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-FeO), 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.

Two-dimensional (2D) materials from naturally occurring minerals are promising and possess interesting physical properties. A new 2D material "Ilmenene" has been exfoliated from the naturally occurring titanate ore ilmenite (FeTiO 3 ) by employing liquid phase exfoliation in a dimethylformamide solvent by ultrasonic bath sonication. Ilmenene displays a [001] orientation that is confirmed by transmission electron microscopy. Probable charge transfer excitation from Fe 2+ Ti 4+ to Fe 3+ Ti 3+ results in ferromagnetic ordering along with the antiferromagnetic phase accompanied by enhanced anisotropy due to surface spins. The 2D nature and band gap states help ilmenene form a heterojunction photocatalyst with titania nanotube arrays, capable of broad spectrum light harvesting and separating/transferring the photogenerated charges effectively for solar photoelectrochemical water splitting.

Metal tellurides are highly sought after for energy and spintronic applications much of which is owed to its catalytic and magnetic properties. Confining it into twodimensions and improving the surface area enriches its catalytic activity and magnetic properties. Herein, we demonstrate the isolation of ultrathin two-dimensional sheets of manganese(II)telluride having an average thickness of ∼2 nm and flake size of ∼100 nm by means of liquid phase exfoliation presumably for the first time. Vanishing of exchange interactions in two-dimensions results in paramagnetic ordering in manganese(II)telluride sheets while its pristine form prefers antiferromagnetic order. The exfoliated two-dimensional sheets were used to sensitize titania nanotubes to broaden the absorption spectrum and utilize visible light for photoelectrochemical water splitting.

Abstract

No abstract