We collected IR absorption spectra using a Bruker INVE-NIO Fourier transform IR spectrometer with a concentratIR2 multiple reflection silicon ATR head purchased from Harrick Scientific. This ATR unit is designed for micro-liquid samples and has eleven internal reflections with a nominal incident angle of 30 • . We performed background measurements first and then we added 60 µL of sample on the ATR sampling area. We measured all spectra in the 1100 -1800 cm -1 range with 4 cm -1 resolution and 128 scans in transmission mode. We then converted the spectra to absorption mode using the Bruker software.