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Bakır alttaşa yapılan ön işlemin tek tabaka grafen film kalitesine etkisi
(2016) Yılmaz, Mücahit; Eker, Yasin Ramazan
Tekdüze büyük ölçekli grafen tabakaları sentezlemek için çeşitli metotlar önerilmiştir. Bunlardan en çok tercih edileni bakır veya nikel alttaş üzerine kimyasal buhar biriktirme (CVD) yöntemiyle grafen büyütmektir. Son çalışmalarda, kusursuz formasyona sahip tek tabaka grafenin, bakırın kristal yapısına kritik bir şekilde bağlı olduğu bilinmektedir. Bu etkinin yanı sıra, bakır alttaşa yapılan ön işlemin de grafen oluşumunu etkilediği düşünülmüştür. Çalışmada alttaş olarak 25 ?m kalınlıklı bakır folyolar standart temizleme, elektroliz ile parlatma ve tavlama gibi üç farklı ön işlemden geçirilmiştir. Daha sonra metan (CH4) ve hidrojen (H2) proses gazları kullanılarak grafen sentezlenmiştir. Bakır folyonun yapısı ve kalitesi XRD ve XRF ile belirlenmiştir. Büyütme işleminden sonra bakır alttaşların üst yüzeyleri ve alt yüzeyleri Konfokal Raman kullanılarak incelenmiş, oluşan grafenin özellikleri tespit edilmiştir. Sonuç olarak elektroliz ile parlatma ön işleminden geçirilmiş bakır alttaş üzerinde, tek tabaka grafen oluşumu gözlenirken diğer ön işlemlerden geçirilmiş bakır alttaşlar üzerinde çok tabakalı grafenler gözlenmiştir.
Chemical Composition Simplification of the Seydisehir (Konya, Turkey) Alumina Plant Waste
(Springer, 2019) Kalsen, Tugba Selcen Atalay; Karadag, Hakan Burak; Eker, Yasin Ramazan; Kerti, Isil
Red mud, a residue of alumina production from bauxite refining, contains oxides of valuable metals such as Fe, Al, Ti, Si, Na, Ca, etc. The presence of these numerous metal oxides does not allow introducing the highly basic raw red mud within any industrial process, which leads to its storage over a wide land area. In order to simplify the chemical composition of this waste, the effects of weak acid leaching (citric acid) and strong acid leaching (hydrochloric acid) are studied. The treatment efficiency is discussed based on scanning electron microscope and X-ray diffraction analysis of solid product and inductively coupled plasma spectrometry analysis of acidic solutions. The effects of temperature and acid concentration on metals dissolution are estimated by rough kinetic considerations which present results comparable to those in the literature. More than 50% of Al and 50% of Ca detected by inductively coupled plasma mass spectrometry were separated via the organic acid process, while during leaching with HCl whole Ca, Fe, and more than 60% Ti and 80% of Al similarly determined were recovered. This confirms that within the red mud, metals behave differently under several forms with different reactivity toward acidic medium. Therefore, an eventual combination of both acids can be an efficient way to prepare them ready and suitable for possible industrial applications.
