Observation of thermally activated delayed fluorescence (TADF) in conjugated systems redefined the molecular design approach to realize highly efficient organic light emitting diodes (OLEDs) in the early 2010s. Enabling effective reverse intersystem crossing (RISC) by minimizing the difference between singlet and triplet excited state energies (ΔE ST ) is proven to be a widely applicable and fruitful approach, which results in remarkable external quantum efficiencies (EQE). The efficacy of RISC in these systems is mainly dictated by the first-order mixing coefficient (λ), which is proportional to spin-orbit coupling (H SO ) and inversely proportional to ΔE ST . While minimizing ΔE ST has been the focus of the OLED community over the last decade, the effect of H SO in these systems is largely overlooked. Here, molecular systems with increased H SO are designed and synthesized by substituting selected heteroatoms of high-performance TADF materials with heavy-atom selenium. A new series of multicolor TADF materials with remarkable EQEs are achieved. One of these materials, SeDF-B, results in pure blue emission with EQEs approaching 20%. Additionally, flexible graphene-based electrodes are developed for OLEDs and revealed to have similar performance as standard indium tin oxide (ITO) in most cases. These devices are the first report of TADF based OLEDs that utilize graphene-based anodes.

In this research, an electrochemical enzymatic biosensor system for sensitive and selective catechol detection was developed with using boric acid substituted Polyaniline film coated two different electrodes; gold screen‐printed electrode and glassy carbon electrode. Electropolymerization of 3‐aminophenylboronic acid is carried out through various electropolymerization conditions, and the best conditions for biosensors systems are concluded. The developed tyrosinase enzyme‐based biosensor system is used for the determination of catechol. The limit of detections(LOD) of the developed biosensor was 0.25 μM and 1.8 μM with Au SPE and GCE systems, respectively. Additionally, real sample analysis was also performed for controlled catechol added green tea samples.

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Because of its excellent electrochemical properties, extreme redox performance, and ability to mediate the electron transfer between the electrode surface and the reaction site, polyaniline (PANI) is one of the most ideal and well-known conductive polymers for biosensor design. This research developed an electrochemical enzymatic biosensor system with PANI film-coated screen printed electrodes (SPE) using the one-step direct electropolymerization process. PANI electropolymerization was performed in different acidic solutions, and the effects on the electrodeposition of the potential range, potential scan rate, and cycle number are discussed depending on these acidic solutions. The surface morphologies of films prepared with different processes were characterized by usıng the SEM (scanning electron microscopy) technique. A sensitive and selective catechol biosensor was developed by immobilizing the tyrosinase (Tyr) enzyme into PANI film combined with glutaraldehyde as a cross-linking agent. After optimizing the biosensor performance conditions, the developed biosensor measured catechol in green tea samples.

Bu çalışmada, enzimatik biyosensör sistemlerinde sentezlenen ve analiz edilen yeni bir organoboron bazlı monomer geliştirilmiştir. Doğrudan elektropolimerizasyon (tek adımlı) yöntemi kullanılarak, yeni organoboron polimer film kaplı platin ekran baskılı elektrotlar/camsı karbon elektrot ile bir elektrokimyasal enzimatik biyosensör sistemi geliştirildi. Yeni organoboron monomerinin elektropolimerizasyonu, çeşitli elektropolimerizasyon koşullarıyla gerçekleştirildi ve biyosensör sistemleri için en iyi koşullar sonucuna varıldı. Bu tezde geliştirilecek olan organoboron polimer bazlı enzimatik ve elektrokimyasal analizler, kimya ve tarım endüstrisinde en çok analiz edilen fenolik bileşiklerden biri olan katekolün tayini için kullanılacaktır. Örnek belirleme sistemi olarak tirozinaz enziminin kullanıldığı katekol analizi geliştirilmiştir. Geliştirilen biyosensör sistemi ile fenolik bileşenler farklı elektrotlarla 1 µM ile 200 µM arasındaki lineer aralıkta test edilmiştir. Biyosensör performans koşulları optimizasyonundan sonra, yüzde 3 ila yüzde 10 standart sapma aralığında kontrollü katekol katkılı yeşil çay örnekleri için gerçek örnek analizi de yapıldı. Son olarak, geliştirilen biyosensör sisteminin, gerçek zamanlı algılamaya izin veren taşınabilir bir son ürün olarak tasarlanıp ticarileştirilebileceği belirtilmelidir. Doğal gıdaların antioksidan ve antimikrobiyal aktivitelerini belirlemek için belirlenen fenolik bileşiklerin kısmen kalite kontrol analizleri kapsamında yapılmakta olup, geliştirilen organoboron polimer tabanlı biyosensör sistemi daha hızlı, daha ucuz, kesin ve gerçek zamanlı testlere olanak sağlayacaktır.

In this study, a novel boric acid-incorporated polyurethane (BPU) foam was synthesized and its several physical and biological properties were investigated. In order to determine the effect of the incorporated boric acid (BA) particles into the foam, mechanical and physical properties (apparent density, contact angle), analytical (Fourier transform infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, inductively coupled plasma optical emission spectrometry), morphological (scanning electron microscopy (SEM), micro-computed tomography), thermal characteristics (thermogravimetric analysis, differential scanning calorimetry) and antibacterial activity were examined. The addition of BA particles to the PU foam improved the thermal and mechanical properties, as BA strengthened the polymeric structure through hydrogen bonds with PU. Mechanical analyses and contact angle measurements revealed that the BPU foam demonstrated better mechanical properties (94.0 kPa) and higher hydrophobicity values (108.52°) with respect to PU foam (52.9 kPa and 37.35°, respectively). According to microscopy analyses, micro-CT images confirmed SEM images in which PU foam has an open cell structure, whereas BPU foam has a closed cell structure. The antibacterial activity test results demonstrate that incorporation of BA to the PU structure significantly improved the antibacterial properties of the PU foam against both of Gram-positive and Gram-negative bacteria. This study suggests that the addition of BA into PU structure enhanced the antibacterial activities of PU foam while improving its physical, mechanical and thermal properties. As a result, BA incorporation should be classified as a promising alternative to improve the properties of PU foams.