Nanoscience Colloquia 2025

The two-dimensionality of monolayers and heterostructures of transition-metal dichalcogenides lead to a reduced dielectric screening and consequently to relatively strongly bound excitons. 

Not surprisingly, these systems show a wealth of interesting exciton and optical physics phenomena, including the formation of trions, strong luminescence, and multi-exciton phenomena. One of the more intriguing phenomena is that the lack of inversion symmetry in these systems combined with a strong spin-orbit coupling yields a novel quantum mechanical degree of freedom, the valley pseudospin, which is interesting from a fundamental point of view and even has some application potential. 

In this presentation, I will highlight some of the properties of these novel materials as investigated by ultrafast techniques like transient absorption and transient grating spectroscopy, focusing on the pseudospin dynamics, interlayer charge and pseudospin transfer in heterostructures, and enhanced mobility due to interlayer screening effects. 

Halide perovskite semiconductors can merge the highly efficient operational principles of conventional inorganic semiconductors with the low‑temperature solution processability of emerging organic and hybrid materials, offering a promising route towards cheaply generating electricity as well as light. Following a surge of interest in this class of materials, research on colloidal halide perovskite nanocrystals (NCs) has gathered momentum in the last decade. This talk will highlight several findings of our group on their synthesis, for example our recent study on the influence of various exogenous cations and of acid-based equilibria on the growth of perovskite NCs, which can lead to the formation of NCs with peculiar shapes (for example hollow structures) and to NC heterostructures (for example CsPbBr3/PbS heterostructures) by promoting/suppressing the heterogenous nucleation of selected materials. I will also discuss our findings on the ordering of NCs in superstructures, and how cryogenic temperatures can influence the degree of ordering.

Integrated circuits (ICs) fabrication requires cutting-edge nanoengineering techniques. The prevailing approach to enhancing computational power has been to miniaturize components in ICs. However, challenges arise due to the technological constraints of downsizing, interconnections, and materializing these components. Nanoscale 3D printing emerges as a promising solution to these challenges. At Aerosol Intelligence Laboratory (AIL), we have developed a method to print aerosols into expansive arrays of intricate 3D nanoarchitectures using “lines of forces”. This technique is called “Faraday 3D Printing”, inspired by Faraday’s original field of lines, which are here repurposed as  3D nano-drawing tools. Distinct from wavelength-limited techniques, these drawing tools possess no downsizing limit, heralding a horizon for atomic-level manufacturing. Our proprietary system uncovers the vast potential of multi-material printing, a prospect that has remained largely untapped. By adeptly manipulating electric and flow fields, we attain remarkable flexibility in material selection and wafer-scale printing, all while ensuring a high precision. This technology offers the capability to tailor optical, electronic, and mechanical attributes by modifying the material, geometry, feature size, and array periodicity of the printed nanoarchitectures. We contend that the transition from lithography to 3D printing within the spheres of nanoelectronics and nanophotonics signals a monumental paradigm shift, setting the research agenda of AIL for the future.