Electrocatalytic sensing of dopamine: How the Co content in porous LaNixCoxO3 perovskite influences sensitivity?

Abstract

LaNixCo1−xO3 (x = 0.2, 0.4, 0.6, 0.8) perovskites were synthesized by solution combustion method. Rietveld and hkl refinement shows the increase in unit cell parameters and crystallite size as Ni is substituted for Co. Lower symmetry of rhombohedral structure was evident from the widening metal–oxygen band in IR spectra. The porous morphology and uniform elemental distribution of the perovskites were clearly evident from the scanning electron micrograph (SEM). High thermal stability of the perovskites was revealed by the thermogravimetric analysis. Structural analysis by transmission electron microscopy (TEM) shows the presence of domains separated by twin boundaries in the polycrystalline material. Synthesized perovskites were used as the modifiers in the carbon paste electrode for the enhancement of electrocatalytic and sensitivity properties towards the detection and quantification of neurotransmitters. The lower charge transfer resistance and larger electroactive surface area of LaNi0.8Co0.2O3 makes it pertinent to be a modifier in developing biocompatible modified carbon paste electrode based electrochemical sensor for dopamine (DA). The modified sensor exhibits better redox kinetics evidenced by the better current response, lower oxidation potential and smaller peak separation. Excellent detection limits for DA, UA and AAP in the range of 3, 5 and 100 nM was achieved using this sensor. DA quantification was successfully carried out in the presence of uric acid (UA) and acetaminophen (AAP). The fabricated sensor’s high sensitivity, excellent stability made it possible to get high recoveries in real samples such as urine and blood serum.