Teknik Bilimler Meslek Yüksekokulu Koleksiyonu

Permanent URI for this collectionhttps://hdl.handle.net/20.500.13091/1629

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Citation - WoS: 18
Citation - Scopus: 19
Development of Highly Luminescent Water-Insoluble Carbon Dots by Using Calix[4]pyrrole as the Carbon Precursor and Their Potential Application in Organic Solar Cells
(Amer Chemical Soc, 2022) Coşkun, Yağız; Ünlü, Fatma Yelda; Yılmaz, Tuğbahan; Türker, Yurdanur; Aydoğan, Abdullah; Kuş, Mahmut; Ünlü, Caner
Carbon dots (CDs) are carbon-based fluorescent nanomaterials that are of interest in different research areas due to their low cost production and low toxicity. Considering their unique photophysical properties, hydrophobic/amphiphilic CDs are powerful alternatives to metal-based quantum dots in LED and photovoltaic cell designs. On the other hand, CDs possess a considerably high amount of surface defects that give rise to two significant drawbacks: (1) causing decrease in quantum yield (QY), a crucial drawback that limits their utilization in LEDs, and (2) affecting the efficiency of charge transfer, a significant factor that limits the use of CDs in photovoltaic cells. In this study, we synthesized highly luminescent, water-insoluble, slightly amphiphilic CDs by using a macrocyclic compound, calix[4]pyrrole, for the first time in the literature. Calix[4]pyrrole-derived CDs (CP-DOTs) were highly luminescent with a QY of over 60% and size of around 4-10 nm with graphitic structure. The high quantum yield of CP-DOTs indicated that they had less amount of surface defects. Furthermore, CP-DOTs were used as an additive in the active layer of organic solar cells (OSC). The photovoltaic parameters of OSCs improved upon addition of CDs. Our results indicated that calix[4]pyrrole is an excellent carbon precursor to synthesize highly luminescent and water-insoluble carbon dots, and CDs derived from calix[4]pyrrole are excellent candidates to improve optoelectronic devices.
Citation - WoS: 13
Citation - Scopus: 13
Electrical Behaviors of the Co- and Ni-Based Poms Interlayered Schottky Photodetector Devices
(Wiley, 2022) Yıldırım, Murat; Kocyigit, Adem; Torlak, Yasemin; Yenel, Esma; Hussaini, Ali Akbar; Kuş, Mahmut
Polyoxometalates (POMs) are attractive materials for various applications such as energy storage, catalysis and medicine. Here, Co and Ni-based POMs are chemically synthesized and characterized by X-ray diffractometer (XRD) and Fourier transform infrared spectroscopies (FT-IR) for structural characterization. While the morphological behaviors are analyzed by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and atomic force microscopy (AFM), the optical properties are investigated by UV-Vis spectrometer. Electrochemical characterizations are carried out by cyclic voltammetry to determine oxidation levels of the metal centers in the POMs. The CoPOM and NiPOM are inserted in between the Al metal and p-Si semiconductor to obtain Al/CoPOM/p-Si and Al/NiPOM/p-Si Schottky-type photodetector devices. Current-voltage (I-V) and current-transient (I-t) measurements are employed to understand the electrical properties of the Al/CoPOM/p-Si and Al/NiPOM/p-Si devices under dark and various light power intensities. The devices exhibit phototransistor like I-V characteristics in forward biases due to having POMs active layers. Various device parameters are extracted from the I-V measurements and discussed in details. I-t measurements are performed to determine various detector parameters such as responsivity and specific detectivity values for under 2 V and zero biases. The Al/CoPOM/p-Si and Al/NiPOM/p-Si Schottky-type photodetector devices can be employed in optoelectronic applications.
Citation - WoS: 6
Citation - Scopus: 12
Refractory-Metal Chalcogenides for Energy
(Wiley-V C H Verlag Gmbh, 2022) Özel, Faruk; Arkan, Emre; Coşkun, Halime; Deveci, İlyas; Yıldırım, Murat; Yıldırım, Mehmet; Ersöz, Mustafa; Kuş, Mahmut
When it is asked, where can refractory metals be used?, the possible shortest answer is, where cannot they be used? The uses of refractory-metal-based compounds in research and industry are too many to be enumerated; nevertheless, some outstanding examples are briefly mentioned here. Essentially, chalcogenide forms of refractory metals are preferred in the fabrication of high-performance structures. Therefore, expanding the current studies that usually focus on tungsten- and molybdenum-based structures to other materials may open new opportunities. Moreover, research on ternary and quaternary structures can also be a keystone in creating high-performance products. The rationale of the present review is to give a brief overview of the recent history of refractory-metal-based chalcogenides (RMCs). Initially, the framework is confined to the general design and approaches for the synthesis of refractory metal chalcogenides. The assay is continued by extending with characteristic features of materials from crystalline properties to thermoelectric attributes and examining device fabrication processes. Taken together, the device fabrication part where RMCs are mainly used is extensively focused upon. Finally, outlook and future perspectives are given on the design and construction of RMCs to enable future inspiration and innovation.
Sepiolite Enhances Biomineralization Activity of the Cementoblasts
(2020) Hakkı, Sema; Bozkurt, Şerife Buket; Yenel, Esma; Kuş, Mahmut
Aim: The inductive potentials of graft materials are important for regenerative therapies. Thus, this study was conducted using cementoblasts (OCCM-30) tooth root lining cells to determine whether sepiolite affected proliferation, mRNA expressions of genes associated with cementum/bone and biomineralization. Materials and Methods: The media containing released components of sepiolite (100 mg/ml ratio; waited 72 hrs in 5%FBS containing media) were used for cementoblast’s treatments. Proliferation of the cells was evaluated using a real-time cell analyzer (RTCA) for 170 hrs. After total RNA isolation on days 3 and 6, cDNA synthesis was performed. Bone sialoprotein (BSP), osteocalcin (OCN), collagen type I (COL-I), runt-related transcription factor 2 (Runx2), and alkaline phosphatase (ALP) transcripts were examined employing quantitative RT-PCR. Biomineralization of the cementoblasts was evaluated on day 8 via von Kossa staining. Results: Sepiolite decreased proliferation of the cementoblasts when compared to untreated control group. While there was no change for BSP mRNA expression for both time points, sepiolite up-regulated OCN, Runx2, COL-I and ALP mRNA expressions (p <0.01) on days 3 and 6 when compared to control. Sepiolite stimulated mineralized nodule formation of the cementoblasts when compared to mineralization media group (positive control). Conclusion: The findings of this study demonstrated that sepiolite enhances the functions of the cementoblasts involving new cementum formation which is critical for periodontal regeneration. Results suggested that sepiolite has potential as a graft material in dentistry and medicine.

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