Laser treatment of tattoo pigment PG-36

Worldwide, tattooed population has been significantly increasing for a long time, especially among young people (1). To date, because of an improved self-image or social stigmatization, we simultaneously observe the opposite tendency: many tattooed individuals undergo a therapy of tattoo removal, the most common removal pathway being treatment with Q-Switch laser. In spite of this, few though remarkable investigations have been carried out aimed at understanding the tattoo inks decomposition patterns (2-3). Inks are typically made of two components: the pigment and the vehicle. In the present study, we investigate the chemical processes, and the morphological changes following the laser and ultrasound treatment of the pigment commercially known as PG36, a fully halogenated copper-phtalocyanate, with formula C32H16Br6Cl10N8Cu (Fig. 1a) which imparts yellowish green color to some of the most common inks on the market. Laser treatments were carried out with a Nd:YAG laser, operating at 532 nm, with a fluence of 50 mJ/mm2, on two different dispersions of the pigment, i.e. in isopropanol and in water. The decomposition fragments were, then, analyzed by GC-mass. The morphology variations were monitored by Scanning Electron Microscopy. In Fig. 1b) and c) the SEM micrographs are reported before and after 30 minutes sonication of the pigment with The ultrasound treatment, change the morphology from the typical b arrangement of the phtalocyanine aggregates to roundish agglomerates. The rearranged compound still contain Br and Cl, though it cannot be inferred whether a fragmentation occurred. We found out that the laser treatment yields very complex fragmentation patterns, which include the generation of toxic fragments such as BrCN and ClCN, regardless of the dispersion solvent.