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Huang X, Li X, Zhang Y, Li X, Zhang P, Song H, Huang Q, Fu G. Influence mechanisms of linoleic acid and oleic acid on the gel properties of egg yolk protein. JOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE 2024; 104:6787-6798. [PMID: 38567870 DOI: 10.1002/jsfa.13507] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/06/2024] [Revised: 03/07/2024] [Accepted: 04/03/2024] [Indexed: 04/18/2024]
Abstract
BACKGROUND Gel property is among the crucial functional properties of egg yolk (EY), which determines the texture and flavor of EY products. In the present study, the effects of two unsaturated fatty acids [monounsaturated fatty acid oleic acid (OA) and diunsaturated fatty acid linoleic acid (LA)] on the gel properties of EY protein were investigated. RESULTS Compared with the blank group, the addition of LA and OA (10-50 g kg-1) improved the gel hardness (from 270.54 g to 385.85 g and 414.38 g, respectively) and viscosity coefficient (from 0.015 Pa.sn to 11.892 Pa.sn and 1.812 Pa.sn, respectively). The surface hydrophobicity of EY protein increased to a maximum value of 40 g kg-1 with the addition of both fatty acids (39.06 μg and 41.58 μg, respectively). However, excess unsaturated fatty acids (≥ 50 g kg-1) disrupted the completeness of the gel matrix and weakened the structural properties of the EY gel. CONCLUSION Both fatty acids improved the gel properties of EY protein. At the same addition level, OA was superior to LA in improving gel properties. The present study provides a theoretical underpinning for the sensible application of unsaturated fatty acids in improving EY gel properties. © 2024 Society of Chemical Industry.
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Affiliation(s)
- Xinyuan Huang
- State Key Laboratory of Food Science and Resources, Nanchang University, Nanchang, China
- School of Public Health, Guizhou Province Engineering Research Center of Health Food Innovative Manufacturing, Guizhou Medical University, Guiyang, China
- Engineering Research Centre of Fujian-Taiwan Special Marine Food Processing and Nutrition of Ministry of Education, College of Food Science, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Xin Li
- State Key Laboratory of Food Science and Resources, Nanchang University, Nanchang, China
- School of Public Health, Guizhou Province Engineering Research Center of Health Food Innovative Manufacturing, Guizhou Medical University, Guiyang, China
- Engineering Research Centre of Fujian-Taiwan Special Marine Food Processing and Nutrition of Ministry of Education, College of Food Science, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Yufeng Zhang
- School of Public Health, Guizhou Province Engineering Research Center of Health Food Innovative Manufacturing, Guizhou Medical University, Guiyang, China
- Engineering Research Centre of Fujian-Taiwan Special Marine Food Processing and Nutrition of Ministry of Education, College of Food Science, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Xiefei Li
- State Key Laboratory of Food Science and Resources, Nanchang University, Nanchang, China
- School of Public Health, Guizhou Province Engineering Research Center of Health Food Innovative Manufacturing, Guizhou Medical University, Guiyang, China
| | - Pei Zhang
- School of Public Health, Guizhou Province Engineering Research Center of Health Food Innovative Manufacturing, Guizhou Medical University, Guiyang, China
- Engineering Research Centre of Fujian-Taiwan Special Marine Food Processing and Nutrition of Ministry of Education, College of Food Science, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Hongbo Song
- Engineering Research Centre of Fujian-Taiwan Special Marine Food Processing and Nutrition of Ministry of Education, College of Food Science, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Qun Huang
- State Key Laboratory of Food Science and Resources, Nanchang University, Nanchang, China
- School of Public Health, Guizhou Province Engineering Research Center of Health Food Innovative Manufacturing, Guizhou Medical University, Guiyang, China
- Engineering Research Centre of Fujian-Taiwan Special Marine Food Processing and Nutrition of Ministry of Education, College of Food Science, Fujian Agriculture and Forestry University, Fuzhou, China
| | - Guiming Fu
- State Key Laboratory of Food Science and Resources, Nanchang University, Nanchang, China
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Zhang T, Wang Q, Yang Y, Hou L, Zheng W, Wu Z, Wang Z. Revealing the contradiction between DLVO/XDLVO theory and membrane fouling propensity for oil-in-water emulsion separation. JOURNAL OF HAZARDOUS MATERIALS 2024; 466:133594. [PMID: 38290334 DOI: 10.1016/j.jhazmat.2024.133594] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2023] [Revised: 01/06/2024] [Accepted: 01/20/2024] [Indexed: 02/01/2024]
Abstract
Oil fouling is the crucial issue for the separation of oil-in-water emulsion by membrane technology. The latest research found that the membrane fouling rate was opposite to the widely used theoretical prediction by Derjaguin-Landau-Verwey-Overbeek (DLVO) or extended DLVO (XDLVO) theory. To interpret the contradiction, the molecular dynamics was adopted to explore the molecular behavior of oil and emulsifier (Tween 80) at membrane interface with the assistance of DLVO/XDLVO theory and membrane fouling models. The decreased flux attenuation and fitting of fouling models proved that the existence of Tween 80 effectively alleviated membrane fouling. Conversely, DLVO/XDLVO theory predicted that the membrane fouling should be exacerbated with the increase of Tween 80 concentration in O/W emulsion. This contradiction originated from the different interaction energy between oil/Tween 80 molecules and polyether sulfone (PES) membrane. The favorable free energy of Tween 80 was resulted from the sulfuryl groups in PES and hydrogen bonds (O-H…O) formation further strengthened the interaction. Therefore, Tween 80 could preferentially adsorb on membrane surface and form an isolation layer by demulsification and steric hindrance and resist the aggregation of oil, which effectively alleviated membrane fouling. This study provided a new insight in the interpretation of interaction in O/W emulsion.
