DSpace Arşivi :: by Yazar "Taran, Songul" değerine göre listeleniyor

Yazar "Taran, Songul" seçeneğine göre listele

Listeleniyor 1 - 17 / 17

Annealing effects of photoanode on dye sensitized solar cell performance
(Taylor & Francis Ltd, 2021) Ozkacar, Tugce; Taran, Songul; Gokcen, Muharrem; Orhan, Ersin
Photoanode annealing effects on dye sensitized solar cell (DSSC) performance were investigated. Four different temperatures (300, 400, 500 and 600 degrees C) were used to annealing of the photoanodes. Morphologic properties of the photoanodes were investigated by a field emission scanning electron microscope (FESEM) and atomic force microscope (AFM). The photovoltaic properties of these DSSCs were obtained for these temperatures using a solar simulator for two different type electrolyte with different redox concentration and additive. Also, the series and charge transfer resistances were obtained from the electrochemical impedance spectroscopy (EIS) Nyquist plots of DSSCs.
Chemical ordering effect on structural stability of trimetallic Cu-Au-Pt nanoalloys
(Iop Publishing Ltd, 2020) Taran, Songul; Garip, Ali Kemal; Arslan, Haydar
In this study, the structural stabilities of trimetallic 55-atom icosahedral Cu-Au-Pt nanoalloys with six different nanoalloy systems were investigated. Cu-Au-Pt nanoalloy systems were defined with fixed 13 atom and 42 atom while the loading of other two type atoms varies. The most stable structures of Cu13AunPt42-n, Au13CunPt42-n, Pt(13)Au(n)Cu(42-n,)Cu(42)Au(n)Pt(13-n,)Au(42)Cu(n)Pt(13-n)and Pt(42)Au(n)Cu(13-n)nanoalloys were optimized by using Basin-Hopping algorithm. The most stable structures were obtained at the compositions Cu(13)Au(22)Pt(20)in Cu(13)Au(n)Pt(42-n)nanoalloys, Au(13)Cu(20)Pt(22)in Au(13)Cu(n)Pt(42-n)nanoalloys and Pt(13)Au(24)Cu(18)in Pt(13)Au(n)Cu(42-n)nanoalloys. For Cu42AunPt13-n, Au(42)Cu(n)Pt(13-n)and Pt(42)Au(n)Cu(13-n)nanoalloys, the most stable structures were obtained at the compositions Cu(42)Au(5)Pt(8,)Au(42)Cu(5)Pt(8)and Pt42Au12Cu1, respectively. The chemical ordering effect on optimized structures and segregation tendency of Cu, Au and Pt atoms were described by bond order parameter and order parameter (R), respectively. While segregation, mixing and transition from segregation to mixing were observed in nanoalloys with fixed 13 atom, only segregation was observed in nanoalloys with fixed 42 atom. Au and Pt atoms have a strong tendency to locate on surface and in the core region, respectively with the general tendency of Cu atoms locating closer to Pt atoms than Au atoms.
Dynamical investigation of NinAgm (n + m=147, 309, 561) nanoalloys with core-shell orderings
(Taylor & Francis Ltd, 2024) Zehir, Damla; Taran, Songul; Arslan, Haydar
The structures and dynamical properties of core-shell bimetallic Ni-Ag nanoalloys varying with different sizes and compositions have been studied using Monte Carlo (MC) and Molecular Dynamic (MD) simulations. We have considered the compositions in which the size of the core increases while the total number of atoms is fixed. In this sense, two (Ni13Ag134, Ni55Ag92), three (Ni13Ag296, Ni55Ag254, Ni147Ag162) and four (Ni13Ag548, Ni55Ag506, Ni147Ag414 and Ni309Ag252) compositions were considered for 147, 309 and 561 atoms, respectively. Highly symmetric Mackay icosahedral structures with centred symmetric cores appear for these specific sizes and compositions. Also, smaller Ni atoms tend to occupy the core and Ag atoms prefer to segregate to the surface of the nanoalloy due to its lower surface and cohesive energy. Then, the lowest energy structures obtained by Basin Hopping MC simulations were used as initial configurations for melting simulations. The transitions between different chemical ordering patterns with increasing temperature are possible in these systems while they are still in the solid state. Although there are clear differences in the melting process of the compositions with increasing size of the core, for all cases, surface melting occurs indicating that the Ag shell melts before the inner Ni core.
