Non-Enzymatic Urea Detection Via Using Ag/ZnO Nanorod-Based Catalyst
Authors: Yoon Jaesik , Lee Eunji , Lee Doohee , Oh Tae-Sik , Woo Sung Pil , Yoon Young Soo , Kim Dong-Joo 
Published: February 2020

The level of biological molecules, such as urea, glucose, dopamine, and creatinine has been measured by various sensing platform for biomedical applications. For example, the urea level deviated from the reference values which causes several diseases such as renal and hepatic issues, is closely related to our life. Monitoring of urea is also important for fertilizer production as well as development of indirect hydrogen storage materials.
Various types of urea sensors, including enzymatic sensors, have been researched to measure abovementioned molecules, courtesy of high selectivity and sensitivity. However, enzymatic sensors have the stability problems caused by denaturation of enzyme. A various metals or metal oxides, such as Pt, Cu/CuO, Ni/NiO, Zn/ZnO, have been widely investigated for the detection of different molecules. Among them, Ni based catalyst presents better performance in the electro-catalytic oxidation of molecules such as urea and glucose. Although Ni based catalyst has shown a good performance, problems such as degradation and expansion of the Ni based catalyst structure during the oxidation still exist. Moreover, the level of pH to operate the electrode for detecting the bio molecules indicates the alkaline the solution which is inability to perform in the physiological condition of approximately pH 7. In other words, the concentration of OH-anions is a dominant factor in Ni based catalyst.
In this study, silver catalyst deposited on a synthesized ZnO rods/ carbon substrate was prepared at low-temperature process for the enzyme-free urea sensor. The morphologies and structural properties of Ag catalyst deposited ZnO rods were analyzed by SEM and XRD, and the quantity of the silver catalyst was measured by EDS. Thereafter electrochemical properties of the electrode were performed. The catalytic effect of Ag/ZnO rods electrode for urea sensing was investigated in terms of sensitivity and selectivity. Detailed discussion on the mechanism of Ag/ZnO rods catalytic effect will be given.
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Acknowledgement
This work was supported by Agency for Defense Development (ADD) as global cooperative research for high performance and light weight bio-urine based fuel cell (UD160050BD).