Photonics / Fotonik

Permanent URI for this collectionhttps://hdl.handle.net/11147/2590

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Citation - WoS: 34
Citation - Scopus: 34
Anisotropic and Outstanding Mechanical, Thermal Conduction, Optical, and Piezoelectric Responses in a Novel Semiconducting Bcn Monolayer Confirmed by First-Principles and Machine Learning
(Elsevier, 2022-11) Mortazavi, Bohayra; Fazel Shojaei; Yağmurcukardeş, Mehmet; Alexander Shapeev; Xiaoying Zhuang
Graphene-like nanomembranes made of the neighboring elements of boron, carbon and nitrogen elements, are well-known of showing outstanding physical properties. Herein, with the aid of density functional theory (DFT) calculations, various atomic configurations of the graphene-like BCN nanosheets are investigated. DFT results reveal that depending on the atomic arrangement, the BCN monolayers may display semimetallic Dirac cone or semiconducting electronic nature. BCN nanosheets are also found to exhibit high piezoelectricity and carrier mobilities with considerable in-plane anisotropy, depending on the atomic arrangement. For the predicted most stable BCN monolayer, thermal and mechanical properties are explored using machine learning interatomic potentials. The room temperature tensile strength and lattice thermal conductivity of the most stable BCN monolayer are estimated to be orientation-dependent and remarkably high, over 78 GPa and 290 W/m.K, respectively. In addition, the thermal expansion coefficient of the monolayer BCN at room temperature is estimated to be −3.2 × 10−6 K−1, which is close to that of the graphene. The piezoelectric response of the herein proposed BCN lattice is also predicted to be close to that of the h-BN monolayer. Presented results highlight outstanding physics of the BCN nanosheets.
Bir Ameliyat Robotunun Denetimi için Basitleştirilmiş Dinamik Modeli
(Otomatik Kontrol Türk Milli Komitesi, 2018-09) Ayit, Orhan; Yaşır, Abdullah; Vardarlı, Eren; Kiper, Gökhan; Dede, Mehmet İsmet Can
Bu çalışmanın temel konusu minimal invaziv tipi bir ameliyat olan endoskopik hipofiz tümörü ameliyatında kullanılan endoskopun hareket denetimi için geliştirilen robotik sistemdir. Geliştirilen sistemin bu bildiride ele alınan kısmı, ameliyat sırasında sadece ameliyat bölgesi içinde endoskopu cerrahın anlık isteklerine göre yönlendiren, aktif robot yapısıdır. Söz konusu robot uzak hareket merkezli, 3 serbestlik dereceli, paralel kinematik mimariye sahiptir. Bu çalışmada robotun denetimi için uygun görülen hesaplanmış tork yöntemi için gerekli robotun dinamik analizi sunulmaktadır. Denetim algoritmasının yüksek frekansta çalışabilmesi için dinamik denklemlerde yapılan basitleştirmeler ve bunun sonucunda elde edilen hesaplama zamanı sunulmaktadır.
A Brief History of Silicene
(Springer Verlag, 2017-11) Cahangirov, Seymur; Şahin, Hasan; Le Lay, Guy; Rubio, Angel
Research on silicene shows a fast and steady growth that has increased our tool-box of novel 2D materials with exceptional potential applications in materials science. Especially after the experimental synthesis of silicene on substrates in 2012 it has attracted substantial interest from both theoretical and experimental communities. Every day, new people from various disciplines join this rapidly growing field. The aim of this book is to serve as a fast entry to the field to these newcomers and as a long-living reference to the growing community. To achieve this goal, the book is designed to emphasize the most crucial developments from both theoretical and experimental point of view since the starting of the silicene field back in 1994 with the first theoretical paper proposing the structure of silicene. We provide the general concepts and ideas such that the book is accessible to everybody from graduate students to senior researchers and we refer the reader interested in the detail to the relevant literature. We now start with a brief history of silicene where we highlight, in the chronological order, the important works that shaped our understanding of silicene.