An economical electrocoagulation process of a hazardous anionic azo dye wastewater with the combination of recycled electrodes and solar energy
(Springer Heidelberg, 2023) Akkaya, Gulizar Kurtoglu; Polat, Gokhan; Nalcaci, Gamze; Eker, Yasin Ramazan
The energy and electrode costs are the restrictions of applying electrocoagulation (EC) in wastewater treatment and many attempts have been made to decrease these costs. In this study, an economical EC was investigated to treat a hazardous anionic azo dye wastewater (DW) that threatens the environment and human health. Firstly, an electrode for EC process was produced from recycled aluminum cans (RACs) by remelting in an induction melting furnace. The performance of the RAC electrodes in the EC was evaluated for COD, color removal, and the EC operating parameters such as initial pH, current density (CD), and electrolysis time. Response surface methodology which is based on central composite design (RSM-CCD) was used for the optimization of the process parameters which were found to be pH 3.96, CD 15 mA/cm(2), and electrolysis time 45 min. The maximum COD and color removal values were determined as 98.87% and 99.07%, respectively. The characterization of electrodes and the EC sludge was conducted by XRD, SEM, and EDS analyses for the optimum variables. In addition, the corrosion test was conducted to determine the theoretical lifetime of the electrodes. The results showed that the RAC electrodes show an extended lifetime as compared to their counterparts. Secondly, the energy cost required to treat DW in the EC was aimed to decrease by using solar panels (PV), and the optimum number of PV for the EC was determined by the MATLAB/Simulink. Consequently, the EC with low treatment cost was proposed for the treatment of DW. An economical and efficient EC process for waste management and energy policies was investigated in the present study which will be instrumental in the emergence of new understandings.
Effect of in-/ex-situ annealing temperature on the optical, structural and gas sensing dynamics of CdS nanostructured thin films
(Academic Press Ltd- Elsevier Science Ltd, 2020) Gormez, Arife Efe; Basyooni, Mohamed A.; Zaki, Shrouk E.; Eker, Yasin Ramazan; Sonmez, Erdal; Yilmaz, Mucahit
Effect of in-/ex-situ annealing on the structure, optical, photoluminescence, electrical characterization and gas sensing dynamics on CdS thin films are presented. Raman characterizations showed an increase in the peak intensity with increasing the annealing temperature under ex-situ, while a lower peak intensity observed through the in-situ annealing condition. No shift was observed in the Photoluminescence peaks through the yellow band peaks of in-situ annealed samples, however, a slightly blue shift was observed through the ex-situ annealed samples. High conductivity was observed for all samples, while in the case of in-situ RT, in-situ 100 degrees C, ex-situ 200 degrees C and ex-situ 300 degrees C, a CO2 and O-2 gas sensing activity have been tested. The ex-situ 300 degrees C sample shows a higher response towards CO2 compared with the ex-situ 200 degrees C film. While, both in-situ RT and 100 degrees C sensors show the same response towards CO2 with a high gas response. However, the in-situ 100 degrees C sensor has the highest response compared to in-situ RT film with a high response of 25% at 50 sccm towards O-2.
The effect of Ti to the crystal structure of Li7-3xMxLa3Zr1.8Ti0.2O12 (M= Ga, In) garnet-type solid electrolytes as a second dopant
(Taylor & Francis, 2023) Saran, Sevda; Eker, Yasin Ramazan; Ateş, Şule; Çelik, Gültekin; Baveghar, Hadi; Özkendir, Osman Murat; Atav, Ülfet; Klysubun, Wantana
Garnet-type solid-state electrolytes are promising candidates for solid-state lithium batteries, nevertheless their ionic conductivity is still not enough for commercial applications. On the other hand, doping still is the common way to improve the ionic conductivities of these solid electrolytes. In this study, mono and dual-doped garnet-type solid electrolytes were synthesised by substituting indium (In), gallium (Ga), indium-titanium (In-Ti) and gallium-titanium (Ga-Ti) to the Li7La3Zr2O12 structure by a solid-state reaction method. The contribution of substitutions to the formation of crystal phases was investigated by X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS). On the other hand, morphological analyses were done by scanning electron microscope (SEM) and the ionic conductivities of the solid electrolytes were determined by electrochemical impedance spectroscopy (EIS). The study showed that while Li7-3xInxLa3Zr2O12 (for x = 0.05, 0.10, 0.15, 0.20) and Li7-3xGaxLa3Zr2O12 (for x = 0.05) samples were formed in tetragonal phase with a space group of I41/acd:2, dual substituted Li7-3xInxLa3Zr1.8Ti0.2O12 and Li7-3xGaxLa3Zr1.8Ti0.2O12 solid electrolytes for all x values were formed in cubic phase with a space group of I-43d. The highest conductivity is reached for Li6.85Ga0.05La3Zr1.8Ti0.2O12. The radial distribution function studies showed that when more In and Ga atoms take place in the sites of Li atoms, more O atoms take place in the vicinity of both substituted In and Ga atoms within the Li7La3Zr1.8Ti0.2O12 (LLZTO) crystal framework which can eventuate in a change in the conduction mechanism.
