Scalable Synthesis of Size-Tunable Hydroxyapatite Nanoparticles as Potential Nanofertilizers

• Published in: ACS applied nano materials Vol. 7; no. 8; pp. 8537 - 8546
• Main Authors: Burve, Regina, Loeschner, Katrin, Omura Lund, Yuka, Kiebach, Wolff-Ragnar, Grivel, Jean-Claude
• Format: Journal Article
• Language: English
• Published: American Chemical Society 26.04.2024
• Subjects: hydroxyapatite; size control; nanofertilizer; hydrothermal synthesis; supercritical water; upscalable synthesis
• ISSN: 2574-0970; 2574-0970
• DOI: 10.1021/acsanm.3c04713

Hydroxyapatite is a biocompatible material with various applications. To meet the demand for industrial use of this material, a rapid and upscalable process for the synthesis of hydroxyapatite nanoparticles was developed using an in-house developed two-stage continuous flow hydrothermal reactor. In the framework of this study, phase pure and highly crystalline 30 to 115 nm long hydroxyapatite nanorods were produced for potential use as nanofertilizers. The phase composition of the nanorods was confirmed by X-ray diffraction. Particle size and shape were investigated using transmission electron microscopy. Inductively coupled plasma mass spectrometry was used to determine the Ca:P ratio. It was shown that the use of a second mixing stage allows the particle length to be decreased down to 30 nm without compromising on crystallinity. In addition to using different mixing stages, adjusting the pH and controlling the flow speed allow wide range size tuning of the produced particles. The experimental setup allows for continuous synthesis of phase pure and highly crystalline hydroxyapatite nanorods, ensuring the reproducibility and scalability of the process. Dispersive behavior and dissolution in citrate buffer at a hydroponic pH of 5.5 were studied to evaluate further possibilities of applying produced NPs on the plants.