Materials Science and Engineering / Malzeme Bilimi ve Mühendisliği

Permanent URI for this collectionhttps://hdl.handle.net/11147/4719

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End date: 2019Publisher: search.filters.publisher.American Chemical Society

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Now showing 1 - 10 of 22
  • Article
    Citation - WoS: 4
    Citation - Scopus: 4
    Color-Tunable All-Inorganic Cspbbr3 Perovskites Nanoplatelet Films for Photovoltaic Devices
    (American Chemical Society, 2019) Özcan, Mehmet; Demir, Mustafa Muammer; Özen, Sercan; Şahin, Hasan; Topçu, Gökhan; Demir, Mustafa Muammer; Şahin, Hasan; 04.04. Department of Photonics; 03.09. Department of Materials Science and Engineering; 03. Faculty of Engineering; 04. Faculty of Science; 01. Izmir Institute of Technology
    Herein, we demonstrate a novel coating approach to fabricate CsPbBr3 perovskite nanoplatelet film with heat-free process via electrospraying from precursor solution. A detailed study is carried out to determine the effect of various parameters such as ligand concentration, electric field, flow rate, etc. on the optical properties. By controlling the volume ratios of the oleylamine (OAm) and oleic acid (OA), the coalescing and thickness of the resulting nanoplatelets can be readily tuned that results in control over emission in the range of 100 nm without any antisolvent crystallization or heating processes. The varying electrical field and flow rate was found as inefficient on the emission characteristics of the films. In addition, the crystal films were obtained under ambient conditions on the ITO coated glass surfaces as in the desired pattern. As a result, we demonstrated a facile and reproducible way of synthesizing and coating of CsPbBr3 perovskite nanoplatelets which is suitable for large-scale production. In this method, the ability of tuning the degree of quantum confinement for perovskite nanoplatelets is promising approach for the one-step fabrication of crystal films that may enable the use in optoelectronics.
  • Article
    Citation - WoS: 6
    Citation - Scopus: 8
    Enhanced Spontaneous Emission Rate in a Low-Q Hybrid Photonic-Plasmonic Nanoresonator
    (American Chemical Society, 2019) Gökbulut, Belkıs; Özçelik, Serdar; İnanç, Arda; Demir, Mustafa Muammer; Topçu, Gökhan; Ünlütürk, Seçil Sevim; Özçelik, Serdar; Demir, Mustafa Muammer; İnci, Mehmet Naci; 04.01. Department of Chemistry; 03.09. Department of Materials Science and Engineering; 03. Faculty of Engineering; 04. Faculty of Science; 01. Izmir Institute of Technology
    In this paper, CdTe quantum dots (QDs)-doped single electrospun polymer nanofibers are partially coated with gold nanoparticles to form distinct hybrid photonic-plasmonic nanoresonators to investigate the critical role of the cavity-confined hybrid mode on the modification of the spontaneous emission dynamics of the fluorescent emitters in low-Q photonic cavities. A total enhancement factor of 11.2 is measured via a time-resolved experimental technique, which shows that there is an increase of about three times in the spontaneous emission rate for the QDs-doped gold nanoparticle-decorated nanofibers as they are compared with those uncoated ones. The physical mechanism affecting the spontaneous emission rate of the encapsulated QDs in such a hybrid photonic-plasmonic nanoresonator is explained to be due to regeneration of the mode field in the nanofiber cavity upon the interaction of the dipoles with the surface plasmons of distinctive gold nanoparticles that surround the outer surface of the nanofiber.
  • Article
    Citation - WoS: 31
    Citation - Scopus: 32
    Evaluating the Critical Roles of Precursor Nature and Water Content When Tailoring Magnetic Nanoparticles for Specific Applications
    (American Chemical Society, 2018) Cotin, Geoffrey; Kiefer, Celine; Perton, Francis; Boero, Mauro; Özdamar, Burak; Bouzid, Assil; Begin-Colin, Sylvie; 01. Izmir Institute of Technology
    Because of the broad range of application of iron oxide nanoparticles (NPs), the control of their size and shape on demand remains a great challenge, as these parameters are of upmost importance to provide NPs with magnetic properties tailored to the targeted application. One promising synthesis process to tune their size and shape is the thermal decomposition one, for which a lot of parameters were investigated. But two crucial issues were scarcely addressed: the precursors nature and water content. Two in house iron stearates with two or three stearate chains were synthesized, dehydrated, and then tested in standard synthesis conditions of spherical and cubic NPs. Investigations combined with modeling showed that the precursors nature and hydration rate strongly affect the thermal decomposition kinetics and yields, which, in turn, influence the NP size. The cubic shape depends on the decomposition kinetics but also crucially on the water content. A microscopic insight was provided by first-principles simulation showing an iron reduction along the reaction pathway and a participation of water molecules to the building unit formation.
