Amplified colorimetric detection of Ag+ based on Ag+-triggered peroxidase-like catalytic activity of ZIF-8/GO nanosheets

Recently, noble metal nanozymes have been frequently utilized for the construction of a number of colorimetric probes for monitoring heavy metal ions. However, the high cost of noble metal nanozymes seriously confines their extensive use of such colorimetric methods. Here, an effective noble metal free zeolitic imidazolate frameworks-8/graphene oxide (denoted as ZIF-8/GO) probe has been constructed for colorimetric detection of Ag+ with high selectivity and sensitivity in water and human serum samples. The proposed method is based on the Ag+-triggered peroxidase-like catalytic activity of ZIF-8/GO for oxidizing 3,3′,5,5′-tetramethylbenzidine (TMB) in the existence of H2O2, accompanying an absorption intensity of oxTMB centered at 652 nm and a color change from colorless to blue. The detection limit of this system to Ag+ is 1.43 nM, which is significantly lower than the threshold levels (0.93 μM) for drinking water and other noble metal nanozymes based colorimetric methods. Furthermore, such detection platform shows high selectivity against other metal ions and could be used for detection of Ag+ from environmental water and human serum samples. Because of its low cost, convenient operation, and excellent sensitivity and selectivity, the ZIF-8/GO probe could fulfill all industry requirements for point-of-use monitoring of Ag+ in environmental and biological samples, and fill market vacancy.