3.1. Analysis of characterization data of the bio-nanocomposite
The Ag NPs/CS-Starch bio-composite was synthesized following a stepwise
post-synthetic modification approach. A hydrogel mixture of CS and
starch biopolymers was used as the structure directing template or a
sustainable machinery for the green synthesis of functionalized
nanocomposite particle. The duo had the function of affording stability
to the NPs. Nevertheless, after the synthesis we had the urge to
characterize it using a range of advanced analytical techniques like
FT-IR, SEM, TEM, EDX and XRD.
The hierarchical decoration of the particle could be monitored by FT-IR
analysis. Fig. 1 depicts the compilation of FT-IR spectra of its
precursors, CS, Starch, intermediate CS-Starch hydrogel and the final Ag
NPs/CS-Starch material. Fig. 1a shows the typical vibrations of CS
molecule, being found at 1031 cm-1, 1384
cm-1, 1593 cm-1, 1651
cm-1 and 3350-3500 cm-1, being
attributed to C–N stretching, C–O stretching of CH2-OH
linkage, N-H bending, C=O stretching of amide linkage, O-H and N-H
stretching [14]. Similarly, starch also shows its characteristic
peaks at 3445 cm-1 (broad), 1078
cm-1 and 1658 cm-1 due to overlapped
O-H stretching, alcoholic C–O stretching and O–H bending vibrations
(Fig. 1b) [15]. Fig. 1c, representing the FT-IR spectrum of
CS-Starch composite, is almost an assemblage of Fig. 1a and 1b, with
just a slight shift in vibrations, indicating the successful mixing of
both. The final spectrum of Ag NPs/CS-Starch nanocomposite is also a
look alike of Fig. 1c with a small shifting of vibrational peaks at
higher or lower regions (Fig. 1d). This shift is anticipated derived
from strong interactions of in situ synthesized Ag NPs with the
surface organofunctions of CS-Starch composite.