Optical properties and sensor applications of bimetallic nanostructures of porphyrins

Abstract

The cationic Cu(II) and Fe(III) complexes of tetra(4-pyridyl)porphyrin [T4PyP]4+ have been combined with the anionic [H4TPPS]2− to obtain bimetallic J-aggregate nanostructures defined by the tendency to form the FeIIIOCuII bridge along with electrostatic interactions. The Resonant Raman spectra of the bimetallic structures revealed subtle but detectable changes of two significant bands: 661 cm−1 (attributed to the out-of-plane bending of the Cusingle bondN bond) and 805 cm−1 (sensitive to the nature of the axial ligand opposite to the oxo ligand), both indicating the important role of the metallic centers in the formation of the CuFe nanorod aggregate. The sensing performance of the aggregates was explored monitoring the absorbance changes in the visible region induced by adding different analytes (H2O2, NO2−, SO32− and N3−). The bimetallic nanostructures maintain the J-aggregation structure after successive addition of H2O2 with an increasing absorption response at 435 cm−1 (monomer band); this architecture was the most sensitive arrangement confirming the synergic effect of the two metals.