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.
