Synthesis of rod-shaped nano-hydroxyapatites using Aloe vera plant extract and their characterization

Size-dependent applications of biomaterials are increasing day by day, and rod-shaped biomaterials are drawing researchers attention for their different enhanced properties. Different types of chemicals are used to modify the crystal structure of hydroxyapatites (HAps); however, in this research, plant extract (Aloe vera) was chosen to control the shape of nano-crystalline HAps. This research focused on synthesizing rod-shaped hydroxyapatite using a non-toxic, environmentally friendly, low-cost, and widely available natural source. Hydrothermal technique was used to synthesize nano-hydroxyapatite (nHAp), where different volumes (0, 2.5, 5.0, and 10 mL) of plant extract were added to a water medium with raw materials [Ca(OH)₂ and H₃PO₄]. XRD, FESEM, XPS, FTIR, and optical bandgap energy calculations confirmed the formation of nHAp. Its texture coefficient and preference growth values showed that the (0 0 2) and (0 0 4) planes were the preferred growth direction when Aloe vera extract was used. Crystallite sizes were in the range of 30–72 nm, as per XRD data, and the 88–107 nm length and 31–38 nm width of rod-shaped particles was confirmed by FESEM data. Very low bandgap energies in the range of 3.56–3.81 eV were found for the synthesized nHAp. There were no significant differences in the binding energy according to XPS data, and the calculated as well as direct ratio of Ca/P and O/Ca confirmed the formation of similar nHAps.