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.

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.

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