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.

Early-stage uric acid (UA) abnormality detection is crucial for a healthy human. With the evolution of nanoscience, metal oxide nanostructure-based sensors have become a potential candidate for health monitoring due to their low-cost, easy-to-handle, and portability. Herein, we demonstrate the synthesis of puffy balls-like cobalt oxide nanostructure using a hydrothermal method and utilize them to modify the working electrode for non-enzymatic electrochemical sensor fabrication. The non-enzymatic electrochemical sensor was utilized for UA determination using cyclic voltammetry (CV) and differential pulse voltammetry (DPV). The puffy balls-shaped cobalt oxide nanostructure-modified glassy carbon (GC) electrode exhibited excellent electro-catalytic activity during UA detection. Interestingly, when we compared the sensitivity of non-enzymatic electrochemical UA sensors, the DPV technique resulted in high sensitivity (2158 µA/mM.cm²) compared to the CV technique (sensitivity = 307 µA/mM.cm²). The developed non-enzymatic electrochemical UA sensor showed good selectivity, stability, reproducibility, and applicability in the human serum. Moreover, this study indicates that the puffy balls-shaped cobalt oxide nanostructure can be utilized as electrode material for designing (bio)sensors to detect a specific analyte.

Electrolyte-gated transistor (EGT)-based biosensors are created with nanomaterials to harness the advantages of miniaturization and excellent sensing performance. A cholesterol EGT biosensor based on iron oxide (Fe ₂ O ₃ ) nanoparticles decorated ZnO nanorods is proposed here. ZnO nanorods are directly grown on the seeded channel using a hydrothermal method, keeping in mind the stability of nanorods on the channel during biosensor measurements in an electrolyte. Most importantly, ZnO nanorods can be effectively grown and modified with Fe ₂ O ₃ nanoparticles to enhance stability, surface roughness, and performance. The cholesterol oxidase (ChOx) enzyme is immobilized over Fe ₂ O ₃ nanoparticles decorated ZnO nanorods for cholesterol detection. With cholesterol addition in buffer solution, the electro-oxidation of cholesterol on enzyme immobilized surface led to increased the biosensor’s current response. The cholesterol EGT biosensor detected cholesterol in wide-linear range (i.e., 0.1 to 60.0 mM) with high sensitivity (37.34 μ A mM ⁻¹ cm ⁻² ) compared to conventional electrochemical sensors. Furthermore, we obtained excellent selectivity, fabrication reproducibility, long-term storage stability, and practical applicability in real serum samples. The demonstrated EGT biosensor can be extended with changing enzymes or nanomaterials or hybrid nanomaterials for specific analyte detection.

Two-dimensional (2D) nanostructures are valued for their ultrathin planar surface and high charge carrier mobility, which offer enhanced sensing capabilities. Herein, we synthesised 2D nanoflake–like copper oxide (CuO) nanostructures using a hydrothermal method for electrochemical riboflavin sensor fabrication. Electrochemical analysis of nanoflake–like CuO modified glassy carbon electrode (GCE) was analysed using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS). The differential pulse voltammetry (DPV) technique was used for testing the electrochemical sensing performance of the fabricated riboflavin sensor. The designed sensor detected riboflavin in concentrations ranging from 10 to 1250 nM with a high sensitivity (571.8 μA/μM cm²) and a limit of detection (LOD) of 6.5 nM. The sensor’s excellent electrocatalytic activity towards riboflavin is primarily attributed to the unique CuO nanoflake–like morphology that provides a high surface area. Furthermore, sensors showed excellent selectivity, reproducibility, and stability, essential attributes for precise riboflavin detection and long-term usage. Overall, the electrochemical sensor based on nanoflake–like CuO nanostructures represents a promising platform for sensitive riboflavin detection. An easy synthesis of 2D nanoflake–like CuO nanostructures provides the possibility of future potential applications of these nanomaterials in analytical chemistry domains such as biomedical diagnostics, food analysis, and environmental monitoring.