Effect of various mineral acids during the hydrothermal leaching process of NiTi Alloy
(Pamukkale Univ, 2023) Ozgun, Muhammed Ihsan; Batibay, Ahmet Burcin; Unal, Bayram; Eker, Yasin Ramazan; Terlemez, Arslan
Nickel and titanium-based alloys are commonly used for engineering or medical applications. NiTi alloys are recycled as additive materials at the end of their lifetime. Separate recovery of metals present in NiTi alloy is possible via hydrometallurgical methods; however, NiTi alloys are highly resistant to corrosion. Various mineral acids (H2SO4, HCl, HNO3, H3PO4) have been investigated, and the effect of H2O2 in the leaching medium has also been explored. Different leaching yields have been observed, and correlations between them according to acid treatment conditions have been established. SEM, XRF, and EDS techniques characterized alloys' microstructure and chemical properties. Among mineral acids, H2SO4 and HCl illustrated the highest extraction efficiencies. However, the addition of hydrogen peroxide decreased this efficiency severely. The kinetics of dissolution was obtained through decreased leaching efficiency with the addition of hydrogen peroxide.
Efficient adsorption of lead (II) and copper (II) from aqueous phase using oxidized multiwalled carbon nanotubes/polypyrrole composite
(Taylor & Francis Inc, 2018) Nyairo, Wilfrida Nyanduko; Eker, Yasin Ramazan; Kowenje, Chrispin; Akin, Ilker; Bingol, Haluk; Tor, Ali; Ongeri, David Mokono
Polypyrrole coated oxidized multiwalled carbon nanotubes (oMWCNT/Ppy) were applied to determine the adsorption characteristics of Pb(II) and Cu(II) from their aqueous solutions. Structural and morphological characterization studies using scanning electron microscopy, thermogravimetric analysis, Fourier transform infrared and Raman spectroscopy showed successful preparation of the oMWCNT/Ppy composite. The influence of pH, contact time, and initial metal ion concentration on the adsorption of Pb(II) and Cu(II) was studied. The adsorption processes fitted well with Langmuir isotherm and pseudo-second-order kinetic models. The maximum adsorption capacities for Pb(II) and Cu(II) were determined as 26.32 and 24.39mg/g, respectively. Desorption studies indicated that the oMWCNT/Ppy composite could be reused for five cycles with minimum loss of its initial adsorption capacity.
