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Laal-Dehghani N, Christopher GF. Effects of Interfacial Shear on Particle Aggregation at an Oil/Water Interface. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:9621-9630. [PMID: 35895899 DOI: 10.1021/acs.langmuir.2c01159] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Using a Stokesian dynamics simulation, the microstructure of particle aggregates at an oil/water interface with an applied Couette flow is studied. The results of the aggregation are consistent with previously published experimental work demonstrating multiple regimes of behavior based on the relative strength of shear and capillary forces. In previous work, densification of aggregates at low shear rates was theorized to occur due to short time scale fragmentation/reaggregation of aggregates with rigid particle bonds. In simulations, densification is observed at low shear rates but occurs due to local reorganization of particles due to capillary torques over long time scales. Moderate shear rates create mobile bonds between particles at shorter time scales, allowing aggregates to fragment without reaggregation into smaller isolated clusters, consistent with prior experimental work. At the highest shear rates, aggregation is inhibited completely.
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Affiliation(s)
- Nader Laal-Dehghani
- Department of Mechanical Engineering, Texas Tech University, Lubbock, Texas 79409, United States
| | - Gordon F Christopher
- Department of Mechanical Engineering, Texas Tech University, Lubbock, Texas 79409, United States
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2
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Sabapathy M, Md KZ, Kumar H, Ramamirtham S, Mani E, Basavaraj MG. Exploiting Heteroaggregation to Quantify the Contact Angle of Charged Colloids at Interfaces. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:7433-7441. [PMID: 35678741 DOI: 10.1021/acs.langmuir.2c00348] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
We exploit the aggregation between oppositely charged particles to visualize and quantify the equilibrium position of charged colloidal particles at the fluid-water interface. A dispersion of commercially available charge-stabilized nanoparticles was used as the aqueous phase to create oil-water and air-water interfaces. The colloidal particles whose charge was opposite that of the nanoparticles in the aqueous phase were deposited at the chosen fluid-water interface. Heteroaggregation, i.e., aggregation between oppositely charged particles, leads to the deposition of nanoparticles onto the larger particle located at the interface; however, this only occurs on the surface of the particle in contact with the aqueous phase. This selective deposition of nanoparticles on the surfaces of the particles exposed to water enables the distinct visualization of the circular three-phase contact line around the particles positioned at the fluid-water interface. Since the electrostatic association between the nanoparticles and the colloids at interfaces is strong, the nanoparticle assembly on the larger particles is preserved even after being transferred to solid substrates via dip-coating. This facilitates the easy visualization of the contact line by electron microscopy and the determination of the equilibrium contact angle of colloidal particles (θ) at the fluid-water interface. The suitability of the method is demonstrated by the measurement of the three-phase contact angle of positively and negatively charged polystyrene particles located at fluid-water interfaces by considering particles with sizes varying from 220 nm to 8.71 μm. The study highlights the effect of the size ratio between the nanoparticles in the aqueous phase and the colloidal particles on the accuracy of the measurement of θ.
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Affiliation(s)
- Manigandan Sabapathy
- Advanced Colloid and Interfacial Engineering Laboratory, Department of Chemical Engineering, Indian Institute of Technology Ropar, Rupnagar, Punjab 140001, India
| | - Khalid Zubair Md
- Polymer Engineering and Colloid Science Laboratory (PECS), Department of Chemical Engineering, Indian Institute of Technology Madras, Chennai, Tamil Nadu 600036, India
| | - Hemant Kumar
- Polymer Engineering and Colloid Science Laboratory (PECS), Department of Chemical Engineering, Indian Institute of Technology Madras, Chennai, Tamil Nadu 600036, India
| | - Sashikumar Ramamirtham
- Polymer Engineering and Colloid Science Laboratory (PECS), Department of Chemical Engineering, Indian Institute of Technology Madras, Chennai, Tamil Nadu 600036, India
| | - Ethayaraja Mani
- Polymer Engineering and Colloid Science Laboratory (PECS), Department of Chemical Engineering, Indian Institute of Technology Madras, Chennai, Tamil Nadu 600036, India
| | - Madivala G Basavaraj
- Polymer Engineering and Colloid Science Laboratory (PECS), Department of Chemical Engineering, Indian Institute of Technology Madras, Chennai, Tamil Nadu 600036, India
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3
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Smits J, Prasad Giri R, Shen C, Mendonça D, Murphy B, Huber P, Rezwan K, Maas M. Assessment of nanoparticle immersion depth at liquid interfaces from chemically equivalent macroscopic surfaces. J Colloid Interface Sci 2022; 611:670-683. [PMID: 34974227 DOI: 10.1016/j.jcis.2021.12.113] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2021] [Revised: 12/14/2021] [Accepted: 12/18/2021] [Indexed: 01/22/2023]
Abstract
HYPOTHESIS We test whether the wettability of nanoparticles (NPs) straddling at an air/water surface or oil/water interface can be extrapolated from sessile drop-derived macroscopic contact angles (mCAs) on planar substrates, assuming that both the nanoparticles and the macroscopic substrates are chemically equivalent and feature the same electrokinetic potential. EXPERIMENTS Pure silica (SiO2) and amino-terminated silica (APTES-SiO2) NPs are compared to macroscopic surfaces with extremely low roughness (root mean square [RMS] roughness ≤ 2 nm) or a roughness determined by a close-packed layer of NPs (RMS roughness ∼ 35 nm). Equivalence of the surface chemistry is assessed by comparing the electrokinetic potentials of the NPs via electrophoretic light scattering and of the macroscopic substrates via streaming current analysis. The wettability of the macroscopic substrates is obtained from advancing (ACAs) and receding contact angles (RCAs) and in situ synchrotron X-ray reflectivity (XRR) provided by the NP wettability at the liquid interfaces. FINDINGS Generally, the RCA on smooth surfaces provides a good estimate of NP wetting properties. However, mCAs alone cannot predict adsorption barriers that prevent NP segregation to the interface, as is the case with the pure SiO2 nanoparticles. This strategy greatly facilitates assessing the wetting properties of NPs for applications such as emulsion formulation, flotation, or water remediation.
