Research ArticleChemistry

Regulating the reactivity of black phosphorus via protective chemistry

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Science Advances  11 Nov 2020:
Vol. 6, no. 46, eabb4359
DOI: 10.1126/sciadv.abb4359
  • Fig. 1 Schematic illustration of regulating the reactivity of BP via protective chemistry.

    Protective step 1: Binding Al3+ ions with lone pair electrons on the surface of P atoms decreases surface electron density of BP, leading to a reduced chemical reactivity of BP. Protective step 2: Self-assembly of the hydrophobic dense array on the BP surface isolates BP from surrounding oxygen/water. Deprotective step: Removal of Al3+ ions and hydrophobic dense array on the BP surface by a chelating agent. The treatment recovers the electron density of BP, restoring the original reactivity of the deprotected BP. BDT, 1,2-benzenedithiol; EDTA-4Na, EDTA-tetrasodium.

  • Fig. 2 Characterization of BP/Al3+/BDT.

    (A) TEM image. (B) AFM (height profile along the white line) image. (C) STEM–energy-dispersive x-ray spectroscopy (EDX) elemental mapping images. (D) High-angle annular dark-field (HAADF) image. (E) Magnified HAADF image taken from the selected area in (D). a.u.: arbitrary units. (F) Selected-area electron diffraction (SAED) pattern of BP and BP/Al3+/BDT. (G) FTIR spectra of BP, BP/Al3+, BP/Al3+/BDT, and BDT. (H) 1H NMR spectra of BP, BP/Al3+/BDT, and BDT. (I) Thermogravimetric curves of BP and BP/Al3+/BDT. ppm, parts per million.

  • Fig. 3 Characterization of degraded BP and BP/Al3+/BDT under ambient conditions.

    Polarizing microscope images of (A) bulk BP (0, 1, and 7 days) and (B) bulk BP/Al3+/BDT (0, 30, and 60 days). Insets: Corresponding TEM images. Scale bars, 200 nm. (C and D) HR-XPS spectra of P 2p peaks for BP and BP/Al3+/BDT with ambient exposure for various durations. (E and F) UV-vis spectra of BP and BP/Al3+/BDT dispersed in water for various durations. Insets: variation of the UV-vis absorption ratios at 470 nm (A/A0) of BP (A0: original value).

  • Fig. 4 Mechanism of reactivity decrease in protected BP.

    (A) Full XPS spectra of BP, BP/Al3+, and BP/Al3+/BDT. (B and C) HR-XPS spectra of P 2p and Al 2p. (D to F) Calculated NBO charge of P atom, Al3+ ion, and S atom. Structure model of (G1) BP/Al3+ and (G2) BP/Al3+/BDT. Computational mapping of electron density difference in (G3) BP/Al3+ and (G4) BP/Al3+/BDT. Green regions indicate increased electron density, and blue regions indicate decreased electron density. Contours are shown at the 0.0001 a.u. level. (H) Water contact angles of BP, BP/Al3+, and BP/Al3+/BDT.

  • Fig. 5 Deprotection of BP/Al3+/BDT.

    (A) Schematic illustration of Al3+ ion and BDT removal by EDTA-4Na. (B) Photoluminescence (PL) emission spectra of Al3+ residue on BP/Al3+/BDT after EDTA-4Na treatment. (C) Plot of ln (Ct/C0) as a function of EDTA-4Na treatment time. (D and E) HR-XPS spectra of P 2p, Al 2p, and S 2p for BP, BP/Al3+/BDT, and deprotected BP/Al3+/BDT. (F) Plots of water contact angles and zeta potentials of BP as measured at each protective-deprotective cycle. (G) Polarizing microscope images of bulk BP (0 and 7 days) and bulk deprotected BP/Al3+/BDT (0 and 7 days). (H) Variation of PO43− concentration in solutions of BP and deprotected BP/Al3+/BDT with varying ambient exposure durations. (I) Stability of deprotected BP/Al3+/BDT with a varying residual amount of Al3+ ion on the BP surface. (J) TEM images of BP, BP/Al3+/BDT, and deprotected BP/Al3+/BDT after HAuCl4 (aqueous solution) treatment.

Supplementary Materials

  • Supplementary Materials

    Regulating the reactivity of black phosphorus via protective chemistry

    Xiao Liu, Liangping Xiao, Jian Weng, Qingchi Xu, Wanli Li, Chunhui Zhao, Jun Xu, Yanli Zhao

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