An iron-based 2D material from nature
- Auteur:Ella Cai
- Relâchez le:2018-08-01
An international team has added another two-dimensional material to the expanding list that started with graphene.
Hematene is a three-atom-thick iron oxide mono-layer, which has been made at Rice University in Texas by exfoliating it from the naturally-occurring iron ore heamatite (or ‘hematite’).
Hematene.-Shyam-Sinha-Peter-van-Aken-Max-Planck-Institute-StuttgartTransmission electron image shows a single sheet of hematene. Scale bar 0.5μm
Liquid exfoliation was used, a technique also used to knock graphene from naturally-occurring graphite.
“The two-dimensional morphology of hematene is confirmed by transmission electron microscopy,” said the researcher in the Nature Nanotechnology paper ‘Exfoliation of a non-van der Waals material from iron ore hematite‘.
Hematene-Cristiano-Woellner-Douglas-Galvao-State-University-of-CampinasHematene is the first known two-dimensional non-van der Waals material, consisting of iron (blue) and oxygen (white)
According to the paper, hematene has ferromagnetic order, which heamatite has anti-ferromagnetic order, and it can turn light into electricity – transferring electrons to titanium dioxide nanotubes under the influence of light.
“Hematite absorbs sunlight from ultraviolet to the yellow-orange region, but the charges produced are very short-lived. As a result, they become extinct before they reach the surface,” said University of Houston physicist Oomman Varghese, while, according to the researchers, Hematene is more efficient because photons generate negative and positive charges within a few atoms of the surface. The pairing with titanium dioxide nanotube arrays provides an easy pathway for electrons to leave the hematene, allowing more visible light to be absorbed.
Hematene-Ajayan-Research-Group-Rice-UniversityTransmission electron microscope image showing bi-layer and monolayer hematene. Scale bar = 50nm
While other 2D materials so-far discovered have been held in their original 3D form by van der Waals forces, in heamatite layers of hematene are held by chemical 3D bonding networks.
“Most 2D materials to date have been derived from bulk counterparts that are layered in nature and generally known as van der Waals solids,” said Professor Anantharaman Malie Madom Ramaswamy Iyer of the Cochin University of Science and Technology, India. “2D materials from bulk precursors having non-van der Waals 3D bonding networks are rare, and in this context hematene assumes great significance.”
The research team came from:
Department of Materials Science and NanoEngineering, Rice University, Houston, TX, USA
Department of Physics, Cochin University of Science and Technology, Kochi, Kerala, India
Applied Physics Department and Center for Computational Engineering and Sciences, State University of Campinas – UNICAMP, Campinas, Brazil
Stuttgart Center for Electron Microscopy, Max Planck Institute for Solid State Research, Stuttgart, Germany
Texas Center for Superconductivity, University of Houston, Houston, TX, USA
Scan credit: Shyam Sinha and Peter van Aken, Max Planck Institute for Solid State Research, Stuttgart, Germany
Diagram credit: Cristiano Woellner and Douglas Galvao, State University of Campinas, Brazil
Photo credit: Courtesy of the Ajayan Research Group Rice University
Hematene is a three-atom-thick iron oxide mono-layer, which has been made at Rice University in Texas by exfoliating it from the naturally-occurring iron ore heamatite (or ‘hematite’).
Hematene.-Shyam-Sinha-Peter-van-Aken-Max-Planck-Institute-StuttgartTransmission electron image shows a single sheet of hematene. Scale bar 0.5μm
Liquid exfoliation was used, a technique also used to knock graphene from naturally-occurring graphite.
“The two-dimensional morphology of hematene is confirmed by transmission electron microscopy,” said the researcher in the Nature Nanotechnology paper ‘Exfoliation of a non-van der Waals material from iron ore hematite‘.
Hematene-Cristiano-Woellner-Douglas-Galvao-State-University-of-CampinasHematene is the first known two-dimensional non-van der Waals material, consisting of iron (blue) and oxygen (white)
According to the paper, hematene has ferromagnetic order, which heamatite has anti-ferromagnetic order, and it can turn light into electricity – transferring electrons to titanium dioxide nanotubes under the influence of light.
“Hematite absorbs sunlight from ultraviolet to the yellow-orange region, but the charges produced are very short-lived. As a result, they become extinct before they reach the surface,” said University of Houston physicist Oomman Varghese, while, according to the researchers, Hematene is more efficient because photons generate negative and positive charges within a few atoms of the surface. The pairing with titanium dioxide nanotube arrays provides an easy pathway for electrons to leave the hematene, allowing more visible light to be absorbed.
Hematene-Ajayan-Research-Group-Rice-UniversityTransmission electron microscope image showing bi-layer and monolayer hematene. Scale bar = 50nm
While other 2D materials so-far discovered have been held in their original 3D form by van der Waals forces, in heamatite layers of hematene are held by chemical 3D bonding networks.
“Most 2D materials to date have been derived from bulk counterparts that are layered in nature and generally known as van der Waals solids,” said Professor Anantharaman Malie Madom Ramaswamy Iyer of the Cochin University of Science and Technology, India. “2D materials from bulk precursors having non-van der Waals 3D bonding networks are rare, and in this context hematene assumes great significance.”
The research team came from:
Department of Materials Science and NanoEngineering, Rice University, Houston, TX, USA
Department of Physics, Cochin University of Science and Technology, Kochi, Kerala, India
Applied Physics Department and Center for Computational Engineering and Sciences, State University of Campinas – UNICAMP, Campinas, Brazil
Stuttgart Center for Electron Microscopy, Max Planck Institute for Solid State Research, Stuttgart, Germany
Texas Center for Superconductivity, University of Houston, Houston, TX, USA
- Department of Chemistry, Rice University, Houston, TX, USA
- Department of Physics, University of Houston, Houston, TX, USA
- Honda Research Institute USA Inc., Columbus, OH, USA
- Lawrence Berkeley National Lab, Berkeley, CA, USA
- Department of Earth, Environmental and Planetary Sciences, Rice University, Houston, TX, USA
Scan credit: Shyam Sinha and Peter van Aken, Max Planck Institute for Solid State Research, Stuttgart, Germany
Diagram credit: Cristiano Woellner and Douglas Galvao, State University of Campinas, Brazil
Photo credit: Courtesy of the Ajayan Research Group Rice University
