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Sample records for pheny1 porphyrin glassy

  1. Electrocatalytic behaviour and application of manganese porphyrin/gold nanoparticle- surface modified glassy carbon electrodes

    NASA Astrophysics Data System (ADS)

    Sebarchievici, I.; Tăranu, B. O.; Birdeanu, M.; Rus, S. F.; Fagadar-Cosma, E.

    2016-12-01

    The main purpose of this research was to obtain manganese porphyrin/gold nanoparticle-modified glassy carbon electrodes and to use them for the detection of H2O2. Two sets of modified electrodes were prepared by drop-cast deposition of 5,10,15,20-tetra(4-methyl-phenyl)porphyrinato manganese(III) chloride alone and of the same Mn-porphyrin and gold-colloid solution and comparatively characterized by Raman, UV-vis, ellipsometry, AFM and TEM microscopy, XPS and cyclic voltammetry. XPS spectrum recorded for GC_MnP_nAu modified electrode displayed the characteristic signals of gold nanoparticles. The optical parameters have greater values for GC_MnP_nAu in comparison with GC_MnP, due to increasing charge transfer efficiency. The MnP_nAu film mediates the electron transfer between H2O2 and GC, evidenced by an increase in the current intensity of the anodic peak, and facilitates the electrochemical regeneration of oxidized H2O2 at cathodic potentials. From the cyclic voltammetry experiments a linear relationship between H2O2 concentration vs oxidation and reduction currents was observed. The linear dependence between density of current and the square root of the scan rate indicates that the oxidation and reduction processes of H2O2 are diffusion controlled. The GC_MnP_nAu modified electrode shows great potential as electrochemical sensor for determination of hydrogen peroxide.

  2. Porphyrins

    NASA Astrophysics Data System (ADS)

    Gotelli, George R.; Wall, Jeffrey H.; Kabra, Pokar M.; Marton, Laurence J.

    Historically the term porphyria has been used since it was coined in 1871 to describe a purple colored material extracted from pathological feces (1). The first case of porphyria was reported in 1874, (2, 3), but until the 1930 Nobel Prize winning work of Hans Fischer on the synthesis of protoporphyrin, there was little more than academic interest in porphyrin analysis. During the forty years between 1930 and 1970, the biosynthetic pathways leading to the formation of heme, and the details of porphyrin metabolism, were elucidated. During this time quantitative methods for porphyrins in biological fluids used complex and laborious solvent extraction techniques, requiring large sample volumes and hours to complete. We now know that these methods only partially separated the complex mixture of porphyrins found in biological fluids. These solvent extraction procedures fractionated the porphyrins into two broad groups, uroporphyrins (octacarboxylic) and coproporphyrins (tetracarboxylic). However, intermediate carboxylated porphyrin containing 2, 3, 5, 6, and 7 carboxyl groups are now known to exist in normal and pathlogical excreta, which were not differentiated, but which were included in the two broad uroporphyrin and copropophyrin groups.

  3. Porphyrins

    DOEpatents

    Wijesekera, Tilak; Lyons, James E.; Ellis, Jr., Paul E.

    1996-01-01

    The invention comprises new compositions of matter, which are iron, manganese, cobalt or ruthenium complexes of porphyrins having hydrogen, haloalkyl or haloaryl groups in meso positions, two of the opposed meso atoms or groups being hydrogen or haloaryl, and two of the opposed meso atoms or groups being hydrogen or haloalkyl, but not all four of the meso atoms or groups being hydrogen. The invention also comprises new compositions of matter in which all four of the meso positions are substituted with haloalkyl groups and the beta positions are substituted with halogen atoms. A new method of synthesizing porphyrinogens is also provided. The novel compositions and others made according to the process of the invention are useful as hydrocarbon conversion catalysts; for example, for the oxidation of alkanes and the decomposition of hydroperoxides.

  4. Porphyrins

    DOEpatents

    Wijesekera, T.; Lyons, J.E.; Ellis, P.E. Jr.

    1996-11-05

    The invention comprises new compositions of matter, which are iron, manganese, cobalt or ruthenium complexes of porphyrins having hydrogen, haloalkyl or haloaryl groups in meso positions, two of the opposed meso atoms or groups being hydrogen or haloaryl, and two of the opposed meso atoms or groups being hydrogen or haloalkyl, but not all four of the meso atoms or groups being hydrogen. The invention also comprises new compositions of matter in which all four of the meso positions are substituted with haloalkyl groups and the beta positions are substituted with halogen atoms. A new method of synthesizing porphyrinogens is also provided. The novel compositions and others made according to the process of the invention are useful as hydrocarbon conversion catalysts; for example, for the oxidation of alkanes and the decomposition of hydroperoxides.

  5. Determination of serotonin on a glassy carbon electrode modified by electropolymerization of meso-tetrakis(2-aminophenyl)porphyrin and single walled carbon nanotubes.

    PubMed

    Kim, Seul Ki; Ahmed, Mohammad Shamsuddin; Jeong, Haesang; You, Jung-Min; Jeon, Seungwon

    2011-03-01

    A chemically modified electrode [poly(TAPP)-SWNT/GCE] was prepared by electropolymerization of meso-tetrakis(2-aminophenyl)porphyrin (TAPP)-single walled carbon nanotubes (SWNT) on the surface of a glassy carbon electrode (GCE). This modified electrode was employed as an electrochemical biosensor for the determination of serotonin concentration and exhibited a typical enhance effect on the current response of serotonin and lower oxidation overpotential. The biosensor was very effective to determined 5-HT in a mixture. The linear response was in the range 2.0 x 10(-7) to 1.0 x 10(-5) M, with a correlation coefficient of 0.999 [i(p)(microA) = 3.406 C (microM)+0.132] on the anodic current, with a detection limit of 1 x 10(-9) M. Due to the relatively low currents and different potentials in the electrochemical responses to ascorbic acid and dopamine, the modified electrode is a useful and effective sensing device for the selective and sensitive serotonin determination in the presence of ascorbic acid and dopamine.

  6. Gold nanoparticles decorated on cobalt porphyrin-modified glassy carbon electrode for the sensitive determination of nitrite ion.

    PubMed

    Muthukumar, Palanisamy; Abraham John, S

    2014-05-01

    The present study reports the electrochemical determination of nitrite ion using citrate-gold nanoparticles (cit-AuNPs) decorated on meso-tetra(para-aminophenyl)porphyrinatocobalt(II) (Co(II)MTpAP) self-assembled glassy carbon electrode (GCE). The decoration of cit-AuNPs on Co(II)MTpAP was achieved with the aid of amine groups present on the surface of the self-assembled monolayer (SAM) of Co(II)MTpAP. The SEM image shows that the cit-AuNPs were densely packed on Co(II)MTpAP. The AuNPs decorated electrode was successfully used for the determination of nitrite ion. The cit-AuNPs decorated electrode not only shifted nitrite ion oxidation potential towards less positive potential but also greatly enhanced its current when compared to bare and Co(II)MTpAP SAM modified electrodes. The amperometric current increases linearly while increasing the concentration of nitrite ion ranging from 0.5×10(-6) to 4.7×10(-3) M and the detection limit was found to be 60 nM (S/N=3). Further, the modified electrode was successfully used to determine nitrite ion in the presence of 200-fold excess of common interferents such as Na+, NO3-, I-, K+, CO3(2-), Ca2+, SO4(2-), NH4+, Cl- and glucose. The practical application of the cit-AuNPs decorated electrode was demonstrated by determining nitrite ion in water samples.

  7. Porphyrin Tests

    MedlinePlus

    ... Table adapted from: "Iron and porphyrin metabolism," Clinical Chemistry: Theory, Analysis and Correlation , courtesy of William E. ... Health Professionals ©2001 - by American Association for Clinical Chemistry • Contact Us | Terms of Use | Privacy We comply ...

  8. Synthesis of porphyrin nanostructures

    DOEpatents

    Fan, Hongyou; Bai, Feng

    2014-10-28

    The present disclosure generally relates to self-assembly methods for generating porphyrin nanostructures. For example, in one embodiment a method is provided that includes preparing a porphyrin solution and a surfactant solution. The porphyrin solution is then mixed with the surfactant solution at a concentration sufficient for confinement of the porphyrin molecules by the surfactant molecules. In some embodiments, the concentration of the surfactant is at or above its critical micelle concentration (CMC), which allows the surfactant to template the growth of the nanostructure over time. The size and morphology of the nanostructures may be affected by the type of porphyrin molecules used, the type of surfactant used, the concentration of the porphyrin and surfactant the pH of the mixture of the solutions, and the order of adding the reagents to the mixture, to name a few variables.

  9. Functionalized expanded porphyrins

    DOEpatents

    Sessler, Jonathan L; Pantos, Patricia J

    2013-11-12

    Disclosed are functionalized expanded porphyrins that can be used as spectrometric sensors for high-valent actinide cations. The disclosed functionalized expanded porphyrins have the advantage over unfunctionalized systems in that they can be immobilized via covalent attachment to a solid support comprising an inorganic or organic polymer or other common substrates. Substrates comprising the disclosed functionalized expanded porphyrins are also disclosed. Further, disclosed are methods of making the disclosed compounds (immobilized and free), methods of using them as sensors to detect high valent actinides, devices that comprise the disclosed compounds, and kits.

  10. Soluble porphyrin polymers

    DOEpatents

    Gust, Jr., John Devens; Liddell, Paul Anthony

    2015-07-07

    Porphyrin polymers of Structure 1, where n is an integer (e.g., 1, 2, 3, 4, 5, or greater) ##STR00001## are synthesized by the method shown in FIGS. 2A and 2B. The porphyrin polymers of Structure 1 are soluble in organic solvents such as 2-MeTHF and the like, and can be synthesized in bulk (i.e., in processes other than electropolymerization). These porphyrin polymers have long excited state lifetimes, making the material suitable as an organic semiconductor for organic electronic devices including transistors and memories, as well as solar cells, sensors, light-emitting devices, and other opto-electronic devices.

  11. Synthetic Porphyrins and Metalloporphyrins

    DTIC Science & Technology

    1976-12-10

    last type of complexes to be considered are the sterically hindered macrocycles . Examples of this class of complexes exe the capped" or "crow henhe...group IV metalloporphyrins, phthalocyanines and correspond- log Ru"l and Reol complexes induce smaller shifts than the lanthanides (about 8 ppm vs 25...ROLE W1r ROLE wTr ROLE Wt * ~Synthe tic Porphyrins Synthetic lMetalloporphyrinsj tetrapyrrole macrocycles "Inatural" porphyrins * j meso

  12. Electrocatalytic miRNA Detection Using Cobalt Porphyrin-Modified Reduced Graphene Oxide

    PubMed Central

    De Souza, Camille; Zrig, Samia; Wang, Dengjun; Pham, Minh-Chau; Piro, Benoit

    2014-01-01

    Metalated porphyrins have been described to bind nucleic acids. Additionally, cobalt porphyrins present catalytic properties towards oxygen reduction. In this work, a carboxylic acid-functionalized cobalt porphyrin was physisorbed on reduced graphene oxide, then immobilized on glassy carbon electrodes. The carboxylic groups were used to covalently graft amino-terminated oligonucleotide probes which are complementary to a short microRNA target. It was shown that the catalytic oxygen electroreduction on cobalt porphyrin increases upon hybridization of miRNA strand (“signal-on” response). Current changes are amplified compared to non-catalytic amperometric system. Apart from oxygen, no added reagent is necessary. A limit of detection in the sub-nanomolar range was reached. This approach has never been described in the literature. PMID:24915180

  13. Electrically conducting porphyrin and porphyrin-fullerene electropolymers

    DOEpatents

    Gust, Jr., John Devens; Liddell, Paul Anthony; Gervaldo, Miguel Andres; Bridgewater, James Ward; Brennan, Bradley James; Moore, Thomas Andrew; Moore, Ana Lorenzelli

    2014-03-11

    Compounds with aryl ring(s) at porphyrin meso position(s) bearing an amino group in position 4 relative to the porphyrin macrocycle, and at least one unsubstituted 5 (hydrogen-bearing) meso position with the 10-, 15-, and/or 20-relationship to the aryl ring bearing the amino group, and metal complexes thereof, feature broad spectral absorption throughout the visible region. These compounds are electropolymerized to form electrically conducting porphyrin and porphyrin-fullerene polymers that are useful in photovoltaic applications. The structure of one such electrically conducting porphyrin polymer is shown below. ##STR00001##

  14. Porphyrins, porphyrin metabolism and porphyrias. I. Update.

    PubMed

    Thunell, S

    2000-11-01

    The biosynthesis of porphyrins is one of the most conserved parthways known, about the same sequence of reactions taking place in all species. By associating different metals, porphyrins give rise to the "pigments of life": chlorophyll, haem and cobalamin. The unique tetrapyrrolic structure enables it to function in an array of reactions as a single electron carrier and as a catalyst for redox reactions. In this capacity, it constitutes the prosthetic group of enzymes participating in cellular respiration, in conversion reactions involving steroids and lipophilic xenobiotics, in protective mechanisms directed against oxidative stress and in pathways providing central messenger molecules. The formation of haem is accomplished by a sequence of eight dedicated enzymes encoded by different genes, some being active in ubiquitous as well as in erythroid isoforms. Large differences between the participating enzymes with regard to catalytic power, with low capacity steps positioned early in the catalytic chain, constitute a bar against substrate overloading of enzymes processing porphyrins, thus preventing accumulation in the body of these phototoxic compounds under physiological conditions. Most of the haem in the body is produced by the liver and bone marrow, but the mechanisms applied for the control of the synthesis differ between the two organs. The extremely potent hemeprotein enzymes formed in the liver are rapidly turned over in response to current metabolic needs. They have half-lives in the order of minutes or hours and are restored by fast-acting mechanisms for the de novo synthesis, when needed. Uninterrupted and instant availability of the compound is secured by acute deinhibition of the initial enzyme of the synthetic chain, ubiquitous 5-aminolevulinate synthase (ALAS-1), in response to drain of the free cellular haem pool caused by prevailing demands for hemeproteins or by increased catabolism of the compound. In contrast, in the erythroid progenitor cell

  15. Porphyrin analysis and coal rank. A porphyrin index of coalification

    SciTech Connect

    Bonnett, R.; Hughes, P.S. )

    1989-03-01

    The stable aromatic nature of the porphyrin nucleus might be expected to make biomarkers containing it excellent bases for the study of the maturation of sedimentary deposits. Thus the porphyrin macroring can be thought of as an inert carrier of information contained in eight or nine peripheral substituents the increased cracking of which would reveal increased maturation. For non-migrating fossil fuels such as lignite and coal, a relationship between the distribution of porphyrin molecular mass and coal rank would result. This idea is examined for a series of well characterized bituminous coals from the British Carboniferous. Extraction of porphyrins and metalloporphyrins is carried out with methanolic sulfuric acid, and the gallium porphyrin concentrates are analyzed both by HPLC and by mass spectrometry. A Porphyrin Index of Coalification (PIC Number) is derived and related to other maturity indices. Within the range of examples chosen it appears to provide a useful scientifically-based indicator of coal maturity.

  16. Porphyrin-sensitized solar cells.

    PubMed

    Li, Lu-Lin; Diau, Eric Wei-Guang

    2013-01-07

    Nature has chosen chlorophylls in plants as antennae to harvest light for the conversion of solar energy in complicated photosynthetic processes. Inspired by natural photosynthesis, scientists utilized artificial chlorophylls - the porphyrins - as efficient centres to harvest light for solar cells sensitized with a porphyrin (PSSC). After the first example appeared in 1993 of a porphyrin of type copper chlorophyll as a photosensitizer for PSSC that achieved a power conversion efficiency of 2.6%, no significant advance of PSSC was reported until 2005; beta-linked zinc porphyrins were then reported to show promising device performances with a benchmark efficiency of 7.1% reported in 2007. Meso-linked zinc porphyrin sensitizers in the first series with a push-pull framework appeared in 2009; the best cell performed comparably to that of a N3-based device, and a benchmark 11% was reported for a porphyrin sensitizer of this type in 2010. With a structural design involving long alkoxyl chains to envelop the porphyrin core to suppress the dye aggregation for a push-pull zinc porphyrin, the PSSC achieved a record 12.3% in 2011 with co-sensitization of an organic dye and a cobalt-based electrolyte. The best PSSC system exhibited a panchromatic feature for light harvesting covering the visible spectral region to 700 nm, giving opportunities to many other porphyrins, such as fused and dimeric porphyrins, with near-infrared absorption spectral features, together with the approach of molecular co-sensitization, to enhance the device performance of PSSC. According to this historical trend for the development of prospective porphyrin sensitizers used in PSSC, we review systematically the progress of porphyrins of varied kinds, and their derivatives, applied in PSSC with a focus on reports during 2007-2012 from the point of view of molecular design correlated with photovoltaic performance.

  17. Stacked antiaromatic porphyrins

    PubMed Central

    Nozawa, Ryo; Tanaka, Hiroko; Cha, Won-Young; Hong, Yongseok; Hisaki, Ichiro; Shimizu, Soji; Shin, Ji-Young; Kowalczyk, Tim; Irle, Stephan; Kim, Dongho; Shinokubo, Hiroshi

    2016-01-01

    Aromaticity is a key concept in organic chemistry. Even though this concept has already been theoretically extrapolated to three dimensions, it usually still remains restricted to planar molecules in organic chemistry textbooks. Stacking of antiaromatic π-systems has been proposed to induce three-dimensional aromaticity as a result of strong frontier orbital interactions. However, experimental evidence to support this prediction still remains elusive so far. Here we report that close stacking of antiaromatic porphyrins diminishes their inherent antiaromaticity in the solid state as well as in solution. The antiaromatic stacking furthermore allows a delocalization of the π-electrons, which enhances the two-photon absorption cross-section values of the antiaromatic porphyrins. This feature enables the dynamic switching of the non-linear optical properties by controlling the arrangement of antiaromatic π-systems on the basis of intermolecular orbital interactions. PMID:27901014

  18. Stacked antiaromatic porphyrins

    NASA Astrophysics Data System (ADS)

    Nozawa, Ryo; Tanaka, Hiroko; Cha, Won-Young; Hong, Yongseok; Hisaki, Ichiro; Shimizu, Soji; Shin, Ji-Young; Kowalczyk, Tim; Irle, Stephan; Kim, Dongho; Shinokubo, Hiroshi

    2016-11-01

    Aromaticity is a key concept in organic chemistry. Even though this concept has already been theoretically extrapolated to three dimensions, it usually still remains restricted to planar molecules in organic chemistry textbooks. Stacking of antiaromatic π-systems has been proposed to induce three-dimensional aromaticity as a result of strong frontier orbital interactions. However, experimental evidence to support this prediction still remains elusive so far. Here we report that close stacking of antiaromatic porphyrins diminishes their inherent antiaromaticity in the solid state as well as in solution. The antiaromatic stacking furthermore allows a delocalization of the π-electrons, which enhances the two-photon absorption cross-section values of the antiaromatic porphyrins. This feature enables the dynamic switching of the non-linear optical properties by controlling the arrangement of antiaromatic π-systems on the basis of intermolecular orbital interactions.

  19. [Formylation of porphyrin platinum complexes].

    PubMed

    Rumiantseva, V D; Konovalenko, L I; Nagaeva, E A; Mironov, A F

    2005-01-01

    The formylation reaction of platinum complexes of beta-unsubstituted porphyrins was studied. The interaction of deuteroporphyrin IX derivatives with the Vilsmeyer reagent led to the selective formylation of their macrocycles in the beta position. The resulting formyl derivatives of the porphyrins are of interest for fluorescent immunoassay.

  20. Molecular Simulations of Porphyrins and Heme Proteins

    SciTech Connect

    SHELNUTT,JOHN A.

    2000-01-18

    An overview of the use of classical mechanical molecular simulations of porphyrins, hydroporphyrins, and heme proteins is given. The topics cover molecular mechanics calculations of structures and conformer energies of porphyrins, energies of barriers for interconversion between stable conformers, molecular dynamics of porphyrins and heme proteins, and normal-coordinate structural analysis of experimental and calculated porphyrin structures. Molecular mechanics and dynamics are currently a fertile area of research on porphyrins. In the future, other computational methods such as Monte Carlo simulations, which have yet to be applied to porphyrins, will come into use and open new avenues of research into molecular simulations of porphyrins.

  1. Heteroatom-Containing Porphyrin Analogues.

    PubMed

    Chatterjee, Tamal; Shetti, Vijayendra S; Sharma, Ritambhara; Ravikanth, Mangalampalli

    2017-02-22

    The heteroatom-containing porphyrin analogues or core-modified porphyrins that resulted from the replacement of one or two pyrrole rings with other five-membered heterocycles such as furan, thiophene, selenophene, tellurophene, indene, phosphole, and silole are highly promising macrocycles and exhibit quite different physicochemical properties compared to regular azaporphyrins. The properties of heteroporphyrins depend on the nature and number of different heterocycle(s) present in place of pyrrole ring(s). The heteroporphyrins provide unique and unprecedented coordination environments for metals. Unlike regular porphyrins, the monoheteroporphyrins are known to stabilize metals in unusual oxidation states such as Cu and Ni in +1 oxidation states. The diheteroporphyrins, which are neutral macrocycles without ionizable protons, also showed interesting coordination chemistry. Thus, significant progress has been made in last few decades on core-modified porphyrins in terms of their synthesis, their use in building multiporphyrin arrays for light-harvesting applications, their use as ligands to form interesting metal complexes, and also their use for several other studies. The synthetic methods available in the literature allow one to prepare mono- and diheteroporphyrins and their functionalized derivatives, which were used extensively to prepare several covalent and noncovalent heteroporphyrin-based multiporphyrin arrays. The methods are also developed to synthesize different hetero analogues of porphyrin derivatives such as heterocorroles, heterochlorins, heterocarbaporphyrinoids, heteroatom-substituted confused porphyrins, and so on. This Review summarizes the key developments that have occurred in heteroporphyrin chemistry over the last four decades.

  2. Porphyrins at interfaces

    NASA Astrophysics Data System (ADS)

    Auwärter, Willi; Écija, David; Klappenberger, Florian; Barth, Johannes V.

    2015-02-01

    Porphyrins and other tetrapyrrole macrocycles possess an impressive variety of functional properties that have been exploited in natural and artificial systems. Different metal centres incorporated within the tetradentate ligand are key for achieving and regulating vital processes, including reversible axial ligation of adducts, electron transfer, light-harvesting and catalytic transformations. Tailored substituents optimize their performance, dictating their arrangement in specific environments and mediating the assembly of molecular nanoarchitectures. Here we review the current understanding of these species at well-defined interfaces, disclosing exquisite insights into their structural and chemical properties, and also discussing methods by which to manipulate their intramolecular and organizational features. The distinct characteristics arising from the interfacial confinement offer intriguing prospects for molecular science and advanced materials. We assess the role of surface interactions with respect to electronic and physicochemical characteristics, and describe in situ metallation pathways, molecular magnetism, rotation and switching. The engineering of nanostructures, organized layers, interfacial hybrid and bio-inspired systems is also addressed.

  3. Glassy correlations in nematic elastomers

    NASA Astrophysics Data System (ADS)

    Lu, Bing; Goldbart, Paul; Mao, Xiaoming

    2009-03-01

    We address the physical properties of an isotropic melt or solution of nematogenic polymers that is then cross-linked beyond the vulcanization point. To do this, we construct a replica Landau theory involving a coupled pair of order- parameter fields: one describing vulcanization, the other describing local nematic order. Thermal nematic fluctuations, present at the time of cross-linking, are trapped by cross- linking into the vulcanized network. The resulting glassy nematic fluctuations are analyzed in the Gaussian approximation in two regimes. When the localization length is shorter than the thermal nematic correlation length, the nematic correlations are well captured as glassy correlations. In the opposite regime, fluctuations in the positions of the localized polymers partially wash out the glassy nematic correlations.

  4. Iron Nitrosyl “Natural” Porphyrinates: Does the Porphyrin Matter?

    PubMed Central

    2015-01-01

    The synthesis and spectroscopic characterization of three five-coordinate nitrosyliron(II) complexes, [Fe(Porph)(NO)], are reported. These three nitrosyl derivatives, where Porph represents protoporphyrin IX dimethyl ester, mesoporphyrin IX dimethyl ester, or deuteroporphyrin IX dimethyl ester, display notable differences in their properties relative to the symmetrical synthetic porphyrins such as OEP and TPP. The N–O stretching frequencies are in the range of 1651–1660 cm–1, frequencies that are lower than those of synthetic porphyrin derivatives. Mössbauer spectra obtained in both zero and applied magnetic field show that the quadrupole splitting values are slightly larger than those of known synthetic porphyrins. The electronic structures of these naturally occurring porphyrin derivatives are thus seen to be consistently different from those of the synthetic derivatives, the presumed consequence of the asymmetric peripheral substituent pattern. The molecular structure of [Fe(PPIX-DME)(NO)] has been determined by X-ray crystallography. Although disorder of the axial nitrosyl ligand limits the structural quality, this derivative appears to show the same subtle structural features as previously characterized five-coordinate nitrosyls. PMID:24620710

  5. Fusing Porphyrins and Phospholes: Synthesis and Analysis of a Phosphorus-Containing Porphyrin.

    PubMed

    Higashino, Tomohiro; Yamada, Tomoki; Sakurai, Tsuneaki; Seki, Shu; Imahori, Hiroshi

    2016-09-26

    A phosphole-fused porphyrin dimer, as a representative of a new class of porphyrins with a phosphorus atom, was synthesized for the first time. The porphyrin dimer exhibits remarkably broadened absorption, indicating effective π-conjugation over the two porphyrins through the phosphole moiety. The porphyrin dimer possesses excellent electron-accepting character, which is comparable to that of a representative electron-accepting material, [60]PCBM. These results provide access to a new class of phosphorus-containing porphyrins with unique optoelectronic properties.

  6. Self-Organized Porphyrinic Materials

    PubMed Central

    Drain, Charles Michael; Varotto, Alessandro; Radivojevic, Ivana

    2009-01-01

    The self-assembly and self-organization of porphyrins and related macrocycles enables the bottom-up fabrication of photonic materials for fundamental studies of the photophysics of these materials and for diverse applications. This rapidly developing field encompasses a broad range of disciplines including molecular design and synthesis, materials formation and characterization, and the design and evaluation of devices. Since the self-assembly of porphyrins by electrostatic interactions in the late 1980s to the present, there has been an ever increasing degree of sophistication in the design of porphyrins that self-assemble into discrete arrays or self-organize into polymeric systems. These strategies exploit ionic interactions, hydrogen bonding, coordination chemistry, and dispersion forces to form supramolecular systems with varying degrees of hierarchical order. This review concentrates on the methods to form supramolecular porphyrinic systems by intermolecular interactions other than coordination chemistry, the characterization and properties of these photonic materials, and the prospects for using these in devices. The review is heuristically organized by the predominant intermolecular interactions used and emphasizes how the organization affects properties and potential performance in devices. PMID:19253946

  7. Thermal expansion of glassy polymers.

    PubMed

    Davy, K W; Braden, M

    1992-01-01

    The thermal expansion of a number of glassy polymers of interest in dentistry has been studied using a quartz dilatometer. In some cases, the expansion was linear and therefore the coefficient of thermal expansion readily determined. Other polymers exhibited non-linear behaviour and values appropriate to different temperature ranges are quoted. The linear coefficient of thermal expansion was, to a first approximation, a function of both the molar volume and van der Waal's volume of the repeating unit.

  8. Supramolecular Allosteric Cofacial Porphyrin Complexes

    SciTech Connect

    Oliveri, Christopher G.; Gianneschi, Nathan C.; Nguyen, Son Binh T.; Mirkin, Chad A.; Stern, Charlotte L.; Wawrzak, Zdzislaw; Pink, Maren

    2008-04-12

    Nature routinely uses cooperative interactions to regulate cellular activity. For years, chemists have designed synthetic systems that aim toward harnessing the reactivity common to natural biological systems. By learning how to control these interactions in situ, one begins to allow for the preparation of man-made biomimetic systems that can efficiently mimic the interactions found in Nature. To this end, we have designed a synthetic protocol for the preparation of flexible metal-directed supramolecular cofacial porphyrin complexes which are readily obtained in greater than 90% yield through the use of new hemilabile porphyrin ligands with bifunctional ether-phosphine or thioether-phosphine substituents at the 5 and 15 positions on the porphyrin ring. The resulting architectures contain two hemilabile ligand-metal domains (Rh{sup I} or Cu{sup I} sites) and two cofacially aligned porphyrins (Zn{sup II} sites), offering orthogonal functionalities and allowing these multimetallic complexes to exist in two states, 'condensed' or 'open'. Combining the ether-phosphine ligand with the appropriate Rh{sup I} or Cu{sup I} transition-metal precursors results in 'open' macrocyclic products. In contrast, reacting the thioether-phosphine ligand with RhI or CuI precursors yields condensed structures that can be converted into their 'open' macrocyclic forms via introduction of additional ancillary ligands. The change in cavity size that occurs allows these structures to function as allosteric catalysts for the acyl transfer reaction between X-pyridylcarbinol (where X = 2, 3, or 4) and 1-acetylimidazole. For 3- and 4-pyridylcarbinol, the 'open' macrocycle accelerates the acyl transfer reaction more than the condensed analogue and significantly more than the porphyrin monomer. In contrast, an allosteric effect was not observed for 2-pyridylcarbinol, which is expected to be a weaker binder and is unfavorably constrained inside the macrocyclic cavity.

  9. The Antimicrobial Activity of Porphyrin Attached Polymers

    NASA Astrophysics Data System (ADS)

    Thompson, Lesley

    2008-03-01

    We are interested in testing the antimicrobial activity of a porphyrin that is attached to a polymer. The porphyrin (5-(4-carboxyphenyl)-10,15,20-tris-(4-pryridyl)) was synthesized from methyl 4-formyl benzoate, 4-pyridinecarboxaldehyde, and pyrrole and attached to a copolymer of polystyrene/poly(vinyl benzyl chloride), which was synthesized by free radical polymerization. The antimicrobial activity of the polymer-attached porphyrin was then determined for gram-negative E. Coli grown to 0.80 OD. In this procedure, glass slides were coated with polymer-attached porphyrin via dip-coating, and the E. Coli bacteria were plated in Luria Broth media. The plates were subsequently exposed to light overnight before they were incubated as porphyrins act as photo-sensitizers when irradiated with light. The polymer-attached porphyrin did exhibit antimicrobial activity and parameters that affect its efficiency will be discussed.

  10. Porphyrin coordination polymer nanospheres and nanorods

    DOEpatents

    Wang, Zhongchun; Shelnutt, John A.; Medforth, Craig J.

    2013-09-10

    A porphyrin coordination polymer nanostructure comprising a network of pyridyl porphyrin molecules and coordinating metal ions coordinatively bound through the pyridyl groups. In some embodiments, the porphyrins are metalloporphyrins. A variety of nanostructures are formed by the network polymer, including nanospheres, polygonal nanostructures, nanorods, and nanofibers, depending on a variety of factors including coordination metal ion, porphyrin type, metal of the metalloporphyrin, and degree of agitation during nanostructure formation. Reduction of coordinating metal ions may be used to form metal nanoparticles on the coordination polymer nanostructure.

  11. Porphyrin coordination polymer nanospheres and nanorods

    SciTech Connect

    Wang, Zhongchun; Shelnutt, John A.; Medforth, Craig J.

    2012-12-04

    A porphyrin coordination polymer nanostructure comprising a network of pyridyl porphyrin molecules and coordinating metal ions coordinatively bound through the pyridyl groups. In some embodiments, the porphyrins are metalloporphyrins. A variety of nanostructures are formed by the network polymer, including nanospheres, polygonal nanostructures, nanorods, and nanofibers, depending on a variety of factors including coordination metal ion, porphyrin type, metal of the metalloporphyrin, and degree of agitation during nanostructure formation. Reduction of coordinating metal ions may be used to form metal nanoparticles on the coordination polymer nanostructure.

  12. Controlling porphyrin nanoarchitectures at solid interfaces.

    PubMed

    Hill, Jonathan P; Xie, Yongshu; Akada, Misaho; Wakayama, Yutaka; Shrestha, Lok Kumar; Ji, Qingmin; Ariga, Katsuhiko

    2013-06-18

    Two complementary examples of porphyrin nanoarchitectonics are presented. The fabrication of binary molecular monolayers using two different porphyrin molecules, tetrakis(3,5-di-t-butyl-4-hydroxyphenyl)porphyrin (1) and tetrakis(4-pyridyl)porphyrin (2), by deposition in ultrahigh vacuum was demonstrated. Two unusual heteromolecular monolayer structures were observed, with one exhibiting good separation of 1 molecules within the monolayer. Also, a synthetic nanoarchitectonic approach was used to prepare self-assembled molecular nanowires at a mica substrate. The nanowires could be observed to grow using atomic force microscopy (AFM), and the network structures of the nanowires could be influenced by manipulation using the AFM probe tip.

  13. Search for porphyrins in lunar dust.

    PubMed

    Hodgson, G W; Peterson, E; Kvenvolden, K A; Bunnenberg, E; Halpern, B; Ponnamperuma, C

    1970-01-30

    Evidence for porphyrins was obtained in the Apollo 11 bulk sample of lunar dust by fluorescence spectrometry and analytical demetallation. The indicated porphyrins showed major fluorescence excitation at 390 nanometers. Abundance was about 10(-10) gram of porphyrin per gram of dust. Similar pigments were found in exhaust products from tests of a lunar descent engine. The similarity of results suggests that most if not all of the indicated porphyrin aggregate of the lunar sample probably was synthesized from rocket fuel during the landing of the lunar module. These compounds may be the product of a novel high-temperature synthesis of cosmochemical interest.

  14. Porphyrin Microparticles for Biological and Biomedical Applications

    NASA Astrophysics Data System (ADS)

    Huynh, Elizabeth

    Lipids are one of the critical building blocks of life, forming the plasma membrane of cells. In addition, porphyrins also play an equally important role in life, for example, through carrying oxygen in blood. The importance of both these components is evident through the biological and biomedical applications of supramolecular structures generated from lipids and porphyrins. This thesis investigates new porphyrin microparticles based on porphyrin-lipid architecture and their potential applications in biology and medicine. In Chapter 1, a background on lipid and porphyrin-based supramolecular structures is presented and design considerations for generating multifunctional agents. Chapter 2 describes the generation of a monolayer porphyrin microparticle as a dual-modal ultrasound and photoacoustic contrast agent and subsequently, a trimodal ultrasound, photoacoustic and fluorescence contrast agent. Chapter 3 examines the optical and morphological response of these multimodality ultrasound-based contrast agents to low frequency, high duty cycle ultrasound that causes the porphyrin microparticles to convertinto nanoparticles. Chapter 4 examines the generation of bilayer micrometer-sized porphyrin vesicles and their properties. Chapter 5 presents a brief summary and potential future directions. Although these microscale structures are similar in structure, the applications of these structures greatly differ with potential applications in biology and also imaging and therapy of disease. This thesis aims to explore and demonstrate the potential of new simplified, supramolecular structures based on one main building block, porphyrin-lipid.

  15. Glassy features of crystal plasticity

    NASA Astrophysics Data System (ADS)

    Lehtinen, Arttu; Costantini, Giulio; Alava, Mikko J.; Zapperi, Stefano; Laurson, Lasse

    2016-08-01

    Crystal plasticity occurs by deformation bursts due to the avalanchelike motion of dislocations. Here we perform extensive numerical simulations of a three-dimensional dislocation dynamics model under quasistatic stress-controlled loading. Our results show that avalanches are power-law distributed and display peculiar stress and sample size dependence: The average avalanche size grows exponentially with the applied stress, and the amount of slip increases with the system size. These results suggest that intermittent deformation processes in crystalline materials exhibit an extended critical-like phase in analogy to glassy systems instead of originating from a nonequilibrium phase transition critical point.

  16. Ending Aging in Super Glassy Polymer Membranes

    SciTech Connect

    Lau, CH; Nguyen, PT; Hill, MR; Thornton, AW; Konstas, K; Doherty, CM; Mulder, RJ; Bourgeois, L; Liu, ACY; Sprouster, DJ; Sullivan, JP; Bastow, TJ; Hill, AJ; Gin, DL; Noble, RD

    2014-04-16

    Aging in super glassy polymers such as poly(trimethylsilylpropyne) (PTMSP), poly(4-methyl-2-pentyne) (PMP), and polymers with intrinsic microporosity (PIM-1) reduces gas permeabilities and limits their application as gas-separation membranes. While super glassy polymers are initially very porous, and ultra-permeable, they quickly pack into a denser phase becoming less porous and permeable. This age-old problem has been solved by adding an ultraporous additive that maintains the low density, porous, initial stage of super glassy polymers through absorbing a portion of the polymer chains within its pores thereby holding the chains in their open position. This result is the first time that aging in super glassy polymers is inhibited whilst maintaining enhanced CO2 permeability for one year and improving CO2/N-2 selectivity. This approach could allow super glassy polymers to be revisited for commercial application in gas separations.

  17. Synthesis, optical and electrochemical properties of Zn-porphyrin for dye sensitized solar cell applications

    NASA Astrophysics Data System (ADS)

    Kotteswaran, S.; Pandian, M. Senthil; Ramasamy, P.

    2016-05-01

    Zn-Porphyrin dye has been synthesized by the reaction between aldehydes and pyrrole. The dye structure was confirmed by 1H NMR, 13C NMR spectrum. The functional group of the dye molecule was confirmed by FTIR spectrum. The UV-Vis-NIR absorption spectrum of Zn-Porphyrin in DMF solution was recorded in spectrophotometer. The UV-Vis NIR spectrum of dye exhibits a strong Soret band and Q-band. Cyclic Voltammograms were obtained with three electrode systems: Pt as counter electrode, saturated calomel used as a reference electrode and glassy carbon as working electrode at a scan rate of 100 mV/s. The curves recorded the oxidation of 0.5 mM compound Zn-Porphyrin in a dichloromethane solution containing 0.1M TBAP as supporting electrolyte, reveal two successive quasi reversible redox couples with the first anodic and cathodic peak potentials of -0.2 V and -1 V. The second anodic and cathodic peak potentials are 0.82 V and 0.01 V respectively.

  18. Preparation of porphyrins and their metal complexes

    DOEpatents

    Ellis, Jr., Paul E.; Langdale, Wayne A.

    1997-01-01

    A hydroxyl-containing pyrrolic compound having a hydroxyl group or a hydroxyl-containing group in the 2-position, optionally substituted in the beta positions, is condensed in an acidified two immiscible phase solvent system to produce excellent yields of the corresponding porphyrin or metal porphyrin.

  19. Preparation of porphyrins and their metal complexes

    DOEpatents

    Ellis, P.E. Jr.; Langdale, W.A.

    1997-08-19

    A hydroxyl-containing pyrrolic compound having a hydroxyl group or a hydroxyl-containing group in the 2-position, optionally substituted in the beta positions, is condensed in an acidified two immiscible phase solvent system to produce excellent yields of the corresponding porphyrin or metal porphyrin.

  20. Hierarchical cooperative binary ionic porphyrin nanocomposites.

    PubMed

    Tian, Yongming; Busani, Tito; Uyeda, Gregory H; Martin, Kathleen E; van Swol, Frank; Medforth, Craig J; Montaño, Gabriel A; Shelnutt, John A

    2012-05-18

    Cooperative binary ionic (CBI) solids comprise a versatile new class of opto-electronic and catalytic materials consisting of ionically self-assembled pairs of organic anions and cations. Herein, we report CBI nanocomposites formed by growing nanoparticles of one type of porphyrin CBI solid onto a second porphyrin CBI substructure with complementary functionality.

  1. Syntheses and Functionalizations of Porphyrin Macrocycles

    PubMed Central

    Vicente, Maria da G.H.; Smith, Kevin M.

    2014-01-01

    Porphyrin macrocycles have been the subject of intense study in the last century because they are widely distributed in nature, usually as metal complexes of either iron or magnesium. As such, they serve as the prosthetic groups in a wide variety of primary metabolites, such as hemoglobins, myoglobins, cytochromes, catalases, peroxidases, chlorophylls, and bacteriochlorophylls; these compounds have multiple applications in materials science, biology and medicine. This article describes current methodology for preparation of simple, symmetrical model porphyrins, as well as more complex protocols for preparation of unsymmetrically substituted porphyrin macrocycles similar to those found in nature. The basic chemical reactivity of porphyrins and metalloporphyrin is also described, including electrophilic and nucleophilic reactions, oxidations, reductions, and metal-mediated cross-coupling reactions. Using the synthetic approaches and reactivity profiles presented, eventually almost any substituted porphyrin system can be prepared for applications in a variety of areas, including in catalysis, electron transport, model biological systems and therapeutics. PMID:25484638

  2. Cooperative strings and glassy interfaces.

    PubMed

    Salez, Thomas; Salez, Justin; Dalnoki-Veress, Kari; Raphaël, Elie; Forrest, James A

    2015-07-07

    We introduce a minimal theory of glass formation based on the ideas of molecular crowding and resultant string-like cooperative rearrangement, and address the effects of free interfaces. In the bulk case, we obtain a scaling expression for the number of particles taking part in cooperative strings, and we recover the Adam-Gibbs description of glassy dynamics. Then, by including thermal dilatation, the Vogel-Fulcher-Tammann relation is derived. Moreover, the random and string-like characters of the cooperative rearrangement allow us to predict a temperature-dependent expression for the cooperative length ξ of bulk relaxation. Finally, we explore the influence of sample boundaries when the system size becomes comparable to ξ. The theory is in agreement with measurements of the glass-transition temperature of thin polymer films, and allows quantification of the temperature-dependent thickness hm of the interfacial mobile layer.

  3. Porphyrin-Based Photocatalytic Lithography

    SciTech Connect

    Bearinger, J; Stone, G; Christian, A; Dugan, L; Hiddessen, A; Wu, K J; Wu, L; Hamilton, J; Stockton, C; Hubbell, J

    2007-10-15

    Photocatalytic lithography is an emerging technique that couples light with coated mask materials in order to pattern surface chemistry. We excite porphyrins to create radical species that photocatalytically oxidize, and thereby pattern, chemistries in the local vicinity. The technique advantageously does not necessitate mass transport or specified substrates, it is fast and robust and the wavelength of light does not limit the resolution of patterned features. We have patterned proteins and cells in order to demonstrate the utility of photocatalytic lithography in life science applications.

  4. Porphyrin-based Photocatalytic Nanolithography

    SciTech Connect

    Bearinger, J P; Stone, G; Dugan, L C; Dasher, B E; Stockton, C; Conway, J W; Kuenzler, T; Hubbell, J A

    2009-06-08

    Nanoarray fabrication is a multidisciplinary endeavor encompassing materials science, chemical engineering and biology. We form nanoarrays via a new technique, porphyrin-based photocatalytic nanolithography (PCNL). The nanoarrays, with controlled features as small as 200 nm, exhibit regularly ordered patterns and may be appropriate for (a) rapid and parallel proteomic screening of immobilized biomolecules, (b) protein-protein interactions and/or (c) biophysical and molecular biology studies involving spatially dictated ligand placement. We demonstrate protein immobilization utilizing nanoarrays fabricated via PCNL on silicon substrates, where the immobilized proteins are surrounded by a non-fouling polymer background.

  5. Novel drug delivery strategies for porphyrins and porphyrin precursors

    NASA Astrophysics Data System (ADS)

    Morrow, D. I. J.; Donnelly, R. F.

    2009-06-01

    superficial lesions, such as actinic keratosis. In addition, photodynamic antimicrobial chemotherapy (PACT) is attracting increasing interest for the treatment of infection. However, delivery strategies for topical PDT and PACT are still based on application of rather simplistic cream and solution formulations, with little consideration given to thermodynamics, targeting or the physicochemical properties of the active agent. Purpose-designed dosage forms for topical delivery of aminolevulinic acid or its esters include creams containing penetration enhancers and/or iron chelators, pressure sensitive patches and bioadhesive patches. Such systems aim to enhance drug delivery across the stratum corneum and keratinised debris overlying neoplastic lesions and improve subsequent protoporphyrin IX (PpIX) production. The alternative to using porphyrin precursors is the use of pre-formed photosensitisers. However, owing to their relatively high molecular weights, conventional topical application is not appropriate. Innovative strategies, such as the use of needle-free injections and microneedle arrays, bypass the stratum corneum, enabling rapid and targeted delivery not only porphyrin precursors but also pre-formed photosensitisers. This presentation will review drug delivery work published to date in the fields of PDT and PACT. In addition, the benefits of employing the latest advances in pharmaceutical technology will be highlighted.

  6. Smaragdyrins: emeralds of expanded porphyrin family.

    PubMed

    Pareek, Yogita; Ravikanth, M; Chandrashekar, T K

    2012-10-16

    Porphyrins are tetrapyrrolic 18 π electron conjugated macrocycles with wide applications that range from materials to medicine. Expanded porphyrins, synthetic analogues of porphyrins that contain more than 18 π electrons in the conjugated pathway, have an increased number of pyrroles or other heterocyles or multiple meso-carbon bridges. The expanded porphyrins have attracted tremendous attention because of unique features such as anion binding or transport that are not present in porphyrins. Expanded porphyrins exhibit wide applications that include their use in the coordination of large metal ions, as contrasting agents in magnetic resonance imaging (MRI), as sensitizers for photodynamic therapy (PDT) and as materials for nonlinear optical (NLO) studies. Pentaphyrin 1, sapphyrin 2, and smaragdyrin 3 are expanded porphyrins that include five pyrroles or heterocyclic rings. They differ from each other in the number of bridging carbons and direct bonds that connect the five heterocyclic rings. Sapphyrins were the first stable expanded porphyrins reported in the literature and remain one of the most extensively studied macrocycles. The strategies used to synthesize sapphyrins are well established, and these macrocycles are versatile anion binding agents. They possess rich porphyrin-like coordination chemistry and have been used in diverse applications. This Account reviews developments in smaragdyrin chemistry. Although smaragdyrins were discovered at the same time as sapphyrins, the chemistry of smaragdyrins remained underdeveloped because of synthetic difficulties and their comparative instability. Earlier efforts resulted in the isolation of stable β-substituted smaragdyrins and meso-aryl isosmaragdyrins. Recently, researchers have synthesized stable meso-aryl smaragdyrins by [3 + 2] oxidative coupling reactions. These results have stimulated renewed research interest in the exploration of these compounds for anion and cation binding, energy transfer

  7. Nickel porphyrins for memory optical applications

    DOEpatents

    Shelnutt, John A.; Jia, Songling; Medforth, Craig; Holten, Dewey; Nelson, Nora Y.; Smith, Kevin M.

    2000-01-01

    The present invention relates to a nickel-porphyrin derivative in a matrix, the nickel-porphyrin derivative comprising at least two conformational isomers, a lower-energy-state conformer and a higher-energy-state conformer, such that when the higher-energy-state conformer is generated from the lower-energy-state conformer following absorption of a photon of suitable energy, the time to return to the lower-energy-state conformer is greater than 40 nanoseconds at approximately room temperature. The nickel-porphyrin derivative is useful in optical memory applications.

  8. Porphyrin-aminoquinoline conjugates as telomerase inhibitors.

    PubMed

    Maraval, Alexandrine; Franco, Sonia; Vialas, Corine; Pratviel, Geneviève; Blasco, Maria A; Meunier, Bernard

    2003-03-21

    A series of metalloporphyrins was prepared in order to target the G-quadruplex structure of telomeric DNA for the design of antitelomerase compounds. The initial cationic tetramethylpyridiniumyl porphyrin was modified by the replacement of one or two methylpyridiniumyl groups by one or two 4-aminoquinoline moieties, at the meso position, in order to increase the cell penetration and the quadruplex affinity. The porphyrins were either metallated by manganese or by nickel. The degradation of quadruplex DNA was assayed in vitro with the manganese redox-active derivatives. All porphyrins complexes were capable of inhibiting the telomerase enzyme with IC50 values in the micromolar range (TRAP assay).

  9. Crystal engineering of porphyrin framework solids.

    PubMed

    Goldberg, Israel

    2005-03-14

    This article describes recent achievements made by us and other groups in targeted synthesis of porphyrin-based framework solids by various non-covalent mechanisms of molecular recognition. The self-assembly processes are effected in a tunable manner either by direct association of suitably designed porphyrin building blocks, or by their supramolecular aggregation through external linkers as metal ions and organic bi-dentate ligands. Many of these crystalline porphyrin materials exhibit open architectures and remarkable structural integrity, and their potential application for selective guest storage and molecular sieving is highlighted.

  10. Transition Metal Complexes of Expanded Porphyrins

    PubMed Central

    Sessler, Jonathan L.; Tomat, Elisa

    2008-01-01

    Over the last two decades, the rapid development of new synthetic routes for the preparation of expanded porphyrin macrocycles has allowed exploration of a new frontier consisting of “porphyrin-like” coordination chemistry. In this Account, we summarize our exploratory forays into the still relatively poorly explored area of oligopyrrolic macrocycle metalation chemistry. Specifically, we describe our successful formation of both mono- and binuclear complexes and in doing so highlight the diversity of coordination modes available to expanded porphyrin-type ligands. The nature of the inserted cation, the emerging role of tautomeric equilibria, and the importance of hydrogen-bonding interactions in regulating this chemistry are also discussed. PMID:17397134

  11. Oxoferryl porphyrin/hydrogen peroxide system whose behavior is equivalent to hydroperoxoferric porphyrin.

    PubMed

    Kitagishi, Hiroaki; Tamaki, Mariko; Ueda, Takunori; Hirota, Shun; Ohta, Takehiro; Naruta, Yoshinori; Kano, Koji

    2010-12-01

    The reaction between H(2)O(2) and a pyridine-coordinated ferric porphyrin encapsulated by a cyclodextrin dimer yielded a hydroperoxoferric porphyrin intermediate, PFe(III)-OOH, which rapidly decomposed to oxoferryl porphyrin (PFe(IV)═O). Upon reaction with H(2)O(2), PFe(IV)═O reverted to PFe(III)-OOH, which was converted to carbon monoxide-coordinated ferrous porphyrin under a CO atmosphere. PFe(IV)═O in the presence of excess H(2)O(2) behaves as PFe(III)-OOH.

  12. Molecular mobility in glassy dispersions

    NASA Astrophysics Data System (ADS)

    Mehta, Mehak; McKenna, Gregory B.; Suryanarayanan, Raj

    2016-05-01

    Dielectric spectroscopy was used to characterize the structural relaxation in pharmaceutical dispersions containing nifedipine (NIF) and either poly(vinyl) pyrrolidone (PVP) or hydroxypropyl methylcellulose acetate succinate (HPMCAS). The shape of the dielectric response (permittivity versus log time) curve was observed to be independent of temperature. Thus, for the pure NIF as well as the dispersions, the validity of the time-temperature superposition principle was established. Furthermore, though the shape of the full dielectric response varied with polymer concentration, the regime related to the α- or structural relaxation was found to superimpose for the dispersions, though not with the response of the NIF itself. Hence, there is a limited time-temperature-concentration superposition for these systems as well. Therefore, in this polymer concentration range, calculation of long relaxation times in these glass-forming systems becomes possible. We found that strong drug-polymer hydrogen bonding interactions improved the physical stability (i.e., delayed crystallization) by reducing the molecular mobility. The strength of hydrogen bonding, structural relaxation time, and crystallization followed the order: NIF-PV P>NIF-HPMCAS>NIF. With an increase in polymer concentration, the relaxation times were longer indicating a decrease in molecular mobility. The temperature dependence of relaxation time, in other words fragility, was independent of polymer concentration. This is the first application of the superposition principle to characterize structural relaxation in glassy pharmaceutical dispersions.

  13. Molecular mobility in glassy dispersions.

    PubMed

    Mehta, Mehak; McKenna, Gregory B; Suryanarayanan, Raj

    2016-05-28

    Dielectric spectroscopy was used to characterize the structural relaxation in pharmaceutical dispersions containing nifedipine (NIF) and either poly(vinyl) pyrrolidone (PVP) or hydroxypropyl methylcellulose acetate succinate (HPMCAS). The shape of the dielectric response (permittivity versus log time) curve was observed to be independent of temperature. Thus, for the pure NIF as well as the dispersions, the validity of the time-temperature superposition principle was established. Furthermore, though the shape of the full dielectric response varied with polymer concentration, the regime related to the α- or structural relaxation was found to superimpose for the dispersions, though not with the response of the NIF itself. Hence, there is a limited time-temperature-concentration superposition for these systems as well. Therefore, in this polymer concentration range, calculation of long relaxation times in these glass-forming systems becomes possible. We found that strong drug-polymer hydrogen bonding interactions improved the physical stability (i.e., delayed crystallization) by reducing the molecular mobility. The strength of hydrogen bonding, structural relaxation time, and crystallization followed the order: NIF-PV P>NIF-HPMCAS>NIF. With an increase in polymer concentration, the relaxation times were longer indicating a decrease in molecular mobility. The temperature dependence of relaxation time, in other words fragility, was independent of polymer concentration. This is the first application of the superposition principle to characterize structural relaxation in glassy pharmaceutical dispersions.

  14. Molecular mobility in glassy dispersions

    SciTech Connect

    Mehta, Mehak; McKenna, Gregory B.; Suryanarayanan, Raj

    2016-05-27

    Dielectric spectroscopy was used to characterize the structural relaxation in pharmaceutical dispersions containing nifedipine (NIF) and either poly(vinyl) pyrrolidone (PVP) or hydroxypropyl methylcellulose acetate succinate (HPMCAS). The shape of the dielectric response (permittivity versus log time) curve was observed to be independent of temperature. Thus, for the pure NIF as well as the dispersions, the validity of the time-temperature superposition principle was established. Furthermore, though the shape of the full dielectric response varied with polymer concentration, the regime related to the α- or structural relaxation was found to superimpose for the dispersions, though not with the response of the NIF itself. Hence, there is a limited time-temperature-concentration superposition for these systems as well. Therefore, in this polymer concentration range, calculation of long relaxation times in these glass-forming systems becomes possible. We found that strong drug-polymer hydrogen bonding interactions improved the physical stability (i.e., delayed crystallization) by reducing the molecular mobility. The strength of hydrogen bonding, structural relaxation time, and crystallization followed the order: NIF$-$PV P>NIF$-$HPMCAS>NIF. With an increase in polymer concentration, the relaxation times were longer indicating a decrease in molecular mobility. The temperature dependence of relaxation time, in other words fragility, was independent of polymer concentration. This is the first application of the superposition principle to characterize structural relaxation in glassy pharmaceutical dispersions.

  15. Porphyrin-Based Nanostructures for Photocatalytic Applications

    PubMed Central

    Chen, Yingzhi; Li, Aoxiang; Huang, Zheng-Hong; Wang, Lu-Ning; Kang, Feiyu

    2016-01-01

    Well-defined organic nanostructures with controllable size and morphology are increasingly exploited in optoelectronic devices. As promising building blocks, porphyrins have demonstrated great potentials in visible-light photocatalytic applications, because of their electrical, optical and catalytic properties. From this perspective, we have summarized the recent significant advances on the design and photocatalytic applications of porphyrin-based nanostructures. The rational strategies, such as texture or crystal modification and interfacial heterostructuring, are described. The applications of the porphyrin-based nanostructures in photocatalytic pollutant degradation and hydrogen evolution are presented. Finally, the ongoing challenges and opportunities for the future development of porphyrin nanostructures in high-quality nanodevices are also proposed. PMID:28344308

  16. Porphyrin-loaded nanoparticles for cancer theranostics

    NASA Astrophysics Data System (ADS)

    Zhou, Yiming; Liang, Xiaolong; Dai, Zhifei

    2016-06-01

    Porphyrins have been used as pioneering theranostic agents not only for the photodynamic therapy, sonodynamic therapy and radiotherapy of cancer, but also for diagnostic fluorescence imaging, magnetic resonance imaging and photoacoustic imaging. A variety of porphyrins have been developed but very few of them have actually been employed in clinical trials due to their poor selectivity to tumorous tissue and high accumulation rates in the skin. In addition, most porphyrin molecules are hydrophobic and form aggregates in aqueous media. Nevertheless, the use of nanoparticles as porphyrin carriers shows great promise to overcome these shortcomings. Encapsulating or attaching porphyrins to nanoparticles makes them more suitable for tissue delivery because we can create materials with a conveniently specific tissue lifetime, specific targeting, immune tolerance, and hydrophilicity as well as other characteristics through rational design. In addition, various functional components (e.g. for targeting, imaging or therapeutic functions) can be easily introduced into a single nanoparticle platform for cancer theranostics. This review presents the current state of knowledge on porphyrin-loaded nanoparticles for the interwined imaging and therapy of cancer. The future trends and limitations of prophyrin-loaded nanoparticles are also outlined.

  17. Electron Transport through Porphyrin Molecular Junctions

    NASA Astrophysics Data System (ADS)

    Zhou, Qi

    The goal of this work is to study the properties that would affect the electron transport through a porphyrin molecular junction. This work contributes to the field of electron transport in molecular junctions in the following 3 aspects. First of all, by carrying out experiments comparing the conductance of the iron (III) porphyrin (protected) and the free base porphyrin (protected), it is confirmed that the molecular energy level broadening and shifting occurs for porphyrin molecules when coupled with the metal electrodes, and this level broadening and shifting plays an important role in the electron transport through molecular junctions. Secondly, by carrying out an in-situ deprotection of the acetyl-protected free base porphyrin molecules, it is found out that the presence of acetyl groups reduces the conductance. Thirdly, by incorporating the Matrix-assisted laser desorption/ionization (MALDI) spectrum and the in-situ deprotection prior to formation of molecular junctions, it allows a more precise understanding of the molecules involved in the formation of molecular junctions, and therefore allows an accurate analysis of the conductance histogram. The molecules are prepared by self-assembly and the junctions are formed using a Scanning Tunneling Microscopy (STM) molecular break junction technique. The porphyrin molecules are characterized by MALDI in solution before self-assembly to a gold/mica substrate. The self-assembled monolayers (SAMs) of porphyrins on gold are characterized by Ultraviolet-visible (UV-Vis) reflection spectroscopy to confirm that the molecules are attached to the substrate. The SAMs are then characterized by Angle-Resolved X-ray photoelectron spectroscopy (ARXPS) to determine the thickness and the average molecular orientation of the molecular layer. The electron transport is measured by conductance-displacement (G-S) experiments under a given bias (-0.4V). The conductance value of a single molecule is identified by a statistical analysis

  18. Electrocatalytic Transformation of Carbon Dioxide into Low Carbon Compounds on Conducting Polymers Derived from Multimetallic Porphyrins.

    PubMed

    Dreyse, Paulina; Honores, Jessica; Quezada, Diego; Isaacs, Mauricio

    2015-11-01

    The electrochemical reduction of carbon dioxide is studied herein by using conducting polymers based on metallotetraruthenated porphyrins (MTRPs). The polymers on glassy carbon electrodes were obtained by electropolymerization processes of the monomeric MTRP. The linear sweep voltammetry technique resulted in polymeric films that showed electrocatalytic activity toward carbon dioxide reduction with an onset potential of -0.70 V. The reduction products obtained were hydrogen, formic acid, formaldehyde, and methanol, with a tendency for a high production of methanol with a maximum value of turnover frequency equal to 15.07 when using a zinc(II) polymeric surface. Studies of the morphology (AFM) and electrochemical impedance spectroscopy results provide an adequate background to explain that the electrochemical reduction is governed by the roughness of the polymer, for which the possible mechanism involves a series of one-electron reduction reactions.

  19. Understanding rheological hysteresis in soft glassy materials.

    PubMed

    Radhakrishnan, Rangarajan; Divoux, Thibaut; Manneville, Sébastien; Fielding, Suzanne M

    2017-03-01

    Motivated by recent experimental studies of rheological hysteresis in soft glassy materials, we study numerically strain rate sweeps in simple yield stress fluids and viscosity bifurcating yield stress fluids. Our simulations of downward followed by upward strain rate sweeps, performed within fluidity models and the soft glassy rheology model, successfully capture the experimentally observed monotonic decrease of the area of the rheological hysteresis loop with sweep time in simple yield stress fluids, and the bell shaped dependence of hysteresis loop area on sweep time in viscosity bifurcating fluids. We provide arguments explaining these two different functional forms in terms of differing tendencies of simple and viscosity bifurcating fluids to form shear bands during the sweeps, and show that the banding behaviour captured by our simulations indeed agrees with that reported experimentally. We also discuss the difference in hysteresis behaviour between inelastic and viscoelastic fluids. Our simulations qualitatively agree with the experimental data discussed here for four different soft glassy materials.

  20. Metal complexes of substituted Gable porphyrins as oxidation catalysts

    DOEpatents

    Lyons, J.E.; Ellis, P.E. Jr.; Wagner, R.W.

    1996-01-02

    Transition metal complexes of Gable porphyrins are disclosed having two porphyrin rings connected through a linking group, and having on the porphyrin rings electron-withdrawing groups, such as halogen, nitro or cyano. These complexes are useful as catalysts for the oxidation of organic compounds, e.g. alkanes.

  1. Metal complexes of substituted Gable porphyrins as oxidation catalysts

    DOEpatents

    Lyons, James E.; Ellis, Jr., Paul E.; Wagner, Richard W.

    1996-01-01

    Transition metal complexes of Gable porphyrins having two porphyrin rings connected through a linking group, and having on the porphyrin rings electron-withdrawing groups, such as halogen, nitro or cyano. These complexes are useful as catalysts for the oxidation of organic compounds, e.g. alkanes.

  2. On the Marginal Stability of Glassy Systems

    NASA Astrophysics Data System (ADS)

    Yan, Le; Baity-Jesi, Marco; Müller, Markus; Wyart, Matthieu

    2015-03-01

    In various glassy systems that are out of equilibrium, like spin glasses and granular packings, the dynamics appears to be critical: avalanches involving almost the whole system could happen. A recent conceptual breakthrough argues that such glassy systems sample the ensemble of marginal stable states, which inevitably results into critical dynamics. However, it is unclear how the marginal stability is dynamically guaranteed. We investigate this marginal stability assumption by studying specifically the critical athermal dynamics of the Sherrington-Kirkpatrick model. We discuss how a pseudo-gap in the density distribution of local fields characterizing the marginal stability arises dynamically.

  3. Porphyrinic metal-organic framework as electrochemical probe for DNA sensing via triple-helix molecular switch.

    PubMed

    Ling, Pinghua; Lei, Jianping; Ju, Huangxian

    2015-09-15

    An electrochemical DNA sensor was developed based on the electrocatalysis of porphyrinic metal-organic framework (MOF) and triple-helix molecular switch for signal transduction. The streptavidin functionalized zirconium-porphyrin MOF (PCN-222@SA) was prepared as signal nanoprobe via covalent method and demonstrated high electrocatalysis for O2 reduction. Due to the large steric effect, the designed nanoprobe was blocked for the interaction with the biotin labeled triple-helix immobilized on the surface of glassy carbon electrode. In the presence of target DNA, the assistant DNA in triple-helix will hybridize with target DNA, resulting in the disassembly of triple-helix molecular. Consequently, the end biotin away from the electrode was ''activated'' for easy access to the signal nanoprobe, PCN-222@SA, on the basis of biotin-streptavidin biorecognition. The introduction of signal nanoprobe to a sensor surface led to a significantly amplified electrocatalytic current towards oxygen reduction. Integrating with DNA recycling amplification of Exonuclease III, the sensitivity of the biosensor was improved significantly with detection limit of 0.29 fM. Moreover, the present method has been successfully applied to detect DNA in complex serum matrix. This porphyrinic MOF-based strategy has promising application in the determination of various analytes for signal transduction and has great potential in bioassays.

  4. High efficiency porphyrin sensitized mesoscopic solar cells

    NASA Astrophysics Data System (ADS)

    Giordano, Fabrizio; Yi, Chenyi; Teuscher, Joël.; Zakeeruddin, Shaik M.; Grätzel, Michael

    2014-10-01

    Dye-Sensitized Solar Cells (DSSC) represents a reliable technology, ready for the market and able to compete with silicon solar cells for specific fields of application. Porphyrin dyes allow reaching high power conversion efficiency in conjunction with cobalt redox electrolytes due to larger open circuit potentials. The bigger size of the cobalt complexes compared to standard iodide/triiodide redox couple hampers its percolation through the meso-porous TiO2 network, thus impairing the regeneration process. In case of porphyrin dyes mass transport problems in the electrolyte need to be carefully handled, due to the large size of the sensitizing molecule and the bulky cobalt complexes. Herein we report the study of structural variations on porphyrin sensitizers and their influence on the DSSC performance with cobalt based redox electrolyte.

  5. On the cytoskeleton and soft glassy rheology.

    PubMed

    Mandadapu, Kranthi K; Govindjee, Sanjay; Mofrad, Mohammad R K

    2008-01-01

    The cytoskeleton is a complex structure within the cellular corpus that is responsible for the main structural properties and motilities of cells. A wide range of models have been utilized to understand cytoskeletal rheology and mechanics (see e.g. [Mofrad, M., Kamm, R., 2006. Cytoskeletal Mechanics: Models and Measurements. Cambridge University Press, Cambridge]). From this large collection of proposed models, the soft glassy rheological model (originally developed for inert soft glassy materials) has gained a certain traction in the literature due to the close resemblance of its predictions to certain mechanical data measured on cell cultures [Fabry, B., Maksym, G., Butler, J., Glogauer, M., Navajas, D., Fredberg, J., 2001. Scaling the microrheology of living cells. Physical Review Letters 87, 14102]. We first review classical linear rheological theory in a concise fashion followed by an examination of the soft glassy rheological theory. With this background we discuss the observed behavior of the cytoskeleton and the inherent limitations of classical rheological models for the cytoskeleton. This then leads into a discussion of the advantages and disadvantages presented to us by the soft glassy rheological model. We close with some comments of caution and recommendations on future avenues of exploration.

  6. Inelastic Deformation and Fracture of Glassy Solids

    DTIC Science & Technology

    1991-05-31

    cyclic energy loss but also the so-called dinamic modulus as a function of temperature at a given frequency. As in the case of metal- lic glasses the...interactions molecular structures of several glassy polymers have been obtained by static energy minimization techniques. These include polypropy- lene

  7. Absorption Of Gases By Glassy Polymers

    NASA Technical Reports Server (NTRS)

    Fedors, Robert F.

    1990-01-01

    Report discusses solubility of gas in glassy polymer, both above and below glass-transition temperature (Tg). Thermodynamic arguments brought to bear on previously-developed mathematical models, result being new model that enables calculation of infinite-dilution partial molar volume of solvent in glass or liquid solvent from data on pressure, volume, and temperature of solute in equilibrium with solvent.

  8. Deformation and Fracture Behavior of Metallic Glassy Alloys and Glassy-Crystal Composites

    NASA Astrophysics Data System (ADS)

    Louzguine-Luzgin, D. V.; Vinogradov, A.; Li, S.; Kawashima, A.; Xie, G.; Yavari, A. R.; Inoue, A.

    2011-06-01

    The present work demonstrates the deformation behavior of Zr-Cu-Ni-Al bulk glassy alloys and Zr-Ni-Cu-Al-Pd glassy foils as well as Ni-Cu-Ti-Zr bulk crystal-glassy composites. Fracture of Zr60Cu16Ni14Al10 and Zr64.13Ni10.12Cu15.75Al10 bulk glassy alloys is featured by nearly equal fraction areas of cleavage-like and vein-type relief. The observed pattern of alternating cleavage-like and vein-type patterns illustrates a result of dynamically self-organizing shear propagation at the final catastrophic stage. The deformation behavior of Zr64.13Ni10.12Cu15.75Al10 alloy has also been tested at LN2 temperature. The strength of the sample decreases with temperature, and no clear serrated flow typical for bulk glassy samples tested at room temperature is observed in the case of the samples tested at LN2 temperature. We also studied the deformation behavior of Zr-Ni-Cu-Al-Pd glassy foils thinned to electron transparency in situ in tension in a transmission electron microscope. We also present a Ni-Cu-Ti-Zr crystal-glassy composite material having a superior strength paired with a considerable ductility exceeding 10 pct. The metastable cP2 crystalline phase promotes a strain-induced martensitic transformation leading to pseudoelastic behavior as well as enhanced plasticity at room temperature. Underlying mechanisms of plastic deformation are discussed in terms of the interplay between the dislocation slip in the crystalline phase and the shear deformation in the glassy matrix.

  9. Resonance Raman spectroscopy study of protonated porphyrin

    NASA Astrophysics Data System (ADS)

    Gorski, A.; Starukhin, A.; Stavrov, S.; Gawinkowski, S.; Waluk, J.

    2017-02-01

    Resonance Raman microscopy was used to study the resonance Raman scattering of the diacid (diprotonated form) of free-base porphyrin (21H,23H-porphine) in a crystal powder and KBr pellets. Intensive lines in the spectral range between 100 ÷ 1000 cm- 1 have been detected and assigned as spectral manifestation of out-of-plane modes. The Raman spectra were simulated by means of DFT methods and compared with the experimental data. It is evident from experimental and theoretical results that the activation of out-of-plane modes arises from saddle distortion of the porphyrin macrocycle upon formation of its diprotonated form.

  10. Spectroscopic investigation on porphyrins nano-assemblies onto gold nanorods

    NASA Astrophysics Data System (ADS)

    Trapani, Mariachiara; De Luca, Giovanna; Romeo, Andrea; Castriciano, Maria Angela; Scolaro, Luigi Monsù

    2017-02-01

    The interaction between gold nanorods (Au NRs), synthesized by a conventional seeded growth protocol, and the anionic tetrakis-(4-sulfonatophenyl)porphyrin (TPPS4) has been investigated through various spectroscopic techniques. At neutral pH, the formation of H-aggregates and the inclusion of porphyrin monomers in CTAB micelles covering the nanorods have been evidenced. Under mild acidic conditions (pH = 3) a nano-hybrid assembly of porphyrin J-aggregates and Au NRs has been revealed. For the sake of comparison, Cu(II) and Zn(II) metal porphyrin derivatives as well as a cationic porphyrin have been studied in the same experimental conditions, showing that: i) CuTPPS4 forms porphyrin H-dimers onto the Au NRs; ii) ZnTPPS4 undergoes to demetallation, followed by acidification of the central core and eventually aggregation onto Au NRs; iii) cationic porphyrin does not interact with Au NRs.

  11. Surface morphology and optical properties of porphyrin/Au and Au/porphyrin/Au systems

    PubMed Central

    2013-01-01

    Porphyrin/Au and Au/porphyrin/Au systems were prepared by vacuum evaporation and vacuum sputtering onto glass substrate. The surface morphology of as-prepared systems and those subjected to annealing at 160°C was studied by optical microscopy, atomic force microscopy, and scanning electron microscopy techniques. Absorption and luminescence spectra of as-prepared and annealed samples were measured. Annealing leads to disintegration of the initially continuous gold layer and formation of gold nanoclusters. An amplification of Soret band magnitude was observed on the Au/meso-tetraphenyl porphyrin (TPP) system in comparison with mere TPP. Additional enhancement of luminescence was observed after the sample annealing. In the case of sandwich Au/porphyrin/Au structure, suppression of one of the two porphyrins’ luminescence maxima and sufficient enhancement of the second one were observed. PMID:24373347

  12. Plastic flow modeling in glassy polymers

    SciTech Connect

    Clements, Brad

    2010-12-13

    Glassy amorphous and semi-crystalline polymers exhibit strong rate, temperature, and pressure dependent polymeric yield. As a rule of thumb, in uniaxial compression experiments the yield stress increases with the loading rate and applied pressure, and decreases as the temperature increases. Moreover, by varying the loading state itself complex yield behavior can be observed. One example that illustrates this complexity is that most polymers in their glassy regimes (i.e., when the temperature is below their characteristic glass transition temperature) exhibit very pronounced yield in their uniaxial stress stress-strain response but very nebulous yield in their uniaxial strain response. In uniaxial compression, a prototypical glassy-polymer stress-strain curve has a stress plateau, often followed by softening, and upon further straining, a hardening response. Uniaxial compression experiments of this type are typically done from rates of 10{sup -5} s{sup -1} up to about 1 s{sup -1}. At still higher rates, say at several thousands per second as determined from Split Hopkinson Pressure Bar experiments, the yield can again be measured and is consistent with the above rule of thumb. One might expect that that these two sets of experiments should allow for a successful extrapolation to yet higher rates. A standard means to probe high rates (on the order of 105-107 S-I) is to use a uniaxial strain plate impact experiment. It is well known that in plate impact experiments on metals that the yield stress is manifested in a well-defined Hugoniot Elastic Limit (HEL). In contrast however, when plate impact experiments are done on glassy polymers, the HEL is arguably not observed, let alone observed at the stress estimated by extrapolating from the lower strain rate experiments. One might argue that polymer yield is still active but somehow masked by the experiment. After reviewing relevant experiments, we attempt to address this issue. We begin by first presenting our recently

  13. Porphyrins for boron neutron capture therapy

    DOEpatents

    Miura, Michiko; Gabel, Detlef

    1990-01-01

    Novel compounds for treatment of brain tumors in Boron Neutron Capture Therapy are disclosed. A method for preparing the compounds as well as pharmaceutical compositions containing said compounds are also disclosed. The compounds are water soluble, non-toxic and non-labile boronated porphyrins which show significant uptake and retention in tumors.

