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Hu J, Chi M, He R, Fan J, Gao H, Xie W, Dai K, Sun S, Hu S. Multi-responsive Pickering emulsifiers: a comprehensive study on the emulsification-demulsification behavior of modified chitosan-coated Fe 3O 4 nanocomposites. Phys Chem Chem Phys 2024; 26:20009-20021. [PMID: 39005229 DOI: 10.1039/d4cp01018c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 07/16/2024]
Abstract
The surface characteristics of stimuli-responsive Pickering emulsifiers can be modified by external environmental triggers, making them highly versatile in various applications. In this study, we report three novel organic-inorganic composite structure emulsifiers. These emulsifiers were designed with a core of magnetic Fe3O4 particles, surrounded by a protective silica layer, and coated on the exterior with three distinct types of modified chitosan (CS). Experimental results demonstrate that these emulsifiers can stabilize emulsion systems consisting of liquid paraffin and deionized water at a concentration of 0.5 wt%. The unique properties of the modified CS coatings allowed for the controlled demulsification of two types of emulsions by adjusting the proton concentration. Additionally, these emulsifiers exhibited magnetic-responsive demulsification under the control of an external magnetic field. The findings of this study provide valuable insights into the design and construction of multi-responsive chitosan-based magnetic Pickering emulsifiers with controllable properties.
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Affiliation(s)
- Jianwen Hu
- School of Materials Science and Engineering, China University of Petroleum (East China), Qingdao, 266580, P. R. China.
- Institute of Advanced Materials, China University of Petroleum (East China), Qingdao, 266580, P. R. China
| | - Mingshuo Chi
- School of Materials Science and Engineering, China University of Petroleum (East China), Qingdao, 266580, P. R. China.
- Institute of Advanced Materials, China University of Petroleum (East China), Qingdao, 266580, P. R. China
| | - Runna He
- School of Materials Science and Engineering, China University of Petroleum (East China), Qingdao, 266580, P. R. China.
- Institute of Advanced Materials, China University of Petroleum (East China), Qingdao, 266580, P. R. China
| | - Junjie Fan
- School of Materials Science and Engineering, China University of Petroleum (East China), Qingdao, 266580, P. R. China.
- Institute of Advanced Materials, China University of Petroleum (East China), Qingdao, 266580, P. R. China
| | - Haotian Gao
- School of Materials Science and Engineering, China University of Petroleum (East China), Qingdao, 266580, P. R. China.
- Institute of Advanced Materials, China University of Petroleum (East China), Qingdao, 266580, P. R. China
| | - Wenqing Xie
- School of Materials Science and Engineering, China University of Petroleum (East China), Qingdao, 266580, P. R. China.
- Institute of Advanced Materials, China University of Petroleum (East China), Qingdao, 266580, P. R. China
| | - Kunxiu Dai
- School of Petroleum Engineering, Southwest Petroleum University, Chengdu, 610500, P. R. China
| | - Shuangqing Sun
- School of Materials Science and Engineering, China University of Petroleum (East China), Qingdao, 266580, P. R. China.
- Institute of Advanced Materials, China University of Petroleum (East China), Qingdao, 266580, P. R. China
| | - Songqing Hu
- School of Materials Science and Engineering, China University of Petroleum (East China), Qingdao, 266580, P. R. China.
- Institute of Advanced Materials, China University of Petroleum (East China), Qingdao, 266580, P. R. China
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Gohil RS, Karishma S, Kumar H, Basavaraj MG, Mani E. Demulsification of Pickering Emulsions by Chemical Dissolution of Stabilizers. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2024; 40:11988-11997. [PMID: 38787896 DOI: 10.1021/acs.langmuir.4c00514] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2024]
Abstract
Demulsification of particle-stabilized oil-in-water emulsions is crucial in diverse fields such as treatment of produce water, recovery of valuable products of Pickering emulsion catalysis, and so on. In this work, we investigated a facile method for destabilizing emulsions by dissolving stabilizer particles by the introduction of acid or base. Nanoellipsoidal hematite-stabilized decane-in-water emulsions are destabilized by dissolving hematite with oxalic or hydrochloric acid in situ. Time required for complete demulsification decreased as the acid concentration is increased. The demulsification time is typically on the order of a few hours for the chosen protocol. Similarly, the silica-stabilized decane-water emulsion is demulsified by the addition of aqueous sodium hydroxide. Demulsification kinetics is presented as the temporal change of the emulsion volume with time. Emulsion volume decreases in two stages: an initial slow decrease followed by an exponential decrease. Scanning electron microscopy analysis shows that the stabilizing particles are completely dissolved and recrystallized as salts of respective kinds. An estimate of the desorption free energy suggests that particle size should be reduced to a few nanometers for inducing destabilization. This work describes a facile method to destabilize oil-in-water emulsion, and it can be generalized to any other particle-stabilized emulsions by choosing appropriate chemical reagent for dissolution.
