Photothermal methods as tools for investigation of weakly interacting non-fluorescent phthalocyanines

In this paper, we report the spectroscopic properties of two newly synthesized phthalocyanines when substituted with short and long alkyl chains dissolved in dimethyl sulfoxide. The dyes are non-fluorescent and show a weak tendency for dimer formation. The aggregation process is not clearly visible in the absorption spectra. Therefore, steady-state and time-resolved photothermal methods were applied to evaluate the existence of the dye aggregates and their influence on spectral parameters of the investigated dyes.