WoS İndeksli Yayınlar Koleksiyonu / WoS Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7150
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Article Citation - WoS: 2Citation - Scopus: 31-Octanol Is a Functional Impurity Modifying Particle Size and Photophysical Properties of Colloidal Zncdsse/Zns Nanocrystals(American Chemical Society, 2021) Sevim Ünlütürk, Seçil; Çağır, Ali; Varlıklı, Canan; Özçelik, SerdarImpurities in trioctylphophine (TOP) strongly affect nanocrystal synthesis. 1-Octanol among other contaminants in TOP is identified for the first time as a functional impurity by H-1 NMR. The deliberate addition of 1-octanol into trioctylphosphine reduced particle size and modified photophysical properties of ZnCdSSe/ZnS colloidal nanocrystals. NMR analysis furthermore revealed that 1-octanol is bonded to the nanocrystal surfaces. The ratio of integrals for the O-CH2 protons of 1-octanol, which is the lowest compared to the other ligands, suggests that 1-octanol plays a critical role to tune the particle size of nanocrystals. The increased amount of 1-octanol added into TOP reduces the particle size from 9.8 to 7.2 nm, causing a progressive blue shift in the UV-vis and PL spectra but leaving the alloy composition unaffected. The rate of nonradiative processes is enhanced with the amount of 1-octanol added into TOP, correlating with higher dislocation density observed in the nanocrystals. As a conclusion, 1-octanol is proposed as a functional impurity that varies particle size and nonradiative photophysical processes in the ZnCdSSe/ZnS colloidal nanocrystals.Article Citation - WoS: 2Citation - Scopus: 2Mn2+ Ions Incorporated Into Znsxse1-X Colloidal Quantum Dots: Controlling Size and Composition of Nanoalloys and Regulating Magnetic Dipolar Interactions(IOP Publishing, 2021) Ünlütürk, Seçil Sevim; Akdoğan, Yaşar; Özçelik, SerdarA facile synthesis method is introduced how to prepare magnetically active ultraviolet emitting manganese ions incorporated into ZnSxSe1-x colloidal quantum dot (nanoalloy) at 110 degrees C in aqueous solutions. The reaction time is the main factor to control the hydrodynamic size from 3 to 10 nm and the precursor ratio is significant to tune the alloy composition. ZnS shell layer on the ZnSxSe1-x core was grown to passivate environmental effects. The nanoalloy has ultraviolet emission at 380 nm having a lifetime of 80 ns and 7% quantum yield. The incorporation of Mn2+ ions into the nanoalloys induced magnetic activity but did not modify the structure and photophysical properties of the nanoalloys. Colloidal and powdery samples were prepared and analyzed by electron paramagnetic resonance (EPR) spectroscopy. In the colloidal dispersions, EPR spectra showed hyperfine line splitting regardless of the Mn2+ ion fractions, up to 6%, indicating that Mn2+ ions incorporated into the nanoalloys were isolated. EPR signals of the powdery samples were broadened when the fraction of Mn2+ ions was higher than 0.1%. The EPR spectra were simulated to reveal the locations and interactions of Mn2+ ions. The simulations suggest that the Mn2+ ions are located on the nanoalloy surfaces. These findings infer that the magnetic dipolar interactions are regulated by the initial mole ratio of Mn/Zn and the physical state of the nanoalloys adjusted by preparation methods.Article Citation - WoS: 8Citation - Scopus: 8Reducing the Efficiency Roll Off and Applied Potential-Induced Color Shifts in Cdse@zns/Zns-based Light-Emitting Diodes(American Chemical Society, 2020) Özgüler, Şahika; Diker, Halide; Ünlütürk, Seçil Sevim; Özçelik, Serdar; Varlıklı, CananGreen light-emitting CdSe@ZnS/ZnS (QD) nano-particles were synthesized; the photophysical and morphological properties of their films, which were prepared by spin coating from six different concentrations, corresponding to absorbance values of 0.6, 1.1, 1.6, 2.1, 2.8, and 4.0, were determined. Increasing the absorbance value from 0.6 to 4.0 did not change the photophysical properties of QD films to a large extent, whereas it resulted in an increment in QD film thickness from 20 to 110 nm. The films were utilized as an emissive layer in QD light-emitting diodes with poly(9-vinylcarbazole) (PVK), PVK:2-(4-biphenyllyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (PBD), and PVK:1,3-bis[(4-tert-butylphenyl)-1,3,4-oxadiazolyl]-phenylene (OXD-7) hole-transport layers (HTLs). The presence of PBD or OXD-7 in PVK reduced the efficiency values but played a positive role in the color purity and efficiency roll off. The maximum color temperature and electroluminescence wavelength shifts obtained with applied potential were 109, 50, and 50 K and 11, 5, and 5 nm for pure-PVK, PVK:PBD, and PVK:OXD-7-based devices, respectively. Hole mobility, capacitance (at 10(3) Hz), and charge-transfer efficiency values were 9.0 x 10(-7), 6.8 x 10(-7), and 4.2 x 10(-7) cm(2) V s(-1), 1.7, 1, and 1 nF, and 6.90%, 15.50%, and 16.10% for pure-PVK, PVK:PBD, and PVK:OXD-7-based devices, respectively. Enhanced color purity and lowered efficiency roll off obtained with PVK:PBD and PVK:OXD-7 HTLs were attributed to decreased capacitance, increased charge-transfer efficiency, and reduced Joule heating.Article Citation - WoS: 8Citation - Scopus: 7Engineered Silica Nanoparticles Are Biologically Safe Vehicles To Deliver Drugs or Genes To Liver Cells(Elsevier Ltd., 2021) Tüncel, Özge; Kahraman, Erkan; Bağcı, Gülsün; Atabey, Neşe; Özçelik, SerdarEngineered silica nanoparticles (SiNP) are emerging materials for medical applications. Evaluating biological responses of specific cells treated with engineered silica nanoparticles is however essential. We synthesized and characterized the physicochemical properties of silica nanoparticles with two different sizes of 10 and 100 nm (10SiNP and 100SiNP) dispersed in cell culture medium. HuH-7, an epithelial-like human hepatoblastoma cell line and SK-HEP-1, a liver sinusoidal endothelial cell line (LSEC) are employed to evaluate their biological responses for the SiNP treatment. Primary human lymphocytes are used to assess genotoxicity recommended by OECD guidelines while erythrocytes are used to assess hemolytic activity. The engineered silica nanoparticles are not able to produce radical species, to alter the mitochondrial membrane potential, and induce any adverse effects on cell proliferation. The colony formation ability of HuH-7 hepatoblastoma cells was not affected following the SiNP treatment. Furthermore, SiNPs do not induce hemolysis of red blood cells and are not genotoxic. These findings suggest that SiNPs regardless of the size, amount, and incubation time are biologically safe vehicles to deliver drugs or genes to the liver. © 2020 Elsevier B.V.