This work focuses on the systematic investigation of the shape,s ize, and composition-controlled synthesis of perovskite nanocrystals (NCs) under inert gas-free conditions and using pre-synthesized precursor stocksolutions.Inthe case of CsPbBr 3 NCs,w ef ind that the lowering of reaction temperature from ~175 to 100 8 8Ci nitially leads to ac hange of morphology from bulk-like 3D nanocubes to 0D nanocubes with 3D-quantum confinement, while at temperatures below 100 8 8Ct he reaction yields 2D nanoplatelets (NPls) with 1Dquantum confinement. However,t oo ur surprise,a th igher temperatures (~215 8 8C), the reaction yields CsPbBr 3 hexapod NCs,w hich have been rarely reported. The synthesis is scalable,a nd their halide composition is tunable by simply using different combinations of precursor solutions.T he versatility of the synthesis is demonstrated by applying it to relatively less explored shape-controlled synthesis of FAPbBr 3 NCs.D espite the synthesis carried out in the air,b oth the inorganic and hybrid perovskite NCs exhibit nearly-narrow emission without applying any size-selective separation, and it is precisely tunable by controlling the reaction temperature.

CONSPECTUS: For decades, plasmonic nanoparticles have been extensively studied due to their extraordinary properties, related to localized surface plasmon resonances. A milestone in the field has been the development of the so-called seedmediated growth method, a synthetic route that provided access to an extraordinary diversity of metal nanoparticles with tailored size, geometry and composition. Such a morphological control came along with an exquisite definition of the optical response of plasmonic nanoparticles, thereby increasing their prospects for implementation in various fields. The susceptibility of surface plasmons to respond to small changes in the surrounding medium or to perturb (enhance/quench) optical processes in nearby molecules, has been exploited for a wide range of applications, from biomedicine to energy harvesting. However, the possibilities offered by plasmonic nanoparticles can be expanded even further by their careful assembly into either disordered or ordered structures, in 2D and 3D. The assembly of plasmonic nanoparticles gives rise to coupling/hybridization effects, which are strongly dependent on interparticle spacing and orientation, generating extremely high electric fields (hot spots), confined at interparticle gaps. Thus, the use of plasmonic nanoparticle assemblies as optical sensors have led to improving the limits of detection for a wide variety of (bio)molecules and ions. Importantly, in the case of highly ordered plasmonic arrays, other novel and unique optical effects can be generated. Indeed, new functional materials have been developed via the assembly of nanoparticles into highly ordered architectures, ranging from thin films (2D) to colloidal crystals or supercrystals (3D). The progress in the design and fabrication of 3D supercrystals could pave the way toward next generation plasmonic sensors, photocatalysts, optomagnetic components, metamaterials, etc. In this Account, we summarize selected recent advancements in the field of highly ordered 3D plasmonic superlattices. We first analyze their fascinating optical properties, for various systems with increasing degrees of complexity, from an individual metal nanoparticle through particle clusters with low coordination numbers, to disordered self-assembled structures and finally to supercrystals. We then describe recent progress in the fabrication of 3D plasmonic supercrystals, focusing on specific strategies but without delving into the forces governing the self-assembly process. In the last section, we provide an overview of the potential applications of plasmonic supercrystals, with a particular emphasis on those related with surface-enhanced Raman scattering (SERS) sensing, followed by a brief highlight of the main conclusions and remaining challenges.

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