文摘
Gold-nanoparticles (AuNPs) protected by thiolates of methylthio end-capped terthiophene 1a and quaterthiophene 2a partially annelated with bicyclo[2.2.2]octene (BCO) unit(s) were designed and synthesized. AuNP covered with nonannelated terthiophene 3a was also synthesized for comparison. The formation of the AuNPs was confirmed by absorption spectra and transmission electron microscopy (TEM) measurements. The electric conductivities of AuNP-1a鈥?/b> and AuNP-3a鈥?/b> films were moderate (10鈥? S cm鈥?) due to conduction through core-to-core tunneling, whereas the conductivity of AuNP-2a鈥?/b> films was very low (<10鈥? S cm鈥?). The low conductivity of AuNP-2a鈥?/b> films would be due to a larger separation distance between the particles by two sterically demanding BCO units as suggested by the TEM analysis and DFT calculations. Importantly, after doping with iodine vapor, the enhancements in the conductivities of AuNP-1a鈥?/b> and AuNP-3a鈥?/b> were only 4- and 10-fold, respectively. In sharp contrast, the conductivity of AuNP-2a鈥?/b> after I2-doping was increased by more than 104-fold. The latter conductivity was comparable to the previously reported conductivities of AuNPs directly linked by oligothiophenes, and these results are consistent with the hypothesis that the electric conduction through 蟺-dimers of oxidized oligothiophenes is as effective as through covalently linked oligothiophenes.
