Novel green synthesis of hydroxyapatite uniform nanorods via microwave-hydrothermal route using licorice root extract as template

Hydroxyapatite (HAp) nanorods were synthesized in the presence of licorice root extract (LE) as a green organic template (or biotemplate) at 125 degrees C through a microwave-hydrothermal synthesis route. The products were characterized for shape, size, crystallinity, and phase purity. For the sample prepared in the presence of LE (denoted as HAp_L, powder X-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) revealed a uniform hexagonal phase nanorod product with average dimensions of 105 nm length and 25 nm width. The control sample, prepared in the absence of LE (denoted as HAp_W), showed less crystallinity and poorer morphology. Thermogravimetric analyses (TGA) and differential thermal analyses (DTA) indicated minor moisture contents in both samples. Fourier transform infrared spectroscopy (FT-IR) indicated carbonate-free samples. Raman spectroscopy confirmed the phase purity of the products. Energy-dispersive X-ray spectroscopy (EDX) analysis showed that product HAp_L has a Ca/P atomic ratio close to the theoretical value of HAp. Compared to HAp_W, zeta-potential measurements have shown that suspensions of sample HAp_L were more stable in different aqueous salt solutions. Particle size distribution analysis (PSA) showed a narrow size distribution for sample HAp_L with an average particle size of 105 nm which is advantageous over the apparently multi-disperse sample HAp_W. Nitrogen adsorption/desorption isotherms for both samples showed type III trends, having H-3 hysteresis loops in the P/P-o range between 0.9 and 1.

Automated summary

Hydroxyapatite nanorods were successfully synthesized using licorice root extract as a green organic template, resulting in high crystallinity and good morphology. Samples prepared with licorice root extract showed advantages in stability and particle size distribution compared to the control samples without the extract.