Assembling substrate-less plasmonic metacrystals at the oil/water interface for multiplex ultratrace analyte...

Area of Science:

• Nanotechnology
• Materials Science
• Spectroscopy

Background:

• Current substrate-less Surface-Enhanced Raman Spectroscopy (SERS) platforms rely on uncontrolled nanoparticle aggregation or simple arrays.
• The influence of ordered nanoparticle lattice structures on SERS detection capabilities remains largely unexplored.

Purpose of the Study:

• To investigate the in situ SERS sensing capabilities of large-area plasmonic metacrystals formed by self-assembled silver octahedra.
• To determine how different nanoparticle lattice structures affect SERS enhancement and detection limits.

Main Methods:

• Organizing silver octahedral building blocks into two distinct metacrystal structures (hexagonal close-packed and open square) at the oil/water interface.
• Evaluating the SERS performance of these metacrystals for detecting analytes in both aqueous and organic phases.

Main Results:

• The open square metacrystal, with lower packing density, exhibited significantly stronger SERS enhancement compared to the denser hexagonal metacrystal.
• This enhancement is attributed to larger plasmonic hotspot areas within the square metacrystal at the excitation wavelength.
• Quantitative ultratrace detection of analytes (nano-molar levels) with analytical enhancement factors up to 10^8 was achieved.
• In situ multiplex detection across both phases was demonstrated without signal quantitation loss.

Conclusions:

• Self-assembled nanoparticle lattice structure is a critical factor in optimizing SERS sensing platforms.
• The open square metacrystal design offers a promising approach for highly sensitive and quantitative ultratrace analyte detection.
• This work advances the development of advanced SERS sensors for simultaneous multi-phase analysis.