Ligand-Field Engineered White Copper-Based Nanozyme: Low-Background Detection for Sensitive Discrimination of Wine Origin.

Copper-based nanozymes are effective mimics of polyphenol oxidase. However, the d9 electron configuration of Cu(II) with facile d-d transitions causes most copper-based nanozymes to appear black, blue, or brown, thereby introducing background interference, whereas white copper-based nanozymes remain unexplored. Herein, a white copper-based nanozyme with low background interference and multienzyme-like activity was constructed through the synergy of strong and weak field ligands. Compared with other colored copper-based nanozymes, the white nanozyme can increase the signal-to-noise ratio more than 4-fold, and its color remains highly stable over 28 days in an aerobic environment. When loaded onto a paper-based platform, the white nanozyme offers ultralow background and a high signal-to-noise ratio. Leveraging its multienzyme-like activity, the nanozyme enables sensitive discrimination of various markers in wine, with a minimum distinguishable concentration as low as 50 nM. This customized white nanozyme technology effectively reduces the detection background interference of copper-based nanozymes, and the ligand field strategy holds promise for color customization of other metal-based nanozymes.