Structural, textural and acid–base properties of carbonate-containing hydroxyapatites

Silvester, Lishil; Lamonier, Jean‐François; Vannier, Rose‐Noëlle; Lamonier, Carole; Capron, Mickäel; Mamede, Anne-Sophie; Pourpoint, Frédérique; Gervasini, Antonella; Dumeignil, Franck

doi:10.1039/c4ta01628a

Cited by 117 publications

(140 citation statements)

References 42 publications

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“…8). In previous reports, a good correlation was derived between anisotropic crystallite shape obtained from XRD and grain shape observed in SEM [38]. Our results herein suggested that there might be an intrinsic relation between the Ca/P ratio and size of HAP RPB , which need further investigation in the future.…”

Section: Size-controlled Synthesis Of Hap Rpbsupporting

confidence: 79%

Synthesis and characterization of hydroxyapatite nanoparticles prepared by a high-gravity precipitation method

Han

Wang

et al. 2015

Ceramics International

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Section: Size-controlled Synthesis Of Hap Rpbsupporting

confidence: 79%

Synthesis and characterization of hydroxyapatite nanoparticles prepared by a high-gravity precipitation method

Han

Wang

et al. 2015

Ceramics International

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“…also reported a shoulder signal at high chemical shift, around 5.4 ppm, which they attributed to surface nonprotonated phosphate groups on the basis of the dependence of this contribution on thermal treatment and on the pH of solution let in contact with the sample. 40 Such surface PO 4 3− assignment might also explain the relative higher contribution of this species in the stoichiometric compound (and also in over stoichiometric compounds, results not shown, and in ref 32) compared to the under-stoichiometric one: one may reasonably expect a higher concentration of terminal nonprotonated phosphate groups at the surface of a stoichiometric compound. Indeed, beyond the increase of the PO 4 3− /HPO 4 2− relative concentration in the bulk with increasing the Ca/P ratio [Ca 10−x (HPO 4 ) x (PO 4 ) 6−x ) (OH) 2−x ], 10 the same trend is expected to occur at the surface.…”

Section: H Mas Inversion Recoverymentioning

confidence: 89%

Discrimination of Surface and Bulk Structure of Crystalline Hydroxyapatite Nanoparticles by NMR

et al. 2015

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Solid state 1 H and 31 P NMR spectroscopy was used to characterize wellcrystallized hydroxyapatite samples of different stoichiometry prepared by a precipitation route. The aim of the paper was to investigate the bulk structural features of samples with different stoichiometry and to discriminate signals related to the surface from those related to the bulk. Thanks to the implementation of (i) in situ thermal pretreatment at 623 K, (ii) filling of the NMR rotor in a controlled atmosphere, (iii) relative proton enrichment of the surface performed under controlled isotopic H-D exchanges, and (iv) specific NMR sequences including inversion recovery measurements, two-dimensional HETCOR and DQSQ spectra, new resolved NMR signals originating from the surface and from the bulk were identified alongside already reported signals associated with adsorbed water, structural phosphates, and OH groups. In particular, considering the influence of the stoichiometry, it was possible to identify a specific signature associated with defective hydrogenophosphate groups present in the bulk. Despite the well-ordered surface terminations of the nanoparticles, specific surface signals associated with nonprotonated and protonated surface terminating phosphate groups could be identified. In addition, from the three resolved 1 H signals associated with columnar OH channels, two from the bulk and one from the surface, a structural model describing the relative organization of hydroxyl groups running along the c axis inside the columnar OH channel in the well-crystallized particles is proposed: the two types of bulk hydroxyls are associated with the presence of both up and down orientations of their related protons in a same tunnel. Corresponding 1 H signatures of the surface-terminating hydroxyls or structured water molecules emerging from the OH channels were also identified. Moreover, in addition to the broad 5.1 ppm line associated with water adsorbed on calcium cations and hydrogenophosphate groups, the 1.1 ppm line is ascribed to structured external water molecules stacking in continuity to the OH channels.

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“…16, binding energy shift of a protonated base (B site) being larger than for an electron doublet donation (L site). Specific examples have been published for acidic zeolites and silica-aluminas [109] and basic hydroxyapatites [110], and one usually analyses Fig. 15 Relationship between m N-H vibration of pyrrole and N 1s and O 1s binding energy values for Yand X-type FAU zeolites (top and bottom lines, respectively) and scheme of the adsorption adapted from Ref.…”

Section: Xps Techniquementioning

confidence: 99%

Acid–base characterization of heterogeneous catalysts: an up-to-date overview

Védrine

2015

Res Chem Intermed

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In this overview, we focus on the different and current methods of acidbase characterization of heterogeneous catalysts and on their potential relation with catalytic properties in gas and liquid phases. Special emphasis is drawn on the main techniques currently employed such as the use of Hammett's indicators, the use of basic or acidic probes of different strength for adsorption measurements in microcalorimetry and of their thermal programmed desorption, the use of other techniques such as FTIR, ESR, NMR, photoluminescence, Raman, UV-Vis, and XPS, to identify and describe acid-base sites, the use of model catalytic reactions, and of theoretical/modeling approaches. Relationships between such a characterization and catalytic properties in different acid or base reactions are discussed, and implemented for different catalysts and different reactions. The concept of thermodynamic acidity/basicity (determined via chemical physical characterization) versus reactivity (determined via catalytic properties) of acid-base sites is presented, and explains why relationships between acid-base properties and catalytic properties are very often met but are difficult to be established unambiguously and cannot be generalized. The case of acid-base properties in liquid phase ''polar'' (water, alcohol) and ''apolar'' (cyclohexane) as ''effective'' and ''intrinsic'' properties, respectively, and their relation with catalytic properties in liquid phase are also discussed.Keywords Acid-base properties of solid catalysts Á Related catalytic properties Á Intrinsic versus effective acidity/basicity Á Acidity/basicity in liquid polar or apolar media

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Structural, textural and acid–base properties of carbonate-containing hydroxyapatites

Abstract: HAP solids were prepared with different Ca/P ratios and Na+ cations before being characterized by XRD, XPS, LEIS, NMR, IR, and TGA. Their acid–base properties were then measured and discussed in relation to the characterization results.

Cited by 117 publications

References 42 publications

Synthesis and characterization of hydroxyapatite nanoparticles prepared by a high-gravity precipitation method

Synthesis and characterization of hydroxyapatite nanoparticles prepared by a high-gravity precipitation method

Discrimination of Surface and Bulk Structure of Crystalline Hydroxyapatite Nanoparticles by NMR

Acid–base characterization of heterogeneous catalysts: an up-to-date overview

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