High-Indexed Intermetallic Pt₃Sn Nanozymes with High Activity and Specificity for Sensitive Immunoassay

Great efforts have been made to expand the application fields of nanozymes, which puts forward requirements for nanozymes with both superior catalytic activity and specificity. Herein, we reported the high-indexed intermetallic Pt₃Sn (H-Pt₃Sn) with high peroxidase-like activity and specificity. The resultant H-Pt₃Sn exhibits a specific activity of 345.3 U/mg, which is 1.82 times higher than Pt. Moreover, H-Pt₃Sn possesses negligible oxidase-like and catalase-like activities, achieving superior catalytic specificity toward H₂O₂ activation. Experimental and theoretical calculations reveal both the splitting energy for adsorbed H₂O₂ and the energy barrier for the rate-determining step of H-Pt₃Sn are significantly decreased compared with Pt₃Sn and Pt. Finally, a nanozyme-linked immunosorbent assay is successfully developed, achieving the sensitive and accurate colorimetric detection for carcinoembryonic antigen with a low detection limit of 0.49 pg/mL and showing practical feasibility in serum sample detection.