Photonics / Fotonik
Permanent URI for this collectionhttps://hdl.handle.net/11147/2590
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Article Citation - WoS: 3Citation - Scopus: 3Green Fabrication of Lanthanide-Doped Hydroxide-Based Phosphors: Y(oh)(3):eu3+ Nanoparticles for White Light Generation(Beilstein-Institut Zur Forderung der Chemischen Wissenschaften, 2019) Güner, Tuğrul; Kuş, Anılcan; Özcan, Mehmet; Genç, Aziz; Şahin, Hasan; Demir, Mustafa MuammerPhosphors can serve as color conversion layers to generate white light with varying optical features, including color rendering index (CRI), high correlated color temperature (CCT), and luminous efficacy. However, they are typically produced under harsh synthesis conditions such as high temperature, high pressure, and/or by employing a large amount of solvent. In this work, a facile, water-based, rapid method has been proposed to fabricate lanthanide-doped hydroxide-based phosphors. In this sense, sub-micrometer-sized Y(OH)(3):Eu3+ particles (as red phosphor) were synthesized in water at ambient conditions in <= 60 min reaction time. The doping ratio was controlled from 2.5-20 mol %. Additionally, first principle calculations were performed on Y(OH)(3):Eu3+ to understand the preferable doping scenario and its optoelectronic properties. As an application, these fabricated red phosphors were integrated into a PDMS/YAG:Ce3+ composite and used to generate white light. The resulting white light showed a remarkable improvement (approximate to 24%) in terms of luminous efficiency, a slight reduction of CCT (from 3900 to 3600 K), and an unchanged CRI (approximate to 60) as the amount of Y(OH)(3):Eu3+ was increased.Article Citation - WoS: 3Citation - Scopus: 4Experimental and First-Principles Investigation of Cr-Driven Color Change in Cesium Lead Halide Perovskites(American Institute of Physics, 2019) Özen, Sercan; Güner, Tuğrul; Topçu, Gökhan; Özcan, Mehmet; Demir, Mustafa Muammer; Şahin, HasanHerein, we report room temperature Cr-doping for all-inorganic perovskites that have attracted great attention in recent years due to their extraordinary optical properties, low cost, and ease of synthesis. Incorporation of Cr 3 + ions into the perovskite crystal lattices is achieved by following a facile route involving an antisolvent recrystallization method at room temperature. It is shown that both Cr-doping and formation of crystals in the CsPbBr x Cl 3 - x phase are provided by increasing the concentration of the CrCl 3 solution. It is also observed that the doping procedure leads to the emergence of three types of distinctive peaks in the PL spectrum originating from CsPbBr x Cl 3 - x domains (476-427nm), Cr-strained host lattices (515nm), and midgap states formed by Cr dopants (675-775nm). It is also found that the Cr-doped perovskites emitting a dark violaceous color change their color to white with a high color rendering index (88) in 30-day time intervals. Easy-tunable optical properties of all-inorganic Cs perovskites indicate their great potential for future optoelectronic device applications.Article Citation - WoS: 3Citation - Scopus: 4Soluble Cytotoxic Ruthenium(ii) Complexes With 2-Hydrazinopyridine(Pleiades Publishing, 2019) Soliman, A. A.; Attaby, F. A.; Alajrawy, O., I; Majeed, S. R.; Şahin, C.; Varlıklı, CananNew water soluble Ru(II) binary complex [Ru(C5H7N3)(X)(H2O)(2)] with 2-hydrazinopyridine and its ternary complexes with X = dichloride, oxalate, malonate or pyrophosphate ligands have been synthesized. The complexes have been characterized using elemental analyses, mass, IR, and UV-Vis. spectroscopies, cyclic voltammetry, magnetic susceptibility, and thermal analysis. The complexes are diamagnetic and the electronic spectral data showed that peaks are due to low spin octahedral Ru(II) complexes. The optimized structures of the complexes 1-4 indicate distorted octahedral geometry with bond angles around the ruthenium atom ranged from 80.44 degrees to 99.64 degrees. The values of the electronic energies (-635 to -1145 a.u.), the highest occupied molecular orbital energies (-0.181 to 0.073 a.u.) and lowest unoccupied molecular orbital energies (-0.056 to 0.167 a.u.) indicate the stability of the complexes. The complexes are polarized as indicated from the dipole moment values (9.39-14.27 Debye). The complexes have noticeable cytotoxicity with IC50 (mu M): 0.011-0.062 (HepG-2), 0.015-0.080 (MCF-7), 0.015-0.116 (HCT-116), and PC-3 (0.034-0.125).Article Citation - WoS: 28Citation - Scopus: 28Enhanced Stability of Single-Layer W-Gallenene Through Hydrogenation(American Chemical Society, 2018) Badalov, S. V.; Yağmurcukardeş, Mehmet; Peeters, François M.; Şahin, HasanUsing density functional theory based first-principles calculations, the effect of surface hydrogenation on the structural, dynamical, electronic, and mechanical properties of monolayer washboard-gallenene (w-gallenene) is investigated. It is found that the dynamically stabilized strained monolayer of w-gallenene has a metallic nonmagnetic ground state. Both one-sided and two-sided hydrogenations of w-gallenene suppress its dynamical instability even when unstrained. Unlike one-sided hydrogenated monolayer w-gallenene (os-w-gallenene), two-sided hydrogenated monolayer w-gallenene (ts-w-gallenene) possesses the same crystal structure as w-gallenene. Electronic band structure calculations reveal that monolayers of