Colloidal Synthesis Of Fluorescent MoX2 (X = S, Se) Nanosheets Via a Design Of Experiments Approach

Gabriele Pippia^a, Anastasia Rousaki^a, Matteo Barbone^b^,^c, Jonas Billet^a, Rosaria Brescia^d, Anatolii Polovitsyn^d, Beatriz Martín-García^d, Marko Petric^b^,^c, Amine Ben-Mhenni^b, Isabel Van Driessche^a, Peter Vandenabeele^a, Kai Müller^b^,^c, Iwan Moreels^a

^aGent University, Department of Chemistry, BE, Ghent, Belgium

^bWalter Schottky Institute, Technische Universität München, Am Coulombwall 4, Garching, Germany

^cMunich Center for Quantum Science and Technology (MCQST), Schellingstraße, 4, München, Germany

^dIstituto Italiano di Tecnologia, via Morego 30, 16163 Genova (GE), Italy

Materials for Sustainable Development Conference (MATSUS)
Proceedings of nanoGe Spring Meeting 2022 (NSM22)

#NANOQ22. Colloidal Semiconductor nanocrystals for Quantum Technologies

Online, Spain, 2022 March 7th - 11th

Organizers: Francesco Di Stasio, Iwan Moreels and Riccardo Sapienza

Contributed talk, Gabriele Pippia, presentation 300
DOI: https://doi.org/10.29363/nanoge.nsm.2022.300
Publication date: 7th February 2022

Transition metal dichalcogenide (TMD) nanosheets have become an intensively investigated topic in the field of 2D nanomaterials, due to their semiconductor nature, the direct band gap transition and the broken inversion symmetry going from bulk to monolayer. These properties makes TMDs suitable for different technological applications such as photovoltaics, valleytronics, or hydrogen evolution reactions (HER), or transistors. Among them, MoX₂ (X = S, Se) are only direct-gap semiconductors when their thickness is reduced to a monolayer, hence an important effort is devoted to obtain single layer TMDs. Colloidal synthesis of TMDs has been developed in recent years as it provides a cost-efficient and scalable way to produce few-layer TMDs having homogenous size and thickness, yet obtaining a monolayer has proved challenging. Here we present a general method for the colloidal synthesis of mono- and few-layer MoX₂ (X = S, Se) using elemental chalcogenide and metal chloride as precursors. Using a synthesis with slow injection of the MoCl₅ precursor under nitrogen atmosphere, and optimizing the synthesis parameters with a Design Of Experiments (DOE) approach, we obtained a monolayer MoX₂ sample with the required semiconducting (2H) phase, a band gap of 1.96 eV for 2H-MoS₂ and 1.67 eV for 2H-MoSe₂, respectively, both displaying fluorescence at cryogenic and elevated temperatures. A correlation between the blue shifted absorption spectrum and the spectral difference between the Raman modes was established and confirmed that a single-layer thickness was obtained.

Acknowledgements:

This project has received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement No. 714876 PHOCONA). A. R. thanks the Research Foundation–Flanders (FWO‐Vlaanderen) for her postdoctoral fellowship (12X1919N)

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