Co3O4@β-cyclodextrin with synergistic peroxidase-mimicking performance as a signal magnification approach for colorimetric determination of ascorbic acid

Transition metal oxides nanoparticles have shown enzyme-mimetic performance. It was demonstrated that the Co3O4@beta-cyclodextrin nanoparticles (Co3O4@beta-CD NPs) showed a higher peroxidase-mimicking catalytic activity than pure Co3O4 NPs. beta-CD molecules were coated onto the surface of Co3O4 NPs via a one-pot synthesis method. Co3O4@beta-CD NPs displayed higher affinity to 3,3',5,5'-tetramethylbenzidine (TMB) through Michaelis-Menten mechanism after modification with beta-CD. The catalytic efficiency of Co3O4@beta-CD NPs for TMB oxidation was 9.5-fold higher than that of the pure Co3O4 NPs because of the effective host-guest interactions between Co3O4@beta-CD NPs and TMB. Further, the hydrophobic cavity of beta-CD while hosting TMB could reduce the transfer distance of electrons between TMB and Co3O4 catalyst, which could lead to faster oxidation of TMB. The synergistic effects between Co3O4 and beta-CD enhanced the peroxidase-mimicking property. The efficient and visual colorimetric determination of Ascorbic Acid (AA) assay was achieved. The limit of detection was 1.09 mu M (S/N = 3) and the linear range was 10-60 mu M based on the Co3O4@beta-CD NPs peroxidase-mimicking-mediated 3.0-fold signal magnification strategy. Moreover, the outstanding selectivity toward the detection of AA was achieved, which could exhibit prospects in biomedical analysis.