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Affiliation(s)
- Renuka S Gohil
- Department of Chemical Engineering, Indian Institute of Technology Madras, Chennai 600036, Tamil Nadu, India
| | - S Karishma
- Department of Chemical Engineering, Indian Institute of Technology Madras, Chennai 600036, Tamil Nadu, India
| | - Hemant Kumar
- Department of Chemical Engineering, Indian Institute of Technology Madras, Chennai 600036, Tamil Nadu, India
| | - Madivala G Basavaraj
- Department of Chemical Engineering, Indian Institute of Technology Madras, Chennai 600036, Tamil Nadu, India
| | - Ethayaraja Mani
- Department of Chemical Engineering, Indian Institute of Technology Madras, Chennai 600036, Tamil Nadu, India
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Wang Y, Guo Y, Dong P, Lin K, Du P, Cao J, Cheng Y, Cheng F, Yun S, Feng C. Water-in-oil Pickering emulsion using ergosterol as an emulsifier solely. Food Res Int 2024; 186:114374. [PMID: 38729731 DOI: 10.1016/j.foodres.2024.114374] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2024] [Revised: 04/08/2024] [Accepted: 04/17/2024] [Indexed: 05/12/2024]
Abstract
As a crucial component of the fungal cell membranes, ergosterol has been demonstrated to possess surface activity attributed to its hydrophobic region and polar group. However, further investigation is required to explore its emulsification behavior upon migration to the oil-water interface. Therefore, this study was conducted to analyze the interface properties of ergosterol as a stabilizer for water in oil (W/O) emulsion. Moreover, the emulsion prepared under the optimal conditions was utilized to load the water-soluble bioactive substance with the chlorogenic acid as the model molecules. Our results showed that the contact angle of ergosterol was 117.017°, and its dynamic interfacial tension was obviously lower than that of a pure water-oil system. When the ratio of water to oil was 4: 6, and the content of ergosterol was 3.5 % (ergosterol/oil phase, w/w), the W/O emulsion had smaller particle size (438 nm), higher apparent viscosity, and better stability. Meanwhile, the stability of loaded chlorogenic acid was improved under unfavorable conditions (pH 1.2, 90 °C, ultraviolet irradiation, and oxidation), which were 73.87 %, 59.53 %, 62.53 %, and 69.73 %, respectively. Additionally, the bioaccessibility of chlorogenic acid (38.75 %) and ergosterol (33.69 %), and the scavenging rates of the emulsion on DPPH radicals (81.00 %) and hydroxyl radicals (82.30 %) were also enhanced. Therefore, a novel W/O Pickering emulsion was prepared in this work using ergosterol as an emulsifier solely, which has great potential for application in oil-based food and nutraceutical formulations.
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Affiliation(s)
- Yaxin Wang
- College of Food Science and Engineering, Shanxi Agricultural University, Taigu 030801, China
| | - Yuanhao Guo
- College of Food Science and Engineering, Shanxi Agricultural University, Taigu 030801, China
| | - Pengfei Dong
- College of Food Science and Engineering, Shanxi Agricultural University, Taigu 030801, China
| | - Kai Lin
- College of Food Science and Engineering, Shanxi Agricultural University, Taigu 030801, China
| | - Pengya Du
- College of Food Science and Engineering, Shanxi Agricultural University, Taigu 030801, China
| | - Jinling Cao
- College of Food Science and Engineering, Shanxi Agricultural University, Taigu 030801, China; Shanxi Key Laboratory of Edible Fungi for Loess Plateau, Taigu 030801, China
| | - Yanfen Cheng
- College of Food Science and Engineering, Shanxi Agricultural University, Taigu 030801, China; Shanxi Key Laboratory of Edible Fungi for Loess Plateau, Taigu 030801, China
| | - Feier Cheng
- College of Food Science and Engineering, Shanxi Agricultural University, Taigu 030801, China; Shanxi Key Laboratory of Edible Fungi for Loess Plateau, Taigu 030801, China
| | - Shaojun Yun
- College of Food Science and Engineering, Shanxi Agricultural University, Taigu 030801, China; Shanxi Key Laboratory of Edible Fungi for Loess Plateau, Taigu 030801, China.