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Affiliation(s)
- Joeri Smits
- Advanced Ceramics, University of Bremen, Am Biologischen Garten 2, Bremen D-28359, Germany.
| | - Rajendra Prasad Giri
- Institute of Experimental and Applied Physics, Kiel University, Kiel D-24098, Germany.
| | - Chen Shen
- Deutsches Elektronen-Synchrotron DESY, Notkestraße 85, Hamburg D-22607, Germany.
| | - Diogo Mendonça
- Advanced Ceramics, University of Bremen, Am Biologischen Garten 2, Bremen D-28359, Germany; Department of Mechanical Engineering, Federal University of Santa Catarina, Florianopolis 88040-900, Brazil.
| | - Bridget Murphy
- Institute of Experimental and Applied Physics, Kiel University, Kiel D-24098, Germany; Ruprecht-Haensel Laboratory, Kiel University, Kiel 24118, Germany.
| | - Patrick Huber
- Deutsches Elektronen-Synchrotron DESY, Notkestraße 85, Hamburg D-22607, Germany; Hamburg University of Technology, Institute for Materials and X-Ray Physics, Eißendorfer Straße 42, Hamburg 21073, Germany; Hamburg University, Center for Hybrid Nanostructures ChyN, Luruper Chaussee 149, Hamburg 22607, Germany.
| | - Kurosch Rezwan
- Advanced Ceramics, University of Bremen, Am Biologischen Garten 2, Bremen D-28359, Germany; MAPEX Center for Materials and Processes, University of Bremen, Bibliothekstraße 1, Bremen D-28359, Germany.
| | - Michael Maas
- Advanced Ceramics, University of Bremen, Am Biologischen Garten 2, Bremen D-28359, Germany; MAPEX Center for Materials and Processes, University of Bremen, Bibliothekstraße 1, Bremen D-28359, Germany.
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4
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Guzmán E, Martínez-Pedrero F, Calero C, Maestro A, Ortega F, Rubio RG. A broad perspective to particle-laden fluid interfaces systems: from chemically homogeneous particles to active colloids. Adv Colloid Interface Sci 2022; 302:102620. [PMID: 35259565 DOI: 10.1016/j.cis.2022.102620] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2021] [Revised: 02/22/2022] [Accepted: 02/23/2022] [Indexed: 01/12/2023]
Abstract
Particles adsorbed to fluid interfaces are ubiquitous in industry, nature or life. The wide range of properties arising from the assembly of particles at fluid interface has stimulated an intense research activity on shed light to the most fundamental physico-chemical aspects of these systems. These include the mechanisms driving the equilibration of the interfacial layers, trapping energy, specific inter-particle interactions and the response of the particle-laden interface to mechanical perturbations and flows. The understanding of the physico-chemistry of particle-laden interfaces becomes essential for taking advantage of the particle capacity to stabilize interfaces for the preparation of different dispersed systems (emulsions, foams or colloidosomes) and the fabrication of new reconfigurable interface-dominated devices. This review presents a detailed overview of the physico-chemical aspects that determine the behavior of particles trapped at fluid interfaces. This has been combined with some examples of real and potential applications of these systems in technological and industrial fields. It is expected that this information can provide a general perspective of the topic that can be exploited for researchers and technologist non-specialized in the study of particle-laden interfaces, or for experienced researcher seeking new questions to solve.
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Affiliation(s)
- Eduardo Guzmán
- Departamento de Química Física, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, Ciudad Universitaria s/n, 28040 Madrid, Spain; Unidad de Materia Condensada, Instituto Pluridisciplinar, Universidad Complutense de Madrid, Paseo Juan XXIII 1, 28040 Madrid, Spain.
| | - Fernando Martínez-Pedrero
- Departamento de Química Física, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, Ciudad Universitaria s/n, 28040 Madrid, Spain.
| | - Carles Calero
- Departament de Física de la Matèria Condensada, Facultat de Física, Universitat de Barcelona, Avenida Diagonal 647, 08028 Barcelona, Spain; Institut de Nanociència i Nanotecnologia, IN2UB, Universitat de Barcelona, Avenida, Diagonal 647, 08028 Barcelona, Spain
| | - Armando Maestro
- Centro de Fı́sica de Materiales (CSIC, UPV/EHU)-Materials Physics Center MPC, Paseo Manuel de Lardizabal 5, 20018 San Sebastián, Spain; IKERBASQUE-Basque Foundation for Science, Plaza Euskadi 5, 48009 Bilbao, Spain
| | - Francisco Ortega
- Departamento de Química Física, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, Ciudad Universitaria s/n, 28040 Madrid, Spain; Unidad de Materia Condensada, Instituto Pluridisciplinar, Universidad Complutense de Madrid, Paseo Juan XXIII 1, 28040 Madrid, Spain
| | - Ramón G Rubio
- Departamento de Química Física, Facultad de Ciencias Químicas, Universidad Complutense de Madrid, Ciudad Universitaria s/n, 28040 Madrid, Spain; Unidad de Materia Condensada, Instituto Pluridisciplinar, Universidad Complutense de Madrid, Paseo Juan XXIII 1, 28040 Madrid, Spain.
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5
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Guzmán E, Abelenda-Núñez I, Maestro A, Ortega F, Santamaria A, Rubio RG. Particle-laden fluid/fluid interfaces: physico-chemical foundations. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2021; 33:333001. [PMID: 34102618 DOI: 10.1088/1361-648x/ac0938] [Citation(s) in RCA: 17] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/07/2021] [Accepted: 06/08/2021] [Indexed: 06/12/2023]
Abstract
Particle-laden fluid/fluid interfaces are ubiquitous in academia and industry, which has fostered extensive research efforts trying to disentangle the physico-chemical bases underlying the trapping of particles to fluid/fluid interfaces as well as the properties of the obtained layers. The understanding of such aspects is essential for exploiting the ability of particles on the stabilization of fluid/fluid interface for the fabrication of novel interface-dominated devices, ranging from traditional Pickering emulsions to more advanced reconfigurable devices. This review tries to provide a general perspective of the physico-chemical aspects associated with the stabilization of interfaces by colloidal particles, mainly chemical isotropic spherical colloids. Furthermore, some aspects related to the exploitation of particle-laden fluid/fluid interfaces on the stabilization of emulsions and foams will be also highlighted. It is expected that this review can be used for researchers and technologist as an initial approach to the study of particle-laden fluid layers.
