Fig. 1. FTIR spectra of samples
(a): CAU3, et al; (b): SAU3, et al

Fig. 2. The XPS full spectra of samples
(a): U1, CAU3, CA; (b): U1, SAU3, SA

Fig. 3. XPS C(1s) peak fitting spectra of samples
(a): U1, CAU3, CA; (b): U1, SAU3, SA

Fig. 4. XPS O(1s) peak fitting spectra of samples
(a): U1, CAU3, CA; (b): U1, SAU3, SA

Fig. 5. XPS N(1s) peak fitting spectra of samples
(a): U1 and CAU3; (b): U1 and SAU3

Fig. 6. Total ion chromatogrom of U1 (a), CAU3(b), SAU3 (c) samples in positive mode

Fig. 7. MS spectra of sample characteristic peaks
(a): The MS spectrum for all samples with retention time of 1.09 min was shown; (b) MS spectrum for CAU3 with retention time of 8.40 min shown; (c), (d): MS spectra for SAU3 with retention time of 8.40, 9.53 min shown, respectively