Design of experiments (DOE) for the optimization of hydrothermal synthesis of hydroxyapatite nanoparticles

Abstract

O objetivo deste trabalho foi investigar a influência de diversos parâmetros de reação sobre as propriedades de nanopartículas de hidroxiapatita (HAp) preparadas pelo método hidrotérmico. Os dados da literatura descrevem condições experimentais variadas para a síntese hidrotérmica de HAp. Uma abordagem específica foi então utilizada para avaliar os fatores estatisticamente influentes entre aqueles descritos na literatura. O papel de cada parâmetro experimental também foi discutido no contexto da nucleação de partículas e do mecanismo de crescimento de cristais. Dentro das variáveis selecionadas, temperatura e pH foram os fatores que mais afetaram a composição e morfologia da HAp. Além disso, neste estudo, diferentes morfologias variando de nanopartículas cilíndricas do tipo bastonete a esféricas com várias características foram obtidas com sucesso, o que pode ser aplicável na preparação de várias biocerâmicas de HAp.The aim of this work was to investigate the influence of different reaction parameters on the properties of hydroxyapatite (HAp) nanoparticles prepared by the hydrothermal method. The literature data describe widely different experimental conditions for the hydrothermal synthesis of HAp. A specific approach was therefore used to evaluate the statistically influential factors among those described in the literature. The role of each experimental parameter was also discussed within the framework of particle nucleation and crystal growth mechanism. Among the selected variables, temperature and pH were found to be the most significant factors affecting the composition and morphology of the HAp. Moreover, in the present study, different morphologies ranging from rod-like to spherical nanoparticles with various characteristics were successfully obtained, which can be applicable for the preparation of various HAp bioceramics.

Synthesis and Optimization of Colloidal Hydroxyapatite Nanoparticles by Hydrothermal Processes

“…Crystallite size for all samples except sample E5 showed relatively close sizes with L varying from 12 to 23 nm for most diffraction peaks, only at the peak relative to the plane (002) was 23 studied the synthesis of nanocrystals of HA by a wet chemistry method and observed this same preferential growth in the (002) direction in the c-axis with crystallite sizes between 15-60 ± 5 nm, and lengths of approximately 500 nm confirmed by TEM. 23 Sadat-Shojai et al, 19 in hydrothermal synthesis of HA, also observed this same behavior of preferential growth of the nanoparticles and reported that c-axis size increases when the hydrothermal temperature increases, which is accompanied by decrease in growth in the other directions.…”

“…The experimental conditions used were based on the literature. [17][18][19]25,27,31,32 All matrix calculi were carried out using the free software GUI Octave 33 (version 3.6), in Microsoft Windows 10 Home 64 bits System. Two levels, high (+) and low (-), were defined for each factor, as shown in Table 1.…”

“…With respect to synthesis strategies to obtain colloidal nanoparticles of HA, there are various methods such as hydrothermal, [16][17][18][19] chemical precipitate, 20,21 wet chemical, 22,23 and sol-gel 24 methods. Among these, the hydrothermal method has aroused great interest due to its good repeatability, wide temperature range, the possibility to control the form, size, and shape, simplicity of operation, ability to produce crystalline nanoparticles without posterior thermal treatment, 25 and especially to obtain stable colloidal suspensions of nanoparticles.…”

“…In all experiments the pH was maintained at 9.0. More drastic conditions were employed in Sadat-Shojai et al 19 synthesis, such as reaction time of 60 h, 200 °C in the experiment of higher level, pH variation and additives like urea. In this work an empirical model that allows the control of the shape and size of HA nanoparticles due to the control of the initial experimental conditions was proposed.…”

“…In this work an empirical model that allows the control of the shape and size of HA nanoparticles due to the control of the initial experimental conditions was proposed. Although studies using factorial design to understand the effect of some experimental conditions on the final properties of colloidal HA nanoparticles have been previously published, 19,21,22,24,25,28,29,31 only a few of them evaluated the statistical significance of the effects. Usually, these studies present models that consider the experimental parameters that affect the size of the particles, which were previously identified in univariate studies, but their statistical significance has been ignored, which is not true in multivariate studies.…”