Browsing by Author "Yaman, M."

Now showing 1 - 11 of 11

Open Access
All-chalcogenide glass omnidirectional photonic band gap variable infrared filters
(AIP Publishing, 2009) Kondakci, H. E.; Yaman, M.; Koylu, O.; Dana, A.; Bayındır, Mehmet
We report on the design, fabrication, and characterization of spatially variable infrared photonic band gap filter that consists of thermally evaporated, high refractive indexcontrast, amorphous chalcogenide glass multilayers. Due to graded thickness structure, the filter exhibits a position dependent stop band and a cavity mode ranging from 1.8 to 3.4 μm3.4 μmwavelengths. Reflection measurements on the variable filter agree well with theoretical calculations. These results pave the way to low-loss infrared mirrors, filters, spectral imaging, and miniaturized spectrometers at infrared region.
Open Access
Arrays of indefinitely long uniform nanowires and nanotubes
(Nature Publishing Group, 2011) Yaman, M.; Khudiyev, T.; Ozgur E.; Kanik, M.; Aktas, O.; Ozgur, E. O.; Deniz, H.; Korkut, E.; Bayındır, Mehmet
Nanowires are arguably the most studied nanomaterial model to make functional devices and arrays. Although there is remarkable maturity in the chemical synthesis of complex nanowire structures, their integration and interfacing to macro systems with high yields and repeatability still require elaborate aligning, positioning and interfacing and post-synthesis techniques. Top-down fabrication methods for nanowire production, such as lithography and electrospinning, have not enjoyed comparable growth. Here we report a new thermal size-reduction process to produce well-ordered, globally oriented, indefinitely long nanowire and nanotube arrays with different materials. The new technique involves iterative co-drawing of hermetically sealed multimaterials in compatible polymer matrices similar to fibre drawing. Globally oriented, endlessly parallel, axially and radially uniform semiconducting and piezoelectric nanowire and nanotube arrays hundreds of metres long, with nanowire diameters less than 15ĝ€‰nm, are obtained. The resulting nanostructures are sealed inside a flexible substrate, facilitating the handling of and electrical contacting to the nanowires. Inexpensive, high-throughput, multimaterial nanowire arrays pave the way for applications including nanowire-based large-area flexible sensor platforms, phase-changememory, nanostructure-enhanced photovoltaics, semiconductor nanophotonics, dielectric metamaterials,linear and nonlinear photonics and nanowire-enabled high-performance composites. © 2011 Macmillan Publishers Limited. All rights reserved.
Open Access
Bioinspired optoelectronic nose with nanostructured wavelength-scalable hollow-core infrared fibers
(Wiley, 2011) Yildirim, A.; Vural, M.; Yaman, M.; Bayındır, Mehmet
A digital photonic nose concept based on infrared absorption inside a hollow core infrared transmitting fiber array is presented. Wavelength-scalable photonic band gap fibers filter specific energy photons from a blackbody source, where volatile compounds selectively absorb photons depending on their chemical absorption spectrum. The pattern resulting in the detector array is processed as a binary signature. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.
Open Access
Design, synthesis, anticancer activity, molecular docking and ADME studies of novel methylsulfonyl indole-benzimidazoles in comparison with ethylsulfonyl counterparts
(Royal Society of Chemistry, 2021-04-26) Zengin Karadayı, F.; Yaman, M.; Kışla, M. M.; Konu, Özlen; Ateş-Alagöz, Z.
Cancer poses a world-wide healthcare problem, demanding selective and effective therapy protocols. To address that, a vast amount of therapeutic candidates are being investigated in the field of medicinal chemistry. Accordingly, indole-benzimidazole structures have recently gained considerable interest because of their anticancer properties and estrogen receptor (ER) modulatory actions. In this study, novel methylsulfonyl indole-benzimidazole derivatives have been synthesized upon substitution of respectively the first (R1) and fifth (R2) positions of benzimidazole and indole groups. Structure and activity relationships were then studied via1H NMR, 13C NMR, mass spectral and in silico docking analyses, as well as cell viability measurements. We found that the compounds exhibited substantial affinity levels towards ER alpha (ERα). In addition, the correlation analysis of cytotoxicity profiles between ethyl- and methyl-sulfonyl indole-benzimidazoles revealed a collection of effective and consistent R1 and R2 substitutions. However, for some candidate derivatives, distinctive cytotoxicity levels and varying viability versus ERα affinity correlations were observable across the studies, suggesting that the sulfonyl side chain modifications themselves can also influence the ERα binding levels. These results demonstrated that our novel methylsulfonyl indole-benzimidazole derivatives, similar to their ethylsulfonyl counterparts, exhibit anticancer effects with potential estrogen receptor modulatory actions.
