Ultrarapid, size-controlled, high-crystalline plasma-mediated synthesis of ceria nanoparticles for reagent-free colorimetric glucose test strips

Abstract

We describe an ultrarapid (within several minutes), size-controlled (<100 nm in diameter), and high-crystalline plasma-mediated synthesis of ceria nanoparticles and their application in reagent-free colorimetric test strips. Glucose oxidase (GOx) incorporated onto the paper matrix generates H2O2 with glucose, subsequently inducing color changes of the embedded ceria nanoparticles from white/yellow to yellow/orange without any involvement of colorimetric substrate or dye. The optimized protocol yielded ∼2-fold higher color intensity compared to that of commercially available ceria nanoparticles, presumably due to its much larger surface area and higher Ce3+ content, facilitating the oxidation from Ce3+ to Ce4+ and formation of peroxide complexes at the nanoparticle surfaces. Using the colorimetric test strip, glucose was specifically detected over a wide linear range (0.1−10 mM), with excellent reusability, storage stability, precision, and reproducibility. The innovative plasma-mediated ultrarapid synthesis of size-controlled and high-crystalline ceria nanoparticles and their utilization on reagent-free colorimetric test strip allow for a straightforward sensing platform for the point-of-care detection of glucose and can be expanded to other oxidative enzymes for facile colorimetric detection of various clinically important target molecules.