Molecular Assembly in Synthesized Hydrotalcites of Formula CuxZn6-xA12(OH)16(CO3).4H2O-A Vibrational Spectroscopic Study

Infrared and Raman spectroscopy have been used to characterize synthetic hydrotalcites of formula CuxZn6-xAl2(OH)16(CO3).4H2O . The spectra have been used to assess the molecular assembly of the cations in the hydrotalcite structure. The spectra may be conveniently subdivided into spectral features based (a) upon the carbonate anion (b) the hydroxyl units (c) water units. The Raman spectra of the hydroxyl-stretching region enable bands to be assigned to the CuOH, ZnOH and AlOH units. It is proposed that in the hydrotalcites with minimal cationic replacement that the cations are arranged in a regular array. For the CuxZn6-xAl2(OH)16(CO3).4H2O hydrotalcites, spectroscopic evidence suggests that 'islands' of cations arte formed in the structure. In a similar fashion the bands assigned to the interlayer water suggest that the water molecules are also in a regular well-structured arrangement. Bands are assigned to the hydroxyl stretching vibrations of water. Three types of water are identified (a) water hydrogen bonded to the interlayer carbonate ion (b) water hydrogen bonded to the hydrotalcite hydroxyl surface and (c) interlamellar water. It is proposed that the water is highly structured in the hydrotalcite as it is hydrogen bonded to both the carbonate anion and the hydroxyl surface

X-ray photoelectron spectroscopic and Raman microscopic investigation of the variscite group minerals: variscite, strengite, scorodite and mansfieldite

Several structurally related AsO and PO minerals, were studied with Raman microscopy and X-ray Photoelectron Spectroscopy (XPS). XPS revealed only Fe, As and O for scorodite. The Fe 2p, As 3d, and O 1s indicated one position for Fe, while 2 different environments for O and As were observed. The O 1s at 530.3\ua0eV and the As 3d 5/2 at 43.7\ua0eV belonged to AsO, while minor bands for O 1s at 531.3\ua0eV and As 3d 5/2 at 44.8\ua0eV were due to AsO groups exposed on the surface possibly forming OH-groups. Mansfieldite showed, besides Al, As and O, a trace of Co. The PO equivalent of mansfieldite is variscite. The change in crystal structure replacing As with P resulted in an increase in the binding energy (BE) of the Al 2p by 2.9\ua0eV. The substitution of Fe for Al in the structure of strengite resulted in a Fe 2p at 710.8\ua0eV. An increase in the Fe 2p BE of 4.8\ua0eV was found between mansfieldite and strengite. The scorodite Raman OH-stretching region showed a sharp band at 3513\ua0cm and a broad band around 3082\ua0cm. The spectrum of mansfieldite was like that of scorodite with a sharp band at 3536\ua0cm and broader maxima at 3100\ua0cm and 2888\ua0cm. Substituting Al in the arsenate structure instead of Fe resulted in a shift of the metal-OH-stretching mode by 23\ua0cm towards higher wavenumbers due to a slightly longer H-bonding in mansfieldite compared to scorodite. The intense band for scorodite at 805\ua0cm was ascribed to the symmetric stretching mode of the AsO. The medium intensity bands at 890, 869, and 830\ua0cm were ascribed to the internal modes. A significant shift towards higher wavenumbers was observed for mansfieldite. The strengite Raman spectrum in the 900–1150\ua0cm shows a strong band at 981\ua0cm accompanied by a series of less intense bands. The 981\ua0cm band was assigned to the PO symmetric stretching mode, while the weak band at 1116\ua0cm was the corresponding antisymmetric stretching mode. The remaining bands at 1009, 1023 and 1035\ua0cm were assigned to υ(A) internal modes in analogy to the interpretation of the AsO bands for scorodite and mansfieldite. The variscite spectrum showed a shift towards higher wavenumbers in comparison to the strengite spectrum with the strongest band observed at 1030\ua0cm and was assigned to the symmetric stretching mode of the PO, while the corresponding antisymmetric stretching mode was observed at 1080\ua0cm. Due to the band splitting component bands were observed at 1059, 1046, 1013 and 940\ua0cm. The AsO symmetric bending modes for scorodite were observed at 381 and 337\ua0cm, while corresponding antisymmetric bending modes occurred at 424, 449 and 484\ua0cm. Comparison with other arsenate and phosphate minerals showed that both XPS and Raman spectroscopy are fast and non-destructive techniques to identify these minerals based on their differences in chemistry and the arsenate/phosphate vibrational modes due to changes in the symmetry and the unique fingerprint region of the lattice modes