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Affiliation(s)
- Tong Zhang
- State Key Laboratory of Pollution Control and Resource Reuse, Shanghai Institute of Pollution Control and Ecological Security, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China
| | - Qiaoying Wang
- State Key Laboratory of Pollution Control and Resource Reuse, Shanghai Institute of Pollution Control and Ecological Security, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China.
| | - Yan Yang
- China South-to-North Water Diversion Corporation Limited, Beijing 100036, China
| | - Linxi Hou
- State Key Laboratory of Pollution Control and Resource Reuse, Shanghai Institute of Pollution Control and Ecological Security, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China
| | - Wenjia Zheng
- State Key Laboratory of Pollution Control and Resource Reuse, Shanghai Institute of Pollution Control and Ecological Security, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China
| | - Zhichao Wu
- State Key Laboratory of Pollution Control and Resource Reuse, Shanghai Institute of Pollution Control and Ecological Security, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China
| | - Zhiwei Wang
- State Key Laboratory of Pollution Control and Resource Reuse, Shanghai Institute of Pollution Control and Ecological Security, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China
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Wang Y, Feng T, Xia Q, Zhou C, Cao J. The Influence of Comminuting Methods on the Structure, Morphology, and Calcium Release of Chicken Bones. Front Nutr 2022; 9:910435. [PMID: 35711560 PMCID: PMC9193221 DOI: 10.3389/fnut.2022.910435] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2022] [Accepted: 04/19/2022] [Indexed: 11/13/2022] Open
Abstract
This work aimed at assessing the influence of comminuting methods, including colloid mill, planetary ball mill and dynamic high-pressure microfluidization on the chemical composition, particle properties, morphology and calcium release of chicken bone. The results showed that planetary ball mill and dynamic high-pressure microfluidization could reduce the particle size of bone powder, and the particle size of sample treated by dynamic high-pressure microfluidization reached 446 nm. Chicken bone particles were negatively charged, and the absolute value of zeta potential was significantly reduced after milling treatments. Furthermore, X-ray diffraction and Fourier-transform infrared spectroscopy (FTIR) analysis indicated that the planetary ball mill and dynamic high-pressure microfluidization processes presented no significant effect on the internal chemical structure of bone particles. Compared with the other groups, samples treated by dynamic high-pressure microfluidization released more calcium ions, which was related to the significant effects on surface calcium composition and reducing particle size. Therefore, dynamic high-pressure microfluidization has a great potential in the processing of bone-derived products, particularly for the design and development of bone-derived product with high calcium bioaccessibility.
