Figure 4

Normalized ATR FT-IR spectra of virgin sericin and AgNPs. The intensity was normalized against the absorption at 1,070 cm⁻¹. (A) Original SS shows characteristic absorptions of protein including amide I (1,700 to 1,600 cm⁻¹, asterisk), amide II (1,560 to 1,500 cm⁻¹, asterisk), and amide III (1,300 to 1,200 cm⁻¹, asterisk). (B) SS-capped AgNPs show new functional groups including carboxylate (1,451, 1,404, 1,353 cm⁻¹, asterisk) and amine salt (830 cm⁻¹, asterisk). (C) Thermally treated SS-capped AgNPs show the same functional groups as those in (B).