Fig. 2. FTIR spectra of native HSA and AuNP–HSA corona at 20 °C. (a) IR absorption spectra; (b) secondary-derivative amide I spectra; (c) and (d) curve-fitted inverted second-derivative amide I spectra of HSA and HSA coated on AuNPs at 20 °C. The second-derivative FTIR spectra using a seven-point Savitsky–Golay derivative function.