Developing a new colorimetric bioassay for iodide determination based on gold supported iridium peroxidase catalysts

Citrate and polyvinyl alcohol capped gold nanoparticle (Au-NPs-Cy-PVA) and iridium NPs were incorporated by a chemical reduction method and characterized by UV-Vis, DLS, SEM, EDS, XRD, and FT-IR analysis. A cost-effective and straightforward colorimetric sensor dependent on the redox reaction of 3,4-diaminotoluene biomarker (DA) with Au3+ ions and H2O2 on an Au/Ir-NP catalyst mimicking enzyme-like activity, has been manufactured for the determination of I− in media of interest. At the same time, prepared Au/Ir-NPs can catalyze hydrogen peroxide (H2O2), which is used to reduce Au3+ into gold nanoparticles and oxidise 3,4-diaminotoluene biomarker. I− effectively expands the catalytic activity of Au/Ir-nanoparticles to decompose H2O2 by the interaction between Au+ and Au0 and suppresses the oxidation of 3,4-diaminotoluene biomarker. In a framework which contains Au/Ir-NPs, H2O2, 3,4-diaminotoluene biomarker, and HAuCl4, increasing the I− concentration results in color changes from deep purple to yellow. In light of this principle, in this work, a novel colorimetric technique for the sensitive detection of I− ions was developed. This method has a detection limit of 0.058 μM and a linear range between 0.12 to 5.42 μM. The assays are profoundly selective over other ions and can be effectively applied for the determination of iodine ions in real water samples.