Silver Halide Nanofiber-Based Surface-Enhanced Infrared Absorption Spectroscopy for Detection of Pollutants in Aqueous Environments

Surface-enhanced infrared absorption (SEIRA) spectroscopy under highly controlled laboratory conditions has been extensively applied and is important in many areas of material analysis and sensor development. However, their direct application in aqueous environments remains a significant challenge. Addressing this, our study presents a fiber-based SEIRA technique that utilizes replaceable silver halide polycrystalline infrared (PIR) fiber loops. These fiber loops were modified with silver-poly(vinylpyrrolidone) (Ag-PVP) nanoparticles and applied for acquiring SEIRA spectra of naphthalene, a model polycyclic aromatic hydrocarbon. It was demonstrated that naphthalene dissolved in water at a concentration of 50 μM can be detected directly in aqueous environments under in situ conditions. The distinctive spectral band at 783 cm–1 was used to identify naphthalene in water. An exploratory computational study was conducted to investigate the effect of silver interaction on the naphthalene SEIRA spectrum. The computational and experimental results indicate the absence of a covalent bond of naphthalene to the Ag-PVP nanoparticles, with only physisorption being observed. This study facilitates the applicability of SEIRA to practical, real-world scenarios, including the detection of low-solubility toxic compounds such as naphthalene, which are pertinent to environmental contamination.