Facile synthesis of hydroxyapatite nanoparticles from eggshell biowaste using Azadirachta indica extract as a green template

Abstract

In this study, hydroxyapatite nanoparticles (HANPs) were successfully synthesized from eggshell waste by microwave-assisted (MW) as well as conventional heating precipitation methods and a green template i.e., Azadirachta indica (AI) (neem) leaf extract. The synthesized HANPs were characterized by different analytical techniques such as Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), and thermogravimetric analysis (TGA) for determining their functionality, shape, size, crystallinity, phase purity, and thermal stability. FTIR and Raman spectroscopy confirmed the pure hydroxyapatite phase with no other impurities. SEM and TEM analyses confirmed that HANPs displayed uniform distribution with less agglomeration by the MW method in the presence of AI when compared to the conventional heating method and without AI. TEM analyses revealed that the average size of HANPs from both methods without AI was 30–31 nm in width and 53–55 nm in length while in the presence of AI, it was 27–28 nm in width and 44–46 nm in length. XRD analysis indicated the formation of the pure crystalline structure of nanoparticles. The synthesized HANPs were thermally very stable and had a lower Ca/P ratio (1.81) from the MW method compared to the conventional heating method, which is 1.95. Thus, this study revealed that HANPs synthesized by the MW method in the presence of AI with a smaller crystallite size and less agglomerated particles have great potential to be used in the biomedical fields as well as different fields such as cosmetics, wastewater treatment, and food packaging applications.