Matériaux composites obtenus par greffage de la β- cyclodextrine sur l’hydroxyapatite: caractérisation et application à l’électroanalyse du diquat et du plomb(II)

Abstract

In this work, hydroxyapatite was functionalized by grafting β-cyclodextrin (β-CD) to its surface in order to improve its ion-exchange properties. Hydroxyapatite was naturally obtained from bovine bones following a three-step procedure comprising: pre-calcination at 450 °C, chemical treatment with diammonium phosphate, and calcination at 700 °C. The grafting of β-cyclodextrin to the surface of the resulting material was done using citric acid as a linker and sodium hydrogenphosphate as a catalyst. The different materials obtained were characterized by X-ray Diffractometry (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Thermal Analysis (ATG), and Scanning Electron Microscopy (SEM). From these characterizations, it emerges that the natural hydroxyapatite extracted from bovine bones is pure and crystallized, the treatment with diammonium phosphate induces within this material an amorphous character without however affecting its structure, the grafting of β-CD to the surface of the natural hydroxyapatite has been carried out successfully without affecting the crystalline phases present in the material. The resulting organohydroxyapatite has a more porous structure and better dispersed particles than the unmodified material. The electrochemical characterization of the materials by cyclic voltammetry confirmed the good porosity of the functionalized material while showing that the grafting carried out considerably improved the cation exchange properties of natural hydroxyapatite. The various materials developed were subsequently used to modify a glassy carbon electrode and the resulting electrochemical sensors were applied to detect diquat on the one hand, then lead(II) on the other. Overall, the electrode modified with organohydroxyapatite showed the best sensitivity. In the case of diquat, preliminary studies carried out in cyclic voltammetry have made it possible to elucidate its electrochemical behavior. Differential pulse voltammetry was subsequently used to optimize detection parameters. This made it possible to draw a calibration line in a range ranging from 5 × 10-8 to 50 × 10-8 M and to have a detection limit of 4.6 × 10-10 M. With regard to lead(II), the Differential pulse voltammetry exploited by means of the anodic redissolution method made it possible to optimize the parameters related to the detection and accumulation step of the sensor. Under these optimal conditions, a calibration line was plotted in a concentration range between 2.5 × 10-8 to 20 × 10-8 M, which made it possible to obtain a detection limit equal to 5.06 × 10- 10 M.