Modulating of d-band center in Cu single-atom anchored Co3O4 nanozyme for sensitive immunochromatographic test strip

Immunochromatographic test strip (ITS) has been widely employed for point-of-care diagnoses. However, how to significantly enhance the analytical sensitivity of device-free ITS remains a challenge. Here, we synthesized a Cu single-atom anchored Co 3 O 4 (CuSA/Co 3 O 4 ) nanozyme that possesses ultrahigh peroxidase-mimicking catalytic activity owing to d -band center upshift mediated by Cu single-atom. Molecular orbital analysis demonstrated that d orbitals in CuSA/Co 3 O 4 have stronger orbital hybridization affinity than Co 3 O 4 to H 2 O 2 ′s π* orbitals. This reinforces hydroxyl radical ( OH) production and provides a stronger catalytic colorimetric signal, which is beneficial for improving the sensitivity of ITS. Moreover, we applied the CuSA/Co 3 O 4 to ITS as a signal reporter for monitoring Xanthomonas oryzae pv. oryzicola (Xoc) , the pathogen of rice bacterial leaf streak. The visual limit of detection (LOD) of the developed CuSA/Co 3 O 4 -based ITS was as low as 6.4 × 10 2 CFU mL −1 , which is 25-fold more sensitive than the traditional Au nanoparticles (AuNP)-based ITS. Taken together, this work demonstrates the great potential of CuSA/Co 3 O 4 nanocomposite as a signal reporter to improve the sensitivity of ITS for on-site Xoc detection.