Multiplexed Laser-like Behavior of Monodisperse TiO 2 /Au Composite Microspheres Designed by Microfluidics

To create hybrid whispering-gallery mode (WGM) and localized surface plasmon resonance structures, this work combines gold (Au) nanoparticles (NPs) incorporated within or on the surface of monodisperse titanium dioxide (TiO 2 ) microspheres of tunable diameter by using droplet-based microfluidic technology. We investigated the impact of the spatial organization of plasmonic nanoparticles on optical coupling. Due to the monodispersity of the TiO 2 resonators, coupling between the WGM and the Au plasmonic NPs measured across a statistical ensemble of particles occurs at discrete wavelengths, resulting in enhancements of plasmonic absorption by up to 40 times. These results demonstrate the importance of the material composition and geometry in regulating light confinement, suggesting that these monodisperse microspheres hold great promise for advanced biosensing systems and photocatalytic applications.