Exfoliated semiconducting pure 2H-MoS₂ and 2H-WS₂ assisted by chlorosulfonic acid

Abstract

Chlorosulfonic acid assisted the exfoliation of MoS2 and WS2 resulting in retaining their semiconducting 2H-phase, sharply contrasting the semiconducting-to-metallic phase-transition observed with the currently available exfoliation techniques.

Functionalization of MoS2 with 1,2-dithiolanes: toward donor-acceptor nanohybrids for energy conversion

“…23 The general scheme for the functionalization process is illustrated in Fig. 1 (structural characterization data for 1,2-dithiolanes 1a and 1b are presented at the Supplementary Information, Figs.…”

“…[16][17][18][19][20][21][22] On the other hand, we recently reported a facile approach for the exfoliation of MoS 2 and WS 2 polytypes with trigonal prismatic geometry and semiconducting properties with a direct band-gap, by treating the corresponding bulk materials with chlorosulfonic acid. 23 The TMD layers are protonated by the superacid and kept apart due to developed electrostatic repulsive interactions, however, without being oxidized. Nevertheless, despite the progress achieved so far targeting the exfoliation of MoS 2 , its covalent functionalization is still hampered.…”

Possibility of combining ferroelectricity and Rashba-like spin splitting in monolayers of the1T-type transition-metal dichalcogenidesMX2(M=Bruyer1, Sante2, Barone3 et al. 2016Phys. Rev. B

“…However, the isolated MX 2 layers retaining the properties of those in the bulk can be re-generated by annealing them at elevated temperature 21 , probably because the alkali cations on their surface are removed in the form of alkali metal atoms. It is also noted that separated MX 2 layers retaining the properties of the bulk MX 2 are obtained by using chlorosulfonic acid instead of alkali metals 22 . Therefore, it should be possible to prepare separated t-MoS 2 layers and verify their ferroelectric properties predicted in the present work.…”

“…MoS 2 monolayers obtained via mechanical exfoliation method typically mantain the trigonal prismatic coordination and the acentric (albeit nonpolar) crystal structure; on the other hand, the chemical exfoliation method may result in different octahedral coordinated phases, that can be obtained by distorting the so-called 1T (TiS 2 -like) polytype, alongside the 2H phase [12][13][14][15][16][17][18][19][20][21][22] . The ideal 1T-MX 2 polytype (henceforth labeled as i-MX 2 ) comprises layers of undistorted edgesharing MX 6 octahedra and displays inversion symmetry; however, the metal ions in the layers of 1T-MX 2 dichalcogenides can undergo a variety of metal-atom clustering, depending on its d-electron counting, d…”

“…Experimentally, separated MX 2 layers of 1T-and 2H-MX 2 phases can be obtained by chemically exfoliating them [18][19][20][21][22] . In the typical intercalation-exfoliation method, the binding between adjacent MX 2 layers is loosened by first intercalating alkali metals (e.g., Li, Na, K) between them, and then the layers are separated by solvents [18][19][20][21] .…”