Mahmut Kus
Selcuk University (Selçuk Üniversitesi), Chemical Engineering, Faculty Member
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In this study, a novel method is used to prepare water-soluble CdTe, CdTeSe quantum dots (QDS) and CdTe/CdS core-shell QDs by using Te, Se, NaBH4, and CdCl2 as precursors. It is aimed to prepare polyvinyl alcohol (PVA)/QDs composite... more
In this study, a novel method is used to prepare water-soluble CdTe, CdTeSe quantum dots (QDS) and CdTe/CdS core-shell QDs by using Te, Se, NaBH4, and CdCl2 as precursors. It is aimed to prepare polyvinyl alcohol (PVA)/QDs composite nanofibers by electrospinning process. A series of PVA/QDs nanofiber mats with three different QDs content are prepared. X-ray powder diffraction (XRD) and transmission electron microscopy (TEM) are used to characterize QD nanoparticles. In addition, scanning electron microscopy (SEM) and atomic force microscopy (AFM) are used to characterize the obtained nanofibers. QDs have a good dispersed crystalline structure with an average crystalline sizes between 2–4 nm. According to the morphology analysis, homogeneous and highly porous PVA/QDs mats containing 50–300 nm diameter nanofibers are obtained by the electrospinning process.
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Abstract Material science is one of the decisive tools towards engineering versatile compounds for numerous technological applications. Over the last decades, thiospinels have been attracting great interest due to their unique... more
Abstract Material science is one of the decisive tools towards engineering versatile compounds for numerous technological applications. Over the last decades, thiospinels have been attracting great interest due to their unique characteristics and potential utilizations offering innovative and interesting features. The characteristics of these transition metal sulfides play a key role in many different applications and make thiospinels an essential class of material. To the best of our knowledge, this work, for the first time, summarizes broadband studies on thiospinels reported in the literature. The scope of this review covers all synthesis methods applied over, the chemical and physical properties, and the clean energy applications of thiospinels, which have achieved tremendous significance. It has been underlined and proposed the challenges and future perspectives based on sulfur based ternary compounds. Moreover, this review draws attention to the current and future research needs of thiospinel materials to improve and broaden their applications and thus commercialization.
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Multiple functionality of tungsten polyoxometalate (POM) has been achieved applying it as interfacial layer for solution processed high performance In2O3 thin film transistors, which results in overall improvement of device performance.... more
Multiple functionality of tungsten polyoxometalate (POM) has been achieved applying it as interfacial layer for solution processed high performance In2O3 thin film transistors, which results in overall improvement of device performance. This approach not only reduces off-current of the device by more than two orders of magnitude, but also leads to a threshold voltage reduction, as well as significantly enhances the mobility through facilitated charge injection from the electrode to the active layer. Such a mechanism has been elucidated through morphological and spectroscopic studies.
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A silanol-functionalized polyoxometalate improves the electron collecting interface.
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Interfacial engineering is essential for the development of highly efficient and stable solar cells through minimizing energetic losses at interfaces. Self-assembled monolayers (SAMs) have been shown as a handle to tune the work function... more
Interfacial engineering is essential for the development of highly efficient and stable solar cells through minimizing energetic losses at interfaces. Self-assembled monolayers (SAMs) have been shown as a handle to tune the work function (WF) of indium tin oxide (ITO), improving photovoltaic cell performance and device stability. In this study, we utilize a new class of boronic acid-based fluorine-terminated SAMs to modify ITO surfaces in planar perovskite solar cells. The SAM treatment demonstrates an increase of the WF of ITO, an enhancement of the short-circuit current, and a passivation of trap states at the ITO/[poly(3,4ethylenedioxylenethiophene):poly(styrenesulfonic acid)] interface. Device stability improves upon SAM modification, with efficiency decreasing only 20% after one month. Our work highlights a simple treatment route to achieve hysteresis-free, reproducible, stable, and highly efficient (16%) planar perovskite solar cells.
