A high molar extinction coefficient heteroleptic ruthenium complex, incorporating an electron-rich hexylthio-terminal chain, has been synthesized and demonstrated as an efficient sensitizer for dye-sensitized solar cells. With this new sensitizer excellent power conversion efficiency is 11.5% and 4.7% obtained under an irradiation of full sunlight (air mass 1.5 global) in combination with a volatility electrolyte and solid state hole transporting material, respectively. The devices with low volatility electrolyte showed good stability under visible-light soaking at 60 degrees C during 1000 h of accelerated tests.

SUMMARYArteriovenous malformations (AVMs) are fragile direct connections between arteries and veins that arise during times of active angiogenesis. To understand the etiology of AVMs and the role of blood flow in their development, we analyzed AVM development in zebrafish embryos harboring a mutation in activin receptor-like kinase I (alk1), which encodes a TGFb family type I receptor implicated in the human vascular disorder hereditary hemorrhagic telangiectasia type 2 (HHT2). Our analyses demonstrate that increases in arterial caliber, which stem in part from increased cell number and in part from decreased cell density, precede AVM development, and that AVMs represent enlargement and stabilization of normally transient arteriovenous connections. Whereas initial increases in endothelial cell number are independent of blood flow, later increases, as well as AVMs, are dependent on flow. Furthermore, we demonstrate that alk1 expression requires blood flow, and despite normal levels of shear stress, some flow-responsive genes are dysregulated in alk1 mutant arterial endothelial cells. Taken together, our results suggest that Alk1 plays a role in transducing hemodynamic forces into a biochemical signal required to limit nascent vessel caliber, and support a novel two-step model for HHT-associated AVM development in which pathological arterial enlargement and consequent altered blood flow precipitate a flow-dependent adaptive response involving retention of normally transient arteriovenous connections, thereby generating AVMs.

A dye-sensitized solar cell (DSSC) using Ru complexes as a photosensitizer was first reported by ORegan and Grätzel in 1991.[1] The low-cost, easy preparation make DSSC one of the most promising photovoltaic cells for conversion of sunlight to electricity. Numerous sensitizers have been prepared, and their performance has been tested. [2][3][4][5][6][7][8][9][10] A conversion efficiency of up to 11 % was achieved by using cis-di(thiocyanato)bis(2,2'-bipyridyl-4,4'-dicarboxylate)ruthenium(II) (N3) as a photosensitizer. [11][12] However, the conversion efficiency of DSSCs is still lower than that of the silicon-based photovoltaic cells. To obtain a high conversion efficiency, optimization of the short-circuit photocurrent (I sc ) and open-circuit potential (V oc ) of the cell is essential. The value of V oc depends on the edge of conduction band in TiO 2 and the redox potential of I À / I 3 À , otherwise I sc is related to the interaction between TiO 2 and the sensitizer as well as the absorption coefficient of the sensitizer. The conduction band of TiO 2 was known to have a Nernstian dependence on pH. [13][14] Thus, the molecular engineering of the ruthenium complexes for achieving the highest efficiency was attempted to increase the molar absorption coefficient and reduce the number of protons on the complexes. 4,4'-Dicarboxylic acid-2,2'-bipyridine (dcbpy) has been considered as the best anchoring ligand in Ru sensitizers.[15] Finding new metal-complex sensitizers with higher conversion efficiency was achieved by modifying one of the anchoring ligands. Replacement of one of the dcbpy anchoring ligands with a highly conjugated ancillary ligand represents a molecular engineering approach for increasing the absorption coefficient and therefore the photocurrent density of the sensitizers as reported by Grätzel and coworkers. [16][17][18][19][20] Herein, we report a new ruthenium photosensitizer CYC-B1 in which one of the dcbpy ligands in N3 was replaced with abtpy, a bipyridine ligand substituted with alkyl bithiophene groups. CYC-B1 has the highest absorption coefficient among the Ru-based photosensitizers used in DSSCs, and its power-conversion efficiency is 10 % higher than that of N3 under the same cell fabrication and measuring procedures carried out in our laboratory.CYC-B1 was prepared in a typical one-pot synthesis, [20] and its structure (Scheme 1) was identified from NMR spectroscopy, mass spectrometry, and elemental analysis. The electronic absorption spectra of the free dcbpy and abtpy ligands, CYC-B1, and N3 in DMF are displayed in Figure 1, and the optical data are summarized in Table 1. The absorption maximum (l max ) assigned to the p-p* transition for dcbpy and abtpy are 299 nm and 375 nm, respectively. The absorption maximum of abtpy is red-shifted by 76 nm, which is attributed to its longer conjugation length, compared to that of dcbpy. The absorption spectrum of CYC-B1 shows three bands centered at 553 nm, 400 nm, and 312 nm. Based on comparison with the free abtpy ligand and the homoleptic compl...

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Dye-sensitized solar cells (DSCs) have been explored for photovoltaic applications because of their low cost and impressive conversion efficiency.[1] A DSC with 10 % efficiency was first demonstrated by Grätzel and co-workers using N3 (cis-di(thiocyanato)bis(2,2'-bipyridyl-4,4-dicarboxylate) ruthenium(II)) as a sensitizer.[2] Progress in optimizing ruthenium-based sensitizers for DSCs has been focused primarily on enhancing the light-harvesting ability, and redshifting the metal-to-ligand charge transfer (MLCT) band. [3][4][5][6][7][8][9][10] These results can be achieved by extending the conjugation length of the anchoring or ancillary ligand. [11][12][13][14][15] Furthermore, retaining the photoinduced interfacial charge separation between the dye molecules and TiO 2 is also a crucial strategy to enhance the performance of DSCs. [16] This strategy is beautifully demonstrated by adding a hole-transport segment on the dye molecule in all-solid-state DSCs. [17,18] However, this concept could not be applied to liquid-state DSCs, [19,20] probably because the ruthenium sensitizers have relatively low light-harvesting capacity and large molecular size.We have shown [21,22] that thiophene-derived units are the good candidates for increasing the conjugation length of the ancillary ligand to increase the light-harvesting ability and red-shift the MLCT band of a ruthenium complex. Herein we reveal that thiophene-derived species can be functionalized easily with a alkyl-substituted hole-transport moiety, such as bis(heptyl)carbazole. Ruthenium complexes with ligands functionalized by thiophene, carbazole, and alkyl chains can be regarded as supersensitizers. The efficiency of a liquidstate DSC based on one of these supersensitizers is 9.72 %, which is 1.2 % higher than that (8.51 %) of the N3-based cell at the same fabrication and efficiency measuring conditions. This is the first demonstration that a carbazole moiety in the dye can enhance the performance of a liquid-state DSC. Furthermore, the terminal alkyl chains on the ancillary ligand were also modulated to explore the impact of the sensitizer size on the cell performance in the DSC. In situ photoelectrochemical measurements were used for the first time to study the intramolecular electron-transfer processes of the oxidized dye.The structures of the supersensitizers CYC-B6S and CYC-B6L are depicted in Figure 1. The electronic absorption spectra of these supersensitizers and N3 measured in DMF are displayed in Figure 2, and the optical data are summarized in Table 1. The absorption spectra of the supersensitizers show that the band centered at around 550 nm (which is the characteristic metal-to-ligand charge-transfer (MLCT) transition) is stronger and more red-shifted than that for N3. These results indicate that the spectral response of ruthenium