Dipole–Dipole Interaction-Induced Direct Self-Assembly of Ag2S Quantum Dots into Supercrystals in Solution

Abstract

Long-range ordered supercrystals (SCs) built up by colloidal nanocrystals (NCs) represent a class of novel metamaterials with unique collective properties. While great attention has been paid to the ligand-controlled assembly of NCs, the contribution of the inorganic core is considered limited because of the weak core–core interactions. Here, we report the spontaneous assembly of Ag₂S quantum dots (QDs) into three-dimensional SCs in solution, driven by pronounced dipole–dipole interactions. Dielectric spectroscopy shows a large permanent dipole moment of 516.7 D in 4.2 nm Ag₂S QDs, and multiscale molecular simulation proves the dipole–dipole interaction-driven crystallization of Ag₂S QDs. Moreover, we demonstrate that tuning the dipole–dipole interactions facilitates the formation of diverse nanostructures, including SCs, nanochains, and monodisperse nanoparticles. These findings offer a straightforward strategy for SC synthesis and establish the dipole–dipole interactions as a key driving force of NC self-assembly with broad implications for colloidal nanomaterials and their emergent functionalities.