Carbon Nitride-Supported Zinc Oxide Nanocomposite for the Electrochemical Detection of Dopamine and the Development of Disposable Sensors

The carbon nitride-supported zinc oxide (CNZO) nanocomposite was synthesized through a high-temperature synthesis method, resulting in zinc oxide nanoparticles with an average size of ~44 nm, dispersed on a carbon nitride matrix. X-ray diffraction confirmed the formation of the hexagonal wurtzite phase of zinc oxide, with a space group of P63mc. X-ray photoelectron spectroscopy and Fourier-transform infrared analysis further verified the presence of both zinc oxide and carbon nitride. The CNZO nanocomposite served as a catalyst for the electrochemical detection of dopamine, achieving limit of detection and sensitivity of 2.66 μM and 6.23 μA μM⁻¹ cm⁻² respectively, using square wave voltammetry technique. Cyclic voltammetry experiments demonstrated excellent electroactivity of the CNZO nanocomposite in a neutral pH environment. An electrochemical paper-based analytical device (EPAD) was designed and successfully employed for the electrochemical analysis of dopamine in pharmaceutical samples using CNZO nanocomposites. Additionally, CNZO was used as an active material in the development of a disposable dopamine sensor based on an extended gate field-effect transistor (EG-FET). This sensor exhibited a sensitivity and limit of detection 18.22 μA μM⁻¹ cm⁻² and 0.36 μM, respectively, with a correlation coefficient of 0.99.