Peroxidase-Like Activity Regulation of Support-Engineered Platinum Nanozymes for Sensing Heavy Metal Ions

Small-sized platinum nanoparticles (Pt NPs) exhibit high peroxidase-like activity but suffer from self-agglomeration and poor stability. To solve this problem, using porous aminophenol formaldehyde resin (APF) microspheres as a support, a sulfhydryl-functional Pt NPs-based hybrid nanozyme (APF@Pt NPs) with excellent peroxidase-like activity was designed by anchoring Pt NPs on the surface of APF. High specific surface area and abundant active groups of APF microspheres facilitate the uniform distribution of Pt NPs. This design not only enhances the dispersibility of Pt NPs to prevent aggregation but also exposes more active sites─key factors that contribute to the improved catalytic performance of APF@Pt NPs. Using APF@Pt NPs as a recognition element, a sensitive colorimetric method was developed for mercury ion (Hg2+) detection through specific inhibition of Hg2+ on the peroxidase activity of APF@Pt NPs. This sensor exhibited good linearity (R2 = 0.952) in the range of 0–3.125 μM. The limit of detection (LOD) was as low as 0.096 μM, along with satisfactory recoveries of 98–115% and relative standard deviation (RSD) < 3.75% in real water. Integrated with a hydrogel-sensor and smartphone APP, a real-time and visual intelligent sensing platform enabled a rapid qualitative and quantitative analysis of Hg2+ by RGB analysis in environmental samples. These findings illustrate that the application of APF@Pt NPs provides an effective support-engineered strategy to enhance and regulate the peroxidase-like activity and stability of small-sized Pt NPs. This also presents a multifunctional sensing platform for on-site and real-time monitoring of heavy metals in complex environmental samples.