Quasi-3D Plasmonic Nanowell Array for Molecular Enrichment and SERS-Based Detection.

Area of Science:

• Plasmonics
• Nanotechnology
• Surface Chemistry

Background:

• Plasmonic nanostructures are crucial for enhancing light-matter interactions in sensing.
• Achieving uniform plasmonic substrates with high sensitivity and reproducibility remains a challenge.
• Existing methods often suffer from signal variability and limited quantitative analysis capabilities.

Purpose of the Study:

• To develop a quasi-three-dimensional (3D) plasmonic nanowell array with high structural uniformity for enhanced molecular detection.
• To investigate the role of densely packed gold nanoparticles (Au NPs) and nanogaps in signal amplification.
• To demonstrate the potential for quantitative analysis and sensitive detection of analytes using surface-enhanced Raman spectroscopy (SERS).

Main Methods:

• Fabrication of quasi-3D plasmonic nanowell arrays using nanoimprint lithography and thin film deposition.
• Surface modification with a self-assembled monolayer (SAM) of perfluorodecanethiol (PFDT) to control gold nanoparticle growth.
• Characterization of nanostructure uniformity and plasmonic properties.
• Demonstration of molecular detection using surface-enhanced Raman spectroscopy (SERS).

Main Results:

• Achieved a highly uniform quasi-3D plasmonic nanowell array with periodic hexagonal gold nanowells densely covered by gold nanoparticles (375 μm⁻²).
• Observed strong near-field enhancement due to plasmonic nanogaps, resulting in uniform SERS response (RSD of 5.3%).
• Demonstrated analyte pre-concentration within nanowells via evaporation-induced effects, leading to highly sensitive lactic acid detection.

Conclusions:

• The quasi-3D plasmonic nanowell array offers a superior platform for molecular detection due to its high sensitivity and signal uniformity.
• Nanoimprint lithography combined with controlled 3D nanoparticle growth minimizes spatial variation in Raman intensity, enabling quantitative analysis.
• This nanostructure is a promising candidate for advanced biosensing applications requiring precise and reliable molecular detection.