Environmental-friendly synthesis of Au-Ag alloy nanoparticles using Anethum graveolens leaf extract and their application to Surface Enhanced Raman Scattering (SERS)

We report an Environmental-friendly method for the synthesis of Au-Ag alloy nanoparticles (ANPs) by using Anethum graveolens fresh leaf extract as a reducing and stabilizing agent. The precursor solutions of Au (HAuCl4: 3H2O), Ag (AgNO3) and leaf extract were mixed by varying molar ratios and heated with continuous stirring at 70℃ for an hour leads a formation of Au-Ag ANPs with different atomic compositions. The periodic observation of colour changes indicated the formation of Au-Ag ANPs and got confirmed by the measurement of UV-Vis spectroscopy. The synthesized Au-Ag ANPs were characterized for morphological and elemental composition using Transmission Electron Microscopy (TEM) in conventional and scanning TEM (STEM) mode. The TEM image analysis shows that the synthesized Au-Ag ANPs were found to be in spherical shape with a broad size distribution with a mean size of 23 ± 18 nm. The energy dispersive X-ray (EDX) spectrometry in the STEM mode confirms the formation of Au-Ag ANPs . To show that these biosynthesized Au-Ag ANPs can be used as SERS (Surface Enhanced Raman Scattering) substrates, we carried out SERS studies using Crystal Violet (CV) and Rhodamine 6G (R6G) as test molecules by using 514.5 nm laser excitation wavelength. The detection level achieved was 50µM of CV and R6G, which would lead to exploring biosensing applications.