Conjugates of Zinc Tetramethylpyridylporphyrinate with Colloidal Gold Nanoparticles Stabilized with Citrate

Due to electrostatic interaction of Au 30900 /Cit colloidal nanoparticles with 5,10,15,20-tetrakis(4’-N-methylpyridyl) porphine complex with zinc two different nanoconjugates of constant composition are formed one after another, the UV-Vis spectra of which differ from those of initial reagents. The formation of the first, more stable, compound is accompanied by a decrease in intensity and a red shift of the Soret bands and surface plasmon resonance (SPR) band of the conjugated reagents, which retain their spectral identity. The formation of the second conjugate is accompanied by an increase in the intensity of the Soret band while the SPR band is not changed significantly. It has been suggested that the first to form is a nanoconjugate with only one tetracation, which reduces the ability of the nanoparticle to further conjugation.