Effect of the photoanode fabrication condition, electrolyte type and illumination type on dye-sensitized solar cells performance
(Indian Acad Sciences, 2021) Orhan, Ersin; Gokcen, Muharrem; Taran, Songul
The combination of the photoanode fabrication condition, electrolyte type and light source effect on dye-sensitized solar cell (DSSC) performance were investigated. Three different photoanodes (C-1, C-2 and C-3) were used with different fabrication conditions with two different redox concentration electrolytes (30 and 50 mM) for each photoanode. For these six different combinations, DSSC performances were obtained for 12 different situations using two different light sources, AM 1.5 simulated and ultraviolet (UV-365 nm) illumination. It was obtained that the HI30 electrolyte has higher efficiency for UV illumination and the AN50 electrolyte has higher efficiency for AM1.5 simulated illumination. It was also obtained that the C-2 cell with double layer immersed in dye solution has higher efficiency for both two illumination types and two electrolytes.
Electrical property investigation of the Au/n-Si and Au/PVA plus benzimidazole Co complex/n-Si diodes under ultraviolet illumination
(Springer, 2021) Gokcen, Muharrem; Taran, Songul; Orhan, Ersin
Polyvinyl alcohol (PVA) was doped using the di[1-(2-ethoxyethyl)-5-nitrobenzimidazole] cobalt dichloride and this polymeric composite was used as an interface in Au/n-Si diodes. The basic electrical properties of these fabricated Au/n-Si (MS) and Au/PVA+Co complex/n-Si (MPS) diodes were examined measuring voltage-dependent current (I(V)) data in various ultraviolet illumination intensities and room temperature. Electrical parameters of the MS and MPS diodes were calculated by thermionic emission, Norde, and Card & Rhoderick method. It was found that the ideality factor (n) values of the MS diode increased from 6.7 to 13.4 while the MPS ones increased from 3.4 to 7.5 with increasing illumination. Also, the photo-responsivity (PR) of MPS diode was obtained for P = 50 mW/cm(2) (365 nm UV) as 0.29 A/W at - 5.00 V and 4.01 mA/W at 0 V.
High photo-responsivity Au/polyvinyl alcohol (PVA)+di[1-(2-ethoxyethyl)-5-nitrobenzimidazole] copper dichloride/n-Si UV photodiode
(Elsevier Science Sa, 2020) Gokcen, Muharrem; Orhan, Ersin; Taran, Songul
Au/n-Si metal/semiconductor (MS) type diode was transformed into a metal/polymer/semiconductor (MPS) type diode by polyvinyl alcohol (PVA)+benzimidazole Cu complex interfacial layer to achieve better photodiode properties. Au/PVA + benzimidazole Cu complex/n-Si MPS diode's electronic and photo-responsivity (PR) properties were investigated by current-voltage (I-V) measurements under various ultraviolet (UV) (365 nm wavelength) illumination intensities (from 50 to 250 mW/cm(2)) and at room temperature. It was found that the difference between the dark and high UV illumination I(V) plots of the MPS diode exceeds 10(5) times. Thus, this higher response to UV illumination has caused the reverse region current of the diode exceeds the forward region current since the first UV illumination level (50 mW/cm(2)). This ensures both the MPS diode has a very high PR value and allows that the diode working direction can be adjusted with UV exposure. The remarkably high PR values were obtained for P = 100 mW/cm(2) as 11.01 A/W at -4.84 V, and 2.14 mA/W at 0 V. Also, main electronic parameters of the MPS diode were calculated by thermionic emission, Ohm law, Cheung&Cheung and Card&Rhoderick methods. The series resistance (Rs) values calculated for each Cheung&Cheung function are compatible each other and there is an acceptable coherence with obtained values by ohmic approach. For the surface states density (N-ss) of the MPS diode obtained for each UV illumination, it was found that they are higher than the dark ones and they shifted to lower energy region. (c) 2020 Elsevier B.V. All rights reserved.
Investigation of the Chemical Ordering and Structural Properties of the Trimetallic (PtNi)@Ag Nanoalloys
(Springer/Plenum Publishers, 2021) Taran, Songul; Garip, Ali Kemal; Arslan, Haydar
The effect of systematic Ni atom addition on the chemical ordering properties of the nanoalloys has been studied for PtNi@Ag core-shell systems in which Ag atoms full occupy the shell of the icosahedral structure. We concentrate only on the chemical ordering optimization within a given geometric structure and we have core-shell system compositions (Pt13-nNinAg42 and Pt55-nNinAg92 for PtNi@Ag) with size of 55 and 147. Local relaxations were performed by using Monte Carlo Basin-Hopping algorithm within Gupta potential. Results show that it is energetically favourable to substitute Ni atoms for Pt13-nNinAg42 and Pt55-nNinAg92 systems. Excess energy variations were calculated to compare the relative stability. The atomic mixing degrees of Pt, Ni and Ag atoms were discussed by using order parameter (R) indicator. It is observed that the Ni atoms prefer to locate with closer to Pt atoms than Ag atoms due to tendency of occupying the core regions of the icosahedral structures. The local pressures of the atoms were also examined to clarify the composition effect on atomic stress and pressure. It is also observed that in trimetallic PtNi@Ag core-shell nanoalloys, the strain on the core atoms can be released by substituting Pt atoms with Ni atoms.
