Abstract
Amongst different living organisms studied as potential candidates for the green synthesis of copper nanoparticles, algal biomass is presented as a novel and easy-to-handle method. However, the role of specific biomolecules and their contribution as reductant and capping agents has not yet been described. This contribution reports a green synthesis method to obtain copper oxide nanoparticles (CuO-NPs) using separated protein fractions from an aqueous extract of brown algae Macrocystis pyrifera through size exclusion chromatography (HPLC-SEC). Proteins were detected by a UV/VIS diode array, time-based fraction collection was carried out, and each collected fraction was used to evaluate the synthesis of CuO-NPs. The characterization of CuO-NPs was evaluated by Dynamic Light Scattering (DLS), Z-potential, Fourier Transform Infrared (FTIR), Transmission Electron Microscope (TEM) equipped with Energy Dispersive X-ray Spectroscopy (EDS) detector. Low Molecular Weight (LMW) and High Molecular Weight (HMW) protein fractions were able to synthesize spherical CuO-NPs. TEM images showed that the metallic core present in the observed samples ranged from 2 to 50 nm in diameter, with spherical nanostructures present in all containing protein samples. FTIR measurements showed functional groups from proteins having a pivotal role in the reduction and stabilization of the nanoparticles. The highly negative zeta potential average values from obtained nanoparticles suggest high stability, expanding the range of possible applications. This facile and novel protein-assisted method for the green synthesis of CuO-NPs may also provide a suitable tool to synthesize other nanoparticles that have different application areas.
Highlights
We first tested the ability of different size-separated protein fractions from an aqueous extract of the brown algae M. pyrifera for the green synthesis of CuO-NPs
The first color change indicative of copper reduction was observed at 24 h, with a slight color change from light blue to light green when pellets were observed after a spin; this phenomenon was not observed in control fractions (1–2 and 10–11)
Due to differences between the fractions, there is still room for further optimization of CuO-NPs green synthesis. This present work demonstrated a successful and straightforward strategy based on a biomolecule-assisted technique for the green synthesis of copper ion bioreduction into copper nanoparticles, using proteins precipitated from an aqueous extract of
Summary
The capping process may be performed by biological agents, such as proteins, instead of chemicals, such as polyvinylpyrrolidone (PVP), to stabilize the nucleation process and obtain long-term stable NPs [4,5]. Those environment-friendly and cost-effective methods produce NPs of different compositions, sizes, morphologies, and dispersion, which may affect their final property and application [6,7,8]. An autoclaved aqueous extract from the green microalgae Botryococcus braunii produced CuO-NPs in a size range between
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