Ligand-Driven Exchange Coupling in Graphene-Based Magnetic Materials

Abstract

Several forms of graphene-based magnetic materials have been investigated via density-functional theory utilizing dispersion correction and full geometry optimization. Our calculated results show that the perinaphthenyl radical (R 1 ) has a spin of 1/2. However, in its [R 1 ] 2 dimer structure, the net spin becomes zero due to an antiferromagnetic spin-exchange between radicals. To avoid antiferromagnetic spin-exchange of identical face-to-face radicals, the alternating stack of composition R 1 /D 25 /R 1 (with D 25 = graphene-based diamagnetic molecule C 34 H 16 ) has been designed and investigated. As expected, our calculated results con rm that the alternating stack R 1 /D 25 /R 1 has a ferromagnetic spin-exchange between two R 1 radicals with the spin-exchange coupling of J/k B = 277 K, and the spin moment of m = 2 μ B (Bohr magneton unit). In order to explore ways to tailor spin-exchange coupling in stacks, ve other R 1 /D 25 /R 1 -based alternating stacks with different ligand con gurations of R 1 have been designed and investigated. Interestingly, ferromagnetic spin-exchange in stacks can be enhanced by substituting ligands having a weak electron af nity for H atoms of a R 1 molecule, while it can be weakened by substituting ligands having high electron af nity for H atoms of a R 1 radical. These results can be explained in terms of the competitive hybridization between the HOMO (highest occupied molecular orbital) of radicals and the HOMO and LUMO (lowest unoccupied molecular orbital) of diamagnetic molecules. These results would give some indication for how the spin-exchange coupling in graphene-based alternating stacks can be tailored.

Plasma-Assisted Preparation of MoS₂/Graphene/MOF Hybrid Materials and Their Electrochemical Behaviours

“…Graphene also increases the electric conductivity of the very poor-conductive organic ligands inside MOF structure. 10,11) To utilize graphene as a boat carrying MoS 2 seeds hybridized within metal-organic frameworks, we herein propose the fabrication of an innovative composite material which is based on MoS 2 , graphene and MOF. With the analogous structure of graphene and MoS 2 , their composite could be synthesized via a plasma-enhanced electrochemical exfoliation process (PE 3 P) as in our previous work.…”