Oxidase-like mimic of Ag@Ag 3 PO 4 microcubes as a smart probe for ultrasensitive and selective Hg 2+ detection

• Published in: Dalton transactions : an international journal of inorganic chemistry Vol. 45; no. 7; pp. 3048 - 3054
• Main Authors: Chai, Dong-Feng, Ma, Zhuo, Qiu, Yunfeng, Lv, Yu-Guang, Liu, Hong, Song, Chao-Yu, Gao, Guang-Gang
• Format: Journal Article
• Language: English
• Published: 2016
• ISSN: 1477-9226; 1477-9234
• DOI: 10.1039/C5DT04192A

An oxidase-like mimic system based on facilely synthesized Ag@Ag 3 PO 4 microcubes (Ag@Ag 3 PO 4 MCs) was designed and utilized to detect mercury ions with high selectivity and ultrasensitivity. Ag@Ag 3 PO 4 MCs with an average size of ca. 1.6 μm were synthesized by the reaction of [Ag(NH 3 ) 2 ] + complex and Na 2 HPO 4 and subsequent photoreduction under ultraviolet light. The as-prepared Ag@Ag 3 PO 4 MCs can effectively catalyze the oxidation of 3,3′,5,5′-tetramethylbenzidine (TMB) and o -phenylenediamine (OPD) in the presence of dissolved oxygen in slightly acidic solution, exhibiting oxidase-like activities rather than peroxidase-like activity. Interestingly, the introduction of Ag nanoparticles (AgNPs) on the surfaces of Ag 3 PO 4 MCs can dramatically enhance the oxidase-like activities due to a synergistic effect between AgNPs and Ag 3 PO 4 MCs, as evidenced by the faster oxidation speed of TMB and OPD than that of native Ag 3 PO 4 MCs in the presence of dissolved oxygen. The enzyme kinetics can be well-explained by the Michaelis–Menten equation. As “poisoning” inhibitor, Hg 2+ ions can inhibit the enzyme reaction catalyzed by Ag 3 PO 4 MCs or Ag@Ag 3 PO 4 MCs. On the basis of this effect, a colorimetric Hg 2+ sensor was developed by the enzyme inhibition reaction of Ag 3 PO 4 MCs or Ag@Ag 3 PO 4 MCs. The excellent specific interaction of Hg–Ag or Hg 2+ –Ag + provides high selectivity for Hg 2+ over interfering metal ions. Meanwhile, the sensitivity of this sensor to Hg 2+ is extremely excellent with a limit of detection as low as 0.253 nM for Ag@Ag 3 PO 4 MCs. Considering the advantages of low detection limit, low cost, facile preparation, and visualization, the colorimetric Ag@Ag 3 PO 4 MCs sensor shows high promise for the testing of Hg 2+ in water samples.