Demir, Mustafa
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Name Variants
Demir, Mustafa M.
Demir, Mustafa Muammer
Demir, Mustafa Muammer
Job Title
Prof. Dr.
Email Address
mdemir@iyte.edu.tr
ORCID ID
Scopus Author ID
Turkish CoHE Profile ID
Google Scholar ID
WoS Researcher ID
Scholarly Output
123
Articles
83
Citation Count
1713
Supervised Theses
33
123 results
Scholarly Output Search Results
Now showing 1 - 10 of 123
Article Citation Count: 95Synthesis of amidoximated polyacrylonitrile fibers and its application for sorption of aqueous uranyl ions under continuous flow(Elsevier Science Sa, 2012) Horzum, Nesrin; Shahwan, Talal; Parlak, Onur; Demir, Mustafa M.; Demir, MustafaThis study reports a feasible method for the removal of radioactive U(VI) ions from aqueous systems via column sorption under continuous flow. Electrospun polyacrylonitrile (PAN) fibers were used as sorbent materials in a homemade minicolumn. The nitrite groups on the fibers' surface were modified to amidoxime groups using hydroxylamine hydrochloride. Surface modification was observed to enhance the sorption capacity of PAN fibers toward uranium ions by more than 4-fold by virtue of the chelating ability of the amidoxime groups. The experiments investigated the effect of pH, initial concentration, and repetitive loading on the sorption properties of amidoximated PAN fibers. Based on the overall results, the surface-modified fibers seem to be a suitable potential sorbent material for applications in environmental cleanup, particularly for nuclear plants. (C) 2012 Elsevier B.V. All rights reserved.Article Citation Count: 25Types of the scaling in hyper saline geothermal system in northwest Turkey(Pergamon-elsevier Science Ltd, 2014) Demir, Mustafa M.; Baba, Alper; Atilla, Vedat; Inanli, Mustafa; Demir, MustafaTuzla is an active geothermal area located in northwestern Turkey, 80 km south of the city of Canakkale and 5 km from the Aegean Coast. The geothermal brine from this area, which is dominated by NaCl, has a typical temperature of 173 degrees C. Rapid withdrawal of fluid to ambient surface conditions during sampling causes precipitation of various compounds known as scaling. Scaling is one of the important problems in Tuzla geothermal system that reduces the efficiency of the geothermal power plant and causes economical loss. The aim of this study was to determine the type of scaling as a first step towards preventing its formation. The scales formed in the geothermal system were divided into two groups according to location: the ones that formed in downhole and the ones that accumulated along the surface pipeline. Both scales were examined in terms of their elemental composition, structure and morphology using XRF, XRD, and SEM, respectively. The former was found to be mainly composed of PbS (Galena) and CaCO3 (aragonite or calcite). In contrast, the latter was heterogeneous in nature and consisted of mainly saponite like amorphous structure along with submicrometer-sized amorphous silica particles, layered double magnesium and iron hydroxide, and NaCl. (C) 2013 Elsevier Ltd. All rights reserved.Article Citation Count: 66Sorption Efficiency of Chitosan Nanofibers toward Metal Ions at Low Concentrations(Amer Chemical Soc, 2010) Horzum, Nesrin; Boyaci, Ezel; Eroglu, Ahmet E.; Shahwan, Talal; Demir, Mustafa M.; Demir, MustafaChitosan fibers showing narrow diameter distribution with a mean of 42 nm were produced by electrospinning and utilized for the sorption of Fe(III), Cu(II), Ag(I), and Cd(II) ions from aqueous solutions. The ion concentrations in the supernatant solutions were determined using inductively coupled plasma-mass spectrometry (ICP-MS). The filtration efficiency of the fibers toward these ions was studied by both batch and microcolumn methods. High efficiency in sorption of the metal ions was obtained in the both methods. The effects of sorbent amount (0.10-0.50 mg), shaking time (15-120 min), initial metal ion concentration (10.0-1000.0 mu g.L-1), and temperature (25 and 50 degrees C) on the extent of sorption were examined. The sorbent amount did not significantly alter the efficiency of sorption; however, shaking time, temperature, and metal ion concentration were found to have a strong influence on sorption. By virtue of its mechanical integrity, the applicability of the chitosan mat in solid phase extraction under continuous flow looks promising.Article Citation Count: 6Enhanced Spontaneous Emission Rate in a Low-Q Hybrid Photonic-Plasmonic Nanoresonator(Amer