Efficient MoWO3/VO2/MoS2/Si UV Schottky photodetectors; MoS2 optimization and monoclinic VO2 surface modifications
(Nature Portfolio, 2020) Basyooni, Mohamed A.; Zaki, Shrouk E.; Shaban, Mohamed; Eker, Yasin Ramazan; Yilmaz, Mucahit
The distinctive properties of strongly correlated oxides provide a variety of possibilities for modulating the properties of 2D transition metal dichalcogenides semiconductors; which represent a new class of superior optical and optoelectronic interfacing semiconductors. We report a novel approach to scaling-up molybdenum disulfide (MoS2) by combining the techniques of chemical and physical vapor deposition (CVD and PVD) and interfacing with a thin layer of monoclinic VO2. MoWO3/VO2/MoS2 photodetectors were manufactured at different sputtering times by depositing molybdenum oxide layers using a PVD technique on p-type silicon substrates followed by a sulphurization process in the CVD chamber. The high quality and the excellent structural and absorption properties of MoWO3/VO2/MoS2/Si with MoS2 deposited for 60 s enables its use as an efficient UV photodetector. The electronically coupled monoclinic VO2 layer on MoS2/Si causes a redshift and intensive MoS2 Raman peaks. Interestingly, the incorporation of VO2 dramatically changes the ratio between A-exciton (ground state exciton) and trion photoluminescence intensities of VO2/(30 s)MoS2/Si from < 1 to > 1. By increasing the deposition time of MoS2 from 60 to 180 s, the relative intensity of the B-exciton/Aexciton increases, whereas the lowest ratio at deposition time of 60 s refers to the high quality and low defect densities of the VO2/(60 s)MoS2/Si structure. Both the VO2/(60 s)MoS2/Si trion and A-exciton peaks have higher intensities compared with (60 s) MoS2/Si structure. The MoWO3/VO2/(60 s) MoS2/Si photodetector displays the highest photocurrent gain of 1.6, 4.32 x 10(8) Jones detectivity, and similar to 1.0 x 10(10) quantum efficiency at 365 nm. Moreover, the surface roughness and grains mapping are studied and a low semiconducting-metallic phase transition is observed at similar to 40 degrees C.
Efficient Removal of Lead(II) Ions from Aqueous Solutions Using Methyl-?-Cyclodextrin Modified Graphene Oxide
(Springer, 2017) Nyairo, Wilfrida Nyanduko; Eker, Yasin Ramazan; Kowenje, Chrispin; Zor, Erhan; Bingol, Haluk; Tor, Ali; Ongeri, David Mokono
Graphene oxide (GO) and graphene oxide modified with methyl-beta-cyclodextrin denoted as GO-m beta CD were prepared and applied as adsorbents to determine the adsorption characteristics of Pb(II) from aqueous solutions. The characteristic results of Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), Raman spectroscopy, and scanning electron microscopy (SEM) showed that m beta CD was successfully physically attached to GO to form the GO-m beta CD nano-composite. The adsorption equilibrium and kinetics of the adsorbents were well described by Langmuir isotherm and pseudo-second-order models, respectively. The maximum Pb(II) adsorption capacity of GO-m beta CD (at pH = 6 and room temperature) was determined as 312.5 mg/g which was significantly higher than that of GO (217.39 mg/g). This indicates that the modification of GO with m beta CD enhances the adsorption capacity of GO. The desorption studies show that the adsorbent GO-m beta CD can be used for at least five cycles with non-significant loss of its initial adsorption capacity for Pb(II) ions.
Fast optoelectronic gas sensing with p-type V2O5/WS2/Si heterojunction thin film
(Elsevier Science Sa, 2023) Basyooni, Mohamed A.; Zaki, Shrouk E.; Eker, Yasin Ramazan
The efficiency of ultraviolet (UV) illumination in gas adsorption/desorption is remarkable due to its capacity to activate and energize CO2 molecules, rendering them more reactive and prone to surface interactions. A heterojunction device for room-temperature optoelectronic gas sensing has been fabricated. This was achieved through the deposition of an orthorhombic vanadium pentoxide (V2O5) thin film onto a wafer scale 2D p-type tungsten disulfide (WS2)/silicon (Si). The incorporation of the V2O5 layer brings about alterations in WS2's electronic properties, resulting in increased energy states for photo-generated carriers and a promising approach to enhance the intensity of exciton and trion peaks. Specifically, the WS2 film exhibits a carrier concentration of 3.67 x 1018 cm-3, while incorporating the V2O5 layer significantly raises this concentration to 1.20 x 1020 cm-3. The experiments reveal a rapid response time of 0.4 s and a recovery time of 0.2 s, respectively, demonstrating the swift desorption capability of the device in a CO2 environment. Remarkably, this device exhibits high optoelectronic performances, boasting a detectivity of 1.22 x 1013 Jones and a responsivity of 177.21 A/W. These findings have the potential to advance the development of improved gas-sensing devices, offering heightened sensitivity and selectivity in diverse optoelectronic applications.
