Trimesic acid-coated copper oxide nanoparticles boost fiber-optic sensor detection of PFOA and PFOS

Researchers have built a fiber-optic surface plasmon resonance sensor that uses copper oxide nanoparticles coated with trimesic acid to detect two notorious 'forever chemicals', PFOA and PFOS, reporting maximum sensitivities of 3.59 and 2.76 nanometers per micromolar respectively, with detection limits of 1.40 and 4.73 micromolar. The study, published in the Journal of Nanoparticle Research, describes how surface functionalization turns metal oxide nanoparticles into chemically tunable interfaces for optical sensing. Copper oxide nanoparticles were chosen because they enhance the refractive index sensitivity of fiber-optic SPR platforms and provide chemically active surfaces that readily accept ligand functionalization.

The team characterized the functionalized nanoparticles using FTIR, thermogravimetric analysis, TEM, SEM, dynamic light scattering, and zeta potential measurements, all of which supported successful surface modification. The characterization also revealed a structural nuance with practical consequences. Cryogenic-TEM showed primary particle diameters of approximately 6 nanometers, while DLS measurements of the same material in aqueous suspension indicated micron-scale hydrodynamic aggregates.

In other words, the nanoparticles are small individually but cluster together in water, a behavior the authors note as aggregation under aqueous conditions. To test sensing performance, the functionalized nanoparticles were integrated into the fiber-optic SPR platform and exposed to perfluorooctanoic acid and perfluorooctane sulfonate. The sensor produced a concentration-dependent optical response to both analytes, meaning the shift in the resonance signal grew with increasing concentration.

The response was not equal for the two compounds. The sensor reached its maximum sensitivity of 3.59 nanometers per micromolar for PFOA, compared with 2.76 nanometers per micromolar for PFOS, and detected PFOA at lower concentrations, with a detection limit of 1.40 micromolar against 4.73 micromolar for PFOS. According to the study, the stronger response toward PFOA is consistent with its greater retention at the functionalized sensing interface, an interpretation supported by X-ray photoelectron spectroscopy analysis.

However, the authors are careful to state that the specific molecular interactions responsible for the differential response remain to be elucidated, leaving open questions about why the carboxylic acid-terminated surface favors PFOA over the sulfonate-headgroup PFOS. The work demonstrates that trimesic acid functionalization of copper oxide nanoparticles provides a simple and tunable sensing interface for detecting PFOA and PFOS by fiber-optic SPR. Because the findings come from a fabricated sensor platform characterized under controlled conditions, with aggregation observed in aqueous suspension and interaction mechanisms not yet resolved, the reported sensitivities and detection limits describe the laboratory device rather than a validated field-deployment method.

Subject of Research: Trimesic acid-functionalized copper oxide nanoparticles for fiber-optic SPR detection of PFOA and PFOS

Article Title: Trimesic acid-functionalized copper oxide nanoparticles for fiber-optic surface plasmon resonance detection of PFOA and PFOS

Article References: Vikas, Swed, N., Yaseen, N., Pitruzzella, R., Cennamo, N., Nobili, L. G., Saccomandi, P., & Weitz, I. S. (2026). Trimesic acid-functionalized copper oxide nanoparticles for fiber-optic surface plasmon resonance detection of PFOA and PFOS. Journal of Nanoparticle Research, 28(11), Article 278. https://doi.org/10.1007/s11051-026-06798-5

Image Credits: AI Generated

DOI: 10.1007/s11051-026-06798-5

Keywords: PFOA, PFOS, PFAS, copper oxide nanoparticles, trimesic acid, fiber-optic SPR, surface plasmon resonance, optical sensing, surface functionalization, cryogenic-TEM, detection limit, chemical sensors