Uniform Spray-Coated Flexible SERS Substrates for Enhanced Molecular Detection

Area of Science:

• Materials Science
• Analytical Chemistry
• Nanotechnology

Background:

• Developing stable and uniform substrates is crucial for flexible Surface-Enhanced Raman Spectroscopy (SERS) sensors.
• Existing flexible SERS platforms face challenges in maintaining signal consistency and structural integrity.

Purpose of the Study:

• To fabricate a robust and highly sensitive flexible SERS platform for on-site detection.
• To enhance the uniformity, stability, and reproducibility of SERS substrates through optimized fabrication.
• To demonstrate the platform's capability for quantitative analysis of organic molecules and pesticide residues.

Main Methods:

• Fabrication of a composite substrate (Au@NG@PDMS) using nitrogen-doped graphite-coated gold nanoparticles (Au@NG) integrated with a polydimethylsiloxane (PDMS) film via microarray spray-coating.
• Characterization of nanoparticle structure and chemical stability using Transmission Electron Microscopy (TEM) and Raman spectroscopy.
• Optimization of solvent evaporation rates during spray-coating to improve substrate uniformity and SERS performance.

Main Results:

• The nitrogen-doped graphite shell provided excellent chemical stability to the gold nanoparticles against acidic, alkaline, and oxidative conditions.
• The flexible Au@NG@PDMS substrate demonstrated high SERS signal reproducibility under repeated mechanical deformations (bending and stretching).
• Highly sensitive and quantitative detection of crystal violet (10 nM to 10 µM) and trace thiram residues (20 ng/mL) on apple surfaces was achieved.

Conclusions:

• The developed flexible SERS substrate exhibits superior structural stability, signal uniformity, and surface conformability.
• The optimized spray-coating technique significantly enhances SERS performance and reproducibility.
• The platform shows great promise for practical applications in agricultural monitoring and on-site pesticide residue detection.