Browsing by Author "Topçu G."

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Investigation of lithium sorption efficiency using swcnt functionalized electrospun fiber mats from the hypersaline geothermal brine
(Trans Tech Publications Ltd, 2018) Çelik A.; Topçu G.; Isik T.; Baba A.; Horzum N.; Demir, M.M.
Geothermal mining from brines becomes increasingly important with the increasing demand for rare earth elements in various engineering applications. Geothermal fluids contain valuable minerals and metals such as silica, zinc, lithium, and other materials that can be processed to recover these products. Solution mining by nature is challenging because of variable composition as well as the concentration of the interfering ions, particularly calcium and magnesium, and the presence of interfering ions increases the recovery costs requiring additional steps. The aim of this study is the fabrication of single-walled carbon nanotube functionalized electrospun chitosan, poly(methyl methacrylate) (PMMA), and polyacrylonitrile (PAN) fiber mats. Effect of polymer type, dilution factor, and surface modification on the sorption of lithium (Li+) ions was investigated. The maximum sorption performance was obtained with SWCNT functionalized PAN (15 wt%) fiber mats and they have sorption percentage as 55% at diluted (1/100) brine samples. © 2018 Trans Tech Publications, Switzerland.
Non-iridescent structural colors from uniform-sized SiO2 colloids
(Elsevier B.V., 2018) Topçu G.; Güner T.; Demir, M.M.
Structural colors have recently attracted interest from diverse fields of research due to their ease of fabrication and eco-friendliness. These types of colors are, in principle, achieved by periodically arranged submicron-diameter colloidal particles. The interaction of light with a structure containing long-range ordered colloidal particles leads to coloration; this usually varies depending on the angle of observation (iridescence). However, the majority of the applications demand constant color that is independent of the viewing angle (non-iridescence). In this work, silica colloids were obtained using the Stöber method at different sizes from 150 to 300 nm in an alcoholic dispersion. The casting of the dispersion on a substrate leaves behind a photonic crystal showing a colorful iridescent film. However, centrifugation and redispersion of the SiO2 particles into fresh solvent may cause the formation of small, aggregated silica domains in the new dispersion. The casting of this dispersion allows for the development of photonic glass, presumably due to the accumulation of aggregates showing stable colloidal film independent of viewing angle. Moreover, depending on the size of the silica colloids, non-iridescent photonic glasses with various colors (violet, blue, green, and orange) are obtained. © 2018 Elsevier B.V.
Polarized emission from CsPbBr3 nanowire embedded-electrospun PU fibers
(Institute of Physics Publishing, 2018) Gü Ner T.; Topçu G.; Savaci U.; Genç A.; Turan S.; Sari E.; Demir, M.M.
Interest in all-inorganic halide perovskites has been increasing dramatically due to their high quantum yield, band gap tunability, and ease of fabrication in compositional and geometric diversity. In this study, we synthesized several hundreds of nanometer long and ∼4 nm thick CsPbBr3 nanowires (NWs). They were then integrated into electrospun polyurethane (PU) fibers to examine the polarization behavior of the composite fiber assembly. Aligned electrospun fibers containing CsPbBr3 NWs showed a remarkable increase in the degree of polarization from 0.17-0.30. This combination of NWs and PU fibers provides a promising composite material for various applications such as optoelectronic devices and solar cells. © 2018 IOP Publishing Ltd.