Colorimetric sensors constructed with one dimensional PtNi nanowire and Pt nanowire nanozymes for Hg detection.

Background: 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 Hg 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 Hg is of great significance.

Results: A sensitive Hg 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 (HO) 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 Hg 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 Hg threshold (10 nM) for drinking water set by the US Environmental Protection Agency.

Significance: The two nanozyme colorimetric sensors have been successfully used for the evaluation of Hg 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.