Selective non-enzymatic electrochemical detection of dopamine using nickel molybdate nano-dots anchored on CNT fiber microelectrodes

Abstract

This research demonstrates the hydrothermal synthesis of α-nickel molybdate nano-dots (α-NiMoO₄) and their fabrication on a carbon nanotube fiber (CNTF), serving as an electrocatalyst for non-enzymatic electrochemical sensing of dopamine (DA). Several analytical techniques, such as, scanning electron microscopy (SEM), X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDX), and Fourier transform infrared spectroscopy (FTIR), were employed for morphological analysis, crystallinity and elemental composition analysis and characteristic bond vibration analysis of NiMoO₄, respectively. The characterization revealed the presence of ∼10 nm α-NiMoO₄ nano-dots with a significant amount of NiO. The NiMoO₄@CNTF electrode exhibited a remarkable sensitivity and selectivity towards DA, despite the presence of other interfering species, including glucose (Glu), uric acid (UA), ascorbic acid (AA), urea and NaCl. A comparative study of the bare CNTF and NiMoO₄@CNTF electrode revealed the boosted capabilities of the fabricated flexible microelectrode with a sensitivity of 2.02 mA cm⁻² mM⁻¹, a detection limit of 58.2 μM, and a quantitation limit of 0.176 mM, with a linearity range of 0.1–1.2 mM. In comparison, bare CNTF exhibited a sensitivity of 1.4 mA cm⁻² mM⁻¹, a detection limit of 107 μM, and a quantitation limit of 0.321 mM, with a linearity range of 0.1–0.7 mM. The enhanced performance of NiMoO₄@CNTF was attributed to an increase in the active sites due to the large surface area of the NiMoO₄ nano-dots, causing fast electron kinetics and improving the sensor's sensitivity and reliability. The outcomes of this study could foster innovation in designing electrochemical sensors based on metal molybdates/double metal oxides with carbon-based nanomaterials for sensing electroactive biomolecules through real-time medical analysis.