Novel 3,4-disubstituted thiophenes for weak passivation of Au nanoparticles

Novel self-assembled monolayers of 3,4-disubstituted thiophenes (3,4-dioctylthiophene and 3,4-diheptyloxythiophene) were prepared and characterized by contact angle measurements, ellipsometry and X-ray photoelectron spectroscopy. In addition, Au nanoparticles passivated with the 3,4-disubstituted thiophenes (3,4-dioctylthiophene and 3,4-diheptyloxythiophene) and monosubstituted thiophene (3-octylthiophene) were synthesized and characterized by UV/visible spectroscopy, transmission electron microscopy and dynamic light scattering. The Au nanoparticles had diameters in the range 5–7 nm. The Au nanoparticles stabilized with the thiophene derivatives were, as expected, less stable than the Au nanoparticles passivated with decanethiol and didecylsulfide. Surprisingly, the particles passivated with the monosubstituted 3-octylthiophene were more stable than the 3,4-dioctyl and 3,4-diheptyloxythiophene passivated particles. Such lower stability Au nanoparticles may find uses as negative tone resists in the formation of nanowires by e-beam lithography, via the more readily cleavable Au–S bond