Water-soluble benzylidene cyclopentanone dye for two-photon photopolymerization

A novel water-soluble benzylidene cyclopentanone dye was synthesized by introducing four sodium carboxylate groups into 2,5-Bis-[4-(diethylamino)-benzylidene]-cyclopentanone (BDEA). Its two-photon absorption (TPA) cross-section in water solution was determined by nonlinear transmission method with Ti:sapphire femtosecond laser as exciting light source. 287 GM at 800 nm was obtained, which was quite larger than TPA cross-section of water-soluble xanthene dyes. Using this new dye as initiator, two-photon polymerization (TPP) of water-soluble acrylate could be induced directly. Low threshold energy of 0.51 mW and a high resolution of 400 nm were achieved, indicating this dye would have extensive application prospects in TPP under aqueous environments.