438 results on '"S. Toprak"'
Search Results
2. Silver nanoparticles with excellent biocompatibility block pseudotyped SARS-CoV-2 in the presence of lung surfactant
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Govind Gupta, Bejan Hamawandi, Daniel J. Sheward, Ben Murrell, Leo Hanke, Gerald McInerney, Magda Blosi, Anna L. Costa, Muhammet S. Toprak, and Bengt Fadeel
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human lung epithelium ,nanoparticles ,pseudovirus ,silver ,spike protein ,Biotechnology ,TP248.13-248.65 - Abstract
Silver (Ag) is known to possess antimicrobial properties which is commonly attributed to soluble Ag ions. Here, we showed that Ag nanoparticles (NPs) potently inhibited SARS-CoV-2 infection using two different pseudovirus neutralization assays. We also evaluated a set of Ag nanoparticles of different sizes with varying surface properties, including polyvinylpyrrolidone (PVP)-coated and poly (ethylene glycol) (PEG)-modified Ag nanoparticles, and found that only the bare (unmodified) nanoparticles were able to prevent virus infection. For comparison, TiO2 nanoparticles failed to intercept the virus. Proteins and lipids may adsorb to nanoparticles forming a so-called bio-corona; however, Ag nanoparticles pre-incubated with pulmonary surfactant retained their ability to block virus infection in the present model. Furthermore, the secondary structure of the spike protein of SARS-CoV-2 was perturbed by the Ag nanoparticles, but not by the ionic control (AgNO3) nor by the TiO2 nanoparticles. Finally, Ag nanoparticles were shown to be non-cytotoxic towards the human lung epithelial cell line BEAS-2B and this was confirmed by using primary human nasal epithelial cells. These results further support that Ag nanoparticles may find use as anti-viral agents.
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- 2022
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3. Quantitative conversion of biomass in giant DNA virus infection
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Mikael Kördel, Martin Svenda, Hemanth K. N. Reddy, Emelie Fogelqvist, Komang G. Y. Arsana, Bejan Hamawandi, Muhammet S. Toprak, Hans M. Hertz, and Jonas A. Sellberg
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Medicine ,Science - Abstract
Abstract Bioconversion of organic materials is the foundation of many applications in chemical engineering, microbiology and biochemistry. Herein, we introduce a new methodology to quantitatively determine conversion of biomass in viral infections while simultaneously imaging morphological changes of the host cell. As proof of concept, the viral replication of an unidentified giant DNA virus and the cellular response of an amoebal host are studied using soft X-ray microscopy, titration dilution measurements and thermal gravimetric analysis. We find that virions produced inside the cell are visible from 18 h post infection and their numbers increase gradually to a burst size of 280–660 virions. Due to the large size of the virion and its strong X-ray absorption contrast, we estimate that the burst size corresponds to a conversion of 6–12% of carbonaceous biomass from amoebal host to virus. The occurrence of virion production correlates with the appearance of a possible viral factory and morphological changes in the phagosomes and contractile vacuole complex of the amoeba, whereas the nucleus and nucleolus appear unaffected throughout most of the replication cycle.
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- 2021
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4. Editorial: Recent Advances in Waste-Heat Harvesting via Thermoelectrics: From Theory to Materials and Devices
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Muhammet S. Toprak, Sedat Ballikaya, and Emrah Celik
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thermoelectric (TE) ,thermogenerator (TEG) ,nanostructure ,severe plastic deformation (SPD) ,figure of merit (ZT) ,Technology - Published
- 2021
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5. Targeted therapeutic effect against the breast cancer cell line MCF-7 with a CuFe2O4/silica/cisplatin nanocomposite formulation
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B. Rabindran Jermy, Vijaya Ravinayagam, Widyan A. Alamoudi, Dana Almohazey, Hatim Dafalla, Lina Hussain Allehaibi, Abdulhadi Baykal, Muhammet S. Toprak, and Thirunavukkarasu Somanathan
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anticancer ,cisplatin ,copper ferrite ,drug delivery ,multifunctional ,nanomedicine ,nanotherapeutics ,spherical silica ,tumour therapy ,Technology ,Chemical technology ,TP1-1185 ,Science ,Physics ,QC1-999 - Abstract
The combination of magnetic nanoparticles with a porous silica is a composite that has attracted significant attention for potential multifunctional theranostic applications. In this study, 30 wt % CuFe2O4 was impregnated into a matrix of monodispersed spherical hydrophilic silica (HYPS) nanoparticles through a simple dry impregnation technique. The chemotherapy drug cisplatin was loaded through electrostatic equilibrium adsorption over 24 h in normal saline solution. The presence of cubic spinel CuFe2O4 on HYPS was confirmed through powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR) and diffuse reflectance UV–vis spectroscopy (DR UV–vis) analysis. The HYPS particles showed a surface area of 170 m2/g, pore size of 8.3 nm and pore volume of 0.35 cm3/g. The cisplatin/CuFe2O4/HYPS nanoformulation showed the accumulation of copper ferrite nanoparticles on the surface and in the pores of HYPS with a surface area of 45 m2/g, pore size of 16 nm and pore volume of 0.18 cm3/g. Transmission electron microscopy (TEM) and energy dispersive X-ray (EDX) mapping analysis showed the presence of homogeneous silica particles with nanoclusters of copper ferrite distributed on the HYPS support. Vibrating sample magnetometry (VSM) analysis of CuFe2O4/HYPS showed paramagnetic behavior with a saturated magnetization value of 7.65 emu/g. DRS UV–vis analysis revealed the functionalization of cisplatin in tetrahedral and octahedral coordination in the CuFe2O4/HYPS composite. Compared to other supports such as mesocellular foam and silicalite, the release of cisplatin using the dialysis membrane technique was found to be superior when CuFe2O4/HYPS was applied as the support. An in vitro experiment was conducted to determine the potential of CuFe2O4/HYPS as an anticancer agent against the human breast cancer cell line MCF-7. The results show that the nanoparticle formulation can effectively target cancerous cells and could be an effective tumor imaging guide and drug delivery system.
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- 2019
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6. The Effect of Crystal Mismatch on the Thermoelectric Performance Enhancement of Nano Cu2Se
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Yunus Demirci, Aminu Yusuf, Bejan Hamawandi, Muhammet S. Toprak, and Sedat Ballikaya
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thermoelectric effect ,microwave assisted thermolysis ,nano Cu2Se ,nano Fe325Co075Sb12 ,crystal mismatch ,thermal conductivity ,Technology - Abstract
In the past decades, Cu2−xSe compounds have attracted great attention due to the inclusion of non-toxic and abundant elements, besides having a promising thermoelectric (TE) performance. In this work, we investigated the effect of a crystal mismatch of a nanoinclusion phase on the TE properties of Cu2−xSe. Nano-Cu2Se was synthesized using microwave assisted thermolysis, while the p-type skutterudite, Fe3.25Co0.75Sb12 (FeCoSb), compound was synthesized using a chemical alloying route. Nano-Cu2Se, and (nano-Cu2Se)1−x(nano-FeCoSb)x composites, where x = 0.05 and 0.1, were prepared via mechanical alloying followed by Spark Plasma Sintering process. Structural properties were evaluated by PXRD and SEM analysis, while the high temperature transport properties were examined via electrical conductivity, Seebeck coefficient, and thermal conductivity measurements in the temperature range of 300–800 K. Powder X-ray diffraction (PXRD) confirmed a single phase of nano Cu2Se, while the samples with FeCoSb inclusion consist of two phases as Cu2Se and CoSb3. SEM micrographs of all samples show that Cu2Se has randomly oriented grains with different sizes. Cu2Se samples with a FeCoSb inclusion show a rather different structure. In these samples, a rod-shaped FeCoSb phase, with a size varying between 20 and 100 nm, showed an inhomogeneous distribution in the structure and stacked between the Cu2Se layers. Transport data indicate that crystal mismatch between Cu2Se and FeCoSb has a strong effect on the TE transport properties. Electrical conductivity decreases but Seebeck coefficient enhances with nano FeCoSb inclusion. Total thermal conductivity was suppressed by 30% and ZT value enhanced by 15% with 5% nano FeCoSb inclusion at 750 K, likely due to a decrease in the electronic contribution of the thermal conductivity. Structural and transport data show that small amount of nanoinclusion of FeCoSb has a beneficial effect on the TE performance of nano Cu2Se at temperatures below 800 K.
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- 2021
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7. A Comparative Study on the Thermoelectric Properties of Bismuth Chalcogenide Alloys Synthesized through Mechanochemical Alloying and Microwave-Assisted Solution Synthesis Routes
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Bejan Hamawandi, Hamta Mansouri, Sedat Ballikaya, Yunus Demirci, Martina Orlovská, Nafiseh Bolghanabadi, Seyed Abdolkarim Sajjadi, and Muhammet S. Toprak
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thermoelectric material ,mechanochemical alloying ,microwave-assisted reaction ,nanostructured thermoelectrics ,Seebeck coefficient ,electrical conductivity ,Technology - Abstract
The way a material is synthesized and processed has an immense effect on its microstructure, which in turn has a big impact on its transport properties. Here, we compare the thermoelectric (TE) properties of n- and p-type Bi2−xSbxTe3 (x: 0 and 1.5) materials synthesized through two different routes, specifically mechanochemical alloying (MA)—as a solid-state synthesis route—and microwave(MW)-assisted polyol synthesis—as a solution synthesis route. Reaction time is significantly reduced in the MW synthesis, leading to significantly lower energy consumption (i.e., higher energy efficiency) per batch than using the MA route. The resultant materials are compared for their crystallinity, phase purity, morphology, and microstructure. Spark plasma sintering was used to prepare pellets, and the resultant consolidates were evaluated for their transport properties. TE properties and microstructure of the specimens were investigated in relation to processing conditions and composition. MA samples formed fused structures (from 200 nm to several micrometers in size) composed of smaller particles. MW-synthesized materials exhibited hexagonal platelet morphology, high crystallinity, and phase purity. They also showed lower thermal conductivity, leading to a higher resultant TE figure-of-merit ZT. TE properties of Bi2−xSbxTe3 samples were studied on sintered cylindrical pellet samples, where the highest ZT values achieved were 1.04 (at 440 K) for MW-Bi2Te3 and 0.76 (at 523 K) for MW-Bi0.5Sb1.5Te3 samples, while MA-Bi2Te3 and MA-Bi0.5Sb1.5Te3 samples showed maximum ZT values of 0.74 (at 460 K) and 0.27 (at 300 K), respectively, as n- and p-type TE materials. The observed trend is much higher ZT values for MW samples, ascribed to their higher degree of texturing and nanostructured grains reducing the thermal conductivity, thus achieving a better overall performance, verifying the prospect to enhance ZT using MW-assisted solution synthesis approach.
