Theoretical Study of the Self-Assembly and Optical Properties of 1D Chains of Magnetic-Plasmonic Nanoparticles

A study is presented of the self-assembly arid optical liehavior of one-dimensional (1D) chains of colloidal magnetic plasmonic core shell Fe3O4@Au nanoparticles. The superparamagnetic core enables adaptive magnetophoretic control of the particles and provides interparticle coupling that drives the assembly process. The plasmonic shell provides unique optical and photothermal properties of assembled structures. Monte Carlo analysis and full wave field theory are combined to investigate the self-assembly and Optical properties of 1D chains, respectfully. The Monte Carlo simulations demonstrate that the particle volume fraction and surface charge can be tailored to control the formation, aggregation, and spacing of chains. The optical analysis shows that as a chain forms its absorption spectrum red shifts and asymptotically converges to that of an infinite chain. In addition, strong field enhancement occurs in the gaps between neighboring particles at plasmon resonance, while photothermal transduction is focused and enhanced Within the center of the chain. The ability to adaptively Control the magnetic and optical behavior of colloidal plasmonic particles, using an external field opens up a host of opportunities for novel imaging, sensing, theranostic, and optofluidic applications. Moreover, while the theory is demonstrated for the analysis of ID particle chains, the numerical methods readily extend to 2D and 3D assemblies of multilayered core shell nanoparticles that have magnetic and plasmonic layers. As such, this approach is useful for the rational design of optically functional colloids and the bottom-up fabrication of nanostructured interfaces and media with novel magnetic and photonic functionality.