Simple synthesis of flower-like ZnO@Pt composites for dual-mode colorimetric detecting Hg2+ with smartphone and UV–vis

Background Mercury is one of the most toxic heavy metal contaminants that can be harmful to human health through the food chain. Recently, the colorimetric detection of heavy metals based on nanozyme catalytic activity has received extensive interest due to the simplicity, signal visibility and suitability for in situ detection. However, the majority of these nanozymes that can be utilized for detecting mercury with high synthesis temperature and complicated synthesis methods, which limited their practical application. Results In this work, flower-like ZnO@Pt composites were simply synthesized at room temperature , the flower-like structure and the high electron mobility of ZnO endow ZnO@Pt with stronger peroxidase-like activity. Consequently, dual-mode (UV–vis and smartphone) colorimetric sensors were designed to detect Hg 2+ . In UV–vis mode, the Hg 2+ concentration linear range was 10–400 nM, and the limit of detection (LOD) was 0.54 nM. In smartphone mode, the Hg 2+ concentration linear range was 50–1250 nM, and the LOD was 29.8 nM. A parallel analysis in 3 real water samples was confirmed by ICP-MS, the results showed good correlations (R 2  > 0.98), indicating the practical reliability of these sensors. Significance The novel flower-like ZnO@Pt composites with high stability, catalytic activity and Hg 2+ response were simply synthesized at room temperature, simplifying the synthesis steps and reducing costs. The sensitivity of the developed colorimetric sensor in UV–vis mode was 3–145 times higher than that of the similar methods. The colorimetric sensor in smartphone mode broadened the detection range and improved the portability of Hg 2+ detection. Thus, the dual-mode (UV–vis and smartphone) colorimetric sensors providing new detection modes for rapid monitoring of Hg 2+ in environmental water.