| | - Cuiping Feng
- College of Food Science and Engineering, Shanxi Agricultural University, Taigu 030801, China.
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Rey M, Kolker J, Richards JA, Malhotra I, Glen TS, Li NYD, Laidlaw FHJ, Renggli D, Vermant J, Schofield AB, Fujii S, Löwen H, Clegg PS. Interactions between interfaces dictate stimuli-responsive emulsion behaviour. Nat Commun 2023; 14:6723. [PMID: 37872193 PMCID: PMC10593850 DOI: 10.1038/s41467-023-42379-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/07/2022] [Accepted: 10/10/2023] [Indexed: 10/25/2023] Open
Abstract
Stimuli-responsive emulsions offer a dual advantage, combining long-term storage with controlled release triggered by external cues such as pH or temperature changes. This study establishes that thermo-responsive emulsion behaviour is primarily determined by interactions between, rather than within, interfaces. Consequently, the stability of these emulsions is intricately tied to the nature of the stabilizing microgel particles - whether they are more polymeric or colloidal, and the morphology they assume at the liquid interface. The colloidal properties of the microgels provide the foundation for the long-term stability of Pickering emulsions. However, limited deformability can lead to non-responsive emulsions. Conversely, the polymeric properties of the microgels enable them to spread and flatten at the liquid interface, enabling stimuli-responsive behaviour. Furthermore, microgels shared between two emulsion droplets in flocculated emulsions facilitate stimuli-responsiveness, regardless of their internal architecture. This underscores the pivotal role of microgel morphology and the forces they exert on liquid interfaces in the control and design of stimuli-responsive emulsions and interfaces.
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Affiliation(s)
- Marcel Rey
- School of Physics and Astronomy, The University of Edinburgh, Peter Guthrie Tait Road, Edinburgh, EH9 3FD, UK.
- Department of Physics, University of Gothenburg, SE-41296, Gothenburg, Sweden.
| | - Jannis Kolker
- Institute for Theoretical Physics II: Soft Matter, Heinrich-Heine University Düsseldorf, D-40225, Düsseldorf, Germany
| | - James A Richards
- School of Physics and Astronomy, The University of Edinburgh, Peter Guthrie Tait Road, Edinburgh, EH9 3FD, UK
| | - Isha Malhotra
- Institute for Theoretical Physics II: Soft Matter, Heinrich-Heine University Düsseldorf, D-40225, Düsseldorf, Germany
| | - Thomas S Glen
- School of Physics and Astronomy, The University of Edinburgh, Peter Guthrie Tait Road, Edinburgh, EH9 3FD, UK
| | - N Y Denise Li
- School of Physics and Astronomy, The University of Edinburgh, Peter Guthrie Tait Road, Edinburgh, EH9 3FD, UK
| | - Fraser H J Laidlaw
- School of Physics and Astronomy, The University of Edinburgh, Peter Guthrie Tait Road, Edinburgh, EH9 3FD, UK
| | - Damian Renggli
- Department of Materials, ETH Zürich, Vladimir-Prelog-Weg 5, 8093, Zürich, Switzerland
| | - Jan Vermant
- Department of Materials, ETH Zürich, Vladimir-Prelog-Weg 5, 8093, Zürich, Switzerland
| | - Andrew B Schofield
- School of Physics and Astronomy, The University of Edinburgh, Peter Guthrie Tait Road, Edinburgh, EH9 3FD, UK
| | - Syuji Fujii
- Department of Applied Chemistry, Faculty of Engineering, Osaka Institute of Technology, 5-16-1 Omiya, Asahi-ku, Osaka, 535-8585, Japan
- Nanomaterials Microdevices Research Center, Osaka Institute of Technology, 5-16-1 Omiya, Asahi-ku, Osaka, 535-8585, Japan
| | - Hartmut Löwen
- Institute for Theoretical Physics II: Soft Matter, Heinrich-Heine University Düsseldorf, D-40225, Düsseldorf, Germany
| | - Paul S Clegg
- School of Physics and Astronomy, The University of Edinburgh, Peter Guthrie Tait Road, Edinburgh, EH9 3FD, UK
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Destabilization of Pickering emulsions by interfacial transport of mutually soluble solute. J Colloid Interface Sci 2023; 633:166-176. [PMID: 36442288 DOI: 10.1016/j.jcis.2022.10.133] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2022] [Revised: 10/21/2022] [Accepted: 10/26/2022] [Indexed: 11/19/2022]
