Surface etching-dependent geometry tailoring and multi-spectral information of Au@AuAg yolk-shell nanostructure with...

In this paper, a novel Au@AuAg yolk-shell heterogeneous nanostructure is designed as plasmonic spectroscopic sensor based on surface etching for ultrasensitive detection of trace cobalt ions (Co²⁺). Due to the surface diffusion of gold atoms, the Ag at one end of the core gold nanobipyramids (Au NBPs) is retained, and Au@AuAg yolk-shell nanostructure with asymmetric core is prepared. The alloy shell is coupled to Au NBPs and the interface of asymmetric Ag respectively, the two local surface plasmon resonance bands will have obvious reverse changes depending on the surface morphology of the shell. By using this distinct plasmon response generated by Co²⁺ induced surface etching, which is driven by discrepancy of double-peaks, a sensing method has been established to realize multi-information spectral detection of Co²⁺. There is a good linear relationship between the intensity ratio and the Co²⁺ concentration in the range of 1-100 nM, in which the limit of detection is 0.2 nM. This method further improves the sensing capability by combining multiple pieces of strongly changing spectral information, and demonstrates great advantages and potential of Au@AuAg yolk-shell heterogeneous nanostructure as a multi-information plasmonic sensor based on etched shell surface for trace detection.