Photophysics of tetracarboxy-zinc phthalocyanine photosensitizers

Zinc-tetracarboxy-phthalocyanine (ZnPc(COOH)(4)) was synthesized by a melting method and basic hydrolysis. A ZnPc(COOH)(4)/Fe(3)O(4)/Ch composite was prepared by immobilization of ZnPc(COOH)(4) onto Fe(3)O(4)/chitosan nanoparticles by a simple immersion method. The photophysical properties were studied using UV-vis spectrophotometry, fluorescence spectroscopy and time-correlated single photon counting (TCSPC) in different aqueous solutions. The UV-vis spectra of the ZnPc(COOH)(4)/Fe(3)O(4)/Ch composite displays absorption by the aromatic rings, with a Q band exhibited at λ(max) = 702 nm. Moreover, the ZnPc(COOH)(4)/Fe(3)O(4)/Ch composite exhibits long triplet-state lifetimes of 1.6 μs and 12.3 μs, crucial for application as a photosensitizer. A triplet quantum yield of 0.56 for the ZnPc(COOH)(4)/Fe(3)O(4)/Ch composite in DMSO/H(2)O was achieved. FTIR showed that the conjugation of ZnPc(COOH)(4) with Fe(3)O(4)/chitosan nanoparticles was achieved by electrostatic interaction.