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.