Bottom-up Synthesis of Highly Chiral Two-Dimensional Transition Metal Dichalcogenides Nanostructures

Chiral nanomaterials have recently stimulated large interest in the scientific community due their potential applications in several technologically relevant fields, such as: sensing, catalysis and photonics.^[1–3] The development of novel synthetic procedures to induce chirality in inorganic nanostructures is a challenging task, which has garnered the interest of researchers worldwide. In particular, the use of chiral ligands to passivate the surface of plasmonic and excitonic nanocrystals has shown to be an efficient technique to introduce chirality, giving rise to a plethora of inorganic nanostructures with unique chiroptical properties.^[2] Assemblies of small nanoparticles into chiral structures have been successfully proven to expand the chirality of the single monomeric unit into a collective behaviour.^[2] More complex nanostructure growth in the presence of a chiral ligand as a directing agent shows complex morphologies, hierarchical chirality and superior chiroptical properties.^[4–6]<br/>Two dimensional transition metal dichalcogenides (TMDCs) nanostructures have recently become of large research interest due to their potential broad range of applications spanning from photonics,^[7]to energy storage.^[8]Previous studies from our group reported the first observation of chiroptical properties in MoS₂ produced via top-down exfoliation in the presence of a chiral inductor.^[9]However, top-down processes such as liquid-phase exfoliation are affected by several drawbacks, including a large degree of heterogeneity in the materials produced as well as poor control of nanostructure morphology and relatively low chiroptical activity. Due to these intrinsic issues related to the synthetic procedure, the fine control of the optical and chiroptical properties, the understanding of the origin of the symmetry break, as well as applications of the nanomaterials are challenging. For these reasons, we are currently investigating other strategies to produce chiral two-dimensional TMDCs with higher control of the nanomaterials’ morphology. In particular, our investigation covers the introduction of chirality in bottom-up colloidal two-dimensional TMDCs. Bottom-up syntheses are well-known procedures successfully applied to produce high-quality 2D TMDCs nanostructures with high control on morphology, crystallographic structure and chemical composition.^[10]Our observations demonstrate the induction of chirality in MoS₂ nanocrystals prepared by bottom-up synthesis, using chiral ligands to control the breaking of the mirror symmetry during the material formation. This approach allow accessing to nanocrystals with complex and tunable morphology as well as superior chiroptical properties. Moreover, our study dedicate particular attention to the origin of chirality and the involvement of chiral coordination complexes in the formation of the chiral inorganic nanostructures. Thanks to the superior control on morphology accessible by bottom-up methods, this strategy allows for the production of high quality chiral nanostructures with potential application in a broad range of technologically relevant fields.<br/> <br/>[1] J. Liu, L. Yang, P. Qin, S. Zhang, K. K. L. Yung, Z. Huang, <i>Adv. Mater.</i> <b>2021</b>, <i>33</i>, 2005506.<br/>[2] H. Cao, E. Yang, Y. Kim, Y. Zhao, W. Ma, <i>Adv. Sci.</i> <b>2024</b>, <i>2306979</i>, 1–34.<br/>[3] S. Jiang, N. A. Kotov, <i>Adv. Mater.</i> <b>2023</b>, <i>35</i>, 1–19.<br/>[4] J. Zhang, R. A. L. Vallée, Z. Kochovski, W. Zhang, C. Shen, F. Bertram, N. Pinna, <i>Angew. Chemie - Int. Ed.</i> <b>2023</b>, <i>62</i>, e202305353.<br/>[5] Á. Coogan, L. Hughes, F. Purcell-Milton, S. Cardiff, V. Nicolosi, Y. K. Gun’Ko, <i>J. Phys. Chem. C</i> <b>2022</b>, <i>126</i>, 18980–18987.<br/>[6] H. E. Lee, H. Y. Ahn, J. Mun, Y. Y. Lee, M. Kim, N. H. Cho, K.<br/>[7] Mak, K. F. et al. J. Nat. Photonics 2016, 10, 212-226.<br/>[8] Choi, W. et al. Mater. Today 2017, 20, 116− 130.<br/>[9] Purcell-Milton, F. et a.l. ACS Nano 2018, 12, 954-964.<br/>[10] Coogan, A. et al. Mater. Adv. 2021, 2, 146-164.