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- 2020
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8. Modulation of Conductivity of Alginate Hydrogels Containing Reduced Graphene Oxide through the Addition of Proteins
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Ahmed Raslan, Jesús Ciriza, Ana María Ochoa de Retana, María Luisa Sanjuán, Muhammet S. Toprak, Patricia Galvez-Martin, Laura Saenz-del-Burgo, and Jose Luis Pedraz
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hydrogel ,alginate ,reduced graphene oxide ,conductivity ,collagen ,Pharmacy and materia medica ,RS1-441 - Abstract
Modifying hydrogels in order to enhance their conductivity is an exciting field with applications in cardio and neuro-regenerative medicine. Therefore, we have designed hybrid alginate hydrogels containing uncoated and protein-coated reduced graphene oxide (rGO). We specifically studied the adsorption of three different proteins, BSA, elastin, and collagen, and the outcomes when these protein-coated rGO nanocomposites are embedded within the hydrogels. Our results demonstrate that BSA, elastin, and collagen are adsorbed onto the rGO surface, through a non-spontaneous phenomenon that fits Langmuir and pseudo-second-order adsorption models. Protein-coated rGOs are able to preclude further adsorption of erythropoietin, but not insulin. Collagen showed better adsorption capacity than BSA and elastin due to its hydrophobic nature, although requiring more energy. Moreover, collagen-coated rGO hybrid alginate hydrogels showed an enhancement in conductivity, showing that it could be a promising conductive scaffold for regenerative medicine.
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- 2021
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9. Minute-Made, High-Efficiency Nanostructured Bi2Te3 via High-Throughput Green Solution Chemical Synthesis
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Bejan Hamawandi, Hazal Batili, Moon Paul, Sedat Ballikaya, Nuzhet I. Kilic, Rafal Szukiewicz, Maciej Kuchowicz, Mats Johnsson, and Muhammet S. Toprak
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nanochemistry ,bismuth telluride ,thermoelectric ,nanoparticles ,colloidal synthesis ,green chemistry ,Chemistry ,QD1-999 - Abstract
Scalable synthetic strategies for high-quality and reproducible thermoelectric (TE) materials is an essential step for advancing the TE technology. We present here very rapid and effective methods for the synthesis of nanostructured bismuth telluride materials with promising TE performance. The methodology is based on an effective volume heating using microwaves, leading to highly crystalline nanostructured powders, in a reaction duration of two minutes. As the solvents, we demonstrate that water with a high dielectric constant is as good a solvent as ethylene glycol (EG) for the synthetic process, providing a greener reaction media. Crystal structure, crystallinity, morphology, microstructure and surface chemistry of these materials were evaluated using XRD, SEM/TEM, XPS and zeta potential characterization techniques. Nanostructured particles with hexagonal platelet morphology were observed in both systems. Surfaces show various degrees of oxidation, and signatures of the precursors used. Thermoelectric transport properties were evaluated using electrical conductivity, Seebeck coefficient and thermal conductivity measurements to estimate the TE figure-of-merit, ZT. Low thermal conductivity values were obtained, mainly due to the increased density of boundaries via materials nanostructuring. The estimated ZT values of 0.8–0.9 was reached in the 300–375 K temperature range for the hydrothermally synthesized sample, while 0.9–1 was reached in the 425–525 K temperature range for the polyol (EG) sample. Considering the energy and time efficiency of the synthetic processes developed in this work, these are rather promising ZT values paving the way for a wider impact of these strategic materials with a minimum environmental impact.
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- 2021
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10. Carbon Quantum Dots Conjugated Rhodium Nanoparticles as Hybrid Multimodal Contrast Agents
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Giovanni M. Saladino, Nuzhet I. Kilic, Bertha Brodin, Bejan Hamawandi, Idris Yazgan, Hans M. Hertz, and Muhammet S. Toprak
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X-ray fluorescence ,carbon quantum dots ,contrast agents ,dual-mode imaging ,nanomedicine ,hybrid nanostructure ,Chemistry ,QD1-999 - Abstract
Nanoparticle (NP)-based contrast agents enabling different imaging modalities are sought for non-invasive bio-diagnostics. A hybrid material, combining optical and X-ray fluorescence is presented as a bioimaging contrast agent. Core NPs based on metallic rhodium (Rh) have been demonstrated to be potential X-ray Fluorescence Computed Tomography (XFCT) contrast agents. Microwave-assisted hydrothermal method is used for NP synthesis, yielding large-scale NPs within a significantly short reaction time. Rh NP synthesis is performed by using a custom designed sugar ligand (LODAN), constituting a strong reducing agent in aqueous solution, which yields NPs with primary amines as surface functional groups. The amino groups on Rh NPs are used to directly conjugate excitation-independent nitrogen-doped carbon quantum dots (CQDs), which are synthesized through citrate pyrolysis in ammonia solution. CQDs provided the Rh NPs with optical fluorescence properties and improved their biocompatibility, as demonstrated in vitro by Real-Time Cell Analysis (RTCA) on a macrophage cell line (RAW 264.7). The multimodal characteristics of the hybrid NPs are confirmed with confocal microscopy, and X-ray Fluorescence (XRF) phantom experiments.
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- 2021
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11. Effects of the Antimicrobial Peptide LL-37 and Innate Effector Mechanisms in Colistin-Resistant Klebsiella pneumoniae With mgrB Insertions
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Hissa M. Al-Farsi, Salma Al-Adwani, Sultan Ahmed, Carmen Vogt, Anoop T. Ambikan, Anna Leber, Amina Al-Jardani, Saleh Al-Azri, Zakariya Al-Muharmi, Muhammet S. Toprak, Christian G. Giske, and Peter Bergman
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cross-resistance ,colistin ,LL-37 ,innate immunity ,zeta potential ,whole blood killing assay ,Microbiology ,QR1-502 - Abstract
BackgroundColistin is a polypeptide antibiotic drug that targets lipopolysaccharides in the outer membrane of Gram-negative bacteria. Inactivation of the mgrB-gene is a common mechanism behind colistin-resistance in Klebsiella pneumoniae (Kpn). Since colistin is a cyclic polypeptide, it may exhibit cross-resistance with the antimicrobial peptide LL-37, and with other innate effector mechanisms, but previous results are inconclusive.ObjectiveTo study potential cross-resistance between colistin and LL-37, as well as with other innate effector mechanisms, and to compare virulence of colistin-resistant and susceptible Kpn strains.Materials/MethodsCarbapenemase-producing Kpn from Oman (n = 17) were subjected to antimicrobial susceptibility testing and whole genome sequencing. Susceptibility to colistin and LL-37 was studied. The surface charge was determined by zeta-potential measurements and the morphology of treated bacteria was analyzed with electron microscopy. Bacterial survival was assessed in human whole blood and serum, as well as in a zebrafish infection-model.ResultsGenome-analysis revealed insertion-sequences in the mgrB gene, as a cause of colistin resistance in 8/17 isolates. Colistin-resistant (Col-R) isolates were found to be more resistant to LL-37 compared to colistin-susceptible (Col-S) isolates, but only at concentrations ≥50 μg/ml. There was no significant difference in surface charge between the isolates. The morphological changes were similar in both Col-R and Col-S isolates after exposure to LL-37. Finally, no survival difference between the Col-R and Col-S isolates was observed in whole blood or serum, or in zebrafish embryos.ConclusionCross-resistance between colistin and LL-37 was observed at elevated concentrations of LL-37. However, Col-R and Col-S isolates exhibited similar survival in serum and whole blood, and in a zebrafish infection-model, suggesting that cross-resistance most likely play a limited role during physiological conditions. However, it cannot be ruled out that the observed cross-resistance could be relevant in conditions where LL-37 levels reach high concentrations, such as during infection or inflammation.
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- 2019
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12. Investigation of the Heteroepitaxial Process Optimization of Ge Layers on Si (001) by RPCVD
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Yong Du, Zhenzhen Kong, Muhammet S. Toprak, Guilei Wang, Yuanhao Miao, Buqing Xu, Jiahan Yu, Ben Li, Hongxiao Lin, Jianghao Han, Yan Dong, Wenwu Wang, and Henry H. Radamson
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Ge ,optimization ,parameter ,threading dislocation ,strain ,RPCVD ,Chemistry ,QD1-999 - Abstract
This work presents the growth of high-quality Ge epilayers on Si (001) substrates using a reduced pressure chemical vapor deposition (RPCVD) chamber. Based on the initial nucleation, a low temperature high temperature (LT-HT) two-step approach, we systematically investigate the nucleation time and surface topography, influence of a LT-Ge buffer layer thickness, a HT-Ge growth temperature, layer thickness, and high temperature thermal treatment on the morphological and crystalline quality of the Ge epilayers. It is also a unique study in the initial growth of Ge epitaxy; the start point of the experiments includes Stranski–Krastanov mode in which the Ge wet layer is initially formed and later the growth is developed to form nuclides. Afterwards, a two-dimensional Ge layer is formed from the coalescing of the nuclides. The evolution of the strain from the beginning stage of the growth up to the full Ge layer has been investigated. Material characterization results show that Ge epilayer with 400 nm LT-Ge buffer layer features at least the root mean square (RMS) value and it’s threading dislocation density (TDD) decreases by a factor of 2. In view of the 400 nm LT-Ge buffer layer, the 1000 nm Ge epilayer with HT-Ge growth temperature of 650 °C showed the best material quality, which is conducive to the merging of the crystals into a connected structure eventually forming a continuous and two-dimensional film. After increasing the thickness of Ge layer from 900 nm to 2000 nm, Ge surface roughness decreased first and then increased slowly (the RMS value for 1400 nm Ge layer was 0.81 nm). Finally, a high-temperature annealing process was carried out and high-quality Ge layer was obtained (TDD=2.78 × 107 cm−2). In addition, room temperature strong photoluminescence (PL) peak intensity and narrow full width at half maximum (11 meV) spectra further confirm the high crystalline quality of the Ge layer manufactured by this optimized process. This work highlights the inducing, increasing, and relaxing of the strain in the Ge buffer and the signature of the defect formation.
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- 2021
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13. Thermoelectric Inks and Power Factor Tunability in Hybrid Films through All Solution Process
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José F. Serrano-Claumarchirant, Bejan Hamawandi, Adem Ergül, Andrés Cantarero, Clara M. Gómez, Pankaj Priyadarshi, Neophytos Neophytou, and Muhammet S. Toprak
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thermoelectric organic−inorganic hybrids thermoelectric power factor interface engineering nanoparticles bismuth telluride antimony telluride, microwave synthesis ,TK ,QD ,General Materials Science ,QC - Abstract
Thermoelectric (TE) materials can have a strong benefit to harvest thermal energy if they can be applied to large areas without losing their performance over time. One way of achieving large-area films is through hybrid materials, where a blend of TE materials with polymers can be applied as coating. Here, we present the development of all solution-processed TE ink and hybrid films with varying contents of TE Sb2Te3 and Bi2Te3 nanomaterials, along with their characterization. Using (1-methoxy-2-propyl) acetate (MPA) as the solvent and poly (methyl methacrylate) as the durable polymer, large-area homogeneous hybrid TE films have been fabricated. The conductivity and TE power factor improve with nanoparticle volume fraction, peaking around 60–70% solid material fill factor. For larger fill factors, the conductivity drops, possibly because of an increase in the interface resistance through interface defects and reduced connectivity between the platelets in the medium. The use of dodecanethiol (DDT) as an additive in the ink formulation enabled an improvement in the electrical conductivity through modification of interfaces and the compactness of the resultant films, leading to a 4–5 times increase in the power factor for both p- and n-type hybrid TE films, respectively. The observed trends were captured by combining percolation theory with analytical resistive theory, with the above assumption of increasing interface resistance and connectivity with polymer volume reduction. The results obtained on these hybrid films open a new low-cost route to produce and implement TE coatings on a large scale, which can be ideal for driving flexible, large-area energy scavenging technologies such as personal medical devices and the IoT.
