Browsing by Author "Rajan, Yesudoss Christu"

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Porphyrin sensitizers with pi-extended pull units for dye-sensitized solar cells
(2013)
Reddy, Nagannagari Masi
;
Pan, Tsung-Yu
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Rajan, Yesudoss Christu
;
Guo, Bo-Cheng
;
Lan, Chi-Ming
New pi-extended porphyrin dyes YD26-YD29 with long alkoxyl chains at the ortho positions of the meso-phenyls, and meta di-tert-butylphenyl-substituted porphyrins YD12-CN, and YD13-CN were synthesized for dye-sensitized solar cells, and their optical, electrochemical and photovoltaic properties were investigated and compared with those of YD12 and YD13. The absorption spectra of YD26-YD29 showed a slight red shift of Soret bands and blue shift of Q bands as compared to the meta-substituted porphyrins due to the electron-donating effects of dioctyloxy substituents at the ortho-positions of the meso-phenyl rings. Replacement of the carboxyl with a cyanoacrylic acid as the anchoring group results in significant broadening and red shifts of the absorptions, which is due to the strong electronic coupling between the pull unit and the porphyrin ring facilitated by the C C triple bond. The electrochemical studies and quantum-chemical calculations (DFT) indicated that the ortho alkoxy-substituted sensitizers exhibit lower oxidation potential, i.e. a higher HOMO energy level, and their HOMO-LUMO gaps are comparable to the meta-substituted analogues. The photovoltaic measurements confirmed that the ortho-octyloxy groups in the two meso-phenyls of YD26 and YD27 play a significant role in preventing dye aggregation thereby enhancing the corresponding short-circuit current density and open-circuit voltage. The power conversion efficiency (eta) of YD26 is 8.04%, which is 11% higher than that of YD12, whereas the efficiency of YD27 is 6.03%, which is 135% higher than that of YD13. On the other hand, the poor performance of YD28 and YD29 is due to the floppy structural nature and limited molecular rigidity of the cyanoacrylic acid anchor.
Synthesis of novel supramolecular triads bearing a H-bonded perylene bisimide core
(2012-09-23)
Rajan, Yesudoss Christu
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Shellaiah, Muthaiah
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Huang, Ching-Ting
;
Lin, Hsin-Chieh
;
Lin, Hong-Cheu
Two novel hydrogen-bonded (H-bonded) triads consisting of triazine derivatives complexed with a perylene bisimide core were synthesized and characterized. NMR, UV/vis, and fluorescence spectra of these supramolecular triads confirmed the formation of strong multiple H-bonding, which were also proven to be nano-sized H-aggregates by X-ray diffraction (XRD) measurements. (C) 2012 Elsevier Ltd. All rights reserved.
Synthesis of novel triarylamine-based dendrimers with N-4,N-6-dibutyl-1,3,5-triazine-4,6-diamine probe for electron/energy transfers in H-bonded donor-acceptor-donor triads and as efficient Cu2+ sensors
(2012)
Shellaiah, Muthaiah
;
Rajan, Yesudoss Christu
;
Lin, Hong-Cheu
;
材料科學與工程學系
;
Department of Materials Science and Engineering
Two novel highly soluble triarylamine dendrimers TPAD1 and TPAD2 with N-4,N-6-dibutyl-1,3,5-triazine-4,6-diamine probe were synthesized via normal synthetic routes. Both dendrimers (TPAD1 and TPAD2) form H-bonded donor-acceptor-donor (D-A-D) supramolecular triads TPAD1-PBI-TPAD1 and TPAD2-PBI-TPAD2 with 3,4,9,10-perylene tetra carboxylic diimide derivative (PBI). The presence of multiple H-bonds in the solution state was elucidated by H-1 NMR titrations and IR spectral studies. J-aggregations and electron/energy transfers provided by both dendrimers were verified by UV-Vis and photoluminescence (PL) titrations with PBI and the particle sizes of supramolecular triads were calculated by X-ray diffraction (XRD) analysis. Similarly, both dendrimers also showed sensitivities towards Cu2+ in comparison with 19 interfering metal ions, which were evidenced via UV-Vis and PL titraions in both single and dual metal systems. The maximum detection limit of Cu2+ ions was determined to be 20 ppm from PL titrations for both dendrimers, and the 1 : 2 stoichiometry of the complexes formed by both dendrimers (TPAD1-Cu2+ and TPAD2-Cu2+) were calculated by Job plots based on UV-Vis absorption titrations. More importantly, the binding mechanism of the 1,3,5-triazine-4,6-diamine probe of both dendrimers was well characterized by H-1 and C-13 NMR titrations ([D-8] THF : D2O = 2 : 1 in vol.) and supported by the fluorescence reversibility by adding metal ions and PMDTA sequentially.