Open Access
High selectivity boolean olfaction using hollow-core wavelength-scalable Bragg fibers
(American Chemical Society, 2012) Yaman, M.; Yildirim, A.; Kanik, M.; Cinkara, T. C.; Bayındır, Mehmet
A new odorant detection scheme, based on infrared absorption of volatile organics inside an optofluidic channel array, is discussed in terms of its selectivity. The sensor unit of the array is a hollow core Bragg fiber that selectively (spectrally) guides an incident continuum radiation. The presence of infrared absorbing molecules in the channel results in the quenching of the otherwise transmitted signal. Each fiber unit in the array is designed and fabricated so that it is sensitive to specific chemical bonds and the bond environment, but at the same time, each fiber is also broadly sensitive to a large number of chemicals due to their infrared absorbance spectra. The cumulative array response data, using an appropriate threshold, enable selective binary sampling of the infrared fingerprint of hundreds of molecules. The selectivity of the system is quantitatively investigated with computer simulations and found to be exponentially increasing with the number of fibers in the array. Relatively simple data analysis using binary logic combined with the high selectivity of the novel scheme paves the way for ubiquitous application of electronic noses in toxic gas detection, food quality control, environmental monitoring, and breath analysis for disease diagnostics. © 2011 American Chemical Society.
Open Access
Large and dynamical tuning of a chalcogenide Fabry-Perot cavity mode by temperature modulation
(Optical Society of America, 2010) Yaman, M.; Kondakci, H. E.; Bayındır, Mehmet
Te-enriched chalcogenide glass Ge15As25Se15Te45 (GAST) is synthesized, thermo-optically characterized and used to fabricate a one dimensional photonic crystal cavity mode that is dynamically and reversibly tuned by temperature modulation. The optical cavity mode is designed using GAST and As2S3 glasses after fully determining their temperature dependence of the complex refractive indices in the visible and near infrared spectrum using spectroscopic ellipsometry. By making use of the very large thermo-optic coefficient (dn/dT = 4x10(-4)/degrees C) of GAST glass at 1.2 mu m, the cavity mode of the multilayer was tuned reversibly more than 16 nm, which is, to the best of our knowledge, an order of magnitude larger for this kind of cavity modulation. Wide and dynamical spectral tuning of low bandgap chalcogenide glasses via temperature modulation can be utilized in photonic crystal based integrated optics, quantum dot resonance matching, solid state and gas laser components, and infrared photonic crystal fibers. (C) 2010 Optical Society of America
Open Access
Macroscopic assembly of indefinitely long and parallel nanowires into large area photodetection circuitry
(American Chemical Society, 2012) Ozgur E.; Aktas, O.; Kanik, M.; Yaman, M.; Bayındır, Mehmet
Integration of nanowires into functional devices with high yields and good reliability turned out to be a lot more challenging and proved to be a critical issue obstructing the wide application of nanowire-based devices and exploitation of their technical promises. Here we demonstrate a relatively easy macrofabrication of a nanowire-based imaging circuitry using a recently developed nanofabrication technique. Extremely long and polymer encapsulated semiconducting nanowire arrays, mass-produced using the iterative thermal drawing, facilitate the integration process; we manually aligned the fibers containing selenium nanowires over a lithographically defined circuitry. Controlled etching of the encapsulating polymer revealed a monolayer of nanowires aligned over an area of 1 cm 2 containing a 10 × 10 pixel array. Each light-sensitive pixel is formed by the contacting hundreds of parallel photoconductive nanowires between two electrodes. Using the pixel array, alphabetic characters were identified by the circuitry to demonstrate its imaging capacity. This new approach makes it possible to devise extremely large nanowire devices on planar, flexible, or curved substrates with diverse functionalities such as thermal sensors, phase change memory, and artificial skin. © 2012 American Chemical Society.
