*Article* **Nanohybrid Assemblies of Porphyrin and Au10 Cluster Nanoparticles**

#### **Mariachiara Trapani 1, Maria Angela Castriciano 1,\*, Andrea Romeo 1,2, Giovanna De Luca 2, Nelson Machado 3, Barry D. Howes 3, Giulietta Smulevich 3 and Luigi Monsù Scolaro 1,2,\***


Received: 26 June 2019; Accepted: 16 July 2019; Published: 18 July 2019

**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.

**Keywords:** gold clusters; plating; porphyrin; chirality; SERS
