Surface and bulk properties, catalytic activities and selectivities in methane oxidation on near-stoichiometric calcium hydroxyapatites

Sugiyama, Shigeru; Minami, Toshimitsu; Moriga, Toshihiro; Hayashi, Hiromu; Koto, Kichiro; Tanaka, Michie; Moffat, J.B.

doi:10.1039/jm9960600459

Cited by 54 publications

(37 citation statements)

References 28 publications

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“…Multiple scattering effects were not considered, since only the nearest coordination shells are probed at these low energies. Such a simplification has already been employed for the study of non-stoichiometric apatites [44] and bioactive glasses [45] and bone [46] by K-edge EXAFS spectroscopy.…”

Section: Solid State Nmrmentioning

confidence: 99%

Magnesium incorporation into hydroxyapatite

Laurencin¹,

Almora‐Barrios²,

Leeuw³

et al. 2011

Biomaterials

308

190

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The incorporation of Mg in hydroxyapatite (HA) was investigated using multinuclear solid state NMR, X-ray absorption spectroscopy (XAS) and computational modeling. High magnetic field 43 Ca solid state NMR and Ca K-edge XAS of a ~10% Mg-substituted HA were performed, bringing direct evidence of the preferential substitution of Mg in the Ca(II) position. 1 H and 31 P solid state NMR show that the environment of the anions is disordered in this substituted apatite phase. Both Density Functional Theory (DFT) and interatomic potential computations of Mg-substituted HA structures are in agreement with these observations. Indeed, the incorporation of low levels of Mg in the Ca(II) site is found to be more favourable energetically, and the NMR parameters calculated from these optimized structures are consistent with the experimental data. Calculations provide direct insight in the structural modifications of the HA lattice, due to the strong contraction of the M•••O distances around Mg. Finally, extensive interatomic potential calculations also suggest that a local clustering of Mg within the HA lattice is likely to occur.

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Section: Solid State Nmrmentioning

confidence: 99%

Magnesium incorporation into hydroxyapatite

Laurencin¹,

Almora‐Barrios²,

Leeuw³

et al. 2011

Biomaterials

308

190

View full text Add to dashboard Cite

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“…Increasing the X PEA reduced the crystallinity and particle size of Hap, meaning the inhibition of crystal and particle growth of Hap. The PEA ions were incorporated by substitution of surface PO 4 3-of Hap, leading to the formation of surface aminoethyl groups and decrease of number of surface P-OH groups. The n AE was increased with an increment of X PEA from 0.08 to 0.56 molecules/nm 2 .…”

Section: Discussionmentioning

confidence: 99%

“…After stirring, 150 ml of aqueous solutions containing H 3 PO 4 and PEA at different PEA/(PEA+H 3 PO 4 ) molar ratios were added to the Ca(OH) 2 solution. The total amount of H 3 PO 4 and PEA was adjusted to 3.84 mmol 24) . Hereafter, molar ratio PEA/(PEA+H 3 PO 4 ) was abbreviated as X PEA .…”

Section: Methodsmentioning

confidence: 99%

“…Before the measurement, the samples were outgassed at 300°C for 2 h. Spectrum a of the Hap at X PEA = 0 possesses a strong absorption band at 3570 cm -1 and a weak one at 3658 cm -1 . The former band is assigned to the OH -ions in the Hap lattice and the latter one is to the O-H stretching vibration mode of isolated surface P-OH groups generated by protonation of surface PO 4 3-ions to maintain the charge balance of Hap particles [7][8][9] . At X PEA = 0.05, the surface P-OH bands weaken and new weak bands appear at 2957, 2927 and 2868 cm -1 , which can be ascribed to the C-H stretching vibration mode of aminoethyl groups of PEA grafted on the Hap surface (spectrum b).…”

Section: Surface Structure and Property Of Pea-grafted Hapmentioning

confidence: 99%

“…Synthetic colloidal Hap particles find many applications such as adsorbents for chromatography to separate protein and enzyme, catalysts for dehydration and dehydrogenation of alcohols, methane oxidation, and artificial teeth and bones [1][2][3][4][5][6] . These properties relate to the various surface properties of Hap, e.g., surface functional groups, acidity and basicity, surface charge, hydrophilicity and porosity.…”

Section: Calciummentioning

confidence: 99%

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Preparation and Surface Characterization of Calcium Hydroxyapatite Grafting of Phosphoethanolamine

