Smartphone-assisted portable swabs for thiram specific analysis based on target-regulated CuWO4 nanozyme activity combined with sample pretreatment

Pesticide residues pose significant risks to consumer health. Therefore, it is essential to develop convenient and practical detection methods. Nanozyme colorimetric sensing is widely used for pesticide detection. However, improving its sensitivity and selectivity remains a major challenge. In this study, a smartphone-assisted portable test swab fabricated using CuWO 4 as the extractant, combined with solid-phase extraction (SPE), was designed for the colorimetric detection of thiram (THR). Based on the specific binding between the Cu sites in CuWO 4 and THR, interference was eliminated after the SPE to improve selectivity. Moreover, the sensitivity improved after SPE enrichment. Additionally, THR enhanced the peroxidase-like activity of CuWO 4 , whereas tungsten as a co-catalyst further boosted the nanozyme activity, thereby improving the detection sensitivity (limit of detection: 19 nM). The experimental results demonstrate that this method exhibits high stability and good selectivity, with recoveries in real samples ranging from 90.8 % to 112.4 %.