Probing the unexpected behavior of AuNPs migrating through nanofibers: a new strategy for the fabrication of carbon nanofiber–noble metal nanocrystal hybrid nanostructures

Abstract

The intimate relationship of electrochemical sensors with high sensitivity and reliability has stimulated intensive research on developing versatile materials with excellent electrocatalytic activity. Here, we reported a novel strategy for the design of novel nanostructure-based electrochemical biosensors originating from an unexpected behavior of Au nanoparticles (AuNPs) embedded in the interior of polyacrylonitrile nanofibers (Au–PANFs), which can migrate to the external surfaces of the carbon nanofibers (Au–CNFs) during the graphitization process. Small and uniform AuNPs embedded in PANFs were synthesized via a combination of electrospinning and in situ reduction. With the conversion from the amorphous structures of PANFs to graphene layered structures of CNFs, the AuNPs can migrate from the interior of PANFs to the external surfaces of CNFs. The migration of AuNPs through the nanofiber matrix is strongly dependent on the graphitization temperature and heating rates. Three different heating rates of 2, 5, and 10 °C min⁻¹ and graphitization temperatures of 600, 800, and 1000 °C were employed to investigate the migration and the exposed density of AuNPs on the CNFs. These novel nanomaterials were constructed as a nonenzymatic H₂O₂ electrochemical sensor and the sensors based on Au–CNFs with increased density of exposed AuNPs exhibit significantly promoted electrochemical activity. The Au–CNFs (1000 °C, 2 °C min⁻¹) with high exposed density and small sizes of AuNPs possess higher specific surface area and active sites, leading to higher electrocatalytic activity. The present investigations provide a general route for the fabrication of nanostructures for novel electrochemical sensors, energy storage devices and so on.