Bimetallic surfaces (Ni-Ag) as highly sensitive and self-regenerating Hg vapor detector

The fabrication of bimetallic systems (Ni-Ag) onto quartz crystal microbalances (QCMs) via galvanic replacement reaction shows good capability as possible Hg vapor sensors; however, there is limited understanding of the diffusion behavior between the Hg and the bimetallic nanostructures. The modified QCMs were characterized using scanning electron microscope, X-ray diffraction, X-ray photoelectron spectroscopy and Secondary ion mass spectrometry (SIMS). When exposed to Hg vapor, the modified QCMs were observed to have greater and quicker sorption capacity; the best performing modified Ni-Ag QCM was able to absorb 75ng/cm² in 56.24 minutes compared to the Ag control which absorb the same amount in 951.54 minutes. Furthermore, these types of sensors are found to self regenerate (return to their baseline frequency) without any external inputs, presenting great potential to be developed as online Hg sensors. SIMS depth profiling was used to study the diffusion behaviour of the Hg in these bimetallic nanostructures after exposure to Hg vapor. The data showed that the ability of the nanostructure to self-regenerate is due to the Hg atoms diffusing only down to the interface between Ag and Ni thus allowing the Hg escape from the surface.