Influence of the π-Bridge-Fused Ring and Acceptor Unit Extension in D-π-A-Structured Organic Dyes for Highly Efficient Dye-Sensitized Solar Cells.

Three new D-π-A-structured organic dyes, coded as SGT-138, SGT-150, and SGT-151, with the expansion of π-conjugation in the π-bridge and acceptor parts have been developed to adjust HOMO/LUMO levels and to expand the light absorption range of organic dyes. Referring to the SGT-137 dye, the π-bridge group was extended from the 4-hexyl-4H-thieno[3,2-b]indole (TI) to the 9-hexyl-9H-thieno[2',3':4,5]thieno[3,2-b]indole (TII), and the acceptor group was extended from (E)-3-(4-(benzo[c][1,2,5]thiadiazol-4-yl)phenyl)-2-cyanoacrylic acid (BTCA) to (E)-3-(4-(benzo[c][1,2,5]thiadiazol-4-ylethynyl)phenyl)-2-cyanoacrylic acid (BTECA), where TII was introduced as a π-bridging unit for the first time. It was determined that both extensions are promising strategies to enhance the light-harvesting ability. They present several features, such as (i) efficiently intensifying the extinction coefficient and expanding the absorption bands; (ii) exhibiting enhanced intramolecular charge transfer in comparison with the SGT-137; and (iii) being favorable to photoelectric current generation of dye-sensitized solar cells (DSSCs) with cobalt electrolytes. In particular, the π-spacer extension from TI to TII was useful for modulating the HOMO energy levels, while the acceptor extension from BTCA to BTECA was useful for modulating the LUMO energy levels. These phenomena could be explained with the aid of density functional theory calculations. Finally, the DSSCs based on new SGT-dyes with an HC-A1 co-adsorbent presented good power conversion efficiencies as high as 11.23, 11.30, 11.05, and 10.80% for SGT-137, SGT-138, SGT-150, and SGT-151, respectively. Furthermore, it was determined that the use of the bulky co-adsorbent, HC-A1, can effectively suppress the structural relaxation of dyes in the excited state, thereby enhancing the charge injection rate of SGT-dyes. The observations in time-resolved photoluminescence were indeed consistent with the variation in the PCE, quantitatively.

A Eu(III) tetrakis(ß-diketonate) dimeric complex: photophysical properties, structural elucidation by Sparkle/AM1 calculations, and doping into PMMA films and nanowires.

Reaction of Ln(III) with a tetrakis(diketone) ligand H4L [1,1'-(4,4'-(2,2-bis((4-(4,4,4-trifluoro-3-oxobutanoyl) phenoxy)methyl)propane-1,3-diyl)bis(oxy)bis(4,1-phenylene))bis(4,4,4-trifluorobutane-1,3-dione)] gives new podates which, according to mass spectral data and Sparkle/AM1 calculations, can be described as dimers, (NBu4[LnL])2 (Ln = Eu, Tb, Gd:Eu), in both solid-state and dimethylformamide (DMF) solution. The photophysical properties of the Eu(III) podate are compared with those of the mononuclear diketonate (NBu4[Eu(BTFA)4], BTFA = benzoyltrifluoroacetonate), the crystal structure of which is also reported. The new Eu(III) dimeric complex displays bright red luminescence upon irradiation at the ligand-centered band in the range of 250-400 nm, irrespective of the medium. The emission quantum yields and the luminescence lifetimes of (NBu4[EuL])2 (solid state: 51% ± 8% and 710 ± 2 µs; DMF: 31% ± 5% and 717 ± 1 µs) at room temperature are comparable to those obtained for NBu4[Eu(BTFA)4] (solid state: 60 ± 9% and 730 ± 5 µs; DMF: 30 ± 5% and 636 ± 1 µs). Sparkle/AM1 calculations were utilized for predicting the ground-state geometries of the Eu(III) dimer. Theoretical Judd-Ofelt and photoluminescence parameters, including quantum yields, predicted from this model are in good agreement with the experimental values, proving the efficiency of this theoretical approach implemented in the LUMPAC software (http://lumpac.pro.br). The kinetic scheme for modeling energy transfer processes show that the main donor state is the ligand triplet state and that energy transfer occurs on both the (5)D1 (44.2%) and (5)D0 (55.8%) levels. Furthermore, the newly obtained Eu(III) complex was doped into a PMMA matrix to form highly luminescent films and one-dimensional nanowires having emission quantum yield as high as 67%-69% (doping concentration = 4% by weight); these materials display bright red luminescence even under sunlight, so that interesting photonic applications can be foreseen.

Graphene nanoplatelets doped with N at its edges as metal-free cathodes for organic dye-sensitized solar cells.

Challenging precious Pt-based electrocatalysts for dye-sensitized solar cells (DSSCs), graphene nanoplatelets that are N-doped at the edges (NGnPs) are prepared via simply ball-milling graphite in the presence of nitrogen gas. DSSCs based on specific nanoplatelets designated "NGnP5" display superior photovoltaic performance (power conversion efficiency, 10.27%) compared to that of conventional Pt-based devices (9.96%). More importantly, the NGnP counter electrode exhibits outstanding electrochemical stability and electrocatalytic activity with a cobalt-complex redox couple.

The effects of small sized rice bowl on carbohydrate intake and dietary patterns in women with type 2 diabetes.

BACKGROUND: The main source of carbohydrate in the Korean diet is rice, which is usually served in a rice bowl. This study investigated the impact of a meal plan using smaller rice bowls on dietary energy intake and macronutrient composition in overweight or obese patients with type 2 diabetes mellitus. METHODS: A total of 67 women with type 2 diabetes were enrolled in our study. We divided these participants into three groups: a normal-weight group (NW; body mass index [BMI] < 23 kg/m(2); n = 17), an overweight group (OW; 23 /= 25 kg/m(2); n = 26). Three-day dietary records were analyzed for total energy intake (TEI) and macronutrient composition both before enrollment and two weeks after patients received instruction in a dietary plan based on using a small (200 mL) rice bowl. RESULTS: After the intervention, TEI decreased in the OW and OB groups. Decreased carbohydrate (NW, -4 +/- 5%; OW, -4 +/- 5%; OB, -3 +/- 6%) and increased fat intakes were found in all three groups, which complies with Korean Diabetes Association recommendations. The protein proportion of TEI significantly increased only in the OW group. Body weight decreased both in the OW and OB groups. CONCLUSION: A short-term, small-rice-bowl-based meal plan was effective for body weight control and macronutrient balance in overweight or obese women in Korea with type 2 diabetes.

Sensitized near-IR luminescence of lanthanide complexes based on push-pull diketone derivatives.

Lanthanide complexes with two push-pull diketone derivatives as sensitizers have been developed as synthons for near-infrared emitting materials. The ligand substituents consist of a carbazole moiety with hole-transport properties and an aromatic or heteroaromatic unit. According to quantitative NMR analysis and complementary HPLC experiments, the diketones are predominantly in their enolic form in polar solvents such as THF and MeCN at room temperature. The preferred cis-enol form contributes strongly to the binding of lanthanide ions (Ln = Nd, Gd, Er). The resulting tris(diketonate) ternary complexes with terpyridine (Ln = Nd, Er) display sizeable near-IR emission with long luminescence lifetimes.