Presence Of AuNPs Research Articles

Gold Nanoparticle Enhanced Charge Transfer in Thin Film Assemblies of Porphyrin−Fullerene Dyads

Photoinduced vectorial electron transfer in a molecularly organized porphyrin-fullerene (PF) dyad film is enhanced by the interlayer charge transfer from the porphyrin moiety of the dyad to an octanethiol protected (dcore approximately 2 nm) gold nanoparticle (AuNP) film. By using the time-resolved Maxwell displacement charge (TRMDC) method, the charge separation distance was found to increase by 5 times in a multilayer film structure where the gold nanoparticles face the porphyrin moiety of the dyad, that is, AuNP|PF, compared to the case of the PF layer alone. Films were assembled by the Langmuir-Blodgett (LB) method using octadecylamine (ODA) as the matrix compound. Atomic force microscopy (AFM) images of the monolayers revealed that AuNPs are arranged into continuous, islandlike structures and PF dyads form clusters. The porphyrin reference layer was assembled with the AuNP layer to gain insight on the interaction mechanism between porphyrin and gold nanoparticles. Interlayer electron transfer was also observed between the AuNPs and porphyrin reference, but the efficiency is lower than that in the AuNP|PF film. Fluorescence emission of the reference porphyrin is slightly quenched, and fluorescence decay becomes faster in the presence of AuNPs. The proposed mechanism for the electron transfer in the AuNP|PF film is thus the primary electron transfer from the porphyrin to the fullerene followed by a secondary hole transfer from the porphyrin to the AuNPs, resulting in an increased charge separation distance and enhanced photovoltage.

Synthesis of nanocomposite gold-semiconductor materials by seed-growth method

Gold-semiconductor nanocomposite hybrid materials were synthesized by applying the seed-growth approach. Citrate stabilized gold nanoparticles were prepared by the reduction of HAuCl 4 with borohydride and used as seeds. The structural and morphological features of semiconductor materials i.e. CdS, CuS, NiS, and PbS in the presence of Au NP were examined with the help of UV–Visible spectroscopy, phase contrast microscopy, transmission electron microscopy (TEM) and X-ray diffraction measurements. The experimental results revealed that a network of semiconductor-Au NP nanocomposite material is formed in each case.