MULTINUCLEAR SOLID STATE NUCLEAR MAGNETIC RESONANCE FOR STUDYING CsPbBr3 NANOCUBES

In recent years, metal halide perovskites (MHPs) have aroused a lot of enthusiasm in the materials science community due to their unique tunability, which allows a fine regulation of the desired properties. CsPbBr3 perovskite nanocrystals (Fig. 1) have shown highly attractive light emitting properties, thanks to their narrow emission bandwidths, high quantum-yield values, and the possibility to perform a fine tune of the emission wavelength by controlling the size of the nanocrystals [1]. In the last few years, Solid-State NMR spectroscopy (SSNMR) has emerged as one of the main techniques for an in-depth structural and dynamic characterization of MHPs [2-3]. In this work, a multinuclear SSNMR approach was adopted for a structural study of cubic CsPbBr3 nanoparticles stabilized with oleic acid and oleylamine. In particular, the surface ligands and their interactions with the nanocubes surface were investigated by 1H and 13C NMR experiments, while the structural investigation of the perovskite nanocubes was addressed by exploiting 207Pb and 133Cs spectral properties in comparison with bulk CsPbBr3. Static 207Pb NMR spectra indicated a possible contribution of chemical shift anisotropy from the 207Pb nuclei of the outer layer. The 133Cs NMR spectra showed signals with different chemical shifts for cesium atoms in at least three regions of the nanocubes, from the inner core to the surface, which were interpreted in terms of cubic layers with different distances from the surface using a simple geometrical model. This interpretation was also supported by 133Cs longitudinal relaxation time measurements [4]. Fig. 1. Structure of CsPbBr3 perovskite References [1] T.J.N. Hooper, Y. Fang, A.A.M. Brown, S.H. Pu, T.J. White. Nanoscale, 13, 15770 (2021) [2] D.J. Kubicki, S.D. Stranks, C.P. Grey, L. Emsley. Nat. Rev. Chem., 5, 624-645 (2021) [3] L. Piveteau, V. Morad, M.V. Kovalenko. J. Am. Chem. Soc., 142, 19413-19437 (2020) [4] A. Scarperi et al. Pure Appl. Chem. (2023) https://doi.org/10.1515/pac-2023-0110