Colloidal perovskite nanocrystals based on formamidinium lead halide (FAPbX 3 ) have been synthesized by the ligand-assisted reprecipitation method using PbX 2 − dimethyl sulfoxide complexes as precursors at room temperature. Well-defined cubic-shaped FAPbX 3 nanocrystals have been obtained with a size d of ∼10 nm. The synthesized FAPbX 3 nanocrystals show bright photoluminescence with a high photoluminescence quantum yield (75% for FAPbBr 3 ). The lifetimes of FAPbBr 3 nanocrystals were measured for the samples isolated at several different centrifugal speeds. The photoluminescence can be tuned from the blue to nearinfrared region (λ peak = 408−784 nm) by changing either the amount of oleylamine or the composition of X. The color expression range is 135% of the NTSC standard. The bandwidth of the photoluminescence spectra of FAPbX 3 nanocrystals is narrow (full width at half-maximum of 18−48 nm). FAPbX 3 nanocrystals show thermal stability that is better than that of MAPbBr 3 nanocrystals.

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Matrix-free assemblies of polymer-grafted nanoparticles (PGNs) enable mechanically robust materials for a variety of structural, electronic, and optical applications. Recent quasi-static mechanical studies have identified the key parameters that enhance canopy entanglement and promote plasticity of the PGNs below T g . Here we experimentally explore the high-strain-rate shock impact behavior of polystyrene grafted NPs and compare their energy absorption capabilities to that of homopolystyrene for film thicknesses ranging from 75 to 550 nm and for impact velocities from 350 to 800 m/s. Modeling reveals that the initial shock compression results in a rapid temperature increase at the impact site. The uniformity of this heating is consistent with observations of greater kinetic energy absorption per mass (E p *) of thinner films due to extensive viscoplastic deformation of molten film around the penetration site. Adiabatic heating is insufficient to raise the temperature at the exit surface of the thickest films resulting in increased strain localization at the impact periphery with less melt elongation. The extent and distribution of entanglements also influence E p *. Structurally, each NP acts as a giant cross-link node, coupling surrounding nodes via the number of canopy chains per NP and the nature and number of entanglements between canopies anchored to different NPs. Load sharing via this dual network, along with geometrical factors such as film thickness, lead to extreme E p * arising from the sequence of instantaneous adiabatic shock heating followed by visco-plastic drawing of the film by the projectile. These observations elucidate the critical factors necessary to create robust polymer-nanocomposite multifunctional films.