Photophysics of tetracarboxy-zinc phthalocyanine photosensitizers

Abstract

Zinc-tetracarboxy-phthalocyanine (ZnPc(COOH)₄) was synthesized by a melting method and basic hydrolysis. A ZnPc(COOH)₄/Fe₃O₄/Ch composite was prepared by immobilization of ZnPc(COOH)₄ onto Fe₃O₄/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/Fe₃O₄/Ch composite displays absorption by the aromatic rings, with a Q band exhibited at λ_max = 702 nm. Moreover, the ZnPc(COOH)₄/Fe₃O₄/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/Fe₃O₄/Ch composite in DMSO/H₂O was achieved. FTIR showed that the conjugation of ZnPc(COOH)₄ with Fe₃O₄/chitosan nanoparticles was achieved by electrostatic interaction.