Mechanism of automotive clearcoat damage by dragonfly eggs investigated bysurface enhanced Raman scattering

Dragonflies are attracted by the reflection of sunlight on car surfaces and lay their eggs on the clearcoat resin. Considering that the surface can re ach up to 93 degrees C and that during the egg hardening process (sclerotiz ation) H2O2 is released, cysteine and cystine residues present in the egg p rotein can be oxidized to sulfinic and sulfonic acids. These are strong aci ds which, like acid rain, can hydrolyze the acrylic/melamine resin causing damage where the eggs were laid. Confocal Raman spectroscopy revealed that the spectra obtained from damaged and intact portions of the clearcoat were similar, in agreement with infrared absorption spectroscopy data. These da ta demonstrate that the attack by eggs, H2SO4 and cysteine/H2O2 only promot es solubilization of resin through acid hydrolysis of the resin eater and a mide moieties. Furthermore, surface enhanced Raman scattering (SERS) spectr a obtained from dragonfly eggs and cysteine/H2O2 reaction products treated with a silver colloid were very similar, thus confirming the presence of su lfinic and sulfonic acids. (C) 2000 Elsevier Science Ltd. All rights reserv ed.