Fast Growth Synthesis of Silver Dendrite Crystals Assisted by Sulfate Ion and Its Application for Surface-Enhanced Raman Scattering

This paper reports the fast growth synthesis of silver (Ag) dendrite crystals on a copper (Cu) substrate assisted by sulfate (SO42-) ions based on a electroless galvanic displacement reaction between solid Cu and Ag(I) ion. The growth of Ag dendrites is succeeded by using an aqueous solution of Ag+ ion and a Cu foil. Interestingly, the morphology, apparent color, and growth rate of Ag dendrites on Cu foil using 2.5 mM Ag2SO4 aqueous solution are different from that of 5.0 mM AgNO3 aqueous solution even though they contain the same concentration of Ag+ ion. The growth rate of Ag dendrites is proved to be much accelerated for a solution of Ag+ ions with SO42-. The growth process can be readily observed under a microscope. The resultant Ag dendrites are characterized by scanning electron microscopy, transmission electron microscopy, X-ray powder diffraction, energy-dispersive X-ray spectroscopy, and X-ray photoelectron spectroscopy. The effect of SO42- ion on the growth of Ag dendrites on Cu foil has been investigated in detail. The diffusion-limited growth and oriented attachment explain the formation of the Ag dendrites under the nonequilibrium growth conditions. The synthesized Ag dendrites have been successfully employed as a Raman probe for surface-enhanced Raman spectroscopic (SERS) analysis of melamine. The SERS results demonstrate that Ag dendrites can be a useful solid substrate for SERS analysis. Our work provides a very simple, convenient, cost-effective, and fast route to synthesize Ag dendrites which is potentially useful in SERS.