Polymer-Ligated Uniform Lead Chalcogenide Nanoparticles with Tunable Size and Robust Stability Enabled by Judiciously Designed Surface Chemistry

Despite recent progress in synthesis, self-assembly, and utility of low band gap lead chalcogenide nanoparticles (NPs) due to their intriguing optoelectronic characteristics, their compositional instability in ambient condition remains a great challenge for long-term practical applications. Herein, we report a unique strategy via capitalization on a set of starlike block copolymers as nanoreactors for in situ crafting of uniform lead chalcogenide NPs with readily tailored sizes, surface chemistry, near-infrared (NIR) optoelectronic properties, and more importantly, markedly enhanced stability against air exposure. The intimate and permanent tethering of the outer blocks of starlike block copolymers on the surface of lead chalcogenide NPs imparts their effective dispersion in both the solution and dry state. The diameter of the resulting NPs can be conveniently tuned by regulating the molecular weight (i.e., length) of the inner hydrophilic blocks of starlike block copolymers, manifesting the progressive red shift in the NIR absorption and emission as the diameter of the NPs increases. Most intriguingly, judiciously alternating the compositions and chain lengths of the outer blocks of the starlike block copolymers renders remarkably improved stability of lead chalcogenide NPs in ambient condition, representing no spectral change in both position and intensity for 30 days as compared to rapid and complete quenching of emission in 1 day in conventional small-molecular-ligand-capped counterparts. In principle, our starlike block copolymer nanoreactor strategy can be easily extended to synthesize functional NPs other than metal chalcogenides for investigation into their dimension-dependent physical properties and self-assembly as well as various applications.