A Raman and infrared spectroscopic characterisation of the phosphate mineral phosphohedyphane Ca2Pb3(PO4)3Cl from the Roote mine, Nevada, USA

Phosphohedyphane Ca2Pb3(PO4)3Cl is rare Ca and Pb phosphate mineral that belongs to the apatite supergroup. We have analysed phosphohedyphane using SEM with EDX, and Raman and infrared spectroscopy. The chemical analysis shows the presence of Pb, Ca, P and Cl and the chemical formula is expressed as Ca2Pb3(PO4)3Cl. The very sharp Raman band at 975 cm−1 is assigned to the PO43-ν1 symmetric stretching mode. Raman bands noted at 1073, 1188 and 1226 cm−1 are to the attributed to the PO43-ν3 antisymmetric stretching modes. The two Raman bands at 835 and 812 cm−1 assigned to the AsO43-ν1 symmetric stretching vibration and AsO43-ν3 antisymmetric stretching modes prove the substitution of As for P in the structure of phosphohedyphane. A series of bands at 557, 577 and 595 cm−1 are attributed to the ν4 out of plane bending modes of the PO4 units. The multiplicity of bands in the ν2, ν3 and ν4 spectral regions provides evidence for the loss of symmetry of the phosphate anion in the phosphohedyphane structure. Observed bands were assigned to the stretching and bending vibrations of phosphate tetrahedra. Some Raman bands attributable to OH stretching bands were observed, indicating the presence of water and/or OH units in the structure.

SEM, EDX, infrared and Raman spectroscopic characterization of the silicate mineral yuksporite

The mineral yuksporite (K,Ba)NaCa2(Si,Ti)4O11(F,OH)⋅H2O has been studied using the combination of SEM with EDX and vibrational spectroscopic techniques of Raman and infrared spectroscopy. Scanning electron microscopy shows a single pure phase with cleavage fragment up to 1.0 mm. Chemical analysis gave Si, Al, K, Na and Ti as the as major elements with small amounts of Mn, Ca, Fe and REE. Raman bands are observed at 808, 871, 930, 954, 980 and 1087 cm−1 and are typical bands for a natural zeolite. Intense Raman bands are observed at 514, 643 and 668 cm−1. A very sharp band is observed at 3668 cm−1 and is attributed to the OH stretching vibration of OH units associated with Si and Ti. Raman bands resolved at 3298, 3460, 3562 and 3628 cm−1 are assigned to water stretching vibrations.

SEM, EDX and Raman and infrared spectroscopic study of brianyoungite Zn3(CO3,SO4)(OH)4 from Esperanza Mine, Laurion District, Greece

The mineral brianyoungite, a carbonate–sulphate of zinc, has been studied by scanning electron microscopy (SEM) with chemical analysis using energy dispersive spectroscopy (EDX) and Raman and infrared spectroscopy. Multiple carbonate stretching modes are observed and support the concept of non-equivalent carbonate units in the brianyoungite structure. Intense Raman band at 1056 cm−1 with shoulder band at 1038 cm−1 is assigned to the CO32− ν1 symmetric stretching mode. Two intense Raman bands at 973 and 984 cm−1 are assigned to the symmetric stretching modes of the SO42− anion. The observation of two bands supports the concept of the non-equivalence of sulphate units in the brianyoungite structure. Raman bands at 704 and 736 cm−1 are assigned to the CO32− ν4 bending modes and Raman bands at 507, 528, 609 and 638 cm−1 are assigned to the CO32− ν2 bending modes. Multiple Raman and infrared bands in the OH stretching region are observed, proving the existence of water and hydroxyl units in different molecular environments in the structure of brianyoungite. Vibrational spectroscopy enhances our knowledge of the molecular structure of brianyoungite.

A Raman and infrared spectroscopic study of the sulphate mineral aluminite Al2(SO4)(OH)4·7H2O

The mineral aluminite has been studied using a number of techniques, including scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDX) and Raman and infrared spectroscopy. Raman spectroscopy identifies multiple sulphate symmetric stretching modes in line with the three sulphate crystallographically different sites. Raman spectroscopy also identifies a low intensity band at 1069 cm−1 which may be attributed to a carbonate symmetric stretching mode, indicating the presence of thaumasite. The observation of multiple bands in this ν4 spectral region offers evidence for the reduction in symmetry of the sulphate anion from Td to C2v or even lower symmetry. The Raman band at 3588 cm−1 is assigned to the OH unit stretching vibration and the broad feature at around 3439 cm−1 to water stretching bands. Water stretching vibrations are observed at 3157, 3294, 3378 and 3439 cm−1. Vibrational spectroscopy enables an assessment of the molecular structure of aluminite to be made.

