Browsing by Author "Daglar, B."

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Open Access
Anemone-like nanostructures for non-lithographic reproducible large-area and ultra-sensitive SERS substrates
(Royal Society of Chemistry, 2014) Daglar, B.; Demirel, G. B.; Khudiyev, T.; Dogan, T.; Tobail O.; Altuntas, S.; Buyukserin F.; Bayındır, Mehmet
The melt-infiltration technique enables the fabrication of complex nanostructures for a wide range of applications in optics, electronics, biomaterials, and catalysis. Here, anemone-like nanostructures are produced for the first time under the surface/interface principles of melt-infiltration as a non-lithographic method. Functionalized anodized aluminum oxide (AAO) membranes are used as templates to provide large-area production of nanostructures, and polycarbonate (PC) films are used as active phase materials. In order to understand formation dynamics of anemone-like structures finite element method (FEM) simulations are performed and it is found that wetting behaviour of the polymer is responsible for the formation of cavities at the caps of the structures. These nanostructures are examined in the surface-enhanced-Raman-spectroscopy (SERS) experiment and they exhibit great potential in this field. Reproducible SERS signals are detected with relative standard deviations (RSDs) of 7.2-12.6% for about 10 000 individual spots. SERS measurements are demonstrated at low concentrations of Rhodamine 6G (R6G), even at the picomolar level, with an enhancement factor of ∼1011. This high enhancement factor is ascribed to the significant electric field enhancement at the cavities of nanostructures and nanogaps between them, which is supported by finite difference time-domain (FDTD) simulations. These novel nanostructured films can be further optimized to be used in chemical and plasmonic sensors and as a single molecule SERS detection platform.
Open Access
Enhanced performance of dye-sensitized solar cells by omnidirectional antireflective coatings
(S P I E - International Society for Optical Engineering, 2015) Ulusoy, T. G.; Daglar, B.; Yildirim, A.; Ghobadi, A.; Bayındır, Mehmet; Okyay, Ali Kemal
Organically modified silica (ORMOSIL)-coated dye-sensitized solar cells (DSSCs) with improved energy conversion efficiency are demonstrated. ORMOSIL-coated DSSC surfaces exhibit omnidirectional low reflectivity over a broad range of wavelengths (400-800 nm). The short-circuit current density (JSC) is enhanced up to 23% at normal incidence (θ=0 deg) as a result of ORMOSIL coating. In addition, JSC enhancement is even higher at larger angles of incidence; 84% enhancement was observed at θ=30 deg. Moreover, ORMOSIL coating is superhydrophobic with a contact angle of 155 deg. © The Authors. Published by SPIE under a Creative Commons Attribution 3.0 Unported License. Distribution or reproduction of this work in whole or in part requires full attribution of the original publication, including its.
Open Access
Extremely fast and highly selective detection of nitroaromatic explosive vapours using fluorescent polymer thin films
(The Royal Society of Chemistry, 2013-05-22) Demirel, G. B.; Daglar, B.; Bayındır, Mehmet
A novel sensing material based on pyrene doped polyethersulfone worm-like structured thin film is developed using a facile technique for detection of nitroaromatic explosive vapours. The formation of pi-pi stacking in the thin fluorescent film allows a highly sensitive fluorescence quenching which is detectable by the naked eye in a response time of a few seconds.
Open Access
Fluorescent paper strips for highly sensitive and selective detection of nitroaromatic analytes in water samples
(Wiley - V C H Verlag GmbH & Co. KGaA, 2017) Daglar, B.; Demirel, G. B.; Bayındır, Mehmet
A portable, low-cost, flexible, sensitive and selective paper-based sensor was proposed for nitroaromatic explosive detection in water samples. The sensor was designed to achieve π-π stacking formation between emaraldine base polyaniline (PANI) and pyrene (Py) molecules. This π-π stacking formation enables a sensitive turn-off fluorescence quenching under the principle of photo-induced electron transfer (PET) mechanism. PANI−Py absorbed paper strips were immersed into the aqueous mediums of analytes and the fluorescence quenching was observed under a simple UV lamp by naked-eye. Paper strips exhibited∼ 96 % quenching efficiency and the limit of detection was calculated about 9.59 ng/ml. Self-quenching efficiency test showed that the sensor can be used for several weeks under the adequate storing conditions. In addition, experimental findings revealed that the paper-based PANI−Py strips work with high precision in real-samples such as tap water with∼ 85 % quenching efficiency. Moreover the reusability investigations showed that PANI−Py paper-based sensor can be reused 5 times with 54 % sensitivity.
Open Access
A motion-and sound-activated, 3D-printed chalcogenide-based triboelectric nanogenerator
(Wiley-VCH Verlag, 2015) Kanik, M.; Say, M. G.; Daglar, B.; Yavuz, A. F.; Dolas, M. H.; El-Ashry, M. M.; Bayındır, Mehmet
A multilayered triboelectric nanogenerator (MULTENG) that can be actuated by acoustic waves, vibration of a moving car, and tapping motion is built using a 3D-printing technique. The MULTENG can generate an open-circuit voltage of up to 396 V and a short-circuit current of up to 1.62 mA, and can power 38 LEDs. The layers of the triboelectric generator are made of polyetherimide nanopillars and chalcogenide core-shell nanofibers.