Abstract
HYPOTHESIS Pickering emulsions (PEs) once formed are highly stable because of very high desorption energies (∼107 kBT) associated with particles adsorbed to the interfaces. The destabilization of PEs is required in many instances for recovery of valuable chemicals, products and active compounds. We propose to exploit interfacial instabilities develop by the addition of different types of solutes to PEs as a route to engineer their destabilization. EXPERIMENTS PEs stabilized by (i) spherical particles, (ii) non-spherical particles, (iii) oppositely charged particle-particle mixtures, and (iv) oppositely charged particle-polyelectrolyte mixtures are formulated. Different types of solutes are added to these highly stable PEs and the macroscopic as well as microscopic changes induced in the PEs is recorded by visual observation and bright field optical microscopy. FINDINGS Our results point to a simple yet robust method to induce destabilization of PEs by transiently perturbing the oil-water interface by transport of a mutually soluble solute across the interface. The generality of the method is demonstrated for different kind of solutes and stabilizers including particles of different sizes (nm to µm), shapes (sphere, spheroids, spherocylinders) and types (polystyrene, metal oxides). The method works for both oil-in-water (o/w) and water-in-oil (w/o) PEs with different kinds of non-polar solvents as oil-phase. However, the method fails when the solute is insoluble in one of the phases of PEs. The study opens up a new approach to destabilization of particle stabilized emulsions.
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Alsmaeil AW, Kouloumpis A, Potsi G, Hammami MA, Kanj MY, Giannelis EP. Probing the Interfacial Properties of Oil-Water Interfaces Decorated with Ionizable, pH Responsive Silica Nanoparticles. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2023; 39:3118-3130. [PMID: 36791471 DOI: 10.1021/acs.langmuir.2c03286] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
Particle-stabilized emulsions (Pickering emulsions) have recently attracted significant attention in scientific studies and for technological applications. The interest stems from the ease of directly assembling the particles at interfaces and modulating the interfacial properties. In this paper, we demonstrate the formation of stable, practical emulsions leveraging the assembly of ionizable, pH responsive silica nanoparticles, surface-functionalized by a mixture of silanes containing amine/ammonium groups, which renders them positively charged. Using pH as the trigger, the assembly and the behavior of the emulsion are controlled by modulating the charges of the functional groups of the nanoparticle and the oil (crude oil). In addition to their tunable charge, the particular combination of silane coupling agents leads to stable particle dispersions, which is critical for practical applications. Atomic force microscopy and interfacial tension (IFT) measurements are used to monitor the assembly, which is controlled by both the electrostatic interactions between the particles and oil and the interparticle interactions, both of which are modulated by pH. Under acidic conditions, when the surfaces of the oil and the nanoparticles (NPs) are positively charged, the NPs are not attracted at the interface and there is no significant reduction in the IFT. In contrast, under basic conditions in which the oil carries a high negative charge and the amine groups on the silica are deprotonated while still positively charged because of the ammonium groups, the NPs assemble at the interface in a closely packed configuration yielding a jammed state with a high dilatational modulus. As a result, two oil droplets do not coalesce even when pushed against each other and the emulsion stability improves significantly. The study provides new insights into the directed assembly of nanoparticles at fluid interfaces relevant to several applications, including environmental remediation, catalysis, drug delivery, food technology, and oil recovery.