  14. Metallic nanoshells on porphyrin-stabilized emulsions

    DOEpatents

    Wang, Haorong; Song, Yujiang; Shelnutt, John A; Medforth, Craig J

    2013-10-29

    Metal nanostructures formed by photocatalytic interfacial synthesis using a porphyrin-stabilized emulsion template and the method for making the nanostructures. Catalyst-seeded emulsion droplets are employed as templates for hollow-nanoshell growth. The hollow metal nanospheres may be formed with or without inclusions of other materials.

  15. Porphyrin colorimetric indicators in molecular and nano-architectures.

    PubMed

    Xie, Yongshu; Hill, Jonathan P; Charvet, Richard; Ariga, Katsuhiko

    2007-09-01

    One of the most important outcomes of organic nanotechnologies could be development of well-integrated systems for sensing of particular chemical species. Use of color indicators is an attractive approach to guest reporting. Of the known chromophores, porphyrin and its derivatives are the most widely studied functional chromophores in a diverse range of research fields. In this review, recent developments in colorimetric indicator functions of porphyrin derivatives and related compounds in their molecular and nano-architectures are reviewed according to the classification: (i) rather simple porphyrin derivatives, (ii) porphyrin conjugates, (iii) porphyrins embedded in bulk materials, and (iv) porphyrins in organized films. Porphyrin derivatives with unusual structures, such as expanded and N-confused ones have been used for color indicators in specific cases. Electron and energy transfers in porphyrins conjugated with other functional moieties resulted in dynamic sensing systems including switch-on and switch-off actions. Immobilization of porphyrin color indicators in appropriate matrices is important for practical applications. Use of supramolecular films such as self-assembled monolayers, Langmuir-Blodgett films, and layer-by-layer assemblies as porphyrin nanoarchitectures often offers opportunities for colorimetric outputs based on control of their aggregate structures.

  16. Equation of state of heated glassy carbon

    NASA Technical Reports Server (NTRS)

    Sekine, Toshimori; Ahrens, Thomas J.

    1991-01-01

    New Hugoniot data are presented for glassy carbon preheated to 1550 K and shocked to 20 GPa. The high-temperature Hugoniot is very similar to the principal Hugoniot. This results argues against the diffusional mechanism for the shock-induced transformaton of amorphous carbon to diamond, although the present results are obviously limited to below 20 GPa. This study provides the first Higoniot data for carbon preheated to significantly high temperatures.

  17. Wafer-level microstructuring of glassy carbon

    NASA Astrophysics Data System (ADS)

    Hans, Loïc. E.; Prater, Karin; Kilchoer, Cédric; Scharf, Toralf; Herzig, Hans Peter; Hermerschmidt, Andreas

    2014-03-01

    Glassy carbon is used nowadays for a variety of applications because of its mechanical strength, thermal stability and non-sticking adhesion properties. One application is glass molding that allows to realize high resolution diffractive optical elements on large areas and at affordable price appropriate for mass production. We study glassy carbon microstructuring for future precision compression molding of low and high glass-transition temperature. For applications in optics the uniformity, surface roughness, edge definition and lateral resolution are very important parameters for a stamp and the final product. We study different methods of microstructuring of glassy carbon by etching and milling. Reactive ion etching with different protection layers such as photoresists, aluminium and titanium hard masks have been performed and will be compare with Ion beam etching. We comment on the quality of the structure definition and give process details as well as drawbacks for the different methods. In our fabrications we were able to realize optically flat diffractive structures with slope angles of 80° at typical feature sizes of 5 micron and 700 nm depth qualified for high precision glass molding.

  18. Langmuir-Blodgett films of amphiphilic push-pull porphyrins

    SciTech Connect

    Chou, H.; Chen, C.T.; Stork, K.F.; Bohn, P.W.; Suslick, K.S. )

    1994-01-13

    A series of nitrophenyl-amidophenyl-substituted porphyrins with n-C[sub 17]H[sub 35] tails have been synthesized and fully characterized. Good Langmuir-Blodgett films of these materials can be prepared on water and transferred successfully to glass slides. Mean molecular areas for the series were measured and found to increase from 80 to 230 A[sup 2] as the number of aliphatic chains increased from one to four. As determined by linear dichroic measurements, this change in area does not correspond to a change in the orientation of the porphyrin with respect to the surface. In the absence of the steric constraints of multiple aliphatic chains, porphyrin-porphyrin stacking permits close packing of the rings. As the number of aliphatic chains on the porphyrin periphery increases, however, the porphyrin planes must pack more loosely. Thus, the porphyrin macrocycle orientation is determined by interactions between porphyrin rings and between porphyrins and the aqueous (or polar glass) surface. In contrast, the differences in the observed mean molecular area are determined independently by packing constraints imposed by the pendant hydrocarbon chains. 13 refs., 3 figs., 1 tab.

  19. Water-splitting using photocatalytic porphyrin-nanotube composite devices

    DOEpatents

    Shelnutt, John A.; Miller, James E.; Wang, Zhongchun; Medforth, Craig J.

    2008-03-04

    A method for generating hydrogen by photocatalytic decomposition of water using porphyrin nanotube composites. In some embodiments, both hydrogen and oxygen are generated by photocatalytic decomposition of water.

  20. Past and future: porphyria and porphyrins.

    PubMed

    Norman, Robert A

    2005-01-01

    Porphyria is a compelling disease--disrupted enzyme pathways, heightened sensitivities, and a fascinating history tied in with tales of Dracula. This review discusses the history, pathophysiology, classification, and treatment of porphyria. It further discusses the way in which research on the etiologies of the various porphyrias has led to the development of porphyrin-based photodynamic therapy, which shows great promise in targeted therapy for a variety of serious pathologies.

  1. Porphyrin and heme metabolism and the porphyrias.

    PubMed

    Bonkovsky, Herbert L; Guo, Jun-Tao; Hou, Weihong; Li, Ting; Narang, Tarun; Thapar, Manish

    2013-01-01

    Porphyrins and metalloporphyrins are the key pigments of life on earth as we know it, because they include chlorophyll (a magnesium-containing metalloporphyrin) and heme (iron protoporphyrin). In eukaryotes, porphyrins and heme are synthesized by a multistep pathway that involves eight enzymes. The first and rate-controlling step is the formation of delta-aminolevulinic acid (ALA) from glycine plus succinyl CoA, catalyzed by ALA synthase. Intermediate steps occur in the cytoplasm, with formation of the monopyrrole porphobilinogen and the tetrapyrroles hydroxymethylbilane and a series of porphyrinogens, which are serially decarboxylated. Heme is utilized chiefly for the formation of hemoglobin in erythrocytes, myoglobin in muscle cells, cytochromes P-450 and mitochondrial cytochromes, and other hemoproteins in hepatocytes. The rate-controlling step of heme breakdown is catalyzed by heme oxygenase (HMOX), of which there are two isoforms, called HMOX1 and HMOX2. HMOX breaks down heme to form biliverdin, carbon monoxide, and iron. The porphyrias are a group of disorders, mainly inherited, in which there are defects in normal porphyrin and heme synthesis. The cardinal clinical features are cutaneous (due to the skin-damaging effects of excess deposited porphyrins) or neurovisceral attacks of pain, sometimes with weakness, delirium, seizures, and the like (probably due mainly to neurotoxic effects of ALA). The treatment of choice for the acute hepatic porphyrias is intravenous heme therapy, which repletes a critical regulatory heme pool in hepatocytes and leads to downregulation of hepatic ALA synthase, which is a biochemical hallmark of all forms of acute porphyria in relapse.

  2. Water uptake impedance of glassy organic aerosols

    NASA Astrophysics Data System (ADS)

    Peter, T.; Zobrist, B.; Krieger, U. K.; Luo, B. P.; Soonsin, V.; Marcolli, C.; Koop, T.

    2009-04-01

    Depending on their concentration and composition, aerosols affect various atmospheric properties and processes, such as atmospheric chemistry and Earth's radiative budget. The atmospheric aerosol itself is a complex mixture of various inorganic and organic components, whereas the organic fraction can represent more than 50% of the total aerosol mass. It was recently shown that aerosols high in organics may be present in a glassy state (Zobrist et al., ACP, 8, 5221-5244, 2008). The glassy nature of the aerosols may influence their properties and restrict their functionalities severely, e.g. their water uptake, heterogeneous chemical reactions in their bulk or on their surfaces, as well as ice nucleation and ice crystal growth. Here, we present the first experiments on the water uptake by single levitated glassy aerosol particles using an electrodynamic balance (EDB). Sucrose was chosen as a model substance, which comprises functional groups typical of organic species in the atmosphere. In addition we developed a microphysical model, which enables us to calculate the liquid diffusion inside a glassy particle using water diffusion coefficients in aqueous sucrose particles adapted from the literature. As the diffusion coefficient of water in the particle, D(cH2O), depends on the water concentration cH2O itself, the solution of the diffusion equation presents an interesting non-linear problem. The combined experimental and modelling approach allows describing in detail the water uptake by glassy aerosols at atmospherically relevant temperatures and relative humidities (RH). Hygroscopicity cycles were perfomed in the EDB starting from a crystalline (non-spherical) sucrose particle at 291 K. No water uptake was observed while RH was increased until the particle deliquesces at roughly 85% RH leading to a liquid (spherical) particle. In the subsequent drying cycle, surprisingly no efflorescence was observed when the particle was dried to below 5% and it remained spherical

  3. Glassy dynamics in thin films of polystyrene

    NASA Astrophysics Data System (ADS)

    Fukao, Koji; Koizumi, Hiroki

    2008-02-01

    Glassy dynamics was investigated for thin films of atactic polystyrene by complex electric capacitance measurements using dielectric relaxation spectroscopy. During the isothermal aging process the real part of the electric capacitance increased with time, whereas the imaginary part decreased with time. It follows that the aging time dependences of real and imaginary parts of the electric capacitance were primarily associated with change in volume (film thickness) and dielectric permittivity, respectively. Further, dielectric permittivity showed memory and rejuvenation effects in a similar manner to those observed for poly(methyl methacrylate) thin films. On the other hand, volume did not show a strong rejuvenation effect.

  4. Hole transport in porphyrin thin films

    NASA Astrophysics Data System (ADS)

    Savenije, Tom J.; Goossens, Albert

    2001-09-01

    Hole transport in p-type organic semiconductors is a key issue in the development of organic electronic devices. Here the diffusion of holes in porphyrin thin films is investigated. Smooth anatase TiO2 films are coated with an amorphous thin film of zinc-tetra(4-carboxyphenyl) porphyrin (ZnTCPP) molecules acting as sensitizer. Optical excitation of the porphyrin stimulates the injection of electrons into the conduction band of TiO2. The remaining holes migrate towards the back electrode where they are collected. Current-voltage and capacitance-voltage analysis reveal that the TiO2/ZnTCPP system can be regarded as an n-p heterojunction, with a donor density of ND=2.0×1016 cm-3 for TiO2 and an acceptor density NA=4.0×1017 cm-3 for ZnTCPP films. The acceptor density in porphyrin films increases to 1.3×1018 cm-3 upon irradiation with 100-mW cm-2 white light. Intensity-modulated photocurrent spectroscopy, in which ac-modulated irradiation is applied, is used to measure the transit times of the photogenerated holes through the films. A reverse voltage bias hardly affects the transit time, whereas a small forward bias yields a decrease of the transit time by two orders of magnitude. Application of background irradiation also reduces the transit time considerably. These observations are explained by the presence of energy fluctuation of the highest-occupied molecular orbital level in the porphyrin films due to a dispersed conformational state of the molecules in the amorphous films. This leads to energetically distributed hole traps. Under short circuit and reverse bias, photogenerated holes reside most of the time in deep traps and their diffusivity is only 7×10-11 cm2 s-1. Deep traps are filled by application of a forward bias and by optical irradiation leading to reduction of the transit time and a concomitant increase of the diffusivity up to 2×10-7 cm2 s-1.

  5. Functionalization of carbon nanotubes with water-insoluble porphyrin in ionic liquid: direct electrochemistry and highly sensitive amperometric biosensing for trichloroacetic acid.

    PubMed

    Tu, Wenwen; Lei, Jianping; Ju, Huangxian

    2009-01-01

    A functional composite of single-walled carbon nanotubes (SWNTs) with hematin, a water-insoluble porphyrin, was first prepared in 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM][PF(6)]) ionic liquid. The novel composite in ionic liquid was characterized by scanning electron microscopy, ultraviolet absorption spectroscopy, and electrochemical impedance spectroscopy, and showed a pair of direct redox peaks of the Fe(III)/Fe(II) couple. The composite-[BMIM][PF(6)]-modified glassy carbon electrode showed excellent electrocatalytic activity toward the reduction of trichloroacetic acid (TCA) in neutral media due to the synergic effect among SWNTs, [BMIM][PF(6)], and porphyrin, which led to a highly sensitive and stable amperometric biosensor for TCA with a linear range from 9.0x10(-7) to 1.4x10(-4) M. The detection limit was 3.8x10(-7) M at a signal-to-noise ratio of 3. The TCA biosensor had good analytical performance, such as rapid response, good reproducibility, and acceptable accuracy, and could be successfully used for the detection of residual TCA in polluted water. The functional composite in ionic liquid provides a facile way to not only obtain the direct electrochemistry of water-insoluble porphyrin, but also construct novel biosensors for monitoring analytes in real environmental samples.

  6. Photodynamic inactivation of Penicillium chrysogenum conidia by cationic porphyrins.

    PubMed

    Gomes, Maria C; Woranovicz-Barreira, Sandra M; Faustino, Maria A F; Fernandes, Rosa; Neves, Maria G P M S; Tomé, Augusto C; Gomes, Newton C M; Almeida, Adelaide; Cavaleiro, José A S; Cunha, Angela; Tomé, João P C

    2011-11-01

    This work reports the photophysical and biological evaluation of five cationic porphyrins as photosensitizers (PS) for the photodynamic inactivation (PDI) of Penicillium chrysogenum conidia. Two different cationic porphyrin groups were synthesized from 5,10,15,20-tetrakis(4-pyridyl)porphyrin and 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin. The photostability and singlet oxygen generation studies showed that these molecules are photostable and efficient singlet oxygen generators. PDI experiments of P. chrysogenum conidia conducted with 50 μmol L(-1) of photosensitiser under white light at a fluence rate of 200 mW cm(-2) over 20 min showed that the most effective PS caused a 4.1 log reduction in the concentration of viable conidia. The present results show that porphyrins 1a and 1b are more efficient PSs than porphyrin 2a while porphyrins 1c and 2b show no inactivation of P. chrysogenum. It is also clear that the effectiveness of the molecule as PS for antifungal PDI is strongly related with the porphyrin substituent groups, and consequently their solubility in physiological media. The average amount of PS adsorbed per viable conidium was a determining factor in the photoinactivation efficiency and varied between the different studied PSs. Cationic PSs 1a and 1b might be promising anti-fungal PDI agents with potential applications in phytosanitation, biofilm control, bioremediation, and wastewater treatment.

  7. Photocontrol over cooperative porphyrin self-assembly with phenylazopyridine ligands.

    PubMed

    Hirose, Takashi; Helmich, Floris; Meijer, E W

    2013-01-02

    The cooperative self-assembly of chiral zinc porphyrins is regulated by a photoresponsive phenylazopyridine ligand. Porphyrin stacks depolymerize into dimers upon axial ligation and the strength of the coordination is regulated by its photoinduced isomerization, which shows more than 95 % conversion ratio for both photostationary states.

  8. Cyano- and polycyanometallo-porphyrins as catalysts for alkane oxidation

    DOEpatents

    Ellis, Jr., Paul E.; Lyons, James E.

    1995-01-01

    New compositions of matter comprising cyano-substituted metal complexes of porphyrins are catalysts for the oxidation of alkanes. The metal is iron, chromium, manganese, ruthenium, copper or cobalt. The porphyrin ring has cyano groups attached thereto in meso and/or .beta.-pyrrolic positions.

  9. Cyano- and polycyanometallo-porphyrins as catalysts for alkane oxidation

    DOEpatents

    Ellis, Jr., Paul E.; Lyons, James E.

    1993-01-01

    New compositions of matter comprising cyano-substituted metal complexes of porphyrins are catalysts for the oxidation of alkanes. The metal is iron, chromium, manganese, ruthenium, copper or cobalt. The porphyrin ring has cyano groups attached thereto in meso and/or .beta.-pyrrolic positions.

  10. Cyano- and polycyanometallo-porphyrins as catalysts for alkane oxidation

    DOEpatents

    Ellis, P.E. Jr.; Lyons, J.E.

    1995-01-17

    New compositions of matter comprising cyano-substituted metal complexes of porphyrins are catalysts for the oxidation of alkanes. The metal is iron, chromium, manganese, ruthenium, copper or cobalt. The porphyrin ring has cyano groups attached thereto in meso and/or [beta]-pyrrolic positions.

  11. Cyano- and polycyanometallo-porphyrins as catalysts for alkane oxidation

    DOEpatents

    Ellis, P.E. Jr.; Lyons, J.E.

    1993-05-18

    New compositions of matter comprising cyano-substituted metal complexes of porphyrins are catalysts for the oxidation of alkanes. The metal is iron, chromium, manganese, ruthenium, copper or cobalt. The porphyrin ring has cyano groups attached thereto in meso- and/or [beta]-pyrrolic positions.

  12. Photochemistry of porphyrins: a model for the origin of photosynthesis

    NASA Technical Reports Server (NTRS)

    Mercer-Smith, J. A.; Mauzerall, D. C.

    1984-01-01

    A series of porphyrins and catalysts has been prepared as a model for the origin of photosynthesis on the primordial earth. These compounds have been used to test the hypotheses that (1) the biosynthetic pathway to chlorophyll recapitulates the evolutionary history of photosynthesis, and (2) the proto-photosythetic function of biogenetic porphyrins (biosynthetic chlorophyll precursors) was the oxidation of organic molecules by photoexcited porphyrins with the attendant emission of molecular hydrogen. This paper describes experiments in which photoexcited biogenetic porphyrins oxidize ethylenediamine tetraacetic acid (EDTA). The concomitant reduction of protons to hydrogen gas occurs in the presence of a colloidal platinum catalyst. The addition of methyl viologen, a one-electron shuttle, increases the amount of molecular hydrogen generated during long irradiations and the quantum yield of hydrogen production. When the porphyrin and catalyst are held in association by molecular complexes, the increased efficiency of electron transfer produces higher yields of hydrogen gas.

  13. Highly non-planar dendritic porphyrin for pH sensing: observation of porphyrin monocation.

    PubMed

    Thyagarajan, Sujatha; Leiding, Thom; Arsköld, Sindra Peterson; Cheprakov, Andrei V; Vinogradov, Sergei A

    2010-11-01

    Metal-free porphyrin-dendrimers provide a convenient platform for the construction of membrane-impermeable ratiometric probes for pH measurements in compartmentalized biological systems. In all previously reported molecules, electrostatic stabilization (shielding) of the core porphyrin by peripheral negative charges (carboxylates) was required to shift the intrinsically low porphyrin protonation pK(a)'s into the physiological pH range (pH 6-8). However, binding of metal cations (e.g., K(+), Na(+), Ca(2+), Mg(2+)) by the carboxylate groups on the dendrimer could affect the protonation behavior of such probes in biological environments. Here we present a dendritic pH nanoprobe based on a highly non-planar tetraaryltetracyclohexenoporphyrin (Ar(4)TCHP), whose intrinsic protonation pK(a)'s are significantly higher than those of regular tetraarylporphyrins, thereby eliminating the need for electrostatic core shielding. The porphyrin was modified with eight Newkome-type dendrons and PEGylated at the periphery, rendering a neutral water-soluble probe (TCHpH), suitable for measurements in the physiological pH range. The protonation of TCHpH could be followed by absorption (e.g., ε(Soret)(dication)∼270,000 M(-1) cm(-1)) or by fluorescence. Unlike most tetraarylporphyrins, TCHpH is protonated in two distinct steps (pK(a)'s 7.8 and 6.0). In the region between the pK(a)'s, an intermediate species with a well-defined spectroscopic signature, presumably a TCHpH monocation, could be observed in the mixture. The performance of TCHpH was evaluated by pH gradient measurements in large unilamellar vesicles. The probe was retained inside the vesicles and did not pass through and/or interact with vesicle membranes, proving useful for quantification of proton transport across phospholipid bilayers. To interpret the protonation behavior of TCHpH we developed a model relating structural changes on the porphyrin macrocycle upon protonation to its basicity. The model was validated by

  14. Deformation and failure of glassy materials

    NASA Astrophysics Data System (ADS)

    Rottler, Joerg Gerhard

    Elastoplastic deformation of disordered solids and the formation of polymer crazes in amorphous polymer glasses are studied using large-scale molecular dynamics simulations. It is shown that the pressure-modified von Mises criterion accurately describes the maximum shear yield stress under general loading conditions. The pressure coefficient is insensitive to most model parameters, but is related to the bead geometry in analogy to friction coefficients. The yield stress decreases linearly with rising temperature and the strain rate dependence can be described by a power-law, or in a limited range, by a logarithm. The rate dependence does not vary with temperature, which is inconsistent with simple rate-state models of thermal activation such as the Eyring model. An analysis of the dynamics of the local stress distribution as well as modern phenomenological theories of rheology of glassy materials are discussed in light of these findings. We then present a comprehensive investigation of the deformation of glassy polymeric systems into a dense load-bearing network of fibrils and voids called a craze at large strains. This expansion takes place in the form of a drawing process, where the strain rate is strongly localized in a narrow interface region between dense polymer and craze. The expansion is controlled by some polymer chain segments between entanglements that are stretched taut during crazing. We also find that the distribution of tension in the craze develops an exponential force tail in close analogy to compressed jammed systems such as granular media. This highly anisotropic stress distribution and the localization of large forces on relatively few chains indicate that earlier models of the crazing process that treat the polymer as a viscous fluid with hydrodynamic interactions are incorrect. Simulations and simple scaling arguments are presented that describe craze breakdown through disentanglement or chain scission. Glassy polymers exhibit an unusually

  15. New water-soluble Mn-porphyrin with catalytic activity for superoxide dismutation and peroxynitrite decomposition.

    PubMed

    Asayama, Shoichiro; Nakajima, Takumi; Kawakami, Hiroyoshi

    2011-07-01

    We have synthesized a new water-soluble cationic Mn-porphyrin with catalytic activity for both superoxide dismutation and peroxynitrite decomposition. The resulting Mn-porphyrin also showed higher stability for reactive oxygen species such as hydrogen peroxide and lower cytotoxicity, when compared with a control normal Mn-porphyrin. Furthermore, the new porphyrin recovered the viability of lipopolysaccharide-stimulated macrophage RAW 264.7 cells but the control Mn-porphyrin did not.

  16. Simulations of Soft Glassy Matter with Ripening

    NASA Astrophysics Data System (ADS)

    Hwang, Hyun Joo; Riggleman, Robert; Crocker, John

    2015-03-01

    Soft glassy matter (SGM) such as foams, emulsions, and colloids, exhibit interesting rheological properties that have long defied explanation. In particular, the shear modulus of these materials displays weak power law frequency dependence. To understand the origin of this property in more depth, we have built a three-dimensional, modified Bubble Dynamics model. The bubbles interact with a purely repulsive harmonic potential and ripen according to diffusion-based governing equations. An energy minimizer is implemented to quasi-statically relax topological rearrangements in the system as ripening proceeds. Preliminary results show that the model displays expected intermittent particle rearrangements and a weakly frequency-dependent shear modulus behaving like a power law fluid. We find that the anomalous relaxation properties and avalanche-like nature of the rearrangements can be related to different measures of the systems potential energy landscape.

  17. Glassy Dynamics, Cell Mechanics and Endothelial Permeability

    PubMed Central

    Hardin, Corey; Rajendran, Kavitha; Manomohan, Greeshma; Tambe, Dhananjay T.; Butler, James P.; Fredberg, Jeffrey J.; Martinelli, Roberta; Carman, Christopher V.; Krishnan, Ramaswamy

    2013-01-01

    A key feature of all inflammatory processes is disruption of the vascular endothelial barrier. Such disruption is initiated in part through active contraction of the cytoskeleton of the endothelial cell (EC). Because contractile forces are propagated from cell to cell across a great many cell-cell junctions, this contractile process is strongly cooperative and highly nonlocal. We show here that the characteristic length scale of propagation is modulated by agonists and antagonists that impact permeability of the endothelial barrier. In the presence of agonists including thrombin, histamine, and H202, force correlation length increases, whereas in the presence of antagonists including sphingosine-1-phosphate, hepatocyte growth factor, and the rho kinase inhibitor, Y27632, force correlation length decreases. Intercellular force chains and force clusters are also evident, both of which are reminiscent of soft glassy materials approaching a glass transition. PMID:23638866

  18. Active fluidization in dense glassy systems.

    PubMed

    Mandal, Rituparno; Bhuyan, Pranab Jyoti; Rao, Madan; Dasgupta, Chandan

    2016-07-20

    Dense soft glasses show strong collective caging behavior at sufficiently low temperatures. Using molecular dynamics simulations of a model glass former, we show that the incorporation of activity or self-propulsion, f0, can induce cage breaking and fluidization, resulting in the disappearance of the glassy phase beyond a critical f0. The diffusion coefficient crosses over from being strongly to weakly temperature dependent as f0 is increased. In addition, we demonstrate that activity induces a crossover from a fragile to a strong glass and a tendency of active particles to cluster. Our results are of direct relevance to the collective dynamics of dense active colloidal glasses and to recent experiments on tagged particle diffusion in living cells.

  19. Shear banding in soft glassy materials.

    PubMed

    Fielding, S M

    2014-10-01

    Many soft materials, including microgels, dense colloidal emulsions, star polymers, dense packings of multilamellar vesicles, and textured morphologies of liquid crystals, share the basic 'glassy' features of structural disorder and metastability. These in turn give rise to several notable features in the low frequency shear rheology (deformation and flow properties) of these materials: in particular, the existence of a yield stress below which the material behaves like a solid, and above which it flows like a liquid. In the last decade, intense experimental activity has also revealed that these materials often display a phenomenon known as shear banding, in which the flow profile across the shear cell exhibits macroscopic bands of different viscosity. Two distinct classes of yield stress fluid have been identified: those in which the shear bands apparently persist permanently (for as long as the flow remains applied), and those in which banding arises only transiently during a process in which a steady flowing state is established out of an initial rest state (for example, in a shear startup or step stress experiment). Despite being technically transient, such bands may in practice persist for a very long time and so be mistaken for the true steady state response of the material in experimental practice. After surveying the motivating experimental data, we describe recent progress in addressing it theoretically, using the soft glassy rheology model and a simple fluidity model. We also briefly place these theoretical approaches in the context of others in the literature, including elasto-plastic models, shear transformation zone theories, and molecular dynamics simulations. We discuss finally some challenges that remain open to theory and experiment alike.

  20. Computer simulations of athermal and glassy systems

    NASA Astrophysics Data System (ADS)

    Xu, Ning

    2005-12-01

    We performed extensive molecular dynamics simulations to better understand athermal and glassy systems near jamming transitions. We focused on four related projects. In the first project, we decomposed the probability distribution P(φ) of finding a collectively jammed state at packing fraction φ into two distinct contributions: the density of CJ states rho(φ) and their basins of attraction beta(φ). In bidisperse systems, it is likely that rho(φ) controls the shape of P(φ) in the large system size limit, and thus the most likely random jammed state may be used as a protocol independent definition of random close packing in this system. In the second project, we measured the yield stress in two different ensembles: constant shear rate and constant stress. The yield stress measured in the constant stress ensemble is larger than that measured in the constant shear rate ensemble, however, the difference between these two measurements decreases with increasing system size. In the third project, we investigated under what circumstances nonlinear velocity profiles form in frictionless granular systems undergoing boundary driven planar shear flow. Nonlinear velocity profiles occur at short times, but evolve into linear profiles at long times. Nonlinear velocity profiles can be stabilized by vibrating these systems. The velocity profile can become highly localized when the shear stress of the system is below the constant force yield stress, provided that the granular temperature difference across the system is sufficiently large. In the fourth project, we measured the effective temperature defined from equilibrium fluctuation-dissipation relations in athermal and glassy systems sheared at constant pressure. We found that the effective temperature is strongly controlled by pressure in the slowly sheared regime. Thus, this effective temperature and pressure are not independent variables in this regime.

  1. Anodic electrosynthesis of some peroxy compounds on glassy carbon electrodes

    SciTech Connect

    Khomutov, N.E.; Zakhodyakina, N.A.; Svirida, L.V.; Nesvat, N.V.

    1987-11-10

    The authors present the results of a study of the anodic electrosynthesis of hydrogen peroxide and its derivatives on glassy carbon in solutions of sodium carbonate and sodium carbonate with sodium borate. We studied the kinetics of anodic processes on glassy carbon with the aid of polarization measurements and a method for determining the concentrations of active oxygen in the anolyte and the current efficiency. The current efficiencies with respect to active oxygen obtained on glassy carbon in the mixed solution of sodium borate and sodium carbonate are close to the current efficiencies which are observed on platinum anodes in the industrial electrosynthesis of perborates.

  2. A Statistical Approach to Relaxation in Glassy Materials.

    DTIC Science & Technology

    1984-11-01

    Approach to Relaxation in Glassy Materials bya by DTIC Et. ECTE Karina Weron M A. and S "z’ Aleksander Weron ApptovC fcv - " Technical Report No. 82...STATISTICAL APPROACH TO RELAXATION IN GLASSY MATERIALS 12. PERSONAL AUTHOR(S) Karina Weron and Aleksander Weron 13.. TYPE OF REPORT 13b. TIME COVERED 14. DATE...CLASSIFICATION OF THIS PAGE A Statistical Approach to Relaxation in Glassy Materials1 Karina Weron Institute of Physics Technical University of Wroclaw 50-370

  3. Biosynthetic porphyrins and the origin of photosynthesis

    NASA Technical Reports Server (NTRS)

    Mauzerall, D.; Ley, A.; Mercer-Smith, J. A.

    1986-01-01

    Since the prebiotic atmosphere was anaerobic, if not reducing, a useful function of primordial photosynthesis would have been to photooxidize reduced substrates such as Fe(+2), S(-2) or reduced organic molecules and to emit hydrogen. Experiments have shown that the early biogenic pigments uroporphyrin and coproporphyrin do photooxidize organic compounds and emit hydrogen in the presence of a platinum catalyst. These experiments were carried out in dilute aqueous solution near neutral pH under anaerobic atmosphere, and quantum yields near 10-2 were obtained. Thus relevant prebiotic conditions were maintained. Rather then to further optimize conditions, attempts were made to replace the platinum catalyst by a more prebiotically suitable catalyst. Trials with an Fe4S4(SR)4 cluster, in analogy to the present hydrogenase and nitrogenase, were not successful. However, experiments using cobalt complexes to catalyze the formation of hydrogen are promising. In analogy with biological photosynthetic systems which group pigments, electron transfer molecules and enzymes in clusters for efficiency, it was found that binding the biogenic porphyrins to the polyvinyl alcohol used to support the platinum catalyst did increase the quantum yield of the reaction. It was also found that ultraviolet light can serve to photo-oxidize porphyrinogens to porphyrins under anaerobic conditions. Thus the formation of the colorless porphyriogens by the extraordinarily simple biosynthetic pathway would not be a problem because of the prevalence of UV light in the prebiotic, anoxic atmosphere.

  4. Porphyrin Interactions with Wild Type and Mutant Mouse Ferrochelatase

    SciTech Connect

    Ferreira, Gloria C.; Franco, Ricardo; Lu, Yi; Ma, Jian-Guo; Shelnutt, John A.

    1999-05-19

    Ferrochelatase (EC 4.99.1.1), the terminal enzyme of the heme biosynthetic pathway, catalyzes Fe2+ chelation into protoporphyrin IX. Resonance Raman and W-visible absorbance spectroscopes of wild type and engineered variants of murine ferrochelatase were used to examine the proposed structural mechanism for iron insertion into protoporphyrin by ferrochelatase. The recombinant variants (i.e., H207N and E287Q) are enzymes in which the conserved amino acids histidine-207 and glutamate-287 of murine ferrochelatase were substituted with asparagine and glutamine, respectively. Both of these residues are at the active site of the enzyme as deduced from the Bacillus subtilis ferrochelatase three-dimensional structure. Addition of free base or metalated porphyrins to wild type ferrochelatase and H207N variant yields a quasi 1:1 complex, possibly a monomeric protein-bound species. In contrast, the addition of porphyrin (either free base or metalated) to E287Q is sub-stoichiometric, as this variant retains bound porphyrin in the active site during isolation and purification. The specificity of porphyrin binding is confirmed by the narrowing of the structure-sensitive resonance Raman lines and the vinyl vibrational mode. Resonance Raman spectra of free base and metalated porphyrins bound to the wild type ferrochelatase indicate a nonplanar distortion of the porphyrin macrocycle, although the magnitude of the distortion cannot be determined without first defining the specific type of deformation. Significantly, the extent of the nonplanar distortion varies in the case of H207N- and E287Q-bound porphyrins. In fact, resonance Raman spectral decomposition indicates a homogeneous ruffled distortion for the nickel protoporphyrin bound to the wild type ferrochelatase, whereas both a planar and ruffled conformations are present for the H207N-bound porphyrin. Perhaps more revealing is the unusual resonance , 3 Raman spectrum of the endogenous E287Q-bound porphyrin, which has

  5. Adhesion in hydrogels and model glassy polymers

    NASA Astrophysics Data System (ADS)

    Guvendiren, Murat

    Two main topics are addressed in this dissertation: (1) adhesion in hydrogels; (2) interfacial interactions between model glassy polymers. A self-assembly technique for the formation of hydrogels from acrylic triblock copolymer solutions was developed, based on vapor phase solvent exchange. Structure formation in the gels was characterized by small angle X-ray scattering, and swelling was measured in controlled pH buffer solutions. Strong gels are formed with polymer weight fractions between 0.01 and 0.15, and with shear moduli between 0.6 kPa and 3.5 kPa. Adhesive functionality, based on 3,4-dihydroxy-L-phenylalanine (DOPA) was also incorporated into the triblock copolymers. The effect of DOPA concentration on gel formation and swelling was investigated in detail. The adhesive properties of DOPA-functionalized hydrogels on TiO2 were investigated with an axisymmetric adhesion method. It was shown that the presence of DOPA enhances the adhesive properties of the hydrogels, but that the effect is minimized at pH values below 10, where the DOPA groups are hydrophobic. Thin film membranes were produced in order to study the specific interactions between DOPA and TiO2 and DOPA and tissue, using a membrane inflation method. The presence of DOPA in the membranes enhances the adhesion on TiO 2 and tissue, although adhesion to tissue requires that the DOPA groups be oxidized while in contact with the tissue of interest. Porous hydrogel scaffolds for tissue engineering applications were formed by adding salt crystals to the triblock copolymer solution prior to solvent exchange. Salt was then leached out by immersing the gel into water. Structures of the porous hydrogels were characterized by confocal laser scanning microscopy. These hydrogels were shown to be suitable for tissue regeneration and drug delivery applications. Diffusion-mediated adhesion between two component miscible polymer systems having very different glassy temperatures was also investigated. Axisymmetric

  6. Preparation and biodistribution of copper-67-labeled porphyrins and porphyrin-A6H immunoconjugates.

    PubMed

    Bhalgat, M K; Roberts, J C; Mercer-Smith, J A; Knotts, B D; Vessella, R L; Lavallee, D K

    1997-02-01

    The synthetic porphyrins, N-benzyl-5,10,15,20-tetrakis (4-carboxyphenyl) porphine (N-bzHTCPP) and N-4-nitrobenzyl-5-(4-carboxyphenyl)-10,15,20-tris(4-sulfophenyl) porphine (N-bzHCS3P), represent excellent radiocopper chelating agents that may find utility in antibody-mediated diagnosis and/or therapy. N-bzHCS3P was conjugated to an anti-renal cell carcinoma (RCC) antibody, A6H, and labeled with copper-67. 67CuCS3P-A6H was studied for its biodistribution in human RCC xenograft-bearing nude mice, along with the radiolabeled free porphyrins. The porphyrins resulted in tumor:blood ratios in the range of 3 to 4 after 48 h. The radiolabeled antibody achieved a tumor:blood ratio of over 16 after 45 h, indicating accumulation at the desired site. However, unwanted localization also occurred in the liver and spleen, which will have to be rectified before realizing the full potential of this approach.

  7. No inherent glassiness in a Penrose tiling quasicrystal

    SciTech Connect

    Strandburg, K.J.; Dressel, P.R.

    1988-11-01

    Consideration of the structure of the Penrose pattern has led to speculation that a system with a Penrose tiling ground state might be subject to inherent glassy behavior. Monte Carol simulations show, using a simple model of the energetics, that there is no inherent glassiness in the Penrose tiling. Thermodynamic quantities measured are completely reversible, displaying no observable hysterisis, and the system may be easily cooled from a highly disordered configuration into its lowest energy state. 11 refs., 7 figs.

  8. High Strain Rate Mechanical Properties of Glassy Polymers

    DTIC Science & Technology

    2012-07-25

    Force Materiel Command  United States Air Force  Eglin Air Force Base AFRL-RW-EG-TP-2012-008 High Strain Rate...TITLE AND SUBTITLE High Strain Rate Mechanical Properties of Glassy Polymers 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT...1990s, a range of experimental data has been generated describing the response of glassy polymers to high strain rate loading in compression. More

  9. Challenging Density Functional Theory Calculations with Hemes and Porphyrins

    PubMed Central

    de Visser, Sam P.; Stillman, Martin J.

    2016-01-01

    In this paper we review recent advances in computational chemistry and specifically focus on the chemical description of heme proteins and synthetic porphyrins that act as both mimics of natural processes and technological uses. These are challenging biochemical systems involved in electron transfer as well as biocatalysis processes. In recent years computational tools have improved considerably and now can reproduce experimental spectroscopic and reactivity studies within a reasonable error margin (several kcal·mol−1). This paper gives recent examples from our groups, where we investigated heme and synthetic metal-porphyrin systems. The four case studies highlight how computational modelling can correctly reproduce experimental product distributions, predicted reactivity trends and guide interpretation of electronic structures of complex systems. The case studies focus on the calculations of a variety of spectroscopic features of porphyrins and show how computational modelling gives important insight that explains the experimental spectra and can lead to the design of porphyrins with tuned properties. PMID:27070578

  10. Enhancing PDT drug delivery by enzymatic cleavage of porphyrin phosphates

    NASA Astrophysics Data System (ADS)

    Xu, Bing; Liang, Gaolin; Wang, Ling; Yang, Zhimou; Chan, Kalok; Chang, Chi K.

    2007-02-01

    A new anionic porphyrin-phosphate conjugate has been made as the substrate of phosphatase to evaluate its cellular-uptake and potential targeting on cancer cells, taking advantage of the over-expression of phosphatases associated with the development of cancers. The phosphate groups increase the hydrophilicity of porphyrin dityrosine phosphate and facilitate its formulation in aqueous solvent. Upon hydrolysis by phosphatase after cellular uptaking, the more hydrophobic porphyrin-dityrosine promises to give better cellular retention. Indeed, the phosphate conjugate displayed a much better PDT effect than that of the parent porphyrin at the same concentration (10 μM) and light dosage on HeLa cells, indicating the enzyme-cleavage reaction occurred in HeLa cells plays a role. Photosenzitizers utilizing enzyme-cleavage might be a promising approach for photodynamic therapy.

  11. Studies on porphyrin photoproducts in solution, cells, and tumor tissue

    NASA Astrophysics Data System (ADS)

    Koenig, Karsten; Schneckenburger, Herbert; Rueck, Angelika C.; Koenig, Roland

    1994-07-01

    Light excitation of photosensitizing porphyrins leads to cytotoxic reactions. In addition, photobleaching and photoproduct formation occur indicating photosensitizer destruction. Photoproducts from hematoporphyrin (HP) fluoresce in aqueous solution at 642 nm, whereas photoproducts from protoporphyrin (PP) in hydrophobic environment emit around 670 nm and exhibit pronounced absorption at 665 nm. Photoproduct formation depends on singlet oxygen. The photoproducts exhibit faster fluorescence decay kinetics compared with nonirradiated porphyrins, as shown by time-grated spectroscopy and fluorescence decay measurements. Photoproduct fluorescence was observed during light exposure of cells and of tumor-bearing, nude mice, following administration of Hematoporphyrin Derivative (HpD), tetramethyl-HP, and PP. Photoconversion was also detected with naturally-occurring porphyrins (PP-producing bacteria) and ALA-simulated biosynthesis of PP in tumor tissue and in skin lesions of patients (psoriasis, mycosis fungoides). The efficiency of PDT with porphyrin photoproducts was found to be low in spite of the strong electronic transitions in the red spectral region.

  12. meso-meso linked porphyrin-[26]hexaphyrin-porphyrin hybrid arrays and their triply linked tapes exhibiting strong absorption bands in the NIR region.

    PubMed

    Mori, Hirotaka; Tanaka, Takayuki; Lee, Sangsu; Lim, Jong Min; Kim, Dongho; Osuka, Atsuhiro

    2015-02-11

    We describe the synthesis and characterization of directly meso-meso linked porphyrin-[26]hexaphyrin-porphyrin hybrid oligomers and their triply linked (completely fused) hybrid tapes. meso-meso Linked Ni(II) porphyrin-[26]hexaphyrin-Ni(II) porphyrin trimers were prepared by methanesulfonic acid-catalyzed cross-condensation of meso-formyl Ni(II) porphyrins with a 5,10-diaryltripyrrane followed by oxidation with 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ). The Ni(II) porphyrin moieties were converted to Zn(II) porphyrins via an indirect route involving reduction of the [26]hexaphyrin to its 28π congener, acid-induced denickelation, oxidation of the [28]hexaphyrin, and finally Zn(II) ion insertion. Over the course of these transformations, porphyrin-[28]hexaphyrin-porphyrin trimers have been revealed to take on a Möbius aromatic twisted structure for the [28]hexaphyrin segment. Oxidation of meso-meso linked hybrid trimer bearing 5,15-diaryl Zn(II) porphyrins with DDQ/Sc(OTf)3 under mild conditions resulted in meso-meso coupling oligomerization, affording the corresponding dimeric (hexamer), trimeric (nonamer), and tetrameric (dodecamer) oligomers. On the other hand, oxidation of a meso-meso linked hybrid trimer bearing 5,10,15-triaryl Zn(II) porphyrin terminals with DDQ/Sc(OTf)3 under harsher conditions afforded a meso-meso, β-β, β-β triply linked hybrid porphyrin tape, which displays a sharp and intense absorption band at 1912 nm. Comparison of this extremely red-shifted absorption band with those of Zn(II) porphyrin tapes suggests that the bathochromic-shifting capability of a [26]hexaphyrin unit is large, almost equivalent to that of four individual Zn(II) porphyrin units. As demonstrated, the fusion of porphyrins to [26]hexaphyrin offers an efficient means to expand their conjugation networks, significantly expanding the capabilities attainable for these chromophores.

  13. Direct-patterning of porphyrin dot arrays and lines using electrohydrodynamic jet printing.

    PubMed

    Song, Chi Ho; Back, Sung Yul; Yu, Sung Il; Lee, Hyoung Jin; Kim, Beom Soo; Yang, Nam Yeol; Jeong, Soo Hoa; Ahn, Heejoon

    2012-01-01

    In this research, we have fabricated micron-sized patterns of porphyrins on silicon substrates using an electrohydrodynamic (EHD) jet printing technique. Optical and fluorescence microscopies have been used to examine the shape and fluorescence property of porphyrin patterns. The morphology of the porphyrin patterns printed with variously formulated porphyrin inks and the effects of applied voltage, working distance, and substrate properties on the morphology of patterns were investigated using scanning electron microscopy (SEM) and atomic force microscopy (AFM). We have also demonstrated the acid-vapor sensing capability of the porphyrins by exposing the porphyrin patterns on Si substrates to nitric acid vapor.

  14. Synthesis, Electrochemistry, and Photophysics of Aza-BODIPY Porphyrin Dyes.

    PubMed

    Pascal, Simon; Bucher, Léo; Desbois, Nicolas; Bucher, Christophe; Andraud, Chantal; Gros, Claude P

    2016-03-24

    The synthesis of dyad and triad aza-BODIPY-porphyrin systems in two steps starting from an aryl-substituted aza-BODIPY chromophore is described. The properties of the resulting aza-BODIPY-porphyrin conjugates have been extensively investigated by means of electrochemistry, spectroelectrochemistry, and absorption/emission spectroscopy. Fluorescence measurements have revealed a dramatic loss of luminescence intensity, mainly due to competitive energy transfer and photoinduced electron transfer involving charge separation followed by recombination.

  15. Glassy state of native collagen fibril?

    NASA Astrophysics Data System (ADS)

    Gevorkian, S. G.; Allahverdyan, A. E.; Gevorgyan, D. S.; Hu, C.-K.

    2011-07-01

    Our micromechanical experiments show that viscoelastic features of type-I collagen fibril at physiological temperatures display essential dependence on the frequency and speed of heating. For temperatures of 20-30 °C the internal friction has a sharp maximum for a frequency less than 2 kHz. Upon heating the internal friction displays a peak at a temperature Tsoft(v) that essentially depends on the speed of heating v: Tsoft≈70°C for v=1°C/min, and Tsoft≈25°C for v=0.1°C/min. At the same temperature Tsoft(v) Young's modulus passes through a minimum. All these effects are specific for the native state of the fibril and disappear after heat-denaturation. Taken together with the known facts that the fibril is axially ordered as quasicrystal, but disordered laterally, we interpret our findings as indications of a glassy state, where Tsoft is the softening transition.

  16. Impact of iron porphyrin complexes when hydroprocessing algal HTL biocrude

    SciTech Connect

    Jarvis, Jacqueline M.; Sudasinghe, Nilusha M.; Albrecht, Karl O.; Schmidt, Andrew J.; Hallen, Richard T.; Anderson, Daniel B.; Billing, Justin M.; Schaub, Tanner M.

    2016-10-01

    We apply Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) for direct characterization of iron-porphyrins in hydrothermal liquefaction (HTL) biocrude oils derived from two algae: Tetraselmis sp. and cyanobacteria. The ironporphyrin compounds are shown to cause catalyst bed plugging during hydroprocessing due to iron deposition. Inductively-coupled plasma optical emission spectrometry (ICPOES) was utilized for iron quantitation in the plugged catalyst beds formed through hydroprocessing of the two HTL biocrudes and identifies an enrichment of iron in the upper five centimeters of the catalyst bed for Tetraselmis sp. (Fe=100,728 ppm) and cyanobacteria (Fe=115,450 ppm). Direct infusion FT-ICR MS analysis of the two HTL biocrudes with optimized instrument conditions facilitates rapid screening and identification of iron-porphyrins without prior chromatographic separation. With FT-ICR MS we identify 138 unique iron-porphyrin compounds in the two HTL biocrudes that are structurally similar to metal-porphyrins (e.g. Ni and V) observed in petroleum. No ironporphyrins are observed in the cyanobacteria HTL biocrude after hydroprocessing, which indicates that iron-porphyrin structures in the HTL biocrude are degraded during hydroprocessing. Hydrodemetallization reactions that occur through hydroprocessing of HTL biocrudes could be responsible for the decomposition of iron-porphyrin structures leading to metal deposition in the catalyst bed that result in catalyst deactivation and bed plugging, and must be addressed for effective upgrading of algal HTL biocrudes.

  17. Porphyrins in photodynamic therapy - a search for ideal photosensitizers.

    PubMed

    Pushpan, S K; Venkatraman, S; Anand, V G; Sankar, J; Parmeswaran, D; Ganesan, S; Chandrashekar, T K

    2002-03-01

    The utility of light as a therapeutic agent can be traced back over thousands of years when it was used in Ancient Egypt, India and China to treat a variety of skin diseases like psoriasis, vitiligo, rickets, cancer and psychosis. The isolation of porphyrins and their inherent tumor localizing properties coupled with its ability to generate reactive singlet oxygen when activated by light of particular wavelength which in turn results in cytotoxicity led to the emergence of a new modality namely, photodynamic therapy (PDT) as a therapeutic tool. The higher degree of selectivity offered by this modality and fewer side effects when compared to chemotherapy and radiotherapy has prompted the researchers around the globe to generate new photosensitizers. Porphyrins and expanded porphyrins are one class of molecules under intense investigation due to their photosensitizing ability for PDT application. Expanded porphyrins result from the expansion of the phi electron conjugation by increasing the number of heterocyclic rings or bridging carbons of the existing porphyrin framework. These chromophores show strong absorptions in the red region (650-800 nm) compared to that of normal 18phi porphyrins. The strong absorption of light by a water soluble nontoxic photosensitizing molecule in the therapeutic window resulting in maximum penetration of light into the tissues coupled with high singlet oxygen production will conceptualize an ideal photosensitizer. This review highlights various porphyrinoid sensitizers reported till date and their photosensitizing ability both in vitro and in vivo studies. Furthermore, the urgent need for developing ideal photosensitizer for PDT will also be highlighted.

  18. Antimicrobial and antiviral activity of porphyrin photosensitization

    NASA Astrophysics Data System (ADS)

    Malik, Zvi; Ladan, Hava; Nitzan, Yeshayahu; Smetana, Zehava

    1994-03-01

    In order to photosensitize Gram (-) bacteria such as Pseudomonas aeuruginosa and Escherichia coli, we introduced the small peptide polymyxin-B nona-peptide (PBNP) which stimulated the translocation of porphyrin through the outer membrane of these bacteria and makes PDT possible. Gram negative cell killing by the use of PBNP and DP broadens the antibacterial spectrum of photodynamic inactivation and opens new horizons for this modality as a wide spectrum drug when antibiotic resistance is the main concern. Plasmidial and chromosomal DNA damage in S. aureus and E. coli cells was mediated by DP photosensitization. The major observation was the disappearance of the plasmid supercoiled fraction. The chromosomal DNA was also affected and its degradation products were detected after treatment.

  19. Crystal fields of porphyrins and phthalocyanines

    NASA Astrophysics Data System (ADS)

    Johnson, P. S.; Boukahil, I.; Himpsel, F. J.; Kennedy, C.; Jersett, N.; Cook, P. L.; Garcia-Lastra, J. M.

    2014-03-01

    Polarization-dependent X-ray absorption spectroscopy at the N 1s and metal 2p edges is combined with density functional and atomic multiplet calculations to determine the crystal field parameters 10Dq, Ds, and Dt of transition metal (Mn, Fe, Co, Ni) phthalocyanines and octaethylporphyrins. Octaethyl porphyrins are observed to lie flat on Si with native oxide, while phthalocyanines lie on edge. Strong polarization dependence is found at all edges, which facilitates a unique determination of the crystal field parameters. Crystal field values from PBE density functional calculations provide helpful starting values, which are refined by fitting atomic multiplet calculations to the data. Since the crystal field affects electron-hole separation in solar cells, the systematic set of crystal field parameters obtained here can be useful for optimizing dyes for solar cells.

  20. DNA interaction and photocleavage properties of porphyrins containing cationic substituents at the peripheral position.

    PubMed

    Mettath, S; Munson, B R; Pandey, R K

    1999-01-01

    A series of mono- and disubstituted cationic porphyrins (1-8) were synthesized and investigated for their ability to bind and cleave DNA in the presence of light. In these porphyrins, the cationic substituents were introduced at various peripheral positions, i.e., the non-meso positions of the porphyrin system. The modes of binding of these porphyrins to DNA were investigated by UV-vis spectroscopy, circular dichroism, and an unwinding assay. The intrinsic binding constants Kb of these porphyrins to calf thymus DNA was found to be in the range 10(4)-10(5) M-1. Two of the zinc(II) complexes of non-meso-substituted cationic porphyrins (5 and 8) were found to bind to DNA via intercalation, which is in contrast to the previously reported outside-binding mode for the Zn(II) complexes of meso-substituted cationic porphyrins. Except for monocationic porphyrin 1 and Ni(II) dicationic porphyrin 6, all the other porphyrins were found to be efficient photocleavers of DNA. The DNA photocleavage characteristics of this series of cationic porphyrins were found to depend on the structural characteristics of the poprhyrins such as (a) length of the side chain of the cationic substituents (2 vs 4), (b) the position of the side chain on the porphyrin ring (4 vs 7), and (c) the presence of the chelating metal in 3, 5, and 8 as compared to the nonmetallo porphyrins 2, 4, and 7, respectively.

  1. Ultra-smooth glassy graphene thin films for flexible transparent circuits

    PubMed Central

    Dai, Xiao; Wu, Jiang; Qian, Zhicheng; Wang, Haiyan; Jian, Jie; Cao, Yingjie; Rummeli, Mark H.; Yi, Qinghua; Liu, Huiyun; Zou, Guifu

    2016-01-01

    Large-area graphene thin films are prized in flexible and transparent devices. We report on a type of glassy graphene that is in an intermediate state between glassy carbon and graphene and that has high crystallinity but curly lattice planes. A polymer-assisted approach is introduced to grow an ultra-smooth (roughness, <0.7 nm) glassy graphene thin film at the inch scale. Owing to the advantages inherited by the glassy graphene thin film from graphene and glassy carbon, the glassy graphene thin film exhibits conductivity, transparency, and flexibility comparable to those of graphene, as well as glassy carbon–like mechanical and chemical stability. Moreover, glassy graphene–based circuits are fabricated using a laser direct writing approach. The circuits are transferred to flexible substrates and are shown to perform reliably. The glassy graphene thin film should stimulate the application of flexible transparent conductive materials in integrated circuits. PMID:28138535

  2. Shear banding in soft glassy materials

    NASA Astrophysics Data System (ADS)

    Fielding, S. M.

    2014-10-01

    Many soft materials, including microgels, dense colloidal emulsions, star polymers, dense packings of multilamellar vesicles, and textured morphologies of liquid crystals, share the basic ‘glassy’ features of structural disorder and metastability. These in turn give rise to several notable features in the low frequency shear rheology (deformation and flow properties) of these materials: in particular, the existence of a yield stress below which the material behaves like a solid, and above which it flows like a liquid. In the last decade, intense experimental activity has also revealed that these materials often display a phenomenon known as shear banding, in which the flow profile across the shear cell exhibits macroscopic bands of different viscosity. Two distinct classes of yield stress fluid have been identified: those in which the shear bands apparently persist permanently (for as long as the flow remains applied), and those in which banding arises only transiently during a process in which a steady flowing state is established out of an initial rest state (for example, in a shear startup or step stress experiment). Despite being technically transient, such bands may in practice persist for a very long time and so be mistaken for the true steady state response of the material in experimental practice. After surveying the motivating experimental data, we describe recent progress in addressing it theoretically, using the soft glassy rheology model and a simple fluidity model. We also briefly place these theoretical approaches in the context of others in the literature, including elasto-plastic models, shear transformation zone theories, and molecular dynamics simulations. We discuss finally some challenges that remain open to theory and experiment alike.

  3. A fluorene-modified porphyrin for efficient dye-sensitized solar cells.

    PubMed

    Wu, Cheng-Hua; Pan, Tsung-Yu; Hong, Shang-Hao; Wang, Chin-Li; Kuo, Hshin-Hui; Chu, Yang-Yun; Diau, Eric Wei-Guang; Lin, Ching-Yao

    2012-05-07

    Porphyrins bearing a polyaromatic or a heterocyclic group are prepared to study their fundamental and photovoltaic properties. Solar cells sensitized with a fluorene-modified porphyrin outperform other dyes in the series, reaching ~90% efficiency of N719 dye.

  4. A porous covalent porphyrin framework with exceptional uptake capacity of saturated hydrocarbons oil spill cleanup

    SciTech Connect

    Wang, Xi-Sen; Liu, Jian; Bonefont, Jean M.; Yuan, Da-Qiang; Thallapally, Praveen K.; Ma, Shengqian

    2013-01-21

    Yamamoto homo-coupling reaction of tetra(4-bromophenyl)porphyrin afforded a porous covalent porphyrin framework, PCPF-1, which features strong hydrophobicity and oleophilicity and demonstrates exceptional adsorptive capacities for saturated hydrocarbons and gasoline.

  5. Porphyrin and bodipy molecular rotors as microviscometers

    NASA Astrophysics Data System (ADS)

    Kimball, Joseph Daniel, III

    Viscosity, a fluid's internal resistance to flow and resist molecular diffusion, is a fundamental property of fluid media. Determining the bulk viscosity of a fluid has been easy to relatively simple to accomplish for many years, yet in the recent decade there has been a focus on techniques to measure a fluid's microviscosity. Microviscosity differs from bulk viscosity such that microviscosity is the friction experienced by a single particle interacting with its micron-sized local environment. Macroscopic methods to evaluate the viscosity are well established, but methods to determine viscosity on the microscale level remains unclear. This work determines the viability of three molecular rotors designed as probes for microviscosity in organic media, ionic liquids, and in the cellular microenvironment. Understanding microviscosity is important because it one of the main properties of any fluid and thus has an effect on any diffusion related processes. A variety of mass and signal transport phenomena as well as intermolecular interactions are often governed by viscosity. Molecular rotors are a subclass of intramolecular charge transfer fluorophores which form a lower energy twisted state. This results in a charge separated species which is highly sensitive to its surrounding microenviroment's viscosity as high viscosity limits its ability to form this twisted state. Once excited, there are deactivation routes which the excited fluorophore can undergo: radiative and non-radiative. Both were studied in this work. In the case of a radiative decay, as seen in porphyrin dimer, the energy is released in the form of a photon and is seen as a shifted band in the emission structure. The conformation of the porphyrin dimer was found to be influenced differently by ionic liquids as compared to molecular solvents, indicating the microheterogenous nature of ionic liquids play a role in the conformation. For non-radiative decays, BODIPY dyads and triads were investigated. The

  6. Thermodynamics of Supercooled and Glassy Water

    NASA Astrophysics Data System (ADS)

    Debenedetti, Pablo G.

    1998-03-01

    The behavior of metastable water at low temperatures is unusual. The isothermal compressibility, the isobaric heat capacity, and the magnitude of the thermal expansion coefficient increase sharply upon supercooling, and structural relaxation becomes extremely sluggish at temperatures far above the glass transition(Angell, C.A., Annu. Rev. Phys. Chem., 34, 593, 1983)(Debenedetti, P.G., Metastable Liquids. Concepts and Principles, Princeton University Press, 1996). Water has two distinct glassy phases, low- and high-density amorphous ice (LDA, HDA). The transition between LDA and HDA is accompanied by sharp volume and enthalpy changes, and appears to be first-order(Mishima, O., L.D.Calvert, and E. Whalley, Nature, 314, 76, 1985)(Mishima, O., J. Chem. Phys., 100, 5910, 1994). The understanding of these observations in terms of an underlying global phase behavior remains incomplete(Speedy, R.J., J. Phys. Chem., 86, 982, 1982)(Poole, P.H., F. Sciortino, U. Essman, and H.E. Stanley, Nature, 360, 324, 1992)(Sastry, S., P.G. Debenedetti, F. Sciortino, and H.E. Stanley, Phys. Rev. E, 53, 6144, 1996)(Tanaka, H., Nature, 380, 328, 1996)(Xie, Y., K.F. Ludwig, G. Morales, D.E. Hare, and C.M. Sorensen, Phys. Rev. Lett., 71, 2050, 1993). Microscopic theories and computer simulations suggest several scenarios that can reproduce some experimental observations. Interesting and novel ideas have resulted from this body of theoretical work, such as the possibility of liquid-liquid immiscibility in a pure substance(Poole, P.H., F.Sciortino, T.Grande, H.E. Stanley, and C.A. Angell, Phys. Rev. Lett., 73, 1632, 1994)(Roberts, C.J., and P.G. Debenedetti, J. Chem. Phys., 105, 658, 1996)(Roberts, C.J., P.G. Debenedetti, and A.Z. Panagiotopoulos, Phys. Rev. Lett., 77, 4386, 1996)(Harrington, S., R. Zhang, P.H. Poole, F. Sciortino, and H.E. Stanley, Phys. Rev. Lett., 78, 2409, 1997). In this talk I will review the experimental facts, discuss their theoretical interpretation, and identify key

  7. Quasi-equilibrium in glassy dynamics: an algebraic view

    NASA Astrophysics Data System (ADS)

    Franz, Silvio; Parisi, Giorgio

    2013-02-01

    We study a chain of identical glassy systems in a constrained equilibrium, where each bond of the chain is forced to remain at a preassigned distance to the previous one. We apply this description to mean-field glassy systems in the limit of a long chain where each bond is close to the previous one. We show that this construction defines a pseudo-dynamic process that in specific conditions can formally describe real relaxational dynamics for long times. In particular, in mean-field spin glass models we can recover in this way the equations of Langevin dynamics in the long time limit at the dynamical transition temperature and below. We interpret the formal identity as evidence that in these situations the configuration space is explored in a quasi-equilibrium fashion. Our general formalism, which relates dynamics to equilibrium, puts slow dynamics in a new perspective and opens the way to the computation of new dynamical quantities in glassy systems.

  8. Peculiarities of the enthalpy relaxation of a glassy crystal

    NASA Astrophysics Data System (ADS)

    Delcourt, O.; Descamps, M.; Even, J.; Bertault, M.; Willart, J. F.

    1997-02-01

    The relaxation of a supercooled orientational glassy crystal is investigated by differential scanning calorimetry. Aging performed both below and above Tg reveal two original features. (i) The glassy compound relaxes beyond the simple return to equilibration of the metastable rotator phase. The state which is reached upon aging however reverses back to the metastable state when crossing Tg. (ii) Upon reheating a transition between a low temperature ordered phase and the rotator phase is observed whose occurrence strongly depends on the aging conditions. The calorimetric signature of this transition and the usual glass relaxation endotherm are superimposed when annealing is performed below Tg. These results suggest that the peculiarities of the structure and dynamics of orientational glassy crystals lead to an effective acceleration of the relaxation process and enable the system to search for enthalpy states lower than it is usual for a glass.

  9. Void nucleation and disentanglement in glassy amorphous polymers

    NASA Astrophysics Data System (ADS)

    Mahajan, Dhiraj K.; Singh, Bhupinder; Basu, Sumit

    2010-07-01

    Cavitation in glassy polymers is known to result from highly triaxial states of local stress and the presence of impurities. Understanding of cavitation, particularly void nucleation, is important as cavities are precursors to crazes, which in turn lead to fracture. In this work we study the early stages of void nucleation in glassy amorphous polymers by imposing, in well designed molecular dynamics simulations, highly triaxial states of stress on ensembles of entangled linear macromolecular chains and monitoring the evolution of the entanglement network. Our results demonstrate that deformation induced disentanglement and rearrangement of topological constraints along individual chains play an important role in the early stages of void nucleation. Even in the glassy state, deformation causes significant changes in the rheological constraints on a chain though the number of interchain binary contacts may not change much.

  10. Optical speckles of blood proteins embedded in porous glassy substrate

    NASA Astrophysics Data System (ADS)

    Holden, T.; Dehipawala, S.; Kokkinos, D.; Berisha, A.; Cheung, E.; Nguyen, A.; Golebiewska, U.; Schneider, P.; Tremberger, G., Jr.; Lieberman, D.; Cheung, T.

    2012-03-01

    Blood protein molecules could be embedded in porous glassy substrate with 10-nm pores. The embedding principle is based on blood cell dehydration with the destruction of the cell membrane, and reconstitution and centrifuge could yield a suitable solution for doping into a porous glassy medium. The doped glassy substrate speckle pattern under laser illumination could be used to characterize the protein size distribution. Calibration with known protein embedded samples would result in an optical procedure for the characterization of a blood sample. Samples embedded with larger kilo-Dalton protein molecule show more variation in the speckle patterns, consistent with protein folding interaction inside a pore cavity. A regression model has been used to correlate the protein molecule sizes with speckle sizes. The use of diffusion mean free path information to study protein folding in the embedding process is briefly discussed.

  11. Synthesis and antiprotozoal activity of original porphyrin precursors and derivatives.

    PubMed

    Abada, Zahra; Cojean, Sandrine; Pomel, Sébastien; Ferrié, Laurent; Akagah, Bernardin; Lormier, Anh Tuan; Loiseau, Philippe M; Figadère, Bruno

    2013-09-01

    Importance of heme in African trypanosomes, Leishmania sp. and Plasmodium sp. metabolisms justifies considering the potential of porphyrins and their precursors and derivatives as potential antiparasitic agents by interfering with heme metabolism. Consequently, twenty-four porphyrin precursors and derivatives were evaluated against Leishmania donovani, Trypanosoma brucei and Plasmodium sp. The best active compound against Trypanosoma brucei brucei was a new porphyrin derivative; compound 4i, with a MEC value of 6.25 μM justifying further in vivo evaluation. Whereas these compounds were not active against intramacrophage amastigotes of L. donovani, another new porphyrin derivative, compound 4f was active in vitro against Plasmodium falciparum at 20 nM and a slight delay of mice survival was observed on the Plasmodium berghei/Swiss mice model at 50 μmol/kg/day × 4. Pharmacomodulations should be further developed relying on a better knowledge on the porphyrin behaviour into the parasites comparatively to host cells.

  12. Fluorescence spectroscopy for endogenous porphyrins in human facial skin

    NASA Astrophysics Data System (ADS)

    Seo, I.; Tseng, S. H.; Cula, G. O.; Bargo, P. R.; Kollias, N.

    2009-02-01

    The activity of certain bacteria in skin is known to correlate to the presence of porphyrins. In particular the presence of coproporphyrin produced by P.acnes inside plugged pores has been correlated to acne vulgaris. Another porphyrin encountered in skin is protoporphyrin IX, which is produced by the body in the pathway for production of heme. In the present work, a fluorescence spectroscopy system was developed to measure the characteristic spectrum and quantify the two types of porphyrins commonly present in human facial skin. The system is comprised of a Xe lamp both for fluorescence excitation and broadband light source for diffuse reflectance measurements. A computer-controlled filter wheel enables acquisition of sequential spectra, first excited by blue light at 405 nm then followed by the broadband light source, at the same location. The diffuse reflectance spectrum was used to correct the fluorescence spectrum due to the presence of skin chromophores, such as blood and melanin. The resulting fluorescence spectra were employed for the quantification of porphyrin concentration in a population of healthy subjects. The results show great variability on the concentration of these porphyrins and further studies are being conducted to correlate them with skin conditions such as inflammation and acne vulgaris.

  13. Synthesis and spectroscopic properties of a soluble semiconducting porphyrin polymer.

    PubMed

    Schmitz, Robert A; Liddell, Paul A; Kodis, Gerdenis; Kenney, Michael J; Brennan, Bradley J; Oster, Nolan V; Moore, Thomas A; Moore, Ana L; Gust, Devens

    2014-09-07

    A semiconducting porphyrin polymer that is solution processable and soluble in organic solvents has been synthesized, and its spectroscopic and electrochemical properties have been investigated. The polymer consists of diarylporphyrin units that are linked at meso-positions by aminophenyl groups, thus making the porphyrin rings an integral part of the polymer backbone. Hexyl chains on two of the aryl groups impart solubility. The porphyrin units interact only weakly in the ground electronic state. Excitation produces a local excited state that rapidly evolves into a state with charge-transfer character (CT) involving the amino nitrogen and the porphyrin macrocycle. Singlet excitation energy is transferred between porphyrin units in the chain with a time constant of ca. 210 ps. The final CT state has a lifetime of several nanoseconds, and the first oxidation of the polymer occurs at ca. 0.58 V vs. SCE. These properties make the polymer a suitable potential excited state electron donor to a variety of fullerenes or other acceptor species, suggesting that the polymer may find use in organic photovoltaics, sensors, and similar applications.

  14. The Erevan howardite: Petrology of glassy clasts and mineral chemistry

    NASA Technical Reports Server (NTRS)

    Nazarov, M. A.; Ariskin, A. A.

    1993-01-01

    The Erevan howardite is a polymict regolith breccia containing xenoliths of carbonaceous chondrites. In this work, we studied glassy clasts, which could be considered as primary quenched melts, and mineral chemistry of the breccia. The study reveals that the Erevan howardite consists of common rocks of the HED suite. However, unique glassy clasts, which are present in some eucritic melts, were identified. The mineral chemistry and the simulation of crystallization of the melts suggest that the compositions of the melts reflect those of some primary lithologies of EPB.

  15. Course 14: Hiking through Glassy Phases: Physics beyond Aging

    NASA Astrophysics Data System (ADS)

    Berthier, L.; Viasnoff, V.; White, O.; et al.

    Experiments performed on a wide range of glassy materials display many interesting phenomena, such as aging behavior. In recent years, a large body of experiments probed this nonequilibrium glassy dynamics through elaborate protocols, in which external parameters are shifted, or cycled in the course of the experiment. We review here these protocols, as well as experimental and numerical results. Then, we critically discuss various theoretical approaches put forward in this context. Emphasis is put more on the generality of the phenomena than on a specific system. Experiments are also suggested.

  16. Interfacial organization of achiral porphyrins via unidirectional compression: a general method for chiroptical porphyrin assemblies of selected chirality.

    PubMed

    Zhang, Xiao; Wang, Yanping; Chen, Penglei; Rong, Yunlong; Liu, Minghua

    2016-05-18

    Porphyrins are considered to be important scaffolds bridging supramolecular chemistry and chiral chemistry, where chirality selection via physical effects such as directional stirring and spin-coating has aroused particular interest. Nevertheless, these protocols could only work on a limited number of achiral porphyrins. It still remains a formidable challenge to pave a general avenue for the construction of chiral assemblies using achiral porphyrins. By means of a unique Langmuir-Schaefer (LS) technique of a unidirectional compression configuration, we herein have demonstrated that a series of achiral porphyrins could be facilely organized to form chiral interfacial assemblies of controlled supramolecular chirality. It has been disclosed that such a fascinating chirality selection scenario is intimately related to the direction of the compression-generated vortex-like flow, while the compression speed, one of the most significant parameters of the Langmuir technique, contributes less to this issue. With regard to a surface-pressure-dependent chirality selection phenomenon, it is suggested that the directional vortex-like flow generated by lateral compression might play a role in promoting the preferential growth of chiral assemblies showing an enhanced yet controlled CD signal. Our protocol might be, to some extent, a general method for achieving chiral porphyrin assemblies of controlled chirality.

  17. Interaction of porphyrins with CdTe quantum dots.

    PubMed

    Zhang, Xing; Liu, Zhongxin; Ma, Lun; Hossu, Marius; Chen, Wei

    2011-05-13

    Porphyrins may be used as photosensitizers for photodynamic therapy, photocatalysts for organic pollutant dissociation, agents for medical imaging and diagnostics, applications in luminescence and electronics. The detection of porphyrins is significantly important and here the interaction of protoporphyrin-IX (PPIX) with CdTe quantum dots was studied. It was observed that the luminescence of CdTe quantum dots was quenched dramatically in the presence of PPIX. When CdTe quantum dots were embedded into silica layers, almost no quenching by PPIX was observed. This indicates that PPIX may interact and alter CdTe quantum dots and thus quench their luminescence. The oxidation of the stabilizers such as thioglycolic acid (TGA) as well as the nanoparticles by the singlet oxygen generated from PPIX is most likely responsible for the luminescence quenching. The quenching of quantum dot luminescence by porphyrins may provide a new method for photosensitizer detection.