  • Article
    Citation - WoS: 93
    Citation - Scopus: 95
    Single-Layer Janus-Type Platinum Dichalcogenides and Their Heterostructures
    (American Chemical Society, 2019) Kahraman, Zeynep; Kandemir, Ali; Yağmurcukardeş, Mehmet; Şahin, Hasan; Şahin, Hasan; Kahraman, Zeynep; 04.04. Department of Photonics; 04. Faculty of Science; 01. Izmir Institute of Technology
    Ultrathin two-dimensional Janus-type platinum dichalcogenide crystals formed by two different atoms at opposite surfaces are investigated by performing state-of-the-art density functional theory calculations. First, it is shown that single-layer PtX2 structures (where X = S, Se, or Te) crystallize into the dynamically stable IT phase and are indirect band gap semiconductors. It is also found that the substitutional chalcogen doping in all PtX2 structures is favorable via replacement of surface atoms with a smaller chalcogen atom, and such a process leads to the formation of Janus-type platinum dichalcogenides (XPtY, where X and Y stand for S, Se, or Te) which are novel single-layer crystals. While all Janus structures are indirect band gap semiconductors as their binary analogues, their Raman spectra show distinctive features that stem from the broken out-of-plane symmetry. In addition, it is revealed that the construction of Janus crystals enhances the piezoelectric constants of PtX2 crystals significantly both in the in plane and in the out-of-plane directions. Moreover, it is shown that vertically stacked van der Waals heterostructures of binary and ternary (Janus) platinum dichalcogenides offer a wide range of electronic features by forming bilayer heterojunctions of type-I, type-II, and type-III, respectively. Our findings reveal that Janus-type ultrathin platinum dichalcogenide crystals are quite promising materials for optoelectronic device applications.
  • Article
    Citation - WoS: 5
    Citation - Scopus: 5
    Enhancement of the Spontaneous Emission Rate of Perovskite Nanowires Coupled Into Cylindrical Hollow Nanocavities Formed on the Surface of Polystyrene Microfibers
    (American Chemical Society, 2019) Gökbulut, Belkis; İnanç, Arda; Demir, Mustafa Muammer; Güner, Tuğrul; Demir, Mustafa Muammer; İnci, M. Naci; 03.09. Department of Materials Science and Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    Fluorescent CsPbBr3 nanowires are uniformly integrated into a porous polystyrene matrix in the form of microfibers to investigate the changes in their spontaneous emission rate. Cylindrical hollow nanocavities, ranging from 75 to 160 nm in diameter, are grown on the surface of the polymer microfibers during the fabrication process, which allow coupling light that is emitted from the excited CsPbBr3 nanowires. Time-resolved experiments elucidate that the spontaneous emission rate of the perovskite nanowires is observed to increase by a factor of 4.9, upon coupling of the excited optical modes into the nanocavities, which is demonstrated to be in good agreement with our theoretical calculations.
  • Article
    Citation - WoS: 72
    Citation - Scopus: 77
    Gd3+-Doped Alpha-Cspbi3 Nanocrystals With Better Phase Stability and Optical Properties
    (American Chemical Society, 2019) Güvenç, Çetin Meriç; Şahin, Hasan; Yalçınkaya, Yenal; Demir, Mustafa Muammer; Özen, Sercan; Şahin, Hasan; Demir, Mustafa Muammer; 04.04. Department of Photonics; 03.09. Department of Materials Science and Engineering; 03. Faculty of Engineering; 04. Faculty of Science; 01. Izmir Institute of Technology
    Black alpha-CsPbI3 perovskites are unable to maintain their phase stability under room conditions; hence, the alpha-CsPbI3 phase transforms into a thermodynamically stable yellow delta-CsPbI3 phase within a few days, which has a nonperovskite structure and high band gap for optoelectronic applications. This phase transformation should be prevented or at least retarded to make use of superior properties of alpha-CsPbI3 in optoelectronic applications. In this study, Gd3+ doping was employed with the aim of increasing the stability of alpha-CsPbI3. All doped alpha-CsPbI3 nanocrystals with various levels of Gd3+, between 5 and 15 mol %, have shown greater phase stability than that of the pure alpha-CsPbI3 phase from 5 days up to 11 days under ambient conditions. This prolonged phase stability can be attributed to three potential reasons: increased tolerance factor of the perovskite structure, distorted cubic symmetry, and decreased defect density in nanocrystals. Urbach energy values suggest the reduction of defect density in the doped nanocrystals. Also, use of 10 mol % Gd3+ as a dopant material increases the photoluminescence quantum yield from 70 to 80% and fluorescence lifetime of alpha-CsPbI3 from 47.4 to 64.4 ns. Further, density functional theory calculations are in a good agreement with the experimental results.
