Abstract
Here we introduce an environmentally friendly approach to fabricate a simple and cost-effective plasmonic paper for detecting food additives using surface-enhanced Raman spectroscopy (SERS). The plasmonic paper is fabricated by in situ growth of gold nanoparticles (AuNPs) on filter paper (FP). To facilitate this green fabrication process we applied a double-layered coating of biopolymers chitosan (CS) and alginate (ALG) onto the FP using a layer-by-layer (LbL) assembly through electrostatic interactions. Compared to single-layer biopolymer coatings double-layered biopolymer-coated paper ALG/CS/FP significantly improves the reduction properties. Consequently effective in situ growth of AuNPs can be achieved as seen in high density of AuNP formation on the substrate. The resulting plasmonic paper provides high SERS performance with an enhancement factor (EF) of 5.7 ? 1010 and a low limit of detection (LOD) as low as 1.37 ? 10-12 M 4-mercaptobenzoic acid (4-MBA). Furthermore it exhibits spot-to-spot reproducibility with a relative standard deviation (RSD) of 8.2% for SERS analysis and long-term stability over 50 days. This paper-based SERS substrate is applied for melamine (MEL) detection with a low detection limit of 0.2 ppb which is sufficient for monitoring MEL contamination in milk based on food regulations. Additionally we demonstrate a simultaneous detection of ?-agonists including ractopamine (RAC) and salbutamol (SAL) exhibiting the multiplexing capability and versatility of the plasmonic paper in food contaminant analysis. The development of this simple plasmonic paper through the LbL biopolymer assembly not only paves the way for novel SERS substrate fabrication but also broadens the application of SERS technology in food contaminant monitoring. ? 2024 The Authors. Published by American Chemical Society.
