Plasmonic Janus microspheres are designed from Pickering emulsions. A regular array of dimples is prepared on the surface of the microspheres using an array of particles at the emulsion interface as templates, on which plasmonic nanostructures are created by directional deposition of metal. This class of plasmonic microgranules with a controlled plasmonic property will provide new opportunities for various optical applications.Metal nanostructures have been created in a film format to develop unique plasmonic properties. Here, well?defined metal nanostructures are designed on the surface of microspheres to provide plasmonic microgranules. As conventional techniques are inadequate for nanofabrication on spherical surfaces, photocurable emulsion drops with a regular array of silica particles are employed at the interface to create periodic nanostructures. The silica particles, originating from the dispersed phase, fully cover the interface by forming a non?close?packed hexagonal array after drop generation, and slowly protrude to the continuous phase during aging while their interparticle separation decreases. Therefore, hexagonal arrays of spherical dimples with controlled geometry and separation are created on the surface of microspheres by photocuring the drops and removing the particles. Directional deposition of either aluminum or gold results in a continuous film with a hexagonal array of holes on the outermost surface and isolated curved disks in dimples, which renders the hemisphere of microspheres plasmonically colored. The resonant wavelength is controlled by adjusting the aging time, metal thickness, and size of silica particles, providing various plasmonic colors. This granular format of the plasmonic Janus microspheres will open a new avenue of optical applications including active color pixels, optical barcodes, and microsensors.

» Author: Jong Bin Kim, Su Yeon Lee, Nam Gi Min, Seung Yeol Lee, Shin?Hyun Kim

» Reference: doi:10.1002/adma.202001384

» Publication Date: 14/05/2020

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