Effect of heat-treatment temperature on the structure of calcium phosphate synthesized by wet precipitation

Abstract

In this work, nanometric calcium phosphate (CaP) was synthesized by wet chemical precipitation using Ca(OH)2 and H3(PO4). The subsequent heat treatment was carried out varying from 25 °C to 1000 °C, to study the changes caused in the structure of the final product through XRD, FTIR, Fluorescence, Raman, UV–Vis, DLS, Zeta Potential, SEM and TEM/EDS analyses. Cell viability was measured via MTS assays. XRD showed that the crystallinity of the synthetic calcium phosphate obtained increases with increasing heat-treatment temperature, getting close to the structure of hydroxyapatite. In the FTIR, Raman and UV–vis spectroscopic analyses, carbonate removal from the synthesized CaP structure at high heat-treatment temperatures was observed. Samples T800 and T1000 showed greater fluorescence. DLS measurements revealed the formation of aggregates at heat-treatment temperatures lower than 800 °C. According to the Zeta Potential measurements, T1000 is the most stable colloid (−28.4 ± 1.4 mV). The thermal treatment also affected the morphology of the samples, and nanowhiskers, nanorods and nanocubes were observed. In addition, the viability assay revealed that a decrease in particle sizes in CaP samples led to a decrease in metabolic activity, showing that the correct choice of particle size is the key to producing compounds that favor cell proliferation, making it a promising material for bone tissue engineering.