With the advent of graphene, the most studied of all two-dimensional materials, many inorganic analogues have been synthesized and are being exploited for novel applications. Several approaches have been used to obtain large-grain, high-quality materials. Naturally occurring ores, for example, are the best precursors for obtaining highly ordered and large-grain atomic layers by exfoliation. Here, we demonstrate a new two-dimensional material ‘hematene’ obtained from natural iron ore hematite (α-Fe2O3), which is isolated by means of liquid exfoliation. The two-dimensional morphology of hematene is confirmed by transmission electron microscopy. Magnetic measurements together with density functional theory calculations confirm the ferromagnetic order in hematene while its parent form exhibits antiferromagnetic order. When loaded on titania nanotube arrays, hematene exhibits enhanced visible light photocatalytic activity. Our study indicates that photogenerated electrons can be transferred from hematene to titania despite a band alignment unfavourable for charge transfer.
Subscribe to Journal
Get full journal access for 1 year
only $14.08 per issue
All prices are NET prices.
VAT will be added later in the checkout.
Rent or Buy article
Get time limited or full article access on ReadCube.
All prices are NET prices.
Butler, S. Z. et al. Progress, challenges, and opportunities in two-dimensional materials beyond graphene. ACS Nano 7, 2898–2926 (2013).
Ajayan, P. M., Kim, P. & Banerjee, K. Two-dimensional van der Waals materials. Phys. Today 69, 38–44 (2016).
Novoselov, K. S. et al. Two-dimensional atomic crystals. Proc. Natl Acad. Sci. USA 102, 10451–10453 (2005).
Service, R. F. Beyond graphene. Science 348, 490–492 (2015).
Mas-Balleste, R., Gomez-Navarro, C., Gomez-Herrero, J. & Zamora, F. 2D materials: to graphene and beyond. Nanoscale 3, 20–30 (2011).
Xu, M. S., Liang, T., Shi, M. M. & Chen, H. Z. Graphene-like two-dimensional materials. Chem. Rev. 113, 3766–3798 (2013).
Kan, E. et al. Two-dimensional hexagonal transition-metal oxide for spintronics. J. Phys. Chem. Lett. 4, 1120–1125 (2013).
Marelli, M. et al. Hierarchical hematite nanoplatelets for photoelectrochemical water splitting. ACS Appl. Mater. Interfaces 6, 11997–12004 (2014).
Mishra, M. & Chun, D.-M. α-Fe2O3 as a photocatalytic material: a review. Appl. Catal. A 498, 126–141 (2015).
Chen, J., Xu, L., Li, W. & Gou, X. α-Fe2O3 nanotubes in gas sensor and lithium-ion battery applications. Adv. Mater. 17, 582–586 (2005).
Zeng, H., Li, J., Liu, J. P., Wang, Z. L. & Sun, S. Exchange-coupled nanocomposite magnets by nanoparticle self-assembly. Nature 420, 395–398 (2002).
Sivula, K., Le Formal, F. & Grätzel, M. Solar water splitting: progress using hematite (α-Fe2O3) photoelectrodes. ChemSusChem 4, 432–449 (2011).
Teja, A. S. & Koh, P.-Y. Synthesis, properties, and applications of magnetic iron oxide nanoparticles. Prog. Cryst. Growth Charact. Mater. 55, 22–45 (2009).
Kennedy, J. H. & Frese, K. W. Photooxidation of water at α‐Fe2O3 electrodes. J. Electrochem. Soc. 125, 709–714 (1978).
Kennedy, J. H. & Frese, K. W. Flatband potentials and donor densities of polycrystalline α‐Fe2O3 determined from Mott–Schottky plots. J. Electrochem. Soc. 125, 723–726 (1978).
Scanlon, D. O. et al. Band alignment of rutile and anatase TiO2. Nat. Mater. 12, 798–801 (2013).
deFaria, D. L. A., Silva, S. V. & de Oliveira, M. T. Raman microspectroscopy of some iron oxides and oxyhydroxides. J. Raman Spectrosc. 28, 873–878 (1997).
McCarty, K. F. Inelastic light scattering in α-Fe2O3: phonon vs magnon scattering. Solid State Commun. 68, 799–802 (1988).