Fast response of CO2 room temperature gas sensor based on Mixed-Valence Phases in Molybdenum and Tungsten Oxide nanostructured thin films
(Elsevier Sci Ltd, 2020) Basyooni, Mohamed A.; Zaki, Shrouk E.; Ertugrul, Sezin; Yilmaz, Mucahit; Eker, Yasin Ramazan
Molybdenum - tungsten oxide (Mo1-xWxO3, x = 1, 0.8, and 0.6) nanostructured thin films-based room temperture (RT) gas sensors are prepared by means of reactive RF magnetron co-sputtering at 400 degrees C. The structural, morphology, topography, optical, and electrical characterizations of the prepared sensors are carried out by XRD Rietveld structure refinement analyses, SEM, AFM, UV-VIS spectrophotometer, and source meter. By controlling the deposition temperture of 400 degrees C, a co-existing phase of MoO3 and MoO2 in WO3 matrix is presented with high oxygen vacancies concentration as calculated from the XRD Rietveld Refinement analyses. By increasing the Mo content, the calculated oxygen vacancies concentration increases by factor of 1.36. The optical characterization of Mo0.2W0.6O3 thin film shows a high transparent of 99.6% at 500 nm. The prepared thin films have successfully tested to detect carbon dioxide (CO2) at RT (20 degrees C) with high selectivity and repeatability. The Mo0.4W0.6O3 sensor film shows an electrical Schottky contact with fast response and recovery times towards CO2 under UV light activation. Mo0.4W0.6O3 thin film under dark and UV conditions were able to detect low CO2 concentration of 2 and 0.5 sccm CO2 M RT, respectively. Under UV illumination, Mo0.4W0.6O3 film shows a fast response and recovery time of 6.53 and 8.05 sat 0.5 sccm with sensitivity of 29.19%. Under UV photonic activation, higher electron concentration is presented in the oxide surface, which leads to high probability for reaction with CO2 molecules, and consequently enhanced the chemisorption of CO2. The enhanced CO2 gas sensitivity and fast response may refer to the high oxygen vacancies concentration and the active role of the grain boundaries in MoO2, MoO3 and WO3 mixed-valence nanostructured under UV activation.
Green preparation of a novel red mud@carbon composite and its application for adsorption of 2,4-dichlorophenoxyacetic acid from aqueous solution
(Springer Heidelberg, 2017) Kazak, Omer; Eker, Yasin Ramazan; Akin, Ilker; Bingol, Haluk; Tor, Ali
This study reports the eco-friendly preparation of a novel composite material consisting of red mud and carbon spheres, denoted as red mud@C composite, and its application for the removal of 2,4-dichlorophenoxyacetic acid herbicide (2,4-D) from aqueous solution. The preparation route has a green approach because it follows the low-energy consuming one-step hydrothermal process by using starch as a renewable carbon precursor and red mud as a waste from aluminum production industry. Characterization of the red mud@C composite was performed by FT-IR, TGA, SEM, TEM, BET, XRD, and Raman microscopy analyses. The batch adsorption studies revealed that the red mud@C composite has higher 2,4-D adsorption efficiency than those of the red mud and the naked carbon spheres. The maximum removal at initial pH of 3.0 is explained by considering the pKa of 2,4-D and pH of point of zero charge (pH(pzc)) of the composite material. The adsorption equilibrium time was 60 min, which followed the pseudo-second-order kinetic model together with intra-particle diffusion model. The isotherm analysis indicated that Freundlich isotherm model better represented the adsorption data, with isotherm parameters of k [15.849 (mg/g) (mg/L)(-1/n) ] and n (2.985). The prepared composite is reusable at least 5 cycles of adsorption-desorption with no significant decrease in the adsorption capacity.
