1,720,987 research outputs found
Water Soluble Porphyrin based Solar Cell
No full textSecond Place winner of oral presentations at the 7th Annual Symposium on Graduate Research and Scholarly Projects (GRASP) held at the Marcus Welcome Center, Wichita State University, May 4, 2011.Research completed at the Department of ChemistryPorphyrins are organic chromophores with structure very close to naturally occurring pigment in leaves Chlorophyll. In addition, blood cells are red due to iron porphyrins. These versatile porphyrins are simple to synthesize and easy to modify for different applications. By introducing ionic charges they could be made water soluble. Water Soluble Porphyrins (WSP) are known to interact with DNA and their application includes medical and catalysis. Currently harvesting solar energy has become the top priority in research. Different types of porphyrins are also being studied at present as potential sensitizer. Here we report unique way of using 3 different types of WSP for harvesting sunlight. Our simple strategy is to utilize positively charged WSP to decorate negatively charged tin oxide nanoparticles. This kind of anion-cation interaction led to a strong interaction between them. We used UV-visible absorption spectroscopy, Fluorescence spectroscopy, to investigate their strength of interaction. In order, to understand their effectiveness in solar energy harvesting, we conducted photo electrochemical experiment on WSP modified tin oxide electrodes. Our results showed Incident Photon Conversion Efficiency (IPCE) around 91% at 450 nm. In other word, 91 out of 100 photons corresponding to 450 nm light is converted to current
Biomimetic solar cells
No full textPaper presented to the 6th Annual Symposium on Graduate Research and Scholarly Projects (GRASP) held at the Hughes Metropolitan Complex, Wichita State University, April 23, 2010.Research completed at the Department of Chemistry, College of Liberal Arts and SciencesEco friendly energy resources are becoming important due to the predicted oil depletion and soared CO₂ emission. Of available alternatives, solar energy finds special attention due to its vast availability and high power density of 1000 watts per square meter. Various mechanisms have been carefully employed to harvest the solar power including semiconductor silicon based photovoltaic, inorganic/organic dye sensitized or bulk hetero junction solar devices. Some of the latter devices utilize donor-acceptor supramolecular systems designed based on natural photosynthesis. Here, self-assembly of energy donor and acceptor are proved to be an important criterion.In the present study, we demonstrate an elegant method of self-assembly to modify TiO₂ surface using coordinating ligands followed by immobilization of a variety of photosensitizers and dyads. In this method, in addition of testing the photoelectrochemical behavior of different zinc tetrapyrroles, it also allowed us to introduce fairly complex structures involving more than one donor entities. Of all macrocycles studied, zinc porphyrin-ferrocene dyad markedly improved the current-voltage performance of the photoelectrochemical cell due to an electron transfer-hole migration mechanism. Incident photon-to-current efficiency values up to 37%, highest values ever reported for this type of electrodes was obtained for the electrode modified with the dyad, highlighting the importance of photocells built based on biomimetic principles for efficient harvesting of solar energy
Biomimetic solar cells
No full textThe project completed at the Wichita State University Department of Chemistry. Presented at the 7th Annual Capitol Graduate Research Summit, Topeka, KS, 2010Eco friendly energy resources are becoming important due to the predicted oil depletion and soared CO2 emission. Of available alternatives, solar energy finds special attention due to its vast availability and high power density of 1000 watts per square meter. Various mechanisms have been carefully employed to harvest the solar power including semiconductor silicon based photovoltaic, inorganic/organic dye sensitized or bulk heterojunction solar devices. Some of the latter devices utilize donor-acceptor supramolecular systems designed based on natural photosynthesis. Here, self-assembly of energy donor and acceptor is proved to be an important criterion.
In the present study, we demonstrate an elegant method of self-assembly to modify TiO2 surface using coordinating ligands followed by immobilization of a variety of photosensitizers and dyads. This method, in addition of testing the photoelectrochemical behavior of simple zinc tetrapyrroles also allows us to introduce fairly complex structures involving more than one donor and/or acceptor entities. As will be demonstrated, of all macrocycles studied, a biomimetic zinc porphyrin-ferrocene dyad markedly improves the current-voltage performance of the photoelectrochemical cell due to an electron transfer-hole migration mechanism. Incident photon-to-current efficiency value up to 37%, highest value reported for this type of devices is obtained for the electrode modified with the dyad, highlighting the importance of photocells built based on biomimetic principles for efficient harvesting of solar energy
Electropolymerization of Triphenylamine appended Zinc Porphyrin to form Porphyrin-Fullerene dyads at the electrode surface for photochemical studies
No full textPaper presented to the 5th Annual Symposium on Graduate Research and Scholarly Projects (GRASP) held at the Hughes Metropolitan Complex, Wichita State University, May 1, 2009.Research completed at Department of Chemistry College of Liberal Arts & SciencesPorphyrins with their attractive chemical properties qualify to seek potential technological applications including solar energy conversion, sensors, catalysts, biomedicine, molecular electronics, and photonics. Many of these applications require the Porphyrin to be on a surface, preferably in a conducting polymer matrix. Electro polymerization is a convenient method to produce such a conducting porphyrin polymer on the electrode surface. Compared to chemical methods, an electrochemical method is simple, and ensures good electrical conductivity across the interface. In the present study, we report electro polymerization of tetrakis N,N-diphenylaminoporphyrinatozinc(II) on the electrode surface. Subsequently, porphyrin-fullerene dyad is formed via axial coordination of a phenylimidazole appended fullerene. The film formation was monitored by electrochemical quartz crystal microbalance, and characterized by surface and optical methods. The newly formed donor-acceptor dyad was further utilized in photoelectrochemical applications to convert light energy directly into electricity
Molecular tetrads comprised of Zinc porphyrin-boron dipyrrin-triphenylamine triad to probe sequential energy/electron transfer events via axial ligation with C₆₀imidazole entity
Get PDFPaper presented to the 6th Annual Symposium on Graduate Research and Scholarly Projects (GRASP) held at the Hughes Metropolitan Complex, Wichita State University, April 23, 2010.Research completed at the Department of Chemistry, College of Arts and SciencesThere is a growing interest to mimic major processes in natural photosynthesis via artificial systems in order to harvest solar energy.
In the present study, we wish to report newly synthesized molecular triads comprised of Zinc porphyrin-boron dipyrrin-triphenylamine entities.Further, supramolecular tetrad is formed by axial ligation of imidazole functionalized fullerene. Systematic spectral, electrochemical and emission studies are performed to probe sequential energy transfer followed by electron transfer events in the newly synthesized triads. Computational studies using B3LYP/3-21G* are performed to arrive at the geometry and electronic structures. Photochemical study using time-resolved emission is performed to probe electron transfer events. Further, organic photocells are being built to directly convert light energy into electricity
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Get PDF“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Get PDFWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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