X-ray Photoelectron spectroscopic and Raman spectroscopic study of bayldonite from Wheal Carpenter, Cornwall, UK

Bayldonite [CuPb(AsO)(OH)], Wheal Carpenter (Cornwall, UK) was studied by X-ray Photoelectron Spectroscopy and Raman Microscopy. X-ray Photoelectron Spectroscopy revealed single copper, lead and arsenic positions in the crystal structure. Two oxygen bands with a 1:4 ratio were associated oxygen positions in arsenate- and hydroxyl-groups, excluding the presence of acidic arsenate groups. The relatively large difference in binding energy for the two oxygen bands was interpreted as being due to the dynamic Jahn-Teller distortion of the copper octahedral in the bayldonite crystal structure. Raman microscopy showed bands at 804 and 837\ua0cm assigned to arsenate antisymmetric stretching mode and the symmetric stretching mode. Supported by the X-ray Photoelectron Spectroscopic results the bands at 726, 761, 822 and 886\ua0cm were assigned to copper-hydroxyl modes. Bands around 497\ua0cm were assigned to the arsenate antisymmetric bending modes and around 427\ua0cm to the symmetric bending modes. The 539\ua0cm band was associated with a copper-hydroxyl stretching mode or another υ. The region 250–400\ua0cm showed sharp bands at 313 and 328\ua0cm with weaker bands at 298 and 342\ua0cm assigned to copper-oxygen and/or lead-oxygen stretching modes

Intercalation of Hydrotalcites with Hexacyanoferrate(II) and (III)-a ThermoRaman Spectroscopic Study

Raman spectroscopy using a hot stage indicates that the intercalation of hexacyanoferrate(II) and (III) in the interlayer space of a Mg,Al hydrotalcites leads to layered solids where the intercalated species is both hexacyanoferrate(II) and (III). Raman spectroscopy shows that depending on the oxidation state of the initial hexacyanoferrate partial oxidation and reduction takes place upon intercalation. For the hexacyanoferrate(III) some partial reduction occurs during synthesis. The symmetry of the hexacyanoferrate decreases from Oh existing for the free anions to D3d in the hexacyanoferrate interlayered hydrotalcite complexes. Hot stage Raman spectroscopy reveals the oxidation of the hexacyanoferrate(II) to hexacyanoferrate(III) in the hydrotalcite interlayer with the removal of the cyanide anions above 250 °C. Thermal treatment causes the loss of CN ions through the observation of a band at 2080 cm-1. The hexacyanoferrate (III) interlayered Mg,Al hydrotalcites decomposes above 150 °C

Konstruksi gender dalam Novel Isinga karya Dorothea Rosa Herliany

Molecular structures of the basic copper arsenate minerals olivenite, cornubite, cornwallite, and clinoclase were studied using a combination of infrared emission spectroscopy and Raman spectroscopy. Infrared emission spectra of the basic copper arsenates were obtained over the temperature range 100 to 1000°C. The IR emission spectra of the four minerals are different, in line with differences in crystal structure and composition. The Raman spectra are similar, particularly in the OH-stretching region, but characteristic differences in the deformation regions are observed. Differences are also observed in the arsenate stretching and bending regions. Infrared emission studies show that the minerals are completely dehydroxylated by 550°C

Spectrochimica Acta Part A 62 (2005) 176-180 Raman spectroscopy of halotrichite from Jaroso, Spain

Abstract Raman spectroscopy complimented with infrared ATR spectroscopy has been used to characterise a halotrichite FeSO 4 ·Al 2 (SO 4 ) 3 ·22H 2 O from The Jaroso Ravine, Almeria, Spain. Halotrichites form a continuous solid solution series with pickingerite and chemical analysis shows that the jarosite contains 6% Mg 2+ . Halotrichite is characterised by four infrared bands at 3569.5, 3485.7, 3371.4 and 3239.0 cm −1 . Using Libowitsky type relationships, hydrogen bond distances of 3.08, 2.876, 2.780 and 2.718Å were determined. Two intense Raman bands are observed at 987.7 and 984.4 cm −1 and are assigned to the ν 1 symmetric stretching vibrations of the sulphate bonded to the Fe 2+ and the water units in the structure. Three sulphate bands are observed at 77 K at 1000.0, 991.3 and 985.0 cm −1 suggesting further differentiation of the sulphate units. Raman spectrum of the ν 2 and ν 4 region of halotrichite at 298 K shows two bands at 445.1 and 466.9 cm −1 , and 624.2 and 605.5 cm −1 , respectively, confirming the reduction of symmetry of the sulphate in halotrichite