Carbon Nanotube/Silica Coaxial Nanocable as a Three-Dimensional Support for Loading Diverse Ultra-High-Density Metal Nanostructures: Facile Preparation and Use as Enhanced Materials for Electrochemical Devices and SERS

In this paper, we have reported a very simple strategy (combined sonication with sol-gel techniques) for synthesizing well-defined silica-coated carbon nanotube (CNT) coaxial nanocable without prior CNT functionalization. After functionalization with NH2 group, the CNT/silica coaxial nanocable has been employed as a three-dimensional support for loading ultra-high-density metal or hybrid nanoparticles (NPs) such as gold NPs, Au/Pt hybrid NPs, Pt hollow NPs, and Au/Ag core/shell NPs. Most importantly, it is found that the ultra-high-density Au/Pt NPs supported on coaxial nanocables (UASCN) could be used as enhanced materials for constructing electrochemical devices with high performance. Four model probe molecules (O-2, CH3OH, H2O2, and NH2NH2) have been investigated on UASCN-modified glassy carbon electrode (GCE). It was observed that the present UASCN exhibited high electrocatalytic activity toward diverse molecules and was a promising electrocatalyst for constructing electrochemical devices with high performance. For instance, the detection limit for H2O2 with a signal-to-noise ratio of 3 was found to be 0.3 mu M, which was lower than certain enzyme-based biosensors. And the detection limit for hydrazine is <0.5 mu M, which was lower than amperometric hydrazine sensors based on functional nanomaterials such as zinc oxide nanonails, CNTs-modified electrodes, o-aminophenol grafted GCE electrode, and multilayer film containing cobalt phthalocyanine. Furthermore, the as-obtained high-density gold/silver core/shell NPs supported on coaxial nanocables could be used as a good surface-enhanced Raman scattering (SERS) substrate for the detection of different molecules [4-aminothiophenol (4-ATP) and adenine], showing the great potential of CNT/SiO2/(Au/Ag) as a convenient and powerful SERS substrate for biological tags and biological molecular detection.