Materials Science and Engineering / Malzeme Bilimi ve Mühendisliği
Permanent URI for this collectionhttps://hdl.handle.net/11147/4719
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Article Citation - WoS: 10Citation - Scopus: 9Recyclability of Cspbbr3 Quantum Dot Glass Nanocomposites for Their Long-Standing Use in White Leds(2022) Vahedigharehchopogh, Naji; Erol, Erdinç; Kıbrıslı, Orhan; Genç, Aziz; Çelikbilek Ersundu, Miray; Ersundu, Ali ErçinThe embedding of CsPbBr3 perovskite quantum dots (PQDs) in an inorganic glass matrix not only protects them against chemical, thermal, and photodegradation but also provides an effective strategy to isolate toxic elements such as Pb from the environment for a long period of time. Herein, the recyclability of glass is another important feature that contributes to environmental sustainability. Hence, effective and efficient recycling technologies are needed for the widespread use of PQD glass nanocomposites (GNCs) in many commercial applications. However, studies on the recyclability of CsPbBr3 PQD GNCs have not been conducted so far. Therefore, in this work, we investigate the structural, thermal, optical, and photoluminescence properties of recycled CsPbBr3 PQD GNCs to assess their suitability as long-standing and reusable luminescent materials. For this purpose, the recyclability of GNCs is checked by three repeated melt-quenching and subsequent heat-treatment processes. Although the color emission properties of GNCs under the same heat-treatment conditions show a slight variation after each recycling step, PQD GNCs almost retain their PLQY even after the last recycling step. Ultimately, a prototype white light-emitting diode is constructed by coupling recycled PQD GNCs and a commercial red phosphor on top of a blue LED chip showing high-performance with CIE color coordinates of x = 0.3228, y = 0.3470 and a CCT value of 5920 K. The findings of this work reveal that the recyclability of PQD GNCs holds great promise for a more sustainable technology.Article Citation - WoS: 17Citation - Scopus: 19Strong Coupling of Carbon Quantum Dots in Liquid Crystals(American Chemical Society, 2022) Sarısözen, Sema; Polat, Nahit; Mert Balcı, Fadime; Güvenç, Çetin Meriç; Kocabaş, Çoşkun; Yağlıoğlu, Halime Gül; Balcı, SinanCarbon quantum dots (CDs) have recently received a tremendous amount of interest owing to their attractive optical properties. However, CDs have broad absorption and emission spectra limiting their application ranges. We herein, for the first time, show synthesis of water-soluble red emissive CDs with a very narrow line width (∼75 meV) spectral absorbance and hence demonstrate strong coupling of CDs and plasmon polaritons in liquid crystalline mesophases. The excited state dynamics of CDs has been studied by ultrafast transient absorption spectroscopy, and CDs display very stable and strong photoluminescence emission with a quantum yield of 35.4% and a lifetime of ∼2 ns. More importantly, we compare J-aggregate dyes with CDs in terms of their absorption line width, photostability, and ability to do strong coupling, and we conclude that highly fluorescent CDs have a bright future in the mixed light-matter states for emerging applications in future quantum technologies.Article Citation - WoS: 3Citation - Scopus: 5Physically Unclonable Security Patterns Created by Electrospinning, and Authenticated by Two-Step Validation Method(IOP Publishing, 2022) Taşcıoğlu, Didem; Atçı, Arda; Sevim Ünlütürk, Seçil; Özçelik, SerdarCounterfeiting is a growing economic and social problem. For anticounterfeiting, random and inimitable droplet/fiber patterns were created by the electrospinning method as security tags that are detectable under UV light but invisible in daylight. To check the authenticity of the original security patterns created; images were collected with a simple smartphone microscope and a database of the recorded original patterns was created. The originality of the random patterns was checked by comparing them with the patterns recorded in the database. In addition, the spectral signature of the patterns in the droplet/fiber network was obtained with a simple and hand-held spectrometer. Thus, by reading the spectral signature from the pattern, the spectral information of the photoluminescent nanoparticles was verified and thus a second-step verification was established. In this way, anticounterfeiting technology that combines ink formula, unclonable security pattern creation and two-level verification is developed.Article Citation - WoS: 3Citation - Scopus: 3Monolayer Aste2: Stable Robust Metal in 2d, 1d and 0d(Wiley, 2018) Badalov, S. V.; Kandemir, Ali; Şahin, HasanThe structural, phononic, and electronic properties of the monolayer structures of AsTe2 are characterized by performing density functional theory (DFT) calculations. Total energy optimization and phonon calculations reveal that single layers of the 2H-AsTe2 and 1T-AsTe2 phases form dynamically stable crystal structures. Electronic structure analysis also shows that both 2H and 1T phases have nonmagnetic metallic character. It is also predicted that the metallic nature of the ultra-thin both 2H-AsTe2 and 1T-AsTe2 structures remain unchanged even under high biaxial strain values. For further examination of the dimensionality effect in the robust metallicity in 2D AsTe2 phases, electronic characteristics of 1D nanoribbons and 0D quantum dots are also investigated. It is found that independent from the dimension and crystallographic orientations 0D and 1D structures of 2H- and 1T-AsTe2 structures have metallic behavior. It is found that single layers of AsTe2 are quite promising materials for nanodevice applications owing to the robust metallic character.Article Citation - Scopus: 2Enthalpy-Driven Selective Loading of Cdse0.75s0.25 Nanoalloys in Triblock Copolymer Polystyrene-B(Elsevier Ltd., 2016) Aşkın, Görkem; Çeçen, Volkan; Ünlütürk, Seçil Sevim; Özçelik, Serdar; Demir, Mustafa MuammerCdSe0.75S0.25 nanoalloys were blended with asymmetric triblock copolymer of polystyrene-b-polyisoprene-b-polystyrene(PS-SIS) in tetrahydrofuran. The fraction of styrene block varies from 14 to 22% with respect to isoprene by mass. The morphology of the copolymer cast film experiences a phase change from cylinder to lamella. CdSe0.75S0.25 nanoalloys were prepared by two-phase method. The surface of the nanoalloys was capped by either oleic acid (OA) or n-tri-octylphosphonic acid (TOPO) in situ. The mean diameter of the alloyed particles is around 12 nm in both systems. The chemical nature of the nanoalloy surface was found to influence the dispersion of the particles over polymer volume. The size of the nanoalloy domains in PS is 50 nm, on average, consisting of approximately 0.7 wt% nanoalloys. However, the size of the nanoalloy domains is smaller when they are loaded into PS-SIS. The structure formation is predominantly determined by enthalpic compatibilization. Atomic force microscopy results suggest that the nanoalloys capped with TOPO sequester into PS-rich domains and enlarge the domain. On the other hand, the ones capped with OA prefer to locate in polyisoprene domains. The increase of particles over 1.0 wt% distorts the lamella structure.