Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
Browse
14 results
Search Results
Now showing 1 - 10 of 14
Article Citation - WoS: 5Citation - Scopus: 4Polarity Induced Vapochromism and Vapoluminescence of Polythiophene Derivatives for Volatile Organic Compounds Classification(Elsevier, 2023) Karabacak, Soner; Qun, David Lee Chao; Ammanath, Gopal; Yeasmin, Sanjida; Yağmurcukardeş, Mehmet; Palaniappan, Alagappan; Liedberg, Bo; Yıldız, Ümit HakanPolarity induced vapochromic and vapoluminescent properties of cationic poly-3-alkoxythiophene derivatives (PT) casted on polyvinylidene fluoride (PVDF) membranes are reported. PT with six different pendant groups are designed to differentially interact with volatile organic compounds (VOC) of varying polarities, thereby enabling their classification. PT exhibit a rapid vapochromic response with a concurrent modulation of vapoluminescence due to the non-covalent cation-? interactions between the pendant groups and the PT backbone. Adsorption of VOC on pendant groups alters the conformation of PT backbone, thus resulting in an increase in intensity and blue shifting of fluorescence emission within the visible spectrum. The vapoluminescent responses are found to be more sensitive with a limit of detection (LOD) of ?7 ppm and a wider dynamic range as compared to the vapochromic responses with a LOD of ?60 ppm for the detection of a model VOC: chloroform. Notably, all the PT illustrate an instantaneous recovery of colour and luminescence upon desorption of VOC. PT interaction with VOC of varying polarities was ascertained using density functional theory (DFT) and principal component analysis (PCA) methodologies. In summary, the polarity induced vapochromic and vapoluminescent properties of PT could yield a selective and sensitive vapochromic and fluorometric dual-mode VOC detection platform. © 2023Article Citation - WoS: 32Citation - Scopus: 31Wien Effect in Interfacial Water Dissociation Through Proton-Permeable Graphene Electrodes(Nature Research, 2022) Cai, Junhao; Griffin, Eoin; Guarochico-Moreira, Victor H.; Barry, D.; Xin, B.; Yağmurcukardeş, Mehmet; Zhang, Sheng; Geim, Andre K.; Peeters, François M.; Lozada-Hidalgo, MarceloStrong electric fields can accelerate molecular dissociation reactions. The phenomenon known as the Wien effect was previously observed using high-voltage electrolysis cells that produced fields of about 107 V m−1, sufficient to accelerate the dissociation of weakly bound molecules (e.g., organics and weak electrolytes). The observation of the Wien effect for the common case of water dissociation (H2O ⇆ H+ + OH−) has remained elusive. Here we study the dissociation of interfacial water adjacent to proton-permeable graphene electrodes and observe strong acceleration of the reaction in fields reaching above 108 V m−1. The use of graphene electrodes allows measuring the proton currents arising exclusively from the dissociation of interfacial water, while the electric field driving the reaction is monitored through the carrier density induced in graphene by the same field. The observed exponential increase in proton currents is in quantitative agreement with Onsager’s theory. Our results also demonstrate that graphene electrodes can be valuable for the investigation of various interfacial phenomena involving proton transport.Article Citation - WoS: 40Citation - Scopus: 38Anisotropic and Outstanding Mechanical, Thermal Conduction, Optical, and Piezoelectric Responses in a Novel Semiconducting Bcn Monolayer Confirmed by First-Principles and Machine Learning(Elsevier, 2022) Mortazavi, Bohayra; Fazel Shojaei; Yağmurcukardeş, Mehmet; Alexander Shapeev; Xiaoying ZhuangGraphene-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.Article Citation - WoS: 40Citation - Scopus: 38Gas Permeation Through Graphdiyne-Based Nanoporous Membranes(Nature Research, 2022) Zhou, Zhihua; Tan, Yongtao; Yang, Qian; Bera, Achintya; Xiong, Zecheng; Yağmurcukardeş, Mehmet; Kim, MinsooNanoporous membranes based on two dimensional materials are predicted to provide highly selective gas transport in combination with extreme permeance. Here we investigate membranes made from multilayer graphdiyne, a graphene-like crystal with a larger unit cell. Despite being nearly a hundred of nanometers thick, the membranes allow fast, Knudsen-type permeation of light gases such as helium and hydrogen whereas heavy noble gases like xenon exhibit strongly suppressed flows. Using isotope and cryogenic temperature measurements, the seemingly conflicting characteristics are explained by a high density of straight-through holes (direct porosity of ∼0.1%), in which