Abstract
Au/Ag bimetallic dendrites were synthesized successfully from the corresponding aqueous solution via the AC electrodeposition method. Both of the morphologies and compositions could be tuned by the electrolyte concentration and AC frequency. The prepared bimetallic dendrites were characterized by scanning electron microscopy (SEM), energy dispersive X-ray spectrometer (EDS), transmission electron microscopy (TEM) and UV–vis spectroscopy. The underlying dendrite growth mechanism was then proposed in the context of the Directed Electrochemical Nanowires Assembly (DENA) models. Owing to the unscreened voltage dropping in the electrolyte bulk, electromigration dominates the species flux process, and cations tend to accumulate in areas with strong electric field intensity, such as electrode edges. Moreover, Faradaic AC-electro-osmosis (ACEO) flow could increase the effective diffusion layer thickness in these areas during the electrochemical reaction, and leads to dendrite growth. Further Micro-Raman observations illustrated that the Au/Ag bimetallic dendrites exhibited pronounced surface-enhanced Raman scattering (SERS) activity, using 4-mercaptopyridine (4-MP) as model molecules.
Highlights
Surface-enhanced Raman scattering (SERS) is one of the most effective spectroscopic methods used for analytes detection, such as living cells,[1] chemical agents,[2,3] immunoassays,[4,5] DNA,[6,7] and glucose,[8,9] owing to its low detection limits and excellent selectivity
Following characterization illustrated that both of the morphologies and compositions could be tuned by the electrolyte concentration and AC frequency
Based on the experimental facts, we suggested a physical picture of the dendrite growth
Summary
Surface-enhanced Raman scattering (SERS) is one of the most effective spectroscopic methods used for analytes detection, such as living cells,[1] chemical agents,[2,3] immunoassays,[4,5] DNA,[6,7] and glucose,[8,9] owing to its low detection limits and excellent selectivity. The growth velocity depends on the square root of the applied AC frequency, and increases linearly with the bulk concentration of the electrolyte, while tip radius is anti-correlated with the frequency. Thereby, both growth velocity and the diameter of the dendrites could be tuned by the concentration and frequency. To our knowledge, there are few studies on the synthesis of Au/Ag bimetallic dendrites via this method In this manuscript, we report on the successful synthesis of Au/Ag dendrites by applying an AC signal of varying frequency, from the corresponding aqueous salt solution between the prepared Platinum microelectrodes. Further Raman observations showed that the Au/Ag bimetallic dendrites exhibited pronounced SERS activity, which are promising for use as SERS substrates for bio-chemical analyte detection
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