Synthesis and Characterization of Two-Dimensional Mn+1Xn Layers Derived from the MAX Phases

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NON-TECHNICAL SUMMARY: Atomically thin two-dimensional (2D) materials have unique properties compared to their conventional three-dimensional counterparts. Graphene, which is a single atomic layer of carbon, is the most illustrious and studied of these newly emerging 2D materials. Graphene, however, is limited to just one element - carbon. Recently, a new family of 2D early transition metal (e.g. titanium, vanadium, niobium, etc.) carbides and carbonitrides (so called MXene) was reported. These 2D materials offer a large variety of chemical compositions compared to graphene and they can exist in different numbers of atomic layers. MXenes may have a wide range of potential applications, ranging from composite reinforcements, to industrial catalysts, to energy storage and electronic devices. Before the best application can be identified, however, the fundamental physics of these materials must be developed and the synthesis-structure-property relationships must be established. Combined experimental and theoretical work will be used to understand the surface chemistry, structure and properties of MXenes compounds. This work could result in batteries that charge in minutes for thousands of cycles or robust supercapacitors that can be used for very high power energy storage applications such as regenerative breaking in cars. TECHNICAL DETAILS: Recently, a new family of 2D early transition metal (e.g. titanium, vanadium, niobium, etc.) carbides and carbonitrides (so called MXene) was discovered. The latter offer a large variety of chemical compositions, as multiple atoms can co-exist in the 2D sheets. Furthermore MXenes exist in 3, 5 or 7 atomic layers. The as-synthesized MXene surfaces are functionalized with OH, O, and/or F. Theoretical calculations predict that the MXenes can be either conductors or semiconductors depending on their surface chemistry. MXenes may have a wide range of potential applications, ranging from composite reinforcements, to industrial catalysts, to energy storage and electronic devices. Since this class of solids is quite new, the fundamental basic science of these materials must be developed and their synthesis-structure-property relationships need to be established. The aims of this project are: (i) isolate single MXene layers on different substrates, (ii) determine whether these layers have attractive electronic properties like graphene and could thus be used as transistors, (iii) measure the electrical and optical characteristics of these films, as a function of surface terminations and MXene chemistry, (iv) disperse the 2D sheets in various solvents, including water, and form stable suspensions, (v) use various spectroscopy techniques to investigate MXene surfaces and correlate them to theoretical first principles calculations to fully understand the surface chemistry and its effect on properties, (vi) investigate how MXene surfaces can be chemically functionalized and understand the effects of such functionalization on the aforementioned properties, and (vii) spin-coat MXene thin films and measure their optical and transport properties. This work offers exciting research opportunities for students - undergraduate students will be trained on state of the art equipment and graduate students will work towards their doctorates.