Electrochemical determination of glucose in blood serum and sweat samples by the strontium doped Co₃O₄

This work reports the noninvasive electrochemical determination of glucose by strontium doped cobaltic cobalt oxide nanostructures (Sr-Co₃O₄). The Sr-Co₃O₄ is prepared by three conventional methods namely hydrothermal, magnetic stirring, and ultrasound. Among all, the hydrothermal method effectively incorporated the Sr in the Co₃O₄ lattice. The Sr percentage and Co oxidation states were investigated by x-ray photoelectron spectroscopy. The Sr has a more ionic radius than cobalt, therefore, it is occupied in the octahedral site. As a result, the non-stoichiometric oxygen content was increased in the Co₃O₄ lattices, which are the main contributor to the electrochemical determination of glucose. The results revealed that hydrothermally synthesized Sr-Co₃O₄ (HSC) exhibited improved electrocatalytic activity such as low peak potential (0.55 V) and high current (116 µA) towards glucose oxidation than the other electrocatalysts. The HSC/GCE revealed a good sensitivity (9.01 ± 0.15 µA mM⁻¹ cm⁻²) and low LoD (31 ± 3 nM). Also, high selectivity was observed towards glucose detection in the presence of co-interfering species. Moreover, the Sr-Co₃O₄ is applied in real-time monitoring of glucose in blood serum and sweat samples which received good recoveries.