Browsing by Author "Pola, Murali Krishna"

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A fully-aqueous red-fluorescent probe for selective optical sensing of Hg2+ and its application in living cells
(2016-07)
Pola, Murali Krishna
;
Raju, Mandapati V. Ramakrishnam
;
Lin, Chein-Ming
;
Putikam, Raghunath
;
Lin, Ming-Chang
A new red-fluorescent mercury ion sensor material is designed and synthesized, which is composed of at weezer-shaped hydrophilic probe containing bifurcated soft-base atoms N and S coupled with 2-dicyanomethylene-3-cyano-4,5,5-trimethyl-2,5-dihydrofuran (TCF) unit. By virtue of the strong electron-accepting nature of TCF unit (as a push pull chromophore), this designed sensor material can selectively detect Hg2+ over various tested metal ions in a 100% aqueous medium via naked-eye and photoluminescence (PL) observations. Theoretical and time-resolved photoluminescence measurements further confirmed the selectivity and reversibility of the probe towards Hg2+ via intramolocular charge transfer mechanism in this sensor material. Moreover, the living cell tests by confocal fluorescence images of this sensor material towards Hg2+ were also investigated. Finally, distinguished absorption changes and fluorescence quenching spectral appearances allowed us to present the selective optical indicator of Hg2+ via TCF moiety for the first time. (C) 2016 Elsevier Ltd. All rights reserved.
Control of Crystal Structures and Optical Properties with Hybrid Formamidinium and 2-Hydroxyethylammonium Cations for Mesoscopic Carbon-Electrode Tin-Based Perovskite Solar Cells
(2018-09-01)
Tsai, Cheng-Min
;
Lin, Yu-Pei
;
Pola, Murali Krishna
;
Narra, Sudhakar
;
Jokar, Efat
Alcohol-based bifunctional ammonium cations, 2-hydroxyethylammonium (HEA(+)), HO(CH2)(2)NH3+, were introduced into formamidinium (FA(+)) tin-based perovskites (HEA(x)FA(1-x)Snl(3); x = 0-1) to absorb light in carbon-based mesoscopic solar cells. We found that HEAP cations play a key role to control the crystal structures, the lattice structures altered from orthorhombic (x = 0) to rhombohedral (x = 0.2-0.4) with greater symmetry. When x was increased to 0.6-1.0, tin and iodide vacancies were formed to generate 3D-vacant perovskites (HEA(x)FA(1-x)Sn(0.6)I(2.33), x >= 0.6) with a tetragonal structure. Tin-based perovskites in this series were fabricated into mesoporous solar cells using one-step drop-cast (DC), two-step solvent-extraction (SE), and SE + 3% ethyl-enediammonium diiodide (EDAI(2)) as an additive. After optimization of device performance with the SE + 3% EDAI2 approach, the HEA(0.4)FA(0.6)SnI(3) (HEAT = 40%) device gave the best photovoltaic performance with J(sc) = 18.52 mA cm(-2)) V-OC 371 mV, FF = 0.562, and overall efficiency 17 = 3.9% after the device was stored for a period of 340 h.
Novel fluoride-substituted donor/acceptor polymers containing benzodithiophene and quinoxaline units for use in low-band gap solar cells
(2016-09)
Singh, Ashutosh
;
Singh, Ravinder
;
Lin, Chein-Min
;
Pola, Murali Krishna
;
Chang, Chiao-Kai
In this study we used Stille polycondensation to synthesize a series of low-band gap fluoride-substituted conjugated polymers containing electron-donating benzodithiophene (BDT) and electron-accepting quinoxaline (Qx) units, with the latter presenting either two or four fluoride atoms. These donor/acceptor polymers exhibited a broad absorption range (from 300 to 750 nm), with band gap energies of less than 1.20 eV (measured using cyclic voltammetry). Because of their strongly electron-donating thiophene units, the donor/acceptor polymers featuring the more highly fluorinated structures possessed the lowest band gaps (as low as 1.14 eV) and, thus, induced the greatest photovoltaic performance among these tested polymers. The highest power conversion efficiency (2.13%) was obtained from the polymer solar cell featuring an active layer of the polymer PTF2 blended with PC70BM (1:1.5, w/w), with a short-circuit current density, open circuit voltage, and fill factor of 8.7 mA cm(-2), 0.72 V, and 0.34, respectively. (C) 2016 Elsevier Ltd. All rights reserved.
