Abstract
In this study, iron oxide nanoparticles were synthesized through a simple, cost-effective, and environmentally friendly green synthesis route using aqueous rose extract as a natural reducing and stabilizing agent. The synthesized nanoparticles were combined with graphene oxide (GO) and employed to modify a carbon paste electrode (CPE) for the simultaneous electrochemical detection of dopamine (DOP) and tryptophan (TRP). The fabricated Fe2O3/Fe3O4-GO/CPE sensor was characterized using cyclic voltammetry (CV), differential pulse voltammetry (DPV), and chronoamperometry. The modified electrode exhibited significantly enhanced electrocatalytic activity, sensitivity, and electron transfer capability compared with the bare electrode. Under optimized conditions, the sensor demonstrated wide linear dynamic ranges of 0.5-300 μM for dopamine and 1-300 μM for tryptophan, with low detection limits of 0.32 μM and 0.47 μM, respectively. The proposed sensor also showed excellent repeatability, good stability, high selectivity against common interfering species, and enhanced electroactive surface area due to the synergistic effect of iron oxide nanoparticles and graphene oxide. These results indicate that the developed nanocomposite-modified electrode is a promising, sensitive, and low-cost electrochemical platform for the simultaneous determination of biologically important analytes in pharmaceutical and biomedical applications. Future studies may focus on applying the proposed sensor to real biological and pharmaceutical samples and further improving its performance for portable and point-of-care electrochemical sensing applications.