GENERAL SEMINAR: Dr. Doru Constantin, Institut Charles Sadron, CNRS, Strasbourg, France
I will discuss two recent applications of SAXS-based techniques to elucidating the structure of more or less crystalline structures formed by nanometric building blocks, with an emphasis on the space and time resolution of the methods.
In a first study [1], we used a microbeam to investigate the interplay between the shape of anisotropic nanoparticles and a tunable “prismatic confinement” leading to their self-assembly into supercrystals (SCs) confined by cavities with polygonal cross-section. We used a multiscale characterization strategy to determine the orientation and structure of the SCs individually and at the ensemble level. Our findings highlight the role of the mold-SC interface in guiding the growth of distinct crystal domains: each side of the mold directs the formation of a monodomain that extends until it encounters another, leading to the creation of grain boundaries.
In an ongoing collaboration with the MATCA team at INFM, Bucharest, and the group of Michel Barsoum at Drexel University (Philadelphia, PA, USA), we studied the morphology of TiO2 ribbons in solution and their assembly into 3D crystals upon drying [2,3], elucidating the initial and final structures. Our next goal is to follow in detail the evolution of the dispersion as a function of concentration (in the colloidal state), allowing us to explore in detail the phase diagram of this new family of colloidal objects, as a function of synthesis method, nature of the solvent (water, alcohols, acetone, DMSO etc.) and concentration [4]. As the suspension dries, we follow the stacking process, whose kinetics is a point of particular focus.
[1] Prismatic Confinement Induces Tunable Orientation in Plasmonic Supercrystals
Wajdi Chaâbani et al., ACS Nano, 18, 9566-9575 (2024).
[2] Structural Analysis of Colloidal Titania‐Based Ribbons and Their Self‐Assembly upon Drying
S. Boukhris et al., Small Structures, 6, 2500017 (2025).
M. A. Ibrahim et al., Matter, 8, 102260 (2025).
[4] In situ monitoring the self-assembly of colloidal titanate ribbons
S. Boukhris et al.,in preparation.
This event is supported by the mobility project of the Romanian Ministry of Education and Research, CNCS-UEFISCDI, project number 10/29/09/2025, within PNCDI IV.