sp-Hybridized Carbon Modulates the Spin States of Ir Nanozyme for Efficient Oxygen Activation.

The kinetics of oxidase-like (OXD-like) nanozymes are significantly influenced by the electronic configuration of their active sites. In this study, a nanozyme that features unique electronic interactions was created by in situ construction of iridium nanoparticles on graphdiyne-coated carbon nanotube (Ir/GDY/CNT). This configuration enables efficient and specific oxygen activation through a spin-state modulation mechanism. The incorporation of sp-hybridized carbon (sp-C) facilitates a transition in the electronic structure of the Ir sites from low-spin to high-spin states via electronic metal-support interactions. This enhances the adsorption strength and electron transfer between the Ir sites and reactants/intermediates, leading to an improved OXD-like activity. The Ir/GDY/CNT nanozyme demonstrates a 6.2-fold enhancement in OXD-like activity compared to pristine iridium nanoparticles, and a 2.5-fold improvement over Ir/CNT. Capitalizing on this improved catalytic performance, a colorimetric sensor was developed for the detection of organophosphorus pesticides. The sensor exhibits a wide linear range (0.1-1200 ng mL-1) and ultralow detection limit (0.03 ng mL-1), outperforming previously reported systems. This work establishes a generalizable strategy for developing high-performance OXD-like nanozymes through spintronics-level engineering, which presents significant potential for environmental and diagnostic applications.