Electronic, Magnetic and Vibrational Properties of Single Layer Aluminum Oxide
(2022-02-09) Özyurt, A. Kutay; Molavali, Deniz; Şahin, Hasan
The structural, magnetic, vibrational and electronic properties of single layer aluminum oxide (AlO2) are investigated by performing state-of-the-art first-principles calculations. Total energy optimization and phonon calculations reveal that aluminum oxide forms a distorted octahedral structure (1T'-AlO2) in its single layer limit. It is also shown that surfaces of 1T'-AlO2 display magnetic behavior originating from the O atoms. While the ferromagnetic (FM) state is the most favorable magnetic order for 1T'-AlO2, transformation to a dynamically stable antiferromagnetic (AFM) state upon a slight distortion in the crystal structure is also possible. It is also shown that Raman activities (350-400 cm^-1) obtained from the vibrational spectrum can be utilized to distinguish the possible magnetic phases of the crystal structure. Electronically, both FM and the AFM phases are semiconductors with an indirect band gap and they can form a type-III vdW heterojunction with graphene-like ultra-thin materials. Moreover, it is predicted that presence of oxygen defects that inevitably occur during synthesis and production do not alter the magnetic state, even at high vacancy density. Apparently, ultra-thin 1T'-AlO2 with its stable crystal structure, semiconducting nature and robust magnetic state is a quite promising material for nanoscale device applications.
Citation - WoS: 3
Citation - Scopus: 2
Fabrication and Characterization of a Solution Processed Flexible Thermal Sensor by Using Chemically Synthesized Go and Rgo
(Institute of Electrical and Electronics Engineers Inc., 2019) Bozkurt, Hakan; Diker, Halide; Varlıklı, Canan
Graphene oxide (GO) was reduced by ascorbic acid which is an environmental-friendly reductant and obtained sample was named as reduced GO (rGO). Stable dispersions of GO and rGO were prepared in N,N-Dimethylformamide (DMF). Compared to GO sample, rGO was determined to have more thermal stability, smaller sheet size and lower surface energy. GO and rGO dispersions were drop-casted on aluminum (Al) coated acetate substrate and used as thermal sensor. Fabricated sensors were tested from 25 °C to 150 °C. The sensors fabricated with GO, were not stabile against driven temperature changes. However, rGO ones, presented no thermal hysteresis effect after the first heating step. This sensor (Al/rGO/Al) acted like an NTC (Negative Temperature Coefficient) thermistor. The resistance of the rGO sensor was changed between 42 k? to 25 k? depending on the test temperature range (25 °C to 150 °C). Average beta value was calculated as 519.7649 K. © 2019 IEEE.
Citation - WoS: 5
Citation - Scopus: 11
Freestanding Silicene
(Springer Verlag, 2017-11) Cahangirov, Seymur; Şahin, Hasan; Le Lay, Guy; Rubio, Angel
Obtaining a freestanding 2D graphene flake is relatively easy because it has a naturally occurring 3D layered parent material, graphite, made up of graphene layers weakly bound to each other by van der Waals interaction. In fact, graphite is energetically more favorable than diamond (which is one of the most stable and hard materials on Earth) that is the sp3 hybridized allotrope of carbon. To prepare freestanding graphene, it is enough to come up with a smart procedure for isolating the weakly bound layers of graphite. The same is also true for other layered materials like hexagonal boron nitride, black phosphorus, metal dichalcogenides and oxides. Silicene, on the other hand, doesn’t have a naturally occurring 3D parent material since silicon atoms prefer sp3 hybridization over sp2 hybridization. This makes the synthesis of freestanding silicene very hard, if not impossible. However, it is possible to epitaxially grow silicene on metal substrates and make use of its intrinsic properties by transferring it to an insulating substrate (Tao et al. 2015). In this chapter, we focus on intrinsic properties of freestanding silicene in the absence of the metallic substrate.
