Green engineered biomolecule-capped copper nanoparticle using aqueous leaf extract of the Manilkara zapota

Among the several transition metals known to mankind, the synthesis of Cu has remained a major challenge owing to their instinctive oxidative power under ambient conditions [1]. This research focused on green engineering and characterization of copper nanoparticles (CuNPs) using Manilkara zapota (M. zapota) leaf extract under surfactant-free conditions. Use of leaf extract of M. zapota for the synthesis of CuNPs is a novel step towards the biogenic synthesis of CuNPs. This method avoids the use of external reducing and stabilizing agents, templates, non-toxic and solvents. The approach of biosynthesis appears to be cost efficient, eco-friendly, compatibility for biomedical and pharmaceutical applications and easy alternative to conventional methods of CuNPs synthesis. The flavonoid and other phenolics of the leaf extract of M. zapota were not only responsible for the reduction of the CuSO4 but also function as capping ligands to the surfaces of the CuNPs [2], as confirmed by FT-IR spectroscopy. The effects of different synthesis parameters like pH, temperature, quantity of extract, concentration of metal salt and time on the formation of nanoparticles have been investigated. The biogenic copper nanoparticles were characterized by UV–Vis spectrophotometer showing a typical resonance (SPR) at about 508 nm which is specific for CuNPs and confirming the bioreduction and stabilization of nanoparticles. Also, no characteristic absorption band for copper oxide around 800 nm was observed [3]. Comparative studies of FTIR spectra of the extract and copper nanoparticles reveal the involvement of different functional groups in stabilization. XRD analysis was performed to confirm the crystalline nature of the copper nanoparticles. TEM analysis suggested that the nanoparticles were predominantly spherical in nature with size ranging from 22 to 45 nm. The present investigation highlighted an effective protocol for green synthesis of biomolecule-loaded copper nanoparticle and can be extended effectively to large scale production of CuNPs for a broad spectrum of environmental, biological and industrial applications.