# Contact-Accessible Silver Nanoparticle-Decorated Electrospun Carbon Fibers for Microplastics Detection by SERS

## TL;DR

This paper introduces a new 3D plasmonic platform using silver nanoparticle-decorated carbon fibers to improve microplastic detection via SERS.

## Contribution

A rapid, chemical-free fabrication method for 3D SERS substrates that enhances microplastic detection through improved contact and field confinement.

## Key findings

- AgNPs@ECF substrates enhance SERS signals for microplastics due to improved particle–substrate contact.
- Sub-micrometer particles show the strongest SERS enhancement due to multiple fiber junction interactions.
- Ultrasmall and large particles exhibit reduced enhancement due to limited contact or field decay.

## Abstract

Reliable detection of microplastics by surface-enhanced Raman scattering (SERS) is often hindered by poor particle–substrate contact and limited access to plasmonic hotspots on conventional planar substrates optimized for molecular adsorption. Here, we report a rapid microwave-assisted carbothermal shock strategy to fabricate silver nanoparticle-decorated electrospun carbon fibers (AgNPs@ECF) as a three-dimensional plasmonic platform tailored for solid microplastic sensing. Localized microwave-induced heating in a mixed ethanol–hexane system enables Ag nanoparticle nucleation and anchoring on conductive carbon fibers within 45 s, yielding a mechanically compliant, junction-rich architecture without chemical reductants or vacuum processing. The AgNPs@ECF composite was evaluated using morphologically weathered polystyrene (PS) and polyethylene terephthalate (PET) microplastics, along with size-controlled PS bead standards ranging from ~50 nm to 45 μm. Across these models, SERS response is governed primarily by particle–substrate contact geometry and near-field accessibility rather than polymer type. The strongest enhancement occurs in the sub-micrometer regime, where particles can engage multiple AgNP-decorated fiber junctions, while ultrasmall and large, smooth particles show reduced enhancement due to limited contact or rapid field decay. Spatially resolved Raman mapping and finite-difference time-domain simulations support a contact-dominated enhancement mechanism, revealing localized field confinement at particle–fiber interfaces. These results establish the design principles for three-dimensional SERS substrates targeting heterogeneous solid particulates, demonstrating that contact-accessible plasmonic architectures are critical for reliable microplastic detection under realistic solid-particle measurement conditions.