Concentration-Dependent Layer-Stacking and the Influence on Phase-Conversion in Colloidally Synthesized WSe₂...

Area of Science:

• Materials Science
• Nanotechnology
• Solid State Chemistry

Background:

• Transition metal dichalcogenides (TMDs) like WSe2 exhibit unique electronic and optical properties.
• Phase control in TMD synthesis is crucial for tuning material properties.
• Solution-phase synthesis offers a scalable route to TMD nanocrystals.

Purpose of the Study:

• To investigate the effect of precursor concentration on WSe2 nanocrystal layer number.
• To understand how layer number influences phase conversion in WSe2.
• To provide insights for controlling phase in solution-phase TMD synthesis.

Main Methods:

• Synthesis of WSe2 nanocrystals by varying tungsten hexacarbonyl (W(CO)6) and diphenyl diselenide (Ph2Se2) concentrations.
• Analysis of nanocrystal layer number as a function of precursor ratios.
• Investigation of phase conversion from 2M to 2H phases using spectroscopic or diffraction methods.
• Density functional theory (DFT) calculations to determine interlayer binding energies.

Main Results:

• Tungsten diselenide (WSe2) nanocrystal layer number is controllable via precursor concentration.
• High selenium (Se) and Se/W ratios lead to increased WSe2 nanocrystal layers.
• Increased WSe2 layer number reduces phase conversion from the 2M to the 2H phase.
• DFT calculations show increased interlayer binding energy with more layers.

Conclusions:

• Precursor concentration is a key parameter for controlling WSe2 nanocrystal dimensionality.
• Stronger interlayer interactions in multilayered WSe2 may inhibit phase conversion.
• This work offers a strategy for directing phase in solution-phase synthesis of TMDs.