Fullerenlere Alternatif Yeni Asetil Köprülü Perilendiimidlerin Sentezi ve Akseptör Özelliklerinin Fotofiziksel Süreçlerle Araştırılması
(2019) Varlıklı, Canan
Organik güneş hücresi (OGH) nde elektrik üretimi, donörün ışığı soğruması ekziton oluşumu, ekziton difüzyonu, ayrışması ve elektron transfer süreçleri, elektron ve boşlukların katot ve anotta toplanması ile gerçekleşir. Literatürde birçok farklı elektron verici (D) ve alıcı (A) malzeme geliştirilmektedir. A malzemeleri içerisinde en sık kullanılanlardan birisi fulleren ve türevleridir. Bu türevlerin üretimi oldukça zor ve yüksek maliyetlidir. Bu sebeple, literatürde son 10 yıl da, fulleren içermeyen OGHne olan ilginin arttığı görülmektedir. Perilendiimidler (PDIler), görünür bölgedeki yüksek molar soğurma katsayıları ve elektron ilgileri ile dikkat çekmektedir. Ancak, PDIlerin genel organik çözgenlerdeki çözünürlükleri düşük, agregatlaşma eğilimleri fazladır. Güçlü perilen-perilen etkileşimleri film fazında mikroboyutlara ulaşabilecek kristalitler oluşturabilmektedir. Bu durum ise, ekziton haraketliliğini ve elektron ve boşlukların elektrotlarda toplanmasını olumsuz etkilemektedir. Bu proje kapsamında, izomerik saflıkta 1,6- ve 1,7- bis[(trifenil)(4-etinil-fenil)silan)- N,N′-di(2- etilhekzil)-perilen-3, 4, 9, 10-tetrakarboksilikasit diimid [1,6 ve 1,7-Di(TPhSi)APDI] sentezlenmiş, 1H ve 13C NMR ile karakterize edilmiştir. Saf izomerlerin absorpsiyon ve fotoluminesans özellikleri, indirgenme potansiyelleri, en yüksek enerjili elektron içeren moleküler orbital ve en düşük enerjili elektron içermeyen moleküler orbital enerji seviyeleri tespit edilmiştir. Referans olarak sentezlenen N,N′-di(2-etilhekzil)-perilen-3, 4, 9, 10- tetrakarboksilikasit diimid [PDI(2EH)] ve 1,6- ve 1,7-Di-TPhSiAPDI(2EH) in çözelti ve film fazı fotofiziksel özellikleri incelenmiştir. Yeni sentezlenen PDI türevlerinin ve ticari fulleren türevinin (PCBM), ticari bir donör olan poli[N-9'-heptadekanil-2,7-karbazol-alt-5,5-(4',7'-di-2- thienyl-2',1',3'-benzothiadiazole)] (PCDTBT) ile çözelti ve film fazındaki etkileşimleri izlenerek, karşılaştırılmıştır. Filmlerin morjolojik özellikleri atomik kuvvet mikroskobu ölçümleri ile tespit edilmiştir. 1,7-Di-TPhSiAPDI(2EH) in agregatlaşma eğiliminin ve fotokararlılığının PDI(2EH) den düşük, soğurma dalga boyunun, elektron ilgisinin ve yaşam ömrünün PDI(2EH) den yüksek ve molar soğurma katsayısının PDI(2EH) ile aynı seviyede olduğu tespit edilmiştir. Bu özellikleri ile yeni molekülün uygun D malzeme kullanımı ile hazırlanacak OGH aygıtında, PDI(2EH) den yüksek verim vereceği düşünülmüştür.
Citation - WoS: 7
Citation - Scopus: 10
Germanene, Stanene and Other 2d Materials
(Springer Verlag, 2017-11) Cahangirov, Seymur; Şahin, Hasan; Le Lay, Guy; Rubio, Angel
Germanene and stanene (also sometimes written stannene or called tinene) are 2D materials composed of germanium and tin atoms respectively arranged in a honeycomb structure similarly to graphene and silicene. The atomic structure of freestanding germanene and stanene is buckled like in the case of silicene (see Figure 2.4DFT calculations (Kresse and Joubert, Phys Rev B 59:1758-1775, 1999) performed by projector augmented wave (PAW) method (BlÖchl, Phys Rev B 50:17953-17979, 1994) and adopting PBE functional (Perdew et al. Phys Rev Lett 77:3865-3868, 1996) result in a lattice constants 4.06 and 4.67Å and buckling heights of 0.69 and 0.85Å for germanene and stanene respectively.