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Affiliation(s)
- Ahmed Wasel Alsmaeil
- Robert Frederick Smith School of Chemical and Biomolecular Engineering, Cornell University, Ithaca, New York 14850, United States
- EXPEC Advanced Research Center, Saudi Aramco, Dhahran 31261, Saudi Arabia
| | - Antonios Kouloumpis
- Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14850, United States
| | - Georgia Potsi
- Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14850, United States
| | - Mohamed Amen Hammami
- Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14850, United States
| | - Mazen Yousef Kanj
- College of Petroleum Engineering & Geosciences, King Fahd University of Petroleum & Minerals, Dhahran 31261, Saudi Arabia
| | - Emmanuel P Giannelis
- Department of Materials Science and Engineering, Cornell University, Ithaca, New York 14850, United States
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Biswas S, Karishma S, Ramesh B, Jeganmohan M, Mani E. Light-induced destabilisation of oil-in-water emulsions using light-active bolaform surfactants. SOFT MATTER 2023; 19:199-207. [PMID: 36503968 DOI: 10.1039/d2sm01207c] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
External stimuli-induced destabilisation of oil-in-water emulsions is of both fundamental and technological importance. In this work we synthesize light-active bolaform-type surfactants (LABSs) and show the preparation of decane-in-water emulsions over a range of surfactant and salt concentrations. Under ultraviolet (UV) illumination, LABSs undergo trans to cis isomerization affecting their interfacial activity. Therefore when stable emulsions stabilized by LABSs are exposed to UV light, they undergo partial destabilization. To induce interfacial flow, a small amount of volatile solvent (methanol, ethanol, tetrahydrofuran, etc.) is added at the emulsification stage and in this case complete phase separation is observed. This study demonstrates a facile route to induce destabilization of surfactant-stabilized emulsions using benign solvents and minimal use of energy (UV light) and this method could be of importance in wastewater treatment, enhanced oil recovery, protein separation, etc. where emulsion destabilization is desired.
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Affiliation(s)
- Soumodeep Biswas
- Department of Chemical Engineering, Indian Institute of Technology Madras, Chennai, India.
| | - S Karishma
- Department of Chemical Engineering, Indian Institute of Technology Madras, Chennai, India.
| | - Balu Ramesh
- Department of Chemistry, Indian Institute of Technology Madras, Chennai, India
| | | | - Ethayaraja Mani
- Department of Chemical Engineering, Indian Institute of Technology Madras, Chennai, India.
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8
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Acter S, Vidallon MLP, King JP, Teo BM, Tabor RF. Photothermally responsive Pickering emulsions stabilised by polydopamine nanobowls. J Mater Chem B 2021; 9:8962-8970. [PMID: 34569589 DOI: 10.1039/d1tb01796a] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Pickering emulsions with stimuli responsive properties have attracted mounting research attention owing to their potential for on-demand destabilisation of emulsions. However, a combination of biocompatibility and long-term stability are essential to efficiently apply such systems in biomedical applications, and this remains a significant challenge. To address current limitations, here we report the formation of photothermally responsive oil-in-water (o/w) Pickering emulsions fabricated using biocompatible stabilisers and showing prolonged stability. For the first time, we explore polydopamine (PDA) bowl-shaped mesoporous nanoparticles (PDA nanobowls) as a Pickering stabiliser without any surface modification or other stabiliser present. As-prepared PDA nanobowl-stabilised Pickering emulsions are shown to be pH responsive, and more significantly show high photothermal efficiency under near-infrared illumination due the incorporation of PDA into the system, which has remarkable photothermal response. These biocompatible, photothermally responsive o/w Pickering emulsion systems show potential in controlled drug release applications stimulated by NIR illumination.
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Affiliation(s)
- Shahinur Acter
- School of Chemistry, Monash University, Clayton, Victoria 3800, Australia.
| | | | - Joshua P King
- School of Chemistry, Monash University, Clayton, Victoria 3800, Australia.
| | - Boon Mian Teo
- School of Chemistry, Monash University, Clayton, Victoria 3800, Australia.
| | - Rico F Tabor
- School of Chemistry, Monash University, Clayton, Victoria 3800, Australia.