heavy atoms are adsorbed on the walls, partially blocking Knudsen flows. Our work offers important insights into intricate transport mechanisms playing a role at nanoscale.Article Citation - WoS: 6Citation - Scopus: 7Interface-Dependent Phononic and Optical Properties of Geo/Moso Heterostructures(Royal Society of Chemistry, 2022) Yağmurcukardeş, Mehmet; Sözen, Yiğit; Başkurt, Mehmet; Peeters, François M.; Şahin, HasanThe interface-dependent electronic, vibrational, piezoelectric, and optical properties of van der Waals heterobilayers, formed by buckled GeO (b-GeO) and Janus MoSO structures, are investigated by means of first-principles calculations. The electronic band dispersions show that O/Ge and S/O interface formations result in a type-II band alignment with direct and indirect band gaps, respectively. In contrast, O/O and S/Ge interfaces give rise to the formation of a type-I band alignment with an indirect band gap. By considering the Bethe-Salpeter equation (BSE) on top of G0W0 approximation, it is shown that different interfaces can be distinguished from each other by means of the optical absorption spectra as a consequence of the band alignments. Additionally, the low-and high-frequency regimes of the Raman spectra are also different for each interface type. The alignment of the individual dipoles, which is interface-dependent, either weakens or strengthens the net dipole of the heterobilayers and results in tunable piezoelectric coefficients. The results indicate that the possible heterobilayers of b-GeO/MoSO asymmetric structures possess various electronic, optical, and piezoelectric properties arising from the different interface formations and can be distinguished by means of various spectroscopic techniques.Article Citation - WoS: 7Citation - Scopus: 6Anisotropic Etching of Cvd Grown Graphene for Ammonia Sensing(Institute of Electrical and Electronics Engineers Inc., 2022) Yağmurcukardeş, Nesli; Bayram, Abdullah; Aydın, Hasan; Yağmurcukardeş, Mehmet; Açıkbaş, Yaser; Peeters, François M.; Çelebi, CemBare chemical vapor deposition (CVD) grown graphene (GRP) was anisotropically etched with various etching parameters. The morphological and structural characterizations were carried out by optical microscopy and the vibrational properties substrates were obtained by Raman spectroscopy. The ammonia adsorption and desorption behavior of graphene-based sensors were recorded via quartz crystal microbalance (QCM) measurements at room temperature. The etched samples for ambient NH3 exhibited nearly 35% improvement and showed high resistance to humidity molecules when compared to bare graphene. Besides exhibiting promising sensitivity to NH3 molecules, the etched graphene-based sensors were less affected by humidity. The experimental results were collaborated by Density Functional Theory (DFT) calculations and it was shown that while water molecules fragmented into H and O, NH3 interacts weakly with EGPR2 sample which reveals the enhanced sensing ability of EGPR2. Apparently, it would be more suitable to use EGRP2 in sensing applications due to its sensitivity to NH3 molecules, its stability, and its resistance to H2O molecules in humid ambient.Article Citation - WoS: 62Citation - Scopus: 59Exponentially Selective Molecular Sieving Through Angstrom Pores(Nature Publishing Group, 2021) Sun, Pengzhan; Yağmurcukardeş, Mehmet; Zhang, R.; Kuang, Wenjun; Lozada-Hidalgo, Marcelo; Liu, B. L.; Geim, Andre K.Two-dimensional crystals with angstrom-scale pores are widely considered as candidates for a next generation of molecular separation technologies aiming to provide extreme, exponentially large selectivity combined with high flow rates. No such pores have been demonstrated experimentally. Here we study gas transport through individual graphene pores created by low intensity exposure to low kV electrons. Helium and hydrogen permeate easily through these pores whereas larger species such as xenon and methane are practically blocked. Permeating gases experience activation barriers that increase quadratically with molecules’ kinetic diameter, and the effective diameter of the created pores is estimated as ∼2 angstroms, about one missing carbon ring. Our work reveals stringent conditions for achieving the long sought-after exponential selectivity using porous two-dimensional membranes and suggests limits on their possible performance.Article Citation - WoS: 1Citation - Scopus: 1First-Principles Investigation of Structural, Raman and Electronic Characteristics of Single Layer Ge3n4(Elsevier, 2022) Yayak, Yankı Öncü; Sözen, Yiğit; Tan, Fırat; Güngen, Deniz; Gao, Q.; Kang, J.; Yağmurcukardeş, Mehmet; Şahin, HasanBy