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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 structures of 2 F-adsorbed graphene with different binding configurations. The bond length and angles are also summarized in Table 2.
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fig05: The optimized structures of 2 F-adsorbed graphene with different binding configurations. The bond length and angles are also summarized in Table 2.

Mentions: The optimized structures for 2 F-adsorbed graphene are shown in Figure 5 and summarized in Table 2. Obviously, in all five cases, when the second fluorine is on the same side of the graphene plane, the CF is significantly pulled out of the plane. Such phenomena have also been observed by other researchers.18d One overall effect of these CF defects is to buckle the otherwise flat graphene layer. However, when the second fluorine binds on the opposite side of the graphene plane, the CF are less significantly pulled out of graphene plane. As one can see that the amount of CF buckling (ZCF) from graphene plane highly depends on the two F-binding configurations. When the separation of 2 F is far enough (cases D and E), the ZCF value does not change too much for both configurations. As seen from Table 2 and Figure 5, except for case C, the binding energy of 2 F-adsorbed graphene is larger when the fluorine atoms are bonded on the opposite sides of the graphene plane. This is due to the effects of F-F repulsion. Obviously, the total binding energy (Eb) of 2 F-adsorbed graphene depends not only on the F−CF (rC−F) bond length, but also on the buckling configuration of graphene. As one can see that among them, case A has shortest rC−F and largest ZCF, hence possessing largest Eb.


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 structures of 2 F-adsorbed graphene with different binding configurations. The bond length and angles are also summarized in Table 2.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

fig05: The optimized structures of 2 F-adsorbed graphene with different binding configurations. The bond length and angles are also summarized in Table 2.
Mentions: The optimized structures for 2 F-adsorbed graphene are shown in Figure 5 and summarized in Table 2. Obviously, in all five cases, when the second fluorine is on the same side of the graphene plane, the CF is significantly pulled out of the plane. Such phenomena have also been observed by other researchers.18d One overall effect of these CF defects is to buckle the otherwise flat graphene layer. However, when the second fluorine binds on the opposite side of the graphene plane, the CF are less significantly pulled out of graphene plane. As one can see that the amount of CF buckling (ZCF) from graphene plane highly depends on the two F-binding configurations. When the separation of 2 F is far enough (cases D and E), the ZCF value does not change too much for both configurations. As seen from Table 2 and Figure 5, except for case C, the binding energy of 2 F-adsorbed graphene is larger when the fluorine atoms are bonded on the opposite sides of the graphene plane. This is due to the effects of F-F repulsion. Obviously, the total binding energy (Eb) of 2 F-adsorbed graphene depends not only on the F−CF (rC−F) bond length, but also on the buckling configuration of graphene. As one can see that among them, case A has shortest rC−F and largest ZCF, hence possessing largest Eb.

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