Cascaded microsphere-coupled surface-enhanced Raman spectroscopy (CMS-SERS) for ultrasensitive trace-detection

Area of Science:

• Analytical Chemistry
• Materials Science
• Spectroscopy

Background:

• Surface-enhanced Raman spectroscopy (SERS) is a sensitive analytical technique.
• Dielectric micro-/nano-structures offer enhanced Raman scattering with low energy loss.
• Existing SERS substrates have limitations in sensitivity and cost-effectiveness.

Purpose of the Study:

• To develop a novel hybrid SERS substrate for enhanced Raman scattering.
• To investigate the performance of a cascaded microsphere-coupled SERS substrate.
• To achieve ultra-sensitive trace detection of molecules.

Main Methods:

• Fabrication of a cascaded structure using a large microsphere (LMS) and a small microsphere array with silver nanoparticles.
• Utilizing the hybrid substrate for molecular concentration, light intensity boosting, and far-field emission direction.
• Detection of 4-nitrothiphenol molecules in aqueous solution.

Main Results:

• Demonstrated a novel hybrid SERS substrate for the first time.
• Achieved a maximum Raman intensity enhancement factor greater than 10⁸.
• Reached a limit of detection as low as 10^-11 M for 4-nitrothiphenol.

Conclusions:

• The cascaded microsphere-coupled SERS substrate offers giant Raman enhancement.
• This hybrid structure is superior to traditional SERS substrates.
• The developed strategy enables cost-effective and ultrahigh-sensitive trace detection.