  18. Out-of-Plane Coordinated Porphyrin Nanotubes with Enhanced Singlet Oxygen Generation Efficiency

    NASA Astrophysics Data System (ADS)

    Zhao, Qiang; Wang, Yao; Xu, Yanshuang; Yan, Yun; Huang, Jianbin

    2016-08-01

    A supramolecular porphyrin nanotube displaying J-aggregation feature was constructed by out-of-plane coordinated bismuth-porphyrin. Significantly, compared to traditional J-aggregated porphyrin suffering from fluorescence and singlet oxygen quenching, the nanotube exhibits excellent bio-imaging ability and enhanced production efficiency of singlet oxygen. The out-of-plane structure of bismuth to porphyrin makes the aggregation an appropriate material for theranostics. Furthermore, it is also a potential radio-therapeutic drug owing to the presence of radio-active bismuth. Thus, the self-assembly of out-of-plane coordinated porphyrin can be a facile approach toward effective therapy of tumors and other diseases.

  19. Enhanced Anion Transport Using Some Expanded Porphyrins as Carriers.

    DTIC Science & Technology

    1991-01-01

    Schiff base "expanded porphyrin ," 1, which when diprotonated effectively binds chloride anion in the solid state.8- 10 In addition, we present the results...ray diffraction structure of the mixed HCI1-IBF 4 salt (28BF 4 ) of a novel non-aromatic anthracene derived "expanded porphyrin ." 4,5,9-31 -tetraethyl...step, an acid catalyzed 1: 1 Schiff - base condensation between I ,8-diaminoanthracene 4 and 2,5-bis((3-ethylS_-formyl-4- methy’lpyrrol-2-yl) methyl

  20. Synthesis and characterization of "face-to-face" porphyrins.

    PubMed Central

    Collman, J P; Elliott, C M; Halbert, T R; Tovrog, B S

    1977-01-01

    The syntheses of four binary porphyrins, two of which are constrained to a "face-to-face" conformation, and their Co2+ and Cu2+ derivatives are described. Electron spin resonance indicates that the intermetallic separation in the binuclear "face-to-face" porphyrins is about 6.5-6.8 A. Electronic spectra and proton magnetic resonance spectra support the postulated "face-to-face" conformations. A hypothesis that related compounds may serve as multielectron redox catalysts for O2 and N2 is presented. PMID:189304

  1. Micropatterning of porphyrin nanotubes thin film using focused laser writing.

    PubMed

    Gupta, Jyotsana; Lim, Xiaodai; Sow, Chorng-Haur; Vijayan, C

    2011-05-01

    We report an effective process to create micropatterns on a thin film of porphyrin nanotubes PNTs on Si substrate using focused laser beam. The optical properties of the newly synthesized porphyrin nanotubes are investigated and micropatterning is demonstrated using laser fabrication, an increasingly important tool in various fields of research. We made use of this laser cutting method to create interesting and useful two-dimensional patterned structures. The shapes and sizes of the structures created can be controlled by varying the power of the laser, angle of incident of the focused laser beam, the relative speed with which the laser beam traverse through the film and the magnification of objective lens used.

  2. Molecular nanostamp based on one-dimensional porphyrin polymers.

    PubMed

    Kanaizuka, Katsuhiko; Izumi, Atsushi; Ishizaki, Manabu; Kon, Hiroki; Togashi, Takanari; Miyake, Ryosuke; Ishida, Takao; Tamura, Ryo; Haga, Masa-aki; Moritani, Youji; Sakamoto, Masatomi; Kurihara, Masato

    2013-08-14

    Surface design with unique functional molecules by a convenient one-pot treatment is an attractive project for the creation of smart molecular devices. We have employed a silane coupling reaction of porphyrin derivatives that form one-dimensional polymer wires on substrates. Our simple one-pot treatment of a substrate with porphyrin has successfully achieved the construction of nanoscale bamboo shoot structures. The nanoscale bamboo shoots on the substrates were characterized by atomic force microscopy (AFM), UV-vis spectra, and X-ray diffraction (XRD) measurements. The uneven and rigid nanoscale structure has been used as a stamp for constructing bamboo shoot structures of fullerene.

  3. Influence of nonplanarity and extended conjugation on porphyrin basicity.

    PubMed

    Finikova, Olga S; Cheprakov, Andrei V; Carroll, Patrick J; Dalosto, Sergio; Vinogradov, Sergei A

    2002-12-30

    Thermodynamic basicities of several new nonplanar water soluble tetraaryltetracyclohexano- (Ar(4)TCHP) and tetraaryltetrabenzoporphyrins (Ar(4)TBP) have been measured and correlated with their structural parameters. While the degrees of nonplanarity in these porphyrins are similar, Ar(4)TCHPs exhibit significantly higher basicities than Ar(4)TBPs and than planar tetraarylporphyrins. Low basicities of distorted Ar(4)TBPs are believed to be due to extended pi-conjugation, which causes delocalization of the core electron density in these porphyrins and reduces negative charges at the protonation site.

  4. Photoinduced conductivity of a porphyrin-gold composite nanowire

    SciTech Connect

    Kilina, Svletana; Balatsky, Alexander; Kilin, Dmitri S; Prezhdo, Oleg; Tsemekhman, Kiril

    2009-01-01

    Negatively charged phosphine groups on the backbone of DNA are known to attract gold nanoclusters from a colloid, assembling the clusters at fixed intervals. Bridging these intervals with porphyrin-dye linkers forms an infinite conducting chain, a quantum wire whose carrier mobility can be enhanced by photoexcitation. The resulting nanoassembly can be used as a gate: a wire with a controllable conductivity. The electronic structure of the porphyrin-gold wire is studied here by density functional theory, and the conductivity of the system is determined as a function of the photoexcitation energy. Photoexcitations of the dye are found to enhance the wire conductivity by orders of magnitude.

  5. Reductive precipitation of metals photosensitized by tin and antimony porphyrins

    DOEpatents

    Shelnutt, John A.; Gong, Weiliang; Abdelouas, Abdesselam; Lutze, Werner

    2003-09-30

    A method for reducing metals using a tin or antimony porphyrin by forming an aqueous solution of a tin or antimony porphyrin, an electron donor, such as ethylenediaminetetraaceticacid, triethylamine, triethanolamine, and sodium nitrite, and at least one metal compound selected from a uranium-containing compound, a mercury-containing compound, a copper-containing compound, a lead-containing compound, a gold-containing compound, a silver-containing compound, and a platinum-containing compound through irradiating the aqueous solution with light.

  6. A nonplanar porphyrin-based receptor molecule for chiral amine ligands

    SciTech Connect

    MUZZI,CINZIA M.; MEDFORTH,CRAIG J.; SMITH,KEVIN M.; JIA,SONG-LING; SHELNUTT,JOHN A.

    2000-03-06

    A novel porphyrin-based receptor molecule for chiral amine ligands is described in which nonplanarity of the porphyrin macrocycle is used to orient the ligand and to enhance porphyrin-ligand interactions. The porphyrin macrocycle provides a versatile platform upon which to build elaborate superstructures, and this feature coupled with a rich and well-developed synthetic chemistry has led to the synthesis of many elegant models of heme protein active sites and numerous porphyrin-based receptor molecules. One design feature which is not usually considered in the design of porphyrin-based receptor molecules is nonplanarity of the porphyrin ring, although there are a few systems such as the pyridine sensitive Venus Flytrap and the chirality-memory molecule which illustrate that nonplanar porphyrin-based receptors can display unique and interesting behavior. Given the novel properties of these receptors and the continuing interest in the effects of nonplanarity on the properties of porphyrins the authors decided to investigate in more detail the potential applications of nonplanarity in the design of porphyrin-based receptors. Herein, they describe the design, synthesis, and characterization of a new kind of nonplanar porphyrin-based receptor molecule for chiral amines.

  7. Effects of Immersion Solvent on Photovoltaic and Photophysical Properties of Porphyrin-Sensitized Solar Cells.

    PubMed

    Hayashi, Hironobu; Higashino, Tomohiro; Kinjo, Yuriko; Fujimori, Yamato; Kurotobi, Kei; Chabera, Pavel; Sundström, Villy; Isoda, Seiji; Imahori, Hiroshi

    2015-08-26

    Memory effects in self-assembled monolayers (SAMs) of zinc porphyrin carboxylic acid on TiO2 electrodes have been demonstrated for the first time by evaluating the photovoltaic and electron transfer properties of porphyrin-sensitized solar cells prepared by using different immersion solvents sequentially. The structure of the SAM of the porphyrin on the TiO2 was maintained even after treating the porphyrin monolayer with different neat immersion solvents (memory effect), whereas it was altered by treatment with solutions containing different porphyrins (inverse memory effect). Infrared spectroscopy shows that the porphyrins in the SAM on the TiO2 could be exchanged with the same or analogous porphyrin, leading to a change in the structure of the porphyrin SAM. The memory and inverse memory effects are well correlated with a change in porphyrin geometry, mainly the tilt angle of the porphyrin along the long molecular axis from the surface normal on the TiO2, as well as with kinetics of electron transfer between the porphyrin and TiO2. Such a new structure-function relationship for DSSCs will be very useful for the rational design and optimization of photoelectrochemical and photovoltaic properties of molecular assemblies on semiconductor surfaces.

  8. Porphyrin-cross-linked hydrogel for fluorescence-guided monitoring and surgical resection.

    PubMed

    Lovell, Jonathan F; Roxin, Aron; Ng, Kenneth K; Qi, Qiaochu; McMullen, Jesse D; DaCosta, Ralph S; Zheng, Gang

    2011-09-12

    We demonstrate that porphyrins can be used as efficient cross-linkers to generate a new class of hydrogels with enabling optical properties. Tetracarboxylic acid porphyrins reacted with PEG diamines to form a condensation polyamide in a range of appropriate conditions, with respect to reaction time, diisopropylethylamine initiator concentration, porphyrin-to-PEG ratio, porphyrin concentration, and PEG size. The network structure of the hydrogel maintained a porphyrin spacing that prevented excessive fluorescence self-quenching despite high porphyrin density. The near-infrared properties readily enabled low background, noninvasive fluorescence monitoring of the implanted hydrogel in vivo, as well as its image-guided surgical removal in real time using a low-cost fluorescence camera prototype. Emission could be tuned by incorporating copper metalloporphyrins into the network. The approach of creating hydrogels using cross-linking porphyrin comonomers creates opportunities for new polymer designs with strong optical character.

  9. Laser flash photolysis generation and kinetic studies of porphyrin-manganese-oxo intermediates. Rate constants for oxidations effected by porphyrin-Mn(V)-oxo species and apparent disproportionation equilibrium constants for porphyrin-Mn(IV)-oxo species.

    PubMed

    Zhang, Rui; Horner, John H; Newcomb, Martin

    2005-05-11

    Porphyrin-manganese(V)-oxo and porphyrin-manganese(IV)-oxo species were produced in organic solvents by laser flash photolysis (LFP) of the corresponding porphyrin-manganese(III) perchlorate and chlorate complexes, respectively, permitting direct kinetic studies. The porphyrin systems studied were 5,10,15,20-tetraphenylporphyrin (TPP), 5,10,15,20-tetrakis(pentafluorophenyl)porphyrin (TPFPP), and 5,10,15,20-tetrakis(4-methylpyridinium)porphyrin (TMPyP). The order of reactivity for (porphyrin)Mn(V)(O) derivatives in self-decay reactions in acetonitrile and in oxidations of substrates was (TPFPP) > (TMPyP) > (TPP). Representative rate constants for reaction of (TPFPP)Mn(V)(O) in acetonitrile are k = 6.1 x 10(5) M(-1) s(-1) for cis-stilbene and k = 1.4 x 10(5) M(-1) s(-1) for diphenylmethane, and the kinetic isotope effect in oxidation of ethylbenzene and ethylbenzene-d(10) is k(H)/k(D) = 2.3. Competitive oxidation reactions conducted under catalytic conditions display approximately the same relative rate constants as were found in the LFP studies of (porphyrin)Mn(V)(O) derivatives. The apparent rate constants for reactions of (porphyrin)Mn(IV)(O) species show inverted reactivity order with (TPFPP) < (TMPyP) < (TPP) in reactions with cis-stilbene, triphenylamine, and triphenylphosphine. The inverted reactivity results because (porphyrin)Mn(IV)(O) disproportionates to (porphyrin)Mn(III)X and (porphyrin)Mn(V)(O), which is the primary oxidant, and the equilibrium constants for disproportionation of (porphyrin)Mn(IV)(O) are in the order (TPFPP) < (TMPyP) < (TPP). The fast comproportionation reaction of (TPFPP)Mn(V)(O) with (TPFPP)Mn(III)Cl to give (TPFPP)Mn(IV)(O) (k = 5 x 10(8) M(-1) s(-1)) and disproportionation reaction of (TPP)Mn(IV)(O) to give (TPP)Mn(V)(O) and (TPP)Mn(III)X (k approximately 2.5 x 10(9) M(-1) s(-1)) were observed. The relative populations of (porphyrin)Mn(V)(O) and (porphyrin)Mn(IV)(O) were determined from the ratios of observed rate constants for

  10. Observation of vanadyl porphyrins and sulfur-containing vanadyl porphyrins in a petroleum asphaltene by atmospheric pressure photonionization Fourier transform ion cyclotron resonance mass spectrometry.

    PubMed

    Qian, Kuangnan; Mennito, Anthony S; Edwards, Kathleen E; Ferrughelli, Dave T

    2008-07-01

    Vanadyl (VO) porphyrins and sulfur-containing vanadyl (VOS) porphyrins of a wide carbon number range (C(26) to C(52)) and Z-number range (-28 to -54) were detected and identified in a petroleum asphaltene by atmospheric pressure photonionization (APPI) and Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS). APPI provides soft ionization of asphaltene molecules (including VO and VOS porphyrins), generating primarily molecular ions (M(+.)). The ultra-high mass resolving power (m/Delta m(FWHM) approximately 500 K) of FTICR-MS enabled resolution and positive identification of elemental formulae for the entire family of VO and VOS porphyrins in a complicated asphaltene matrix. Deocophylerythro-etioporphyrin (DPEP) is found to be the most prevalent structure, followed by etioporphyrins (etio)- and rhodo (benzo)-DPEP. The characteristic Z-distribution of VO porphyrins suggests benzene and naphthene increment in the growth of porphyrin ring structures. Bimodal carbon number distributions of VO porphyrins suggest possible different origins of low and high molecular weight species. To our knowledge, the observation of VOS porphyrins in a petroleum product has not previously been reported. The work is also the first direct identification of the entire vanadyl porphyrin family by ultra-high resolution mass spectrometry without chromatographic separation or demetallation.

  11. Playback interference of glassy-winged sharp shooter communication

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Animal communication is vital to reproduction, particularly for securing a mate. Insects commonly communicate by exchanging vibrational signals that are transmitted through host plants. The glassy-winged sharpshooter (GWSS), Homalodisca vitripennis, is an important vector of Xylella fastidiosa, a pl...

  12. Thermodynamic behavior of glassy state of structurally related compounds.

    PubMed

    Kaushal, Aditya Mohan; Bansal, Arvind Kumar

    2008-08-01

    Thermodynamic properties of amorphous pharmaceutical forms are responsible for enhanced solubility as well as poor physical stability. The present study was designed to investigate the differences in thermodynamic parameters arising out of disparate molecular structures and associations for four structurally related pharmaceutical compounds--celecoxib, valdecoxib, rofecoxib, and etoricoxib. Conventional and modulated temperature differential scanning calorimetry were employed to study glass forming ability and thermodynamic behavior of the glassy state of model compounds. Glass transition temperature of four glassy compounds was in a close range of 327.6-331.8 K, however, other thermodynamic parameters varied considerably. Kauzmann temperature, strength parameter and fragility parameter showed rofecoxib glass to be most fragile of the four compounds. Glass forming ability of the compounds fared similar in the critical cooling rate experiments, suggesting that different factors were determining the glass forming ability and subsequent behavior of the compounds in glassy state. A comprehensive understanding of such thermodynamic facets of amorphous form would help in rationalizing the approaches towards development of stable glassy pharmaceuticals.

  13. A method to quantify glassy-winged sharpshooter egg maturation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    To identify factors affecting glassy-winged sharpshooter egg production, a method to accurately estimate the number of mature eggs produced during a short-term assay is needed. Egg production is typically quantified by determining the number of eggs deposited during the assay plus the number of matu...

  14. Aryl Diazonium Chemistry for the Surface Functionalization of Glassy Biosensors.

    PubMed

    Zheng, Wei; van den Hurk, Remko; Cao, Yong; Du, Rongbing; Sun, Xuejun; Wang, Yiyu; McDermott, Mark T; Evoy, Stephane

    2016-03-14

    Nanostring resonator and fiber-optics-based biosensors are of interest as they offer high sensitivity, real-time measurements and the ability to integrate with electronics. However, these devices are somewhat impaired by issues related to surface modification. Both nanostring resonators and photonic sensors employ glassy materials, which are incompatible with electrochemistry. A surface chemistry approach providing strong and stable adhesion to glassy surfaces is thus required. In this work, a diazonium salt induced aryl film grafting process is employed to modify a novel SiCN glassy material. Sandwich rabbit IgG binding assays are performed on the diazonium treated SiCN surfaces. Fluorescently labelled anti-rabbit IgG and anti-rabbit IgG conjugated gold nanoparticles were used as markers to demonstrate the absorption of anti-rabbit IgG and therefore verify the successful grafting of the aryl film. The results of the experiments support the effectiveness of diazonium chemistry for the surface functionalization of SiCN surfaces. This method is applicable to other types of glassy materials and potentially can be expanded to various nanomechanical and optical biosensors.

  15. Aryl Diazonium Chemistry for the Surface Functionalization of Glassy Biosensors

    PubMed Central

    Zheng, Wei; van den Hurk, Remko; Cao, Yong; Du, Rongbing; Sun, Xuejun; Wang, Yiyu; McDermott, Mark T.; Evoy, Stephane

    2016-01-01

    Nanostring resonator and fiber-optics-based biosensors are of interest as they offer high sensitivity, real-time measurements and the ability to integrate with electronics. However, these devices are somewhat impaired by issues related to surface modification. Both nanostring resonators and photonic sensors employ glassy materials, which are incompatible with electrochemistry. A surface chemistry approach providing strong and stable adhesion to glassy surfaces is thus required. In this work, a diazonium salt induced aryl film grafting process is employed to modify a novel SiCN glassy material. Sandwich rabbit IgG binding assays are performed on the diazonium treated SiCN surfaces. Fluorescently labelled anti-rabbit IgG and anti-rabbit IgG conjugated gold nanoparticles were used as markers to demonstrate the absorption of anti-rabbit IgG and therefore verify the successful grafting of the aryl film. The results of the experiments support the effectiveness of diazonium chemistry for the surface functionalization of SiCN surfaces. This method is applicable to other types of glassy materials and potentially can be expanded to various nanomechanical and optical biosensors. PMID:26985910

  16. Fast electronic relaxation in lathanide porphyrins

    NASA Astrophysics Data System (ADS)

    Tsvirko, M. P.; Stelmakh, G. F.; Pyatosin, V. E.; Solovyov, K. N.; Kachura, T. F.; Piskarskas, A. S.; Gadonas, R. A.

    1986-08-01

    The photophysical processes in porphyrin complexes of lanthanides (Ln) and their correlation with Ln 3+ ion characteristics have been studied by picosecond transient spectroscopy and spectrofluorimetry. The lifetimes of the S 2, S 1 and T 1 π-electron states have been determined for the Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu complexes of tetrabenzporphin (TBP). Depending on the nature of the Ln 3+ ion the non-radiative decay rates of the Ln TBP (π, π*) states vary by several orders of magnitude: from 3 × 10 11 to > 2 × 10 13 s -1 for the S 2 decay, from 2 × 10 10 to > 2 × 10 11 s -1 for the S 1 decay and from 6 × 10 2 to 3 × 10 10 s -1 for the T 1 decay. The T 1 deactivation rate constant of paramagnetic complexes decreases exponentially with the energy gap between the T 1 level and the nearest lower-lying accepting 4f-level beginning with Δ E ≈ 4000 cm -1. For Δ E < 4000 cm -1 there is a tendency toward stabilization of the τ -1T values. By example of the Dy, Tb, Ho, Er and Tm complexes it is shown that combination states, in which the Ln 3+_ ion and the macrocyclic ligand are excited simultaneously, participate in the deactivation of the S 2 and S 1 states. The anomalously high rates of deactivation of the S 2, S 1 and T 1 states in the case of Eu, Yb and Sm complexes are due to the charge-transfer states involved in relaxation processes.

  17. An expeditious synthesis of tailed tren-capped porphyrins.

    PubMed

    Even, Pascale; Ruzié, Christian; Ricard, David; Boitrel, Bernard

    2005-09-29

    [structure: see text] A one-pot two-step versatile synthesis of tailed tren-capped porphyrins has been achieved. The two resulting ligands demonstrate that this expeditious method can be applied to various axial bases to obtain highly functionalized macromolecules attractive for heme modeling purposes. Dioxygen binding of the pyridine-tailed iron complex is reported as a direct application.

  18. Porphyrin Induced Laser Deactivation of Trypsinogen-Trypsin Conversion

    NASA Astrophysics Data System (ADS)

    Perido, Joanna; Brancaleon, Lorenzo

    2015-03-01

    Pancreatitis is caused by the inflammation of the pancreas, where the digestive enzyme trypsin is activated from the precursor enzyme trypsinogen while still in the pancreas. The presence of trypsin in the pancreas causes auto-activation of trypsinogen, resulting in greater inflammation and auto-digestion of the pancreas. In severe cases, this cascade effect can lead to organ failure, diabetes, and pancreatic cancer. Our hypothesis is that if trypsinogen is prevented from auto-activating into trypsin, then this cascade can be stopped. We propose to do this by inducing conformational changes in trypsinogen when bound to a photoactive porphyrin dye. Porphyrins are comprised of four linked heterocyclic groups forming a flat ring, and bind well with proteins such as trypsinogen. In this study we used spectroscopic techniques to probe the binding of meso-tetrakis (4-sulfonatephenyl) porphyrin (TSPP) to trypsinogen in vitro, as a preliminary step to then prompt and characterize conformational changes of trypsinogen through irradiation. If conformational changes are detected the trypsinogen will be tested for trypsin inactivation. This investigation may provide promising initial results to the possible use of porphyrins as an inhibitor of the self-activation of trypsinogen into trypsin, and a potential inhibitor of pancreatitis. MARC*U-STAR.

  19. Hexamodal imaging with porphyrin-phospholipid-coated upconversion nanoparticles.

    PubMed

    Rieffel, James; Chen, Feng; Kim, Jeesu; Chen, Guanying; Shao, Wei; Shao, Shuai; Chitgupi, Upendra; Hernandez, Reinier; Graves, Stephen A; Nickles, Robert J; Prasad, Paras N; Kim, Chulhong; Cai, Weibo; Lovell, Jonathan F

    2015-03-11

    Hexamodal imaging using simple nanoparticles is demonstrated. Porphyrin-phospholipids are used to coat upconversion nanoparticles in order to generate a new biocompatible material. The nanoparticles are characterized in vitro and in vivo for imaging via fluorescence, upconversion, positron emission tomography, computed tomography, Cerenkov luminescence, and photoacoustic tomography.

  20. Potentiometric detection and removal of copper using porphyrins

    PubMed Central

    2013-01-01

    Background Copper is an essential trace element with a great importance in industry, environment and biological systems. The great advantage of ion-selective sensors in comparison with other proposed techniques is that they are measuring the free metal ion activity which is responsible for their toxicity. Porphyrins are known to be among the best ionophores in formulation of ion-selective sensors. Results A symmetrically substituted meso-porphyrin, namely: 5,10,15,20-tetrakis(4-allyloxyphenyl)porphyrin (TAPP) was used in the construction of a new copper selective-sensor and was also tested for the removal of copper from waste waters. The potentiometric response characteristics (slope and selectivity) of copper-selective electrodes based on TAPP in o-nitrophenyloctylether (o-NPOE), dioctyl phtalate (DOP) and dioctyl sebacate (DOS) plasticized with poly(vinyl chloride) membranes are compared. Conclusions The best results were obtained for the membrane plasticized with DOP. The sensor has linear response in the range 1x10-7 – 1x10-1 M with 28.4 ± 0.4 mV/decade near-Nernstian slope towards copper ions and presents good selectivity. Due to its chelating nature, the same porphyrin was also tested for the retention of copper from synthetic copper samples, showing a maximum adsorption capacity of 280 mg/g. PMID:23829792

  1. Condensed phase photoacoustic spectroscopic detection of porphyrins and dyes

    SciTech Connect

    Voigtman, E.; Jurgensen, A.; Winefordner, J.

    1981-08-01

    A simple piezoelectric detection system suitable for performing highly sensitive liquid-phase photoacoustic spectroscopy is presented. Performance of the system with respect to linearity, solvent effects, and excitation pulse characteristics is experimentally evaluated and compared with theoretical figures of merit. Limits of detection for various porphyrins, laser dyes, and drugs are presented.

  2. Bis(porphyrin)-anthraquinone triads: synthesis, spectroscopy, and photochemistry.

    PubMed

    Giribabu, L; Reeta, P Silviya; Kanaparthi, Ravi Kumar; Srikanth, Malladi; Soujanya, Y

    2013-04-11

    Molecular triads based on bis(porphyrin)-anthraquinone having azomethine bridge at the pyrrole-β position have been designed and synthesized. Both free-base AQ-(H2)2 and zinc AQ-(Zn)2 triads are characterized by elemental analysis, MALDI-MS, (1)H NMR, UV-visible, and fluorescence spectroscopy (steady-state and time-resolved) as well as electrochemical method. The absorption spectra of both Soret and Q-bands of the triads are red-shifted by 12-20 nm with respect to their monomer units. The study supported by theoretical calculations manifests that there exists a negligible electronic communication in the ground state between the donor porphyrin and acceptor anthraquinone of these triads. However, interestingly, both the triads exhibit significant fluorescence emission quenching (51-92%) of the porphyrin emission compared to their monomeric units. The emission quenching is attributed to the excited-state intramolecular photoinduced electron transfer from porphyrins to anthraquinone. The electron-transfer rates (kET) of these triads are found in the range 1.0 × 10(8) to 7.7 × 10(9) s(-1) and are found to be solvent dependent.

  3. 21 CFR 862.1595 - Porphyrins test system.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Porphyrins test system. 862.1595 Section 862.1595 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED... metabolism), and other diseases characterized by alterations in the heme pathway. (b) Classification. Class...

  4. Modulation of Group I Ribozyme Activity by Cationic Porphyrins

    PubMed Central

    Matsumura, Shigeyoshi; Ito, Tatsunobu; Tanaka, Takahiro; Furuta, Hiroyuki; Ikawa, Yoshiya

    2015-01-01

    The effects of cationic porphyrins on the catalytic activities of four group I ribozymes were investigated. A cationic porphyrin possessing four pyridinium moieties (pPyP) inhibited two group IC3 ribozymes (Syn Rz and Azo Rz) and a group IC1 ribozyme (Tet Rz). In the case of a group IA2 ribozyme (Td Rz), however, pPyP served not only as an inhibitor but also as an activator, and the effects of pPyP were dependent on its concentration. To analyze the structural and electronic factors determining the effects of pPyP on group I ribozymes, three cationic porphyrins (pPyNCP, pPyF4P, and TMPyP) were also examined. As interactions between small organic molecules and nucleic acids are attractive and important issues in biochemistry and biotechnology, this study contributes to the development of porphyrin-based molecules that can modulate functions of structured RNA molecules. PMID:25811638

  5. 21 CFR 862.1595 - Porphyrins test system.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Porphyrins test system. 862.1595 Section 862.1595 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED... treatment of lead poisoning, porphyrias (primarily inherited diseases associated with disturbed...

  6. 21 CFR 862.1595 - Porphyrins test system.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Porphyrins test system. 862.1595 Section 862.1595 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED... treatment of lead poisoning, porphyrias (primarily inherited diseases associated with disturbed...

  7. Synthesis of metallic nanoshells on porphyrin-stabilized emulsions

    DOEpatents

    Wang, Haorong; Song, Yujiang; Shelnutt, John A.; Medforth, Craig J.

    2011-12-13

    Metal nanostructures formed by photocatalytic interfacial synthesis using a porphyrin-stabilized emulsion template and the method for making the nanostructures. Catalyst-seeded emulsion droplets are employed as templates for hollow-nanoshell growth. The hollow metal nanospheres may be formed with or without inclusions of other materials.

  8. Porphyrin involvement in redshift fluorescence in dentin decay

    NASA Astrophysics Data System (ADS)

    Slimani, A.; Panayotov, I.; Levallois, B.; Cloitre, T.; Gergely, C.; Bec, N.; Larroque, C.; Tassery, H.; Cuisinier, F.

    2014-05-01

    The aim of this study was to evaluate the porphyrin involvement in the red fluorescence observed in dental caries with Soprolife® light-induced fluorescence camera in treatments mode (SOPRO, ACTEON Group, La Ciotat, France) and Vistacam® camera (DÜRR DENTAL AG, Bietigheim-Bissingen, Germany). The International Caries Detection and Assessment System (ICDAS) was used to rand the samples. Human teeth cross-sections, ranked from ICDAS score 0 to 6, were examined by epi-fluorescence microscopy and Confocal Raman microscopy. Comparable studies were done with Protoporphyrin IX, Porphyrin I and Pentosidine solutions. An RGB analysis of Soprolife® images was performed using ImageJ Software (1.46r, National Institutes of Health, USA). Fluorescence spectroscopy and MicroRaman spectroscopy revealed the presence of Protoporphyrin IX, in carious enamel, dentin and dental plaque. However, the presence of porphyrin I and pentosidine cannot be excluded. The results indicated that not only porphyrin were implicated in the red fluorescence, Advanced Glygation Endproducts (AGEs) of the Maillard reaction also contributed to this phenomenon.

  9. Tailoring porphyrin-based electron accepting materials for organic photovoltaics.

    PubMed

    Rawson, Jeff; Stuart, Andrew C; You, Wei; Therien, Michael J

    2014-12-17

    The syntheses, potentiometric responses, optical spectra, electronic structural properties, and integration into photovoltaic devices are described for ethyne-bridged isoindigo-(porphinato)zinc(II)-isoindigo chromophores built upon either electron-rich 10,20-diaryl porphyrin (Ar-Iso) or electron-deficient 10,20-bis(perfluoroalkyl)porphyrin (Rf-Iso) frameworks. These supermolecules evince electrochemical responses that trace their geneses to their respective porphyrinic and isoindigoid subunits. The ethyne linkage motif effectively mixes the comparatively weak isoindigo-derived visible excitations with porphyrinic π-π* states, endowing Ar-Iso and Rf-Iso with high extinction coefficient (ε ∼ 10(5) M(-1)·cm(-1)) long-axis polarized absorptions. Ar-Iso and Rf-Iso exhibit total absorptivities per unit mass that greatly exceed that for poly(3-hexyl)thiophene (P3HT) over the 375-900 nm wavelength range where solar flux is maximal. Time-dependent density functional theory calculations highlight the delocalized nature of the low energy singlet excited states of these chromophores, demonstrating how coupled oscillator photophysics can yield organic photovoltaic device (OPV) materials having absorptive properties that supersede those of conventional semiconducting polymers. Prototype OPVs crafted from the poly(3-hexyl)thiophene (P3HT) donor polymer and these new materials (i) confirm that solar power conversion depends critically upon the driving force for photoinduced hole transfer (HT) from these low-band-gap acceptors, and (ii) underscore the importance of the excited-state reduction potential (E(-/*)) parameter as a general design criterion for low-band-gap OPV acceptors. OPVs constructed from Rf-Iso and P3HT define rare examples whereby the acceptor material extends the device operating spectral range into the NIR, and demonstrate for the first time that high oscillator strength porphyrinic chromophores, conventionally utilized as electron donors in OPVs, can also

  10. Electronic Structure and Dynamics of Nitrosyl Porphyrins

    PubMed Central

    Scheidt, W. Robert; Barabanschikov, Alexander; Pavlik, Jeffrey W.; Silvernail, Nathan J.; Sage, J. Timothy

    2010-01-01

    Nitric oxide (NO) is a signalling molecule employed to regulate essential physiological processes. Thus, there is great interest in understanding the interaction of NO with heme, which is found at the active site of many proteins that recognize NO, as well those involved in its creation and elimination. We summarize what we have learned from investigations of the structure, vibrational properties, and conformational dynamics of NO complexes with ferrous porphyrins, as well as computational investigations in support of these experimental studies. Multi-temperature crystallographic data reveals variations in the orientational disorder of the nitrosyl ligand. In some cases, equilibria among NO orientations can be analyzed using the vant Hoff relationship and the free energy and the enthalpy of the solid-state transitions evaluated experimentally. DFT calculations predict that intrinsic barriers to torsional rotations are smaller than thermal energies at physiological temperatures, and the coincidence of observed NO orientations with minima in molecular mechanics potentials indicates that nonbonded interactions with other chemical groups control the conformational freedom of the bound NO. In favorable cases, reduced disorder at low temperatures exposes subtle structural features including off-axis tilting of the Fe–NO bond and anisotropy of the equatorial Fe–N bonds. We also present the results of nuclear resonance vibrational spectroscopy (NRVS) measurements on oriented single crystals of [Fe(TPP)(NO)] and [Fe(TPP)(1-MeIm)(NO)]. These describe the anisotropic vibrational motion of Fe in five-and six-coordinate heme-NO complexes, and reveal vibrations of all Fe-ligand bonds as well as low frequency molecular distortions associated with the doming of the heme upon ligand binding. Quantitative comparison with predicted frequencies, amplitudes and directions facilitates identification of vibrational modes, but also suggests that commonly used DFT functionals are not

  11. Comparison of maturity based on steroid and vanadyl porphyrin parameters: A new vanadyl porphyrin maturity parameter for higher maturities

    NASA Astrophysics Data System (ADS)

    Sundararaman, Padmanabhan; Moldowan, J. Michael

    1993-03-01

    Correlations are demonstrated between steroid maturity parameters and the porphyrin maturity parameter (PMP) which is based on the ratio of specific vanadyl porphyrins C 28E /(C 28E + C 32D) measured by HPLC. Measurements from a global selection of > 100 rock extracts and oils show that PMP parallels changes in the C 29-sterane 20S/(20S + 20R) and tri/(tri + mono) aromatic steroid ratios, and that all three parameters appear to attain their maximum values at similar maturity levels. The triaromatic steroid side chain cracking parameter, TA I/(I + II), reaches approximately 20% of its maximum value when PMP has reached 100%. These results suggest that PMP is effective in the early to peak portion of the oil window. A new parameter, PMP-2, based on changes in the relative concentrations of two peaks in the HPLC fingerprint (vanadyl "etio" porphyrins), appears effective in assessing the maturity of source rocks beyond peak oil generation. In combination with PMP this parameter extends the effective range of vanadyl porphyrins parameters to higher maturities as demonstrated by a suite of oils from the Oriente Basin, Ecuador, South America.

  12. The Role of Porphyrin-Free-Base in the Electronic Structures and Related Properties of N-Fused Carbazole-Zinc Porphyrin Dye Sensitizers

    PubMed Central

    Li, Xing-Yu; Zhang, Cai-Rong; Wu, You-Zhi; Zhang, Hai-Min; Wang, Wei; Yuan, Li-Hua; Yang, Hua; Liu, Zi-Jiang; Chen, Hong-Shan

    2015-01-01

    Dye sensitizers can significantly affect power conversion efficiency of dye-sensitized solar cells (DSSCs). Porphyrin-based dyes are promising sensitizers due to their performances in DSSCs. Here, based upon a N-fused carbazole-zinc porphyrin-free-base porphyrin triad containing an ethynyl-linkage (coded as DTBC), the novel porphyrin dyes named DTBC-MP and DTBC-TP were designed by varying the porphyrin-free-base units in the π conjugation of DTBC in order to study the effect of porphyrin-free-base in the modification of electronic structures and related properties. The calculated results indicate that, the extension of the conjugate bridge with the porphyrin-free-base unit results in elevation of the highest occupied molecular orbital (HOMO) energies, decrease of the lowest unoccupied molecular orbital (LUMO) energies, reduction of the HOMO-LUMO gap, red-shift of the absorption bands, and enhancement of the absorbance. The free energy changes demonstrate that introducing more porphyrin-free-base units in the conjugate bridge induces a faster rate of electron injection. The transition properties and molecular orbital characters suggest that the different transition properties might lead to a different electron injection mechanism. In terms of electronic structure, absorption spectra, light harvesting capability, and free energy changes, the designed DTBC-TP is a promising candidate dye sensitizer for DSSCs. PMID:26610469

  13. 2H NMR studies of supercooled and glassy aspirin

    NASA Astrophysics Data System (ADS)

    Nath, R.; Nowaczyk, A.; Geil, B.; Bohmer, R.

    2007-11-01

    Acetyl salicylic acid, deuterated at the methyl group, was investigated using 2H-NMR in its supercooled and glassy states. Just above the glass transition temperature the molecular reorientations were studied using stimulated-echo spectroscopy and demonstrated a large degree of similarity with other glass formers. Deep in the glassy phase the NMR spectra look similar to those reported for the crystal [A. Detken, P. Focke, H. Zimmermann, U. Haeberlen, Z. Olejniczak, Z. T. Lalowicz, Z. Naturforsch. A 50 (1995) 95] and below 20 K they are indicative for rotational tunneling with a relatively large tunneling frequency. Measurements of the spin-lattice relaxation times for temperatures below 150 K reveal a broad distribution of correlation times in the glass. The dominant energy barrier characterizing the slow-down of the methyl group is significantly smaller than the well defined barrier in the crystal.

  14. Understanding soft glassy materials using an energy landscape approach.

    PubMed

    Hwang, Hyun Joo; Riggleman, Robert A; Crocker, John C

    2016-09-01

    Many seemingly different soft materials-such as soap foams, mayonnaise, toothpaste and living cells-display strikingly similar viscoelastic behaviour. A fundamental physical understanding of such soft glassy rheology and how it can manifest in such diverse materials, however, remains unknown. Here, by using a model soap foam consisting of compressible spherical bubbles, whose sizes slowly evolve and whose collective motion is simply dictated by energy minimization, we study the foam's dynamics as it corresponds to downhill motion on an energy landscape function spanning a high-dimensional configuration space. We find that these downhill paths, when viewed in this configuration space, are, surprisingly, fractal. The complex behaviour of our model, including power-law rheology and non-diffusive bubble motion and avalanches, stems directly from the fractal dimension and energy function of these paths. Our results suggest that ubiquitous soft glassy rheology may be a consequence of emergent fractal geometry in the energy landscapes of many complex fluids.

  15. Diamond film growth on Ti-implanted glassy carbon

    NASA Astrophysics Data System (ADS)

    Brewer, M. A.; Brown, I. G.; Evans, P. J.; Hoffman, A.

    1993-09-01

    The growth of diamond thin films on glassy carbon substrates has been investigated as a function of deposition time for different surface treatments. Implantation of Ti to a dose of 1.7 x 10 exp 17/sq cm and abrasion with diamond powder have both been examined to determine their effect on film nucleation and growth. At the shorter deposition times studied, diamond nucleation was observed on all test samples with those subjected to the abrasive pretreatment exhibiting the higher growth rates. However, the adhesion and uniformity of films on unimplanted glassy carbon were found to deteriorate significantly following deposition runs of 14 and 21 h duration. This was attributed to a destabilization of the underlying surface caused by plasma erosion.

  16. Loss of halogens from crystallized and glassy silicic volcanic rocks

    USGS Publications Warehouse

    Noble, D.C.; Smith, V.C.; Peck, L.C.

    1967-01-01

    One hundred and sixty-four F and Cl analyses of silicic welded tuffs and lavas and glass separates are presented. Comparison of the F and Cl contents of crystallized rocks with those of nonhydrated glass and hydrated glassy rocks from the same rock units shows that most of the halogens originally present were lost on crystallization. An average of about half of the F and four-fifths of the Cl originally present was lost. Analyses of hydrated natural glasses and of glassy rocks indicate that in some cases significant amounts of halogens may be removed from or added to hydrated glass through prolonged contact with ground water. The data show that the original halogen contents of the groundmass of a silicic volcanic rock can be reliably determined only from nonhydrated glass. ?? 1967.

  17. Understanding soft glassy materials using an energy landscape approach

    NASA Astrophysics Data System (ADS)

    Hwang, Hyun Joo; Riggleman, Robert A.; Crocker, John C.

    2016-09-01

    Many seemingly different soft materials--such as soap foams, mayonnaise, toothpaste and living cells--display strikingly similar viscoelastic behaviour. A fundamental physical understanding of such soft glassy rheology and how it can manifest in such diverse materials, however, remains unknown. Here, by using a model soap foam consisting of compressible spherical bubbles, whose sizes slowly evolve and whose collective motion is simply dictated by energy minimization, we study the foam's dynamics as it corresponds to downhill motion on an energy landscape function spanning a high-dimensional configuration space. We find that these downhill paths, when viewed in this configuration space, are, surprisingly, fractal. The complex behaviour of our model, including power-law rheology and non-diffusive bubble motion and avalanches, stems directly from the fractal dimension and energy function of these paths. Our results suggest that ubiquitous soft glassy rheology may be a consequence of emergent fractal geometry in the energy landscapes of many complex fluids.

  18. Morphology and formation process of diamond from glassy carbon

    NASA Astrophysics Data System (ADS)

    Miyamoto, Manabu; Akaishi, Minoru; Ohsawa, Toshikazu; Yamaoka, Shinobu; Fukunaga, Osamu

    1989-10-01

    Under static high pressure conditions in the presence of a catalyst metal, a diamond formation process was studied using glassy carbon as a starting source, which was prepared by pyrolysis of furfuryl alcohol resin. Above 1200 °C of the pyrolysis temperature, diamond formation was clearly observed in Ni, Fe, Co and their alloy catalysts. The hydrogen content in the starting carbon has a drastic effect on the diamond formation. The maximum content of the hydrogen in the glassy carbon had to be between 1200 and 2200 ppm to see diamond formation. In the Fe-rich catalyst, a characteristic needle-like diamond was formed due to the texture of the carbon source and the nature of the catalyst.

  19. Glassy correlations and thermal fluctuations in nematic elastomers

    NASA Astrophysics Data System (ADS)

    Lu, Bing; Xing, Xiangjun; Ye, Fangfu; Goldbart, Paul

    2010-03-01

    By means of the vulcanization theory framework we address the properties of nematic elastomers prepared in the isotropic liquid state and subsequently randomly cross-linked beyond the gelation point. We base our analysis on a model replica Landau free energy, in which the vulcanization order parameter is coupled to the order parameter describing the local degree of nematic ordering, retaining fluctuation terms to the Gaussian level. We explore how the cross-linking renormalizes the thermal correlations of the local nematic order, and also results in frozen-in, glassy nematic correlations. We examine these thermal and glassy correlations for two different preparation histories of the system: in the first, the cross-linking is done at temperatures close to the isotropic-nematic transition; in the other, the cross-linking is done at higher temperatures, but the system is subsequently cooled to near this transition temperature.

  20. Probing glassy states in binary mixtures of soft interpenetrable colloids.

    PubMed

    Stiakakis, E; Erwin, B M; Vlassopoulos, D; Cloitre, M; Munam, A; Gauthier, M; Iatrou, H; Hadjichristidis, N

    2011-06-15

    We present experimental evidence confirming the recently established rich dynamic state diagram of asymmetric binary mixtures of soft colloidal spheres. These mixtures consist of glassy suspensions of large star polymers to which different small stars are added at varying concentrations. Using rheology and dynamic light scattering measurements along with a simple phenomenological analysis, we show the existence of re-entrance and multiple glassy states, which exhibit distinct features. Cooperative diffusion, as a probe for star arm interpenetration, is proven to be sensitive to the formation of the liquid pockets which signal the melting of the large-star-glass upon addition of small stars. These results provide ample opportunities for tailoring the properties of soft colloidal glasses.

  1. Global equation of state for a glassy material: Fused silica

    SciTech Connect

    Boettger, J.C.

    1994-09-01

    A new SESAME equation of state (EOS) for fused silica has been generated using the computer program GRIZZLY and will be added to the SESAME library as material number 7387. This new EOS provides better agreement with experimental data than was achieved by all previous SESAME EOSs for fused silica. Material number 7387 also constitutes the most realistic SESAME-type EOS generated for any glassy material thus far.

  2. Localization and Glassy Dynamics in the Immune System

    NASA Astrophysics Data System (ADS)

    Sun, Jun; Earl, David J.; Deem, Michael W.

    We discuss use of the generalized NK model to examine evolutionary dynamics within the immune system. We describe how randomness and diversity play key roles in the immune response and how their effects are captured by this hierarchical spin glass model. We discuss analytical aspects of the model as well as practical applications to design of the annual influenza vaccine. We discuss the subtle role that the glassy evolutionary dynamics plays in suppressing autoimmune disease.

  3. Ultrasonic treatment of glassy carbon for nanoparticle preparation.

    PubMed

    Levêque, Jean-Marc; Duclaux, Laurent; Rouzaud, Jean-Noël; Reinert, Laurence; Komatsu, Naoki; Desforges, Alexandre; Afreen, Sadia; Sivakumar, Manickam; Kimura, Takahide

    2017-03-01

    Glassy carbon particles (millimetric or micrometric sizes) dispersions in water were treated by ultrasound at 20kHz, either in a cylindrical reactor, or in a "Rosette" type reactor, for various time lengths ranging from 3h to 10h. Further separations sedimentation allowed obtaining few nanoparticles of glassy carbon in the supernatant (diameter <200nm). Thought the yield of nanoparticle increased together with the sonication time at high power, it tended to be nil after sonication in the cylindrical reactor. The sonication of glassy carbon micrometric particles in water using "Rosette" instead of cylindrical reactor, allowed preparing at highest yield (1-2wt%), stable suspensions of carbon nanoparticles, easily separated from the sedimented particles. Both sediment and supernatant separated by decantation of the sonicated dispersions were characterized by laser granulometry, scanning electron microscopy, X-ray microanalysis, and Raman and infrared spectroscopies. Their multiscale organization was investigated by transmission electron microscopy as a function of the sonication time. For sonication longer than 10h, these nanoparticles from supernatant (diameter <50nm) are aggregated. Their structures are more disordered than the sediment particles showing typical nanometer-sized aromatic layer arrangement of glassy carbon, with closed mesopores (diameter ∼3nm). Sonication time longer than 5h has induced not only a strong amorphization (subnanometric and disoriented aromatic layer) but also a loss of the mesoporous network nanostructure. These multi-scale organizational changes took place because of both cavitation and shocks between particles, mainly at the particle surface. The sonication in water has induced also chemical effects, leading to an increase in the oxygen content of the irradiated material together with the sonication time.

  4. High Strain Rate Tensile and Compressive Effects in Glassy Polymers

    DTIC Science & Technology

    2013-02-08

    polymers under high strain rates has been determined in compression. Some research programs have studied the combined effects of temperature and strain rate...glassy polymers to high strain rate loading in compression. More recently, research programs that study the combined effects of temperature and strain...Force Materiel Command  United States Air Force  Eglin Air Force Base AFRL-RW-EG-TP-2013-006 High Strain Rate

  5. Two–Photon Oxygen Sensing with Quantum Dot–Porphyrin Conjugates

    PubMed Central

    Lemon, Christopher M.; Karnas, Elizabeth; Bawendi, Moungi G.; Nocera, Daniel G.

    2013-01-01

    Supramolecular assemblies of a quantum dot (QD) associated to palladium(II) porphyrins have been developed to detect oxygen (pO2) in organic solvents. Palladium porphyrins are sensitive in the 0–160 torr range, making them ideal phosphors for in vivo biological oxygen quantification. Porphyrins with meso pyridyl substituents bind to the surface of the QD to produce self–assembled nanosensors. Appreciable overlap between QD emission and porphyrin absorption features results in efficient Förster resonance energy transfer (FRET) for signal transduction in these sensors. The QD serves as a photon antenna, enhancing porphyrin emission under both one– and two–photon excitation, demonstrating that QD–palladium porphyrin conjugates may be used for oxygen sensing over physiological oxygen ranges. PMID:23978247

  6. Excitonic Coupling and Femtosecond Relaxation of Zinc Porphyrin Oligomers Linked with Triazole Bridge: Dynamics and Modeling.

    PubMed

    Bukreev, Alexey; Mikhailov, Konstantin; Shelaev, Ivan; Gostev, Fedor; Polevaya, Yuliya; Tyurin, Vladimir; Beletskaya, Irina; Umansky, Stanislav; Nadtochenko, Victor

    2016-03-31

    The synthesis of new zinc porphyrin oligomers linked by a triazole bridge was carried out via "click" reaction. A split in the porphyrin oligomer B-band was observed. It was considered as evidence of exciton-excitonic coupling. The relaxation of excited states in Q-band porphyrin oligomers was studied by the femtosecond laser spectroscopy technique with a 20 fs pump pulse. The transient oscillations of two B-band excitonic peaks have a π-radian shift. For explanation of the coherent oscillation, a theoretical model was developed. The model considered the combination of the exciton-excitonic coupling between porphyrin rings in dimer and weak exciton-vibronic coupling in one porphyrin ring. By varying the values of the structural parameters of porphyrins (the strength values of this couplings and measure of symmetry breaking), we obtained correspondence between the experimental data (phase shift and amplitudes of the spectrum oscillations) and the predictions of the model developed here.

  7. Magnetoresistance, electrical conductivity, and Hall effect of glassy carbon

    SciTech Connect

    Baker, D.F.

    1983-02-01

    These properties of glassy carbon heat treated for three hours between 1200 and 2700/sup 0/C were measured from 3 to 300/sup 0/K in magnetic fields up to 5 tesla. The magnetoresistance was generally negative and saturated with reciprocal temperature, but still increased as a function of magnetic field. The maximum negative magnetoresistance measured was 2.2% for 2700/sup 0/C material. Several models based on the negative magnetoresistance being proportional to the square of the magnetic moment were attempted; the best fit was obtained for the simplest model combining Curie and Pauli paramagnetism for heat treatments above 1600/sup 0/C. Positive magnetoresistance was found only in less than 1600/sup 0/C treated glassy carbon. The electrical conductivity, of the order of 200 (ohm-cm)/sup -1/ at room temperature, can be empirically written as sigma = A + Bexp(-CT/sup -1/4) - DT/sup -1/2. The Hall coefficient was independent of magnetic field, insensitive to temperature, but was a strong function of heat treatment temperature, crossing over from negative to positive at about 1700/sup 0/C and ranging from -0.048 to 0.126 cm/sup 3//coul. The idea of one-dimensional filaments in glassy carbon suggested by the electrical conductivity is compatible with the present consensus view of the microstructure.

  8. Yield Stress Enhancement in Glassy-Polyethylene Block Copolymers

    NASA Astrophysics Data System (ADS)

    Mulhearn, William; Register, Richard

    Polyethylene (PE) has the highest annual production volume of all synthetic polymers worldwide, and is valuable across many applications due to its low cost, toughness, processability, and chemical resistance. However, PE is not well suited to certain applications due to its modest yield stress and Young's modulus (approximately 30 MPa and 1 GPa, respectively for linear, high-density PE). Irreversible deformation of PE results from dislocation of crystal stems and eventual crystal fragmentation under applied stress. The liquid-like amorphous fraction provides no useful mechanical support to the crystal fold surface in a PE homopolymer, so the only method to enhance the force required for crystal slip, and hence the yield stress, is crystal thickening via thermal treatment. An alternative route towards modifying the mechanical properties of PE involves copolymerization of a minority high-glass transition temperature block into a majority-PE block copolymer. In this work, we investigate a system of glassy/linear-PE block copolymers prepared via ring-opening metathesis polymerization of cyclopentene and substituted norbornene monomers followed by hydrogenation. We demonstrate that a large change in mechanical properties can be achieved with the addition of a short glassy block (e.g. a doubling of the yield stress and Young's modulus versus PE homopolymer with the addition of 25 percent glassy block). Furthermore, owing to the low interaction energy between PE and the substituted polynorbornene blocks employed, these high-yield PE block copolymers can exhibit single-phase melts for ease of processability.

  9. Exploration for facultative endosymbionts of glassy-wingedsharpshooter (Hemiptera: Cicadellidae)

    SciTech Connect

    Montllor-Curley, C.; Brodie, E.L.; Lechner, M.G.; Purcell, A.H.

    2006-07-01

    Homalodisca vitripennis (Germar) (Hemiptera: Cicadellidae),glassy-winged sharpshooter, was collected in California and severalstates in the southeastern United States in 2002 and 2003 and analyzedfor endosymbiotic bacteria. Hemolymph, eggs, and bacteriomes wereexamined for the presence of bacteria by polymerase chain reaction. Asubset of hemolymph and egg samples had their 16S rRNA gene ampliconscloned and sequenced or analyzed by restriction digest patterns ofsamples compared with known bacterial DNA. Baumannia cicadellinicola, oneof the primary symbionts of glassy-winged sharpshooter, was found in themajority of hemolymph samples, although it has been considered until nowto reside primarily inside the specialized host bacteriocytes. Wolbachiasp., a common secondary symbiont in many insect taxa investigated todate, was the second most frequently detected bacterium in hemolymphsamples. In addition, we detected bacteria that were most closely related(by 16S rRNA gene sequence) to Pseudomonas, Stenotrophomonas, andAcinetobacter in hemolymph samples of one and/or two glassy-wingedsharpshooters, but their origin is uncertain.

  10. Glassy materials for lithium batteries: electrochemical properties and devices performances

    NASA Astrophysics Data System (ADS)

    Duclot, Michel; Souquet, Jean-Louis

    Amorphous or glassy materials may be used as electrolyte or electrode materials for lithium primary or secondary batteries. A first generation proceeded from classical coin cells in which the organic electrolyte was replaced by a high lithium conductive glassy electrolyte. The solid components were assembled under isostatic pressure. The main advantages of such cells are a good storage stability and ability to operate until 200°C. Nevertheless, the high resistivity of the glassy electrolyte below room temperature and a limited depth for charge and discharge cycles makes these cells not competitive compared to conventional lithium-ion batteries. More promising, are the thin films solid state microbatteries realised by successive depositions of electrodes and electrolyte. The low resistance of the electrolyte amorphous layer allows cycling at temperatures as low as -10°C. The total thickness of thin film batteries, including packaging is less than 100 μm. A capacity of about 100 μAh cm -2 with over 10 4 charge-discharge cycles at 90% in depth of discharge is well suited for energy independent smart cards or intelligent labels, which represent for these devices a large and unrivalled market.

  11. Quantifying glassy and crystalline basalt partitioning in the oceanic crust

    NASA Astrophysics Data System (ADS)

    Moore, Rachael; Ménez, Bénédicte

    2016-04-01

    The upper layers of the oceanic crust are predominately basaltic rock, some of which hosts microbial life. Current studies of microbial life within the ocean crust mainly focus on the sedimentary rock fraction, or those organisms found within glassy basalts while the potential habitability of crystalline basalts are poorly explored. Recently, there has been recognition that microbial life develops within fractures and grain boundaries of crystalline basalts, therefore estimations of total biomass within the oceanic crust may be largely under evaluated. A deeper understanding of the bulk composition and fractionation of rocks within the oceanic crust is required before more accurate estimations of biomass can be made. To augment our understanding of glassy and crystalline basalts within the oceanic crust we created two end-member models describing basalt fractionation: a pillow basalt with massive, or sheet, flows crust and a pillow basalt with sheeted dike crust. Using known measurements of massive flow thickness, dike thickness, chilled margin thickness, pillow lava size, and pillow lava glass thickness, we have calculated the percentage of glassy versus crystalline basalts within the oceanic crust for each model. These models aid our understanding of textural fractionation within the oceanic crust, and can be applied with bioenergetics models to better constrain deep biomass estimates.

  12. Fast algorithms for glassy materials: methods and explorations

    NASA Astrophysics Data System (ADS)

    Middleton, A. Alan

    2014-03-01

    Glassy materials with frozen disorder, including random magnets such as spin glasses and interfaces in disordered materials, exhibit striking non-equilibrium behavior such as the ability to store a history of external parameters (memory). Precisely due to their glassy nature, direct simulation of models of these materials is very slow. In some fortunate cases, however, algorithms exist that exactly compute thermodynamic quantities. Such cases include spin glasses in two dimensions and interfaces and random field magnets in arbitrary dimensions at zero temperature. Using algorithms built using ideas developed by computer scientists and mathematicians, one can even directly sample equilibrium configurations in very large systems, as if one picked the configurations out of a ``hat'' of all configurations weighted by their Boltzmann factors. This talk will provide some of the background for these methods and discuss the connections between physics and computer science, as used by a number of groups. Recent applications of these methods to investigating phase transitions in glassy materials and to answering qualitative questions about the free energy landscape and memory effects will be discussed. This work was supported in part by NSF grant DMR-1006731. Creighton Thomas and David Huse also contributed to much of the work to be presented.

  13. Thermodynamics of water sorption in high performance glassy thermoplastic polymers

    PubMed Central

    Scherillo, Giuseppe; Petretta, Mauro; Galizia, Michele; La Manna, Pietro; Musto, Pellegrino; Mensitieri, Giuseppe

    2014-01-01

    Sorption thermodynamics of water in two glassy polymers, polyetherimide (PEI) and polyetheretherketone (PEEK), is investigated by coupling gravimetry and on line FTIR spectroscopy in order to gather information on the total amount of sorbed water as well as on the different species of water molecules absorbed within the polymers, addressing the issue of cross- and self-interactions occurring in the polymer/water systems. Water sorption isotherms have been determined at temperatures ranging from 30 to 70°C while FTIR spectroscopy has been performed only at 30°C. The experimental analysis provided information on the groups present on the polymer backbones involved in hydrogen bonding interactions with absorbed water molecules. Moreover, it also supplied qualitative indications about the different “populations” of water molecules present within the PEEK and a quantitative assessment of these “populations” in the case of PEI. The results of the experimental analysis have been interpreted using an equation of state theory based on a compressible lattice fluid model for the Gibbs energy of the polymer-water mixture, developed by extending to the case of out of equilibrium glassy polymers a previous model intended for equilibrium rubbery polymers. The model accounts for the non-equilibrium nature of glassy polymers as well as for mean field and for hydrogen bonding interactions, providing a satisfactory quantitative interpretation of the experimental data. PMID:24860802

  14. Thermodynamics of Water Sorption in High Performance Glassy Thermoplastic Polymers

    NASA Astrophysics Data System (ADS)

    Mensitieri, Giuseppe; Scherillo, Giuseppe; Petretta, Mauro; Galizia, Michele; La Manna, Pietro; Musto, Pellegrino

    2014-05-01

    Sorption thermodynamics of water in two glassy polymers, polyetherimide (PEI) and polyetheretherketone (PEEK), is investigated by coupling gravimetry and on line FTIR spectroscopy in order to gather information on the total amount of sorbed water as well as on the different species of water molecules absorbed within the polymers, addressing the issue of cross- and self-interactions occurring in the polymer/water systems. Water sorption isotherms have been determined at temperatures ranging fro 30 to 70°C while FTIR spectroscopy has been performed only at 30°C. The experimental analysis provided information on the groups present on the polymer backbones involved in hydrogen bonding interactions with absorbed water molecules. Moreover, it also supplied qualitative indications about the different’populations’ of water molecules present within the PEEK and a quantitative assessment of these ‘populations’ in the case of PEI.The results of the experimental analysis have been interpreted using an equation of state theory based on a compressible lattice fluid model for the Gibbs energy of the polymer-water mixture, developed by extending to the case of out of equilibrium glassy polymers a previous model intended for equilibrium rubbery polymers. The model accounts for the non equilibrium nature of glassy poymers as well as for mean field and for hydrogen bonding interactions, providing a satisfactory quantitative interpretation of the experimental data.

  15. Porphyrin-Based Dye-Sensitized Solar Cells (DSSCs): a Review.

    PubMed

    Birel, Özgül; Nadeem, Said; Duman, Hakan

    2017-02-16

    The current review aims to collect short information about photovoltaic performance and structure of porphyrin-based sensitizers used in dye-sensitized solar cells (DSSC). Sensitizer is the key component of the DSSC device. Structure of sensitizer is important to achieve high photovoltaic performance. Porphyrin derivatives are suitable for DSSC applications due to their thermal, electronic and photovoltaic properties. It describes some electrochemical and spectral properties as well as thestructure of porphyrin dyes used in dye based-solar cells.

  16. The Determination of Quantum Yield in the Fluoresence Spectra of Porphyrins

    NASA Astrophysics Data System (ADS)

    ćati, Odeta; Kristo, Kejda; Spiro, Marenglen; Xhuvani, Emil; Babani, Fatbardha; Tafa, Dentila

    2010-01-01

    The porphyrins, natural macromolecules, and especially the glycosylated ones, are recently used in the photodynamic therapy of different kinds of tumor cells. The porphyrins are injected through intravenous way in the human body. Under appropriate radiation of tumor zone with light in UV region, oxidation processes of the porphyrins occur through different mechanizms. As a result, inside the tumor, is producing oxygen in singlet state which is lethal for the tumor cells. The spectroscopic study of the porphyrins, both the absorbtion and the fluoresence spectroscopy, reveals some properties of the porphyrins which are ralated with their eventual application in the photodynamic therapy. So, from the value of the quantum yield, which is an important quantity that derives from the measurement of fluoresence of porphyrins, one can judge, through which mechanizm, the oxidation process does occurs. This suggest how the porphyrin should be used in the therapy, as monomers or as aggregates. The porphyrins are sinthetised in the Laboratory of Chemistry of Natural Compaunds, in the University of Limoges. The spectra has been taken by means of a photospectrometer, in the University of Tirana. The fluoresence spectra of the "protected" and "unprotected" porphyrins are studied. The determination of the quantum yield has been done through the comparison of porphyrins spectra, with them of Rhodamine B, which has a large fluoresence, in the same region of spectrum where does occurr the fluoresence of porphyrins. In order to do that, the calculations of the surface under the fluoresence spectra and under the Rhodamine one, is necessary. Also, the extintion of the fluoresence of some "protected" porphyrins, in polar solution, has been detected. These extintion of fluoresence has to do with the formation of agregates, of dimers, which can be confirmed from the absorbtion spectra.

  17. Effect of hypoxia on porphyrin metabolism in bone marrow mesenchymal stem cells.

    PubMed

    Poleshko, A G; Lobanok, E S; Volotovskii, I D

    2014-05-01

    Under hypoxic conditions, aminolevulinic acid-induced accumulation of porphyrin pigments and increase in heme content was observed in bone marrow mesenchymal stem cells. The expression of transferrin receptor CD71 responsible for Fe(2+) transport into the cell was also enhanced. Blockade of porphyrin-transporting protein ABCG2 with fumitremorgin C under conditions of normoxia and hypoxia induced accumulation of porphyrin pigments; in hypoxia, these changes were more pronounced.

  18. Microscale determination of the spectral characteristics and carbon-isotopic compositions of porphyrins

    NASA Technical Reports Server (NTRS)

    Popp, B. N.; Hayes, J. M.; Boreham, C. J.

    1993-01-01

    Molar extinction coefficients for band III of Ni porphyrins are calculated from results of spectrophotometric and manometric analyses of individual etioporphyrins, DPEP, cyclic, and diDPEP porphyrins known to initially be pure from mass spectrometry, 1H NMR, and analytical HPLC studies. A method for determining carbon-isotopic compositions and purity of micromolar quantities of individual porphyrins using combined spectrophotometric and manometric techniques is presented.

  19. A search for porphyrin biomarkers in Nonesuch Shale and extraterrestrial samples.

    NASA Technical Reports Server (NTRS)

    Rho, J. H.; Bauman, A. J.; Boettger, H. G.; Yen, T. F.

    1973-01-01

    An organic solvent extract of billion year old Nonesuch Shale was examined for porphyrins by means of fluorometry and high resolution mass spectrometry. It appears to contain at least three or more classes of porphyrins, one similar to tetraphenyl porphin and the others more complex. Many are apparently chelated with copper, nickel, zinc, iron and vanadyl and are highly aromatic. We have also examined the extracts of Apollo 11, 12 and 14 surface fines for porphyrins by spectrophotofluorometry, but we found none.

  20. Investigation of glassy state molecular motions in thermoset polymers

    NASA Astrophysics Data System (ADS)

    Tu, Jianwei

    This dissertation presents the investigation of the glassy state molecular motions in isomeric thermoset epoxies by means of solid-state deuterium (2H) NMR spectroscopy technique. The network structure of crosslinked epoxies was altered through monomer isomerism; specifically, diglycidyl ether of bisphenol A (DGEBA) was cured with isomeric amine curatives, i.e., the meta-substituted diaminodiphenylsulfone (33DDS) and para-substituted diaminodiphenylsulfone (44DDS). The use of structural isomerism provided a path way for altering macroscopic material properties while maintaining identical chemical composition within the crosslinked networks. The effects of structural isomerism on the glassy state molecular motions were studied using solid-state 2H NMR spectroscopy, which offers unrivaled power to monitor site-specific molecular motions. Three distinctive molecular groups on each isomeric network, i.e., the phenylene rings in the bisphenol A structure (BPA), the phenylene rings in the diaminodiphenylsulfone structure (DDS), and the hydroxypropoyl ether group (HPE) have been selectively deuterated for a comprehensive study of the structure-dynamics- property relationships in thermoset epoxies. Quadrupolar echo experiments and line shape simulations were employed as the main research approach to gain both qualitative and quantitative motional information of the epoxy networks in the glassy state. Quantitative information on the geometry and rate of the molecular motions allows the elucidation of the relationship between molecular motions and macro physical properties and the role of these motions in the mechanical relaxation. Specifically, it is revealed that both the BPA and HPE moieties in the isomeric networks have almost identical behaviors in the deep glassy state, which indicates that the molecular motions in the glassy state are localized, and the correlation length of the motions does not exceed the length of the DGEBA repeat unit. BPA ring motions contribute

  1. Porphyrin as an ideal biomarker in the search for extraterrestrial life.

    PubMed

    Suo, Zhiyong; Avci, Recep; Schweitzer, Mary Higby; Deliorman, Muhammedin

    2007-08-01

    A key issue in astrobiological research is identifying target molecules that are unambiguously biological in origin and can be easily detected and recognized. We suggest porphyrin derivatives as an ideal target, because these chromophores are global in distribution and found in virtually all living organisms on Earth, including microorganisms that may approximate the early evolution of life on Earth. We discuss the inherent qualities that make porphyrin ideally suited for astrobiological research and discuss methods for detecting porphyrin molecules in terrestrial sedimentary environments. We present preliminary data to support the use of ToFSIMS as a powerful technique in the identification of porphyrins.

  2. Effect of fatty acids on the complexation of proteins with porphyrins

    NASA Astrophysics Data System (ADS)

    Gyulkhandanyan, Grigor V.

    2011-02-01

    Porphyrins binding and transport to tumor is the one of the central tasks of photodynamic therapy of tumor (PDT). The main carriers of porphyrins (photosensitizers) in the blood are lipoproteins, serum albumin and hemoglobin. In studying the phenomenon of complexation of proteins with ligands must take into considering the real conditions that exist in the organism and, in particular, take into considering the presence of fatty acids in blood. Up to date the role of fatty acids (palmitic and stearic) in the binding of porphyrins with proteins not been determined. A key step in solving of these problems is to determine the binding constants of porphyrin-protein pairs and effect of fatty acids on this process. The most direct and sufficiently accurate methods of solving such problems are complementary methods of absorption and fluorescence spectroscopy. The results of spectral studies on the binding of porphyrins to serum albumin and hemoglobin in the presence of fatty acids demonstrated a significant decrease in the degree of binding pair porphyrin-albumin and porphyrin-hemoglobin with increasing concentrations of fatty acids in solution. The results lead to the conclusion that for hemoglobin the presence in a solution of fatty acids on binding to the porphyrins affected more significantly than for serum albumin. Thus, in natural conditions, when in the blood presented fatty acids the preference between hemoglobin and serum albumin in the binding and in the transport of porphyrins should be given to serum albumin.

  3. Synthesis and binding properties of arylethyne-linked porphyrin-zinc complexes for organic electronics applications.

    PubMed

    Reainthippayasakul, W; Paosawatyanyong, B; Bhanthumnavin, W

    2013-05-01

    Conjugated meso-alkynyl 5,15-dimesitylporphyrin metal complexes have been synthesized by Sonogashira coupling reaction in good yields. Alkynyl groups were chosen as a link at the meso positions in order to extend the pi-conjugated length of porphyrin rings. These synthesized porphyrin derivatives were characterized by 1H NMR spectroscopy and MALDI-TOF mass spectrometry. Moreover, UV-visible spectroscopy and fluorescence spectroscopy were also used to investigate their photophysical properties. It has been demonstrated that central metal ions as well as meso substituents on porphyrin rings affected the electronic absorption and emission spectra of the compounds. Spectroscopic results revealed that alkyne-linked porphyrin metal complexes showed higher pi-conjugation compared with porphyrin building blocks resulting in red shifts in both absorption and emission spectra. Coordination properties of synthesized porphyrins were preliminarily investigated by UV-visible absorption and fluorescence emission spectroscopic titration with pyridine as axial ligand. The formation of porphyrin-pyridine complexes resulted in significant red shifts in absorption spectra and decrease of fluorescence intensity in emission spectra. Moreover, the 1H NMR titration experiments suggested that central metal ions play an important role to coordinate with pyridine and the coordination of porphyrin zinc(II) complex with pyridine occur in a 1:1 ratio. From these spectroscopic results, alkyne-linked porphyrin metal complexes offer potential applications as materials for optical organic nanosensors.

  4. Boronated porphyrins in NCT: Results with a new potent tumor localizer

    SciTech Connect

    Kahl, S.B.; Koo, M.S.; Laster, B.H.; Fairchild, R.G.

    1988-01-01

    Several chemical methods are available for the solubilization of boronated porphyrins. We have previously reported the tumor localization of nido carboranyl porphyrins in which the icosahedral carborane cages have been opened to give B/sub 9/C/sub 2/ anions. One of these species has shown tumor boron levels of nearly 50 ..mu..g B/g when delivered by week-long subcutaneous infusions. We report here recent in vivo experiments with a new, highly water-soluble porphyrin based on the hematoporphyrin-type of compound in which aqueous solubility is achieved using the two propionic acid side chains of the ''natural'' porphyrin frame. 7 refs.

  5. Porphyrins as Photoredox Catalysts: Experimental and Theoretical Studies.

    PubMed

    Rybicka-Jasińska, Katarzyna; Shan, Wenqian; Zawada, Katarzyna; Kadish, Karl M; Gryko, Dorota

    2016-11-30

    Metalloporphyrins not only are vital in biological systems but also are valuable catalysts in organic synthesis. On the other hand, catalytic properties of free base porphyrins have been less explored. They are mostly known as efficient photosensitizers for the generation of singlet oxygen via photoinduced energy transfer processes, but under light irradiation, they can also participate in electron transfer processes. Indeed, we have found that free base tetraphenylporphyrin (H2TPP) is an efficient photoredox catalyst for the reaction of aldehydes with diazo compounds leading to α-alkylated derivatives. The performance of a porphyrin catalyst can be optimized by tailoring various substituents at the periphery of the macrocycle at both the β and meso positions. This allows for the fine tuning of their optical and electrochemical properties and hence their catalytic activity.

  6. Molecular structures of porphyrin-quinone models for electron transfer

    SciTech Connect

    Fajer, J.; Barkigia, K.M.; Melamed, D.; Sweet, R.M.; Kurreck, H.; Gersdorff, J. von; Plato, M.; Rohland, H.C.; Elger, G.; Moebius, K.

    1996-08-15

    Synthetic porphyrin-quinone complexes are commonly used to mimic electron transport in photosynthetic reaction centers and to probe the effects of energetics, distances, and relative orientations on rates of electron transfer between donor-acceptor couples. The structures of two such models have been determined by X-ray diffraction. The redox pairs consist of a zinc porphyrin covalently linked to benzoquinone in cis and trans configurations via a cyclohexanediyl bridge. The crystallographic studies were undertaken to provide a structural foundation for the extensive body of experimental and theoretical results that exists for these compounds in both the ground and photoinduced charge-separated states. The results validate conclusions reached from theoretical calculations, EPR and two-dimensional NMR results for these states. 15 refs., 6 figs., 2 tabs.