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Affiliation(s)
- Eduardo Guzmán
- Departamento de Química Física, Universidad Complutense de Madrid, Madrid, Spain
- Instituto Pluridisciplinar, Universidad Complutense de Madrid, Madrid, Spain
| | - Irene Abelenda-Núñez
- Departamento de Química Física, Universidad Complutense de Madrid, Madrid, Spain
| | | | - Francisco Ortega
- Departamento de Química Física, Universidad Complutense de Madrid, Madrid, Spain
- Instituto Pluridisciplinar, Universidad Complutense de Madrid, Madrid, Spain
| | - Andreas Santamaria
- Instituto Pluridisciplinar, Universidad Complutense de Madrid, Madrid, Spain
- Institut Laue-Langevin, Grenoble, France
| | - Ramón G Rubio
- Departamento de Química Física, Universidad Complutense de Madrid, Madrid, Spain
- Instituto Pluridisciplinar, Universidad Complutense de Madrid, Madrid, Spain
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6
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Molaei M, Chisholm NG, Deng J, Crocker JC, Stebe KJ. Interfacial Flow around Brownian Colloids. PHYSICAL REVIEW LETTERS 2021; 126:228003. [PMID: 34152169 DOI: 10.1103/physrevlett.126.228003] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2020] [Revised: 03/21/2021] [Accepted: 04/08/2021] [Indexed: 06/13/2023]
Abstract
Understanding the flow created by particle motion at interfaces is a critical step toward understanding hydrodynamic interactions and colloidal self organization. We have developed correlated displacement velocimetry to measure flow fields around interfacially trapped Brownian particles. These flow fields can be decomposed into interfacial hydrodynamic multipoles, including force monopole and dipole flows. These structures provide key insights essential to understanding the interface's mechanical response. Importantly, the flow structure shows that the interface is incompressible for scant surfactant near the ideal gaseous state and contains information about interfacial properties and hydrodynamic coupling with the bulk fluid. The same dataset can be used to predict the response of the interface to applied, complex forces, enabling virtual experiments that produce higher order interfacial multipoles.
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Affiliation(s)
- Mehdi Molaei
- Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - Nicholas G Chisholm
- Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - Jiayi Deng
- Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - John C Crocker
- Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
| | - Kathleen J Stebe
- Chemical and Biomolecular Engineering, University of Pennsylvania, Philadelphia, Pennsylvania 19104, USA
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7
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Ji X, Wang X, Zhang Y, Zang D. Interfacial viscoelasticity and jamming of colloidal particles at fluid-fluid interfaces: a review. REPORTS ON PROGRESS IN PHYSICS. PHYSICAL SOCIETY (GREAT BRITAIN) 2020; 83:126601. [PMID: 32998118 DOI: 10.1088/1361-6633/abbcd8] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Colloidal particles can be adsorbed at fluid-fluid interfaces, a phenomenon frequently observed in particle-stabilized foams, Pickering emulsions, and bijels. Particles adsorbed at interfaces exhibit unique physical and chemical behaviors, which affect the mechanical properties of the interface. Therefore, interfacial colloidal particles are of interest in terms of both fundamental and applied research. In this paper, we review studies on the adsorption of colloidal particles at fluid-fluid interfaces, from both thermodynamic and mechanical points of view, and discuss the differences as compared with surfactants and polymers. The unique particle interactions induced by the interfaces as well as the particle dynamics including lateral diffusion and contact line relaxation will be presented. We focus on the rearrangement of the particles and the resultant interfacial viscoelasticity. Particular emphasis will be given to the effects of particle shape, size, and surface hydrophobicity on the interfacial particle assembly and the mechanical properties of the obtained particle layer. We will also summarize recent advances in interfacial jamming behavior caused by adsorption of particles at interfaces. The buckling and cracking behavior of particle layers will be discussed from a mechanical perspective. Finally, we suggest several potential directions for future research in this area.
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Affiliation(s)
- Xiaoliang Ji
- Soft Matter & Complex Fluids Group, School of Physical Science and Technology, Northwestern Polytechnical University, Xi'an, 710129, People's Republic of China
| | - Xiaolu Wang
- Institute of Welding and Surface Engineering Technology, Faculty of Materials and Manufacturing, Beijing University of Technology, Beijing, 100124, People's Republic of China
| | - Yongjian Zhang
- Shaanxi Key Laboratory of Surface Engineering and Remanufacturing, Xi'an University, Xi'an 710065, People's Republic of China
| | - Duyang Zang
- Soft Matter & Complex Fluids Group, School of Physical Science and Technology, Northwestern Polytechnical University, Xi'an, 710129, People's Republic of China
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8
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Razavi S, Lin B, Lee KYC, Tu RS, Kretzschmar I. Impact of Surface Amphiphilicity on the Interfacial Behavior of Janus Particle Layers under Compression. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:15813-15824. [PMID: 31269790 DOI: 10.1021/acs.langmuir.9b01664] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Langmuir monolayers of silica/gold Janus particles with two different degrees of amphiphilicity have been examined to study the significance of particle surface amphiphilicity on the structure and mechanical properties of the interfacial layers. The response of the layers to the applied compression provides insight into the nature and strength of the interparticle interactions. Different collapse modes observed for the interfacial layers are linked to the amphiphilicity of Janus particles and their configuration at the interface. Molecular dynamics simulations on nanoparticles with similar contact angles provide insight on the arrangement of particles at the interface and support our conclusion that the interfacial configuration and collapse of anisotropic particles at the air/water interface are controlled by particle amphiphilicity.
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Affiliation(s)
- Sepideh Razavi
- Chemical, Biological, and Materials Engineering , University of Oklahoma , Norman , Oklahoma 73019 , United States
| | | | | | - Raymond S Tu
- Department of Chemical Engineering , City College of the City University of New York , New York , New York 10031 , United States
| | - Ilona Kretzschmar
- Department of Chemical Engineering , City College of the City University of New York , New York , New York 10031 , United States
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9
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Rahman SE, Laal-Dehghani N, Christopher GF. Interfacial Viscoelasticity of Self-Assembled Hydrophobic/Hydrophilic Particles at an Air/Water Interface. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:13116-13125. [PMID: 31539264 DOI: 10.1021/acs.langmuir.9b02251] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Hydrophobic/hydrophilic mixtures of latex particles at an air/water interface self-assemble, creating space filling, interconnected aggregates as the relative surface fractions of the dissimilar particles approach 0.5, which is reflected both in qualitative observation and fractal dimension of the microstructure. It is hypothesized that this change in microstructure occurs due to an asymmetry in the electrostatic interaction between similar and dissimilar particles caused by polarization of hydrophilic particles by hydrophobic particles. The changes in both microstructure and interparticle interactions significantly impact the interfacial viscoelasticity. As greater shape complexity is observed, interfacial complex moduli can increase by as much as 3 orders of magnitude and interfaces become more elastic.