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Affiliation(s)
- Ying Wang
- School of Food and Health, Beijing Technology and Business University, Beijing, China
| | - Tao Feng
- State-Owned Assets and Laboratory Management Office, Anhui Polytechnic University, Anhui, China
| | - Qiang Xia
- College of Food and Pharmaceutical Sciences, Ningbo University, Ningbo, China
| | - Changyu Zhou
- College of Food and Pharmaceutical Sciences, Ningbo University, Ningbo, China
| | - Jinxuan Cao
- School of Food and Health, Beijing Technology and Business University, Beijing, China
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Liu L, Huang X, Geng F, Huang Q. Optimization of preparation process of egg white protein/
κ
‐carrageenan composite film. J FOOD PROCESS PRES 2021. [DOI: 10.1111/jfpp.16167] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Affiliation(s)
- Lan Liu
- Fujian Provincial Key Laboratory of Quality Science and Processing Technology in Special Starch College of Food Science Fujian Agriculture and Forestry University Fuzhou China
- School of Public Health Guizhou Medical University Guiyang China
| | - Xiang Huang
- Fujian Provincial Key Laboratory of Quality Science and Processing Technology in Special Starch College of Food Science Fujian Agriculture and Forestry University Fuzhou China
- School of Public Health Guizhou Medical University Guiyang China
| | - Fang Geng
- Key Laboratory of Coarse Cereal Processing (Ministry of Agriculture and Rural Affairs) School of Food and Biological Engineering Chengdu University Chengdu China
| | - Qun Huang
- Fujian Provincial Key Laboratory of Quality Science and Processing Technology in Special Starch College of Food Science Fujian Agriculture and Forestry University Fuzhou China
- School of Public Health Guizhou Medical University Guiyang China
- Key Laboratory of Coarse Cereal Processing (Ministry of Agriculture and Rural Affairs) School of Food and Biological Engineering Chengdu University Chengdu China
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5
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Physicochemical and structural characteristics of nano eggshell calcium prepared by wet ball milling. Lebensm Wiss Technol 2020. [DOI: 10.1016/j.lwt.2020.109721] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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AHN SI, CHOGSOM C, LEE YK, KWAK HS, CHANG YH. Optimization of the conditions for producing water-in-oil-in-water microemulsions and spray-dried microcapsule of tomato extract powder. FOOD SCIENCE AND TECHNOLOGY 2019. [DOI: 10.1590/fst.42017] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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7
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Min JY, Lee YK, Chang YH, Kwak HS. Red ginseng extract capsule fabricated using W/O/W emulsion techniques. INTERNATIONAL JOURNAL OF FOOD PROPERTIES 2018. [DOI: 10.1080/10942912.2017.1354016] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Affiliation(s)
- Ji-Young Min
- Department of Food Science and Technology, Sejong University, Seoul, Korea
| | - Yun-Kyung Lee
- Department of Food and Nutrition, Kyung Hee University, Seoul, Korea
| | - Yoon Hyuk Chang
- Department of Food and Nutrition, Kyung Hee University, Seoul, Korea
| | - Hae-Soo Kwak
- Department of Food Science and Technology, Sejong University, Seoul, Korea
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8
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Khademi M, Wang W, Reitinger W, Barz DPJ. Zeta Potential of Poly(methyl methacrylate) (PMMA) in Contact with Aqueous Electrolyte-Surfactant Solutions. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:10473-10482. [PMID: 28915350 DOI: 10.1021/acs.langmuir.7b02487] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/28/2023]
Abstract
The addition of surfactants can considerably impact the electrical characteristics of an interface, and the zeta potential measurement is the standard method for its characterization. In this article, a comprehensive study of the zeta potential of poly(methyl methacrylate) (PMMA) in contact with aqueous solutions containing an anionic, a cationic, or a zwitterionic surfactant at different pH and ionic strength values is conducted. Electrophoretic mobilities are inferred from electrophoretic light scattering measurements of the particulate PMMA. These values can be converted into zeta potentials using permittivity and viscosity measurements of the continuous phase. Different behaviors are observed for each surfactant type, which can be explained with the various adsorption mechanisms on PMMA. For the anionic surfactant, the absolute zeta potential value below the critical micelle concentration (CMC) increases with the concentration, while it becomes rather constant around the CMC. At concentrations above the CMC, the absolute zeta potential increases again. We propose that hydrophobic-based adsorption and, at higher concentrations, the competing micellization process drive this behavior. The addition of cationic surfactant results in an isoelectric point below the CMC where the negative surface charge is neutralized by a layer of adsorbed cationic surfactant. At concentrations near the CMC, the positive zeta potential is rather constant. In this case, we propose that electrostatic interactions combined with hydrophobic adsorption are responsible for the observed behavior. The zeta potential in the presence of zwitterionic surfactant is influenced by the adsorption, because of hydrophobic interactions between the surfactant tail and the PMMA surface. However, there is less influence, compared to the ionic surfactants. For all three surfactant types, the zeta potential changes to more-negative or less-positive values for alkaline pH values, because of hydroxide adsorption. An increase of the ionic strength decreases the absolute value of the zeta potential, because of the shielding effects.
