Optical and paramagnetic properties of size-controlled ink particles isolated from Sepia officinalis

The optical and paramagnetic properties of size-controlled ink particles isolated from ink sacs of Sepia officinalis were investigated. Topographic images of atomic force microscopy (AFM) revealed that the average heights of the large and small ink particles were 156 nm and 5.3 nm respectively. The ultraviolet-visible (UV-VIS) spectral features of aqueous solutions of ink particles were dependent on particle size. Electron spin resonance (ESR) spectra suggested that the ink particles are highly pure for paramagnetic species and are of reliable quality. These size-controlled ink particles are suitable for a basic study of melanin-related materials.