Makale KoleksiyonuArticle Collectionhttps://hdl.handle.net/20.500.12511/44842024-03-28T14:34:06Z2024-03-28T14:34:06ZNon-destructive covalent surface alkylation of graphitic carbon nitride for enhanced photocatalytic dye degradation in waterArat, RefikFidan, TuçeYüce, MeralKurt, HasanBayazıt, Mustafa Kemalhttps://hdl.handle.net/20.500.12511/121472024-02-09T12:29:04Z2024-01-01T00:00:00ZNon-destructive covalent surface alkylation of graphitic carbon nitride for enhanced photocatalytic dye degradation in water
Arat, Refik; Fidan, Tuçe; Yüce, Meral; Kurt, Hasan; Bayazıt, Mustafa Kemal
Graphitic carbon nitride (g-CN) is a promising material for various applications due to its unique electronic, optical, and photocatalytic properties, tunable by surface modifications. Herein, a novel and straightforward approach to the covalent addition of low molecular weight polyethylene glycol (PEG550) to g-CNs surface following non-destructive chemistry benefiting from simultaneous activation of hydroxyl and free-amine surface groups by a weak base, potassium carbonate, is for the first time described. The resulting g-CN-PEG550 exhibits almost two-fold enhanced water solubility due to 1 PEG550 chain addition for every ∼ 128 g-CN atoms, detected by thermogravimetric analysis. Complementary X-ray photoelectron spectroscopy elemental analysis of the isolated g-CN-PEG550 displays an increased C─O chemical environment attributed to the covalent addition of carbon- and oxygen-rich PEG550 to the g-CN surface. The g-CN-PEG550 photocatalyst performs 2.5-fold better in degrading rhodamine B due to its enhanced light absorption, improved water-dispersibility, and the efficient separation of photogenerated electron-hole pairs compared to the as-prepared g-CN. The study underscores the potential use of covalently PEGylated oxygen-rich g-CNs in photocatalytic applications.
2024-01-01T00:00:00ZPlasmonic titanium nitride nanohole arrays for refractometric sensingGünaydın, Beyza NurGülmez, MertTorabfam, MiladPehlivan, Zeki SemihTütüncüoğlu, AtacanKayalan, Cemre IrmakSaatçioğlu, ErhanBayazıt, Mustafa KemalYüce, MeralKurt, Hasanhttps://hdl.handle.net/20.500.12511/120112023-12-18T05:19:05Z2023-01-01T00:00:00ZPlasmonic titanium nitride nanohole arrays for refractometric sensing
Günaydın, Beyza Nur; Gülmez, Mert; Torabfam, Milad; Pehlivan, Zeki Semih; Tütüncüoğlu, Atacan; Kayalan, Cemre Irmak; Saatçioğlu, Erhan; Bayazıt, Mustafa Kemal; Yüce, Meral; Kurt, Hasan
Group IVB metal nitrides have attracted great interest as alternative plasmonic materials. Among them, titanium nitride (TiN) stands out due to the ease of deposition and relative abundance of Ti compared to those of Zr and Hf metals. Even though they do not have Au or Ag-like plasmonic characteristics, they offer many advantages, from high mechanical stability to refractory behavior and complementary metal oxide semiconductor-compatible fabrication to tunable electrical/optical properties. In this study, we utilized reactive RF magnetron sputtering to deposit plasmonic TiN thin films. The flow rate and ratio of Ar/N2 and oxygen scavenging methods were optimized to improve the plasmonic performance of TiN thin films. The stoichiometry and structure of the TiN thin films were thoroughly investigated to assess the viability of the optimized operation procedures. To assess the plasmonic performance of TiN thin films, periodic nanohole arrays were perforated on TiN thin films by using electron beam lithography and reactive ion etching methods. The resulting TiN periodic nanohole array with varying periods was investigated by using a custom microspectroscopy setup for both reflection and transmission characteristics in various media to underline the efficacy of TiN for refractometric sensing.
