Dithieno[3,2-b:2',3'-d]pyrrole-benzo[c][1,2,5]thiadiazole conjugate small molecule donors: effect of fluorine content on their photovoltaic properties.

Two new small molecule donors, namely ICT4 and ICT6 with D1-A-D2-A-D1 architecture having 2,4-bis(2-ethylhexyl)-4H-dithieno[3,2-b:2',3'-d]pyrrole (EHDTP, D1) and 4,8-bis((2-ethylhexyl)oxy)benzo[1,2-b:4,5-b']dithiophene (OBDT, D2) as the terminal and central donor, and benzo[c][1,2,5]thiadiazole (BT for ICT4) and 5,6-difluorobenzo[c][1,2,5]thiadiazole (F2BT for ICT6) as the acceptor (A) moieties, are synthesized and their optical, electronic and photovoltaic properties are investigated. Both ICT4 and ICT6 have considerable solubility in various solvents and possess efficient light absorption ability [ε (×105 mol-1 cm-1) is 0.99 and 1.06, respectively for ICT4 and ICT6] and appropriate frontier molecular orbital energy offsets with [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM). Bulk heterojunction solar cells (BHJSCs) are fabricated using ICT4/ICT6 and PC71BM as donors and acceptors, respectively and BHJSCs with two-step annealed (thermal followed by solvent vapor annealing) active layers of ICT4 and ICT6 show overall power conversion efficiencies (PCEs) of 5.46% and 7.91%, respectively. The superior photovoltaic performance of the ICT6 based BHJSCs is due to the favourable morphology with a nanoscale interpenetrating network in the ICT6:PC71BM active layer induced by the fluorine atoms on the BT acceptor, which significantly enhances the dissociation of excitons, charge transport and the charge collection efficiency, and suppresses bimolecular recombination in the BHJ. The observed higher PCE of 7.91% indicates that ICT6 is one of the best BT based donor material for small molecular BHJSCs.

A dithieno[3,2-b:2',3'-d]pyrrole based, NIR absorbing, solution processable, small molecule donor for efficient bulk heterojunction solar cells.

A novel, NIR absorbing organic small molecular donor material denoted as ICT3 with an A-D-D-D-A architecture having dithieno[3,2-b:2',3'-d]pyrrole (DTP) and butylrhodanine as donor and acceptor moieties, respectively, is synthesized and its thermal, photophysical, electrochemical and photovoltaic properties are explored. ICT3 has excellent stability over a broad range of temperatures with a decomposition temperature (Td corresponds to 5% weight loss) of 372 °C, soluble in most common organic solvents (solubility up to 30 mg mL-1) and suitable for solution processing during device fabrication. ICT3 has broad (520-820 nm) and intense visible region absorption (molar excitation coefficient is 1.69 × 105 mol-1 cm-1) and has suitable HOMO and LUMO energy levels with the [6,6]-phenyl-C71-butyric acid methyl ester (PC71BM) acceptor for efficient exciton dissociation and charge transfer. Bulk heterojunction solar cells (BHJSCs) with an indium tin oxide (ITO)/poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS)/ICT3:PC71BM/poly(9,9-bis(3'-(N,N-dimethylamino)propyl)fluorene-2,7-diyl)-alt-(9,9-dioctylfluorene-2,7-diyl) (PFN)/aluminium (Al) structure are fabricated and the BHJSCs with the active layer as cast from chloroform solution displayed a power conversion efficiency (PCE) of 3.04% (JSC = 8.22 mA cm-2, VOC = 0.86 V and FF = 0.43). Annealing the active layer significantly improved the PCE of these BHJSCs. While thermal annealing of the active layer improved the PCE of the BHJSCs to 4.94%, thermal followed by solvent vapour annealing enhanced the PCE to 6.53%. X-ray diffraction and atomic force microscopy analyses are carried out on the active layer and these results revealed that annealing treatment improves the crystallinity and nanoscale morphology of the active layer, enriches the device exciton generation and dissociation efficiency, charge transport and collection efficiency and reduces carrier recombination. The observed higher PCE (6.53%) of the BHJSCs having ICT3 with a DTP donor moiety broadens the scope to develop new, efficient DTP based small molecular donor materials for BHJSCs.

Selective interactions of trivalent cations Fe³âº, Al³âº and Cr³âº turn on fluorescence in a naphthalimide based single molecular probe.

