Emerging metal ion-coordinated black phosphorus nanosheets and black phosphorus quantum dots with excellent stabilities

Abstract

In this work, emerging metal ion-coordinated black phosphorus nanosheets (M@BPNSs) and quantum dots (M@BPQDs) were prepared via the sonication-assisted liquid-phase exfoliation of bulk black phosphorus (BP) crystals in the presence of a metal ion (M) and solvothermal reaction of the exfoliated few-layer M@BP nanosheets. Based on theoretical calculations, a bonding mode exists between M and BP. Consequently, the adsorption energies of M on BP via the bonding mode are lower than that of M on BP via the non-bonding mode. Under the bonding mode, the adsorption energy of Zn²⁺ (−2.04 eV) on BP is lower than other M. Zn²⁺, serves as the preferred M and can be easily adsorbed on the surface of BP. We experimentally prepared emerging M@BPNSs and M@BPQDs, characterized, and compared various morphologies, microstructures and spectra under different conditions. It is verified, that the surface coordination of M with BP protects BP from oxidization and degradation of its nanostructures upon exposure to O₂ and H₂O. In comparison to the bare BPNSs, Zn@BPNSs showed high microstructural stability. Moreover, in comparison to bare BPQDs, Zn@BPQDs exhibited high colloidal stability and excellent stabilities with fluorescence and photothermal conversion performances. The long-term stabilities are due to the M-coordination with BP through P–M bonding on BP nanostructures. Thus, the excellent long-term stabilities in microstructure, fluorescence and photothermal conversion levels endow the emerging two-dimensional M@BPNSs and zero-dimensional M@BPQDs with great prospects towards promising applications, especially in electronics, optoelectronics, optical and biomedical fields.