Synthesis and Characterization of Porphyrin-Functionalized Shell-Isolated GoldNanoparticles for Metal Ion Detection

Porphyrins provide a versatile spectroscopic probe for the detection of toxic heavy metal ions. Chelation with transition metals can result in measurable changes in their spectral signatures by absorbance, fluorescence, and Raman scattering. These can be amplified by near-by interactions with gold nanoparticles. Synthesis of silica coated gold nanoparticles functionalized with 9,10,15,20-tetrakis (4-aminophenyl 1)-21H,23H-porphyrin (TAPP) with an undecyl link is described. This material was characterized for potential detection of Zn2+, Cu2+, and Cd2+ in aqueous solutions. Metal-ion dependent shifts in the Soret absorption band were distinguished using Principal Component Analysis (PCA). Detection by fluorescence for each metal ion using this material was observed at concentrations of 1.5 x 10-5 M. Finally, a Raman enhancement factor of 5.7 was observed.