Research Interests: Chemical Engineering, Biochemistry, Microbiology, Neuroscience, Biophysics, and 15 moreMaterials Science, Molecular Biology, Biotechnology, Cancer, Ecology, Interface engineering, Medicine, Hysteresis, Interface, Perovskite, Monolayer, Indium, Indium tin oxide, Passivation, and Perovskite solar cell
Effective interface engineering has been shown to play a vital role in facilitating efficient charge carrier transport thus boosting the performance of organic photovoltaic devices. Herein we employ water soluble lacunary polyoxometalates... more
Effective interface engineering has been shown to play a vital role in facilitating efficient charge carrier transport thus boosting the performance of organic photovoltaic devices. Herein we employ water soluble lacunary polyoxometalates (POMs) as multifunctional interlayers between the titanium oxide (TiO2) electron extraction/transport layer and the organic photoactive film to simultaneously enhance the efficiency, lifetime and photostability of polymer solar cells. A significant reduction in work function (WF) of TiO2 upon POM deposition was observed, with the magnitude being controlled by the negative charge of the anion and the selection of the addenda atom (W or Mo). By inserting a POM interlayer with ∼10 nm thickness into the device structure, a significant improvement of the power conversion efficiency was obtained; the optimized POM modified PTB7:PC70BM-based (poly[[4,8-bis[(2-ethylhexyl)oxy]benzo[1,2-b:4,5-b']dithiophene-2,6-diyl][3-fluoro-2-[(2-ethylhexyl) carbonyl] ...
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The current study reports the application of chalcopyrite semiconductor CuInS2 (CIS) nanofibers for the reduction of CO2 to CO with a remarkable Faradaic efficiency of 77 ± 4%. Initially the synthesis of CuInS2 nanofibers was carried out... more
The current study reports the application of chalcopyrite semiconductor CuInS2 (CIS) nanofibers for the reduction of CO2 to CO with a remarkable Faradaic efficiency of 77 ± 4%. Initially the synthesis of CuInS2 nanofibers was carried out by adaptable electrospinning technique. To reduce the imperfection in the crystalline fiber, polyacrylonitrile (PAN) was selected as template polymer. Afterward, the desired chemical structure of nanofibers was achieved through sulfurization process. Making continuous CuInS2 nanofibers on the cathode surface by the electrospinning method brings the advantages of being economical, environmentally safe, and versatile. The obtained nanofibers of well investigated size and diameter according to the SEM (scanning electron microscope) were used in electrochemical studies. An improvement of Faradaic efficiency was achieved with the catalytic active CuInS2 in nanofibrous structure as compared to the solution processed CuInS2. This underlines the important e...
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The penternary chalcogenides Cu2CoSn(SeS)4 and Cu2ZnSn(SeS)4 were successfully synthesized by hot-injection method and employed as a catalytic materials for efficient counter electrodes in dye-synthesized solar cells (DSSCs). The... more
The penternary chalcogenides Cu2CoSn(SeS)4 and Cu2ZnSn(SeS)4 were successfully synthesized by hot-injection method and employed as a catalytic materials for efficient counter electrodes in dye-synthesized solar cells (DSSCs). The structural, compositional, morphological and optical properties of these pentenary semiconductors were characterized by X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM), energy-dispersive spectrometer (EDS) and ultraviolet-visible (UV–Vis) spectroscopy. The Cu2CoSn(SeS)4 and Cu2ZnSn(SeS)4 nanocrystals had a single crystalline, kesterite phase, adequate stoichiometric ratio, 18–25 nm particle sizes which are forming nanospheres and band gap energy of 1.18 and 1.45 eV, respectively. Furthermore, the electrochemical impedance spectroscopy and cyclic voltammograms indicated that Cu2CoSn(SeS)4 nanocrystals as counter electrodes exhibited better electrocatalytic activity for the reduction of iodine/iodide electrolyte than that o...
