Complementary microstructural and chemical analyses of Sepia officinalis endoskeleton

Cuttlebone exhibiting high compressive strength is a very interesting material from the biomimetic materials' technology point of view. Its microstructure and chemical composition were characterized by complementary analytical techniques. Structural features of the skeleton were revealed by SEM, micro-Raman, FT-IR and XRD measurements. XRD analyses showed that the only mineral phase present in the samples is aragonite. 2D-maps obtained from micro-Raman analyses for peaks attributed to aragonite (1100 cm-1) and chitin (1660 cm-1) revealed that the septa are richer in chitin and pillars in aragonite. 2D-distributions of elements detected by a electron microprobe showed that Ca-rich locations are poor in Mg, Na, and Br. Ca is mainly present at those locations where aragonite prevails. Bromine, sodium and magnesium are most likely located in the organic matrix. The average content of the elements, as determined by ICP-OES, was: Na - 1.0%, Mg - 0.133%, K - 0.26%, Fe - 0.03% and Sr - 0.28%. Using the elemental CHN analysis the following amounts of nitrogen, carbon and hydrogen were detected: 1.42%, 15.36% and 0.68%, respectively. The elemental analysis together with TGA measurements allowed evaluating the approximate concentration of organic matter in the cuttlebone at the level of 10%.