FT-IR Spectra Collection. FT-IR measurements were performed
in the mid-infrared region (4000−650 cm−1
) using a Nicolet 6700
(Thermo Scientific Co.) FT-IR spectrophotometer, configured with an
attenuated total reflectance (ATR) sampling technique, deuterated
triglycine sulfate (DTGS) detector, and KBr beam splitter controlled
by OMNIC software. Samples to be analyzed were placed on a
diamond crystal sampling plate and clamped with a pointed tip. A
background scan was obtained before every sample scan with an empty
sample plate. In addition, the ATR crystals and pointed tip were
cleaned to remove any interference from the preceding sample. A total
of 32 successive scans from each sample were collected at 4 cm−1
intervals, and averaged spectra of each sample were used for analysis.