Biogenic Synthesis of Silver Nanoparticles Using Cnidium officinale Extract and Their Catalytic Reduction of 4-Nitroaniline

Silver nanoparticles (AgNPs) with two different morphologies were synthesized using aqueous extract of Cnidium officinale rhizomes under different reaction conditions and applied to the facile aqueous phase reduction of 4-nitroaniline (4-NA) as catalysts. The synthesized AgNPs are characterized by UV-Visible spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD) method and high resolution transmission electron microscopy (HR-TEM) with energy dispersive X-ray spectroscopy (EDS) analysis. HR-TEM showed that the synthesized AgNPs had two different morphological forms; truncated triangular prism shapes with a mean size of similar to 35 nm and spherical shapes with a mean size of similar to 9 nm. The HR-TEM and XRD results are consistent with the standard values. The catalytic activities of both AgNPs were compared on the reduction of 4-NA in water by NaBH4 as a reducing agent. The reduction of 4-NA was monitored using UV-Visible spectroscopy. The similar to 9 nm (spherical) sized AgNPs showed superior catalytic activity than the larger AgNPs. The calculated rate constant (k) for the catalytic reduction of 4-nitroanilie by spherical AgNPs was 11.16 x 10(-3) s(-1).