Open Access
One-pot preparation of fluorinated mesoporous silica nanoparticles for liquid marble formation and superhydrophobic surfaces
(American Chemical Society, 2011) Yildirim, A.; Budunoglu, H.; Daglar, B.; Deniz, H.; Bayındır, Mehmet
One-pot synthesis of fluorinated mesoporous silica nanoparticles (FMSNs) is reported. Uniform mesoporous nanoparticles are prepared by condensation of tetraethyl orthosilicate (TEOS) and fluoroalkyl containing organotriethoxy silane monomers, respectively. The method enables selective deposition of fluorine atoms on the surface of the particles. FMSNs are used to prepare stable liquid marbles with water. An organo-modified silica sol is used with FMSNs to prepare mechanically stable superhydrophobic surfaces (water contact angle of 161 degrees). The mechanical stability of the surface is investigated with water dripping and adhesive tape tests. The prepared FMSNs are promising building blocks for robust, large-area, and multifunctional self-cleaning surfaces.
Open Access
Plasmonically enhanced hot electron based photovoltaic device
(Optical Society of American (OSA), 2013) Atar F.B.; Battal, E.; Aygun L.E.; Daglar, B.; Bayındır, Mehmet; Okyay, Ali Kemal
Hot electron photovoltaics is emerging as a candidate for low cost and ultra thin solar cells. Plasmonic means can be utilized to significantly boost device efficiency. We separately form the tunneling metal-insulator-metal (MIM) junction for electron collection and the plasmon exciting MIM structure on top of each other, which provides high flexibility in plasmonic design and tunneling MIM design separately. We demonstrate close to one order of magnitude enhancement in the short circuit current at the resonance wavelengths. © 2013 Optical Society of America.
Open Access
Polymeric nanocarriers for expected nanomedicine: Current challenges and future prospects
(Royal Society of Chemistry, 2014) Daglar, B.; Ozgur, E.; Corman, M. E.; Uzun, L.; Demirel, G. B.
Polymeric nanocarriers have an increasingly growing potential for clinical applications. The current and future expectation from a polymeric nanocarrier is to exhibit both diagnostic and therapeutic functions. Living organisms are very complex systems and have many challenges for a carrier system such as biocompatibility, biodistribution, side-effects, biological barriers. Therefore, a designed polymeric nanocarrier should possess multifunctional properties to overcome these obstacles towards its target site. However, currently there are few polymeric systems that can be used for both therapy and imaging in clinic studies. In the literature, there are many studies for developing new generation polymeric nanocarriers to obtain future smart and multifunctional nanomedicine. In this review, we discuss the new generation and promising polymeric nanocarriers, which exhibit active targeting, triggered release of contents, and imaging capability for in vivo studies.
Open Access
Soft biomimetic tapered babostructures for large-area antireflective surfaces and SERS sensing
(Royal Society of Chemistry, 2013) Daglar, B.; Khudiyev, T.; Demirel, G. B.; Buyukserin, F.; Bayındır, Mehmet
We report a facile fabrication method for the fabrication of functional large area nanostructured polymer films using a drop casting technique. Reusable and tapered silicon molds were utilized in the production of functional polymers providing rapid fabrication of the paraboloid nanostructures at the desired structural heights without the requirement of any complex production conditions, such as high temperature or pressure. The fabricated polymer films demonstrate promising qualities in terms of antireflective, hydrophobic and surface enhanced Raman spectroscopy (SERS) features. We achieved up to 92% transmission from the single-side nanostructured polymer films by implementing optimized nanostructure parameters which were determined using a finite difference time domain (FDTD) method prior to production. Large-area nanostructured films were observed to enhance the Raman signal with an enhancement factor of 4.9 x 10(6) compared to bare film, making them potentially suitable as freestanding SERS substrates. The utilized fabrication method with its demonstrated performances and reliable material properties, paves the way for further possibilities in biological, optical, and electronic applications.
Open Access
Superhydrophobic and omnidirectional antireflective surfaces from nanostructured ormosil colloids
(American Chemical Society, 2013-02-13) Yildirim, A.; Khudiyev, T.; Daglar, B.; Budunoglu, H.; Okyay, Ali Kemal; Bayındır, Mehmet
A large-area superhydrophobic and omnidirectional antireflective nanostructured organically modified silica coating has been designed and prepared. The coating mimics the self-cleaning property of superhydrophobic lotus leaves and omnidirectional broad band antireflectivity of moth compound eyes, simultaneously. Water contact and sliding angles of the coating are around 160 and 10, respectively. Coating improves the transmittance of the glass substrate around 4%, when coated on a single side of a glass, in visible and near-infrared region at normal incidence angles. At oblique incidence angles (up to 60) improvement in transmission reaches to around 8%. In addition, coatings are mechanically stable against impact of water droplets from considerable heights. We believe that our inexpensive and durable multifunctional coatings are suitable for stepping out of the laboratory to practical outdoor applications.