Novel synthesis of hierarchical flower-like silver assemblies with assistance of natural organic acids for surface-enhanced Raman spectroscopy

Using ascorbic acid as reducing agent and different organic acids (e.g., oxalic acid, DL-malic acid and citric acid) as structure-directing agents, a novel class of hierarchical flower-like silver mesoparticles with tunable size and shape were synthesized in high yield. The chemical structures of organic acids with different carbon chain length and functional groups have been found to play critical roles in the process of assembling metal nanoparticles into hierarchical complex structures. The anisotropic morphologies of as-synthesized silver structures could readily be tuned by simply varying the concentrations of reagents and the growth temperature. This synthesis method provides a new synthetic strategy for the anisotropic growth and morphology control of metallic particles. The textured flower-like Ag mesoparticles with hierarchical three-dimensional structures could generate abundant surface plasmon resonance hot spots and exhibit an excellent surface-enhanced Raman scattering (SERS) activity, revealing the promising potential for practical applications in single-particle and particle-array SERS sensing.