Chemistry / Kimya
Permanent URI for this collectionhttps://hdl.handle.net/11147/4072
Browse
8 results
Search Results
Article Citation - WoS: 6Citation - Scopus: 8Enhanced Spontaneous Emission Rate in a Low-Q Hybrid Photonic-Plasmonic Nanoresonator(American Chemical Society, 2019) Gökbulut, Belkıs; İnanç, Arda; Topçu, Gökhan; Ünlütürk, Seçil Sevim; Özçelik, Serdar; Demir, Mustafa Muammer; İnci, Mehmet NaciIn this paper, CdTe quantum dots (QDs)-doped single electrospun polymer nanofibers are partially coated with gold nanoparticles to form distinct hybrid photonic-plasmonic nanoresonators to investigate the critical role of the cavity-confined hybrid mode on the modification of the spontaneous emission dynamics of the fluorescent emitters in low-Q photonic cavities. A total enhancement factor of 11.2 is measured via a time-resolved experimental technique, which shows that there is an increase of about three times in the spontaneous emission rate for the QDs-doped gold nanoparticle-decorated nanofibers as they are compared with those uncoated ones. The physical mechanism affecting the spontaneous emission rate of the encapsulated QDs in such a hybrid photonic-plasmonic nanoresonator is explained to be due to regeneration of the mode field in the nanofiber cavity upon the interaction of the dipoles with the surface plasmons of distinctive gold nanoparticles that surround the outer surface of the nanofiber.Article Citation - WoS: 25Citation - Scopus: 25Colloidal Bimetallic Nanorings for Strong Plasmon Exciton Coupling(American Chemical Society, 2020) Güvenç, Çetin Meriç; Mert Balcı, Fadime; Sarısözen, Sema; Polat, Nahit; Balcı, SinanNobel-metal nanostructures strongly localize and manipulate light at nanoscale dimension by supporting surface plasmon polaritons. In fact, the optical properties of the nobel-metal nanostructures strongly depend on their morphology and composition. Until now, various metal nanostructures such as nanocubes, nanoprisms, nanorods, and recently hollow nanostructures have been demonstrated. In addition, the plasmonic field can be further enhanced at nanoparticle dimers and aggregates because of highly localized and intense optical fields, which is known as "plasmonic hot spots". However, colloidally synthesized and circular-shaped nanoring nanostructures with plasmonic hot spots are still lacking. We, herein, show for the first time that colloidal bimetallic nanorings with plasmonic nanocavities and tunable plasmon resonance wavelengths can be synthesized via colloidal synthesis and galvanic replacement reactions. In addition, in the strong coupling regime, plasmons in nanorings and excitons in J-aggregates interact strongly and nanoring-shaped colloidal plexcitonic nanoparticles are demonstrated. The results reveal that the optical properties of the nanoring and the onset of strong coupling can be tamed by the galvanic replacement reaction. Further, the plasmonic nanocavity in the nanorings has immense potential for applications in sensing and spectroscopy because of the space, enclosed by the plasmonic nanocavity, is empty and accessible to a variety of molecules, ions, and quantum dots.Article Citation - WoS: 5Citation - Scopus: 6Determination of Force-Free Wet Adhesion of Mussel-Inspired Polymers To Spin Labeled Surface(Elsevier, 2017) Kırpat, İklima; Göksel, Yaman; Karakuş, Erman; Emrullahoğlu, Mustafa; Akdoğan, YaşarHydration repulsive forces oppose the adhesive interactions, especially in the force-free conditions. Here, we studied spontaneous wet adhesion of 3,4-dihydroxyphenylalanine (DOPA) functionalized poly(ethylene glycol) (PEG) polymers inspired by marine mussels. Using electron paramagnetic resonance (EPR) spectroscopy, we can monitor spontaneous adhesion of DOPA containing polymer to suspended spin labeled hydrophobic polystyrene nanobeads at molecular level. The surface coverage up to 82% is obtained from EPR measurements. However, in the force-free condition, EPR measurements do not show any detectable DOPA based adhesion to hydrophilic silica nanobead.Article Citation - WoS: 15Citation - Scopus: 15Bodipy-Conjugated Chitosan Nanoparticles as a Fluorescent Probe(Taylor and Francis Ltd., 2017) Bor, Gizem; Üçüncü, Muhammed; Emrullahoğlu, Mustafa; Tomak, Aysel; Şanlı Mohamed, GülşahRecently, development of fluorescent nanoparticle-based probes for various bioimaging applications has attracted great attention. This work aims to develop a new type fluorescent nanoparticle conjugate and evaluate its cytotoxic effects on A549 and BEAS 2B cell lines. Throughout the study, ionically crosslinked chitosan nanoparticles (CNs) were conjugated with carboxylated 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene (BODIPY-COOH). The results of conjugates (BODIPY-CNs) were investigated with regard to their physic-chemical, optical, cytotoxic properties and cellular internalization. The morphology of BODIPY-CNs was found to be spherical in shape and quite uniform having average diameter of 70.25 ± 11.99 nm. Cytotoxicty studies indicated that although BODIPY-COOH itself was quite toxic on both A549- and BEAS 2B-treated cells, CNs increased the cell viability of both cell lines via conjugation to BODIPY-COOH fluorescent