Investigation of degradation pathways of Cu2O electrodes during glucose electrochemical detection.

• Alexander Sohn, Chemistry, University of Delaware
• Thomas Dick, , University of Delaware

• Rachel Davidson, Chemistry and Biochemistry, University of Delaware
• Minh Dang, Chemistry and Biochemistry, University of Delaware

With 830 million cases of diabetes globally there is a large need for more accessible ways to quantify and monitor glucose levels in blood and interstitial fluid. Our research focuses on understanding the mechanisms of degradation of copper oxide electrodes used as non-enzymatic electrochemical biosensors for glucose detection and quantification. Under an oxidizing potential in an alkaline environment glucose is oxidized by copper oxide electrodes to generate a current signal, which is used to detect and quantify glucose. However, in alkaline aqueous solutions, Cu+ is unstable which leads to degradation and changes in the electrode’s morphology and surface binding sites, affecting the sensor’s ability to reproducibly quantify glucose.  Our goals are to determine how changing the morphology of the Cu-based electrode influences its stability. To this end we synthesized Cu-based electrodes with different morphologies through electrodeposition, and explored how they performed as glucose sensors. Cu2O was synthesized on indium tin oxide (ITO) coated glass using a copper sulfate Cu precursor and potassium sulfate as the supporting electrolyte in a three-electrode cell. By varying the concentration of copper sulfate and the ratio of potassium sulfate to copper sulfate, three distinct morphologies of Cu2O were obtained. We discovered that of the three (cube, star, and octahedral), the cube-shaped morphology exhibited the most degradation in 24 hours of glucose sensing, with SEM images suggesting that the degradation occurred at an increasing rate over time. For all the morphologies, the bulk chemical composition remained Cu2O, but the surface oxidized to CuO after about 30 minutes of catalysis. In the future, both star-shaped and octahedral morphologies could be employed in copper-based non-enzymatic sensors for better accuracy and longevity due to their incredible stability. However, a method would need to be derived to consistently remove the particle surface after it has been oxidized.