Synthesis of Ceria (CeO2) Nanoparticles and Their Application in Colorimetric Probes for the Determination of Ascorbic Acid

Nanoceria (CeO2 nanoparticles) are among the most unique and promising lanthanide nanomaterials with sensing applicability. In this study, the redox reactivity of nanoceria was exploited for biomedical application based on changes in the physicochemical properties of the nanoparticles on interaction with ascorbic acid (Vitamin C). Nanoceria were synthesized by the microwave-assisted method using ammonium ceric nitrate [(NH4)(2)Ce(NO3)(6)] as the precursor and diethylene glycol (DEG) as the stabilizer and capping agent. The powder X-ray diffraction (p-XRD) studies of the nanoparticles showed that the synthesized particles are of a pure single-phase matched with a cubic structure. Data from Scanning Electron Microscopy (SEM) & Transmission Electron Microscopy (TEM) analysis were also used to estimate the average size of the particles, and a range of value between 6.8-7.1 nm was obtained which agrees with the value obtained using Debye-Sherrer's relation (6.8 +/- 0.2 nm). On interacting the nanoceria with ascorbic acid, a color change from light yellow to reddish orange (oxidation of ascorbic acid) was observed, and at the same time, the Ce4+ is being reduced to Ce3+. The reaction between the nanoceria and ascorbic acid was done at a constant concentration of nanoceria with varying amounts of ascorbic acid. This reaction was monitored using the UV-Vis Spectrometry, and the spectra obtained showed that the intensity of the peak decreases with decreasing concentration of the ascorbic acid. Furthermore, the reduction of Ce4+ to Ce3+ was justified by the blue shift in the lambda(max) from 344 nm to 254 nm. Data obtained also showed a detection limit of 20 ppm ascorbic acid. The nanoceria were also used to fabricate a paper strip which tested positive for the colorimetric detection of ascorbic acid.