Self-Assembled PbS/CdS Quantum Dot Films with Switchable Symmetry and Emission

Precise tuning of optoelectronic properties of solid-state materials assembled from colloidal semiconductor nanocrystals (quantum dots, QDs) is of utmost importance for future optoelectronic technologies. Tuning can be achieved through varying composition, size, chemical environment, and arrangement of QDs; however, little is known about the possibility of achieving dynamic, reversibly switchable systems of QDs. Here, we report on the assembly of PbS/CdS core/shell quantum dots films, which exhibit reversibly switchable symmetry. Dynamic nanostructured assemblies were achieved by conjugating QDs with the two types of thermoresponsive, promesogenic ligands. The 3D arrangement of PbS/CdS nanoparticles in thin films was characterized by means of temperature-dependent small-angle X-ray measurements. Using optical techniques, we show that structural reconfiguration allows modulating the PL spectrum of QD solids in a reversible and predictable manner. Moreover, fabricated QD solids enable 3 orders of magnitude faster switchability than state-of-the-art examples of liquid crystalline quantum dots. We anticipate that the present methodology will allow for the assembly of various QD solids where structure and optoelectronic properties can be dynamically controlled.