Smartphone-assisted Ce-POM/CuBTC peroxidase-like colorimetric detection of H₂O₂ and ascorbic acid in food samples

Rapid and accurate detection of hydrogen peroxide (H₂O₂) and ascorbic acid (AA) in food industry is critical to human health. Herein, a novel Ce-based polyoxometalate [Ce(H₂O)₉][Cu(H₂O)(2,6-pdca)]₃H[SiW₁₂O₄₀]·5H₂O (Ce-POM) (2,6-H₂pdca = 2,6-pyridine-dicarboxylic acid) was designed and loaded onto Cu-based benzene-1,3,5-tricarboxylate (CuBTC) to obtain Ce-POM/CuBTC, which can catalyze H₂O₂ to oxidize 3,3',5,5'-tetramethylbenzidine (TMB) to blue ox-TMB, while AA can reduce ox-TMB. Consequently, a dual-function colorimetric detection system was established with detection limits of 0.45 μM (H₂O₂) and 2.63 μM (AA), and linear ranges of 1-80 μM (H₂O₂) and 5-400 μM (AA). We further developed a smartphone-assisted paper-based device (PAD) using Ce-POM/CuBTC for on-site detection. Additionally, the mice skin toxicity study showed that Ce-POM/CuBTC had no adverse effects on the skin, body weight and important organs of mice, confirming its good biosafety. The colorimetric system was successfully applied to real sample detection, demonstrating the application potential of rare earth POMs composites in food safety.