Browsing by Author "Ozgur E."
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Item 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, MehmetNanowires 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.Item Open Access Colorimetric detection of ultrathin dielectrics on strong interference coatings(OSA - The Optical Society, 2018) Ayas S.; Bakan, G.; Ozgur E.; Celebi, K.; Torunoglu, G.; Dana, A.Metal films covered with ultrathin lossy dielectrics can exhibit strong interference effects manifested as the broad absorption of the incident light resulting in distinct surface colors. Despite their simple bilayer structures, such surfaces have only recently been scrutinized and applied mainly to color printing. Here, we report the use of such surfaces for colorimetric detection of ultrathin dielectrics. Upon deposition of a nanometer-thick dielectric on the surface, the absorption peak red shifts, changing the surface color. The color contrast between the bare and dielectric-coated surfaces can be detected by the naked eye. The optical responses of the surfaces are characterized for nanometer-thick SiO2, Al2O3, and bovine serum albumin molecules. The results suggest that strong interference surfaces can be employed as biosensors.Item Open Access Impact of mesoporous silica nanoparticle surface functionality on hemolytic activity, thrombogenicity and non-specific protein adsorption(Royal Society of Chemistry, 2013) Yildirim, A.; Ozgur E.; Bayındır, MehmetAlthough numerous mesoporous silica nanoparticle (MSN) drug carriers and theranostic agents with various surface functionalities have been designed in the last decade, their biocompatibility remains a matter of intensive debate. Here, we systematically evaluated interactions of a series of MSNs possessing different surface functional groups (ionic, polar, neutral, and hydrophobic) with blood constituents, in terms of their hemolytic activity, thrombogenicity, and adsorption of blood proteins on their surfaces. Using a hemolysis assay we showed that surface functionalization can reduce or even completely prevent the hemolytic activity of bare MSNs. We investigated thrombogenicity of MSNs by measuring prothrombin time (PT) and activated partial thromboplastin time (aPTT). We observed that none of the MSNs used in this study exhibit significant thrombogenic activity. Lastly, we examined non-specific protein adsorption on MSN surfaces using human serum albumin (HSA) and gamma globulins (γGs) and found that surface functionalization with ionic groups can greatly reduce protein adsorption. Demonstration of the surface functionalization having a crucial impact on blood compatibility might serve as a guideline for further investigation related to the design of mesoporous silica systems for biomedical applications, and shed light on research towards the ultimate goal of developing smart theranostic systems. © The Royal Society of Chemistry 2013.Item Open Access Label-free optical biodetection of pathogen virulence factors in complex media using microtoroids with multifunctional surface functionality(American Chemical Society, 2018) Toren, P.; Ozgur E.; Bayındır, MehmetEarly detection of pathogens or their virulence factors in complex media has a key role in early diagnosis and treatment of many diseases. Nanomolar and selective detection of Exotoxin A, which is a virulence factor secreted from Pseudomonas aeruginosa in the sputum of Cystic Fibrosis (CF) patients, can pave the way for early diagnosis of P. aeruginosa infections. In this study, we conducted a preliminary study to demonstrate the feasibility of optical biodetection of P. aeruginosa Exotoxin A in a diluted artificial sputum mimicking the CF respiratory environment. Our surface engineering approach provides an effective biointerface enabling highly selective detection of the Exotoxin A molecules in the complex media using monoclonal anti-Exotoxin A functionalized microtoroids. The highly resilient microtoroid surface toward other constituents of the sputum provides Exotoxin A detection ability in the complex media by reproducible measurements. In this study, the limit-of-detection of Exotoxin A in the complex media is calculated as 2.45 nM.Item 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, MehmetIntegration 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.Item Open Access A new route for fabricating on-chip chalcogenide microcavity resonator arrays(Wiley-VCH Verlag, 2014-07) Aktas, O.; Ozgur E.; Tobail, O.; Kanik, M.; Huseyinoglu, E.; Bayındır, MehmetHigh-yield production and on-chip integration of high-Q chalcogenide microresonators with various sizes and geometrical shapes (spherical, spheroidal, and ellipsoidal) and with sub-nanometer surface roughness is achieved. The high-throughput and low-cost production of chalcogenide spherical microresonators works via inducing a Plateau-Rayleigh instability within a multimaterial fiber in extended lengths. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.Item Open Access Oligonucleotide-based label-free detection with optical microresonators: strategies and challenges(Royal Society of Chemistry, 2016) Toren, P.; Ozgur E.; Bayındır, MehmetThis review targets diversified oligonucleotide-based biodetection techniques, focusing on the use of microresonators of whispering gallery mode (WGM) type as optical biosensors mostly integrated with lab-on-a-chip systems. On-chip and microfluidics combined devices along with optical microresonators provide rapid, robust, reproducible and multiplexed biodetection abilities in considerably small volumes. We present a detailed overview of the studies conducted so far, including biodetection of various oligonucleotide biomarkers as well as deoxyribonucleic acids (DNAs), ribonucleic acids (RNAs) and proteins. We particularly advert to chemical surface modifications for specific and selective biosensing.Item Open Access Phosphonate based organosilane modification of a simultaneously