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Heterogeneous Structure of Chemically Derived Two Dimensional Crystals

Speaker: 
Dr Goki Eda
Date: 
Thu, 27/09/2012 - 12:00pm to 1:00pm
Location: 
S13-M01-11 (Physics Conference Room)
Event Type: 
Seminars

Abstract:

Layered compounds in which individual layers are held together by weak van der Waals forces represent a rich source of two-dimensional (2D) molecular crystals. The ability to isolate atomically thin 2D crystals from layered parent structures enables observation of intriguing physical phenomena associated with its dimensionality while also opening up new perspectives on potential applications. Solution-based exfoliation of layered materials is a scalable route to producing 2D crystals and manipulating them in bulk quantities. In this talk, I will discuss chemical exfoliation of graphite and molybdenum disulfide (MoS2) and their unique properties.

Chemical exfoliation often leads to chemical and physical modification of the initial material. The electronic properties of the derived 2D crystals deviate from those of the pristine materials, thus leading to emergence of properties absent in the pristine materials. In the case of graphene, strong covalent modification by oxygen functionalization in the exfoliation process leads to localization of pi electrons and formation of local energy gaps. This manifests as unique photoluminescence behavior in graphene oxide.

Similar but non-chemical modification takes place in some layered transition metal dichalcogenides (LTMD) leading to remarkable changes in their electronic properties. Chemical exfoliation of MoS2 and WS2 compounds via lithium intercalation leads to formation of 2D sheets with unique mixed phase structures. Potential applications of these materials will be discussed.

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