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Affiliation(s)
- Mahmoud Khademi
- Department of Chemical Engineering, Queen's University , Kingston, Ontario, Canada K7L 3N6
| | - Wuchun Wang
- Department of Chemical Engineering, Queen's University , Kingston, Ontario, Canada K7L 3N6
| | - Wolfgang Reitinger
- Department of Chemical Engineering, Queen's University , Kingston, Ontario, Canada K7L 3N6
| | - Dominik P J Barz
- Department of Chemical Engineering, Queen's University , Kingston, Ontario, Canada K7L 3N6
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Ambade SB, Ambade RB, Lee W, Mane RS, Yoon SC, Lee SH. Development of highly transparent seedless ZnO nanorods engineered for inverted polymer solar cells. NANOSCALE 2014; 6:12130-12141. [PMID: 25201162 DOI: 10.1039/c4nr03080j] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
This work reports on inverted polymer solar cells (IPSCs) based on highly transparent (>95%), hydrophobic, seedless ZnO nanorods (NRs) as cathode buffers with extremely enhanced electrical characteristics. The transparent NR suspension with stability for more than a year is achieved by adding a small amount of 2-(2-methoxyethoxy) acetic acid (MEA). The ability of the stable nanorod suspension to easily spin-coat is certainly an advance to the fabrication of films over large areas and to replace the conventional seeding method to grow one-dimensional nanostructures for use in optoelectronic devices. We observe a strong correlation between the photovoltaic performance and the transparency of ZnO NRs. IPSCs using poly-3-hexylthiophene (P3HT) and [6,6]-phenyl C60 butyric acid methyl ester (PCBM) mixtures in the active layer and transparent (MEA-capped) ZnO NRs as cathode buffers exhibit a power conversion efficiency of 3.24% under simulated AM 1.5G, 100 mW cm(-2) illumination.
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Affiliation(s)
- Swapnil B Ambade
- School of Semiconductor and Chemical Engineering, Chonbuk National University, 664-14, 1-ga Deokjin-dong, Deokjin-gu, Jeonju, Jeonbuk 561-756, Republic of Korea.
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TAKAYANAGI T, INOUE G, IKUTA A. Analysis of Binding Equilibrium of Phenylalkylamines to Brij 58 Micelle through the Measurement of Electrophoretic Mobility by CZE. CHROMATOGRAPHY 2014. [DOI: 10.15583/jpchrom.2014.024] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Affiliation(s)
- Toshio TAKAYANAGI
- Division of Chemistry and Biochemistry, Graduate School of Natural Science and Technology, Okayama University
| | - Genki INOUE
- Division of Chemistry and Biochemistry, Graduate School of Natural Science and Technology, Okayama University
| | - Ayumi IKUTA
- Division of Chemistry and Biochemistry, Graduate School of Natural Science and Technology, Okayama University
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11
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Mijan MA, Kim DH, Kwak HS. Physicochemical properties of nanopowdered eggshell. Int J Food Sci Technol 2013. [DOI: 10.1111/ijfs.12451] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Affiliation(s)
- Mohammad Al Mijan
- Department of Food Science and Technology; Sejong University; Seoul 143-747 Korea
| | - Dong-Hwi Kim
- Department of Food Science and Technology; Sejong University; Seoul 143-747 Korea
| | - Hae-Soo Kwak
- Department of Food Science and Technology; Sejong University; Seoul 143-747 Korea
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12
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Lin CH, Ferguson GS, Chaudhury MK. Electrokinetics of polar liquids in contact with nonpolar surfaces. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2013; 29:7793-7801. [PMID: 23701297 DOI: 10.1021/la4008813] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Zeta potentials of several polar protic (water, ethylene glycol, and formamide) as well as polar aprotic (dimethyl sulfoxide) liquids were measured in contact with three nonpolar surfaces using closed-cell electroosmosis. The test surfaces were chemisorbed monolayers of alkyl siloxanes, fluoroalkyl siloxanes, and polydimethylsiloxanes (PDMS) grafted on glass slides. All these liquids exhibited substantial electrokinetics in contact with the nonpolar surfaces with these observations: the electrokinetic effect on the fluorocarbon-coated surface is the strongest and on a PDMS grafted surface, the effect is the weakest. Even though these hygroscopic liquids contain small amounts of water, the current models of charging based on the adsorption of hydroxide ions at the interface or the dissociation of pre-existing functionalities (e.g., silanol groups) appear to be insufficient to account for the various facets of the experimental observations. The results illustrate how ubiquitous the phenomenon of electrokinetics is with polar liquids contacting such apparently passive nonpolar surfaces. We hope that these results will inspire further experimental and theoretical studies in this important area of research that has potential practical implications.
