Electrochemical Ultrasensitive Sensing of Uric Acid on Non-Enzymatic Porous Cobalt Oxide Nanosheets-Based Sensor

Abstract

Transition metal oxide (TMO)-based nanomaterials are effectively utilized to fabricate clinically useful ultra-sensitive sensors. Different nanostructured nanomaterials of TMO have attracted a lot of interest from researchers for diverse applications. Herein, we utilized a hydrothermal method to develop porous nanosheets of cobalt oxide. This synthesis method is simple and low temperature-based. The morphology of the porous nanosheets like cobalt oxide was investigated in detail using FESEM and TEM. The morphological investigation confirmed the successful formation of the porous nanosheet-like nanostructure. The crystal characteristic of porous cobalt oxide nanosheets was evaluated by XRD analysis, which confirmed the crystallinity of as-synthesized cobalt oxide nanosheets. The uric acid sensor fabrication involves the fixing of porous cobalt oxide nanosheets onto the GCE (glassy carbon electrode). The non-enzymatic electrochemical sensing was measured using CV and DPV analysis. The application of DPV technique during electrochemical testing for uric acid resulted in ultra-high sensitivity (3566.5 µAmM−1cm−2), which is ~7.58 times better than CV-based sensitivity (470.4 µAmM−1cm−2). Additionally, uric acid sensors were tested for their selectivity and storage ability. The applicability of the uric acid sensors was tested in the serum sample through standard addition and recovery of known uric acid concentration. This ultrasensitive nature of porous cobalt oxide nanosheets could be utilized to realize the sensing of other biomolecules.

Highly Sensitive Electrochemical Non-Enzymatic Uric Acid Sensor Based on Cobalt Oxide Puffy Balls-like Nanostructure

“…Figure 5 a depicts the CV response curve of the cobalt oxide puffy balls/GC sensor for 0 mM and 25 mM UA concentrations. A sharp increase in current response is seen in the presence of UA due to the UA oxidation, where the p-type nature of the cobalt oxide semiconductor plays a crucial role in swift electron transfer to the electrode surface by providing excess hole concentration [ 30 , 36 , 37 ]. A detailed UA sensing mechanism over cobalt oxide is proposed by Hu et al [ 45 ].…”

“…The electrochemical analysis was performed using EIS, CV, and DPV measurements. We utilized the previously optimized cobalt oxide amount and pH to get the optimum sensing response of the fabricated sensor [ 36 , 37 , 38 ]. The CV was performed in a 5 mM probe solution of potassium hexacyanoferrate (purity ≥ 9 9%, K 3 [Fe(CN) 6 ]) in 0.1 M KCl under varying scan rates from 10 mVs −1 to 200 mVs −1 .…”

“…Nanostructures of cobalt oxide are being used to construct non-enzymatic electrochemical sensors due to simple and low-cost synthesis processes, chemical stability, and fast charge transfer property [ 29 , 30 , 35 ]. Recently, nano-berry, porous, and hexagonal nanosheet-like nanostructures of cobalt oxides were utilized to fabricate non-enzymatic UA sensors [ 36 , 37 , 38 ]. Kogularasu et al synthesized polyhedron-shaped Co 3 O 4 nanostructures to construct a high-sensitivity hydrogen peroxide sensor [ 39 ].…”

Hexagonal cobalt oxide nanosheet-based enzymeless electrochemical uric acid sensor with improved sensitivity

“…29 In addition, it was also reported that the p-type nature of the cobalt oxide nanostructure provided excess holes (charge carriers) which resulted in the easy capture of electrons from the oxidation of UA. 33…”

“…29 In addition, it was also reported that the p-type nature of the cobalt oxide nanostructure provided excess holes (charge carriers) which resulted in the easy capture of electrons from the oxidation of UA. 33 Next, the CV response curves were measured in various UA concentrations (5-400 mM) in PBS buffer at a 50 mV s À1 scan rate (Fig. 7b).…”