  7. Spatially resolved micro-photoluminescence imaging of porphyrin single crystals

    NASA Astrophysics Data System (ADS)

    Marin, Dawn M.; Castaneda, Jose; Kaushal, Meesha; Kaouk, Ghallia; Jones, Daniel S.; Walter, Michael G.

    2016-08-01

    We describe the collection of both time-resolved and steady-state micro-photoluminescence data from solution-grown single crystals of 5,15-bis(4-carbomethoxyphenyl)porphyrin (BCM2PP). Linking molecular orientation and structure with excited-state dynamics is crucial for engineering efficient organic solar cells, light-emitting diodes, and related molecular electronics. Photoluminescence features of single porphyrin crystals were imaged using a laser scanning confocal microscope equipped with time-correlated single photon counting (TCSPC). We show enhanced exciton lifetimes (τs1 = 2.6 ns) and stronger steady-state emission in crystalline BCM2PP samples relative to semicrystalline thin films (τs1 = 1.8 ns).

  8. Synthesis and Characterization of a New Perhalogenated Porphyrin

    SciTech Connect

    Jia, Songling; Medforth, Craig J.; Nelson, Nora Y.; Nurco, Daniel J.; Shelnutt, John; Smith, Kevin M.

    1999-05-19

    The first synthesis of an octahalotetraalkylporphyrin [2,3,7,8,12,13,17,18 -octabromo-5,10,15,20- tetrakis(trifluoromethyl)porphinato nickel(II)] is reported; this perhalogenated porphyrin has several novel properties including a very nonplanar ruffled structure with an unusually short Ni- N distance, an extremely red-shifted optical spectrum, and hindered rotation of the trifluoromethyl groups ({Delta}G278K =47 kJ mol-1).

  9. Porphyrin-based Nanostructure-Dependent Photodynamic and Photothermal Therapies

    NASA Astrophysics Data System (ADS)

    Jin, Cheng S.

    This thesis presents the investigation of nanostructure-dependent phototherapy. We reviewed the liposomal structures for delivery of photosensitizers, and introduced a novel class of phototransducing liposomes called "porphysomes". Porphysomes are self-assembled from high packing density of pyropheophorbide alpha-conjugated phospholipids, resulting in extreme self-quenching of porphyrin fluorescence and comparable optical absorption to gold nanoparticles for high photothermal efficiency. We demonstrated this self-assembly of porphyrin-lipid conjugates converts a singlet oxygen generating mechanism (photodynamic therapy PDT activity) of porphyrin to photothermal mechanism (photothermal therapy PTT activity). The efficacy of porphysome-enhanced PTT was then evaluated on two pre-clinical animal models. We validated porphysome-enabled focal PTT to treat orthotopic prostate cancer using MRI-guided focal laser placement to closely mimic the current clinic procedure. Furthermore, porphysome-enabled fluorescence-guided transbronchial PTT of lung cancer was demonstrated in rabbit orthotopic lung cancer models, which led to the development of an ultra-minimally invasive therapy for early-stage peripheral lung cancer. On the other hand, the nanostructure-mediated conversion of PDT to PTT can be switched back by nanoparticle dissociation. By incorporating folate-conjugated phospholipids into the formulation, porphysomes were internalized into cells rapidly via folate receptor-mediated endocytosis and resulted in efficient disruption of nanostructures, which turned back on the photodynamic activity of densely packed porphyrins, making a closed loop of conversion between PDT and PTT. The multimodal imaging and therapeutic features of porphysome make it ideal for future personalized cancer treatments.

  10. A single crystalline porphyrinic titanium metal–organic framework

    DOE PAGES

    Yuan, Shuai; Liu, Tian -Fu; Feng, Dawei; ...

    2015-04-28

    We successfully assembled the photocatalytic titanium-oxo cluster and photosensitizing porphyrinic linker into a metal–organic framework (MOF), namely PCN-22. A preformed titanium-oxo carboxylate cluster is adopted as the starting material to judiciously control the MOF growth process to afford single crystals. This synthetic method is useful to obtain highly crystalline titanium MOFs, which has been a daunting challenge in this field. Moreover, PCN-22 demonstrated permanent porosity and photocatalytic activities toward alcohol oxidation.

  11. Potential use of radiolabelled porphyrins for tumor scanning

    SciTech Connect

    Thaller, R.A.; Lyster, D.M.; Dolphin, D.

    1983-01-01

    Fe-TMPI, Fe-TCP and protohemins showed high initial uptake using tissue culture techniques with mouse tumor cells (P815). However, the tumor uptake in the in vivo model was poor. Of the radionuclides investigated, iron labelled to TMPI demonstrated the best uptake by tumor in vitro. As has been previously demonstrated, the unnatural meso-arylporphyrin derivatives showed better uptake than did naturally occurring porphyrins and their derivatives.

  12. The equipment for the preparation of micro and nanoscale metallic glassy fibers.

    PubMed

    Ding, D W; Yi, J; Liu, G L; Sun, Y T; Zhao, D Q; Pan, M X; Bai, H Y; Wang, W H

    2014-10-01

    A supercooled liquid extraction method and apparatus for micro and nanoscale metallic glassy fiber preparation was developed. Using the fiber fabrication equipment, micro to nanoscale metallic glassy fibers with diameter ranging from 70 nm to 300 μm can be obtained by wire drawing in the supercooled liquid region of metallic glasses via superplastic deformation. The obtained metallic glassy fibers possess precisely designed and controlled sizes, high structural uniformity and high degree of surface smoothness.

  13. Cationic porphyrin derivatives for application in photodynamic therapy of cancer

    NASA Astrophysics Data System (ADS)

    Prack McCormick, Bárbara P.; Florencia Pansa, M.; Milla Sanabria, Laura N.; Carvalho, Carla M. B.; Faustino, M. Amparo F.; Neves, Maria Graça P. M. S.; Cavaleiro, José A. S.; Rumie Vittar, Natalia B.; Rivarola, Viviana A.

    2014-04-01

    Current studies in photodynamic therapy (PDT) against cancer are focused on the development of new photosensitizers (PSs), with higher phototoxic action. The aim of this study was to compare the therapeutic efficiency of tri-cationic meso-substituted porphyrin derivatives (Tri-Py+-Me-PF, Tri-Py+-Me-Ph, Tri-Py+-Me-CO2Me and Tri-Py+-Me-CO2H) with the well-known tetra-cationic T4PM. The phototoxic action of these derivatives was assessed in human colon adenocarcinoma cells by cell viability, intracellular localization and nuclear morphology analysis. In the experimental conditions used we determined that after light activation -PF, -Ph and -CO2Me cause a more significant decline of cell viability compared to -CO2H and T4PM. These results suggest that the nature of the peripheral substituent influences the extent of cell photodamage. Moreover, we have demonstrated that PS concentration, physicochemical properties and further light activation determine the PDT response. All porphyrins were clearly localized as a punctuated pattern in the cytoplasm of the cells, and the PDT scheme resulted in apoptotic cell death after 3 h post-PDT. The tri-cationic porphyrin derivatives Tri-Py+-Me-PF, Tri-Py+-Me-Ph and Tri-Py+-Me-CO2Me showed a promising ability, making them good photosensitizer candidates for oncological PDT.

  14. [Bulk heterojunction solar cell based on porphyrin compounds].

    PubMed

    Zhang, Tian-hui; Zhao, Su-ling; Piao, Ling-yu; Xu, Zheng; Kong, Chao

    2012-01-01

    Three kinds of porphyrins which can abbreviate as TPP, TPPCu and TMPPFeCl were synthesized by one-step method with mixed solvents. Then these porphyrin materials were used as donors to fabricate organic solar cells with PCBM as accepter by the solution processing of spin-coating method. The structure is ITO/porphyrin : PCBM/Al. The photovoltaic characterizations of these devices were investigated. The device based on TPP : PCBM shows the best performance with an open circuit voltage (V(OC)) of 0.52 V, a short circuit current (J(SC)) of 0.98 mA x cm(-2), and fill factor (FF) of 30.1%. Then the influence of different weight ratio of TPP : PCBM was researched. The best weight ratio of TPP : PCBM is 1 : 1. Increasing or decreasing the quatity of TPP would make J(SC) and V(OC) of the device deterioration and have little effect on the FF.

  15. Photobactericidal porphyrin-cellulose nanocrystals: synthesis, characterization, and antimicrobial properties.

    PubMed

    Feese, Elke; Sadeghifar, Hasan; Gracz, Hanna S; Argyropoulos, Dimitris S; Ghiladi, Reza A

    2011-10-10

    Adherence and survival of pathogenic bacteria on surfaces leading to concomitant transmission to new hosts significantly contributes to the proliferation of pathogens, which in turn considerably increases the threat to human health, particularly by antibiotic-resistant bacteria. Consequently, more research into effective surface disinfection and alternative materials (fabrics, plastics, or coatings) with antimicrobial and other bioactive characteristics is desirable. This report describes the synthesis and characterization of cellulose nanocrystals that were surface-modified with a cationic porphyrin. The porphyrin was appended onto the cellulose surface via the Cu(I)-catalyzed Huisgen-Meldal-Sharpless 1,3-dipolar cycloaddition having occurred between azide groups on the cellulosic surface and porphyrinic alkynes. The resulting, generally insoluble, crystalline material, CNC-Por (5), was characterized by infrared and diffusion (1)H NMR spectroscopies, gel permeation chromatography, and thermogravimetric analysis. Although only suspended, and not dissolved, in an aqueous system, CNC-Por (5) showed excellent efficacy toward the photodynamic inactivation of Mycobacterium smegmatis and Staphylococcus aureus , albeit only slight activity against Escherichia coli . The synthesis, properties, and activity of CNC-Por (5) described herein serve as a benchmark toward our overall objectives of developing novel, potent, bioactive, photobactericidal materials that are effective against a range of bacteria, with potential utilization in the health care and food preparation industries.

  16. Antimicrobial activity of new porphyrins of synthetic and natural origin

    NASA Astrophysics Data System (ADS)

    Gyulkhandanyan, Grigor V.; Ghazaryan, Robert K.; Paronyan, Marina H.; Ulikhanyan, Ghukas I.; Gyulkhandanyan, Aram G.; Sahakyan, Lida A.

    2012-03-01

    Antimicrobial photodynamic inactivation has been successfully used against Gram (+) microorganisms, but most of the photosensitizers (PSs) on Gram (-) bacteria acts weakly. PSs are the natural or synthetic origin dyes, mainly porphyrins. We have synthesized more than 100 new cationic porphyrins and metalloporphyrins with different functional groups (hydroxyethyl, butyl, allyl, methallyl) and metals (cobalt, iron, copper, zinc, silver and other); from the nettle have also been purified pheophytin (a+b) and pheophytin (a) and have synthesized their Ag-and Zn-metalloporphyrins. It was found that in the dark (cytotoxic) mode, the most highly efficiency against microorganisms showed Agmetalloporphyrins of both types of porphyrins (synthetic and natural). Metalloporphyrin of natural origin Ag-pheophytin (a + b) is a strong antibacterial agent and causes 100% death as the Gram (+) microorganisms (St. aureus and MRSA) and the Gram (-) microorganisms (E.coli and Salmonella). It is established that for the destruction of Gram (+) and Gram (-) microorganisms in photodynamic mode cationic water-soluble synthetic metalloporphyrins, especially Zn-TBut4PyP, many times more effective than pheophytins. In vivo conditions on mice established that the best therapeutic activity against various strains of the microorganism St. aureus has the synthetic metalloporphyrin Ag-TBut4PyP. It is significantly more efficient than known drug "Chlorophyllipt" (2.5-3 times) and leads the survival rate of animals up to 50-60%.

  17. Porphyrins as Molecular Electronic Components of Functional Devices

    PubMed Central

    Jurow, Matthew; Schuckman, Amanda E.; Batteas, James D.; Drain, Charles Michael

    2010-01-01

    The proposal that molecules can perform electronic functions in devices such as diodes, rectifiers, wires, capacitors, or serve as functional materials for electronic or magnetic memory, has stimulated intense research across physics, chemistry, and engineering for over 35 years. Because biology uses porphyrins and metalloporphyrins as catalysts, small molecule transporters, electrical conduits, and energy transducers in photosynthesis, porphyrins are an obvious class of molecules to investigate for molecular electronic functions. Of the numerous kinds of molecules under investigation for molecular electronics applications, porphyrins and their related macrocycles are of particular interest because they are robust and their electronic properties can be tuned by chelation of a metal ion and substitution on the macrocycle. The other porphyrinoids have equally variable and adjustable photophysical properties, thus photonic applications are potentiated. At least in the near term, realistic architectures for molecular electronics will require self-organization or nanoprinting on surfaces. This review concentrates on self-organized porphyrinoids as components of working electronic devices on electronically active substrates with particular emphasis on the effect of surface, molecular design, molecular orientation and matrix on the detailed electronic properties of single molecules. PMID:20936084

  18. Crystallization of the glassy grain boundary phase in silicon nitride ceramics

    NASA Technical Reports Server (NTRS)

    Drummond, Charles H., III

    1991-01-01

    The role was studied of the intergranular glassy phase in silicon nitride as-processed with yttria as a sintering aid. The microstructure, crystallization, and viscosity of the glassy phase were areas studied. Crystallization of the intergranular glassy phase to more refractory crystalline phases should improve the high temperature mechanical properties of the silicon nitride. The addition of a nucleating agent will increase the rate of crystallization. The measurement of the viscosity of the glassy phase will permit the estimation of the high temperature deformation of the silicon nitride.

  19. Thermodynamic analysis of porphyrin binding to Momordica charantia (bitter gourd) lectin.

    PubMed

    Sultan, Nabil A M; Maiya, Bhaskar G; Swamy, Musti J

    2004-08-01

    Owing to the use of porphyrins in photodynamic therapy for the treatment of malignant tumors, and the preferential interaction of lectins with tumor cells, studies on lectin-porphyrin interaction are of significant interest. In this study, the interaction of several free-base and metalloporphyrins with Momordica charantia (bitter gourd) lectin (MCL) was investigated by absorption spectroscopy. Difference absorption spectra revealed that significant changes occur in the Soret band region of the porphyrins on binding to MCL. These changes were monitored to obtain association constants (Ka) and stoichiometry of binding. The tetrameric MCL binds four porphyrin molecules, and the stoichiometry was unaffected by the presence of the specific sugar, lactose. In addition, the agglutination activity of MCL was unaffected by the presence of the porphyrins used in this study, clearly indicating that porphyrin and carbohydrate ligands bind at different sites. Both cationic and anionic porphyrins bind to the lectin with comparable affinity (Ka =10(3)-10(5) m(-1)). The thermodynamic parameters associated with the interaction of several porphyrins, obtained from the temperature dependence of the Ka values, were found to be in the range: DeltaH degrees = -98.1 to -54.4 kJ.mol(-1) and DeltaS degrees =-243.9 to -90.8 J.mol(-1).K(-1). These results indicate that porphyrin binding to MCL is governed by enthalpic forces and that the contribution from binding entropy is negative. Enthalpy-entropy compensation was observed in the interaction of different porphyrins with MCL, underscoring the role of water structure in the overall binding process. Analysis of CD spectra of MCL indicates that this protein contains about 13%alpha-helix, 36%beta-sheet, 21%beta-turn, and the rest unordered structures. Binding of porphyrins does not significantly alter the secondary and tertiary structures of MCL.

  20. Some Recent Developments in Structure and Glassy Behavior of Proteins

    NASA Astrophysics Data System (ADS)

    Hu, Chin-Kun

    2012-02-01

    We have used ARVO developed by us to find that the ratio of volume and surface area of proteins in Protein Data Bank distributed in a very narrow region [1]. Such result is useful for the determination of protein 3D structures. It has been widely known that a spin glass model can be used to understand the slow relaxation behavior of a glass at low temperatures [2]. We have used molecular dynamics and simple models of polymer chains to study relaxation and aggregation of proteins under various conditions and found that polymer chains with neighboring monomers connected by rigid bonds can relax very slowly and show glassy behavior [3]. We have also found that native collagen fibrils show glassy behavior at room temperatures [4]. The results of [3] and [4] about the glassy behavior of polymers or proteins are useful for understanding the mechanism for a biological system to maintain in a non-equilibrium state, including the ancient seed [5], which can maintain in a non-equilibrium state for a very long time. (1) M.-C. Wu, M. S. Li, W.-J. Ma, M. Kouza, and C.-K. Hu, EPL, in press (2011); (2) C. Dasgupta, S.-K. Ma, and C.-K. Hu. Phys. Rev. B 20, 3837-3849 (1979); (3) W.-J. Ma and C.-K. Hu, J. Phys. Soc. Japan 79, 024005, 024006, 054001, and 104002 (2010), C.-K. Hu and W.-J. Ma, Prog. Theor. Phys. Supp. 184, 369 (2010); S. G. Gevorkian, A. E. Allahverdyan, D. S. Gevorgyan and C.-K. Hu, EPL 95, 23001 (2011); S. Sallon, et al. Science 320, 1464 (2008).

  1. Arabidopsis GLASSY HAIR genes promote trichome papillae development

    PubMed Central

    Kirik, Viktor

    2013-01-01

    Specialized plant cells form cell walls with distinct composition and properties pertinent to their function. Leaf trichomes in Arabidopsis form thick cell walls that support the upright growth of these large cells and, curiously, have strong light-reflective properties. To understand the process of trichome cell-wall maturation and the molecular origins of this optical property, mutants affected in trichome light reflection were isolated and characterized. It was found that GLASSY HAIR (GLH) genes are required for the formation of surface papillae structures at late stages of trichome development. Trichomes in these mutants appeared transparent due to unobstructed light transmission. Genetic analysis of the isolated mutants revealed seven different gene loci. Two—TRICHOME BIREFRINGENCE (TBR) and NOK (Noeck)—have been reported previously to have the glassy trichome mutant phenotype. The other five glh mutants were analysed for cell-wall-related phenotypes. A significant reduction was found in cellulose content in glh2 and glh4 mutant trichomes. In addition to the glassy trichome phenotype, the glh6 mutants showed defects in leaf cuticular wax, and glh6 was found to represent a new allele of the eceriferum 10 (cer10) mutation. Trichomes of the glh1 and glh3 mutants did not show any other phenotypes beside reduced papillae formation. These data suggest that the GLH1 and GLH3 genes may have specific functions in trichome papillae formation, whereas GLH2, GLH4, and GLH6 genes are also involved in deposition of other cell-wall components. PMID:24014871

  2. Evidence for a glassy state in strongly driven carbon

    NASA Astrophysics Data System (ADS)

    Brown, C. R. D.; Gericke, D. O.; Cammarata, M.; Cho, B. I.; Döppner, T.; Engelhorn, K.; Förster, E.; Fortmann, C.; Fritz, D.; Galtier, E.; Glenzer, S. H.; Harmand, M.; Heimann, P.; Kugland, N. L.; Lamb, D. Q.; Lee, H. J.; Lee, R. W.; Lemke, H.; Makita, M.; Moinard, A.; Murphy, C. D.; Nagler, B.; Neumayer, P.; Plagemann, K.-U.; Redmer, R.; Riley, D.; Rosmej, F. B.; Sperling, P.; Toleikis, S.; Vinko, S. M.; Vorberger, J.; White, S.; White, T. G.; Wünsch, K.; Zastrau, U.; Zhu, D.; Tschentscher, T.; Gregori, G.

    2014-06-01

    Here, we report results of an experiment creating a transient, highly correlated carbon state using a combination of optical and x-ray lasers. Scattered x-rays reveal a highly ordered state with an electrostatic energy significantly exceeding the thermal energy of the ions. Strong Coulomb forces are predicted to induce nucleation into a crystalline ion structure within a few picoseconds. However, we observe no evidence of such phase transition after several tens of picoseconds but strong indications for an over-correlated fluid state. The experiment suggests a much slower nucleation and points to an intermediate glassy state where the ions are frozen close to their original positions in the fluid.

  3. Evidence for a glassy state in strongly driven carbon.

    PubMed

    Brown, C R D; Gericke, D O; Cammarata, M; Cho, B I; Döppner, T; Engelhorn, K; Förster, E; Fortmann, C; Fritz, D; Galtier, E; Glenzer, S H; Harmand, M; Heimann, P; Kugland, N L; Lamb, D Q; Lee, H J; Lee, R W; Lemke, H; Makita, M; Moinard, A; Murphy, C D; Nagler, B; Neumayer, P; Plagemann, K-U; Redmer, R; Riley, D; Rosmej, F B; Sperling, P; Toleikis, S; Vinko, S M; Vorberger, J; White, S; White, T G; Wünsch, K; Zastrau, U; Zhu, D; Tschentscher, T; Gregori, G

    2014-06-09

    Here, we report results of an experiment creating a transient, highly correlated carbon state using a combination of optical and x-ray lasers. Scattered x-rays reveal a highly ordered state with an electrostatic energy significantly exceeding the thermal energy of the ions. Strong Coulomb forces are predicted to induce nucleation into a crystalline ion structure within a few picoseconds. However, we observe no evidence of such phase transition after several tens of picoseconds but strong indications for an over-correlated fluid state. The experiment suggests a much slower nucleation and points to an intermediate glassy state where the ions are frozen close to their original positions in the fluid.

  4. Nonequilibrium thermodynamics of the soft glassy rheology model

    NASA Astrophysics Data System (ADS)

    Fuereder, Ingo; Ilg, Patrick

    2013-10-01

    The soft glassy rheology (SGR) model is a mesoscopic framework which proved to be very successful in describing flow and deformation of various amorphous materials phenomenologically (e.g., pastes, slurries, foams, etc.). In this paper, we cast SGR in a general, model-independent framework for nonequilibrium thermodynamics called general equation for the nonequilibrium reversible-irreversible coupling. This leads to a formulation of SGR which clarifies how it can properly be coupled to hydrodynamic fields, resulting in a thermodynamically consistent, local, continuum version of SGR. Additionally, we find that compliance with thermodynamics imposes the existence of a modification to the stress tensor as predicted by SGR.

  5. Positronics of radiation-induced effects in chalcogenide glassy semiconductors

    SciTech Connect

    Shpotyuk, O.; Kozyukhin, S. A.; Shpotyuk, M.; Ingram, A.; Szatanik, R.

    2015-03-15

    Using As{sub 2}S{sub 3} and AsS{sub 2} glasses as an example, the principal possibility of using positron annihilation spectroscopy methods for studying the evolution of the free volume of hollow nanoobjects in chalcogenide glassy semiconductors exposed to radiation is shown. The results obtained by measurements of the positron annihilation lifetime and Doppler broadening of the annihilation line in reverse chronological order are in full agreement with the optical spectroscopy data in the region of the fundamental absorption edge, being adequately described within coordination defect-formation and physical-aging models.

  6. Microscale rheology of a soft glassy material close to yielding.

    PubMed

    Jop, Pierre; Mansard, Vincent; Chaudhuri, Pinaki; Bocquet, Lydéric; Colin, Annie

    2012-04-06

    Using confocal microscopy, we study the flow of a model soft glassy material: a concentrated emulsion. We demonstrate the micro-macro link between in situ measured movements of droplets during the flow and the macroscopic rheological response of a concentrated emulsion, in the form of scaling relationships connecting the rheological "fluidity" with local standard deviation of the strain-rate tensor. Furthermore, we measure correlations between these local fluctuations, thereby extracting a correlation length which increases while approaching the yielding transition, in accordance with recent theoretical predictions.

  7. Evidence for a glassy state in strongly driven carbon

    SciTech Connect

    Brown, C. R. D.; Gericke, D. O.; Cammarata, M.; Cho, B. I.; Gwangju Inst. of Science and Technology, Gwangju; Inst. for Basic Science, Gwangju ; Döppner, T.; Engelhorn, K.; Förster, E.; Fortmann, C.; Fritz, D.; Galtier, E.; Glenzer, S. H.; Harmand, M.; Heimann, P.; Kugland, N. L.; Lamb, D. Q.; Lee, H. J.; Lee, R. W.; Lemke, H.; Makita, M.; Moinard, A.; Murphy, C. D.; Nagler, B.; Neumayer, P.; Plagemann, K. -U.; Redmer, R.; Riley, D.; Rosmej, F. B.; Sperling, P.; Toleikis, S.; Vinko, S. M.; Vorberger, J.; White, S.; White, T. G.; Wünsch, K.; Zastrau, U.; Zhu, D.; Tschentscher, T.; Gregori, G.

    2014-06-09

    Here, we report results of an experiment creating a transient, highly correlated carbon state using a combination of optical and x-ray lasers. Scattered x-rays reveal a highly ordered state with an electrostatic energy significantly exceeding the thermal energy of the ions. Strong Coulomb forces are predicted to induce nucleation into a crystalline ion structure within a few picoseconds. However, we observe no evidence of such phase transition after several tens of picoseconds but strong indications for an over-correlated fluid state. The experiment suggests a much slower nucleation and points to an intermediate glassy state where the ions are frozen close to their original positions in the fluid.

  8. Isoindoline nitroxide-labeled porphyrins as potential fluorescence-suppressed spin probes.

    PubMed

    Liu, F; Zou, T J; Tan, Z L; Chen, S; Wu, Z H; Yan, G P; Zhang, Q; Liang, S C; Yang, J

    2017-02-07

    A series of isoindoline nitroxide-labeled porphyrins were synthesized by the reaction of 5-phenyldipyrromethane and 5-(4'-carboethoxy-methyleneoxyphenyl)dipyrromethane with 5-formyl-1,1,3,3-tetramethylisoindolin-2-yloxyl (FTMIO) using the Lindsey method. The corresponding water-soluble spin-labeled porphyrins were also prepared. Subsequently, these compounds were characterized and their in vitro properties were evaluated. The electrochemical assay demonstrated that these isoindoline nitroxide-labeled porphyrins had similar electrochemical and redox properties to 5-carboxy-1,1,3,3-tetramethylisoindolin-2-yloxyl (CTMIO). The electron paramagnetic resonance test showed that these porphyrins exhibited hyperfine splittings and characteristic spectra of CTMIO with typical nitroxide g-values and nitrogen isotropic hyperfine coupling constants. The in vitro cytotoxicity assay indicated that these porphyrins possessed low cytotoxicity to human renal tubular epithelial 293T cells (normal cells) and human hepatoma HepG2 cells (tumor cells). Fluorescence spectroscopy revealed that free base isoindoline nitroxide-labeled porphyrins exhibited fluorescence suppression characteristic of nitroxide-fluorophore systems. In vitro fluorescene imaging demonstrated that the reduced isoindoline nitroxide-labeled porphyrins eliminated fluorescence suppression and displayed strong red fluorescence imaging in HepG2 cells. Thus these isoindoline nitroxide-labeled porphyrins may be considered potentially as biological spin probes for fluorescence imaging and EPR spectroscopy.

  9. Liquid chromatography of urinary porphyrins for the biological monitoring of occupational exposure to porphyrinogenic substances

    SciTech Connect

    Colombi, A.; Maroni, M.; Ferioli, A.; Valla, C.; Coletti, G.; Foa, V.

    1983-01-01

    Very sensitive and precise analytical methods for measuring total porphyrin excretion and the relative amounts of different porphyrins in urine are required in order to monitor the biological effects of porphyrinogenic substances in workers and the general population. Many analytical steps of a HPLC method for measuring porphyrins as methyl esters in urine have been perfected. Sensitivity is 0.1 microgram/1 for each type of porphyrin, and average recovery is 92% in the range of 50-450 micrograms/liter porphyrins. The coefficient of variation is 3.4% within a series and 12.5% between series. Chemical oxidation before analysis and appropriate storing of the samples are the key points in achieving high quality results. The urinary excretion of porphyrins in healthy male workers varies within the range 21 to 161 micrograms/liter (95% limits of a group of 78 subjects). Concomitant factors, like drug use or liver disorders, were found to alter urinary porphyrin excretion. The proposed method permits the detection of extremely small alterations in porphyrin excretion resulting from occupational exposure to industrial chemicals such as, for example, mild coproporphyrinuria or early stages of chemical porphyria induced by polyhalogenated arylhydrocarbons.

  10. Cooperative self-assembly of porphyrins with polymers possessing bioactive functions.

    PubMed

    Zhao, Lizhi; Qu, Rui; Li, Ang; Ma, Rujiang; Shi, Linqi

    2016-11-15

    Natural porphyrin derivatives possess many interesting functions in biological systems. They are integrated into proteins that are essential for biological activities. Many efforts have been dedicated to mimic the microenvironment and augment the function of porphyrin/protein scaffolds. To achieve such goals, self-assembly has become one of the popular methods to construct porphyrin/protein-mimicking materials owing to its various choices of building blocks and a simple preparation process over chemical modification. Desirable characteristics of building blocks for protein mimicking include high molecular weight, predictable conformations in solution, and appropriate functional residuals. With these aims in mind, polymers are ideal candidates due to their multiple-level hierarchies derived from their chemical and spatial structures. In this review, design strategies for the cooperative self-assembly of porphyrins with polymers and the main efforts towards the implementation of porphyrin/polymer assembly for biomimetic composites with bioactive functions will be addressed.

  11. Absorption and fluorescence properties of aryl substituted porphyrins in different media

    NASA Astrophysics Data System (ADS)

    Bozkurt, Serap Seyhan; Merdivan, Melek; Ayata, Sevda

    2010-02-01

    Absorption and fluorescence properties of aryl substituted porphyrins, 5,10,15,20-tetra-4-oxy(aceticacid)phenylporphyrin (TAPP), 5,10,15,20-tetra-(4-phenoxyphenyl) porphyrin (TPPP), 5,10,15,20-tetra-(3-bromo-4-hydroxyphenyl) porphyrin (TBHPP), and 5,10,15,20-tetra-p-chloromethylphenyl porphyrin (CMPP) were investigated. The UV/vis absorption, fluorescence and excited spectra as the fluorescence quantum yields and fluorescence lifetimes for the compounds were measured in organic solvents (chloroform (CHCl 3), tetrahydrofuran (THF)) and immobilized media (PVC film, sol-gel matrix). The fluorescence quantum yields of TAPP and TPPP were higher than the others. The fluorescence lifetimes of all studied porphyrin derivates were found to be fifty percent lower and their fluorescence intensities were increased fifty percent more in both of immobilized mediums, as compared to organic solvents.

  12. The direct synthesis of organic-containing clays and thermal analysis of porphyrin-clay complexes

    SciTech Connect

    Carrado, K.A.; Anderson, K.B.; Grutkoski, P.S.

    1991-01-01

    Synthetic TMA-montmorillonites have now been made in conjunction with synthetic porphyrin-hectorites reported earlier. In order to help progress towards preparation of porphyrin-containing aluminosilicate clays, the thermal stability of porphyrin-clay systems has been examined in detail. Results from TGA and Py-GC-MS indicate that the porphyrin nucleus is extremely stable in the present of clay minerals. Substituents on the nucleus such as pyridinium or anilinium are, on the other hand, slightly destabilized. In addition, the presence of transition metals like Fe(III) in metalloporphyrins appears to catalyze decomposition of the porphyrin nucleus to some degree. The use of Py-GC-MS in conjunction with TGA results greatly clarified the assignment of weight loss peaks. 18 refs., 3 figs.

  13. Out-of-Plane Coordinated Porphyrin Nanotubes with Enhanced Singlet Oxygen Generation Efficiency

    PubMed Central

    Zhao, Qiang; Wang, Yao; Xu, Yanshuang; Yan, Yun; Huang, Jianbin

    2016-01-01

    A supramolecular porphyrin nanotube displaying J-aggregation feature was constructed by out-of-plane coordinated bismuth-porphyrin. Significantly, compared to traditional J-aggregated porphyrin suffering from fluorescence and singlet oxygen quenching, the nanotube exhibits excellent bio-imaging ability and enhanced production efficiency of singlet oxygen. The out-of-plane structure of bismuth to porphyrin makes the aggregation an appropriate material for theranostics. Furthermore, it is also a potential radio-therapeutic drug owing to the presence of radio-active bismuth. Thus, the self-assembly of out-of-plane coordinated porphyrin can be a facile approach toward effective therapy of tumors and other diseases. PMID:27527403

  14. Fusing porphyrins with polycyclic aromatic hydrocarbons and heterocycles for optoelectronic applications

    DOEpatents

    Thompson, Mark E.; Diev, Viacheslav; Hanson, Kenneth; Forrest, Stephen R.

    2015-08-18

    A compound that can be used as a donor material in organic photovoltaic devices comprising a non-activated porphyrin fused with one or more non-activated polycyclic aromatic rings or one or more non-activated heterocyclic rings can be obtained by a thermal fusion process. The compounds can include structures of Formula I: ##STR00001## By heating the reaction mixture of non-activated porphyrins with non-activated polycyclic aromatic rings or heterocyclic rings to a fusion temperature and holding for a predetermined time, fusion of one or more polycyclic rings or heterocyclic rings to the non-activated porphyrin core in meso,.beta. fashion is achieved resulting in hybrid structures containing a distorted porphyrin ring with annulated aromatic rings. The porphyrin core can be olygoporphyrins.

  15. Electrical studies on silver based fast ion conducting glassy materials

    SciTech Connect

    Rao, B. Appa Kumar, E. Ramesh Kumari, K. Rajani Bhikshamaiah, G.

    2014-04-24

    Among all the available fast ion conductors, silver based glasses exhibit high conductivity. Further, glasses containing silver iodide enhances fast ion conducting behavior at room temperature. Glasses of various compositions of silver based fast ion conductors in the AgI−Ag{sub 2}O−[(1−x)B{sub 2}O{sub 3}−xTeO{sub 2}] (x=0 to1 mol% in steps of 0.2) glassy system have been prepared by melt quenching method. The glassy nature of the compounds has been confirmed by X-ray diffraction. The electrical conductivity (AC) measurements have been carried out in the frequency range of 1 KHz–3MHz by Impedance Analyzer in the temperature range 303–423K. The DC conductivity measurements were also carried out in the temperature range 300–523K. From both AC and DC conductivity studies, it is found that the conductivity increases and activation energy decreases with increasing the concentration of TeO{sub 2} as well as with temperature. The conductivity of the present glass system is found to be of the order of 10{sup −2} S/cm at room temperature. The ionic transport number of these glasses is found to be 0.999 indicating that these glasses can be used as electrolyte in batteries.

  16. Evaluation of urinary porphyrin excretion in neonates born to mothers exposed to airborne hexachlorobenzene.

    PubMed Central

    Ozalla, Dolores; Herrero, Carmen; Ribas-Fitó, Núria; To-Figueras, Jordi; Toll, Agustí; Sala, Maria; Grimalt, Joan; Basagaña, Xavier; Lecha, Màrius; Sunyer, Jordi

    2002-01-01

    The existence of a link between hexachlorobenzene (HCB) and porphyria cutanea tarda has been known for a long time. However, the epidemiologic data on effects on health caused by prenatal exposure have not provided convincing evidence that HCB alters porphyrin metabolism. Our objectives were to analyze urinary porphyrin excretion and HCB in maternal serum and fetal cord blood in neonates born in a village (Flix) near a chlorinated solvent factory, to detect possible adverse effects in urinary porphyrin excretion caused by prenatal exposure, and to assess their relationship with HCB blood levels. We conducted a cross-sectional study in the Porphyria Unit at a tertiary care facility in Barcelona, Spain, and the Pediatric Unit of the Móra d'Ebre Hospital, the reference hospital of the study area. We included in the study all neonates (n = 68) born in Móra d'Ebre Hospital 1997-1999 and their mothers. We obtained 68 urine specimens of singleton neonates on the third day after birth to test for urinary porphyrin excretion. We obtained 52 fetal cord blood and 56 maternal serum samples for HCB analysis. Total urinary porphyrins were quantified using spectrofluorometry. Porphyrin profile was determined by HPLC. Serum HCB was analyzed by gas chromatography coupled with electron capture detection. In total population, median HCB levels were 1.08 ng/mL in cord blood and 3.31 ng/mL in maternal serum. Total urinary porphyrin concentration was 37.87 micromol/mol creatinine. Coproporphyrin I and coproporphyrin III were the major porphyrins excreted. We found no positive relationship between urinary porphyrin excretion and HCB levels. However, we observed an association between maternal smoking and coproporphyrin excretion. Although high environmental levels of HCB are reported in the town of Flix, we found no alteration in urinary porphyrin excretion. PMID:11836151

  17. Glaser-mediated synthesis and photophysical characterization of diphenylbutadiyne-linked porphyrin dyads.

    PubMed

    Youngblood, W Justin; Gryko, Daniel T; Lammi, Robin K; Bocian, David F; Holten, Dewey; Lindsey, Jonathan S

    2002-04-05

    The Pd-mediated Glaser coupling of a zinc monoethynyl porphyrin and a magnesium monoethynyl porphyrin affords a mixture of three 4,4'-diphenylbutadiyne-linked dyads comprised of two zinc porphyrins (Zn-pbp-Zn), two magnesium porphyrins (Mg-pbp-Mg), and one metalloporphyrin of each type (Zn-pbp-Mg). The latter is easily isolated due to the greater polarity of the magnesium versus the zinc chelate. Exposure of Zn-pbp-Mg to silica gel results in selective demetalation, affording Zn-pbp-Fb where Fb = free base porphyrin. This synthesis route employs the magnesium porphyrin as a latent form of the Fb porphyrin, thereby avoiding copper insertion during the Glaser reaction, and as a polar entity facilitating separation. The absorption spectrum of Zn-pbp-Mg or Zn-pbp-Fb is the sum of the spectra of the component parts, while in each case the fluorescence spectrum upon illumination of the Zn porphyrin is dominated by emission from the Mg or Fb porphyrin. Time-resolved absorption spectroscopy shows that the energy-transfer rate constants are (11 ps)(-1) and (37 ps)(-1) for Zn-pbp-Mg and Zn-pbp-Fb, respectively, corresponding to energy-transfer quantum yields of 0.995 and 0.983, respectively. The calculated Förster through-space rates are (1900 ps)(-1) and (1100 ps)(-1) for Zn-pbp-Mg and Zn-pbp-Fb, respectively. Accordingly, the through-bond process dominates for both dyads with a through-bond:through-space energy-transfer ratio of > or =97:1. Collectively, the studies show that the 4,4'-diphenylbutadiynyl linker supports fast and efficient energy transfer between Zn and Mg or Fb porphyrins.

  18. Effects of glassy-winged sharpshooter feeding, size, and lipid content on egg maturation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The glassy-winged sharpshooter (Homalodisca vitripennis) is synovigenic and must feed during the adult stage to produce eggs. While glassy-winged sharpshooter egg production is related to adult feeding, rates of egg production are variable. In this study, effects of lipid allocation to eggs and fema...

  19. Evaluation of grapevine as a host for the glassy-winged sharpshooter

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Grapevine was evaluated as a feeding and oviposition host for the glassy-winged sharpshooter. Two sets of experiments were conducted. The first set compared performance and preference of glassy-winged sharpshooter females for grapevine (cv. Chardonnay) versus cowpea (Vigna unguiculata cultivar black...

  20. Silicon-tin oxynitride glassy composition and use as anode for lithium-ion battery

    DOEpatents

    Neudecker, Bernd J.; Bates, John B.

    2001-01-01

    Disclosed are silicon-tin oxynitride glassy compositions which are especially useful in the construction of anode material for thin-film electrochemical devices including rechargeable lithium-ion batteries, electrochromic mirrors, electrochromic windows, and actuators. Additional applications of silicon-tin oxynitride glassy compositions include optical fibers and optical waveguides.

  1. Aggregates of a cationic porphyrin as supramolecular probes for biopolymers.

    PubMed

    Occhiuto, Ilaria Giuseppina; Samperi, Mario; Trapani, Mariachiara; De Luca, Giovanna; Romeo, Andrea; Pasternack, Robert F; Scolaro, Luigi Monsù

    2015-12-01

    The copper(II) derivative of the dicationic trans-bis(N-methylpyridinium-4-yl)diphenylporphyrin (t-CuPagg) forms large fractal aggregates in aqueous solution under moderate ionic strength conditions. A kinetic investigation of the aggregation process allows for a choice of experimental conditions to quickly obtain stable assemblies in solution. These positively charged aggregates are able to interact efficiently with negatively charged chiral species, (including bacterial spores) leading to induced circular dichroism signals in the Soret region of the porphyrin, now acting as a sensitive chiroptical probe.

  2. Manganese Porphyrins Catalyze Selective C-H Bond Halogenations

    SciTech Connect

    Liu, Wei; Groves, John T.

    2010-08-31

    We report a manganese porphyrin mediated aliphatic C-H bond chlorination using sodium hypochlorite as the chlorine source. In the presence of catalytic amounts of phase transfer catalyst and manganese porphyrin Mn(TPP)Cl 1, reaction of sodium hypochlorite with different unactivated alkanes afforded alkyl chlorides as the major products with only trace amounts of oxygenation products. Substrates with strong C-H bonds, such as neopentane (BDE =~100 kcal/mol) can be also chlorinated with moderate yield. Chlorination of a diagnostic substrate, norcarane, afforded rearranged products indicating a long-lived carbon radical intermediate. Moreover, regioselective chlorination was achieved by using a hindered catalyst, Mn(TMP)Cl, 2. Chlorination of trans-decalin with 2 provided 95% selectivity for methylene-chlorinated products as well as a preference for the C2 position. This novel chlorination system was also applied to complex substrates. With 5α-cholestane as the substrate, we observed chlorination only at the C2 and C3 positions in a net 55% yield, corresponding to the least sterically hindered methylene positions in the A-ring. Similarly, chlorination of sclareolide afforded the equatorial C2 chloride in a 42% isolated yield. Regarding the mechanism, reaction of sodium hypochlorite with the MnIII porphyrin is expected to afford a reactive MnV=O complex that abstracts a hydrogen atom from the substrate, resulting in a free alkyl radical and a MnIV—OH complex. We suggest that this carbon radical then reacts with a MnIV—OCl species, providing the alkyl chloride and regenerating the reactive MnV=O complex. The regioselectivity and the preference for CH2 groups can be attributed to nonbonded interactions between the alkyl groups on the substrates and the aryl groups of the manganese porphyrin. The results are indicative of a bent [Mnv=O---H---C] geometry due to the C—H approach to the Mn

  3. Porphyrins and their synthesis from dipyrromethanes and aldehydes

    DOEpatents

    Wijesekera, Tilak; Lyons, James E.; Ellis, Jr., Paul E.

    1998-01-01

    The invention comprises new compositions of matter, which are iron, manganese, cobalt or ruthenium complexes of porphyrins having hydrogen, haloalkyl or haloaryl groups in meso positions, two of the opposed meso atoms or groups being hydrogen or haloaryl, and two of the opposed meso atoms or groups being hydrogen or haloalkyl, but not all four of the meso atoms or groups being hydrogen. The invention also comprises new compositions of matter in which all four of the meso positions are substituted with haloalkyl groups and the beta positions are substituted with halogen atoms. A new method of synthesizing porphyrinogens is also provided.

  4. Porphyrins and their synthesis from dipyrromethanes and aldehydes

    DOEpatents

    Wijesekera, T.; Lyons, J.E.; Ellis, P.E. Jr.

    1998-06-02

    The invention comprises new compositions of matter, which are iron, manganese, cobalt or ruthenium complexes of porphyrins having hydrogen, haloalkyl or haloaryl groups in meso positions, two of the opposed meso atoms or groups being hydrogen or haloaryl, and two of the opposed meso atoms or groups being hydrogen or haloalkyl, but not all four of the meso atoms or groups being hydrogen. The invention also comprises new compositions of matter in which all four of the meso positions are substituted with haloalkyl groups and the beta positions are substituted with halogen atoms. A new method of synthesizing porphyrinogens is also provided.

  5. Self-assembly of a chiral porphyrin at surfaces

    NASA Astrophysics Data System (ADS)

    Iavicoli, Patrizia; Linares, Mathieu; Pérez del Pino, Ángel; Lazzaroni, Roberto; Amabilino, David B.

    2008-10-01

    Evaporation of solutions of a new synthetic tetra meso-amidophenyl-substituted porphyrin derivative on graphite leads to different morphologies at the air-solid interface, whose nature depends on the solvent in which the molecule was dissolved. Fibres-which were shown to be a stable aggregate form of the compound by molecular modelling-are observed by AFM, although they do not seem to have the structure which was predicted. The reason for this situation appears to be the dominance of surface-molecule interactions over those between the molecules themselves. On mica surfaces, dewetting takes place, leading to relatively well-defined monolayer and bilayer domains.

  6. Inverted meso-aryl porphyrins with heteroatoms; characterization of thia, selena, and oxa N-confused porphyrins.

    PubMed

    Pushpan, S K; Srinivasan, A; Anand, V R; Chandrashekar, T K; Subramanian, A; Roy, R; Sugiura, K; Sakata, Y

    2001-01-12

    Synthesis and characterization of inverted porphyrins containing S, Se, and O are reported. A simple 3 + 1 MacDonald-type condensation using modified tripyrrane containing the N-confused ring and diols afforded various N-confused porphyrins 6a-f in 19-30% yield. The single-crystal X-ray structure of 6b shows a ruffled conformation with tilt angles of 21.11 degrees and 31.23 degrees for the N-confused ring and the adjacent pyrrole ring III, respectively, revealing its severe nonplanarity. Significant changes in C alpha-C beta, C beta-C beta, and C alpha-X bond lengths are observed in 6b relative to free thiophene and pyrrole, suggesting the altered delocalization pathway in the modified N-confused porphyrins. The two molecules in the unit cell show a cyclophane-type noncovalent dimer with a face to face orientation of two N-confused pyrrole rings as a result of the presence of weak N-H...N and C-H...N intermolecular hydrogen bonds involving pyrrole-NH, the N atom of the N-confused ring, and the C atom of the pyrrole ring. A detailed 1H and 13C NMR study by 1D and 2D methods allowed assignments of all the peaks in the free base and protonated forms. NMR studies reveal the presence of three different tautomeric forms in solution for 6c in CDCl3 at low temperature. UV-visible studies reveal absorption band shifts upon heteroatom substitution, and the magnitudes of these shifts are dependent on the nature of the heteroatom. In all cases both monoprotonated and diprotonated species have been identified, and on addition of acid, the first proton goes to the outer N2 atom of the N-confused ring.

  7. Porphyrins as excellent dyes for dye-sensitized solar cells: recent developments and insights.

    PubMed

    Higashino, Tomohiro; Imahori, Hiroshi

    2015-01-14

    Dye-sensitized solar cells (DSSCs) have attracted much attention as an alternative to silicon-based solar cells because of their low-cost production and high power conversion efficiency. Among various sensitizers, numerous research activities have been focused on porphyrins due to their strong absorption bands in the visible region, versatile modifications of their core, and facile tuning of the electronic structures. In 2005-2007, Officer and Grätzel et al. had achieved a rapid increase in the power conversion efficiency of porphyrin DSSCs from a few percent to as much as 7%. Encouraged by these pioneering works, further high-performance porphyrin dyes have been developed in the last decade. These studies have provided us profound hints for the rational design of sensitizers toward highly efficient DSSCs. Push-pull structures and/or π-extensions have made porphyrins panchromatic in visible and even near-infrared regions. Consequently, porphyrin sensitizers have exhibited power conversion efficiencies that are comparable to or even higher than those of well-established highly efficient DSSCs based on ruthenium complexes. So far the power conversion efficiency has increased up to ca. 13% by using a push-pull porphyrin with a cobalt-based redox shuttle. In this perspective, we review the recent developments in the synthetic design of porphyrins for highly efficient DSSCs.

  8. Tissue distribution and kinetics of endogenous porphyrins synthesized after topical application of ALA in different vehicles

    PubMed Central

    Casas, A; Fukuda, H; Batlle, A M del C

    1999-01-01

    The use of 5-aminolaevulinic acid (ALA) is gaining increasing attention for photosensitization in photodynamic therapy of superficially localized tumours. The aim of this work was to determine the kinetics of porphyrin generation in tissues after topical application of ALA delivered in different vehicles on the skin overlying the tumour and normal skin of mice. Maximal accumulation was found in tumour 3 h after ALA application in both cream and lotion preparations. Normal and overlying tumour skin tissues showed different kinetic patterns, reflecting histological changes when the latter is invaded by tumour cells. Liver, kidney, spleen and blood porphyrins also raised from basal levels, showing that ALA and/or ALA-induced porphyrins reach all tissues after topical application. During the first 24 h of ALA topical application, precursors and porphyrins are excreted by both urine and faeces. ALA lotion applied on the skin overlying the tumour induced higher accumulation of tumoural porphyrins than cream, and lotion applied on normal skin appeared to be the most efficient upon inducing total body porphyrins. This work has demonstrated the great influence of the formulation of ALA vehicle on penetration through the skin. Knowledge of the kinetics of porphyrin generation after different conditions of ALA application is needed for the optimization of diagnosis and phototherapy in human tumours. © 1999 Cancer Research Campaign PMID:10487606

  9. Supramolecular ssDNA templated porphyrin and metalloporphyrin nanoassemblies with tunable helicity.

    PubMed

    Sargsyan, Gevorg; Leonard, Brian M; Kubelka, Jan; Balaz, Milan

    2014-02-10

    Free-base and nickel porphyrin-diaminopurine conjugates were formed by hydrogen-bond directed assembly on single-stranded oligothymidine templates of different lengths into helical multiporphyrin nanoassemblies with highly modular structural and chiroptical properties. Large red-shifts of the Soret band in the UV/Vis spectroscopy confirmed strong electronic coupling among assembled porphyrin-diaminopurine units. Slow annealing rates yielded preferentially right-handed nanostructures, whereas fast annealing yielded left-handed nanostructures. Time-dependent DFT simulations of UV/Vis and CD spectra for model porphyrin clusters templated on the canonical B-DNA and its enantiomeric form, were employed to confirm the origin of observed chiroptical properties and to assign the helicity of porphyrin nanoassemblies. Molar CD and CD anisotropy g factors of dialyzed templated porphyrin nanoassemblies showed very high chiroptical anisotropy. The DNA-templated porphyrin nanoassemblies displayed high thermal and pH stability. The structure and handedness of all assemblies was preserved at temperatures up to +85 °C and pH between 3 and 12. High-resolution transition electron microscopy confirmed formation of DNA-templated nickel(II) porphyrin nanoassemblies and their self-assembly into helical fibrils with micrometer lengths.

  10. The effect on photohaemolysis of variation in the structure of the porphyrin photosensitizer.

    PubMed Central

    de Paolis, A; Chandra, S; Charalambides, A A; Bonnett, R; Magnus, I A

    1985-01-01

    A comparison of the photosensitizing ability of a variety of porphyrins for photohaemolysis gives the following order of activity: protoporphyrin greater than deuteroporphyrin, mesoporphyrin, haematoporphyrin dimethyl ester much greater than haematoporphyrin diacetate, haematoporphyrin greater than haematoporphyrin monoacetate, coproporphyrin III, haematoporphyrin derivative, coproporphyrin III tetramethyl ester greater than uroporphyrin I, meso-tetra-(N-methyl-4-pyridinium)porphyrin tetratoluene-p-sulphonate, meso-tetra-(p-carboxyphenyl)porphyrin, protoporphyrin dimethyl ester, meso-tetra-(p-hydroxy-sulphonylphenyl)porphyrin tetrasodium salt, uroporphyrin III, deuteroporphyrin-3,8-disulphonic acid and protohaemin. The results for the metal-free porphyrins are rationalized in terms of solubility and partition properties, and a model is proposed for the incorporation of amphipathic porphyrins into the membrane lipid bilayer. Experiments with erythrocytes from patients with erythropoeitic protoporphyria and with normal erythrocytes to which porphyrin was added in a deuterium oxide medium do not lead to an increase in the rate of photohaemolysis. A possible explanation for this somewhat surprising observation is outlined. PMID:2985045

  11. Photochemical generation and kinetic studies of a putative porphyrin-ruthenium(V)-oxo species.

    PubMed

    Zhang, Rui; Vanover, Eric; Luo, Weilong; Newcomb, Martin

    2014-06-21

    Photo-disproportionation of a bis-porphyrin-diruthenium(IV) μ-oxo dimer gave a porphyrin-ruthenium(III) species and a putative porphyrin-ruthenium(V)-oxo species that can be detected and studied in real time via laser flash photolysis methods. As determined by its spectral and kinetic behavior, the same oxo transient was also formed by photolysis of a porphyrin-ruthenium(III) N-oxide adduct. Second-order rate constants for reactions with several substrates at 22 °C were determined; representative values of rate constants were kox = 6.6 × 10(3) M(-1) s(-1) for diphenylmethanol, kox = 2.5 × 10(3) M(-1) s(-1) for styrene, and kox = 1.8 × 10(3) M(-1) s(-1) for cyclohexene. The putative porphyrin-ruthenium(V)-oxo transient reacted 5-6 orders of magnitude faster than the corresponding trans-dioxoruthenium(VI) porphyrins, and the rate constants obtained in this work were similar to those of the corrole-iron(V)-oxo derivative. The high reactivity for the photochemically generated ruthenium-oxo species in comparison to other porphyrin-metal-oxo intermediates suggests that it is a true ruthenium(V)-oxo species.

  12. Novel porphyrin-preparation, characterization, and applications in solar energy conversion.

    PubMed

    Lu, Jianfeng; Li, Hao; Liu, Shuangshuang; Chang, Yu-Cheng; Wu, Hui-Ping; Cheng, Yibing; Wei-Guang Diau, Eric; Wang, Mingkui

    2016-03-07

    Porphyrins have been demonstrated as one of the most efficient sensitizers in dye-sensitized solar cells (DSSC). Herein, we investigated a series of porphyrin sensitizers functionalized with various π-spacers, such as phenyl for LD14, thiophene for LW4, thiophene-phenyl for LW5, and 2,1,3-benzothiadiazole (BTD)-phenyl for LW24. Photo-physical investigation by means of time-resolved fluorescence and nanosecond transient absorption spectroscopy revealed an accelerated inner charge transfer in porphyrins containing the BTD-phenyl π-spacer. Implementation of an auxiliary electron-deficient BTD unit to the porphyrin spacer also results in a broad light-harvesting ability extending up to 840 nm, contributing to an enhanced charge transfer character from the porphyrin ring to the anchoring group. When utilized as a sensitizer in DSSCs, the LW24 device achieved a power conversion efficiency of 9.2%, higher than those based on LD14 or LW5 porphyrins (PCE 9.0% or 8.2%, respectively) but lower than that of the LW4 device (PCE 9.5%). Measurements of transient photovoltage decays demonstrate that the LW24 device features the up-shifted potential band edge of the conduction band of TiO2, but involves serious charge recombination in the dye/TiO2 interface. The findings provide insights into the molecular structure and the charge-transfer characteristics for designing efficient porphyrin sensitizers for DSSC applications.

  13. Diketopyrrolopyrrole-porphyrin conjugates as broadly absorbing sensitizers for dye-sensitized solar cells.

    PubMed

    Warnan, Julien; Favereau, Ludovic; Meslin, Frédéric; Severac, Marjorie; Blart, Errol; Pellegrin, Yann; Jacquemin, Denis; Odobel, Fabrice

    2012-08-01

    A series of four new push-pull zinc porphyrin-based dyes was synthesised for hybrid photovoltaic solar cells with a view to enhancing the light-harvesting efficiency at approximately 550 nm with a diketopyrrolopyrrole (DPP) unit. The strength of the donor side of the push-pull porphyrin was tuned by affixing the electron-rich 4,4'-dimethoxydiphenylamine group at the meso position of the macrocycle, and the influence of the distance between the semiconductor surface and the porphyrin chromophore was assessed by introducing different π-conjugated spacers. Charge-transfer transitions over great distances were characterised by electronic absorption spectroscopy and DFT calculations. The absorption and photoactivity spectra of the new bichromophoric dyes spans the whole visible spectrum to the red, implying a better light-harvesting efficiency than regular porphyrin as the absorption spectra of DPP and porphyrin complement one another. Photovoltaic conversion efficiencies accordingly increase from 2.40 to 5.19 %. Interestingly, the best overall efficiency was reached with dye 3, which lacks the powerful donating group in the meso position of the porphyrin core. Optical and electrochemical measurements coupled to time dependent (TD)-DFT calculations give insight into the deleterious effect of the 4,4'-dimethoxydiphenylamine unit on the photovoltaic performances, paving the way towards the design of efficient push-pull porphyrin-based sensitizers.

  14. Evidence for a glassy state in strongly driven carbon

    DOE PAGES

    Brown, C. R. D.; Gericke, D. O.; Cammarata, M.; ...

    2014-06-09

    Here, we report results of an experiment creating a transient, highly correlated carbon state using a combination of optical and x-ray lasers. Scattered x-rays reveal a highly ordered state with an electrostatic energy significantly exceeding the thermal energy of the ions. Strong Coulomb forces are predicted to induce nucleation into a crystalline ion structure within a few picoseconds. However, we observe no evidence of such phase transition after several tens of picoseconds but strong indications for an over-correlated fluid state. The experiment suggests a much slower nucleation and points to an intermediate glassy state where the ions are frozen closemore » to their original positions in the fluid.« less

  15. Glassy dynamics of nanoparticles in semiflexible ring polymer nanocomposite melts

    PubMed Central

    Zhou, Xiaolin; Jiang, Yangwei; Deng, Zhenyu; Zhang, Linxi

    2017-01-01

    By employing molecular dynamics simulations, we explore the dynamics of NPs in semiflexible ring polymer nanocomposite melts. A novel glass transition is observed for NPs in semiflexible ring polymer melts as the bending energy (Kb) of ring polymers increases. For NPs in flexible ring polymer melts (Kb = 0), NPs move in the classic diffusive behavior. However, for NPs in semiflexible ring polymer melts with large bending energy, NPs diffuse very slowly and exhibit the glassy state in which the NPs are all irreversibly caged be the neighbouring semiflexible ring polymers. This glass transition occurs well above the classical glass transition temperature at which microscopic mobility is lost, and the topological interactions of semiflexible ring polymers play an important role in this non-classical glass transition. This investigation can help us understand the nature of the glass transition in polymer systems. PMID:28290546

  16. Glassy dynamics of nanoparticles in semiflexible ring polymer nanocomposite melts

    NASA Astrophysics Data System (ADS)

    Zhou, Xiaolin; Jiang, Yangwei; Deng, Zhenyu; Zhang, Linxi

    2017-03-01

    By employing molecular dynamics simulations, we explore the dynamics of NPs in semiflexible ring polymer nanocomposite melts. A novel glass transition is observed for NPs in semiflexible ring polymer melts as the bending energy (Kb) of ring polymers increases. For NPs in flexible ring polymer melts (Kb = 0), NPs move in the classic diffusive behavior. However, for NPs in semiflexible ring polymer melts with large bending energy, NPs diffuse very slowly and exhibit the glassy state in which the NPs are all irreversibly caged be the neighbouring semiflexible ring polymers. This glass transition occurs well above the classical glass transition temperature at which microscopic mobility is lost, and the topological interactions of semiflexible ring polymers play an important role in this non-classical glass transition. This investigation can help us understand the nature of the glass transition in polymer systems.

  17. Surface treatment of Glassy Polymeric Carbon artifacts for medical applications

    SciTech Connect

    Rodrigues, M. G.; Zimmerman, R. L.; Rezende, M. C.

    1999-06-10

    Glassy Polymeric Carbon (GPC) has been used for mechanical cardiac valves. GCP valves are chemically biocompatible and durable, but less thromboresistant than biological valves. Enhanced thromboresistance of mechanical cardiac components with porous surface has been demonstrated. The endothelialized tissue blood-contacting surface adheres to the porous prosthetic component and decreases the formation of thrombus. Our experience has shown that the porosity of GPC can be increased and controlled by MeV ion bombardment. We report here that the surface roughness of heat-treated GPC bombarded with C, O, Si and Au is also enhanced. The surface roughness of the ion-bombarded samples is on a smaller scale than those roughened by sand blasting (measurements made with Perthomete S and P). The roughness decreases slightly after heat treatment, in linear proportion to the shrinkage of the test piece. Possible beneficial effects of the imbedded ions on tissue adherence and thromboresistance must be determined by in vivo animal experiments.

  18. Evidence for a glassy state in strongly driven carbon

    PubMed Central

    Brown, C. R. D.; Gericke, D. O.; Cammarata, M.; Cho, B. I.; Döppner, T.; Engelhorn, K.; Förster, E.; Fortmann, C.; Fritz, D.; Galtier, E.; Glenzer, S. H.; Harmand, M.; Heimann, P.; Kugland, N. L.; Lamb, D. Q.; Lee, H. J.; Lee, R. W.; Lemke, H.; Makita, M.; Moinard, A.; Murphy, C. D.; Nagler, B.; Neumayer, P.; Plagemann, K.-U.; Redmer, R.; Riley, D.; Rosmej, F. B.; Sperling, P.; Toleikis, S.; Vinko, S. M.; Vorberger, J.; White, S.; White, T. G.; Wünsch, K.; Zastrau, U.; Zhu, D.; Tschentscher, T.; Gregori, G.

    2014-01-01

    Here, we report results of an experiment creating a transient, highly correlated carbon state using a combination of optical and x-ray lasers. Scattered x-rays reveal a highly ordered state with an electrostatic energy significantly exceeding the thermal energy of the ions. Strong Coulomb forces are predicted to induce nucleation into a crystalline ion structure within a few picoseconds. However, we observe no evidence of such phase transition after several tens of picoseconds but strong indications for an over-correlated fluid state. The experiment suggests a much slower nucleation and points to an intermediate glassy state where the ions are frozen close to their original positions in the fluid. PMID:24909903

  19. Determination of Fracture Patterns in Glass and Glassy Polymers.

    PubMed

    Baca, Allison C; Thornton, John I; Tulleners, Frederic A

    2016-01-01

    The study of fractures of glass, glassy-type materials, and plastic has long been of interest to the forensic community. The focus of this interest has been the use of glass and polymer fractures to associate items of evidence under the assumption that each fracture is different. Generally, it is well-accepted that deviations exist; however, the emphasis has been on classifying and predicting fracture rather than determining that each fracture is different. This study documented the controlled fracture patterns of 60 glass panes, 60 glass bottles, and 60 plastic tail light lens covers using both dynamic impact and static pressure methods under closely controlled conditions. Each pattern was intercompared, and based on the limited specimens tested in this study, the results illustrate that the fracture patterns are different. Further repetitive studies, under controlled conditions, will be needed to provide more statistical significance to the theory that each fracture forms a nonreproducible fracture pattern.

  20. Poly(4-vinylpyridine)-coated glassy carbon flow detectors

    SciTech Connect

    Wang, J.; Golden, T.; Tuzhi, P.

    1987-03-01

    The performance of a thin-layer flow detector with a glassy carbon electrode coated with a film of protonated poly(4-vinylpyridine) is described. Substantial improvement in the selectivity of amperometric detection for liquid chromatography and flow injection systems is observed as a result of excluding cationic species from the surface. The detector response was evaluated with respect to flow rate, solute concentration, coating scheme, film-to-film reproducibility, and other variables. Despite the increase in diffusional resistance, low detection limits of ca. 0.04 and 0.10 ng of ascorbic acid and uric acid, respectively, are maintained. Protection from organic surfactants can be coupled to the charge exclusion effect by using a bilayer coating, with a cellulose acetate film atop the poly(4-vinylpyridine) layer. Applicability to urine sample is demonstrated.

  1. Development of an Automatic Fabrication System for Cast Glassy Alloys

    NASA Astrophysics Data System (ADS)

    Yokoyama, Yoshihiko

    2015-04-01

    The developed automatic fabrication system comprised three component functions: weighing, alloying, and casting. The measurement error of automatic weighing specimen was about less 1 pct for Zr-based master alloys (approximately 30 g). Especially, sufficient stirrer effect of arc-melting ingot for homogeneity can be achieved by the development of sinusoidal arcing and applying magnetic field. In order to achieve superior homogeneity of the glass structure with no secondary phase ( i.e., an intermetallic compound with a high melting temperature), a prealloying process should be advisable. In this study, high reliability of the density and mechanical properties of automatic processed cast glassy alloys (CGAs) was successfully obtained. The developed automatic fabrication process has a potential to accelerate the industrial application of CGAs in the near future.

  2. Porphyrin Based neuton capture agents for cancer therapy

    DOEpatents

    Vicente, Maria Da; Shetty, Shankar Jayaram; Jaquinod, Laurent; Smith, Kevin M.

    2006-06-27

    The invention describes the synthesis of a panel of novel carbon-carbon linked carboranyl-containing 5,10,15,20-tetraphenylporphyrins bearing 25–44% boron by weight. In certain embodiments, a phenyl porphyrin compound has a carboranyl group attached to the phenyl group by a carbon-carbon linkage, wherein the phenyl group corresponds to the following formula embedded image
    where R7 through R11 are hydrogen, a carboranyl group, or are selected from the group consisting of hydroxyl, NMe3+, PMePh2+, PO(OH)2, SO3H, COOH, and NH2. In this embodiment, the carboranyl group is attached to the phenyl group by a carbon-carbon linkage, either one or two of R7 through R11 are other than hydrogen; and the phenyl porphyrin compound contains at least one phenyl group having at least one of said carboranyl groups.

  3. Magnetic and electronic properties of porphyrin-based molecular nanowires

    SciTech Connect

    Zheng, Jia-Jia; Li, Qiao-Zhi; Dang, Jing-Shuang; Zhao, Xiang; Wang, Wei-Wei

    2016-01-15

    Using spin-polarized density functional theory calculations, we performed theoretical investigations on the electronic and magnetic properties of transition metal embedded porphyrin-based nanowires (TM-PNWs, TM = Cr, Mn, Co, Ni, Cu, and Zn). Our results indicate that Ni-PNW and Zn-PNW are nonmagnetic while the rest species are magnetic, and the magnetic moments in TM-PNWs and their corresponding isolated monomer structures are found to be the same. In addition, the spin coupling in the magnetic nanowires can be ignored leading to their degenerate AFM and FM states. These results can be ascribed to the weak intermetallic interactions because of the relatively large distances between neighbor TM atoms. Among all TM-PNW structures considered here, only Mn-PNW shows a half-metallic property while the others are predicted to be semiconducting. The present work paves a new way of obtaining ferromagnetic porphyrin-based nanowires with TM atoms distributed separately and orderly, which are expected to be good candidates for catalysts, energy storage and molecular spintronics.

  4. Surface-confined Ullmann coupling of thiophene substituted porphyrins

    NASA Astrophysics Data System (ADS)

    Beggan, J. P.; Boyle, N. M.; Pryce, M. T.; Cafolla, A. A.

    2015-09-01

    The covalent coupling of (5,10,15,20-tetrabromothien-2-ylporphyrinato)zinc(II) (TBrThP) molecules on the Ag(111) surface has been investigated under ultra-high-vacuum conditions, using scanning tunnelling microscopy and x-ray photoelectron spectroscopy. The findings provide atomic-level insight into surface-confined Ullmann coupling of thiophene substituted porphyrins, analyzing the progression of organometallic intermediate to final coupled state. Adsorption of the TBrThP molecules on the Ag(111) surface at room temperature is found to result in the reductive dehalogenation of the bromothienyl substituents and the subsequent formation of single strand and crosslinked coordination networks. The coordinated substrate atoms bridge the proximal thienyl groups of the organometallic intermediate, while the cleaved bromine atoms are bound on the adjacent Ag(111) surface. The intermediate complex displays a thermal lability at ˜423 K that results in the dissociation of the proximal thienyl groups with the concomitant loss of the surface bound bromine. At the thermally induced dissociation of the intermediate complex the resultant thienylporphyrin derivatives covalently couple, leading to the formation of a polymeric network of thiophene linked and meso-meso fused porphyrins.

  5. Tin-porphyrin-assisted formation of coordination frameworks

    NASA Astrophysics Data System (ADS)

    Titi, Hatem M.

    2016-09-01

    Novel 3D networks synthesized by two different methods are reported in this article. Structure 1 {[CdL2]·(solvent)}n consists of CdII-single metallic nodes held together by coordinated isonicotinate ligands (L) to form a 3D chiral framework (P41212). The resulting structure exhibits threefold-interpenetrated dia coordination networks. After a few weeks the crystals were re-measured to form 1a {[Cd(L)2(H2O)]·DMF}n with two interpenetrated dia nets which is thermodynamically more stable. On the other hand, the addition of the tin(IV)-porphyrin to the same reaction mixture led to the formation of 3D pseudo-isostructures, based on oxo-centered CdII and MnII/III cluster nodes, 2 {[Cd3(OH)L4(H2O)3](ClO4)}n and 3 {[Mn3(O)L4(DMF)3](ClO4)}n. These structures represent topologically bcg nets. Possible synthetic mechanism was proposed to emphasize the role of the tin(IV)-porphyrin that led to the construction of oxo-centered trinuclear clusters in 2 and 3.

  6. Porphyrin-laser photodynamic induction of focal brain necrosis

    SciTech Connect

    Stroop, W.G.; Battles, E.J.; Townsend, J.J.; Schaefer, D.C.; Baringer, J.R.; Straight, R.C. )

    1989-09-01

    A noninvasive photodynamic method has been developed to produce focal brain necrosis using porphyrin activated in vivo with laser light. After peripheral injection of the photosensitive porphyrin derivative, Photofrin I, mice were irradiated on the posterior lateral aspect of the head through the intact depilated scalp with 632 nm argon-dye laser light. Animals were studied at one, two and seven days after irradiation. Blood-brain barrier damage was detected by the intravenous injection of Evans blue, horseradish peroxidase and heterologous immunoglobulins. At one and two days after irradiation, the lesions were characterized by extravasation of immunoglobulin and Evans blue, and by edema, ischemia and infiltration by monocytes. On the seventh day after irradiation, the lesion was smaller than it had been two days after irradiation, and had reactive changes at its edges and coagulative necrosis at its center. Extravasation of Evans blue and immunoglobulin was markedly reduced by the seventh day after irradiation, but uptake of horseradish peroxidase by macrophages located at the periphery of the lesion was evident.

  7. Magnetic and electronic properties of porphyrin-based molecular nanowires

    NASA Astrophysics Data System (ADS)

    Zheng, Jia-Jia; Li, Qiao-Zhi; Dang, Jing-Shuang; Wang, Wei-Wei; Zhao, Xiang

    2016-01-01

    Using spin-polarized density functional theory calculations, we performed theoretical investigations on the electronic and magnetic properties of transition metal embedded porphyrin-based nanowires (TM-PNWs, TM = Cr, Mn, Co, Ni, Cu, and Zn). Our results indicate that Ni-PNW and Zn-PNW are nonmagnetic while the rest species are magnetic, and the magnetic moments in TM-PNWs and their corresponding isolated monomer structures are found to be the same. In addition, the spin coupling in the magnetic nanowires can be ignored leading to their degenerate AFM and FM states. These results can be ascribed to the weak intermetallic interactions because of the relatively large distances between neighbor TM atoms. Among all TM-PNW structures considered here, only Mn-PNW shows a half-metallic property while the others are predicted to be semiconducting. The present work paves a new way of obtaining ferromagnetic porphyrin-based nanowires with TM atoms distributed separately and orderly, which are expected to be good candidates for catalysts, energy storage and molecular spintronics.

  8. Toxicity of polychlorinated biphenyl with special reference to porphyrin metabolism

    SciTech Connect

    Sano, S.; Kawanishi, S.; Seki, Y.

    1985-02-01

    Oral administration of a commercial PCB mixture to chickens caused a hepatic-type porphyria characterized by hepatic accumulation and urinary excretion of uroporphyrin. To clarify the mechanism of the porphyrinogenic activity of these PCBs, the authors studied the structural requirement of synthetic PCB for porphyrinogenic activities by using the cultured chick embryo liver cells and examined the relationship between induction of delta-aminolevulinic acid (ALA) synthetase and inhibition of uroporphyrinogen decarboxylase. They established that the porphyrinogenic effect of PCBs exhibits a sharply defined structure-activity relationship in that only 3,4,3',4'-tetrachlorobiphenyl and 3,4,5,3',4',5'-hexachlorobiphenyl produced a marked accumulation of uroporphyrin. They also demonstrated that in ALA-supplemented cultures, these same compounds lead to accumulation of a large amount of uroporphyrin III, whereas with other PCBs, which were weak inducers of porphyrin synthesis, the accumulated porphyrin was mostly protoporphyrin. Kinetic studies of the sequential decarboxylation of uroporphyrinogen with purified uroporphyrinogen decarboxylase were performed. The 3,4,3',4'-tetrachlorobiphenyl and 3,4,5,3',4',5'-hexachlorobiphenyl strongly inhibit uroporphyrinogen decarboxylase directly at two steps. The results confirmed that porphyrinogenic PCBs primarily inhibit uroporphyrinogen decarboxylase, leading to a depletion of heme as a result of which synthesis of ALA synthetase increased.