hydrogenated derivatives of w-gallenene exhibit also metallic nonmagnetic ground state. Moreover, the linear-elastic constants, in-plane stiffness and Poisson ratio, are enhanced by hydrogenation, which is opposite to the behavior of other hydrogenated monolayer crystals. Furthermore, monolayer w-gallenene and ts-w-gallenene remain dynamically stable up to relatively higher biaxial strains as compared to borophene. With its enhanced dynamical stability, robust metallic character, and enhanced linear-elastic properties, hydrogenated monolayer w-gallenene is a potential candidate for nanodevice applications as a two-dimensional flexible metal.Article Citation - WoS: 93Citation - Scopus: 95Single-Layer Janus-Type Platinum Dichalcogenides and Their Heterostructures(American Chemical Society, 2019) Kahraman, Zeynep; Kandemir, Ali; Yağmurcukardeş, Mehmet; Şahin, HasanUltrathin 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: 72Citation - Scopus: 77Gd3+-Doped Alpha-Cspbi3 Nanocrystals With Better Phase Stability and Optical Properties(American Chemical Society, 2019) Güvenç, Çetin Meriç; Yalçınkaya, Yenal; Özen, Sercan; Şahin, Hasan; Demir, Mustafa MuammerBlack 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: 35Citation - Scopus: 36Colloidal Nanodisk Shaped Plexcitonic Nanoparticles With Large Rabi Splitting Energies(American Chemical Society, 2019) Mert Balcı, Fadime; Sarısözen, Sema; Polat, Nahit; Balcı, SinanWhen plasmons supported by metal nanoparticles interact strongly with molecular excitons or excitons of semiconducting quantum dots, plexcitons are formed in the strong coupling regime. The hybrid plexcitonic nanoparticles with a wide range of sizes and shapes have been synthesized by using wet chemistry methods or have been fabricated on solid substrates by using lithographic techniques. In order to deeply understand plasmon-exciton interaction at the nanoscale dimension and boost the performance of nanophotonic devices made of plexcitonic nanoparticles, new types of plexcitonic nanoparticles with tunable optical properties and outstanding stability at room temperature are urgently needed. Herein, we for the first time report pure colloidal nanodisk shaped plexcitonic nanoparticles with very large Rabi splitting energies, i.e., more than 350 meV. We synthesize silver nanoprisms by using seed mediated synthesis and then convert nanoprisms to nanodisks at a high temperature. Localized plasmon resonance of the silver nanodisk in the visible spectrum can be effectively tuned by heating. Subsequently, self-assembly of J-aggregate dyes on plasmonic nanodisks produces plexcitonic nanoparticles. We envision that colloidal nanodisk shaped plexcitonic nanoparticles with very large Rabi splitting energies and outstanding stability at room temperature will enlarge the application of plexcitonic nanoparticles in a variety of fields such as polariton laser, biosensor, plasmon molecular nanodevices, and energy flow at nanoscale dimensions.Article Citation - WoS: 15Citation - Scopus: 15Vertical van der waals heterostructure of single layer InSe and SiGe(American Chemical Society, 2019) Eren, İsmail; Özen, Sercan; Sözen, Yiğit; Yağmurcukardeş, Mehmet; Şahin, HasanWe present a first-principles investigation on the stability, electronic structure, and mechanical response of ultrathin heterostructures composed of single layers of InSe and SiGe. First, by performing total energy optimization and phonon calculations, we show that single layers of InSe and SiGe can form dynamically stable heterostructures in 12 different stacking types. Valence and conduction band edges of the heterobilayers form a type-I heterojunction having a tiny band gap ranging between 0.09 and 0.48 eV. Calculations on elastic-stiffness tensor reveal that two mechanically soft single layers form a heterostructure which is stiffer than the constituent layers because of relatively strong interlayer interaction. Moreover, phonon analysis shows that the bilayer heterostructure has highly Raman active modes at 205.3 and 43.7 cm(-1), stemming from the out-of-plane interlayer mode and layer breathing mode, respectively. Our results show that, as a stable type-I heterojunction, ultrathin heterobilayer of InSe/SiGe holds promise for nanoscale device applications.Article Citation - WoS: 31Citation - Scopus: 34Highly Efficient Supercapacitor Using Single-Walled Carbon Nanotube Electrodes and Ionic Liquid Incorporated Solid Gel Electrolyte(SAGE Publications, 2018) Siyahjani, Shirin; Öner, Saliha; Singh, Pramod K.; Varlıklı, CananGel polymer electrolyte (GPE) comprising a low viscosity ionic liquid, that is, 1-propyl-3-methyl imidazolium bis(trifluoromethyl sulfonyl)imide (PMI-TFSI, viscosity 38 cP at 20°C) and a polymer, that is, polyvinyl alcohol (PVA) have been prepared using solution cast technique and characterized by impedance spectroscopy, X-ray diffraction, differential scanning calorimetry, optical microscopy, and Fourier transform infrared spectroscopy. Blending PMI-TFSI with PVA matrix hindered the crystallinity of polymer matrix and presented remarkable enhancement in electrical conductivity with a conductivity maxima at 250 wt% PMI-TFSI. The prepared electric double-layer capacitor using single-walled carbon nanotube as symmetric electrodes and PVA:250 wt% PMI-TFSI as GPE presented a capacitance value of about 28 F g−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.