Browsing by Subject "Nanoribbon"

Now showing 1 - 4 of 4

Open Access
Electronic properties of Li-doped zigzag graphene nanoribbons
(Elsevier B.V., 2016) Narin, P.; Kutlu, E.; Sarikavak-Lisesivdin, B.; Lisesivdin, S. B.; Özbay, Ekmel
Zigzag graphene nanoribbons (ZGNRs) are known to exhibit metallic behavior. Depending on structural properties such as edge status, doping and width of nanoribbons, the electronic properties of these structures may vary. In this study, changes in electronic properties of crystal by doping Lithium (Li) atom to ZGNR structure are analyzed. In spin polarized calculations are made using Density Functional Theory (DFT) with generalized gradient approximation (GGA) as exchange correlation. As a result of calculations, it has been determined that Li atom affects electronic properties of ZGNR structure significantly. It is observed that ZGNR structure exhibiting metallic behavior in pure state shows half-metal and semiconductor behavior with Li atom.
Open Access
First-principles calculations of Pd-terminated symmetrical armchair graphene nanoribbons
(Elsevier, 2013) Kuloglu, A. F.; Sarikavak-Lisesivdin, B.; Lisesivdin, S. B.; Özbay, Ekmel
The effects of Palladium (Pd) termination on the electronic properties of armchair graphene nanoribbons (AGNRs) were calculated by using ab initio calculations. After a geometric optimization process, the electronic band structures, density of states, and binding energies of AGNRs with Na = 5-15 were calculated. Pd-termination was found to significantly influence the electronic properties of AGNRs. In DOS, many Q0D and Q1D type states were observed. Binding energy (BE) for single-side or both-side Pd-terminated structures represents characteristic drops with the increasing GNR width. With the increasing GNR width, the BEs of these structures become similar to hydrogenated structures. Because of the GNR width, dependent BE also gave information on the possible stiffness information, in which all of this information can be used in studies where controlled binding to graphene is required.
Open Access
Spontaneous high piezoelectricity in poly ( vinylidene fluoride ) nanoribbons produced by iterative thermal size reduction technique
(American Chemical Society, 2014-08-18) Kanik, M.; Aktas, O.; Sen, H. S.; Durgun, Engin; Bayındır, Mehmet
We produced kilometer-long, endlessly parallel, spontaneously piezoelectric and thermally stable poly(vinylidene fluoride) (PVDF) micro- and nanoribbons using iterative size reduction technique based on thermal fiber drawing. Because of high stress and temperature used in thermal drawing process, we obtained spontaneously polar gamma phase PVDF micro- and nanoribbons without electrical poling process. On the basis of X-ray diffraction (XRD) analysis, we observed that PVDF micro- and nanoribbons are thermally stable and conserve the polar gamma phase even after being exposed to heat treatment above the melting point of PVDF. Phase transition mechanism is investigated and explained using ab initio calculations. We measured an average effective piezoelectric constant as -58.5 pm/V from a single PVDF nanoribbon using a piezo evaluation system along with an atomic force microscope. PVDF nanoribbons are promising structures for constructing devices such as highly efficient energy generators, large area pressure sensors, artificial muscle and skin, due to the unique geometry and extended lengths, high polar phase content, high thermal stability and high piezoelectric coefficient. We demonstrated two proof of principle devices for energy harvesting and sensing applications with a 60 V open circuit peak voltage and 10 mu A peak short-circuit current output.
Open Access
Supramolecular chirality in self-assembled peptide amphiphile nanostructures
(Royal Society of Chemistry, 2015) Garifullin, R.; Güler, Mustafa O.
Induced supramolecular chirality was investigated in the self-assembled peptide amphiphile (PA) nanosystems. Having shown that peptide chirality can be transferred to the covalently-attached achiral pyrene moiety upon PA self-assembly, the chiral information is transferred to molecular pyrene via weak noncovalent interactions. In the first design of a supramolecular chiral system, the chromophore was covalently attached to a peptide sequence (VVAGH) via an ε-aminohexanoic acid spacer. Covalent attachment yielded a PA molecule self-assembling into nanofibers. In the second design, the chromophore was encapsulated within the hydrophobic core of self-assembled nanofibers of another PA consisting of the same peptide sequence attached to lauric acid. We observed that supramolecular chirality was induced in the chromophore by PA assembly into chiral nanostructures, whether it was covalently attached, or noncovalently bound.