Infrared Spectroscopy Characterization of Marine Shells
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Infrared Spectroscopy Characterization of Marine Shells Octavio Gomez-Martinez1, Daniel H. Aguilar1, Patricia Quintana1, Juan J. Alvarado-Gil1, Dalila Aldana2, Laura L. Diaz-Flores, Martin Yañez-Limon, Cinvestav-Unidad Querétaro Libramiento Norponiente No. 2000, Fracc. Real de Juriquilla. Querétaro, Qro. 76230 México 1 Applied Physics Department 2 Marine Resources Department Cinvestav-Unidad Mérida, C. Ant. a Prog. km. 6, A.P. 73 Cordemex, Mérida Yucatán, 97310, México ABSTRACT Fourier Transform infrared spectroscopy has been employed to study the shells of two kind of mollusks, American oysters (Crassostrea virginica) and mussels (Ischadium recurvum). It is shown that it is possible to distinguish the different calcium carbonate lattice vibrations in each case, mussel shells present aragonite vibration frequencies, and the oyster shells present those corresponding to calcite. The superposition, shift and broadening of the infrared bands are discussed. Changes in the vibration modes due to successive thermal treatments are also reported. INTRODUCTION During the last few years an important interest on biomineralized materials has been developed, not only for their importance in the basic study of the mechanisms of biomineralization, but these materials show interesting and outstanding optical, thermal and mechanical properties [1,2]. In particular the study of the biomineralized materials has been performed by a wide variety of techniques [2,3]. It is well known that the involved process and the control of the living organism on the material growth leads to a wide variety of interesting differences in similar organisms depending on environmental conditions. One of the most interesting issues involved is the development of calcium carbonate by mollusks in its different polymorphs as calcite and aragonite. In this paper the infrared molecular modes of vibration of the shells of mollusks are analyzed by Fourier transform infrared spectroscopy. Our main purpose is the detailed analysis of the infrared bands and their superposition: in order to get a better understanding of these mechanisms the infrared spectra of the shells under thermal treatment are also reported. Two species living in the same environment have been chosen; American oyster (Crassostrea virginica) and mussel (Ischadium recurvum). In these species it has been shown that the heat transport in the shells is strongly influenced by the corresponding crystalline structure [4].
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EXPERIMENTAL DETAILS Oysters and mussels were sampled in the Mecoacan Tabasco lagoon in Mexico. The sampled animals were transported to Merida City in isothermic containers. The approximate age of the animals was about a year. Mollusks were detached from the shells, these were cleaned with detergents, then the shells were powdered in a ceramic mortar up to obtaining a very fine powder. The obtained samples were mixed using 95% of KBr and 5% of the sample and pressed into pellets. The infrared spectra were obtained using a Fourier Transform Infrared Spectrometer, Nicolet Avat
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