Raman and infrared spectroscopic study of turquoise minerals

Raman and infrared spectra of three well-defined turquoise samples, CuAl6(PO4)4(OH)8·4H2O, from Lavender Pit, Bisbee, Cochise county, Arizona; Kouroudaiko mine, Faleme river, Senegal and Lynch Station, Virginia were studied, interpreted and compared. Observed Raman and infrared bands were assigned to the stretching and bending vibrations of phosphate tetrahedra, water molecules and hydroxyl ions. Approximate O–H⋯O hydrogen bond lengths were inferred from the Raman and infrared spectra. No Raman and infrared bands attributable to the stretching and bending vibrations of (PO3OH)2− units were observed.

Use of near-infrared Raman spectroscopy to detect IgG and IgM antibodies against Toxoplasma gondii in serum samples of domestic cats

Near-infrared Raman spectroscopy (NIRS) is a particularly promising technique that is being used in recent years for many biomedical applications. Optical spectroscopy has gained increasing prominence as a tool for quantitative analysis of biological samples, clinical diagnostic, concentration measurements of blood metabolites and therapeutic drugs, and analysis of the chemical composition of human tissues. Toxoplasmosis is an important zoonosis in public health, and domestic cats are the most important transmitters of the disease. This disease can be detected by several serological tests, which usually have a high cost and require a long time. The goal of this work was to investigate a new method to diagnosis Toxoplasma gondii infections using NIRS. In order to confirm antibody detection, 24 cat blood scrum samples were analyzed by the Raman spectra, from which 23 presented positive serology to toxoplasmosis and one was a reference negative serum. Characteristic Raman peaks allowed differentiation between negative and positive sera, confirming the possibility of antibody detection by Raman spectroscopy. These results give the first evidence that this technique can be useful to quantify antibodies in cat sera.

Raman spectroscopic study of the uranyl mineral pseudojohannite Cu6.5[(UO2)4O4(SO4)2]2(OH)5.25H2O

Raman spectra of pseudojohannite were studied and related to the structure of the mineral. Observed bands were assigned to the stretching and bending vibrations of (UO2)2+ and (SO4)2- units and of water molecules. The published formula of pseudojohannite is Cu6.5(UO2)8\[O8](OH)5\[(SO4)4].25H2O; however Raman spectroscopy does not detect any hydroxyl units. Raman bands at 805 and 810 cm-1 are assigned to (UO2)2+ stretching modes. The Raman bands at 1017 and 1100 cm-1 are assigned to the (SO4)2- symmetric and antisymmetric stretching vibrations. The three Raman bands at 423, 465 and 496 cm-1 are assigned to the (SO4)2- ν2 bending modes. The bands at 210 and 279 cm-1 are assigned to the doubly degenerate ν2 bending vibration of the (UO2)2+ units. U-O bond lengths in uranyl and O-H…O hydrogen bond lengths were calculated from the Raman and infrared spectra.

Raman spectroscopic study of the antimonate mineral lewisite (Ca,Fe,Na)2(Sb,Ti)2O6(O,OH)7

The mineral lewisite, (Ca,Fe,Na)2(Sb,Ti)2O6(O,OH)7 an antimony bearing mineral has been studied by Raman spectroscopy. A comparison is made with the Raman spectra of other minerals including bindheimite, stibiconite and roméite. The mineral lewisite is characterised by an intense sharp band at 517 cm-1 with a shoulder at 507 cm-1 assigned to SbO stretching modes. Raman bands of medium intensity for lewisite are observed at 300, 356 and 400 cm-1. These bands are attributed to OSbO bending vibrations. Raman bands in the OH stretching region are observed at 3200, 3328, 3471 cm-1 with a distinct shoulder at 3542 cm-1. The latter is assigned to the stretching vibration of OH units. The first three bands are attributed to water stretching vibrations. The observation of bands in the 3200 to 3500 cm-1 region suggests that water is involved in the lewisite structure. If this is the case then the formula may be better written as Ca, Fe2+, Na)2(Sb, Ti)2(O,OH)7 •xH2O.

