Catalytic-Assembly of Nanoparticle Supercrystals by a pH-Controlled DNA Strand-Displacement Circuit

DNA-directed "bonding" of nanoparticle "atoms" has led to highly ordered 3D superlattices of nanomaterial units with programmable crystalline orders. However, it remains a great challenge for the system to avoid being trapped in disordered metastable states toward long-range-ordered nanoparticle arrays. In this work, we present a pH-responsive, enthalpy-mediated strategy to address this dilemma by incorporating a CG-C⁺ triplex DNA structure into a strand-displacement circuit that programs the catalytic assembly of DNA-grafted gold nanoparticles. The integration of such a pH-responsive DNA motif allows for precise regulation of noncovalent bonding interactions between DNA-conjugated nanoparticles over a long time span at room temperature, helping the system to escape from disordered intermediate states. On the basis of this strategy, both catalytic-assembly kinetics and the quality of nanoparticle superlattices are easily tunable by solution pH and catassembler concentration. High-quality face-centered cubic superlattices and microsized rhombic dodecahedral single crystals with a body-centered cubic structure are then achieved in acidic media supplemented with a low concentration of catassembler. The present work is highly promising toward the isothermal growth of high-quality, uniform supercrystals with diverse lattice symmetries and dynamic functions.