Chiral Inorganic Nanoparticle-Based Aerogels

Chirality, a fundamental feature in biological systems, is increasingly being introduced into inorganic nanomaterials to exploit their unique optical and catalytic properties. Indeed, considerable progress has been made in the synthesis and characterisation of chiral inorganic nanoparticles and their self-assembly into chiral nanostructures. However, many fundamental questions remain about how chirality arises in these systems, how it influences material properties, and what potential applications can be developed.
Within this framework, the current work focuses on the fabrication of chiral inorganic gels and aerogels at the macroscopic scale and the investigation of their unique structural, morphological, and chiroptical properties. While chiral organic gels have been extensively studied, there is very little literature on inorganic chiral gels. In this study, chiral nanoparticles are synthesised by wet-chemical methods using molecular precursors and chiral ligands to imprint chirality into the inorganic core during nucleation and growth. These nanoparticles are then assembled into gels and aerogels.
Aerogels consist of three-dimensional porous networks and preserve the size-dependent properties of their nanoparticle building blocks in a macroscopic form. With their high porosity and surface area, aerogels provide an ideal structure for gas-phase photocatalysis. This project focuses on the preparation of chiral TiO₂-based aerogels for potential applications in asymmetric photocatalysis. TiO₂ is selected for its UV active band gap, and chirality is introduced using L/D-Threoninol, a molecule that binds to TiO₂ surface without preventing particle formation in the reaction solution, generates a chiroptical signal, and forms stable dispersions in water, which is critical for the subsequent gelation process. The dependence of nanoparticle chiroptical activity on ligand concentration and binding mode is investigated, and the concept of chiral memory in TiO₂ is explored to determine whether chirality is retained after ligand removal. In addition, the transfer of chirality from the nanoparticle scale to the macroscopic gel structure is investigated, together with the role of surface ligands in controlling the gelation behaviour.