Fructose sensing via a flexible photoelectrochemical microfluidic fuel cell based on a ZnO/praseodymium composite

Abstract

Fatty liver and other related diseases are caused mainly by fructose consumption from nonalcoholic sweetened beverages; therefore, the development of new techniques, materials, and practical devices for its quantification is important for clinical diagnosis. In the present work, composites based on zinc oxide (ZnO) and different praseodymium concentrations were prepared by precipitation in alkaline aqueous media. Composites of ZnO/praseodymium were characterized by ultraviolet/visible-near infrared (UV/Vis-NIR) and Fourier transform infrared (FTIR) spectroscopies, thermogravimetry (TGA), X-ray diffraction (XRD) and scanning electron microscopy (SEM). The composites consisted of ZnO microparticles of cabbage-like morphologies with sizes of 850 ± 253 nm and a thickness of 36.6 ± 1 nm, which were decorated with praseodymium particles of rice-like morphology with different sizes depending on the praseodymium concentration. The composites exhibited photoactivity in the UV and visible regions, with characteristic absorbances due to the presence of fluorophores in the near-infrared region. ZnO/praseodymium composites were characterized electrochemically in half-cells under visible light irradiation at different fructose concentrations to determine their detection limit, which was between 30 and 40 mM fructose. The composite with 2% praseodymium with respect to Zn²⁺ showed the best linearity; therefore, it was tested as a photoanode for fructose oxidation in a flexible and transparent photoelectrochemical microfluidic fuel cell with an interval of 5 to 50 mM fructose, with a 40 mM fructose concentration and a power density of 0.142 mW/cm² under illumination compared with 0.101 mW/cm² in the dark (∼ 40% higher).