Infrared spectral fingerprints of the toxicity effects of CH3NH3PbI3 and CH3NH3SnI3 photovoltaic perovskites

We use Fourier-Transform infrared spectromicroscopy to study at the molecular level the effect of exposure of human A549 and SH-SY5Y cell lines to the perovskites CH<sub>3</sub>NH<sub>3</sub>PbI<sub>3</sub> (MAPbI<sub>3</sub>) and CH<sub>3</sub>NH<sub>3</sub>SnI<sub>3</sub> (MASnI<sub>3</sub>). By monitoring the infrared absorption of amide bands over a few days following exposure to the metals, we observe the appearance of a strong band at 1628 cm-1. This band is tentatively assigned to the extensive formation of intermolecular β-sheet structures. A similar response is observed after exposure of the cells to CuSO<sub>4</sub>, suggesting that the mechanism underlying the observed spectroscopic changes is not specific for Pb<sup>2+</sup> and Sn<sup>2+</sup>, and it may be associated to a generic cellular response to stressful environmental conditions.<br>