High-Performance Negative Self-Powered ?-MoO3/Ir/?-MoO3 Photodetectors: Probing the Influence of Coulomb Deep Traps
(Amer Chemical Soc, 2023) Basyooni, Mohamed A.; Tihtih, Mohammed; Zaki, Shrouk E.; Eker, Yasin Ramazan
Nanostructures of ultrathin 2D MoO3 semiconductors have gained significant attention in the field of transparent optoelectronics and nanophotonics due to their exceptional responsiveness. In this study, we investigate self-powered alpha-MoO3/Ir/alpha-MoO3 photodetectors, focusing on the influence of induced hot electrons in ultrathin alpha-MoO3 when combined with an ultrathin Ir plasmonic layer. Our results reveal the presence of both positive and negative photoconductivity at a 0 V bias voltage. Notably, by integrating a 2 nm Ir layer between post-annealed alpha-MoO3 films, we achieve remarkable performance metrics, including a high I-ON/I-OFF ratio of 3.8 x 10(6), external quantum efficiency of 132, and detectivity of 3.4 x 10(11) Jones at 0 V bias. Furthermore, the response time is impressively short, with only 0.2 ms, supported by an exceptionally low MoO3 surface roughness of 0.1 nm. The observed negative photoresponse is attributed to O-2 desorption from the MoO3 surface, resulting in increased carrier density and reduced mobility in the Ir layer due to Coulomb trapping and oxygen vacancy deep levels. Consequently, this leads to a decreased carrier mobility and diminished current in the heterostructure. Our findings underscore the enormous potential of ultrathin MoO3 semiconductors for high-performance negative conductivity optoelectronics and photonic applications.
In-situ magnetization of porous carbon beads by pyrolysis of waste red mud doped polysulfone beads for efficient oil sorption
(Elsevier Science Sa, 2020) Kazak, Omer; Eker, Yasin Ramazan; Tor, Ali
This study describes for the first time the preparation of in-situ magnetic porous carbon beads (MPC beads) through simple phase inversion and subsequent pyrolysis of red mud doped polysulfone beads. Red mud, which is the main industrial waste resulted from the aluminium production, contains an important amount of Fe2O3. Characterization studies demonstrated the in-situ carbo-reduction of Fe2O3 species into magnetic Fe3O4 thanks to polysulfone carbon source, involving then the synthesis of MPC beads. Owing to hydrophobic surface and macroporous structure, the MPC beads were evaluated on the sorption of various oils, including gasoline, diesel oil, mineral oil and olive oil from water. The maximum sorption capacity of the MPC beads for examined oils were determined as olive oil (2.018 +/- 0.162 g/g)>mineral oil (1.418 +/- 0.138 g/g)> diesel oil (1.316 +/- 0.062 g/g)>gasoline (1.235 +/- 0.028 g/g). Moreover, the MPC beads were regenerable by heat treatment and there was no change in their sorption capacities in the first ten consecutive sorption-desorption cycles. Consequently, the suggested approach on the pyrolysis of waste red mud doped polysulfone beads was successful at preparing in-situ MPC beads, which can be efficiently used for oil spills clean-up from water with easier separation by a magnet.
The Influence of Al2O3 and TiO2 Additives on the Electrical Resistivity of Epoxy Resin-Based Composites at Low Temperature
(Wiley-V C H Verlag Gmbh, 2019) Eker, Yasin Ramazan; Ozcan, Muciz; Ozkan, Ali Osman; Kırıkçı, Hülya
Electrical insulation is a major security problem in aerospace applications where temperature can reach relatively low values. Epoxy resins are well known as easily formable dielectric materials and can be used to prepare complex insulator parts. In this study, the electrical performance of bisphenol A/epichlorohydrin epoxy resin matrix-based nanocomposites containing 1, 3, or 6 wt% titanium oxide (TiO2) or aluminium oxide (Al2O3) nanofillers are investigated. Composites are characterized with thermogravimetric analysis, scanning electron microscopy-coupled electron dispersive spectroscopy, and confocal Raman spectroscopy. Furthermore, the role of additives and their ratio on the resistivity performance of the composites are evaluated from 77 to 500 K by applying a direct current voltage from 1 to 20 V. It is observed that the electrical properties of the matrix are directly influencing the insulation performance of the nanocomposite. For example, the abrupt decrease at 370 K of the positive temperature coefficient of the resin for all nanocomposites. It is found that the most resistive composite contains 3 wt% TiO2 nanoparticles with a value above 3.7.10(10) omega from 77 to 370 K at 20 V. As a result, this work gives information on to the choice of appropriate insulator materials in extreme working conditions.