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Affiliation(s)
- Syed Ehsanur Rahman
- Department of Mechanical Engineering , Texas Tech University , Lubbock , Texas 79409 , United States
| | - Nader Laal-Dehghani
- Department of Chemical Engineering , Purdue University , West Lafayette , Indiana 47907 , United States
| | - Gordon F Christopher
- Department of Mechanical Engineering , Texas Tech University , Lubbock , Texas 79409 , United States
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10
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Aloi A, Vilanova N, Isa L, de Jong AM, Voets IK. Super-resolution microscopy on single particles at fluid interfaces reveals their wetting properties and interfacial deformations. NANOSCALE 2019; 11:6654-6661. [PMID: 30896703 DOI: 10.1039/c8nr08633h] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
Solid particles adsorbed at fluid interfaces are crucial for the mechanical stability of Pickering emulsions. The key parameter which determines the kinetic and thermodynamic properties of these colloids is the particle contact angle, θ. Several methods have recently been developed to measure the contact angle of individual particles adsorbed at liquid-liquid interfaces, as morphological and chemical heterogeneities at the particle surface can significantly affect θ. However, none of these techniques enables the simultaneous visualization of the nanoparticles and the reconstruction of the fluid interface to which they are adsorbed, in situ. To tackle this challenge, we utilize a newly developed super-resolution microscopy method, called iPAINT, which exploits non-covalent and continuous labelling of interfaces with photo-activatable fluorescent probes. Herewith, we resolve with nanometer accuracy both the position of individual nanoparticles at a water-octanol interface and the location of the interface itself. First, we determine single particle contact angles for both hydrophobic and hydrophilic spherical colloids. These experiments reveal a non-negligible dependence of θ on particle size, from which we infer an effective line tension, τ. Next, we image elliptical particles at a water-decane interface, showing that the corresponding interfacial deformations can be clearly captured by iPAINT microscopy.
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Affiliation(s)
- A Aloi
- Institute for Complex Molecular Systems, Eindhoven University of Technology, Post Office Box 513, 5600 MB Eindhoven, The Netherlands. and Laboratory of Self-Organizing Soft Matter, Department of Chemistry and Chemical Engineering, Eindhoven University of Technology, Post Office Box 513, 5600 MB Eindhoven, The Netherlands and Laboratory of Macromolecular and Organic Chemistry, Department of Chemistry and Chemical Engineering, Eindhoven University of Technology, Post Office Box 513, 5600 MB Eindhoven, The Netherlands
| | - N Vilanova
- Institute for Complex Molecular Systems, Eindhoven University of Technology, Post Office Box 513, 5600 MB Eindhoven, The Netherlands. and Laboratory of Macromolecular and Organic Chemistry, Department of Chemistry and Chemical Engineering, Eindhoven University of Technology, Post Office Box 513, 5600 MB Eindhoven, The Netherlands
| | - L Isa
- Laboratory for Interfaces, Soft Matter and Assembly, Department of Materials, ETH Zurich, Vladimir-Prelog Weg 5, 8093 Zürich, Switzerland
| | - A M de Jong
- Institute for Complex Molecular Systems, Eindhoven University of Technology, Post Office Box 513, 5600 MB Eindhoven, The Netherlands. and Laboratory of Molecular Biosensing, Department of Applied Physics, Eindhoven University of Technology, Post Office Box 513, 5600 MB Eindhoven, The Netherlands
| | - I K Voets
- Institute for Complex Molecular Systems, Eindhoven University of Technology, Post Office Box 513, 5600 MB Eindhoven, The Netherlands. and Laboratory of Self-Organizing Soft Matter, Department of Chemistry and Chemical Engineering, Eindhoven University of Technology, Post Office Box 513, 5600 MB Eindhoven, The Netherlands and Laboratory of Macromolecular and Organic Chemistry, Department of Chemistry and Chemical Engineering, Eindhoven University of Technology, Post Office Box 513, 5600 MB Eindhoven, The Netherlands and Laboratory of Physical Chemistry, Department of Chemistry and Chemical Engineering, Eindhoven University of Technology, Post Office Box 513, 5600 MB Eindhoven, The Netherlands
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11
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Yadav A, Hinch EJ, Tirumkudulu MS. Capillary-Induced Motion of Particles Bridging Interfaces of a Free-Standing Thin Liquid Film. PHYSICAL REVIEW LETTERS 2019; 122:098001. [PMID: 30932550 DOI: 10.1103/physrevlett.122.098001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/04/2018] [Revised: 12/20/2018] [Indexed: 06/09/2023]
Abstract
We demonstrate a new form of capillary force experienced by neutrally buoyant spherical particles adsorbed simultaneously at both interfaces of a thin liquid film of spatially varying thickness. The force is proportional to the slope of the interface and the difference between the local contact angle and the equilibrium value, and exists even when the two bounding interfaces have zero curvature. We derive the expression for the force, which when balanced against the hydrodynamic drag gives the trajectory of the particle. The measured trajectories for spherical particles of varying diameters in thin films compare well with predictions.
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Affiliation(s)
- Abhishek Yadav
- Department of Chemical Engineering, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
| | - E John Hinch
- Department of Applied Mathematics and Theoretical Physics, University of Cambridge, Wilberforce Road, Cambridge CB3 0WA, United Kingdom
| | - Mahesh S Tirumkudulu
- Department of Chemical Engineering, Indian Institute of Technology Bombay, Powai, Mumbai 400076, India
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12
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Ballard N, Law AD, Bon SAF. Colloidal particles at fluid interfaces: behaviour of isolated particles. SOFT MATTER 2019; 15:1186-1199. [PMID: 30601564 DOI: 10.1039/c8sm02048e] [Citation(s) in RCA: 51] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
The adsorption of colloidal particles to fluid interfaces is a phenomenon that is of interest to multiple disciplines across the physical and biological sciences. In this review we provide an entry level discussion of our current understanding on the physical principles involved and experimental observations of the adsorption of a single isolated particle to a liquid-liquid interface. We explore the effects that a variation of the morphology and surface chemistry of a particle can have on its ability to adhere to a liquid interface, from a thermodynamic as well as a kinetic perspective, and the impact of adsorption behaviour on potential applications. Finally, we discuss recent developments in the measurement of the interfacial behaviour of nanoparticles and highlight open questions for future research.
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Affiliation(s)
- Nicholas Ballard
- POLYMAT - University of the Basque Country (UPV/EHU), Centro Joxe Mari Korta, Avenida de Tolosa 72, 20018, Donostia-San Sebastian, Spain.
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13
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Rey M, Yu T, Guenther R, Bley K, Vogel N. A Dirty Story: Improving Colloidal Monolayer Formation by Understanding the Effect of Impurities at the Air/Water Interface. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:95-103. [PMID: 30543431 DOI: 10.1021/acs.langmuir.8b02605] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Colloidal monolayers are important tools to fabricate surface structures at the nanoscale. A typical monolayer fabrication strategy involves the self-assembly of colloidal building blocks at liquid interfaces, which are subsequently deposited on a solid substrate. Even though this process is well established, the resulting order of the particles within the colloidal monolayer differs between batches of colloidal particles and can even change with the age of the dispersion. In this study, we investigate the origins of this variation of monolayer quality for polystyrene particles synthesized by surfactant-free emulsion polymerization. We correlate the interfacial behavior of the colloidal particles at the air/water interface on a Langmuir trough with the resulting quality of the monolayer after transfer to a solid substrate. We identify surface-active impurities as a major cause for a disturbed self-assembly of the colloidal particles. These impurities form during the particle synthesis and consist of copolymers of styrene, the comonomer acrylic acid, and sulfonate species from the initiator. We show that they can be removed by cleaning protocols to increase the monolayer quality. However, our experiments demonstrate that the impurities reappear over time even for cleaned dispersions, indicating desorption from the surface of the colloidal particles. We identify strategies to avoid the presence of the impurities at the air/water interface or to inhibit their effect on the self-assembly process. These simple guidelines improve the quality of the resulting colloidal monolayer, which is a prerequisite for the reliable fabrication of high-quality surface nanostructures from colloidal templates.