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Upendar S, Mani E, Basavaraj MG. Pickering emulsions stabilized by sphere-spheroid mixtures. J DISPER SCI TECHNOL 2021. [DOI: 10.1080/01932691.2020.1798778] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Affiliation(s)
- Siliveru Upendar
- Polymer Engineering and Colloid Science Lab (PECS Lab), Department of Chemical Engineering, Indian Institute of Technology Madras, Chennai, Tamil Nadu, India
| | - Ethayaraja Mani
- Polymer Engineering and Colloid Science Lab (PECS Lab), Department of Chemical Engineering, Indian Institute of Technology Madras, Chennai, Tamil Nadu, India
| | - Madivala G. Basavaraj
- Polymer Engineering and Colloid Science Lab (PECS Lab), Department of Chemical Engineering, Indian Institute of Technology Madras, Chennai, Tamil Nadu, India
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Kumar H, Dugyala VR, Basavaraj MG. Phase Inversion of Ellipsoid-Stabilized Emulsions. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2021; 37:7295-7304. [PMID: 34100620 DOI: 10.1021/acs.langmuir.1c00456] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The efficacy of anisotropic particles in Pickering emulsion stabilization, attributed to shape-induced capillary interactions, is well-documented in the literature. In this contribution, we show that the surface of hematite ellipsoids can be modified in situ by the addition of oleic acid to effect transitional phase inversion of Pickering emulsions. Interestingly, incorporation of oleic acid results in the formation of nonspherical emulsion drops. The phase inversion of oil-in-water to water-in-oil and the transition in shape of emulsion drops from spherical to nonspherical is observed in two different particle systems, namely, nanoellipsoids and microellipsoids. The surface of spherical emulsion drops stabilized by particles or particles along with high concentration of oleic acid is found to consist of ellipsoids arranged in a close-packed configuration with their major axis parallel to the interface. In contrast, at intermediate oleic acid concentration, the surface of nonspherical emulsion drops is observed to be covered with loosely packed particle monolayer, with the ellipsoids at the oil/water interface taking up many different orientations. Using contact angle goniometry, the change in the wettability of hematite particles due to adsorption of oleic acid is established to be the mechanism responsible for the phase inversion of Pickering emulsions.
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Affiliation(s)
- Hemant Kumar
- Polymer Engineering and Colloid Science(PECS) Laboratory, Department of Chemical Engineering, Indian Institute of Technology Madras, Chennai - 600036, Tamil Nadu, India
| | - Venkateshwar Rao Dugyala
- Department of Chemical Engineering, Indian Institute of Science Education and Research Bhopal, Bhopal 462 066 Madhya Pradesh, India
| | - Madivala G Basavaraj
- Polymer Engineering and Colloid Science(PECS) Laboratory, Department of Chemical Engineering, Indian Institute of Technology Madras, Chennai - 600036, Tamil Nadu, India
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12
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Shahid S, Basavaraj MG. Controlling the microstructure of emulsions by exploiting particle-polyelectrolyte association. J Colloid Interface Sci 2021; 597:409-421. [PMID: 33895698 DOI: 10.1016/j.jcis.2021.03.148] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2020] [Revised: 03/05/2021] [Accepted: 03/25/2021] [Indexed: 11/20/2022]
Abstract
HYPOTHESIS Albeit solid stabilized emulsions are studied for several decades, the surface of the emulsion drops most often are coated with densely packed and jammed monolayer of particles. However, a control over the area that the particles occupy on the drop surface is necessary, especially in applications involving controlled release of active compounds from emulsions. We hypothesize that it is possible to achieve precise control over the concentration of particles on the surface of emulsions by tailoring the adsorption of different species in a multi-component dispersion used for emulsification. EXPERIMENTS To this end, we carry out emulsification of oil and aqueous dispersions consisting of a combination of oppositely charged colloidal particles and polyelectrolyte. The droplet size distribution and storage stability of the oil-in-water emulsions, the microstructure, the percentage area of the drop surface occupied by the particles and the adsorption behavior of particle-polyelectrolyte binary dispersions are investigated. FINDINGS Our results demonstrate that the association between oppositely charged colloidal particles and polyelectrolyte can be exploited to obtain surface active species that aid in the formation of emulsions. Moreover, we found that the concentration of particle-polyelectrolyte complexes and polyelectrolyte in the dispersions used in emulsification greatly influence the mean diameter of the emulsions and their microstructure. Our findings provide a strategy to achieve control over surface coverage of particles on the emulsion droplets across a wide range - from a theoretically possible maximum, ≈90%, to as low as ≈5%. Interestingly, the emulsions formulated are found to possess excellent storage stability irrespective of the particle coverage on the drop surface.