  9. Imaging of photoinduced tautomerism in single porphyrin molecules

    NASA Astrophysics Data System (ADS)

    Jäger, Regina; Chizhik, Anna M.; Chizhik, Alexey I.; Mack, Hans-Georg; Lyubimtsev, Alexey; Hanack, Michael; Meixner, Alfred J.

    2011-10-01

    In this work we present our new experimental and theoretical results upon investigations of the photoinduced tautomerism processes of single metal-free porphyrin-type molecules. During tautomerization a molecule changes its structure, therefore the excitation transition dipole moment (TDM) of the molecule changes its orientation. Using confocal microscopy in combination with azimuthally and radially polarized laser beams we are able to determine the orientation of the TDM as well as the orientation of a single molecule itself. In the case of tautomerism we are able to visualize this process and even the involved isomers separately. The study first focuses on two symmetrical compounds: a phthalocyanine and a porphyrin. Additionally, differences of the single molecules embedded in a polymer matrix or just spin-coated on a glass cover slide and under nitrogen flow are investigated. In the latter case we observe a higher frequency of the change of the TDM orientation. The experimental studies are supplemented by quantum chemical calculations. Variations of the molecular substituents, the environment and excitation wavelength can give new insights into the excited-state tautomerism process of a single molecule. We also introduce some suggestions for future experiments to support the understanding of the photoinduced tautomerism.

  10. Giant Stark effect in double-stranded porphyrin ladder polymers

    NASA Astrophysics Data System (ADS)

    Pramanik, Anup; Kang, Hong Seok

    2011-03-01

    Using the first-principles calculations, we have investigated the stability and the electronic structure of two types of recently synthesized one-dimensional nanoribbons, i.e., double-stranded zinc(II) porphyrin ladder polymer (LADDER) arrays. First, electronic structure calculations were used to show that the LADDER is a semiconductor. Most importantly, the application of a transverse electric field significantly reduces the band gap of the LADDER, ultimately converting the LADDER to a metal at a field strength of 0.1 V/Å. The giant Stark effect in this case is almost as strong as that in boron nitride nanotubes and nanoribbons. In the presence of an electric field, hole conduction and electronic conduction will occur entirely through spatially separated strands, rendering these materials useful for nanoelectronic devices. Second, the substitution of hydrogen atoms in the porphyrin units or that of zinc ions with other kinds of chemical species is found to increase the binding strength of the LADDER and reduce the band gap.

  11. Anticancer Gold(III) Porphyrins Target Mitochondrial Chaperone Hsp60.

    PubMed

    Hu, Di; Liu, Yungen; Lai, Yau-Tsz; Tong, Ka-Chung; Fung, Yi-Man; Lok, Chun-Nam; Che, Chi-Ming

    2016-01-22

    Identification of the molecular target(s) of anticancer metal complexes is a formidable challenge since most of them are unstable toward ligand exchange reaction(s) or biological reduction under physiological conditions. Gold(III) meso-tetraphenylporphyrin (gold-1 a) is notable for its high stability in biological milieux and potent in vitro and in vivo anticancer activities. Herein, extensive chemical biology approaches employing photo-affinity labeling, click chemistry, chemical proteomics, cellular thermal shift, saturation-transfer difference NMR, protein fluorescence quenching, and protein chaperone assays were used to provide compelling evidence that heat-shock protein 60 (Hsp60), a mitochondrial chaperone and potential anticancer target, is a direct target of gold-1 a in vitro and in cells. Structure-activity studies with a panel of non-porphyrin gold(III) complexes and other metalloporphyrins revealed that Hsp60 inhibition is specifically dependent on both the gold(III) ion and the porphyrin ligand.

  12. Glassy fragmental rocks of Macquarie Island (Southern Ocean): Mechanism of formation and deposition

    NASA Astrophysics Data System (ADS)

    Dickinson, J. A.; Harb, N.; Portner, R. A.; Daczko, N. R.

    2009-04-01

    Glassy fragmental rocks are interlayered with pillow basalt and tabular basalt on Macquarie Island (54°30' S, 158°54' E). These facies formed along the Proto-Macquarie Spreading Ridge between 6 and 12 Ma and have since been uplifted and exposed on the apex of the Macquarie Ridge Complex. Through a combination of field and microscopic analyses, we investigate the submarine production, transportation, deposition and lithification of basalt and sideromelane clasts within a spreading-ridge environment. The findings of this study indicate that these glassy grains form predominantly by cooling-contraction granulation of pillow lava rinds while crystalline basalt clasts are derived from the fragmentation of pillows along concentric and radial cooling joints. Hyaloclastite breccias consist of crystalline volcanic clasts in a matrix of glassy fragments, and are termed pillow-fragment breccias when clasts identifiable as pillows account for > 25% of the cobble-sized fraction. This glassy fragmental sediment was transported predominantly by short-lived grain flows and deposited as a result of syn-eruptive talus accumulation. The above interpretations culminate in the production of a depositional model: these glassy fragmental rocks formed on the slopes of pillow cones following gravitational collapse of a destabilised cone flank along the Proto-Macquarie Spreading Ridge. Scanning electron microscopy reveals that palagonite alteration rims on glassy grains lithify the sediment. The findings may be used as an analogue for the formation of glassy fragmental rocks along past and present mid-oceanic ridges.

  13. Porphyrin π-stacking in a heme protein scaffold tunes gas ligand affinity.

    PubMed

    Weinert, Emily E; Phillips-Piro, Christine M; Marletta, Michael A

    2013-10-01

    The role of π-stacking in controlling redox and ligand binding properties of porphyrins has been of interest for many years. The recent discovery of H-NOX domains has provided a model system to investigate the role of porphyrin π-stacking within a heme protein scaffold. Removal of a phenylalanine-porphyrin π-stack dramatically increased O2, NO, and CO affinities and caused changes in redox potential (~40mV) without any structural changes. These results suggest that small changes in redox potential affect ligand affinity and that π-stacking may provide a novel route to engineer heme protein properties for new functions.

  14. Self-assembling discotic liquid crystal porphyrin into more controllable ordered nanostructure mediated by fluorophobic effect

    SciTech Connect

    Zhou, Xiaoli; Kang, Shin-Woong; Kumar, Satyendra; Li, Quan

    2009-09-02

    The novel nanoscale discotic liquid crystal porphyrin with partial chain perfluorination, which has the same basic structure as the best photoreceptor in nature (chlorophyll), shows an exceptionally enhanced tendency to self-assemble into ordered nanostructure. Defect-free homeotropically aligned fluorinated porphyrin thin films were, for the first time, fabricated and characterised. The ability to self-assemble large {pi}-conjugated discotic molecules into highly ordered nanostructure via partial chain perfluorination provides new insight for the bottom-up nanofabrication of molecular devices. The controllable ordered porphyrin nanostructure with directed molecular arrangement holds great promise for use in high-performance electronic devices.

  15. Aggregation of asphaltene model compounds using a porphyrin tethered to a carboxylic acid.

    PubMed

    Schulze, Matthias; Lechner, Marc P; Stryker, Jeffrey M; Tykwinski, Rik R

    2015-07-07

    A Ni(II) porphyrin functionalized with an alkyl carboxylic acid (3) has been synthesized to model the chemical behavior of the heaviest portion of petroleum, the asphaltenes. Specifically, porphyrin 3 is used in spectroscopic studies to probe aggregation with a second asphaltene model compound containing basic nitrogen (4), designed to mimic asphaltene behavior. NMR spectroscopy documents self-association of the porphyrin and aggregation with the second model compound in solution, and a Job's plot suggests a 1 : 2 stoichiometry for compounds 3 and 4.

  16. Fluorenyl porphyrins for combined two-photon excited fluorescence and photosensitization

    NASA Astrophysics Data System (ADS)

    Mongin, Olivier; Hugues, Vincent; Blanchard-Desce, Mireille; Merhi, Areej; Drouet, Samuel; Yao, Dandan; Paul-Roth, Christine

    2015-04-01

    The two-photon absorption (2PA), the luminescence and the photosensitization properties of porphyrin-cored fluorenyl dendrimers and meso-substituted fluorenylporphyrin monomer, dimer and trimer are described. In comparison with model tetraphenylporphyrin, these compounds combine enhanced (non-resonant) 2PA cross-sections in the near infrared and enhanced fluorescence quantum yields, together with maintained singlet oxygen generation quantum yields. 'Semi-disconnection' between fluorenyl groups and porphyrins (i.e. direct meso substitution) proved to be more efficient than non-conjugated systems (based on efficient FRET between fluorenyl antennae and porphyrins). These results are of interest for combined two-photon imaging and photodynamic therapy.

  17. Palladium-catalyzed amination of meso-(bromophenyl)porphyrins with diamines and azamacrocycles.

    PubMed

    Mikhalitsyna, E A; Tyurin, V S; Khrustalev, V N; Lonin, I S; Beletskaya, I P

    2014-03-07

    Novel diamino and azamacrocycle functionalized porphyrins were efficiently synthesized by palladium-catalyzed amination of mono- and bis(meso-(bromophenyl))porphyrins. The optimization of reaction conditions allowed us to achieve high yields of products with substrates of different types. Supramolecular utility of the thus obtained aminoporphyrins was shown by investigations of processes of coordination self-assembly in solution by NMR and UV-Vis spectroscopy. The crystalline 1D-coordination polymer formed via self-assembly of N,N-dimethylethylenediamine substituted zinc porphyrin was characterized by X-ray diffraction.

  18. Estimation of porphyrin concentration in the kerogen fraction of shales using high-resolution reflectance spectroscopy

    NASA Technical Reports Server (NTRS)

    Holden, Peter N.; Gaffey, Michael J.; Sundararaman, P.

    1991-01-01

    An interpretive model for estimating porphyrin concentration in bitumen and kerogen from spectral reaflectance data in the visible and near-ultraviolet region of the spectrum is derived and calibrated. Preliminary results obtained using the model are consistent with concentrations determined from the bitumen extract and suggest that 40 to 60 percent of the total porphyrin concentration remains in the kerogen after extraction of bitumen from thermally immature samples. The reflectance technique will contribute to porphyrin and kerogen studies and can be applied at its present level of development to several areas of geologic and paleo-oceanographic research.

  19. Light-induced electrical switching of porphyrin-covered silicon nanowire FETs (presentation video)

    NASA Astrophysics Data System (ADS)

    Cuniberti, Gianaurelio

    2014-03-01

    Nanowires represent excellent building blocks for future nanoelectronics, due to their efficient charge transport characteristics. Here we present light-induced switching behaviour of porphyrin-coated silicon nanowire field effect transistors (Si NW FETs) and demonstrate their capabilities for design of hybrid nanodevices - consisting of organic complexes and inorganic nanowires. Switching of Si NW FETs highly reflects the electrical change of porphyrin molecules by light. To demonstrate significant factors of concentration-dependent switching of porphyrin-covered devices, electrical charging mechanism through molecules and nanowires has been understood, that allows the systematic integration of the hybrid devices.

  20. Polymorphism in glassy silicon: Inherited from liquid-liquid phase transition in supercooled liquid

    NASA Astrophysics Data System (ADS)

    Zhang, Shiliang; Wang, Li-Min; Zhang, Xinyu; Qi, Li; Zhang, Suhong; Ma, Mingzhen; Liu, Riping

    2015-02-01

    Combining molecular dynamics (MD) simulation and Voronoi polyhedral analyses, we discussed the microstructure evolution in liquid and glassy silicon during cooling by focusing on the fraction of various clusters. Liquid-liquid phase transition (LLPT) is detected in supercooled liquid silicon However, freezing the high-density liquid (HDL) to the glassy state is not achieved as the quenching rate goes up to 1014 K/s. The polyamorphism in glassy silicon is found to be mainly associated with low-density liquid (LDL).

  1. Au nanoparticles and graphene quantum dots co-modified glassy carbon electrode for catechol sensing

    NASA Astrophysics Data System (ADS)

    Zhao, Xuan; He, Dawei; Wang, Yongsheng; Hu, Yin; Fu, Chen

    2016-03-01

    In this letter, the gold nanoparticles and graphene quantum dots were applied to the modification of glassy carbon electrode for the detection of catechol. The synergist cooperation between gold nanoparticles and graphene quantum dots can increase specific surface area and enhance electronic and catalytic properties of glassy carbon electrode. The detection limit of catechol is 0.869 μmol/L, demonstrating the superior detection efficiency of the gold nanoparticles and graphene quantum dots co-modified glassy carbon electrode as a new sensing platform.

  2. Fluorinated Dodecaphenylporphyrins: Synthetic and Electrochemical Studies Including the First Evidence of Intramolecular Electron Transfer Between an Fe(II) Porphyrin -Anion Radical and an Fe(I) Porphyrin

    SciTech Connect

    D'Souza, F.; Forsyth, T.P.; Fukuzumi, S.; Kadish, K.M.; Krattinger, B.; Lin, M.; Medforth, C.J.; Nakanishi, I.; Nurco, D.J.; Shelnutt, J.A.; Smith, K.M.; Van Caemelbecke, E.

    1998-10-19

    Dodecaphenylporphyrins with varying degrees of fluorination of the peripheral phenyl rings (FXDPPS) were synthesized as model compounds for studying electronic effects in nonplan~ porphyrins, and detailed electrochemical studies of the chloroiron(HI) complexes of these compounds were undertaken. The series of porphyrins, represented as FeDPPCl and as FeFXDPPCl where x = 4, 8 (two isomers), 12, 20,28 or 36, could be reversibly oxidized by two electrons in dichloromethane to give n-cation radicals and n-dications. All of the compounds investigated could also be reduced by three electrons in benzonitrile or pyridine. In benzonitrile, three reversible reductions were observed for the unfluorinated compound FeDPPC1, whereas the FeFXDPPCl complexes generally exhibited irreversible first and second reductions which were coupled to chemical reactions. The chemical reaction associated with the first reduction involved a loss of the chloride ion after generation of Fe FXDPPC1. The second chemical reaction involved a novel intramolecular electron transfer between the initially generated Fe(H) porphyrin n-anion radical and the final Fe(I) porphyrin reduction product. In pyridine, three reversible one electron reductions were observed with the second reduction affording stable Fe(II) porphyrin o - anion radicals for ail of the complexes investigated.

  3. Micelle-Encapsulated Quantum Dot-Porphyrin Assemblies as in Vivo Two-Photon Oxygen Sensors

    PubMed Central

    Lemon, Christopher M.; Karnas, Elizabeth; Han, Xiaoxing; Bruns, Oliver T.; Kempa, Thomas J.; Fukumura, Dai; Bawendi, Moungi G.; Jain, Rakesh K.; Duda, Dan G.; Nocera, Daniel G.

    2016-01-01

    Micelles have been employed to encapsulate the supramolecular assembly of quantum dots with palladium(II) porphyrins for the quantification of O2 levels in aqueous media and in vivo. Förster resonance energy transfer from the quantum dot (QD) to the palladium porphyrin provides a means for signal transduction under both one- and two-photon excitation. The palladium porphyrins are sensitive to O2 concentrations in the range of 0–160 Torr. The micelle-encapsulated QD-porphyrin assemblies have been employed for in vivo multiphoton imaging and lifetime-based oxygen measurements in mice with chronic dorsal skinfold chambers or cranial windows. Our results establish the utility of the QD-micelle approach for in vivo biological sensing applications. PMID:26149349

  4. Synthesis, Spectroscopic, and Biological Studies on New Zirconium(IV) Porphyrins with Axial Ligand

    PubMed Central

    Bajju, Gauri D.; Devi, Gita; Katoch, Sapna; Bhagat, Madhulika; Deepmala; Ashu; Kundan, Sujata; Anand, Sunil Kumar

    2013-01-01

    A series of parasubstituted tetraphenylporphyrin zirconium(IV) salicylate complexes (SA/5-SSAZr(IV)RTPP, R = p-H, p-CH3, p-NO2, p-Cl, SA = salicylate, and 5-SSA = 5-sulfosalicylate) have been synthesized, and the spectral properties of free base porphyrins, their corresponding metallated, and axially ligated zirconium(IV) porphyrin compounds were compared with each other. A detailed analysis of ultraviolet-visible (UV-vis), proton nulcear magnetic resonance (1H NMR) spectroscopy, infrared (IR) spectroscopy, and elemental analysis suggested the transformation from free base porphyrins to zirconium(IV) porphyrins. The ability of the metal in this complex for extra coordination of solvent molecules was confirmed by ESI-MS spectra. Besides the fluorescence, cyclic voltammetry, and thermogravimetric studies, the complexes were also screened for antimicrobial and anticancer activities. Among all the complexes, 5-SSAZr(p-NO2TPP) shows high antibacterial activity. PMID:24106455

  5. Noncovalent functionalization of single-walled carbon nanotubes with water-soluble porphyrins

    NASA Astrophysics Data System (ADS)

    Chen, Jinyu

    2005-03-01

    We have employed water-soluble porphyrin molecules [meso-(tetrakis-4-sulfonatophenyl) porphine dihydrochloride] to solubilize individual single-walled carbon nanotubes (SWNTs), resulting in aqueous solutions that are stable for several weeks. The porphyrin-nanotube complexes have been characterized with absorption and fluorescence spectroscopy, and with AFM. We find that the porphyrin/SWNT interaction is specific to the free base form, and that this interaction increases the effective pKa value for the protonation of the free base. Under mildly acidic conditions (pH less than 5) nanotube-mediated J-aggregates form which are unstable in solution and result in precipitation of the nanotubes over the course of a few days. Porphyrin-coated SWNTs can be precisely aligned on hydrophilic poly(dimethylsiloxane) (PDMS) surfaces by combing SWNT solution along a desired direction and then transferred to silicon substrates by stamping. Parallel SWNT networks and SWNT crossbars have been fabricated in this manner.

  6. XAFS and crystallographic studies of Ni(II) porphyrins in single crystals and in solution

    SciTech Connect

    Renner, M.W.; Furenlid, L.R.; Barkigia, K.M.; Fajer, J.

    1996-09-01

    Abstract. Nickel porphyrins serve as models for the active sites of several biological processes. Crystallographic and EXAFS results for a Ni meso-tetrapropyl porphyrin (NiTPrP) yield different Ni-N distances in solution and in the solid state. The Ni-N distances determined by single crystal polarized XAS and X-ray diffraction agree well. Polarized XANES experiments further establish that the pre-edge feature observed in square planar Ni(II) complexes is a ls-4pz transition. The single crystal and solution EXAFS results demonstrate that conformational variations of the porphyrin macrocycle can readily be imposed by environmental and/or packing forces and can thereby modulate the chemical and physical properties of porphyrinic chromophores and prosthetic groups.

  7. Synthesis and different substituent effects on spectral and electrochemical properties of porphyrin nicotinic acid binary compounds

    NASA Astrophysics Data System (ADS)

    Wang, Dong; Cheng, Xiuli; Shi, Yuhua; Sun, Erjun; Tang, Xuexin; Zhuang, Changfu; Shi, Tongshun

    2009-01-01

    The porphyrin nicotinic acid binary compounds with different substituents in porphine rings (5-(4-nicotinicoxyldecyloxy)phenyl-10,15,20-triphenylporhyrin 2a, 5-(4-nicotinicoxyldecyloxy)phenyl-10,15,20-tri(4-chlorophenyl)porphyrin 2b and 5-(4-nicotinicoxyldecyloxy)phenyl-10,15,20-tri(4-methoxyphenyl)porphyrin 2c) were synthesized. All of them have been characterized, assigned and analyzed by UV-vis, IR, MS and 1H NMR spectra. Their electrochemical and spectroscopic properties were studied by using cyclic voltammetry, fluorescence spectra and Resonance Raman spectra. Different substituents have a little influence on electrochemical behavior and fluorescence spectra. In the Resonance Raman spectra, the substituent has little influence on the skeleton vibration of porphyrin and has much influence on the vibration of phenyl.

  8. Bis(cyano) Iron(III) Porphyrinates: What Is the Ground State?

    PubMed

    Li, Jianfeng; Noll, Bruce C; Schulz, Charles E; Scheidt, W Robert

    2015-07-06

    The synthesis of six new bis(cyano) iron(III) porphyrinate derivatives is reported. The anionic porphyrin complexes utilized tetraphenylporphyrin, tetramesitylporphyrin, and tetratolylporphyrin as the porphyrin ligand. The potassium salts of Kryptofix-222 and 18-C-6 were used as the cations. These complexes have been characterized by X-ray structure analysis, solid-state Mössbauer spectroscopy, and EPR spectroscopy, both in frozen CH2Cl2 solution and in the microcrystalline state. These data show that these anionic complexes can exist in either the (dxz,dyz)(4)(dxy)(1) or the (dxy)(2)(dxz,dyz)(3) electronic configuration and some can clearly readily interconvert. This is a reflection that these two states can be very close in energy. In addition to the effects of varying the porphyrin ligand, subtle effects of the cyanide ligand environment in the solid state and in solution are sufficient to shift the balance between the two electronic states.

  9. Bio-inspired photoresponse of porphyrin-attached gold nanoparticles on a field-effect transistor.

    PubMed

    Miyachi, Mariko; Yamanoi, Yoshinori; Nakazato, Kazuo; Nishihara, Hiroshi

    2014-09-01

    A bio-inspired photoresponse was engineered in porphyrin-attached Au nanoparticles (AuNPs) on a field-effect transistor (FET). The system mimics photosynthetic electron transfer, using porphyrin derivatives as photosensitizers and AuNPs as photoelectron counting devices. Porphyrin-protected AuNPs were immobilized onto the gate of an FET via the formation of self-assembled monolayers. Photoinduced electron transfer from the porphyrin led to single electron transfer at the Au nanoparticles, which was monitored via a changing gate voltage on the FET in the presence of organic electrolyte. The further attachment of other functional molecules to this system should enable various other potential functionalities. This article is part of a special issue entitled: photosynthesis research for sustainability: keys to produce clean energy.

  10. Methods and intermediates for the synthesis of dipyrrin-substituted porphyrinic macrocycles

    SciTech Connect

    Yu, Lianhe; Muthukumaran, Kannan; Sreedharan, Prathapan; Lindsey, Jonathan S.

    2010-05-25

    The present invention provides dipyrrin substituted porphyrinic macrocycles, intermediates useful for making the same, and methods of making the same. Such compounds may be used for purposes including the making of molecular memory devices, solar cells and light harvesting arrays.

  11. Methods and intermediates for the synthesis of dipyrrin-substituted porphyrinic macrocycles

    SciTech Connect

    Yu, Lianhe; Muthukumaran, Kannan; Sreedharan, Prathapan; Lindsey, Jonathan S

    2012-03-06

    The present invention provides dipyrrin substituted porphyrinic macrocycles, intermediates useful for making the same, and methods of making the same. Such compounds may be used for purposes including the making of molecular memory devices, solar cells and light harvesting arrays.

  12. Methods and intermediates for the synthesis of dipyrrin-substituted porphyrinic macrocycles

    SciTech Connect

    Yu, Lianhe; Muthukumaran, Kannan; Sreedharan, Prathapan; Lindsey, Jonathan S.

    2011-05-24

    The present invention provides dipyrrin substituted porphyrinic macrocycles, intermediates useful for making the same, and methods of making the same. Such compounds may be used for purposes including the making of molecular memory devices, solar cells and light harvesting arrays.

  13. Luminescence diagnostics of malignant tumors in the IR spectral range using Yb-porphyrin metallocomplexes

    NASA Astrophysics Data System (ADS)

    Ivanov, A. V.; Rumyantseva, V. D.; Shchamkhalov, K. S.; Shilov, I. P.

    2010-12-01

    The creation and application of new low-toxic photosensitizers for the luminescence diagnostics of cancer are considered. The new photosensitizers weakly generate singlet oxygen, exhibit developed luminescence, and retain the tumor-tropic properties of the therapeutic photosensitizers. Twenty one ytterbium complexes of porphyrin compounds that differ by the substituents at the periphery of the porphyrin ring are synthesized. The absorption and luminescence spectra and the luminescence decay curves of these substances are studied. The primary toxicological and pharmacokinetic investigations are performed for the most promising compounds in the organisms of experimental animals. The experimental data prove that the Yb-porphyrin complexes are promising as low-toxic markers for the luminescence diagnostics of malignant tumors in the IR spectral range (975-985 nm) that are free of the phototoxicity typical of the conventional porphyrins at a relatively high luminescence contrast and the selective accumulation in tissue.

  14. Highly asymmetrical porphyrins with enhanced push-pull character for dye-sensitized solar cells.

    PubMed

    Kurotobi, Kei; Toude, Yuuki; Kawamoto, Kyosuke; Fujimori, Yamato; Ito, Seigo; Chabera, Pavel; Sundström, Villy; Imahori, Hiroshi

    2013-12-09

    A porphyrin π-system has been modulated by enhancing the push-pull character with highly asymmetrical substitution for dye-sensitized solar cells for the first time. Namely, both two diarylamino moieties as a strong electron-donating group and one carboxyphenylethynyl moiety as a strong electron-withdrawing, anchoring group were introduced into the meso-positions of the porphyrin core in a lower symmetrical manner. As a result of the improved light-harvesting property as well as high electron distribution in the anchoring group of LUMO, a push-pull-enhanced, porphyrin-sensitized solar cell exhibited more than 10% power conversion efficiency, which exceeded that of a representative highly efficient porphyrin (i.e., YD2)-sensitized solar cell under optimized conditions. The rational molecular design concept based on highly asymmetric, push-pull substitution will open the possibilities of further improving cell performance in organic solar cells.

  15. Energy transfer on demand: photoswitch-directed behavior of metal-porphyrin frameworks.

    PubMed

    Williams, Derek E; Rietman, Joseph A; Maier, Josef M; Tan, Rui; Greytak, Andrew B; Smith, Mark D; Krause, Jeanette A; Shustova, Natalia B

    2014-08-27

    In this paper, a photochromic diarylethene-based derivative that is coordinatively immobilized within an extended porphyrin framework is shown to maintain its photoswitchable behavior and to direct the photophysical properties of the host. In particular, emission of a framework composed of bis(5-pyridyl-2-methyl-3-thienyl)cyclopentene (BPMTC) and tetrakis(4-carboxyphenyl)porphyrin (H4TCPP) ligands anchored by Zn(2+) ions can be altered as a function of incident light. We attribute the observed cyclic fluorescence behavior of the synthesized porphyrin-BPMTC array to activation of energy transfer (ET) pathways through BPMTC photoisomerization. Time-resolved photoluminescence measurements show a decrease in average porphyrin emission lifetime upon BPMTC insertion, consistent with an ET-based mechanism. These studies portend the possible utilization of photochromic ligands to direct chromophore behavior in large light-harvesting ensembles.

  16. Chiroptical properties of an alternatingly functionalized cellotriose bearing two porphyrin groups

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Alternatingly functionalized cellulose molecules have potential applications in optoelectronics and molecular receptors. For example, cellulose-based solar cells have been proposed. As a prototype for such molecules, the trisaccharide fragment of cellulose was modified by attachment of porphyrin gro...

  17. Investigation of Porphyrin and Lipid Supramolecular Assemblies for Cancer Imaging and Therapy

    NASA Astrophysics Data System (ADS)

    Ng, Kenneth Ka-Seng

    Aerobic life on earth is made possible through the functions of the porphyrin. These colorful and ubiquitous chromophores are efficient at concentrating and converting sunlight into chemical energetic potential which sustain biological life. Humans have had a longstanding fascination with these molecules, especially for their applications in photodynamic therapy. The photophysical properties of porphyrins are highly influenced by their surrounding environment. Intermolecular interactions between these pigments can lead to excited state quenching, energy transfer and large changes to their absorption and fluorescence spectra. This thesis is focused on utilizing molecular self-assembly strategies to develop nanoscale porphyrin and phospholipid structures. The rationale being that intermolecular interactions between porphyrins in these nanostructures can induce changes which can be exploited in novel biomedical imaging and therapeutic applications. Four lipid-based structural platforms are studied including: nanoemulsions, bilayer discs and nanovesicles. In Chapter 1, I provide a background on the photophysics of porphyrins and the effect of intermolecular porphyrin interactions on photophysical properties. I also discuss phospholipids and their self-assembly process. Lastly I review current biomedical photonics techniques and discuss how these strategies can be used in conjugation with porphyrin and lipid supramolecular assemblies. In Chapter 2, I investigate the influence that loading a novel bacteriochlorin photosensitizer into a protein-stabilized lipid emulsion has on its spectral properties. I discovered that while the dye can be incorporated into the lipid emulsion, no changes were observed in its spectral properties. In Chapter 3, an amphipathic alpha-helical protein is used to stabilize and organize porphyrin-lipid molecules into bilayer discs. Close packing between porphyrin molecules causes quenching, which can be reversed by structural degradation of the

  18. Syntheses of oligonucleotide derivatives with P(V) porphyrin and their properties.

    PubMed

    Shimidzu, T; Segawa, H; Kitamura, M; Nimura, A

    1992-01-01

    Two types of oligonucleotide derivatives which are substituted by P(V) porphyrin at the phosphorus atom of an internucleotidic linkage and at the 5'-terminal internucleotidic linkage via a spacer were synthesized (Fig. 1), and hybridization capabilities of them with complementary oligonucleotides were evaluated. A novel method for a sensing of oligonucleotide by the fluorescence quenching via photo-induced electron transfer between the P(V) porphyrin labeled oligonucleotide and pyrene-labeled one on the oligonucleotide template is reported.

  19. Porphyrins-Functionalized Single-Walled Carbon Nanotubes Chemiresistive Sensor Arrays for VOCs.

    PubMed

    Shirsat, Mahendra D; Sarkar, Tapan; Kakoullis, James; Myung, Nosang V; Konnanath, Bharatan; Spanias, Andreas; Mulchandani, Ashok

    2012-09-02

    Single-walled carbon nanotubes (SWNTs) have been used extensively for sensor fabrication due to its high surface to volume ratio, nanosized structure and interesting electronic property. Lack of selectivity is a major limitation for SWNTs-based sensors. However, surface modification of SWNTs with a suitable molecular recognition system can enhance the sensitivity. On the other hand, porphyrins have been widely investigated as functional materials for chemical sensor fabrication due to their several unique and interesting physico-chemical properties. Structural differences between free-base and metal substituted porphyrins make them suitable for improving selectivity of sensors. However, their poor conductivity is an impediment in fabrication of prophyrin-based chemiresistor sensors. The present attempt is to resolve these issues by combining freebase- and metallo-porphyrins with SWNTs to fabricate SWNTs-porphyrin hybrid chemiresistor sensor arrays for monitoring volatile organic carbons (VOCs) in air. Differences in sensing performance were noticed for porphyrin with different functional group and with different central metal atom. The mechanistic study for acetone sensing was done using field-effect transistor (FET) measurements and revealed that the sensing mechanism of ruthenium octaethyl porphyrin hybrid device was governed by electrostatic gating effect, whereas iron tetraphenyl porphyrin hybrid device was governed by electrostatic gating and Schottky barrier modulation in combination. Further, the recorded electronic responses for all hybrid sensors were analyzed using a pattern-recognition analysis tool. The pattern-recognition analysis confirmed a definite pattern in response for different hybrid material and could efficiently differentiate analytes from one another. This discriminating capability of the hybrid nanosensor devices open up the possibilities for further development of highly dense nanosensor array with suitable porphyrin for E-nose application.

  20. Chiral and achiral basket-handle porphyrins: short synthesis and stereostructures of these versatile building blocks.

    PubMed

    Gehrold, Andreas C; Bruhn, Torsten; Schneider, Heidi; Radius, Udo; Bringmann, Gerhard

    2015-01-16

    Both, chiral and achiral basket-handle porphyrins were synthesized via a short, reliable, and efficient route in multigram quantities. Standard synthetic protocols such as metalation of the macrocycle, halogenation, and borylation of the porphyrin core or alkyl- and arylation with lithium organyls were successfully adapted. The planar-chiral representatives were resolved into their enantiomers, whose absolute configurations were determined by comparison of experimental CD spectra with TDCAM-B3LYP calculated ones.

  1. A strategy to design highly efficient porphyrin sensitizers for dye-sensitized solar cells.

    PubMed

    Chang, Yu-Cheng; Wang, Chin-Li; Pan, Tsung-Yu; Hong, Shang-Hao; Lan, Chi-Ming; Kuo, Hshin-Hui; Lo, Chen-Fu; Hsu, Hung-Yu; Lin, Ching-Yao; Diau, Eric Wei-Guang

    2011-08-21

    We designed highly efficient porphyrin sensitizers with two phenyl groups at meso-positions of the macrocycle bearing two ortho-substituted long alkoxyl chains for dye-sensitized solar cells; the ortho-substituted devices exhibit significantly enhanced photovoltaic performances with the best porphyrin, LD14, showing J(SC) = 19.167 mA cm(-2), V(OC) = 0.736 V, FF = 0.711, and overall power conversion efficiency η = 10.17%.

  2. An Electron Acceptor with Porphyrin and Perylene Bisimides for Efficient Non-Fullerene Solar Cells.

    PubMed

    Zhang, Andong; Li, Cheng; Yang, Fan; Zhang, Jianqi; Wang, Zhaohui; Wei, Zhixiang; Li, Weiwei

    2017-03-01

    A star-shaped electron acceptor based on porphyrin as a core and perylene bisimide as end groups was constructed for application in non-fullerene organic solar cells. The new conjugated molecule exhibits aligned energy levels, good electron mobility, and complementary absorption with a donor polymer. These advantages facilitate a high power conversion efficiency of 7.4 % in non-fullerene solar cells, which represents the highest photovoltaic performance based on porphyrin derivatives as the acceptor.

  3. Interaction of a tricationic meso-substituted porphyrin with guanine-containing polyribonucleotides of various structures

    NASA Astrophysics Data System (ADS)

    Ryazanova, Olga; Zozulya, Victor; Voloshin, Igor; Glamazda, Alexander; Dubey, Igor; Dubey, Larysa; Karachevtsev, Victor

    2016-09-01

    The interaction of a tricationic water-soluble meso-(N-methylpyridinium)-substituted porphyrin, TMPyP3+, derived from classic TMPyP4, with double-stranded poly(G)  ṡ  poly(C) and four-stranded poly(G) polyribonucleotides has been studied in aqueous buffered solutions, pH 6.9, of low and near-physiological ionic strengths in a wide range of molar phosphate-to-dye ratios (P/D). To clarify the binding modes of TMPyP3+ to biopolymers various spectroscopic techniques, including absorption and polarized fluorescence spectroscopy, Raman spectroscopy, and resonance light scattering, were used. As a result, two competitive binding modes were revealed. In solution of low ionic strength outside binding of the porphyrin to the polynucleotide backbone with self-stacking prevailed at low P/D ratios (P/D  <  3.5). It manifested itself by the substantial quenching of porphyrin fluorescence. Also the formation of large-scale porphyrin aggregates was observed near the stoichiometric binding ratio. The spectral changes observed at P/D  >  30 including emission enhancement were supposed to be caused by the embedding of partially stacked porphyrin J-dimers into the polymer groove. TMPyP3+ binding to poly(G) induced a fluorescence increase 2.5 times as large as that observed for poly(G)  ṡ  poly(C). In solution of near-physiological ionic strength the efficiency of external porphyrin binding was reduced substantially due to the competitive binding of Na+ ions with the polymer backbone. The spectroscopic characteristics of porphyrin bound to polynucleotides at different conditions were compared with those for free porphyrin.

  4. Porphyrin molecules boost the sensitivity of epitaxial graphene for NH3 detection

    NASA Astrophysics Data System (ADS)

    Iezhokin, I.; den Boer, D.; Offermans, P.; Ridene, M.; Elemans, J. A. A. W.; Adriaans, G. P.; Flipse, C. F. J.

    2017-02-01

    The sensitivity of quasi-free standing epitaxial graphene for NH3 detection is strongly enhanced by chemical functionalization with cobalt porphyrins resulting in a detection limit well below 100 ppb. Hybridization between NH3 and cobalt porphyrins induces a charge transfer to graphene and results in a shift of the graphene Fermi-level as detected by Hall measurements and theoretically explained by electronic structure calculations.

  5. Local Electric Field Effects on Rhodium-Porphyrin and NHC-Gold Catalysts

    DTIC Science & Technology

    2015-01-05

    AFRL-OSR-VA-TR-2015-0023 (NII) - Local Electric Field Effects on Rhodium-Porphyrin and NHC-Gold Catalysts MATTHEW KANAN LELAND STANFORD JUNIOR UNIV...Effects on Rhodium-Porphyrin and NHC-Gold Catalysts Principal Investigator: Matthew W. Kanan Project Publications: 1. “An Electric Field–Induced Change...design—i.e. controlling selectivity by changing the molecular structure of the reactants, catalysts or other reaction components. The overall goal of

  6. Hybrid orbital deformation (HOD) effect and spectral red-shift property of nonplanar porphyrin.

    PubMed

    Zhou, Zaichun; Cao, Chenzhong; Liu, Qiuhua; Jiang, Rongqing

    2010-04-16

    A series of 5,15-meso,meso-strapped nonplanar porphyrins with different degrees of ruffling distortion, as a model system, have been synthesized and characterized. The spectral red-shift of the nonplanar porphyrins was experimentally demonstrated to mainly originate from the hybrid orbital deformation (HOD) effect due to the distortion in the tetrapyrrole macrocycle, which confirmed previous explanations to the red-shift phenomenon.

  7. Mating behavior and intraspecific vibrational mimicry in the glassy-winged sharpshooter, homalodisca vitripennis (hemiptera: cicadellidae)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Vibrational communication is widespread in insects, particularly in leafhoppers where the pair formation process is mediated by species-specific vibrational signals. One important pest using vibrational communication, glassy-winged sharpshooter (GWSS), Homalodisca vitripennis, is a vector of Xylella...

  8. Sub-nanoscale nanoimprint fabrication of atomically stepped glassy substrates of silicate glass and acryl polymer

    NASA Astrophysics Data System (ADS)

    Yoshimoto, Mamoru

    2015-11-01

    In the nanoimprint process, the resolution limit of patterning has attracted much attention from both scientific and industrial aspects. In this article, we briefly review the main achievements of our research group on sub-nanoscale nanoimprint fabrication of atomically patterned glassy substrates of oxide glass and polymer. By applying the sapphire (α-Al2O3 single crystal) wafers with self-organized nanopatterns of atomic steps as thermal nanoimprinting molds, we successfully transferred their nanoscale patterns onto the surfaces of glassy substrates such as soda-lime silicate glasses and poly(methyl methacrylate) polymers. The surfaces of nanoimprinted glassy materials exhibited regularly arrayed atomic stairs with 0.2-0.3 nm step height, which were in good agreement with the sub-nanopatterns of sapphire molds. These atomically stepped morphologies on the glassy substrates were found to be stable for about 1 year.

  9. Determination of Volatility and Element Fractionation in Glassy Fallout Debris by SIMS

    SciTech Connect

    Williamson, Todd L.; Tenner, Travis Jay; Bonamici, Chloe Elizabeth; Kinman, William Scott; Pollington, Anthony Douglas; Steiner, Robert Ernest

    2016-05-10

    The purpose of this report is to characterize glassy fallout debris using the Trinity Test and then characterize the U-isotopes of U3O8 reference materials that contain weaponized debris.

  10. Probing the viscoelastic response of glassy polymer films using atomic force microscopy.

    PubMed

    Yang, Guanwen; Rao, Nanxia; Yin, Zejie; Zhu, Da-Ming

    2006-05-01

    The mechanical properties of glassy films and glass surfaces have been studied using an atomic force microscope (AFM) through various imaging modes and measuring methods. In this paper, we discuss the viscoelastic response of a glassy surface probed using an AFM. We analyzed the force-distance curves measured on a glassy film or a glassy surface at temperatures near the glass transition temperature, Tg, using a Burgers model. We found that the material's characteristics of reversible anelastic response and viscous creep can be extracted from a force-distance curve. Anelastic response shifts the repulsive force-distance curve while viscous creep strongly affects the slope of the repulsive force-distance curve. When coupled with capillary force, due to the condensation of a thin layer of liquid film at the tip-surface joint, the anelasticity and viscous creep can alter the curve significantly in the attractive region.

  11. Quasi-one-dimensional models for glassy dynamics

    NASA Astrophysics Data System (ADS)

    Pal, Prasanta

    2011-12-01

    We describe analytical calculations and simulations of the quasi-one-dimensional (Q1-D) model for glassy dynamics. In the Q1-D models, hard rods undergo single-file diffusion through a series of narrow channels connected by J intersections. The topology of the model is specified by J, the maximum number of rods in each middle channel K, and the number of rods N. We assume that the rods cannot turn at the intersections, and thus there is a single, continuous route through the system. This model displays hallmarks of glassy dynamics including caging behavior and subdiffusion, rapid growth in the structural relaxation time and collective particle rearrangements. The mean-square displacement Sigma(t) for the Q1-D model displays four dynamical regimes: 1) short-time diffusion Sigma( t) ˜ t, 2) a plateau Sigma(t) ˜ t0 caused by caging behavior, 3) single-file diffusion characterized by anomalous scaling Sigma(t) ˜ t0.5 at intermediate times, and 4) a crossover to long-tine diffusion Sigma(t) ˜ t for times that grow with the system size. We develop a general procedure for calculating analytically the structural relaxation time tD, beyond which the system undergoes long-time diffusion, as a function of density and system topology. The method involves several steps: 1) uniquely defining the set of microstates for the system and transitions among them, 2) constructing networks of connected microstates and identifying minimal, closed, directed loops that give rise to structural relaxation, 3) calculating the probabilities for obtaining each of the microstates that form the closed loops and for transitioning from one microstate to another, and 4) using these probabilities to deduce the dependence of tD on packing fraction. We find that to obeys power-law scaling tD ˜ (φ g-φ)-alpha, where φ g (the packing fraction corresponding to complete kinetic arrest) and alpha depend on the system topology, and can be calculated exactly. The analytical calculations are supported

  12. Porphyrin-silicon hybrid field-effect transistor with individually addressable top-gate structure.

    PubMed

    Seol, Myeong-Lok; Choi, Sung-Jin; Kim, Chang-Hoon; Moon, Dong-Il; Choi, Yang-Kyu

    2012-01-24

    A conductance-controllable hybrid device that utilizes the photoinduced charge transfer behavior of a porphyrin in a field-effect transistor (FET) with a nanogap is proposed and analyzed. A conventional metal-oxide-semiconductor (MOS) structure is modified to form a nanogap in which the porphyrin can be embedded. The conductance of an inversion channel is controlled by the negatively charged, optically activated porphyrin molecules. The proposed nanogap-formed MOSFET structure solves the conventional dilemma that a top-gate cannot be used for an organic-inorganic hybrid device because the top-gate blocks an entire area of a channel where organic material should be immobilized. The top-gate structure has much practicality compared with the back-gate structure because each device can be controlled individually. Furthermore, the device is highly compatible with the chip-based integrated system because the fabrication process follows the standard complementary metal-oxide-semiconductor (CMOS) technology. The charge transfer mechanisms between silicon and porphyrin are analyzed using devices with different doping polarities and geometrical parameters. The results show that the influence of the negative charge of the porphyrin in the device is reversed when opposite doping polarities are used. The device characteristics can be comprehensively evaluated using the energy band diagram analysis and simulation. The possible application of the proposed device for nonvolatile memory is demonstrated using the optical charging and electrical discharging behavior of the porphyrins.

  13. Synthesis and characterization of porphyrin nanotubes/rods for solar radiation harvesting and solar cells

    NASA Astrophysics Data System (ADS)

    Mongwaketsi, N.; Khamlich, S.; Klumperman, B.; Sparrow, R.; Maaza, M.

    2012-05-01

    Energy transfer and electron transfer events as they occur between well arranged light harvesting antenna molecules, the reaction center and other factors determine the function of natural photosynthesis. The overall small reorganization energy and the well-balanced electronic coupling between each component bear key characters for the unique efficiency of natural photosynthesis. Such aspects permit the design and assembly of artificial systems that efficiently process solar energy, replicating the natural processes. The rich and extensive transitions seen in porphyrin-based materials hold great expectation as light harvesting building blocks in the construction of molecular architectures, allowing an efficient use of the solar spectrum. Hence in this study porphyrin nanorods are synthesized and characterized for future application in the construction of the artificial light harvesting system. Understanding the sizes and growth mechanism of porphyrins nanorods by self-assembly and molecular recognition is essential for their successful implementation in nanodevices. Spectroscopic and microscopic studies were carried out to investigate the effect that time, concentration and solvents have on the fabrication of porphyrin nanorods by ionic self-assembly of two oppositely charged porphyrins. We investigate in details the heteroaggregate behavior formation of [H4TPPS4]2- and [SnTPyP]2+ mixture by means of the UV-vis spectroscopy and aggregates structure and morphology by transmission electron microscopy (TEM). This study demonstrates the potential for using different concentrations and solvents to influence the physical and optical properties of porphyrin based nanorods.

  14. Structural consequences of spin conversion in a sterically encumbered Ni(II) porphyrin

    SciTech Connect

    Barkigia, K.M.; Nelson, N.Y.; Renner, M.W.; Smith, K.M.; Fajer, J.

    1999-10-14

    The crystal structure of a pyridine-ligated, high-spin Ni(II) complex of 2,3,7,8,12,13,17,18-octabromo-5, 15-bis(isopropyl)-10,20-bis(isopropylidenyl) porphyrin, is reported and compared to the unligated, low-spin Ni(II) complex previously reported. The results demonstrate that conversion to high-spin Ni(II) in nonplanar, sterically encumbered porphyrins induces a significant core expansion about the Ni while nonplanarity is still retained. The expansion of the core parameters (Ni-N, Ct-C{alpha}, Ct-Cmexo) and the Ni-N{sub axial} distances are characteristic of the d{sub x{sup 2}{minus}y{sup 2}} orbital occupancies in high-spin Ni(II) porphyrins and document the structural consequences of the spin conversion in severely nonplanar Ni(II) porphyrins. The stereochemical results are particularly relevant to ligation effects in nonplanar Ni biomolecules and synthetic porphyrins increasingly used as biomimetic models of conformational effects in chromophores and prosthetic groups in vivo, and to the remarkably wide range of lifetimes observed for excited (d,d) states in nonplanar, sterically constrained Ni(II) porphyrins in which the d{sub x{sup 2}{minus}y{sup 2}} and d{sub z{sup 2}} orbitals are also populated.

  15. Investigation of photodynamic activity of water-soluble porphyrins in vitro and in vivo

    NASA Astrophysics Data System (ADS)

    Gyulkhandanyan, Grigor V.; Ghambaryan, Sona S.; Amelyan, Gayane V.; Ghazaryan, Robert K.; Arsenyan, Flora H.; Gyulkhandanyan, Aram G.

    2006-02-01

    Photodynamic therapy (PDT) is the method of photosensitized tumor treatment. It is based on the photosensitizer (PS) selective accumulation in tumors, its subsequent activation under the light influence and oxygen active form formation that results in tumor destruction. Photodynamic action of some new water-soluble porphyrins was investigated in our laboratory. Dose-dependent effect of these porphyrins was shown on PC-12 murine pheochromocytoma cell line. The results revealed that the efficiency of the investigated porphyrins decreased in the following way: TOEPyP (meso-tetra-(4-N-oxyethylpyridyl)porphyrin) > Zn-TOEPyP > Ag-TOEPyP. It was shown that TOEPyP possessed nearly the same photodynamic activity (LD50) as well-known photosensitizer chlorin e6. These porphyrins have also demonstrated quite high photodynamic activity in vivo. The results were obtained in the experiments on white mice with engrafted C-180 (Croker's sarcoma). Antitumor activity of these porphyrins in the dark was 30-40%, whereas photodynamic activity was 45-60%.

  16. Light-harvesting and ultrafast energy migration in porphyrin-based metal-organic frameworks.

    PubMed

    Son, Ho-Jin; Jin, Shengye; Patwardhan, Sameer; Wezenberg, Sander J; Jeong, Nak Cheon; So, Monica; Wilmer, Christopher E; Sarjeant, Amy A; Schatz, George C; Snurr, Randall Q; Farha, Omar K; Wiederrecht, Gary P; Hupp, Joseph T

    2013-01-16

    Given that energy (exciton) migration in natural photosynthesis primarily occurs in highly ordered porphyrin-like pigments (chlorophylls), equally highly ordered porphyrin-based metal-organic frameworks (MOFs) might be expected to exhibit similar behavior, thereby facilitating antenna-like light-harvesting and positioning such materials for use in solar energy conversion schemes. Herein, we report the first example of directional, long-distance energy migration within a MOF. Two MOFs, namely F-MOF and DA-MOF that are composed of two Zn(II) porphyrin struts [5,15-dipyridyl-10,20-bis(pentafluorophenyl)porphinato]zinc(II) and [5,15-bis[4-(pyridyl)ethynyl]-10,20-diphenylporphinato]zinc(II), respectively, were investigated. From fluorescence quenching experiments and theoretical calculations, we find that the photogenerated exciton migrates over a net distance of up to ~45 porphyrin struts within its lifetime in DA-MOF (but only ~3 in F-MOF), with a high anisotropy along a specific direction. The remarkably efficient exciton migration in DA-MOF is attributed to enhanced π-conjugation through the addition of two acetylene moieties in the porphyrin molecule, which leads to greater Q-band absorption intensity and much faster exciton-hopping (energy transfer between adjacent porphyrin struts). The long distance and directional energy migration in DA-MOF suggests promising applications of this compound or related compounds in solar energy conversion schemes as an efficient light-harvesting and energy-transport component.

  17. Real-time porphyrin detection in plaque and caries: a case study

    NASA Astrophysics Data System (ADS)

    Timoshchuk, Mari-Alina I.; Ridge, Jeremy S.; Rugg, Amanda L.; Nelson, Leonard Y.; Kim, Amy S.; Seibel, Eric J.

    2015-02-01

    An ultrathin scanning fiber endoscope, originally developed for cancer diagnosis, was used in a case study to locate plaque and caries. The imaging system incorporated software mitigation of background auto-fluorescence (AF). In conventional fluorescence imaging, varying AF across a tooth surface can mask low-level porphyrin signals. Laser-induced auto-fluorescence signals of dental tissue excited using a 405-nm laser typically produce fluorescence over a wavelength range extending from 440-nm to 750-nm. Anaerobic bacterial metabolism produces various porphyrin species (eg. protoporphyrin IX) that are located in carious enamel, dentin, gingivitis sites, and plaque. In our case study, these porphyrin deposits remained as long as one day after prophylaxis. Imaging the tooth surface using 405-nm excitation and subtracting the natural AF enhances the image contrast of low-level porphyrin deposits, which would otherwise be masked by the high background AF. In a case study, healthy tissues as well as sites of early and advanced caries formations were scanned for visual and quantitative signs of red fluorescence associated with porphyrin species using a background mitigation algorithm. Initial findings show increasing amplitudes of red fluorescence as caries severity increases from early to late stages. Sites of plaque accumulation also displayed red fluorescence similar to that found in carious dental tissue. The use of real-time background mitigation of natural dental AF can enhance the detection of low porphyrin concentrations that are indicators of early stage caries formation.

  18. Spectroscopic STM studies of single gold(III) porphyrin molecules.

    PubMed

    Müllegger, Stefan; Schöfberger, Wolfgang; Rashidi, Mohammad; Reith, Lorenz M; Koch, Reinhold

    2009-12-16

    Low-temperature scanning tunneling microscopy, a well-established technique for single-molecule investigations in an ultrahigh vacuum environment, has been used to study the electronic properties of Au(III) 5,10,15,20-tetraphenylporphyrin (AuTPP) molecules on Au(111) at the submolecular scale. AuTPP serves as a model system for chemotherapeutically relevant Au(III) porphyrins. For the first time, real-space images and local scanning tunneling spectroscopy data of the frontier molecular orbitals of AuTPP are presented. A comparison with results from density functional theory reveals significant deviations from gas-phase behavior due to a non-negligible molecule/substrate interaction. We identify the oxidation state of the central metal ion in the adsorbed AuTPP as Au(3+).

  19. Physicochemical properties of potential porphyrin photosensitizers for photodynamic therapy

    NASA Astrophysics Data System (ADS)

    Kempa, Marta; Kozub, Patrycja; Kimball, Joseph; Rojkiewicz, Marcin; Kuś, Piotr; Gryczyński, Zugmunt; Ratuszna, Alicja

    2015-07-01

    This research evaluated the suitability of synthetic photosensitizers for their use as potential photosensitizers in photodynamic therapy using steady state and time-resolved spectroscopic techniques. Four tetraphenylporphyrin derivatives were studied in ethanol and dimethyl sulfoxide. The spectroscopic properties namely electronic absorption and emission spectra, ability to generate singlet oxygen, lifetimes of the triplet state, as well as their fluorescence quantum yield were determined. Also time-correlated single photon counting method was used to precisely determine fluorescence lifetimes for all four compounds. Tested compounds exhibit high generation of singlet oxygen, low generation of fluorescence and they are chemical stable during irradiation. The studies show that the tested porphyrins satisfy the conditions of a potential drug in terms of physicochemical properties.

  20. Electron injection dynamics in high-potential porphyrin photoanodes.

    PubMed

    Milot, Rebecca L; Schmuttenmaer, Charles A

    2015-05-19

    There is a growing need to utilize carbon neutral energy sources, and it is well known that solar energy can easily satisfy all of humanity's requirements. In order to make solar energy a viable alternative to fossil fuels, the problem of intermittency must be solved. Batteries and supercapacitors are an area of active research, but they currently have relatively low energy-to-mass storage capacity. An alternative and very promising possibility is to store energy in chemical bonds, or make a solar fuel. The process of making solar fuel is not new, since photosynthesis has been occurring on earth for about 3 billion years. In order to produce any fuel, protons and electrons must be harvested from a species in its oxidized form. Photosynthesis uses the only viable source of electrons and protons on the scale needed for global energy demands: water. Because artificial photosynthesis is a lofty goal, water oxidation, which is a crucial step in the process, has been the initial focus. This Account provides an overview of how terahertz spectroscopy is used to study electron injection, highlights trends from previously published reports, and concludes with a future outlook. It begins by exploring similarities and differences between dye-sensitized solar cells (DSSCs) for producing electricity and a putative device for splitting water and producing a solar fuel. It then identifies two important problems encountered when adapting DSSC technology to water oxidation-improper energy matching between sensitizer energy levels with the potential for water oxidation and the instability of common anchoring groups in water-and discusses steps to address them. Emphasis is placed on electron injection from sensitizers to metal oxides because this process is the initial step in charge transport. Both the rate and efficiency of electron injection are analyzed on a sub-picosecond time scale using time-resolved terahertz spectroscopy (TRTS). Bio-inspired pentafluorophenyl porphyrins are

  1. Dispersion-corrected DFT calculations on C(60)-porphyrin complexes.

    PubMed

    Liao, Meng-Sheng; Watts, John D; Huang, Ming-Ju

    2009-06-07

    The quality of the newly added, empirical dispersion correction in density functional theory (DFT) calculations is examined for several supramolecular complexes of fullerene (C(60)) with free-base and metal porphyrins (Por). The benzene dimer (C(6)H(6))(2), naphthalene dimer (C(10)H(8))(2), and anthracene dimer (C(14)H(10))(2) were also included in the study for comparison. Three density functionals, two damping functions, and two types of basis sets were employed in the computations. The estimated dispersion energies in the fullerene-porphyrin systems are rather large, ranging from 0.5 eV in C(60).ZnP to 1 eV in C(60).H(2)TPP. Any dispersion-corrected DFT (DFT + E(disp)) method is shown to perform well for C(60).H(2)TPP, C(60).ZnTPP, and C(60).ZnP, where the intermolecular distances are relatively large. But large basis sets, e.g. TZP (triple-zeta + one polarization function), are required in order to obtain reliable results with DFT + E(disp). In the case of C(60).FeP, where the intermolecular distance R is short, the DFT + E(disp) calculated R depends on the damping function as well as on the DFT method, and all the DFT + E(disp) calculations lead to significant changes in the relative energies of the various spin states. The quality of the DFT + E(disp) calculated results on C(60).FeP is hard to judge here without detailed experimental data on a C(60).FePor complex. Owing to error cancellation, the pure DFT calculations with a smaller DZP (double-zeta + one polarization function) basis set without any correction are shown to give quite accurate results.

  2. Double Ring Expansion from an Aromatic [18]Porphyrin(1.1.1.1) to an Antiaromatic [20]Porphyrin(2.1.2.1).

    PubMed

    Umetani, Masataka; Tanaka, Takayuki; Kim, Taeyeon; Kim, Dongho; Osuka, Atsuhiro

    2016-07-04

    Double ring expansion from a 5,15-diarylporphyrin to a 5,16-diaryl-10,11,21,22-tetradehydro[20]porphyrin(2.1.2.1) occurred through a reaction sequence consisting of oxidation with PbO2 to 5,15-dioxoporphodimethene, a Corey-Fuchs reaction with tetrabromomethane in the presence of triphenylphosphine, and Fritsch-Buttenberg-Wiechell rearrangement triggered by tert-butyllithium. The obtained tetradehydro[20]porphyrin(2.1.2.1) and its mono- and dihydrogenated congeners exhibited 20 π antiaromatic character, whereas overhydrogenated congeners bearing a saturated bridge were nonaromatic owing to disrupted π conjugation.

  3. Stabilization of higher-valent states of iron porphyrin by hydroxide and methoxide ligands: electrochemical generation of iron(IV)-oxo porphyrins.

    PubMed Central

    Lee, W A; Calderwood, T S; Bruice, T C

    1985-01-01

    An electrochemical study of hydroxide- and methoxide-ligated iron(III) tetraphenylporphyrins possessing ortho-phenyl substituents that block mu-oxo dimer formation has been carried out. Ligation by these strongly basic oxyanions promotes the formation of iron(IV)-oxo porphyrins upon one-electron oxidation. Further one-electron oxidation of the latter provides the iron(IV)-oxo porphyrin pi-cation radical. These results are discussed in terms of chemical model studies and the enzymatic intermediate compounds I and II of the peroxidases. PMID:3859865

  4. Synthesis of porphyrins bearing 1-4 hydroxymethyl groups and other one-carbon oxygenic substituents in distinct patterns

    PubMed Central

    Yao, Zhen; Bhaumik, Jayeeta; Dhanalekshmi, Savithri; Ptaszek, Marcin; Rodriguez, Phillip A.; Lindsey, Jonathan S.

    2007-01-01

    Porphyrins that bear one-carbon oxygenic substituents (hydroxymethyl, formyl, ester) directly attached to the macrocycle afford a compact architecture that is attractive for diverse applications. Routes to 9 porphyrins bearing such groups in distinct architectures (A4-, trans-A2-, trans-A2B2-, trans-AB- and trans-AB2C-porphyrins) have been explored (A = hydroxymethyl), including porphyrins bearing two one-carbon units in different oxidation states (hydroxymethyl/ester, formyl/ester). The hydroxymethyl group was introduced via TBDMS-protected dipyrromethane precursors. PMID:18037972

  5. Rational syntheses of cyclic hexameric porphyrin arrays for studies of self-assembling light-harvesting systems.

    PubMed

    Yu, L; Lindsey, J S

    2001-11-02

    Two new cyclic hexameric arrays of porphyrins have been prepared in a rational, convergent manner. The porphyrins in each cyclic hexamer are joined by diphenylethyne linkers affording a wheel-like array with a diameter of approximately 35 A. One array is comprised of five zinc (Zn) porphyrins and one free base (Fb) porphyrin (cyclo-Zn(5)FbU) while the other is comprised of an alternating sequence of two Zn porphyrins and one Fb porphyrin (cyclo-Zn(2)FbZn(2)FbU). The prior synthesis employed a one-flask template-directed process and afforded alternating Zn and Fb porphyrins or all Zn porphyrins. More diverse metalation patterns are attractive for manipulating the flow of excited-state energy in the arrays. The rational synthesis of each array employed three Pd-mediated coupling reactions with four tetraarylporphyrin building blocks bearing diethynyl, diiodo, bromo/iodo, or iodo/ethynyl groups. The final ring closure yielding the cyclic hexamer was achieved by reaction of a porphyrin pentamer + porphyrin monomer or the joining of two porphyrin trimers. In the presence of a tripyridyl template, the yields of the 5 + 1 and 3 + 3 reactions ranged from 10 to 13%. The 5 + 1 reaction in the absence of the template proceeded in 3.5% yield, thereby establishing the structure-directed contribution to cyclic hexamer formation. The 3 + 3 route relied on successive ethyne + iodo/bromo coupling reactions. One template-directed route to cyclo-Zn(2)FbZn(2)FbU employed a magnesium porphyrin, affording cyclo-Zn(2)FbZn(2)MgU from which magnesium was selectively removed. The arrays exhibit absorption spectra that are nearly the sum of the spectra of the component parts, indicating weak electronic coupling. Fluorescence spectroscopy showed that the quantum yield of energy transfer in toluene at room temperature from the Zn porphyrins to the Fb porphyrin(s) was 60% in cyclo-Zn(5)FbU and 90% in cyclo-Zn(2)FbZn(2)FbU. Two dipyridyl-substituted porphyrins, a Zn tetraarylporphyrin and a Fb

  6. Porphyrin entrapment and release behavior of microporous organic hollow spheres: fluorescent alerting systems for existence of organic solvents in water.

    PubMed

    Jin, Jaewon; Kim, Bolyong; Park, Nojin; Kang, Sungah; Park, Joon Hyun; Lee, Sang Moon; Kim, Hae Jin; Son, Seung Uk

    2014-12-07

    This work reports on the controllable guest entrapment and release behavior of microporous organic hollow spheres (MOHs). Porphyrins which are soluble in both water and methanol were entrapped in the MOHs using methanol solution. The water-soluble porphyrins entrapped in MOHs were not extracted by water due to the hydrophobicity of microporous organic shells. In contrast, the porphyrins were released gradually into aqueous solution by adding water-soluble organic solvents. The release behavior depended on the kind of organic solvents used and on the alkyl chain length of the porphyrin compounds. These properties were applied for the fluorescent alert towards the existence of organic solvents in flowing aqueous media.

  7. Strain localization in glassy polymers under cylindrical confinement.

    PubMed

    Shavit, Amit; Riggleman, Robert A

    2014-06-14

    Although the origin of ductility in crystalline materials is well understood through the motion of dislocations and defects, a similar framework for understanding deformation in amorphous materials remains elusive. In particular, the difference in the mechanical response for small-molecule amorphous solids, such as organic glasses that are typically brittle, and polymer glasses, which are frequently very tough, has not been systematically explored. Here, we employ molecular dynamics simulations to investigate the mechanical response of model glassy polymers confined to a nanoscopic pillar under tensile deformation. We vary the chain length, cooling rate for forming the glass, and the deformation rate and investigate the changes in the mechanical response. We find that samples that are cooled at a slower rate and deformed at a slower rate are more prone to localization of the strain response, or shear banding. Interestingly, this effect is independent of chain length over the range of parameters we have investigated so far, and we believe this is the first direct observation of shear banding in deformed polymer glasses under cylindrical confinement. Finally, by using the isoconfigurational ensemble approach, we provide evidence that the location where the shear band forms is due to structural features that are frozen in place during sample preparation.

  8. Mathematical modeling of glassy-winged sharpshooter population.

    PubMed

    Yoon, Jeong-Mi; Hrynkiv, Volodymyr; Morano, Lisa; Nguyen, Anh Tuan; Wilder, Sara; Mitchell, Forrest

    2014-06-01

    Pierce's disease (PD) is a fatal disease of grapevines which results from an infection by the plant pathogen Xyllela fastidiosa. This bacterium grows in the xylem (water-conducting) vessels of the plant blocking movement of water. PD can kill vines in one year and poses a serious threat to both the California and the expanding Texas wine industries. Bacteria are vectored from one vine to the next by a number of xylem feeding insect species. Of these, the Glassy-winged Sharpshooter (GWSS) is considered to be the primary xylem feeding insect in Texas vineyards. An extensive database of the xylem-feeding population frequencies was collected by USDA-APHIS for Texas vineyards over multiple years. This project focused on a subset of data, GWSS frequencies within 25 vineyards in Edwards Plateau located in central Texas. The proposed model investigates the natural population dynamics and the decline in GWSS, likely the result of pest management campaigns on the insects within the region. The model is a delay Gompertz differential equation with harvesting and immigration terms, and we use the data to estimate the model parameters.

  9. Frequency-dependent conductivity in bismuth-vanadate glassy semiconductors

    NASA Astrophysics Data System (ADS)

    Ghosh, Aswini

    1990-01-01

    The first measurements are reported for the frequency-dependent (ac) conductivity (real as well as imaginary parts) for various compositions of the bismuth-vanadate glassy semiconductors in the frequency range 102-105 Hz and in the temperature range 77-420 K. The behavior of the ac conductivity is broadly similar to what has been observed previously in many other types of amorphous semiconductors, namely, nearly linear frequency dependence and weak temperature dependence. The experimental results are analyzed with reference to various theoretical models based on quantum-mechanical tunneling and classical hopping over barriers. The analysis shows that the temperature dependence of the ac conductivity is consistent with the simple quantum-mechanical tunneling model at low temperatures; however, this model completely fails to predict the observed temperature dependence of the frequency exponent. The overlapping-large-polaron tunneling model can explain the temperature dependence of the frequency exponent at low temperatures. Fitting of this model to the low-temperature data yields a reasonable value of the wave-function decay constant. However, this model predicts the temperature dependence of the ac conductivity much higher than what actual data showed. The correlated barrier hopping model is consistent with the temperature dependence of both the ac conductivity and its frequency exponent. This model provides reasonable values of the maximum barrier heights but higher values of characteristic relaxation times.

  10. Surface temperatures and glassy state investigations in tribology, part 1

    NASA Technical Reports Server (NTRS)

    Winer, W. O.; Sanborn, D. M.

    1978-01-01

    The research in this report is divided into two categories: (1) lubricant rheological behavior, and (2) thermal behavior of a simulated elastohydrodynamic contact. The studies of the lubricant rheological behavior consists of high pressure, low shear rate viscosity measurements, viscoelastic transition measurements, by volume dilatometry, dielectric transitions at atmospheric pressure and light scattering transitions. Lubricant shear stress-strain behavior in the amorphous glassy state was measured on several fluids. It appears clear from these investigations that many lubricants undergo viscoplastic transitions in typical EHD contacts and that the lubricant has a limiting maximum shear stress it can support which in turn will determine the traction in the contact except in cases of very low slide-roll ratio. Surface temperature measurements were made for a naphthenic mineral oil and a polyphenyl ether. The maximum surface temperature in these experiments was approximately symmetrical about the zero slide-roll ration except for absolute values of slide-roll ratio greater than about 0.9. Additional surface temperature measurements were made in contacts with rough surfaces where the composite surface roughness was approximately equal to the EHD film thickness. A regression analysis was done to obtain a predictive equation for surface temperatures as a function of pressure, sliding speed, and surface roughness. A correction factor for surface roughness effects to the typical flash temperature analysis was found.

  11. Dielectric studies of molecular motions in glassy and liquid nicotine

    NASA Astrophysics Data System (ADS)

    Kaminski, K.; Paluch, M.; Ziolo, J.; Ngai, K. L.

    2006-06-01

    The dielectric permittivity and loss spectra of glassy and liquid states of nicotine have been measured over the frequency range 10-2-109 Hz. The relaxation spectra are similar to common small molecular glass-forming substances, showing the structural α-relaxation and its precursor, the Johari-Goldstein β-relaxation. The α-relaxation is well described by the Fourier transform of the Kohlrausch-Williams-Watts stretched exponential function with an approximately constant stretch exponent that is equal to 0.70 as the glass transition temperature is approached. The dielectric α-relaxation time measured over 11 orders of magnitude cannot be described by a single Vogel-Fulcher-Tamman-Hesse equation. The most probable Johari-Goldstein β-relaxation time determined from the dielectric spectra is in good agreement with the primitive relaxation time of the coupling model calculated from parameters of the structural α-relaxation. The shape of the dielectric spectra of nicotine is compared with that of other glass-formers having about the same stretch exponent, and they are shown to be nearly isomorphic. The results indicate that the molecular dynamics of nicotine conform to the general pattern found in other glass-formers, and the presence of the universal Johari-Goldstein secondary relaxation, which plays a role in the crystallization of amorphous pharmaceuticals.

  12. Cryptoachneliths: Hidden glassy ash in composite spheroidal lapilli

    NASA Astrophysics Data System (ADS)

    Carracedo Sánchez, M.; Arostegui, J.; Sarrionandia, F.; Larrondo, E.; Gil Ibarguchi, J. I.

    2010-09-01

    Cryptoachneliths, perceptible by means of electron microscopy but unresolved under the optical microscope, occur unnoticed inside spheroidal lapilli of ultrabasic composition of the Cabezo Segura volcano (Calatrava volcanic province, Spain). The cryptoachneliths are glassy spherical particles that have compositions of Al-rich silicate with minor amounts of Fe, Ca and other elements. The smallest cryptoachneliths of < 1 μm in diameter (nanoachneliths) joined by coalescence to form microspheres > 1 μm (microachneliths) and homogeneous less regular masses of similar composition. Nano and microachneliths welded each other or to other types of volcanic particles (crystals, crystal fragments, spinning droplets, cognate lithic clasts, etc.) to form spheroidal lapilli and even bomb size clasts within proximal fall deposits of the Cabezo Segura volcano. The welding processes took place inside the eruptive column, previous to the fall of the spheroidal lapilli on top of the volcanic cone. The presence of the cryptoachneliths implies that lapilli and even bomb size tephra within deposits formed during explosive eruptions of low-viscosity basic to ultrabasic magmas should be carefully examined in order to establish key parameters of eruption dynamics, like size, amount and distribution of juvenile fine particles.

  13. Mechanics of particulate composites with glassy polymer binders in compression

    PubMed Central

    Jordan, J. L.; Spowart, J. E.; Kendall, M. J.; Woodworth, B.; Siviour, C. R.

    2014-01-01

    Whether used as structural components in design or matrix materials for composites, the mechanical properties of polymers are increasingly important. The compressive response of extruded polymethyl methacrylate (PMMA) rod with aligned polymer chains and Al–Ni–PMMA particulate composites are investigated across a range of strain rates and temperatures. The particulate composites were prepared using an injection-moulding technique resulting in highly anisotropic microstructures. The mechanics of these materials are discussed in the light of theories of deformation for glassy polymers. The experimental data from this study are compared with PMMA results from the literature as well as epoxy-based composites with identical particulates. The PMMA exhibited the expected strain rate and temperature dependence and brittle failure was observed at the highest strain rates and lowest temperatures. The Al–Ni–PMMA composites were found to have similar stress–strain response to the PMMA with reduced strain softening after yield. Increasing volume fraction of particulates in the composite resulted in decreased strength. PMID:24711495

  14. Redox behavior of biofilm on glassy carbon electrode.

    PubMed

    Sridharan, D; Manoharan, S P; Palaniswamy, N

    2011-10-01

    Marine and freshwater biofilm usually shift the open circuit potential (OCP) of stainless steel towards the electropositive direction by +450 mV vs SCE. The nature of oxide film and bacterial metabolism were also correlated with ennoblement process by various investigators. Glassy carbon electrode (GCE) was used in the present study and a shifting of potential in the positive side (+450 mV) was noticed. It indicates that biofilm contributes to the ennoblement process without any n/p-type semiconducting oxide film. The nature of the cathodic curve for the biofilm covered GCE is compared with the previous literature on the electrochemical behavior of stainless steel. The present study explains the oxidation and reduction peaks of biofilm covered GCE by cyclic voltammetry. Electrochemical impedance result reveals the diffusion process within the manganese biofilm. The present study confirms the previous investigations that the manganese biofilm rules the electrochemical behavior of materials and suggests that oxide film is not necessary to assist the ennoblement process.