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Affiliation(s)
- Marcel Rey
- Institute of Particle Technology , Friedrich-Alexander University Erlangen-Nürnberg , Cauerstrasse 4 , 91058 Erlangen , Germany
| | - Taotao Yu
- Institute of Particle Technology , Friedrich-Alexander University Erlangen-Nürnberg , Cauerstrasse 4 , 91058 Erlangen , Germany
| | - Roman Guenther
- Institute of Particle Technology , Friedrich-Alexander University Erlangen-Nürnberg , Cauerstrasse 4 , 91058 Erlangen , Germany
| | - Karina Bley
- Institute of Particle Technology , Friedrich-Alexander University Erlangen-Nürnberg , Cauerstrasse 4 , 91058 Erlangen , Germany
| | - Nicolas Vogel
- Institute of Particle Technology , Friedrich-Alexander University Erlangen-Nürnberg , Cauerstrasse 4 , 91058 Erlangen , Germany
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14
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A Facile Interfacial Self-Assembly of Crystalline Colloidal Monolayers by Tension Gradient. MICROMACHINES 2018; 9:mi9060297. [PMID: 30424230 PMCID: PMC6187851 DOI: 10.3390/mi9060297] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/11/2018] [Revised: 06/08/2018] [Accepted: 06/10/2018] [Indexed: 12/13/2022]
Abstract
Many self-assembly approaches of colloidal monolayers have flourished but with some shortages, such as complexity, time-consumption, parameter sensitivity, and high-cost. This paper presents a facile, rapid, well-controlled, and low-cost method to prepare monolayers by directly adding silica particle suspensions containing water and ethanol to different liquids. A detailed analysis of the self-assembly process was conducted. The particles dove into water firstly, then moved up under the effect of the buoyancy and the tension gradient. The tension gradient induced the Marangoni convection and the relative motion between the water and the particles. At last, the particles were adsorbed at the air-water interface to minimize the free energy. The quality of the monolayers depended on the addition of sodium dodecyl sulfonate or ethanol in the water subphase. An interfacial polymerization of ethyl 2-cyanoacrylate was used to determine the contact angles of the particles at different subphase surfaces. The value of the detachment energy was positively associated with the contact angle and the surface tension. When the detachment energy decreased to a certain value, some particles detached from the surface, leading to the formation of a quasi-double layer. We also observed that the content of ethanol in suspensions influenced the arrangement of particles.
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15
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Kim PY, Dinsmore AD, Hoagland DA, Russell TP. Wetting, meniscus structure, and capillary interactions of microspheres bound to a cylindrical liquid interface. SOFT MATTER 2018; 14:2131-2141. [PMID: 29488991 DOI: 10.1039/c7sm02454a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Wetting, meniscus structure, and capillary interactions for polystyrene microspheres deposited on constant curvature cylindrical liquid interfaces, constructed from nonvolatile ionic or oligomeric liquids, were studied by optical interferometry and optical microscopy. The liquid interface curvature resulted from the preferential wetting of finite width lines patterned onto planar silicon substrates. Key variables included sphere diameter, nominal (or average) contact angle, and deviatoric interfacial curvature. Menisci adopted the quadrupolar symmetry anticipated by theory, with interfacial deformation closely following predicted dependences on sphere diameter and nominal contact angle. Unexpectedly, the contact angle was not constant locally around the contact line, the nominal contact angle varied among seemingly identical spheres, and the maximum interface deviation did not follow the predicted dependence on deviatoric interfacial curvature. Instead, this deviation was up to an order-of-magnitude larger than predicted. Trajectories of neighboring microspheres visually manifested quadrupole-quadrupole interactions, eventually producing square sphere packings that foreshadow interfacial assembly as a potential route to hierarchical 2D particle structures.
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Affiliation(s)
- Paul Y Kim
- Department of Polymer Science and Engineering, University of Massachusetts Amherst, Amherst, Massachusetts 01003, USA.
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16
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Scanlon MD, Smirnov E, Stockmann TJ, Peljo P. Gold Nanofilms at Liquid–Liquid Interfaces: An Emerging Platform for Redox Electrocatalysis, Nanoplasmonic Sensors, and Electrovariable Optics. Chem Rev 2018; 118:3722-3751. [DOI: 10.1021/acs.chemrev.7b00595] [Citation(s) in RCA: 80] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- Micheál D. Scanlon
- The Bernal Institute and Department of Chemical Sciences, School of Natural Sciences, University of Limerick (UL), Limerick V94 T9PX, Ireland
| | - Evgeny Smirnov
- Laboratoire d’Electrochimie Physique et Analytique (LEPA), École Polytechnique Fédérale de Lausanne (EPFL), Rue de l’Industrie 17, CH-1951 Sion, Switzerland
| | - T. Jane Stockmann
- Interfaces, Traitements, Organisation et Dynamique des Systèmes, CNRS-UMR 7086, Sorbonne Paris Cité, Paris Diderot University, 15 Rue J.A. Baïf, 75013 Paris, France
| | - Pekka Peljo
- Laboratoire d’Electrochimie Physique et Analytique (LEPA), École Polytechnique Fédérale de Lausanne (EPFL), Rue de l’Industrie 17, CH-1951 Sion, Switzerland
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17
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Effect of contact angle and contact angle hysteresis on the floatability of spheres at the air-water interface. Adv Colloid Interface Sci 2017; 248:69-84. [PMID: 28780963 DOI: 10.1016/j.cis.2017.07.031] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2017] [Revised: 07/21/2017] [Accepted: 07/25/2017] [Indexed: 11/22/2022]
Abstract
The floatability of solid particles on the water surface governs many natural phenomena and industrial processes including film flotation and froth flotation separation of coal and valuable minerals. For many years, the contact angle (CA) has been postulated as the key factor in determining the particle floatability. Indeed, the maximum force (tenacity) supporting the flotation of fine spheres was conjectured to occur when the apical angle of the contact circle is equal to the contact angle. In this paper, the model predictions are reviewed and compared with experimental results. It is shown that CA can be affected by many physical and chemical factors such as surface roughness and chemical heterogeneity and can have a range of values known as the CA hysteresis. This multiple-valued CA invalidates the available theories on the floatability of spheres. Even the intuitive replacement of CA by the advancing (maximum) CA in the classical theories can be wrong. A few new examples are also reviewed and analyzed to demonstrate the significance of CA variation in controlling the particle floatability. They include the pinning of the contact line at the sharp edge, known as the Gibbs inequality condition, and the nearby interaction among floating particles, known as lateral inter-particle interaction. It is concluded that our quantitative understanding of the floatability of real particles being irregular and heterogeneous both morphologically and chemically is still far from being satisfactory.
