UC Riverside

Plasmonic nanoparticles are known for their unique optical properties originating from the localized surface plasmon resonance. Assembling plasmonic nanoparticles into secondary superstructures induces plasmonic coupling, producing tunable optical properties. However, current assembly strategies lack dynamic control over the assembly, limiting real-time applications. Magnetic assembly has proven to be an effective strategy to manipulate the interaction between magneto-plasmonic nanoparticles, generating dynamically tunable optical properties featuring fast response, full reversibility, and remote control. This dissertation focuses on developing optically functional nanostructures by magnetically assembling plasmonic nanoparticles into secondary superstructures. In the first part, one-dimensional (1D) plasmonic photonic crystals with angular-dependent structural colors are fabricated by assembling magneto-plasmonic nanoparticles under an external magnetic field. Different from conventional 1D photonic crystals, the assembled 1D nanochains show angular-dependent colors from the selective activation of photonic diffraction and plasmonic scattering. In the second part, we develop magnetically tunable plasmonic chiral nanostructures by assembling magneto-plasmonic nanoparticles under a helical magnetic field from a cubic permanent magnet. The handedness and magnitude and position of the resulting circular dichroism (CD) spectra can be dynamically tuned by the orientation and strength of the helical magnetic field. In addition, we find that the chiral nanostructures are not formed from the helical alignment of magneto-plasmonic nanoparticles, but instead, the nanoparticles align along the magnetic field direction to form 1D linear periodic nanochains, which further assemble into chiral superstructures under the helical magnetic field. This assembly incorporates plasmonic coupling, photonic diffraction, and chirality into a single system, allowing multi-mode colors with selective activation and dynamic tunability. Furthermore, this helical magnetic assembly method is developed to fabricate chiral luminescent nanostructures by assembling magneto-luminescent hybrid clusters under the helical magnetic field, realizing magnetically tunable circularly polarized luminescence. In the last part, we develop a general strategy for fabricating plasmonic chiral nanostructures by stacking polymer films containing magnetically assembled linear plasmonic nanochains and further demonstrate dynamic control over the chiral optical properties by controlling the stacking angle. Overall, the magnetic assembly of plasmonic nanoparticles generates novel optical properties with dynamic tunability, promising for color displays, sensors, and optical devices.