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

Abstract

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.