Emerging advances in plasmonic nanoassemblies for biosensing and cell imaging

Integrating discrete plasmonic nanoparticles into assemblies can induce plasmonic coupling that produces collective plasmonic properties, which are not available for single nanoparticles. Theoretical analysis revealed that plasmonic coupling derived from assemblies could produce stronger electromagnetic field enhancement effects. Thus, plasmonic assemblies enable better performance in plasmon-based applications, such as enhanced fluorescence and Raman effects. This makes them hold great potential for trace analyte detection and nanomedicine. Herein, we focus on the recent advances in various plasmonic nanoassembles such as dimers, tetramers, and core-satellite structures, and discuss their applications in biosensing and cell imaging. The fabrication strategies for self-assembled plasmonic nanostructures are described, including top-down strategies, self-assembly methods linked by DNA, ligand, polymer, amino acid, or proteins, and chemical overgrowth methods. Thereafter, their applications in biosensor and cell imaging based on dark-field imaging, surface-enhanced Raman scattering, plasmonic circular dichroism, and fluorescence imaging are discussed. Finally, the remaining challenges and prospects are elucidated.