Browsing by Author "Demirel, G. B."
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Item 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, MehmetThe 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.Item 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, MehmetA 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.Item 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, MehmetA 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.Item Open Access Pluronic polymer capped biocompatible mesoporous silica nanocarriers(Royal Society of Chemistry, 2013) Yildirim, A.; Demirel, G. B.; Erdem, R.; Senturk, B.; Tekinay, T.; Bayındır, MehmetA facile self-assembly method is described to prepare PEGylated silica nanocarriers using hydrophobic mesoporous silica nanoparticles and a pluronic F127 polymer. Pluronic capped nanocarriers revealed excellent dispersibility in biological media with cyto- and blood compatibilities. © 2013 The Royal Society of Chemistry.Item 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.Item 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, MehmetWe 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.