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18
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Stocco A, Nobili M. A comparison between liquid drops and solid particles in partial wetting. Adv Colloid Interface Sci 2017; 247:223-233. [PMID: 28728667 DOI: 10.1016/j.cis.2017.06.014] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2017] [Revised: 05/19/2017] [Accepted: 06/30/2017] [Indexed: 01/06/2023]
Abstract
In this critical review we compare two geometries in partial wetting: a liquid drop on a planar substrate and a spherical particle at a planar liquid interface. We show that this comparison is far from being trivial even if the same physical interactions are at play in both geometries. Similarities and differences in terms of free energies and frictions will be discussed. Contact angle hysteresis, the impact of surface roughness and line pinning on wetting will be described and compared to selected experimental findings.
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19
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Zhang Y, Wang S, Zhou J, Zhao R, Benz G, Tcheimou S, Meredith JC, Behrens SH. Interfacial Activity of Nonamphiphilic Particles in Fluid-Fluid Interfaces. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:4511-4519. [PMID: 28422501 DOI: 10.1021/acs.langmuir.7b00599] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
Surfactants can adsorb in fluid-fluid interfaces and lower the interfacial tension. Like surfactants, particles with appropriate wettability can also adsorb in fluid-fluid interfaces. Despite many studies of particle adsorption at fluid interfaces, some confusion persists regarding the ability of (simple, nonamphiphilic) particles to reduce the interfacial tension. In the present work, the interfacial activity of silica nanoparticles at air-water and hexadecane-water interfaces and of ethyl cellulose particles at the interface of water with trimethylolpropane trimethacrylate was analyzed through pendant drop tensiometry. Our measurements strongly suggest that the particles do significantly affect the interfacial tension provided that they have a strong affinity to the interface by virtue of their wettability and that no energy barrier to adsorption prevents them from reaching the interface. A simplistic model that does not explicitly account for any particle-particle interactions is found to yield surprisingly good predictions for the effective interfacial tension in the presence of the adsorbed particles. We further propose that interfacial tension measurements, when combined with information about the particles' wetting properties, can provide a convenient way to estimate the packing density of particles in fluid-fluid interfaces. These results may help to understand and control the assembly of nonamphiphilic nanoparticles at fluid-fluid interfaces, which is relevant to applications ranging from surfactant-free formulations and food technology to oil recovery.
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Affiliation(s)
- Yi Zhang
- School of Chemical & Biomolecular Engineering, Georgia Institute of Technology , Atlanta, Georgia 30332-0100, United States
| | - Songcheng Wang
- School of Chemical & Biomolecular Engineering, Georgia Institute of Technology , Atlanta, Georgia 30332-0100, United States
| | - Jiarun Zhou
- School of Chemical & Biomolecular Engineering, Georgia Institute of Technology , Atlanta, Georgia 30332-0100, United States
| | - Ruiyang Zhao
- School of Chemical & Biomolecular Engineering, Georgia Institute of Technology , Atlanta, Georgia 30332-0100, United States
| | - Gregory Benz
- School of Chemical & Biomolecular Engineering, Georgia Institute of Technology , Atlanta, Georgia 30332-0100, United States
| | - Stephane Tcheimou
- School of Chemical & Biomolecular Engineering, Georgia Institute of Technology , Atlanta, Georgia 30332-0100, United States
| | - J Carson Meredith
- School of Chemical & Biomolecular Engineering, Georgia Institute of Technology , Atlanta, Georgia 30332-0100, United States
| | - Sven H Behrens
- School of Chemical & Biomolecular Engineering, Georgia Institute of Technology , Atlanta, Georgia 30332-0100, United States
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20
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Contact angle variation on single floating spheres and its impact on the stability analysis of floating particles. Colloids Surf A Physicochem Eng Asp 2017. [DOI: 10.1016/j.colsurfa.2017.01.057] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022]
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21
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Chen Q, Stricek I, Gray MR, Liu Q. Influence of hydrophobicity distribution of particle mixtures on emulsion stabilization. J Colloid Interface Sci 2017; 491:179-189. [PMID: 28027467 DOI: 10.1016/j.jcis.2016.12.045] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2016] [Revised: 12/18/2016] [Accepted: 12/19/2016] [Indexed: 10/20/2022]
Abstract
Whilst emulsions stabilized by uniform particles are well established, the emulsification behavior of heterogeneous mixtures of particles with varying hydrophobicity is rarely examined. Consequently, the influence of the distribution of particle hydrophobicity on oil-water emulsion stabilization is poorly understood. In the present work, the wettability of the bitumen froth fine solids from Alberta oil sands was studied by film flotation and toluene-water emulsification tests, before and after a hydrothermal treatment at 300-420°C. This approach provided a series of populations of particles with different distributions of hydrophobicity. The initial fine particles in the bitumen froth had a critical surface tension ranging from 26 to 56mN/m, with a mean value of 39mN/m. Hydrothermal treatment at 300-420°C progressively shifted the hydrophobicity distribution of the fine particles, resulting in a lower mean critical surface tension and a narrower critical surface tension range. The emulsifying capacity of the fine particle mixtures, as indicated by the volume of the produced toluene-water emulsions, was unrelated to the mean critical surface tension. Instead, emulsification depended on the proportion of a specific sub-fraction of particles with a critical surface tension of 27-30mN/m. This sub-fraction of particles, with intermediate hydrophobicity, dominated the emulsification behavior of the particle mixtures.
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Affiliation(s)
- Qiang Chen
- Department of Chemical and Materials Engineering, University of Alberta, Edmonton, AB T6G 1H9, Canada
| | - Igor Stricek
- Department of Chemical and Materials Engineering, University of Alberta, Edmonton, AB T6G 1H9, Canada
| | - Murray R Gray
- Department of Chemical and Materials Engineering, University of Alberta, Edmonton, AB T6G 1H9, Canada
| | - Qi Liu
- Department of Chemical and Materials Engineering, University of Alberta, Edmonton, AB T6G 1H9, Canada.