  15. Catalytic electron-transfer oxygenation of substrates with water as an oxygen source using manganese porphyrins.

    PubMed

    Fukuzumi, Shunichi; Mizuno, Takuya; Ojiri, Tetsuya

    2012-12-03

    Manganese(V)-oxo-porphyrins are produced by the electron-transfer oxidation of manganese-porphyrins with tris(2,2'-bipyridine)ruthenium(III) ([Ru(bpy)(3)](3+); 2 equiv) in acetonitrile (CH(3)CN) containing water. The rate constants of the electron-transfer oxidation of manganese-porphyrins have been determined and evaluated in light of the Marcus theory of electron transfer. Addition of [Ru(bpy)(3)](3+) to a solution of olefins (styrene and cyclohexene) in CH(3)CN containing water in the presence of a catalytic amount of manganese-porphyrins afforded epoxides, diols, and aldehydes efficiently. Epoxides were converted to the corresponding diols by hydrolysis, and were further oxidized to the corresponding aldehydes. The turnover numbers vary significantly depending on the type of manganese-porphyrin used owing to the difference in their oxidation potentials and the steric bulkiness of the ligand. Ethylbenzene was also oxidized to 1-phenylethanol using manganese-porphyrins as electron-transfer catalysts. The oxygen source in the substrate oxygenation was confirmed to be water by using (18)O-labeled water. The rate constant of the reaction of the manganese(V)-oxo species with cyclohexene was determined directly under single-turnover conditions by monitoring the increase in absorbance attributable to the manganese(III) species produced in the reaction with cyclohexene. It has been shown that the rate-determining step in the catalytic electron-transfer oxygenation of cyclohexene is electron transfer from [Ru(bpy)(3)](3+) to the manganese-porphyrins.

  16. Noncovalent functionalization of carbon nanotubes with porphyrins: meso-tetraphenylporphine and its transition metal complexes.

    PubMed

    Basiuk, Elena V; Basiuk, Vladimir A; Santiago, Patricia; Puente-Lee, Iván

    2007-01-01

    Noncovalent functionalization of carbon nanotubes with meso-tetraphenylporphine (H2TPP) and its metal(II) complexes NiTPP and CoTPP was studied by means of different experimental techniques and theoretical calculations. As follows from the experimental adsorption curves, free H2TPP ligand exhibits the strongest adsorption of three porphyrins tested, followed by CoTPP and NiTPP. At the highest porphyrin concentrations studied, the adsorption at multi-walled carbon nanotubes was about 2% (by weight) for H2TPP, 1% for CoTPP, and 0.5% for NiTPP. Transmission electron microscopy observations revealed carbon nanotubes with a variable degree of surface coverage with porphyrin molecules. According to scanning electron microscopy, the nanotubes glue together rather than debundle; apparently, a large porphyrin excess resulting in polymolecular adsorption is essential for exfoliation/debundling of the nanotube ropes. The nanotube/porphyrins hybrids were studied by infrared and Raman spectroscopy, as well as by scanning tunneling microscopy. Electronic structure calculations were performed at the B3LYP/LANL2MB theoretical level with the unsubstituted porphine (H2P) and its Co(II) complex, on one hand, and open-end armchair (5,5) (ANT) and zigzag (8,0) (ZNT) SWNT models, on the other hand. The interaction of H2P with ANT was found to be by 3.9 kcal mol(-1) stronger than that of CoP. At the same time, CoP+ZNT complex is more stable by 42.7 kcal mol(-1) as compared to H2P+ZNT According to these calculated results, the free porphyrins interact less selectively with zigzag and armchair (i.e., semiconducting and metallic) nanotubes, whereas the difference becomes very large for the metal porphyrins. HOMO-LUMO structure, electrostatic potential and spin density distribution for the paramagnetic cobalt(II) complexes were analyzed.

  17. Comprehensive physiology and toxicology of ecdysogens--The metabolically activated porphyrin-ecdysteroid complexes in insects.

    PubMed

    Sláma, Karel; Zhylitskaya, Halina

    2016-01-01

    The polyhydroxylated derivatives of 6-keto,7-dehydrocholesterol (ecdysone, ecdysteroids, Ecd) are natural compounds widely distributed in plants. They exhibit strong anabolic, vitamin D-like, pharmacological effects in vertebrate animals and in the human body. In the larval stages of insects, injections of pure Ecd cause serious pathophysiological, "hyperecdysonic" syndromes associated with neuromuscular paralysis, premature cuticular apolysis and complete inhibition of ecdysis. Ecds do not penetrate insect cuticle. For this reason, all previous attempts to induce ecdysone responses by topical applications of Ecd failed. In this work, we tried to induce the topical effects of Ecd by preparation of more lipophilic complexes, with 2 or 4 molecules of 20-hydroxyecdysone (E20) attached to a relatively large nucleus of the porphyrin. The resulting porphyrin-E20 complexes (ecdysogens) have been subjected to standardised assays for ecdysone activity in the ligatured larvae ("dauerlarvae") of the greater waxmoth (Galleria mellonella). Similarly like the free E20 alone, porphyrin-E20 complexes had no effect when applied on the body surface or administered in the larval diet. When injected, however, they exhibited delayed effects, but the adverse ("hyperecdysonic") pathophysiological syndromes were reduced or abolished. It is concluded, therefore, that the replacement of pathophysiological, precocious or "hyperecdysonic" moults by the larval-pupal transformation, was due to successive metabolic liberation of the biologically active, free E20 from the porphyrin-E20 complex. The biological status of Ecd does not agree with their definition as the prothoracic gland (PG) hormone of insects, nor with the assumptions about a growth hormone of plants. A possibility that the most important status of Ecd may depend on the pharmacological properties of a sterolic D6 vitamin has been discussed.

  18. Fabrication of Ni-Nb-Sn metallic glassy alloy powder and its microwave-induced sintering behavior.

    PubMed

    Xie, Guoqiang; Li, Song; Louzguine-Luzgin, D V; Cao, Ziping; Yoshikawa, Noboru; Sato, Motoyasu; Inoue, Akihisa

    2009-01-01

    In the present study, we prepared Ni59.35Nb34.45Sn6.2 metallic glassy alloy powder by an argon gas atomization process. Microwave (MW)-induced heating and sintering was carried out by a single-mode 2.45 GHz MW applicator in the separated magnetic field or electric field using the obtained glassy powders. The structure and thermal stability of the sintered glassy alloy specimens were investigated.

  19. How important are glassy SOA ice nuclei for the formation of cirrus clouds?

    NASA Astrophysics Data System (ADS)

    Zhou, C.; Penner, J. E.; Lin, G.; Liu, X.; Wang, M.

    2014-12-01

    Extremely low ice numbers (i.e. 5 - 100 / L) have been observed in the tropical troposphere layer (TTL) in a variety of field campaigns. Various mechanisms have been proposed to explain these low numbers, including the effect of glassy secondary organic aerosol acting as heterogeneous ice nuclei (IN). In this study, we explored these effects using the CAM5.3 model. SOA fields were provided by an offline version of the University of Michigan-IMPACT model, which has a detailed process-based mechanism that describes aerosol microphysics and SOA formation through both gas phase and multiphase reactions. The transition criterion of SOA to glassy heterogeneous IN follows the parameterization developed by Wang et al. 2012. With this parameterization, glassy SOA IN form mainly when the temperature (T) is lower than 210K. In the default CAM5.3 set-up in which only the fraction of Aitken mode sulfate aerosols with diameter larger than 100nm participate in the ice nucleation (Liu and Penner 2005 parameterization), glassy SOA IN are shown to decrease the ice number (Ni) by suppressing some of the homogeneous freezing at low temperatures thereby leading to an improved representation of the relationship between Ni and T compared to the observations summarized by Kramer et al. 2009. However, when we allow the total number of the Aitken mode sulfate particles to participate in homogeneous freezing, glassy SOA IN have only a small impact on the relationship between Ni and T. If the subgrid updraft velocity is decreased to 0.1 m/s (compared to 0.2 m/s in the default set-up), there is a large decrease of Ni, since homogeneous freezing is more easily suppressed by glassy SOA IN at these updrafts. We also present the effects of glassy SOA IN using an alternative ice nucleation scheme (Barahona and Nenes, 2009).

  20. Glassy dynamics in CuMn thin-film multilayers

    NASA Astrophysics Data System (ADS)

    Zhai, Qiang; Harrison, David C.; Tennant, Daniel; Dalhberg, E. Dan; Kenning, Gregory G.; Orbach, Raymond L.

    2017-02-01

    Thin-film multilayered spin-glass CuMn/Cu structures display glassy dynamics. The freezing temperature Tf was measured for 40 layers of CuMn films of thickness L =4.5 ,9.0 , and 20.0 nm, sandwiched between nonmagnetic Cu layers of thickness ≈60 nm. The Kenning effect, Tf∝lnL , is shown to follow from power-law dynamics where the correlation length grows from nucleation as ξ (t ,T ) =c1a0(t/τ0) c2(T /Tg) , leading to [(Tf/Tg) c2ln(tco/τ0) ] +lnc1=ln(L /a0) . Here, Tg is the bulk spin-glass temperature, c1 and c2 are constants determined from the spin-glass dynamics, tco is the time for the correlation length to grow to the film thickness, τ0 is a characteristic exchange time ≈ℏ /kBTg , and a0 is the average Mn-Mn separation. For t ≥tco , the magnetization dynamics are simple activated, with a single activation energy Δmax(L ) /kBTg=(1 /c2) [ln(L /a0) -lnc1] that does not change with time. Values for all these parameters are found for the three values of L explored in these measurements. We find experimentally Δmax(L ) /kB =907 , 1246, and 1650 K, respectively, for the three CuMn thin-film multilayer thicknesses, consistent with power-law dynamics. We perform a similar analysis based on the activated dynamics of the droplet model and find a much larger spread for Δmax(L ) than found experimentally.

  1. Modeling mechanophore activation within a crosslinked glassy matrix

    NASA Astrophysics Data System (ADS)

    Silberstein, Meredith N.; Min, Kyoungmin; Cremar, Lee D.; Degen, Cassandra M.; Martinez, Todd J.; Aluru, Narayana R.; White, Scott R.; Sottos, Nancy R.

    2013-07-01

    Mechanically induced reactivity is a promising means for designing self-reporting materials. Mechanically sensitive chemical groups called mechanophores are covalently linked into polymers in order to trigger specific chemical reactions upon mechanical loading. These mechanophores can be linked either within the backbone or as crosslinks between backbone segments. Mechanophore response is sensitive to both the matrix properties and placement within the matrix, providing two avenues for material design. A model framework is developed to describe reactivity of mechanophores located as crosslinks in a glassy polymer matrix. Simulations are conducted at the molecular and macromolecular scales in order to develop macroscale constitutive relations. The model is developed specifically for the case of spiropyran (SP) in lightly crosslinked polymethylmethacrylate (PMMA). This optically trackable mechanophore (fluorescent when activated) allows the model to be assessed in terms of observed experimental behavior. The force modified potential energy surface (FMPES) framework is used in conjunction with ab initio steered molecular dynamics (MD) simulations of SP to determine the mechanophore kinetics. MD simulations of the crosslinked PMMA structure under shear deformation are used to determine the relationship between macroscale stress and local force on the crosslinks. A continuum model implemented in a finite element framework synthesizes these mechanochemical relations with the mechanical behavior. The continuum model with parameters taken directly from the FMPES and MD analyses under predicts stress-driven activation relative to experimental data. The continuum model, with the physically motivated modification of force fluctuations, provides an accurate prediction for monotonic loading across three decades of strain rate and creep loading, suggesting that the fundamental physics are captured.

  2. Charge Transport and Glassy Dynamics in Ionic Liquids

    SciTech Connect

    Sangoro, Joshua R; Kremer, Friedrich

    2012-01-01

    Ionic liquids (ILs) exhibit unique features such as low melting points, low vapor pressures, wide liquidus temperature ranges, high thermal stability, high ionic conductivity, and wide electrochemical windows. As a result, they show promise for use in variety of applications: as reaction media, in batteries and supercapacitors, in solar and fuel cells, for electrochemical deposition of metals and semiconductors, for protein extraction and crystallization, and many others. Because of the ease with which they can be supercooled, ionic liquids offer new opportunities to investigate long-standing questions regarding the nature of the dynamic glass transition and its possible link to charge transport. Despite the significant steps achieved from experimental and theoretical studies, no generally accepted quantitative theory of dynamic glass transition to date has been capable of reproducing all the experimentally observed features. In this Account, we discuss recent studies of the interplay between charge transport and glassy dynamics in ionic liquids as investigated by a combination of several experimental techniques including broadband dielectric spectroscopy, pulsed field gradient nuclear magnetic resonance, dynamic mechanical spectroscopy, and differential scanning calorimetry. Based on EinsteinSmoluchowski relations, we use dielectric spectra of ionic liquids to determine diffusion coefficients in quantitative agreement with independent pulsed field gradient nuclear magnetic resonance measurements, but spanning a broader range of more than 10 orders of magnitude. This approach provides a novel opportunity to determine the electrical mobility and effective number density of charge carriers as well as their types of thermal activation from the measured dc conductivity separately. We also unravel the origin of the remarkable universality of charge transport in different classes of glass-forming ionic liquids.

  3. Bio-inspired cofacial Fe porphyrin dimers for efficient electrocatalytic CO2 to CO conversion: Overpotential tuning by substituents at the porphyrin rings

    PubMed Central

    Zahran, Zaki N.; Mohamed, Eman A.; Naruta, Yoshinori

    2016-01-01

    Efficient reduction of CO2 into useful carbon resources particularly CO is an essential reaction for developing alternate sources of fuels and for reducing the greenhouse effect of CO2. The binuclear Ni, Fe−containing carbon monoxide dehydrogenase (CODHs) efficiently catalyzes the reduction of CO2 to CO. The location of Ni and Fe at proper positions allows their cooperation for CO2 to CO conversion through a push−pull mechanism. Bio−inspired from CODHs, we used several cofacial porphyrin dimers with different substituents as suitable ligands for holding two Fe ions with suitable Fe−Fe separation distance to efficiently and selectively promote CO2 to CO conversion with high turnover frequencies, TOFs. The substituents on the porphyrin rings greatly affect the catalysis process. By introducing electron-withdrawing/-donating groups, e.g. electron-withdrawing perfluorophenyl, at all meso positions of the porphyrin rings, the catalysis overpotential, η was minimized by ≈0.3 V compared to that obtained by introducing electron-donating mesityl groups. The Fe porphyrin dimers among reported catalysts are the most efficient ones for CO2 to CO conversion. Control experiments indicate that the high performance of the current CO2 to CO conversion catalysts is due to the presence of binuclear Fe centers at suitable Fe−Fe separation distance. PMID:27087483

  4. Bio-inspired cofacial Fe porphyrin dimers for efficient electrocatalytic CO2 to CO conversion: Overpotential tuning by substituents at the porphyrin rings

    NASA Astrophysics Data System (ADS)

    Zahran, Zaki N.; Mohamed, Eman A.; Naruta, Yoshinori

    2016-04-01

    Efficient reduction of CO2 into useful carbon resources particularly CO is an essential reaction for developing alternate sources of fuels and for reducing the greenhouse effect of CO2. The binuclear Ni, Fe‑containing carbon monoxide dehydrogenase (CODHs) efficiently catalyzes the reduction of CO2 to CO. The location of Ni and Fe at proper positions allows their cooperation for CO2 to CO conversion through a push‑pull mechanism. Bio‑inspired from CODHs, we used several cofacial porphyrin dimers with different substituents as suitable ligands for holding two Fe ions with suitable Fe‑Fe separation distance to efficiently and selectively promote CO2 to CO conversion with high turnover frequencies, TOFs. The substituents on the porphyrin rings greatly affect the catalysis process. By introducing electron-withdrawing/-donating groups, e.g. electron-withdrawing perfluorophenyl, at all meso positions of the porphyrin rings, the catalysis overpotential, η was minimized by ≈0.3 V compared to that obtained by introducing electron-donating mesityl groups. The Fe porphyrin dimers among reported catalysts are the most efficient ones for CO2 to CO conversion. Control experiments indicate that the high performance of the current CO2 to CO conversion catalysts is due to the presence of binuclear Fe centers at suitable Fe‑Fe separation distance.

  5. Porphyrin-beta-oligo-ethynylenephenylene-[60]fullerene triads: synthesis and electrochemical and photophysical characterization of the new porphyrin-oligo-PPE-[60]fullerene systems.

    PubMed

    Lembo, Angelo; Tagliatesta, Pietro; Guldi, Dirk M; Wielopolski, Mateusz; Nuccetelli, Marzia

    2009-03-05

    The synthesis and electrochemical and photophysical studies of new electron donor-acceptor arrays, bearing porphyrins covalently linked to fullerene, are described. In the reported investigation, phenyleneethynylene subunits were chosen as a linking bridge to guarantee a high conjugation degree between the donor (i.e., porphyrin), the molecular bridge (i.e., oligo-phenyleneethynylenes), and the acceptor (i.e., fullerene). To enhance the electronic interactions through the extended pi-system, the molecular bridge has been directly linked to the beta-pyrrole position of the porphyrin ring, generating a new example of donor-bridge-acceptor systems where, for the first time, the meso-phenyl ring of the macrocycle is not used to hold the "bridge" between porphyrin and fullerene moieties. This modification allows altering the chemical and physical properties of the tetrapyrrole ring. Steady-state and time-resolved fluorescence studies together with transient absorption measurements reveal that in nonpolar media (i.e., toluene) transduction of singlet excited-state energy governs the excited-state deactivation, whereas in polar media (i.e., tetrahydrofuran) charge transfer prevails generating a long-lived radical ion pair state. The lifetimes hereof range from 300 to 700 ns. The study also sheds light onto the wirelike behavior of the oligo-phenyleneethynylene bridges, for which a damping factor (beta) of 0.11 +/- 0.05 A(-1) has been determined in the current study.

  6. Porphyrin Based Near Infrared-Absorbing Materials for Organic Photovoltaics

    NASA Astrophysics Data System (ADS)

    Zhong, Qiwen

    photosynthesis. Photosynthesis uses light from the sun to drive a series of chemical reactions. Most natural photosynthetic systems utilize chlorophylls to absorb light energy and carry out photochemical charge separation that stores energy in the form of chemical bonds. The sun produces a broad spectrum of light output that ranges from gamma rays to radio waves. The entire visible range of light (400-700 nm) and some wavelengths in the NIR (700-1000 nm), are highly active in driving photosynthesis. Although the most familiar chlorophyll-containing organisms, such as plants, algae and cyanobacteria, cannot use light longer than 700 nm, anoxygenic bacterium containing bacteriochlorophylls can use the NIR part of the solar spectrum. No organism is known to utilize light of wavelength longer than about 1000 nm for photosynthesis. NIR light has a very low-energy content in each photon, so that large numbers of these low-energy photons would have to be used to drive the chemical reactions of photosynthesis. This is thermodynamically possible but would require a fundamentally different molecular mechanism that is more akin to a heat engine than to photochemistry. Early work on developing light absorbing materials for OPVs was inspired by photosynthesis in which light is absorbed by chlorophyll. Structurally related to chlorophyll is the porphyrin family, which has accordingly drawn much interest as the potential light absorbing component in OPV applications. In this dissertation, the design and detail studies of several porphyrin-based NIR absorbing materials, including pi--extended perylenyl porphryins and pyrazole-containing carbaporphyrins, as well as porphyrin modified single-walled carbon nanotube hybrids, will be presented, dedicating efforts to develop novel and application-oriented materials for efficient utilization of sustainable solar energy.

  7. Sitting-Atop metallo-porphyrin complexes: experimental and theoretical investigations on such elusive species.

    PubMed

    De Luca, Giovanna; Romeo, Andrea; Scolaro, Luigi Monsù; Ricciardi, Giampaolo; Rosa, Angela

    2009-09-07

    The interaction between the sodium cation and two meso-aryl porphyrins (tetraphenylporphyrin, TPP, and tetra(4-methoxyphenyl)porphyrin, TMPP) leads to the formation of new species that have been identified as Sitting-Atop (SAT) complexes, where the metal ion interacts with the N atoms of the porphyrin core without the concomitant deprotonation of the N-H groups. These species have been attained in low polarity solvent through the interaction of the porphyrin free bases with sodium tetrakis[3,5-bis(trifluoromethyl)phenyl]borate (NaTFPB), and investigated in situ through a combination of spectroscopic techniques, such as UV/vis absorption and fluorescence (static and time-resolved), resonance light scattering, FT-IR, and (1)H NMR. All spectroscopic evidence points to the occurrence of a single equilibrium between each parent compound and its SAT complex, ruling out the presence of other metallo-, protonated, or aggregated porphyrins in solution. The 1:1 stoichiometry of the adducts has been determined via continuous variation method (Job's plot), and an estimate of the corresponding association constants in CH(2)Cl(2) at 298 K have been obtained by UV/vis titration (K(eq) = (9 +/- 4) x 10(5) L mol(-1) and (5 +/- 2) x 10(6) L mol(-1) for TPP and TMPP, respectively). Density-functional theory (DFT) calculations on SAT model complexes, [NaTPP(PF(6))] and [NaTMPP(PF(6))], have provided information on the molecular structure of these elusive species and on the nature and strength of the sodium-porphyrin interaction. It is found that the sodium ion is bound to the four nitrogen atoms of the porphyrin core. The involvement of the pyrrolic N atoms results in a modest but not negligible elongation of the N-H bonds, pyramidalization of the hydrogen atoms, and blue shift of the N-H stretching frequencies. Electronic structure and energy decomposition analysis reveal that covalent interactions, mainly consisting of porphyrin to sodium charge transfer interactions, are an

  8. Electrochemistry and catalytic properties for dioxygen reduction using ferrocene-substituted cobalt porphyrins.

    PubMed

    Sun, Bin; Ou, Zhongping; Meng, Deying; Fang, Yuanyuan; Song, Yang; Zhu, Weihua; Solntsev, Pavlo V; Nemykin, Victor N; Kadish, Karl M

    2014-08-18

    Cobalt porphyrins having 0-4 meso-substituted ferrocenyl groups were synthesized and examined as to their electrochemical properties in N,N'-dimethylformamide (DMF) containing 0.1 M tetra-n-butylammonium perchlorate as a supporting electrolyte. The examined compounds are represented as (Fc)n(CH3Ph)(4-n)PorCo, where Por is a dianion of the substituted porphyrin, Fc and CH3Ph represent ferrocenyl and/or p-CH3C6H4 groups linked at the four meso-positions of the macrocycle, and n varies from 0 to 4. Each porphyrin undergoes two reversible one-electron reductions and two to six one-electron oxidations in DMF, with the exact number depending upon the number of Fc groups on the compound. The first electron addition is metal-centered to generate a Co(I) porphyrin. The second is porphyrin ring-centered and leads to formation of a Co(I) π-anion radical. The first oxidation of each Co(II) porphyrin is metal-centered to generate a Co(III) derivative under the given solution conditions. Each ferrocenyl substituent can also be oxidized by one electron, and this occurs at more positive potentials. Each compound was investigated as a catalyst for the electoreduction of dioxygen when adsorbed on a graphite electrode in 1.0 M HClO4. The number of electrons transferred (n) during the catalytic reduction was 2.0 for the three ferrocenyl substituted compounds, consistent with only H2O2 being produced as a product of the reaction. Most monomeric cobalt porphyrins exhibit n values between 2.6 and 3.1 under the same solution conditions, giving a mixture of H2O and H2O2 as a reduction product, although some monomeric porphyrins can give an n value of 4.0. Our results in the current study indicate that appending ferrocene groups directly to the meso positions of a porphyrin macrocycle will increase the selectivity of the oxygen reduction, resulting in formation of only H2O2 as a reaction product. This selectivity of the electrocatalytic oxygen reduction reaction is explained on the basis

  9. Femtosecond fluorescence dynamics of porphyrin in solution and solid films: the effects of aggregation and interfacial electron transfer between porphyrin and TiO2.

    PubMed

    Luo, Liyang; Lo, Chen-Fu; Lin, Ching-Yao; Chang, I-Jy; Diau, Eric Wei-Guang

    2006-01-12

    The excited-state relaxation dynamics of a synthetic porphyrin, ZnCAPEBPP, in solution, coated on a glass substrate as solid films, mixed with PMMA and coated on a glass substrate as solid films, and sensitized on nanocrystalline TiO2 films were investigated by using femtosecond fluorescence up-conversion spectroscopy with excitation in the Soret band, S2. We found that the S2--> S1 electronic relaxation of ZnCAPEBPP in solution and on PMMA films occurs in 910 and 690 fs, respectively, but it becomes extremely rapid, <100 fs, in solid films and TiO2 films due to formation of porphyrin aggregates. When probed in the S1 state of porphyrin, the fluorescence transients of the solid films show a biphasic kinetic feature with the rapid and slow components decaying in 1.9-2.4 and 19-26 ps, respectively. The transients in ZnCAPEBPP/TiO2 films also feature two relaxation processes but they occur on different time scales, 100-300 fs and 0.8-4.1 ps, and contain a small offset. According to the variation of relaxation period as a function of molecular density on a TiO2 surface, we assigned the femtosecond component of the TiO2 films as due to indirect interfacial electron transfer through a phenylethynyl bridge attached to one of four meso positions of the porphyrin ring, and the picosecond component arising from intermolecular energy transfer among porphyrins. The observed variation of aggregate-induced relaxation periods between solid and TiO2 films is due mainly to aggregation of two types: J-type aggregation is dominant in the former case whereas H-type aggregation prevails in the latter case.

  10. Porphyrin and nonporphyrin photosensitizers in oncology: preclinical and clinical advances in photodynamic therapy.

    PubMed

    O'Connor, Aisling E; Gallagher, William M; Byrne, Annette T

    2009-01-01

    Photodynamic therapy (PDT) is now a well-recognized modality for the treatment of cancer. While PDT has developed progressively over the last century, great advances have been observed in the field in recent years. The concept of dual selectivity of PDT agents is now widely accepted due to the relative specificity and selectivity of PDT along with the absence of harmful side effects often encountered with chemotherapy or radiotherapy. Traditionally, porphyrin-based photosensitizers have dominated the PDT field but these first generation photosensitizers have several disadvantages, with poor light absorption and cutaneous photosensitivity being the predominant side effects. As a result, the requirement for new photosensitizers, including second generation porphyrins and porphyrin derivatives as well as third generation photosensitizers has arisen, with the aim of alleviating the problems encountered with first generation porphyrins and improving the efficacy of PDT. The investigation of nonporphyrin photosensitizers for the development of novel PDT agents has been considerably less extensive than porphyrin-based compounds; however, structural modification of nonporphyrin photosensitizers has allowed for manipulation of the photochemotherapeutic properties. The aim of this review is to provide an insight into PDT photosensitizers clinically approved for application in oncology, as well as those which show significant potential in ongoing preclinical studies.

  11. Conformational effects of peripheral substituents and axial ligands in sterically crowded porphyrins

    SciTech Connect

    Nurco, D.J.; Smith, K.M.; Fajer, J.

    1997-12-31

    Crystallographic results for peripherally substituted porphyrins illustrate effects of steric crowding, axial ligation and {pi}-{pi} interactions on the structures of metalloporphyrins that begin to resemble the architectures found for porphyrinic prosthetic groups and chromophores in vivo. (1) Metalloporphyrins with multiple peripheral substituents can adopt planar, saddled, ruffled or {open_quotes}wavy{close_quotes} conformations that persist upon axial ligation of the metal. (2) In porphyrins with substituents at all peripheral positions, the substituents form pockets that force the axial ligands to align in specific orientations relative to each other and to the axes defined by the porphyrin estrogens. (3) The enforced alignment of the axial ligands caused by the substituent pocket prevents aromatic ligands from rotating around the coordination axis with intriguing consequences: the axial ligands can be forced to tip off axis because of steric crowding by adjacent molecules in the crystal lattice. (4) In porphyrins with meso substituents only, the axial ligands are free to rotate but {pi}-{pi} interactions and collacial stacking between adjacent molecules in the crystal also induce off-axis ligand tilts.

  12. Photodynamic inactivation of recombinant bioluminescent Escherichia coli by cationic porphyrins under artificial and solar irradiation.

    PubMed

    Alves, Eliana; Carvalho, Carla M B; Tomé, João P C; Faustino, Maria A F; Neves, Maria G P M S; Tomé, Augusto C; Cavaleiro, José A S; Cunha, Angela; Mendo, Sónia; Almeida, Adelaide

    2008-11-01

    A faster and simpler method to monitor the photoinactivation process of Escherichia coli involving the use of recombinant bioluminescent bacteria is described here. Escherichia coli cells were transformed with luxCDABE genes from the marine bioluminescent bacterium Vibrio fischeri and the recombinant bioluminescent indicator strain was used to assess, in real time, the effect of three cationic meso-substituted porphyrin derivatives on their metabolic activity, under artificial (40 W m(-2)) and solar irradiation (approximately 620 W m(-2)). The photoinactivation of bioluminescent E. coli is effective (>4 log bioluminescence decrease) with the three porphyrins used, the tricationic porphyrin Tri-Py+-Me-PF being the most efficient compound. The photoinactivation process is efficient both with solar and artificial light, for the three porphyrins tested. The results show that bioluminescence analysis is an efficient and sensitive approach being, in addition, more affordable, faster, cheaper and much less laborious than conventional methods. This approach can be used as a screening method for bacterial photoinactivation studies in vitro and also for the monitoring of the efficiency of novel photosensitizer molecules. As far as we know, this is the first study involving the use of bioluminescent bacteria to monitor the antibacterial activity of porphyrins under environmental conditions.

  13. Host-guest complexation of [60]fullerenes and porphyrins enabled by "click chemistry".

    PubMed

    Ho, Khanh-Hy Le; Hijazi, Ismail; Rivier, Lucie; Gautier, Christelle; Jousselme, Bruno; de Miguel, Gustavo; Romero-Nieto, Carlos; Guldi, Dirk M; Heinrich, Benoit; Donnio, Bertrand; Campidelli, Stéphane

    2013-08-19

    Herein the synthesis, characterization, and organization of a first-generation dendritic fulleropyrrolidine bearing two pending porphyrins are reported. Both the dendron and the fullerene derivatives were synthesized by Cu(I) -catalyzed alkyne-azide cycloaddition (CuAAC). The electron-donor-acceptor conjugate possesses a shape that allows the formation of supramolecular complexes by encapsulation of C60 within the jaws of the two porphyrins of another molecule. The interactions between the two photoactive units (i.e., C60 and Zn-porphyrin) were confirmed by cyclic voltammetry as well as by steady-state and time-resolved spectroscopy. For example, a shift of about 85 mV was found for the first reduction of C60 in the electron-donor-acceptor conjugate compared with the parent molecules, which indicates that C60 is included in the jaws of the porphyrin. The fulleropyrrolidine compound exhibits a rich polymorphism, which was corroborated by AFM and SEM. In particular, it was found to form supramolecular fibrils when deposited on substrates. The morphology of the fibrils suggests that they are formed by several rows of fullerene-porphyrin complexes.

  14. Vacuum-Deposited Porphyrin Protective Films on Graphite: Electrochemical Atomic Force Microscopy Investigation during Anion Intercalation.

    PubMed

    Yivlialin, Rossella; Bussetti, Gianlorenzo; Penconi, Marta; Bossi, Alberto; Ciccacci, Franco; Finazzi, Marco; Duò, Lamberto

    2017-02-01

    The development of graphene products promotes a renewed interest toward the use of graphite in addition to the historical one for its proven viability as battery electrode. However, when exposed to harsh conditions, the graphite surface ages in ways that still need to be fully characterized. In applications to batteries, to optimize the electrode performances in acid solutions, different surface functionalizations have been studied. Among them, aromatic molecules have been recently proposed. In this communication, we report on the protective effect exerted by a physical-vapor-deposited porphyrin layer. Metal-free tetra-phenyl-porphyrins were deposited on a highly oriented pyrolytic graphite crystal to study the modifications that occur during anion intercalation in graphite. The graphite electrode was plunged in an electrolyte solution of 1 M sulfuric acid and subjected to cyclic voltammetry. The results indicate that blister formation, the characteristic swelling of graphite surface induced by anion intercalation, is significantly perturbed by the porphyrin overlayer; the process is inhibited in those areas where the protective porphyrin film is present. We ascribe the inhibition of the anion intercalation to the protective porphyrin wetting layer.

  15. A Perspective on the Trends and Challenges Facing Porphyrin-Based Anti-Microbial Materials.

    PubMed

    Jiang, Lu; Gan, Ching Ruey Raymond; Gao, Jian; Loh, Xian Jun

    2016-07-01

    The emergence of multidrug resistant bacterium threatens to unravel global healthcare systems, built up over centuries of medical research and development. Current antibiotics have little resistance against this onslaught as bacterium strains can quickly evolve effective defense mechanisms. Fortunately, alternative therapies exist and, at the forefront of research lays the photodynamic inhibition approach mediated by porphyrin based photosensitizers. This review will focus on the development of various porphyrins compounds and their incorporation as small molecules, into polymers, fibers and thin films as practical therapeutic agents, utilizing photodynamic therapy to inhibit a wide spectrum of bacterium. The use of photodynamic therapy of these porphyrin molecules are discussed and evaluated according to their electronic and bulk material effect on different bacterium strains. This review also provides an insight into the general direction and challenges facing porphyrins and derivatives as full-fledged therapeutic agents and what needs to be further done in order to be bestowed their rightful and equal status in modern medicine, similar to the very first antibiotic; penicillin itself. It is hoped that, with this perspective, new paradigms and strategies in the application of porphyrins and derivatives will progressively flourish and lead to advances against disease.

  16. Co-Fe-B-Si-Nb bulk glassy alloys with superhigh strength and extremely low magnetostriction

    SciTech Connect

    Chang Chuntao; Shen Baolong; Inoue, Akihisa

    2006-01-02

    Co-based bulk glassy alloys with diameters up to 4 mm were formed in a [(Co{sub 1-x}Fe{sub x}){sub 0.75}B{sub 0.2}Si{sub 0.05}]{sub 96}Nb{sub 4} system. The bulk glassy alloys exhibit a superhigh fracture strength of 3980-4170 MPa and Young's modulus of 190-210 GPa. The bulk glassy alloys also exhibit excellent soft-magnetic properties, i.e., high saturation magnetization of 0.71-0.97 T, low coercive force of 0.7-1.8 A/m, high permeability of 1.48-3.25x10{sup 4}, and extremely low saturation magnetostriction of 0.55-5.76x10{sup -6}. The first successful synthesis of the Co-Fe-B-Si-based bulk glassy alloys exhibiting superhigh fracture strength and excellent soft-magnetic properties with extremely low magnetostriction is encouraging for future development of Co-based bulk glassy alloys as new engineering and functional materials.

  17. Understanding the Physical Aging Behavior of Glassy Polystyrene Layers in Close Contact with Rubbery Domains

    NASA Astrophysics Data System (ADS)

    Roth, Connie; Rauscher, Phil; Pye, Justin; Baglay, Roman

    2014-03-01

    Recent advances in synthesis strategies and processing methods have led to new nanostructured polymer blend and block-copolymer materials containing domain sizes less than 100 nm with glassy and rubbery domains in close proximity. Given the outsized role interfacial perturbations have played in causing large changes in the glass transition temperature Tg and physical aging of ultrathin single-layer films, we are interested in studying how the presence of glassy-rubbery interfaces between neighboring polymer domains may alter the local stability and physical aging of confined glassy layers. Using a polystyrene (PS) / poly(n-butyl methacrylate) (PnBMA) weakly immiscible system with 7 nm interfacial width, we demonstrate how ellipsometry can be used to isolate the physical aging rate of thin PS layers atop rubbery PnBMA layers. Despite a 25-30 K reduction in the average Tg of 84 nm thick PS layers atop PnBMA as measured by fluorescence, we observe no change in the PS aging rate relative to bulk. These results are in contrast with previous works on single-layer polymer films that have found the local aging rate to often be correlated with local Tg changes. This appears not to be the case for glassy PS layers atop rubbery PnBMA suggesting some additional factor is affecting the structural relaxation occurring near the glassy-rubbery interface.

  18. Mechanisms of crazing in glassy polymers revealed by molecular dynamics simulations

    NASA Astrophysics Data System (ADS)

    Mahajan, Dhiraj K.; Hartmaier, Alexander

    2012-08-01

    Mechanisms leading to initiation of crazing type failure in a glassy polymer are not clearly understood. This is mainly due to the difficulty in characterizing the stress state and polymer configuration sufficiently locally at the craze initiation site. Using molecular dynamics simulations, we have now been able to access this information and have shown that the local heterogeneous deformation leads to craze initiation in glassy polymers. We found that zones of high plastic activity are constrained by their neighborhood and become unstable, initiating crazing from these sites. Furthermore, based on the constant flow stresses observed in the unstable zones, we conclude that microcavitation is the essential local deformation mode to trigger crazing in glassy polymers. Our results demonstrate the basic difference in the local deformation mode as well as the conditions that lead to either shear-yielding or crazing type failures in glassy polymers. We anticipate our paper to help in devising a new criterion for craze initiation that not only considers the stress state, but also considers local deformation heterogeneities that form the necessary condition for crazing in glassy polymers.

  19. Design and characterization of alkoxy-wrapped push-pull porphyrins for dye-sensitized solar cells.

    PubMed

    Ripolles-Sanchis, Teresa; Guo, Bo-Cheng; Wu, Hui-Ping; Pan, Tsung-Yu; Lee, Hsuan-Wei; Raga, Sonia R; Fabregat-Santiago, Francisco; Bisquert, Juan; Yeh, Chen-Yu; Diau, Eric Wei-Guang

    2012-05-07

    Three alkoxy-wrapped push-pull porphyrins were designed and synthesized for dye-sensitized solar cell (DSSC) applications. Spectral, electrochemical, photovoltaic and electrochemical impedance spectroscopy properties of these porphyrin sensitizers were well investigated to provide evidence for the molecular design.

  20. Porphyrins from Messel oil shale (Eocene, Germany): Structure elucidation, geochemical and biological significance, and distribution as a function of depth

    NASA Astrophysics Data System (ADS)

    Ocampo, Rubén; Bauder, Claude; Callot, Henry J.; Albrecht, Pierre

    1992-02-01

    The extraction and isolation procedures of twenty nickel porphyrins (seven alkylporphyrins, thirteen carboxylic acids) from lacustrine Messel shale (Eocene, Germany), as well as the unequivocal structural assignments (obtained using 200 and 400 MHz nuclear magnetic resonance (NMR), nuclear Overhauser effect, mass spectrometry and total or partial synthesis of six reference compounds) are described. Ten porphyrins could be specifically correlated with biological precursors: algal chlorophyll c (4), bacteriochlorophylls d (3) and heme (3), while the remaining ones may arise from several chlorophylls. The structures of these fossil pigments mostly confirm the classical "Treibs scheme," including the origin of some porphyrins from nonchlorophyll sources. They also show that, even in a very immature sediment, deep modifications occur, including, in particular, extensive degradation of chlorophyll E ring. The composition of the porphyrin fractions of Messel oil shale was also studied as a function of depth. A porphyrin acids/alkylporphyrins ratio varying from 0.35 to 24.8 demonstrated that the apparent homogeneity of the shale is not reflected on the molecular scale. This was confirmed when the abundance of the twenty individual porphyrins of known structure was measured along the core. Significant correlations between individual porphyrins were found: fossils of bacteriochlorophylls d, homolog pairs of porphyrins (3-H/3-ethyl), etc.

  1. Construction of a zinc porphyrin-fullerene-derivative based nonenzymatic electrochemical sensor for sensitive sensing of hydrogen peroxide and nitrite.

    PubMed

    Wu, Hai; Fan, Suhua; Jin, Xiaoyan; Zhang, Hong; Chen, Hong; Dai, Zong; Zou, Xiaoyong

    2014-07-01

    Enzymatic sensors possess high selectivity but suffer from some limitations such as instability, complicated modified procedure, and critical environmental factors, which stimulate the development of more sensitive and stable nonenzymatic electrochemical sensors. Herein, a novel nonenzymatic electrochemical sensor is proposed based on a new zinc porphyrin-fullerene (C60) derivative (ZnP-C60), which was designed and synthesized according to the conformational calculations and the electronic structures of two typical ZnP-C60 derivatives of para-ZnP-C60 (ZnP(p)-C60) and ortho-ZnP-C60 (ZnP(o)-C60). The two derivatives were first investigated by density functional theory (DFT) and ZnP(p)-C60 with a bent conformation was verified to possess a smaller energy gap and better electron-transport ability. Then ZnP(p)-C60 was entrapped in tetraoctylammonium bromide (TOAB) film and modified on glassy carbon electrode (TOAB/ZnP(p)-C60/GCE). The TOAB/ZnP(p)-C60/GCE showed four well-defined quasi-reversible redox couples with extremely fast direct electron transfer and excellent nonenzymatic sensing ability. The electrocatalytic reduction of H2O2 showed a wide linear range from 0.035 to 3.40 mM, with a high sensitivity of 215.6 μA mM(-1) and a limit of detection (LOD) as low as 0.81 μM. The electrocatalytic oxidation of nitrite showed a linear range from 2.0 μM to 0.164 mM, with a sensitivity of 249.9 μA mM(-1) and a LOD down to 1.44 μM. Moreover, the TOAB/ZnP(p)-C60/GCE showed excellent stability and reproducibility, and good testing recoveries for analysis of the nitrite levels of river water and rainwater. The ZnP(p)-C60 can be used as a novel material for the fabrication of nonenzymatic electrochemical sensors.

  2. The photophysical properties of expanded porphyrins: relationships between aromaticity, molecular geometry and non-linear optical properties.

    PubMed

    Lim, Jong Min; Yoon, Zin Seok; Shin, Jae-Yoon; Kim, Kil Suk; Yoon, Min-Chul; Kim, Dongho

    2009-01-21

    Porphyrins, which consist of four pyrrolic subunits, are a ubiquitous class of naturally occurring compound with versatile photophysical properties. As an extension of the basic structure of the porphyrin macrocycle, there have been a multitude of approaches to synthesize expanded porphyrins with more than four pyrrole rings, leading to the modification of the macrocyclic ring size, planarity, number of pi-electrons and aromaticity. However, the relationship between the photophysical properties and the structures of expanded porphyrins has not been systematically investigated. The main purpose of this article is to describe the structure-property relationships of a variety of expanded porphyrins based on experimental and theoretical results, which include steady-state and time-resolved spectroscopic characterizations, non-linear absorption ability and nucleus-independent chemical shift calculations.

  3. Evidence for porphyrins bound, via ester bonds, to the Messel oil shale kerogen by selective chemical degradation experiments

    NASA Astrophysics Data System (ADS)

    Huseby, B.; Ocampo, R.

    1997-09-01

    High amounts of nickel mono- and di-acid porphyrins were released from Messel oil shale kerogen (Eocene, Germany) by selective chemical degradation (acid and base hydrolysis). The released porphyrin fractions were quantified (UV-vis) and their constituents isolated and characterized at the molecular level (UV-vis, MS, NMR). The mono-acid porphyrin fraction released contained four compounds of similar abundance which arise from an obvious chlorophyll or bacteriochlorophyll precursor. The di-acid porphyrin fraction was, however, dominated by far by one compound, mesoporphyrin IX, which must have originated from heme-like precursors (heme, cytochromes, etc.). These results show unambigously that the released mono- and di-acid porphyrins were linked to the macromolecular kerogen network via ester bonds and suggest that precursor heme-like pigments could be selectively and/or more readily incorporated into the macromolecular kerogen network than precursor chlorophylls and bacteriochlorophylls.

  4. Highly Efficient Cooperative Catalysis by Co III (Porphyrin) Pairs in Interpenetrating Metal-Organic Frameworks

    SciTech Connect

    Lin, Zekai; Zhang, Zhi-Ming; Chen, Yu-Sheng; Lin, Wenbin

    2016-12-02

    A series of porous twofold interpenetrated In-CoIII(porphyrin) metal–organic frameworks (MOFs) were constructed by in situ metalation of porphyrin bridging ligands and used as efficient cooperative catalysts for the hydration of terminal alkynes. The twofold interpenetrating structure brings adjacent CoIII(porphyrins) in the two networks parallel to each other with a distance of about 8.8 Å, an ideal distance for the simultaneous activation of both substrates in alkyne hydration reactions. As a result, the In-CoIII(porphyrin) MOFs exhibit much higher (up to 38 times) catalytic activity than either homogeneous catalysts or MOF controls with isolated CoIII(porphyrin) centers, thus highlighting the potential application of MOFs in cooperative catalysis.

  5. Conservation of the conformation of the porphyrin macrocycle in hemoproteins.

    PubMed Central

    Jentzen, W; Ma, J G; Shelnutt, J A

    1998-01-01

    The out-of-plane distortions of porphyrins in hemoproteins are characterized by displacements along the lowest-frequency out-of-plane normal coordinates of the D4h-symmetric macrocycle. X-ray crystal structures are analyzed using a computational procedure developed for determining these orthogonal displacements. The x-ray crystal structures of the heme groups are described within experimental error, using the set composed of only the lowest frequency normal coordinate of each out-of-plane symmetry type. That is, the distortion is accurately simulated by a linear combination of these orthonormal deformations, which include saddling (B2u), ruffling (B1u), doming (A2u), waving (Eg), and propellering (A1u). For example, orthonormal structural decomposition of the hemes in deoxymyoglobins reveals a predominantly dom heme deformation combined with a smaller wav(y) deformation. Generally, the heme conformation is remarkably similar for proteins from different species. For cytochromes c, the conformation is conserved as long as the amino acids between the cysteine linkages to the heme are homologous. Differences occur if this short segment varies in the number or type of residues, suggesting that this small segment causes the nonplanar distortion. Some noncovalently linked hemes like those in the peroxidases also have highly conserved characteristic distortions. Conservation occurs even for some proteins with a large natural variation in the amino acid sequence. PMID:9533688

  6. The coordination and atom transfer chemistry of titanium porphyrin complexes

    SciTech Connect

    Hays, James Allen

    1993-11-05

    Preparation, characterization, and reactivity of (η2- alkyne)(meso-tetratolylpoprphrinato)titanium(II) complexes are described, along with inetermetal oxygen atom transfer reactions involving Ti(IV) and Ti(III) porphyrin complexes. The η2- alkyne complexes are prepared by reaction of (TTP)TiCl2 with LiAlH4 in presence of alkyne. Structure of (OEP)Ti(η2-Ph-C≡C-Ph) (OEP=octaethylporphryin) was determined by XRD. The compounds undergo simple substitution to displace the alkyne and produce doubly substituted complexes. Structure of (TTP)Ti(4-picoline)2 was also determined by XRD. Reaction of (TTP)Ti=O with (OEP)Ti-Cl yields intermetal O/Cl exchange, which is a one-electron redox process mediated by O atom transfer. Also a zero-electron redox process mediated by atom transfer is observed when (TTP)TiCl2 is reacted with (OEP)Ti=O.

  7. Formation of Au and tetrapyridyl porphyrin complexes in superfluid helium.

    PubMed

    Feng, Cheng; Latimer, Elspeth; Spence, Daniel; Al Hindawi, Aula M A A; Bullen, Shem; Boatwright, Adrian; Ellis, Andrew M; Yang, Shengfu

    2015-07-14

    Binary clusters containing a large organic molecule and metal atoms have been formed by the co-addition of 5,10,15,20-tetra(4-pyridyl)porphyrin (H2TPyP) molecules and gold atoms to superfluid helium nanodroplets, and the resulting complexes were then investigated by electron impact mass spectrometry. In addition to the parent ion H2TPyP yields fragments mainly from pyrrole, pyridine and methylpyridine ions because of the stability of their ring structures. When Au is co-added to the droplets the mass spectra are dominated by H2TPyP fragment ions with one or more Au atoms attached. We also show that by switching the order in which Au and H2TPyP are added to the helium droplets, different types of H2TPyP-Au complexes are clearly evident from the mass spectra. This study suggests a new route for the control over the growth of metal-organic compounds inside superfluid helium nanodroplets.

  8. Excitation energy transfer in covalently bonded porphyrin heterodimers

    NASA Astrophysics Data System (ADS)

    Paschenko, V. Z.; Konovalova, N. V.; Bagdashkin, A. L.; Gorokhov, V. V.; Tusov, V. B.; Yuzhakov, V. I.

    2012-04-01

    We describe the photophysical properties of heterodimers that are formed by the free base 2-(2-carboxyvinyl)-5,10,15,20-tetraphenylporphyrin and the zinc complex of 5-( p-aminophenyl)-10,15,20-triphenylporphyrin and that are covalently bonded by the amide link. These dimers differ in the configuration of the double bond in the spacer group. We determine fluorescence quantum yields of heterodimers and their porphyrin components. The energy transfer rate constants have been estimated from the measured fluorescence lifetimes and fluorescence excitation spectra and, also, they have been calculated from the steady-state absorption and fluorescence spectra according to the Förster theory. We have found that the efficiency of the intramolecular energy transfer in heterodimers is 0.97-0.99, and the energy migration rate constants have been found to be (1.82-4.49) × 1010 s-1. The results of our investigation show that synthesized heterodimers can be used as efficient light-harvesting elements in solar energy conversion devices.

  9. Photoinitiated destruction of composite porphyrin-protein polymersomes.

    PubMed

    Robbins, Gregory P; Jimbo, Masaya; Swift, Joe; Therien, Michael J; Hammer, Daniel A; Dmochowski, Ivan J

    2009-03-25

    Bilayer vesicles assembled from amphiphilic diblock copolymers (polymersomes) adopt asymmetric structures when loaded with moderate concentrations (>or=1.5 mg/mL) of horse spleen ferritin (HSF) or its iron-free variant (HSAF). Incorporation of both ferritin and a zinc porphyrin dimer (PZn(2)) generates photoresponsive vesicles: irradiation with focused light of near-UV to near-IR wavelengths induces polymersome deformation and destruction on the minute time scale. To investigate this phenomenon, polymersomes were loaded with dye-labeled ferritin and PZn(2). Confocal microscopy identified BODIPY-FL-labeled ferritin at the membrane, whereas Cy3-labeled ferritin was found both at the membrane and throughout the aqueous core. Fluorescence recovery after photobleaching (FRAP) experiments confirmed that Cy3- and BODIPY-FL-labeled ferritin and PZn(2) exhibited slow diffusion at the membrane, consistent with membrane association. Furthermore, micropipette aspiration experiments revealed increased elastic moduli and altered bending rigidity in vesicles incorporating HSAF. Finally, a small molecule (biocytin) was encapsulated within the ferritin-PZn(2) vesicles and released upon exposure to light. These data indicate synergy between ferritin, whose membrane association lowers the barrier to deformation, and PZn(2), which embeds in the membrane, harvests light energy and produces local heating that may lead to membrane budding. This appears to be a general protein-polymer membrane phenomenon, as replacement of ferritin with bovine serum albumin or equine skeletal myoglobin resulted in vesicles with similar asymmetric morphology and photosensitivity.

  10. Magnetic circular dichroism of porphyrin lanthanide M3+ complexes.

    PubMed

    Andrushchenko, Valery; Padula, Daniele; Zhivotova, Elena; Yamamoto, Shigeki; Bouř, Petr

    2014-10-01

    Lanthanide complexes exhibit interesting spectroscopic properties yielding many applications as imaging probes, natural chirality amplifiers, and therapeutic agents. However, many properties are not fully understood yet. Therefore, we applied magnetic circular dichroism (MCD) spectroscopy, which provides enhanced information about the underlying electronic structure to a series of lanthanide compounds. The metals in the M(3+) state included Y, La, Eu, Tb, Dy, Ho, Er, Tm, Yb, and Lu; the spectra were collected for selected tetraphenylporphin (TPP) and octaethylporphin (OEP) complexes in chloroform. While the MCD and UV-VIS absorption spectra were dominated by the porphyrin signal, metal binding significantly modulated them. MCD spectroscopy was found to be better suited to discriminate between various species than absorption spectroscopy alone. The main features and trends in the lanthanide series observed in MCD and absorption spectra of the complexes could be interpreted at the Density Functional Theory (DFT) level, with effective core potentials on metal nuclei. The sum over state (SOS) method was used for simulation of the MCD intensities. The combination of the spectroscopy and quantum-chemical computations is important for understanding the interactions of the metals with the organic compounds.

  11. Sphingomyelin Liposomes Containing Porphyrin-phospholipid for Irinotecan Chemophototherapy

    PubMed Central

    Carter, Kevin A; Luo, Dandan; Razi, Aida; Geng, Jumin; Shao, Shuai; Ortega, Joaquin; Lovell, Jonathan F

    2016-01-01

    Porphyrin-phospholipid (PoP) liposomes can entrap anti-cancer agents and release them in response to near infrared (NIR) light. Doxorubicin, when remotely loaded via an ammonium sulfate gradient at a high drug-to-lipid ratio, formed elongated crystals that altered liposome morphology and could not be loaded into liposomes with higher PoP content. On the other hand, irinotecan could also be remotely loaded but did not form large crystals and did not induce liposome elongation. The loading, stability, and NIR light-triggered release of irinotecan in PoP liposomes was altered by the types of lipids used and the presence of PEGylation. Sphingomyelin, which has been explored previously for liposomal irinotecan, was found to produce liposomes with relatively improved serum stability and rapid NIR light-triggered drug release. PoP liposomes composed from sphingomyelin, cholesterol and 2 molar percent PoP rapidly released irinotecan in vivo in response to NIR irradiation as monitored by intravital microscopy and also induced effective tumor eradication in mice bearing MIA Paca-2 subcutaneous tumor xenografts. PMID:27877238

  12. Effect of entanglements on mechanical properties of glassy polymers

    NASA Astrophysics Data System (ADS)

    Hoy, Robert Scott

    Glass forming polymers are of great industrial importance and scientific interest because of their unique mechanical properties, which arise from the connectivity and random-walk-like structure of the constituent chains. In this thesis I study the relation of entanglements to the mechanical properties of model polymer glasses and brushes using molecular dynamics simulations. We perform extensive studies of glassy strain hardening, which stabilizes polymers against strain localization and fracture. Fundamental inconsistencies in existing entropic models of strain hardening imply that our understanding of its microscopic origins is far from complete. The dependence of stress on strain and entanglement density is consistent with experiment and entropic models. However, many of the assumptions of these models are totally inconsistent with our simulation results. The dependence on temperature, rate and interaction strength can be understood as reflecting changes in the plastic flow stress rather than a network entropy. A substantial energetic contribution to the stress rises rapidly as segments between entanglements are pulled taut. The thermal component of stress is less sensitive to entanglements, mostly irreversible, and directly related to the rate of local plastic arrangements. The deformation of the entanglement network is not affine to the macroscopic stretch. Entangled and unentangled chains show the same strain hardening when plotted against the microscopic chain orientation rather than the macroscopic strain. The entropic back stress responsible for shape recovery arises from chain orientation rather than entanglement. We also present some other results unrelated to strain hardening. We analyze the entanglement of polymer brushes embedded in long-chain melts and in implicit good and theta solvents. The melt-embedded brushes are more self-entangled than those in the solvents. The degree of self-entanglement of the brushes in the solvents follows a simple

  13. Temporal disconnectivity of the energy landscape in glassy systems

    NASA Astrophysics Data System (ADS)

    Lempesis, Nikolaos; Boulougouris, Georgios C.; Theodorou, Doros N.

    2013-03-01

    An alternative graphical representation of the potential energy landscape (PEL) has been developed and applied to a binary Lennard-Jones glassy system, providing insight into the unique topology of the system's potential energy hypersurface. With the help of this representation one is able to monitor the different explored basins of the PEL, as well as how - and mainly when - subsets of basins communicate with each other via transitions in such a way that details of the prior temporal history have been erased, i.e., local equilibration between the basins in each subset has been achieved. In this way, apart from detailed information about the structure of the PEL, the system's temporal evolution on the PEL is described. In order to gather all necessary information about the identities of two or more basins that are connected with each other, we consider two different approaches. The first one is based on consideration of the time needed for two basins to mutually equilibrate their populations according to the transition rate between them, in the absence of any effect induced by the rest of the landscape. The second approach is based on an analytical solution of the master equation that explicitly takes into account the entire explored landscape. It is shown that both approaches lead to the same result concerning the topology of the PEL and dynamical evolution on it. Moreover, a "temporal disconnectivity graph" is introduced to represent a lumped system stemming from the initial one. The lumped system is obtained via a specially designed algorithm [N. Lempesis, D. G. Tsalikis, G. C. Boulougouris, and D. N. Theodorou, J. Chem. Phys. 135, 204507 (2011), 10.1063/1.3663207]. The temporal disconnectivity graph provides useful information about both the lumped and the initial systems, including the definition of "metabasins" as collections of basins that communicate with each other via transitions that are fast relative to the observation time. Finally, the two examined

  14. Direct Imaging of Dynamic Glassy Behavior in a Strained Manganite Film

    NASA Astrophysics Data System (ADS)

    Kundhikanjana, Worasom; Sheng, Zhigao; Yang, Yongliang; Lai, Keji; Ma, Eric Yue; Cui, Yong-Tao; Kelly, Michael A.; Nakamura, Masao; Kawasaki, Masashi; Tokura, Yoshinori; Tang, Qiaochu; Zhang, Kun; Li, Xinxin; Shen, Zhi-Xun

    2015-12-01

    Complex many-body interaction in perovskite manganites gives rise to a strong competition between ferromagnetic metallic and charge-ordered phases with nanoscale electronic inhomogeneity and glassy behaviors. Investigating this glassy state requires high-resolution imaging techniques with sufficient sensitivity and stability. Here, we present the results of a near-field microwave microscope imaging on the strain-driven glassy state in a manganite film. The high contrast between the two electrically distinct phases allows direct visualization of the phase separation. The low-temperature microscopic configurations differ upon cooling with different thermal histories. At sufficiently high temperatures, we observe switching between the two phases in either direction. The dynamic switching, however, stops below the glass transition temperature. Compared with the magnetization data, the phase separation was microscopically frozen, while spin relaxation was found in a short period of time.

  15. Fate of a genetically modified bacterium in foregut of glassy-winged sharpshooter (Hemiptera: Cicadellidae).

    PubMed

    Ramirez, José L; Perring, Thomas M; Miller, Thomas A

    2008-10-01

    Symbiotic control is a new strategy being investigated to prevent the spread of insect-transmitted pathogens by reducing vector competence. We are developing this strategy to reduce the spread of Xylella fastidiosa by Homalodisca vitripennis (Germar) [formerly Homalodisca coagulata (Say)] (Hemiptera: Cicadellidae), the glassy-winged sharpshooter. In this study, the fate of a transformed symbiotic bacterium, Alcaligenes xylosoxidans variety denitriicans (S1Axd), in the foregut of glassy-winged sharpshooter when fed on citrus (Citrus spp.) and grape (Vitris spp.) was assessed. TaqMan-based quantitative real-time polymerase chain reaction (PCR) was used to detect and quantify bacterial cells remaining in the foregut at 0, 2, 4, 9, and 12 d after acquisition. S1Axd titer dropped rapidly by 2 d after acquisition, but in spite of this, at end of the 12-d experimental period, 45 and 38% of the glassy-winged sharpshooters retained the transformed bacteria, when fed on grape and citrus, respectively.

  16. Broadband terahertz time-domain spectroscopy : crystalline and glassy drug materials

    NASA Astrophysics Data System (ADS)

    Kojima, Seiji; Shibata, Tomohiko; Igawa, Hikaru; Mori, Tatsuya

    2014-03-01

    Low-energy IR active modes of glassy and crystalline drug materials were studied by the broadband Terahertz Time Domain Spectroscopy (THz-TDS) in the frequency range from 0.5 to 6.5 THz using a Cherenkov type THz generator. In order to determine the real and imaginary parts of complex dielectric constant, all samples were measured by the transmission using a pure pellet without mixing polyethylene. For glassy indomethacine, the broadband THz spectrum of real part of dielectric constant shows step-wise decrease with the increase of frequency, while the imaginary part shows a broad peak at about 3 THz reflecting quenched glassy disordered structure. The observed spectra of crystalline racemic ketoprofen show the noncoincidence of peak frequencies between low-frequency Raman scattering and THz absorbance spectra. It can be attributed to the fact that the mutual exclusion principle between Raman and IR activities holds below 6 THz.

  17. Direct Imaging of Dynamic Glassy Behavior in a Strained Manganite Film.

    PubMed

    Kundhikanjana, Worasom; Sheng, Zhigao; Yang, Yongliang; Lai, Keji; Ma, Eric Yue; Cui, Yong-Tao; Kelly, Michael A; Nakamura, Masao; Kawasaki, Masashi; Tokura, Yoshinori; Tang, Qiaochu; Zhang, Kun; Li, Xinxin; Shen, Zhi-Xun

    2015-12-31

    Complex many-body interaction in perovskite manganites gives rise to a strong competition between ferromagnetic metallic and charge-ordered phases with nanoscale electronic inhomogeneity and glassy behaviors. Investigating this glassy state requires high-resolution imaging techniques with sufficient sensitivity and stability. Here, we present the results of a near-field microwave microscope imaging on the strain-driven glassy state in a manganite film. The high contrast between the two electrically distinct phases allows direct visualization of the phase separation. The low-temperature microscopic configurations differ upon cooling with different thermal histories. At sufficiently high temperatures, we observe switching between the two phases in either direction. The dynamic switching, however, stops below the glass transition temperature. Compared with the magnetization data, the phase separation was microscopically frozen, while spin relaxation was found in a short period of time.

  18. Molecular modeling of mechanical stresses on proteins in glassy matrices: Formalism

    NASA Astrophysics Data System (ADS)

    Hatch, Harold W.; Debenedetti, Pablo G.

    2012-07-01

    We present an expression for the calculation of microscopic stresses in molecular simulation, which is compatible with the use of electrostatic lattice sums such as the Ewald sum, with the presence of many-body interactions, and which allows local stresses to be calculated on surfaces of arbitrarily complex shape. The ultimate goal of this work is to investigate microscopic stresses on proteins in glassy matrices, which are used in the pharmaceutical industry for the long-term storage and stabilization of labile biomolecules. We demonstrate the formalism's usefulness through selected results on ubiquitin and an α-keratin fragment, in liquid and glassy states. We find that atomic-level normal stresses on hydrophilic side-chains exhibit a similar fingerprint in both proteins, and protein-level normal stresses increase upon vitrification. Both proteins experience compressive stresses of the order of 102 bar in the glassy state.

  19. Glassiness and exotic entropy scaling induced by quantum fluctuations in a disorder-free frustrated magnet.

    PubMed

    Klich, I; Lee, S-H; Iida, K

    2014-04-01

    When spins are arranged in a lattice of triangular motif, the phenomenon of frustration leads to numerous energetically equivalent ground states, and results in exotic states such as spin liquid and spin ice. Here we report an alternative situation: a system, classically a liquid, freezes in the clean limit into a glassy state induced by quantum fluctuations. We call such glassy state a spin jam. The case in point is a frustrated magnet, where spins are arranged in a triangular network of bipyramids. Quantum corrections break the classical degeneracy into a set of aperiodic spin configurations forming local minima in a rugged energy landscape. This is established by mapping the problem into tiling with hexagonal tiles. The number of tessellations scales with the boundary length rather than its volume, showing the absence of local zero-energy modes. Low-temperature thermodynamics is discussed to compare it with other glassy materials.

  20. Comparative analysis of the conformations of symmetrically and asymmetrically deca- and undecasubstituted porphyrins bearing meso-alkyl or -aryl groups

    SciTech Connect

    Senge, M.O.; Medforth, C.J.; Forsyth, T.P.

    1997-03-12

    Conformational analysis of highly substituted porphyrins, has potential implications for modeling the behavior of macrocycles in tetrapyrrole-containing protein complexes and during catalytic reactions. In order to study the influence of different substituent patterns of the conformation of the porphyrin macrocycle, a series of metal free and nickel(II) decasubstituted porphyrins bearing aryl or ethyl groups at opposite meso positions and alkyl groups at the pyrrole positions have been synthesized and characterized by X-ray crystallography. Crystal structures of the free-base porphyrins with 5,15-diaryl substituents showed negligible out-of-plane distortion but a large amount of in-plane distortion along the 5,15-axis accompanied by large bond angle changes similar to those previously seen for related porphyrins with 5,15-dialkyl substituents. Nickel(II) complexes of the 5,15-diaryl-substituted porphyrins show planar or modestly nonplanar conformations, suggesting that these complexes are not intrinsically nonplanar, whereas a complex with 5,15-diethyl substituents has a very ruffled conformation similar to those observed for related complexes with other metals. The nickel(II) complexes are also elongated along the 5,15-axis in a qualitatively similar but less dramatic fashion than are the free-base porphyrins. Spectroscopic studies ({sup 1}H NMR, optical, and resonance Raman spectroscopy) suggest that conformations similar to those determined by X-ray crystallography are present in solution for the 5,15-disubstituted porphyrins containing both aryl and alkyl mesosubstituents were also investigated. Metal-free 5,15-dialkyl- and 5,15-diaryl-substituted porphyrins. Several asymmetric nickel(II) and metal-free deca- and undecasubstituted porphyrins containing both aryl and alkyl mesosubstituents were also investigated.

  1. Nonlinear optical properties of porphyrin and chlorophyll dimers studied by degenerated four wave mixing

    SciTech Connect

    Chen, L.X.Q.

    1992-01-01

    As one of the important elements in natural and artificial electron transfer and energy transfer processes, porphyrin and its derivatives have received much attention in photoelectronics and photoelectronic materials. As our first attempt to relate the [pi]-[pi] electronic couplings between porphyrin macrocycles to apparent third order nonlinear susceptibilities, we measured [chi]([sup 3]) for several porphyrin and chlorophyll a derivatives, including dimers with different configurations. Our preliminary results show that the dimers have enhanced [chi]([sup 3]) compared to those of the monomer. This enhancement is related to the relative orientations between the two macrocycles in the dimers. The parallel dimers with close face-to-face distances seem to have the highest enhancement in [chi]([sup 3]). Thus, we believe that [chi]([sup 3]) is strongly related to the [pi]-[pi] electronic coupling between the two conjugated ring systems.

  2. Nonlinear optical properties of porphyrin and chlorophyll dimers studied by degenerated four wave mixing

    SciTech Connect

    Chen, L.X.Q.

    1992-12-31

    As one of the important elements in natural and artificial electron transfer and energy transfer processes, porphyrin and its derivatives have received much attention in photoelectronics and photoelectronic materials. As our first attempt to relate the {pi}-{pi} electronic couplings between porphyrin macrocycles to apparent third order nonlinear susceptibilities, we measured {chi}({sup 3}) for several porphyrin and chlorophyll a derivatives, including dimers with different configurations. Our preliminary results show that the dimers have enhanced {chi}({sup 3}) compared to those of the monomer. This enhancement is related to the relative orientations between the two macrocycles in the dimers. The parallel dimers with close face-to-face distances seem to have the highest enhancement in {chi}({sup 3}). Thus, we believe that {chi}({sup 3}) is strongly related to the {pi}-{pi} electronic coupling between the two conjugated ring systems.

  3. Controls on porphyrin concentrations of Pennsylvanian organic-rich shales, Western U.S.A.

    USGS Publications Warehouse

    Clayton, J.L.; Michael, G.E.

    1990-01-01

    Organic-rich black shales of Middle Pennsylvanian (Desmoinesian) age occur over much of the central U.S. and as far west as the northern Denver and southeastern Powder River basins. Total organic carbon contents (Corg) are commonly greater than 10 wt %. Porphyrin concentrations (vanadyl + nickel) are as high as 40000 ppm relative to extractable bitumen. In bulk, the organic matter contained in the shales is mostly type II and III (Rock-Eval hydrogen indexes 200-400 mg of hydrocarbons/g of Corg). The finding of high porphyrin concentrations in type III organic matter is unusual but can be explained by a depositional model wherein high preservation of primary organic production (water column photosynthesis) is combined with substantial input of allochthonous organic matter. The allochthonous organic matter (low porphyrin concentration) may come from erosion during advance of the sea across the area or from fluvial transport from shore.

  4. Toward understanding metal-binding specificity of porphyrin: a conceptual density functional theory study.

    PubMed

    Feng, Xin-Tian; Yu, Jian-Guo; Lei, Ming; Fang, Wei-Hai; Liu, Shubin

    2009-10-08

    Porphyrin is a key cofactor of hemoproteins. The complexes it forms with divalent metal cations such as Fe, Mg, and Mn compose an important category of compounds in biological systems, serving as a reaction center for a number of essential life processes. Employing density functional theory (DFT) and conceptual DFT approaches, the structural properties and reactivity of (pyridine)(n)-M-porphyrin complexes were systematically studied for the following selection of divalent metal cations: Mg, Ca, Cr, Mn, Co, Ni, Cu, Zn, Ru, and Cd with n varying from 0, 1, to 2. Metal selectivity and porphyrin specificity were investigated from the perspective of both structural and reactivity properties. Quantitative structural and reactivity relationships have been discovered between bonding interactions, charge distributions, and DFT chemical reactivity descriptors. These results are beneficial to our understanding of the chemical reactivity and metal cation specificity for heme-containing enzymes and other metalloproteins alike.

  5. Expanded Porphyrin-Anion Supramolecular Assemblies: Environmentally Responsive Sensors for Organic Solvents and Anions.

    PubMed

    Zhang, Zhan; Kim, Dong Sub; Lin, Chung-Yon; Zhang, Huacheng; Lammer, Aaron D; Lynch, Vincent M; Popov, Ilya; Miljanić, Ognjen Š; Anslyn, Eric V; Sessler, Jonathan L

    2015-06-24

    Porphyrins have been used frequently to construct supramolecular assemblies. In contrast, noncovalent ensembles derived from expanded porphyrins, larger congeners of naturally occurring tetrapyrrole macrocycles, are all but unknown. Here we report a series of expanded porphyrin-anion supramolecular assemblies. These systems display unique environmentally responsive behavior. Addition of polar organic solvents or common anions to the ensembles leads to either a visible color change, a change in the fluorescence emission features, or differences in solubility. The actual response, which could be followed easily by the naked eye, was found to depend on the specifics of the assembly, as well as the choice of analyte. Using the ensembles of this study, it proved possible to differentiate between common solvents, such as diethyl ether, THF, ethyl acetate, acetone, alcohol, acetonitrile, DMF, and DMSO, identify complex solvent systems, as well as distinguish between the fluoride, chloride, bromide, nitrate, and sulfate anions.

  6. Porphyrin network polymers prepared via a click reaction and facilitated oxygen permeation through their membranes.

    PubMed

    Chikushi, Natsuru; Ohara, Emiko; Hisama, Ayako; Nishide, Hiroyuki

    2014-05-01

    Network polymers of cobaltporphyrin derivatives are prepared by a facile click reaction via the Michael addition of acetoacetate-substituted tetraphenyl cobaltporphyrin and tri- or tetra-acrylates. The conversion is saturated for 1 h in the presence of a catalyst, which almost reaches the same gelation point of the formed network polymers. Deeply and homogeneously red-colored membranes with a sub-micrometer thickness are yielded on a porous supporting membrane. They are still tough even with a very high content of the rigid porphyrin residue. The oxygen permeability is high, at 10-100 Barrer, and the oxygen/nitrogen permselectivity (PO2/PN2) is significantly enhanced with the porphyrin content reaching 30, for the membranes with ca. 70 wt% porphyrin content.

  7. Synthesis and Luminescence of Soluble meso-Unsubstituted Tetrabenzo- and Tetranaphtho[2,3]porphyrins

    PubMed Central

    Finikova, Olga S.; Cheprakov, Andrei V.; Vinogradov, Sergei A.

    2008-01-01

    Syntheses of soluble tetrabenzoporphyrins (TBP) and tetranaphtho[2,3]porphyrins (TNP), with multiple substituents in the conjugated aromatic rings but bearing no substituents in the meso-positions, is reported. Both types of porphyrins were obtained by direct aromatization of precursor porphyrins, annealed with either cyclohexene or dihydronaphthalene fragments. TBPs and TNPs possess powerful absorption bands in the near-infrared (λ 610-710 nm, ϵ = 100,000-300,000 M-1 cm-1) and exhibit strong luminescence. Free bases and Zn complexes fluoresce with quantum yields of up to 50%, whereas Pd and Pt complexes phosphoresce in solutions at ambient temperatures. Remarkably, the phosphorescence quantum yields of Pd and Pt TBPs reach as high as 20-50%, which places them among the brightest near-infrared phosphors known to date. PMID:16268634

  8. Spectral-luminescent study of the porphyrin-diketones and their complexes

    NASA Astrophysics Data System (ADS)

    Papkovsky, Dmitri B.; Ponomarev, Gelii V.

