Preparation and characterization of SDS-stabilized hydrophobic porphyrinic nanoaggregates in water

Porphyrin nanoaggregates formed in the interior of colloidal suspensions can be considered as examples of supramolecular systems with self-organized architecture. Due to their peculiar optical and electrochemical properties such as decrease of fluorescence, increase of conductivity and possible electron transfer, these aggregates can be used in the design and fabrication of optoelectronic devices, such as organic solar cells and optical and electrochemical sensors. In this paper, we first describe the synthesis of a series of hydrophobic tetraphenylporphyrins by a change in the order of reagents addition that results in high yields of the desired products. These products were then employed to obtain stable suspensions of porphyrinic nanoaggregates in aqueous solutions of sodium dodecyl sulfate (SDS). The aggregates resulting of the encapsulation of the tetraphenylporphyrins into the micelles of the surfactant were studied by dynamic light scattering (DLS), atomic force microscopy (AFM) and UV-vis and fluorescence spectroscopies. The results indicate that the nanoggregates have a spherical morphology with particles whose average size ranges between 46–78 nm and ζ-potential values (higher than 55 mV), indicative of excellent stability. Optical characterization was used to determine the classification of nanoaggregates, according to the observed shifts on the absorption spectra.