Chemical Soc, 2019) Gokbulut, Belkis; Inanc, Arda; Topcu, Gokhan; Unluturk, Secil S.; Ozcelik, Serdar; Demir, Mustafa M.; Inci, M. Naci; Demir, MustafaIn 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.Master Thesis Preparation of electrospun composite fibers based on PS-PI-PS/CdSxSe1-x nanoparticles(Izmir Institute of Technology, 2011) Aşkın, Görkem; Demir, Mustafa; Demir, Mustafa Muammer; Özçelik, SerdarPolymeric fibrous films were prepared based on polystyrene-b-polyisoprene-bpolystyrene triblock copolymer (SIS) and CdSxSe1-x nanoparticles by electrospinning process. SIS with 14 wt % Styrene (14% PS-SIS) and 22 wt % Styrene (22% PS-SIS) triblock copolymers were employed. Both of them undergo microphase separation. While the former shows cylinder-like morphology, the latter exhibits the lamellae one. CdSxSe1-x partciles were stabilized by two different surfactant molecules: i) n-trioctylphosphine oxide (TOPO) and ii) oleic acid (OA). When the particles were blended with 22% PS-SIS, particles capped with TOPO preferentially filled to PS domain whereas particles capped with OA loaded into the PI domain. Composite electrospun fibers were prepared with a diameter of 1.5 mm on average. Electrospinning parameters (potential difference, solution concentration, flow rate) were investigated on fiber morphology. The films are colorless under day light and have strong green emission under UV light.Article Citation Count: 23Perylene-embedded electrospun PS fibers for white light generation(Elsevier Sci Ltd, 2019) Guner, Tugrul; Aksoy, Erkan; Demir, Mustafa M.; Varlikli, Canan; Demir, MustafaPerylene dyes have been employed in the fabrication of white light due to their superior photophysical properties and relatively easy synthetic methods. However, their molecular aggregation in solid state is one of the main handicaps since it causes deviation in their optical properties and quenches photoluminescence quantum yields (Phi(f)). Investigation of the photophysical properties of a green (PTE), a yellow (PDI) and a new red (DiPhAPDI) emitting perylene derivative in solution, drop-casted films, polystyrene (PS) fibers and PS fibers embedded in poly (dimethyl siloxane) (PDMS) showed that PS:dye fibers prevent aggregation to some extend and allows high Of of dyes. The Of values of PTE, PDI and DiPhAPDI were all higher than 93.0% in solution and 84.8%, 94.3% and 73.6%, respectively in PS:dye fibers. Embedding the fibers in PDMS improved the photostabilities of the dyes two folds compared to their solution phases. The prepared dye containing fibers were combined together into a single PDMS film and utilized as a frequency conversion layer on a blue LED. Fabricated samples were found to show high color rendering index (>= 90), adjustable CCT (7500 K-5000 K), and power efficiency values exceeding 2001m/W depending on the used fiber amount in mass.Article Citation Count: 27Formation of Pseudoisocyanine J-Aggregates in Poly(vinyl alcohol) Fibers by Electrospinning(Amer Chemical Soc, 2009) Demir, Mustafa M.; Ozen, Bengisu; Ozcelik, Serdar; Demir, MustafaSubmicrometer diameter, light emitting fibers of poly(vinyl alcohol) (PVA) doped with pseudoisocyanine (1, 1'-diethyl-2,2'-cyanine bromide, PIC) dye were prepared by electrospinning. A horizontal setup was employed with a stationary collector consisting of two parallel-positioned metal strips separated by a void gal). Formation of uniaxially aligned and randomly deposited fibers in electrospun films was confirmed by microscopy. Photoluminescence (PL) spectroscopy is used to evaluate spectral properties of both types of fibers doped with PIC. While PIC molecules were individually dispersed in PVA Solution, they assemble into J-aggregates upon electrospinning when the weight fraction of PIC molecules is above 2.5 wt%. The formation of J-aggregates was observed in both randomly deposited and Uniaxially aligned electrospun fibers. Moreover, the fibers aligned uniaxially showed a high degree of polarized emission (PL(parallel to)/PL(perpendicular to) = 10), arising from the orientation of J-aggregates along the fiber axis. On the other hand, isotropic emission of J-aggregates was observed from the fibers deposited randomly. As a conclusion, electrospinning was found to be an efficient and a practical method to form highly oriented J-aggregates dispersed into polymer fibers. To the best Of Our knowledge, it is the first time formation of J-aggregates (a bottom-up approach) and electrospinning (a top-down approach) is successfully combined.Book