MoO3 nanowire growth on VO2/WO3 for thermochromic applications
(Royal Soc Chemistry, 2024) Houimi, Amina; Kabatas, Mohamed A. Basyooni-M.; Yilmaz, Mucahit; Eker, Yasin Ramazan
This study explores the structural, electronic, and optical properties of sandwich-structured thin films composed of WO3, MoWO3, and MoO3 as window layers on VO2/WO3 via a physical vapor deposition method. Morphological analysis demonstrates the evolution of distinct nanowires, offering insights into the lattice strain of the VO2 layer toward high-performance thermochromatic devices. Temperature-dependent sheet resistivity is investigated, showcasing significant improvements in conductivity for samples with MoO3 as a window layer. The electrical and optical properties of the MoO3/VO2/WO3 device showed a phase transition temperature (T-c) of 36.8 degrees C, a transmittance luminous (T-lum) of 54.57%, and a solar modulation ability (Delta T-sol) of 12.43. This comprehensive analysis contributes to understanding the growth of nanowires on multi-layered thin films, offering valuable insights into potential applications in bright windows.
Nanostructured MoS2 and WS2 Photoresponses under Gas Stimuli
(Mdpi, 2022) Basyooni, Mohamed A.; Zaki, Shrouk E.; Alfryyan, Nada; Tihtih, Mohammed; Eker, Yasin Ramazan; Attia, Gamal F.; Yilmaz, Mucahit
This study was on the optoelectronic properties of multilayered two-dimensional MoS2 and WS2 materials on a silicon substrate using sputtering physical vapor deposition (PVD) and chemical vapor deposition (CVD) techniques. For the first time, we report ultraviolet (UV) photoresponses under air, CO2, and O-2 environments at different flow rates. The electrical Hall effect measurement showed the existence of MoS2 (n-type)/Si (p-type) and WS2 (P-type)/Si (p-type) heterojunctions with a higher sheet carrier concentration of 5.50 x 10(5) cm(-2) for WS2 thin film. The IV electrical results revealed that WS2 is more reactive than MoS2 film under different gas stimuli. WS2 film showed high stability under different bias voltages, even at zero bias voltage, due to the noticeably good carrier mobility of 29.8 x 10(2) cm(2)/V. WS2 film indicated a fast rise/decay time of 0.23/0.21 s under air while a faster response of 0.190/0.10 s under a CO2 environment was observed. Additionally, the external quantum efficiency of WS2 revealed a remarkable enhancement in the CO2 environment of 1.62 x 10(8) compared to MoS2 film with 6.74 x 10(6). According to our findings, the presence of CO2 on the surface of WS2 improves such optoelectronic properties as photocurrent gain, photoresponsivity, external quantum efficiency, and detectivity. These results indicate potential applications of WS2 as a photodetector under gas stimuli for future optoelectronic applications.