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- 2022
14. On the Effect of Modified Carbohydrates on the Size and Shape of Gold and Silver Nanostructures
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Idris Yazgan, Abdurrahman Gümüş, Kutalmış Gökkuş, Mehmet Ali Demir, Senanur Evecen, Hamide Ayçin Sönmez, Roland M. Miller, Fatma Bakar, Ayhan Oral, Sergei Popov, and Muhammet S. Toprak
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sugar ligands ,modified carbohydrates ,colloidal synthesis ,plasmonics ,gold-Au ,silver-Ag ,Chemistry ,QD1-999 - Abstract
Gold (Au) and silver (Ag) nanostructures have widespread utilization from biomedicine to materials science. Therefore, their synthesis with control of their morphology and surface chemistry have been among the hot topics over the last decades. Here, we introduce a new approach relying on sugar derivatives that work as reducing, stabilizing, and capping agents in the synthesis of Au and Ag nanostructures. These sugar derivatives are utilized alone and as mixture, resulting in spherical, spheroid, trigonal, polygonic, and star-like morphologies. The synthesis approach was further tested in the presence of acetate and dimethylamine as size- and shape-directing agents. With the use of transmission electron microscopy (TEM), selected area electron diffraction (SAED), x-ray diffraction (XRD), scanning electron microscopy (SEM), and ultraviolet-visible (UV-vis) absorption spectroscopy techniques, the particle size, shape, assembly, aggregation, and film formation characteristics were evaluated. NPs’ attributes were shown to be tunable by manipulating the sugar ligand selection and sugar ligand/metal-ion ratio. For instance, with an imine side group and changing the sugar moiety from cellobiose to lactose, the morphology of the Ag nanoparticles (NPs) transformed from well dispersed cubic to rough and aggregated. The introduction of acetate and dimethylamine further extended the growth pattern and morphological properties of these NPs. As examples, L5 AS, G5AS, and S5AS ligands formed spherical or sheet-like structures when used alone, which upon the use of these additives transformed into larger multicore and rough NPs, revealing their significant effect on the NP morphology. Selected samples were tested for their stability against protein corona formation and ionic strength, where a high chemical stability and resistance to protein coating were observed. The findings show a promising, benign approach for the synthesis of shape- and size-directed Au and Ag nanostructures, along with a selection of the chemistry of carbohydrate-derivatives that can open new windows for their applications.
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- 2020
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15. Composition Tuning of Nanostructured Binary Copper Selenides through Rapid Chemical Synthesis and Their Thermoelectric Property Evaluation
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Bejan Hamawandi, Sedat Ballikaya, Mikael Råsander, Joseph Halim, Lorenzo Vinciguerra, Johanna Rosén, Mats Johnsson, and Muhammet S. Toprak
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thermoelectric ,chalcogenides ,Cu2−xSe ,microwave synthesis ,nanomaterial ,XPS ,Chemistry ,QD1-999 - Abstract
Reduced energy consumption and environmentally friendly, abundant constituents are gaining more attention for the synthesis of energy materials. A rapid, highly scalable, and process-temperature-sensitive solution synthesis route is demonstrated for the fabrication of thermoelectric (TE) Cu2−xSe. The process relies on readily available precursors and microwave-assisted thermolysis, which is sensitive to reaction conditions; yielding Cu1.8Se at 200 °C and Cu2Se at 250 °C within 6–8 min reaction time. Transmission electron microscopy (TEM) revealed crystalline nature of as-made particles with irregular truncated morphology, which exhibit a high phase purity as identified by X-ray powder diffraction (XRPD) analysis. Temperature-dependent transport properties were characterized via electrical conductivity, Seebeck coefficient, and thermal diffusivity measurements. Subsequent to spark plasma sintering, pure Cu1.8Se exhibited highly compacted and oriented grains that were similar in size in comparison to Cu2Se, which led to its high electrical and low thermal conductivity, reaching a very high power-factor (24 µW/K−2cm−1). Density-of-states (DOS) calculations confirm the observed trends in electronic properties of the material, where Cu-deficient phase exhibits metallic character. The TE figure of merit (ZT) was estimated for the materials, demonstrating an unprecedentedly high ZT at 875 K of 2.1 for Cu1.8Se sample, followed by 1.9 for Cu2Se. Synthetic and processing methods presented in this work enable large-scale production of TE materials and components for niche applications.
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- 2020
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16. Synthesis and Cytotoxicity Studies on Ru and Rh Nanoparticles as Potential X-Ray Fluorescence Computed Tomography (XFCT) Contrast Agents
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Yuyang Li, Kian Shaker, Martin Svenda, Carmen Vogt, Hans M. Hertz, and Muhammet S. Toprak
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polyol synthesis ,nanoparticles ,bio-imaging ,x-ray fluorescence ,contrast agent ,xfct ,Chemistry ,QD1-999 - Abstract
X-Ray fluorescence computed tomography (XFCT) is an emerging biomedical imaging technique, which demands the development of new contrast agents. Ruthenium (Ru) and rhodium (Rh) have spectrally attractive Kα edge energies, qualifying them as new XFCT bio-imaging probes. Metallic Ru and Rh nanoparticles are synthesized by polyol method, in the presence of a stabilizer. The effect of several reaction parameters, including reaction temperature time, precursor and stabilizer concentration, and stabilizer molecular weight, on the size of particles, were studied. Resultant materials were characterized in detail using XRD, TEM, FT-IR, DLS-zeta potential and TGA techniques. Ru particles in the size range of 1−3 nm, and Rh particles of 6−9 nm were obtained. At physiological pH, both material systems showed agglomeration into larger assemblies ranging from 12−104 nm for Ru and 25−50 nm for Rh. Cytotoxicity of the nanoparticles (NPs) was evaluated on macrophages and ovarian cancer cells, showing minimal toxicity in doses up to 50 μg/mL. XFCT performance was evaluated on a small-animal-sized phantom model, demonstrating the possibility of quantitative evaluation of the measured dose with an expected linear response. This work provides a detailed route for the synthesis, size control and characterization of two materials systems as viable contrast agents for XFCT bio-imaging.
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- 2020
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17. Facile Solution Synthesis, Processing and Characterization of n- and p-Type Binary and Ternary Bi–Sb Tellurides
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Bejan Hamawandi, Sedat Ballikaya, Hazal Batili, Viking Roosmark, Martina Orlovská, Aminu Yusuf, Mats Johnsson, Rafal Szukiewicz, Maciej Kuchowicz, and Muhammet S. Toprak
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chalcogenides ,microwave-assisted synthesis ,polyol synthesis ,thermoelectric ,zt ,power factor ,thermal conductivity ,nanomaterial ,xps ,Technology ,Engineering (General). Civil engineering (General) ,TA1-2040 ,Biology (General) ,QH301-705.5 ,Physics ,QC1-999 ,Chemistry ,QD1-999 - Abstract
The solution synthesis route as a scalable bottom-up synthetic method possesses significant advantages for synthesizing nanostructured bulk thermoelectric (TE) materials with improved performance. Tuning the composition of the materials directly in the solution, without needing any further processing, is important for adjusting the dominant carrier type. Here, we report a very rapid (2 min) and high yield (>8 g/batch) synthetic method using microwave-assisted heating, for the controlled growth of Bi2−xSbxTe3 (x: 0−2) nanoplatelets. Resultant materials exhibit a high crystallinity and phase purity, as characterized by XRD, and platelet morphology, as revealed by SEM. Surface chemistry of as-made materials showed a mixture of metallic and oxide phases, as evidenced by XPS. Zeta-potential analysis exhibited a systematic change of isoelectric point as a function of the material composition. As-made materials were directly sintered into pellets by using spark plasma sintering process. TE performance of Bi2−xSbxTe3 pellets were studied, where the highest ZT values of 1.04 (at 440 K) for Bi2Te3 and 1.37 (at 523 K) for Sb2Te3 were obtained, as n- and p-type TE materials. The presented microwave-assisted synthesis method is energy effective, a truly scalable and reproducible method, paving the way for large scale production and implementation of towards large-area TE applications.