Bersani, D., Lottici, P. P. & Montenero, A. Micro-Raman investigation of iron oxide films and powders produced by sol-gel syntheses. J. Raman Spectrosc. 30, 355–360 (1999).
Campbell, I. H. & Fauchet, P. M. The effects of microcrystal size and shape on the one phonon Raman spectra of crystalline semiconductors. Solid State Commun. 58, 739–741 (1986).
Jang, J.-W. et al. Enabling unassisted solar water splitting by iron oxide and silicon. Nat. Commun. 6, 7447 (2015).
Shim, S. H. & Duffy, T. S. Raman spectroscopy of Fe2O3 to 62 GPa. Am. Mineral. 87, 318–326 (2002).
Chastain, J., King, R. C. & Moulder, J. Handbook of X-ray Photoelectron Spectroscopy: A Reference Book of Standard Spectra for Identification and Interpretation of XPS Data (Physical Electronics, Eden Prairie, MN, 1995).
Lu, X. et al. Oxygen-deficient hematite nanorods as high-performance and novel negative electrodes for flexible asymmetric supercapacitors. Adv. Mater. 26, 3148–3155 (2014).
He, Y. P. et al. Size and structure effect on optical transitions of iron oxide nanocrystals. Phys. Rev. B 71, 125411 (2005).
Thomas, P., Sreekanth, P. & Abraham, K. E. Nanosecond and ultrafast optical power limiting in luminescent Fe2O3 hexagonal nano morphotype. J. Appl. Phys. 117, 053103 (2015).
Wheeler, D. A., Wang, G., Ling, Y., Li, Y. & Zhang, J. Z. Nanostructured hematite: synthesis, characterization, charge carrier dynamics, and photoelectrochemical properties. Energy Environ. Sci. 5, 6682–6702 (2012).
Zou, B. et al. Anomalous optical properties and electron-phonon coupling enhancement in Fe2O3 nanoparticles coated with a layer of stearates. J. Phys. Chem. Solids 58, 1315–1320 (1997).
Cornell, R. M. & Schwertmann, U. The Iron Oxides: Structure, Properties, Reactions, Occurrences and Uses (John Wiley & Sons, Weinheim, 2003).
Nosé, S. A unified formulation of the constant temperature molecular dynamics methods. J. Chem. Phys. 81, 511–519 (1984).
Hill, A. et al. Neutron diffraction study of mesoporous and bulk hematite, α-Fe2O3. Chem. Mater. 20, 4891–4899 (2008).
Robinson, P., Harrison, R. J. & McEnroe, S. A. Lamellar magnetism in the haematite-ilmenite series as an explanation for strong remanent magnetization. Nature 418, 517–520 (2002).
Grønvold, F. & Samuelsen, E. J. Heat capacity and thermodynamic properties of α-Fe2O3 in the region 300–1050 K. antiferromagnetic transition. J. Phys. Chem. Solids 36, 249–256 (1975).
Morin, F. J. Magnetic susceptibility of α-Fe2O3 and α-Fe2O3 with added titanium. Phys. Rev. 78, 819–820 (1950).
Moriya, T. Anisotropic superexchange interaction and weak ferromagnetism. Phys. Rev. 120, 91–98 (1960).
Zysler, R. D. et al. Size effects in the spin–flop transition of hematite nanoparticles. J. Magn. Magn. Mater. 272–276, 1575–1576 (2004).
Schroeer, D. & Nininger, R. C. Morin transition in α-Fe2O3 microcrystals. Phys. Rev. Lett. 19, 632–634 (1967).
Sorescu, M., Brand, R. A., Mihaila-Tarabasanu, D. & Diamandescu, L. The crucial role of particle morphology in the magnetic properties of haematite. J. Appl. Phys. 85, 5546–5548 (1999).
Jiao, F. et al. Ordered mesoporous Fe2O3 with crystalline walls. J. Am. Chem. Soc. 128, 5468–5474 (2006).
Liu, L., Kou, H.-Z., Mo, W., Liu, H. & Wang, Y. Surfactant-assisted synthesis of α-Fe2O3 nanotubes and nanorods with shape-dependent magnetic properties. J. Phys. Chem. B 110, 15218–15223 (2006).
Rollmann, G., Rohrbach, A., Entel, P. & Hafner, J. First-principles calculation of the structure and magnetic phases of hematite. Phys. Rev. B 69, 165107 (2004).