Negative Photoconductivity in 2D ?-MoO3/Ir Self-Powered Photodetector: Impact of Post-Annealing
(Mdpi, 2023) Basyooni-M. Kabatas, Mohamed A.; Zaki, Shrouk E.; Rahmani, Khalid; En-nadir, Redouane; Eker, Yasin Ramazan
Surface plasmon technology is regarded as having significant potential for the enhancement of the performance of 2D oxide semiconductors, especially in terms of improving the light absorption of 2D MoO3 photodetectors. An ultrathin MoO3/Ir/SiO2/Si heterojunction Schottky self-powered photodetector is introduced here to showcase positive photoconductivity. In wafer-scale production, the initial un-annealed Mo/2 nm Ir/SiO2/Si sample displays a sheet carrier concentration of 5.76 x 10(11)/cm(2), which subsequently increases to 6.74 x 10(12)/cm(2) after annealing treatment, showing a negative photoconductivity behavior at a 0 V bias voltage. This suggests that annealing enhances the diffusion of Ir into the MoO3 layer, resulting in an increased phonon scattering probability and, consequently, an extension of the negative photoconductivity behavior. This underscores the significance of negative photoconductive devices in the realm of optoelectronic applications.
Novel preparation of activated carbon by cold oxygen plasma treatment combined with pyrolysis
(Elsevier Science Sa, 2017) Kazak, Omer; Eker, Yasin Ramazan; Bingol, Haluk; Tor, Ali
This study reports an original approach based on the inserting of a cold oxygen plasma treatment as oxidation stage between two pyrolysis processes for the preparation of an activated carbon from vinasse as a waste from the distillation of fermented sugar beet. The effects of pyrolysis temperature and plasma application time on the structural and morphological properties of the prepared carbon materials were investigated by Thermal Gravimetric Analysis (TGA), Fourier Transform Infrared Spectroscopy (FT-IR), Raman Spectroscopy, Scanning Electron Microscopy-Energy Dispersive X-ray Spectroscopy (SEM-EDX) techniques and gas adsorption measurements (BET). The results of the different conditions indicated that the structure properties of the obtained activated carbon were significantly dependent on the pyrolysis temperature. As an optimum condition, the application of oxygen plasma for 5 min between pyrolysis processes at 1000 C-omicron provided an eligible activated carbon with surface area (832.3 m(2)/g) and mainly microporous structure. After preliminary examinations on various dyes, the adsorption performance of the activated carbon with highest surface area was specifically evaluated using methylene blue as a model dye in aqueous solution as functions of various operating parameters. Langmuir adsorption capacity (909.091 mg/g) of the prepared activated carbon toward methylene blue was superior than most of the other adsorbents. (C) 2017 Elsevier B.V. All rights reserved.
A novel red mud@sucrose based carbon composite: Preparation, characterization and its adsorption performance toward methylene blue in aqueous solution
(Elsevier Sci Ltd, 2017) Kazak, Omer; Eker, Yasin Ramazan; Akin, Ilker; Bingol, Haluk; Tor, Ali
A novel carbonaceous composite material containing red mud and sucrose based carbon spheres, named as RM@ C composite, has been prepared via one-step hydrothermal carbonization (HTC) process. The prepared RM@ C composite is an environmentally friendly material because it utilized the red mud, a waste emerged from aluminium manufacturing, and sucrose, a renewable carbon precursor, in the one-step HTC process. After characterization of the composite material by XRD, FT-IR, TGA and SEM-EDX techniques, and specific surface area, pore size distribution and pH of zero point of charge (pHzpc) measurements, its batch adsorption performance was examined on the methylene blue in aqueous solution. The effective adsorption was achieved at pH = 11. At pH 11, the adsorption performance of RM@ C was superior to both red mud and naked carbon spheres. Kinetic analysis revealed that adsorption equilibrium is attained in 60 min and it is governed by the pseudo-second-order kinetic model together with intra-particle diffusion model. On the basis of isotherm analysis, Langmuir isotherm model better expressed the experimental data than Freundlich model. The Langmuir adsorption capacity of the composite material toward methylene blue was determined as 76.92 mg/g. The adsorption of methylene blue gradually decreased with increasing the ionic strength of the solution. The RM@ C composite can be reused at least five cycles of adsorption-desorption without significant changes in the adsorption efficiency.

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