Simultaneous detection of <scp>l</scp>-aspartic acid and glycine using wet-chemically prepared Fe₃O₄@ZnO nanoparticles: real sample analysis

An easy and reliable wet-chemical method was used to synthesize iron oxide doped zinc oxide nanoparticles (Fe₃O₄@ZnO NPs) at a low-temperature under alkaline medium. The electrochemical characteristics of Fe₃O₄@ZnO NPs were investigated by using different electrochemical techniques such as UV-vis, FTIR, XRD, FESEM, XEDS, and XPS. A sensor was fabricated by deposition of a thin covering of Fe₃O₄@ZnO NPs onto a flat dried glassy carbon electrode (GCE) with a polymer matrix with conducting characteristics (Nafion, Nf). l-Aspartic acid and glycine were detected simultaneously by using the modified GCE/Fe₃O₄@ZnO NPs/Nf sensor in enzyme free conditions. Calibration curves were found to be linear for l-aspartic acid (<i>R</i> ² = 0.9593) and glycine (<i>R</i> ² = 0.8617) over a broad range of detected bio-molecule concentration (100.0 pM to 100.0 mM). The analytical sensing parameters, for example sensitivity, linear dynamic range (LDR), limit of detection (LOD), and limit of quantification (LOQ), of the proposed sensor (GCE/Fe₃O₄@ZnO NPs/Nf) were calculated at two potentials (+0.4 V and +0.7 V) from the calibration plot for l-aspartic acid (126.58 pM μM^-1 cm², 100.0 pM to 10.0 μM, ≈97.5 pM, and 325.0 mM) and glycine (316.46 pM μM^-1 cm², 1.0 μM to 1.0 mM, ≈13.5 pM, and 450.0 mM), respectively, by using a reliable current-voltage (<i>I</i>-<i>V</i>) technique. The synthesis of Fe₃O₄@ZnO NPs by means of a wet-chemical route is a good advancement for the development of doped nanomaterial based sensors from the perspective of enzyme-free detection of biological molecules in health-care areas. This proposed GCE/Fe₃O₄@ZnO NPs/Nf sensor was used for the particular detection of l-aspartic acid and glycine in real samples (human and rabbit serum and urine) and found to achieve reasonable and accepted results.