Three absorption peaks corresponding to amide groups were also observed. These three absorption peaks were at 1627 cm−1, 1538 cm−1, and 1238 cm−1, coinciding with amide Cdouble bond; length as m-dashO stretching, amide Nsingle bondH bending (plus Csingle bondN stretching), and amide Nsingle bondH bending (or CH2 vibration) in glycine, respectively