Synthesis and fluorescence turn-on behavior of a naphthalimide based probe is described. Selective interactions of trivalent cations Fe(3+), Al(3+) or Cr(3+) with probe 1 inhibit the PET operating in the probe, and thereby, permit the detection of these trivalent cations present in aqueous samples and live cells. Failure of other trivalent cations (Eu(3+), Gd(3+) and Nb(3+)) to inhibit the PET process in 1 demonstrates the role of chelating ring size vis-à-vis ionic radius in the selective recognition of specific metal ions.

A novel FRET 'off-on' fluorescent probe for the selective detection of Fe³âº, Al³âº and Cr³âº ions: its ultrafast energy transfer kinetics and application in live cell imaging.

A rhodamine-naphthalimide dyad probe, 1, that selectively responds to the addition of trivalent metal ions (Fe(3+) or Al(3+) or Cr(3+)) via ultrafast Förster resonance energy transfer (FRET) from naphthalimide to rhodamine is designed and synthesized. 1 is highly selective to the trivalent metal ions and the presence of other monovalent or divalent metal ions do not affect its detection ability. The probe is highly sensitive and it can respond to the presence of trivalent metal ions even at sub-micromolar levels. 1 is stable over a broad range of pH, non-toxic under experimental conditions and suitable to the fluorescence bio-imaging of live cells exposed to trivalent metal ions. The trivalent metal ion induced ultrafast energy transfer kinetics of 1 is explored using time resolved fluorescence experiments.

A naphthalimide based PET probe with Fe3+ selective detection ability: theoretical and experimental study.

A naphthalimide based fluorescent probe '1' that operates based on photoinduced electron transfer phenomenon is synthesized and its chemosensory application is explored. Among various metal ions, 1 selectively detects Fe(3+) with a detection limit of 3.0 × 10(-8) M. 1 is stable at physiological pH, nontoxic under experimental conditions and suitable for the detection of Fe(3+) ions present in aqueous samples and live cells.

Tuning copper(II) ion selectivity: the role of basicity, size of the chelating ring and orientation of coordinating atoms.

Incorporation of the triazolyl moiety modulates the basicity and effective size of the chelating ring, changes the stoichiometry in complex formation and thereby imparts Cu(2+) ion selectivity.

A highly selective and efficient single molecular FRET based sensor for ratiometric detection of Fe3+ ions.

A highly selective and efficient single molecular FRET based sensor has been developed for the ratiometric detection of Fe(3+) in aqueous samples and live cells.

Solvent-assisted selective detection of sub-micromolar levels of Cu2+ ions in aqueous samples and live-cells.

Two new rhodamine­indole conjugates 1 and 2 were synthesized for studying their ability to probe specific metal ions at physiological pH in the presence of other competing metal ions. In non-aqueous medium, probe 1 predominantly binds Cu(2+) ions with considerable interference from Fe(3+) and Ni(2+) ions. However, in aqueous medium, 1 exhibits a higher degree of selectivity for Cu(2+) ions with little interference from Fe(3+) ions, and no interference from Ni(2+) ions. The probe 2, obtained by tethering a triazole moiety with probe 1, selectively binds Cu(2+) ions in aqueous medium even in the presence of other metal ions including Fe(3+) ions. The sensitivity of probe 2 to pH variation and interaction with various amino acids were also investigated. The excellent stability of 2 in physiological pH conditions, non-toxicity, non-interference of amino acids in the detection process, and the remarkable selectivity for Cu(2+) ions in aqueous medium allowed the use of 2 in the imaging of live fibroblast cells treated with Cu(2+).

Incorporation of triazole into a quinoline-rhodamine conjugate imparts iron(III) selective complexation permitting detection at nanomolar levels.

Two new rhodamine based probes 1 and 2 for the detection of Fe(3+) were synthesized and their selectivity towards Fe(3+) ions in the presence of other competitive metal ions tested. The probe 1 formed a coloured complex with Fe(3+) as well as Cu(2+) ions and revealed the lack of adequate number of coordination sites for selective complexation with Fe(3+). Incorporation of a triazole unit to the chelating moiety of 1 resulted in the probe 2, that displayed Fe(3+) selective complex formation even in the presence of other competitive metal ions like Li(+), Na(+), K(+), Cu(2+), Mg(2+), Ca(2+), Sr(2+), Cr(3+), Mn(2+), Fe(2+), Co(2+), Ni(2+), Zn(2+), Cd(2+), Hg(2+) and Pb(2+). The observed limit of detection of Fe(3+) ions (5 × 10(-8) M) confirmed the very high sensitivity of 2. The excellent stability of 2 in physiological pH conditions, non-interference of amino acids, blood serum and bovine serum albumin (BSA) in the detection process, and the remarkable selectivity for Fe(3+) ions permitted the use of 2 in the imaging of live fibroblast cells treated with Fe(3+) ions.