Avoiding Kinetic Trapping in the Self-Assembly of DNA-Functionalized Gold Nanoparticles by Using an Enthalpy-Mediated Strategy

Conventional thermal annealing, known as the entropy-mediated strategy, is commonly used in directing the self-assembly of DNA-functionalized gold nanoparticles (DNA-AuNPs). The enthalpy-mediated strategy is another tractable approach, which can circumvent metastability by controlling the dynamic pathways at a condition with temperature remaining constant. However, the lack of direct measurements and observations of the assembly processes limits our understanding of the mechanism of how the systems avoid kinetic trapping and realize the phase transition successfully. In this work, we introduce a toy model for the self-assembly of DNA-AuNPs, which that the enthalpy- mediated strategy can effectively avoid undesired defects during the self-assembly. The effectiveness of this strategy in directing the self-assembly is proved through coarse-grained molecular dynamics simulations of DNA-AuNPs, which achieve the crystallization through orderly structural transformations. On the basis of that, we study the assembly processes which are controlled by enthalpy-mediated and entropy-mediated strategies. The DNA-AuNPs in the self-assembly controlled by the entropy-mediated strategy organize themselves during the thermal annealing process and are slowly frozen to achieve the crystallization. In contrast, we find that DNA-AuNPs in the primary stage of self-assembly which is controlled by the enthalpy-mediated strategy experience an organization-breakdown-reorganization process before forming stable crystallites, highlighting the importance of bond reversibility in the structural transitions and in avoiding the kinetic traps.