Lecturer: |
Dr. Yi Gi-Ra is a professor of Pohang University of Science and Techonology. He received his PhD from the Korea Advanced Institute of Science and Technology (KAIST) in 2003. After a postdocs at University of California, Santa Barbara in America, he started his work as senior researcher in LG Chem Research Park in 2002 and then moved to Korea Basic Science Institute in 2004. He moved to Chungbuk in 2009 and became an assistant professor in Chungbuk National University. He enter Sungkyunkwan University in 2012 and become asscociate professor in 2013. He moved to Pohang University of Science and Techonology in 2020. His current research interests include photonic crystals, colloidal assembly, mesoporous nanoparticles and colorimetiric sensor arrays. Dr. Yi has published over 240 peer-reviewed papers (H-index = 58, total citations > 11,000 based on Google Scholar) and numerous books and book chapters. He is the editor of “Macromolecular Research”, the associate Editor of “Frontiers in Materials” and the editorial board of “Particle & Particle Systems Characterization”. |
Abstract: |
Colloidal clusters are prepared by assembling positively charged cross-linked polystyrene (PS) particles onto negatively charged liquid cores of swollen polymer particles. PS particles at the interface of the liquid core are closely packed around the core due to interfacial wetting. Then, by evaporating solvent in the liquid cores, polymers in the cores are solidified and the clusters are cemented. As the swelling ratio of PS cores increases, cores at the center of colloidal clusters are exposed, forming patchy colloidal clusters. Finally, by density gradient centrifugation, high-purity symmetric colloidal clusters are obtained. When silica-PS core-shell particles are swollen and serve as the liquid cores, hybrid colloidal clusters are obtained in which each silica nanoparticle is relocated to the liquid core interface during the swelling-deswelling process breaking symmetry in colloidal clusters as the silica nanoparticle in the core is comparable in size with the PS particle in the shell. The configuration of colloidal clusters is determined once the number of particles around the liquid core is given, which depends on the size ratio of the liquid core and shell particle. Since hybrid clusters are heavier than PS particles, they can be purified using centrifugation. Finally, colloidal clusters and patchy clusters are coated with DNA brushes for building up superstructures. |