means of density functional theory-based first-principle calculations, the structural, vibrational and electronic properties of single-layer Ge3N4 are investigated. Structural optimizations and phonon band dispersions reveal that single-layer ultrathin form of Ge3N4 possesses a dynamically stable buckled structure with large hexagonal holes. Predicted Raman spectrum of single-layer Ge3N4 indicates that the buckled holey structure of the material exhibits distinctive vibrational features. Electronic band dispersion calculations indicate the indirect band gap semiconducting nature of single-layer Ge3N4. It is also proposed that single-layer Ge3N4 forms type-II vertical heterostructures with various planar and puckered 2D materials except for single-layer GeSe which gives rise to a type-I band alignment. Moreover, the electronic properties of single-layer Ge3N4 are investigated under applied external in-plane strain. It is shown that while the indirect gap behavior of Ge3N4 is unchanged by the applied strain, the energy band gap increases (decreases) with tensile (compressive) strain. © 2021 Elsevier B.V.Article Citation - WoS: 35Citation - Scopus: 40Two-Dimensional Covalent Crystals by Chemical Conversion of Thin Van Der Waals Materials(American Chemical Society, 2019) Sreepal, Vishnu; Yağmurcukardeş, Mehmet; Vasu, Kalangi S.; Kelly, Daniel J.; Taylor, Sarah F. R.; Şahin, Hasan; Kravets, Vasyl G.; Nair, Rahul R.Most of the studied two-dimensional (2D) materials have been obtained by exfoliation of van der Waals crystals. Recently, there has been growing interest in fabricating synthetic 2D crystals which have no layered bulk analogues. These efforts have been focused mainly on the surface growth of molecules in high vacuum. Here, we report an approach to making 2D crystals of covalent solids by chemical conversion of van der Waals layers. As an example, we used 2D indium selenide (InSe) obtained by exfoliation and converted it by direct fluorination into indium fluoride (InF3), which has a nonlayered, rhombohedral structure and therefore cannot possibly be obtained by exfoliation. The conversion of InSe into InF3 is found to be feasible for thicknesses down to three layers of InSe, and the obtained stable InF3 layers are doped with selenium. We study this new 2D material by optical, electron transport, and Raman measurements and show that it is a semiconductor with a direct bandgap of 2.2 eV, exhibiting high optical transparency across the visible and infrared spectral ranges. We also demonstrate the scalability of our approach by chemical conversion of large-area, thin InSe laminates obtained by liquid exfoliation, into InF3 films. The concept of chemical conversion of cleavable thin van der Waals crystals into covalently bonded noncleavable ones opens exciting prospects for synthesizing a wide variety of novel atomically thin covalent crystals.Article Citation - WoS: 234Citation - Scopus: 234Quantum Properties and Applications of 2d Janus Crystals and Their Superlattices(American Institute of Physics, 2020) Yağmurcukardeş, Mehmet; Qin, Y.; Özen, Sercan; Sayyad, M.; Peeters, François M.; Tongay, S.; Şahin, HasanTwo-dimensional (2D) Janus materials are a new class of materials with unique physical, chemical, and quantum properties. The name "Janus" originates from the ancient Roman god which has two faces, one looking to the future while the other facing the past. Janus has been used to describe special types of materials which have two faces at the nanoscale. This unique atomic arrangement has been shown to present rather exotic properties with applications in biology, chemistry, energy conversion, and quantum sciences. This review article aims to offer a comprehensive review of the emergent quantum properties of Janus materials. The review starts by introducing 0D Janus nanoparticles and 1D Janus nanotubes, and highlights their difference from classical ones. The design principles, synthesis, and the properties of graphene-based and chalcogenide-based Janus layers are then discussed. A particular emphasis is given to colossal built-in potential in 2D Janus layers and resulting quantum phenomena such as Rashba splitting, skyrmionics, excitonics, and 2D magnetic ordering. More recent theoretical predictions are discussed in 2D Janus superlattices when Janus layers are stacked onto each other. Finally, we discuss the tunable quantum properties and newly predicted 2D Janus layers waiting to be experimentally realized. The review serves as a complete summary of the 2D Janus library and predicted quantum properties in 2D Janus layers and their superlattices.