Apatite Raman

William Schopf studied supercrustal rock samples from Akilia Raman and ion microscopic photographs showed the presence of carbon-containing inclusions in grains of apatite. The carbon isotope ratio was determined by secondary ion mass spectroscopy (SIMS) the 813C value was -29% 4%, in agreement with earlier analyses. This in turn confirmed the values obtained by Mojzsis (1996), which had been questioned by Lepland et al. three years later. The final verdict on the oldest fossils in western Greenland may not be reached for several years yet (McKeegan et al., 2007 Eiler, 2007). 

It is well known that vanadium can replace phosphorus or arsenic in the apatite lattice. Most of the orthovanadates which crystallize in this form have been investigated by IR and Raman spectroscopic techniques 62—64). The results of these studies are summarized in Table 4. The space group of all of these compounds is certainly C ft with the VO4 ion lying on a C site. Therefore, one should always find a nine band spectrum. Phosphorus apatites behave similarly, as seen in Ref. (65). 

Many vibrational spectroscopic investigations (FTIR and Raman) concerning FA have been reported, in particular, in the early works of Baddiel and Berry [15], Bhatnagar [16], Levitt et al. [17] and Klee [18], Some studies also relate, among others, to the far-infrared region [19] and to the influence of high-pressure conditions [20], In particular, these techniques have been used for comparative analysis of FA with other apatites, such as HA or chlorapatite. 

The vibration bands relative to phosphate groups in the apatite structure differ from the normal modes of the P04 isolated ion, due to distortions of the PO4 tetrahedra in the apatite lattice and vibrational coupling [4]. Therefore, site-group and factor-group analyses were applied [15,16,18,21] to elucidate the vibrational spectra observed (Fig. 5) and band assignments of infrared (IR) and Raman bands have been given (Table 3). 

S. R. Levitt, K.C. Blakeslee, R.A. Condrate, Infrared spectra and laser-Raman spectra of several apatites, Memoires de la Societe Royale des Sciences de Liege, Collection in 8 20 (1970) 121-141. 

G. Penel, G. Leroy, C. Rey, B. Sombret, J.P. Huvenne, E. Bres, Infrared and Raman microspectrometry study of fluor- fluor-hydrox- and hydroxy-apatite powders, J. Mater. Sci. Mater. Med. 8 (1997) 271-276. 

Crystallinity is a metric related to mineral maturity and is a measure of mineral crystallite size, mineral maturity, and the amount of substitution into the apatitic lattice. Crystallinity increases when crystals are larger and more perfect (i.e. less substitution). It is directly proportional to the inverse width of the 002 reflection (c-axis reflection) in the powder x-ray diffraction pattern of bone mineral. Several features in the infrared spectra of bone correlate with mineral crystallinity, most of which are components of the phosphate Vi,V3 envelope [8]. Any of these correlations should be usable in the Raman spectrum provided there are no other overlapping Raman peaks. However, there has been less emphasis on crystallinity in the bone Raman literature and only the inverse width of the phosphate Vi band has been used as a measure of crystallinity [9-12]. 

Carbonate band assignment has been more difficult in Raman spectra than in the infrared [15] because of near overlap of the major carbonate Vi mode at 1070cm-1 with a component of phosphate V3 at 1076cm-1 in carbonated apatites [16]. These bands have earlier been reported as coincident [17] or have been assumed to be a single broad carbonate band [18]. Most investigators have used the ratio of the carbonate Vi band/phosphate Vi band as a measure of the carbonate/phosphate ratio. It is likely that in many cases this error is small, but for lightly carbonated mineral, typically freshly precipitated mineral, the error may be important. Remeasurement or reinterpretation of some Raman spectroscopic data may be needed. 

The second provenance criterion is based on the identification of inclusions in gemstones. Micro-Raman spectrometry was used for this task in almandine garnets. Various inclusions were observed like apatite, zircon, monazite, calcite, and quartz and two of them, curved needles of sillimanite (Al2Si05) and 10-pm metamict radioactive crystals, were specifically found in archaeological garnets. Fig. 6 shows the Raman spectra of a sillimanite needle, which is a mineral formed under a high temperature and high pressure metamorphism. 

Fowler BO (1977) I. Polarized Raman spectra of apatites. II. Raman bands of carbonate ions in human tooth enamel. Mineralized Tissue Research Communications Vol 3, no. 68 Fratzl P, Fratzl-Zelman N, Klaushofer K, Vogl G, Roller K (1991) Nucleation and growth of mineral crystals in bone studied by small-angle X-ray scattering. Calcif Tissue Inti 48 407-413 Fratzl P, Schreiber S, Boyde A (1996) Characterization of bone mineral crystals in horse radius by small-angle X-ray scattering. Calcif Tissue Inti 58 341-346... 

Tran, H.V. (2004) Investigation into the thermal dehydroxylation and decomposition of hydroj apatite during atmospheric plasma spraying NM R and Raman spectroscopic study of as-sprayed coatings and coatings incubated in simulated body fluid. Unpublished Ph.D. 

Figure 31 Three Raman spectra of an arsenate-phosphate solid solution (Ca, Sr)s[As04, POJaCF, OH)) displaying the variations in band position and intensity as PO4 is replaced by ASO4, and concomitantly Ca is replaced by Sr, from apatite (below. As and Sr poor) upward to fermorite (above, As and Sr rich). (After Ref. 50.)...

Penel, G. et al (2005) Composition of bone and apatitic biomaterials as revealed by intravital Raman microspectroscopy. Bone, 36 (5), 893-901. 

Gamsjaeger, S. etal (2011) Bone material properties in actively bone-forming trabeculae in postmenopausal women with osteoporosis after three years of treatment with once-yearly Zoledronic acid. J. Bone Miner. Res., 26 (1), 12—18. Awonusi, A., Morris, M.D., and Tecklenburg, M.M. (2007) Carbonate assignment and calibration in the Raman spectrum of apatite. Calcif. 

Nishino, M. etal (1981) The laser-Raman spectroscopic studies on human-enamel and precipitated carbonate-containing apatites. / Dent Res., 60, 751-755. 

Willamson, B.E. (1982) Low-temperature laser Raman spectroscopy of synthetic carbonated apatites and dental enamel. Aust / Chem., 35,... 

The differences in fertilizer-soil reactions of calcium and magnesium (pyro-) phosphates, respectively, were successfully determined by Raman and synchrotron infrared microspectroscopic studies. All calcium orthophosphates convert to hydroxyapatite in soil over time. On the other hand, magnesium orthophosphates react only as far as trimagnesium phosphate because of then-inability to form an apatite structure. Thus, for the magnesium-based compound, phosphorus remains in a plant-available form. Also, the pyrophosphates of calcium and magnesium react very differently. Calcium pyrophosphate did not react in soil, whereas magnesium pyrophosphate quickly forms dimagnesium phosphate. Furthermore, mineral phases of soils were detectable by infrared microspectroscopy. 

Bone implants are commonly made of metal coated in a similar material to bone, i.e. synthetic hydro5Q apatite, to improve the biocompatility and to aid bonding between the natural bone and the implant. Raman studies of bone implants utilize the spectral difference between bone and that of synthetic hydro5Q apatite. The synthetic material lacks many of the characteristic Raman vibrations of bone and those of phosphate have significantly reduced band-widths. Thus, it is possible to study the interface between the implant and the recipient s bone. Biomineralization of implants coated with materials other than hydrojQ apatite can be followed by monitoring the intensity of the phosphate vibration related to those produced by the coating material. 

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