White LED light-based photocatalysis enhances the green synthesis of silver nanoparticles by Trigonella foenum-graecum seeds’ aqueous extract

Abstract

Trigonella foenum-graecum is a medicinally important plant that has abundant phytochemicals with high antioxidant and metal-chelating potential. The extract of the leaves and seeds have the potential to synthesize metal nanoparticles; however, the rate of silver nanoparticles synthesis is significantly low in case of the seeds. The objective of this study was to enhance the rate of synthesis of silver nanoparticles by photocatalysis. The extraction and characterization of the aqueous extract of the seed was followed by optimization of the silver nanoparticles synthesis. The GCMS analysis of the aqueous extract identified the presence of carbohydrates, amino acids, lipids and secondary metabolites. Photocatalytic synthesis of silver nanoparticles in the dark and under 250, 825 and 2000 lumens of white LED light at a constant temperature yielded approximately 0.1%, 3%, 4% and 5.5% nanoparticles, respectively. Likewise, the mean diameters of the nanoparticles in the dark and under 2000 lumens were approximately 21 and 52 nm respectively. The light intensity influenced the elemental composition of the nanoparticles, wherein the percentage silver with 250 and 2000 lumens was approximately 16% and 20%, respectively. However, the silver nanoparticles synthesized by the aqueous extract had limited stability. Nanoparticles synthesized under 2000 lumens decomposed in less than 72 h, whereas nanoparticles synthesized in 250 and 825 lumens were significantly stable for three days. However, the nanoparticles synthesized in the dark demonstrated the highest stability of seven days. Therefore, the aqueous extract in combination with photocatalytic activity of white LED light, significantly enhanced the silver nanoparticles yield, but with limited stability.