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22
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Mao C, Kong M, Yang Q, Li G, Huang Y. Vorticity Deformation in Polymeric Emulsions Induced by Anisotropic Ellipsoids. ACS Macro Lett 2016; 5:900-903. [PMID: 35607219 DOI: 10.1021/acsmacrolett.6b00456] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We study the influence of particle shape on shear-induced droplet deformation in polymeric emulsions. During shearing, droplets become elongated and rotate periodically about their major axes while aligning along the vorticity direction in ellipsoid-filled emulsions, while similar behavior is not observed in the pristine, microsphere-filled or ellipsoid-filled inverse systems. Based on the Jeffery orbit theory, the formation of anisotropic droplets with extremely small Reynolds number due to arrested coalescence in Newtonian matrix and strong confinement effect are suggested to be responsible for the vorticity alignment of droplets during slow shearing.
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Affiliation(s)
- Chaoying Mao
- College of Polymer Science
and Engineering, State Key Laboratory of Polymer Materials Engineering
of China, Sichuan University, Chengdu 610065, China
| | - Miqiu Kong
- College of Polymer Science
and Engineering, State Key Laboratory of Polymer Materials Engineering
of China, Sichuan University, Chengdu 610065, China
| | - Qi Yang
- College of Polymer Science
and Engineering, State Key Laboratory of Polymer Materials Engineering
of China, Sichuan University, Chengdu 610065, China
| | - Guangxian Li
- College of Polymer Science
and Engineering, State Key Laboratory of Polymer Materials Engineering
of China, Sichuan University, Chengdu 610065, China
| | - Yajiang Huang
- College of Polymer Science
and Engineering, State Key Laboratory of Polymer Materials Engineering
of China, Sichuan University, Chengdu 610065, China
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23
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Zanini M, Isa L. Particle contact angles at fluid interfaces: pushing the boundary beyond hard uniform spherical colloids. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2016; 28:313002. [PMID: 27299800 DOI: 10.1088/0953-8984/28/31/313002] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Micro and nanoparticles at fluid interfaces have been attracting increasing interest in the last few decades as building blocks for materials, as mechanical and structural probes for complex interfaces and as models for two-dimensional systems. The three-phase contact angle enters practically all aspects of the particle behavior at the interface: its thermodynamics (binding energy to the interface), dynamics (motion and drag at the interface) and interactions with the interface (adsorption and wetting). Moreover, many interactions among particles at the interface also strongly depend on the contact angle. These concepts have been extensively discussed for non-deformable, homogeneous and mostly spherical particles, but recent progress in particle synthesis and fabrication has instead moved in the direction of producing more complex micro and nanoscale objects, which can be responsive, deformable, heterogenous and/or anisotropic in shape, surface chemistry and material properties. These new particles have a much greater potential for applications and new science, and the study of their behavior at interfaces has only very recently started. In this paper, we critically review the current state of the art of the experimental methods available to measure the contact angle of micro and nanoparticles at fluid interfaces, indicating their strengths and limitations. We then comment on new particle systems that are currently attracting increasing interest in relation to their adsorption and assembly at fluid interfaces and discuss if and which ones of the current techniques are suited to investigate their properties at interfaces. Based on this discussion, we will finally try to indicate a direction in which new experimental methods should develop in the future to tackle the new challenges posed by the novel types of particles that more and more often are used at interfaces.
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Affiliation(s)
- Michele Zanini
- Department of Materials, Laboratory for Interfaces, Soft matter and Assembly, ETH Zurich, Vladimir-Prelog-Weg 5, 8093 Zurich, Switzerland
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24
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Gao P, Yi Z, Xing X, Ngai T, Jin F. Influence of an Additive-Free Particle Spreading Method on Interactions between Charged Colloidal Particles at an Oil/Water Interface. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2016; 32:4909-4916. [PMID: 27108987 DOI: 10.1021/acs.langmuir.6b01362] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/05/2023]
Abstract
The assembly and manipulation of charged colloidal particles at oil/water interfaces represent active areas of fundamental and applied research. Previously, we have shown that colloidal particles can spontaneously generate unstable residual charges at the particle/oil interface when spreading solvent is used to disperse them at an oil/water interface. These residual charges in turn affect the long-ranged electrostatic repulsive forces and packing of particles at the interface. To further uncover the influence arising from the spreading solvents on interfacial particle interactions, in the present study we utilize pure buoyancy to drive the particles onto an oil/water interface and compare the differences between such a spontaneously adsorbed particle monolayer to the spread monolayer based on solvent spreading techniques. Our results show that the solvent-free method could also lead particles to spread well at the interface, but it does not result in violent sliding of particles along the interface. More importantly, this additive-free spreading method can avoid the formation of unstable residual charges at the particle/oil interface. These findings agree well with our previous hypothesis; namely, those unstable residual charges are triboelectric charges that arise from the violently rubbing of particles on oil at the interface. Therefore, if the spreading solvents could be avoided, then we would be able to get rid of the formation of residual charges at interfaces. This finding will provide insight for precisely controlling the interactions among colloidal particles trapped at fluid/fluid interfaces.
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Affiliation(s)
- Peng Gao
- Hefei National Laboratory for Physical Sciences at the Microscale, Department of Chemical Physics, Department of Polymer Science and Engineering, CAS Key Laboratory of Soft Matter Chemistry, University of Science and Technology of China , Hefei 230026, PR China
| | - Zonglin Yi
- Department of Chemistry, The Chinese University of Hong Kong , Shatin, N. T. Hong Kong
- Shenzhen Municipal Key Laboratory of Chemical Synthesis of Medicinal Organic Molecules, Shenzhen Research Institute, The Chinese University of Hong Kong , Shenzhen 518057, China
| | - Xiaochen Xing
- Hefei National Laboratory for Physical Sciences at the Microscale, Department of Chemical Physics, Department of Polymer Science and Engineering, CAS Key Laboratory of Soft Matter Chemistry, University of Science and Technology of China , Hefei 230026, PR China
| | - To Ngai
- Department of Chemistry, The Chinese University of Hong Kong , Shatin, N. T. Hong Kong
- Shenzhen Municipal Key Laboratory of Chemical Synthesis of Medicinal Organic Molecules, Shenzhen Research Institute, The Chinese University of Hong Kong , Shenzhen 518057, China
| | - Fan Jin
- Hefei National Laboratory for Physical Sciences at the Microscale, Department of Chemical Physics, Department of Polymer Science and Engineering, CAS Key Laboratory of Soft Matter Chemistry, University of Science and Technology of China , Hefei 230026, PR China
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25
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Bossler F, Koos E. Structure of Particle Networks in Capillary Suspensions with Wetting and Nonwetting Fluids. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2016; 32:1489-501. [PMID: 26807651 PMCID: PMC4757740 DOI: 10.1021/acs.langmuir.5b04246] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/18/2015] [Revised: 01/20/2016] [Indexed: 05/17/2023]
Abstract
The mechanical properties of a suspension can be dramatically altered by adding a small amount of a secondary fluid that is immiscible with the bulk phase. The substantial changes in the strength of these capillary suspensions arise due to the capillary force inducing a percolating particle network. Spatial information on the structure of the particle networks is obtained using confocal microscopy. It is possible, for the first time, to visualize the different types of percolating structures of capillary suspensions in situ. These capillary networks are unique from other types of particulate networks due to the nature of the capillary attraction. We investigate the influence of the three-phase contact angle on the structure of an oil-based capillary suspension with silica microspheres. Contact angles smaller than 90° lead to pendular networks of particles connected with single capillary bridges or clusters comparable to the funicular state in wet granular matter, whereas a different clustered structure, the capillary state, forms for angles larger than 90°. Particle pair distribution functions are obtained by image analysis, which demonstrate differences in the network microstructures. When porous particles are used, the pendular conformation also appears for apparent contact angles larger than 90°. The complex shear modulus can be correlated to these microstructural changes. When the percolating structure is formed, the complex shear modulus increases by nearly three decades. Pendular bridges lead to stronger networks than the capillary state network conformations, but the capillary state clusters are nevertheless much stronger than pure suspensions without the added liquid.
