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

Abstract

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.