Fig. 1. Molecular structural model of homocysteine

Fig. 2. THz characteristic absorption spectrum of homocysteine calculated by DFT

Fig. 3. Spectra characterization of 1.68 mol/L homocysteine. (a) Time domain spectra; (b) frequency domain spectra; (c) absorption spectrum

Fig. 4. THz absorption spectra of homocysteine solutions with different concentrations

Fig. 5. Linear relationship between absorption coefficient and concentration of homocysteine with different concentrations at 1.29 THz and 1.93 THz