Synthesis and characterization of a sulfur-containing phthalocyanine-gold nanoparticle hybrid

This work reports on the synthesis and characterization of a new gold nanoparticle-zinc phthalocyanine system, AuNP-S(Bu-t)(3) ZnPc, prepared by a ligand exchange reaction of tetraoctylammonium bromide with a novel unsymmetrically substituted zinc phthalocyanine which contains one thioester group in the peripheral position [AcS(Bu-t)(3) ZnPc]. The AuNp-S(Bu-t)(3) ZnPc hybrid was characterized using UV-vis and H-1 NMR spectroscopies. Transmission electron microscopy allowed the estimation of the size, which was calculated to be similar to 5 nm. AuNPs-S(tBu) 3 ZnPc conjugate showed much lower fluorescence quantum yield values than the AcS(Bu-t)(3) ZnPc demonstrating either an energy or electron transfer from the ZnPc to the AuNP. The AuNP-S(Bu-t)(3) ZnPc hybrid has been anchored to a TiO2 semiconducting layer using lipoic acid. A solid configuration of TiO2 -lipoic acid-AuNP-S(Bu-t)(3) ZnPc has been prepared by anchoring lipoic acid to the TiO2 (TiO2 -LA) and introducing later the TiO2 -LA with free thiol groups in a toluene solution of AuNP-S(Bu-t)(3) ZnPc. We have also observed by UV-vis and fluorescence measurements the importance of the ZnPc in avoiding AuNP aggregation on the TiO2 surface.