Speaker:Professor Wang Dayang
Date:June. 26, 2019
Location:Lecture Hall, Old Building of the School of Chemistry and Chemical Engineering, Central Campus
1998, polymer chemistry and physics, Department ofChemistry, Jilin University, Ph.D.,
1999-2003, H. mohwald,Interface Department of Max PlanckColloidalInterface Institute, postdoctoral,
2003-2010,Interface Department of Max PlanckColloidalInterface Institute,group leader,
2010-2015,Ian wark Institute, University of South Australia,LifetimeProfessor ofPhysicalChemistry,
2014, School ofChemistry, Jilin University, Professor of Changbaishan scholar lecture,
2015-2017, School ofTechnology, Royal Melbourne University,Professor of the Department of chemical engineering,
2016 to now, Jilin University,Professor of theSchool ofChemistry,
Abstract:The stabilization of Pickering emulsion is commonly recognized as a result of large energy for solid particles to be removed from oil/water interfaces to either of bulk phases. This detachment energy rapidly falls to less 10 KT when the contact angle of the particles at the interfaces is lower than 20 degree. As such, highly hydrophilic particles cannot effectively stabilize emulsions. Here we demonstrate that when the electrostatic repulsion between charged particles and oil droplets is significantly reduced close to zero by varying the dispersion pH, the particles can effectively and efficiently stabilize oil-in-water emulsions; the emulsions can remain stable for several months. This works not only for silica particles with sizes ranging from 15 nm to 250 nm, stabilized with and without lysine, but also for 14 nm gold nanoparticles stabilized by citrate. According to our current experimental data, we attribute this unusual emulsion stabilization by highly hydrophilic particles to the Van Der Waals attractive energy between oil droplets and the particle ensembles enclosing the droplets. This is very different from classic Pickering emulsion stabilization, which is determined dominantly by the surface wetting energy of solid particles, and thus opens up a new mechanism for emulsion stabilization.
Refs.:1. Hydrophobic-Force-Driven Removal of Organic Compounds from Water byReduced Graphene Oxides Generated in Agarose Hydrogels,Angew. Chem. Int. Ed.57 (2018), 11177-11181.2.Van der Waals Emulsions: Emulsions Stabilized by Surface- Inactive, Hydrophilic Particles via van der Waals Attraction,Angew. Chem. Int. Ed.57 (2018), 9510-9514. 3. A Simple Nanocellulose Coating for Self-Cleaning upon Water Action: Molecular Design of Stable Surface Hydrophilicity,Angew, Chem. Ini. Ed.56 (2017), 9053-9057. 4. Hydrogel-Assisted Transfer of Graphene Oxide into Nonpolar Organic Media for Oil Decontamination,Angew. Chem. Int. Ed.55 (2016), 6853-6857. 5. lon-Spccific Oil Repellency of Polyelcctrolyte Multilayers in Water: Molecular Insightinto Charged Surface Hydrophilicity,Chem. Int. Ed.54 (2015),4851-4856.
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Edited by Zhang Hao