Growth Mediated Disassembly of Cucurbit[8]uril Cross-linked Static Cubic Self-assembly of Silver Nanoparticles

Static self-assembly resides in thermodynamically stable global minima of the energy landscape, whereas dynamic self-assembly occupies local minima of the energy profile and remains in the ordered state for a limited time via dissipation of energy to surroundings. This makes the spatiotemporal control over the assembly and disassembly mechanism easily controllable in the case of dynamic self-assembly. However, due to the higher thermal stability of static self-assembly, it is very challenging to perform reverse engineering on these types of systems. Herein we report growth reaction-based reversal of static silver cubes obtained via cucurbit[8]uril (CB[8]) crosslinked self-assembly of silver nanoparticles (AgNP). The AgNP building units with variable CB[8] surface coverage have been used as seeds onto which deposition of gold via growth reaction has been performed. The disassembly of supracube structure has been controlled by the formation of [AuCl₄]⁻–CB[8] complex and successive reduction of [AuCl₄]⁻ to Au⁰ on the surface of the seed. The resulting monodispersed isotropic nanoparticles, formed from the CB[8] based cubic self-assembly after growth, exhibit Au−Ag bimetallic nature. Quenching of the fluorogenic response from the hydrophobic dye coumarin-7, added after growth, suggests direct interaction with the metallic nanoparticle surface after disassembly and thereby confirms successful growth reaction mediated reversal of self-assembly.