Electrical Characterization\nof Self-Assembled 1D Gold\nNanoparticle Chains: Implications for Chemiresistor Sensors

The introduction\nof dipoles on gold nanoparticle surfaces\nprovides\nthe formation of chain-like nanoparticle assemblies in solution under\nambient conditions. Here, we present studies on influencing and controlling\nthe strength of the induced dipole by thiols. Aromatic thiols lead\nto enhanced surface dipoles, where electron-donating functions can\nfurther increase the interaction. Thereby, particle–particle\ndistances and chemical environment at the particle interface were\nmanipulated, which resulted in different tunneling resistances <i>R</i><sub>g</sub> in these 1D structures. Here, <i>R</i><sub>g</sub> seemed to be mostly dominated by the interparticle distance\nrather than the type of ligand. Temperature-dependent current–voltage\nmeasurements of thiol-bearing nanoparticle chains revealed two different\ntransport mechanisms. For temperatures <170 K, a thermally activated\nelectron tunneling takes place, which depends on the charging energy <i>E</i><sub>c</sub>. Whereas for higher temperatures, a transition\nto an electron hopping process occurs determined by the involved thiol\nand nanoparticle shape. For structures with strong interparticle electronic\ncoupling, the conduction mechanism is almost temperature-independent,\nwhich makes them promising candidates for highly sensitive chemiresistor\nsensors.