Tanaka

Uchida

2010

Phosphorus Research Bulletin

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Calcium hydroxyapatite (Ca 10 (PO 4 ) 6 (OH) 2 : Hap) particles grafting of O-phosphoethanolamine (NH 2 (CH 2 ) 2 OPO 3 H 2 : PEA) were prepared by a coprecipitation method with a mixture of Ca(OH) 2 , H 3 PO 4 and PEA at different PEA/(PEA+H 3 PO 4 ) molar ratios in aqueous media at 85°C. The crystallinity and particle size of Hap were decreased with an increase of PEA/(PEA+H 3 PO 4 ) ratio, revealing that the crystal and particle growth of Hap were inhibited by grafting of PEA. The surface aminoethyl groups were generated by substituting the surface PO 4 3-of Hap with PEA ions, giving rise to the decrease of surface P-OH groups of Hap. The number of surface aminoethyl groups was increased with increasing the PEA/(PEA+H 3 PO 4 ) ratio and was ranged from 0.08 to 0.56 molecules/nm 2 . The surface aminoethyl groups would act as the irreversible adsorption sites of CO 2 .

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Structure and Surface Study of Hydroxyapatite‐Based Materials

Costentin

Drouet

Salles

et al. 2022

Design and Applications of Hydroxyapatite‐Based Catalysts

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In addition to designing catalytic materials ever more active and selective, the emergence of new classes of greener catalysts remains very challenging. The apatite family system with hydroxyapatite (HA) structure appears as a good candidate for catalysis due to its ecocompatibility properties, its sorption ability toward organic molecules, and its tunable composition resulting into modulation of its surface properties. Depending on their mode of preparation, these inexpensive and environment-friendly apatitic calcium phosphates exhibit properties of relevance to catalysis, such as large surface area and various morphologies.However, most studies focused so far on the catalytic performance of these compounds, while the study of structure-reactivity relationships required for rationalized optimization remains rather limited. This chapter aims at providing tools to help understand the catalytic behavior of apatite compounds, giving details about their structure, surface properties, and reactivity; this will include both stoichiometric and nonstoichiometric compounds, sometimes biomimetic and potentially substituted. A special attention is dedicated to recent advances in the characterization of their structural properties (bulk and surface/interphase) that have a strong impact on their reactivity, through both experimental and computational approaches to study the mechanisms occurring in the structure or at the crystals surface, as well as thermodynamic and dynamical properties. Remaining characterization challenges for apatite-based catalysts will also be discussed. 1.an influence on the charges carried by the cation and on the related strength of the Ca-O interaction [127], which results in different adsorption properties with guest molecules. To go further, quantum calculations coupled with NMR (Nuclear Magnetic Resonance) resultsshowed the impact of the presence of OHions on the migration of Ca 2+ as well as the rotation of PO4 3groups [128]. In the hydroxyapatite structure, phosphate ions PO4 3are the largest components of the structure. As such, they provide a primary backbone via 3D compact-like piling, generating interstitial sites for the other ions of the structure. Metal cations such as Ca 2+ occupy two types of crystallographic sites, denoted Ca1 (4 sites per unit formula) and Ca2 (6 sites per unit formula), see Figure 2. Ca1 sites are localized along the trigonal axis with the coordinates (1/4, 3/4, 1/2) and (3/4, 1/4, 1/2), forming linear columns along the c-axis. Ca2 sites in contrast form equilateral triangles at z = 1/4 and z = 3/4 on the sixfold screw (senary) 63 axes. Adjacent Ca1 and Ca2 sites are linked through shared oxygen atoms from PO4 tetrahedra. Ca1 sites generate (distorted) polyhedra where the metal ion is in ninefold coordination, while in Ca2 sites it is in sevenfold coordination.The Ca2 triangles contribute to delimit so-called "apatitic channels" where ions such as OHare axially located (Figure 3) [116,120]. In calcium hydroxyapatite, the Ca2 triangular sites correspond to the narrow...

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Surface and bulk properties, catalytic activities and selectivities in methane oxidation on near-stoichiometric calcium hydroxyapatites

Cited by 54 publications

References 28 publications

Magnesium incorporation into hydroxyapatite

Magnesium incorporation into hydroxyapatite

Preparation and Surface Characterization of Calcium Hydroxyapatite Grafting of Phosphoethanolamine

Structure and Surface Study of Hydroxyapatite‐Based Materials

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