Solution-Processed Bulk Heterojunction Solar Cells with Silyl End-Capped Sexithiophene

We fabricated solution-processed organic photovoltaic cells (OPVs) using substituted two sexithiophenes, a,w-bis(dimethyl-n-octylsilyl)sexithiophene (DSi-6T) and a,w-dihexylsexithiophene (DH-6T), as electron donors, and [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) as an electron acceptor. Solution-processed OPVs using DH-6T and DSi-6T showed good photovoltaic properties in spite of their poor solubility. The best performance was observed on DSi-6T : PCBM 1 : 5 (w/w) blend cell with an open circuit voltage (Voc) of 0.63 V, short circuit current density (Jsc) of 1.34 mA/cm2, fill factor (FF) of 55%, and power conversion efficiency of 0.44% under AM 1.5 G illumination. Although DH-6T has higher hole mobility than DSi-6T, the DSi-6T : PCBM blend cell showed higher hole mobility than DH-6T : PCBM cell. Therefore, DSi-6T cell showed higher device performance than DH-6T cell due to its silyl substitutions, which lead to the increase of the solubility. The incorporation of solution-processed TiO2 interfacial layer in the DSi-6T : PCBM devices significantly enhances FF due to the reduced charge recombination near active layer/Al interface

Large expert-curated database for benchmarking document similarity detection in biomedical literature search

Document recommendation systems for locating relevant literature have mostly relied on methods developed a decade ago. This is largely due to the lack of a large offline gold-standard benchmark of relevant documents that cover a variety of research fields such that newly developed literature search techniques can be compared, improved and translated into practice. To overcome this bottleneck, we have established the RElevant LIterature SearcH consortium consisting of more than 1500 scientists from 84 countries, who have collectively annotated the relevance of over 180 000 PubMed-listed articles with regard to their respective seed (input) article/s. The majority of annotations were contributed by highly experienced, original authors of the seed articles. The collected data cover 76% of all unique PubMed Medical Subject Headings descriptors. No systematic biases were observed across different experience levels, research fields or time spent on annotations. More importantly, annotations of the same document pairs contributed by different scientists were highly concordant. We further show that the three representative baseline methods used to generate recommended articles for evaluation (Okapi Best Matching 25, Term Frequency-Inverse Document Frequency and PubMed Related Articles) had similar overall performances. Additionally, we found that these methods each tend to produce distinct collections of recommended articles, suggesting that a hybrid method may be required to completely capture all relevant articles. The established database server located at https://relishdb.ict.griffith.edu.au is freely available for the downloading of annotation data and the blind testing of new methods. We expect that this benchmark will be useful for stimulating the development of new powerful techniques for title and title/abstract-based search engines for relevant articles in biomedical research.Peer reviewe

Finishing the euchromatic sequence of the human genome

The sequence of the human genome encodes the genetic instructions for human physiology, as well as rich information about human evolution. In 2001, the International Human Genome Sequencing Consortium reported a draft sequence of the euchromatic portion of the human genome. Since then, the international collaboration has worked to convert this draft into a genome sequence with high accuracy and nearly complete coverage. Here, we report the result of this finishing process. The current genome sequence (Build 35) contains 2.85 billion nucleotides interrupted by only 341 gaps. It covers ∼99% of the euchromatic genome and is accurate to an error rate of ∼1 event per 100,000 bases. Many of the remaining euchromatic gaps are associated with segmental duplications and will require focused work with new methods. The near-complete sequence, the first for a vertebrate, greatly improves the precision of biological analyses of the human genome including studies of gene number, birth and death. Notably, the human enome seems to encode only 20,000-25,000 protein-coding genes. The genome sequence reported here should serve as a firm foundation for biomedical research in the decades ahead