Kontos, A. I. et al. Self-organized anodic TiO2 nanotube arrays functionalized by iron oxide nanoparticles. Chem. Mater. 21, 662–672 (2009).
Pelaez, M. et al. A review on the visible light active titanium dioxide photocatalysts for environmental applications. Appl. Catal. B 125, 331–349 (2012).
Rao, B. M., Torabi, A. & Varghese, O. K. Anodically grown functional oxide nanotubes and applications. MRS Commun. 6, 375–396 (2016).
Paulose, M. et al. Anodic growth of highly ordered TiO2 nanotube arrays to 134 µm in length. J. Phys. Chem. 110, 16179–16184 (2006).
Ohsaka, T., Izumi, F. & Fujiki, Y. Raman spectrum of anatase, TiO2. J. Raman Spectrosc. 7, 321–324 (1978).
LaTempa, T. J., Feng, X., Paulose, M. & Grimes, C. A. Temperature-dependent growth of self-assembled hematite (α-Fe2O3) nanotube arrays: rapid electrochemical synthesis and photoelectrochemical properties. J. Phys. Chem. C. 113, 16293–16298 (2009).
Plimpton, S. Fast parallel algorithms for short-range molecular dynamics. J. Comput. Phys. 117, 1–19 (1995).
van Duin, A. C. T., Dasgupta, S., Lorant, F. & Goddard, W. A. ReaxFF: a reactive force field for hydrocarbons. J. Phys. Chem. A 105, 9396–9409 (2001).
Aryanpour, M., van Duin, A. C. T. & Kubicki, J. D. Development of a reactive force field for iron−oxyhydroxide systems. J. Phys. Chem. A 114, 6298–6307 (2010).
Hoover, W. G. Canonical dynamics: equilibrium phase-space distributions. Phys. Rev. A 31, 1695–1697 (1985).
Clark, S. J. et al. First principles methods using CASTEP. Z. Krist. Cryst. Mater. 220, 567–570 (2005).
Perdew, J. P. et al. Atoms, molecules, solids, and surfaces: applications of the generalized gradient approximation for exchange and correlation. Phys. Rev. B 46, 6671–6687 (1992).
Pozun, Z. D. & Henkelman, G. Hybrid density functional theory band structure engineering in hematite. J. Chem. Phys. 134, 224706 (2011).
A.P.B. acknowledges University Grants Commission, Government of India for Basic Scientific Research (BSR) Fellowship (Grant No. No.F.25-1/2013-14 (BSR)/5-22/2007(BSR) dated 30/05/2014). A.P.B., S.R., C.S.T, A.A., V.K. and P.M.A. acknowledge the US Army Research Office MURI grant W911NF-11-1-0362 for financial assistance. A.P.B., P.M.A. and R.V. acknowledge support from the Airforce Office of Scientific Research (AFOSR) through Grant No. FA9550-14-1-0268. C.F.W. thanks the São Paulo Research Foundation (FAPESP) Grant No. 2016/12340-9 for financial support. Computational and financial support from the Center for Computational Engineering and Sciences at Unicamp through the FAPESP/CEPID Grant No. 2013/08293-7 is acknowledged. L.D and C.-W.C. thank the US Air Force Office of Scientific Research Grant FA9550-15-1-0236, the T. L. L. Temple Foundation, the John J. and Rebecca Moores Endowment, and the State of Texas through the Texas Center for Superconductivity at the University of Houston for financial support. O.K.V. thanks Shell International Exploration and Production Inc. Game Changer and New Energies Research and Technology group for financial support. A.M.R. acknowledges India based neutrino observatory (INO) for the travel grant and University Grants Commission (UGC), India for awarding UGC-BSR Faculty Fellowship.
The authors declare no competing interests.
Publisher’s note: Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.
About this article
Cite this article
Puthirath Balan, A., Radhakrishnan, S., Woellner, C.F. et al. Exfoliation of a non-van der Waals material from iron ore hematite. Nature Nanotech 13, 602–609 (2018). https://doi.org/10.1038/s41565-018-0134-y
IEEE Transactions on Nanotechnology (2020)
The Journal of Physical Chemistry C (2020)
ACS Applied Materials & Interfaces (2020)
Journal of Materials Chemistry A (2020)