Terahertz Detection of Acid Blue 113 Dye Using Hybrid Hydrogels

Abstract

The detection of pollutant dyes in the environment, particularly in waterways, can be extended and potentially simplified using terahertz spectroscopy. The use of hydrogels to absorb these contaminants from water and create solid samples with moderate transparency at terahertz frequencies evidently facilitates spectroscopic analysis. In this study, we demonstrate that chitosan and poly(vinyl alcohol) hydrogels, as well as their cross-linked and nanocomposite hybrid blends, efficiently capture the acid blue 113 azo dye (AB113). We show that terahertz transmittance and refractive index measurements conducted on these hydrogel materials offer an effective alternative method for detecting water contaminants, especially azo dyes. The terahertz transmittance spectra provide evidence of azo dye molecules within the hydrogel membranes. Additionally, considering the alterations in the hydrogels’ refractive index due to the sorption of AB113 dye molecules, we derived an analytical model to accurately estimate the amount of dye sorbed by the polymeric networks. The findings of this study establish a practical and promising approach for both qualitative and quantitative terahertz detection of AB113 dye using hybrid hydrogels. A detailed comparison with optical and infrared spectroscopy is also provided for reference.