Multipurpose Sensor Based on a Polymethacrylate Matrix Nanocomposite with Immobilized Gold Nanoparticles for the...

An optical sensor based on a polymethacrylate matrix (PMM) with immobilized gold nanoparticles (Au⁰ NPs) has been developed for the determination of pollutants in environmental samples. The nanoparticles are synthesized by chemical reduction of Au(III) to Au⁰ using sodium borohydride, which yields conglomerates of spherical particles with an absorption maximum at 530 nm. The time stability of the nanocomposite is demonstrated, as well as the ability to control the nanoparticle loading in the matrix by varying the concentration of the HAuCl₄ solution. The analytical capability of the PMM-Au⁰ system is demonstrated for the direct determination of tetracycline in river water in two linear concentration ranges: 0.001-0.010 mg/L and 0.025-0.100 mg/L, with detection limits of 0.0005 mg/L and 0.012 mg/L, respectively. The determination of tetracycline is based on the enhancement of its intrinsic fluorescence at 520 nm by gold nanoparticles in the solid phase following solid-phase extraction from water in the anionic form H₂TC^- using PMM-Au⁰. The colorimetric determination of thiocyanate anions is based on a color change of the PMM-Au⁰ nanocomposite from red to blue, corresponding to a shift in the plasmon absorption maximum from 530 nm to 630 nm. The sensor exhibits a linear response in the thiocyanate concentration range of 0.3-50.0 mg/L, with a detection limit of 0.1 mg/L. Thus, the multifunctional PMM-Au⁰ sensor has been used for the determination of various analytes employing different modes of analytical signal readout after minimal sample preparation.