Fourier-Transform Infrared Spectroscopy (FTIR)

FTIR spectra of powder samples were obtained using a Vertex 70 IR Spectrophotometer (Bruker Optics, Billerica, MA, USA) with a golden gate attenuated total reflectance (ATR) accessory (Specac, Fort Washington, PA, USA). Dry air was purged through the ATR cell and the detector unit during the analysis. A background scan was recorded before each sample measurement and the spectra were obtained in the range of 400–4000 cm⁻¹. Each spectrum was obtained as an average of 64 scans.