Raman spectroscopic study of the mineral finnemanite Pb5(As3+O3)3Cl

The arsenite minerals finnemanite Pb5(As3+O3)3Cl been studied by Raman spectroscopy. The most intense Raman band at 871 cm-1 is assigned to the ν1 (AsO3)3- symmetric stretching vibration. Three Raman bands at 898, 908 and 947 cm-1 are assigned to the ν3 (AsO3)3- antisymmetric stretching vibration. The observation of multiple antisymmetric stretching vibrations suggest that the (AsO3)3- units are not equivalent in the molecular structure of finnemanite. Two Raman bands at 383 and 399 cm-1 are assigned to the ν2 (AsO3)3- bending modes. DFT calculations enabled the position of AsO32- symmetric stretching mode at 839 cm-1, the antisymmetric stretching mode at 813 cm-1, and the deformation mode at 449 cm-1 to be calculated. Raman bands are observed at 115, 145, 162, 176, 192, 216 and 234 cm-1 as well. The two most intense bands are observed at 176 and 192 cm-1. These bands are assigned to PbCl stretching vibrations and result from transverse/ longitudinal splitting. The bands at 145 and 162 cm-1 may be assigned to Cl-Pb-Cl bending modes.

Raman spectroscopic study of the antimony containing mineral partzite Cu2Sb2(O,OH)7

Raman spectroscopy of the mineral partzite Cu2Sb2(O,OH)7 complimented with infrared spectroscopy were studied and related to the structure of the mineral. The Raman spectrum shows some considerable complexity with a number of overlapping bands observed at 479, 520, 594, 607 and 620 cm-1 with additional low intensity bands found at 675, 730, 777 and 837 cm-1. Raman bands of partzite in the spectral region 590 to 675 cm-1 are attributable the ν1 symmetric stretching modes. The Raman bands at 479 and 520 cm-1 are assigned to the ν3 antisymmetric stretching modes. Raman bands at 1396 and 1455 cm-1 are attributed to SbOH deformation modes. A complex pattern resulting from the overlapping band of the water and OH units is found. Raman bands are observed at 3266, 3376, 3407, 3563, 3586 and 3622 cm-1. The first three bands are assigned to water stretching vibrations. The three higher wavenumber bands are assigned to the stretching vibrations of the OH units. It is proposed that based upon observation of the Raman spectra that water is involved in the structure of partzite. Thus the formula Cu2Sb2(O,OH)7 may be better written as Cu2Sb2(O,OH)7 •xH2O

Raman spectroscopic study of the hydroxy-arsenate mineral geminite Cu(AsO3OH)•H2O

The mineral geminite, an hydrated hydroxy-arsenate mineral of formula Cu(AsO3OH)•H2O, has been studied by Raman and infrared spectroscopy. Two minerals from different origins were investigated and the spectra proved quite similar. In the Raman spectra of geminite, four bands are observed at 813, 843, 853 and 885 cm-1. The assignment of these bands is as follows: (a) The band at 853 cm-1 is assigned to the AsO43- ν1 symmetric stretching mode (b) the band at 885 cm-1 is assigned to the AsO3OH2- ν1 symmetric stretching mode (c) the band at 843 cm-1 is assigned to the AsO43- ν3 antisymmetric stretching mode (d) the band at 813 cm-1 is ascribed to the AsO3OH2- ν3 antisymmetric stretching mode. Two Raman bands at 333 and 345 cm-1 are attributed to the ν2 AsO4 3- bending mode and a set of higher wavenumber bands are assigned to the ν4 AsO43- bending mode. A very complex set of overlapping bands is observed in both the Raman and infrared spectra. Raman bands are observed at 2288, 2438, 2814, 3152, 3314, 3448 and 3521 cm-1. Two Raman bands at 2288 and 2438 cm-1 are ascribed to very strongly hydrogen bonded water. The broader Raman bands at 3152 and 3314 cm-1 may be assigned to adsorbed water and not so strongly hydrogen bonded water in the molecular structure of geminate. Two bands at 3448 and 3521 cm-1 are assigned to the OH stretching vibrations of the (AsO3OH)2- units. Raman spectroscopy identified Raman bands attributable to AsO43- and AsO3OH2- units.

