Mediated Generation of Conjugate Acid by UV and Blue Sensitizers with Upconversion Nanoparticles at 980 nm.

NIR and UV exposure of systems comprising upconversion nanoparticles (UCNP) based on NaYF4 :Tm/Yb@NaYF4 , a sensitizer absorbing either in the blue or UV region, and an onium salt with weak coordinating anion resulted in formation of conjugate acid (con-H+ ). That was namely Ivocerin (di(4-methoxybenzoyl)diethylgermane), ITX (2-iso-propyl thioxanthone), anthracene, pyrene, rubrene, camphore quinone, and a strong fluorescent coumarin (1,1,6,6,8-pentamethyl-2,3,5,6-tetrahyhdro-1H,4H-11-oxa-3a-aza-benzo[de]anthracene-10-one). Quantification occurred by treatment with Rhodamine B lactone whose color switched to intensive red after photolytic formation of con-H+ . Exposure with a NIR laser at 980 nm resulted in less con-H+ compared to 395 nm where all sensitizers absorb radiation. UCNP did not mainly interfered formation of con-H+ . The different rates obtained in both experiments responsibly explain the failure and success to initiate polymerization of epoxides applying ether 980 nm or 395 nm excitation, respectively.