THE INVESTIGATION OF PHOTOCHEMICAL REACTIONS OF PHOTOTOXIC ANTIMALARIAL COMPOUNDS

The goal of this research is to provide information that will lead to the development of new non-phototoxic anitmalarial compounds. The goal was approached by first learning the chemical mechanism of phototoxicity of six representative compounds 1a-f; (alpha)-{(diethyl-, -dihexyl-, and -dioctyl-aminomethyl)}-2-(3\u27,4\u27-dichlorophenyl)-6-methoxy-4-quinolinemethanol (1a, 1b, and 1c) and (alpha)-{(diethyl-, -dibutyl-, and -dihexyl-aminomethyl)}-2-(4\u27-methoxyphenyl)-6-methoxy-7-chloro- 4-quinolinemethanol (1d, 1e, and 1f). The photochemical reaction of these compounds was investigated in 2-propanol. Similar photochemical fragmentation reactions occurred in all compounds. Five products (15-19), formed via cleavage of the whole side chain (bond a cleavage) and cleavage of bond between (alpha)-carbon and hydroxy carbon (bond b cleavage), were isolated and identified; 2-(3\u27,4\u27-dichlorophenyl)-6- methoxyquinoline (15), 2-(3\u27,4\u27-dichlorophenyl)-4-hydroxymethyl-6- methoxyquinoline (16), 2-(3\u27,4\u27-dichlorophenyl)-6-methoxyquinoline- 4-carboxaldehyde (17), 2-(3\u27,4\u27-dichlorophenyl)-4-((alpha),(beta)-dihydroxy-(beta)- methyl-propyl)-6-methoxyquinoline (18), and the pinacol-type of dimer of 16 (19). A radical mechanism was proposed for the formation of 15-19. Quantum yields of the photochemical reaction of 1a-f were measured to determine if the efficiency of the reaction parallels the degree of phototoxicity of 1a-f. A good qualitative correlation was observed. Fluorescence study of 1a-d, 2-(3\u27,4\u27-dichlorophenyl)-4-ethyl-6-methoxyquinoline, 2-(3\u27,4\u27-dichlorophenyl)-4-((alpha)-hydroxyethyl)-6-methoxyquinoline, and 2-(4\u27-methoxyphenyl)-4-((alpha)-hydroxyethyl)- 6-methoxy-7-chloroquinoline was performed to investigate whether intramolecular exciplex formation between an aliphatic amine group and quinoline ring could intervene in the photochemistry of 2-arylquinolinemethanols. Significant intramolecular fluorescence quenching by the aliphatic amine group of 1a-d was noticed. Sensitization irradiations of 1a with triplet sensitizers failed to produce 16-19, producing only 15 in low yield. The reaction of 1a-f was partially quenched by oxygen. The singlet excited state and an intramolecular exciplex of 2-arylquinolinemethanols were postulated to be reactive states for their photochemical reactions. Photochemical reactions of cinchonidine (33a), quinine (33b), cinchonine (33c), quinidine (33d), and mefloquine (50) were investigated. 5-Vinylquinuclidine-2-carboxaldehyde (34) was isolated and identified as a major product in the reaction of 33a-d. The formation of 34 was rationalized by a charge transfer mechanism. Bond b cleavage was blocked by the bicyclic amine group, quinuclidine of 33a-d. A different photochemical reaction was observed in the photolysis of 50 from those of 1a-f and 33a-d, and 2,8-bis(trifluoromethyl)-4-carbomethoxyquinoline was isolated as the major photoproduct in methanol. Finally, structural changes to increase charge transfer character in the intramolecular exciplex and to increase the efficiency of intersystem crossing were suggested as ways to stop or diminish the phototoxicity of 2-arylquinolinemethanols

Direct and indirect single electron transfer (SET)-photochemical approaches for the preparation of novel phthalimide and naphthalimide-based lariat-type crown ethers

In this review, we describe direct and indirect photochemical approaches that have been developed for the preparation of phthalimide- and naphthalimide-based, lariat-type crown ethers. The direct route utilizes a strategy in which nitrogen-linked side chains containing polyethoxy-tethered phthalimides and naphthalimides, possessing terminal α-trialkylsilyl groups, are synthesized utilizing concise routes and UV-irradiation to form macrocyclic ring systems. In contrast, the indirect route developed for the synthesis of lariat-type crown ethers employs sequences in which SET-promoted macrocyclization reactions of α-trialkylsilyl-terminated, polyethoxy-tethered phthalimides and naphthalimides are followed by a side chain introduction through substitution reactions at the amidol centers in the macrocyclic ethers. The combined observations made in these investigations demonstrate the unique features of SET-promoted photocyclization reactions that make them well-suited for the use in the synthesis of functionalized crown ethers. In addition, while some limitations exist for the general use of SET-photochemical reactions in large-scale organic synthesis, important characteristics of the photoinduced macrocyclization reactions make them applicable to unique situations in which high temporal and spatial control is required

Electroluminescent characteristics of novel platinum-porphyrin complex

Novel platinum complex of porphyrin with methyl and cyclohexyl substituents, PtMECHP, was designed and synthesized for use as a red phosphorescent material. PtMECHP was employed as an emission dopant in the OLED and the elctro-optical characteristics were investigated. The OLED was fabricated by vacuum deposition, and the layer-structure of device was ITO/NPD/PtMECHP(10%) in CBP/BCP/Alq/LiF/Al to exhibit brightness of 53 cd/m2 at 11 mA/cm2 and the external quantum efficiency of 1.2% at the same current density. The maximum EL band was detected at 650 nm with red phosphorescence. © 2007 Elsevier B.V. All rights reserved.1