2023-01-01T00:00:00ZIntegrated entropy-EDAS methods for the electrified car selection problemÇaloğlu Büyükselçuk, ElifTozan, Hakanhttps://hdl.handle.net/20.500.12511/112162023-07-19T08:35:35Z2022-01-01T00:00:00ZIntegrated entropy-EDAS methods for the electrified car selection problem
Çaloğlu Büyükselçuk, Elif; Tozan, Hakan
Increasing air pollution affects the environment and life negatively. For a sustainable environment and life, people, voluntary organizations, and governments need to work on the solution of this problem. The biggest sources of air pollution are transportation vehicles. For this reason, many countries in Europe have stated that they will use solely electrified cars to reduce air pollution in the future. Therefore, in this study, it is aimed to determine the best electrified car. The result obtained can support consumers that to intend to buy an electrified vehicle in the decision-making process. This problem is a typical multi-criteria decision making (MCDM) problem and some MCDM techniques are used to solve these problems. Here, the Entropy method was used to determine the weights of the selection criteria. Selection criteria was determined according to comprehensive literature survey and interviews with sales representatives. The EDAS (Evaluation based on Distance from Average Solution) method was used to rank the electrified car alternatives that sold in Turkey. As a result of the evaluation, the most important criteria was determined by the price of the vehicle, the net battery capacity, and the electric motor power. According to these criteria, the electrified car manufactured in China was chosen as the best.
2022-01-01T00:00:00ZAn integrated performance measurement framework for restaurant chains: A case study in IstanbulPınarbaşı, AyşegülAydın, UmutKaradayı, Melis AlmulaTozan, Hakanhttps://hdl.handle.net/20.500.12511/111112023-06-21T08:16:54Z2022-01-01T00:00:00ZAn integrated performance measurement framework for restaurant chains: A case study in Istanbul
Pınarbaşı, Ayşegül; Aydın, Umut; Karadayı, Melis Almula; Tozan, Hakan
Companies that continue to operate in a competitive market strive the most efficient use of their resources in order to remain competitive. Nowadays, with increasing customer feedback, properly analyzing customer needs and requests and producing services in accordance with expectations have become increasingly important due to the large number of companies competing in the same market, and this is especially important to be at the forefront of competitors in the food services industry. There are risks and uncertainties owing to the continuously changing demand for food service enterprises, the difficulty to regulate interest and comparable charges, the competitive environment, and currency rate hikes. In light of all of these circumstances, restaurants require a versatile tool to effectively measure and analyze their performance. Therefore, this study combines Principal Component Analysis (PCA) and Categorical Data Envelopment Analysis (CAT-DEA) to analyze the performance of 15 dealers in Istanbul, divided into three categories: steakhouse, kebab, and meatball-doner. The results demonstrate that each category has just one efficient restaurant, for a total of three efficient restaurants out of fifteen. In addition to the suggested CAT-DEA-based framework, three research hypotheses are constructed and analyzed to investigate the link between restaurant performance and various environmental factors (or relevant indicators) in the food service industry.; Rekabetçi bir piyasada faaliyet göstermeye devam eden şirketler, rekabetçi kalabilmek için kaynaklarını en verimli şekilde kullanmaya çalışırlar. Artan müşteri geri bildirimleri ile birlikte, aynı pazarda rekabet eden çok sayıda firma nedeniyle, müşteri ihtiyaç ve isteklerini doğru analiz etmek ve beklentilere uygun hizmet üretmek giderek daha önemli hale geldi ve bu durum özellikle gıda hizmetleri endüstrisinde rekabette ön planda olmak için önemlidir. Yiyecek hizmeti işletmelerine yönelik sürekli değişen talep, faiz ve karşılaştırılabilir ücretlerin düzenlenmesindeki zorluk, rekabet ortamı ve kur artışları nedeniyle bu sektörde riskler ve belirsizlikler bulunmaktadır. Tüm bu koşullar ışığında restoranlar, performanslarını etkin bir şekilde ölçmek ve analiz etmek için çok yönlü bir araca ihtiyaç duyarlar. Bu nedenle, bu çalışma, İstanbul'da et lokantası, kebap ve köfte-döner olmak üzere üç kategoriye ayrılmış 15 bayinin performansını analiz etmek için Temel Bileşenler Analizi (PCA) ve Kategorik Veri Zarflama Analizini (CAT-DEA) birleştirmektedir. Sonuçlar, her bir kategorinin yalnızca bir verimli restorana sahip olduğunu ve on beş bayiden toplamda üç bayinin verimli olduğunu göstermektedir. Önerilen CAT-DEA tabanlı yaklaşıma ek olarak, yemek hizmeti endüstrisinde restoran performansı ile çeşitli çevresel faktörler (veya ilgili göstergeler) arasındaki bağlantıyı araştırmak için üç araştırma hipotezi oluşturulmuş ve analiz edilmiştir.
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