Stability and magnetic behaviour of 19-, 23-and 26-atom trimetallic Pt-Ni-Ag nanoalloys
(Taylor & Francis Ltd, 2020) Taran, Songul; Arslan, Haydar
A systematic investigation of Pt2NinAg17-n, Pt(3)Ni(n)Ag(20-n)and Pt(4)Ni(n)Ag(22-n)trimetallic nanoalloy systems has been performed. We are particularly interested in learning the effect of systematic Ni atom addition on the stability, chemical ordering and magnetic behaviour of the nanoalloys. We have performed Gupta and Density Functional Theory (DFT) approaches on chosen systems. Our excess energy analysis showed that the most stable structure of the 19-, 23- and 26-atom nanoalloy systems found at Gupta level does not agree with those of DFT. However, DFT results confirm the Gupta level calculations for the lowest energy structures of the trimetallic systems with small shifts on bond lengths. We have computed the order parameter (R) and it was observed that Ag atoms prefer to locate on the surface and Pt atoms mostly prefer to locate in the inner site of the trimetallic nanoalloys. Besides, inner sites are heavily compressed with the substitution of Ni atoms for most compositions. It was also obtained that total magnetic moment of the nanoalloys follows an almost linear dependence on the Ni atom concentration. Thus, it can be said that total magnetic moment can be enhanced by ternary alloying with 3d magnetic element like Ni.
Structural and dynamical properties of Au-Pd bimetallic nanoalloys supported on MgO(001)
(Taylor & Francis Ltd, 2021) Taran, Songul; Arslan, Haydar
In this study, structural and dynamical properties of Au-Pd bimetallic nanoalloys supported on MgO(001) surface were investigated. Bimetallic nanoalloys were defined with three different compositions that represents 1:1(50%-50%), 1:3(25%-75%) and 3:1(75%-25%). The putative global minimum structures of bimetallic Au-Pd nanoalloys adsorbed on MgO(001) were examined. It was obtained that Au and Pd nanoparticles exhibit a preference both (001) and (111) epitaxial grown on MgO(001) and Au-Pd bimetallic nanoalloys favour (001) epitaxy on MgO(001). The obtained lowest energy structures were used initially for melting simulations. The melting temperatures of AunPd3n nanoalloys were obtained generally higher than the melting temperatures of AunPdn and Au3nPdn nanoalloys.
Structural and dynamics properties of double icosahedral Pd-Ag-Pt trimetallic clusters
(World Scientific Publ Co Pte Ltd, 2020) Garip, Ali Kemal; Taran, Songul
Using Monte Carlo Basin-hopping algorithm within the Gupta potential, a systematic investigation has been performed for the best chemical ordering structures of 19-atom trimetallic PdnAg(17-n)Pt2 nanoclusters with double icosahedral geometry. The structures with the lowest energy at Gupta level are then re-optimized by DFT relaxations and the DFT relaxations confirmed the lowest energy structures obtained at the Gupta level indicating the double icosahedron structure is favorable for 19-atom PdnAg(17-n)Pt2 nanoclusters. It was observed that the caloric curves exhibit a smoother transition with structural isomerizations other than a sharp jump behavior.
