Here, we report plasmonic metamolecules with dynamically controllable optical magnetism. A dynamic metamolecule (DMM) is constructed by decorating gold or silver nanobeads on a thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) hydrogel sphere, which generates uniform core-satellite-Type assembly structures with an interbead distance, allowing for strong interparticle coupling. Experimental and simulation results revealed strong magnetic dipole and quadrupole modes observable in the far field both for gold and silver DMMs when the temperature was set above the lower critical solution temperature (LCST) of PNIPAM. Interestingly, gold DMMs showed stronger and more pronounced magnetic resonances than silver DMMs, despite the general notion that silver nanostructures possess superior plasmonic properties. The strong magnetic coupling and structural uniformity along with the ability to dynamically control the assembly structure allowed us to probe distinct optical magnetism in gold and silver and experimentally observe magnetic quadrupole in solution-phase metamolecules for the first time.
Bibliographical noteFunding Information:
S.-J.P. acknowledges the financial support from the National Research Foundation (NRF) of Korea (NRF-2018R1A2B3001049) and the Science Research Center (SRC) funded by NRF (NRF-2017R1A5A1015365). Z.F., C.N.W., and O.I. acknowledge funding from the Penn Laboratory for Research in Structure of Matter (LRSM) funded by NSF MRSEC grant (DMR-1720530), the Department of Chemistry (summer fellowship for O.I.), and the School of Arts and Sciences Dean’s Global Inquiries Fund at the University of Pennsylvania (Funded visit to South Korea for C.N.W.). C.N.W. was supported by a fellowship from the REACT for the Human Habitats Program at Penn (through NSF PIRE Grant #OISE-1545884). E.C.C. acknowledges the financial support from the NRF (NRF-2019R1A2C1004306).
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