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Facilitated transport of Rhodamine B through a novel polymer inclusion membrane (PIM) containing CdTeSe Quantum Dots (QDs) as a carrier reagent has been investigated.
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We report synthesis of Fluorene–Carbazole derivatives as caping agent for CdSeS nanocrystals to improve the performance of polymer nanocrystal hybrid solar cells.
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New photocatalytic systems for H2 evolution have been reported by using Cu2ZnSnS4, Cu2ZnSnSe4, and Cu2ZnSnSe4−xSx nanofiber catalysts under visible light irradiation.
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Copper-based quaternary chalcogenide Cu2FeSnS4 (CFTS) is an important material due to its indium-free nature and presence of earth-abundant elements. Herein, CFTS nanofibers have been first fabricated via a facile two-step approach using... more
Copper-based quaternary chalcogenide Cu2FeSnS4 (CFTS) is an important material due to its indium-free nature and presence of earth-abundant elements. Herein, CFTS nanofibers have been first fabricated via a facile two-step approach using a simple and inexpensive electrospinning technique. X-ray diffraction and scanning electron microscopy techniques were used to determine structural, morphological, and compositional features of the obtained films. Nanofibers annealed at 500 °C for 1 h were characterized by (112), (200), (220), (312) preferred orientations via X-ray diffraction method. Nanofibers showed well crystallization and tetragonal phase. The average diameters of obtained fibers were found to be 100 ± 50 nm. Cyclic voltammograms showed that CFTS fibers showed p-type behavior.
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Research Interests: Chemistry, Analytical Chemistry, Kinetics, Calixarene, Medicine, and 15 moreAdsorption, Method, Gibbs Free Energy, Technique, Quartz crystal microbalance, Free Energy, Relative Humidity, Application, Humidity Sensor, Room Temperature, Humidity, Langmuir, Substrate, Atmospheric Humidity, and Adsorption kinetic
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ABSTRACT We report sensing different polycyclic aromatic hydrocarbons (PAHs) with colloidal CdTe nanocrystals. The effect of molecular structure on quenching rate for 2-hyroxy-1-naphthaldehyde (2H–1N), 9,10-phenanthraquinone (PQ),... more
ABSTRACT We report sensing different polycyclic aromatic hydrocarbons (PAHs) with colloidal CdTe nanocrystals. The effect of molecular structure on quenching rate for 2-hyroxy-1-naphthaldehyde (2H–1N), 9,10-phenanthraquinone (PQ), 9-anthracenecarboxaldehyde (9-AC) and quinoline (Q) is presented. The quenching rate constants are observed to be strongly dependent on the molecular structure. PQ, consisting of two carbonyl groups, shows the highest rate constant while Q shows the worst one. Both static and dynamic quenching are simultaneously observed for PQ and 2H–1N. Therefore extended Stern–Volmer equations are used to calculate rate constants. Results showed that dynamic quenching is a dominant process. The rate constants for PQ, 2H–1N, 9-AC and Q are calculated to be 64.84, 10.73, 10.66 and 1.85 respectively.
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Sahara desert sand (SaDeS) was employed as a mineral sorbent for retaining organic dyes from aqueous solutions. Natural sand has demonstrated a strong affinity for organic dyes but significantly lost its adsorption capacity when it was... more
Sahara desert sand (SaDeS) was employed as a mineral sorbent for retaining organic dyes from aqueous solutions. Natural sand has demonstrated a strong affinity for organic dyes but significantly lost its adsorption capacity when it was washed with water. Therefore, characterization of both natural and water washed sand was performed by XRD, BET, SEM and FTIR techniques. It was found that water-soluble kyanite, which is detected in natural sand, is the dominant factor affecting adsorbance of cationic dyes. The sand adsorbs over 75% of cationic dyes but less than 21% for anionic ones. Among the dyes studied, Methylene Blue (MB) demonstrated the strongest affinity for Sahara desert sand (Q(e)=11.98 mg/g, for initial dye solution concentration 3.5 x 10(-5)mol/L). The effects of initial dye concentration, the amount of the adsorbent, the temperature and the pH of the solution on adsorption capacity were tested by using Methylene Blue as model dye. Pseudo-first-order, pseudo-second-order and intraparticle diffusion models were applied. It was concluded that adsorption of Methylene Blue on Sahara desert sand followed pseudo-second order kinetics. Gibbs free energy, enthalpy change and entropy change were calculated and found -6411 J/mol, -30360 J/mol and -76.58 J/mol K, respectively. These values indicate that the adsorption is an exothermic process and has a spontaneous nature at low temperatures.
