Two-Photon Acid Generation Systems Based on Dibenzylidene Ketone Dyes Intermolecular Sensitization

Abstract

A couple of two-photon absorption dyes containing triphenylamine groups as the electron donor were synthesized. They were combined with commonly used photoacid generator <i>N</i>-(trifluoromethanesulfonyloxy)-1,8-naphthalimide (NIOTf) to build two-photon acid generation systems (2PAGs). The photochemical and photophysical properties of these dyes as well as their photosensitizing mechanism were investigated. Both of the two dyes have a greatly enhanced two-photon absorption cross-section over 1000 GM. The photoacid quantum yields of 2PAGs were measured in acetonitrile solution by one-photon process. Fluorescence quenching experiments were carried out and confirmed the electron transfer mechanism in resin films. Also, the acid-catalyzed chemical amplification processes in resin films were studied with a Ti/sapphire regenerative amplifier by attenuated total reflectance Fourier transform infrared spectroscopy, and both 2PAGs exhibited superior efficiencies via two-photon absorption in comparison with isopropylthioxanthone/NIOTf system and NIOTf itself. The two-photon lithography (TPL) was carried out on a Ti/sapphire femtosecond laser system successfully with chemically amplified positive resists based on the achieved 2PAGs and the proceeding power for TPL was as low as 0.24 mW. The results suggest that these 2PAGs can be used as high-efficiency initiator for two-photon chemically amplified positive resist