Ab-initio calculations have been performed to study the geometry and electronic structure of boron (B) and nitrogen (N) doped graphene sheet. The effect of doping has been investigated by varying the concentrations of dopants from 2 % (one atom of the dopant in 50 host atoms) to 12 % (six dopant atoms in 50 atoms host atoms) and also by considering different doping sites for the same concentration of substitutional doping. All the calculations have been performed by using VASP (Vienna Ab-initio Simulation Package) based on density functional theory. By B and N doping p-type and n-type doping is induced respectively in the graphene sheet. While the planar structure of the graphene sheet remains unaffected on doping, the electronic properties change from semimetal to semiconductor with increasing number of dopants. It has been observed that isomers formed differ significantly in the stability, bond length and band gap introduced. The band gap is maximum when dopants are placed at same sublattice points of graphene due to combined effect of symmetry breaking of sub lattices and the band gap is closed when dopants are placed at adjacent positions (alternate sublattice positions). These interesting results provide the possibility of tuning the band gap of graphene as required and its application in electronic devices such as replacements to Pt based catalysts in Polymer Electrolytic Fuel Cell (PEFC).
Herein,
we report the design, synthesis, and structural characterization
of a novel 2-fold interpenetrated CuII metal–organic
framework Cu-MOF-1 [{Cu2(L)(oba)2}·DMF·H2O]α. A
single-crystal X-ray analysis reveals that Cu-MOF-1 exhibits
a doubly (1 + 1) interpenetrated three-dimensional structure with
6-connected
mab
topology. Moreover,
Cu-MOF-1 showed high fluorescence stability in methanol
solution and selectively detected nitroaromatics with high quenching
constants and low detection limits of 0.31 × 105 M–1 and 22.65 μM for 2,4,6-TNP; 1.34 × 105 M–1 and 18.7 μM for 4-NPH; and 1.49
× 105 M–1 and 14.07 μM for
4-NA. Notably, ligand L itself did not display any type
of recognition for any nitroaromatics in methanol solution. The sensing
of NACs by Cu-MOF-1 followed mostly the resonance energy
transfer mechanism; however, in the case of 4-NPH and 2,4,6-TNP an
electron transfer mechanism also exists. Importantly, Cu-MOF-1 shows recyclability up to five cycles without any significant
loss in quenching efficiency.
We study and compare some of the possible isomers of BN co-doped graphene on the basis of their composition and electronic properties. The effect of doping has been studied theoretically by substituting the C atoms of graphene with an equal amount of B/N with their concentration varying from 4 % (2 atoms of the dopant in 50 host atoms) to 24 % and choosing different doping sites for each concentration. We made use of VASP (Vienna Abinitio Simulation Package) software based on density functional theory to perform all calculations. While the resulting geometries do not show much of distortion on doping, the electronic properties show a transition from semimetal to semiconductor with increasing number of dopants as in the case of individual B and N doping. The study shows that the BN doping introduces the band gap at the Fermi level unlike individual B and N doping which causes the shifting of Fermi level. High value of the cohesive energy indicates the stability of the resulting heterostructures. Isomers formed by choosing different doping sites differ significantly in relative stability and band gap introduced and these aspects, to a great extent, depend upon position of B and N atoms in the heterostructure.
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