fig5

Figure 5. (A) Synthetic procedure for Fe₃O₄@PDA@MIL(Ti)-PEI-Nb; (B) FT-IR spectra of (i) Fe₃O₄, (ii) Fe₃O₄@PDA, (iii) Fe₃O₄@PDA@MIL(Ti)-PEI, (iv) Fe₃O₄@PDA@MIL(Ti)-PEI-Nb; (C) XPS spectrum of Fe₃O₄@PDA@MIL(Ti)-PEI-Nb; (D) SEM image of Fe₃O₄@PDA@MIL(Ti)-PEI-Nb; (E) TEM image of Fe₃O₄@PDA@MIL(Ti)-PEI-Nb; (F) EDX spectrum of Fe₃O₄@PDA@MIL(Ti)PEI-Nb. The inset in (F) is the primary elements content table of EDX; Mass spectra of human saliva: (G) before and (H) after enrichment with Fe₃O₄@PDA@MIL(Ti)-PEI-Nb. (A-H) are reprinted with permission from Ref.^[102], Copyright © 2021 by Elsevier Ltd. FT-IR: Fourier transform infrared spectroscopy; XPS: X-ray diffraction; SEM: scanning electron microscope; TEM: transmission electron microscope; EDX: energy-dispersive X-ray spectroscopy.