Structural and magnetic properties of polyicosahedral Ni-Pt-Cu ternary nanoalloys
(Iop Publishing Ltd, 2021) Taran, Songul; Yildirim, Huseyin; Arslan, Haydar
In this study, a series of simulations were carried out to study the effects of size, composition and geometric structure on the structural and magnetic properties of ternary Ni-Pt-Cu nanoalloys. Different sizes and compositions were considered to compare the structural stability and magnetic behavior of Ni2Pt n Cu17-n (n = 0-17), Ni3Pt n Cu20-n (n = 0-20) and Ni4Pt n Cu22-n (n = 0-22) nanoalloy systems. We performed combinations of Gupta and density functional theory (DFT) simulations to check the validity of atomistic potentials against DFT. We calculated the excess energy to analyze the relative stability of Ni-Pt-Cu nanoalloys. The most negative excess energy values at the Gupta level are obtained in the compositions Ni2Pt5Cu12 in Ni2PtnCu17-n, Ni3Pt8Cu12 in Ni3PtnCu20-n and Ni4Pt9Cu13 in Ni4Pt n Cu22-n nanoalloys. While the most stable compositions Ni2Pt5Cu12 and Ni3Pt8Cu12 at the Gupta level do not agree with those obtained at the DFT level, the lowest energy values were obtained in the same composition Ni4Pt9Cu13 of 26-atom trimetallic nanoalloys at the Gupta and DFT levels. It was also found that most of the atoms on surface sites suffer tensile strain with substitution of Pt atoms. We have also investigated the total magnetic moments of the nanoalloys. In addition, the correlation of the local magnetic moments and charges of the atoms in these systems were discussed. It was found that total magnetic moments of trimetallic nanoalloys follow an almost linear dependence on the Pt concentration, despite the small concentration of Ni atoms and the weak magnetic properties of Pt atoms.
Synthesis and characterization of novel benzimidazole cobalt and copper complexes and applying in Au/PVA/n-Si diode
(Elsevier, 2020) Gokcen, Muharrem; Orhan, Ersin; Taran, Songul
A new stable solid di[1-(2-ethoxyethyl)-5-nitrobenzimidazole] cobalt dichloride (2) and di[1-(2-ethoxyethyl)-5nitrobenzimidazole] copper dichloride (3) were prepared by the combination of 1-(2-ethoxyethyl)-5-nitrobenzimidazole (1) with metal salts (CoCl2 center dot 6H(2)O and CuCl2 center dot H2O). Synthesized di[1-(2-ethoxyethyl)-5-nitrobenzimidazole] cobalt dichloride (2) and di[1-(2-ethoxyethyl)-5-nitrobenzimidazole] copper dichloride (3) were identified by H-1 NMR and C-13 NMR spectroscopic techniques and elemental analysis. Poly vinyl alcohol (PVA) polymer with and without novel benzimidazole cobalt and copper complexes dopant interfacial layers were used in Au/n-Si diodes. The basic electrical properties of these fabricated four diodes were examined using currentvoltage (I-V) measurements in dark and room temperature. The n and I0 values of all MPS diodes are smaller than the MS diode and the Phi(B0) values are greater.
Synthesis of benzimidazole moiety heteroleptic ruthenium complex and use as sensitizer in dye-sensitized solar cells
(Springer Heidelberg, 2021) Orhan, Ersin; Gokcen, Muharrem; Taran, Songul
The new benzimidazole functional heteroleptic ruthenium complex dye (BRD) was prepared for dye-sensitized solar cells (DSSCs). The compound was identified by various spectroscopic techniques and photovoltaic performances of this BRD DSSC were investigated and compared with Z907 (cis-diisothiocyanato-(2,2 '-bipyridyl-4,4 '-dicarboxylic acid)-(2,2 '-bipyridyl-4,4 '-dinonyl) ruthenium(II)) DSSCs. It was found that [Ruthenium (4,4 '-dicarboxylic acid-2,2 '-bipyridine) (1-(2-ethoxyethyl)-2-(pyridine-2-yl)benzimidazole) (NCS)(2)] (2) has a thermal stability below 300 degrees C. Two different electrolytes were used to get the effect on photovoltaic parameters. The photovoltaic measurements of the BRD and Z907 DSSCs were carried out under 100 mW/cm(2) (AM1.5) illumination. Short-circuit current density (J(sc)) values were obtained as 8.20 and 7.32 mA/cm(2) for AN50 and HI30 electrolytes, respectively. The photovoltaic efficiencies were obtained as 3.03% and 2.82% for AN50 and HI30 electrolytes, respectively.
Theoretical insights into the structural and magnetic properties of trimetallic Ni-Co-Rh nanoalloys
(Springer/Plenum Publishers, 2023) Taran, Songul; Arslan, Haydar
In this study, we have investigated structural and magnetic properties of the nanoalloys of size 38 atoms of compositions Ni32Co6-nRhn and 55 atoms of compositions Ni42Co13-nRhn. We have performed simulation searches for the lowest energy structures at Gupta level and then performed DFT re-optimization for these structures. The lowest energy structures of Ni32Co6-nRhn and Ni42Co13-nRhn nanoalloys at Gupta level were found to be truncated octahedron and icosahedron structure, respectively. The lowest energy values were found to be at the compositions Ni32Co4Rh2 in Ni32Co6-nRhn and Ni42Co1Rh12 in Ni42Co13-nRhn nanoalloys. Ni atoms full occupy only the surface of the truncated octahedron and icosahedron structure with the exception of bimetallic Ni42Rh13 nanoalloy. Since the energetic stability of the truncated octahedron and icosahedron can be rationalized in terms of local atomic pressure, we have calculated the local atomic pressures of the compositions. We have also investigated the size, geometric structure, and composition effects on magnetic properties as well as stability.
