You are here:
A One-Step Delamination Procedure to Form Single Sheet Iron(III)-(oxy)Hydroxides
Citation:
Huang, L., L. Fang, T. Hassenkam, K. N. Dalby, K. G. Scheckel, AND H. B. Hansen. A One-Step Delamination Procedure to Form Single Sheet Iron(III)-(oxy)Hydroxides. Liz Dunn (ed.), Journal of Materials Chemistry A. Royal Society of Chemistry, Cambridge, Uk, 1(43):13664-13671, (2013).
Impact/Purpose:
A new type of nanosheet with atomic thickness and ultimate two-dimensional (2D) anisotropy has attracted much attention.1-3 This new class of materials exhibits novel physico-chemical properties distinct from bulk or even nano-sized materials.1 The formation of 2D nanosheets of iron-(oxy)hydroxides, here termed single sheet iron-(oxy)hydroxide (SSI), has never been reported although great effort has been made to do so.12-14 The two major challenges for synthesis of SSI are (i) identification of a source comprising SSI, and (ii) development of a method to isolate the SSI from the source. There are only two known sources that contain SSI: iron(II) hydroxide and layered iron(II)-iron(III) hydroxides. The latter which are known as green rusts (GRs) belong to the family of layered double hydroxides (LDHs).26 In the present work we have investigated this approach for the first time: delamination of the dodecanoate-intercalated iron(III)-(oxy)hydroxide LDH via deprotonation of the hydroxyl groups of the host metal-(oxy)hydroxide, resulting in charge reversal and hence repulsion between the dodecanoate interlayer and the metal-(oxy)hydroxide layers. The resulting product has been investigated by means of atomic force microscopy (AFM), transmission electron microscopy (TEM) with selected area electron diffraction (SAED), X-ray photoelectron spectroscopy (XPS), X-ray absorption spectroscopy (XAS) and other techniques. The delamination takes place with one-step dispersion in aqueous NaOH solution at room temperature excluding high-temperature reaction and toxic organic solvents used in similar studies.4-8
Description:
The dispersion of a layered iron(III)-(oxy)hydroxide intercalated with dodecanoate (oxGRC12, Fe3IIIO2.18(OH)3.13(C12H23O2)0.56(SO4)0.47; derived from the corresponding layered iron(II)-iron(III)-hydroxide) in 0.1 M sodium hydroxide results in delamination of oxGRC12 with formation of separate planar layers of iron(III)-(oxy)hydroxides, here termed single sheet iron-(oxy)hydroxides (SSI). Delamination is confirmed by powder X-ray diffraction while Fourier transform infrared spectroscopy reveals the removal of dodecanoate from the parent compound. Atomic force microscopy shows that SSI has a thickness of 1 nm and the lateral size ranging from 100 to 200 nm. The observed thickness of SSI is double the thickness of the iron(III)-(oxy)hydroxide layers (0.48 nm) which is attributed to water layers adsorbed on both sides of SSI. The SSI shows a high tendency to aggregate. High resolution transmission electron microscopy and selected area electron diffraction confirm that SSI inherits the in-plane crystal structure from its parent layered compound. Both the hyperfine parameters and the X-ray absorption spectrum show a similar local iron coordination in SSI before and after delamination. The extended X-ray absorption fine structure spectra also show that the FeO6 octahedron has expanded to some extent (1–2%) after delamination. O1s X-ray photoelectron spectra of SSI reveal extensive deprotonation of hydroxyl groups in SSI, reflecting a layer charge reversal during delamination. To the best of our knowledge, this is the first report of planar 2D nanosheets of iron-(oxy)hydroxide with the thickness of 1 nm.
