Colorimetric sensors constructed with one dimensional PtNi nanowire and Pt nanowire nanozymes for Hg²⁺ detection

In recent years, environmental pollution has attracted widespread global attention. Among them, environmental problems caused by heavy metal pollution pose a serious threat to human health and ecosystems. Mercury is a common heavy metal pollutant with high toxicity and wide distribution. Excessive intake of Hg²⁺ can cause permanent and severe damage to the nervous system, respiratory system, and kidneys in the human body. Therefore, developing both accurate and fast detection methods for Hg²⁺ is of great significance.

A sensitive Hg²⁺ colorimetric sensor is designed based on PtNi nanowires (NWs) and Pt NWs with peroxidase-mimetic activity. PtNi NWs and Pt NWs catalyze the reaction of 3,3', 5,5'-tetramethylbenzidine (TMB) with hydrogen peroxide (H₂O₂) to produce blue oxidized TMB (oxTMB). The specific interaction of Pt-Hg significantly inhibits the peroxidase-mimetic activity of PtNi NW and Pt NW nanozymes, resulting in a lighter blue color. It is worth noting that compared with specific activity (SA) of Pt NWs (3.31 U/mg), PtNi NWs own superior SA (10.43 U/mg), which inevitably leads to a wider linear range of Hg²⁺ analysis (1 nM-200 μM) and a lower detection limit (0.6748 nM) for PtNi NWs-based colorimetric sensor, versus linear range (4 nM-5 μM) and LOD of 1.198 nM for Pt NWs-based colorimetric sensor, which are far below the Hg²⁺ threshold (10 nM) for drinking water set by the US Environmental Protection Agency.

The two nanozyme colorimetric sensors have been successfully used for the evaluation of Hg²⁺ in complex river water and tap water. Due to the advantages of simple operation, fast response, and high sensitivity, colorimetric sensors have broad application prospects in environmental monitoring.