials Science and Engineering
| | - Kristen Bremmell
- School of Pharmacy and Medical Sciences
- University of South Australia
- Adelaide 5000
- Australia
| | - Hans J. Griesser
- Future Industries Institute
- University of South Australia
- Mawson Lakes
- Australia
| | - Peter Kingshott
- Interdisciplinary Nanoscience Centre
- Faculty of Science
- Aarhus University
- Denmark
- Department of Chemistry and Biotechnology
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Everts JC, van der Linden MN, van Blaaderen A, van Roij R. Alternating strings and clusters in suspensions of charged colloids. Soft Matter 2016; 12:6610-6620. [PMID: 27439990 DOI: 10.1039/c6sm01283c] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
We report the formation of alternating strings and clusters in a binary suspension of repulsive charged colloids with double layers larger than the particle size. Within a binary cell model we include many-body and charge-regulation effects under the assumption of a constant surface potential, and consider their repercussions on the two-particle interaction potential. We find that the formation of induced dipoles close to a charge-reversed state may explain the formation of these structures. Finally, we will touch upon the formation of dumbbells and small clusters in a one-component system, where the effective electrostatic interaction is always repulsive.
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Affiliation(s)
- J C Everts
- Institute for Theoretical Physics, Center for Extreme Matter and Emergent Phenomena, Utrecht University, Princetonplein 5, 3584 CC Utrecht, The Netherlands.
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Abstract
Cluster formation of oppositely charged colloidal particles is studied numerically. A simple Brownian dynamics method with a screened-Coulomb (Yukawa) potential is employed for numerical simulations. An equilibrium phase which consists of clusters and unassociated particles is obtained. It is shown that the equilibrium association number of clusters and their shapes are determined by charge numbers and charge ratio of the binary particles. The phase diagram of cluster formation for various charge numbers and their ratios is obtained. A simple relation between the association number and the charge ratio is found. It is demonstrated that in the case of high charge ratio the cluster takes a multilayer structure which is highly symmetric. It is also pointed out that the cluster-particle interaction changes dynamically in the cluster formation process, which is involved in the selection of final cluster structure.
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Affiliation(s)
- Tohru Okuzono
- Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya 467-8603, Japan
| | - Kana Odai
- Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya 467-8603, Japan
| | - Tatsuhiro Masuda
- Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya 467-8603, Japan
| | - Akiko Toyotama
- Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya 467-8603, Japan
| | - Junpei Yamanaka
- Graduate School of Pharmaceutical Sciences, Nagoya City University, Nagoya 467-8603, Japan
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Abstract
The target of this investigation is the systematic characterization of the low-energy structures of charged colloidal clusters that may be important to understand the self-assembling process of biomolecules. The aggregation of charged colloidal particles is governed by the attractive short-ranged Morse potential and the Yukawa repulsive tail to describe the long-range charge effect. A global optimization strategy, based on our own evolutionary algorithm, was adopted to discover the low-energy structures of colloidal clusters composed of up to 20 particles. A detailed analysis of the low-energy structures involving charged particles shows that the appearance of the Bernal spiral as the most stable motif occurs, first, at N = 6, but it is favored for larger clusters (N ≥ 13); for 6 ≤ N ≤ 12, there is a competition between the spiral (which is favored for higher charges) and more spherical-like structures. Finally, we study binary clusters composed by two sets of differently charged colloidal particles. Although a great diversity of low-energy structures is observed (especially for aggregates with one of the components in excess), the global minimum is disputed by three structural motifs depending on the composition of the cluster and, in some cases, on the range of the Morse potential.
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Affiliation(s)
- S M A Cruz
- Departamento de Química, Universidade de Coimbra , 3004-535 Coimbra, Portugal
| | - J M C Marques
- Departamento de Química, Universidade de Coimbra , 3004-535 Coimbra, Portugal
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Toyotama A, Okuzono T, Yamanaka J. Spontaneous Formation of Eutectic Crystal Structures in Binary and Ternary Charged Colloids due to Depletion Attraction. Sci Rep 2016; 6:23292. [PMID: 26984298 DOI: 10.1038/srep23292] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2015] [Accepted: 03/01/2016] [Indexed: 11/18/2022] Open
Abstract
Crystallization of colloids has extensively been studied for past few decades as models to study phase transition in general. Recently, complex crystal structures in multi-component colloids, including alloy and eutectic structures, have attracted considerable attention. However, the fabrication of 2D area-filling colloidal eutectics has not been reported till date. Here, we report formation of eutectic structures in binary and ternary aqueous colloids due to depletion attraction. We used charged particles + linear polyelectrolyte systems, in which the interparticle interaction could be represented as a sum of the electrostatic, depletion, and van der Waals forces. The interaction was tunable at a lengthscale accessible to direct observation by optical microscopy. The eutectic structures were formed because of interplay of crystallization of constituent components and accompanying fractionation. An observed binary phase diagram, defined by a mixing ratio and inverse area fraction of the particles, was analogous to that for atomic and molecular eutectic systems. This new method also allows the adjustment of both the number and wavelengths of Bragg diffraction peaks. Furthermore, these eutectic structures could be immobilized in polymer gel to produce self-standing materials. The present findings will be useful in the design of the optical properties of colloidal crystals.
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