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Affiliation(s)
- Shumaila Shahid
- Polymer Engineering and Colloid Science Laboratory, Department of Chemical Engineering, Indian Institute of Technology Madras, Chennai - 600036, Tamil Nadu, India
| | - Madivala G Basavaraj
- Polymer Engineering and Colloid Science Laboratory, Department of Chemical Engineering, Indian Institute of Technology Madras, Chennai - 600036, Tamil Nadu, India.
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13
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Meijer JM, Rossi L. Preparation, properties, and applications of magnetic hematite microparticles. SOFT MATTER 2021; 17:2354-2368. [PMID: 33514989 DOI: 10.1039/d0sm01977a] [Citation(s) in RCA: 19] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
Hematite microparticles are becoming increasingly important components in the soft matter field. The remarkable combination of magnetic and photocatalytic properties that characterize them, coupled with the variety of uniform and monodisperse shapes that they can be synthesized in, makes them a one of a kind colloidal model system. Thanks to these properties, hematite microparticles have been recently applied in several important soft matter applications, spanning from novel colloidal building blocks for self-assembly to necessary tools to investigate and understand fundamental problems. In this review article we provide a detailed overview of the traditional methods available for the preparation of hematite microparticles of different shapes, devoting special attention on some of the most common hiccups that could hider a successful synthesis. We furthermore review the particles' most important physico-chemical properties and their most relevant applications in the soft matter field.
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Affiliation(s)
- J M Meijer
- Department of Applied Physics, Eindhoven University of Technology, 5600 MB Eindhoven, The Netherlands
| | - L Rossi
- Department of Chemical Engineering, Delft University of Technology, 2629 HZ Delft, The Netherlands.
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14
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Fernandez-Rodriguez MA, Martín-Molina A, Maldonado-Valderrama J. Microgels at interfaces, from mickering emulsions to flat interfaces and back. Adv Colloid Interface Sci 2021; 288:102350. [PMID: 33418470 DOI: 10.1016/j.cis.2020.102350] [Citation(s) in RCA: 40] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Revised: 12/18/2020] [Accepted: 12/18/2020] [Indexed: 12/22/2022]
Abstract
In this review, we cover the topic of p(NIPAM) based microgels at interfaces, revisiting classical studies in light of the newest ones. In particular, we focus on their use as emulsifiers in the so-called mickering emulsions, i.e. Pickering emulsion stabilized by soft particles. Given the complexity of the experimental characterization and simulation of these soft particles at interfaces, the review is structured in progressive complexity levels, until we reach the highly interesting and promising responsiveness to stimuli of mickering emulsions. We start from the lowest level of complexity, the current understanding of the behavior of single microgels confined at a flat interface. Then, we discuss their collective behavior upon crowding, their responsiveness at interfaces, and their macroscopic properties as microgel films. Once we have the necessary characterization tools, we proceed to discuss the complex and convoluted picture of responsive mickering emulsions. The way is rough, with current controversial and contradicting studies, but it holds promising results as well. We state open questions worth of being tackled by the Soft Matter community, and we conclude that it is worth the trouble of continuing after the master theory of microgel interfacial activity, as it will pave the way to widely adopt responsive mickering emulsions as the worthy Pickering emulsion successors.
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Affiliation(s)
| | - Alberto Martín-Molina
- Department of Applied Physics, University of Granada, Campus de Fuentenueva s/n, 18071 Granada, Spain; Institute Carlos I for Theoretical and Computational Physics, University of Granada, Campus de Fuentenueva s/n, 18071 Granada, Spain
| | - Julia Maldonado-Valderrama
- Department of Applied Physics, University of Granada, Campus de Fuentenueva s/n, 18071 Granada, Spain; Excellence Unit "ModellingNature" (MNat), , University of Granada, Spain.
