Arrayed nanopore silver thin films for surface-enhanced Raman scattering

Area of Science:

• Materials Science
• Nanotechnology
• Spectroscopy

Background:

• Surface-enhanced Raman scattering (SERS) relies on active substrates for signal amplification.
• Nanoporous silver thin films on anodic aluminum oxide (AAO) offer potential for SERS applications due to their unique structures and electromagnetic field enhancement.
• Fabrication of uniform, large-area nanoporous films with controlled morphology is essential for consistent SERS performance.

Purpose of the Study:

• To develop and characterize novel SERS substrates by transferring nanoporous silver thin films onto flexible polymer substrates (PMMA and PDMS).
• To investigate the influence of pore size on SERS performance for these new substrates.
• To evaluate the sensitivity and enhancement capabilities of the fabricated SERS substrates for molecular detection.

Main Methods:

• Fabrication of arrayed nanoporous silver thin films on AAO templates by precisely controlling sputtering parameters.
• Transfer of nanoporous silver films onto polymethylmethacrylate (PMMA) and polydimethylsiloxane (PDMS) substrates using a template-assisted sol-gel phase inverse-imprinting process.
• Evaluation of SERS performance using Rhodamine 6G (R6G) as a model molecule, analyzing detection limits and enhancement factors (EF).

Main Results:

• Successfully fabricated Ag nanoporous thin films on PMMA and PDMS substrates exhibiting significantly enhanced SERS signals.
• Observed opposite pore size-dependent SERS tendencies for the PMMA and PDMS substrates, attributed to varying electric field enhancements around different pore diameters.
• Achieved a low R6G detection limit of 10⁻⁶ mol L⁻¹ and an SERS EF exceeding 10⁶ for the Ag nanoporous thin film on PMMA.

Conclusions:

• The developed Ag nanoporous thin films on PMMA and PDMS serve as highly sensitive SERS substrates.
• The pore size-dependent SERS behavior highlights the importance of structural control for optimizing substrate performance.
• These substrates demonstrate significant potential for label-free detection of biomolecules and single-molecule sensing applications.