Raman investigation of pigmentary molecules in the molluscan biogenic matrix

Raman spectra of the pigments of several marine mollusc shells have been obtained using the 514.5 nm laser line of an Ar+ laser. Shell species were chosen to obtain a variety of colour. The spectra obtained for the molluscan pigments indicated that they are polyacetylenic in nature, and, from the spectral features, it was deduced that the pigments were carotenoids, with unmethylated polyacetylenic backbones of various conjugation lengths. A logarithmic relationship was established between the number of conjugated double bonds (N) and the C=C vibration (vi) of previous reported data for finite polyacetylenic systems, and this relationship was used to evaluate the data obtained in this study. The aragonite and calcite phases of CaCO3 were also identified to be present in different species of molluscs. Copyright (C) 2006 John Wiley & Sons, Ltd.