Phase Behavior and Magnetic Response of DNA-mediated Gold and Iron Oxide Nanoparticle Assemblies

Gold nanoparticles (NPs) have long been long served as model systems to study phase behavior of DNA-assisted NP assemblies. Incorporation of different types of nano-objects into DNA-NP systems opens attractive possibilities for the material design. Furthermore, it also allows enriching a self-assembly behavior by an introduction of non-specific yet controllable interparticle interactions. Herein, we report the DNA-mediated assembly of a heterogeneous system comprising gold and superparamagnetic iron oxide (IO) NPs. We systematically studied the phase diagram of the assembled systems by varying a system's composition, DNA design and environmental conditions. Our studies show that by controlling a balance between non-specific and DNA-recognition interactions via system design the assembled phase can be switched between a face-centered cubic (fcc) structure of a IO assembly and a superlattice formed by Au-IO core-shells clusters. We also observed that structure of assemblies is responsive to the magnetic field.