Synthesis of Silver Nanoparticles Using Azadirachta indica Leaf Extracts for Heavy Metal Sensing

Abstract

Silver nanoparticles (AgNPs) was synthesized via cheap bio-reduction and green method from leaf extracts of Azadirachta indica. The technique was optimized by studying variables such as  pH, temperature and concentration of the plant extracts. Gas Chromatography Mass Spectroscopy (GC-MS) results indicated the presence of phytonutrients such as Piperidine, 2-Azacyclooctanone, 4-Dibenzofuranamine, Lauric anhydride, Cyclododecanol and Sorbic acid as the phytonutrients responsible for the reduction and resilience process. FT-IR results gave absorption bands indicating the presence of -OH, -NH and -C=O functional groups, while particle size analysis revealed an average particle size which is less than 100 nm, thus confirming the formation of a nanoparticle. UV-Vis investigation of the nanoparticles synthesized with concentration of 12.5 mg/mL produced a strong plasmon resonance band with an absorbance of 0.223 at 400 nm after 24 hrs incubation time and at a minimal concentration of 6.25 mg/mL, the absorbance further decreased with a hypsochromic shift to 600 nm. The synthesized silver nanoparticles showed excellent optical property towards the selected heavy metals with virtual color change and a shift in absorbance towards higher value. Selective detection of Pb²⁺, Cu²⁺ and Cd²⁺ was also confirmed by UV-visible spectra which is well pronounced with Pb²⁺ having the highest absorbance.