Controlling the assembly and spin transport of tetrathiafulvalene carboxylate coated iron oxide nanoparticles

We report a solution phase based assembly method to tune the transport mechanism and magnetoresistance (MR) of Fe3O4 nanoparticles (NPs). The NP topological arrangement is altered by the NP coating of tetrathiafulvalene carboxylic acid (TTFCOOH) or its dicarboxylic analogue (TTF(COOH)(2)). Consequently, the transport mechanism of the assembly switches from tunneling to Mott hopping. The MR ratios of the Fe3O4 NP assemblies can be further tuned by the polarity of the solvent used in the ligand exchange process. The TTF(COO)(2)-coated Fe3O4 NP assembly has a 5% room temperature MR ratio, which is the highest value among all TTF-COO-Fe3O4 NP assemblies reported so far.