Abstract
A highly sensitive, selective and stable electrochemical sensor for detection of uric acid (UA) in aqueous solution has been successfully developed by deposition of exfoliated graphitic-like carbon nitride (g-C3N4) nanosheets on glassy carbon electrode (GCE). The synthesized g-C3N4 was confirmed by X-ray diffraction (XRD), Fourier-transform infrared (FT-IR) and Raman spectroscopies. Field-emission scanning electron microscopy (FE-SEM) and High-resolution transmission electron microscopy (HR-TEM) were used to investigate the crystalline structure of g-C3N4. The elemental composition was characterized by energy-dispersive X-ray spectroscopy (EDXS). Compared to bare GCE, exfoliated g-C3N4 nanosheets (NS) modified GCE exhibited higher catalytic current for UA electro-oxidation at reduced over potential in 0.1 M phosphate buffered saline solution (PBS), which is essential to discriminate interfering analytes. g-C3N4 NS modified GCE showed a linear relationship between the electrochemical signal and the UA concentration from 100 to 1000 μM with fast response by differential pulse voltammetry (DPV). The common interferent molecules such as dopamine, ascorbic acid, folic acid, paracetamol, lactic acid, oxalic acid, cysteine, and ciprofloxacin were tested in 0.1 M PBS for the g-C3N4 NS modified GCE. It was found that these molecules did not affect the oxidation current of UA when they co-existed in the same buffer solution. Moreover, the modified sensor probe was tested for UA in urine samples with satisfactory recovery values. The proposed sensor offers high accuracy, sensitivity, simple fabrication and low cost. We suggest that g-C3N4 NS based sensor can be useful for UA analysis in medical, environmental, food and industrial applications.
Highlights
Reports have demonstrated that the ultrathin g-C3N4 NS have better electrochemical activity and stability than bulk g-C3N4; this suggests that exfoliated ultrathin g-C3N4 NS are a promising candidate material for electrochemical applications.[32,33,34,35,36,37,38]
Where Ip is the oxidation peak current (A), n is the number of transferred electrons per mole, A is the active surface area of the electrode, D is the diffusion coefficient, C is concentration and ν is the scan rate (V/s). These results indicated that the oxidation of Uric acid (UA) on g-C3N4 NS/glassy carbon electrode (GCE) is a diffusion-controlled electrochemical processes (Fig. 8b).[63]
These results suggested that UA detection on g-C3N4 NS/GCE sensor is highly selective without any
Summary
Uric acid (UA) is found to have great significance in the physiology functions of living organisms and is involved in numerous biological processes.[1,2] Serum UA is the primary water-insoluble end product of purine metabolism in the human body and it is an important biomolecule present in urine and blood.[3,4] Excessive, unusually low, or highly time-variable UA concentration is associated with clinical disorders such as gout, pneumonia, type 2 diabetes, leukemia, toxemia during pregnancy, chronic renal disease, multiple sclerosis, hypertension and metabolic disorders.[5,6,7,8,9,10] A simple and low cost method for determination of UA concentration would be useful since UA serves as a marker for the diagnosis of above conditions. Various standard analytical methods have been developed to determine UA such as high performance liquid chromatography (HPLC), a potentiometric enzyme electrode, flow-injection analysis, amperometry etc.[11,12,13,14,15,16] These methods have some drawbacks such as high cost, tedious sample preparation, slow measurement, unsuitability for use outside of a laboratory setting, and requirement to be performed by skilled technicians. Among these options, electrochemical sensors (ECS) are attractive for detection of bio-molecules which exhibit electrochemical activity. Reports have demonstrated that the ultrathin g-C3N4 NS have better electrochemical activity and stability than bulk g-C3N4; this suggests that exfoliated ultrathin g-C3N4 NS are a promising candidate material for electrochemical applications.[32,33,34,35,36,37,38]
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