protein resistant and bioconjugable silica surface(Royal Society of Chemistry, 2014) Ozgur E.; Toren, P.; Bayındır, MehmetA facile method to coat silica surfaces with THPMP is introduced, forming simultaneously a protein resistant and bioconjugable surface. The coating is experimentally identified and its anti-fouling and bioconjugable characteristics are demonstrated.Item Open Access Real-time and selective detection of single nucleotide DNA mutations using surface engineered microtoroids(American Chemical Society, 2015) Toren, P.; Ozgur E.; Bayındır, MehmetMictoroids, as optical biosensors, can provide beneficial biosensing platforms to understand DNA alterations. These alterations could have significant clinical importance, such as the case of Pseudomonas aeruginosa, which is a commonly found pathogen in Cystic Fibrosis (CF) patients-causing poor prognosis by undergoing mutations during disease steps, gaining virulence and drug resistance. To provide a preliminary diagnosis platform for early-stage bacterial mutations, biosensing with a selective microtoroid surface was suggested. For this purpose, microtoroids with high quality factors were fabricated. The microtoroid surfaces were coated with (3-aminopropyl) triethoxysilane (APTES)/trimethylmethoxysilane (TMMS) mixed silane solution followed by EDC/NHS chemistry for covalent conjugation of DNA probes. Ethanolamine capping was applied to avoid unspecific interactions. The confocal studies confirmed homogeneous functionalization of the microtoroid surface. The DNA hybridization was demonstrated to be affected from the probe length. The optical biosensors showed a significant response (∼22 pm) to the complementary strand of the mutated type P. aeruginosa DNA, while showing substantially low and late response (∼5 pm) to the point mismatch strand. The limit of detection (LOD) for the complementary strand was calculated as 2.32 nM. No significant response was obtained for the noncomplementary strand. The results showed the microtoroids possessed selective surfaces in terms of distinguishing DNA alterations.Item Open Access Structural coloring in large scale core-shell nanowires(American Chemical Society, 2011) Khudiyev, T.; Ozgur E.; Yaman, M.; Bayındır, MehmetWe 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.Item Open Access Thermally tunable ultrasensitive infrared absorption spectroscopy platforms based on thin phase-change films(American Chemical Society, 2016-11) Bakan, G.; Ayas S.; Ozgur E.; Celebi, K.; Dana, A.The thermal tunability of the optical and electrical properties of phase-change materials has enabled the decades-old rewritable optical data storage and the recently commercialized phase-change memory devices. Recently, phase-change materials, in particular, Ge2Sb2Te5 (GST), have been considered for other thermally configurable photonics applications, such as active plasmonic surfaces. Here, we focus on nonplasmonic field enhancement and demonstrate the use of the phase-change materials in ultrasensitive infrared absorption spectroscopy platforms employing interference-based uniform field enhancement. The studied structures consist of patternless thin GST and metal films, enabling simple and large-area fabrication on rigid and flexible substrates. Crystallization of the as-fabricated amorphous GST layer by annealing tunes (redshifts) the field-enhancement wavelength range. The surfaces are tested with ultrathin chemical and biological probe materials. The measured absorption signals are found to be comparable or superior to the values reported for the ultrasensitive infrared absorption spectroscopy platforms based on plasmonic field-enhancement.Item Open Access Universal infrared absorption spectroscopy using uniform electromagnetic enhancement(American Chemical Society, 2016) Ayas S.; Bakan, G.; Ozgur E.; Celebi, K.; Dana, A.Infrared absorption spectroscopy has greatly benefited from the electromagnetic field enhancement offered by plasmonic surfaces. However, because of the localized nature of plasmonic fields, such field enhancements are limited to nanometer-scale volumes. Here, we demonstrate that a relatively small, but spatially uniform field enhancement can yield a superior infrared detection performance compared to the plasmonic field enhancement exhibited by optimized infrared nanoantennas. A specifically designed CaF2/Al thin film surface is shown to enable observation of stronger vibrational signals from the probe material, with wider bandwidth and a deeper spatial extent of the field enhancement as compared to such plasmonic surfaces. It is demonstrated that the surface structure presented here can enable chemically specific and label-free detection of organic monolayers using surface-enhanced infrared spectroscopy, indicating a great potential in highly sensitive yet cost-effective biomolecular sensing applications.Item Open Access Wafer-scale arrays of high-Q silica optical microcavities(OSA - The Optical Society, 2017) Ozgur E.; Huseyinoglu E.; Dana, A.On-chip high-Q microcavities possess significant potential in terms of integration of optical microresonators into functional optoelectronic devices that could be used in various applications, including biosensors, photonic-integrated circuits, or quantum optics experiments. Yet, despite the convenience of fabricating wafer-scale integrated microresonators with moderate Q values using standard microfabrication techniques, surface-tension-induced microcavities (STIMs), which have atomic-level surface roughness enabling the observation of Q values larger than 106, could only be produced using individual thermal treatment of every single microresonator within the devised area. Here, we demonstrate a facile method for large-scale fabrication of silica STIMs of various morphologies. Q values exceeding 106 are readily obtained using this technique. This study represents a significant advancement toward fabrication of wafer-scale optoelectronic circuitries.