Hexagonal Close-Packed Au@Ag Superlattices for Versatile and Cost-Effective SERS Platforms.

Area of Science:

• Materials Science
• Nanotechnology
• Analytical Chemistry

Background:

• Developing cost-effective and scalable surface-enhanced Raman scattering (SERS) substrates is crucial for advancing chemical and biological sensing technologies.
• Current SERS substrates often rely on complex fabrication methods like physical deposition of noble metal nanostructures, hindering large-scale production.
• There is a need for efficient, low-cost SERS platforms that overcome the limitations of existing techniques.

Purpose of the Study:

• To introduce hexagonal close-packed plasmonic superlattices as a novel, efficient, and low-cost SERS platform.
• To compare the SERS performance of different nanosphere compositions (Ag, Au, Au@Ag) and sizes.
• To demonstrate the applicability of the developed SERS platform for identifying and quantifying diverse biochemical targets.

Main Methods:

• Fabrication of hexagonal close-packed plasmonic superlattices using scalable seed-mediated growth and interfacial self-assembly.
• Systematic comparison of SERS performance using silver (Ag), gold (Au), and gold-over-silver (Au@Ag) nanospheres of varying sizes.
• Characterization of substrate uniformity and sensitivity through Raman mapping experiments and simulations.

Main Results:

• Plasmonic superlattices fabricated with 55 nm Au@Ag nanospheres exhibited superior SERS performance, including the strongest Raman response and highest sensitivity.
• The Au@Ag NS-based substrates demonstrated the lowest detection limits and good spatial uniformity across the SERS platform.
• Simulations and experiments confirmed that Au@Ag nanospheres provide an optimal balance between hotspot density and plasmonic field intensity.

Conclusions:

• Hexagonal close-packed plasmonic superlattices, particularly those using 55 nm Au@Ag nanospheres, represent an efficient, low-cost, and scalable SERS platform.
• The optimized Au@Ag nanosphere composition and arrangement enhance SERS capabilities for sensitive detection and quantification of biochemical analytes.
• This SERS platform holds significant promise for practical applications in chemical and biological sensing due to its performance and broad applicability.