One-Step Fabrication of Cobalt(II,III) Oxide@Poly(o-Phenylenediamine) for Non-Enzymatic Electrochemical Lactate Detection

A non-enzymatic electrochemical sensor for lactate detection was developed by simultaneously electrodepositing cobalt(II,III) oxide (Co 3 O 4 ) and electropolymerizing poly(o-phenylenediamine) (PoPD). This one-step approach resulted in Co 3 O 4 nanoparticles uniformly distributed on the PoPD film, forming a robust and conductive matrix with enhanced physicochemical properties. This design delivered high sensitivity and selectivity for lactate detection, with a broad detection range of 1–300 mM, a detection limit of 0.66 mM (3S B /m), and reproducibility of ≤5.75% RSD. The sensor demonstrated robust selectivity against common interferences, including inorganic ions, glucose, uric acid, urea, and creatinine. Its practical application was validated with sweat samples, showing strong agreement with results from a lactate dehydrogenase assay.