Citation - WoS: 47
Citation - Scopus: 51
Highly Porous Poly(o-Phenylenediamine) Loaded Magnetic Carboxymethyl Cellulose Hybrid Beads for Removal of Two Model Textile Dyes
(Springer, 2022-10) Arıca, Tuğçe Aybüke; Balcı, Fadime Mert; Balcı, Sinan; Arıca, Mehmet Yakup
Ensuring the removal of complex dyes from wastewater is a topic of great interest as it is vital for the environment. The present study reports a facile preparation method for poly(o-phenylenediamine) [p(o-PDA)] micro-particles loaded to magnetic carboxymethyl cellulose (CMC) hydrogel beads as adsorbents. The prepared products were characterized by FTIR, TGA, VSM, SEM, BET, and zeta sizer. The Fe3O4@p(o-PDA)@CMC beads were used for the removal of Reactive Blue 4 (RB-4) and Congo Red (CR) textile dyes from an aqueous medium. Different factors, such as adsorbent dose, initial pH, ionic strength, contact time, temperatures, and initial RB-4 and CR concentrations were examined. The maximum adsorption capacities of the RB-4 dye and CR at optimum pH 5 reached 398.7 and 524.6 mg/g in 120 min, respectively. The adsorption of RB-4 and CR on the hybrid magnetic beads can be due to the electrostatic, hydrogen bonding, and π-π interactions. Moreover, the magnetic hybrid beads showed easy regeneration ability and good reusability. The adsorbent can be a very good candidate for the efficient removal of micro-pollutant from wastewater.
Citation - Scopus: 1
Multilayer Silicene
(Springer Verlag, 2017-11) Cahangirov, Seymur; Şahin, Hasan; Le Lay, Guy; Rubio, Angel
Silicon does not have a naturally occurring layered allotrope like graphite. However, it is possible to grow monolayer silicene on substrates, as we have seen in Chap. 3. Extending this idea further, one may wonder whether it is possible to synthesize layered silicon structures by continuing the growth started as a monolayer silicene. In this chapter we discuss the experimental and theoretical works that are based on this idea of multilayer silicene growth.
Citation - WoS: 4
Citation - Scopus: 4
A Polymeric Copper Complex Based on a Pyrazole Derivative: Synthesis, Spectroscopic, X-Ray, and Biological Activity Studies
(John Wiley and Sons Inc., 2024) Amin,M.A.; Diker,H.; Şahin,O.; Varlıklı, Canan; Soliman,A.A.
A novel 1D coordination polymeric copper complex based on 4-(4′-nitrophenylhydrazono)-5-trifluoromethyl-2,4-dihydropyrazol-3-one was prepared and characterized spectroscopically and thermally and via X-ray crystallographic investigation. The prepared copper-based structure was proved to have a 1D coordination polymer. X-ray studies showed that the polymeric copper complex was of octahedral geometry, the ligand acted as a bidentate ligand, and the nitro group attached to the ligand acted as a bridging group. The cytotoxic activities of the copper polymer were evaluated including against MCF-7 cells (breast cancer cell line), HepG-2 cells (hepatocellular carcinoma), and HCT-116 cells (colon cancer cell line). The morphological alterations of the complex treated cells were investigated using an inverted microscope. The cell cycle and apoptosis were evaluated and reported. The copper polymer exhibited the best antitumor activity against HepG-2 cells (35.22 ± 4.80 μM) while also causing a decline in the G2/M phase and a remarkable enhancement in the early apoptosis. © 2024 John Wiley & Sons, Ltd.