  • Article
    Citation - WoS: 17
    Citation - Scopus: 17
    Monitoring the Doping and Diffusion Characteristics of Mn Dopants in Cesium Lead Halide Perovskites
    (American Chemical Society, 2018) Güner, Tuğrul; Şahin, Hasan; Akbalı, Barış; Demir, Mustafa Muammer; Özcan, Mehmet; Topçu, Gökhan; Demir, Mustafa Muammer; Şahin, Hasan; 04.04. Department of Photonics; 03.09. Department of Materials Science and Engineering; 03. Faculty of Engineering; 04. Faculty of Science; 01. Izmir Institute of Technology
    Cesium lead perovskites, in the form of CsPbX3 or Cs4PbX6, have been widely used for various optoelectronic applications due to their exceptionally good optical properties. In this study, the effect of Mn doping on the structural and optical properties of cesium lead halide perovskite crystals are investigated from both experimental and theoretical points of view. It is found that adding MnCl2 during the synthesis not only leads to a Mn-driven structural phase transition from Cs4PbBr6 to CsPbCl3 but also triggers the Br- to Cl- halide exchange. On the other hand, it is observed that, under UV illumination, the color of Mn-doped crystals changes from orange to blue in approximately 195 h. While the intensity of Mn-originated photoluminescence emission exponentially decays in time, the intensity of CsPbCl3-originated emission remains unchanged. In addition, diffusive motion of Mn ions results in both a growing population of MnO2 at the surface and transition of the host into a cesium-rich Cs4PbCl6 phase.
  • Article
    Citation - WoS: 12
    Citation - Scopus: 12
    Ordering of Air-Oxidized Decanethiols on Au(111)
    (American Chemical Society, 2018) Sotthewes, Kai; Kap, Özlem; Kap, Özlem; Wu, Hairong; Thompson, Damien; Huskens, Jurriaan; Zandvliet, Harold J. W.; 03.09. Department of Materials Science and Engineering; 03. Faculty of Engineering; 01. Izmir Institute of Technology
    Self-assembled monolayers (SAMs) of alkanethiols on gold are a commonly used platform for nanotechnology owing to their ease of preparation and high surface coverage. Unfortunately, the gold-sulfur bond is oxidized at ambient conditions which alters the stability and structure of the monolayer. We show using scanning tunneling microscopy and X-ray photoelectron spectroscopy that decanethiolate molecules oxidize into decanesulfonates that organize into a hitherto unknown striped phase. Air-exposed SAMs oxidize, as can be determined by a shift of the S 2p peak and the appearance of O 1s photoelectrons as part of the decanethiol monolayer transforms into a lamellae-like decanesulfonate structure when exposed to air. The herringbone structure of the Au(111) surface is preserved, indicating that the interaction between the molecules and the surface is rather weak as these findings are substantiated by density functional theory calculations.
  • Article
    Citation - WoS: 6
    Citation - Scopus: 6
    First-Principles Study of Dissociation Processes for the Synthesis of Fe and Co Oxide Nanoparticles
    (American Chemical Society, 2018) Özdamar, Burak; Bouzid, Assil; Ori, Guido; Massobrio, Carlo; Boero, Mauro; 01. Izmir Institute of Technology
    Thermal decomposition is a practical and reliable tool to synthesize nanoparticles with monodisperse size distribution and reproducible accuracy. The nature of the precursor molecules and their interaction with the environment during the synthesis process have a direct impact on the resulting nanoparticles. Our study focuses on widely used transition-metal (Co, Fe) stearates precursors and their thermal decomposition reaction pathway. We show how the nature of the metal and the presence or absence of water molecules, directly related to the humidity conditions during the synthesis process, affect the decomposition mechanism and the resulting transition-metal oxide building blocks. This, in turn, has a direct effect on the physical and chemical properties of the produced nanoparticles and deeply influences their composition and morphology.
  • Article
    Citation - WoS: 36
    Citation - Scopus: 38
    Effect of Molecular Architecture on Cell Interactions and Stealth Properties of Peg
    (American Chemical Society, 2017) Özer, İmran; Tomak, Aysel; Tomak, Aysel; Baran, Yusuf; Bulmuş, Volga; Baran, Yusuf; Bulmuş Zareie, Volga; 03.01. Department of Bioengineering; 04.03. Department of Molecular Biology and Genetics; 03. Faculty of Engineering; 04. Faculty of Science; 01. Izmir Institute of Technology
    PEGylation, covalent attachment of PEG to therapeutic biomolecules, in which suboptimal pharmacokinetic profiles limiting their therapeutic utility are of concern, is a widely applied technology. However, this technology has been challenged by reduced bioactivity of biomolecules upon PEGylation and immunogenicity of PEG triggering immune response and abrogating clinical efficacy, which collectively necessitate development of stealth polymer alternatives. Here we demonstrate that comb-shape poly[oligo(ethylene glycol) methyl ether methacrylate] (POEGMA), a stealth polymer alternative, has a more compact structure than PEG and self-organize into nanoparticles in a molecular weight dependent manner. Most notably, we show that comb-shape POEGMA promotes significantly higher cellular uptake and exhibits less steric hindrance imposed on the conjugated biomolecule than PEG. Collectively, comb-shape POEGMA offers a versatile alternative to PEG for stealth polymer-biomolecule conjugation applications.