Phase Transformation on Multilayer 2M-WS₂ for Improved Surface-enhanced Raman Scattering

Area of Science:

• Materials Science
• Nanotechnology
• Spectroscopy

Background:

• Two-dimensional (2D) transition metal dichalcogenides (TMDCs) are excellent platforms for surface-enhanced Raman scattering (SERS).
• Phase transformation in 2D TMDCs offers a strategy to tune SERS performance.

Purpose of the Study:

• To investigate the SERS performance of multilayer 2M-WS₂.
• To explore the impact of phase transformation on the SERS capabilities of 2D WS₂.

Main Methods:

• Multilayer 2M-WS₂ nanosheets were subjected to thermal annealing and laser treatment.
• Phase transition from 2M-WS₂ to 2H-WS₂ was induced.
• SERS performance was evaluated using CV molecules, comparing phase-transformed 2H-WS₂ with commercially pure 2H-WS₂ (P-2H-WS₂).

Main Results:

• Thermally induced phase transition from 2M-WS₂ to 2H-WS₂ was achieved.
• Phase-transformed 2H-WS₂ exhibited SERS properties comparable to 2M-WS₂, outperforming P-2H-WS₂.
• Detection limits for CV molecules were 3 orders of magnitude lower, and Raman intensity enhancements were 10-37 times higher compared to P-2H-WS₂.
• Accelerated charge transfer in phase-transformed 2H-WS₂ was attributed to bandgap reduction and vacancy-induced reorganization.

Conclusions:

• Metal-to-semiconductor phase transition in 2D TMDCs is a viable strategy for enhancing SERS.
• Phase-transformed 2H-WS₂ demonstrates superior SERS activity due to modified electronic properties and defect engineering.