Slow Anion-Exchange Reaction of Cesium Lead Halide Perovskite Nanocrystals in Supramolecular Gel Networks

One-Dimensionally Arranged Quantum-Dot Superstructures Guided by a Supramolecular Polymer Template

Colloidal quantum dots (QDs) exhibit important photophysical properties, such as long-range energy diffusion, miniband formation, and collective photoluminescence, when aggregated into well-defined superstructures, such as three-dimensional (3D) and two-dimensional (2D) superlattices. However, the construction of one-dimensional (1D) QD superstructures, which have a simpler arrangement, is challenging; therefore, the photophysical properties of 1D-arranged QDs have not been studied previously. Herein, we report a versatile strategy to obtain 1D-arranged QDs using a supramolecular polymer (SP) template. The SP is composed of self-assembling cholesterol derivatives containing two amide groups for hydrogen bonding and a carboxyl group as an adhesion moiety on the QDs. Upon mixing the SP and dispersed QDs in low-polarity solvents, the QDs self-adhered to the SP and self-arranged into 1D superstructures through van der Waals interactions between the surface organic ligands of the QDs, as confirmed by transmission electron microscopy. Furthermore, we revealed efficient photoinduced fluorescence resonance energy transfer between the 1D-arranged QDs by an in-depth analysis of the emission spectra and decay curves.

Water-assisted preparation of ethanol-dispersed CsPbBr3 perovskite nanocrystals and emissive gel

Cesium lead halide perovskite nanocrystals (PNCs) are highly attractive for optoelectronic applications due to their tunable bandgap, large absorption cross section and efficient photoluminescence. However, the dynamic ligand binding and ionic lattice make PNCs extremely sensitive to polar solvents, which greatly hinders the applications of PNCs. In this work, we first synthesize ethanol-dispersed PNCs with the assistance of water using glycyrrhizic acid (GA) as the sole capping ligand. The prepared PNCs with a mean size of 14.5 nm exhibit a narrow and symmetric emission band (full width at half maximum: 18 nm) and photoluminescence (PL) quantum yield (QY) of ~38.1%. Different with the common sense, the addition of water promotes the formation of GA-passivated PNCs due to the accelerated reaction rate of precursors and the H⁺ dissociation of GA at presence of Lewis base water. Furthermore, the ethanol-dispersed PNCs can be further transformed into emissive ethanol gels with improved stability. Our findings provide a novel strategy to achieve stable colloidal PNCs in polar solvents.