Spectroscopic characterisation of hydroxyapatite and nanocrystalline apatite with grafted aminopropyltriethoxysilane: nature of silane–surface interaction

Abstract

Heterogenised homogeneous catalysis is commonly performed with molecular catalysts grafted on solids via adsorption or via a covalent molecular link. Covalent grafting of organic groups on solid supports is usually carried out by silylation, using functionalised trialkoxysilanes. Among these solids supports, very few studies have been published on apatites. In the present work, aminopropyltriethoxysilane (APTES) grafting was performed in toluene on different apatitic supports: crystallised stoichiometric hydroxyapatites differing by the drying method, freeze-dried (HAP) and dried at 100°C (HAPD), and a nanocrystalline apatite. All materials were fully characterised, before and after grafting, for better understanding of the nature of the alkoxysilane/surface interaction. The data show a clear competition between the covalent grafting of APTES and its polycondensation reaction, depending on the nature of the solid support surface. Silylation is accompanied by APTES covalent grafting to oxygen atom of the hydroxyl groups of the apatitic structure and/or of the OH -species that are present on the surface hydrated layer. This work clarifies the nature of silane grafting onto selected apatitic surfaces and especially the influence of the composition and properties of the apatitic surfaces on the process of silylation.

Effect of hydroxyapatite filler concentration on mechanical properties of poly (methyl methacrylate) denture base

“…The presence of bands for the carboxyl group (~ 1720 cm −1 ) and SiO group (~ 1300-1200 cm −1 ) indicate the availability of the coupling agent on the surface of the hydroxyapatite. This observation is in agreement with the one made by Michelot et al [26]. Silane coupling agents are long molecules that react with the polymer matrix at one end while the other end reacts with the ceramic filler.…”

Glycerol valorization to lactic acid catalyzed by hydroxyapatite‐supported palladium particles

“…also were utilized to interpret the structural properties of the Pd/HAP catalysts. The detection of the vibration modes of the PO 4 3− groups in the HAP structure, namely the sharp and well‐defined peaks at ν1 (960–961 cm −1 ), ν2 (430–450 cm −1 ), ν3 (1035–1048 cm −1 and 1070–1075 cm −1 ) and ν4 (587–604 cm −1 ) confirms the apatite structure in all of the Pd/HAP catalysts …”

“…The detection of the vibration modes of the PO 4 3− groups in the HAP structure, namely the sharp and well-defined peaks at 1 (960-961 cm −1 ), 2 (430-450 cm −1 ), 3 (1035-1048 cm −1 and 1070-1075 cm −1 ) and 4 (587-604 cm −1 ) confirms the apatite structure in all of the Pd/HAP catalysts. 39,40 Fresh Pd 3 /HAP exhibits vibrational modes in the 645-651 cm −1 region, which is the main Raman mode of palladium oxide (PdO). However, this characteristic peak is absent in those catalysts with lower Pd loading.…”

Crown ether functionalized magnetic hydroxyapatite as eco‐friendly microvessel inorganic‐organic hybrid nanocatalyst in nucleophilic substitution reactions: an approach to benzyl thiocyanate, cyanide, azide and acetate derivatives

“…To avoid the aggregation of nanoparticles and to improve their chemical stability, the surface of the nanoparticles has been coated with different materials, such as silica, MCM‐41, polymer and hydroxyapatite . Among them hydroxyapatite, a mineral form of calcium apatite, which is shown by Ca 10 (PO 4 ) 6 (OH) 2 has several unique properties such as lower cost of production, availability and environment friendly nature which can make hydroxyapatite‐encapsulated magnetic nanocrystallites an excellent support for the preparation of heterogeneous catalysts in organic chemistry …”

“…[16][17][18][19][20][21][22][23] Among them hydroxyapatite, a mineral form of calcium apatite, which is shown by Ca 10 (PO 4 ) 6 (OH) 2 has several unique properties such as lower cost of production, availability and environment friendly nature which can make hydroxyapatite-encapsulated magnetic nanocrystallites an excellent support for the preparation of heterogeneous catalysts in organic chemistry. [24][25][26][27][28][29][30][31][32][33][34][35][36][37][38] Crown ethers performing as excellent phase-transfer catalyst in asymmetric reactions have been reported in several papers, with high enantioselectivities and yields observed applying these compounds; in this work, hydroxyapatite coated uniform γ-Fe 2 O 3 core-shell particles were synthesized and crown ether immobilized on an insoluble support presents can lead to the formation of novel nanocomposites, which combines and enhances the characteristics of the components, such as the electronic, thermal, and catalytic properties and molecular recognition of the macrocyclic hosts. With this goal in mind and in continuation of ongoing research into the employment of grafted diformyl dibenzo-18-crown-6 ether as a stationary micro-vessel and heterogeneous catalyst in organic transformations,herein, we report our results on the preparation and characterization of a novel organic-inorganic magnetic nanocomposite, γ-Fe 2 O 3 @HAp-Crown, and explored its application in the nucleophilic substitution reactions as a proficient, harmless to the environment, recyclable and magnetic powerful solid catalyst with good stability.…”