Browsing by Subject "Dual emission"

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    Intramolecular through-space charge-transfer in naphthalene-based compounds and development of an efficient heterogeneous catalytic method for the aerobic C-H oxidation of alkylarenes
    (2023-09) Çalıkyılmaz, Eylül
    The transfer of electrons between two molecules or between different groups attached to a molecule is known as charge transfer. Electronic communication can take place either through chemical bonds or through space. Intramolecular through-space charge transfer occurs between donor and acceptor parts of a molecule depending on the electron density difference, the distance between them, and their relative positions. The main objective of the project is to study the phenomenon of intramolecular through-space charge transfer in naphthalene-based organic materials. We investigated the charge transfer in 1,8-substituted naphthalene derivatives and the effect of different electron-donating and electron-withdrawing groups. To investigate the role of these groups, a variety of control substrates which have different electronic structures were synthesized. Subsequently, it was determined which substances possess a charge transfer band by examining the UV-Vis spectra of these substances. Additionally, it was found that substances with charge transfer bands in UV-Vis absorption spectroscopy had multiple emission values when fluorescence spectra were analyzed. In addition, to observe the effect of different solvents on charge transfer, the substance with observed charge transfer was dissolved in different solvents and examined in terms of color, absorption, and emission values. A key objective of the second part is to develop an environmentally friendly and efficient earth-abundant metal hydroxide catalyst that can be used in aerobic C-H activation reactions for a variety of organic compounds. Metal hydroxides are used for this purpose because of their ability to operate at relatively low temperatures and it allows metal hydroxides to act as highly effective catalysts for oxidation reactions. As an earth-abundant metal-containing catalyst, FexMn(1-x)(OH)y has been prepared by the Özensoy research group with different elemental ratios. In addition, the concentration of NaOH was systematically investigated during the synthesis of the catalyst. The catalytic activities of all catalysts were studied in the aerobic oxidation of fluorene to fluorenone as a model reaction. The optimized conditions were used for the oxidation of diphenylmethane to benzophenone. Subsequently, diphenylmethanes functionalized with electron-donating and electron-withdrawing groups were synthesized, and the yields of oxidation reactions were determined. Finally, the results of the kinetic isotope effect experiment were combined with the yields of the previous experiments to shed light on the mechanism of oxidation.
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    Light-Emitting diodes with Cu-Doped colloidal quantum wells: from ultrapure green, tunable dual-emission to white light
    (WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim, 2019) Liu, B.; Sharma, Manoj; Yu, J.; Shendre, S.; Hettiarachchi, C.; Sharma, Ashma; Yeltik, Aydan; Wang, L.; Sun, H.; Dang, C.; Demir, Hilmi Volkan
    Copper‐doped colloidal quantum wells (Cu‐CQWs) are considered a new class of optoelectronic materials. To date, the electroluminescence (EL) property of Cu‐CQWs has not been revealed. Additionally, it is desirable to achieve ultrapure green, tunable dual‐emission and white light to satisfy the various requirement of display and lighting applications. Herein, light‐emitting diodes (LEDs) based on colloidal Cu‐CQWs are demonstrated. For the 0% Cu‐doped concentration, the LED exhibits Commission Internationale de L'Eclairage 1931 coordinates of (0.103, 0.797) with a narrow EL full‐wavelength at half‐maximum of 12 nm. For the 0.5% Cu‐doped concentration, a dual‐emission LED is realized. Remarkably, the dual emission can be tuned by manipulating the device engineering. Furthermore, at a high doping concentration of 2.4%, a white LED based on CQWs is developed. With the management of doping concentrations, the color tuning (green, dual‐emission to white) is shown. The findings not only show that LEDs with CQWs can exhibit polychromatic emission but also unlock a new direction to develop LEDs by exploiting 2D impurity‐doped CQWs that can be further extended to the application of other impurities (e.g., Mn, Ag).