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Electronic Structures, Bonding Configurations, and Band-Gap-Opening Properties of Graphene Binding with Low-Concentration Fluorine.

Duan Y, Stinespring CD, Chorpening B - ChemistryOpen (2015)

Bottom Line: The lowest-binding energy state is found to correspond to two CF defects on nearest neighbor sites, with one fluorine above the carbon plane and the other below the plane.The binding energy decreases with decreasing fluorine concentration due to the interaction between neighboring fluorine atoms.The obtained results are useful for sensor development and nanoelectronics.

View Article: PubMed Central - PubMed

Affiliation: National Energy Technology Laboratory, United States Department of Energy 626 Cochrans Mill Road, Pittsburgh, PA, 15236, USA.

ABSTRACT
To better understand the effects of low-level fluorine in graphene-based sensors, first-principles density functional theory (DFT) with van der Waals dispersion interactions has been employed to investigate the structure and impact of fluorine defects on the electrical properties of single-layer graphene films. The results show that both graphite-2 H and graphene have zero band gaps. When fluorine bonds to a carbon atom, the carbon atom is pulled slightly above the graphene plane, creating what is referred to as a CF defect. The lowest-binding energy state is found to correspond to two CF defects on nearest neighbor sites, with one fluorine above the carbon plane and the other below the plane. Overall this has the effect of buckling the graphene. The results further show that the addition of fluorine to graphene leads to the formation of an energy band (BF) near the Fermi level, contributed mainly from the 2p orbitals of fluorine with a small contribution from the p orbitals of the carbon. Among the 11 binding configurations studied, our results show that only in two cases does the BF serve as a conduction band and open a band gap of 0.37 eV and 0.24 eV respectively. The binding energy decreases with decreasing fluorine concentration due to the interaction between neighboring fluorine atoms. The obtained results are useful for sensor development and nanoelectronics.

No MeSH data available.


Related in: MedlinePlus

The optimized structure of 1 F-adsorbed graphene. a) Initial configuration. b) Optimized structure; rCF=1.575 Å.
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fig04: The optimized structure of 1 F-adsorbed graphene. a) Initial configuration. b) Optimized structure; rCF=1.575 Å.

Mentions: Figure 4 shows the initial and optimized configuration for 1 F-adsorbed graphene. As seen here, after binding with fluorine to form the CF defect, the carbon atom was pulled about 0.5 Å above the graphene plane (see the ZCF value in Table 2). As a result the F−CF−C bond angle becomes 102.4 °. This represents a 12.4 ° deviation from the initial bond angle of 90 °, and is approaching the 109.5 ° bond angle associated with sp3 hybridization. In addition, the optimized F−CF bond length (rC−F) is 1.575 Å. The binding energy (Eb) of fluorine on graphene, which is calculated as the energy difference between the optimized F-bonded configuration and the individual pure graphene and a single fluorine atom in a 20×20×20 box, is −2.07 eV. This indicates the chemical bonding of F−CF is very strong, as expected.


Electronic Structures, Bonding Configurations, and Band-Gap-Opening Properties of Graphene Binding with Low-Concentration Fluorine.

Duan Y, Stinespring CD, Chorpening B - ChemistryOpen (2015)

The optimized structure of 1 F-adsorbed graphene. a) Initial configuration. b) Optimized structure; rCF=1.575 Å.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4608533&req=5

fig04: The optimized structure of 1 F-adsorbed graphene. a) Initial configuration. b) Optimized structure; rCF=1.575 Å.
Mentions: Figure 4 shows the initial and optimized configuration for 1 F-adsorbed graphene. As seen here, after binding with fluorine to form the CF defect, the carbon atom was pulled about 0.5 Å above the graphene plane (see the ZCF value in Table 2). As a result the F−CF−C bond angle becomes 102.4 °. This represents a 12.4 ° deviation from the initial bond angle of 90 °, and is approaching the 109.5 ° bond angle associated with sp3 hybridization. In addition, the optimized F−CF bond length (rC−F) is 1.575 Å. The binding energy (Eb) of fluorine on graphene, which is calculated as the energy difference between the optimized F-bonded configuration and the individual pure graphene and a single fluorine atom in a 20×20×20 box, is −2.07 eV. This indicates the chemical bonding of F−CF is very strong, as expected.

Bottom Line: The lowest-binding energy state is found to correspond to two CF defects on nearest neighbor sites, with one fluorine above the carbon plane and the other below the plane.The binding energy decreases with decreasing fluorine concentration due to the interaction between neighboring fluorine atoms.The obtained results are useful for sensor development and nanoelectronics.

View Article: PubMed Central - PubMed

Affiliation: National Energy Technology Laboratory, United States Department of Energy 626 Cochrans Mill Road, Pittsburgh, PA, 15236, USA.

ABSTRACT
To better understand the effects of low-level fluorine in graphene-based sensors, first-principles density functional theory (DFT) with van der Waals dispersion interactions has been employed to investigate the structure and impact of fluorine defects on the electrical properties of single-layer graphene films. The results show that both graphite-2 H and graphene have zero band gaps. When fluorine bonds to a carbon atom, the carbon atom is pulled slightly above the graphene plane, creating what is referred to as a CF defect. The lowest-binding energy state is found to correspond to two CF defects on nearest neighbor sites, with one fluorine above the carbon plane and the other below the plane. Overall this has the effect of buckling the graphene. The results further show that the addition of fluorine to graphene leads to the formation of an energy band (BF) near the Fermi level, contributed mainly from the 2p orbitals of fluorine with a small contribution from the p orbitals of the carbon. Among the 11 binding configurations studied, our results show that only in two cases does the BF serve as a conduction band and open a band gap of 0.37 eV and 0.24 eV respectively. The binding energy decreases with decreasing fluorine concentration due to the interaction between neighboring fluorine atoms. The obtained results are useful for sensor development and nanoelectronics.

No MeSH data available.


Related in: MedlinePlus