Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
Browse
2 results
Search Results
Article Citation - WoS: 26Citation - Scopus: 27Developing a Facile 1 Method for Highly Luminescent Colloidal Cdsxse1_x Ternary Nanoalloys†(Royal Society of Chemistry, 2013) Ünlü, Caner; Ünal Tosun, Gülçin; Sevim, Seçil; Özçelik, SerdarWe report a facile method to synthesize highly luminescent colloidal CdSxSe1 xternary nanoalloys. The synthesis is achieved exactly in one-step, one-pot and at low temperature, by applying the two-phase thermal approach. The optical and structural properties of the nanoalloys were characterized by various techniques. Photoluminescence of the nanoalloys is tunable from 435 to 545 nm by either the size or the composition of the nanoalloys. Highly luminescent nanoalloys having quantum yields up to 90% were prepared. The hydrodynamic size of the nanoalloys can be varied from 1.4 to 10.0 nm by the reaction time. DLS measurements showed that the size distribution of the nanoalloys is monodispersed. TEM images confirmed the size and the size distribution of the nanoalloys. The sulfur fraction in the nanoalloy composition, measured by XRD and verified by EDX, is modulated from 0.17 to 0.95 by increasing the amount of thiourea in the chalcogenide mixture. The sulfur-rich nanoalloys are formed when the initial mole ratio of the chalcogenide (S : Se) is equal or higher than eleven-fold. The gradient and homogeneous internal structures are revealed by analysis of the alloy composition as a function of the growth time. We propose that the two-phase approach, a non-injection technique, is a facile and versatile method to develop highly luminescent CdSxSe1 x nanoalloys without an inorganic coating layer.Article Citation - WoS: 15Citation - Scopus: 15Controlling Spontaneous Emission of Cdse Nanoparticles Dispersed in Electrospun Fibers of Polycarbonate Urethane(American Chemical Society, 2009) Demir, Mustafa Muammer; Soysal, Duygu; Ünlü, Caner; Kuş, Mahmut; Özçelik, SerdarLuminescent fibrous composite films consisting of submicrometer diameter fibers were prepared by electrospinning of segmented polycarbonate urethane (PCU) in dimethyl formamide and tri-n-octylphosphine oxide (TOPO)-capped CdSe nanocrystals (5 nm in diameter) in toluene. Using a pair of conductive electrodes separated with an air gap, we successfully produced randomly deposited and uniaxially aligned electrospun fibers. The surface structure of the electrospun fibers was studied using atomic force microscopy (AFM) and was compared to the corresponding film prepared by casting. In cast film, tapping mode AFM imaging suggests that hard urethane segments organize into rodlike morphology dispersed in soft polycarbonate. When PCU/ CdSe dispersions were subjected to electrospinning, copolymer domains were forced to arrange into lamella along the fiber axis due to elongational flow and high stretching. Molecular orientation in the domains of the composite fibers was confirmed by polarized infrared spectroscopy. We demonstrated that formation of the oriented domains by electrospinning develops a hierarchical structure, which consequently modifies spectral properties because new multiple sharp lines appeared in the photoluminescence (PL) spectra of the fibers. In contrast to randomly deposited fibers, the PL intensity of uniaxially aligned fibers was found to be angle dependent. We propose that the elongated internal structure within the fibers controls the spontaneous emission of CdSe nanoparticles dispersed throughout the electrospun mat. A discussion on the nature of the controlled spontaneous emission is provided.