Electrostatic co-assembly of nanoparticles with oppositely charged small molecules into static and dynamic superstructures

Coulombic interactions can be used to assemble charged nanoparticles into higher-order structures, but the process requires oppositely charged partners that are similarly sized. The ability to mediate the assembly of such charged nanoparticles using structurally simple small molecules would greatly facilitate the fabrication of nanostructured materials and harnessing their applications in catalysis, sensing, and photonics. Here we show that small molecules having as few as three electric charges can effectively induce attractive interactions between oppositely charged nanoparticles in water. These interactions can guide the assembly of charged nanoparticles into colloidal crystals of a quality previously only thought to result from their cocrystallization with oppositely charged nanoparticles of a similar size. Transient nanoparticle assemblies can be generated using positively charged nanoparticles and multiply charged anions that are enzymatically hydrolyzed into mono- and/or dianions. Our findings demonstrate an approach for the facile fabrication, manipulation, and further investigation of static and dynamic nanostructured materials in aqueous environments. [Figure: see text]