Laser-Induced Formation of Metal−Molecule−Metal Junctions between Au Nanoparticles As Probed by Surface-Enhanced Raman Spectroscopy

Laser power dependent p-aminothiophenol (PATP) adsorption on Au nanoparticles (NPs) has been systematically investigated using surface-enhanced Raman spectroscopy. Molecular junctions (MJs) were found to form between NPs with the quinonoid PATP as the bridge molecule with an external energy provided by the incident laser. The relative Raman intensities of b2 modes to a1 modes increased with the increasing laser power. The abnormal enhancement of b2 modes is most possibly attributed to the laser-induced formation of the quinonoid PATP molecule. The formation of MJs depends on the laser illumination time, the aggregation states of NPs, and the surface coverage of PATP. Furthermore, the MJs formation process is reversible, which depends on the laser power and the illuminated time.