    2001-08-01

    Syntheses of octaethylporphine-diketone (OEPDK) and its platinum(II) and palladium(II) complexes (PtOEPDK, PdOEPDK) were optimized, and the dyes were isolated in a pure form in preparative quantities. They were characterized by the NMR, UV-VIS absorption and emission spectroscopy. Electronic spectra of these dyes (absorption and luminescence) were investigated in detail, and compared to corresponding porphyrins and porphyrin-monoketones. OEPDK showed a strong fluorescence at about 700 nm, while PtOEPDK and PdOEPDK showed very weak room-temperature phosphorescence in the region of 850-1100 nm and practically no fluorescence. Protonation mechanisms were studied for these dyes. Protonation at sites other than pyrrole nitrogen atoms was shown to occur, corresponding protomeric spectral forms are presented. The possibilities of the use of porphyrin-diketones as longwave fluorescent and phosphorescent probes are discussed.

  9. A nuclear magnetic resonance study of the interactions of antimalarial drugs with porphyrins.

    PubMed

    Moreau, S; Perly, B; Chachaty, C; Deleuze, C

    1985-05-29

    Haematins (hydroxyferriprotoporphyrin IX) constitute a possible receptor for antimalarial drugs such as chloroquine or quinine. This paper reports the study of the interactions of these two molecules with two tetrapyrrole (haematin and uroporphyrin I) by 1H-NMR spectroscopy. This method provided us with the geometry of the interactions in aqueous medium. The interaction consists of a close stacking of the porphyrin ring and the quinoleine moiety of the drugs. Using a porphyrin ring current model it was possible to reach the spatial relationships of the interacting species. It was concluded that hydrophobic forces play a key role in the interaction. The porphyrin plane can accommodate wide structural variations of the interacting species, leading to a weak specificity. The consequences on the mode of action of antimalarial drugs are discussed.

  10. Methodological CASPT2 study of the valence excited states of an iron-porphyrin complex.

    PubMed

    Ben Amor, Nadia; Soupart, Adrien; Heitz, Marie-Catherine

    2017-02-01

    The singlet valence excited states of an iron-porphyrin-pyrazine-carbonyl complex are investigated up to the Soret band (about 3 eV) using multi-state complete active space with perturbation at the second order (MS-CASPT2). This complex is a model for the active site of carboxy-hemoglobin/myoglobin. The spectrum of the excited states is rather dense, comprising states of different nature: d→π* transitions, d→d states, π→π* excitations of the porphyrin, and doubly excited states involving simultaneous intra-porphyrin π→π* and d→d transitions. Specific features of the MS-CASPT2 method are investigated. The effect of varying the number of roots in the state average calculation is quantified as well as the consequence of targeted modifications of the active space. The effect of inclusion of standard ionization potential-electron affinity (IPEA) shift in the perturbation treatment is also investigated.

  11. Third-order nonlinear optical properties and photophysical mechanism of a novel In-porphyrin polymer

    NASA Astrophysics Data System (ADS)

    Ni, Kaizao; Liu, Dajun; Li, Zhongguo; Xiao, Zhengguo; Yang, Junyi; Song, Yinglin

    2014-12-01

    We use the time-resolved degenerated PO pump-probe technique to investigate the nonlinear absorption and nonlinear refraction dynamics of a novel porphyrin derivate, Indium-Porphyrin functionalized with polymethylmethacrylate (InPor-MMA26), dissolved in DMF at 532 nm in picosecond domain simultaneously. The results indicate that the nonlinear optical responses are induced by solution molecular excited state nonlinearity only, without the existence of two-photon absorption or Kerr refraction. Combined with five-energy-level model, all nonlinear optical parameters are determined by analyzing the experimental curves and confirmed by 4 ns Z-scan at 532 nm. The sample has a good reverse saturable absorption and reasonable positive refraction. With the proper lifetime and intersystem crossing time, this sample can be a candidate for optical limiting. The polymer attached to porphyrin directly by chemical bonds. This makes it have better homogeneity compared to physical mixing in the form of film.

  12. Differences in faecal profiles of porphyrins among river otters exposed to the Exxon Valdez oil spill.

    PubMed

    Blajeski, A; Duffy, L K; Bowyer, R T

    1996-01-01

    Abstract River otters (Lutra canadensis) living in marine environments of Prince William Sound, Alaska, exposed to crude oil from the Exxon Valdez spill in March 1989, showed significantly elevated levels of faecal porphyrin over those of otters from non-oiled areas (oiled mean = 48.2, andnon-oiled mean = 34.5 nmol g(-1) dry faeces). Profiles of uro-, hepta-, hexa-, penta-, copro-, andprotoporphyrin profiles were qualitatively characterized by high-performance liquid chromatography. These findings suggest that river otters may serve as a suitable indicator species in which porphyrin profiles can be used to monitor the effects of marine andfreshwater crude oil exposure. Also, this is the first model showing the effects of an oil spill on porphyrins on a free-ranging mammal using a non-lethal methodology. These effects were detectable 1 year after the spill andfollowing a major effort to clean oil from the shorelines of Prince William Sound.

  13. Nonlinear optical behavior of porphyrin functionalized nanodiamonds: an efficient material for optical power limiting.

    PubMed

    Muller, Olivier; Pichot, Vincent; Merlat, Lionel; Schmidlin, Loic; Spitzer, Denis

    2016-05-10

    The nonlinear optical mechanisms and the optical limiting behavior of porphyrin functionalized detonation nanodiamonds are investigated and compared to the conventional detonation nanodiamonds (DNDs). The optical limiting behavior is characterized by means of nonlinear transmittance, Z-scan, and scattered intensity measurements when submitted to a nanosecond pulsed Nd:YAG laser operating at the second harmonic wavelength. We found that the largest nonlinear attenuation was observed on the 4,4',4'',4'''-(porphyrin-5, 10, 15, 20-tetrayl) tetrakis benzoic acid (PCOOH) suspension. Using Z-scan experiments, it is shown that nonlinear refraction predominates in the unfunctionalized DND suspension, while nonlinear absorption is the most relevant mechanism in the porphyrin functionalized DNDs. Furthermore, a stronger backscattered intensity signal is highlighted for the unfunctionalized DNDs through nonlinear scattering measurements.

  14. Heterogeneous biomimetic catalysis using iron porphyrin for cyclohexane oxidation promoted by chitosan

    NASA Astrophysics Data System (ADS)

    Huang, Guan; Liu, Yao; Cai, Jing Li; Chen, Xiang Feng; Zhao, Shu Kai; Guo, Yong An; Wei, Su Juan; Li, Xu

    2017-04-01

    This study investigates how ligands modulate metalloporphyrin activity with the goal of producing a practical biomimetic catalyst for use in the chemical industry. We immobilized iron porphyrinate [iron-tetrakis-(4-sulfonatophenyl)-porphyrin; Fe(III) (TPPS)] on powdered chitosan (pd-CTS) to form an immobilized catalyst Fe(III) (TPPS)/pd-CTS, which was characterized using modern spectroscopic techniques and used for catalytic oxidation of cyclohexane with O2. Amino coordination to iron porphyrin in Fe(III) (TPPS)/pd-CTS altered the electron cloud density around the iron cation, probably by reducing the activation energy of Fe(III) (TPPS) and raising the reactivity of the iron ion catalytic center, thereby improving the catalytic efficiency. One milligram of Fe(III) (TPPS) catalyst can be reused three times for the oxidation reaction to yield an average of 22.9 mol% of cyclohexanone and cyclohexanol.

  15. A novel ethacrynic acid sensor based on a lanthanide porphyrin complex in a PVC matrix.

    PubMed

    Zhang, X B; Guo, C C; Xu, J B; Shen, G L; Yu, R Q

    2000-05-01

    Lanthanide porphyrin complexes synthesized by a solid state method were used to prepare a novel ethacrynic acid (EA) sensor. The sensor, based on pentane-2,4-dionato(meso-tetraphenylporphinato)terbium [TbTPP(acac)] with an optimized membrane composition, exhibits a Nernstian response to EA- ion in the concentration range 7.4 x 10(-6)-1.0 x 10(-1) mol l-1 with a pH range from 3.2 to 6.8 and a fast response time of 30 s. The electrode shows improved selectivity towards EA- ion with respect to common co-existing ions compared with the previously reported EA sensor. As electroactive materials, lanthanide porphyrin complexes show better potentiometric response characteristics than copper porphyrin complexes. The effect of solvent mediators and lipophilic ion additives was studied and the experimental conditions were optimized. The electrode was applied to the determination of EA in human urine samples with satisfactory results.

  16. Temperature-dependent conformations of a membrane supported zinc porphyrin tweezer by 2D fluorescence spectroscopy.

    PubMed

    Widom, Julia R; Lee, Wonbae; Perdomo-Ortiz, Alejandro; Rappoport, Dmitrij; Molinski, Tadeusz F; Aspuru-Guzik, Alán; Marcus, Andrew H

    2013-07-25

    We studied the equilibrium conformations of a zinc porphyrin tweezer composed of two carboxylphenyl-functionalized zinc tetraphenyl porphyrin subunits connected by a 1,4-butyndiol spacer, which was suspended inside the amphiphilic regions of 1,2-distearoyl-sn-glycero-3-phosphocholine (DSPC) liposomes. By combining phase-modulation two-dimensional fluorescence spectroscopy (2D FS) with linear absorbance and fluorimetry, we determined that the zinc porphyrin tweezer adopts a mixture of folded and extended conformations in the membrane. By fitting an exciton-coupling model to a series of data sets recorded over a range of temperatures (17-85 °C) and at different laser center wavelengths, we determined that the folded form of the tweezer is stabilized by a favorable change in the entropy of the local membrane environment. Our results provide insights toward understanding the balance of thermodynamic factors that govern molecular assembly in membranes.

  17. Transformations of N-confused porphyrin triggered by insertion of silicon(IV).

    PubMed

    Skonieczny, Janusz; Latos-Grazyński, Lechosław; Szterenberg, Ludmiła

    2009-08-03

    N-confused porphyrin, 5,10,15,20-tetraaryl-2-aza-21-carbaporphyrin, dissolved in triethylamine reacts with dichloromethylsilane yielding the methylsilicon(IV) complex of 5,10,15,20-tetraaryl-2-aza-21-hydroxy-21-carbaporphyrin. Addition of aldehydes or ketones (acetone, acetaldehyde acetophenone, butanone, propanal, benzaldehyde, p-methylbenzaldehyde, p-methoxybenzaldehyde, terephthaldehyde) into the insertion mixture triggered the profound transformation of N-confused porphyrin to form the methylsilicon(IV) complex of N-fused porphyrin derivative substituted at the inner C(9) position by a hydroxyalkyl moiety derived from aldehyde or ketone. The macrocyle is structurally related to an aromatic N-fused inner phlorin while the coordination polyhedron of bound silicon resembles the trigonal bipyramid. The macrocyclic ligand coordinates in the facial mode as the three pyrrolic nitrogen donors lie at the vertices of the single trigonal face. The meridional positions of the trigonal bipyramid are occupied by two pyrrolic nitrogen donors and a sigma-methyl ligand. The coordination sphere is completed by apical coordination of the alkoxy oxygen atom derived from alkanal or alkonone. The incorporation of aldehydes and ketones is stereoselective. Acidic desililation of alkanal compounds yields two aromatic N-confused porphyrin derivatives, that is, 3-(1-hydroxyalkyl)-5,10,15,20-tetraaryl-2-aza-21-carbaporphyrin and its oxidation product 3-alkanoyl-5,10,15,20-tetraaryl-2-aza-21-carbaporphyrin. The acid triggered desililation of ketone derivatives produces the equimolar amounts of N-confused porphyrin and ketone. The first spectroscopically identified step involves the protonation of the C(7) position affording the non-aromatic silicon(IV) complex. The density functional theory (DFT) has been applied to model the molecular and electronic structure of all species identified in the course of silicon insertion into the N-confused and N-fused porphyrin.

  18. Photophysical properties of porphyrins with sterically distorted and partially screened macrocycles

    NASA Astrophysics Data System (ADS)

    Ivashin, N. V.; Shchupak, E. E.; Panarin, A. Yu.; Sagun, E. I.

    2015-06-01

    We have experimentally studied the spectral-luminescent and photophysical properties, as well as interaction processes with molecular oxygen, of eclipsed β-alkyl-substituted porphyrins para-methoxyphenyl rings of which in opposite meso-positions of the macrocycle are linked with each other in the ortho-position with the (-OCH2)-Ph-(CH2O-) bridge. Using methods of the density functional theory, we have calculated the structures of these porphyrins in the ground and lowest triplet states, electronic transitions and vibrational states, and matrix elements of the direct spin-orbit interaction. It has been found that the lifetime of the T 1 state of the investigated compounds is noticeably shortened due to the enhancement of the internal conversion. This enhancement is caused by the conformational dynamics, which promotes increasing Franck-Condon factors and the spin-orbit interaction between the T 1 and S 0 states. Nevertheless, this does not lead to a considerable decrease in the singlet-oxygen formation quantum yield. We have calculated the structures of a porphin dimer and possible dimeric forms of examined porphyrins. It has been shown that distortion of the porphyrin macrocycle according to type of ruffling weakly affects the binding energy of the porphyrin macrocycles in the dimer, this effect being unable to prevent aggregation. At the same time, the screening of the macrocycle by the phenyl ring lowers the probability of formation of oligomeric structures, which, in view of the determined photophysical properties of investigated compounds, may be used in photochemical applications that require elevated concentrations of porphyrins.

  19. Binary ionic porphyrin nanosheets: electronic and light-harvesting properties regulated by crystal structure.

    PubMed

    Tian, Yongming; Beavers, Christine M; Busani, Tito; Martin, Kathleen E; Jacobsen, John L; Mercado, Brandon Q; Swartzentruber, Brian S; van Swol, Frank; Medforth, Craig J; Shelnutt, John A

    2012-03-07

    Crystalline solids self-assembled from anionic and cationic porphyrins provide a new class of multifunctional optoelectronic micro- and nanomaterials. A 1 : 1 combination of zinc(II) tetra(4-sulfonatophenyl)porphyrin (ZnTPPS) and tin(IV) tetra(N-methyl-4-pyridiniumyl)porphyrin (SnTNMePyP) gives porphyrin nanosheets with high aspect ratios and varying thickness. The room temperature preparation of the nanosheets has provided the first X-ray crystal structure of a cooperative binary ionic (CBI) solid. The unit cell contains one and one-half molecules of aquo-ZnTPPS(4-) (an electron donor) and three half molecules of dihydroxy-SnTNMePyP(4+) (an electron acceptor). Charge balance in the solid is reached without any non-porphyrinic ions, as previously determined for other CBI nanomaterials by non-crystallographic means. The crystal structure reveals a complicated molecular arrangement with slipped π-π stacking only occurring in isolated dimers of one of the symmetrically unique zinc porphyrins. Consistent with the crystal structure, UV-visible J-aggregate bands indicative of exciton delocalization and extended π-π stacking are not observed. XRD measurements show that the structure of the Zn/Sn nanosheets is distinct from that of Zn/Sn four-leaf clover-like CBI solids reported previously. In contrast with the Zn/Sn clovers that do exhibit J-aggregate bands and are photoconductive, the nanosheets are not photoconductive. Even so, the nanosheets act as light-harvesting structures in an artificial photosynthesis system capable of reducing water to hydrogen but not as efficiently as the Zn/Sn clovers.

  20. Cutaneous porphyrins exhibit anti-stokes fluorescence that is detectable in sebum (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Tian, Giselle; Zeng, Haishan; Zhao, Jianhua; Wu, Zhenguo; Al Jasser, Mohammed; Lui, Harvey; Mclean, David I.

    2016-02-01

    Porphyrins produced by Propionibacterium acnes represent the principal fluorophore associated with acne, and appear as orange-red luminescence under the Wood's lamp. Assessment of acne based on Wood's lamp (UV) or visible light illumination is limited by photon penetration depth and has limited sensitivity for earlier stage lesions. Inducing fluorescence with near infrared (NIR) excitation may provide an alternative way to assess porphyrin-related skin disorders. We discovered that under 785 nm CW laser excitation PpIX powder exhibits fluorescence emission in the shorter wavelength range of 600-715 nm with an intensity that is linearly dependent on the excitation power. We attribute this shorter wavelength emission to anti-Stokes fluorescence. Similar anti-Stokes fluorescence was also detected focally in all skin-derived samples containing porphyrins. Regular (Stokes) fluorescence was present under UV and visible light excitation on ex vivo nasal skin and sebum from uninflamed acne, but not on nose surface smears or sebum from inflamed acne. Co-registered CW laser-excited anti-Stokes fluorescence and fs laser-excited multi-photon fluorescence images of PpIX powder showed similar features. In the skin samples because of the anti-Stokes effect, the NIR-induced fluorescence was presumably specific for porphyrins since there appeared to be no anti-Stokes emission signals from other typical skin fluorophores such as lipids, keratins and collagen. Anti-Stokes fluorescence under NIR CW excitation is more sensitive and specific for porphyrin detection than UV- or visible light-excited regular fluorescence and fs laser-excited multi-photon fluorescence. This approach also has higher image contrast compared to NIR fs laser-based multi-photon fluorescence imaging. The anti-Stokes fluorescence of porphyrins within sebum could potentially be applied to detecting and targeting acne lesions for treatment via fluorescence image guidance.

  1. Slow motion, trapping, and sorting of water- and chloroform-soluble porphyrins in nanowells.

    PubMed

    Bhosale, Sheshanath; Bhosale, Sidhanath; Wang, Tianyu; Li, Guangtao; Siggel, Ulrich; Fuhrhop, Jürgen-Hinrich

    2004-10-13

    A two-step self-assembly procedure on smooth, aminated silica particles established holey monolayers. At first, single, flat-lying porphyrin tetraamides (A) were bound covalently, followed by the build-up of a rigid monolayer made of diamido bolaamphiphiles (bolas) around the porphyrin islands. "Nanowells" around porphyrin (A) bottoms with a uniform diameter of 2.2 nm and varying depths of 0.6, 1.0, or 1.5 nm depending on the length of the applied bolas were thus obtained. Oligoethylene headgroups solubilized the particles in water, ethanol, and chloroform/ethanol, and two hydrogen bond chains between the secondary amide groups prevented swelling of the monolayer. Manganese(III) porphyrinates (B) migrated from the bulk solution to the bottom of the form-stable nanowells with a speed of about 1 pm/s and were trapped there above porphyrin (A). After isolation of the (A,B) particles by centrifugation or ultrafiltration, the particles were suspended in a chloroform solution of a chlorin (C), which was also fixated irreversibly on the bottom of the nanowells. The nanowells thus contained three different porphyrins A,B,C in a noncovalent stack. The reverse sequence A,C,B was built-up correspondingly, first in chloroform/ethanol, and then in water. The "sorting" of A,B,C and A,C,B systems was characterized by visible spectra, sequence-dependent fluorescence quenching, and cyclic voltammetry of the top component. The molecular sorting method is the first of its kind and should be generally useful for the production of noncovalent reaction systems on any smooth surface.

  2. Iron(II) porphyrins induced conversion of nitrite into nitric oxide: A computational study.

    PubMed

    Zhang, Ting Ting; Liu, Yong Dong; Zhong, Ru Gang

    2015-09-01

    Nitrite reduction to nitric oxide by heme proteins was reported as a protective mechanism to hypoxic injury in mammalian physiology. In this study, the pathways of nitrite reduction to nitric oxide mediated by iron(II) porphyrin (P) complexes, which were generally recognized as models for heme proteins, were investigated by using density functional theory (DFT). In view of two type isomers of combination of nitrite and Fe(II)(P), N-nitro- and O-nitrito-Fe(II)-porphyrin complexes, and two binding sites of proton to the different O atoms of nitrite moiety, four main pathways for the conversion of nitrite into nitric oxide mediated by iron(II) porphyrins were proposed. The results indicate that the pathway of N-bound Fe(II)(P)(NO2) isomer into Fe(III)(P)(NO) and water is similar to that of O-bound isomer into nitric oxide and Fe(III)(P)(OH) in both thermodynamical and dynamical aspects. Based on the initial computational studies of five-coordinate nitrite complexes, the conversion of nitrite into NO mediated by Fe(II)(P)(L) complexes with 14 kinds of proximal ligands was also investigated. Generally, the same conclusion that the pathways of N-bound isomers are similar to those of O-bound isomer was obtained for iron(II) porphyrin with ligands. Different effects of ligands on the reduction reactions were also found. It is notable that the negative proximal ligands can improve reactive abilities of N-nitro-iron(II) porphyrins in the conversion of nitrite into nitric oxide compared to neutral ligands. The findings will be helpful to expand our understanding of the mechanism of nitrite reduction to nitric oxide by iron(II) porphyrins.

  3. Enhancing solar photocatalytic detoxification by adsorption of porphyrins onto TiO sub 2

    SciTech Connect

    Majumder, S.A.; Ondrias, M.R. . Dept. of Chemistry); Prairie, M.R.; Shelnutt, J.A. )

    1991-01-01

    Titanium dioxide (TiO{sub 2}) is a known photocatalyst for solar detoxification of water containing organic contaminants including PCB's and dioxins. Unfortunately, the UV light used by the photocatalyst only comprises about 4% of the strong spectrum. Metalloporphyrins strongly absorb in the visible and near infrared region. Using visible light, we have investigated Ni(II) uroporphyrin (NiUroP), Sn(IV)Cl{sub 2} uroporphyrin (SnUroP) and Sn(IV)Cl{sub 2} tetrakis(p-carboxyphenyl) porphyrin (SnTCPP) as possible enhancers of destruction of a model organic compound, salicylic acid (SA), by means of photosensitization of colloidal TiO{sub 2} particles. All three porphyrins are found to adsorb reversibly onto the colloidal TiO{sub 2} upon variation of pH. Adsorption of porphyrins results in the increased colloidal stability of fine TiO{sub 2} particles in the pH range 5--8. While NiUroP on TiO{sub 2} does not show any enhancement of photodestruction, the adsorption of SnUroP increases the destruction rate compared to that of the bare TiO{sub 2} surface. The effect of ambient oxygen on the observed photolability of the Sn porphyrins and enhancement of photodestruction of SA was also investigated. SnTCPP does not photodecompose upon illumination either in the presence or absence of TiO{sub 2}, but neither does it bind to the photocatalyst at pH 6. At pH 4.5 it adsorbs onto TiO{sub 2} but it also photodecompose at this pH. We are attempting to stabilize the adsorbed porphyrins by adding suitable peripheral substituents onto the porphyrin macrocycle. 27 refs., 6 figs.

  4. Elastic properties of aspirin in its crystalline and glassy phases studied by micro-Brillouin scattering

    NASA Astrophysics Data System (ADS)

    Ko, Jae-Hyeon; Lee, Kwang-Sei; Ike, Yuji; Kojima, Seiji

    2008-11-01

    The acoustic waves propagating along the direction perpendicular to the (1 0 0) cleavage plane of aspirin crystal were investigated using micro-Brillouin spectroscopy from which C11, C55 and C66 were obtained. The temperature dependence of the longitudinal acoustic waves could be explained by normal anharmonic lattice models, while the transverse acoustic waves showed an abnormal increase in the hypersonic attenuation at low temperatures indicating their coupling to local remnant dynamics. The sound velocity as well as the attenuation of the longitudinal acoustic waves of glassy aspirin showed a substantial change at ˜235 K confirming a transition from glassy to supercooled liquid state in vitreous aspirin.

  5. A Thermodynamic Theory of Solid Viscoelasticity. Part 3: Nonlinear Glassy Viscoelasticity, Stability Constraints, Specifications

    NASA Technical Reports Server (NTRS)

    Freed, Alan; Leonov, Arkady I.

    2002-01-01

    This paper, the last in the series, continues developing the nonlinear constitutive relations for non-isothermal, compressible, solid viscoelasticity. We initially discuss a single integral approach, more suitable for the glassy state of rubber-like materials, with basic functionals involved in the thermodynamic description for this type of viscoelasticity. Then we switch our attention to analyzing stability constraints, imposed on the general formulation of the nonlinear theory of solid viscoelasticity. Finally, we discuss specific (known from the literature or new) expressions for material functions that are involved in the constitutive formulations of both the rubber-like and glassy-like, complementary parts of the theory.

  6. lnterferometric Examination of Small (Glassy Spherules and Related Objects in a 5-Graml Lunar Dust Sample.

    PubMed

    Tolansky, S

    1970-01-30

    Over two hundred spherules and cylinders were extracted from the lunar dust sample. Sizes ranged from 0.7 to 0.03 millimeters, and most were shiny glassy objects, which were studied by interferometry. This study reveals very high spcular feflection, frequentperfect sphericity, and clear evidence n some objects of micracking and microchipping. Many spheres were once projectiles. Some have inpacted in free flight with much smaller pices of rocky material, which embedded in the surface. It is conjectured that the glassy spherules originated as a gas-blown shower from a pool of molten glass.

  7. Fabrication and Investigation of Intermetallic Compound-Glassy Phase Composites having Tensile Ductility

    DTIC Science & Technology

    2012-08-09

    with Mg-Y-Cu BGA, MgY phase also has a cP2 B2 structure), Mg-Y-Ag (AgMg phase also has a cP2 B2 structure and is ductile) and Y-Cu-Zn and some other...result were obtained is connected with cP2 TiNi phase which demonstrates martensitic transformations. Choice of alloys and sample preparation...1. The tentative compositions at which bulk glassy phase formation and possible formation of cP2 crystal-glassy composites are Cu-Y (starting from

  8. Effects of xylem-sap composition on glassy-winged sharpshooter egg maturation on high and low quality host plants

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Glassy-winged sharpshooters must feed as adults to produce mature eggs. Cowpea and sunflower are both readily accepted by the glassy-winged sharpshooter for feeding, but egg production on sunflower was reported to be lower than egg production on cowpea. To better understand the role of adult diet in...

  9. Characterization of molecular mobility within the glassy matrix of dry seeds using mechanical properties: pea cotyledon as a test study

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Seed glasses form during maturation drying and regulate seed longevity. Seeds continue to age within the glassy state and, even during cryogenic storage, viability eventually declines. Inevitability of aging suggests some level of molecular motion within the glassy matrix and quantifying these “rel...

  10. Detection of iron-porphyrin proteins with a biochemiluminescent method in search of extraterrestrial life.

    PubMed

    Sotnikov, G G

    1970-01-01

    Iron-porphyrin proteins (catalase, peroxidase, hemoglobin, cytochrome C) represent an important group of redoxenzymes which have vitally important functions in micro-organisms. A biochemiluminescent method was employed for the detection of iron-porphyrin proteins. The reaction of luminol oxidation with H2O2 is accompanied by chemiluminescence. The rate of hydrogen peroxide decomposition increased 10(5)-10(7) -fold in the presence of the above enzymes as compared with ferrous (or ferric) ions. Possible application of this reaction for the detection of iron-porphyrin proteins of microbial origin was studied. Other authors have suggested this reaction for the detection of extraterrestrial life. Kinetics of the above reaction in the presence of iron-porphyrin proteins were shown to differ both in amplitude and duration of the signal from the pattern observed in the presence of non-hemin catalysts. The reaction pattern in the presence of mixed-soil populations is similar to those observed with pure bacterial cultures and individual iron-porphyrin proteins. Photometric tests revealed that among preparations studied the addition of 0.01% lysozyme was the most effective in destroying cell walls in microbial populations. However, removal of cell walls is not a necessary prerequisite for the detection of iron porphyrin since, for effective luminol oxidation with H2O2 the medium should be kept at pH 12.0. Pretreatment of microbial suspensions with ultrasound increased 2-fold the total signal due to iron porphyrins. The above method gives a reproducible signal indicating the presence of iron porphyrins when sterile nutrient media were innoculated with desert soil samples (Repeteck, Kara-Kum) and incubated for 13 hr. The device was able to detect the presence of no less than 10(5) - 10(6) cells per ml. The addition of limonite (Fe2O3 X nH2O) does not result in the appearance of an appreciable signal in the luminol + H2O2 system.

  11. Electron transport property of cobalt-centered porphyrin-armchair graphene nanoribbon (AGNR) junction

    SciTech Connect

    Mondal, Rajkumar; Sarkar, Utpal

    2015-06-24

    We have investigated the electron transport properties of Cobalt-centered (Co-centered) porphyrin molecule using the density functional theory and non-equilibrium greens function method. Here we have reported transmission coefficient as well as current voltage characteristics of Co-centered porphyrine molecule connected between armchair graphene nanoribbons. It has been found that at low bias region i.e., 0 V to 0.3 V it does not contribute any current. Gradual increase of bias voltage results different order of magnitude of current in different bias region.

  12. Magnetic configuration dependence of magnetoresistance in a Fe-porphyrin-like carbon nanotube spintronic device

    SciTech Connect

    Zeng, Jing; Chen, Ke-Qiu

    2014-01-20

    By using nonequilibrium Green's functions in combination with the density functional theory, we investigate the spin-dependent transport properties in a Fe-porphyrin-like carbon nanotube spintronic device. The results show that magnetoresistance ratio is strongly dependent on the magnetic configuration of the Fe-porphyrin-like carbon nanotube. Under the application of the external magnetic field, the magnetoresistance ratio of the device can be increased from about 19% to about 1020% by tuning the magnetic configuration in the device. Our results confirm that the magnetic configuration is a key factor for obtaining a high-performance spintronic device.

  13. Ferryl Protonation in Oxoiron(IV) Porphyrins and Its Role in Oxygen Transfer

    SciTech Connect

    Boaz, Nicholas C.; Bell, Seth R.; Groves, John T.

    2015-02-04

    Ferryl porphyrins, P–FeIV$=$O, are central reactive intermediates in the catalytic cycles of numerous heme proteins and a variety of model systems. There has been considerable interest in elucidating factors, such as terminal oxo basicity, that may control ferryl reactivity. Here in this study, the sulfonated, water-soluble ferryl porphyrin complexes tetramesitylporphyrin, oxoFeIVTMPS (FeTMPS-II), its 2,6-dichlorophenyl analogue, oxoFeIVTDClPS (FeTDClPS-II), and two other analogues are shown to be protonated under turnover conditions to produce the corresponding bis-aqua-iron(III) porphyrin cation radicals. The results reveal a novel internal electromeric equilibrium, P–FeIV$=$O $\\leftrightarrows$ P+–FeIII(OH2)2. Reversible pKa values in the range of 4–6.3 have been measured for this process by pH-jump, UV–vis spectroscopy. Ferryl protonation has important ramifications for C–H bond cleavage reactions mediated by oxoiron(IV) porphyrin cation radicals in protic media. Both solvent O–H and substrate C–H deuterium kinetic isotope effects are observed for these reactions, indicating that hydrocarbon oxidation by these oxoiron(IV) porphyrin cation radicals occurs via a solvent proton-coupled hydrogen atom transfer from the substrate that has not been previously described. The effective FeO–H bond dissociation energies for FeTMPS-II and FeTDClPS-II were estimated from similar kinetic reactivities of the corresponding oxoFeIVTMPS+ and oxoFeIVTDClPS+ species to be ~92–94 kcal/mol. Similar values were calculated from the two-proton P+–FeIII(OH2)2 pKaobs and the porphyrin oxidation potentials, despite a 230 mV range for the iron porphyrins examined. Thus, the iron porphyrin with the lower ring oxidation potential has a compensating higher basicity of the

  14. Ferryl Protonation in Oxoiron(IV) Porphyrins and Its Role in Oxygen Transfer

    DOE PAGES

    Boaz, Nicholas C.; Bell, Seth R.; Groves, John T.

    2015-02-04

    Ferryl porphyrins, P–FeIVmore » $=$O, are central reactive intermediates in the catalytic cycles of numerous heme proteins and a variety of model systems. There has been considerable interest in elucidating factors, such as terminal oxo basicity, that may control ferryl reactivity. Here in this study, the sulfonated, water-soluble ferryl porphyrin complexes tetramesitylporphyrin, oxoFeIVTMPS (FeTMPS-II), its 2,6-dichlorophenyl analogue, oxoFeIVTDClPS (FeTDClPS-II), and two other analogues are shown to be protonated under turnover conditions to produce the corresponding bis-aqua-iron(III) porphyrin cation radicals. The results reveal a novel internal electromeric equilibrium, P–FeIV$=$O $$\\leftrightarrows$$ P+–FeIII(OH2)2. Reversible pKa values in the range of 4–6.3 have been measured for this process by pH-jump, UV–vis spectroscopy. Ferryl protonation has important ramifications for C–H bond cleavage reactions mediated by oxoiron(IV) porphyrin cation radicals in protic media. Both solvent O–H and substrate C–H deuterium kinetic isotope effects are observed for these reactions, indicating that hydrocarbon oxidation by these oxoiron(IV) porphyrin cation radicals occurs via a solvent proton-coupled hydrogen atom transfer from the substrate that has not been previously described. The effective FeO–H bond dissociation energies for FeTMPS-II and FeTDClPS-II were estimated from similar kinetic reactivities of the corresponding oxoFeIVTMPS+ and oxoFeIVTDClPS+ species to be ~92–94 kcal/mol. Similar values were calculated from the two-proton P+–FeIII(OH2)2 pKaobs and the porphyrin oxidation potentials, despite a 230 mV range for the iron porphyrins examined. Thus, the iron porphyrin with the lower ring oxidation potential has a compensating higher basicity of the ferryl oxygen. The solvent-derived proton adds significantly to the driving force for C–H bond scission.« less

  15. Chiral memory via chiral amplification and selective depolymerization of porphyrin aggregates.

    PubMed

    Helmich, Floris; Lee, Cameron C; Schenning, Albertus P H J; Meijer, E W

    2010-12-01

    Chiral memory at the supramolecular level is obtained via a new approach using chiral Zn porphrins and achiral Cu porphyrins. In a "sergeant-and-soldiers" experiment, the Zn "sergeant" transfers its own chirality to Cu "soldiers" and, after chiral amplification, the "sergeant" is removed from the coaggregates by axial ligation with a Lewis base. After this extraction, the preferred helicity observed for the aggregates containing achiral Cu porphyrins reveals a chiral memory effect that is stable and can be erased and partially restored upon subsequent heating and cooling.

  16. Electron-Triggered Metamorphism in Porphyrin-Based Self-Assembled Coordination Polymers.

    PubMed

    Kahlfuss, Christophe; Denis-Quanquin, Sandrine; Calin, Nathalie; Dumont, Elise; Garavelli, Marco; Royal, Guy; Cobo, Saioa; Saint-Aman, Eric; Bucher, Christophe

    2016-11-23

    Viologen-centered electron transfer is used to trigger a complete dissociation of a porphyrin-based supramolecular architecture. In the oxidized state, self-assembly is induced by iterative association of individual porphyrin-based tectons. Dissociation of the self-assembled species is actuated upon changing the redox state of the bipyridium units involved in the tectons from their dicationic state to their radical cation state, the driving force of the disassembling process being the formation of an intramolecularly locked conformation partly stabilized by π-dimerization of both viologen cation radicals.

  17. Oxoferryl porphyrin cation radicals in model systems: Evidence for variable metal-radical spin coupling

    NASA Astrophysics Data System (ADS)

    Bill, E.; Bominaar, E. L.; Ding, X.-Q.; Trautwein, A. X.; Winkler, H.; Mandon, D.; Weiss, R.; Gold, A.; Jayaraj, K.; Toney, G. E.

    1990-07-01

    Magnetic properties of frozen solutions of highly oxidized iron porphyrin complexes were investigated by EPR and Mössbauer spectroscopy. The Mössbauer spectra, recorded at low temperatures in various magnetic fields, were analyzed on the basis of spin Hamiltonian simulations. Spin coupling between ferryl iron (FeIV) and porphyrin cation radical was taken into account explicitly. Hyperfine and spin-coupling parameters are given for several complexes, together with zero-field parameters. One of the complexes exhibits weak spin coupling, it is the first model system exhibiting properties comparable to those of the oxoferryl cation radical enzyme Horse Radish Peroxidase I.

  18. Unique Diagnostic and Therapeutic Roles of Porphyrins and Phthalocyanines in Photodynamic Therapy, Imaging and Theranostics

    PubMed Central

    Josefsen, Leanne B.; Boyle, Ross W.

    2012-01-01

    Porphyrinic molecules have a unique theranostic role in disease therapy; they have been used to image, detect and treat different forms of diseased tissue including age-related macular degeneration and a number of different cancer types. Current focus is on the clinical imaging of tumour tissue; targeted delivery of photosensitisers and the potential of photosensitisers in multimodal biomedical theranostic nanoplatforms. The roles of porphyrinic molecules in imaging and pdt, along with research into improving their selective uptake in diseased tissue and their utility in theranostic applications are highlighted in this Review. PMID:23082103

  19. A porphyrin/β-cyclodextrin conjugated nano-system having a pan-lid molecular structure for smart drug carrier applications.

    PubMed

    Mineo, Placido

    2014-06-14

    In this study, 5,10,15-tri[p(9-methoxy-triethyleneoxy)phenyl]-20-[p-phenylisophthalate-β-cyclodextrin]porphyrin, a compound containing a porphyrin and a β-cyclodextrin unit covalently linked by means of an isophthalic bridge, was synthesized and characterized by NMR, MALDI-TOF mass spectrometry and UV-vis and circular dichroism spectroscopies. This porphyrin/β-cyclodextrin system, with the porphyrin unit connected to the lower rim (OH-2) of the cyclodextrin structure, is water-soluble and no evidence of a self-assembly arrangement between the porphyrin and cyclodextrin units appears. In this way, the β-cyclodextrin cavities remain free, retaining their potential ability of drug-delivery, with the spectroscopic advantage induced by the high absorbance of the porphyrin unit. Furthermore, the porphyrin unit, interacting with the guest and acting as a lid, could have a role in the controlled release process of the drug.

  20. Metallated porphyrin based porous organic polymers as efficient electrocatalysts

    NASA Astrophysics Data System (ADS)

    Lu, Guolong; Zhu, Youlong; Xu, Kongliang; Jin, Yinghua; Ren, Zhiyong Jason; Liu, Zhenning; Zhang, Wei

    2015-10-01

    Developing efficient, stable and low-cost catalysts for Oxygen Reduction Reaction (ORR) is of great significance to many emerging technologies including fuel cells and metal-air batteries. Herein, we report the development of a cobalt(ii) porphyrin based porous organic polymer (CoPOP) and its pyrolyzed derivatives as highly active ORR catalysts. The as-synthesized CoPOP exhibits high porosity and excellent catalytic performance stability, retaining ~100% constant ORR current over 50 000 s in both alkaline and acidic media. Pyrolysis of CoPOP at various temperatures (600 °C, 800 °C, and 1000 °C) yields the materials consisting of graphitic carbon layers and cobalt nanoparticles, which show greatly enhanced catalytic activity compared to the as-synthesized CoPOP. Among them, CoPOP-800/C pyrolyzed at 800 °C shows the highest specific surface area and ORR activity, displaying the most positive half-wave potential (0.825 V vs. RHE) and the largest limited diffusion current density (5.35 mA cm-2) in an alkaline medium, which are comparable to those of commercial Pt/C (20 wt%) (half-wave potential 0.829 V vs. RHE, limited diffusion current density 5.10 mA cm-2). RDE and RRDE experiments indicate that CoPOP-800/C directly reduces molecular oxygen to water through a 4-e- pathway in both alkaline and acidic media. More importantly, CoPOP-800/C exhibits excellent durability and methanol-tolerance under acidic and alkaline conditions, which surpass the Pt/C (20 wt%) system.Developing efficient, stable and low-cost catalysts for Oxygen Reduction Reaction (ORR) is of great significance to many emerging technologies including fuel cells and metal-air batteries. Herein, we report the development of a cobalt(ii) porphyrin based porous organic polymer (CoPOP) and its pyrolyzed derivatives as highly active ORR catalysts. The as-synthesized CoPOP exhibits high porosity and excellent catalytic performance stability, retaining ~100% constant ORR current over 50 000 s in both

  1. Effect of photocurrent enhancement in porphyrin-graphene covalent hybrids.

    PubMed

    Tang, Jianguo; Niu, Lin; Liu, Jixian; Wang, Yao; Huang, Zhen; Xie, Shiqiang; Huang, Linjun; Xu, Qingsong; Wang, Yuan; Belfiore, Laurence A

    2014-01-01

    Graphene oxide (GO) sheets were covalently functionalized with 5-p-aminophenyl-10,15,20-triphenylporphyrin (NH2TPP) by an amidation reaction between the amino group in NH2TPP and carboxyl groups in GO. The Fourier transform infrared spectroscopy, nuclear magnetic resonance, scanning and transmission electron microscopies reveal that NH2TPP covalent bonds form on the double surface of graphene oxide sheets, generating a unique nano-framework, i.e., NH2TPP-graphene-NH2TPP. Its UV-visible spectroscopy reveals that the absorption spectrum is not a linear superposition of the spectra of NH2TPP and graphene oxide, because a 59nm red shift of the strong graphene oxide absorption is observed from 238 to 297nm, with significant spectral broadening between 300 and 700nm. Fluorescence emission spectroscopy indicates efficient quenching of NH2TPP photoluminescence in this hybrid material, suggesting that photo-induced electron transfer occurs at the interface between NH2TPP and GO. A reversible on/off photo-current density of 47mA/cm(2) is observed when NH2TPP-graphene-NH2TPP hybrid sandwiches are subjected to pulsed white-light illumination. Covalently-bound porphyrins decrease the optical HOMO/LUMO band gap of graphene oxide by ≈1eV, according to UV-visible spectroscopy. Cyclic voltammetry predicts a small HOMO/LUMO band gap of 0.84eV for NH2TPP-graphene-NH2TPP hybrid sandwiches, which is consistent with efficient electron transfer and fluorescence quenching.

  2. Fabrication of Glassy and Crystalline Ferroelectric Oxide by Containerless Processing

    NASA Astrophysics Data System (ADS)

    Yoda, Shinichi

    1. Instruction Much effort has been devoted to forming bulk glass from the melt of ferroelectric crystalline materials without adding any network-forming oxides such as SiO2 due to the potential for producing transparent glass ceramics with high dielectric constant and enhanced piezoelectric, pyroelectric and electro-optic effects. However, they require a higher cooling rate than glass formed by conventional techniques. Therefore, only amorphous thin-films have been formed, using rapid quenching with a cooling rate >105 K/s. The containerless processing is an attractive synthesis technique as it can prevent melt contamination, minimize heterogeneous nucleation, and allow melt to achieve deep undercooling for forming metastable phase and glassy material. Recently a new ferroelectric materiel, monoclinic BaTi2 O5 , with Currie temperature as 747 K was reported. In this study, we fabricated a bulk BaTi2 O5 glass from melt using containerless processing to study the phase relations and ferroelectric properties of BaTi2 O5 . To our knowledge, this was the first time that a bulk glass of ferroelectric material was fabricated from melt without adding any network-forming oxide. 2. Experiments BaTi2 O5 sphere glass with 2mm diameter was fabricated using containerless processing in an Aerodynamic Levitation Furnace (ALF). The containerless processing allowed the melt to achieve deep undercooling for glass forming. High purity commercial BaTiO3 and TiO2 powders were mixed with a mole ratio of 1:1 and compressed into rods and then sintered at 1427 K for 10 h. Bulk samples with a mass of about 20 mg were cut from the rod, levitated with the ALF, and then melted by a CO2 laser beam. After quenching with a cooling rate of about 1000 K/s, 2 mm diameter sphere glass could be obtained. To analyze the glass structure, a high-energy x-ray diffraction experiment was performed using an incident photon energy of 113.5 keV at the high-energy x-ray diffraction beamline BL04B2 of SPring-8

  3. Molecular characterization and fingerprinting of vanadyl porphyrin and non-porphyrin compounds in the asphaltenes of heavy crude petroleums using HPLC-GFAA analysis

    SciTech Connect

    Wines, B.K.; Vermeulen, T.; Fish, R.H.

    1983-08-01

    High performance liquid chromatography coupled with graphite furnace atomic absorption (HPLC-GFAA) analysis were used to study the precipitated asphaltene fraction of four heavy crude petroleums. Prudhoe Bay and Wilmington crude oils from Alaska and California, respectively, have low vanadium and asphaltene concentrations. Boscan and Cerro Negro are Venezuelan crudes with high levels of vanadium and asphaltenes. The emphasis of this study is the molecular characterization of classes of vanadyl compounds, with special emphasis placed on differentiating the locations of non-porphyrin and porphyrin compounds in the HPLC-GFAA analyses of the asphaltenes and their solvent extracts. Steric exclusion chromatography (SEC) columns were used to determine the molecular weight distribution of vanadium in the asphaltenes and extracts. Fingerprints obtained from SEC-HPLC-GFAA analysis of asphaltenes or normal and reverse phase HPLC-GFAA analysis of polar extracts provided information on the composition of the asphaltines. 122 references, 27 figures, 7 tables.

  4. Optical Gas Sensing of Ammonia and Amines Based on Protonated Porphyrin/TiO₂ Composite Thin Films.

    PubMed

    Castillero, Pedro; Roales, Javier; Lopes-Costa, Tânia; Sánchez-Valencia, Juan R; Barranco, Angel; González-Elipe, Agustín R; Pedrosa, José M

    2016-12-23

    Open porous and transparent microcolumnar structures of TiO₂ prepared by physical vapour deposition in glancing angle configuration (GLAD-PVD) have been used as host matrices for two different fluorescent cationic porphyrins, 5-(N-methyl 4-pyridyl)-10,15,20-triphenyl porphine chloride (MMPyP) and meso-tetra (N-methyl 4-pyridyl) porphine tetrachloride (TMPyP). The porphyrins have been anchored by electrostatic interactions to the microcolumns by self-assembly through the dip-coating method. These porphyrin/TiO₂ composites have been used as gas sensors for ammonia and amines through previous protonation of the porphyrin with HCl followed by subsequent exposure to the basic analyte. UV-vis absorption, emission, and time-resolved spectroscopies have been used to confirm the protonation-deprotonation of the two porphyrins and to follow their spectral changes in the presence of the analytes. The monocationic porphyrin has been found to be more sensible (up to 10 times) than its tetracationic counterpart. This result has been attributed to the different anchoring arrangements of the two porphyrins to the TiO₂ surface and their different states of aggregation within the film. Finally, there was an observed decrease of the emission fluorescence intensity in consecutive cycles of exposure and recovery due to the formation of ammonium chloride inside the film.

  5. Self-assembly of large-scale aggregates of porphyrin from its dimers and their absorption and luminescence properties

    NASA Astrophysics Data System (ADS)

    Udal'tsov, A. V.; Kazarin, L. A.; Sweshnikov, A. A.

    2001-05-01

    Properties of aggregates of protonated meso-tetraphenylporphine (TPP) dimers have been investigated by absorption and luminescence spectroscopies and scanning electron microscopy. It was found that the absorption and fluorescence spectra obtained at a low and several times higher concentration of porphyrin differ considerably. The changes in absorption spectra of TPP in the water-THF-glycerol (84:6:10, v/v) mixture in the presence of 0.4 N HCl with time and the appearance of a green precipitate after several days indicate aggregation of the porphyrin. The near IR emission at 1000 nm, which is assigned to the fluorescence of donor-acceptor water-porphyrin dimeric complex, is revealed in the fluorescence spectra of TPP in aqueous solution of THF in the presence of 0.4 N HCl at the low concentration of porphyrin on excitation at 465 nm. In contrast, the near IR emission is not observed in the solution with several times higher concentration of porphyrin, but a shoulder at ca 800 nm is appreciable in the corresponding spectrum. The large-scale aggregates of TPP with sizes approximately from 1 μm to several micrometers are found in thin films of the protonated porphyrin. It is proposed that the aggregates are formed as a result of self-assembly from different protonated porphyrin dimers and have an ordered structure.

  6. Optical Gas Sensing of Ammonia and Amines Based on Protonated Porphyrin/TiO2 Composite Thin Films

    PubMed Central

    Castillero, Pedro; Roales, Javier; Lopes-Costa, Tânia; Sánchez-Valencia, Juan R.; Barranco, Angel; González-Elipe, Agustín R.; Pedrosa, José M.

    2016-01-01

    Open porous and transparent microcolumnar structures of TiO2 prepared by physical vapour deposition in glancing angle configuration (GLAD-PVD) have been used as host matrices for two different fluorescent cationic porphyrins, 5-(N-methyl 4-pyridyl)-10,15,20-triphenyl porphine chloride (MMPyP) and meso-tetra (N-methyl 4-pyridyl) porphine tetrachloride (TMPyP). The porphyrins have been anchored by electrostatic interactions to the microcolumns by self-assembly through the dip-coating method. These porphyrin/TiO2 composites have been used as gas sensors for ammonia and amines through previous protonation of the porphyrin with HCl followed by subsequent exposure to the basic analyte. UV–vis absorption, emission, and time-resolved spectroscopies have been used to confirm the protonation–deprotonation of the two porphyrins and to follow their spectral changes in the presence of the analytes. The monocationic porphyrin has been found to be more sensible (up to 10 times) than its tetracationic counterpart. This result has been attributed to the different anchoring arrangements of the two porphyrins to the TiO2 surface and their different states of aggregation within the film. Finally, there was an observed decrease of the emission fluorescence intensity in consecutive cycles of exposure and recovery due to the formation of ammonium chloride inside the film. PMID:28025570

  7. Solution Concentration and Flow Rate of Fe3+-modified Porphyrin (Red Blood Model) on Giant Magnetoresistance (GMR) Sensor Efficiency

    NASA Astrophysics Data System (ADS)

    Aminudin, A.; Tjahyono, D. H.; Suprijadi; Djamal, M.; Zaen, R.; Nandiyanto, A. B. D.

    2017-03-01

    Red blood has been of great interest for scientists since it relates to human’ and living creature’s life sustainability. One of the important compounds in red blood is porphyrin. Here, the purpose of this study was to develop a method for detecting porphyrin concentration using the assistance of giant magnetoresistance. In short of the method, we added Fe3+ solution to the porphyrin, and the mixed solution was introduced to the magnetic field. Next, the magnetized solution was introduced to the magnetic sensor to indicate the existence of porphyrin in the solution. To confirm the effectiveness of our method in detecting porphyrin, we varied the flow rate and concentration of Fe3+-modified porphyrin solution. The result showed that the more concentration and the slower flow rate affected the higher sensitivity gained. Since this developed method is simple but effective for detecting porphyrin concentration, we believe that further development of this method will be benefit for many applications, specifically relating to the medical uses.

  8. Novel zinc porphyrin sensitizers for dye-sensitized solar cells: synthesis and spectral, electrochemical, and photovoltaic properties.

    PubMed

    Lee, Cheng-Wei; Lu, Hsueh-Pei; Lan, Chi-Ming; Huang, Yi-Lin; Liang, You-Ren; Yen, Wei-Nan; Liu, Yen-Chun; Lin, You-Shiang; Diau, Eric Wei-Guang; Yeh, Chen-Yu

    2009-01-01

    Novel meso- or beta-derivatized porphyrins with a carboxyl group have been designed and synthesized for use as sensitizers in dye-sensitized solar cells (DSSCs). The position and nature of a bridge connecting the porphyrin ring and carboxylic acid group show significant influences on the spectral, electrochemical, and photovoltaic properties of these sensitizers. Absorption spectra of porphyrins with a phenylethynyl bridge show that both Soret and Q bands are red-shifted with respect to those of porphyrin 6. This phenomenon is more pronounced for porphyrins 3 and 4, which have a pi-conjugated electron-donating group at the meso position opposite the anchoring group. Upon introduction of an ethynylene group at the meso position, the potential at the first oxidation alters only slightly whereas that for the first reduction is significantly shifted to the positive, thus indicating a decreased HOMO-LUMO gap. Quantum-chemical (DFT) results support the spectroelectrochemical data for a delocalization of charge between the porphyrin ring and the amino group in the first oxidative state of diarylamino-substituted porphyrin 5, which exhibits the best photovoltaic performance among all the porphyrins under investigation. From a comparison of the cell performance based on the same TiO(2) films, the devices made of porphyrin 5 coadsorbed with chenodeoxycholic acid (CDCA) on TiO(2) in ratios [5]/[CDCA] = 1:1 and 1:2 have efficiencies of power conversion similar to that of an N3-based DSSC, which makes this green dye a promising candidate for colorful DSSC applications.

  9. Substrate-borne vibrational signals in intraspecific communication of glassy-winged sharpshooters (GWSS)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Exploitation of vibrational signals for suppressing glassy-winged sharpshooter (GWSS) populations could prove to be a useful tool. However, existing knowledge on GWSS vibrational communication is insufficient to implement a management program for this pest in California. Therefore, the objective of ...

  10. Glassy-winged sharpshooter oviposition effects on foliar grapevine and red-tipped photinia terpenoid levels

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The glassy-winged sharpshooter (GWSS), Homalodisca vitripennis (Germar) (Hemiptera: Cicadellidae), is an important vector of Xylella fastidiosa, the bacterium that causes Pierce's disease of grapevine and is a threat to grape production throughout the United States. Female GWSS deposit egg masses be...

  11. Effects of feeding on glassy-winged sharpshooter lipid content and egg production

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Glassy-winged sharpshooter females emerge without mature eggs, and females must feed to produce mature eggs. As a result, allocation of incoming resources must be balanced between egg production and maintenance of other critical biological functions. Central to this process is allocation of lipids s...

  12. Glassy-winged sharpshooter oviposition effects on photinia volatile chemistry with implications on egg parasitoid effectiveness

    Technology Transfer Automated Retrieval System (TEKTRAN)

    An effective way to limit incidence of Pierce’s disease of grapevine is to reduce populations of glassy-winged sharpshooter (GWSS), Homalodisca vitripennis (Germar) (Hemiptera: Cicadellidae), which transmit the causal bacterium, Xylella fastidiosa. One strategy is to utilize egg parasitoids such as ...

  13. Glassy-winged sharpshooter can use a mechanical mechanism to inoculate Xylella fastidiosa into grapevines

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Xylem-feeding leafhoppers such as the glassy-winged sharpshooter, Homalodisca vitripennis (Cicadellidae: Cicadellinae), are thought to inoculate the bacterium Xylella fastidiosa (Xf) from colonies bound to cuticle of the sharpshooter’s functional foregut (precibarium and cibarium). The mechanism of ...

  14. Phylogenetic analysis of heat shock proteins in Glassy-winged sharpshooter

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Four heat shock protein transcripts were produced from the glassy-winged sharpshooter Homalodisca vitripennis (Germar) (Hemiptera: Cicadellidae) which is the major vector of Xylella fastidiosa, the causal agent of Pierce’s disease of grapes. As genomic information has continued to be produced resea...

  15. Phylogenetic analysis of heat shock proteins in Glassy-winged sharpshooter (Homalodisca vitripennis)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Heat shock proteins were identified in the glassy-winged sharpshooter, GWSS, Homalodisca vitripennis. The overall importance and function of HSPs lie in their ability to maintain protein integrity and activity during stressful conditions, such as extreme heat, cold, drought, or other stresses. The G...

  16. Sequence polymorphism of a glassy-winged sharpshooter phytoreovirus reveals a bottleneck in the Californian population

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The glassy-winged sharpshooter (GWSS; Homalodisca vitripennis Germar) is an invasive insect introduced to California circa 1989. Native to the southeastern U.S. and northeastern Mexico, GWSS is of economic concern as a vector of the Pierce’s disease bacterium Xylella fastidiosa. Recently, a novel ...

  17. Kinetics of phase transformation of carbon nanotubes containing Se85Te10Ag5 glassy composites

    NASA Astrophysics Data System (ADS)

    Upadhyay, A. N.; Singh, Kedar

    2016-12-01

    Carbon nanotubes (CNTs) containing glassy composites [(Se85Te10Ag5)100-X(CNT)X] (X = 0, 3 and 5) have been prepared by the melt-quenching technique. The differential scanning calorimetry (DSC) technique was used to study changes in the kinetics of phase transformations of [(Se85Te10Ag5)100-X(CNT)X] (X = 0, 3 and 5) after the incorporation of CNTs under non-isothermal conditions at different heating rates (5, 10, 15 and 20 K min-1). The calculated values of the activation energy of crystallization (E c) and the Avrami index (n) decrease whereas the activation energy of the glass transition (E g) increases for CNTs containing glass composites; such effects are explained on the basis of effective CNTs mediating through a cross-link with the pure-Se85Te10Ag5 glassy matrix. The superiority of the CNT-Se85Te10Ag5 glassy composite over the pure glassy alloy have also been briefly mentioned in regard to electrical, thermal and mechanical properties at room temperature.

  18. Microarray analysis of diapause in the glassy-winged sharpshooter (Homalodisca vitripennis: Hemiptera)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We identified several genes from the pathway which controls leafhopper diapause. Diapause in the glassy-winged sharpshooter, GWSS, Homalodisca vitripennis, is poorly understood, yet is an important physiological condition which permits leafhoppers to survive adverse conditions such as winter tempera...

  19. Microarray analysis of gene expression and diapause in Glassy-winged Sharpshooter (Homalodisca vitripennis: Hemiptera: Cicadellidae)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The condition of diapause in the glassy-winged sharpshooter, GWSS, Homalodisca vitripennis, is poorly understood. Diapause is better known from other, non hemipteran insects. We used oligonucleotide microarrays to address the specificities of transcriptional responses of adult female GWSS, which wer...

  20. Abundance and consumption rate of glassy-winged sharpshooter (Hemiptera: Cicadellidae) on peaches and plums

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Homalodisca vitripennis, also known as the glassy-winged sharpshooter, is a primary vector of phony peach and plum leaf scald diseases caused by Xylella fastidiosa Wells et al. Two of the following scions, (Prunus persica L. Batch cvs. Flordaking and June Gold and Prunus salicina L. cvs. Methley an...

  1. Optical and mechanical behaviors of glassy silicone networks derived from linear siloxane precursors

    NASA Astrophysics Data System (ADS)

    Jang, Heejun; Seo, Wooram; Kim, Hyungsun; Lee, Yoonjoo; Kim, Younghee

    2016-01-01

    Silicon-based inorganic polymers are promising materials as matrix materials for glass fiber composites because of their good process ability, transparency, and thermal property. In this study, for utilization as a matrix precursor for a glass-fiber-reinforced composite, glassy silicone networks were prepared via hydrosilylation of linear/pendant Si-H polysiloxanes and the C=C bonds of viny-lterminated linear/cyclic polysiloxanes. 13C nuclear magnetic resonance spectroscopy was used to determine the structure of the cross-linked states, and a thermal analysis was performed. To assess the mechanical properties of the glassy silicone networks, we performed nanoindentation and 4-point bending tests. Cross-linked networks derived from siloxane polymers are thermally and optically more stable at high temperatures. Different cross-linking agents led to final networks with different properties due to differences in the molecular weights and structures. After stepped postcuring, the Young's modulus and the hardness of the glassy silicone networks increased; however, the brittleness also increased. The characteristics of the cross-linking agent played an important role in the functional glassy silicone networks.

  2. Preface: Proceedings of the Workshop on Mechanical Behavior of Glassy Materials (Vancouver, 21 23 July 2007)

    NASA Astrophysics Data System (ADS)

    Rottler, Joerg; Kennett, Malcolm; Stamp, Philip

    2008-06-01

    This special issue highlights some of the research topics presented at the workshop on Mechanical Behavior of Glassy Materials, which took place in Vancouver, Canada from 21-23 July 2007. The workshop was organized under the auspices of the Pacific Institute of Theoretical Physics (PITP) with support from the Pacific Institute of Mathematical Sciences (PIMS) and Simon Fraser University (SFU). During this three-day event, 23 invited lectures were presented to an international group of about 40 participants. The full conference program as well as an archive of all presentations can be found online at www.pitp.physics.ubc.ca/confs/glass07/ The aim of the workshop was to bring together theorists and experimentalists working on glassy systems, with mechanical properties as the unifying theme. The talks touched on many aspects of the glass problem, from theories of the glass transition and mode coupling approaches to glassy dynamics, to spin glasses, simulations and theories of amorphous plasticity, the universal origin of ageing and dynamical heterogeneity in glasses, and glassy phenomena in biological systems. The interplay of ideas from high- and low-temperature (quantum) regimes of glasses led to lively discussions that brought researchers in both communities to explore similarities and differences in their respective ideas and physical systems. Progress was made on several fronts, and we hope that everyone involved left with some new perspective on their particular corner of interest in a class of problems that continues to present many challenges.

  3. Columbia River Basalt Chemistry, Degassing, and Eruption Dynamics: Insights From Quenched Glassy Lapilli and Tuffs

    NASA Astrophysics Data System (ADS)

    Davis, K.; Wolff, J.; Rowe, M. C.; Neill, O. K.

    2015-12-01

    Primary eruptive vent areas for several lavas in the Imnaha and Grande Ronde Formations of the Columbia River Basalt exhibit phreatomagmatic character, due to the interaction of rising flood basalt magma with groundwater and/or surface water. Vent constructional forms range from extensive (>1 km) maar complexes with abundant basement lithics to small (<<1 km), lithic-poor low-angle cones. Phreatomagmatic tephra is lithified and variably palagonitized, but glassy basaltic lapilli can be recovered from many locations. Many lapilli have experienced variable degrees of Na leaching but preserve magmatic abundances of most other elements; nonetheless in many cases pristine, unmodified glass is amenable to analysis. In addition, phenocrysts in lapilli have fully glassy melt inclusions. Glassy lapilli have highly variable S contents between ~100 and ~1300 ppm. This is consistent with quenching before degassing was complete, a common feature of phreatomagmatic eruptions. Melt inclusions have ≤2900 ppm S, ≤3400 ppm CO2 and ≤2.6 wt% H2O, allowing estimates of atmospheric input from the main phase of Columbia River volcanism. In addition, the lithophile trace element contents, and petrogenetically significant ratios such as Ba/Nb, of glassy lapilli exhibit differ from those in the equivalent 'stony' lava flows by up to a factor of 2. This suggests that processes in the flow and crystallization of lava serve to modify trace element abundances, and may place limits on the petrogenetic significance of trace element data from crystalline lava samples.

  4. Organized assemblies of single wall carbon nanotubes and porphyrin for photochemical solar cells: charge injection from excited porphyrin into single-walled carbon nanotubes.

    PubMed

    Hasobe, Taku; Fukuzumi, Shunichi; Kamat, Prashant V

    2006-12-21

    Photochemical solar cells have been constructed from organized assemblies of single-walled carbon nanotubes (SWCNT) and protonated porphyrin on nanostructured SnO2 electrodes. The protonated form of porphyrin (H4P2+) and SWCNT composites form 0.5-3.0 microm-sized rodlike structures and they can be assembled onto nanostructured SnO2 films [optically transparent electrode OTE/SnO2] by an electrophoretic deposition method. These organized assemblies are photoactive and absorb strongly in the entire visible region. The incident photon to photocurrent efficiency (IPCE) of OTE/SnO2/SWCNT-H4P2+ is approximately 13% at an applied potential of 0.2 V versus saturated calomel electrode. Femtosecond pump-probe spectroscopy experiments confirm the decay of the excited porphyrin in the SWCNT-H4P2+ assembly as it injects electrons into SWCNT. The dual role of SWCNT in promoting photoinduced charge separation and facilitating charge transport is presented.

  5. Molecular characterization and fingerprinting of vanadyl porphyrin and non-porphyrin compounds in heavy crude petroleums using HPLC-GFAA analysis

    SciTech Connect

    Komlenic, J.J.; Vermeulen, T.; Fish, R.H.

    1982-12-01

    Element-specific high performance liquid chromatography-graphite furnace atomic absorption (HPLC-GFAA) analysis was used to classify vanadyl porphyrin and nonporphyrin compounds present in Boscan, Cerro Negro, Wilmington, and Prudhoe Bay heavy crude oils, containing 1100, 550, 49, and 19 ppM V. The crude oils and pyridine extraction products have been analyzed using the HPLC-GFAA technique with steric exclusion chromatography (SEC) and polar amino-cyano (PAC) columns to yield molecular weight and polarity distributions. 50% of the V present, in the form of low molecular weight vanadyl compounds, is extracted, primarily from the asphaltene fraction of each oil. HPLC-GFAA reveal two classes of extracted vanadyl nonporphyrin compounds. One class, present in Cerro Negro, Wilmington, and Prudhoe Bay pyrdine extract, consists of relatively nonpolar compound(s) with maximum uv-Vis absorbance at 300 nm. The other class, present in Boscan and Cerro Negro crude oils, consists of a more polar nonporphyrin compound(s) with maximum absorbance of 265 nm. The two Venezuelan, high sulfur crude oils contain proportionally greater percentages of vanadyl porphyrin compounds, while the two North American, low sulfur crude oils contain predominantly vanadyl nonporphyrin and nickel porphyrin compounds. A correlation relating V concentration and sulfur and asphaltene content has been observed, while correlations involving V content and depth of burial or age of deposit were not apparent. 21 figures, 5 tables.

  6. Ice cloud processing of ultra-viscous/glassy aerosol particles leads to enhanced ice nucleation ability

    NASA Astrophysics Data System (ADS)

    Wagner, R.; Möhler, O.; Saathoff, H.; Schnaiter, M.; Skrotzki, J.; Leisner, T.; Wilson, T. W.; Malkin, T. L.; Murray, B. J.

    2012-09-01

    The ice nucleation potential of airborne glassy aqueous aerosol particles has been investigated by controlled expansion cooling cycles in the AIDA aerosol and cloud chamber of the Karlsruhe Institute of Technology at temperatures between 247 and 216 K. Four different solutes were used as proxies for oxygenated organic matter found in the atmosphere: raffinose, 4-hydroxy-3-methoxy-DL-mandelic acid (HMMA), levoglucosan, and a multi-component mixture of raffinose with five dicarboxylic acids and ammonium sulphate. Similar to previous experiments with citric acid aerosols, all particles were found to nucleate ice heterogeneously before reaching the homogeneous freezing threshold provided that the freezing cycles were started well below the respective glass transition temperatures of the compounds; this is discussed in detail in a separate article. In this contribution, we identify a further mechanism by which glassy aerosols can promote ice nucleation below the homogeneous freezing limit. If the glassy aerosol particles are probed in freezing cycles started only a few degrees below their respective glass transition temperatures, they enter the liquid regime of the state diagram upon increasing relative humidity (moisture-induced glass-to-liquid transition) before being able to act as heterogeneous ice nuclei. Ice formation then only occurs by homogeneous freezing at elevated supersaturation levels. When ice forms the remaining solution freeze concentrates and re-vitrifies. If these ice cloud processed glassy aerosol particles are then probed in a second freezing cycle at the same temperature, they catalyse ice formation at a supersaturation threshold between 5 and 30% with respect to ice. By analogy with the enhanced ice nucleation ability of insoluble ice nuclei like mineral dusts after they nucleate ice once, we refer to this phenomenon as pre-activation. We propose a number of possible explanations for why glassy aerosol particles that have re-vitrified in contact

  7. Ice cloud processing of ultra-viscous/glassy aerosol particles leads to enhanced ice nucleation ability

    NASA Astrophysics Data System (ADS)

    Wagner, R.; Möhler, O.; Saathoff, H.; Schnaiter, M.; Skrotzki, J.; Leisner, T.; Wilson, T. W.; Malkin, T. L.; Murray, B. J.

    2012-04-01

    The ice nucleation potential of airborne glassy aqueous aerosol particles has been investigated by controlled expansion cooling cycles in the AIDA aerosol and cloud chamber of the Karlsruhe Institute of Technology at temperatures between 247 and 216 K. Four different solutes were used as proxies for oxygenated organic matter found in the atmosphere: raffinose, 4-hydroxy-3-methoxy-DL-mandelic acid (HMMA), levoglucosan, and a multi-component mixture of raffinose with five dicarboxylic acids and ammonium sulphate. Similar to previous experiments with citric acid aerosols, all particles were found to nucleate ice heterogeneously before reaching the homogeneous freezing threshold provided that the freezing cycles were started well below the respective glass transition temperatures of the compounds; this is discussed in detail in a separate article. In this contribution, we identify a further mechanism by which glassy aerosols can promote ice nucleation below the homogeneous freezing limit. If the glassy aerosol particles are probed in freezing cycles started only a few degrees below their respective glass transition temperatures, they enter the liquid regime of the state diagram upon increasing relative humidity (moisture-induced glass-to-liquid transition) before being able to act as heterogeneous ice nuclei. Ice formation then only occurs by homogeneous freezing at elevated supersaturation levels. When ice forms the remaining solution freeze concentrates and re-vitrifies. If these ice cloud processed glassy aerosol particles are then probed in a second freezing cycle at the same temperature, they catalyse ice formation at a supersaturation threshold between 5 and 30% with respect to ice. By analogy with the enhanced ice nucleation ability of insoluble ice nuclei like mineral dusts after they nucleate ice once, we refer to this phenomenon as pre-activation. We propose a number of possible explanations for why glassy aerosols that have re-vitrified in contact with the

  8. Preparation of novel porphyrin nanomaterials based on the pH-responsive shape evolution of porphyrin microspheres.

    PubMed

    Zhang, Wenbo; Xing, Lingbo; Wang, Haisheng; Liu, Xiujun; Feng, Yaqing; Gao, Changyou

    2015-04-14

    The shapes and properties of self-assembled materials can be adjusted easily using environmental stimuli. Yet, the stimulus-triggered shape evolution of organic microspheres in aqueous solution has rarely been reported so far. Here, a novel type of poly(allylamine hydrochloride)-g-porphyrin microspheres (PAH-g-Por MPs) was prepared by a Schiff base reaction between 2-formyl-5,10,15,20-tetraphenylporphyrin (Por-CHO) and PAH doped in 3.5-μm CaCO3 microparticles, followed by template removal. The PAH-g-Por MPs had an average diameter of 2.5 μm and could be transformed into one-dimensional nanorods (NRs) and wormlike nanostructures (WSs) after being incubated for different times in pH 1-4 HCl solutions. The rate and degree of hydrolysis had a significant effect on the formation and morphologies of the nanorods. The NRs@pH1, NRs@pH2, and NRs@pH3 were all composed of the released Por-CHO and the unhydrolyzed PAH-g-Por because of the incomplete hydrolysis of the Schiff base. However, the WSs@pH4 were formed by a pure physical shape transformation, because they had the same composition as the PAH-g-Por MPs and the Schiff base bonds were not hydrolyzed. The self-assembled NRs and WSs exhibited good colloidal stability and could emit stable red fluorescence over a relatively long period of time.

  9. Sol-gel hosts doped with porphyrin derivatives. Part I. Spectroscopy, hole-burning and spectral diffusion

    NASA Astrophysics Data System (ADS)

    Kulikov, S. G.; Veret-Lemarinier, A. V.; Galaup, J. P.; Chaput, F.; Boilot, J. P.

    1997-03-01

    Pure inorganic sol-gel matrices as well as hybrid organic/inorganic xerogels have been doped with porphyrins derivatives and studied using line narrowing techniques. The role of residual hydroxyl groups is investigated. Free-base porphyrins are protonated in pure inorganic hosts, but the matrix acidity is reduced in hybrid matrices or when fluorinated porphyrins derivatives are used. The linear electron-phonon coupling can be controlled with the choice of the organic group in organic/inorganic matrices. Persistent spectral hole widths increase with temperature according a glass-like Tn dependence and evidence of spectral diffusion is shown in one of these systems.

