Supramolecular assemblies and nanoparticle integration studied through quantitative image analysis and 3D reconstruction

Nanoparticle incorporation into supramolecular assemblies is essential for designing hybrid nanostructures with tailored optical and structural properties. However, understanding the interactions that govern the attachment and formation of such composites remains a challenge, particularly when complex structures are involved. In this study, we explore the fabrication of quantum dot (QD)/J-aggregate composites of tetrakis(4-sulfonatophenyl)porphyrin (H₂TPPS₄), where electrostatic interactions between cysteamine-functionalized QDs and negatively charged J-aggregates of H₄TPPS₄ with L-alanine play a key role in their formation. By systematically varying QD concentration, we examine how QD loading influences the structure and attachment pattern of the composites. Quantitative transmission electron microscopy (TEM) image analysis and three-dimensional (3D) TEM tomography were employed to obtain detailed insights into the interparticle spacing, thickness distribution, and 3D morphology of the QD/J-aggregate composites. The results show that higher QD concentrations lead to multilayered structures with decreased interparticle spacing, and TEM tomography reveals the helical arrangement of QDs on the framework of H₄TPPS₄ with L-alanine. This work emphasizes the critical role of advanced imaging techniques and quantitative analyses in understanding the evolution of nanoparticle assemblies, opening new possibilities for the design of advanced hybrid nanostructures.