Stabilization of 1T-MoS₂ Sheets by Imidazolium Molecules in Self-Assembling Hetero-layered Nanocrystals

Abstract

We report a facile, room-temperature assembly of MoS2-based hetero-layered nanocrystals (NCs) containing embedded monolayers of imidazolium (Im), 1-butyl-3-methylimidazolium (BuMeIm), 2-phenylimidazolium, and 2-methylbenzimidazolium molecules. The NCs are readily formed in water solutions by self-organization of the negatively charged, chemically exfoliated 0.6 nm thick MoS2 sheets and corresponding cationic imidazole moieties. As evidenced by transmission electron microscopy, the obtained NCs are anisotropic in shape, with thickness varying in the range 5-20 nm and lateral dimensions of hundreds of nanometers. The NCs exhibit almost turbostratic stacking of the MoS2 sheets, though the local order is preserved in the orientation of the imidazolium molecules with respect to the sulfide sheets. The atomic structure of NCs with BuMeIm molecules was solved from powder X-ray diffraction data assisted by density functional theory calculations. The performed studies evidenced that the MoS2 sheets of the NCs are of the nonconventional 1T-MoS2 (metallically conducting) structure. The sheets' puckered outer surface is formed by the S atoms and the positioning of the BuMeIm molecules follows the sheet nanorelief. According to thermal analysis data, the presence of the BuMeIm cations significantly increases the stability of the 1T-MoS2 modification and raises the temperature for its transition to the conventional 2H-MoS2 (semiconductive) counterpart by ∼70 °C as compared to pure 1T-MoS2 (∼100 °C). The stabilizing interaction energy between inorganic and organic layers was estimated as 21.7 kcal/mol from the calculated electron density distribution. The results suggest a potential for the design of few-layer electronic devices exploiting the charge transport properties of monolayer thin MoS2.

Enhancement of 1T‐MoS2 Superambient Temperature Stability and Hydrogen Evolution Performance by Intercalating a Phenanthroline Monolayer

“…Such architecture is realized in the heterolayered MoS 2 ‐organic nanocrystals assembled in liquid media at room temperature from negatively charged MoS 2 monolayers and organic cationic species [26–28] . In this type of hybrid structures, the sulfide layers was proven to adopt the geometry of 1T‐MoS 2 and their S atoms participate in the NH…S, CH…S and π…S interactions with the guest molecules as shown for several compounds by the PXRD pattern modeling and DFT calculations [29–31] . The 1T structure is stabilized in the sulfide layers of these compounds as compared to pure 1T‐MoS 2 phase as evidenced by an increase of the 1T‐2H transition temperature [30,32] .…”

“…In this type of hybrid structures, the sulfide layers was proven to adopt the geometry of 1T‐MoS 2 and their S atoms participate in the NH…S, CH…S and π…S interactions with the guest molecules as shown for several compounds by the PXRD pattern modeling and DFT calculations [29–31] . The 1T structure is stabilized in the sulfide layers of these compounds as compared to pure 1T‐MoS 2 phase as evidenced by an increase of the 1T‐2H transition temperature [30,32] . Therefore, it was of great interest to study how stabilization of 1T‐MoS 2 by organic cations may influence its properties in HER.…”

Nanostructured tungsten sulfides: insights into precursor decomposition and the microstructure using X-ray scattering methods

“…[24][25][26][27][28][29][30][31] Refinement of turbostratic disorder in exfoliated and restacked MoS 2 intercalated with organic cations has recently been demonstrated. [32][33][34] Total scatteringalso known as pair distribution function (PDF)has only scarcely been applied to such layered compounds, e.g. to lithiated MoS 2 , 35 restacked WS 2 , 36 Ag x MoS 2 37 or a molybdenum polysulfide chalcogel.…”

Electrodeposition of MoS2for Charge Storage in Electrochemical Supercapacitors

“…This exhibits a broad strong (002) peak at approximately 14.5°, consistent with the formation of crystalline MoS 2 . 34,35 From the (002) peak width in Figure 3, the grain size is estimated as 4.3 nm from the Scherrer equation. However, higher peaks that could distinguish between the 2H and 3R polytypes are not observed.…”