Synthesis and Characterization of Hydroxyapatite Nanoparticles

Hydroxyapatite nanoparticles (HAp NPs), with the chemical formula Ca₁₀(PO₄)₆(OH)₂, emulate the mineral component of bone and tooth, making them pivotal in biomedical, environmental and catalytic applications. Synthesis routes range from wet-chemical co-precipitation and sol-gel processes to hydrothermal, microwave-assisted and biogenic methods. Control of parameters such as pH, temperature, precursor concentration and reaction time enables tuning of particle size, morphology and phase composition. Typical characterisation employs X-ray diffraction (XRD) to assess phase purity and crystallite size, transmission electron microscopy (TEM) and scanning electron microscopy (SEM) for morphology, Fourier transform infrared spectroscopy (FTIR) for chemical bonding, and Brunauer–Emmett–Teller (BET) analysis for specific surface area. Advances in surface functionalisation and ionic substitution further modulate bioactivity, mechanical strength and sorption properties. Together, these developments underpin tailored HAp NPs for bone regeneration scaffolds, drug delivery platforms, coatings with antimicrobial function and as selective sorbents for environmental remediation.

Research from Nature Portfolio

Recent work has unveiled the design of liquid-crystalline HAp nanorods by employing acidic macromolecules to direct rod-shaped colloids into orientationally ordered fluids. Under applied magnetic fields or shear, these materials exhibit reversible alignment, magneto-optical modulation and hierarchical self-assembly, as revealed by atomic-scale TEM imaging of inorganic–organic hybrid structures. In a complementary study, a facile hydrothermal procedure incorporating ethylenediaminetetraacetic acid and monoethanolamine has been shown to yield pure monetite plates, hydroxyapatite nanosheets and nanofibres simply by varying the monoethanolamine concentration. Morphology and phase composition were characterised by SEM, Raman spectroscopy and powder XRD, demonstrating precise control over crystalline form and dimensionality for bone-like applications.

Synthesis and Characterization of Hydroxyapatite Nanoparticles publication trend

The graph below shows the total number of articles in synthesis and characterization of hydroxyapatite nanoparticles across all publications each year (not limited to Nature Index journals).

Technical terms

Hydrothermal synthesis: A technique in which aqueous precursors react under elevated temperature and pressure to produce crystalline nanoparticles.

Co-precipitation: A wet-chemical method where soluble calcium and phosphate salts are mixed to form insoluble HAp nuclei, which grow into nanoparticles.

Crystallite size: The dimension of a coherently diffracting domain within a particle, as inferred from XRD peak broadening.

Liquid-crystalline phase: A state of matter with fluidity and long-range orientational order, here formed by HAp nanorods in colloidal suspension.

Phase purity: The extent to which a sample comprises a single crystalline phase, without secondary calcium phosphate phases such as monetite or brushite.

References

1. Liquid Crystalline Hydroxyapatite Nanorods Orchestrate Hierarchical Bone‐Like Mineralization. Small (2024).
2. Comparing Methods for Calculating Nano Crystal Size of Natural Hydroxyapatite Using X-Ray Diffraction. Nanomaterials (2020).
3. Stimuli-responsive hydroxyapatite liquid crystal with macroscopically controllable ordering and magneto-optical functions. Nature Communications (2018).
4. From monetite plate to hydroxyapatite nanofibers by monoethanolamine assisted hydrothermal approach. Scientific Reports (2018).
5. The pH Effect on the Growth of Hexagonal and Monoclinic Hydroxyapatite Synthesized by the Hydrothermal Method. Journal of Nanomaterials (2020).