Electrochemical biosensor based on one-dimensional MgO nanostructures for the simultaneous determination of ascorbic acid, dopamine, and uric acid

• MgO tadpoles, nanobelts, and nanorods have been synthesized by DC arc plasma jet CVD.
• MgO nanobelts show high electrocatalytic activity toward small biomolecules.
• The electrocatalytic activity of the MgO nanobelts depends on their surface morphology.
• A MgO nanobelt-based electrochemical biosensor detects ascorbic acid, uric acid, and dopamine with high sensitivity and selectivity.

One-dimensional (1D) MgO nanostructures of various morphologies including tadpole-like nanobelts (tadpoles), nanobelts, and nanorods were synthesized via direct current (DC) arc plasma jet chemical vapor deposition (CVD). The effect of morphology on the biosensing properties of the nanostructures was investigated by comparing their electrochemical properties. Compared with tadpoles and nanorods, the MgO nanobelts had excellent electrocatalytic activity toward ascorbic acid (AA), dopamine (DA) and uric acid (UA). The response of the MgO nanobelts to the analytes was twice that of the tadpoles. A MgO nanobelt-modified electrode was thus fabricated for the simultaneous determination of AA, DA, and UA. The peak separations between AA and DA, DA and UA, and AA and UA for this electrode were 111, 161, and 272 mV, respectively. The linear response ranges of the electrodes were 2.5–15 and 25–150 μM for AA, 0.125–7.5 μM for DA, and 0.5–3 and 5–30 μM for UA. The calculated detection limits were 0.2, 0.05, and 0.04 μM (S/N = 3), respectively. The excellent electrocatalytic activity of the MgO nanobelts can be attributed to various surface defects such as low-coordination anions (O5C2− and O4C2− at the terrace and edge sites, and O3C2− at the corner and kink sites). Additionally, electron tunneling between these surface defects is possible. These defects have a strong adsorption capacity toward AA, DA, and UA. This affinity improves sensitivity and decreases the detection limits of the MgO nanobelt electrodes.

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