Strong Interfacial Electronic Coupling Between Porphyrins and Au Nanoparticles through Carbodithioate-Based Linker Groups

Tae-Hong Park and Michael J. Therien

UV-vis and emission spectra (inset) of 1-Au (black) and 2-Au (red). Excitation spectrum of 1-Au (blue).

• Porphyrin functionalized gold nanoparticles, 1-Au and 2-Au were obtained via ligand exchange reactions.
   
• The mean core sizes of 1-Au and 2-Au are ~2 nm.
   
• The electronic absorption spectrum of 1-Au shows a novel band that tails past 650 nm and is not observed in the corresponding 2-Au spectrum.
   
• 1-Au emits with large Stokes shift at 77 K, while 2-Au does not.
   
• The 1-Au excitation spectrum demonstrates that the low-temp emission derives from an excited state populated by absorption at wavelengths > 650 nm.
   
• 1-Au’s absorptive and emissive states derive from a charge resonance interaction between the porphyrin chromophores and the Au surface mediated by the π-conjugated ethynyl-benzodithioate moiety.