Synthesis and Optoelectronic Properties of Solid Solution MXenes

NON-TECHNICAL DESCRIPTION: MXenes are a large class of two-dimensional carbides and nitrides that exhibit exceptional electronic, optical and charge storage properties. They were discovered at Drexel University a decade ago. MXenes are comprised of layers of metal atoms connected by carbon or nitrogen atoms and having thickness of less than one nanometer.

Their unique combination of electronic conductivity and tunable optical properties, such as a wide range of plasmonic colors, may be a game-changer in optics and electronics. More than 30 different MXene compositions have been synthesized; dozens more are predicted to exist. However, in spite of total number of publications on MXenes approaching 3000, just a few solid solutions (structures with a random mix of metal atoms) have been reported.

Solid solution MXenes that are synthesized in this study greatly expand the family of two-dimensional (2D) materials and offer an opportunity for precise tuning of electronic and optical properties of MXenes. These materials can find applications in the manufacturing of transparent conductive electrodes for solar cells, smart windows, transparent heaters, optical filters, etc.

Courses covering synthesis and characterization of MXenes are developed as a part of this project and offered online. Graduate and undergraduate students participating in this project are offered research co-operative education and internships at the National Nanofabrication Facility in South Korea to learn nanofabrication and perform fabrication and testing of MXene-based optical devices, such as transparent light emission diodes and electrically tunable optical filters.

TECHNICAL DETAILS: The primary goal of this work is to establish direct experimental relationships between chemical compositions of solid solution MXene and their resulting properties. Solid solution MXene research is expanded into diverse structures and chemistries in order to study and generalize these relationships, and thus to enable specific optical and plasmonic properties to be rationally chosen based on the desired application.

This project includes (i) synthesis of quaternary MAX phase precursors with the desired compositions; (ii) finding the appropriate conditions for topochemical conversion of the MAX precursors into MXenes, (iii) determining the conductivity and optical properties of MXenes, and (iv) using an array of advanced characterization techniques to determine the composition and structure of solid-solution MXenes and correlate them with the measured properties.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.