centered at 1660cm1 denotes the significant α-helix content of
HSA [45]. In the presence of AuNPs,the center of amide I band
shifts down to 1657 cm1, possibly implying less compact structures of HSA on the AuNPs surface and the presence of citrate
[45,46]. Noticeably,the shift of a center of amide II band to higher
wavenumbers indicates that many hydrogen bonds are produced
to affect predominantly N–H bending vibrations [47]. These data
support the idea that during the evolution of HSA–AuNPs conjugate,the internal HSA hydrogen bonds break and the intermolecular hydrogen bonds between HSA and AuNPs are formed
possibly by hydrogen bonding between the amino acid residues
(–NH2) of HSA and the carboxyl group (–COOH) of citrate on the
surface of AuNPs,accompanied by simple loss of water of hydration [43,47].