Synthesis of chiral copper (II) oxide nanosheets via treatment of layered double hydroxides Áine Coogan 1 , Lucia Hughes 1,2, Finn Purcell-Milton 1,3 , Seán Cardiff 1,4 , Valeria Nicolosi 1,2 and Yurii Gun'ko 1
1 Trinity College Dublin, Ireland, 2 CRANN and AMBER Research Centres, Trinity College Dublin, Ireland, 3 Technological University Dublin, Ireland, 4 School of Physics, Trinity College Dublin, Ireland
In recent years, much research has focused on the development of new chiral inorganic nanostructures, including a wide variety of materials, such as spherical quantum dots, nanowires, and tetrapods, among others. 1-3 However, the induction of chirality in 2D materials is minimally explored. 4 Layered double hydroxides (LDHs) are a class of ionic 2D nanomaterials that are known for their porous laminar structures and anion-exchange properties. As such, they can host a wide variety of species in their interlayer – including chiral molecules.Despite this unique property, to the best of our knowledge there are minimal reports on the effect of chiral ligands on the properties of LDHs, and the potential for chirality induction. In addition, chiral copper (II) oxide (CuO) is a material of significant interest due to its potential applications in non-linear optics and the treatment of Parkinson's disease. 5,6 However, the synthesis often requires moderate-to-high temperatures, as well as additional surfactants and symmetry- breaking agents. 7 To the best of our knowledge, no reports exist on the synthesis of chiral CuO at room temperature, or by using LDHs as precursors. In this work, we report the synthesis and investigation of chiral copper (II) oxide nanosheets by post-synthetic treatment of copper-aluminium LDHs. The initial LDH nanomaterials have been synthesised by a simple, scalable co-precipitation procedure. Then, the resultant 2D nanomaterials were treated with L- and D-Phenylalanine at room temperature in aqueous, basic conditions, resulting in materials with induced chirality, and circular dichroism (CD) response in the visible region, far beyond the onset of the CD signal from the original ligand. Time- dependent CD and powder X-Ray diffraction (pXRD) studies demonstrate a gradual transformation from achiral LDH nanosheets, to chiral CuO nanosheet clusters, exhibiting g-factors of up to 0.0035. We anticipate that these materials could have potential future applications in enantiomeric separation and asymmetric catalysis. References 1. M. P. Moloney, Y. K. Gun’ko and J. M. Kelly, Chemical Communications , 2007, 3900–3902. 2. D. Kehoe, E. Mates-Torres, P. Samokhvalov, M. García-Melchor and Y. K. Gun’ko, Journal of Physical Chemistry C , 2022, 126 , 434–443. 3. J. E. Govan, E. Jan, A. Querejeta, N. A. Kotov and Y. K. Gun’ko, Chemical Communications , 2010, 46 , 6072–6074. 4. F. Purcell-Milton, R. McKenna, L.J. Brennan, et. al.ACS Nano , 2018, 12 , 954–964. 5. G.S. Boltaev, R.A. Ganeev, P.S. Krishnendu, K.Zhang and C. Guo, Scientific Reports 2019 9:1 , 2019, 9 , 1–8. 6. C. Hao, A. Qu, L. Xu, M. Sun, H. Zhang, C. Xu and H. Kuang, J Am Chem Soc , 2019, 141 , 1091–1099. 7. Y. Duan, X. Liu, L. Han, S. Asahina, D. Xu, Y. Cao, Y. Yao and S. Che, J Am Chem Soc , 2014, 136 , 7193–7196.
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