Nanomaterial-based enzyme mimics (nanozymes) are currently a new forefront of chemical research. However, the application of nanozymes is limited by their low catalytic activity and low turnover numbers. Cerium dioxide nanoparticles (nanoceria) are among the few with oxidase activity. Herein, we report an interesting finding addressing their limitations. The oxidase activity of nanoceria is improved by over 100-fold by fluoride capping, making it more close to real oxidases. The turnover number reached 700 in 15 min, drastically improved from similar to 15 turnovers for the naked particles. The mechanism is attributed to surface charge modulation and facilitated electron transfer by F(-)capping based on zeta-potential and free radical measurements. Ultrasensitive sensing of fluoride was achieved with a detection limit of 0.64 mu M F- in water and in toothpastes, while no other tested anions can achieve the activity enhancement.
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