Open Access
Operator representation and class transitions in elementary cellular automata
(Complex Systems Publications,, 2022) İbrahimi, M.; Güçlü, A.; Jahangirov, Naide; Yaman, M.; Gülseren, Oğuz; Jahangirov, Seymur
We exploit the mirror and complementary symmetries of elementary cellular automata (ECAs) to rewrite their rules in terms of logical operators. The operator representation based on these fundamental symmetries enables us to construct a periodic table of ECAs that maps all unique rules in clusters of similar asymptotic behavior. We also expand the elementary cellular automaton (ECA) dynamics by introducing a parameter that scales the pace with which operators iterate the system. While tuning this parameter continuously, further emergent behavior in ECAs is unveiled as several rules undergo multiple phase transitions between periodic, chaotic and complex (class 4) behavior. This extension provides an environment for studying class transitions and complex behavior in ECAs. Moreover, the emergence of class 4 structures can potentially enlarge the capacity of many ECA rules for universal computation.
Open Access
Photonic bandgap infrared spectrometer
(Optical Society of America, 2010) Kondakci, H.E.; Yaman, M.; Dana, A.; Bayındır, Mehmet
We propose and demonstrate an infrared (IR) absorption spectrometer, made with a spatially variable photonic bandgap (PBG) structure, a blackbody source, and a simple IR detector, to identify the IR molecular fingerprints of analyte molecules. The PBG-based structure consists of thermally evaporated, IR transparent, high-refractive-index chalcogenide quarter-wave stacks (QWS) with a cavity layer. Spatial variation of the very sharp transmission peak due to the QWS cavity mode allows the structure to be used as a variable IR filter. Our proposed IR-PBG spectrometer can be used for detection and identification of volatile organic compounds.
Open Access
Structural coloring in large scale core-shell nanowires
(American Chemical Society, 2011) Khudiyev, T.; Ozgur E.; Yaman, M.; Bayındır, Mehmet
We demonstrated two complementary size-dependent structural coloring mechanisms, interference and scattering, in indefinitely long core-shell nanowire arrays. The unusual nanostructures are comprised of an amorphous semiconducting core and a polymer shell layer with disparate refractive indices but with similar thermomechanical properties. Core-shell nanowires are mass produced from a macroscopic semiconductor rod by using a new top-to-bottom fabrication approach based on thermal size reduction. Nanostructures with diameters from 30 to 200 nm result in coloration that spans the whole visible spectrum via resonant Mie scattering. Nanoshell coloration based on thin film interference is proposed as a structural coloration mechanism which becomes dominant for nanowires having 700-1200 nm diameter. Controlled color generation in any part of visible and infrared spectral regions can be achieved by the simple scaling down procedure. Spectral color generation in mass-produced uniform core-shell nanowire arrays paves the way for applications such as spectral authentication at nanoscale, light-scattering ingredients in paints and cosmetics, large-area devices, and infrared shielding. © 2011 American Chemical Society.
Open Access
Template free preparation of nanoporous organically modified silica thin films on flexible substrates
(Royal Society of Chemistry, 2011) Yildirim, A.; Budunoglu, H.; Yaman, M.; Güler, Mustafa O.; Bayındır, Mehmet
We report the preparation and characterization of nanoporous organically modified silica (ormosil) thin films at room temperature and neutral pH conditions from homogeneous methyl silsesquioxane (MSQ) gels. Universally applicable and stable colloidal ormosil suspensions are prepared from the gels by sonication and coated to the substrates including glass, paper and plastics. The nanoporosity and thickness of the films can be tuned, which makes them suitable for certain applications including sensing, functional coatings, and low-dielectric materials. We demonstrate the antireflection property of the films on glass, cellulose acetate (CA) and polyetherimide (PEI) substrates. The films on CA and PEI retain their antireflection property after multiple bending cycles. Furthermore, films are intrinsically hydrophobic, over a wide pH range, with static contact angles up to 143 degrees on paper and 123 degrees on glass and CA. Producing nanoporous ormosil thin films on flexible substrates may expand their use in low cost electronic, optical devices and sensors, and lab-on-paper applications.