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ABSTRACT Perylene-diimide (PDI) thin film was fabricated by spin coating method on p-Si single-crystal substrate to prepare Au/PDI/p-Si Schottky device. The electrical properties of the Au/PDI/p-Si Schottky device were investigated by... more
ABSTRACT Perylene-diimide (PDI) thin film was fabricated by spin coating method on p-Si single-crystal substrate to prepare Au/PDI/p-Si Schottky device. The electrical properties of the Au/PDI/p-Si Schottky device were investigated by current-voltage (I–V) measurements in the temperature range 80–300 K and room temperature capacitance-voltage (C–V) measurement. Results showed a rectification behavior. Junction parameters such as ideality factor (n), barrier height (ϕB0), series resistance (Rs) interface state density (Nss), built-in potential (Vbi), carrier concentration (NA), and the width of the depletion layer (WD) were obtained from the I–V and C–V measurements. The values of ideality factor (n) and barrier height (BH) for the Au/PDI/p-Si structure from the I–V measurements were obtained as 1.77 and 0.584 eV at 300 K, 7.78 and 0.176 eV at 80 K, respectively. It was seen that the BH value of 0.584 eV calculated for the Au/PDI/p-Si structure was significantly larger than the value of 0.34 eV of conventional Au/p-Si Schottky diodes at room temperature. Thus, modification of the interfacial potential barrier for Au/p-Si diodes has been achieved using a thin interlayer of the peryleen-diimide organic semiconductor; this has been ascribed to the fact that the peryleen-diimide interlayer increases the effective barrier height because of the interface dipole induced by passivation of the organic layer. Furthermore, the energy distribution of the interface state density determined from I–V characteristics increases exponentially with bias from 1.11 × 1012 eV−1 cm−2 at (0.556−Ev) eV to 11.01 × 1013 eV−1 cm−2 at (0.449−Ev) eV.
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In this study, our hypothesis was to demonstrate the usability of a natural clay structure as scaffold layer in perovskite solar cells (PSCs). Sepiolite, which is a natural and environmentally friendly clay structure, has a very high... more
In this study, our hypothesis was to demonstrate the usability of a natural clay structure as scaffold layer in perovskite solar cells (PSCs). Sepiolite, which is a natural and environmentally friendly clay structure, has a very high active surface area and can easily be dispersed in solvents. In addition we predicted that crystallization could easily occur on their surfaces due to their surface chemistry. In the study, we firstly used a natural clay as scaffold layer in PSCs. It is observed that, efficiency, reproducibility and stability of PSCs have been significantly improved. Improvements in efficiency have been observed to be between 30–50% depending on the type of perovskite solvent used. In addition, the surface chemistry of the sepiolite resulted in better crystallization as well as stability. Due to its high-water adsorption capability, sepiolite makes the perovskite crystal more stable by trapping the residual water molecules as well as penetrated water molecules from envi...