Synthesis and Applications of Cyano-Vinylene-Based Polymers Containing Cyclopentadithiophene and Dithienosilole Units for Photovoltaic Cells
(2011-08-01)
Padhy, Harihara
;
Sahu, Duryodhan
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Patra, Dhananjaya
;
Pola, Murali Krishna
;
Huang, Jen-Hsien
Two beta-cyano-thiophenevinylene-based polymers containing cyclopentadithiophene (CPDT-CN) and dithienosilole (DTS-CN) units were synthesized via Stille coupling reaction with Pd(PPh(3))(4) as a catalyst. The effects of the bridged atoms (C and Si) and cyano-vinylene groups on their thermal, optical, electrochemical, charge transporting, and photovoltaic properties were investigated. Both polymers possessed the highest occupied molecular orbital (HOMO) levels of about -5.30 eV and the lowest unoccupied molecular orbital (LUMO) levels of about -3.60 eV, and covered broad absorption ranges with narrow optical band gaps (ca. 1.6 eV). The bulk heterojunction polymer solar cell (PSC) devices containing an active layer of electron-donor polymers (CPDT-CN and DTS-CN) blended with an electron-acceptor, that is, [6,6]-phenyl-C(61)-butyric acid methyl ester (PC(61)BM) or [6,6]-phenyl-C(71)-butyric acid methyl ester (PC(71)BM), in different weight ratios were explored under 100 mW/cm(2) of AM 1.5 white-light illumination. The PSC device based on DTS-CN:PC(71)BM (1:2 w/w) exhibited a best power conversion efficiency (PCE) value of 2.25% with V(oc) = 0.74 V, J(sc) = 8.39 mA/cm(2), and FF = 0.36. (C) 2011 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 49: 3417-3425, 2011
Synthesis of fluorinated benzotriazole (BTZ)- and benzodithiophene (BDT)-based low-bandgap conjugated polymers for solar cell applications
(2017-04)
Pola, Murali Krishna
;
Boopathi, Karunakara Moorthy
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Padhy, Harihara
;
Raghunath, Putikam
;
Singh, Ashutosh
A series of donor acceptor (D-A) polymers (P1-P3) based on benzodithiophene (BDT) and electron- accepting benzotriazole (BTZ) units containing thiophene linkers with/without alkyl side-chains were designed and synthesized via Stille coupling polymerization method. The effects of polymers with multiple fluorinated BTZ groups on their thermal, optical, electrochemical, and photovoltaic properties were investigated. These polymers possessed the highest occupied molecular orbital (HOMO) levels ranged -5.38 to -5.6 eV and the lowest unoccupied molecular orbital (LUMO) levels ranged -3.55 to -3.57 eV, which covered broad absorption ranges with low optical bandgaps. The bulk heterojunction (BHJ) polymer solar cell (PSC) devices containing an active layer of D-A polymers blended with different weight ratios of electron-acceptor [6,6]-phenyl-C-71-butyric acid methyl ester (PC71BM) were explored under 100 mW cm(-2) of AM 1.5 white-light illumination, where the maximum power conversion efficiency (PCE) value of 3% (with J(sc) = 7.70 mA/cm(2), FF = 54.04, and V-oc = 0.72 V) was obtained in the PSC device consisting of polymer P3. (C) 2016 Elsevier Ltd. All rights reserved.
Synthesis of Main-Chain Metallo-Copolymers Containing Donor and Acceptor Bis-Terpyridyl Ligands for Photovoltaic Applications
(2012-04-13)
Padhy, Harihara
;
Ramesh, Mohan
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Patra, Dhananjaya
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Satapathy, Rudrakanta
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Pola, Murali Krishna
Two random (ZnII-based P1P2) and two alternating (RuII-based P3P4) metallo-copolymers containing bis-terpyridyl ligands with various central donor (i.e., fluorene or carbazole) and acceptor (i.e., benzothiadiazole) moieties were synthesized. The effects of electron donoracceptor interactions with metal (ZnII and RuII) ions on their thermal, optical, and electrochemical properties were investigated. Because of the strong ICT transitions between donor and acceptor ligands in both ZnII- and RuII-based metallo-coplymers and MLCT transitions in RuII-based metallo-coplymers, the absorption spectra covered a broad range of 260750 nm with the band gaps of 1.571.77 eV. In addition, the introduction of RuII-based metallo-coplymer P4 mixed with PC60BM as an active layer of the BHJ solar cell device exhibited the highest PCE value up to 0.90%.