Electron paramagnetic resonance, optical absorption, IR and Raman spectral studies on pelecypod shell

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Abstract

Pelecypod shell originated from Kolleru lake of Andhra Pradesh is used in the present work. It contains Mn(II) and Fe(III) in traces. The EPR spectrum of the compound is due to Mn(II) which is in three independent sites. The three g values are evaluated with slight differences. The hyperfine component varies from 9.33 to 9.49 mT. The zero field splitting parameter is also ranges from 43.8(1) to 44.1(1) mT. Using the covalence parameter the number of ligands around metal is estimated as 20. In EPR spectrum Fe(III) is identified. The optical absorption spectrum is attributed to Mn(II) in octahedral geometry. Further 10 Dq band is attributed to Fe(II) in the optical absorption spectrum. NIR spectral results are due to water fundamentals, whereas IR and Raman spectrum is due to carbonate ion fundamentals.

Introduction

Soft-bodied un-segmented animals with shell either external or internal placed under the phylum mollusca. Based on external features mollusca is classified into five classes. They are amphineura, scaphopoda, gastropoda, pelecypoda and cephalopoda. Ox-shaped foot bearers are pelecypods. In these, two shell valves externally cover the body. They usually live nearly buried in mud or sand at the bottom of fresh water pond or lake. When the structure of shell is observed through a cross-section it consists of three layers called periostracum, prismatic layer and pearly layer. Among these periostracum is the outermost greenish-brown thin, translucent, horny layer, formed by a chitin-like horny organic substance, the conchiolin. The prismatic layer is the middle layer consists of minute prisms or crystals of calcium carbonate and gives strength to the shell. Pearly layer or nacreous layer consists of a smooth iridescent surface. Further it contains alternate layers of calcium carbonate and conchiolin. Soft body parts, outer periostracum and middle prismatic layers of the dead animal gradually get decomposed by the action of microorganisms. The organic substance present in the pearly layer of shell gradually undergoes fossilasation. Under these circumstances calcium ions may be replaced by magnesium, manganese, iron ions. The proportion of the CaCO3 in the entire shell varies from 89 to 99%, whereas that of phosphate of lime from 1 to 2% [1]. Mollusca fossils have the importance in identifying petroleum or valuable oil deposits and also in the preparation of pearl. Electron paramagnetic resonance (EPR) studies on the shells of seawater mussel mytilus conradinus and the exoskeletons of fresh water snail, pila globosa were reported [2], [3]. No attempt has been made with respect to optical absorption and electron paramagnetic resonance (EPR) studies on pelecypod shell. Therefore in this work the authors report the EPR, optical absorption, Raman and IR spectral studies of pelecypod shell at room temperature.

Section snippets

Experimental studies

A pink powdered sample of pelecypod from Kolleru, Andhra Pradesh, India (Museum No.: R1017) is used in the present work. EPR spectra of the powdered sample are recorded at room temperature (RT) on JEOL JES-TE100 ESR spectrometer operating at X-band frequencies (υ = 9.1–9.5 GHz), having a 100 kHz field modulation to obtain a first derivative EPR spectrum. DPPH with a g value of 2.0036 is used for g factor calculations. Optical absorption spectrum of the sample was recorded at room temperature in the

IR and Raman spectroscopy

For the analysis of vibrational spectra of pelecypoda shell both ATR-IR and Raman spectra are shown in Fig. 5(a) and (b) one over the other for convenience. The vibrational analytical data with other reported [26], [27], [28] samples are presented in Table 4. The intense sharp band observed in IR spectrum at 874 cm−1 has been assigned to ν2(A2) mode [29]. The broad band at 1419 cm−1 with maximum half width and with two components (1309 and 1402 cm−1) are assigned to ν3(E) mode of CO32− ion and is

Conclusions

  • 1.

    The EPR results of the shell sample shows that both Fe(III) and Mn(II) are present in the compound and Mn(II) present in distorted octahedral environment. The percentage of covalency obtained for Mn(II) is 6%. The observed and calculated A values are in good agreement. Also the EPR results suggest that Mn(II) is placed between four carbonate ions and two oxygen atoms octahedral geometry.

  • 2.

    The optical absorption studies indicate that Mn(II) ion in the sample is present in distorted octahedral

References (30)

  • K.V. Narasimhulu et al.

    Spectrochim. Acta

    (2000)
  • R.L. Frost et al.

    Thermochim. Acta

    (2004)
  • P. Samba Siva Rao

    Spectrochim. Acta

    (1996)
  • A.M.F. Benial et al.

    Spectrochim. Acta

    (1999)
  • Y.N. Naidu et al.

    Polyhedron

    (1992)
  • S. Lakshmi Reddy et al.

    Spectrochim. Acta

    (2006)
  • K.V. Narasimhulu et al.

    Spectrochim. Acta

    (2000)
  • R.L. Kotpal

    Mollusca

    (1978)
  • C.P. Lakshmi Prasuna et al.

    Spectrochim. Acta

    (2004)
  • R.L. Frost et al.

    Raman Spectrosc.

    (2003)
  • B. Bleaney et al.

    Electron Paramagnetic Resonance of Transition Ions

    (1970)
  • L.K. White et al.

    J. Phys. Chem.

    (1977)
  • O. Matumura

    J. Phys. Soc. Jpn.

    (1959)
  • E. Simanck et al.

    J. Phys. Chem. Solids

    (1970)
  • V. Wieringen

    Discuss. Faraday Soc.

    (1955)

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