Long-Range Plasmon-Induced Anisotropic Growth of an Organic Semiconductor between Isotropic Gold Nanoparticles

Plasmon-induced diazonium reduction was used to graft an organic semiconductor, namely oligo(bisthienylbenzene) (BTB), onto square arrays of gold nanoparticles (NPs) of various diameters. Grafting was evidenced by scanning electron microscopy (SEM) measurements by the extinction spectra of the localized surface plasmon resonance, as well as by Raman and energy dispersive X-ray (EDX) spectroscopies. We show that BTB is selectively deposited around the NPs. The thickness of the layer increases with increasing irradiation time and reaches a limit which depends on the size of the NPs with the thicker organic layers being generated for smaller NPs. Under polarized irradiation, BTB growth is strongly anisotropic. Starting from arrays with square gratings and spherical NPs, long-range plasmon-induced anisotropic growth makes it possible to generate in the direction of the polarized light, lines, columns, or lines and columns of NPs connected by an organic semiconductor. These results demonstrate that the growth is due to hot electrons.