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- 2020
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18. Effects of Ce–Dy rare earths co-doping on various features of Ni–Co spinel ferrite microspheres prepared via hydrothermal approach
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Murat Sertkol, N. Tashkandi, Alex Trukhanov, Aylin Yildiz, Yassine Slimani, Abdulhadi Baykal, Munirah Abdullah Almessiere, Bayram Unal, Hakan Güngüneş, Ayyar Manikandan, Muhammet S. Toprak, and Güngüneş, Hakan
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Spheres ,Materials science ,Analytical chemistry ,Ferrite microsphere ,Cofe2o4 ,Dielectric ,Magnetic-Properties ,Biomaterials ,Bohr magneton ,symbols.namesake ,Ferrimagnetism ,Hyperfine structure ,Nife2o4 Nanoparticles ,Conductivity ,Mining engineering. Metallurgy ,Magnetooptical Properties ,Magnetic moment ,NiCo spinel ferrites ,Hollow Microspheres ,Ferrimagnetic ,Optical-Properties ,Metals and Alloys ,TN1-997 ,Coercivity ,Hyperfine interaction ,Surfaces, Coatings and Films ,Metals ,Remanence ,Dielectric properties ,Ceramics and Composites ,symbols ,Ferrite (magnet) ,Powders ,Substitution - Abstract
The effects of Ce-Dy co-doping on the crystal structure, optical, dielectric, magnetic properties, and hyperfine interactions of Ni-Co spinel ferrite microspheres synthesized hydrothermally have been studied. A series of ferrites with the general formula Ni0.5-Co0.5CexDyxFe2-2xO4 were synthesized with x values ranging from 0.00 to 0.10. The phase, crystallinity, and morphology of ferrite microspheres were analyzed by X-ray powder diffractometry (XRD), scanning and transmission electron microscopes (SEM and TEM), respectively. The structural analyses of the synthesized ferrite microspheres confirmed their high purity and cubic crystalline phase. The Diffuse reflectance spectroscopic (DRS) measurements were presented to calculate direct optical energy band gaps (E-g) and is found in the range 1.63 eV - 1.84 eV. Fe-57 Mossbauer spectroscopy showed that the hyperfine magnetic field of tetrahedral (A) and octahedral (B) sites decreased with the substitution of Dy3+-Ce3+ ions that preferrentially occupy the B site. The impact of the rare-earth content (x) on the magnetic features of the prepared NiCo ferrite microspheres was investigated by analyzing M-H loops, which showed soft ferrimagnetism. The magnetic features illustrate a great impact of the incorporation of Ce3+-Dy3+ ions within the NiCo ferrite structure. The saturation magnetization (M-s), remanence (M-r), and coercivity (H-c) increased gradually with increasing Ce-Dy content. At x = 0.04, M-s, M-r, and H-c attain maximum values of about 31.2 emu/g, 11.5 emu/g, and 512.4 Oe, respectively. The Bohr magneton (n(B)) and magneto-crystalline anisotropy constant (K-eff) were also determined and evaluated with correlation to other magnetic parameters. Further increase in Ce3+-Dy3+ content (i.e., x >= 0.06) was found to decrease M-s, M-r, and H-c values. The variations in magnetic parameters (M-s, M-r, and H-c) were largely caused by the surface spins effect, the variations in crystallite/particle size, the distribution of magnetic ions into the different sublattices, the evolutions of magneto-crystalline anisotropy, and the variations in the magnetic moment (n(B)). The squareness ratios were found to be lower than the predicted theoretical value of 0.5 for various samples, indicating that the prepared Ce-Dy substituted NiCo ferrite microspheres are composed of NPs with single-magnetic domain (SMD). Temperature and frequency-dependent electrical and dielectric measurements have been done to estimate the ac/dc conductivity, dielectric constant, and tangent loss values for all the samples. The ac conductivity measurements confirmed the power-law rules, largely dependent on Ce-Dy content. Impedance analysis stated that the conduction mechanisms in all samples are mainly due to the grains-grain boundaries. The dielectric constant of NiCo ferrite microspheres give rise to normal dielectric distribution, with the frequency depending strongly on the Ce-Dy content. The observed variation in tangential loss with frequency can be attributed to the conduction mechanism in ferrites, like Koop's phenomenological model. (C) 2021 The Author(s). Published by Elsevier B.V. Deanship for Scientific Research of Imam Abdulrahman Bin Faisal University [2020-164-IRMC] The authors acknowledge the financial supports provided by the Deanship for Scientific Research of Imam Abdulrahman Bin Faisal University (Project application No. 2020-164-IRMC) . WOS:000702874100011 2-s2.0-85112331089
- Published
- 2021
19. Ultrasound-assisted synthesis and magnetic investigations of Ni0.4Cu0.4Zn0.2GaxGdxFe2-2xO4 (0.00 ≤ x ≤ 0.04) nanosized spinel ferrites
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Y. Slimani, M. A. Almessiere, A. Demir Korkmaz, A. Baykal, A. Manikandan, H. Gungunes, and M. S. Toprak
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General Materials Science ,General Chemistry - Published
- 2022
20. Functional Coatings for X-ray Fluorescent Nanoparticles
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G. M. Saladino, N. I. Kilic, K. Shaker, Y. Li, B. Hamawandi, C. Vogt, B. Brodin, M. Svenda, I. Yazgan, H. M. Hertz, and M. S. Toprak
- Published
- 2022
21. 3D MODELING OF HISTORICAL DOGER CARAVANSARIES BY DIGITAL PHOTOGRAMMETRY
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M. Yakar, M. Uysal, A. S. Toprak, and N. Polat
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Technology ,Engineering (General). Civil engineering (General) ,TA1-2040 ,Applied optics. Photonics ,TA1501-1820 - Abstract
Caravansaries are sort of bigger khan that established on the busy trade roads to provide any kind of supplies but essentially all Caravansaries on Anatolia are established for caravans' accommodations which are passing through on caravan rout. After the Turks had chosen being Muslim, the land that Islam religion spread on it has expanded. As a result of this expansion it is required a safe route for trade caravans. During the ruling time of Seljuk's Empire, Caravansaries took the most advanced form. Sultans of the Seljuk's Empire were aware of importance of trade and economy. That's why they established Caravansaries near marines, between the important trade centers and on Anatolian lands which is a bridge between East and West. But these trade routes has changed at the time of Ottoman Empire. Many of the historical places in the world have been totally or partly destroyed by natural events and human activities such as earthquake, flood and fire until the present day and still going on. Documentation is essentially required for protection and restoration these historical places and photogrammetry is one of the most effective method for documentation of cultural heritages. In this study, it is aimed to get 3D models of Doger Caravansaries which is established in Afyonkarahisar for relief and advertising. Doger Caravansaries was built in 15. Century at Sultan II Murat eras but the exact date of building is not known. The structure has rectangular plan in width. The total length of it is 56.50 in meters. The Caravansaries is consisting of attached two parts. The first part has two floors. There are pointed arched niches in the two sides of the wall and there are windows (iron barred) in the middle of the each niche. The door is fillet low arched. First floor rises on four elephant foot columns and ten other small columns. Short sides are covered by two each cross squinch and the other parts with barrel vault. There is a ladder with only ten remain levels opposite the main gate. Today, it has been cancelled to reach upstairs. The underside of the satires is empty. There are two loophole windows at the both two short side. The columns that are near the long walls are bounded each other with arches and overlaid with cross squinches. The rooms in the second floor have domes. One of these rooms was arranged as prey room. The second part of Caravansaries is single storey and walls made of rubble. There are four columns inside the room and they bounded with arches. Back side of the rooms were destroyed by earth quake and restored. This restoration was not appropriate with its original plan but the good one is that the Caravansaries was saved from totally comedown. It is aimed to survey Doger Caravansaries Photogrammetricaly and generate 3D model covered by real tissues. In this study, South NTS-352 Total Station is used to constitute a closed polygon with 6 point. The coordinates of polygon points are calculated by distance and direction measurements. Levelling was carried out for determining the height of polygon points. Photographs was taken by Nikon D7000 camera. 3D model and faces were created in Photomodeler software.
- Published
- 2013
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22. PHOTO REALISTIC 3D MODELING WITH UAV: GEDİK AHMET PASHA MOSQUE IN AFYONKARAHİSAR
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M. Uysal, A. S. Toprak, and N. Polat
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Technology ,Engineering (General). Civil engineering (General) ,TA1-2040 ,Applied optics. Photonics ,TA1501-1820 - Abstract
Many of the cultural heritages in the world have been totally or partly destroyed by natural events and human activities such as earthquake, flood and fire until the present day. Cultural heritages are legacy for us as well; it is also a fiduciary for next generation. To deliver this fiduciary to the future generations, cultural heritages have to be protected and registered. There are different methods for applying this registry but Photogrammetry is the most accurate and rapid method. Photogrammetry enables us to registry cultural heritages and generating 3D photo-realistic models. Nowadays, 3D models are being used in various fields such as education and tourism. In registration of complex and high construction by Photogrammetry, there are some problems in data acquisition and processing. Especially for high construction's photographs, some additional equipment is required such as balloon and lifter. In recent years The Unmanned Aerial Vehicles (UAV) are commonly started to be used in different fields for different goals. In Photogrammetry, The UAVs are being used for particularly data acquisition. It is not always easy to capture data due to the situation of historical places and their neighbourhood. The use of UAVs for documentation of cultural heritage will make an important contribution. The main goals of this study are to survey cultural heritages by Photogrammetry and to investigate the potential of UAVs in 3D modelling. In this purpose we surveyed Gedik Ahmet Pasha Mosque photogrammetricly by UAV and will produce photorealistic 3D model. Gedik Ahmet Pasha, The Grand Vizier of Fatih Sultan Mehmet, has been in Afyonkarahisar during the campaign to Karaman between the years of 1472–1473. He wanted Architect Ayaz Agha to build a complex of Bathhouse, Mosque and a Madrasah here, Afyon, due to admiration of this city. Gedik Ahmet Pasha Mosque is in the centre of this complex. Gedik Ahmet Pasha Mosque is popularly known as Imaret Mosque among the people of Afyon. Gedik Ahmet Pasha Complex is a foundation. For this reason all its expenses are recorded. Furthermore renovations of all buildings in this complex are placed on them with a inscription. According to records and inscriptions The Imaret Mosque has been restored several times. The two significant of these restorations were made after the earthquakes in 1668 and 1792. Lastly, after the renewing lead plating of domes in 1969, the Mosque has gotten its current final situation. The dimensions of Mosque are 29.20 x 35.40 in meter and it has built by a plan of inverse capital (T). There are two domes covering the main worship and it is one of the most important examples of Ottoman architecture with three of dome both side in direction of east to west. At the north side of the Mosque, there is a place for last congregations with five domes. Minaret is at the north-east side of the mosque. It has got one balcony (surrounding the minaret) and has been structured by cut stone with a shape of fluting. It has been covered by dark blue tile between these flutings. The main gate of mosque is made of pen inlaid marble. It is aimed to survey Gedik Ahmet Pasha Mosque photogrammetricly and to model it in 3D photo-realistic. In this study, South NTS-352 Total Station is used to constitute a closed polygon with 8 point. We used 350 ground control point in the field study. It is made levelling to measure elevation of polygon points. For photographs, we used Canon A 180 camera and UAV. Photomodeler software is used to process both camera's and UAV's photographs independently. The facades of mosque are derived and all 3D models of Mosque were merged. This merged model is covered with high resolution photographs for obtaining 3D photo-realistic models of Gedik Ahmet Pasha Mosque.
- Published
- 2013
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23. Investigation of the hydrogen evolution on Ni deposited titanium oxide nano tubes
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Şahin, E. Altunbaş, Doğru Mert, B., Döşlü, S. Toprak, Kardaş, G., and Yazıcı, B.
- Published
- 2012
- Full Text
- View/download PDF
24. Facile synthesis of nanographene by a high-yield and scalable method
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Zahra Haghjoo, Majid Ziaratban, Armin Gholizadeh, Amir Babaei, and Muhammet S. Toprak
- Subjects
010302 applied physics ,Diffraction ,Materials science ,Atomic force microscopy ,Process Chemistry and Technology ,Bilayer ,02 engineering and technology ,021001 nanoscience & nanotechnology ,01 natural sciences ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Shear (sheet metal) ,symbols.namesake ,Chemical engineering ,Transmission electron microscopy ,Yield (chemistry) ,0103 physical sciences ,Materials Chemistry ,Ceramics and Composites ,symbols ,0210 nano-technology ,Raman spectroscopy ,Microwave - Abstract
The aim of this work was to synthesize nanographene (NG) through a simple, efficient, and cost-effective method. In this regard, a combination of microwave (MW) and shear mixing with a kitchen blender was used. Atomic force microscopy (AFM), Raman spectroscopy, transmission electron microscopy (TEM) and X-ray diffraction (XRD) analysis were used to investigate the structure of synthesized NG. The Results of the characterizations demonstrated that most of the synthesized NG exhibited 0D structure and bilayer characteristics. The obtained results introduce a method for synthesizing NG at a large scale through a combination of MW and shear, in a relatively short time, without any need for purification.
- Published
- 2020
25. Click chemical assembly and validation of bio-functionalized superparamagnetic hybrid microspheres
- Author
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Muhammet S. Toprak, Gunaratna Kuttuva Rajarao, Bejan Hamawandi, Giovanni Marco Saladino, and Carmen Vogt
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Materials science ,Materials Science (miscellaneous) ,Magnetic separation ,Nanochemistry ,Nanoparticle ,Cell Biology ,Atomic and Molecular Physics, and Optics ,chemistry.chemical_compound ,Colloid ,chemistry ,Chemical engineering ,Magnetic nanoparticles ,Glutaraldehyde ,Electrical and Electronic Engineering ,Physical and Theoretical Chemistry ,Hybrid material ,Biotechnology ,Superparamagnetism - Abstract
Surface derivatized magnetic nanoparticles have been commonly used for magnetic separation. Facile mechanisms are needed to be developed for the design of bio-functionalized magnetic hybrid materials, where the surfaces can be re-generated for the re-use of the developed platforms. Superparamagnetic iron oxide nanoparticles with a diameter below 10 nm were synthesized via a novel microwave-assisted hydrothermal method in the presence of citrate ions, which allowed to obtain uniform and negatively charged nanoparticles. These were then coupled with Poly-l-lysine (PLL), forming micrometer-sized self-assembled spherical entities. Cross-linking the PLL within these microspheres with glutaraldehyde stabilized them chemically and mechanically. The active bio-functionality was introduced by a protein grafting methodology, using m-maleimidobenzoyl-N-hydroxysulfosuccinimide ester (SMBS). The Moringa oleifera Coagulant Protein (MOCP) from a seed extract was employed for its characteristic coagulation activity. The performance of the MOCP functionalized microspheres was evaluated as a function of turbidity removal of problematic colloidal clay from water via magnetic separation, resulting in over 80% of activity within 15 min. Surface of these hybrid materials can be re-generated by treatment with alcohol, allowing their easy magnetic separation and re-use. The rapid and strong response with tunable magnetic property makes these hybrid microspheres a powerful tool for many potential applications, due to the general applicability of the developed methodology.
