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 NaYF 4 :Tm/Yb@NaYF 4 , 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- i -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.