Development of single-use thin film electrodes based on Zn2SnO4 on In2O3: SnO2 substrates with their biosensing applications

Dopamine (DA) has a significant impact on the emergence and treatment of certain diseases (e.g., Alzheimer's and Parkinson's diseases). Therefore, monitoring of DA is important, and using biosensors is a favorable option instead of time-consuming and expensive conventional methods. In biosensor manufacturing, thin films have become a rapidly emerging field. In this study, a non-enzymatic electrochemical biosensor based on thin film electrodes is developed for monitoring DA levels. The thin film electrodes (ZTO/ITO) are developed by deposition of Zn2SnO4 (ZTO) on In2O3:SnO2 (ITO) substrates by magnetron sputtering. 3-aminopropyltriethoxysilane (APTES) is used to modify the surface of these electrodes. Physical, optical, and structural properties of the electrodes are determined by applying surface profilometry, UV-VIS-NIR spectrophotometry, X-ray diffraction (XRD), and scanning electron microscopy (SEM) measurements. According to these measurements, it has been observed that the ZTO/ITO combination has a higher optical transmission value than the bare ITO, depending on the deposition time and the oxygen concentration used during ZTO deposition. In addition, the ITO thin film has a crystalline structure, while the ZTO thin film has an amorphous structure and both thin films have a good surface morphology. As electrochemical analysis, cyclic voltammetry (CV), electrochemical impedance spec-troscopy (EIS), and differential pulse voltammetry (DPV) measurements are performed. As a result of CV and EIS measurements, a remarkable change (63.54%) was observed after applying APTES modification onto the surface of ZTO/ITO electrode, and the ones obtained by DPV showed successful detection of DA by APTES modified ZTO/ITO. In addition, the experiments in the presence of interferences such as ascorbic acid (AA), uric acid (UA), bovine serum albumin (BSA), and fish sperm double-stranded DNA (fsDNA) show that the electrodes can be successfully applied for voltammetric determination of DA. The detection limit of DA was estimated to be 0.013 mu M in the range of DA between 0.1 and 1 mu M, and sensitivity was calculated and found to be 11.057 mu A mu g(-1) mL cm(-2), which means ZTO/ITO electrodes have a good sensitivity.