Infrared and infrared emission spectroscopic study of China typical kaolinite and halloysite

The structure and thermal stability between typical China kaolinite and halloysite were analysed by X-ray diffraction (XRD), infrared spectroscopy, infrared emission spectroscopy (IES) and Raman spectroscopy. Infrared emission spectroscopy over the temperature range of 300 to 700 °C has been used to characterise the thermal decomposition of both kaolinite and halloysite. Halloysite is characterised by two bands in the water bending region at 1629 and 1648 cm-1, attributed to structure water and coordinated water in the interlayer. Well defined hydroxyl stretching bands at around 3695, 3679, 3652 and 3625 cm-1 are observed for both kaolinite and halloysite. In the 550 °C infrared emission spectrum of halloysite is similar to that of kaolinite in 650-1350 cm-1 region. The infrared emission spectra of halloysite were found to be considerably different to that of kaolinite at lower temperatures. This difference is attributed to the fundamental difference in the structure of the two minerals.

Dussertite BaFe3+3(AsO4)2(OH)5 : a Raman spectroscopic study of a hydroxy-arsenate mineral

The mineral dussertite, a hydroxy-arsenate mineral of formula BaFe3+3(AsO4)2(OH)5, has been studied by Raman complimented with infrared spectroscopy. The spectra of three minerals from different origins were investigated and proved quite similar, although some minor differences were observed. In the Raman spectra of Czech dussertite, four bands are observed in the 800 to 950 cm-1 region. The bands are assigned as follows: the band at 902 cm-1 is assigned to the (AsO4)3- ν3 antisymmetric stretching mode, at 870 cm-1 to the (AsO4)3- ν1 symmetric stretching mode, and both at 859 cm-1 and 825 cm-1 to the As-OM2+/3+ stretching modes/and or hydroxyls bending modes. Raman bands at 372 and 409 cm-1 are attributed to the ν2 (AsO4)3- bending mode and the two bands at 429 and 474 cm-1 are assigned to the ν4 (AsO4)3- bending mode. An intense band at 3446 cm-1 in the infrared spectrum and a complex set of bands centred upon 3453 cm-1 in the Raman spectrum are attributed to the stretching vibrations of the hydrogen bonded (OH)- units and/or water units in the mineral structure. The broad infrared band at 3223 cm-1 is assigned to the vibrations of hydrogen bonded water molecules. Raman spectroscopy identified Raman bands attributable to (AsO4)3- and (AsO3OH)2- units.

A Raman spectroscopic study of the antimony mineral klebelsbergite Sb4O4(OH)2(SO4)

Many minerals based upon antimonite and antimonate anions remain to be studied. Most of the bands occur in the low wavenumber region, making infrared spectroscopy difficult to use. This problem can be overcome by using Raman spectroscopy. Raman spectra of the mineral klebelsbergite Sb4O4(OH)2(SO4) were studied, and related to the structure of the mineral. Raman bands observed at 971 cm-1 and a series of overlapping bands are observed at 1029, 1074, 1089, 1139 and 1142 cm-1 are assigned to the SO42- ν1 symmetric and ν3 antisymmetric stretching modes. Two Raman bands are observed at 662 and 723 cm-1 and assigned to the SbO ν3 antisymmetric and ν1 symmetric stretching modes. The intense Raman bands at 581, 604 and 611 cm-1 are assigned to the ν4 SO42- bending modes. Two overlapping bands at 481 and 489 cm-1 are assigned to the ν2 SO42- bending mode. Low intensity bands at 410, 435 and 446 cm-1 may be attributed to OSbO bending modes. The Raman band at 3435 cm-1 is attributed to the OH stretching vibration of the OH units. Multiple Raman bands for both SO42- and SbO stretching vibrations support the concept of the non-equivalence of these units in the klebelsbergite structure. It is proposed that two sulphate anions are distorted to different extents in the klebelsbergite structure.

Raman spectroscopy of hydrogene-arsenate group (AsO3OH) in solid-state compounds: cobalt mineral phase burgessite Co2(H2O)4[AsO3OH]2•H2O

Raman spectrum of burgessite, Co2(H2O)4[AsO3OH]2.H2O was studied, interpreted and compared with its infrared spectrum. The stretching and bending vibrations of (AsO3) and As-OH units together with the stretching, bending and libration modes of water molecules and hydroxyl ions were assigned. The range of O-H...O hydrogen bond lengths was inferred from the Raman and infrared spectra of burgessite. The presence of (AsO3OH)2- units in the crystal structure of burgessite was proved in agreement with its recently solved crystal structure. Raman and infrared spectra of erythrite inferred from the RRUFF database are used for comparison.