- Published
- 2020
26. Toxicity of metal and metal oxide nanoparticles
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Hanna L. Karlsson, Muhammet S. Toprak, and Bengt Fadeel
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Human health ,Materials science ,Human exposure ,Engineered nanomaterials ,Toxicity ,Nanotechnology ,Metal oxide nanoparticles ,Nanomaterials - Abstract
Engineered nanomaterials hold great potential in many sectors of society, not least in medicine. However, the increasing production and use of engineered nanomaterials also raises concerns about inadvertent exposure and the potential for adverse effects on human health and the environment. This chapter provides an overview of metal and metal oxide nanoparticles, their applications, and the potential for human exposure. This is followed by a discussion of general principles of nanoparticle-induced toxicity and methods for toxicity testing of nanomaterials. Careful assessment of the material properties is required for a full understanding of nanomaterial toxicity; a section of the chapter is therefore devoted to physicochemical characterization. This is followed by a detailed description of the current knowledge concerning 12 of the most important metal and metal oxide nanoparticles, with a systematic evaluation of in vitro (cell culture) and in vivo (animal) toxicity studies. Ecotoxicological effects are not discussed because the chapter is focused on implications for human health.
- Published
- 2022
27. Contributors
- Author
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Jan Aaseth, Peter Aggett, Antero Aitio, Agneta Åkesson, Maria Albin, Jan Alexander, Christian B.I. Andersen, Ole Andersen, Pietro Apostoli, Michael Aschner, Rowa Bakadlag, Lars Barregard, David C. Bellinger, Ingvar A. Bergdahl, Balazs Berlinger, Alfred Bernard, Carolina Bigert, Poul Bjerregaard, Robyn Blain, Lennart K. Blomqvist, Beatrice Bocca, Stephan Bose-O'Reilly, Karin Broberg, Ronald P. Brown, Esben Budtz-Jørgensen, Samuel W. Caito, Tiffany Carle, Chien-Jen Chen, Xiao Chen, Lung-Chi Chen, C.-H. Selene J. Chou, Mitchell D. Cohen, Max Costa, Giuseppe De Palma, Alison Elder, Carl-Gustaf Elinder, Bengt Fadeel, Obaid M. Faroon, Bruce A. Fowler, Hitomi Fujishiro, Silvia Fustinoni, Lars Gerhardsson, Philippe Grandjean, Per Gustavsson, Yolanda Hedberg, Seiichiro Himeno, Xi Huang, Per A. Hultman, Ivo Iavicoli, Taiyi Jin, Robert L. Jones, Hanna L. Karlsson, Larry S. Keith, Yangho Kim, Catherine B. Klein, Michael Kleinman, David Kotelchuck, Yukinori Kusaka, Philip J. Landrigan, Per E. Leffler, Veruscka Leso, Alex Heng Li, Dominique Lison, Shan Liu, Roberto G. Lucchini, Polina Maciejczyk, Koren K. Mann, Nikki Maples-Reynolds, Michael J. Maroney, Airton C. Martins, Mary S. Matsui, Daphne B. Moffett, Lisbeth Birk Møller, M. Moiz Mumtaz, Makiko Nakano, Benoit Nemery, Koji Nogawa, Gunnar F. Nordberg, Monica Nordberg, Angelica Ortiz, Agneta Oskarsson, Elena A. Ostrakhovitch, Cezary M. Pałczyński, Natalia Pawlas, Daniela Pelclova, Maria Pesonen, K. Michael Pollard, Lothar Rink, Flavia Ruggieri, Patricia Ruiz, Harold H. Sandstead, Tiina Santonen, Kazuhiro Sato, Hiroshi Satoh, Deepak Saxena, Greet Schoeters, Bengt Sjögren, Staffan Skerfving, Donald R. Smith, Dexter W. Sullivan, Daigo Sumi, Hong Sun, Hille Suojalehto, Akiyo Tanaka, Milton Tenenbein, George D. Thurston, Francisco A. Tomei Torres, Muhammet S. Toprak, Carolyn A. Tylenda, Julian F. Tyson, Tomohiro Umemura, Margaret H. Whittaker, Jana Wolf, Wenbo Yan, Robert A. Yokel, and Rudolfs K. Zalups
- Published
- 2022
28. Low Noise High Linearity Current Readout Topologies for Potentiostat Circuitry
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O. Zafer Batur, S. Toprak, and R. Acar Vural
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Physics ,business.industry ,Electrical engineering ,Linearity ,Noise (electronics) ,Potentiostat ,law.invention ,CMOS ,law ,Current conveyor ,Operational amplifier ,business ,Voltage ,Electronic circuit - Abstract
In this work, two current readout architectures are investigated for potentiostat design; bidirectional current conveyor based potentiostat (BCC-P) and first generation current conveyor based potentiostat (CCI-P). They are designed in CMOS 180 nm TSMC technology with standard 1.8 V supply voltage and are evaluated in terms of input referred noise, linearity, accuracy, current range and power consumption. The integrated input referred noise of the BCC-P and CCI-P circuits are 0.432 pA and 153 pA between 0.01 Hz - 1 kHz, respectively. Although each circuit has similar opamps circuits, BCC-P is found to be more advantageous in terms of current linearity and noise.
- Published
- 2021
29. Proteomics Analysis Reveals Distinct Corona Composition on Magnetic Nanoparticles with Different Surface Coatings: Implications for Interactions with Primary Human Macrophages.
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Carmen Vogt, Maria Pernemalm, Pekka Kohonen, Sophie Laurent, Kjell Hultenby, Marie Vahter, Janne Lehtiö, Muhammet S Toprak, and Bengt Fadeel
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Medicine ,Science - Abstract
Superparamagnetic iron oxide nanoparticles (SPIONs) have emerged as promising contrast agents for magnetic resonance imaging. The influence of different surface coatings on the biocompatibility of SPIONs has been addressed, but the potential impact of the so-called corona of adsorbed proteins on the surface of SPIONs on their biological behavior is less well studied. Here, we determined the composition of the plasma protein corona on silica-coated versus dextran-coated SPIONs using mass spectrometry-based proteomics approaches. Notably, gene ontology (GO) enrichment analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis revealed distinct protein corona compositions for the two different SPIONs. Relaxivity of silica-coated SPIONs was modulated by the presence of a protein corona. Moreover, the viability of primary human monocyte-derived macrophages was influenced by the protein corona on silica-coated, but not dextran-coated SPIONs, and the protein corona promoted cellular uptake of silica-coated SPIONs, but did not affect internalization of dextran-coated SPIONs.
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- 2015
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30. SPECT/CT lymphoscintigraphy can accurately localize the sentinel lymph nodes and the clipped node in breast cancer patients undergoing targeted axillary dissection after neoadjuvant chemotherapy
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E. Dilege, B. Celik, S. Toprak, S. Sucu, O. Agcaoglu, O. Falay, and N. Kapucuoglu
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Cancer Research ,Oncology - Published
- 2022
31. Laboratory x-ray fluorescence computed tomography for in vivo preclinical imaging
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Hans M. Hertz, Bertha Brodin, Giovanni Marco Saladino, Kian Shaker, Kenth Andersson, Yurika Katsu-Jiménez, Carmen Vogt, Martin Svenda, Raoul Kuiper, Marie Arsenian-Henriksson, Aida Rodriguez-Garcia, Jakob C. Larsson, Yuyang Li, and Muhammet S. Toprak
- Subjects
Materials science ,medicine.diagnostic_test ,In vivo ,medicine ,X-ray fluorescence ,Low dose ct ,Computed tomography ,Tomography ,Fluorescence ,Preclinical imaging ,Biomedical engineering - Abstract
Laboratory x-ray fluorescence (XRF) computed tomography (XFCT) with nanoparticles (NPs) as contrast agents now allows for in vivo preclinical imaging and longitudinal studies at low radiation dose. We present on developments of our XFCT arrangement capable of low-dose (
- Published
- 2021
32. Targeted therapeutic effect against the breast cancer cell line MCF-7 with a CuFe2O4/silica/cisplatin nanocomposite formulation
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Muhammet S. Toprak, Widyan Alamoudi, Dana Almohazey, Lina Hussain Allehaibi, Abdulhadi Baykal, Vijaya Ravinayagam, Hatim Dafalla, B. Rabindran Jermy, and T. Somanathan
- Subjects
Materials science ,cisplatin ,nanotherapeutics ,General Physics and Astronomy ,Nanoparticle ,02 engineering and technology ,lcsh:Chemical technology ,anticancer ,010402 general chemistry ,lcsh:Technology ,01 natural sciences ,Full Research Paper ,Nanoclusters ,Adsorption ,Nanotechnology ,lcsh:TP1-1185 ,General Materials Science ,Electrical and Electronic Engineering ,Fourier transform infrared spectroscopy ,lcsh:Science ,multifunctional ,Nanocomposite ,lcsh:T ,copper ferrite ,021001 nanoscience & nanotechnology ,nanomedicine ,tumour therapy ,lcsh:QC1-999 ,0104 chemical sciences ,Nanoscience ,Transmission electron microscopy ,drug delivery ,Magnetic nanoparticles ,Surface modification ,lcsh:Q ,0210 nano-technology ,lcsh:Physics ,spherical silica ,Nuclear chemistry - Abstract
The combination of magnetic nanoparticles with a porous silica is a composite that has attracted significant attention for potential multifunctional theranostic applications. In this study, 30 wt % CuFe2O4 was impregnated into a matrix of monodispersed spherical hydrophilic silica (HYPS) nanoparticles through a simple dry impregnation technique. The chemotherapy drug cisplatin was loaded through electrostatic equilibrium adsorption over 24 h in normal saline solution. The presence of cubic spinel CuFe2O4 on HYPS was confirmed through powder X-ray diffraction (PXRD), Fourier transform infrared spectroscopy (FTIR) and diffuse reflectance UV–vis spectroscopy (DR UV–vis) analysis. The HYPS particles showed a surface area of 170 m2/g, pore size of 8.3 nm and pore volume of 0.35 cm3/g. The cisplatin/CuFe2O4/HYPS nanoformulation showed the accumulation of copper ferrite nanoparticles on the surface and in the pores of HYPS with a surface area of 45 m2/g, pore size of 16 nm and pore volume of 0.18 cm3/g. Transmission electron microscopy (TEM) and energy dispersive X-ray (EDX) mapping analysis showed the presence of homogeneous silica particles with nanoclusters of copper ferrite distributed on the HYPS support. Vibrating sample magnetometry (VSM) analysis of CuFe2O4/HYPS showed paramagnetic behavior with a saturated magnetization value of 7.65 emu/g. DRS UV–vis analysis revealed the functionalization of cisplatin in tetrahedral and octahedral coordination in the CuFe2O4/HYPS composite. Compared to other supports such as mesocellular foam and silicalite, the release of cisplatin using the dialysis membrane technique was found to be superior when CuFe2O4/HYPS was applied as the support. An in vitro experiment was conducted to determine the potential of CuFe2O4/HYPS as an anticancer agent against the human breast cancer cell line MCF-7. The results show that the nanoparticle formulation can effectively target cancerous cells and could be an effective tumor imaging guide and drug delivery system.
