Browsing by Subject "energy transfer"

Now showing 1 - 4 of 4

Open Access
Light harvesting and efficient energy transfer in boron dipyrrin dyads and derivatization for potential utility in dye-sensitized solar cells
(2008) Barın, Gökhan
In bichromophoric supramolecular systems light is harvested by antenna components and excitation energy is channeled into an acceptor component. We have designed and synthesized novel energy transfer cassettes which are based on boradiazaindacene (BODIPY) units. Facile synthesis of long wavelength absorbing distyryl BODIPY dyes has been applied successfully in this study. In the first part of the thesis, efficient energy transfer from energy donor BODIPYs to long wavelength absorbing distyryl BODIPY core was demonstrated. To observe the antenna effect quantitatively, we have designed the cassettes with an increasing number of energy donor components. Based on these observations, in the second part of the thesis, we have introduced a light-harvesting photosensitizer for dye-sensitized solar cell (DSSC) purposes. The target molecule absorbs in visible and near-IR region and energy transfer is demonstrated successfully. Our design appears to be highly promising for DSSC.
Open Access
Low thermal-mass LEDs: Size effect and limits
(Optical Society of American (OSA), 2014) Lu, S.; Liu W.; Zhang, Z.-H.; Tan, S.T.; Ju, Z.; Ji, Y.; Zhang X.; Zhang, Y.; Zhu, B.; Kyaw, Z.; Hasanov, N.; Sun X.W.; Demir, Hilmi Volkan
In this work, low thermal-mass LEDs (LTM-LEDs) were developed and demonstrated in flip-chip configuration, studying both experimentally and theoretically the enhanced electrical and optical characteristics and the limits. LTM-LED chips in 25 × 25 μm2, 50 × 50 μm2, 100 × 100 μm2 and 200 × 200 μm2 mesa sizes were fabricated and comparatively investigated. Here it was revealed that both the electrical and optical properties are improved by the decreasing chip size due to the reduced thermal mass. With a smaller chip size (from 200 μm to 50 μm), the device generally presents higher current density against the bias and higher power density against the current density. However, the 25 × 25 μm2 device behaves differently, limited by the fabrication margin limit of 10 μm. The underneath mechanisms of these observations are uncovered, and furthermore, based on the device model, it is proven that for a specific flip-chip fabrication process, the ideal size for LTM-LEDs with optimal power density performance can be identified. ©2014 Optical Society of America
Open Access
Novel multichromophoric energy transfer cassettes based on functionalized BODIPY dyes
(2012) Çeltek, Gizem
Energy necessity is one of the leading problems in the world due to the developing technologies and strategies. There are many energy sources, which are being used for years, however; conversion and transfer of the energy is a problem in many fields due to energy loss. In this manner, the efficiency of energy transfer is very crucial. For this purpose, we have designed multichromophoric molecules, which can absorb the light with donor parts, then transfer the energy to the acceptor site. During this process, energy loss is tried to be prevented by lowering the distance between the donor and acceptor Boradiazaindacene (BODIPY) molecules. Three different energy transfer cassettes are synthesized and characterized. The design of the supramolecule, in means of spectral overlap and distance between the donor and the acceptor site are observed to affect the energy transfer efficiency. Through functional design, these molecules absorb and emit light in different wavelengths. Substation of distyryl and tetrastyryl groups to the acceptor BODIPY core changes the emission and absorption maxima. Increasing number of styryl groups attached to the molecule shifts the spectrum to the red part of the visible region. Through rational design, these molecules can be used in applications of energy transfer and broad spectrum absorber purposes.
Open Access
Structures and free energy landscapes of the wild-type and A30P mutant-type α-synuclein proteins with dynamics
(2013) Wise-Scira O.; Aloglu, A.K.; Dunn, A.; Sakallioglu I.T.; Coskuner O.
The genetic missense A30P mutation of the wild-type α-synuclein protein results in the replacement of the 30th amino acid residue from alanine (Ala) to proline (Pro) and was initially found in the members of a German family who developed Parkinson's disease. Even though the structures of these proteins have been measured before, detailed understanding about the structures and their relationships with free energy landscapes is lacking, which is of interest to provide insights into the pathogenic mechanism of Parkinson's disease. We report the secondary and tertiary structures and conformational free energy landscapes of the wild-type and A30P mutant-type α-synuclein proteins in an aqueous solution environment via extensive parallel tempering molecular dynamics simulations along with thermodynamic calculations. In addition, we present the residual secondary structure component transition stabilities at the atomic level with dynamics in terms of free energy change calculations using a new strategy that we reported most recently. Our studies yield new interesting results; for instance, we find that the A30P mutation has local as well as long-range effects on the structural properties of the wild-type α-synuclein protein. The helical content at Ala18-Gly31 is less prominent in comparison to the wild-type α-synuclein protein. The β-sheet structure abundance decreases in the N-terminal region upon A30P mutation of the wild-type α-synuclein, whereas the NAC and C-terminal regions possess larger tendencies for β-sheet structure formation. Long-range intramolecular protein interactions are less abundant upon A30P mutation, especially between the NAC and C-terminal regions, which is linked to the less compact and less stable structures of the A30P mutant-type rather than the wild-type α-synuclein protein. Results including the usage of our new strategy for secondary structure transition stabilities show that the A30P mutant-type α-synuclein tendency toward aggregation is higher than the wild-type α-synuclein but we also find that the C-terminal and NAC regions of the A30P mutant-type α-synuclein are reactive toward fibrillzation and aggregation based on atomic level studies with dynamics in an aqueous solution environment. Therefore, we propose that small molecules or drugs blocking the specific residues, which we report herein, located in the NAC- and C-terminal regions of the A30P mutant-type α-synuclein protein might help to reduce the toxicity of the A30P mutant-type α-synuclein protein. © 2013 American Chemical Society.