molecule up to 67% for A549 and 74% for BEAS 2B cells. These results may suggest a possible utilization of the new fluorescent nanoparticle-based probe for bioimaging in biology and medicine.Article Citation - WoS: 30Citation - Scopus: 30Glycidyl-Methacry Late-Based Electrospun Mats and Catalytic Silver Nanoparticles(John Wiley and Sons Inc., 2008) Demir, Mustafa Muammer; Uğur, Gökçe; Gülgün, Mehmet A.; Menceloğlu, Yusuf Z.P(AN-GMA) and PGMA fibers coated with monodisperse silver nanoparticles have been prepared by a combination of electrospinning and electroless plating. The morphology of the electrospun fibers remains unchanged after surface hydrazination. Oxidation of hydrazine in an ammoniacal solution of AgNO 3 reduces and deposits silver atoms along the fiber surface, which then coalesce to Ag particles. The size of the silver nanoparticles is varied between 20-60 nm. Since the density of the active sites for silver reduction is lower in P(AN-GMA), a smaller particle size could be obtained. The catalytic activity of the silver nanoparticles has been confirmed.Article Citation - WoS: 15Aggregation of Fillers Blended Into Random Elastomeric Networks: Theory and Comparison With Experiments(John Wiley and Sons Inc., 2006) Demir, Mustafa Muammer; Menceloğlu, Yusuf Ziya; Erman, BurakA theoretical model describing aggregation of filler particles in amorphous elastomers is proposed. The model is based on a counting technique originally used in genome analysis to characterize the size and distribution of overlapping segments randomly placed on a DNA molecule. In the present model, the particles are first assumed to aggregate randomly upon mixing into the elastomer and then-sizes are calculated. The sizes and distributions of aggregates are also studied in the presence of attractive interparticle forces. Results of the proposed model are compared with experimental data on silica-filled end-linked poly(dimethyl-siloxane) networks. Comparison of the theory and experiment shows that the random aggregation assumption where no attractive forces exist between the particles is not valid and a significant attraction between the silica particles is needed in the theory to justify the experimental data obtained using atomic force microscopy. For filler content below 1.45 vol.-%, the model agrees, qualitatively, with experiment and shows the increase in cluster size with increasing amount of filler. It also explains the increase in the dispersion of aggregate sizes with increasing amount of filler.Article Citation - WoS: 20Citation - Scopus: 23Rhodamine-Immobilised Electrospun Chitosan Nanofibrous Material as a Fluorescence Turn-On Hg2+ Sensor(John Wiley and Sons Inc., 2016) Horzum, Nesrin; Mete, Derya; Karakuş, Erman; Üçüncü, Muhammed; Emrullahoğlu, Mustafa; Demir, Mustafa MuammerA turn-on fluorescence sensing system for mercuric (Hg2+) ions relying on a modified rhodamine B–chitosan fluorophore moiety was developed. This novel sensing approach relies on the simultaneous electrospinning of chitosan and rhodamine B hydrazide with phenylisothiocyanate functionality in hexafluoroisopropanol solution at 3.4 kV cm−1. The electrospun mats exhibited not only considerably enhanced fluorescence intensity in the presence of mercury ions, a result attributed to the ring opening of the spirolactam unit of the rhodamine-based fluorophore, but also a remarkably high sensitivity and selectivity toward Hg2+. In effect, the strategy has the potential to open new avenues in the design and development of other high-performance nanofibrous sensing materials for detecting target metal species of environmental interest.Article Citation - WoS: 6Citation - Scopus: 6Hierarchial Coassembly of a Cyanine Dye in Poly(vinyl Alcohol) Fibrous Films by Electrospinning(American Chemical Society, 2013) Demir, Mustafa Muammer; Horzum, Nesrin; Özen, Bengisu; Özçelik, SerdarWe report molecular aggregate formation of TTBC (1,1′,3,3′- tetraethyl-5,5′,6,6′-tetrachlorobenzimidazolocarbocyanine) in submicrometer-sized PVA (poly(vinyl alcohol)) fibers by electrospinning. The formation of the molecular aggregate is examined by solution and instrumental parameters of electrospinning. The precursor solution of PVA/TTBC, in the range of 0.016-0.065 wt % is subjected to electrospinning under an electrical field ranging from 0.95 to 1.81 kV cm-1. Both randomly deposited and uniaxially aligned fibers are achieved by using two parallel-positioned metal strips as counter electrode. Photoluminescence and polarized Fourier transform infrared spectroscopies are employed to determine spectral properties of the fibers. H-aggregates are formed within the electrospun fibers, regardless of their alignment, and H- and J-type aggregates coexist in the alternative spin-coated and the cast films. A strongly polarized photoluminescence emission is observed in the direction of uniaxially aligned fibers as a result of the orientation of the H-aggregates along the fiber axis. We demonstrate that electrospinning is a process capable of forming and orienting TTBC aggregates during the structural development of the polymer/dye nanofibers. These fibrous films may potentially find applications in optics and electronics.