- Published
- 2019
33. Design impact on the performance of Ge PIN photodetectors
- Author
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Xuewei Zhao, Chao Zhao, Daoqun Liu, Wenwu Wang, Jun Luo, Zhihua Li, Xingxing Ke, Guilei Wang, Muhammet S. Toprak, Mahdi Moeen, and Henry H. Radamson
- Subjects
010302 applied physics ,Materials science ,business.industry ,Contact resistance ,Photodetector ,Condensed Matter Physics ,Epitaxy ,01 natural sciences ,Atomic and Molecular Physics, and Optics ,Electronic, Optical and Magnetic Materials ,Responsivity ,Quality (physics) ,0103 physical sciences ,Optoelectronics ,Electrical and Electronic Engineering ,business ,Dark current - Abstract
This article presents the impact of epitaxial quality, contact resistance and profile of Ge PIN photodetectors (PDs) on dark current and responsivity. The PD structures were processed with either s ...
- Published
- 2019
34. Optical and X-ray Fluorescent Nanoparticles for Dual Mode Bioimaging
- Author
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Kian Shaker, Bertha Brodin, Carmen Vogt, Martin Svenda, Hans M. Hertz, Giovanni Marco Saladino, Yuyang Li, and Muhammet S. Toprak
- Subjects
inorganic chemicals ,Fluorophore ,Materials science ,Biocompatibility ,X-ray fluorescence ,General Physics and Astronomy ,Nanoparticle ,Contrast Media ,Nanotechnology ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,Article ,law.invention ,chemistry.chemical_compound ,XFCT ,Confocal microscopy ,law ,General Materials Science ,Ceramic ,bioimaging ,Fluorescent Dyes ,X-Rays ,General Engineering ,X-ray ,technology, industry, and agriculture ,contrast agent ,021001 nanoscience & nanotechnology ,Silicon Dioxide ,Fluorescence ,0104 chemical sciences ,core−shell nanoparticles ,chemistry ,visual_art ,visual_art.visual_art_medium ,Nanoparticles ,fluorescent dye doping ,silica coated nanoparticles ,0210 nano-technology - Abstract
Nanoparticle (NP) based contrast agents detectable via different imaging modalities (multimodal properties) provide a promising strategy for noninvasive diagnostics. Core-shell NPs combining optical and X-ray fluorescence properties as bioimaging contrast agents are presented. NPs developed earlier for X-ray fluorescence computed tomography (XFCT), based on ceramic molybdenum oxide (MoO2) and metallic rhodium (Rh) and ruthenium (Ru), are coated with a silica (SiO2) shell, using ethanolamine as the catalyst. The SiO2 coating method introduced here is demonstrated to be applicable to both metallic and ceramic NPs. Furthermore, a fluorophore (Cy5.5 dye) was conjugated to the SiO2 layer, without altering the morphological and size characteristics of the hybrid NPs, rendering them with optical fluorescence properties. The improved biocompatibility of the SiO2 coated NPs without and with Cy5.5 is demonstrated in vitro by Real-Time Cell Analysis (RTCA) on a macrophage cell line (RAW 264.7). The multimodal characteristics of the core-shell NPs are confirmed with confocal microscopy, allowing the intracellular localization of these NPs in vitro to be tracked and studied. In situ XFCT successfully showed the possibility of in vivo multiplexed bioimaging for multitargeting studies with minimum radiation dose. Combined optical and X-ray fluorescence properties empower these NPs as effective macroscopic and microscopic imaging tools.
- Published
- 2021
35. Preclinical in vivo x-ray fluorescence computed tomography
- Author
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Jakob C. Larsson, Kian Shaker, Aida Rodriguez-Garcia, Hans M. Hertz, Yuyang Li, Muhammet S. Toprak, Kenth Andersson, Marie Arsenian-Henriksson, Carmen Vogt, Yurika Katsu-Jiménez, and Raoul Kuiper
- Subjects
medicine.diagnostic_test ,In vivo ,business.industry ,Chemistry ,medicine ,X-ray fluorescence ,Low dose ct ,Computed tomography ,Molecular imaging ,Nuclear medicine ,business ,Fluorescence ,Preclinical imaging - Abstract
X-ray fluorescence computed tomography (XFCT) with nanoparticles (NPs) as contrast agents has reached technical maturity allowing for in vivo preclinical imaging in the laboratory setting. We present the first in vivo longitudinal study with XFCT where mice were 5 times each during an 8-week period. Imaging is performed with low radiation dose (
- Published
- 2021
36. Modulation of conductivity of alginate hydrogels containing reduced graphene oxide through the addition of proteins
- Author
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María Luisa Sanjuán, Laura Saenz-del-Burgo, José Luis Pedraz, Muhammet S. Toprak, Ahmed Raslan, Jesús Ciriza, Patricia Gálvez-Martín, Ana M. Ochoa de Retana, and Eusko Jaurlaritza
- Subjects
Langmuir ,Conductivity ,Nanocomposite ,biology ,Graphene ,Alginate ,Oxide ,Pharmaceutical Science ,macromolecular substances ,Article ,law.invention ,RS1-441 ,chemistry.chemical_compound ,Hydrogel ,Pharmacy and materia medica ,Adsorption ,Chemical engineering ,chemistry ,law ,Self-healing hydrogels ,biology.protein ,Collagen ,Reduced graphene oxide ,Elastin - Abstract
This article belongs to the Special Issue Rational Design and Characterization of Hydrogels to Improve Pharmaceutical and Biomedical Applicability., Modifying hydrogels in order to enhance their conductivity is an exciting field with applications in cardio and neuro-regenerative medicine. Therefore, we have designed hybrid alginate hydrogels containing uncoated and protein-coated reduced graphene oxide (rGO). We specifically studied the adsorption of three different proteins, BSA, elastin, and collagen, and the outcomes when these protein-coated rGO nanocomposites are embedded within the hydrogels. Our results demonstrate that BSA, elastin, and collagen are adsorbed onto the rGO surface, through a non-spontaneous phenomenon that fits Langmuir and pseudo-second-order adsorption models. Protein-coated rGOs are able to preclude further adsorption of erythropoietin, but not insulin. Collagen showed better adsorption capacity than BSA and elastin due to its hydrophobic nature, although requiring more energy. Moreover, collagen-coated rGO hybrid alginate hydrogels showed an enhancement in conductivity, showing that it could be a promising conductive scaffold for regenerative medicine., This study was financially supported by the Basque Country Government [grant number T907-16].
- Published
- 2021
37. Thermoelectric Performance Of Cu2Se Doped With Rapidly Synthesized Gel-Like Carbon Dots
- Author
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Muhammet S. Toprak, Emrah Celik, Cagri Oztan, Roger M. Leblanc, Yiqun Zhou, Victoria L. Coverstone, Sedat Ballikaya, and Bejan Hamawandi
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Materials science ,Dopant ,Scanning electron microscope ,Mechanical Engineering ,Doping ,Metals and Alloys ,Analytical chemistry ,02 engineering and technology ,010402 general chemistry ,021001 nanoscience & nanotechnology ,Microstructure ,01 natural sciences ,0104 chemical sciences ,Mechanics of Materials ,Seebeck coefficient ,Thermoelectric effect ,Materials Chemistry ,Grain boundary ,0210 nano-technology ,Powder diffraction - Abstract
As an earth-abundant, inexpensive and non-toxic compound, Copper Selenide (Cu2Se) is a frequently investigated material for thermoelectric (TE) conversion applications. In this research, stoichiometric Cu2Se compounds were systematically doped with gel-like Carbon Dots (CDs), that were fabricated using a rapid and straightforward solvothermal method, at weight ratios of 2, 5 and 10%. The resultant ingots were spark plasma sintered and their TE performance was characterized. Scanning electron microscopy (SEM), energy dispersive X-Ray spectroscopy (EDX) and powder X-ray diffraction (PXRD) were used to correlate the microstructure to the TE properties. Based on these measurements, CD doping strategy on Cu2Se yielded highly compacted, single phase grains with minimal oxidation. Characterization demonstrated a continuous enhancement of TE figure of merit (ZT) to a maximum of 2.1 at the optimum dopant ratio of 2 wt %. This enhancement was mainly due to the energy filtering effect of CD interfaces along the grain boundaries, and phonon scattering which increased the Seebeck coefficient and reduce the thermal conductivity. Doping beyond 2 wt% was recorded to inhibit this improvement. This research paved the path towards broader utilization of rapidly fabricated CDs to enhance TE conversion performance. (C) 2020 Elsevier B.V. All rights reserved.
