In Situ Two-Step Preparation of 3D NiCo-BTC MOFs on a Glassy Carbon Electrode and a Graphitic Screen Printed Electrode as Nonenzymatic Glucose-Sensing Platforms

In the present study, a rational two-step strategy is employed for the green, fast, very simple, and highly controllable synthesis of the bimetallic nickel-cobalt-based metal-organic frameworks (MOFs) on glassy carbon substrates by in situ transformation of nickel-cobalt-layered double hydroxide nanosheet (NiCo-LDHs NSs) intermediates into nickel-cobalt-benzene tricarboxylic acid MOFs (E-NiCo-BTC MOFs). The structural characteristics of the electrode materials in each step were investigated via Fourier transform infrared spectroscopy, X-ray diffraction, energy dispersive X-ray spectroscopy, elemental mapping, field emission scanning electron microscopy, and transmittance electron microscopy. In addition, the electrocatalytic behavior of the E-NiCo-BTC/GCE as a nonenzymatic sensing platform toward glucose electro-oxidation was evaluated via cyclic voltammetry, amperometry, and electrochemical impedance spectroscopy techniques. The as-prepared sensing platform shows two linear dynamic ranges of 0.001-1.78 mM with a sensitivity of 1789 mu A mM(-1) cm(-2) and 1.78-5.03 mM with a sensitivity of 1436 mu A mM-1 cm-2 together with acceptable selectivity against interfering species, high poisoning resistance against chloride ions, and high repeatability and reproducibility of glucose electro-oxidation responses. The value of the detection limit based on a signal to noise ratio of 3 (S/N = 3) was calculated to be 0.187 mu M. Moreover, the electrochemical responses of E-NiCo-BTC/GCE were compared to those of modified electrodes via hydrothermal-based NiCo-BTC MOFs and corresponding monometallic based modified electrodes obtained via an in situ method. Finally, in order to investigate the commercialization capability and to develop the proposed sensor from lab-to-market, the same in situ two-step strategy with some variations was used to modify the graphitic screen-printed electrode. This sensing platform showed acceptable responses toward glucose electro-oxidation with a low fouling effect of the modifier film over a wide range of glucose concentrations (0.0-5.7 mM) and an ignorable real sample matrix effect on the sensor performance as well as good sensitivity (230.5 mu A mM(-1) cm(-2)) and selectivity, which verify the ability of the proposed method for designing accurate and credible low-cost and on-site sensing platforms for practical applications.