Synthesis of an aqueous, air-stable, superconducting 1T′-WS ₂ monolayer ink

Abstract

Liquid-phase chemical exfoliation can achieve industry-scale production of two-dimensional (2D) materials for a wide range of applications. However, many 2D materials with potential applications in quantum technologies often fail to leave the laboratory setting because of their air sensitivity and depreciation of physical performance after chemical processing. We report a simple chemical exfoliation method to create a stable, aqueous, surfactant-free, superconducting ink containing phase-pure 1T′-WS 2 monolayers that are isostructural to the air-sensitive topological insulator 1T′-WTe 2 . The printed film is metallic at room temperature and superconducting below 7.3 kelvin, shows strong anisotropic unconventional superconducting behavior with an in-plane and out-of-plane upper critical magnetic field of 30.1 and 5.3 tesla, and is stable at ambient conditions for at least 30 days. Our results show that chemical processing can make nontrivial 2D materials that were formerly only studied in laboratories commercially accessible.

Acid-Assisted Soft Chemical Route for Preparing High-Quality Superconducting 2M-WS2

“…Synthesis of K 0.5 WS 2 K 0.5 WS 2 was synthesized by high-temperature solid-state methods reported previously; its crystal structure and chemical composition were reported in the same paper …”

“…Examples include gated WTe 2 monolayers, , bulk WTe 2 under pressure, , strained thin flakes of WTe 2 , bulk MoTe 2 in its 1T′ phase, and 1T′-MoS 2 monolayers. , Out of these, 2M-WS 2 has the highest superconducting transition temperature. 2M-WS 2 has been chemically exfoliated to monolayers, and thin films composed of many overlapping monolayers were shown to superconduct below 7.3 K …”

“…27,28 Out of these, 2M-WS 2 has the highest superconducting transition temperature. 2M-WS 2 has been chemically exfoliated to monolayers, and thin films composed of many overlapping monolayers were shown to superconduct below 7.3 K. 29 2M-WS 2 was first synthesized by oxidatively deintercalating potassium from K x WS 2 with K 2 Cr 2 O 7 in dilute H 2 SO 4 . 13 Recently, Lai et al reported that I 2 in acetonitrile can also fully deintercalate potassium from the starting compound to yield 2M-WS 2 .…”

Recent Progress on Phase Engineering of Nanomaterials

“…Importantly, the experimental EXAFS spectrum of the product was fitted perfectly with the theoretical spectrum for 1T′-WS 2 (Figure k). The successful preparation of the 1T′-TMD bulk crystals enabled the large-scale preparation of 1T′-TMD nanosheets by using the chemical intercalation and exfoliation method. , For example, Peng et al . reported that the 1T′-MoS 2 monolayers with a size of up to tens of micrometers can be prepared by the exfoliation of the millimeter-sized 1T′-MoS 2 crystal synthesized by the gas-solid reaction method …”

2D Materials in Flexible Electronics: Recent Advances and Future Prospectives

“…Liquid-mediated exfoliation is believed to be a viable method for producing nanosheets on a large scale. The ability to use these colloidal nanosheet suspensions to produce air-stable inks or thin films has generated significant interest in the approach and its potential . However, before the process can be scaled up, several conditions must be considered, such as solvent selection, sonication power, time, and the use of additives.…”