Ce(III)-modulation over non-enzymatic Pt/CeO2/GO biosensor with outstanding sensitivity and stability for lactic acid detection

A series of non-enzymatic graphene functionalized biosensors was developed via deposition precipitation method for lactic acid (LA) detection, which were characterized by transmission electron microscopy (TEM), Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), gas chromatography-mass spectrometry, liquid chromatography-mass spectrometry, and proton nuclear magnetic resonance (¹H NMR). The electrochemical performances of the non-enzymatic biosensors were measured by means of the electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) method. The comprehensive analysis of structures shows that Pt, CeO2, and GO components interact with each other. During the storing and releasing oxygen, the valence ratio of Ce³⁺/Ce⁴⁺ and the number of oxygen vacancies in CeO2 change accordingly, which can be conducive to increasing electronic transmission capacity and finally leads to the improvement of electrocatalytic performance. Among them, the Pt/CeO2/GO biosensor containing 0.47 at% platinum exhibits an excellent electrochemical detection performance with high sensitivity of 12.3 µA⋅L/ (mmol∙cm²) and a low limit of detection (LOD) of 5.12 μmol/L in a wide linear range from 10 to 900 μmol/L. In addition, the proposed biosensor possesses a promising anti-interference capability, as well as high stability and good reproducibility, which was assessed by testing the cyclic voltammogram in 0.1 mol/L lactic acid one year later. The underlying mechanism was proposed for electrochemical oxidation of LA to carbon dioxide and acetic acid with the synergistic effect among Pt, CeO2, and GO. Furthermore, the results of the standard addition method in real samples (human serum and urine samples) reveal that the lactic acid detection of the non-enzymatic Pt/CeO2/GO biosensor is accompanied by high reliability. Thus, it will be a valuable biosensor for in vitro detection of lactic acid level in clinical samples.