Fabrication of Hydroxyapatite Hierarchical Hollow Microspheres and Potential Application in Water Treatment

Abstract

Many efforts have been made in fabricating three-dimensional (3D) ordered hydroxyapatite (Ca 10 (PO 4 ) 6 (OH) 2 , HAp) nanostructures due to their growing applications as a bone cement, drug deliverer, tooth paste additive, dental implant, gas sensor, ion exchange, catalyst, etc. Here, we developed a new synthetic route to 3D HAp-based hollow microspheres through a water-soluble biopolymer (polyaspartic acid) assisted assembly from HAp nanorods. The as-obtained products were characterized by Xray diffraction (XRD), field emission scanning electron microscopy (FESEM), Fourier transform infrared (FTIR) spectroscopy, transmission electron microscopy (TEM), highresolution TEM (HRTEM), and Brunauer−Emmett−Teller (BET) gas sorptometry. SEM and TEM results showed that 3D HAp hollow microspheres are constructed by a number of one-dimensional (1D) nanorods as primary building units. The influences of the additive polyaspartic acid and reaction time on final morphology and assembled structure of the products were systematically investigated. On the basis of our experimental results, a phenomenological elucidation of the mechanism for growth of the hollow HAp architectures has been proposed. The time-dependent experiments unveil that the HAp hollow microspheres are fabricated following initial formation and subsequent transformation of amorphous calcium phosphate (ACP) spheres. In-depth investigations, based on control experiments and FT-IR, EDX, and XPS analyses, reveal that polyaspartic acid acts as both a chelating and a surface capping agent in the synthesis process. First, polyaspartic acid molecules via calcium ion accumulation induce formation of ACP. At the subsequent stage Ostwald ripening contributes to formation of the hollow microspheres, and polyaspartic acid molecules capping to the surface of HAp crystallites control growth of the short nanorod subunits. Moreover, the adsorption experiments of the hierarchical hollow HAp for different heavy metal ions were conducted, and the results exhibit that the hierarchical hollow HAp have unique selective adsorption activity for heavy metal Pb 2+ . In-depth investigation is still in progress.

Hydroxylapatite nanoparticles: fabrication methods and medical applications

“…For examples, Nathanael et al [164] reported a template-free formation of HAp nanorings with an inner diameter of 70 nm by a combined high gravity and hydrothermal crystal growth approach. Jiang et al [165] reported a template-free route to fabricate nanostructured hollow HAp microspheres assembled with nanorods (50 nm in thickness, 0.5-1 µm in length) by hydrothermal approach using poly(aspartic acid) as both a chelating and a capping agent. Ma and Zhu [166] reported the fabrication of hierarchically nanostructured HAp hollow spheres (assembled from nanorods) using solvothermal method at 200…”

Erratum to: Psammoma bodies in two types of human ovarian tumours: a mineralogical study

“…However, the nature of the granules in amorphous state is obscure. The granules can also be amorphous calcium phosphate (Jiang et al 2012), which is a common precursor of crystalline HAPs. It is not easy to judge whether they are inorganics or undissolved organics when they intergrowth with crystalline solid.…”

Synthesis of Mesoporous Silica@Co–Al Layered Double Hydroxide Spheres: Layer-by-Layer Method and Their Effects on the Flame Retardancy of Epoxy Resins

“…[29][30] The broadened diffraction peaks of Co-Al LDH indicate that the synthetic sample is composed of nanocrystals. 31 Compared the m-SiO2, Co-Al LDH and m-SiO2@Co-Al LDH wide-angle XRD patterns, two relatively weak peaks of m-SiO2@Co-Al LDH at around can be assigned to (003) and (012) of layered Co-Al LDH structure ( Figure 3A). Moreover, the (006) peak of Co-Al LDH and the broad peak between 20 o and 25 o of m-SiO2 were overlapping, so the broad peak of m-SiO2 may cover the weak (006) peak of Co-Al LDH in the m-SiO2@Co-Al LDH structure.…”