Bio-enhancing Structural and Antioxidant Properties of TiO2/HAp Nanocomposites Using Neem Leaf Extract: An Effective Agent for Surface Applications

Abstract

This study reports the novel green synthesis of TiO2/HAp nanocomposites using Azadirachta indica (neem) leaf extract as a bio-reducing and stabilizing agent via the sol–gel method. The novelty lies in the concurrent use of a phytochemically rich botanical source to control nanoparticle nucleation and growth. TiO2/HAp nanocomposites were synthesized by two parallel routes: (i) conventional chemical synthesis using titanium isopropoxide, calcium hydroxide, and orthophosphoric acid, and (ii) plant-mediated green synthesis incorporating 20 mL of Azadirachta indica leaf extract (11.76% v/v) with 150 mg (0.88 mg/mL) of TiO2/HAp, followed by microwave irradiation (70 W, 30 min). The synthesized nanocomposites were characterized using XRD, FTIR spectroscopy, UV–Vis spectroscopy, SEM, and EDX analysis. XRD analysis confirmed the formation of TiO2 (anatase, JCPDS 21-1272) and hexagonal hydroxyapatite (JCPDS 09-0432) phases, with average crystallite sizes of 36.33 nm (chemically synthesized) and 40.44 nm (green-synthesized). FTIR spectroscopy confirmed characteristic Ti–O, PO4³⁻, and O–H functional groups, along with phytochemical signatures in the green-synthesized sample. SEM analysis revealed a uniform, rod-like morphology with minimal aggregation. The DPPH radical scavenging assay demonstrated significantly higher antioxidant activity for the green-synthesized nanocomposites (80.12 ± 1.43% at 500 μg/mL) compared to the chemically synthesized counterpart. The formation of TiO2/HAp nanocomposites has been confirmed by FTIR spectra, and the presence of phytochemical functional groups was identified in the green-synthesized sample, consistent with surface functionalization. The green-synthesized nanocomposites have much better antioxidant properties because they contain bioactive phytochemicals from Azadirachta indica that are retained on the surface. The green-synthesized TiO2/HAp nanocomposites demonstrated higher antioxidant activity, consistent with a contribution from phytochemicals associated with the green-synthesis route; direct quantitative confirmation of surface-bound phytochemical loading remains a priority for future work. These results provide a preliminary basis for further investigation of these materials for antioxidant and surface-functional applications, while biomedical relevance requires additional cytotoxicity, antibacterial, and application-specific validation.