Monitoring of glucose in fermentation processes by using Au/TiO2 composites as novel modified electrodes

This paper demonstrates an effective method of monitoring glucose in fermentation processes based on the development of enzyme-free glucose electrochemical sensors. The sensing electrodes were manufactured by preparing size-controlled Au nanoparticles (NPs), in the form of colloidal solutions, which were dispersed on TiO2 substrates, and then deposited on commercial carbon screen printed electrodes. The as-synthesized samples were fully characterized by transmission electron microscopy, X-ray diffraction, atomic absorption spectroscopy, and UV-visible diffuse reflectance spectroscopy to obtain information about their morphological, structural, and electronic properties. Particularly, the ability to control the size of Au NPs in the colloidal solution by using different reducing agents and stabilizers is presented here. The Au/TiO2-based modified sensors were assembled and tested for glucose monitoring in an alkaline solution. Results of cyclic voltammetry showed the high electrocatalytic activity of these sensors toward glucose oxidation, whereas no response was detected toward ethanol. This suggests the possibility of using this type of sensor for glucose monitoring in the fermentation processes without ethanol interference. The efficient sensing properties of Au NP-embedded TiO2 composites may be ascribed to the higher electrocatalytic activity of smaller Au NPs stabilized on TiO2.