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RISS 인기검색어
- 검색키워드
- 저자 : Sunesh Kumar (검색결과 5 건)
- 무료
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Jeon, Youngbae,Sunesh, Chozhidakath Damodharan,Chitumalla, Ramesh Kumar,Jang, Joonkyung,Choe, Youngson Elsevier 2016 ELECTROCHIMICA ACTA Vol.195 No.-
<P><B>Abstract</B></P> <P>In this paper, we report highly luminescent yellow and orange light-emitting electrochemical cells (LECs) using cationic iridium complexes, i.e., [Ir(ppy)<SUB>2</SUB>(mpbi)]PF<SUB>6</SUB> (Complex 1) and [Ir(bpbt)<SUB>2</SUB>(mpbi)]PF<SUB>6</SUB> (Complex 2), which contain 2-phenylpyridine (ppy) and 2-(4-bromophenyl)benzothiazole (bpbt) as the cyclometalating ligands, respectively, and 2-(4-methyl-2-pyridyl)-1H-benzimidazole (mpbi) as the ancillary ligand. The emissions of Complex 1 and Complex 2 are yellow and yellowish-green in acetonitrile solution. The geometrical, electronic, and optical properties of the two novel Ir complexes were investigated by density functional theory (DFT) and time-dependent DFT using the B3LYP method. LECs incorporating Complexes 1 and 2 emit yellow (553nm) and orange (600nm) electroluminescence, respectively. Upon the meticulous selection of organic ligands, a significant increase in luminescence was achieved for Complex 1 (3636cd/m<SUP>2</SUP>) over that of Complex 2 (2315cd/m<SUP>2</SUP>).</P> <P><B>Highlights</B></P> <P> <UL> <LI> Highly luminescent yellow and orange light-emitting devices were fabricated. </LI> <LI> The emissions of Complex 1 and 2 are yellow and yellowish-green in solution. </LI> <LI> DFT and TDDFT calculations were performed for all complexes. </LI> <LI> A significant increase in luminescence was achieved for Complex 1 (3636cd/m<SUP>2</SUP>). </LI> </UL> </P> <P><B>Graphical abstract</B></P> <P>[DISPLAY OMISSION]</P>
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Subeesh, Madayanad Suresh,Shanmugasundaram, Kanagaraj,Sunesh, Chozhidakath Damodharan,Chitumalla, Ramesh Kumar,Jang, Joonkyung,Choe, Youngson American Chemical Society 2016 The Journal of Physical Chemistry Part C Vol.120 No.22
<P>Albeit their easy accessibility and low cost, small organic molecules are not known for their high electroluminescence in light-emitting electrochemical cells (LECs). To construct a bright low-cost LEC device, the functions of charge transport and charge recombination should be separated in the active layer of LEC devices. Herein, we demonstrate that the widely used host-dopant strategy in organic light-emitting diodes (OLEDs) can significantly improve the electroluminescence from small organic molecule fueled LEC devices, provided the host molecules are carefully selected. Furthermore, performance of host-dopant small-molecule LEC devices hugely relies on the properties of host materials rather than the emitting luminophores. Conversely to the high performance of intramolecular charge-transfer (ICT) molecular systems in OLEDs, doped ICT fluorophores having a low-lying charge-transfer state can behave like exciton loss channels in the high ionic environment of LEC-active layers. Similar to the behavior of previously reported ICT molecules in polar solvents, our synthesized D-pi-A-pi-D phenanthroimidazole derivative exhibited fluorescence quenching and a huge blue shift of emission in the doped thin film of the ionic host. However, even with a less efficient emitter, high electroluminescence was achieved from a host-dopant LEC system. Our best device exhibited a maximum brightness of 5016 cd/m(2) at a current efficiency of 0.73 cd/A. This device outplays our previously reported nondoped LEC (ihpypn-LEC) with a 7-fold increase in the maximum brightness and over a 3-fold increase in the current efficiency at peak brightness. To the best of our knowledge, these peak brightness values recorded here (device 2) are the best among those reported by small organic molecule LEC devices so far. This report reveals the potential of small organic molecules, especially phenanthroimidazole derivatives, in casting bright and efficient low-cost host-dopant LECs with minimum effort and appreciable sustainability.</P>
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Green Electroluminescence from Charged Phenothiazine Derivative
Shanmugasundaram, Kanagaraj,Subeesh, Madayanad Suresh,Sunesh, Chozhidakath Damodharan,Chitumalla, Ramesh Kumar,Jang, Joonkyung,Choe, Youngson American Chemical Society 2016 The Journal of Physical Chemistry Part C Vol.120 No.36
<P>A novel charged green-emitting organic small molecule, PPP, was synthesized and characterized by thermal, photophysical, electrochemical, and electroluminescence investigations. The theoretical properties of PPP were confirmed by means of computational studies. PPP exhibits a good thermal decomposition temperature of 355 degrees C. The compound PPP shows positive solvatochromism upon increasing the solvent polarity due to the more polarized excited state arising from the intramolecular charge transfer in the excited state. Solid-state emission of PPP was slightly red shifted compared to that of its solution emission spectrum, showing the reduced intermolecular interaction in the solid state. Solution-processed LEC devices were fabricated using PPP as a neat light-emitting layer. The fabricated single-component light-emitting electrochemical cell devices exhibited green electroluminescence centered at 530 nm with the CIE coordinates of (0.32, 0.58). Electroluminescent devices operated at very low turn-on voltages reveal a maximum luminance of 499 cd/m(2). These promising results are highly desirable for the development of low-cost lighting devices.</P>
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Daya Nand Sharma,Goura Kisor Rath,Sanjay Thulkar,Sunesh Kumar,Vellaiyan Subramani,Parmod Kumar Julka 대한부인종양학회 2010 Journal of Gynecologic Oncology Vol.21 No.1
Objective: Transrectal ultrasound (TRUS) has been widely used for guiding prostate implants, but not much for interstitial brachytherapy (IBT) of cervix cancer. The aim of our study is to report our experience with TRUS guided high dose rate (HDR) IBT in patients with carcinoma of uterine cervix. Methods: During the year 2005-2006, 25 patients of cervical cancer not suitable for intracavitary radiotherapy (ICRT),were enrolled in this prospective study. We used B-K Medical USG machine (Falcon 2101) equipped with a TRUS probe (8658) having a transducer of 7.5 MHz for IBT. Post procedure, a CT scan was done for verification of needle position and treatment planning. Two weekly sessions of HDR IBT of 8-10 Gy each were given after pelvic external beam radiation therapy. Results: A total of 40 IBT procedures were performed in 25 patients. Average duration of implant procedure was 50minutes. There was no uterine perforation in any of 11 patients in whom central tandem was used. CT scan did not show needle perforation of bladder/rectum in any of the patients. During perioperative period, only 1 procedure (2.5%) was associated with hematuria which stopped within 6 hours. Severe late toxicity was observed in 3 (12%)patients. Overall pelvic control rate was 64%. Conclusion: Our experience suggests that TRUS is a practical and effective imaging device for guiding the IBT procedure of cervical cancer patients. It helps in accurate placements of needles thus avoiding the injury to normal pelvic structures.
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