- Published
- 2021
38. Contributors
- Author
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Jan Aaseth, Peter Aggett, Antero Aitio, Agneta Åkesson, Maria Albin, Jan Alexander, Christian B.I. Andersen, Ole Andersen, Pietro Apostoli, Michael Aschner, Rowa Bakadlag, Lars Barregard, David C. Bellinger, Ingvar A. Bergdahl, Balazs Berlinger, Alfred Bernard, Carolina Bigert, Poul Bjerregaard, Robyn Blain, Lennart K. Blomqvist, Beatrice Bocca, Stephan Bose-O'Reilly, Karin Broberg, Ronald P. Brown, Esben Budtz-Jørgensen, Samuel W. Caito, Tiffany Carle, Chien-Jen Chen, Xiao Chen, Lung-Chi Chen, C.-H. Selene J. Chou, Mitchell D. Cohen, Max Costa, Giuseppe De Palma, Alison Elder, Carl-Gustaf Elinder, Bengt Fadeel, Obaid M. Faroon, Bruce A. Fowler, Hitomi Fujishiro, Silvia Fustinoni, Lars Gerhardsson, Philippe Grandjean, Per Gustavsson, Yolanda Hedberg, Seiichiro Himeno, Xi Huang, Per A. Hultman, Ivo Iavicoli, Taiyi Jin, Robert L. Jones, Hanna L. Karlsson, Larry S. Keith, Yangho Kim, Catherine B. Klein, Michael Kleinman, David Kotelchuck, Yukinori Kusaka, Philip J. Landrigan, Per E. Leffler, Veruscka Leso, Alex Heng Li, Dominique Lison, Shan Liu, Roberto G. Lucchini, Polina Maciejczyk, Koren K. Mann, Nikki Maples-Reynolds, Michael J. Maroney, Airton C. Martins, Mary S. Matsui, Daphne B. Moffett, Lisbeth Birk Møller, M. Moiz Mumtaz, Makiko Nakano, Benoit Nemery, Koji Nogawa, Gunnar F. Nordberg, Monica Nordberg, Angelica Ortiz, Agneta Oskarsson, Elena A. Ostrakhovitch, Cezary M. Pałczyński, Natalia Pawlas, Daniela Pelclova, Maria Pesonen, K. Michael Pollard, Lothar Rink, Flavia Ruggieri, Patricia Ruiz, Harold H. Sandstead, Tiina Santonen, Kazuhiro Sato, Hiroshi Satoh, Deepak Saxena, Greet Schoeters, Bengt Sjögren, Staffan Skerfving, Donald R. Smith, Dexter W. Sullivan, Daigo Sumi, Hong Sun, Hille Suojalehto, Akiyo Tanaka, Milton Tenenbein, George D. Thurston, Francisco A. Tomei Torres, Muhammet S. Toprak, Carolyn A. Tylenda, Julian F. Tyson, Tomohiro Umemura, Margaret H. Whittaker, Jana Wolf, Wenbo Yan, Robert A. Yokel, and Rudolfs K. Zalups
- Published
- 2021
39. Multi-Objective Optimization Of Concentrated Photovoltaic-Thermoelectric Hybrid System Via Non-Dominated Sorting Genetic Algorithm (Nsga Ii)
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Bejan Hamawandi, Hasan Tiryaki, Nevra Bayhan, Sedat Ballikaya, Muhammet S. Toprak, and Aminu Yusuf
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Renewable Energy, Sustainability and the Environment ,020209 energy ,Energy Engineering and Power Technology ,TOPSIS ,02 engineering and technology ,Internal resistance ,Thermoelectric materials ,Multi-objective optimization ,Automotive engineering ,Fuel Technology ,Thermoelectric generator ,020401 chemical engineering ,Nuclear Energy and Engineering ,Hybrid system ,Thermoelectric effect ,0202 electrical engineering, electronic engineering, information engineering ,Electric power ,0204 chemical engineering ,Mathematics - Abstract
Thermoelectric generators harvest additional electrical power when used in combination with concentrated photovoltaic cells given rise to a hybrid system. Overall cost of the system is high; therefore, the parameters of the system need to be optimized to obtain high output performance. This study determines the output performances of four sets of equations (models) used in the hybrid system, using the performance of recently developed nanostructured thermoelectric materials. Seven parameters of the system were optimized through these models using non-dominated genetic algorithm. Models 1 and 2 have the highest performance chosen by TOPSIS decision-making method. The power output and conversion efficiencies of the hybrid system in models 1 and 2 are 426.5 W, 11.45% and 461.12 W, 10.77%, respectively. Likewise, the highest TOPSIS solution for power output of one TEG module operating in the hybrid system and its corresponding efficiency is obtained in model 4 and are 1.97 W and 0.078%, respectively. This validates the fact that TEG operating in a hybrid system has optimum performance at a point when the load resistance is less than its internal resistance.
- Published
- 2021
40. Modeling, design, and synthesis of gram-scale monodispersed silver nanoparticles using microwave-assisted polyol process for metamaterial applications
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Zahra Lalegani, S.A. Seyyed Ebrahimi, Luigi La Spada, Bejan Hamawandi, and Muhammet S. Toprak
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Materials science ,Nanoparticle ,02 engineering and technology ,Microwave-assisted, High yield, Polyol Silver, NPs ,010402 general chemistry ,01 natural sciences ,Silver nanoparticle ,Inorganic Chemistry ,chemistry.chemical_compound ,Polyol ,Electrical and Electronic Engineering ,Physical and Theoretical Chemistry ,Fourier transform infrared spectroscopy ,Spectroscopy ,chemistry.chemical_classification ,Organic Chemistry ,021001 nanoscience & nanotechnology ,Atomic and Molecular Physics, and Optics ,0104 chemical sciences ,Electronic, Optical and Magnetic Materials ,chemistry ,Chemical engineering ,Yield (chemistry) ,Particle ,Absorption (chemistry) ,0210 nano-technology ,Ethylene glycol - Abstract
High-yield monodispersed silver (Ag) nanospheres were modeled, designed, and synthesized by microwave-assisted (MW-assisted) polyol method from AgNO3, polyvinyl pyrrolidone (PVP), and ethylene glycol (EG), as precursors, at 145 °C within a short reaction time of 2 min, and the results were compared to those of conventional polyol method. Maintaining the PVP:AgNO3 molar ratio, the effect of increasing the amounts of AgNO3 and PVP at a constant amount of EG (40 mL) on the final product was evaluated. The synthesized nanoparticles (NPs) were characterized by SEM, UV–Vis spectroscopy, FTIR and DLS analysis. The results showed that with increasing the amount of AgNO3 to 0.5 and 1 g, monodispersed Ag nanoparticles (Ag NPs) with particle sizes of 54 and 61 nm were formed, as per the plasmon absorption peaks at 436 and 442 nm, respectively. Moreover, using 40 mL of the EG solution, we could obtain a high yield of the NPs (~90%). The sub-gram yield was excellently high, offering great opportunities for commercializing the procedure. Also, the proposed study paves a new way for Ag NPs realization for different practical applications ranging from MW to optics.
- Published
- 2020
41. Recent advances in the modification of carbon-based quantum dots for biomedical applications
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Nima Rezaei, Amirhossein Alaghmandfard, Alexander M. Seifalian, Omid Sedighi, Muhammet S. Toprak, Amir Abbas Abedini, and Adrine Malek Khachatourian
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Photoluminescence ,Materials science ,Biocompatibility ,Polymers ,chemistry.chemical_element ,Bioengineering ,Nanotechnology ,02 engineering and technology ,010402 general chemistry ,01 natural sciences ,law.invention ,Biomaterials ,law ,Quantum Dots ,chemistry.chemical_classification ,Graphene ,Doping ,Gene Transfer Techniques ,Polymer ,021001 nanoscience & nanotechnology ,Carbon ,0104 chemical sciences ,chemistry ,Mechanics of Materials ,Quantum dot ,Surface modification ,Graphite ,0210 nano-technology - Abstract
Carbon-based quantum dots (CDs) are mainly divided into two sub-groups; carbon quantum dots (CQDs) and graphene quantum dots (GQDs), which exhibit outstanding photoluminescence (PL) properties, low toxicity, superior biocompatibility and facile functionalization. Regarding these features, they have been promising candidates for biomedical science and engineering applications. In this work, we reviewed the efforts made to modify these zero-dimensional nano-materials to obtain the best properties for bio-imaging, drug and gene delivery, cancer therapy, and bio-sensor applications. Five main surface modification techniques with outstanding results are investigated, including doping, surface functionalization, polymer capping, nano-composite and core-shell structures, and the drawbacks and challenges in each of these methods are discussed.
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- 2020
42. Nitric oxide-dependent biodegradation of graphene oxide reduces inflammation in the gastrointestinal tract
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Jon O. Lundberg, Guotao Peng, Bengt Fadeel, Carmen Vogt, Kostas Kostarelos, Chifundo N. M. Ntola, Tianbo Duan, Sandra Vranic, Klaus Leifer, Lars Bräutigam, Marcelo F. Montenegro, Muhammet S. Toprak, and European Commission
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Raman mapping ,Nitric Oxide Synthase Type II ,Inflammation ,02 engineering and technology ,010402 general chemistry ,Adverse effect ,Nitric Oxide ,01 natural sciences ,Nitric oxide ,chemistry.chemical_compound ,Inducible nitric oxide synthase (iNOS) ,Gastrointestinal tract ,medicine ,Pharmacological inhibition ,Animals ,General Materials Science ,Xanthine oxidase ,Zebrafish ,Neutrophil infiltration ,Gene knockdown ,biology ,Superoxide ,Transgenic strains ,021001 nanoscience & nanotechnology ,Xanthine ,3. Good health ,0104 chemical sciences ,Cell biology ,Nitric oxide synthase ,Gastrointestinal Tract ,chemistry ,biology.protein ,Graphite ,Generating system ,medicine.symptom ,Nitric Oxide Synthase ,0210 nano-technology - Abstract
Understanding the biological fate of graphene-based materials such as graphene oxide (GO) is crucial to assess adverse effects following intentional or inadvertent exposure. Here we provide first evidence of biodegradation of GO in the gastrointestinal tract using zebrafish as a model. Raman mapping was deployed to assess biodegradation. The degradation was blocked upon knockdown of nos2a encoding the inducible nitric oxide synthase (iNOS) or by pharmacological inhibition of NOS using L-NAME, demonstrating that the process was nitric oxide (NO)-dependent. NO-dependent degradation of GO was further confirmed in vitro by combining a superoxide-generating system, xanthine/xanthine oxidase (X/XO), with an NO donor (PAPA NONOate), or by simultaneously producing superoxide and NO by decomposition of SIN-1. Finally, by using the transgenic strain Tg(mpx:eGFP) to visualize the movement of neutrophils, we could show that inhibition of the degradation of GO resulted in increased neutrophil infiltration into the gastrointestinal tract, indicative of inflammation., This work was supported by the European Commission through the Graphene Flagship (grant no. 785219).
- Published
- 2020
43. Longitudinal In-Vivo X-Ray Fluorescence Computed Tomography With Molybdenum Nanoparticles
- Author
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Kian, Shaker, Carmen, Vogt, Yurika, Katsu-Jimenez, Raoul V, Kuiper, Kenth, Andersson, Yuyang, Li, Jakob C, Larsson, Aida, Rodriguez-Garcia, Muhammet S, Toprak, Marie, Arsenian-Henriksson, and Hans M, Hertz
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Molybdenum ,Mice ,Phantoms, Imaging ,X-Rays ,Animals ,Metal Nanoparticles ,Nanoparticles ,Longitudinal Studies ,Tomography, X-Ray Computed ,Fluorescence - Abstract
X-ray fluorescence computed tomography (XFCT) with nanoparticles (NPs) as contrast agents shows potential for molecular biomedical imaging with higher spatial resolution than present methods. To date the technique has been demonstrated on phantoms and mice, however, parameters such as radiation dose, exposure times and sensitivity have not yet allowed for high-spatial-resolution in vivo longitudinal imaging, i.e., imaging of the same animal at different time points. Here we show in vivo XFCT with spatial resolution in the 200- [Formula: see text] range in a proof-of-principle longitudinal study where mice are imaged five times each during an eight-week period following tail-vein injection of NPs. We rely on a 24 keV x-ray pencil-beam-based excitation of in-house-synthesized molybdenum oxide NPs (MoO
- Published
- 2020
44. Quantitative conversion of biomass in giant DNA virus infection
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Muhammet S. Toprak, Komang G. Y. Arsana, Mikael Kördel, Bejan Hamawandi, Emelie Fogelqvist, Martin Svenda, Hemanth K. N. Reddy, Jonas A. Sellberg, and Hans M. Hertz
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0301 basic medicine ,Nucleolus ,viruses ,Science ,Acanthamoeba ,02 engineering and technology ,Genome, Viral ,Virus Replication ,Article ,Virus ,Amoeba (operating system) ,Microbiology in the medical area ,03 medical and health sciences ,Viral factory ,Phagosomes ,Mikrobiologi inom det medicinska området ,Biomass ,Soil Microbiology ,Phagosome ,Microscopy ,Multidisciplinary ,Chemistry ,DNA Viruses ,Virion ,DNA virus ,Viral host response ,X-Ray Microtomography ,021001 nanoscience & nanotechnology ,Cell biology ,Contractile vacuole ,030104 developmental biology ,Viral replication ,Giant Viruses ,DNA, Viral ,Host-Pathogen Interactions ,Thermogravimetry ,Vacuoles ,Medicine ,0210 nano-technology ,Microbiology techniques - Abstract
Bioconversion of organic materials is the foundation of many applications in chemical engineering, microbiology and biochemistry. Herein, we introduce a new methodology to quantitatively determine conversion of biomass in viral infections while simultaneously imaging morphological changes of the host cell. As proof of concept, the viral replication of an unidentified giant DNA virus and the cellular response of an amoebal host are studied using soft X-ray microscopy, titration dilution measurements and thermal gravimetric analysis. We find that virions produced inside the cell are visible from 18 h post infection and their numbers increase gradually to a burst size of 280–660 virions. Due to the large size of the virion and its strong X-ray absorption contrast, we estimate that the burst size corresponds to a conversion of 6–12% of carbonaceous biomass from amoebal host to virus. The occurrence of virion production correlates with the appearance of a possible viral factory and morphological changes in the phagosomes and contractile vacuole complex of the amoeba, whereas the nucleus and nucleolus appear unaffected throughout most of the replication cycle.
