A novel green synthesis and characterization of silver nanoparticles using gum tragacanth and evaluation of their potential catalytic reduction activities with methylene blue and Congo red dyes

Background: A facile and eco-friendly method for green synthesis of silver nanoparticles (AgNPs) has been developed using gum tragacanth (GT) (Astragalus gummifer), an abundantly available natural phyto-exudate in India, employing a novel method of ultrasonication process. Methods: Silver nanoparticles were prepared by the reduction of silver nitrate solution by the aqueous extract of gum tragacanth by ultrasonication method at 45 degrees C for about 45 min. The aqueous extract of the gum acts as a reducing as well as stabilizing agent. Results: The resultant AgNPs were characterized by ultraviolet-visible (UV-Vis) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), and X-ray diffraction (XRD) techniques. The influence of gum concentration and silver precursor concentration on the synthesis of AgNPs was studied. The role and effectiveness of nanoparticles in the catalytic reduction of a cationic dye methylene blue (MB), and an anionic azo dye Congo red (CR), were also studied. FTIR analysis revealed that -OH groups present in the gum matrix might be responsible for the reduction of Ag+ into AgNPs. The X-ray diffraction studies indicated that the resulting AgNPs were highly crystalline with face-centered cubic geometry. TEM studies showed that the average particle size of the synthesized AgNPs was 18 +/- 2 nm. Conclusions: The study highlights the green synthesis of GT-capped AgNPs and the rapid reduction of carcinogenic and toxic contaminants such as MB and CR with the help of GT-capped AgNPs in an eco-friendly manner.