Abstract
Au nanorods were used as plasmonic transducers for investigation of mercury detection through a mechanism of amalgam formation at the nanorod surfaces. Marked scattering color transitions and associated blue shifts of the surface plasmon resonance peak wavelengths (λmax) were measured in individual nanorods by darkfield microscopy upon chemical reduction of Hg(II). Such changes were related to compositional changes occurring as a result of Hg–Au amalgam formation as well as morphological changes in the nanorods’ aspect ratios. The plot of λmax shifts vs. Hg(II) concentration showed a linear response in the 10–100 nM concentration range. The sensitivity of the system was ascribed to the narrow width of single nanorod scattering spectra, which allowed accurate determination of peak shifts. The system displayed good selectivity as the optical response obtained for mercury was one order of magnitude higher than the response obtained with competitor ions. Analysis of mercury content in river and tap water were also performed and highlighted both the potential and limitation of the developed method for real sensing applications.
Highlights
Mercury is a highly toxic heavy metal that is widely dispersed in the environment and can be found in water, air and soil
Au nanorods were used as plasmonic transducers for investigation of mercury detection through a mechanism of amalgam formation at the nanorod surfaces
Au nanorods were synthesized according to an overgrowth method reported by Alvarez-Puebla et al [23]
Summary
Mercury is a highly toxic heavy metal that is widely dispersed in the environment and can be found in water, air and soil. [10,11] Plasmonic nanoparticles have been successfully used for label-free detection of mercury based on colorimetric (mercury-induced aggregation) response in solution, with sensitivity down to nM metal concentration detection.[12,13] Among nanoparticle shapes, nanorods have been identified as ideal candidates for plasmon sensing due to their large spectral shift for a given change in refractive index, which exhibits much higher sensitivity compared to that of spherical counterparts.[14,15,16] For example, sensitive detection of mercury was obtained with Au nanorod solutions spiked with known amounts of Hg(II) in presence of reducing agent NaBH4.[17] High optical selectivity and sensitivity was achieved due to chemical reduction of Hg(II) and consequent formation of an amalgam between mercury and gold, which shifted the maximum absorbance wavelength of the nanorods’ longitudinal plasmon mode. Selectivity was tested by taking similar measurements with competitor ions, which produced optical responses one order of magnitude lower than mercury These results demonstrate the potential suitability of gold nanorods for environmental analysis. Initial investigation on real water matrices showed the high potential of this method for sensitive environmental analysis as well as the need to implement pre-treatment protocols before the presented process can be used for real analytical applications
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
