Semiconductor nanocrystals (NCs) exhibit quantum confinement effects that lead to highly tunable optical and electronic properties. This unique versatility has positioned NCs as key components for next-generation optoelectronic and photonic technologies. By controlling their size, shape, and composition, researchers are working toward a new “periodic table” of artificial atoms, enabling the rational design of materials from the bottom up.[1]

A major challenge - and opportunity! - lies in directing the assembly of these NCs into ordered superstructures that exhibit emergent, collective properties. Such artificial solids hold promise for applications ranging from light management to low-threshold lasing and energy-efficient photonic systems. However, the deterministic control of NC self-assembly remains limited by an incomplete understanding of interparticle interactions.[2]

In this talk, I will present a general strategy to bias the self-assembly of NCs into three-dimensional superstructures with well-defined morphology and high crystalline order. Using emulsion-templated assembly, we guide the formation of spherical supercrystals composed of densely packed, ordered NCs.[3] Time-resolved synchrotron X-ray scattering reveals a ligand-mediated hard-sphere-like crystallization mechanism,[4] yielding single-domain architectures approaching single-crystal quality.[5]

These superstructures exhibit multiscale optical functionality: while their refractive index is determined by the nanocrystal composition, their mesoscale geometry supports Mie resonances, leading to enhanced absorption and scattering.[6] Post-assembly ligand exchange strengthens interparticle coupling, enabling the emergence of whispering gallery modes that confine light along the surface of the superstructure,[7] leading to cross-talk phenomena in superstructure clusters.[8] This optical feedback triggers low-threshold lasing, with emission spectra tunable by optical[9] and dielectric[10] stimuli.

I will conclude by presenting recent advances in the formation of binary and porous nanocrystal solids,[11, 12] opening new avenues for multifunctional, reconfigurable materials. These results underscore the potential of controlled nanocrystal assembly not only for discovering new physical phenomena, but also for developing scalable, bottom-up materials for sustainable photonics and energy-efficient technologies.

[1] E. Marino, et al., Crystal Growth & Design 24 (14), 6060-6080 (2024).               
[2] R. Passante, et al., Nanoscale (in press), DOI: 10.1039/D5NR01288K (2025).  
[3] E Marino, et al., Chem. Mater. 34, 6, 2779–2789 (2022).  
[4] E. Marino, et al., Adv. Mater. 30 (43), 1803433 (2018).        
[5] E. Marino, et al., J. Phys. Chem. C 124 (20), 11256–11264 (2020).        
[6] E. Marino, et al., ACS nano 14 (10), 13806–13815 (2020).
[7] E. Marino, et al., Nano Lett. 22, 12, 4765–4773 (2022).       
[8] P. Castronovo, et al., Nano Lett. 25 (14), 5828-5835 (2025).
[9] S.J. Neuhaus, et al., Nano Lett. 23, 2, 645–651 (2023).       
[10] M. Reale et al., Adv. Opt. Mater. 34 (37), 2402079 (2024).   
[11] E. Marino, et al., Nat. Synth 3, 111–122 (2024).  
[12] E. Marino, et al., Chem. Mater. 36 (8), 3683-3696 (2024).