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Photocatalytic generation of hydrogen by using oleic acid-capped CdS, CdSe, and CdS(0.75)Se(0.25) alloy nanocrystals (quantum dots) has been investigated under visible-light irradiation by employing Na(2)S and Na(2)SO(3) as hole... more
Photocatalytic generation of hydrogen by using oleic acid-capped CdS, CdSe, and CdS(0.75)Se(0.25) alloy nanocrystals (quantum dots) has been investigated under visible-light irradiation by employing Na(2)S and Na(2)SO(3) as hole scavengers. Highly photostable CdS(0.75)Se(0.25) alloy nanocrystals gave the highest hydrogen evolution rate (1466 μmol h(-1) g(-1)), which was about three times higher than that of CdS and seven times higher than that of CdSe.
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INTRODUCTION Electrospinning is common and easy method to prepare fibers. This method is especially used in many applications, such as drug delivery, biosensing, pharmaceutical industry, tissue engineering and solar cell. The indium-free... more
INTRODUCTION Electrospinning is common and easy method to prepare fibers. This method is especially used in many applications, such as drug delivery, biosensing, pharmaceutical industry, tissue engineering and solar cell. The indium-free quaternary chalcogenides (i.e. Cu2ZnSnS4 (CZTS)) have driven much attention for their potential applications in low cost solar cells due to their many advantages including appropriate direct band gap (1.0-1.5 eV), high absorption coefficient, extremely low toxicity, high radiation stability, as well as relative abundance (indium free) of this elements. CZTSs are used in constructing solar cells. Their band gaps are tight and also they have absorption specialty in visible area. They are neither expensive like Ga and In, nor toxic like Se and Cd. Chalgenide based solar cells make possible a critical pathway to cost parity between photovoltaic (PV) and conventional energy sources [1,2]. In this study, we synthesized CZTS nanofibers with the method of e...
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ABSTRACT In the present study, pure and gold nanoparticles (Au NPs) doped TiO2 and CdO thin film were prepared by sol-gel method and the effect of Au NPs doping on the optical, structural and morphological properties of these thin films... more
ABSTRACT In the present study, pure and gold nanoparticles (Au NPs) doped TiO2 and CdO thin film were prepared by sol-gel method and the effect of Au NPs doping on the optical, structural and morphological properties of these thin films was investigated. The prepared thin films were characterized by XRD, SEM and UV-vis-NIR spectra. While the optical band increases from 3.62 to 3.73 for TiO2 thin films and it decreases from 2.20 to 1.55 for CdO thin films with inceasing of Au doping concentration. Analysis of X-ray diffraction (XRD) indicates that the intensities of peaks of the crystalline phase have increased with the increasing of Au nanoparticles concentrations in the all thin films. Scanning electron microscopy (SEM) images demonstrate that the surface morphologies of the samples were affected by the incorporation of Au NPs. Consequently, the most significant results of the present study are that the Au NPs can be used to modify the optical, structural and morphological properties of TiO2 and CdO thin films.
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ABSTRACT Spectral-luminescent properties of the newly synthesized 2-(3′-coumarinyl)-5-(2′-(R-amino)-phenyl)-1,3,4-oxadiazoles has been investigated in solvents of various polarity and hydrogen-bonding ability. It has been found that for... more
ABSTRACT Spectral-luminescent properties of the newly synthesized 2-(3′-coumarinyl)-5-(2′-(R-amino)-phenyl)-1,3,4-oxadiazoles has been investigated in solvents of various polarity and hydrogen-bonding ability. It has been found that for all the studied compounds no excited state intramolecular proton transfer occurs despite the presence of coumarinyl fragment – electron acceptor effect of the coumarinyl fragment is not sufficient to increase the excited state acidity of the amino group. It has been found that the absorption spectra of the studied compounds shift to higher energy with increase in solvent polarity, whereas corresponding fluorescence spectra shift to lower energy with solvent polarity increase. It has been suggested that long-wavelength shifts of the fluorescence spectra of the studied compounds with increase in solvent polarity is caused by the solvent relaxation. The observed solvent relaxation effect allow us to propose some of the studied compounds as potential probes to monitor changes in solvent relaxation in low-polar media and as potential probes for rigidochromic effect.