Reversible Energy Transfer Between a Single Defect in Hbn and Graphene
(OSA - The Optical Society, 2019) Özçeri, Elif; Arı, Ozan; Balcı, Sinan; Kocabaş, Coşkun; Ateş, Serkan
We present a reversible energy transfer between a single defect in hBN and graphene. Dynamic control of Fermi level of graphene results in switching on and off single photon emission from a single quantum emitter. © OSA 2019 © 2019 The Author(s)
Citation - WoS: 1
Citation - Scopus: 2
Silicene on Ag Substrate
(Springer Verlag, 2017-11) Cahangirov, Seymur; Şahin, Hasan; Le Lay, Guy; Rubio, Angel
The isolation of graphene sheets from its parent crystal graphite has given the kick to experimental research on its prototypical 2D elemental cousin, silicene (Brumfiel 2013). Unlike graphene, silicene lacks a layered parent material from which it could be derived by exfoliation, as mentioned in Chap. 2. Hence, the efforts of making the silicene dream a reality were focused on epitaxial growth of silicene on substrates. The first synthesis of epitaxial silicene on silver (111) (Vogt et al. 2012; Lin et al. 2012) and zirconium diboride templates (Fleurence et al. 2012) and next on an iridium (111) surface (Meng et al. 2013), has boosted research on other elemental group IV graphene-like materials, namely, germanene and stanene (Matthes et al. 2013; Xu et al. 2013). The boom is motivated by several new possibilities envisaged for future electronics, typically because of the anticipated very high mobilities for silicene and germanene (Ye et al. 2014), as well as potential optical applications (Matthes et al. 2013). It is also fuelled by their predicted robust 2D topological insulator characters (Liu et al. 2011; Ezawa 2012) and potential high temperature superconductor character (Chen et al. 2013; Zhang et al. 2015). One of the most promising candidates as a substrate is Ag because from the studies of the reverse system, where Ag atoms were deposited on silicon substrate, it was known that Ag and silicon make sharp interfaces without making silicide compounds (Le Lay 1983). Indeed, studies on synthesis and characterization of silicene is mainly focused on using Ag(111) as substrates and hence we think it is important to understand this particular system. In this chapter, we present the experimental and theoretical studies investigating the atomic and electronic structure of silicene on Ag substrates.
Silicon-Based Emitter Compound
(Espacenet, 2018)
The present invention relates to emitter compounds E of formula or salts thereof based on a triazine core, substituted with at least one moiety of formula: and at least one donor moiety. Further, the present invention also refers to a light-emitting layer B comprising the emitter compound E and to an opto-electronic device OD comprising such light-emitting layer B. Moreover, the present invention relates to a method for generating light of a desired wavelength range by means of the opto-electronic device OD.
Single Layer Res2h2: Stability, Raman Activity and Electronic Properties
(Eskişehir Teknik Üniversitesi, 2018) Ünsal, Elif; Şahin, Hasan
In this study, the structural, vibrational and electronic properties of the hydrogenated single layer of ReS2 are investigated byperforming the first principle calculations based on density functional theory. We found that the characteristic properties ofthe monolayer ReS2 can be manipulated upon the hydrogen functionalization. As the monolayer ReS2, the ReS2H2 hasdistorted 1T phase; however, the bonding in Re slab significantly varies with the hydrogenation. Our results demonstrate thatthe full-surface hydrogenation leads to an expansion in lattice and the Re4 tetramer-chains in the monolayer ReS2 areseparated into two dimers in the hydrogenated monolayer. It is calculated that the dynamically stable monolayer of ReS2H2has 26 Raman-active vibrational modes. Constant volume specific heat calculations are also performed and the resultsindicate that at high temperature, the monolayer ReS2 approaches to limit of 3R before the monolayer ReS2H2. By performingthe electronic band structure calculations, it is shown that when the ReS2 surface is fully hydrogenated, there occurs a directto indirect band gap transition and the semiconducting hydrogen-induced monolayer has a band gap of 0.74 eV.
Citation - WoS: 6
Citation - Scopus: 5
Strain engineering of 2D materials
(Springer Verlag, 2017-11) Cahangirov, Seymur; Şahin, Hasan; Le Lay, Guy; Rubio, Angel
When bulk structures are thinned down to their monolayers, degree of orbital interactions, mechanical properties and electronic band dispersion of the crystal structure become highly sensitive to the amount of applied strain. The source of strain on the ultra-thin lattice structure can be (1) an external device or a flexible substrate that can stretch or compress the structure, (2) the lattice mismatch between the layer and neighboring layers or (3) stress induced by STM or AFM tip.

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