  10. Ultrafast Exciton Dynamics of J- and H- Aggregates of Porphyrin Catechol in Aqueous Solution

    NASA Astrophysics Data System (ADS)

    Verma, Sandeep; Ghosh, Hirendra Nath

    Porphyrin catechol found to form J- and H-aggregates in different pH at certain concentration. Ultrafast exciton dynamics of J- and H-aggregates found to be 200 fs and 100 fs respectively as monitored by femtosecond visible spectroscopy

  11. Synthesis of some new porphyrins and their metalloderivatives as potential sensitizers in photo-dynamic therapy

    PubMed Central

    Rostami, Mahboubeh; Rafiee, Leila; Hassanzadeh, Farshid; Dadrass, Ali Reza; Khodarahmi, Ghadam Ali

    2015-01-01

    Porphyrins are a ubiquitous large class of naturally occurring macrocyclic compounds with many significant biological representatives comprising heme and chlorophyll. Some novel adaptable methods for the synthesis of free-based porphyrins as promising sensitizers for the use in photo-dynamic therapy by the virtue of their known tumor affinity, low dark cytotoxicity, and easy synthesis in good to high yields have already been discussed. In the present study, two new porphyrins including TAPFA, as a novel folic acid targeted porphyrin sensitizer, and TAP-Schiff base, as a novel sensitizer with better light absorption, were prepared for the first time and their structures were confirmed by 1H NMR, 13C NMR, FT-IR and UV-Vis spectroscopy as well as CHNS analysis. The compounds were metalized with Zn(II) and Fe(II) metal ions to study how the metal ions can improve the light absorption wavelength and their water solubility. The structures of metalized compounds were also confirmed by FT-IR and UV-Vis spectroscopy. PMID:26779270

  12. Synthesis of some new porphyrins and their metalloderivatives as potential sensitizers in photo-dynamic therapy.

    PubMed

    Rostami, Mahboubeh; Rafiee, Leila; Hassanzadeh, Farshid; Dadrass, Ali Reza; Khodarahmi, Ghadam Ali

    2015-01-01

    Porphyrins are a ubiquitous large class of naturally occurring macrocyclic compounds with many significant biological representatives comprising heme and chlorophyll. Some novel adaptable methods for the synthesis of free-based porphyrins as promising sensitizers for the use in photo-dynamic therapy by the virtue of their known tumor affinity, low dark cytotoxicity, and easy synthesis in good to high yields have already been discussed. In the present study, two new porphyrins including TAPFA, as a novel folic acid targeted porphyrin sensitizer, and TAP-Schiff base, as a novel sensitizer with better light absorption, were prepared for the first time and their structures were confirmed by (1)H NMR, (13)C NMR, FT-IR and UV-Vis spectroscopy as well as CHNS analysis. The compounds were metalized with Zn(II) and Fe(II) metal ions to study how the metal ions can improve the light absorption wavelength and their water solubility. The structures of metalized compounds were also confirmed by FT-IR and UV-Vis spectroscopy.

  13. Photoinduced electron transfer from rail to rung within a self-assembled oligomeric porphyrin ladder

    SciTech Connect

    She, Chunxing; Lee, Suk Joong; McGarrah, James E.; Vura-Weis, Josh; Wasielewski, Michael; Chen, Hanning; Schatz, George C.; Ratner, Mark A.; Hupp, Joseph T.

    2010-01-01

    Photoinduced electron transfer in a self-assembled supramolecular ladder structure comprising oligomeric porphyrin rails and ligated dipyridyltetrazine rungs was characterized by transient absorption spectroscopy and transient direct current photoconductivity to be mainly from an oligomer (rail) to the center of a terminal tetrazine (rung), with the remaining hole being delocalized on the oligomer and subsequent charge recombination in 0.19 ns.

  14. Porphyrin Nanodroplets: Sub-micrometer Ultrasound and Photoacoustic Contrast Imaging Agents.

    PubMed

    Paproski, Robert J; Forbrich, Alexander; Huynh, Elizabeth; Chen, Juan; Lewis, John D; Zheng, Gang; Zemp, Roger J

    2016-01-20

    A novel class of all-organic nanoscale porphyrin nanodroplet agents is presented which is suitable for multimodality ultrasound and photoacoustic molecular imaging. Previous multimodality photoacoustic-ultrasound agents are either not organic, or not yet demonstrated to exhibit enhanced accumulation in leaky tumor vasculature, perhaps because of large diameters. In the current study, porphyrin nanodroplets are created with a mean diameter of 185 nm which is small enough to exhibit the enhanced permeability and retention effect. Porphyrin within the nanodroplet shell has strong optical absorption at 705 nm with an estimated molar extinction coefficient >5 × 10(9) m(-1) cm(-1) , allowing both ultrasound and photoacoustic contrast in the same nanoparticle using all organic materials. The potential of nanodroplets is that they may be phase-changed into microbubbles using high pressure ultrasound, providing ultrasound contrast with single-bubble sensitivity. Multispectral photoacoustic imaging allows visualization of nanodroplets when injected intratumorally in an HT1080 tumor in the chorioallantoic membrane of a chicken embryo. Intravital microscopy imaging of Hep3-GFP and HT1080-GFP tumors in chicken embryos determines that nanodroplets accumulated throughout or at the periphery of tumors, suggesting that porphyrin nanodroplets may be useful for enhancing the visualization of tumors with ultrasound and/or photoacoustic imaging.

  15. Photodynamic efficiency of cationic meso-porphyrins at lipid bilayers: insights from molecular dynamics simulations.

    PubMed

    Cordeiro, Rodrigo M; Miotto, Ronei; Baptista, Maurício S

    2012-12-20

    Porphyrin derivatives have applications as photoactive drugs in photodynamic therapy. However, little is known about their interactions with phospholipid membranes at the molecular level. We employed molecular dynamics simulations to model the binding between a series of cationic meso-(N-methyl-4-pyridinium)phenylporphyrins and anionic phosphatidylglycerol lipid bilayers. This was done in the presence of molecular oxygen within the membrane. The ability of various porphyrins to cause photodamage was quantified in terms of their immersion depth and degree of exposition to a higher oxygen concentration inside the membrane. Simulations showed that the photodynamic efficiency could be improved as the number of hydrophobic phenyl substituents attached to the porphyrinic ring increased. In the specific case of porphyrins containing two hydrophobic and two charged substituents, the cis isomer was significantly more efficient than the trans. These results correlate well with previous experimental observations. They highlight the importance of both the total charge and amphiphilicity of the photosensitizer for its performance in photodynamic therapy.

  16. A Tb–Zn tetra(4-sulfonatophenyl)porphyrin hybrid: Preparation, structure, photophysical and electrochemical properties

    SciTech Connect

    Chen, Wen-Tong; Hu, Rong-Hua; Wang, Yin-Feng; Zhang, Xian; Liu, Juan

    2014-05-01

    A terbium-zinc porphyrin, i.e. [TbZn(TPPS)H{sub 3}O]{sub n} (1) (TPPS=tetra(4-sulfonatophenyl)porphyrin), has been obtained from a solvothermal reaction and structurally analyzed by single-crystal X-ray diffraction. Compound 1 is characteristic of a condensed three-dimensional (3-D) porous open framework with two types of infinite one-dimensional (1-D) chain-like structure. Compound 1 exhibits a void space of 215 Å{sup 3}, which is 9.2% of the unit-cell volume. TG/DTA measurement reveals that the framework of compound 1 is thermally stable up to 336 °C. In order to reveal its photophysical and electrochemical properties, we investigated compound 1 in detail with UV–vis spectra, fluorescence, quantum yield, luminescence lifetime, and CV/DPV. - Graphical abstract: A terbium–zinc porphyrin [TbZn(TPPS)H{sub 3}O]{sub n} has been obtained from a solvothermal reaction. It features a condensed 3-D porous open framework. It shows good thermal stability. - Highlights: • This paper reports a novel terbium–zinc porphyrin. • It features a novel condensed three-dimensional porous open framework. • The title compound is thermally stable up to 336 °C. • It is studied by UV–vis, fluorescence, quantum yield, lifetime, and CV/DPV.

  17. Photodynamic action of porphyrin on Ca2+ influx in endoplasmic reticulum: a comparison with mitochondria.

    PubMed Central

    Ricchelli, F; Barbato, P; Milani, M; Gobbo, S; Salet, C; Moreno, G

    1999-01-01

    We have studied the distribution properties of haematoporphyrin (HP) and protoporphyrin (PP) in mitochondria and endoplasmic reticulum after isolation from rat liver. The photosensitizing efficiency of porphyrin on the Ca2+ influx function of microsomes has been compared with that obtained on Ca2+ uptake in mitochondria. HP and PP are accumulated in microsomes to a greater extent than in mitochondria, both porphyrins binding to membrane protein sites. The Ca2+ influx functions of mitochondria and microsomes, before and after irradiation in the presence of HP or PP, were studied by following the changes in the free Ca2+ concentration in the medium as revealed by the variations in fluorescence intensity of the Ca2+ indicator Calcium Green-1. For the same amount of incorporated porphyrin, the Ca2+ influx function of microsomes is degraded by irradiation more rapidly than that of mitochondria. The protective effect of dithiothreitol suggests that thiol groups in the Ca2+-transporting enzyme are the preferential targets of the photodynamic effect. These results suggest that intracellular Ca2+ movements are altered primarily by the endoplasmic reticulum rather than by mitochondrial damage, in good agreement with other observations made in porphyrin-loaded irradiated cells. PMID:9931319

  18. Novel porphyrin-psoralen conjugates: synthesis, DNA interaction and cytotoxicity studies.

    PubMed

    Kumar, Dalip; Mishra, Bhupendra A; Chandra Shekar, K P; Kumar, Anil; Akamatsu, Kanako; Kurihara, Ryohsuke; Ito, Takeo

    2013-10-21

    A Cu(i)-catalyzed azide-alkyne cycloaddition reaction (CuAAC) has been utilized to prepare novel triazole-linked cationic porphyrin-psoralen conjugates that exhibited significant photocytotoxicity against A549 cancer cells (IC50 = 84 nM).

  19. Optical acetylcholine sensor based on free base porphyrin as a chromoionophore.

    PubMed

    Mroczkiewicz, Monika; Pietrzak, Mariusz; Górski, Łukasz; Malinowska, Elżbieta

    2011-09-21

    In this work, the possibility of application of free base porphyrin as a lipophilic pH chromoionophore for the preparation of optical cation-selective sensors was investigated. The properties of polymeric membranes, containing porphyrins of different structures, namely tetraphenylporphyrin (TPP) and octaethylporphyrin (OEP), were compared. Changes in equilibrium between protonated and deprotonated form of porphyrin, resulting from variations in ACh concentration, were evaluated. The influence of various factors (kind and quantity of anionic additive and porphyrin in the membrane phase, pH of sample solution) on initial equilibrium was studied. The best membrane composition was chosen as: TPP 3 wt.%, KTFPB 175 mol.% relative to ionophore, PVC:o-NPOE (1 : 4) and measuring buffer solution: 0.05 M MES, pH 4.5. Selectivity, response stability, reversibility and repeatability tests were carried out for chosen sensor. Developed sensor allowed for the determination of a model analyte, acetylcholine, at the concentration range of 10(-5) to 10(-2) M, both in stationary and flow-injection system. Sensor response was reversible and repeatable in the mentioned concentration range.

  20. Biological Photothermal Nanodots Based on Self-Assembly of Peptide-Porphyrin Conjugates for Antitumor Therapy.

    PubMed

    Zou, Qianli; Abbas, Manzar; Zhao, Luyang; Li, Shukun; Shen, Guizhi; Yan, Xuehai

    2017-02-08

    Photothermal agents can harvest light energy and convert it into heat, offering a targeted and remote-controlled way to destroy carcinomatous cells and tissues. Inspired by the biological organization of polypeptides and porphyrins in living systems, here we have developed a supramolecular strategy to fabricate photothermal nanodots through peptide-modulated self-assembly of photoactive porphyrins. The self-assembling nature of porphyrins induces the formation of J-aggregates as substructures of the nanodots, and thus enables the fabrication of nanodots with totally inhibited fluorescence emission and singlet oxygen production, leading to a high light-to-heat conversion efficiency of the nanodots. The peptide moieties not only provide aqueous stability for the nanodots through hydrophilic interactions, but also provide a spatial barrier between porphyrin groups to inhibit the further growth of nanodots through the strong π-stacking interactions. Thermographic imaging reveals that the conversion of light to heat based on the nanodots is efficient in vitro and in vivo, enabling the nanodots to be applied for photothermal acoustic imaging and antitumor therapy. Antitumor therapy results show that these nanodots are highly biocompatible photothermal agents for tumor ablation, demonstrating the feasibility of using bioinspired nanostructures of self-assembling biomaterials for biomedical photoactive applications.

  1. Determination of residual manganese in Mn porphyrin-based superoxide dismutase (SOD) and peroxynitrite reductase mimics

    PubMed Central

    Rebouças, Júlio S.; Kos, Ivan; Batinić-Haberle, Ines

    2009-01-01

    The awareness of the beneficial effects of Mn porphyrin-based superoxide dismutase (SOD) mimics and peroxynitrite scavengers on decreasing oxidative stress injuries has increased the use of these compounds as mechanistic probes and potential therapeutics. Simple Mn2+ salts, however, have SOD-like activity in their own right both in vitro and in vivo. Thus, quantification/removal of residual Mn2+ species in Mn-based therapeutics is critical to an unambiguous interpretation of biological data. Herein we report a simple, sensitive, and specific method to determine residual Mn2+ in Mn-porphyrin preparations that combines a hydrometallurgical approach for separation/speciation of metal compounds with a spectrophotometric strategy for Mn determination. The method requires only common chemicals and a spectrophotometer and is based on the extraction of residual Mn2+ by bis(2-ethylhexyl)hydrogenphosphate (D2EHPA) into kerosene, re-extraction into acid, and neutralization followed by UV-vis determination of the Mn2+ levels via a Cd2+-catalyzed metallation of the H2TCPP4− porphyrin indicator. The overall procedure is simple, sensitive, specific, and amenable to adaptation. This quantification method has been routinely used by us for a large variety of water-soluble porphyrins. PMID:19660888

  2. Novel expanded porphyrin sensitized solar cells using boryl oxasmaragdyrin as the sensitizer.

    PubMed

    Mane, Sandeep B; Hu, Jyun-Yu; Chang, Yu-Cheng; Luo, Liyang; Diau, Eric Wei-Guang; Hung, Chen-Hsiung

    2013-08-07

    Oxasmaragdyrin boron complexes were prepared and applied in DSSCs. The HOMO-LUMO energy gap analyses and theoretical calculations revealed that these expanded porphyrins are ideal sensitizers for DSSCs. A device containing oxasmaragdyrin-BF2 as the sensitizer achieves an energy conversion efficiency of 5.7%.

  3. Ligand effects on the X-ray absorption of a nickel porphyrin complex: a simulation study

    NASA Astrophysics Data System (ADS)

    Campbell, Luke; Tanaka, Satoshi; Mukamel, Shaul

    2004-04-01

    We present a simulation of the X-ray absorption near-edge spectrum (XANES) of the metal porphyrin NiTPP (nickel tetraphenylporphyrin) and investigate the changes to the spectrum caused by adding piperidine ligands to the metal atom. The main features in the experimental spectrum (Chen et al., Science 292 (2001) 262) are interpreted in terms of changes in the electronic structure.

  4. Assembly of Multi-Phthalocyanines on a Porphyrin Template by Fourfold Rotaxane Formation.

    PubMed

    Yamada, Yasuyuki; Kato, Tatsuhisa; Tanaka, Kentaro

    2016-08-22

    A stacked assembly composed of a porphyrin and two phthalocyanines was prepared through fourfold rotaxane formation. Two phthalocyanine molecules, bearing four 24-crown-8 units, were assembled onto a porphyrin template incorporating four sidechains with two dialkylammonium ions each through pseudorotaxane formation between crown ether units and ammonium ions. The Staudinger phosphite reaction, as the stoppering reaction, resulted in the formation of the stacked heterotrimer composed of a porphyrin and two phthalocyanines connected through a fourfold rotaxane structure. UV/Vis spectroscopic and electrochemical studies of the heterotrimer indicated that there is a significant electronic interaction between the two phthalocyanine units due to the close stacking. The electrochemical oxidation process of the stacked heterotrimer was studied by cyclic voltammetry and spectroelectrochemistry. Electron paramagnetic resonance (EPR) spectroscopy of a dinuclear Cu(II) complex, in which two Cu(II) phthalocyanines were assembled on a metal-free porphyrin template, revealed that two Cu(II) phthalocyanines were located within the stacking distance, which resulted in an antiferromagnetic interaction between the two S=1/2 spins in the ground state of the Cu(2+) ions in the heterotrimer.

  5. Organisation and ordering of 1D porphyrin polymers synthesised by on-surface Glaser coupling.

    PubMed

    Saywell, Alex; Browning, Abigail S; Rahe, Philipp; Anderson, Harry L; Beton, Peter H

    2016-08-16

    One-dimensional polymer chains consisting of π-conjugated porphyrin units are formed via Glaser coupling on a Ag(111) surface. Scanning probe microscopy reveals the covalent structure of the products and their ordering. The conformational flexibility within the chains is investigated via a comparision of room temperature and cryogenic measurements.

  6. Organic solid state switches incorporating porphyrin compounds and method for producing organic solid state optical switches

    DOEpatents

    Wasielewski, Michael R.; Gaines, George L.; Niemczyk, Mark P.; Johnson, Douglas G.; Gosztola, David J.; O'Neil, Michael P.

    1996-01-01

    A light-intensity dependent molecular switch comprised of a compound which shuttles an electron or a plurality of electrons from a plurality of electron donors to an electron acceptor upon being stimulated with light of predetermined wavelengths, said donors selected from porphyrins and other compounds, and a method for making said compound.

  7. Extending supramolecular fullerene-porphyrin chemistry to pillared metal-organic frameworks

    PubMed Central

    Sun, Dayong; Tham, Fook S.; Reed, Christopher A.; Boyd, Peter D. W.

    2002-01-01

    Porphyrins and fullerenes are spontaneously attracted to each other. This supramolecular recognition element can be exploited to produce ordered arrays of interleaved porphyrins and fullerenes. C60⋅H2TpyP⋅Pb(NO3)2⋅1.5TCE (H2TpyP = tetra-4-pyridylporphyrin; TCE = 1,1,2,2-tetrachloroethane) crystallizes in the tetragonal P4/n space group and the structure has been solved to high resolution. The Pb2+ ions connect the pyridylporphyrins in infinite sheets with an interlayer spacing of 12.1 Å. The fullerenes are intercalated between these layers, acting as pillars. The 6:6 ring juncture bonds of C60 are centered over the porphyrins, bringing the layers into strict tetragonal register. This arranagement identifies the fullerene–porphyrin interaction as a structure-defining element. The same motif is seen in a related ribbon structure having C70 intercalated into HgI2-linked H2TpyTP. The supramolecular design principles involved in assembling these chromophores may have applications in materials science. PMID:11943855

  8. The Silver Complexes of Porphyrins, Corroles, and Carbaporphyrins: Silver in the Oxidation States II and III

    ERIC Educational Resources Information Center

    Bruckner, Christian

    2004-01-01

    Studies in relation to the silver complexes of porphyrins, corroles and carbaporphyrins are presented especially with relation to silver in the oxidation states II and III. It is seen that the Ag(sub III) complex was electrochemically readily and reversibly reduced to the corresponding Ag(sub II) complex, thus indicating that the complex could be…

  9. The severity of hereditary porphyria is modulated by the porphyrin exporter and Lan antigen ABCB6

    PubMed Central

    Fukuda, Yu; Cheong, Pak Leng; Lynch, John; Brighton, Cheryl; Frase, Sharon; Kargas, Vasileios; Rampersaud, Evadnie; Wang, Yao; Sankaran, Vijay G.; Yu, Bing; Ney, Paul A.; Weiss, Mitchell J.; Vogel, Peter; Bond, Peter J.; Ford, Robert C.; Trent, Ronald J.; Schuetz, John D.

    2016-01-01

    Hereditary porphyrias are caused by mutations in genes that encode haem biosynthetic enzymes with resultant buildup of cytotoxic metabolic porphyrin intermediates. A long-standing open question is why the same causal porphyria mutations exhibit widely variable penetrance and expressivity in different individuals. Here we show that severely affected porphyria patients harbour variant alleles in the ABCB6 gene, also known as Lan, which encodes an ATP-binding cassette (ABC) transporter. Plasma membrane ABCB6 exports a variety of disease-related porphyrins. Functional studies show that most of these ABCB6 variants are expressed poorly and/or have impaired function. Accordingly, homozygous disruption of the Abcb6 gene in mice exacerbates porphyria phenotypes in the Fechm1Pas mouse model, as evidenced by increased porphyrin accumulation, and marked liver injury. Collectively, these studies support ABCB6 role as a genetic modifier of porphyria and suggest that porphyrin-inducing drugs may produce excessive toxicities in individuals with the rare Lan(−) blood type. PMID:27507172

  10. Study on the supramolecular system of meso-tetrakis (4-sulfonatophenyl) porphyrin and cyclodextrins by spectroscopy

    NASA Astrophysics Data System (ADS)

    Wang, Xiao-ping; Pan, Jing-hao; Shuang, Shao-min

    2001-12-01

    The ability of β-cyclodextrin (β-CD), sulfurbutylether-β-CD (SBE-β-CD) and hydroxypropyl-β-CD (HP-β-CD) to break the aggregate of the meso-Tetrakis (4-sulfonatophenyl) porphyrin (TPPS 4) and to form 2:1 inclusion complexes has been studied by adsorption and fluorescence spectroscopy. The formation constants are calculated, respectively by fluoremetry, from which the inclusion capacity of different CDs is compared and the inclusion mechanism of charged-β-CD (SBE-β-CD) is quite different from that of parent β-CD. At lower pH, the complexation between HP-β-CD and H 2TPPS 42+ (the form of the diprotonated TPPS 4) hampers the continuous protonation of the pyrrole nitrogen of TPPS 4 and the hydrophobic cavity may prefer to bind an apolar neutral porphyrin molecule. 1HNMR data support the inclusion conformation of the porphyrin-cyclodextrin supramolecular system, indicating the interaction of meso-phenyl groups of TPPS 4 with the cavity of CDs. For this host-guest inclusion model, cyclodextrin, being regarded as the protein component, which acts as a carrier enveloping the active site of heme prosthetic group within its hydrophobic environment, provides a protective sheath for porphyrin, creating artificial analogues of heme-containing proteins. However, the TPPS 4, encapsulated within this saccharide-coated barrier, its physico-chemical, photophysical and photochemical properties changed strongly.

  11. Characterization, direct electrochemistry, and amperometric biosensing of graphene by noncovalent functionalization with picket-fence porphyrin.

    PubMed

    Tu, Wenwen; Lei, Jianping; Zhang, Siyuan; Ju, Huangxian

    2010-09-17

    Reduced graphene oxide (RGO) was prepared and functionalized with picket-fence porphyrin, 5,10,15,20-tetrakis [αααα-2-trismethylammoniomethylphenyl] porphyrin iron(III) pentachloride (FeTMAPP), through π-π interactions. The resulting nanocomposite was characterized by atomic force microscopy (AFM); transmission electron microscopy (TEM); contact angle measurements; and fluorescence, Raman, and UV/Vis absorption spectroscopy. On account of the introduction of positively charged FeTMAPP, the functionalized RGO showed good dispersion in aqueous solution. The RGO could greatly accelerate the electron transfer of FeTMAPP to produce a well-defined redox couple of Fe(III)/Fe(II) at -0.291 and -0.314 V. Due to the synergic effect between RGO and the porphyrin, the nanocomposite showed excellent electrocatalytic activity toward the reduction of chlorite, thus leading to highly sensitive amperometric biosensing at low applied potential. The biosensor for chlorite showed a linear range from 5.0×10(-8) to 1.2×10(-4) mol L(-1) with a detection limit of 2.4×10(-8) mol L(-1) at a signal-to-noise ratio of 3. The picket-fence porphyrin could serve as an efficient species to functionalize graphene for electronic and optical applications.

  12. Quantitative comparison of stylet penetration behaviors of glassy-winged sharpshooter on selected hosts.

    PubMed

    Sandanayaka, W R M; Backus, E A

    2008-08-01

    New Zealand is threatened by invasion of the glassy-winged sharpshooter, Homalodisca vitripennis (Germar) (Hemiptera: Cicadellidae), an important vector of Xylella fastidiosa, a gram-negative bacterium that causes Pierce's disease in grape (Vitis spp.) and scorch diseases in many other horticultural crops. Therefore, an understanding of the host acceptability, feeding behavior, and potential vector efficiency of glassy-winged sharpshooter on New Zealand crops is important. We tested host plant acceptance and feeding behaviors of glassy-winged sharpshooter on three common horticultural crops grown in New Zealand (apple [Malus spp.], grape, and citrus [Citrus spp.]), and a native plant (Metrosideros excelsa [=tomentosa] Richard, pohutukawa), using the electrical penetration graph (EPG) technique. Probing (stylet penetration) behaviors varied among the host plants, primarily due to differences in waveform event durations. Apple and grape were the most accepted host plants, on which glassy-winged sharpshooter spent the majority of its time on the plant probing and readily located and accepted a xylem cell for ingestion. This resulted in long durations of sustained xylem fluid ingestion. In contrast, pohutukawa was the least accepted host. On this plant, glassy-winged sharpshooter spent less time probing and engaged in longer and more frequent testing/searching and xylem-testing activities, rejected xylem cells frequently, and spent less time with stylets resting, before accepting a xylem cell and ultimately performing the same amount of sustained ingestion. Citrus plants contaminated with sublethal insecticide residues were intermediate between these extremes, with some acceptance of xylem, but less ingestion, probably due to presumed partial paralysis of the cibarial muscles. Implications of the results in terms of host plant acceptance and the development of a stylet penetration index are discussed.

  13. Annealing effects on the migration of ion-implanted cadmium in glassy carbon

    NASA Astrophysics Data System (ADS)

    Hlatshwayo, T. T.; Sebitla, L. D.; Njoroge, E. G.; Mlambo, M.; Malherbe, J. B.

    2017-03-01

    The migration behaviour of cadmium (Cd) implanted into glassy carbon and the effects of annealing on radiation damage introduced by ion implantation were investigated. The glassy carbon substrates were implanted with Cd at a dose of 2 × 1016 ions/cm2 and energy of 360 keV. The implantation was performed at room temperature (RT), 430 °C and 600 °C. The RT implanted samples were isochronally annealed in vacuum at 350, 500 and 600 °C for 1 h and isothermally annealed at 350 °C up to 4 h. The as-implanted and annealed samples were characterized by Raman spectroscopy and Rutherford backscattering spectrometry (RBS). Raman results revealed that implantation at room temperature amorphized the glassy carbon structure while high temperature implantations resulted in slightly less radiation damage. Isochronal annealing of the RT implanted samples resulted in some recrystallization as a function of increasing temperature. The original glassy carbon structure was not achieved at the highest annealing temperature of 600 °C. Diffusion of Cd in glassy carbon was already taking place during implantation at 430 °C. This diffusion of Cd was accompanied by significant loss from the surface during implantation at 600 °C. Isochronal annealing of the room temperature implanted samples at 350 °C for 1 h caused Cd to diffuse towards the bulk while isothermal annealing at 500 and 600 °C resulted in the migration of implanted Cd toward the surface accompanied by a loss of Cd from the surface. Isothermal annealing at 350 °C for 1 h caused Cd to diffuse towards the bulk while for annealing time >1 h Cd diffused towards the surface. These results were interpreted in terms of trapping and de-trapping of implanted Cd by radiation damage.

  14. A novel pattern transfer technique for mounting glassy carbon microelectrodes on polymeric flexible substrates

    NASA Astrophysics Data System (ADS)

    Vomero, Maria; van Niekerk, Pieter; Nguyen, Vivian; Gong, Nick; Hirabayashi, Mieko; Cinopri, Alessio; Logan, Kyle; Moghadasi, Ali; Varma, Priya; Kassegne, Sam

    2016-02-01

    We present a novel technology for transferring glassy carbon microstructures, originally fabricated on a silicon wafer through a high-temperature process, to a polymeric flexible substrate such as polyimide. This new transfer technique addresses a major barrier in Carbon-MEMS technology whose widespread use so has been hampered by the high-temperature pyrolysis process (⩾900 °C), which limits selection of substrates. In the new approach presented, patterning and pyrolysis of polymer precursor on silicon substrate is carried out first, followed by coating with a polymer layer that forms a hydrogen bond with glassy carbon and then releasing the ensuing glassy carbon structure; hence, transferring it to a flexible substrate. This enables the fabrication of a unique set of glassy carbon microstructures critical in applications that demand substrates that conform to the shape of the stimulated/actuated or sensed surface. Our findings based on Fourier transform infared spectroscopy on the complete electrode set demonstrate—for the first time—that carbonyl groups on polyimide substrate form a strong hydrogen bond with hydroxyl groups on glassy carbon resulting in carboxylic acid dimers (peaks at 2660 and 2585 cm-1). This strong bond is further confirmed by a tensile test that demonstrated an almost perfect bond between these materials that behave as an ideal composite material. Further, mechanical characterization shows that ultimate strain for such a structure is as high as 15% with yield stress of ~20 MPa. We propose that this novel technology not only offers a compelling case for the widespread use of carbon-MEMS, but also helps move the field in new and exciting directions.

  15. Glassy slags for minimum additive waste stabilization. Interim progress report, May 1993--February 1994

    SciTech Connect

    Feng, X.; Wronkiewicz, D.J.; Bates, J.K.; Brown, N.R.; Buck, E.C.; Dietz, N.L.; Gong, M.; Emery, J.W.

    1994-05-01

    Glassy slag waste forms are being developed to complement glass waste forms in implementing Minimum Additive Waste Stabilization (MAWS) for supporting DOE`s environmental restoration efforts. The glassy slag waste form is composed of various crystalline and metal oxide phases embedded in a silicate glass phase. The MAWS approach was adopted by blending multiple waste streams to achieve up to 100% waste loadings. The crystalline phases, such as spinels, are very durable and contain hazardous and radioactive elements in their lattice structures. These crystalline phases may account for up to 80% of the total volume of slags having over 80% metal loading. The structural bond strength model was used to quantify the correlation between glassy slag composition and chemical durability so that optimized slag compositions were obtained with limited crucible melting and testing. Slag compositions developed through crucible melts were also successfully generated in a pilot-scale Retech plasma centrifugal furnace at Ukiah, California. Utilization of glassy slag waste forms allows the MAWS approach to be applied to a much wider range of waste streams than glass waste forms. The initial work at ANL has indicated that glassy slags are good final waste forms because of (1) their high chemical durability; (2) their ability to incorporate large amounts of metal oxides; (3) their ability to incorporate waste streams having low contents of flux components; (4) their less stringent requirements on processing parameters, compared to glass waste forms; and (5) their low requirements for purchased additives, which means greater waste volume reduction and treatment cost savings.

  16. The effect of pyridyl substituents on the thermodynamics of porphyrin binding to G-quadruplex DNA.

    PubMed

    Rowland, Gerald B; Barnett, Kerry; Dupont, Jesse I; Akurathi, Gopalakrishna; Le, Vu H; Lewis, Edwin A

    2013-12-01

    Most of the G-quadruplex interactive molecules reported to date contain extended aromatic flat ring systems and are believed to bind principally by π-π stacking on the end G-tetrads of the quadruplex structure. One such molecule, TMPyP4, (5,10,15,20-tetra(N-methyl-4-pyridyl)porphyrin), exhibits high affinity and some selectivity for G-quadruplex DNA over duplex DNA. Although not a realistic drug candidate, TMPyP4 is used in many nucleic acid research laboratories as a model ligand for the study of small molecule G-quadruplex interactions. Here we report on the synthesis and G-quadruplex interactions of four new cationic porphyrin ligands having only 1, 2, or 3 (N-methyl-4-pyridyl) substituents. The four new ligands are: P(5) (5-(N-methyl-4-pyridyl)porphyrin), P(5,10) (5,10-di(N-methyl-4-pyridyl)porphyrin), P(5,15) (5,15-di(N-methyl-4-pyridyl)porphyrin), and P(5,10,15) (5,10,15-tri(N-methyl-4-pyridyl)porphyrin). Even though these compounds have been previously synthesized, we report alternative synthetic routes that are more efficient and that result in higher yields. We have used ITC, CD, and ESI-MS to explore the effects of the number of N-methyl-4-pyridyl substituents and the substituent position on the porphyrin on the G-quadruplex binding energetics. The relative affinities for binding these ligands to the WT Bcl-2 promoter sequence G-quadruplex are: K(TMPyP4)≈K(P)(5,15)>KP(5,10,15)>KP(5,10), KP(5). The saturation stoichiometry is 2:1 for both P(5,15) and P(5,10,15), while neither P(5) nor P(5,10) exhibit significant complex formation with the WT Bcl-2 promoter sequence G-quadruplex. Additionally, binding of P(5,15) appears to interact by an 'intercalation mode' while P(5,10,15) appears to interact by an 'end-stacking mode'.

  17. Strain-Level Differences in Porphyrin Production and Regulation in Propionibacterium acnes Elucidate Disease Associations

    PubMed Central

    Johnson, Tremylla; Kang, Dezhi; Barnard, Emma

    2016-01-01

    ABSTRACT Propionibacterium acnes is an important skin commensal, but it is also considered a pathogenic factor in several diseases including acne vulgaris, the most common skin disease. While previous studies have revealed P. acnes strain-level differences in health and disease associations, the underlying molecular mechanisms remain unknown. Recently, we demonstrated that vitamin B12 supplementation increases P. acnes production of porphyrins, a group of proinflammatory metabolites important in acne development (D. Kang, B. Shi, M. C. Erfe, N. Craft, and H. Li, Sci. Transl. Med. 7:293ra103, 2015, doi:10.1126/scitranslmed.aab2009). In this study, we compared the porphyrin production and regulation of multiple P. acnes strains. We revealed that acne-associated type IA-2 strains inherently produced significantly higher levels of porphyrins, which were further enhanced by vitamin B12 supplementation. On the other hand, health-associated type II strains produced low levels of porphyrins and did not respond to vitamin B12. Using a small-molecule substrate and inhibitor, we demonstrated that porphyrin biosynthesis was modulated at the metabolic level. We identified a repressor gene (deoR) of porphyrin biosynthesis that was carried in all health-associated type II strains, but not in acne-associated type IA-2 strains. The expression of deoR suggests additional regulation of porphyrin production at the transcriptional level in health-associated strains. Our findings provide one potential molecular mechanism for the different contributions of P. acnes strains to skin health and disease and support the role of vitamin B12 in acne pathogenesis. Our study emphasizes the importance of understanding the role of the commensal microbial community in health and disease at the strain level and suggests potential utility of health-associated P. acnes strains in acne treatment. IMPORTANCE Propionibacterium acnes is a dominant bacterium residing on skin, and it has been thought

  18. Molecular catalysis of the oxygen reduction reaction by iron porphyrin catalysts tethered into Nafion layers: An electrochemical study in solution and a membrane-electrode-assembly study in fuel cells

    NASA Astrophysics Data System (ADS)

    He, Qinggang; Mugadza, Tawanda; Kang, Xiongwu; Zhu, Xiaobing; Chen, Shaowei; Kerr, John; Nyokong, Tebello

    2012-10-01

    This study was motivated by the need for improved understanding of the kinetics and transport phenomena in a homogeneous catalyst system for the oxygen reduction reaction (ORR). Direct interaction between the sulfonic groups of Nafion and an Fe(III) meso-tetra(N-methyl-4-pyridyl) porphine chloride (Fe(III)TMPyP) compound was observed using FTIR and in situ UV-Vis spectroelectrochemical characterizations. A positive shift of the half wave potential value (E1/2) for ORR on the iron porphyrin catalyst (Fe(III)TMPyP) was observed upon addition of a specific quantity of Nafion ionomer on a glassy carbon working electrode, indicating not only a faster charge transfer rate but also the role of protonation in the oxygen reduction reaction (ORR) process. A membrane electrode assembly (MEA) was made as a sandwich of a Pt-coated anode, a Nafion® 212 membrane, and a Fe(III)TMPyP + Nafion ionomer-coated cathode. This three-dimensional catalysis system has been demonstrated to be working in a H2/O2 proton exchange membrane (PEM) fuel cell test.

  19. Modulation of Energy Transfer into Sequential Electron Transfer upon Axial Coordination of Tetrathiafulvalene in an Aluminum(III) Porphyrin-Free-Base Porphyrin Dyad.

    PubMed

    Poddutoori, Prashanth K; Bregles, Lucas P; Lim, Gary N; Boland, Patricia; Kerr, Russ G; D'Souza, Francis

    2015-09-08

    Axially assembled aluminum(III) porphyrin based dyads and triads have been constructed to investigate the factors that govern the energy and electron transfer processes in a perpendicular direction to the porphyrin plane. In the aluminum(III) porphyrin-free-base porphyrin (AlPor-Ph-H2Por) dyad, the AlPor occupies the basal plane, while the free-base porphyrin (H2Por) with electron withdrawing groups resides in the axial position through a benzoate spacer. The NMR, UV-visible absorption, and steady-state fluorescence studies confirm that the coordination of pyridine appended tetrathiafulvalene (TTF) derivative (TTF-py or TTF-Ph-py) to the dyad in noncoordinating solvents afford vertically arranged supramolecular self-assembled triads (TTF-py→AlPor-Ph-H2Por and TTF-Ph-py→AlPor-Ph-H2Por). Time-resolved studies revealed that the AlPor in dyad and triads undergoes photoinduced energy and/or electron transfer processes. Interestingly, the energy and electron donating/accepting nature of AlPor can be modulated by changing the solvent polarity or by stimulating a new competing process using a TTF molecule. In modest polar solvents (dichloromethane and o-dichlorobenzene), excitation of AlPor leads singlet-singlet energy transfer from the excited singlet state of AlPor ((1)AlPor*) to H2Por with a moderate rate constant (k(EnT)) of 1.78 × 10(8) s(-1). In contrast, excitation of AlPor in the triad results in ultrafast electron transfer from TTF to (1)AlPor* with a rate constant (k(ET)) of 8.33 × 10(9)-1.25 × 10(10) s(-1), which outcompetes the energy transfer from (1)AlPor* to H2Por and yields the primary radical pair TTF(+•)-AlPor(-•)-H2Por. A subsequent electron shift to H2Por generates a spatially well-separated TTF(+•)-AlPor-H2Por(-•) radical pair.

  20. Synthesis of water-soluble silicon-porphyrin: protolytic behaviour of axially coordinated hydroxy groups.

    PubMed

    Remello, Sebastian Nybin; Kuttassery, Fazalurahman; Hirano, Takehiro; Nabetani, Yu; Yamamoto, Daisuke; Onuki, Satomi; Tachibana, Hiroshi; Inoue, Haruo

    2015-12-14

    A new water-soluble silicon(IV)-tetra(4-carboxyphenyl)porphyrin (SiTCPP) with silicon(iv), the second most abundant element on Earth, in the center of porphyrin was synthesized. Fundamental properties including protolytic behaviour of axially coordinating hydroxy groups, and electrochemical behaviour were characterized. The properties were compared with those of silicon(IV)-tetra(2,4,6-trimethylphenyl)porphyrin (SiTMP) and silicon(IV)-tetra(4-trifluoromethylphenyl)porphyrin (SiTFMPP) and discussed in respect to the electron donating/withdrawing effect of the substituents. Two axially coordinating hydroxy groups of SiTCPP exhibit a four-step protolytic behaviour under the acidic conditions along with a single step protolysis of peripheral carboxyl groups. Though SiTCPP and SiTFMPP did not show any reactivity in the photochemical oxygenation of a substrate with K2PtCl6 as a sacrificial electron acceptor, the first oxidation wave in the electrochemical process of SiTCPP and SiTFMPP showed catalytic behaviour in aqueous acetonitrile solution at any pH condition, in contrast to SiTMP which has only a reversible oxidation wave under neutral and weakly acidic conditions. The criteria for the electrochemical oxidative activation of water and the photooxygenation of the substrate were obtained. The higher oxidation wave of Si-porphyrins than ∼0.86 volt vs. SHE is required for the electrochemical oxidation of water, while suitable protecting groups such as a methyl substituent is a requisite for the photochemical oxygenation with K2PtCl6 as a sacrificial electron acceptor.

  1. Determination of threshold dose with delta-aminolevulinic acid-induced porphyrins for effective photodynamic therapy

    NASA Astrophysics Data System (ADS)

    Fritsch, Clemens; Abels, Christoph; Bolsen, Klaus; Ruzicka, Thomas; Goetz, Alwin E.; Goerz, Guenter

    1995-03-01

    In this study the metabolism in tumors and various tissues of intravenously administered (delta) -aminolevulinic acid was investigated. Amelanotic melanoma (A-Mel-3) were implanted in the dorsal skin of Syrian golden hamsters. Distribution and metabolism of i.v. injected (delta) -aminolevulinic acid in blood was studied by determination of (delta) - aminolevulinic acid and protoporphyrin concentration in red blood cells. In addition extraction of various tissues, e.g. tumor, liver, kidney, and normal skin was performed, to verify fluorescence kinetic studies by determination of total porphyrin concentration by photometry and of distribution of the porphyrin metabolites by HPLC. In untreated animals the total porphyrin concentration in all tissues examined were comparably low. In red blood cells the maximal concentration of (delta) -aminolevulinic acid as well as protoporphyrin was detected 45 min after i.v. injection of (delta) -aminolevulinic acid. Porphyrins accumulated in melanoma reaching a maximum tumor:skin tissue ratio of 6.9:1 at 45 min after i.v. injection of (delta) -aminolevulinic acid. A second high tumor:skin tissue ratio of 5.7:1 could be measured at 24 h after injection, but at this point in time the protoporphyrin content in normal skin was higher than 45 min after injection. The kidney may not be strongly affected by i.v. administration of (delta) -aminolevulinic acid, whereas the liver reveals an accumulation of porphyrins, e.g. protoporphyrin. Concluding from these results in this experimental tumor model, i.v. administration of (delta) -aminolevulinic acid seems to be a promising modality to perform photodynamic therapy more effectively and more selectively by irradiation 45 - 180 min after injection of (delta) -aminolevulinic acid.

  2. Computation Sheds Insight into Iron Porphyrin Carbenes' Electronic Structure, Formation, and N-H Insertion Reactivity.

    PubMed

    Sharon, Dina A; Mallick, Dibyendu; Wang, Binju; Shaik, Sason

    2016-08-03

    Iron porphyrin carbenes constitute a new frontier of species with considerable synthetic potential. Exquisitely engineered myoglobin and cytochrome P450 enzymes can generate these complexes and facilitate the transformations they mediate. The current work harnesses density functional theoretical methods to provide insight into the electronic structure, formation, and N-H insertion reactivity of an iron porphyrin carbene, [Fe(Por)(SCH3)(CHCO2Et)](-), a model of a complex believed to exist in an experimentally studied artificial metalloenzyme. The ground state electronic structure of the terminal form of this complex is an open-shell singlet, with two antiferromagnetically coupled electrons residing on the iron center and carbene ligand. As we shall reveal, the bonding properties of [Fe(Por)(SCH3)(CHCO2Et)](-) are remarkably analogous to those of ferric heme superoxide complexes. The carbene forms by dinitrogen loss from ethyl diazoacetate. This reaction occurs preferentially through an open-shell singlet transition state: iron donates electron density to weaken the C-N bond undergoing cleavage. Once formed, the iron porphyrin carbene accomplishes N-H insertion via nucleophilic attack. The resulting ylide then rearranges, using an internal carbonyl base, to form an enol that leads to the product. The findings rationalize experimentally observed reactivity trends reported in artificial metalloenzymes employing iron porphyrin carbenes. Furthermore, these results suggest a possible expansion of enzymatic substrate scope, to include aliphatic amines. Thus, this work, among the first several computational explorations of these species, contributes insights and predictions to the surging interest in iron porphyrin carbenes and their synthetic potential.

  3. The positive influence of fullerene derivatives bonded to manganese(III) porphyrins on water proton relaxation.

    PubMed

    Zou, Toujun; Zhen, Mingming; Chen, Daiqin; Li, Ruimin; Guan, Mirong; Shu, Chunying; Han, Hongbin; Wang, Chunru

    2015-05-21

    Manganese-porphyrin compounds as MRI contrast agents have drawn particular attention due to high relaxivities and unique biodistribution. It has been reported that the charge density of the metal center and steric decompression of the substituents, rather than rotational correlation time, were the key factors to determine the relaxivities of manganese(III) porphyrins. In this study, [6,6]-phenyl-C61-butyric acid (PC61BA) was introduced into 5-(4-aminophenyl)-10,15,20-tris (4-sulfonatophenyl) porphyrin (APTSPP) to investigate the influence on water proton relaxation. The obtained PC61BA-APTSPP-Mn possesses a relaxivity of 19.2 mM(-1) s(-1), which is greater than that of Mn-APTSPP (11.2 mM(-1) s(-1)) and clinically used Gd-DTPA (4.1 mM(-1) s(-1)) at 0.5 T, and even more effective compared with those binding manganese(III) porphyrins to certain macromolecules. It was reasonably speculated that the high relaxivity of PC61BA-APTSPP-Mn should ascribe to the charge density variation of Mn(III) and steric decompression induced by PC61BA. Both fluorescence emission spectra and cyclic voltammetry results verified the presence of electronic communication between PC61BA and APTSPP-Mn. In addition, the hydrodynamic diameter of PC61BA-APTSPP-Mn aggregates was much smaller than that of APTSPP-Mn aggregates, which may contribute to the higher relaxivity by inhibiting the formation of dimers of APTSPP-Mn. Therefore, the introduction of fullerene derivatives is suggested to be a good strategy for the improvement of the relaxivities of manganese(III) porphyrins.

  4. A molecular photovoltaic system based on Dawson type polyoxometalate and porphyrin formed by layer-by-layer self assembly.

    PubMed

    Ahmed, Iftikhar; Farha, Rana; Goldmann, Michel; Ruhlmann, Laurent

    2013-01-18

    Films based on electrostatic interactions between tetracationic porphyrin and Dawson type polyoxometalate are formed by the so called layer-by-layer method. Their photovoltaic performances are investigated by photocurrent transient measurements which showed significant photocurrent response.

  5. Preparation of fluorescent organometallic porphyrin complex nanogels of controlled molecular structure via reverse-emulsion click chemistry.

    PubMed

    Fu, Guo-Dong; Jiang, Hua; Yao, Fang; Xu, Li-Qun; Ling, Jun; Kang, En-Tang

    2012-09-26

    Here, we are the first to report a novel approach to preparing well-defined poly(ethylene glycol) (PEG) fluorescent nanogels, with well-defined molecular structures and desired functionalities via reverse (mini)emulsion copper(I)-catalyzed azide-alkyne cycloaddition (REM-CuAAC). Nanogels with hydroxyl groups and Ga-porphyrin complex (Ga-porphyrin-OH nanogels), as well as with Ga-porphyrin complex and folate functional groups (Ga-porphyrin-FA), are successfully prepared. Nanogels of 30 and 120 nm in diameter are obtained and they exhibit an emission maxima within the wavelength range 700-800 nm. The nanogels could find uses in near infrared (NIR) imaging attributable to their fluorescence and their functionality for cell affinity.

  6. Effects of molecular architecture on fluid ingress behavior of glassy polymer networks

    NASA Astrophysics Data System (ADS)

    Jaskson, Matthew Blaine

    This manuscript demonstrates the synthesis of glassy polymer network isomers to control morphological variations and study solvent ingress behavior independent of chemical affinity. Well-controlled network architectures with varying free volume average hole-sizes have been shown to substantially influence solvent ingress within glassy polymer networks. Bisphenol-A diglycidyl ether (DGEBA), bisphenol-F diglycidyl ether (DGEBF), Triglycidyl p-aminophenol (pAP, MY0510), Triglycidyl maminophenol (mAP, MY0610), and tetraglydicyl-4,4'-diamino-diphenyl methane (TGDDM, MY721) were cured with 3,3'- and 4,4'-diaminodiphenyl sulfone (DDS) at a stoichiometric ratio of 1:1 oxirane to amine active hydrogen to generate a series of network architectures with an average free volume hole-size (Vh) ranging between 54-82 A3. Polymer networks were exposed to water and a broad range of organic solvents ranging in van der Waals (vdW) volumes from 18-88 A3 for up to 10,000h time. A clear relationship between glassy polymer network Vh and fluid penetration has been established. As penetrant vdW volume approached Vh, uptake kinetics significantly decreased, and as penetrant vdW volume exceeded Vh, a blocking mechanism dominated ingress and prevented penetrant transport. These results suggest that reducing the free volume hole-size is a reasonable approach to control solvent properties for glassy polymer networks. New techniques to monitor and predict the diffusion behavior of liquids through glassy networks are also presented. Digital Image Correlation (DIC) was employed to accurately measure the strain developed during case II diffusion. This technique also presented a new theory for a relationship between sample topology and irreversible macroscopic brittle failure induced by solvent absorption. A new modeling technique has been developed which can accurately predict the chemical and physical interactions a solvent may have with a glassy network. This new model can be used as a

  7. Composition of Crustal Melts at the Source Area: Information from Glassy Melt Inclusions in Anatectic Enclaves

    NASA Astrophysics Data System (ADS)

    Acosta-vigil, A.; Cesare, B.; London, D.; Morgan, G. B., VI; Buick, I.; Hermann, J.; Bartoli, O.; Remusat, L.

    2014-12-01

    Crustal anatexis, together with melt extraction and ascent to upper crustal levels, generate plutons and volcanic edifices of granitoid composition. This process constitutes the main mechanism for the differentiation of the continental crust. A recent breakthrough in the study of crustal anatexis is the discovery of former melt inclusions in peritectic minerals of anatectic rocks. These melt droplets show now as glassy inclusions in rapidly cooled anatectic enclaves within volcanic rocks, or as polycrystalline aggregates (nanogranites) in migmatites. Analysis of glassy inclusions and of rehomogenized nanogranites provide direct information on the composition of crustal melts at the source of crustal magmas, on the extent of equilibration between melt and residue, and on the fluid regime during anatexis. A comprehensive geochemical study (≈350 EMP, 100 LA-ICPMS and 80 nanoSIMS analyses) of matrix glasses and glassy melt inclusions in Pl and Grt of anatectic enclaves within El Hoyazo dacite (Betic Cordillera, S Spain), recording melt compositions during regional anatexis at ≈700-850 °C and 0.5-0.7 GPa, shows that melts are leucogranitic (FeOt+MgO+TiO2=1.0-2.0 wt%), moderately to strongly peraluminous (ASI=1.10-1.25), with H2O concentrations well below saturation (3-5 wt%). They are heterogeneous and spread around the 0.5-0.7 GPa haplogranite H2O-undersaturated eutectics. Glassy inclusions in Pl are more heterogeneous, richer in normative Qtz and H2O, and poorer in FeOt and CaO compared to glassy inclusions in Grt and matrix glass. All glasses have moderate to high concentrations of LILE and low to very low concentrations in FRTE, HFSE and REE. Glass inclusions in Pl and Grt have higher concentrations of LILE, lower concentrations of Y, Zr, REE, and lower values of Th/U compared to matrix glasses. Surprisingly, and in spite of the compositional heterogeneity, glasses are at or close to equilibrium with their residue regarding most of the trace elements, except

  8. Photoinduced Partial Unfolding of Tubulin Bound to Meso-tetrakis(sulfonatophenyl) Porphyrin Leads to Inhibition of Microtubule Formation In Vitro

    DTIC Science & Technology

    2013-07-30

    certain porphyrins are able to prompt conformational changes in small globular proteins [7, 8]. In this study, we have adopted a different pro- tein...structural changes by following the formation of microtubules (MTs) in vitro [10, 11]. Tubulin is a ubiquitous, 55 kDa globular protein which natively...by globular ag- gregates with diameters of 80–100 nm. 3.6 Deoxygenated samples Many porphyrins are known to populate their triplet state when

  9. Distance-Dependent Measurements of the Conductance of Porphyrin Nanorods Studied with Conductive Probe Atomic Force Microscopy.

    PubMed

    Zhai, Xianglin; Alexander, Denzel; Derosa, Pedro; Garno, Jayne C

    2017-02-07

    Protocols for nanopatterning porphyrins on Au(111) were developed based on immersion particle lithography. Porphyrins with and without a central metal ion, 5,10,15,20-tetraphenyl-21H,23H-porphyrin (TPP) and 5,10,15,20-tetraphenyl-21H,23H-porphyrin cobalt(II) (CoTPP), were selected for study, which spontaneously formed nanorod geometries depending on concentration parameters. The elongated shapes of the nanorods offers an opportunity for successive distance-dependent conductive probe atomic force microscopy (CP-AFM) measurements along the length of the nanorods. To prepare patterns of TPP and CoTPP nanorods, a mask of silica mesospheres was placed on gold substrates to generate nanoholes within an alkanethiol matrix film. The nanoholes prepared by particle lithography with an immersion step were backfilled with porphyrins by a second immersion step. By controlling the concentration and immersion interval, nanorods of porphyrins were generated with one end of the nanostructure attached to gold within a nanohole. The porphyrin nanorods exhibited slight differences in dimensions at the nanoscale to enable size-dependent measurements of conductive properties. The conductivity along the horizontal direction of the nanorods was evaluated with CP-AFM studies. Changes in conductivity were measured along the long axis of TPP and CoTPP nanorods. The TPP nanorods exhibited conductive profiles of an insulating material, and the CoTPP nanorods exhibited profiles of a semiconductor. The experiments demonstrate the applicability of particle lithography for preparing unique and functional surface platforms of porphyrins to measure distance-dependent conductive properties on gold.

  10. β-Functionalized Push-Pull Porphyrin Sensitizers in Dye-Sensitized Solar Cells: Effect of π-Conjugated Spacers.

    PubMed

    Ishida, Masatoshi; Hwang, Daesub; Zhang, Zhan; Choi, Yung Ji; Oh, Juwon; Lynch, Vincent M; Kim, Dong Young; Sessler, Jonanthan L; Kim, Dongho

    2015-09-07

    A series of new β-functionalized push-pull-structured porphyrin dyes were synthesized so as to investigate the effect of the π-conjugated spacer on the performance of dye-sensitized solar cells (DSSCs). Suzuki- and Heck-type palladium-catalyzed coupling methodologies were used to obtain various β-functionalized porphyrins and β-benzoic acid (ZnPHn) and β-vinylbenzoic acid (ZnPVn) derivatives from β-borylated porphyrin precursors. Photophysical studies of the resulting porphyrins revealed a clear dependence on the nature of the β linker. In particular, it was found that a β-vinylene linkage perturbs the electronic structure of the porphyrin core; this is less true for a β-phenyl linkage. Theoretical analyses provided support for the intrinsic intramolecular charge-transfer character of the β-functionalized, push-pull porphyrins of this study. The extent of charge transfer depends on the nature of the β-conjugated linkage. The photovoltaic performances of the cells sensitized with β-phenylenevinylene ZnPVn exhibited higher power conversion efficiency values than those bearing β-phenyl linkages (ZnPHn). This was ascribed to differences in light-harvesting efficiency. Furthermore, compared to the use of a standard iodine-based electrolyte, the DSSC performance of cells made from the present porphyrins was improved by more than 1 % upon using a cobalt(II/III)-based electrolyte. Under standard AM 1.5 illumination, the highest efficiency, 8.2 %, was obtained by using cells made from the doubly β-butadiene-linked porphyrin.

  11. Ytterbium(III) porpholactones: β-lactonization of porphyrin ligands enhances sensitization efficiency of lanthanide near-infrared luminescence.

    PubMed

    Ke, Xian-Sheng; Yang, Bo-Yan; Cheng, Xin; Chan, Sharon Lai-Fung; Zhang, Jun-Long

    2014-04-07

    The near-infrared (NIR) luminescence efficiency of lanthanide complexes is largely dependent on the electronic and photophysical properties of antenna ligands. Although porphyrin ligands are efficient sensitizers of lanthanide NIR luminescence, non-pyrrolic porphyrin analogues, which have unusual symmetry and electronic states, have been much less studied. In this work, we used porpholactones, a class of β-pyrrolic-modified porphyrins, as ligands and investigated the photophysical properties of lanthanide porpholactones Yb-1 a-5 a. Compared with Yb porphyrin complexes, the porpholactone complexes displayed remarkable enhancement of NIR emission (50-120 %). Estimating the triplet-state levels of porphyrin and porpholactone in Gd complexes revealed that β-lactonization of porphyrinic ligands lowers the ligand T1 state and results in a narrow energy gap between this state and the lowest excited state of Yb(3+) . Transient absorption spectra showed that Yb(III) porpholactone has a longer transient decay lifetime at the Soret band than the porphyrin analogue (30.8 versus 17.0 μs). Thus, the narrower energy gap and longer lifetime arising from β-lactonization are assumed to enhance NIR emission of Yb porpholactones. To demonstrate the potential applications of Yb porpholactone, a water-soluble Yb bioprobe was constructed by conjugating glucose to Yb-1 a. Interestingly, the NIR emission of this Yb porpholactone could be specifically switched on in the presence of glucose oxidase and then switched off by addition of glucose. This is the first demonstration that non-pyrrolic porphyrin ligands enhance the sensitization efficiency of lanthanide luminescence and also display switchable NIR emission in the region of biological analytes (800-1400 nm).

  12. Controlled intracellular generation of reactive oxygen species in human mesenchymal stem cells using porphyrin conjugated nanoparticles

    NASA Astrophysics Data System (ADS)

    Lavado, Andrea S.; Chauhan, Veeren M.; Alhaj Zen, Amer; Giuntini, Francesca; Jones, D. Rhodri E.; Boyle, Ross W.; Beeby, Andrew; Chan, Weng C.; Aylott, Jonathan W.

    2015-08-01

    Nanoparticles capable of generating controlled amounts of intracellular reactive oxygen species (ROS), that advance the study of oxidative stress and cellular communication, were synthesized by functionalizing polyacrylamide nanoparticles with zinc(ii) porphyrin photosensitisers. Controlled ROS production was demonstrated in human mesenchymal stem cells (hMSCs) through (1) production of nanoparticles functionalized with varying percentages of Zn(ii) porphyrin and (2) modulating the number of doses of excitation light to internalized nanoparticles. hMSCs challenged with nanoparticles functionalized with increasing percentages of Zn(ii) porphyrin and high numbers of irradiations of excitation light were found to generate greater amounts of ROS. A novel dye, which is transformed into fluorescent 7-hydroxy-4-trifluoromethyl-coumarin in the presence of hydrogen peroxide, provided an indirect indicator for cumulative ROS production. The mitochondrial membrane potential was monitored to investigate the destructive effect of increased intracellular ROS production. Flow cytometric analysis of nanoparticle treated hMSCs suggested irradiation with excitation light signalled controlled apoptotic cell death, rather than uncontrolled necrotic cell death. Increased intracellular ROS production did not induce phenotypic changes in hMSC subcultures.Nanoparticles capable of generating controlled amounts of intracellular reactive oxygen species (ROS), that advance the study of oxidative stress and cellular communication, were synthesized by functionalizing polyacrylamide nanoparticles with zinc(ii) porphyrin photosensitisers. Controlled ROS production was demonstrated in human mesenchymal stem cells (hMSCs) through (1) production of nanoparticles functionalized with varying percentages of Zn(ii) porphyrin and (2) modulating the number of doses of excitation light to internalized nanoparticles. hMSCs challenged with nanoparticles functionalized with increasing percentages of Zn

  13. Binary ionic porphyrin nanosheets: electronic and light-harvesting properties regulated by crystal structure

    NASA Astrophysics Data System (ADS)

    Tian, Yongming; M. Beavers, Christine; Busani, Tito; Martin, Kathleen E.; Jacobsen, John L.; Mercado, Brandon Q.; Swartzentruber, Brian S.; van Swol, Frank; Medforth, Craig J.; Shelnutt, John A.

    2012-02-01

    Crystalline solids self-assembled from anionic and cationic porphyrins provide a new class of multifunctional optoelectronic micro- and nanomaterials. A 1 : 1 combination of zinc(ii) tetra(4-sulfonatophenyl)porphyrin (ZnTPPS) and tin(iv) tetra(N-methyl-4-pyridiniumyl)porphyrin (SnTNMePyP) gives porphyrin nanosheets with high aspect ratios and varying thickness. The room temperature preparation of the nanosheets has provided the first X-ray crystal structure of a cooperative binary ionic (CBI) solid. The unit cell contains one and one-half molecules of aquo-ZnTPPS4- (an electron donor) and three half molecules of dihydroxy-SnTNMePyP4+ (an electron acceptor). Charge balance in the solid is reached without any non-porphyrinic ions, as previously determined for other CBI nanomaterials by non-crystallographic means. The crystal structure reveals a complicated molecular arrangement with slipped π-π stacking only occurring in isolated dimers of one of the symmetrically unique zinc porphyrins. Consistent with the crystal structure, UV-visible J-aggregate bands indicative of exciton delocalization and extended π-π stacking are not observed. XRD measurements show that the structure of the Zn/Sn nanosheets is distinct from that of Zn/Sn four-leaf clover-like CBI solids reported previously. In contrast with the Zn/Sn clovers that do exhibit J-aggregate bands and are photoconductive, the nanosheets are not photoconductive. Even so, the nanosheets act as light-harvesting structures in an artificial photosynthesis system capable of reducing water to hydrogen but not as efficiently as the Zn/Sn clovers.Crystalline solids self-assembled from anionic and cationic porphyrins provide a new class of multifunctional optoelectronic micro- and nanomaterials. A 1 : 1 combination of zinc(ii) tetra(4-sulfonatophenyl)porphyrin (ZnTPPS) and tin(iv) tetra(N-methyl-4-pyridiniumyl)porphyrin (SnTNMePyP) gives porphyrin nanosheets with high aspect ratios and varying thickness. The room

  14. Towards multielectron photocatalysis: a porphyrin array for lateral hole transfer and capture on a metal oxide surface.

    PubMed

    Brennan, Bradley J; Durrell, Alec C; Koepf, Matthieu; Crabtree, Robert H; Brudvig, Gary W

    2015-05-21

    Current molecular water-oxidation photoelectrocatalytic cells have substantial kinetic limitations under normal solar photon flux where electron-hole recombination processes may outcompete charge buildup on the catalytic centers. One method of overcoming these limitations is to design a system where multiple light-harvesting dyes work cooperatively with a single catalyst. We report a porphyrin monomer/dyad array for analysis of lateral hole transfer on a SnO2 surface consisting of a free-base porphyrin that functions to absorb light and initiate charge injection into the conduction band of SnO2, which leaves a positive charge on the organic moiety, and a free-base porphyrin/Zn-porphyrin dyad molecule that functions as a thermodynamic trap for the photoinduced holes. By using transient absorption spectroscopy, we have determined that the holes on the surface-bound free-base porphyrins are highly mobile via electron self-exchange between close-packed neighbors. The lateral charge-transfer processes were modelled by treating the system statistically with a random-walk method that utilizes experimentally derived kinetic parameters. The results of the modelling indicate that each self-exchange (hop) occurs within 25 ns and that the holes are efficiently transferred to the Zn-porphyrin. This hole-harvesting scheme provides a framework for enhancing the efficiency of multielectron photoelectrocatalytic reactions such as the four-electron oxidation of water.

  15. Porphyrin Binding to Gun4 Protein, Facilitated by a Flexible Loop, Controls Metabolite Flow through the Chlorophyll Biosynthetic Pathway.

    PubMed

    Kopečná, Jana; Cabeza de Vaca, Israel; Adams, Nathan B P; Davison, Paul A; Brindley, Amanda A; Hunter, C Neil; Guallar, Victor; Sobotka, Roman

    2015-11-20

    In oxygenic phototrophs, chlorophylls, hemes, and bilins are synthesized by a common branched pathway. Given the phototoxic nature of tetrapyrroles, this pathway must be tightly regulated, and an important regulatory role is attributed to magnesium chelatase enzyme at the branching between the heme and chlorophyll pathway. Gun4 is a porphyrin-binding protein known to stimulate in vitro the magnesium chelatase activity, but how the Gun4-porphyrin complex acts in the cell was unknown. To address this issue, we first performed simulations to determine the porphyrin-docking mechanism to the cyanobacterial Gun4 structure. After correcting crystallographic loop contacts, we determined the binding site for magnesium protoporphyrin IX. Molecular modeling revealed that the orientation of α6/α7 loop is critical for the binding, and the magnesium ion held within the porphyrin is coordinated by Asn-211 residue. We also identified the basis for stronger binding in the Gun4-1 variant and for weaker binding in the W192A mutant. The W192A-Gun4 was further characterized in magnesium chelatase assay showing that tight porphyrin binding in Gun4 facilitates its interaction with the magnesium chelatase ChlH subunit. Finally, we introduced the W192A mutation into cells and show that the Gun4-porphyrin complex is important for the accumulation of ChlH and for channeling metabolites into the chlorophyll biosynthetic pathway.

  16. The fast method of Cu-porphyrin complex synthesis for potential use in positron emission tomography imaging

    NASA Astrophysics Data System (ADS)

    Kilian, Krzysztof; Pęgier, Maria; Pyrzyńska, Krystyna

    2016-04-01

    Porphyrin based photosensitizers are useful agents for photodynamic therapy and fluorescence imaging of cancer. Additionally, porphyrins are excellent metal chelators, forming stable metalo-complexes and 64Cu isotope can serve as a positron emitter (t1/2 = 12.7 h). The other advantage of 64Cu is its decay characteristics that facilitates the use of 64Cu-porphyrin complex as a therapeutic agent. Thus, 64Cu chelation with porphyrin photosensitizer may become a simple and versatile labeling strategy for clinical positron emission tomography. The present study reports a convenient method for the synthesis of Cu complex with tetrakis(4-carboxyphenyl)porphyrin (TCPP). The experimental conditions for labeling, such as the metal-to-ligand molar ratio, pH and time of reaction were optimized to achieve a high complexation efficiency in a short period of time as possible. In order to accelerate the metallation, the use of substitution reactions of cadmium or lead porphyrin and the presence of reducing agent, such as ascorbic acid, hydroxylamine and flavonoid - morin, were evaluated. The optimum conditions for the synthesis of the copper complex were borate buffer at pH 9 with the addition of 10-fold molar excess, with respect to Cu2 + ions and TCPP and ascorbic acid which resulted in reduction of the reaction time from 30 min to below 1 min.

  17. Effects of Light-Emitting Diode Irradiation on Growth Characteristics and Regulation of Porphyrin Biosynthesis in Rice Seedlings.

    PubMed

    Tran, Lien Hong; Jung, Sunyo

    2017-03-16

    We examined the effects of light quality on growth characteristics and porphyrin biosynthesis of rice seedlings grown under different wavelengths from light emitting diodes (LEDs). After 10 days of exposure to various wavelengths of LEDs, leaf area and shoot biomass were greater in seedlings grown under white and blue LEDs than those of green and red LEDs. Both green and red LED treatments drastically decreased levels of protoporphyrin IX (Proto IX) and Mg-porphyrins compared to those of white LED, while levels of Mg-Proto IX monomethyl ester and protochlorophyllide under blue LED were decreased by 21% and 49%, respectively. Transcript levels of PPO1 were greatly upregulated in seedlings grown under red LED compared to white LED, whereas transcript levels of HO2 and CHLD were upregulated under blue LED. Overall, most porphyrin biosynthetic genes in the Fe-porphyrin branch remained almost constant or upregulated, while most genes in the Mg-porphyrin branch were downregulated. Expression levels of nuclear-encoded photosynthetic genes Lhcb and RbcS noticeably decreased after exposure to blue and red LEDs, compared to white LED. Our study suggests that specific wavelengths of LED greatly influence characteristics of growth in plants partly through altering the metabolic regulation of the porphyrin biosynthetic pathway, and possibly contribute to affect retrograde signaling.

  18. Porphyrin Binding to Gun4 Protein, Facilitated by a Flexible Loop, Controls Metabolite Flow through the Chlorophyll Biosynthetic Pathway*

    PubMed Central

    Kopečná, Jana; Cabeza de Vaca, Israel; Adams, Nathan B. P.; Davison, Paul A.; Brindley, Amanda A.; Hunter, C. Neil; Guallar, Victor; Sobotka, Roman

    2015-01-01

    In oxygenic phototrophs, chlorophylls, hemes, and bilins are synthesized by a common branched pathway. Given the phototoxic nature of tetrapyrroles, this pathway must be tightly regulated, and an important regulatory role is attributed to magnesium chelatase enzyme at the branching between the heme and chlorophyll pathway. Gun4 is a porphyrin-binding protein known to stimulate in vitro the magnesium chelatase activity, but how the Gun4-porphyrin complex acts in the cell was unknown. To address this issue, we first performed simulations to determine the porphyrin-docking mechanism to the cyanobacterial Gun4 structure. After correcting crystallographic loop contacts, we determined the binding site for magnesium protoporphyrin IX. Molecular modeling revealed that the orientation of α6/α7 loop is critical for the binding, and the magnesium ion held within the porphyrin is coordinated by Asn-211 residue. We also identified the basis for stronger binding in the Gun4-1 variant and for weaker binding in the W192A mutant. The W192A-Gun4 was further characterized in magnesium chelatase assay showing that tight porphyrin binding in Gun4 facilitates its interaction with the magnesium chelatase ChlH subunit. Finally, we introduced the W192A mutation into cells and show that the Gun4-porphyrin complex is important for the accumulation of ChlH and for channeling metabolites into the chlorophyll biosynthetic pathway. PMID:26446792

  19. Concerning the deactivation of cobalt(III)-based porphyrin and salen catalysts in epoxide/CO2 copolymerization.

    PubMed

    Xia, Wei; Salmeia, Khalifah A; Vagin, Sergei I; Rieger, Bernhard

    2015-03-09

    Functioning as active catalysts for propylene oxide (PO) and carbon dioxide copolymerization, cobalt(III)-based salen and porphyrin complexes have drawn great attention owing to their readily modifiable nature and promising catalytic behavior, such as high selectivity for the copolymer formation and good regioselectivity with respect to the polymer microstructure. Both cobalt(III)-salen and porphyrin catalysts have been found to undergo reduction reactions to their corresponding catalytically inactive cobalt(II) species in the presence of propylene oxide, as evidenced by UV/Vis and NMR spectroscopies and X-ray crystallography (for cobalt(II)-salen). Further investigations on a TPPCoCl (TPP = tetraphenylporphyrin) and NaOMe system reveal that such a catalyst reduction is attributed to the presence of alkoxide anions. Kinetic studies of the redox reaction of TPPCoCl with NaOMe suggests a pseudo-first order in cobalt(III)-porphyrin. The addition of a co-catalyst, namely bis(triphenylphosphine)iminium chloride (PPNCl), into the reaction system of cobalt(III)-salen/porphyrin and PO shows no direct stabilizing effect. However, the results of PO/CO2 copolymerization by cobalt(III)-salen/porphyrin with PPNCl suggest a suppressed catalyst reduction. This phenomenon is explained by a rapid transformation of the alkoxide into the carbonate chain end in the course of the polymer formation, greatly shortening the lifetime of the autoreducible PO-ring-opening intermediates, cobalt(III)-salen/porphyrin alkoxides.

  20. Effects of Light-Emitting Diode Irradiation on Growth Characteristics and Regulation of Porphyrin Biosynthesis in Rice Seedlings

    PubMed Central

    Tran, Lien Hong; Jung, Sunyo

    2017-01-01

    We examined the effects of light quality on growth characteristics and porphyrin biosynthesis of rice seedlings grown under different wavelengths from light emitting diodes (LEDs). After 10 days of exposure to various wavelengths of LEDs, leaf area and shoot biomass were greater in seedlings grown under white and blue LEDs than those of green and red LEDs. Both green and red LED treatments drastically decreased levels of protoporphyrin IX (Proto IX) and Mg-porphyrins compared to those of white LED, while levels of Mg-Proto IX monomethyl ester and protochlorophyllide under blue LED were decreased by 21% and 49%, respectively. Transcript levels of PPO1 were greatly upregulated in seedlings grown under red LED compared to white LED, whereas transcript levels of HO2 and CHLD were upregulated under blue LED. Overall, most porphyrin biosynthetic genes in the Fe-porphyrin branch remained almost constant or upregulated, while most genes in the Mg-porphyrin branch were downregulated. Expression levels of nuclear-encoded photosynthetic genes Lhcb and RbcS noticeably decreased after exposure to blue and red LEDs, compared to white LED. Our study suggests that specific wavelengths of LED greatly influence characteristics of growth in plants partly through altering the metabolic regulation of the porphyrin biosynthetic pathway, and possibly contribute to affect retrograde signaling. PMID:28300754