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Affiliation(s)
- Frank Bossler
- Karlsruhe Institute
of Technology, Institute for Mechanical
Process Engineering and Mechanics, Straße am Forum 8, 76131 Karlsruhe, Germany
| | - Erin Koos
- Karlsruhe Institute
of Technology, Institute for Mechanical
Process Engineering and Mechanics, Straße am Forum 8, 76131 Karlsruhe, Germany
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26
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Velankar SS. A non-equilibrium state diagram for liquid/fluid/particle mixtures. SOFT MATTER 2015; 11:8393-403. [PMID: 26399221 DOI: 10.1039/c5sm01901j] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
The equilibrium structures of ternary oil/water/surfactant systems are often represented within a triangular composition diagram with various regions of the triangle corresponding to different equilibrium states. We transplant this idea to ternary liquid/fluid/particle systems that are far from equilibrium. Liquid/liquid/particle mixtures or liquid/gas/particle mixtures yield a wide diversity of morphologies including Pickering emulsions, bijels, pendular aggregates, spherical agglomerates, capillary suspensions, liquid marbles, powdered liquids, and particle-stabilized foams. This paper argues that such ternary liquid/fluid/particle mixtures can be unified into a non-equilibrium state diagram. What is common among all these systems is that the morphology results from an interplay between the preferential wettability of the particles, capillarity, and viscous forces encountered during mixing. Therefore all such systems share certain universal features, regardless of the details of the particles or fluids used. These features guide the construction of a non-equilibrium state diagram which takes the form of a triangular prism, where each triangular cross-section of the prism corresponds to a different relative affinity of the particles towards the two fluids. We classify the prism into regions in which the various morphologies appear and also emphasize the major difference between systems in which the particles are fully-wetted by one of the fluids vs. partially-wetted by both fluids. We also discuss how the state diagram may change with mixing intensity or with interparticle attractions.
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Affiliation(s)
- Sachin S Velankar
- Department of Chemical Engineering, University of Pittsburgh, Pittsburgh, PA 15261, USA.
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27
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Sabapathy M, Kollabattula V, Basavaraj MG, Mani E. Visualization of the equilibrium position of colloidal particles at fluid-water interfaces by deposition of nanoparticles. NANOSCALE 2015; 7:13868-13876. [PMID: 26172860 DOI: 10.1039/c5nr03369a] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We present a general yet simple method to measure the contact angle of colloidal particles at fluid-water interfaces. In this method, the particles are spread at the required fluid-water interface as a monolayer. In the water phase a chemical reaction involving reduction of a metal salt such as aurochloric acid is initiated. The metal grows as a thin film or islands of nanoparticles on the particle surface exposed to the water side of the interface. Analyzing the images of particles by high resolution scanning microscopy (HRSEM), we trace the three phase contact line up to which deposition of the metal film occurs. From geometrical relations, the three phase contact angle is then calculated. We report the measurements of the contact angle of silica and polystyrene (PS) particles at different interfaces such as air-water, decane-water and octanol-water. We have also applied this method to measure the contact angle of surfactant treated polystyrene particles at the air-water interface, and we find a non-monotonic change of the contact angle with the concentration of the surfactant. Our results are compared with the well-known gel trapping technique and we find good comparison with previous measurements.
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Affiliation(s)
- Manigandan Sabapathy
- Polymer Engineering and Colloid Science Laboratory, Department of Chemical Engineering, Indian Institute of Technology Madras, Chennai -600 036, India.
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28
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Noguera-Marín D, Moraila-Martínez CL, Cabrerizo-Vílchez MA, Rodríguez-Valverde MA. Particle Segregation at Contact Lines of Evaporating Colloidal Drops: Influence of the Substrate Wettability and Particle Charge-Mass Ratio. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2015; 31:6632-6638. [PMID: 26000909 DOI: 10.1021/acs.langmuir.5b01062] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Segregation of particles during capillary/convective self-assembly is interesting for self-stratification in colloidal deposits. In evaporating drops containing colloidal particles, the wettability properties of substrate and the sedimentation of particles can affect their accumulation at contact lines. In this work we studied the size segregation and discrimination of charged particles with different densities. We performed in-plane particle counting at evaporating triple lines by using fluorescence confocal microscopy. We studied separately substrates with very different wettability properties and particles with different charge-mass ratios at low ionic strength. We used binary colloidal suspensions to compare simultaneously the deposition of two different particles. The particle deposition rate strongly depends on the receding contact angle of the substrate. We further observed a singular behavior of charged polystyrene particles in binary mixtures under "salt-free" conditions explained by the "colloidal Brazil nut" effect.
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Affiliation(s)
- Diego Noguera-Marín
- Biocolloid and Fluid Physics Group, Applied Physics Department, Faculty of Sciences, University of Granada, E-18071 Granada, Spain
| | - Carmen L Moraila-Martínez
- Biocolloid and Fluid Physics Group, Applied Physics Department, Faculty of Sciences, University of Granada, E-18071 Granada, Spain
| | - Miguel A Cabrerizo-Vílchez
- Biocolloid and Fluid Physics Group, Applied Physics Department, Faculty of Sciences, University of Granada, E-18071 Granada, Spain
| | - Miguel A Rodríguez-Valverde
- Biocolloid and Fluid Physics Group, Applied Physics Department, Faculty of Sciences, University of Granada, E-18071 Granada, Spain
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