Preparation and application of thionin-bridged graphene-gold nanoparticle nanohybrids

A universal approach for controllable assembly of gold nanoparticles (AuNPs) on chemically reduced graphene oxide (rGO) is presented. AuNPs were conjugated to thionin (TH)-modified rGO through formation of amide bonds. TH has been used as a bridge to link the AuNPs with rGO in this work. The as-prepared AuNP-TH-rGO nanohybrids were characterized by means of transmission electron microscopy (TEM), ultraviolet-visible-near infrared spectroscopy (UV-vis-NIR), X-ray photoelectron spectroscopy (XPS), Fourier Transform infrared (FTIR) and Raman measurements. The experimental results indicate that the particle size and distribution density of AuNPs on the graphene sheets can be well controlled by adjusting the original size and concentration of AuNPs in the reaction mixture. The AuNPs on the surface of graphene were stable under harsh treatment (e.g., acid, alkaline or ultrasonic treatment). Ligand exchange experimental results show that the AuNP-TH-rGO can be easily further functionalized by sulfhydryl-containing ligands. Compared to poly-L-lysine (PLL) coated rGO, PLL coated AuNP-TH-rGO shows higher NIR absorbance and more effective photothermal efficiency.