A theoretical study on chemical ordering of 38-atom trimetallic Pd-Ag-Pt nanoalloys
(Iop Publishing Ltd, 2020) Taran, Songul; Garip, Ali Kemal; Arslan, Haydar
In this study, truncated octahedron (TO) structure is selected for further analysis and we focus on 38-atom Pd-Pt-Ag trimetallic nanoalloys. The best chemical ordering structures of Pd(n)Ag(32 -n)Pt(6)trimetallic nanoalloys are obtained at Gupta level. The structures with the lowest energy at Gupta level are then re-optimized by density functional theory (DFT) relaxations and DFT results confirm the Gupta level calculations with small shifts on bond lengths indicating TO structure is favorable for 38-atom of Pd(n)Ag(32 -n)Pt(6)trimetallic nanoalloys. The DFT excess energy analysis shows that Pd(8)Ag(24)Pt(6)composition has the lowest excess energy value in common with excess energy analysis at Gupta level. In Pd(8)Ag(24)Pt(6)composition, eight Pd atoms are central sites of 8 (111) hexagonal facets of TO, 24 Ag atoms locate on surface, and 6 Pt atoms locate at the core of the structure. It is also obtained that all of the compositions except Pd(18)Ag(14)Pt(6)and Pd(20)Ag(12)Pt(6)exhibit a octahedral Pt core. Besides, it is observed that there is a clear tendency for Ag atoms to segregate to the surface and also Pt atoms prefer to locate at core due to order parameter (R) variations.
ULTRAVIOLET ILLUMINATION RESPONSIVITY OF THE Au/n-Si DIODES WITH AND WITHOUT POLY (LINOLENIC ACID)-G-POLY (CAPROLACTONE)-G-POLY (T-BUTYL ACRYLATE) INTERFACIAL LAYER
(World Scientific Publ Co Pte Ltd, 2020) Gursel, Umit; Taran, Songul; Gokcen, Muharrem; Ari, Yurdagul; Alli, Abdulkadir
Au/n-Si (MS) and Au/Poly (linolenic acid)-g-poly (caprolactone)-g-poly (t-butyl acrylate) (PLilPCLPtBA)/n-Si (MPS) diodes were fabricated to investigate the electrical and responsivity effects of interfacial layer on the diodes under ultra violet (UV) illumination. Electrospinning method was used for coating of the PLilPCLPtBA polymer layer on n-Si single crystal as nanofibers. Surface formation and nanofiber characteristics of the polymer layer were investigated by an electron microscope. The current-voltage (I-V) measurements of the MS and MPS diodes were carried out in dark and under UV (365 nm) illumination conditions at room temperature. Basic electrical parameters of the diodes; such as reverse bias saturation current (I-0), zero bias barrier height (Phi(B0)), ideality factor (n), series resistance (R-s) and interface state density (N-ss) were extracted from the experimental I-V measurements by thermionic emission and Norde equations. Also, power law of the photocurrents (I-pc) and responsivity (R) behavior were obtained and given comparatively.
Understanding the shape effect on the structural, energetic, magnetic, and pressure properties of the 38 atom-Co-Fe-Pd nanoalloys using Gupta and DFT calculations
(Iop Publishing Ltd, 2024) Yildirim, Huseyin; Taran, Songul; Arslan, Haydar
The alloy of magnetic metals with noble metals plays a key role in showing the magnetism of 3d metals and the catalytic properties of noble metals. A growing body of evidence suggests that 38 atoms is one of the most critical sizes for Ih and TO motifs. This study analyses the roles played by the shape effect on the structures, energies, magnetism, and pressures of Co6FenPd32-n (n = 0-32) nanoalloys and provides evidence regarding this phenomenon. Therefore, this study should be of value to researchers wishing to conduct future experimental and theoretical studies on the catalytic, electronic, optical, and magnetic properties of nanoalloys.

Yazar "Taran, Songul" seçeneğine göre listele

Sayfa Başına Sonuç

Sıralama seçenekleri