Part Citation Count: 2Scaling problem of the geothermal system in Turkey(Crc Press-taylor & Francis Group, 2014) Dogan, Irmak; Demir, Mustafa M.; Baba, Alper; Demir, Mustafa[No Abstract Available]Master Thesis Development of whey protein isolate based nanocomposite food packaging film incorporated with chitosan and zein nanoparticles(Izmir Institute of Technology, 2014) Oymacı, Pelin; Demir, Mustafa; Alsoy Altınkaya, Sacide; Demir, Mustafa MuammerThe purpose of this study was to investigate the effect of chitosan and zein nanoparticles addition on the barrier and mechanical properties of whey protein isolate (WPI) films as an alternative to conventional synthetic packaging materials. Chitosan nanoparticles (CSNP) were produced via ionic gelation method using sodium tripolyphosphate (TPP) and deacetylated chitosan. Zein nanoparticles (ZNP) were synthesized based on antisolvent procedure in the presence of sodium caseinate (SC) to enable dispersion in water. Both plain and nanoparticle added WPI films were prepared by solution casting method. Water vapor barrier and mechanical properties of films were measured and the improvements in these properties with nanoparticle addition was further investigated through surface wetting, morphological, viscoelastic and thermal properties of the films. Both nanoparticles significantly decreased the water vapor permeability (WVP) and improved the mechanical properties of the WPI film. The highest enhancement in barrier and mechanical properties of the WPI films were recorded with 20% (w/w of WPI) CSNP and 120% (w/w of WPI) ZNP addition which corresponded to the maximum nanoparticle loading levels. At these loadings, the average WVP of pure WPI films loaded with ZNP and CSNP decreased by 84% and 57%, and the average tensile strength increased by 304% and 161%, respectively. On the other hand, the nanoparticles did not change the elongation at break significantly. ZNP was found more effective than CSNP in improving barrier and mechanical properties of the WPI films due to its hydrophobic nature and better dispersion in the protein matrix which allowed much higher loadings compared with the maximum loading levels achieved with CSNP. CSNP addition imparted antibacterial activity to the WPI films.Master Thesis Investigation on emission features of TTBC aggregates in PVA fiber mats by electrospinning(Izmir Institute of Technology, 2010) Özen, Bengisu; Demir, Mustafa; Demir, Mustafa Muammer1,1’,3,3’-tetraethyl-5,5’,6,6’ -tetrachlorobenzimidazolocarbocyanine (TTBC) is a frequently used cyanine dye that undergoes two different types of molecular aggregate (J and H-type). Dye molecules, in general, come into aggregation in ionic solutions and solid surfaces without control over the type and orientation of the resulting aggregate. In this research, we focused on electrospinning of aqueous poly(vinyl alcohol) (PVA)/TTBC solutions and investigated whether the aggregate formation could be controlled by solution and instrumental parameters of this process. Initially, TTBC was molecularly dispersed in aqueous PVA solution with a weight fraction of 0.001- 0.65 % and the precursor solution was subjected to electrospinning under electrical field ranging from 0.95-1.81 kV/cm. A stationary horizontal electrospinning set-up was used including two parallel-positioned metal strips as counter electrode. Both randomlydeposited and uniaxially aligned fibers were achieved. For the reason of comparison, reference films were prepared by spin-coating and film casting. Photoluminescence and polarized FTIR spectroscopy techniques were employed to examine spectral properties of the fibers. While H- and J-type aggregates coexist within spin-coated films and only J-aggregates exist within cast films, only H-type aggregates were observed within the fibers regardless of their alignment. A strong polarized emission was obtained from the unaxially aligned fibers due to the orientation of H-aggregates along the fibers. Consequently, electrospinning was found to be an alternative method to bring individually dispersed dye molecules into oriented H-type aggregates within submicron diameter fibers. Similar experimentation was also applied to TTBC/PS and Pyrene/Polystyrene(PS) systems to investigate aggregation behavior of dye molecules. TTBC exhibited similar behavior in PS/Dimethylformamide (DMF) system observed in PVA/H2O system. However, electrospinning has no remarkable influence on aggregation of pyrene in excimers. It slightly disassemble excimer structure.