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Anjali TG, Basavaraj MG. Shape-Anisotropic Colloids at Interfaces. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:3-20. [PMID: 29986588 DOI: 10.1021/acs.langmuir.8b01139] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/20/2023]
Abstract
Research in the 1980s demonstrated the formation of monolayers of particles achieved by interfacial particle trapping as a model system for investigating colloids in two dimensions. Since then, microscopy visualization of two-dimensional particle monolayers and quantification of the microstructure have led to significant fundamental understanding of a number of phenomena such as crystallization, freezing and melting transitions, dislocation dynamics, aggregation kinetics, and others. On the application front, particles at curved interfaces, as often the case in particle-stabilized emulsions and foams, have received considerable attention in the last few decades. The growing interest in the search for novel particles and new strategies to effect emulsion stabilization stems from their application in several disciplines. Moreover, particle-stabilized Pickering emulsions and foams can also be used to derive a number of advanced functional materials. Compared to several accounts of research on spherical colloids at fluid-fluid interfaces, investigations of the behavior of shape-anisotropic particles at interfaces, albeit receiving considerable attention in recent years, are still in a nascent stage. The objective of this feature article is to highlight our recent work in this area. In particular, the adsorption of shape-anisotropic particles to interfaces, wetting behavior, interfacial self-assembly, the response of nonspherical-particle-coated interfaces to compression and shear, and their ability to stabilize emulsions are discussed.
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Affiliation(s)
- Thriveni G Anjali
- Polymer Engineering and Colloid Science (PECS) Laboratory, Department of Chemical Engineering , Indian Institute of Technology Madras , Chennai 600 036 , India
| | - Madivala G Basavaraj
- Polymer Engineering and Colloid Science (PECS) Laboratory, Department of Chemical Engineering , Indian Institute of Technology Madras , Chennai 600 036 , India
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Anjali TG, Basavaraj MG. Influence of pH and Salt Concentration on Pickering Emulsions Stabilized by Colloidal Peanuts. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:13312-13321. [PMID: 30303393 DOI: 10.1021/acs.langmuir.8b02913] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Solid-stabilized emulsions commonly known as Pickering emulsions offer unique benefits such as superior stability and controlled permeability compared to conventional surfactant stabilized emulsions. In this article, the effect of pH, the electrolyte and particle concentration, homogenization speed, and volume fraction of oil on the formation, stability, and the microstructure of emulsion droplets stabilized by micron-size peanut-shaped hematite particles are investigated. The influence of surface charge of particles on emulsification is studied by varying the pH of the dispersing medium, the addition of an electrolyte or a combination of both. Stable O/W emulsions are formed only when the aqueous dispersions at intermediate pH between 4 and 11, and decane (2:1 volume ratio) are vigorously mixed. However, emulsions are not formed when the particles are highly charged that is, at pH 2 and 12. The presence of monovalent salt or high-speed homogenization assists the emulsion formation at pH 3, whereas their combination helps in emulsification at pH 2. However, neither the addition of an electrolyte nor the high-speed homogenization or their combination facilitates the formation of emulsions at pH 12. We show that the image-charge repulsion and the surface charge induced wettability change can explain the influence of both pH and salt concentrations on the formation of Pickering emulsions. Although oil-in-water emulsions typically cream because of the density difference, microscopy observations revealed the presence of a large number of small particle-covered oil droplets in the sediments of the emulsified samples. These drops are observed to be entrapped in dense-particle networks. This leads to a considerable reduction in the number of particles available for the stabilization of floating emulsion droplets and thus influences their size and surface coverage. The possibility of tailoring the stability, droplet size and, the surface coverage discussed in this article can play a crucial role in situations that demand controlled release of active components.
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Affiliation(s)
- Thriveni G Anjali
- Polymer Engineering and Colloid Science (PECS) Laboratory, Department of Chemical Engineering , Indian Institute of Technology Madras , Chennai 600 036 , India
| | - Madivala G Basavaraj
- Polymer Engineering and Colloid Science (PECS) Laboratory, Department of Chemical Engineering , Indian Institute of Technology Madras , Chennai 600 036 , India
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Pentyala P, Shahid M, Ramamirtham S, Basavaraj MG. Porous materials from oppositely charged nanoparticle gel emulsions. Colloids Surf A Physicochem Eng Asp 2018. [DOI: 10.1016/j.colsurfa.2018.02.026] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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