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Affiliation(s)
- Chih-Hsiu Lin
- Department of Chemical Engineering, Lehigh University, Bethlehem, Pennsylvania 18015, USA
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13
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NGUYEN HOANGHAI, CHOI KYEONGOK, KIM DONGEUN, KANG WIESOO, KO SANGHOON. IMPROVEMENT OF OXIDATIVE STABILITY OF RICE BRAN OIL EMULSION BY CONTROLLING DROPLET SIZE. J FOOD PROCESS PRES 2012. [DOI: 10.1111/j.1745-4549.2011.00633.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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14
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Yang Z, Abbott NL. Spontaneous formation of water droplets at oil-solid interfaces. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2010; 26:13797-804. [PMID: 20712383 PMCID: PMC2951552 DOI: 10.1021/la101740p] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
We report observations of spontaneous formation of micrometer-sized water droplets within micrometer-thick films of a range of different oils (isotropic and nematic 4-cyano-4'-pentylbiphenyl (5CB) and silicone, olive and corn oil) that are supported on glass substrates treated with octadecyltrichlorosilane (OTS) and immersed under water. Confocal imaging was used to determine that the water droplets nucleate and grow at the interface between the oils and OTS-treated glass with a contact angle of approximately 130 degrees. A simple thermodynamic model based on macroscopic interfacial energetic arguments consistent with the contact angle of 130 degrees, however, fails to account for the spontaneous formation of the water droplets. zeta-potential measurements performed with OTS-treated glass (-59.0 +/- 16.4 mV) and hydrophobic monolayers formed on gold films (2.0 +/- 0.7 mV), when combined with the observed absence of droplet formation under films of oil supported on the latter surfaces, suggest that the charge of the oil-solid interface promotes partitioning of water to the interfacial region. The hydrophobic nature of the OTS-treated glass promotes dewetting of water accumulated in the interfacial region into droplets (a thin film of water is seen to form on bare glass). The inhibitory effect on droplet formation of both salt (NaCl) and sucrose (0.1-500 mM) added to the aqueous phase was similar, indicating that both solutes lower the chemical potential of the bulk water (osmotic effect) sufficiently to prevent partitioning of the water to the interface between the oil and supporting substrates. These results suggest that charged, hydrophobic surfaces can provide routes to spontaneous formation of surface-supported, water-in-oil emulsions.
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Affiliation(s)
- Zhongqiang Yang
- Department of Chemical & Biological Engineering, University of Wisconsin-Madison 1415 Engineering Drive, Madison, Wisconsin 53706, USA
| | - Nicholas L. Abbott
- Department of Chemical & Biological Engineering, University of Wisconsin-Madison 1415 Engineering Drive, Madison, Wisconsin 53706, USA
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Barz DPJ, Vogel MJ, Steen PH. Determination of the zeta potential of porous substrates by droplet deflection. I. The influence of ionic strength and pH value of an aqueous electrolyte in contact with a borosilicate surface. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2009; 25:1842-1850. [PMID: 19170651 DOI: 10.1021/la802949z] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/27/2023]
Abstract
This paper presents a new method to determine the zeta potential of porous substrates in contact with a liquid. Electroosmosis, arising near the solid/liquid boundaries within a fully saturated porous substrate, pumps against the capillary pressure arising from the surface tension of a droplet placed in series with the pump. The method is based on measuring the liquid/gas interface deflection due to the imposed electric potential difference. The distinguishing features of our technique are accuracy, speed, and reliability, accomplished with a straightforward and cost-effective setup. In this particular setup, a bistable configuration of two opposing droplets is used. The energy barrier between the stable states defines the range of capillary resistance and can be tuned by the total droplet volume. The electroosmotic pump is placed between the droplets. The large surface area-to-volume ratio of the porous substrate enables the pumping strength to exceed the capillary resistance even for droplets small enough that their shapes are negligibly influenced by gravity. Using a relatively simple model for the flow within the porous substrate, the zeta potential resulting from the substrate-liquid combination is determined. Extensive measurements of a borosilicate substrate in contact with different aqueous electrolytes are made. The results of the measurements clarify the influence of the ionic strength and pH value on the zeta potential and yield an empirical relationship important to engineering approaches.
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Affiliation(s)
- Dominik P J Barz
- Forschungszentrum Karlsruhe, IKET - Chemical Process Technology, P.O. Box 3640, D-76021 Karlsruhe, Germany.
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