Amorphous RuTe2 nanorods as efficient peroxidase mimics for colorimetric immunoassay

With great progress in the development of nanozymes, the effect of size, composition and structure on the catalytic activity of nanozymes have been studied extensively, while the effect of phase has rarely been reported. Herein, phase-engineered RuTe 2 nanorods are synthesized with different phase structures and peroxidase (POD)-like activities, which enables an in-depth understanding of their structure-activity relationship. Amorphous RuTe 2 (a-RuTe 2 ) nanorods exhibit superior POD-like activity, which is 3.77 times higher than that of their crystalline counterpart (c-RuTe 2 nanorods). The amorphous phase composed of a large amount of disordered atoms endows the a-RuTe 2 nanozyme with impressive performance. Significantly, given many POD-like nanozymes also show oxidase (OXD)-like activities, the interferences of O 2 limit their applications in colorimetric assay. The proposed a-RuTe 2 nanorods were found to possess negligible OXD-like activity. As a proof-of-concept, an enzyme-linked immunosorbent assay (ELISA) was constructed utilizing a-RuTe 2 nanorods as labels for the detection of prostate-specific antigen (PSA). This a-RuTe 2 nanorods-based ELISA possesses a low detection limit of 32.6 pg mL −1 , which is at least one order of magnitude lower than that of conventional ELISA based on natural horseradish peroxidase. This work provides new insights into the design of high-performance nanozymes based on phase engineering.