Facile and controllable synthesis of triplex Au@Ag–Pt@infinite coordination polymer core–shell nanoparticles for highly efficient immobilization of enzymes and enhanced electrochemical biosensing activity

We present a simple and controllable strategy to synthesize triplex noble metal nanoparticle (NP)-mixed infinite coordination polymer (ICP) core–shell heterostructures (Au@Ag–Pt@ICPs) that are capable of acting as an efficient host matrix for in situ immobilization of enzymes for highly efficient electrochemical biosensing. In this synthesis, both H2PtCl6 and nanoscale metallic Ag (Au@Ag NP) are demonstrated to simultaneously undergo a coordination reaction with an organic ligand, 2,5-dimercapto-1,3,4-thiadiazole, based on a systematic and comprehensive analysis. Besides, the size of the ICP shells can be efficiently tuned by modulation of the amount of DMcT, H2PtCl6 and the size ratio of Au@Ag NPs. Using glucose oxidase as a model enzyme, the Au@Ag–Pt@ICPs based biosensors achieve enhanced electrochemical biosensing performances (e.g., sensitivity, stability and else) in comparison with the pure ICP NP-based biosensors due to the synergistic effects of ICPs and noble metal NPs. Under optimized conditions, they offer a much wider linear range (from 0.5 μM to 3.33 mM), an extremely low detection limit (60 nM, S/N = 3), a very high sensitivity (82.1 μA mM−1 cm−2) and a very high biological affinity (the apparent Michaelis–Menten constant was estimated to be 0.28 mM) as well as good thermal stability and long-term stability. The presented experimental platform/strategy may be extended to the preparation of many other ICP containing bio/nano hybrid materials.