FTIR spectra were collected in transmission mode, with
a resolution of 4 cm-1. The beam size was 6 µm x 6 µm,
imprinting on specimens deposited on 0.2 mm thickness BaF2
windows. Specimens were scanned with steps of 4 µm in both
directions. For each spectrum, 64 scans were accumulated
from 4000 to 500 cm-1 and averaged. Background spectra
were collected every 30 minutes.