The Use of CeO2-TiO2 Nanocomposites as Enzyme Immobilization Platforms in Electrochemical Sensors

The use of metal oxide-based nanoparticles plays a key role in the development of electrochemical sensors with superior properties such as high sensitivity, wide linear range, low limit of detection, and long storage stability. In this work, we aimed to synthesize CeO 2 -TiO 2 mixed metal oxide nanoparticles which were used as substrate materials for the immobilization of biorecognition element for the construction of enzyme-based electrochemical sensors. For this purpose, in the first part of the study, CeO 2 -TiO 2 nanoparticles were prepared via a low temperature co-precipitation method and characterized using X-ray Diffraction (XRD), N 2 -adsorption, and Transmission Electron Microscopy (TEM) methods. The XRD results confirmed the successful synthesis of CeO 2 -TiO 2 mixed metal oxide nanoparticles with the average crystalline size of 8.51 nm. The calculated crystalline size value was compatible with that obtained from the TEM images. The N 2 adsorption results revealed a large surface area of 78.6 cm 2 g -1 which is essential for the construction of electrochemical sensors with improved performance. The electrochemical sensors were developed by the deposition of nanoparticles on the surface of a Pt electrode, followed by the immobilization of lactate oxide enzyme. The electrochemical performance of the sensors was evaluated by cyclic voltammetry (CV) and chronoamperometry methods. The constructed sensors showed a sensitivity of 0.085 ± 0.008 µA µM -1 cm -2 (n=5) with a high reproducibility (RSD % = 1.3) and a wide linear range (0.02-0.6 mM).  In addition, the detection limit towards lactate was found be 5.9 µM. The results indicated that the use of CeO 2 -TiO 2 nanoparticles used as a modifier on the surface of the Pt electrode enabled the construction of electrochemical lactate sensors with high sensitivity.