Nanohybrid Assemblies of Porphyrin and Au10 Cluster Nanoparticles.

Mariachiara Trapani,Giovanna De Luca,Maria Angela Castriciano,Andrea Romeo,Giulietta Smulevich,Nelson Machado,Barry D Howes,Luigi Monsù Scolaro

doi:10.3390/nano9071026

Abstract

The interaction between gold sub-nanometer clusters composed of ten atoms (Au10) and tetrakis(4-sulfonatophenyl)porphyrin (TPPS) was investigated through various spectroscopic techniques. Under mild acidic conditions, the formation, in aqueous solutions, of nanohybrid assemblies of porphyrin J-aggregates and Au10 cluster nanoparticles was observed. This supramolecular system tends to spontaneously cover glass substrates with a co-deposit of gold nanoclusters and porphyrin nanoaggregates, which exhibit circular dichroism (CD) spectra reflecting the enantiomorphism of histidine used as capping and reducing agent. The morphology of nanohybrid assemblies onto a glass surface was revealed by atomic force microscopy (AFM), and showed the concomitant presence of gold nanoparticles with an average size of 130 nm and porphyrin J-aggregates with lengths spanning from 100 to 1000 nm. Surface-enhanced Raman scattering (SERS) was observed for the nanohybrid assemblies.

Highlights

Gold metal nanoparticles with diameters smaller than ~2 nm have received considerable interest in nanoscience because they can be controlled with atomic precision, and, due to discrete energy levels and molecular-like HOMO–LUMO transitions, exhibit optical features fundamentally different from those of larger nanoparticles [1]
The morphology of nanohybrid assemblies onto a glass surface was revealed by atomic force microscopy (AFM), and showed the concomitant presence of gold nanoparticles with an average size of 130 nm and porphyrin J-aggregates with lengths spanning from 100 to 1000 nm
These aggregates are formed under acidic conditions and the partially protonated porphyrins are arranged in a lateral stacking geometry, which leads to the occurrence of very peculiar optical properties [43,44]

Summary

Introduction

Gold metal nanoparticles with diameters smaller than ~2 nm have received considerable interest in nanoscience because they can be controlled with atomic precision, and, due to discrete energy levels and molecular-like HOMO–LUMO transitions, exhibit optical features fundamentally different from those of larger nanoparticles [1]. The formation, in aqueous solutions, of nanohybrid assemblies of porphyrin J-aggregates and Au10 cluster nanoparticles was observed.

Results

Conclusion