Atomic Basal Defect-Rich MoS₂ by One-Step Synthesis and Mechanism Exploration

Area of Science:

• Materials Science
• Nanotechnology
• Surface Chemistry

Background:

• Two-dimensional molybdenum disulfide (2D MoS2) is a promising material for surface-enhanced Raman scattering (SERS) due to its exciton resonance.
• The inert basal plane of MoS2 hinders its SERS performance.
• Defect engineering is a key strategy to enhance the SERS activity of 2D materials.

Purpose of the Study:

• To develop a one-step synthesis strategy for atomically basal defect-rich MoS2.
• To investigate the role of NaCl in the synthesis and defect formation process.
• To demonstrate the enhanced SERS performance of defect-rich MoS2.

Main Methods:

• One-step synthesis of MoS2 in the presence of NaCl.
• Raman spectroscopy to analyze defect formation and material properties.
• Density functional theory (DFT) calculations to understand defect mechanisms.
• SERS measurements using rhodamine 6G as a probe molecule.

Main Results:

• NaCl plays a dual role, promoting MoS2 growth and subsequent basal defect formation (sulfur vacancies).
• Defect generation occurs during the cooling phase of synthesis.
• The ratio of Raman spectral peaks (// to A1g) correlates with basal defect concentration.
• Defect-rich MoS2 achieved a limit of detection of 10^-9 M for rhodamine 6G in SERS.

Conclusions:

• A facile method for synthesizing defect-rich MoS2 with activated basal planes was established.
• The defect engineering strategy significantly enhances SERS performance, comparable to noble metal substrates.
• This approach is potentially applicable to other 2D transition metal dichalcogenides for SERS and other applications like hydrogen evolution reactions.