Near-infrared tetra-substituted aluminum 2,3-naphthalocyanine dyes for optical fiber applications

The synthesis and spectral characterization of several tetra-substituted aluminum 2, 3-naphthalocyanine dyes for the determination of metal ions is reported. The synthesis is done by means of a homogeneous phase reaction, replacing the previously used heterogeneous method. The new scheme allows for improved product yields, higher purity, better product reproducibility and can be monitored at different stages using UV-Vis-near-infrared spectroscopy. The incorporation of electron-donating or -withdrawing groups was found to influence the product yield and to cause a shift in the absorbance maximum. The typical shift in the excitation maximum (of up to 27 nm) enables the dye to match the output of semiconductor laser diodes. In addition the tetra-substituted groups were capable of undergoing an ion-exchange process with the metal ions which produced a change in the fluorescence signal of the dye. Similar results were achieved using an optical fiber metal probe. The detection of metal ions using the near-infrared dyes was accomplished via steady-state fluorescence using both a commerically available instrument and a fiber optic system and also via the fluorescence lifetime technique.