Researchers in Lab of Laser Fabrication in Liquids, Institute of Solid State Physics, Hefei Institutes of Physical Science reported the their research results of facet-dependent selective adsorption of Mn-doped α-Fe₂O₃ nanocrystals toward heavy metal ions in Chemistry of Materials.

Hematite (α-Fe₂O₃ ) is naturally abundant and thermodynamically the most stable semiconductor among ferric oxides. α-Fe₂O₃  has shown important applications in photoelectrochemical water splitting, lithium-ion batteries, gas sensing, and biotechnology.

Recently, morphological control of α-Fe₂O₃  nanocrystals draws much attention for developing effective catalysts. Thus, it would be interesting to synthesize hematite nanocrystalline with exposed active by doping Mn impurities in laser ablation technology.

Researchers find that the face selectivity of Mn-doped α-Fe₂O₃  nanocrystals (NCs) is related to the doping level of elemental Mn.

By increasing the doping level of Mn, they finally successfully obtained isotropic polyhedral nanoparticles (NPs), {116}-faceted saucershaped nanosheets (NSs), and {001}-faceted hexagonal NSs. Interestingly, these Mn-doped α-Fe₂O₃  NCs show a facet-dependent adsorption ability toward Pb(II), Cd(II), and Hg(II) heavy-metal ions, which was further testified by density functional theory (DFT) calculations.

These experimental and computational results not only shed new light on the facet-related properties, but also guide the design of crystals with exposed active facets for specific applications.

This research was supported by China National Key Basic Research Program, National Natural Science Foundation.

Link to the paper: Facet-Dependent Selective Adsorption of Mn-Doped α-Fe₂O₃  Nanocrystals toward Heavy-Metal Ions

Figure 1. (A-C) Typical low-magnification TEM images of the Mn-doped α-Fe₂O₃  NCs with shapes of polyhedral nanoparticles (NPs), saucer shaped nanosheets (NSs), and hexagonal nanosheets (NSs). Insets in panels a-c are size distribution histograms of the Mn-doped α-Fe₂O₃ NCs. (D-F) HRTEM images of individual Mn-doped α-Fe₂O₃ polyhedral NPs, saucer-shaped NSs, and hexagonal NSs. Corresponding typical low-magnification TEM images and SAED patterns displayed in the insets of panels D-F; the scale bar in the inset is 10 nm. (G-I) HADDF-STEM images with superimposed line scans from EDX of Fe, Mn, and O elements across single Mn-doped α-Fe₂O₃ polyhedral NPs, saucer-shaped NSs, and hexagonal NSs. Optimized adsorption structure of heavy-metal atoms Pb and Cd on α-Fe2O3 (001) and (116) surfaces: (J) Pb on (001), (K) Cd on (001), (L) Pb on (116), and (M) Cd on (116). Units of bond length are A. (N) The schematic of facet-dependent selective adsorption of Mn-doped Fe₂O₃.  (Image by YUAN Qinglin )

Contact:

ZHOU Shu

Hefei Institutes of Physical Science (http://english.hf.cas.cn/)

Email: zhous@hfcas.ac.cn