Research on the self-assembly of exfoliated perovskite nanosheets (LaNb2O7−) and cobalt porphyrin utilized for the electrocatalytic oxidation of ascorbic acid

Abstract

A sandwich-structured nanocomposite of LaNb₂O₇/CoTMPyP [5,10,15,20-tetrakis(N-methylpyridinium-4-yl)porphyrinato cobalt(III)] was fabricated via electrostatic interaction between a LaNb₂O₇⁻ colloidal dispersion and a cobalt porphyrin aqueous solution. Several analytic techniques such as X-ray diffraction (XRD), Fourier transform infrared (IR) spectroscopy, ultraviolet-visible (UV-Vis) spectroscopy, and scanning electron microscopy (SEM) were used to characterize the obtained products and the existence of LaNb₂O₇⁻ nanosheets was confirmed by atomic force microscopy (AFM) and transmission electron microscopy (TEM). Furthermore, the stable and well-dispersed colloidal suspension of the LaNb₂O₇⁻ nanosheets, whose zeta potential value was −51.9 mV, was monitored with a Zetasizer Nano instrument. On the other hand, the cyclic voltammetry measurements of the LaNb₂O₇/CoTMPyP film modified GCE exhibited excellent electrocatalytic activities toward ascorbic acid oxidation with the oxidation peak potential shifting from 0.380 V (bare glass carbon electrode) to 0.044 V (modified electrode). The oxidation peak current increased linearly with the square root of the scan rate, implying a diffusion-controlled process. In addition, a detection limit of 4.99 × 10⁻⁵ M was obtained through differential pulse voltammetry with results in a concentration range of 5 × 10⁻⁵ to 9.09 × 10⁻³ M at a signal-to-noise ratio of 3.0.