- Published
- 2020
45. Composition Tuning of Nanostructured Binary Copper Selenides through Rapid Chemical Synthesis and their Thermoelectric Property Evaluation
- Author
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Hamawandi, Bejan, Ballikaya, Sedat, Råsander, Mikael, Halim, Joseph, Vinciguerra, Lorenzo, Rosén, Johanna, Johnsson, Mats, and S. Toprak, Muhammet
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Oorganisk kemi ,ZT ,thermoelectric ,Article ,microwave synthesis ,lcsh:Chemistry ,Inorganic Chemistry ,Cu2−xSe ,lcsh:QD1-999 ,XPS ,chalcogenides ,thermal conductivity ,nanomaterial ,Cu2-xSe - Abstract
Reduced energy consumption and environmentally friendly, abundant constituents are gaining more attention for the synthesis of energy materials. A rapid, highly scalable, and process-temperature-sensitive solution synthesis route is demonstrated for the fabrication of thermoelectric Cu2-xSe. The process relies on readily available precursors and microwave-assisted thermolysis, which is sensitive to reaction conditions; yielding Cu1.8Se at 200 C and Cu2Se at 250 C within 6-8 min reaction time. Transmission electron microscopy (TEM) revealed crystalline nature of as-made particles with irregular truncated morphology, which exhibit a high phase purity as identified by X-ray powder diffraction (XRPD) analysis. Temperature-dependent transport properties were characterized via electrical conductivity, Seebeck coefficient, and thermal diffusivity measurements. Subsequent to spark plasma sintering, pure Cu1.8Se exhibited highly compacted and oriented grains that were similar in size in comparison to Cu2Se, which led to its high electrical and low thermal conductivity, reaching a very high power-factor (24 µW/K-2cm-1). Density-of-states (DOS) calculations confirm the observed trends in electronic properties of the material, where Cu-deficient phase exhibits metallic character. The TE figure of merit (ZT) was estimated for the materials, demonstrating an unprecedentedly high ZT at 875 K of 2.1 for Cu1.8Se sample, followed by 1.9 for Cu2Se. Synthetic and processing methods presented in this work enable large-scale production of TE materials and components for niche applications. Funding agencies: The Swedish Energy Agency [Energimyndigheten, 43521-1], Swedish Research Council [VR, 2018-03462]. SB acknowledges support by Scientific and Technological ResearchCouncil of Turkey [TUBITAK, 216M254] and Scientific Research Projects Coordination Unit of Istanbul University[BAP, 21809, 32641 and 35577]. JR acknowledges support from the Swedish Foundation for Strategic Research[SSF, EM16-0004].
- Published
- 2020
46. Fabrication and thermo-physical characterization of silver nanofluids: An experimental investigation on the effect of base liquid
- Author
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Muhammet S. Toprak and Nader Nikkam
- Subjects
Materials science ,Fabrication ,020209 energy ,General Chemical Engineering ,Nanoparticle ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Energy engineering ,Atomic and Molecular Physics, and Optics ,Characterization (materials science) ,Nanofluid ,Chemical engineering ,Heat exchanger ,0202 electrical engineering, electronic engineering, information engineering ,0210 nano-technology ,Base (exponentiation) - Abstract
Nanofluids (NFs) are solid-liquid composites prepared by stabilizing nanoparticles (NPs) in a base liquid, which is selected based on the technological area of application. For heat exchange applic ...
- Published
- 2018
47. Fabrication and thermo-physical properties characterization of ethylene glycol—MoS2 heat exchange fluids
- Author
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Muhammet S. Toprak, Mohammed Al-Abri, Myo Tay Zar Myint, Joydeep Dutta, Seyed Majid Mohseni, Maissa Souayeh, and Nader Nikkam
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Materials science ,020209 energy ,General Chemical Engineering ,Nanoparticle ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Atomic and Molecular Physics, and Optics ,Viscosity ,chemistry.chemical_compound ,Nanofluid ,chemistry ,Chemical engineering ,0202 electrical engineering, electronic engineering, information engineering ,Particle ,Particle size ,0210 nano-technology ,Dispersion (chemistry) ,Molybdenum disulfide ,Ethylene glycol - Abstract
This study reports on the fabrication and thermo-physical properties evaluation of ethylene glycol (EG) based heat exchange fluids containing molybdenum disulfide nanoparticles (MoS2 NPs) and micrometer sized particles (MPs). For this purpose, MoS2 NPs and MPs (with average size of 90 nm and 1.2 μm; respectively) were dispersed and stabilized in EG with particle loading of 0.25, 0.5, 1 wt%. To study the real effect of MoS2 NP/MP the use of surfactants was avoided and ultrasonic agitation was used for dispersion and preparation of stable MoS2 NFs/MFs. The objectives were investigation of impact of MoS2 particle size (including NP/MP) and particle loading on thermo-physical properties of EG based MoS2 NFs/MFs including thermal conductivity (TC) and viscosity of NFs/MFs at 20 °C. All suspensions (NFs/MFs) exhibited a higher TC than the EG as base liquid and NFs showed higher TC enhancement values than the MFs. A TC enhancement of 16.4% was observed for NFs containing 1 wt% MoS2 NPs while the maximum increase in viscosity of 9.7% was obtained for the same NF at 20 °C. It indicates this NF system may have some potential to be utilized in heat transfer applications.
- Published
- 2017
48. Composition Tuning of Nanostructured Binary Copper Selenides through Rapid Chemical Synthesis and Their Thermoelectric Property Evaluation
- Author
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Hamawandi, Bejan, primary, Ballikaya, Sedat, additional, Råsander, Mikael, additional, Halim, Joseph, additional, Vinciguerra, Lorenzo, additional, Rosén, Johanna, additional, Johnsson, Mats, additional, and S. Toprak, Muhammet, additional
- Published
- 2020
- Full Text
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49. Removal of chromium (VI) from aqueous solutions using surface modified composite nanofibers
- Author
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T. A. Osman, Mamoun Muhammed, Abdusalam Uheida, Muhammet S. Toprak, Walaa S. Nasser, and Alaa Mohamed
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Langmuir ,Aqueous solution ,Materials science ,Inorganic chemistry ,Polyacrylonitrile ,chemistry.chemical_element ,02 engineering and technology ,010501 environmental sciences ,021001 nanoscience & nanotechnology ,01 natural sciences ,Electrospinning ,Surfaces, Coatings and Films ,Electronic, Optical and Magnetic Materials ,Biomaterials ,chemistry.chemical_compound ,Chromium ,Colloid and Surface Chemistry ,Adsorption ,chemistry ,Chemical engineering ,Freundlich equation ,Absorption (chemistry) ,0210 nano-technology ,0105 earth and related environmental sciences - Abstract
A novel material composite nanofibers (PAN-CNT/TiO2-NH2) based on adsorption of Cr(VI) ions, was applied. Polyacrylonitrile (PAN) and carbon nanotube (CNTs)/titanium dioxide nanoparticles (TiO2) functionalized with amine groups (TiO2-NH2) composite nanofibers have been fabricated by electrospinning. The nanostructures and the formation process mechanism of the obtained PAN-CNT/TiO2-NH2 composite nanofibers are investigated using FTIR, XRD, XPS, SEM, and TEM. The composite nanofibers were used as a novel adsorbent for removing toxic chromium Cr(VI) in aqueous solution. The kinetic study, adsorption isotherm, pH effect, initial concentration, and thermodynamic study were investigated in batch experiments. The composite nanofibers had a positive effect on the absorption of Cr(VI) ions under neutral and acidic conditions, and the saturated adsorption reached the highest when pH was 2. The adsorption equilibrium reached within 30 and 180 min with an initial solution concentration increasing from 10 to 300 mg/L, and the process can be better described using nonlinear pseudo first than nonlinear pseudo second order model and Intra-particle diffusion. Isotherm data fitted well using linear and nonlinear Langmuir, Freundlich, Redlich-Peterson, and Temkin isotherm adsorption model. Thermodynamic study showed that the adsorption process is exothermic. The adsorption capacity can remain up to 80% after 5 times usage, which show good durability performance. The adsorption mechanism was also studied by UV–vis and XPS.
- Published
- 2017
50. Experimental investigation on the effect of SiO 2 secondary phase on thermo-physical properties of SiC nanofluids
- Author
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Rahmatollah Khodabandeh, Mohammadreza Behi, Mohsin Saleemi, Muhammet S. Toprak, and Nader Nikkam
- Subjects
Materials science ,Secondary phase ,020209 energy ,General Chemical Engineering ,Nanoparticle ,Nanotechnology ,02 engineering and technology ,021001 nanoscience & nanotechnology ,Condensed Matter Physics ,Atomic and Molecular Physics, and Optics ,Viscosity ,Thermal conductivity ,Nanofluid ,Chemical engineering ,Impurity ,Phase (matter) ,Heat exchanger ,0202 electrical engineering, electronic engineering, information engineering ,0210 nano-technology - Abstract
Nanofluids (NFs), wherein solid nanoparticles (NPs) are dispersed in traditional heat exchange fluids, are recognized for improving the performance of traditional fluids by enhancing their thermal conductivity (TC). The presence of impurities or undesired phases in commercial NPs may influence the thermo-physical properties of NFs including TC and viscosity, which makes it difficult to understand the real effect of NPs on heat transport characteristics of NFs. Moreover, the presence of these impurities in commercial NPs is unavoidable and their removal from commercial NPs with no negative impact on composition of NPs is challenging. To study the impact of impurities on thermo-physical properties of NFs a systematic experimental work was performed using commercial α-SiC and SiO2 NPs as the secondary phase as it commonly co-exists in commercial SiC batches. For this purpose, a series of NFs containing 9 wt% of α-SiC/SiO2 NP mixture with different content of SiO2 NPs from 5 to 50% were fabricated and investigated. The results show that as the undesired impurity phase (SiO2) increases, TC of NFs decreases slightly while viscosity increases dramatically. This may be a sound path to tuning the viscosity of the NFs while the achieved high TC is mildly influenced by the secondary phase.
- Published
- 2017
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