Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
Browse
3 results
Search Results
Article Citation - WoS: 2Citation - Scopus: 2Atomic-scale understanding of dichlorobenzene-assisted poly 3-hexylthiophene-2,5-diyl nanowire formation mechanism(Elsevier Ltd., 2017) Yağmurcukardeş, Mehmet; Kıymaz, D.; Zafer, C.; Senger, Ramazan Tuğrul; Şahin, HasanLow-dimensional Poly 3-hexylthiophene-2,5-diyl (P3HT) structures that serve efficient exciton dissociation in organic solar cells, play a major role in increasing the charge collection, and hence, the efficiency of organic devices. In this study, we theoretically and experimentally investigate the Dichlorobenzene (DCB)-assisted formation of P3HT nanowires. Our experiments show that the solution of DCB molecules drive randomly oriented P3HT polymers to form well-stacked nanowires by stabilizing tail-tail and π−π interactions. Here the question is how DCB molecules migrate into the P3HT layers while forming the nanowire structure. Our density functional theory-based calculations reveal that the vertical migration of the DCB molecules between P3HT layers is forbidden due to a high energy barrier that stems from strong alkyl chain-DCB interaction. In contrast to vertical diffusion, lateral diffusion of DCB molecules in between P3HT layers is much more likely. Our results show that migration of a DCB molecule occurs through the alkyl groups with a low energy barrier. Therefore, laterally diffused DCB molecules assist nucleation of top-to-top stacking of P3HT polymers and formation of well-ordered nanowires.Article Citation - WoS: 19Citation - Scopus: 22Thermal Conductivity Engineering of Bulk and One-Dimensional Si-Ge Nanoarchitectures(Taylor and Francis Ltd., 2017) Kandemir, Ali; Özden, Ayberk; Çağın, Tahir; Sevik, CemVarious theoretical and experimental methods are utilized to investigate the thermal conductivity of nanostructured materials; this is a critical parameter to increase performance of thermoelectric devices. Among these methods, equilibrium molecular dynamics (EMD) is an accurate technique to predict lattice thermal conductivity. In this study, by means of systematic EMD simulations, thermal conductivity of bulk Si-Ge structures (pristine, alloy and superlattice) and their nanostructured one dimensional forms with square and circular cross-section geometries (asymmetric and symmetric) are calculated for different crystallographic directions. A comprehensive temperature analysis is evaluated for selected structures as well. The results show that one-dimensional structures are superior candidates in terms of their low lattice thermal conductivity and thermal conductivity tunability by nanostructuring, such as by diameter modulation, interface roughness, periodicity and number of interfaces. We find that thermal conductivity decreases with smaller diameters or cross section areas. Furthermore, interface roughness decreases thermal conductivity with a profound impact. Moreover, we predicted that there is a specific periodicity that gives minimum thermal conductivity in symmetric superlattice structures. The decreasing thermal conductivity is due to the reducing phonon movement in the system due to the effect of the number of interfaces that determine regimes of ballistic and wave transport phenomena. In some nanostructures, such as nanowire superlattices, thermal conductivity of the Si/Ge system can be reduced to nearly twice that of an amorphous silicon thermal conductivity. Additionally, it is found that one crystal orientation, < 100 >, is better than the < 111 > crystal orientation in one-dimensional and bulk SiGe systems. Our results clearly point out the importance of lattice thermal conductivity engineering in bulk and nanostructures to produce high-performance thermoelectric materials.Article Citation - WoS: 39Citation - Scopus: 43Synthesis and Humidity Sensing Analysis of Zns Nanowires(Elsevier Ltd., 2012) Okur, Salih; Üzar, Neslihan; Tekgüzel, Nesli; Erol, Ayşe; Arıkan, M. ÇetinZnS nanowires synthesized by the vapor-liquid-solid (VLS) method and humidity sensing properties of obtained ZnS nanowires were investigated by quartz crystal microbalance (QCM) method and electrical measurements. The synthesized nanowires were exposed to relative humidity (RH) between 22% and 97% under controlled environment. Our experimental results show that ZnS nanowires have a great potential for humidity sensing applications in room temperature operations. © 2010 Elsevier B.V. All rights reserved.