Enhanced Raman Scattering on In-Plane Anisotropic Layered Materials

Area of Science:

• Materials Science
• Surface Chemistry
• Spectroscopy

Background:

• Surface-enhanced Raman scattering (SERS) relies on chemical mechanism (CM) and electromagnetic enhancement.
• CM involves charge interactions between substrates and molecules, but substrate electronic properties' role is unclear.
• Anisotropic 2D materials, such as black phosphorus (BP) and rhenium disulfide (ReS2), show unique electronic and optical properties.

Purpose of the Study:

• To investigate the anisotropic Raman enhancement on few-layered BP and ReS2.
• To elucidate the role of anisotropic charge interactions in SERS CM.
• To explore the application of anisotropic 2D materials in SERS.

Main Methods:

• Utilized few-layered black phosphorus (BP) and rhenium disulfide (ReS2) as SERS substrates.
• Employed copper phthalocyanine (CuPc) as a Raman probe molecule.
• Performed detailed Raman tensor analysis and density functional theory (DFT) calculations.

Main Results:

• Observed unique anisotropic Raman enhancement on BP and ReS2, absent on isotropic graphene and h-BN.
• Demonstrated that anisotropic charge interactions between 2D materials and CuPc molecules cause angular-dependent Raman enhancement.
• DFT calculations confirmed the significant role of electronic properties in anisotropic charge interactions.

Conclusions:

• Anisotropic charge interactions are responsible for the observed angular dependence in SERS enhancement on BP and ReS2.
• This study provides new insights into the chemical mechanism of SERS.
• Highlights the potential of anisotropic 2D materials for advanced SERS applications and understanding electronic properties.